Effects of Ce content on the modification of Mg_(2)Si phase in Mg-5Al-2Si alloy

The effect of Ce content(0–1.6 wt.%)on the modification of Mg_(2)Si phase in the as-cast Mg-5Al-2Si alloy was investigated.The original Chinese script type Mg_(2)Si phase was refined distinctly and transformed to dispersive block shape gradually by adding Ce element.The length of Chinese script type Mg_(2)Si phase was reduced from 110 to 50μm with increasing Ce content to 1.6 wt.%.The results calculated by Pandat software indicated that the added Ce element first combined with Si to form CeSi_(2)phase,which could serve as the heterogeneous nucleation of Mg_(2)Si phase due to the small lattice mismatch of 7.97%.The modification of Mg_(2)Si phase was mainly attributed to the facts that Ce changed the growth steps of Mg_(2)Si phase and CeSi_(2)promoted the nucleation of Mg_(2)Si phase.With increasing Ce content from 0 wt.%to 1.6 wt.%,the YS,UTS and EL at 150℃were improved from 67.7 MPa,91.2 MPa and 1.6%to 84.2 MPa,128 MPa and 7.5%,respectively.

Morphology modification of Mg_2Si by Sr addition in Mg-4%Si alloy

A modification of Mg2Si in the hypereutectic Mg-4%Si alloy（mass fraction） with Sr was investigated.Two types of Mg2Si in the alloys were found：polygonal primary Mg2Si and Chinese script type eutectic Mg2Si.Adding Al-10% Sr master alloy to the Mg-4%Si alloy clearly reduced the average size of primary Mg2Si and changed the morphology of eutectic Mg2Si from Chinese script type to polyhedral or fine fibre shape.The refinement of primary Mg2Si is mainly attributed to the heterogeneous nucleation mechanism induced by the Sr-rich particles.The modification of eutectic Mg2Si results from the dissolved Sr,which alters the preferred growth manner of the eutectic.

一种P改性的Ag/SiO_(2)催化剂用于草酸二甲酯加氢制乙醇酸甲酯

采用浸渍法分别制备了负载于不同载体的P改性Ag1P/TiO_(2)、Ag1P/ZrO_(2)、AgxP/SiO_(2)催化剂,并用于草酸二甲酯(DMO)加氢制乙醇酸甲酯(MG)的反应中。结果表明,相对于Ag1P/TiO_(2)、Ag1P/ZrO_(2)催化剂,AgxP/SiO_(2)比表面积较大,其中Ag1P/SiO_(2)显示出最大的比表面积及孔容,从而增大了Ag的分散度。P的适量掺杂有助于对H_(2)吸附量的调控,防止过度加氢,从而获得MG的高选择性,而过量的P会导致P5+物种的形成,对反应不利。优选后的最佳催化剂Ag1P/SiO_(2)在最优反应条件下DMO转化率达到94.27%,MG选择性达到92.22%,MG的收率为86.94%。

固溶时间对Ti@(Al-Si-Ti)_(p)/A356复合材料组织及力学性能的影响

采用粉末触变成形技术制备了原位自生心-壳结构增强A356铝基复合材料,并研究了固溶时间对Ti@(Al-Si-Ti)_(p)/A356复合材料显微其组织及力学性能的影响。结果表明,随着固溶时间增加,初生α-Al相颗粒粗化长大;共晶Si相不断溶解,晶界上残余的共晶Si粗化、球状化;Al基体、Ti心部继续反应,增强体颗粒壳层发生相转变。复合材料在545℃固溶处理1 h时,力学性能达到峰值,其抗拉强度、屈服强度和伸长率分别为263.9 MPa、175.1 MPa、20%,比制备态复合材料分别提高了7.3%、21.4%和12.4%,维氏硬度也从59.3 HV提高到72.8 HV。

p-Si/n-Ga_(2)O_(3)异质结制备与特性研究

本实验采用金属有机化学气相沉积(MOCVD)工艺,在p(111)型Si衬底上制备了p-Si/n-Ga_(2)O_(3)结构的PN结。通过X射线衍射仪、原子力显微镜等对样品进行了晶体结构、表面形貌、表面粗糙度等的表征分析;通过磁控溅射与蒸镀方法在样品上生长Ti/Au电极并进行I-V特性曲线、开启电压、开关电流比、反向饱和电流、理想因子、零偏压下的势垒高度等结特性测试,研究了掺杂浓度与薄膜厚度对PN结特性的影响,并对其原因进行了分析;通过二步生长法和缓冲层温度优化实验,减少了Si衬底与β-Ga_(2)O_(3)之间的晶格失配与热失配带来的影响,对薄膜与器件特性进行了优化。最终获得了表面粗糙度最低可达到4.21 nm的高质量n型β-Ga_(2)O_(3)薄膜,以及具有较低理想因子(42.1)的PN结。

SiC_(p)含量对SiC_(p)/Al-1.2Mg-0.6Si铝基复合材料组织和性能影响

采用粉末冶金法制备SiC_(p)/Al-1.2Mg-0.6Si铝基复合材料,分析了该复合材料的均匀性和界面结合情况,探讨了几种体积分数该复合材料的显微组织和性能变化。结果表明,SiC颗粒和基体之间的界面清晰平滑,界面结合良好,但随着热压温度的增加,SiC与基体间的微观缩孔和析出相逐渐增多。随着SiC颗粒含量的增加,材料的弹性模量、热导率显著提高,弯曲强度先升高后下降,而热膨胀系数逐渐降低。

低填充P-Si基阻燃体系协效阻燃PA66的制备及性能

尼龙66(PA66)作为一种广泛使用的工程塑料,因其优异的力学性能和加工性能而备受青睐。然而,PA66的可燃性限制了其在某些安全要求较高的应用领域的发展。为了解决这一问题,可通过构建P-Si基协效阻燃体系,对PA66进行熔融共混改性,以期提高其阻燃性能、力学性能及热稳定性。采用熔融共混法制备PA66复合材料,利用二乙基次磷酸铝(ADP)、次磷酸铝(AHP)及纳米二氧化硅(SiO2)构建多元协效阻燃体系,并系统研究了ADP/AHP/SiO2协效阻燃体系对PA66性能的影响,对PA66复合材料的阻燃性能、力学性能及热稳定性进行了综合评价。实验结果表明,ADP/AHP/SiO2协效阻燃体系显著提升了PA66的阻燃性能,当添加总量为9份时,PA66复合材料的阻燃等级达到V-0级别,极限氧指数高达34.3%。此外,PA66复合材料的拉伸性能也得到了显著提升,拉伸强度和拉伸弹性模量分别提高了27%和36%。热重测试显示,PA66复合材料的热稳定性也有明显改善。ADP/AHP/SiO2协效阻燃体系不仅显著提高了PA66的阻燃性能,还有效改善了其力学性能和热稳定性。该体系的引入为PA66的工程应用提供了有力支持,具有重要的实际应用价值和市场前景。

Numerical Analysis on the Effect of n-Si on Cu(In, Ga)Se2 Based Thin-Films for High-Performance Solar Cells by 1D-SCAPS

We report the performances of a chalcopyrite Cu(In, Ga)Se2 CIGS-based thin-film solar cell with a newly employed high conductive n-Si layer. The data analysis was performed with the help of the 1D-Solar Cell Capacitance Simulator (1D-SCAPS) software program. The new device structure is based on the CIGS layer as the absorber layer, n-Si as the high conductive layer, i-In2S3, and i-ZnO as the buffer and window layers, respectively. The optimum CIGS bandgap was determined first and used to simulate and analyze the cell performance throughout the experiment. This analysis revealed that the absorber layer’s optimum bandgap value has to be 1.4 eV to achieve maximum efficiency of 22.57%. Subsequently, output solar cell parameters were analyzed as a function of CIGS layer thickness, defect density, and the operating temperature with an optimized n-Si layer. The newly modeled device has a p-CIGS/n-Si/In2S3/Al-ZnO structure. The main objective was to improve the overall cell performance while optimizing the thickness of absorber layers, defect density, bandgap, and operating temperature with the newly employed optimized n-Si layer. The increase of absorber layer thickness from 0.2 - 2 µm showed an upward trend in the cell’s performance, while the increase of defect density and operating temperature showed a downward trend in solar cell performance. This study illustrates that the proposed cell structure shows higher cell performances and can be fabricated on the lab-scale and industrial levels.

Al-Si-P master alloy and its modification and refinement performance on Al-Si alloys

An Al-Si-P master alloy has been developed by an in-situ reaction and the electron probe microanalyzer （EPMA） results show that there are many pre-formed AlP particles contained in the master alloy. Silicon introduced into the system plays an important role in remarkably improving the distribution and content of AlP particles due to their similar crystal structure and lattice parameters. ZL109 alloys have shown fast modification response to the addition of 0.5% Al-15Si-3.5P master alloy at 720℃, with a mass of primary Si precipitating in size of about 15 μm. Also, coarse primary Si grains in AI-30Si alloy can be refined dramatically from 150 μm to 37 μm after the addition of 2.0% Al-15Si-3.5P master alloy at 850℃. The P recovery of the Al-15Si-3.5P master alloy is much higher than that of a Cu-8.5P master alloy due to the pre-formed AlP particles.

Effect of Sr modification on microstructure and thermal conductivity of hypoeutectic Al−Si alloys

Trace amount of Sr(0.05 wt.%)was added into the hypoeutectic Al−Si(3−12 wt.%Si)alloys to modify their microstructure and improve thermal conductivity.The results showed that the thermal conductivity of hypoeutectic Al−Si alloys was improved by Sr modification,and the increment and increasing rate of the thermal conductivity gradually increased with Si content increasing.The improvement of thermal conductivity was primarily related to the morphology variation of eutectic Si phases.In Sr-modified Al−Si alloys,the morphology of eutectic Si phases was a mixed morphology of fiber structure and fine flaky structure,and the proportion of the fine flaky eutectic Si phases gradually decreased with Si content increasing.Under the Si content reaching 9 wt.%,the proportion of fine flaky eutectic Si phases was nearly negligible in Sr-modified alloys.Correspondingly,the increment and increasing rate of thermal conductivity of Sr-modified alloys reached the maximum and tended to be stable.

Modification effect of lanthanum on primary phase Mg_2Si in Mg-Si alloys

The modifying effect of La addition on primary phase Mg2Si in Mg-5Si alloys was investigated. The results showed that a proper amount of La could effectively modify the primary phase Mg2Si, Based on the present experiment, the optimal modification effect was obtained with an addition of about 0.5 wt.% La. The size of the primary phase MgzSi was considerably reduced to 25μm or less and the morphology was modified from a coarse dendritic shape to a polyhedral shape. However, when the addition of La increased to 0.8 wt.% or higher, the primary Mg2Si grew into a coarse dendritic morphology again. Moreover, it was found that some LaSi2 compounds were formed during solidification and the amount of the compounds appeared to increase gradually with increasing La content.

Modification and refinement mechanism of Mg_2Si phase in Sr-containing AZ61-0.7Si magnesium alloy

The effect of Sr on modification and refinement of the Mg 2 Si phase in an AZ61-0.7Si magnesium alloy has been investigated and analyzed.The results indicate that Sr can effectively modify and refine the Chinese-script shaped Mg2Si phase in the AZ61-0.7Si alloy.By adding 0.06wt.%-0.12wt.%Sr to AZ61-0.7Si alloy,the Mg2Si phase in the alloy can be changed from the initial coarse Chinese-script shape to fine granule and/or irregular polygonal shapes.Accordingly,the Sr-containing AZ61-0.7Si alloy exhibits higher tensile and creep properties than the AZ61-0.7Si alloy without Sr modification.The mechanism on modification and refinement of the Mg2Si phase in Sr-containing AZ61-0.7Si alloy is possibly related to the following two aspects:(1)adding Sr may form the Al4Sr phase which can serve as the heterogeneous nucleus for the Mg2Si particles and/or(2)adding Sr may lower the onset crystallizing temperature and increase the undercooling level.

Influences of complex modification of P and RE on microstructure and mechanical properties of hypereutectic Al-20Si alloy

P and RE complex modification of hypereutectic Al-Si alloys was conducted. The influences of P, RE content on the microstructure and mechanical properties of alloys were investigated. The complex modifications of P and RE make the coarse block primary silicon obviously refined and the large needle eutectic silicon modified to the fine fibrous or lamella ones. P mainly refines the primary silicon, but excess P is unfavorable to the refinement of primary silicon. RE can well refine the primary and eutectic silicon, but its modification effect on the eutectic silicon is more obvious. P can repress the modification of RE on the eutectic silicon. The alloys with the additions of 0.08% P and 0.60% RE have the optimal microstructure and the highest mechanical properties. Compared with the unmodified alloy, the primary silicon of alloys can be refined from 66.4 μm to 23.3 μm and the eutectic silicon can be refined from 8.3 μm to 5.2 μm. The tensile strength is improved from 256 MPa to 306 MPa and the elongation is improved from 0.35% to 0.48%.

Influence of Sb modification on microstructures and mechanical properties of Mg2 Si/AM60 composites

The refining effect and mechanism of Sb on Mg2Si and the microstructure of the matrix were investigated.The results indicate that there are Mg3Sb2 particles in the composites with the addition of Sb,and Mg3Sb2 can promote the formation of fine polygonal type Mg2Si by providing nucleation site.Meanwhile,the grain size of Sb modified alloy is finer than that of the matrix. The improved microstructure results in the improvement of mechanical properties.The ultimate tensile strength is increased by 12.2%with the addition of 0.8%Sb.

Modification mechanism of hypereutectic Al-Si alloy with P-Na addition

Effect of P-Na united modification on Al-22%Si-1.0%Cu-0.5%Mg-0.5%Mn alloy was studied. The results show that the refining effect of P-Na addition on primary silicon is superior to that of P and the former could modify eutectic silicon at the same time. Effects of P-Na modification on crystallization and microstructure of hypereutectic Al-Si alloys were studied with Electron-Scanning Microscope, Electron-Probe and X-ray diffractometer. The modification mechanism represents that on one hand, the primary silicon is refined by AlP as heterogeneous nucleus; on the other hand, when Na is added at the same time, P atoms are difficult to diffuse in the melt, and then enrichs on the growing faces of silicon phase. Moreover, a SiP compound was also discovered in Si crystals, which prevents the growth of silicon phase and refines the primary silicon.

Modification effect of Yb and Na_3PO_4 on microstructure of Mg_2Si/Mg-4Si alloy and mechanism

The modification effects of ytterbium(Yb), Na_3PO_4 and Yb + Na_3PO_4 on primary Mg_2Si phase in Mg-4Si alloys were investigated by means of X-ray diffraction(XRD), optical microscopy(OM), scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS) analysis in this work. The results indicate that the morphology of the primary Mg_2Si phase apparently changes from coarse dendrites to fine dispersive polygonal particles and the mean size decreases from 276.6 μm to 7.1 μm, with combined modification of 0.8wt.% Yb and 2.64 wt.% Na_3PO_4. Such a morphological evolution results in improvement in the ultimate tensile strength and elongation of the alloys as compared to the base alloy. This may be attributed to the formation of the YbP particles that acted as the heterogeneous nucleation substrates for the primary Mg_2Si particles, resulting in a refined distribution of these precipitates. The results of XRD examination show that there was no reaction between Si and Yb or Na_3PO_4. Solo addition of Yb or Na_3PO_4 into the melt has no real modification effect on the microstructure, but the primary Mg_2Si particles and α-Mg phases become coarser than that in the unmodified alloy.

Modification effect of pure rare earth metal La on as-cast hypereutectic Al-17%Si alloys

The modification effect of La addition on the microstructural characteristics of hypereutectic Al 17%Si alloys was studied. Microstructures were examined using conventional optical microscopy and electron probe X ray microanalyzer. The morphology of Si crystal was evaluated by quantitative metallographical analysis. The results indicate that simultaneous modification to both primary and eutectic Si crystals is obtained by the addition of pure rare earth metal La in the hypereutectic Al 17%Si alloys while the optimal effect of La is obtained at a rather large scale. La begins to form intermetallic compound when its concentration exceeds approximately 1%, which appears as dark platelets in etched specimens. Electron probe X ray microanalysis experiment shows that La rich platelet could be represented as Al 1Si 2La 2 consisting of LaSi 2 and some unknown ternary Al x Si y La phase.

United modification of Al-24Si alloy by Al-P and Al-Ti-C master alloys

The modification effect of a new type of Al-P master alloy on Al-24Si alloys was investigated. It is found that excellent modification effect can be obtained by the addition of this new type of Al-P master alloy into Al-24Si melt and the average primary Si grain size is decreased below 47 μm from original 225 μm. It is also found that the TiC particles in the melt coming from Al8Ti2C can improve the modification effect of the Al-P master alloy. When the content of TiC particles in the Al-24Si melt is 0.03%, the improvement reaches the maximum and keeps steady with increasing content of TiC particles. Modification effect occurs at 50 min after the addition of the Al-P master alloy and TiC particles, and keeps stable with prolonging holding time.

Effect of mixed rare earth oxides and CaCO_3 modification on the microstructure of an in-situ Mg_2Si/Al-Si composite

The effects of mixed rare earth oxides and CaCO3 on the microstructure of an in-situ Mg2Si/Al-Si hypereutectic alloy composite were investigated by optical microscope,scanning electron microscope,and energy dispersive spectrum analysis. The results showed that the morphol-ogy of the primary Mg2Si phase particles changed from irregular or crosses to polygonal shape,their sizes decreased from 75 μm to about 25 μm,and the compound of both the oxide and CaCO3 was better than either the single mixed rare earth o...

Modification ofβ-Al_5FeSi Compound in Recycled Al-Si-Fe Cast Alloy by Using Sr,Mg and Cr Additions

The effects of Sr,Mg,Cr,Sr/Mg and Sr/Cr combined additions on the Fe-containing intermetallic phase in a recycled Al-Si-Fe cast alloy are investigated.The experimental results show that the additions of Cr and Sr/Cr successfully modified the platelet and flake-likeβ-Al-5FeSi phases （β-compound） into the fibrousα-Al-8Fe-2Si （α-compound）.The additions of Sr and Sr/Mg were less effective to modify theβ-compound into theα-compound,while the eutectic Si was fully modified into the fibrous morphology.A small secondary dendrite arm spacing （DAS） was found in the Sr-added,Cr-added and Sr/Cr-added alloys,especially in a steel mold.The Sr,Sr/Cr and Sr/Mg combined additions modify the eutectic Si simultaneously.A sludge phase was found in the addition of Cr-added,Sr/Cr-added and Mg-added alloys,especially in the graphite mold casting.The volume fraction ofβ-compounds was decreased by the addition of various modifying elements. The Cr and Sr/Cr combined additions are very effective to modify theβ-compound for the recycled Al-Si-Fe based alloys.