基于LabVIEW的电磁波峰焊测温系统

在电磁波峰焊接过程中波峰焊锡炉的温度对焊接质量影响很大,焊接之前必须进行温度测量。采用热电偶、MAX6675模块、Arduino控制器和计算机组成的温度测控系统对电磁波峰焊焊料的温度进行实时监控测量,并结合Lab VIEW将温度数据和温度变化曲线形象地展示出来,从而及时反馈温度变化数据,提高焊接质量。实验结果表明:测量所得的温度数据与预期值吻合。     

The {110} reflection in X‐ray diffraction of MXene films: Misinterpretation and measurement via non‐standard orientation

It has been claimed that disappearance of the {110} reflection in powder X‐ray diffraction of MXene films and powders is indicative of shearing or general disorder of restacking of the flakes. Here we show this to be incorrect and provide experimental justification. The disappearance of this peak arises from a combination of sample texture and orientation. Furthermore, our methods provide a simple way to estimate a unit cell parameters when the relevant reflections are not present in most reports of MXene films.     

High temperature physical and mechanical properties of large-scale Ti2AlC bulk synthesized by self-propagating high temperature combustion synthesis with pseudo hot isostatic pressing

The electrical, thermal, and mechanical properties as well as the effect of the temperature of large-scale Ti₂AlC bulk synthesized by self-propagating high temperature combustion synthesis with pseudo hot isostatic pressing were investigated in detail. With increasing temperature, the lattice defects contribute to the decreasing phonon thermal conductivity, and the electrical resistivity increases linearly from room temperature (RT) to 900 °C. The RT flexural strength, compressive strength, fracture toughness, work of fracture, and Vickers hardness were measured to be 606 ± 20 MPa, 1057 ± 84 MPa, 6.9 ± 0.2 MPa m^1/2, 158 ± 12 J/m², and 4.7 ± 0.2 GPa, respectively. With increasing temperature, the flexural and compressive strengths both keep almost unchanged in the zone of brittle failure, but decrease sharply as the plastic deformation occurs. The brittle-plastic transition temperature under flexure (900–950 °C) is higher than compression (700–800 °C). Interestingly, a non-catastrophic failure is observed in the SENB test, with the high work of fracture (158 ± 12 J/m²).     

Low-temperature diffusion bonding of Ti3Si(Al)C2 ceramic with Au interlayer

Herein, a reliable diffusion bonding of Ti₃Si(Al)C₂ ceramic is achieved by applying Au foil as an interlayer at 650 °C for 30 min with an axial pressure of 20 MPa. This novel method significantly decreases the bonding temperature, which is about 150 °C lower than the lowest bonding temperature from current research to the best of our knowledge. Maximum shear strength of 58 MPa is achieved at 650 °C among the bonding temperature range of 600 °C~800 °C. The microstructure evolution mechanism and the relationship between microstructure and mechanical property are discussed. The facile mutual diffusion of Au with de-intercalated Al and Si from Ti₃Si(Al)C₂ is considered critical in achieving sound interfacial bonding.     

Microstructural evolution during high-temperature oxidation of spark plasma sintered Ti2AlN ceramics

Microstructures of Ti₂AlN ceramics synthesized and simultaneously consolidated from starting mixtures of Ti/Al/TiN powders by spark plasma sintering (SPS) were characterized using X-ray diffraction, scanning electron microscopy, focused ion beam (FIB) and transmission electron microscopy (TEM). When sintered for 10 min at 1300 °C, nearly single-phase Ti₂AlN ceramics with elongated (∼22 × 6 × 6 μm) grains were obtained. After sintering for 10 min at 1200 °C and chemical etching, Ti₂AlN nanowhiskers (150-200 nm dia., 1-5 μm long) were exposed in pores coexisting with TiAl, TiN and Ti₂AlN grains. FIB-TEM studies revealed single-crystal Ti₂AlN nanowhiskers in a TiAl matrix with orientation relationship [1 1 −2 0]_H//[−1 0 1]_γ, (0 0 0 1)_H//(1 1 1)_γ, γ = TiAl, H = Ti₂AlN. The nanowhiskers are believed to form by diffusion of TiN into TiAl during SPS and to be exposed during the chemical etch. Microstructural development during high-temperature oxidation of dense Ti₂AlN ceramics for 1 h at <1200 °C involves gradual formation on the surface of layered microstructures containing anatase, rutile and α-Al₂O₃. After 1 h at >1200 °C, more complex layered microstructures containing Al₂TiO₅, rutile, α-Al₂O₃ and continuous voids layers form. After heating to 1100 °C for 1 h and cooling to room temperature, planar defects are observed in surface TiO₂ grains identified as stacking faults bounded by partial dislocations. After heating for 1 h at 1400 °C and cooling to room temperature, cracks propagate in TiO₂ grains. It is believed that planar defects and cracks arise from stress generation in the oxide scale. Thermal stresses formed on cooling may arise from thermal expansion mismatch of phases (TiO₂, Al₂O₃ and Al₂TiO₅) in the oxide scale, the high anisotropy of thermal expansion in Al₂TiO₅ and thermal expansion mismatch between the oxide scale and Ti₂AlN substrate. Growth stresses formed during the isothermal oxidation treatment may arise from the volume changes associated with oxidation reactions of Ti₂AlN. An oxidation mechanism for Ti₂AlN ceramics is proposed, which involves initial reaction with atmospheric oxygen to form oxide phases, demixing of the mixed oxide phases, void formation due to the Kirkendall effect and gaseous NO_x release. Oxidation of Ti₂AlN <1200 °C with 1 h hold times is limited, while above this temperature the oxide scale grows rapidly, and Ti₂AlN ceramics undergo heavy oxidation.     

基于嵌入式以太网的煤矿安全智能监控系统设计

针对煤矿安全存在的问题,设计了一种基于微控制器MAX7651和AX88796的嵌入式以太网智能监控系统,该系统不但有功能易于拓展、组态灵活的特点,而且具有很高的性价比,可很好地满足中小型煤矿安全监控的需要。     

一种新型快速的机器人三维图形仿真建模方法

以MOTOMAN-SV3X机器人为原型,在3DSMAX中进行机器人各部件的实体建模,编制了CpenGL导入3DSMAX模型文件的接口软件.借助OpenGL图形库,使用Visual C＋＋6.0编制了MOTOMAN机器人的图形仿真和控制软件.这种方法在PC机上可以快速建模并满足仿真形象逼真的要求.     

串行数据采集无线数据传输模块的设计

以AT89C2051单片机为核心,设计了一个用串行A/D转换器MAX1226进行数据采集,单片无线收发芯片PTR2000进行数据传输的模块,给出了硬件构成,软件设计及部分程序.该模块电路简单、使用方便,有采样精度高、可靠稳定、功耗低等优点,能较好地实现数据的串行采集和无线传输,应用在工业数据采集、工业控制、医疗监护等场合.     

MAX相Ti3SiC2管材在高温高压水和过热蒸汽中的腐蚀行为

MAX相材料有作为事故容错燃料(accident tolerant fuel,ATF)包壳材料的潜力,为了全面了解MAX相材料在模拟正常工况下的腐蚀行为,使用基体为Ti₃SiC₂的MAX相陶瓷管材于400℃/10.3 MPa过热蒸气,360℃/18.6 MPa去离子水、3.5μL/L Li+1000μL/L B溶液和70μL/L Li溶液4种不同的水化学条件中进行腐蚀试验,采用XRD、SEM和FIB/TEM观察分析腐蚀前后样品的显微组织、晶体结构和成分。结果表明,Ti₃SiC₂管材在4种条件下的腐蚀速率均远高于参比Zr-4合金,腐蚀后主要检测到腐蚀产物TiO₂,且其表面疏松多孔,未形成保护性的氧化膜。     

Medium-entropy (Ti,Zr, Hf)2SC MAX phase

Medium- and high-entropy alloys or ceramics for tuning the physicochemical properties of materials by the combination of multiple principal elements have received much interest. Herein, a medium-entropy (Ti, Zr, Hf)₂SC phase was synthesized attributing to the structural and chemical diversity of MAX phases. The crystal structure of (Ti, Zr, Hf)₂SC was determined by the Rietveld refinement of XRD, SEM, and atom-resolved TEM along with EDS elemental analysis. Phase evolution of X-ray diffraction patterns and TG/DSC curves were employed to reveal the synthesis mechanism of (Ti, Zr, Hf)₂SC from 2TiC–Zr–ZrC-2HfH₂-3.2FeS reactant system. The Vicker's hardness and the electrical resistivity of (Ti, Zr, Hf)₂SC were found higher than those of Ti₂SC, but the thermal conductivity of (Ti, Zr, Hf)₂SC was lower.