Airport pavements are prone to early defects during the construction phase, and their early performance during the construction phase is significantly affected by the external temperature field. This article takes the concrete pavement of Xiamen Xiang’an New Airport as an example and uses a three-dimensional (3D) humidity simulation program for cement concrete pavement to study the evolution behavior of the early stage humidity field of the pavement in a humid and hot climate environment. The results indicate that the evolution law of the humidity field of the concrete pavement slab was consistent with the environmental field, presenting a 24 h periodic variation. The environmental field had a significant impact on the humidity of the surface layer of the pavement slab, and the humidity decreased rapidly with time. There was a humidity gradient on both the horizontal plane and the cutting plane of the slab, the horizontal humidity was concentrated from the boundary into the middle of the slab, and the sectional humidity was concentrated from the top to the bottom of the slab. Environmental parameters, construction parameters, and material and structural parameters all influenced humidity through humidity exchange or by changing the saturated vapor pressure inside the slab. The humidity field was most sensitive to environmental humidity and maintenance methods, but less sensitive to material parameters and structural parameters. Through analysis, it is advisable to avoid hot seasons, choose periods of increased environmental humidity, adopt appropriate maintenance methods during construction to reduce humidity stress on the slab, and therefore decrease early stage deterioration and improve service life. Under environmental loads, the volume deformation of road slabs due to temperature and humidity differences affects the service performance of cement concrete. The runway of the studied coastal airport in a humid and hot area is located in a coastal environment with typical high temperatures, high humidity, and strong winds. Previous research demonstrated that the runway is even more severely damaged by the natural environment than by wheel loads. The early performance of cement concrete pavement slabs during the construction phase is significantly affected by the external temperature field. Under the impact of a certain temperature and humidity field, the pavement slabs could crack due to excessive shrinkage stress and are extremely prone to the occurrence of early construction defects during the construction stage . Thus, hThe temperature difference and its impact on cement concrete pavement have been studied extensively ,4,5,6,7.Unfortunately, the research on humidity fields has mainly focused on a two-dimensional (2D) perspective, and the impact of the diffusion effect on humidity fields could not be considered in a multidimensional manner. Moreover, there has been a lack of understanding of the behavior of the humidity evolution process of concrete pavement slabs from the curing period to the service period, and comparative research on humidity fields in different regions has also rarely been reported. Based on the above issues, the present paper intends to research the three-dimensional (3D) humidity field characteristics of the slabs at an early stage through 3D humidity numerical simulation. Research has shown that the environmental field has a significant impact on the humidity of concrete panels, with the horizontal direction having the greatest impact on the slab corners and the smallest impact on the slab corners. The humidity at the bottom of the slab in the direction of slab thickness is greater than that at the top of the slab, and the humidity difference varies periodically with the environment. This study can provide theoretical support for further improving pavement performance.In a certain area of concrete, the internal moisture variation under the influence of humidity diffusion and cement hydration can be expressed asW is the total moisture variation, ∆dW is the moisture variation caused by diffusion, and ∆Ws is the self-drying moisture variation caused by cement hydration.In the equation, ∆h) is approximately linearly related to the variation in moisture content (∆W). After writing Equation (1) as a differential equation, it can be transformed intoDue to the fact that the internal moisture of concrete is in a thermodynamic equilibrium state, it can be explained based on the principles of adsorption and desorption. The variation of in the internal relative humidity of concrete Humidity diffusion modelThe expressions and differential equations of the three components in Equation (2) are as follows:Researchers conducted numerical research on humidity diffusion based on Fick’s law and mass conservation law . As showLet In the equation, the humidity diffusion coefficient ion of h , which cn is the regression coefficient of the nonlinear diffusion equation of humidity, representing the declining rate of In the equation, (2)Temperature correction modelWhen the moisture content in the pores remains unchanged, the saturated vapor pressure changes with temperature, indirectly affecting the relative humidity tion (6) :(6)κ=0.0In the equation, (3)Self-drying modelThe relationship between the relative humidity variation In the equation, The hydration degree In the equation, terature .(1)Initial momentThe boundary model between the initial humidity value and the moisture exchange between the internal and external is a key factor in determining humidity diffusion. The conditions of the selected initial humidity value and boundary conditions are as follows:The concrete is defaulted to be fully saturated when it is first formed, and the humidity at the initial moment is(2)Surface boundary conditionsThe water exchange between the environment and concrete is a complicated process, and it is difficult to calculate using pure theoretical models. The concrete evaporation rate model obtained by Al-Fadhala and Hover  was seleIn the equation, The formula of the free water surface evaporation rate proposed by Paul was selected:In Equation (12), In Equation (13), (3)Lower surface boundary conditionsAssuming that the lower surface of the concrete is in a sealed state without humidity exchange, the boundary conditions areThe unit water diffusion modes at different locations within the slab are different. The units were divided into six types based on the number of diffusion surfaces. A 3D humidity diffusion equation was established as an example using a six-sided diffusion unit of 3D diffusion. The 3D differential format isThe equation was listed at the initial node of the period, the forward difference quotient was taken for the left side of the equation, and the center difference quotient was taken for the right side. The difference format at any node Let It can be simplified asSome parameters in Equation (17) can be calculated using the following equations:The relative humidity value of the internal units (3D diffusion) of the concrete pavement slab can be calculated using the differential format of Equation (17). The differential format for calculating the relative humidity of the slab corner (1D diffusion) and slab edge (2D diffusion) units can be obtained by multiplying the corresponding sub items in Equation (17) by 1/2.The pavement slab was divided into 20 units along the length and width directions and was divided into 6 units along the depth direction by an integer multiple of 0.02 m. Taking the pavement slab with the size of 5 m × 4.5 m × 0.24 m as the example, there was a total of 2400 units with the size of 25 cm × 22.5 cm × 40 m, each depth plane containing 441 nodes, and the entire model had a total of seven layers, with a total of 3087 nodes. The specific mesh generation is shown in For the pavement construction of a coastal airport in a humid and hot area, the typical summer weather of high temperature and humidity was selected as the reference condition, and the meteorological environment of July in Xiamen was selected, including environmental temperature, humidity, windspeed, and solar radiation intensity, as shown in 2 and a windspeed of 7.5 m/s. The environmental temperature, humidity, windspeed, and solar radiation in January, April, July, and October all changed during day and night, with varying amplitudes, and the temperature changed prominently between the four seasons.It can be seen from Based on the 3D humidity field simulation program for cement concrete pavements, the 3D evolution behavior of the humidity field of cement concrete pavement at early stage under the reference condition without maintenance during summer construction was calculated, and the results are shown in From the above figure, it can be seen that the evolution behavior of the 3D humidity field of the cement concrete pavement of the coastal airport in the humid and hot region under the reference working condition environmental field at early stage mainly exhibited the following properties:(1) As can be seen from (2) From the top to the bottom of the slab, the humidity field exhibited a significant difference, and the difference increased with time. The humidity of the slab surface at the distance of 4 cm from the top of the slab decreased from 100% to about 98.2% in the first 3 days, and the humidity of the slab surface at the distance of 8 cm from the top of the slab decreased from 100% to about 99.97%, and the relative humidity gradually decreased with time. The influence of the environmental field on the 3D humidity field inside the concrete gradually decreased along the depth direction. For the pavement concrete, the environmental field had the greatest impact at a distance of about 4 cm from the surface layer. This location was located at the boundary between the slurry extraction layer and the concrete layer, and the humidity stress caused by the humidity field tended to cause peeling damage.(3) The humidity on the same plane slab was larger inside and smaller outside, and the dividing line gathered towards the middle of the slab with time. As can be seen from (4) Slab edges were more sensitive to the environment than the middle of the slab. From the analysis of (3), it can be concluded that when the external environment humidity was high, the humidity at the slab edge was higher than in the middle of the slab. Conversely, when the environmental humidity was low, the humidity at the slab edge was lower than in the middle of the slab.From the above analysis, it could be deduced that the environmental field had an obvious influence on the distribution of 3D humidity field properties of the concrete pavement slabs at an early stage, which can be summarized as the following aspects:(1) The environmental field had an obvious influence on the humidity of the surface layer of concrete slabs. The humidity of the slab surface changed periodically with the environment, but there was a certain lag compared to the environmental field. The humidity variation in the first 2 days fluctuated weakly with the environment, and then the fluctuation amplitude gradually increased until it was consistent with the environmental variations.(2) The humidity gradient inside the concrete slab along the slab thickness direction was significant. The humidity difference between the top and bottom of the concrete slab was always negative, namely, the relative humidity gradually increased from the top to the bottom of the slab. This was ascribed to the fact that the bottom of the slab did not contact with the external environment and was generally in a saturated state, while the slab surface underwent real-time humidity exchange with the environment. Due to the periodic variation in the relative humidity at the top of the slab with the environmental field, the humidity difference between the bottom and top of the slab also exhibited periodic variation.(3) The humidity gradient on the horizontal surface of the concrete slab was significant. The relative humidity of the slab panel gradually concentrated towards the center of the slab with time. The closer it was to the top of the slab, the more obvious the trend was. The humidity boundary was similar to the shape of the slab, and gradually retracted from the edge to the center of the slab until it reached balanced status.(4) The sensitivity of the relative humidity of slab center, slab edge, and slab corner to the environment was slab center< slab edge< slab corner. Slab corner humidity was the most sensitive to the external environment, followed by slab edge, and the slab center. The reason is that there were three sides of the slab corner that were in contact with the external environment, which caused humidity exchange, making it easier to balance with the environmental humidity. Nevertheless, only one surface was in contact with the external environment, and the humidity diffusion speed was the slowest. Two surfaces of the slab were in contact with the external environment, and the humidity diffusion speed was between the slab center and the slab corner.The middle part of the slab was taken as the analysis object; based on the 3D humidity simulation program for cement concrete pavement slabs, the effects of different factors on the evolution behavior of the 3D humidity field of concrete pavement slabs were studied based on the above working conditions.The impact of different humidity environments on the relative humidity (RH) at the top of the concrete pavement slab and the humidity difference (ΔRH) between the bottom and the top of the slab was analyzed. The calculation results were shown in As can be seen from (1) The environmental humidity field had a significant impact on the humidity field of the pavement. Under different humidity conditions, the relative humidity value in January at 7 days was the highest, with an RH of 94.328%. The RH in April was similar to that in July, reaching approximately 91%, and the relative humidity value in October was the lowest, with an RH of 88.128%. The relative humidity difference in January was the smallest, with the absolute value of ΔRH being 5.672%. The relative humidity difference was the largest in October, with the absolute value of ΔRH being 11.872%. The results were consistent with the monthly humidity laws in (2) The relative humidity curve in the slab was consistent with the law of the humidity field and fluctuated in a daily cycle. It can be seen from (3) Environmental field fluctuations had a significant impact on the humidity of the slab. After finishing the pouring of the concrete slab, the top of the slab was in direct contact with the external environment, resulting in a humidity difference between the slab surface and the environmental field, and therefore causing the relative humidity in the slab to gradually decrease from 100% with time. In (4) The variations in relative humidity in the first 2 days were caused by both cement hydration and environmental humidity, and then they were mainly affected by environmental humidity field. The relative humidity curve in the slab top over the previous 2 days decreased significantly, and the sinusoidal rule was not obvious because of the intense hydration reaction from the previous 2 days and the consistent consumption of internal moisture. The curve of relative humidity reflected the duplicate effect of hydration consumption humidity and moisture exchange. After 2 days, hydration was basically completed, and the relative humidity curve mainly reflected the humidity exchange effect with environmental humidity.See As can be seen from the figure, the relative humidity decreased with windspeed, and the humidity difference increased with windspeed, but the amplitude of decrease and increase were relatively small. At 7 days, the windspeed increased from 2 m/s to 6 m/s, and the relative humidity at the top and in the middle of the slab only decreased by 0.593%, while the humidity difference increased by 0.59%. The reason is that airflow facilitated moisture evaporation, and the greater the windspeed, the faster the moisture evaporation occurs. Meanwhile, this also accelerated the moisture exchange between the air and the slab. In coastal environments, the effect of windspeed on air humidity was not prominent. When the slab humidity and environmental humidity were in balance, the water exchange reached an equilibrium state. The declining rate of concrete humidity was determined by the concrete humidity diffusion coefficients; thus, the influence of windspeed was not significant.2, 600 W/m2, 900 W/m2, and 1200 W/m2.Shown in As can be seen from the above figure, solar radiation had a significant influence on the humidity value of the concrete slabs. The greater the solar radiation value, the greater the fluctuation in the relative humidity and humidity difference curves. The curve of the first 3 days was mainly affected by the internal hydration of the concrete, and the impact of environmental factors on its fluctuating amplitude was relatively slight. After 3 days, the fluctuation amplitude gradually increased, and the maximum relative humidity difference reached 2.62% at 7 days. The reason is that the increase in solar radiation leads to an increase in the temperature of the concrete slab, but a decrease in the saturated vapor pressure inside the concrete, thereby leading to a decrease in the saturated humidity inside the concrete, manifested as a decrease in the relative humidity value of the concrete slab. The results of this study are somewhat in compliance with those reported by Nasir et al.  on hot wFive different types of Portland cement were selected, and their performance on the relative humidity at the top of the concrete slab and the humidity difference between the bottom and the top of the slab were also calculated. The results are shown in Based on the above figure, it can be observed that the cement component had little impact on the relative humidity of the top of the concrete pavement slab, and the relative humidity difference between the concrete slabs of different types of cement was less than 0.5%. Due to the humidity exchange between the slab surface and the external environment, the humidity level at the bottom of the slab was greater than at the top of the slab, while the humidity difference between the bottom and the top of different cement concrete slabs was less than 0.5%.The influence of cement type on the humidity field of the concrete pavement slabs was mainly reflected in the aspect of heat release from cement hydration. Nevertheless, cement hydration mainly occurred before concrete setting, at which time the relative humidity value inside the concrete was relatively high and generally in a saturated state. The temperature difference generated by the heat release from the hydration of different types of cement on the inside of the concrete was insufficient to exert an obvious impact on the relative humidity, namely, there was a phenomenon that the relative humidity curves of different types of cement concrete pavement slabs basically overlapped.Shown in It can be seen from the above figure that the relative humidity at the top of the concrete slab decreased with the water–cement ratio, and the relative humidity difference between different water–cement ratios was more significant with time. The law of the relative humidity difference between the bottom and the top of the slab was the same as the relative humidity at the slab top. The reason is that the increase in water–cement ratio led to an increase in free water content in the concrete, thereby accelerating the hydration of the cement, as well as enhancing the heat generated by hydration, resulting in an increase in the internal temperature of the concrete, and accelerating the evaporation of water. The combined action of the two effects would reduce the humidity on the top of the concrete slab. The curve after 2 days mainly reflected the humidity exchange between the concrete slab and the external environment. The lower the relative humidity of the slab top was, the more obvious the humidity exchange was. The curve reflected that the relative humidity of the slab top varied periodically with environmental humidity. The relative humidity difference between the peaks and troughs of different water–cement ratios slightly increased with time, but the amplitude was not significant. The findings of this study are in agreement with those reported by Khan et al.  wherein The effect of pavement slab thickness on relative humidity at the top of the slab and the humidity difference between the bottom and the top of the slab were analyzed. The calculation results are shown in It can be seen from Due to the periodic variation in daily meteorological data and significant differences between peak and trough values, paving concrete pavement at different times exposes the pavement slabs to different initial environmental fields, which inevitably exerted a certain impact on the humidity diffusion of the pavement slabs. To analyze the influencing rule, concrete pouring was conducted at four times, viz. 0:00 h, 6:00 h, 12:00 h, and 18:00 h. The calculation results are shown in According to the analysis in (1) The fluctuation laws of the relative humidity curve at the top of the concrete slab at different paving times was the same, and the difference between the peaks and troughs on the time axis was the same as the difference at the paving time, that is, the relative humidity curve at the top of each slab fluctuated cyclically for 24 h from paving time.(2) After 24 h of paving at different times, the humidity at the top of the slab showed a downward trend, with the maximum decline in the relative humidity curve occurring when paving at 00:00, with an amplitude of 1.541%. At 18:00, the decreasing trend of the paving relative humidity curve was the smallest, with an amplitude of 1.189%.Compared to the environmental humidity in (3) The relative humidity curve at the top of the slab at different pouring times gradually increased with time. As can be seen from (4) Three typical curing methods, i.e., no curing, water curing, and geotextile + water curing, were used to explore the impact of curing methods on the humidity field of the concrete slabs. The environmental humidity of the water curing was proposed to be maintained at 70%, and the environmental humidity of the geotextile + water curing was proposed to be maintained in a saturated state. The calculation results are shown in As can be seen from the figure, the curing method had a significant impact on the humidity field at the top of the concrete slab and the humidity difference between the bottom and the top of the slab; the details are listed as follows:(1) Except for the environmental humidity of 100%, the relative humidity curve at the top of the slab and the humidity difference curve at the bottom and the top of the slab possessed the same fluctuation rules, which fluctuated periodically with the environment for 24 h. This indicated that the humidity field was closely related to environmental temperature, windspeed, and solar radiation, in addition to being affected by environmental humidity, and was represented by the combined effect of various factors.(2) During water curing, the relative humidity value at each time point on the top of the concrete slab was greater than that with no curing, and the difference between the peaks and troughs of the relative humidity curve on the top of the concrete slab with water curing was smaller than with no curing.(3) During geotextile + water curing, the relative humidity of each part inside the concrete slab was 100%, which was the most ideal state for concrete strength growth and internal stress.From the above analysis, it can be seen that if no maintenance measures are taken when the concrete pavement is poured, the humidity of the slab dramatically decreases, resulting in a large humidity difference inside the slab, and forming a stress gradient that induces early stage cracking. As a result, a reasonable curing method is an important measure to ensure strength growth and other properties, and to prevent microcracks and cracks in the concrete.There are many factors that affect the 3D humidity field behavior of concrete pavement slabs. To study the sensitivity of each factor, a single factor was altered while ensuring that other parameters remained unchanged, and the sensitivity of each single factor to the concrete’s humidity field behavior was also analyzed separately.Single-factor sensitivity was divided into three levels: high (S ≥ 2%), medium (1 ≤ S < 2), and low (S < 1%). According to the numerical simulation program for the 3D humidity field of the cement concrete pavement, the sensitivity of each factor is shown in As can be seen from From the perspective of influencing characteristics, the influence of various parameters on the 3D humidity field of the concrete pavement slabs was mainly divided into two aspects, namely, direct influence and indirect influence.(1) Direct influence refers to the variation in relative humidity value through the internal moisture of the concrete slab. The curing method, environmental humidity, environmental temperature, windspeed, cement type, and water–cement ratio all affected the humidity field by altering the moisture of the concrete slab. Among them, environmental humidity and curing methods influenced the humidity field by moisture exchange with the concrete slabs, environmental temperature and windspeed affected the humidity field by diffusing moisture from the concrete slabs, while the cement type and water–cement ratio affected the humidity field by absorbing moisture through chemical reactions.(2) Indirect influence refers to the variations in relative humidity values through the saturated vapor pressure inside the concrete slab. Environmental temperature, solar radiation, cement type, and water–cement ratio all affected the saturated vapor pressure inside the concrete slab by changing the temperature of the slab. The indirect influence was generally weak and only had a fluctuating performance on the relative humidity of the slab but had little impact on the internal moisture content of the concrete within a certain period of time.(1) The environmental field had a significant impact on the humidity of the surface of the concrete slabs. After the pouring of the concrete panel is completed, the humidity at 2 cm in the middle of the panel, 2 cm~6 cm at the corner, and 1/2 of the edge of the panel decreases to the lowest stage value, and the trend of humidity change basically coincides with the fluctuation trend of environmental humidity.(2) The sensitivity of the surface humidity of concrete panels to the environment varies significantly. The order of sensitivity to the environment is board corner, board edge 1/2, and board center 2 cm.(3) The humidity gradient inside the concrete panel is significant along the thickness direction, and at the same time, the humidity of the road panel concentrates towards the middle and bottom of the board. The difference between the humidity boundaries of 2 cm, 4 cm, and 6 cm from the top of the board and the maximum humidities in the slabs during the first 28 days are 1.3%, 2.3%, and 2.9%, respectively.(4) Environmental parameters, construction parameters, and material and structural parameters all affected slab humidity through humidity exchange or by changing the saturated vapor pressure inside the slab. Environmental humidity and curing methods were highly sensitive to the humidity field of the concrete slabs, followed by windspeed. Solar radiation, cement type, water–cement ratio, and thickness were less sensitive to the humidity fields of the concrete slabs. During construction, hot seasons should be avoided; the periods should be increased to pour concrete in a selected ambient humidity. Moreover, appropriate curing methods should be adopted to reduce the humidity stress of slabs, eliminate early stage defects, and thereby improve their service life.


Syntactic complexity, widely acknowledged as a key predictor of writing quality, has gained increasing attention in the realm of academic writing. A notable line of inquiry has centered on the factors that potentially influence syntactic complexity in academic writing. Instead of attending to one factor, the study focuses on multiple factors to examine how language background affects syntactic complexity across years and disciplines. Specifically, it compares the syntactic complexity in English academic writing between L1 English and L1 Chinese university students across four years and/or three disciplines. Fine-grained indices, which include five clausal indices and eight phrasal indices, are utilized to capture specific syntactic features for a full understanding and description of the syntactic preferences shown by L1 English and L1 Chinese students in academic discourse. The results revealed that L1 English students tended to produce more noun phrases in academic writing than L1 Chinese students with the increase of years. Additionally, both cohorts of students followed similar syntactic patterns in cross-disciplinary contexts, with highly frequent use of complex nominals in the Physical Sciences and clausal structures in the Social Sciences. In instances where language background, year, and discipline interact, texts produced by Chinese English learners exhibited reliance on the syntactic features of adverbial clauses, attributive adjectives, and pre-modifying nouns across all disciplines in the early years of their academic journey. Ultimately, some pedagogical implications for academic writing courses are put forward in an attempt to provide valuable insights for enhancing academic literacy among both L1 and L2 students. Syntactic complexity, referring to the extent of diversity and sophistication of sentential forms in language output , 2, has Over the past two decades, academic writing has stood out in the field of L2 writing. Syntactic complexity in both published research articles and non-professional writing  has received extensive attention . NumerouA growing body of work has targeted both native and non-native speakers to scrutinize whether and how language background impacts syntactic complexity. The majority of these studies have adopted the same large-grained indices to assess the language output of L1 and L2 academic writing from the dimensions of length of production units, amount of subordination, amount of coordination, and degree of phrasal sophistication –37. HoweOther research has opted for fine-grained indices primarily focusing on a variety of compressed constructions of noun phrases based on the assumption that a nominal style is more pronounced in formal academic writing , 39. AccThe development of syntactic complexity has been a central concern of L2 writing research. Numerous studies have followed the syntactic development trajectories of individuals or groups of learners over a period of time from a longitudinal perspective , 40–43, Longitudinal and cross-sectional work on the development of syntactic complexity in academic writing has collectively revealed several trends. For instance, learners tend to pack meaning into phrasal constructions rather than clausal coordination and subordination as they accumulate academic writing experience and develop academic writing skills , 41. In Writing in academic contexts is governed by shared communicative purposes and endorsed communicative conventions among members of a given discourse community . The useRecently, some scholars have come to consider disciplinary variation when exploring students’ academic discourse , 27, 45.Current research that has addressed the effects of multiple factors on syntactic complexity in academic writing is relatively scarce , 32, 45.In contrast to the study by Staples et al. , the preAre there differences in the syntactic complexity of English academic writing produced by L1 English and L1 Chinese students as the year progresses? If so, what are the differences?Are there differences in the syntactic complexity of English academic writing produced by L1 English and L1 Chinese students within or among disciplines? If so, what are the differences?Is there a significant interaction between language background, year, and discipline? If so, what are the specific features?All the data collected and analyzed in this study were drawn from the British Academic Written English Corpus (BAWE), which contains academic writing from students at different UK universities. The corpus covers good-standard (Distinction and Merit) academic texts of various genres  written by students from L1 English and multiple L1 non-English countries throughout four years of study  and across four discipline groups .Table 1. Other considerations regarding sub-corpora are also mentioned. This corpus is evidently incapable of providing a platform for a longitudinal study, and it is considered to be a cross-section from the undergraduate to graduate levels. Additionally, the study did not narrow down the genres of the two sub-corpora, mainly on account of the need for sufficient sample size and the different genre preferences among disciplines, e.g., more case studies in the Life Sciences, methodology recount in the Physical Sciences, and essays in the Social Sciences. Lastly, given the characteristics of BAWE that all texts gathered were rated to a good standard, it is necessary to reiterate that the aim of the study is not to identify the gap between syntactic complexity in Chinese-L1 students’ academic writing and that of English-L1 students but to interpret to what extent syntactic features are influenced by linguistic backgrounds and whether this influence is mediated by year and discipline.Based on the research focus, this study only examined written texts from L1 English and L1 Chinese speakers. Due to the lack of Chinese student samples in the Arts and Humanities, we focused on the Life Sciences (LS), Physical Sciences (PS), and Social Sciences (SS). Also, because the number of texts from L1 English writers far exceeded that of L1 Chinese writers in the corpus, to avoid the detrimental effects of uneven sample size, we used SPSS to randomly sample the L1 pool to ensure that the number of L1 texts in each year and discipline matched that of the L2 texts. Ultimately, a total of 472 academic writings made up this study corpus, including two sub-corpora from L1 and L2. The L1 sub-corpus contains randomized 236 writing texts generated by native speakers from four years of LS, PS, and SS disciplines, and the L2 sub-corpus comes from the same amount of academic writing by Chinese students. The number of texts, total word count, and mean word count for each year and discipline of the two groups are presented in The Tool for the Automatic Analysis of Syntactic Sophistication and Complexity (TAASSC) developed by Kyle  served aTable 2). Among these types, finite and non-finite dependent clauses exhibit three syntactic functions: adverbial, complement, and noun modifier [We did not employ all the indices provided by TAASSC due to the potential inflation of Type-I errors that could arise from testing a multitude of indices . Insteadmodifier . In thismodifier  under phTable 2). Alongside these six dependent types, two general phrasal complexity indices were similarly identified, namely, dependents per nominal  and the standard deviation of dependents per nominal , corresponding to phrasal sophistication and diversity.TAASSC provides a sufficient array of phrasal complexity indices, which can be broadly categorized into three groups: phrase types , particular dependent types , and particular dependent types associated with phrase types . Given the special focus of this study on hypothesized complex nominals as a marker of advanced academic writing, only the second category of phrasal complexity indices was utilized, comprising different parts of speech (POS) modifying nominal phrases. These involve attributive adjectives, post-modifying prepositional phrases, non-finite verbs or verb phrases, pre-modifying nouns, non-clausal adverbs, and that- or wh-relative clauses  did not. After the sqrt transformation of the five indices, all data showed normal distribution and homogeneity of variance. The indices that yielded significant differences in the analysis were further conducted with univariate tests and pairwise comparisons adjusted by Bonferroni to observe specific variations. Effect sizes were based on Cohen , with thp < 0.001, η2 = .300) and year  = 3.535, p < 0.001, η2 = .092) had a significant main effect on the syntactic complexity and that there was an interaction effect  = 2.071, p < 0.001, η2 = .056). Therefore, follow-up univariate analyses were performed to trace the impact on each index, as presented in Table 3. The results showed an interaction between background and year for 6 of the 13 indices, of which 3 indices  represent the global complexity and 3 indices  are nominal phrases. The study further examined simple effects of background baseline within each level in combination with other effects and pairwise comparisons using Bonferroni adjustment to determine between-group differences for each year.Factorial MANOVA revealed that background  = 14.923, Fig 1 shows the means of six indices that interacted between background and year. For dependents per clause, significant differences were found in the 1st  and 4th  year, with more use by L1 English students than L1 Chinese students in the first year (p < 0.05), and vice versa in the fourth year (p < 0.01). When it comes to clausal diversity, also known as dependents per clause (standard deviation), texts from L1 Chinese writers were more varied in clauses in the final year than L1 English writers’ texts . Similarly, the statistical change occurred only in the fourth year, but the difference was that dependents per nominals were written more by L1 English students than by L1 Chinese students . It is evident that L1 Chinese writers produced more noun modifiers than L1 English writers until the third year . The feature of relative clause modifiers in L1 writing was more prominent than those in L2 writing throughout the four years of study . There were also significant differences between the two groups in terms of adverbial modifiers, with higher frequency in L1 texts in the 1st and 2nd year .p < 0.001, η2 = .297) and discipline  = 10.604, p < 0.001, η2 = .233) on clausal and phrasal complexity, and an interaction effect  = 2.515, p < 0.001, η2 = .067) was also found. As illustrated in Table 4, the interaction effects of background and discipline appeared significantly with clausal indices of dependents per clause and clausal complements, as well as phrasal indices of dependents per nominal, prepositional modifiers, and relative clause modifiers.According to multivariate tests, there was a main effect of background  = 14.743, Fig 2 illustrates the means of five indices that interacted between language background and discipline. Pairwise comparisons showed significant differences in dependents per clause in SS, where Chinese-L1 writers used more clauses than English-L1 writers . This index was higher in SS than in other disciplines for both backgrounds. Between-group differences revealed that L1 English students tended to produce more clausal complements than L1 Chinese students in academic texts in LS , while within-group differences reflected high outputs of this measure for both L1 and L2 backgrounds in the SS discipline. The L2 group showed a higher frequency of producing dependents per nominal in LS , while the L1 group tended to use it more in PS . Both groups had higher phrasal complexity in the PS discipline. Significant differences between L1 English and L1 Chinese students’ prepositional modifiers index were found in LS and PS, with a lower frequency appearing in L1 academic texts of LS  and vice versa in PS . In addition, L1 writing exhibited a higher frequency of relative clause modifiers than L2 writing in both LS  and SS .Table 5) revealed an interaction effect between language background, year, and discipline  = 1.893, p < 0.001, η2 = .053) and further explored four indices, including dependents per clause (standard deviation), adverbial clauses, adjectival modifiers, and noun modifiers. Fig 3 manifests the variation in the mean values of the four significant indices over four years and across three disciplines. Pairwise comparisons demonstrated the differences between students from the two backgrounds across different disciplines and years in relation to clausal diversity. Specifically, the statistics for native speakers were significantly higher than those for students from China in the LS discipline during the first year , but no difference was observed in the next three years. In PS, L2 texts showed more diverse clause structures than L1 texts only in the fourth year . There was no difference between students from both backgrounds in SS over four years.A three-factor ANOVA , the second and third years of PS , and the second year of SS , all of which had more production from Chinese-L1 than English-L1 writers. The difference regarding adjectival modifiers existed only for the second-year LS discipline  and first-year PS discipline , again which showed a higher index for Chinese writers. The variation in the feature of nouns as modifiers were mainly in the 2nd year of LS , the 1st year of PS , and the first three years of SS , and all were higher for L2 English learners.Exploring the index of adverbial clauses, there were significant differences in the first and third years of LS , alongside phrase types . Furthermore, students are encouraged to revise their own academic work under the guidance of teachers, with a specific focus on how loosely structured content can be reconfigured into denser and information-centric forms anchored by noun phrases. This practical exercise aids in deepening their comprehension of academic writing features. Simultaneously, educators should not overlook the language discrepancies inherent in different academic disciplines. They should orchestrate a range of discipline-specific instructional activities to elucidate the distinct functions and communicative purposes conveyed by clauses and phrases, such as explanatory power and explicitness, to cater to the diverse disciplinary features of academic writing. Additionally, educators who teach Chinese students should recognize the syntactic traits exhibited in the academic writing of native speakers, along with the similarities and differences in performance observed among Chinese English learners. Interventions should be tailored in alignment with the syntactic preferences of Chinese students, which have been shaped by cultural, linguistic, and academic backgrounds, rather than imposing native norms into the L2 context. For instance, an augmentation of students’ awareness and practice concerning particular noun phrase structures, including adjective modifiers and noun modifiers, could potentially expedite their adaptation to linguistic features as they initiate their engagement with academic writing.The limitations of the study also need to be mentioned. First, the sample sizes collected by the study at each level may not be large enough, which probably limits the generalizability of the results to a larger target group. This is mainly determined by the number of Chinese students’ texts in the corpus. Furthermore, the study selected major indices from TAASSC, which may not cover all common syntactic structures in academic writing. Therefore, a larger sample size and more comprehensive indices will be included in future studies in order to further compare the academic syntactic complexity of students from diverse L2 countries and L1 backgrounds.


The synthesis method offers significant advantages, reducing both synthesis time and energy consumption by 90–98% compared to conventional approaches. The synthesized nanohybrids are characterized through FESEM, EDX, XRD, and Raman spectroscopy to understand their morphology and functional group interactions. These nanohybrids are incorporated into 20W40 engine oil following synthesis, and a comprehensive assessment of their properties is conducted. This evaluation covers critical parameters like viscosity index, stability, volatility, as well as tribological properties, oxidation resistance, and thermal conductivity of the oil-nanohybrid system. Results demonstrate that adding just 0.05 wt% of MoS2-graphene nanohybrid leads to a remarkable 58.82% reduction in friction coefficient and a significant 36.26% decrease in the average wear scar diameter. Additionally, oxidation resistance improves by 19.21%, while thermal conductivity increases notably by 19.83% (at 100 °C). The study demonstrates the synergistic effects of these nanohybrids in reducing friction and wear, enhancing oxidation resistance, and improving thermal conductivity. In conclusion, this research highlights the potential of microwave-synthesized MoS2-graphene nanohybrid as promising tribological additives for diesel engine oils. Their successful integration could significantly enhance the performance and durability of critical mechanical components in diesel engines, representing a significant advancement in lubrication technology.This research explores the potential of microwave-synthesized MoS Nanolubricants are typically composed of a base lubricant, such as mineral or synthetic oil, and nanoparticles that are added to the base lubricant to improve its properties. The nanoparticles used in nanolubricants can be of various materials, such as metal oxides, carbon-based materials, and layered materials. Adding nanoparticles to the base lubricant enhances its properties, such as viscosity, thermal stability, and tribological properties, and helps reduce friction and wear in engine components3.Lubrication of engine components is essential for ensuring efficient operation, minimizing wear and tear, and extending the engine’s lifespan. One of the latest advancements in engine lubrication is the use of nanolubricants, which are designed to enhance the performance of conventional lubricants by reducing friction and wear at the nanoscale level2) is a two-dimensional material with unique tribological properties, making it a promising candidate for lubrication applications. The layered structure of MoS2 is characterized by strong interlayer covalent bonds and weak van der Waals forces between molecular layers, allowing the formation of a slippery surface that reduces friction and wear between moving parts5. The van der Waals gap plays a critical role in intercalation and lubrication properties. The MoS2 is used extensively in solid lubrication, lubrication additives in oils, and self-lubricating polymer materials. Various forms of MoS2, such as flower-like microspheres and ultrathin nanosheets, have been synthesized and evaluated for their tribological properties. Tang et al. synthesized MoS2 flower-like microspheres, which demonstrated superior anti-wear and friction-reducing properties when used as a lubrication additive compared to pure base oil6. Song et al. prepared ultrathin MoS2 nanosheets as lubricating additives and found that their tribological and extreme pressure properties were significantly enhanced due to the good dispersion and ultrathin shape of the nanosheets7. MoS2’s unique structural and mechanical properties enable it to reduce friction and wear and prevent deposition, making it an important additive in various industrial applications. Ongoing research is focused on developing innovative techniques to synthesize and utilize MoS2 to enhance its tribological properties further and broaden its range of applications. For example, Song et al. synthesized MoS2/graphene oxide hybrid nanosheets and reported that they exhibited excellent tribological performance and could be potentially used as lubricant additives8. Moreover, Chen et al. synthesized a composite material of MoS2 and boron nitride, which possessed superior tribological properties as a lubricating additive9.Molybdenum disulfide  base oil as a high-performance additive, with tribological performance that surpasses that of other carbon additives, such as graphite and carbon black. The tribological behavior of graphene is also influenced by its surface functionalization, which can be tailored to enhance its lubrication properties. For instance, Tao Bai et al. synthesized polyurethane-graphene oxide and Fe3O4 nanocomposites and observed a significant reduction in the coefficient of friction and wear rate compared to neat polyurethane12.Graphene, a two-dimensional material of carbon atoms arranged in a hexagonal lattice, possesses exceptional tribological properties that make it an attractive candidate for various industrial applications. Its high chemical inertness, extreme strength, and easy shear capability on its densely packed and atomically smooth surface are favourable attributes for its impressive friction and wear behavior. Numerous recent studies have explored graphene’s potential as a solid or colloidal liquid lubricant. Liang et al.2) and graphene have attracted significant attention in the field of tribology due to their unique mechanical and structural properties. MoS2, with its layered and two-dimensional structure, exhibits excellent tribological behavior as a solid lubricant due to its low friction and wear properties. On the other hand, graphene possesses exceptional mechanical strength, chemical stability, and easy shear capability on its densely packed and atomically smooth surface. Combining these two materials as a nanocomposite further enhances their tribological properties, making them a valuable additive in various industrial applications. The high shear strength of graphene and the layered structure of MoS2 may result in a synergistic effect, reducing friction and wear. Due to their excellent mechanical and structural properties MoS2/graphene nanocomposites may emerge as promising materials for tribological applications.Molybdenum disulfide , laser ablation, and others, as previously documented 16. The primary objective of this study is to investigate and elucidate the underlying mechanisms responsible for the substantial performance enhancement of base oil upon incorporating MoS2-graphene nanohybrid additives. In pursuit of this objective, we have conducted a comprehensive examination of several key parameters, including the coefficient of friction (COF), average wear scar diameter (WSD), oxidation induction time (OIT), and thermal conductivity. Notably, this investigation represents a new effort, as no prior research has systematically explored all these crucial parameters in the context of hybrid nanoparticles. Our foremost aim is to understand the influence exerted by hybrid MoS2-graphene nanohybrid additives on the behavior of engine oil. This knowledge holds the potential to facilitate the development of advanced lubricants characterized by superior performance characteristics. The outcomes of this research endeavor are poised to yield valuable insights into enhancing engine oil performance by incorporating MoS2-graphene nanohybrid additives, specifically within the domain of diesel-based engine oil applications. Consequently, this research may pave the way for a more sustainable future, marked by a reduced carbon footprint and cost-effective maintenance practices within energy conservation and efficiency.In this research, we used an innovative approach to synthesize MoS2, graphene nanoparticles, and synthesized MoS2-graphene nanohybrid. The diffraction peaks at 2θ = 14.5°, 33.0°, 39.3°, 58.5°, and 69.7° in Fig. 2 phase (JCPDS no.371492)18. The graphene diffraction peaks are depicted as a single major peak at 2θ = 24.6° from the (002). The hybrid nanoparticle had no additional peaks or substantial changes from the original MoS2 or graphene diffraction spectra. The estimation of crystallite size in the MoS2-graphene nanohybrid was conducted using the Scherrer equation:Figure 2-graphene nanohybrid was determined to be 94.46 nm.Here D represents the crystallite size in nanometers, K is the Scherrer constant with a value of 0.9, λ denotes the wavelength of X-rays, β corresponds to the full width at half maximum (FWHM), and θ represents the peak position. Applying Eq. , the cal2, Graphene and MoS2-graphene nanohybrid. The Raman spectrum of MoS2 shows 2 strong peaks; the first (in 367 cm−1) is associated with the E12g vibrational mode, whereas the second (in 406 cm−1) is associated with the A1g mode. On the other hand, these modes correspond to in-plane vibrations of sulphur atoms in one direction, molybdenum atoms in the other, and out-of-plane vibrations (A1g) of sulphur atoms. The graphene phase also contributes to the Raman spectrum and the characteristic G and 2D peaks of graphene can be observed at around 1580 cm−1 and 2700 cm−1, respectively. However, it was observed that only MoS2 spectra were visible in the Raman spectra of the nanohybrid, while the spectra of graphene were not detected. This phenomenon can be attributed to the strong Raman scattering from MoS2 compared to graphene. The electronic band structure of MoS2 allows for strong resonance enhancement of the Raman signal. Thus, the Raman scattering from MoS2 dominates over the Raman scattering from graphene. Moreover, the laser used in Raman spectroscopy cannot penetrate through the MoS2 layers to excite the underlying graphene layers. The MoS2 layers encapsulate the graphene layers, so the Raman signal from the graphene layers were not observed20.The Raman spectra in Fig. 2-graphene nanohybrid at various magnifications, an EDX spectrum, and elemental mapping. The MoS2 nanoparticles are shown to be consistently grown over graphene surfaces with curved edges that are uniformly faceted. The images show regions where the MoS2 and graphene are in close proximity, indicating that they are well-dispersed and that there is good interfacial interaction between the two phases. The microwave synthesis platform has proven highly effective in producing a MoS2-graphene nanohybrid with intriguing characteristics. Moreover, the resulting hybrid exhibits flake sizes ranging from 100 to 150 nm, confirming the size in the nanometer range. This nano-sized structure imparts significant advantages, primarily promoting efficient reaction kinetics and reducing the likelihood of nanoparticle aggregation21. Furthermore, the microwave synthesis method enables the MoS2 nanoparticles to encapsulate the surface of graphene sheets and intercalate between the MoS2 layers. This unique feature creates an interlayer coupling effect between the hybrid layers, leading to intriguing synergistic properties. The encapsulation of graphene by MoS2 and the intercalation between MoS2 layers not only enhance the structural integrity of the nanocomposite but also facilitate interfacial interactions and promote interlayer charge transfer processes23. In Fig. 2-graphene nanohybrid. The EDS spectrum in Fig. 2-graphene structure. Furthermore, the corresponding quantitative surface analysis depicted in Fig. 2-graphene nanohybrid.Figure 2-graphene nanohybrid. The results from Table 2-graphene nanohybrid leads to a slight decrease in the kinematic viscosity of the oil. This reduction in viscosity can be attributed to the lubricating effect of the MoS2-graphene nanohybrid, which effectively diminishes the friction between the oil molecules and the moving parts. Consequently, this reduction in frictional resistance facilitates the flow of the oil. The presence of the hybrid MoS2-graphene nanohybrid within the oil creates a lubricating boundary layer between the moving parts. This boundary layer acts as a protective barrier, minimizing direct metal-to-metal contact and reducing the energy required for movement. In high shear rate environments, such as those encountered in engine components, the formation of this boundary layer becomes particularly significant26.The findings in Table 2-graphene nanohybrid increases the viscosity index in the nanolubricant compared to the SAE20W40. The viscosity index measures the lubricant’s resistance to changes in viscosity with temperature changes. A higher viscosity index indicates that the lubricant will maintain its viscosity over a wider range of temperatures, which is crucial for engine protection and fuel efficiency27. The increase in the viscosity index reduces the tendency of the lubricant to thicken at low temperatures and thin at high temperatures. This improves the stability of the lubricant and ensures it provides effective engine protection even under extreme operating conditions28.It can be seen that the MoS2-graphene nanohybrid-based nanolubricant in engine oil. This analysis is crucial as it measures the electrical charge of the dispersed nanoparticles within the engine oil, providing valuable insights into the stability of the nanoparticles. The measurement of zeta potential is a widely adopted method employed by researchers for studying nanolubricant stability 30. Figure 2-graphene nanohybrid before and after a period of 14 days. The zeta potential values indicate the dispersion intensity of the nanoparticles in the engine oil, directly influencing the stability of the nanolubricant. Based on Fig. 2-graphene nanohybrid in the engine oil. The increase in zeta potential values is due to the graphene in the nanocomposite having a high surface area and electrical conductivity, which provides a large number of active sites for surface interaction and electrostatic stabilization. The MoS2 in the nanocomposite has a high surface energy and a polar surface, which can further enhance the surface interaction and electrostatic stabilization of the oil droplets31. This improves the charge distribution at the surface of the oil droplets, leading to higher zeta potential. The high zeta potential may prevent the droplets from agglomerating and sticking to engine components, which improves engine performance and prolongs engine life32. The increase in stability reduces the interfacial tension between the oil droplets and the engine components. This may improve the wetting ability of the oil, leading to better lubrication and reduced wear and tear.A zeta potential analysis is conducted to assess the stability of the MoS2-graphene nanohybrid is shown in Fig. 2-graphene nanohybrid based nanolubricants evaporative loss ranged from 9.35 to 11.22%. This can be attributed to several mechanisms of the nanohybrid, which act as a heat sink, absorbing and dissipating the heat generated during engine operation, thereby reducing the evaporation of the lubricant. Furthermore, the nanohybrid reduces the vapor pressure of the nanolubricant engine oil33. The vapor pressure is a measure of the tendency of a fluid to evaporate. The MoS2-Graphene nanohybrid reduces the vapor pressure of the nanolubricant engine oil by adsorbing onto the metal surfaces and forming a protective layer that reduces the surface area available for evaporation. This can lead to a lower mass loss in the NOACK analysis and provides better engine protection34.The NOACK volatility test ASTM D5800 is a standard measure of the evaporation loss of lubricating oils under high-temperature conditions. In the NOACK volatility test, a nanolubricant sample is heated at 250 °C for 60 min with continuous airflow. The weight loss during this process evaluates the oil’s volatility. The test simulates the engine operation conditions, where high temperatures can cause oil to evaporate and lead to oil thickening, deposits, and reduced engine performance. A lower mass loss in the NOACK test indicates that the oil is less prone to evaporation, which is desirable for engine protection and fuel efficiency. The Noack volatility study of nanolubricant with varying concentrations of MoS2-graphene nanohybrid in engine oil. The COF represents the frictional resistance experienced during lubricated sliding. Upon examination of Fig. 2-graphene nanohybrid into the base oil, significant reductions in COF are observed. The COF values for the nanolubricant with 0.1 wt%, 0.05 wt%, 0.01 wt%, and 0.005 wt% concentrations of the MoS2-graphene nanohybrid were determined to be 21.69%, 58.82%, 25.98%, and 17.19% lower, respectively, compared to the base oil. The reduction in COF is due to a highly effective boundary lubrication mechanism. Boundary lubrication occurs when the lubricant film is in direct contact with the solid surfaces, and the lubricant molecules form a protective layer that prevents metal-to-metal contact. The MoS2-graphene nanohybrid is an excellent boundary lubricant because of its unique properties. Firstly, MoS2 and graphene nanoparticles have a layered structure with weak van der Waals forces between the layers. This allows the nanoparticles to easily slide over each other, creating a low-friction surface. Secondly, graphene has a high surface area and may adsorb onto metal surfaces, providing additional lubrication and protection. When MoS2-graphene nanohybrid is added to nanolubricant engine oil, it forms a self-assembled layer on the metal surfaces due to its high affinity to metals36. This layer acts as a barrier between the surfaces and reduces friction by preventing metal-to-metal contact. The MoS2-graphene nanohybrid can also withstand high pressures and temperatures, commonly found in engine operation, without degrading or losing its lubricating properties. Additionally, the MoS2-graphene nanohybrid as an additive in the engine oil also reduces wear and tear on the engine parts, leading to longer engine life and improved performance. This is because the MoS2-graphene nanohybrid forms a protective tribofilm on the metal surfaces, which acts as a sacrificial layer that absorbs the wear and tear, thereby reducing the damage to the underlying metal surfaces37. When the nanohybrid concentration exceeds 0.05 wt%, the COF rises owing to nanoparticle aggregation. When nanoparticles cluster together, they can generate hard particles that behave as abrasives, increasing surface friction.Figure 2-graphene nanohybrid in SAE20W40 diesel engine oil were measured using an optical profilometer in Fig. 2-graphene, the WSD of the nanolubricant was lowered by up to 36.26%. The MoS2-graphene nanohybrid is a highly effective lubricant additive that reduces the average wear scar diameter in nanolubricant engine oil. The MoS2-graphene nanohybrid is a highly effective lubricant additive that may reduce wear by several mechanisms. Firstly, the MoS2-graphene nanohybrid forms a self-assembled layer on the metal surfaces, which acts as a protective barrier that absorbs wear and tear. This layer reduces the amount of material that is removed from the metal surfaces, leading to a lower wear scar diameter. Secondly, the MoS2-graphene nanohybrid reduces wear by reducing friction between the metal surfaces. As discussed earlier, the MoS2-graphene nanohybrid is a highly effective boundary lubricant that reduces friction by forming a low-friction surface on metal surfaces38. This reduces the amount of mechanical wear that occurs during engine operation. Thirdly, the MoS2-graphene nanohybrid reduces wear by improving the thermal and chemical stability of the lubricant. The MoS2-graphene nanohybrid is highly resistant to thermal and chemical degradation, which may prolong the life of the lubricant and reduce the amount of wear that occurs due to thermal and chemical processes39. Figure 2-graphene nanolubricant.The average wear scar diameters (WSD) MoS2-graphene nanohybrid. Figure 2-graphene nanohybrid. This disparity suggests that the addition of nanoparticles, specifically the hybrid MoS2-graphene nanohybrid, exerted a mending effect on the wear surface5. The nanoparticles were hypothesized to deposit within the micro-cracks and defects present on the mating surfaces, thereby facilitating the repair and smoothening of the surface. This mending effect results in a smoother and more uniform surface, reducing the wear scar depth 40. The presence of the hybrid MoS2-graphene nanohybrid was confirmed by examining the Elemental Dispersive X-ray (EDX) spectra. The EDX elemental spectrum revealed the detection of Mo, S, C, and O elements on the wear scar of the ball bearing lubricated with the nanolubricant containing 0.05 wt% hybrid MoS2-graphene nanohybrid. Conversely, no detection of the nanoparticle elements was observed on the wear scar of the ball bearing lubricated solely with the base oil  measures the resistance of the lubricant to oxidation, which leads to the formation of deposits and sludge in the engine, reduced lubricant performance, and increased engine wear. Figure 2-graphene nanohybrid at various concentrations into SAE20W40-based diesel oil considerably enhanced engine oil thermal conductivity. In the present study, the incorporation of 0.05 wt% MoS2-graphene nanohybrid has been demonstrated to significantly enhance heat conductivity by 19.83% (at 100 °C). This enhancement can be attributed to the formation of a thin, continuous film of nanocomposite on the metal surfaces of engine components. The presence of this film promotes better thermal contact between the components and the lubricant, thereby facilitating efficient heat transfer from the engine components to the lubricant. Additionally, the MoS2-graphene nanohybrid contributes to the improved dispersion of the lubricant, resulting in enhanced heat transfer throughout the lubricant system. Consequently, utilizing this nanohybrid exhibits the potential to dissipate heat and improve overall thermal performance effectively.The thermal conductivity of a lubricant plays a vital role in the efficiency of engine operation. In general, higher thermal conductivity leads to better heat dissipation, which can reduce the operating temperature of engine components, increase fuel efficiency, and prolong engine life. Figure 2 in the nanohybrid acts as a bridge between the graphene layers, enhancing the thermal conductivity of the composite45. The thermal conductivity decreases drastically at 0.1 wt% nanohybrid concentration. The higher nanohybrid concentration causes it to aggregate, forming an insulating surface layer in the nanolubricant. These layers can act as thermal barriers, limiting heat transfer between the oil molecules and the nanoparticles, thus reducing the overall thermal conductivity46.The nanohybrid facilitates the formation of a network-like structure in the lubricant, known as percolation mechanism, which can increase the thermal conductivity of the oil. The MoS2-graphene nanohybrid in SAE20W40 diesel-based engine oil. The utilization of the advanced microwave synthesis platform proved to be highly efficient, significantly reducing synthesis time and energy consumption. The synthesis process resulted in the uniform growth of MoS2 nanoparticles on the surface of Graphene nanoparticles through the interaction between their respective functional groups. The addition of 0.05 wt% hybrid MoS2-graphene nanohybrid in SAE20W40 diesel-based engine oil demonstrated remarkable improvements in various performance aspects. Specifically, a significant reduction of 58.82% in the coefficient of friction and 36.26% in the average wear scar diameter was observed compared to the base oil. Moreover, the nanolubricant exhibited notable enhancements in oxidation analysis by 19.21% and thermal conductivity by 19.83% at 100 °C. These findings confirm that the microwave synthesis of hybrid MoS2-graphene nanohybrid offers excellent potential as tribological additives in diesel-based engine oil. The synthesized nanoparticles significantly improve tribological performance, oxidation resistance, and thermal conductivity when incorporated into the engine oil. This research provides valuable recommendations for future studies to advance the application of hybrid MoS2-graphene nanohybrid. Key focal points include refining surface functionalization techniques to enhance compatibility with engine oil, conducting rigorous environmental impact assessments, and validating compatibility through thorough engine testing. Additionally, efforts should concentrate on assessing the scalability of nanoparticle synthesis for commercial production and exploring diverse industrial applications. These areas of emphasis are pivotal for realizing the full potential of hybrid MoS2-graphene nanohybrid in diverse applications. These advancements can potentially enhance the durability and efficiency of mechanical components in engine systems. The synergistic effects of the nanohybrid provide a promising avenue for future research and development of advanced lubricant formulations.In conclusion, this research study successfully investigated the tribological behavior of hybrid MoS2-graphene nanohybrid were of analytical grade and employed without further purification. Ammonium molybdate tetrahydrate ((NH4)6Mo7O24.4H2O) was procured from Fisher Chemicals located in Chicago, USA, whereas thiourea (SC(NH2)2) was sourced from R&M Chemicals based in Dundee, UK. Graphene with a thickness of 8 nm and a specific surface area of approximately 80m2/g was obtained from Graphene Labs Inc, USA. The lubricant oil employed in the experimentation was diesel engine oil with API SAE20W40 CD/SE GL-4.The properties and specifications of the engine oil is shown in Table For the experimentation, all reagents used in synthesizing hybrid MoS2-graphene nanohybrid. In this experimental approach, a solution was prepared by gradually adding 3.7 g of ammonium molybdate tetrahydrate and 6.85 g of thiourea to 105 mL of deionized water. The mixture was stirred for 30 min to ensure homogeneity. Subsequently, 1 g of graphene powder was introduced, and the resulting mixture was subjected to sonication for 30 min. The solution was then transferred to a microwave synthesis platform  and heated to 200 °C for 15 min. After heating, the sample was allowed to cool down to room temperature (26 °C) naturally. Subsequently, the sample was centrifugated, washed with distilled water and ethanol, and finally freeze-dried. The synthesis method of the hybrid MoS2-graphene nanohybrid is illustrated in Fig. The researchers utilized a microwave hydrothermal synthesis technique to synthesize a hybrid MoS2-graphene nanohybrid, including 0.005 wt%, 0.01 wt%, 0.05 wt%, and 0.1 wt%, were dispersed in 100 ml of SAE 20W40 engine oil. The mixture was then homogenized for 10 min using a high-shear lab mixer. To ensure that the nanoparticles were uniformly dispersed in the base oil and to prevent agglomeration, the samples were sonicated in an ultrasonic bath for 30 min.Various concentrations of hybrid MoS2-graphene nanohybrid as a lubricant additive. The size, morphology, and elemental compositions of the nanohybrid were determined using field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy (FESEM and EDX). X-ray diffraction (XRD) with Cu Kα radiation  was employed to study the crystallinity and phase structure of the samples, while Raman spectroscopy was used to analyze the molecular interactions using a 532 nm laser. Additionally, the density, kinematic viscosity, and viscosity index of the samples were measured with a viscometer (Viscometer SWM 3000), and Zetasizer was used to determine the dispersion stability. The Noack volatility test was performed using Thermogravimetric Analysis (TGA). In the NOACK volatility test, nanolubricant engine oil is heated at 250 °C for 60 min with constant airflow. The resulting weight loss indicates the oil’s volatility characteristics, offering insights into its performance under high-temperature conditions.This study utilized various analytical and characterization methods to investigate the properties and performance of hybrid MoS2-Graphene based nanolubricant at various nanoparticle concentrations. Carbon chromium steel balls (Hardness (H), HRC: 65, Density (ρ), gm/cm: 37.79 Surface roughness (Ra), μm: 0.022) were employed, and the rotational speed, applied load, time, and temperature were set to 12,000 rpm, 392.5 N, 3600 s, and 75 °C, respectively, in accordance with ASTM 4172-94. The wear scar images on the metal balls were studied using FESEM and EDX.Tribological analysis was conducted using a four-ball tribotester (Ducom TR-30L) to measure the coefficient of friction (COF) and average wear scar diameter (WSD) of the hybrid MoS2-graphene based nanolubricant with various nanohybrid concentrations. The procedure was carried out at 500 psi, an isothermal temperature of 200 °C, a flow rate of 50 ml/min, and ramping rate of 10 °C/min. The thermal conductivity of the MoS2-graphene based nanolubricant with different nanohybrid concentrations was evaluated using laser flash analysis (LFA HyperFlash). The sample was filled in the sample ring, and the upper and lower sealing discs were sprayed with graphite to promote black body absorption. The sample was heated from room temperature to 120 °C at a rate of 10 °C/min in a nitrogen environment.Furthermore, oxidation analysis was performed using High-Pressure Differential Scanning Calorimeter (HP-DSC) to determine the oxidation induction time (OIT) of MoS


The complex relationship between attention and visual perception can be exemplified and investigated through the Attentional Blink. The attentional blink is characterised by impaired attention to the second of two target stimuli, when both occur within 200 – 500ms. The attentional blink has been well studied in experimental lab settings. However, despite the rise of online methods for behavioural research, their suitability for studying the attentional blink has not been fully addressed yet, the main concern being the lack of control and timing variability for stimulus presentation. Here, we investigated the suitability of online testing for studying the attentional blink with visual objects. Our results show a clear attentional blink effect between 200 to 400ms following the distractor including a Lag 1 sparing effect in line with previous research despite significant inter-subject and timing variability. This work demonstrates the suitability of online methods for studying the attentional blink with visual objects, opening new avenues to explore its underlying processes. The sensory information in our visual field is constantly changing. As a result, the visual system must adapt to the overwhelming number of stimuli it is presented with. Attentional mechanisms filter irrelevant stimuli and select inputs that require further processing –3. TheseThe attentional blink has been well studied in experimental lab settings –16, and The current study attempts to reproduce a picture-based attentional blink effect in a short and simple online study. The study follows a simplified distractor and target design, with random pattern masks as filler stimuli. With this simplified design we aimed to isolate the attentional effects of the distractor and its subsequent impact on target identification accuracy, while minimising the size of the experiment which is important for running in an online environment. We further investigated variability on stimulus presentation timing accuracy and between-subject variability, which are two major concerns that arise from online testing methods. We hope our results and corresponding experiment code may help drive future research into the attentional blink.https://osf.io/atjpe/.All materials and data are available online at M: 22.3, SD: 6.6) participated in the experiment in exchange for course credit. Each participant was to self-assess their vision as normal  to participate in the study. The experiments were approved by the Western Sydney University Human Research Ethics Committee. Participants provided informed written consent and were free to withdraw from the study without consequence. After the study, they were debriefed about the aims of the study. Participant data was analysed anonymously.100 undergraduate psychology students  between distractor present and distractor absent trials.F  = 10.72, p < .001, η2g = 0.005), showing that response accuracy varied between Lag levels. The ANOVA also indicated a main effect of Distractor  showing that the presence of a distractor significantly reduced response accuracy. Finally, the ANOVA revealed a significant interaction between the factors Distractor and Lag , as illustrated in The 4 x 2 ANOVA on response accuracy indicated a main effect for Lag  between all pairs except for Lag1-control, Lag1-Lag4, and Lag4-control. The attentional blink effects were only established when the distractor was at Lag 2 or Lag 3, and there was no evidence for a difference in target accuracy between Lag 1, Lag 4 and the no-distractor (control) condition . These results highlight a clear attentional blink effect at Lag 2, as well as a small carry-over effect at Lag 3.As online experiments do not allow any control over the experiment setup, we asked how reliable the timing was. The present study aimed to establish the replicability of the attentional blink with visual objects in online settings. Our results showed a clear attentional blink effect, with a significant decline in response accuracy when a distractor is present , 26, 27.It is difficult to compare our results to existing lab-based attentional blink work, as our design is unusual compared to standard attentional blink paradigms which are generally using letters and two targets, rather than a target/distractor design. For a more direct comparison into the online replication of more standard attentional blink paradigms, see previous work e.g., , 18. OurOnline experiments are ideally suited for exploring these directions further, as they facilitate data collection from large populations. They can be conducted with a large number of participants (n>100) with relatively little effort whereas recruiting and running 100 participants in a lab-based study is often a time-consuming and expensive process. This is therefore a promising methodological approach to conduct multiple highly powered behavioural experiments in a relatively short time and progress the field faster.Exploratory investigations in the stimulus timing results showed generally highly accurate timing , which highlights the reliability of browser-based experiments. Past work has already shown accurate timing for online experiments , 18, butTo conclude, this study demonstrates the suitability of online attentional blink paradigms with visual objects. Reliable attentional blink effects can be obtained with visual objects online despite stimulus presentation timing issues that might arise in browser-based experiments. This opens new avenues for studying the attentional blink and its underlying processes in large scale online studies.


The complete thermal decomposition loss of PMMA film was effectively avoided by introducing a copper clad layer. After the first thermal transformation process, flat, clean, and high-quality amorphous carbon films were obtained. Next, the in situ obtained amorphous carbon layer underwent a second copper sputtering and thermal transformation process, which resulted in the formation of a final, large-sized, and highly uniform transfer-free multilayer graphene film on the surface of the dielectric substrate. Multi-scale characterization results show that the specimens underwent different microstructural evolution processes based on different mechanisms during the two thermal transformations. The two-step thermal transformation method is compatible with the current semiconductor process and introduces a low-cost and structurally controllable polymeric carbon source into the production of transfer-free graphene. The catalytic protection of the copper layer provides a new direction for accelerating the application of graphene in the field of direct integration of semiconductor devices.Direct in situ growth of graphene on dielectric substrates is a reliable method for overcoming the challenges of complex physical transfer operations, graphene performance degradation, and compatibility with graphene-based semiconductor devices. A transfer-free graphene synthesis based on a controllable and low-cost polymeric carbon source is a promising approach for achieving this process. In this paper, we report a two-step thermal transformation method for the copper-assisted synthesis of transfer-free multilayer graphene. Firstly, we obtained high-quality polymethyl methacrylate (PMMA) film on a 300 nm SiO Graphene’s atomic-level thickness and excellent charge carrier properties have made it a highly sought-after material in the field of semiconductor device integration ,2. In thCompared with gaseous carbon sources , which hExisting studies on the preparation of transfer-free graphene from polymeric carbon sources mainly focus on nickel as a catalyst, which is a kind of magnetic metal and difficult to use in semiconductor processes. Copper, however, has lower carbon solubilization ability  and is iIn this study, PMMA was used as a representative carbon source to investigate its chemical composition evolution during the two-step thermal transformation process for the growth of transfer-free graphene films. The protective and catalytic effects of a metallic copper layer were examined, and the microscopic transformation process from PMMA to amorphous carbon to graphene was elucidated in detail. The role and surface structure evolution of metallic copper films in the thermal transformation of PMMA were also systematically studied. This research provides important insights for ensuring the successful transformation of PMMA into transfer-free graphene films and offers suggestions for further improving the quality of such films based on polymeric carbon sources. The findings of this work can help to enhance the compatibility of graphene film preparation technology with semiconductor processes and promote the application of graphene films in the integrated fabrication of semiconductor devices.−4 Torr) at 100 °C for 5 min to remove water molecule adsorption.The dielectric substrate used in this experiment was a 4-inch, 300 nm thermal silicon oxide wafer prepared by the Advanced Electronic Materials and Devices School Platform of Shanghai Jiao Tong University . The specimens were cut into small slices of approximately 1 cm × 1 cm by a diamond cutting knife. To ensure high-quality spin-coating of the polymer solution, hydrophilic treatment was required due to the hydrophobic nature of the wafers in their natural state. The silicon oxide slices were ultrasonically washed in acetone, deionized water, and ethanol for 15 min each, and the liquid residues were blown off using dry nitrogen before each washing procedure. UV treatment was used to improve the wettability of the polymer solution on the silicon oxide slices and the optimized exposure time is ~30 min. PMMA solution with a mass fraction of 0.5 % was then uniformly spin-coated on the treated silicon oxide slices using a homogenizer, with spinning velocity and time of ~6000 rpm and ~60 s, respectively. The Cu films with a thickness of 200 nm were sputtered using a magnetron sputtering system. The thermal transformation experiments were carried out in a tubular furnace with hydrogen gas protection (~100 sccm). The steady-state temperature and holding time were controlled in the range of 400–950 °C and 10–60 min, respectively, and the specific parameters can be seen in the corresponding figure. After the first thermal transformation, the copper film on the specimen’s surface was removed by nitrogen blowing a. For th2. The surface roughness of the specimen was measured using the MFD-300 atomic force microscope manufactured by Oxford Instruments, with a longitudinal resolution of 0.02 nm and a test range of 20 × 20 μm2. The microtopography and EDS spectrum of the sample were analyzed using the RISE-MAGNA Raman image-scanning electron microscope , with an accelerating voltage of 20 kV, beam current of 200 pA, and optimal focal length of 5 mm. The Raman spectrum and optical photographs of the sample were obtained using the Renishaw inVia Qontor with a laser power of 60 mW, spot size of 0.5 μm, and an acquisition wavenumber range of 1200–2800 cm−1, with the surface mapping sweep step size set to 0.5 μm. Chemical bonding information of the heat-transformed products was analyzed by the Mini Flex 600 XPS spectrometer produced by Rigaku , using monochromaticized Al Kα as the X-ray source, with a test power of 150 W, scanning step size of 1000.0 meV, and residence time of 100 ms. The full spectrum scanning range was 0–1200 eV, while the C 1 s and the Cu 2p3/2 spectrum scanning ranges were 273–296 eV and 924–968 eV, respectively. For electrical performance characterization, a four-probe resistor meter produced by Valley Polymerization Technology Co., Ltd.  was used. The test voltage and current were set to 1.0 V and 10 μA, respectively, with the probe spacing set to 1.0 mm. The number of repeated measurements of single-point resistance was set to 10 times. The ToF-SIMS depth profiles were captured using ION-TOF GmbH  under a chamber pressure of below 5 × 10−9 mbar to analyze the content of Si, O, Cu, and C in each layer of the specimen before and after annealing. For high mass resolution analysis, the spectra mode with pulsed 30 keV Bi3+ (~0.48 pA pulsed current) ion beam was applied. The focused analysis area was 150 × 150 μm2, with 2 keV Cs ion beam sputtering at the same time, 400 × 400 μm2 sputter raster, and noninterlaced mode.Thermogravimetric analysis of PMMA solid particles was carried out using the TGA 8000 thermal analyzer produced by PerkinElmer . The temperature range for analysis was from 25 °C to 700 °C with a heating rate of 10 °C/min, and the gas flow rate was ~40 mL/min in both air and NThe thermogravimetric analysis (TGA) of PMMA particles a reveals−1 and 1580 cm−1, respectively. These characteristic peaks correspond to the defect D peak and graphite-type G peak of the amorphous carbon film. The evolution of the characteristic peaks of amorphous carbon film with thermal transformation temperature indicates that the amorphous carbon film only begins to grow at about 400 °C, and no corresponding characteristic peaks appear below this temperature. The temperature is almost the same as the complete thermal decomposition temperature of PMMA particles in After the first thermal transformation, the morphology of the specimens with the spin-coated PMMA film changed significantly in comparison to the specimens without spin-coated PMMA g. The coAccording to the idea of the first thermal transformation of PMMA film, we carried out a second copper sputtering treatment on the obtained transfer-free amorphous carbon film and proceeded with a series of thermal transformation experiments again. The final morphology of these samples is shown in The copper layer on the surface of the sample undergoes a “dewetting” phenomenon in the high-temperature environment, but it remains intact below the temperature of 850 °C and 60 min. The EDS mapping of the copper film in −1). The appearance of these characteristic peaks confirms the in situ transformation of amorphous carbon film into graphene, and the intensity ratio of 2D peak to G peak determines the multilayer structure of the transfer-free graphene film. The intensity of the 2D peak in the Raman spectrum also indicates that longer thermal transformation time results in graphene film with better crystallization quality. Evaluating the uniformity of the intensity ratio of Raman 2D peaks to G peaks within a certain area of graphene film is another effective way to evaluate the surface uniformity of graphene. 2D/IG result of the red dashed line in 2D/IG ratio of the graphene film obtained in this process is around 0.16, demonstrating that the graphene film has good uniformity. The macroscopic topography photo of the silicon oxide slice after copper layer etching, shown in 2-type structure, which is also the typical structure in graphene film. The peak position at 285.40 eV mainly corresponds to the carbon sp3 bonding structure, which shows that there are some defects in the multilayer graphene film and is also one reason for the apparently defective D peak in the Raman spectrum in 3/2 region  can also provide us with more structural details of the transfer-free graphene films. Meanwhile, by analyzing the bonding type of chemical elements, we can also determine the impurity binding of the graphene film and evaluate the overall quality of the graphene film. XPS results of in situ growth of multilayer graphene films on silicon oxide substrate are shown in 2 region e testifi3 binding bonds in XPS C 1 s spectrum.Since the multilayer graphene film obtained in this project is in situ grown on the silicon oxide substrates, the traditional physical transfer process is avoided, and the electrical four-probe test is particularly convenient. The electrical results show that the surface resistance of the transfer-free multilayer graphene film is below 30 kΩ/□, which is similar to the nitrogen-doped graphene film prepared in the reference . Though 3+, H2, and H2O through the thermal decomposition process, and then gaseous carbon radicals will deposit and stitch on the surface of copper foil to grow graphene films. It is apparent that the polymer carbon source PMMA will undergo gas phase decomposition under high-temperature pyrolysis conditions, resulting in the loss of mass. Therefore, during the first thermal decomposition process in our project, the copper layer on the surface of the specimen loses its original support due to the loss of gaseous products of the lower PMMA layer, and then obvious wrinkles and bulges occur, and the copper layer is easily blown away by gas. It should be mentioned that, based on the structural characterization of the obtained products on the silicon oxide substrate after blowing away the copper layer, it is found that due to the physical barrier of the surface copper layer, the PMMA layer does not undergo complete and thermal pyrolysis with no solid residues, like in the free space, but generates amorphous carbon film on the substrate through amorphous transformation (see By comparing the first and second thermal transformation results, we can clearly see that the copper layer plays significantly different roles in the two thermal transformation processes, and both of these roles are indispensable parts of the synthesis of transfer-free multilayer graphene film. Reference  investigUnlike the PMMA pyrolysis process, the amorphous carbon film does not experience gaseous phase transformation during the second thermal transformation, so the surface copper layer remains intact after the thermal annealing. In order to deeply study the specific changes of each element in this process, the content distributions of Si, O, Cu, and C elements before and after thermal transformation were analyzed by ToF-SIMS, and the results are shown in γ is the interfacial energy, t is the graphene thickness at the interface, and ΔtransG is the graphene formation energy per unit volume with copper catalyzed, respectively [2, which indicates that it is more thermodynamically favorable to synthesize graphene film at the interface. Therefore, under the protection and catalyzation of the copper layer, graphitization transformation occurs, and the graphene multilayer film is ultimately generated (Simplified thermodynamic calculations show that the energy difference before and after the second thermal transformation can be expressed as ectively ,40. The In summary, this study investigated the two-step thermal transformation process of PMMA polymer to obtain transfer-free graphene film on dielectric substrates, utilizing film spin coating, copper layer sputtering, and wet etching techniques. The microstructural evolution of the PMMA film layer was examined, providing valuable insights for in situ graphene film synthesis. The copper layer plays a crucial role in the physical protection and catalytic crystallization processes, and precise control of its structural parameters is important for obtaining high-quality transfer-free graphene film. The two-step thermal transformation process successively yields clean, flat transfer-free amorphous carbon film as low as 400 °C and multilayer graphene film at 850 °C, which is more economical and energy-saving than the nickel-catalyzed method. The quality of these films can be optimized by controlling the initial spin coating and the thermal annealing parameters. Our study deepens the understanding of copper-assisted polymer transformation for graphene growth, without the need for post-transfer procedures. This approach has potential in compatible semiconductor processes and can offer more choices for graphene-based functional device manufacturing.