The present paper summarizes the current status of high resolution electron microscopy (HREM)and the applications of HREM to materials science and condensed matter physics. This review recounts the latest development of high resolution electron microscope, progress of HREM and the applications of HREM, including the crystal structure determination of microcrystalline materials and characterization of the local structure of the defects and nanostructured materials as well as qualitative and quantitative analysis of the grain boundaries, interfaces and interfacial reactions in the advanced materials by means of HREM in combination with electron diffraction,subnanometer level analysis, image simulation and image processing.
Kevlar-49 fiber was modified through cold air plasma treatment and plasma grafting with acrylic monomers. Fracture of aramid fiber/epoxy resin micro composites has been studied by means of single fiber pull-out test. Tow types of pull-out curves are correlated with the different failure modes. A polyacrylic acid-co-ethyl acrylate graft layer can improve the adhesion and protect the fiber from damage caused by interfacial stresses.
The kinetics of Cu ion exchange on Na-montmorillonite clay mineral has been investigated at three temperatures, in three solvents: H2O, ethylene glycol and glycerol. Solvent effects on the reaction rate have been discussed. The thermodynamic activation parameters were calculated and discussed in terms of solvation effects. The determined isokinetic temperature indicates that the reaction is enthalpy controlled where the interaction between solvent and clay surface plays an important role. A reaction mechanism which describes the solvent effect on the rate of Cu ion exchange is proposed.
A series of metal cutting experiments was performed on a CNC lathe to evaluate the performance of various coatings on different tool substrates. The workpiece material was plain medium carbon steel and the cutting tool materials were carbide and cermet inserts coated with various single as well as multilayer coatings. Machining was done under various cutting conditions of speed and feed-rate, and for various durations of Cutting. The output parameters studied were the cutting forces (axial, radial and tangential), the surface roughness of the workpiece, as well as the tool wear (crater and flank wear). From these results, the performances of the various cutting inserts are evaluated and compared. Results show that cutting forces are significantly lower when using coated cermets than when using coated carbides although different coatings on the same substrate also result in different cutting forces. However, there is less difference in the surface roughness of the finished workpiece for the various coatings and substrates.
Based on the thermodynamic model of Kaufman for the calculation of quasibinary and quasiternary system, numerical method for the calculation of stable equilibrium is developed and thermodynamic data of undefined phases are discussed in this work for several ceramic systems.The calculated isothermal sections in Si3N4-Y2O3-SiO2 system meet well with other previous calculated phase diagrams and experimental results. The diagrams in Y2O3-SiO2-BeO and Y2O3-Al2O3-BeO systems are calculated for the approach of prediction.
The kinetics of volatilization of SnS from Sn-Fe mattes was investigatd by using a unique experimental method. A water model test was also carried out for the proper interpretation of the experimental results. It has been demonstrated that the volatilization process displays the first order kinetics with respect to the concentration of SnS in the matte. The process is controlled by the mass transport of SnS in gas phase. The apparent activation energy for the process is found to be 127.4 kJ/mol. The effect of temperature and carrier gas flow rate on the reaction rate is discussed in accordance with the mathematical model developed.
The liquid sintering characteristics have been studied in the sintered compacts of short cast iron fibers added with Ni-Cr based alloy powder at the sintering temperature of 1100℃. With the increase of Ni-Cr based alloy content, the microstructure of sintered compact of short cast iron fibers transformed from pearlite+ferrite to martensite+austenite, meanwhile volume expansion appeared in the sintered compact, leading to more pores. The proper addition of P-Fe powder could restrain the expansion of the sintered compact and increase the strength and hardness of the sintered compact.
The effects of solution (quench) temperature on the properties of SiCw/Al composite have been investigated using tensile tests. The experiments indicate that the solution temperature of the composite fabricated by P/M technique can be raised to 560℃. The tensile strength of the composite is obviously dependent on solution (quench) temperature and the composite solutionized at 540℃ exhibits a maximum of tensile strength and elongation-to-failure. These results can be accounted for by the variation of the dislocation density in the composite.
The sputtering rates of alloys were investigated under constant Ar pressure and voltage supplied.The alloys studied in this work range from binary intermetallic alloys to ternary and quaternary alloys. It is revealed that the sputtering rates of alloy targets under steady states are where q is the sputtering rates of alloys, Ci the weight percentage of i-th component in the alloy,and qi0 the sputtering rate of pure metal of i-th component.
Boro-germanate glasses containing copper, i.e., xCuO(1-x)[GeO2·B2O3] subjected to gamma irradiation, were studied by means of EPR. Comparisons were made with the xCuO·(1-x)[Na2B4O7] system. Irradiation induced centers were detected. These are: electron trapped at a hydrogen compensated germanium ion centers; boron oxygen hole centers and electron trapped at an oxygen vacancy centers. Strong dependence of the paramagnetic irradiation-induced centers concentration on the CuO content of the sample was evidenced.
The work-hardening behaviour in an Fe-Mn-Si-Cr-Ni alloy has been investigated using tensile test at different temperatures and TEM observation. It was found that besides the intersection of εmartensite, the intersections of ε martensite with stacking fault and the cross-slip of dislocation which is difficult to occur in the alloy with low stacking fault energy are also important factors to the temperature dependent work-hardening behaviour.
In this paper, for the first time, Ca1-xLnxSiO3 (Ln=Y. La, x=0.1, 0.2) was synthesized with three methods of high temperature (HT) under atmospheric pressure (AP), high temperature (HT) combined with high pressure (HP) and sol-gel method. The sample obtained at the stable range of 4.3-5.0 GPa pressure and 1050-1100℃ temperature with HT and HP method has a cubic perovskite structure, which has the minimum lattice parameter of 0.3535 nm so far,the sample with triclinic structure was obtained by sintering at atmosphere, and the sample synthesized with sol-gel method has monoclinic structure. SEM analysis shows that rare earth ions take the lattice site of Ca, but the distribution of rare earth ions in the samples synthesized with HT and HP is not homogeneous.
Free radical polymerized palladium polyacrylate was characterized by X-ray diffraction. Various parameters including mean crystallite size, interchain separation and radius of gyration have been calculated and discussed with respect to the concentration of Pd in the polymeric salt. The results show that polymer is predominantly amorphous in nature.
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