Chemical Bond Analysis of Single Crystal Growth of Magnesium Oxide

Starting from the crystallographic structure of magnesium oxide (MgO), both the chemical bond model of solids and Pauling's third rule (polyhedral sharing rule) were employed to quantitatively analyze the chemical bonding structure of constituent atoms and single crystal growth. Our analytical results show that MgO single crystals prefer to grow along the <100> direction and the growth rate of the {100} plane is the slowest one. Therefore, the results show that the {100} plane of MgO crystals can be the ultimate morphology face, which is in a good agreement with our previous experimental results. The study indicate that the structure analysis is an effective tool to control the single-crystal growth.     

In-Situ Observation of SiC Bulk Single Crystal Growth by XRD System

In-situ analysis for SiC bulk single crystal growth was reported using vertical X-ray diffractometer system. A furnace for SiC sublimation growth combined with the XRD system which possessed three kinds of functions including topography, rocking curve measurement and crystal growth rate monitoring was developed. These functions could contribute as a powerful tool finding the optimum growth condition by dynamic observation in the crucible. In this study, the in-situ X-ray topographs succeeded to capture dynamic elongation of defects and dislocation generated in the SiC growing crystals. The in-situ rocking curve measurement reviled appearance of mosaic structure in the SiC crystal grown with high growth rate. The in-situ growth rate monitoring also succeeded very precisely using the direct X-ray beam absorption. On the base of findings and facts obtained by the in-situ observations, the importance for the SiC growth was discussed.     

化学气相传输法分离相邻四元混合轻稀土氧化物

基于稀土氯化物在高温时与KCl生成气态配合物KRECl4的热力学行为差异,将稀土氯化物和KCl按摩尔比1:1混合,另将稀土氧化物、NH4Cl和KCl按RE:N:KCl=1:6:1(RE=La、Ce、Pr、ND)的摩尔比混合,进行化学气相传输反应,研究混合稀土化合物的分离特性.实验结果显示,单一轻稀土氧化物-NH4Cl-KCl传输反应在650℃～800℃的温度范围内稀土沉积量PrCl3＞NdCl3＞LaCl3＞CeCl3.四元相邻混合轻稀土氯化物-KCl传输反应,在不同温度区域内最大分离系数分别为SFLa/Ce(5)=2.51,SFPr/La(5)=3.86,SFNd/La(4)=2.61,SFpr/Ce(5)=9.76,SFNd/ce(4)=4.28,SFNd/Pr(2)=2.50.四元相邻混合轻稀土氧化物-NH4Cl-KCl传输反应,在不同温度区域内最大分离系数分别为SFNdLa/ce(2)=3.01,SFPr/La(6)=3.31,SFNd/La(4)=2.47,SFPr/ce(5)=8.84,SFNd/ce(6)=5.02,SFNd/Pr(2)=2.02.     

Preparation of Anhydrous LnCl3(Ln=Eu, Er, Lu) by Chemical Vapor Transport

Ｔｈｅｐｒｅｐａｒａｔｉｏｎｏｆａｎｈｙｄｒｏｕｓｒａｒｅｅａｒｔｈｈａｌｉｄｅｓｃａｎｂｅｔｒａｃｅｄｂａｃｋｔｏｔｈｅｂｅｇｉｎｎｉｎｇｏｆｔｈｅ20ｔｈｃｅｎｔｕｒｙ[1].Ｔｈｅｐｒｅｐａｒａｔｉｏｎｍｅｔｈｏｄｓｍａｙｂｅｃｌａｓｓｉｆｉｅｄａｓｔｈｒｅｅｔｙｐｅｓ,ｈａｌｏｇｅｎａｔｉｏｎｏｆｍｅｔａｌｓ,ｈａｌｏｇｅｎａｔｉｏｎｏｆｒａｒｅｅａｒｔｈｏｘｉｄｅｓ,ａｎｄｄｅｈｙｄｒａｔｉｏｎｏｆｒａｒｅｅａｒｔｈｈａｌｉｄｅｈｙｄｒａｔｅｓ[2].Ｔｈｅｒｅａｃｔｉｏｎｓｂｅｔｗｅｅｎｒａｒｅ…     

化学气相传输法制备无水氯化镥

以化学气相传输法制取无水ＬｕＣｌ３。Ｌｕ２Ｏ３（ｓ）与Ａｌ２Ｃｌ６（ｇ）在３００℃反应生成ＬｕＣｌ３（ｓ）。反应完成后,利用４００～１８０℃的温度梯度场,实现ＬｕＣｌ３（ｓ）的气相传输分离。剩余氯化铝在２００℃用Ｃｌ２－Ｎ２混合载气去除。产物纯度〉９９．９％。     

Chemical Bond Calculations of Crystal Growth of KDP and ADP

A novel method was proposed to calculate the crystal morphology (or growth habit) on the basis of chemical bond analysis. All constituent chemical bonds were distinguished as relevant and independent bonds according to their variations during the crystallization process. By employing the current method, the influence of specific growth conditions on the crystal morphology can be considered in the structure analysis process. The ideal morphologies of both KDP (KH2PO4) and ADP (NH4H2PO4) crystals were calculated and compared with our obtained crystallites at room temperature, which validates the present calculation method very well.     

SRR99镍基单晶高温合金在落管微重力环境下的枝晶生长行为研究

利用50m长落管研究了SRR99镍基单晶高温合金在微重力与重力环境下的枝晶生长行为。采用金相显微镜观察了试样在微重力(微重力试样)和重力(重力试样)下凝固组织的差异,并利用图像分析软件测量了枝晶的一次臂和二次臂的长度及间距。结果表明,微重力试样在下落过程中从未熔部分外延生长的最大长度约为1.7mm,重力试样的最大长度为1.9mm。微重力试样的一次枝晶干粗大,平均间距约为80μm,而重力试样中存在较多的细小一次枝晶干,一次臂平均间距约为71μm。一次枝晶平均间距在微重力环境下增大20%。微重力试样的二次臂长度较长,且在20～160μm的整个长度范围内较均匀分布;重力试样二次臂长度较短,且集中分布在20～80μm区间内。微重力试样和重力试样的二次枝晶臂平均间距相同,均为17μm。     

反偏籽晶晶向生长Φ2″HB-GaAs单晶

HB-GaAs ( 10 0 )片要偏离生长截面 5 4.7°～ 60°切割 (〈10 0〉和〈111〉之间的夹角是 5 4.7°)。如果籽晶方向与〈10 0〉之间的夹角少于 5 4.7°,称为反偏籽晶。而采用大于 5 4.7°角生长的单晶切割比较困难 ,尤其是厚度小于 3 0 0 μm的晶片。为了减少切割难度 ,可生长反偏籽晶的单晶 ,但要保证单晶能割出Φ2″( 10 0 )圆片 ,必须增加单晶锭的截面积。由于GaAs的热导率小 ,大截面单晶生长要困难得多。通过改变固液截面附近的加热元件结构 ,在特定方向加强了散热 ,延伸了温度梯度的线性范围 ,使用反偏籽晶 ,成功地生长了Φ2″HB GaAs单晶。和正偏籽晶单晶相比 ,这些单晶锭的切割破损率减少了 2 4% ,每 10 0mm长度出片数增加了 3 0 %。     

Stepwise Chlorination-Chemical Vapor Transport Reactions for Bastnaesite Concentrate

Vapor phase extraction and mutual separation of rare earth (RE) elements from bastnaesite concentrate were investigated using stepwise chlorination-chemical vapor transport reactions mediated by vapor complexes LnAlnC13n 3(Ln = RE elements). The bastnaesite was heated to 800 K and chlorinated between 800- 1300 K with ,C C12 SiClr to remove CO2, SiF4 and high volatile chlorides. At the temperature of 1300 K for 6 h, the resulted RE chlorides were chemically transported and mutual separated with the vapor complexes while CaC12 and BaC12 were remained in the residues. Significantly different CVT characteristics were observed for gradually decreased and wave form temperature gradients.     

化学气相传输法分离二元混合稀土氧化物

以KCl为络合物配体,研究与Y2O3离子半径十分接近的Dy2O3、Ho2O3和Er2O3的分离特性以及重稀土氧化物Ho2O3-Er2O3、Er2O3-Tm2O3、Tm2O3-Yb2O3及Yb2O3-Lu2O3之间的分离特性。实验结果表明,分离后主要沉积位置在中温和低温区。不同温度区域的最大分离系数分别为,SFY/Dy=11.49,SFY/Ho=15.28,SFY/Er=6.37。说明Y-Dy、Y-Ho及Y-Er控制一定的温度梯度完全可以达到分离目的。SFHo/Er=1.40,SFEr/Tm=2.21,SFTm/Yb=1.38,SFYb/Lu=4.33,高于传统的湿法分离系数。     

ZnO and Zn1-xMnxO Minicrystal by CVT and Temporal Process of Photoelectrons

The ZnO and Zn1-xMnxO minicrystal were synthesized by chemical vapor transport (CVT). The electron trap structure (donor level) and process on the temporal behavior of photoelectrons of materials were respectively studied by thermo-luminescence and microwave absorption dielectric spectrometry. There are two peaks in the thermo-luminescence spectra in pure ZnO, one is -183 ℃ and the other is -127 ℃, which shows two kinds of electron trap energy level produced by the intrinsic defects in ZnO;but obtain very low thermo-luminescence that only equals to ten percent of pure ZnO in Zn1-xMnxO, which shows that its intensity of electron trap is less. The studies of microwave absorption dielectric spectrometry show that conduction band photoelectrons are two-step exponential decay process in ZnO, the lifetime of rapid process is 83 ns, while slow process is 828 ns, the reason of delay is relaxation effects of electron trap to conduction band photoelectrons. The intensity of electron trap is less in Zn1-xMnxO minicrystal, the relaxation effects of conduction band photoelectrons from electron trap is little, so electrons disappeared quickly at conduction band, and the decay process of photoelectrons is only 10～20 ns.     

Recrystallization of Single Crystal Nickel-Based Superalloy

A series of experiments of investigating the recrystallization of single crystal DD3 superalloy were carried out. The threshold temperature for recrystallization and the effect of annealing temperature on recrystaUization were studied. The results show that the threshold temperature for recrystallization of the shot-peened DD3 samples is be-tween 1 000 ℃ and 1 050℃ under the condition of annealing for 2 h, and the recrystallization depth increases with the rise of the annealing temperature. Below 1 150 ℃, the recrystallization depth increases slowly with the tempera-ture climbing, while above 1 150 ℃, the recrystallization depth increases quickly with the rise of the temperature. The solution of the γ' phase is a critical factor of the recrystallization behavior of DD3 superalloy. In addition, the ki-netics and microstructural evolution of recrystallization at 1 200 ℃ were also studied. It is found that the recrystalli-zation progresses rapidly at 1 200℃ through the growth of fully developed recrystallized grains, and the recrystalli-zation process on the shot-peened surface is similar to that of wrought materials, including nucleation of reerystalliza-tion, growth of new grains into the matrix, and growth of new grains by swallowing up each other.     

CH4化学气相渗透沉积提高焦炭热性质研究

热解炭化学气相渗透沉积具有填充和修整焦炭气孔的功能,利用甲烷高温裂解生成的热解炭在焦炭内外表面渗透沉积可达到提高焦炭热性质的目的。试验结果显示,经过渗透沉积的焦炭抗CO4反应能力大幅提高,CRI和CSR明显改善,分别从31．04％降低到20．28％和从63．24％提高到77．69％。此外,试验还发现,反应的最佳条件为甲烷混合气的体积分数为47％,在51L／h的流量和1000℃的温度下反应6h。     

氧化钨单晶纳米带和纳米线的气相合成

利用W纳米粉和Ni(NO3).26H2O的高温反应,可制备出长度超过20μm,宽度在200～2000nm,厚度在50 nm以下的氧化钨纳米带和长度在20μm以上,直径在100nm以下的氧化钨纳米线。合成的纳米带和纳米线均排列成放射式花状结构。XRD,SEM,TEM和EDS等一系列分析表征结果表明,合成的氧化钨纳米带和纳米线是沿<010>方向生长的,具有完好单晶结构的W18O49相。化学反应热力学分析与计算结果表明,合成的氧化钨纳米带和纳米线是通过气相沉积的方式形成的。     

Recrystallization of a Single Crystal Nickel-Base Superalloy

 A series of experiments of investigating the recrystallization of single crystal DD3 superalloy were carried out. The threshold temperature for recrystallization and the effect of annealing temperature on recrystallization were studied. The results show that the threshold temperature for recrystallization of the shot peened DD3 samples is between 1 000 ℃ and 1 050 ℃ under the condition of annealing for 2 h, and the recrystallization depth increases with the rise of the annealing temperature. Below 1 150 ℃, the recrystallization depth increases slowly with the temperature climbing, while above 1 150 ℃, the recrystallization depth increases quickly with the rise of the temperature. The solution of the γ′ phase is a critical factor of the recrystallization behavior of DD3 superalloy. In addition, the kinetics and microstructural evolution of recrystallization at 1 200 ℃ were also studied. It is found that the recrystallization progresses rapidly at 1 200 ℃ through the growth of fully developed recrystallized grains, and the recrystallization process on the shot peened surface is similar to that of wrought materials, including nucleation of recrystallization, growth of new grains into the matrix, and growth of new grains by swallowing up each other.     

ZnO单晶生长技术的研究进展

ZnO是近期材料领域的研究热点之一,其性能优异,有望成为下一代光电子材料.因此,对ZnO单晶的研究具有重要的理论意义和应用价值.目前生长ZnO单晶的方法有助熔剂法、水热法、气相法、 熔体法,但单晶的尺寸和质量都有待提高.本文从晶体生长理论和工艺出发,对4种方法进行了全面的对比和分析,预测了ZnO体单晶的生长的研究方向.     

提拉法生长立方相KTa1-xNbxO3晶体

报道了用提拉法在KNbO3-KTaO3固熔体体系中生长立方相KTa10xNbxO3晶体。实验采用两种不同的原始配料生长晶体：即生长组分分别为KNbO3：KTaO3（摩尔分数）=0．35：0．65和0．45：0．55，分别得到x=0．14和0．19的KTN晶体，晶体尺寸可达厘米级。分析了晶体的形态特征和宏观缺陷并讨论了各种缺陷的形成机制；利用JXA-8800电子探针技术测定了晶体组分；讨论了影响晶体生长的多种条件。发现温场和提拉速度是影响KTN晶体生长和质量的主要因素。     

Crystal Growth and Properties of Co2+ doped Y3Sc2Ga3O12 Single Crystal

Single crystal of cobalt (Co)-doped Y3Sc2Ga3O12 (YSGG) with the dimensions up to φ20×40mm3 and undoped YSGG crystal with the dimensions up to φ28×60mm3 have been grown using the Czochralski technique. The structure of the crystal was characterized by the X-ray powder diffraction (XRPD) method. The absorbance spectra of the crystal shows that it has strong absorption bands at 606 and 1540nm. The results indicate that the crystal Y3Sc2Ga3O12 may be a kind of good Q-switch material.     

Cz法晶体生长中的流动与传热

本文针对Cz法晶体生长特点,通过数值模拟的方法,对Cz法生长砷化镓单晶时从引晶、放肩、等径至收尾这一完整工艺过程中晶体的温度场、熔体的温度场和速度场进行了计算,从中分析籽晶和坩埚的转向、转速等因素对流动和传热的影响,并与实际的砷化镓单晶生长过程进行比较,从比较结果看,二者基本吻合。     

气相氧化直接制备多针状氧化锌

采用气相氧化法,在温度850—950℃,氧分压≤8％,气体总流量300～330L／h的条件下,用工业锌粉为原料直接氧化制备出多针状氧化锌。SEM显示产物的中心体直径10—15μg,针状体直径0．2～0．8μm,针长60～100μg,XRD分析检测表明产物具有完整的六方纤锌矿型晶体结构。改变制备条件,可在一定范围内对多针状氧化锌的微观形貌和尺寸进行调控。半宽峰分析表明,随着氧分压的降低,半宽峰有所展开,表明晶体的缺陷增加,晶体缺陷主要是氧空位。