Using Iraqi materials to produce lining refractories with international standards
In this study dense high alumina refractories were manufactured according to DIN51053 standards and characterizations (physical, mechanical, and thermal) of fired specimens were investigated. The mixtures of specimens were prepared from different weight percentages of (kaolinite, bauxite with additives of alumina to all mixture ratio). The aims of this study was to benefit of local raw materials to produced high alumina refractory characterized by low porosity, in addition to manufacture thermal insulation to use as lining in different industrial furnaces, and enhance the thermal insulation, thermal stability, and mechanical properties of high alumina refractory by adding alumina. From the results it have been obtained high alumina refractory with high compressive strength, high thermal stability, and thermal insulation also have characterized by low porosities and high bulk density.
Production of High Alumina Fire Brick from Iraqi Clay
The importance of refractory materials in various industries such as lining of kilns, furnaces and the need for exploitation of raw materials which are available in Iraqi industries. So this work deal with the exploitation of Iraqi kaolin from Dewechla deposits, as a raw material in the manufacturing of high alumina fire brick. High alumina fire brick specimens (alumina content about 70%) were prepared by semi-dry pressing, then drying and burned at different temperatures 1200,1300, 1400,1500Cᵒ for 2hr soaking time and 100Cᵒ/hr firing rate. Investigations of these specimens show that, the increasing alumina content will increase the strength, the porosity of the fire products, while the hardness, apparent density, water absorption and permanent linear change will decrease. These properties affected by the firing temperature, where the formations of the mullite phase play a governed role in the behavior and properties of the final products. In addition, the results reveal that the fire brick products appear to withstand thermal shock resistance; it can be used as thermal insulator in various industries. The thermal conductivity and density behavior of products containing alumina ˃ 70% are vary as a function of porosity. Thus, the insulating property of the end product can be improved through the porosity and its distribution.
Evaluation of thermal conductivity of alumina reinforced heat cure acrylic resin and some other properties
The polymethylmethacrylate is the most reliable material for the construction of complete and partial dentures, but it has been shown to be lacking an important property which is it's thermal conductivity, where thermal conductivity play an important role in patient satisfaction with complete and partial dentures. This study was designed to improve the thermal conductivity of acrylic resin by adding alumina powder and investigate the effect of this additive filler (Al2O3 powder) on some properties of heat cure PMMA denture base material. Materials and methods: Alumina powder was added to PMMA powder by weight in three different percentages 5% , 7.5% and 10% ,240 specimens were constructed and divided into 6 groups according to the test and each group was subdivided into 4 sub groups according to the percentage of added alumina. The test conducted were thermal conductivity by the use of Lee's disc, water sorption and solubility , surface roughness , surface hardness ( Shore D ) , impact strength ( un notched ) and tensile strength . Data were analyzed by one way analysis of variance test (ANOVA) and least significant differences (LSD). Results: A highly significant increase in thermal conductivity occurred with the addition of Al 2O3 powder while a significant reduction occurred in both impact and tensile strength specimens' tests .Highly significant increase in surface hardness was observed. Also water sorption and solubility decreased significantly. Surface roughness was not affected except a significant increase was observed in surface roughness by the addition of 10% Al2O3 to PMMA. Conclusion: The addition of Al 2O3 powder to acrylic resin improves the thermal conductivity of acrylic resin, at the same time this addition decreases both impact and tensile strength values. On the other hand there was an increase in surface hardness, water sorption and solubility were decreased while surface roughness not affected with small percentages of alumina.