单晶炉勾形磁场装置结构参数的分析与优化

采用有限元法对203.2 mm单晶炉(406.4 mm坩埚)勾形磁场线圈匝数和线圈纵横向层数(纵横向层数比值)以及上下两线圈间距、磁屏蔽体的厚度以及几何结构和尺寸等结构参数对磁场强度Br的影响进行了模拟分析和优化选取.为203.2 mm单晶炉勾形磁场装置结构设计提供了一种可靠的模拟新方法和具有指导意义的经验数据.     

热屏结构对泡生法蓝宝石单晶炉功率影响研究

蓝宝石晶体因优异的综合性能被广泛用于航空航天等高性能要求领域.泡生法是目前生产大直径蓝宝石单晶的主要方法,热场对生产工艺、产品质量和单晶炉功率具有重要影响;并将影响生产成本.本文对氧化锆及钼金属组合式热屏中氧化锆材料内置、外置及材料不同组合方式对泡生法蓝宝石单晶炉功率的影响进行研究,得到合理的热场结构;并与实际生产结果进行验证.结果表明:相比于传统的15层钼保温结构,加入氧化锆保温层会明显降低单晶炉能耗,其中氧化锆内置的热场结构对单晶炉能耗降低影响更为明显;随着氧化锆层由0增加至15层,单晶炉能耗显著降低,相比传统15层钼保温结构,15层氧化锆保温结构炉体功率降低了38;.     

单晶炉低功耗勾形磁场设计与实现

以单晶炉低功耗勾形磁场为研究对象,采用有限元法对主要结构参数进行了模拟分析与优化设计.并对磁场优化设计参数进行了实验验证.结果表明:磁场分布、磁场纵、横向分量强度,以及线圈电压、线圈电流、线圈功率等关键参数的实验结果均满足设计要求;实验结果与模拟结果相吻合,其平均误差小于5;;这说明模拟方法是正确的,结果符合实际、可运用于实际设计.该研究为低功耗勾形磁场设计以及广泛应用提供了一种可靠的模拟方法和经验数据.     

单晶炉低功耗勾形磁场设计与优化

本文提出了一种低功耗的新勾形磁场结构,来解决现有勾形磁场功耗过大的问题.并以8英寸单晶炉勾形磁场为研究对象,利用有限元法对线圈匝数、电流大小、线圈间距等参数对磁场强度及其分布的影响进行了模拟分析和优化设计.结果表明:在坩埚壁处产生横向磁场强度均为492 GS时,线圈内径820 mm、线圈间距200 mm等结构相同,而线圈匝数分别为2400匝的新结构与96匝的现有结构磁场相比,总功率从现有结构的38.9 kW降低到9.8 kW(降低了74.7;).该研究为勾形磁场得以广泛应用提供了一种新的设计思路及设计方法.     

单晶炉横向磁场的优化设计与实现

本文利用有限元法对152.4 mm(6 inch)单晶炉355.6 mm(14 inch)坩埚横向磁场的磁场强度、磁场分布和均匀度,以及线圈匝数、铁芯半径、导线截面积、磁极宽度和高度等影响因素进行了模拟分析和优化.在此基础上得到了磁场的优化参数,并对优化设计参数进行了实验验证.结果表明:模拟方法合理,结果正确、符合实际,可运用于实际设计.为磁场设计提供了一种可靠的模拟新方法和经验数据.     

直拉法单晶炉随动式加热器设计

单晶炉是一种在以高纯氩气为主的惰性气体环境中,用石墨热场加热,将多晶硅材料加以熔化,用直拉法生长单晶硅的设备,在太阳能单晶硅拉制的过程中,如何提高拉晶的速度和质量以及降低设备的能耗一直是单晶硅厂家永恒的追求。本文从机械结构的角度分析了坩埚上升在单晶炉拉晶过程中所造成的拉晶速度下降和额外能耗问题,在此问题的基础上提出了一种加热器随坩埚在拉晶过程中上升的单晶炉结构优化方法,并通过有限元仿真对单晶炉优化前后晶体和熔体的热场以及拉晶过程中加热器功率进行分析。结果表明,改进后的单晶炉不仅可以提高拉晶过程的稳定性和拉晶速度,从而进一步提高单晶炉的拉晶质量和产量,而且还能有效降低单晶炉拉晶的能耗。     

泡生法生长蓝宝石单晶的热场改进与模拟优化

在泡生法蓝宝石单晶生长中,单晶炉内的热场对晶体质量至关重要.本文首先对单晶炉的顶部热屏、环形加热器和炉底保温进行了改进,然后结合计算机数值模拟,对热场改进前、后晶体的轴向和径向温度梯度、晶体表面温度分布、加热器功率等进行分析对比.结果表明:改进后的倾斜热屏增强了单晶炉内的辐射传热,对已生长出的晶体起到了后热作用,降低了晶体内的热应力;对加热器和底部钼保温层的改进,减小了加热器与坩埚间的热阻,增强了炉内的保温作用,使加热功率降低了约8%.     

热屏间距对泡生法蓝宝石单晶生长影响研究

太空、军事和科研等高科技领域的持续发展极大促进了对蓝宝石晶体的需求,泡生法是蓝宝石晶体的主要制造方法之一;热场结构对所得蓝宝石晶体的质量具有重要影响.本文对采用泡生法工艺制造蓝宝石单晶过程中,具有内置7层氧化锆外置8层钼金属的新型热屏结构间距进行研究.通过数值模拟考察热屏间距对单晶炉功率、固-液界面形状和晶体热应力的影响确定了合理的热场结构;并与试验生产结果进行对比验证.结果表明:热屏间距增大使得单晶炉功率明显提升,并引起固-液界面凸度增大;而蓝宝石晶体热应力出现减小.综合考察三个影响因素的影响,最后确定热屏间距为5 mm时单晶炉能耗较低,可用于制造高质量的蓝宝石晶体.     

旋转对Cz法硅晶生长过程中热输运和熔体流动影响的数值模拟

建立了一个120 kg单晶炉的二维轴对称全局模型,分别对无旋转、加入晶体旋转、加入坩埚旋转、同时加入晶体旋转和坩埚旋转的四种工况展开了数值模拟研究.得到了晶体旋转及坩埚旋转对晶体生长过程的拉晶功率、炉内温度分布和熔体流动的影响;得到了不同晶体长度下拉晶炉内的温度分布以及熔体流动的变化规律.结果显示,加入晶体旋转对晶体生长过程的拉晶功率、温度分布和熔体流动的影响小于坩埚旋转的影响;随着晶体长度的增加,晶体旋转及坩埚旋转对温度分布和熔体流动的影响不断减小.因此在单晶炉设计和优化过程中应考虑整个晶体生长过程.     

一种勾形磁场新磁屏蔽体优化设计与分析

本文在勾形磁场现有磁屏蔽体的基础上,提出一种新的磁屏蔽体结构,并以8寸单晶炉新型磁屏蔽体结构的勾形磁场为研究对象,对其进行了模拟分析及优化设计.结果表明:安匝数一定的情况下(33600),采用新型磁屏蔽体的勾形磁场较现有勾形磁场的磁场强度Br,提高了约27.03;;当坩埚侧处产生横向磁场强度均为491Gs时,其功耗下降了约35.97;;该研究为进一步降低功耗提供了一种设计思路及设计方法.     

Relationship of Morphological Types of Dynamic Forms of Crystals

Crystallography Reports - The relationship of morphological spectra (sets of data on the morphological types of real polyhedral crystals and their probabilities under current physicochemical...     

Development of Pauling's concepts of geometric characteristics of atoms

The evolution of the geometric characteristics introduced by Pauling and their dependence on the specific features of the structure and chemical bonds have been considered. The values of the covalent and van der Waals radii are given as well as their relationships and mutual transitions.     

A review of measurement of thermophysical properties of silicon melt

Measurements of thermophysical properties of Si melt and supplementary study of X-ray scattering/diffraction by the authors' group were reviewed. The values obtained differed variously from those of literature. Density was 2–3% larger, surface tension 20–30% smaller, viscosity up to 40% larger, electrical conductivity 8% smaller, spectral emissivity more or less in good agreement with literature values, and thermal diffusivity a few percent larger. An anomalous density jump was found near the melting point. Surface tension and viscosity also showed anomaly. A strange time-dependent change of density was observed over 3 h after melting. X-ray analyses suggested a slight change in local atom ordering, but showed no sign of cluster formation. An addition of 0.1 at% gallium caused the density jump to disappear, while that of boron caused no change. An EXAFS study of the former melt indicated a strong interaction between Ga and Si atoms as if molecules of GaSi₃ existed. The implications of the measured properties are a possibility of soft-turbulence in an Si melt in a relatively large crucible, a more complicated manner of intake of oxygen depleted molten Si from the free surface region to underneath the growing crystal, and a relaxation of the melt after melting arising from trapped gas species.     

A SAXS study of kinetics of aggregation of silica sols

SAXS in situ experiments on the evolution of TMOS solutions during hydrolysis and polycondensation lead to power laws with scaling exponents ≈ 2. It is suggested that this could be the result of the polydispersity of the samples and that only an apparent fractal dimension can be obtained in this way. Kinetic studies tend to indicate that agglomeration in the sol is the result of a diffusion-controlled process.     

Generation of crystal structures of heteromolecular compounds by the method of discrete modeling of packings

Within the method of discrete modeling of packings, an algorithm of generation of possible crystal structures of heteromolecular compounds containing two or three molecules in the primitive unit cell, one of which has an arbitrary shape and the other (two others) has a shape close to spherical, is proposed. On the basis of this algorithm, a software package for personal computers is developed. This package has been approved for a number of compounds, investigated previously by X-ray diffraction analysis. The results of generation of structures of five compounds—four organic salts (with one or two spherical anions) and one solvate—are represented.     

Study of the possibility of interactive control of the surface profile of X-ray optical elements

We investigate the possibility of controlling the curvature parameters of parabolic mirrors that are modular elements of two types consisting of a base and thin inserts placed at the opposite side of the work surface. In the first type of modular elements, bending is controlled by the difference in the coefficients of the thermal expansion of the base and inserts. In the second type of elements, the profile is changed by the piezoelectric straining of the inserts under an electric field. A correlation is established between the parameters of modular elements and their surface curvature profile.     

Investigation of the Mechanism of Influence of Stress Corrosion on the Development of Macroplastic Instabilities of Aluminum–Magnesium Alloy

Crystallography Reports - Macroscopic jumps of plastic deformation (few percent in amplitude) on creep curves of aluminum–magnesium alloy, caused by a local effect of concentrated solution of...     

Mechanism of thermal expansion of structural modifications of zinc pyrovanadate

Crystal chemical characteristics of the α and β modifications of Zn₂V₂O₇ are calculated based on in situ high-temperature X-ray measurements. The expansion of the structure is found to be strongly anisotropic up to the negative volumetric thermal expansion of the α-Zn₂V₂O₇ unit cell in the temperature range of 300–600°С, α _V =–17.94 × 10^–6 1/K. The transformations of the “hard” and “soft” sublattices with an increase temperature and at the phase transition are considered in detail. It is shown that the negative volumetric thermal expansion of α-Zn₂V₂O₇ is due to the degeneracy of the zigzag-like shape of zinc–oxygen columns at constant distances between their vertices.     

Dependence of the parameters of equations of viscous flow on chemical composition of silicate melts

The temperature dependence of viscosity of silicate melts is discussed in the framework of the Avramov–Milchev (AM) equation. The composition is described by means of two parameters: the molar fraction, x, and the “lubricant fraction”, l. The molar fraction is the sum of the molar parts x_i of all oxides dissolved in SiO₂, the molar fraction of the latter being 1 ? x. It is shown that, with sufficient precision, two of the parameters of the AM equation can be presented as unique functions of the molar fraction. On the other hand, x is not sufficient to determine properly the reference temperature T_r , at which viscosity is η_r = 10¹³ [dPa.s]. Therefore, additional parameter, “lubricant fraction” l, is introduced. For each of the components, l_i is a product of molar part x_i and a specific dimensionless coefficient 0 ≤ k_i ≤ 1 accounting for the specific contribution of this component to the increased mobility of the system. It is demonstrated that, for l > 0, the reference temperature is related to the “lubricant fraction” l through the reference temperature T_r,SiO2 of pure SiO₂.     

Comparative analysis of two methods of calculation of the orientation of domain walls in ferroelastics

Two types of domain-wall equations are analyzed: the equations derived by the Sapriel method and the equations obtained by interface matching of the thermal-expansion tensor. It is shown that, for W-type domain walls, these methods yield the same equations. For W′-type domain walls, the equations obtained by different methods coincide for proper ferroelastics and differ for improper ferroelastics.