晶体锗切削温度场的理论建模及数值模拟

针对晶体锗切削加工过程,首先采用热源法及温度叠加原理建立了切削温度场的理论数学模型。然后运用MATLAB软件分别计算出切削速度分别为1.5、2.0、2.5m/s,进给量分别为0.02、0.025mm/r时工件在剪切变形区的温度场,分析了不同切削速度、不同进给量下的温度变化。最后,采用DEFORM-3D软件进行三维切削仿真分析,获得了不同切削参数下工件温度场的云图。计算结果与仿真结果表明:切削速度与进给量的增大会导致切削温度的升高,刀具与工件开始接触时,切削温度、进给量与时间呈线性急剧增加,但温度升高到一定值后会保持相对稳定。相同增量下,进给量对切削温度的影响大于切削速度。不同切削速度和进给量下的仿真结果与理论计算结果误差均小于10%。     

协同萃取锗和镓工艺中反萃取锗的改进研究

本文针对作者早先研究成功的“电锌厂回收铟锗镓新工艺”存在的不足之处即反萃取锗进行了研究.着重研究了一种新的反萃取剂——AN-64,并给出了可供选择采用的两条从反萃液中回收锗的工艺路线.本方法既克服了 HF 反萃法有毒、腐蚀性强、需二次萃取富集且从反萃液回收锗困难以及氨水及反萃取法反萃率低的缺点,同时也保持了 HF 反萃取法反萃率高和氨水反萃取法无毒、腐蚀性小、不需二次富集且从反萃液中回收锗容易的优点,是一种比较成功的反萃取锗的新方法.     

单晶锗微结构的超声振动辅助微切削加工

为解决单晶锗微结构元件超精密金刚石切削加工的技术难题,提出采用超声振动辅助切削技术提高单晶锗的临界未变形切屑厚度,并推导了微结构切削中切屑厚度的理论计算公式. 进行微圆弧金刚石刀具的振动辅助微切削实验,研究临界未变形切屑厚度随振幅的变化规律,分析微槽表面加工质量和切屑形貌等. 分析4.5 μm和10.0 μm深的十字槽、矩形凸台等微结构的加工质量,针对微槽边缘的加工损伤问题,采用“切深递减”同时结合横向进给的工艺方法. 实验结果表明:微槽切削中切削深度的理论计算值存在较大的误差,应选用直接测量法;振动辅助切削的临界未变形切屑厚度随着振幅的增加而增大,最高达到了704 nm,是普通切削深度的5.2倍. 与普通切削相比,振动辅助加工可以在一定程度上降低微槽表面粗糙度. 采用振动辅助微切削技术能够在大切深条件下加工出具有较高表面质量和轮廓精度的微结构,能够有效解决微槽侧面加工损伤问题,微槽表面粗糙度R_a值低至3.09 nm.     

基于划刻实验的单晶锗材料去除机理研究

采用Cube压头对单晶锗进行变载与恒载纳米划刻实验, 利用扫描电子显微镜和原子力显微镜对已加工表面进行观测, 根据表面形貌将划刻过程分为延性域、脆塑转变域及脆性域三种, 对各个阶段的表面成型及材料去除方式进行了研究。使用最小二乘法对不同阶段划刻力进行非线性拟合, 并利用相关系数检验拟合函数可靠性, 结果表明划刻力与划刻深度存在强相关性。同时分析了单晶锗的弹性回复率随划刻距离的变化趋势, 结果表明工件的弹性回复率将从纯弹性阶段的1逐步回落至0.76左右。基于脆塑转变临界载荷, 以裂纹萌生位置作为脆塑转变标志, 首次结合工件已加工表面弹性回复, 提出一种适用于计算单晶锗的脆塑转变临界深度模型, 其脆塑转变临界深度为489 nm。     

Fast,Scalable Synthesis of Micronized Ge3N4@C with a High Tap Density for Excellent Lithium Storage

Nanostructuring has significantly contributed to alleviating the huge volume expansion problem of the Ge anodes. However, the practical use of nanostructured Ge anodes has been hindered due to several problems including a low tap density, poor scalability, and severe side reactions. Therefore, micrometer-sized Ge is desirable for practical use of Ge-based anode materials. Here, micronized Ge₃N₄ with a high tap density of 1.1 mg cm⁻² has been successfully developed via a scalable wet oxidation and a subsequent nitridation process of commercially available micrometer-sized Ge as the starting material. The micronized Ge₃N₄ shows much-suppressed volume expansion compared to micrometer-sized Ge. After the carbon coating process, a thin carbon layer (≈3 nm) is uniformly coated on the micronized Ge₃N₄, which significantly improves electrical conductivity. As a result, micronized Ge₃N₄@C shows high reversible capacity of 924 mAh g⁻¹ (2.1 mAh cm⁻²) with high mass loading of 3.5 mg cm⁻² and retains 91% of initial capacity after 300 cycles at a rate of 0.5 C. Additionally, the effectiveness of Ge₃N₄@C as practical anodes is comprehensively demonstrated for the full cell, showing stable cycle retention and especially excellent rate capability, retaining 47% of its initial capacity at 0.2 C for 12 min discharge/charge condition.     

Influences of vacancy defects on thermal conductivities of Ge thin films

The effects of vacancy defects on the thermal conductivity of Ge thin films were investigated by employing molecular dynamics(MD) simulations and theoretical analysis based on the Boltzmann equation.Both the MD and theoretical results show that the lattice thermal conductivity dramatically decreases with the increasing of vacancy concentration at 400 and 500 K.In addition,the dependence of vacancy concentration on the thermal conductivity of Ge thin films becomes less sensitive as the temperature increases.Theoretical results also confirm that the major part of the lattice thermal conductivity reduction is associated with the point-defect scattering and phonon-phonon scattering processes.     

In‐situ Observations of Nanoscale Effects in Germanium Nanowire Growth with Ternary Eutectic Alloys

Vapour‐liquid‐solid (VLS) techniques are popular routes for the scalable synthesis of semiconductor nanowires. In this article, in‐situ electron microscopy is used to correlate the equilibrium content of ternary (Au_0.75Ag_0.25–Ge and Au_0.65Ag_0.35–Ge) metastable alloys with the kinetics, thermodynamics and diameter of Ge nanowires grown via a VLS mechanism. The shape and geometry of the heterogeneous interfaces between the liquid eutectic and solid Ge nanowires varies as a function of nanowire diameter and eutectic alloy composition. The behaviour of the faceted heterogeneous liquid–solid interface correlates with the growth kinetics of the nanowires, where the main growth facet at the solid nanowire–liquid catalyst drop contact line lengthens for faster nanowire growth kinetics. Pronounced diameter dependent growth kinetics, as inferred from liquid–solid interfacial behaviour, is apparent for the synthesised nanowires. Direct in‐situ microscopy observations facilitates the comparison between the nanowire growth behaviour from ternary (Au–Ag–Ge) and binary (Au–Ge) eutectic systems.     

非对称面电极硅基锗金属-半导体-金属光电探测器的设计

针对金属-半导体-金属(MSM)光电探测器暗电流抑制的机理,本文提出了一种具有非对称面电极结构的硅基锗MSM光电探测器的设计方法,利用ATLAS仿真软件分析了电极结构参数对暗电流的影响,并通过实验得出样品器件的暗电流降低至微安量级。实验结果表明,采用非对称面电极结构设计可以有效抑制硅基锗MSM光电探测器的暗电流,提高器件性能。