氮对纳米硅氮薄膜品化的影响

在电容式耦合等离子体化学气相沉积系统中，用高氢稀释硅烷和氮气为反应气氛制备纳米硅氮（ｎｃ－ＳｉＮｘ：Ｈ）薄膜结果表明：当Ｎ＿２／ＳｉＨ＿４气体流量比（Ｘｎ）从１增加为４时，薄膜的晶态年从５８％降至１４％，晶粒尺寸从１０ｎｍ降至５ｕｍ，Ｎ／Ｓｉ含量比从０．０３增至０．１２．当Ｘｎ≥５，则生成非晶硅氮（ａ－ＳｉＮｘ：Ｈ）薄膜．当Ｘｎ从１增加为１０时，薄膜暗电导率从１０￣（－５）（Ωｃｍ）￣（－１）降至１０￣（－１１）（Ωｃｍ）￣（－１），具有逾渗行为，这与薄膜的晶态率紧密相关．

特种化学气相沉积法制备大面积纳米硅薄膜的微结构和电学性能研究

采用可与Si平面工艺兼容的特殊设计的化学气相沉积系统在玻璃衬底上制备了大面积的纳米Si薄膜。高分辨率电子显微镜和选区电子衍射分析表明 ,成膜温度对薄膜微结构有关键影响 ,衬底温度的升高促进了薄膜晶态率的提高和Si晶粒的长大。 6 6 0℃成膜时非晶Si薄膜基体中镶嵌了尺寸为 8～ 12nm ,晶态率为 5 0 %的纳米Si晶粒 ,具有明显的纳米Si薄膜微结构特征。用变温薄膜暗电导率测试系统研究表明 ,随成膜温度的升高 ,薄膜的晶态率提高、室温暗电导率提高而相应的电导激活能降低 ,用热激活隧道击穿机制解释了纳米Si薄膜微结构与特殊电学性能的关系。研究了原位后续热处理对薄膜微结构和电学性能的影响 ,发现延长热处理时间以及采用低温成膜、高温后续退火的热处理方法能有效提高纳米Si薄膜的晶态率 。

乙烯对纳米硅碳薄膜晶化的影响

在等离子体化学气相沉积系统中采用高氢稀释硅烷加乙烯法制备了ｎｃ－ＳｉＣｘ∶Ｈ薄膜。系统研究了Ｃ２Ｈ４／（Ｃ２Ｈ４＋ＳｉＨ４）（Ｘｃ）气体流量比对ｎｃ－ＳｉＧｘ∶Ｈ薄膜的晶化和其它光电性能的影响。Ｘｃ从０．１增加为０．４时，薄膜的晶态率从４５％下降为１０％，平均晶粒尺寸从１０ｎｍ下降为５．５ｎｍ，对应薄膜中的Ｃ含量从０．０３增加为０．１２。当Ｘｃ≥０．５，生成薄膜为非晶硅碳（ａ－ＳｉＣｘ∶Ｈ）薄膜。随着Ｘｃ从０．１增加为０．８，薄膜的暗电导率从８．５×１０－７（Ωｃｍ）－１下降为９×１０－１２（Ωｃｍ）－１，薄膜的光学能隙随Ｘｃ的增加而增加。

Influence of strain rate on microstructure and formability of AZ31B magnesium alloy sheets

The effects of strain rate on microstructure and formability of AZ31B magnesium alloy sheets were investigated through uniaxial tensile tests and hemispherical punch tests with strain rates of 10^-4, 10^-3, 10^-2, 10^-1 s^-1 at 200℃. The results show that the volume fraction of dynamic recrystallization grains increases and the original grains are gradually replaced by recrystallization grains with the strain rate decreasing. A larger elongation and a smaller r-value are obtained at a lower strain rate, moreover the erichsen values become larger with the strain rate reducing, so the formability improves. This problem arises in part from the enhanced softening and the coordination of recrystallization grains during deformation.

Hot deformation behavior at low-rate strain of 316LN stainless steel

The study on hot deformation behavior of 316LN stainless steel at low-rate strain is very seldom at present. By sam-pling from industrial 316LN stainless steel and carrying out a compression heat deformation test by means of a Gleeble-3800 thermal simulation testing machine at a strain rate of 3×10^-3s^-1 and a deformation temperature of 600 - 1 100℃, true stress- strain curves are obtained. By analyzing the true stress-strain curves and microscopic structure of the samples, it can be conclu-ded that 1 000℃ and slightly higher temperature are suitable for low-rate strain processing of 316LN stainless steel.

Effect of strain rate on hot deformation characteristics of GH690 superalloy

In order to clarify the effect of strain rate on hot deformation characteristics of GH690superalloy,the hot deformationbehavior of this superalloy was investigated by isothermal compression in the temperature range of1000?1200°C and strain raterange of0.001?10s?1on a Gleeble?3800thermo-mechanical simulator.The results reveal that the flow stress is sensitive to the strainrate,and the dynamic recrystallization(DRX)is the principal softening mechanism.The strain rate of0.1s?1is considered to be thecritical point during the hot deformation at1000°C.The DRX process is closely related to the strain rate due to the adiabatictemperature rise.The strain rate has an important influence on DDRX and CDRX during hot deformation.The nucleation of DRXcan be activated by twin boundaries,and there is a lower fraction ofΣ3n(n=1,2,3)boundaries at the intermediate strain rate of0.1s?1.

Dynamic recrystallization and mechanical properties of high-strain-rate hot rolled Mg-5Zn alloys with addition of Ca and Sr

Effects of the sole and the combined addition of Ca and Sr on microstructure and mechanical properties of as-cast and as-rolled Mg-5 Zn alloys were carefully investigated by OM,SEM,hot-compression testing and tensile testing.Ca is more effective than Sr in the microstructural refinement of as-cast alloys.High-strain-rate rolling(HSRR)produces more deformed twins and thus provides more nucleation sites for dynamic recrystallization(DRX).The addition of Ca and Sr can promote dynamic precipitation during HSRR,the precipitation process would consume the storage energy and thus increases the critical strain value of DRX,resulting in the retarded DRX effect by the addition of Ca and/or Sr.The as-rolled Mg-5 Zn-0.4 Ca-0.2 Sr alloy exhibits a good combination of strength and ductility,with the ultimate tensile strength of 317 MPa,the yield strength of 235 MPa and the elongation to rupture of 24%.

Influence of temperature and strain rate on flow stress behavior of twin-roll cast, rolled and heat-treated AZ31 magnesium alloys

The effects of temperature and strain rate on the flow stress behavior of twin-roll cast, rolled and heat-treated AZ31 magnesium alloys were investigated under uniaxial tension. At high temperatures, dynamic recovery, continuous dynamic recrystallization, grain boundary sliding and the activation of additional slip systems lead to an improvement of the ductility of the alloys. The elongation to failure is nearly independent of the strain rate between 473 and 523 K at 10-2 s-1 and 10-1 s-1, which is related to the strain rate dependence of the critical resolved shear stress（CRSS） for nonbasal slip. Despite the high temperature, twins are even observed at 573 K and 10-3 s-1 because they have a low CRSS.

Characterization of hot deformation behavior of Al-Zn-Mg-Mn-Zr alloy during compression at elevated temperature

The hot deformation behavior of Al-6.2Zn-0.70Mg-0.30Mn-0.17 Zr alloy and its microstructural evolution were investigated by isothermal compression test in the deformation temperature range between 623 and 773 K and the strain rate range between 0.01 and 20 s^(-1).The results show that the flow stress decreased with decreasing strain rate and increasing deformation temperature.At low deformation temperature(≤673 K) and high strain rate(≥1 s^(-1)),the main flow softening was caused by dynamic recovery;conversely,at higher deformation temperature and lower strain rate,the main flow softening was caused by dynamic recrystallization.Moreover,the slipping mechanism transformed from dislocation glide to grain boundary sliding with increasing the deformation temperature and decreasing the strain rate.According to TEM observation,numerous Al_3Zr particles precipitated in matrix,which could effectively inhibit the dynamic recrystallization of the alloy.Based on the processing map,the optimum processing conditions for experimental alloy were in deformation temperature range from 730 K to 773 K and strain rate range from 0.033 s^(-1) to 0.18 s^(-1) with the maximum efficiency of 39%.

Optimization of Parameters for Melt Crystallization of p-Cresol

Laboratory-scale experiments were carried out to evaluate the influences of operational parameters on the melt crystallization efficiency for p-cresol purification.The optimal crystallization conditions were determined:dynamic pulsed aeration at 90 L·h-1 and the cooling rate of 0.6-0.8 ℃·min-1,followed by sweating at 0.2-0.3 ℃·min-1 for 40 min.Results also demonstrate that the melt crystallization efficiency is sensitive to feed concentration,which highlights this technology for separation and purification of high purity products.

Effect of catalytic activities of mixed nano ferrites of zinc and copper on decomposition kinetics of lanthanum oxalate hydrate

Nanostructured zinc-copper mixed ferrite was synthesized using sol-gel method. Different compositions of ferrite, Zn_((1-x))Cu_xFe_2O_4(x=0.0, 0.25, 0.50, 0.75), characterized by XRD, reveal single phase inverse spinel in all the samples. With increasing copper content, the crystallite size increases. The surface morphology of all the samples, studied by SEM, shows porous structure of particles. The prepared samples were also analyzed by FT-IR and TEM. Catalytic activity of the samples was studied on lanthanum oxalate decomposition by thermogravimety.The rate constant k has the highest value with x=0.75 and 5%(mole fraction) of the catalyst and is attributed to high copper content, the mixed sites Cu^(2+)-Fe^+ and/or Cu^+-Fe^(2+) ion pairs besides the one component sites Cu^(2+)-Cu^+, Fe^(3+)-Fe^(2+), as a result of mutual charge interaction. In other words, the increasing activity of mixed oxides is attributed to increase in the content of active sites via creation of new ion pairs. With increasing Zn content, particle size increases. Variation of catalytic activity of ferrite powders is due to the changes of the valence state of catalytically active components of the ferrites, which oxidizes the carbon monoxide released from lanthanum oxalate.

Resolution of ghost imaging with entangled photons for different types of momentum correlation

We present an analytical analysis of the spatial resolution of quantum ghost imaging implemented by entangled photons from a general, spontaneously parametric, down-conversion process. We find that the resolution is affected by both the pump beam waist and the nonlinear crystal length. Hence, we determined a method to improve the resolution for a certain imaging setup. It should be noted that the resolution is not uniquely related to the degree of entanglement of the photon pair since the resolution can be optimized for a certain degree of entanglement. For certain types of Einstein-Podolsky-Rosen(EPR) states——namely the momentum-correlated or momentum-positively correlated states——the resolution exhibits a simpler relationship with the pump beam waist and crystal length. Further, a vivid numerical simulation of ghost imaging is presented for different types of EPR states,which supports our analysis. This work discusses applicable references to the applications of quantum ghost imaging.

High Resolution and Wide Dynamic Range Pressure Sensor Based on Two-Dimensional Photonic Crystal

The authors present a new design of high resolution and wide dynamic range photonic crystal pressure sensor. This sensor is based on two-dimensional photonic crystal with square array of silicon rods surrounded by air. The sensor consists of a photonic crystal waveguide which is coupled to a photonic crystal nanocavity. The waveguide is configured by removing one row of Si rods and nanocavity is formed by modifying the radius of one Si rod. The sensor is designed for 1300 nm-1400 nm wavelengths. Simulation results show that resonant wavelength of nanocavity is linearly shifted to larger wavelengths by increasing the pressure. The designed sensor has a linear behavior between 0.1 GPa to 10 GPa of applied pressure and 8 nrrdGPa of pressure sensitivity.