共查询到20条相似文献,搜索用时 62 毫秒
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使用数控焰熔法晶体生长炉和三管燃烧器进行了金红石单晶体的生长工艺实验研究。研究表明,在3个气体参数中,内氧是基础。当内氧流量小于特征值O_(in)(min)=6.6 L/min或大于特征值O_(in)(max)=7.1 L/min时,晶体生长或易于发生熔体流淌,或不易扩肩,生长过程被迫中止,晶体很难生长成为大尺寸晶体;当内氧流量大于6.6 L/min而小于7.1 L/min时,生长过程稳定,能够生长成为大尺寸晶体。当内氧流量为7 L/min时生长出了直径30 mm、长度45 mm的金红石单晶体。通过能谱仪、X射线衍射仪(XRD)和拉曼光谱仪对晶体的组成、结构和键的结构进行表征,表明该晶体为典型的金红石单晶体,生长方向是[110]。 相似文献
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温度梯度和生长速率对CdZnTe-VBM生长晶体的影响 总被引:3,自引:0,他引:3
计算模拟了半导体材料CdZnTe垂直布里奇曼法(CdZnTe-VBM)单晶体生长过程,分析了炉膛温度梯度和坩埚移动速率对结晶界面形态和晶体内组份偏析的影响。计算结果表明炉膛温度梯度和生长速率的变化明显影响固-液界面前沿对流场的形态和强度。界面凹陷深度随着炉膛温度梯度的增加和生长速率减小而减小。炉膛温度梯度的增加和生长速率的减小虽然均能有效的减小径向偏析,但却增加轴向偏析,减小轴向等浓度区的长度。 相似文献
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《无机材料学报》2010,(11)
对新型中红外非线性光学材料CdGeAs2的多晶合成和单晶生长进行了研究.以高纯(99.9999%)As、Ge、Cd为原料,按照CdGeAs2化学计量比并适当富Cd、As配料,采用机械振荡与熔体温度振荡相结合的方法合成出CdGeAs2多晶材料,使用改进的坩埚下降法生长出-15mm×45mm、外观完整无开裂的CdGeAs2单晶体.XRD全谱拟合精修、红外傅里叶分光光度计测试分析表明:合成的CdGeAs2晶体具有单相四方黄铜矿结构,晶格常数为a=b=0.5946nm,c=1.1217nm;生长出的CdGeAs2单晶体结构完整,结晶性好,晶体的易解理面为(101)面,红外透明范围589~4250cm-1,拟合计算出CdGeAs2晶体的禁带宽度为0.67eV. 相似文献
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采用真空坩埚下降法在石墨坩埚中生长了大尺寸CaF2晶体.通过高温氟化获得无水高纯原料,自发成核发育籽晶,以<2mm/h的生长速率,成功生长了直径170mm的CaF2晶体.研究了晶体的顶部析晶形貌、包裹体、解理等生长缺陷. 相似文献
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碘化铅单晶生长及探测器的研究进展 总被引:1,自引:1,他引:0
PbI2单晶体是性能优异的室温半导体核辐射探测器新材料。主要介绍了PbI2晶体生长技术及其室温核辐射探测器研究发展的最新动态,综述了PbI2晶体的3种主要生长方法(气相法、熔体法和凝胶法)的原理和优缺点,重点阐述了熔体法生长PbI2晶体的影响因素及研究进展,提出了PbI2单晶制备技术存在的主要问题和今后的发展方向。 相似文献
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Jung Bin In Hyuk‐Jun Kwon Daeho Lee Costas P. Grigoropoulos 《Small (Weinheim an der Bergstrasse, Germany)》2014,10(4):741-749
The laser‐assisted hydrothermal growth kinetics of a cluster of ZnO nanowires are studied based on optical in situ growth monitoring. The growth yields are orders of magnitude higher than those of conventional hydrothermal methods that use bulk heating. This remarkable improvement is attributed to suppression of precursor depletion occurring by homogeneous growth reactions, as well as to enhanced mass transport. The obtained in situ data show gradually decaying growth kinetics even with negligible precursor consumption. It is revealed that the growth deceleration is caused by thermal deactivation resulting from heat dissipation through the growing nanowires. Finally, it is demonstrated that the tailored temporal modulation of the input power enables sustained growth to extended dimensions. These results provide a key to highly efficient use of growth precursors that has been pursued for industrial use of this functional metal oxide semiconductor. 相似文献
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Although the Arcan specimen has been used frequently for mixed-mode crack growth testing using single-axis servohydraulic test equipment, the specimen and its commonly-used fixturing have features and behaviors that have implications to the proper understanding of results garnered from their use. These implications extend to hardware issues as well, as the Arcan specimen (when mounted at off-axis angles) can generate significant and even potentially damaging side loads on the load frame actuator. This paper discusses a number of the issues associated with the Arcan specimen and Arcan testing. 相似文献
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Jiang Bo Xu Li Chen Wei Zou Chao Yang Yun Fu Yunzhi Huang Shaoming 《Nano Research》2017,10(10):3509-3521
AgNO3 is often used in the preparation of Au nanostructures since Ag-based substances (AgBS) can selectively be adsorbed on Au(100) and significantly modulate the growth of Au nanocrystals.High-index-faceted Au nanostructures have demonstrated excellent performance in catalysis and surface enhanced Raman scattering (SERS),thus attracting the interest of many researchers in the past several decades.Herein,high-index-faceted Pd@Au concave nanocubes (CNCs) were prepared using AgBS as growth-directing agents in the heterogeneous growth of Au on Pd nanocubes (NCs).During the growth of Pd@Au CNCs,Au atoms are initially deposited on the Pd{100} facets leading to the formation of thin Au shells,and then AgBS are quickly adsorbed on the formed Au(100),favoring the growth along 〈111〉 and the formation of Pd@Au CNCs.Transmission electron microscopy (TEM),high resolution transmission electron microscopy (HRTEM),energy dispersive spectroscopy (EDS),high angle annular dark field (HAADF),and scanning transmission electron microscopy EDS (STEMEDS) were used to systematically investigate the growth of Pd@Au CNCs.We also demonstrated that the high-index-faceted Pd@Au CNCs exhibited excellent SERS performances. 相似文献
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G. Feuillet F. Widmann B. Daudin J. Schuler M. Arlery J. L. Rouvi re N. Pelekanos O. Briot 《Materials Science and Engineering: B》1997,50(1-3):233-237
The epitaxial growth of both cubic and hexagonal GaN epilayers is considered here with the aim of comparing their physical properties. In particular, the growth mechanisms at the first stages of growth will be dealt with together with the quality of the growth front. The optical characteristics of the epilayers will be compared by reference to the structure of the defects present within the different types of layers. 相似文献
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添加剂对纳米AlOOH晶体生长形态的影响 总被引:2,自引:0,他引:2
采用多种添加剂,通过控制添加的剂量,实现了片状、须状、块粒状纳米AlOOH在中性环境下的可控制备,打破了原来的必须在酸性环境下制备纳米AlOOH晶须,以及在碱性环境下制备片状纳米AlOOH的常规,建立了中性环境制备各种形貌的纳米AlOOH的新方法。用扫描电镜、透射电镜以及X射线衍射仪,分析了实验样品的形貌特点和晶体结构特点。运用结晶动力学理论解释了AlOOH晶体生长取向及晶体生长形态聚集方式,揭示了晶体的最终形貌与生长过程中的生长基元的内在联系。 相似文献
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Mixed mode fatigue crack growth: A literature survey 总被引:13,自引:0,他引:13
The applications of fracture mechanics have traditionally concentrated on crack growth problems under an opening or mode I mechanism. However, many service failures occur from growth of cracks subjected to mixed mode loadings. This paper reviews the various criteria and parameters proposed in the literature for predictions of mixed mode crack growth directions and rates. The physical basis and limitations for each criterion are briefly reviewed, and the corresponding experimental supports are discussed. Results from experimental studies using different specimen geometries and loading conditions are presented and discussed. The loading conditions discussed consist of crack growth under mode II, mode III, mixed mode I and II, and mixed mode I and III loads. The effects of important variables such as load magnitudes, material strength, initial crack tip condition, mean stress, load non-proportionality, overloads and crack closure on mixed mode crack growth directions and/or rates are also discussed. 相似文献
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Dapeng Wu 《Materials Letters》2009,63(12):1057-1060
Unique ZnO microcrystal composed of hierarchical nanorod arrays was successfully prepared by a surfactant-free process in aqueous solution under moderate temperature. The products were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The as-prepared ZnO microstructures are of hexagonal phase and high purity. On the basis of SEM images and parallel experiments, a possible formation mechanism for this ZnO microcrystal with hierarchical nanorod arrays is proposed and the reaction temperatures are found to have great influence on inducing secondary nucleation and the hierarchical growth. In addition, the optical properties of the ZnO samples were also investigated by the photoluminescence (PL) spectrometer. 相似文献
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钛合金中TiC晶体的配位多面体生长基元与生长习性 总被引:3,自引:0,他引:3
铸造钛合金中存在八面体、棱面枝晶及光滑树枝晶等不同形态的TiC.本文结合定向凝固试样组织,用配位多面体理论分析了钛合金中TiC的生长基元及生长习性.认为TiC的配位多面体生长基元为六配位的TiC6,TiC6生长基元堆积时, {100}面族和{111}面族上的生长速率不同,容易形成以{111}面为显露面的八面体状TiC晶胚.TiC晶胚在熔体中生长时,在生长速率最快的<100>方向上生长出二次枝晶臂,并在生长过程中始终保持小面界面生长特征,最终形成棱面枝晶状TiC.如TiC晶体生长时生长速率慢的面族上形成大量的螺旋位错等缺陷,则棱面消失,形成树枝晶TiC. 相似文献
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本文应用 PBC 理论证实了 MC 碳化物从 Ni 基高温合金熔体中生长的理想形貌是以{111}面为外表面的八面体.认为 MC 的一种生长基元为由金属原子和周围六个碳原子组成的八面体配位体,在近平衡条件下MC 碳化物的晶体生长机制是该配位体沿晶体的{111}面层状生长. 相似文献