Conduction Properties and Scattering Mechanisms in F-doped Textured Transparent Conducting SnO_2 Films Deposited by APCVD

Transparent conducting F-doped texture SnO2 films with resistivity as low as 5× 10-4 Ω ·cm,with carrier concentrations between 3.5 × 1020 and 7× 1020 cm-3 and Hall mobilities from 15.7 to 20.1 cm2/(V/s) have been prepared by atmosphere pressure chemical vapour deposition (APCVD). These polycrystalline films possess a variable preferred orientation, the polycrystallite sizes and orientations vary with substrate temperature. The substrate temperature and fluorine flow rate dependence of conductivity, Hall mobility and carrier conentration fOr the resultingfilms have been obtained. The temperature dependence of the mobiity and carrier concentrationhave been measured over a temperature range 16～400 K. A systematically theoretical analysis on scattering mechanisms for the highly conductive SnO2 films has been given. Both theoretical analysis and experimental results indicate that for these degenerate, polycrystalline SnO2 ：F films in the low temperature range (below 100 K), ionized impurity scattering is main scattering mechanism. However, when the temperature is higher than 100 K, the lattice vibration scattering becomes dominant. The grain boundary scattering makes a small contribution to limit the mobility of the films.

Effect of Icosahedral Phase on Crystallographic Texture and Mechanical Anisotropy of Mg–4%Li Based Alloys

Through investigating and comparing the microstructure and mechanical properties of the as-extruded Mg alloys Mg-4%Li and Mg-4%Li-6%Zn-l.2%Y （in wt%）, it demonstrates that although the formation of I-phase （Mg3Zn6Y, icosahedral structure） could weaken the crystallographic texture and improve the me- chanical strength, the mechanical anisotropy in terms of strength remains in Mg-4%Li-6%Zn-1.2%Y alloy. Failure analysis indicates that for the Mg-4%Li alloy, the fracture surfaces of the tensile samples tested along transverse direction （TD） contain a large number of plastic dimples, whereas the fracture surface exhibits quasi-cleavage characteristic when tensile samples were tested along extrusion direction （ED）. For the Mg-4%Li-6%Zn-I.2%Y alloy, typical ductile fracture surfaces can be observed in both ＂TD＂ and ＂ED＂ samples. Moreover, due to the zonal distribution of broken l-phase particles, the fracture surface of ＂TD＂ samples is characterized by the typical ＂woody fracture＂.

Enhanced Strength and Ductility Due to Microstructure Refinement and Texture Weakening of the GW102K Alloy by Cyclic Extrusion Compression

The cyclic extrusion compression （CEC） was applied to severely deform the as-extruded GW102K （Mg- 10.0Gd-2.0Y-0.5Zr, wt%） alloy at 350, 400, and 450 ℃, respectively. The microstructure, texture, and grain boundary character distribution of the CECed alloy were investigated in the present work. The mechan- ical properties were measured by uniaxial tension at room temperature. The crack initiation on the longitudinal section near the tensile fracture-surface was investigated by high-resolution scanning elec- tron microscopy （SEM）. The result shows that the microstructure was dramatically refined by dynamic recrystallization （DRX）. The initial fiber texture was disintegrated and obviously weakened. The 8-passes/ 350 ℃ CECed alloy exhibited yield strength of 318 MPa with an elongation-to-fracture of 16.8%, increased by 41.3% and 162.5%, respectively. Moreover, the elongation-to-fracture of the 8-passes/450 ℃ CECed alloy significantly increased more than 3 times than that of the received alloy. The cracks were mainly initi- ated at twin boundaries and second phase/matrix interfaces during tensile deformation. The microstructure refinement was considered to result in the dramatically enhanced of the strength and ductility. In ad- dition, the texture randomization during CEC is beneficial for enhancing ductility. The standard positive Hall-Petch relationships have been obtained for the CECed GW102K alloy.

Modeling and experiments of chewing mechanical properties of pellet feed using discrete element method

In order to explore the mechanical properties and breaking behavior of pellet feed during chewing,the experiments of texture mechanics,followed by the modeling and simulation of pellet feed based on the discrete element method were carried out in this research.Five wet basis moisture contents(8%,10%,12%,14%and 16%,respectively),two kinds of loading directions(L and D direction,respectively)of pig pellet feed were selected as variables.First,mechanical parameters including hardness,elasticity,tackiness and chewiness were measured by a texture analyzer.The results of compression tests showed that the hardness of pig pellet feed was 5.44-32.43 N,the elastic index was 0.04-0.94 mm,the tackiness was 0.07-6.63 N,the chewiness was 5.52-27.39 mJ.Moreover,the hardness,tackiness and chewiness of pig pellet feed decreased significantly with the increase of moisture content but the elasticity showed an adverse varying trend.The hardness,elasticity,tackiness and chewiness along D direction outweighed that of L direction in numerical data at the same moisture content.Then,the chewing and breaking processes of pellet feed were simulated based on the discrete element method(DEM)combined with bonding particle model,in which the whole pellet feed were considered as agglomerations of micro-particles and broke when the stress between micro-particles had exceeded the maximum limit.Multi-parameter optimization experiments were carried out using quadratic orthogonal rotation design,in which stiffness coefficient(X_(1)),critical stress(X2)and bonding radius(X_(3))were the influencing factors,hardness(Y_(1)),elasticity(Y_(2)),tackiness(Y_(3))and chewiness(Y_(4))were evaluating indicators.Based on the regression analysis of the Design-Expert 8.0.6 software and response surface analysis method,the relationship between the three influencing factors and evaluating indicators was established.The similarity between experimental and simulated results in feed morphology and mechanical index proved that the modeling method for pellet feed based on DEM was effective and accurate.This work can provide a reference for the feed forming process and the optimization design of the related feed machinery.Meanwhile,the DEM model provided a new method for evaluating the texture and palatability of pellet feed.