Tailoring Magnetic Properties of MAX Phases,a Theoretical Investigation of (Cr2Ti)AlC2 and Cr2AlC

(Cr₂Ti)AlC₂ is a newly discovered MAX phase with ordered occupations of Ti and Cr atoms on M sites. The Cr‐containing MAX phase is expected showing magnetic property, which provides functional applications in spintronics and as self‐monitoring smart coating. The magnetic states of (Cr₂Ti)AlC₂ are predicted by GGA and GGA + U methods and compared to those of Cr₂AlC. The ground states are predicted as FM or AFM‐XX configurations depending on the calculation methods. Analysis of the electronic structure shows that the magnetic moments mainly originate from the net spins of Cr 3d valence electrons, whereas the contribution of other atoms is negligible. The calculated magnetic moments of Cr atoms in (Cr₂Ti)AlC₂ are higher than those in Cr₂AlC due to the larger distance between the out‐plane Cr atoms separated by the intercalated nonmagnetic Ti–C slab. This work provides an insight on tailoring magnetic properties of MAX phases by modifying the crystal structure.     

High‐Temperature Neutron Diffraction,Raman Spectroscopy,and First‐Principles Calculations of Ti3SnC2 and Ti2SnC

Herein, we report—for the first time—on the additive‐free bulk synthesis of Ti₃SnC₂. A detailed experimental study of the structure of the latter together with a secondary phase, Ti₂SnC, is presented through the use of X‐ray diffraction (XRD), and high‐resolution transmission microscopy (HRTEM). A previous sample of Ti₃SnC₂, made using Fe as an additive and Ti₂SnC as a secondary phase, was studied by high‐temperature neutron diffraction (HTND) and XRD. The room‐temperature crystallographic parameters of the two MAX phases in the two samples are quite similar. Based on Rietveld analysis of the HTND data, the average linear thermal expansion coefficients of Ti₃SnC₂ in the a and c directions were found to be 8.5 (2)·10^?6 K^?1 and 8.9 (1)·10^?6 K^?1, respectively. The respective values for the Ti₂SnC phase are 10.1 (3)·10^?6 K^?1 and 10.8 (6)·10^?6 K^?1. Unlike other MAX phases, the atomic displacement parameters of the Sn atoms in Ti₃SnC₂ are comparable to those of the Ti and C atoms. When the predictions of the atomic displacement parameters obtained from density functional theory are compared to the experimental results, good quantitative agreement is found for the Sn atoms. In the case of the Ti and C atoms, the agreement is more qualitative. We also used first principles to calculate the elastic properties of both Ti₂SnC and Ti₃SnC₂ and their Raman active modes. The latter are compared to experiment and the agreement was found to be good.     

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。     

单片机网络在智能化小区中的设计和应用

随着控制技术的发展，控制系统越做越复杂，由单片机构建的控制系统已经由一个单片机组成的系统发展到多个单片机组成的多机控制系统和多个单片机组成的网络系统。在工业监控和民用产品中单片机系统使用的越来越多。随着技术的发展和市场竞争的加剧，生产厂家除了考虑到产品的性能也要考虑到产品成本。Microehip公司的PIC16C57是一款性价比较高的单片机。由该单片机建立起来的系统成本大大降低。本文介绍了一种由PIC16C57单片机建立起来的分级总线型网络系统，系统可以用于工业系统监控和民用楼宇监控系统，该网络系统在硬件和软件上都采取了特别的保护措施，系统具有非常好的稳定性和可靠性。     

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.     

基于MAX262的可程控多频点带通滤波器的设计

基于可编程开关电容有源滤波器MAX262可通过改变外部时钟频率以及采用微处理器接口控制64级中心频率这一特性,给出了一种滤波器设计新方法,采用一个时钟频率,实现了多频点的带通滤波,WAVE仿真结果达到了设计的要求。     

便携式核仪器电源的设计

如何为便携式产品供电一直是备受关注的话题,各种新型的电池及电源管理器件的应用,为人们的生产生活带来巨大方便,在便携式仪器应用上,以可充电电池的应用较为广泛,但是在某些不方便充电的特殊应用场合,充电式电源的便利性就会受到限制,本文便是探讨如何利用可充电电池与传统的碱性干电池相结合,为便携式仪器供电.     

MAX1000控制系统仿真模型转换工具开发

介绍一种最新研制的MAX1000控制系统自动转换到STAR-90仿真支撑系统的转换软件.该软件具有开放、自动化程度高和简单易行的特点,可大大减轻仿真开发工作者的工作量,缩短仿真机研制周期,为DCS的仿真建模提供了一条新的途径.     

捷联IMU信号采集系统的集成化设计

针对传统的IMU信号采集系统尺寸大、成本高和集成度低等不足,介绍了以DSP为核心的集成式IMU信号采集系统的解决方案,详细阐述了系统硬件实现方案和软件实时误差校正算法.该系统具有速度快、体积小、功耗低等特点.     

基于MAX1452的压力传感器温度补偿

传感器精度是影响电-气比例调压阀性能的重要因素。以硅压阻式传感器为例,介绍传感器存在的温度误差,着重阐述采用MAX1452补偿其温度误差的原理,并系统介绍温度补偿的操作流程和校正系数的选择计算,通过实例分析验证压阻传感器经MAX1452补偿后,其温度误差可明显降低。