The research of high-quality grinding technology of large-size Al2O3 single-crystal slice
Al<inf>2</inf>O<inf>3</inf> single crystal has the following unique physical properties of high hardness, high toughness, obvious pleochroism and high refractive index Etc. The paper introduced the processing property of Al<inf>2</inf>O<inf>3</inf> single crystal, described its grinding technology. Then analyzed the characteristics and status of grinding technology of the large-sized Al<inf>2</inf>O<inf>3</inf> single crystal, combined with the relational research, discussed the technology of the grinding stage. Finally the paper summarized a set of precise grinding technology of large-sized Al<inf>2</inf>O<inf>3</inf> slice.
The assessment of plastic deformation in metal cutting
Abstract Because plastic deformation is a nuisance in the metal cutting process, its proper account is of high interest. A new meaning for the chip compression ratio is discussed showing that, on the contrary to shear strain, this parameter represents the true plastic deformation in metal cutting. The chip compression ratio can be used to calculate the total work done by the external force applied to the tool and then might be used for optimization of the cutting process. It is demonstrated that the cutting speed influences the energy spent on the deformation of the chip through temperature, dimensions of the deformation zone adjacent to the cutting edge and velocity of deformation. The separate impacts of these factors have been analyzed and the physical background behind the known experimental dependence of the chip compression ratio on the cutting speed is revealed. The influence of the cutting feed, tool cutting edge angle, cutting edge inclination angle and tool rake angle have also been analyzed.
Recent progress in engineering near-infrared persistent luminescence nanoprobes for time-resolved biosensing/bioimaging
Persistent luminescence nanoprobes (PLNPs) can remain luminescent after ceasing excitation. Due to the ultra-long decay time of persistent luminescence (PersL), autofluorescence interference can be efficiently eliminated by collecting PersL signal after autofluorescence decays completely, thus the imaging contrast and sensing sensitivity can be significantly improved. Since near-infrared (NIR) light shows reduced scattering and absorption coefficient in penetrating biological organs or tissues, near-infrared persistent luminescence nanoprobes (NIR PLNPs) possess deep tissue penetration and offer a bright prospect in the areas of in vivo biosensing/bioimaging. In this review, we firstly summarize the design of different types of NIR PLNPs for biosensing/bioimaging, such as transition metal ions-doped NIR PLNPs, lanthanide ions-doped NIR PLNPs, organic molecules-based NIR PLNPs, and semiconducting polymer self-assembled NIR PLNPs. Notably, organic molecules-based NIR PLNPs and semiconductor self-assembled NIR PLNPs, for the first time, were introduced to the review of PLNPs. Secondly, the effects of different types of charge carriers on NIR PersL and luminescence decay of NIR PLNPs are significantly emphasized so as to build up an in-depth understanding of their luminescence mechanism. It includes the regulation of valence band and conduction band of different host materials, alteration of defect types, depth and concentration changes caused by ion doping, effective radiation transitions and energy transfer generated by different luminescence centers. Given the design and potential of NIR PLNPs as long-lived luminescent materials, the current challenges and future perspective in this rapidly growing field are also discussed.