Carbon agent chemical vapor transport growth of Ga2O3 crystal

Beta-type gallium oxide (β-Ga₂O₃) is a new attractive material for optoelectronic devices. Different methods had been tried to grow high quality β-Ga₂O₃ crystals. In this work, crystal growth of Ga₂O₃ has been carried out by chemical vapor transport (CVT) method in a closed quartz tube using C as transport agent and sapphire wafer as seed. The CVT mass flux has been analyzed by theoretical calculations based on equilibrium thermodynamics and 1D diffusional mass transport. The crystal growth experimental results are in agreement with the theoretical predictions. Influence factors of Ga₂O₃ crystal growth, such as temperature distribution, amount of C as transport agent used, have also been discussed. Structural (XRD) and optical (Raman spectroscopy, photoluminescence spectrum) properties of the CVT-Ga₂O₃ crystal are presented.     

一种基于弹性理论的大采高区段煤柱合理尺寸计算方法

不同工况下区段煤柱两侧支承压力分布及岩体变形存在显著差异，考虑煤柱两侧不同支承压力对煤柱整体稳定性的影响，基于大采高区段煤柱的弹性力学计算模型，分析了支承压力下煤柱任一单元岩体的应力应变分量。通过建立大采高煤柱弹塑性界面上岩体的柱条模型，确定在0.65倍煤柱高度处单元岩体将首先发生水平拉伸破坏，利用虎克定律提出了该单元岩体极限拉应变与煤柱极限平衡区宽度的关系式。依据煤柱破裂区岩体的受力特征，运用摩尔库伦准则推导了煤柱破裂区宽度的计算公式。结果表明：(1)煤柱极限平衡区宽度与岩体极限拉应变和弹性模量反相关，与煤柱埋深和煤柱高度正相关；(2)煤柱高度及其与顶底板的界面摩擦角是影响破裂区宽度的关键性因素；(3)煤柱两侧不同工况下，煤柱岩体极限拉应变与其所受侧压呈正变关系，区段煤柱采空区侧所受侧压较巷道侧偏大，采空区侧岩体的极限拉应变也相应较大，表现为采空侧极限平衡区宽度较巷道侧偏小。最后，将上述理论公式应用于陕北某矿30109工作面大采高区段煤柱极限平衡区和破裂区宽度的分析计算，给出了该工作面两侧区段煤柱的合理宽度及其支护方案。工程应用表明，30109工作面区段巷道围岩变形控制效果良好，满足...