N5基体与NiCrAlY粘结层界面元素互扩散行为研究

采用EB-PVD技术在镍基合金ReneN5基体表面沉积NiCrAlY粘结层,并对试样进行1000℃不同时间的恒温氧化处理,通过SEM、EDS、XRD研究了基体与粘接层界面元素互扩散行为和反应区的形成机制。结果表明:在1000℃条件下,NiCrAlY粘结层中的Al、Cr元素会向N5基体扩散,形成以β-NiAl和α-Cr相为主的互扩散反应区;而N5基体中的Ni元素则会向NiCrAlY粘结层扩散,形成以γ′-Ni_3Al相为主的二次反应区和以难熔金属为主的TCP相。     

Large electrocaloric effect with ultrawide temperature span in Na1/2Bi1/2TiO3-based lead-free ceramics

Innovative cooling technologies are recognized by many industries as a crucial part of their system design. A large electrocaloric effect (ECE) and extended working temperature are the key issues hindering the realization of electrocaloric refrigeration technology. In this work, large ECE (ΔT = 0.8–0.9°C @ 4 kV/mm) with an ultrawide temperature span from 30 to 120°C is noted for lead-free (Na_1/2Bi_1/2)_0.80Sr_0.20(Zn_1/3Nb_2/3)_xTi_1-xO₃ ceramics. The excellent ECE performance can be ascribed to the evolution of polar nanoregions. Our work suggests that this material is promising for applications in solid-state refrigeration systems with a broad range of operating temperatures.     

Achieving both high electromechanical properties and temperature stability in textured PMN-PT ceramics

Textured piezoelectric ceramics, such as textured Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT) ceramics, have attracted considerable attention from both academia and industry, as they possess crystal-like piezoelectric properties, high composition homogeneity, and low manufacturing cost. However, the main difficulty with the textured piezoelectric ceramics is the presence of BaTiO₃ (BT) templates, which greatly reduces their piezoelectricity and phase transition temperature. Thus, it is highly recommended to fabricate textured piezoelectric ceramics using as few templates as possible. Here, we successfully fabricated high-quality <001>-textured PMN-28PT ceramics (texturing degree of 99%) by using an extremely small amount of BT templates (1 vol.%) with the help of CuO/B₂O₃ sintering aids. The textured PMN-28PT ceramic exhibits 80% piezoelectric coefficient (d₃₃ ∼ 1200 pC/N), 96% electromechanical coefficient (k₃₃ ∼ 88%) and the same temperature stability (T_rt ∼ 100, T_c ∼ 150°C) when compared to its single crystal counterpart. In addition, by using an alternating current electric field poling (AC-poling), the piezoelectric coefficient d₃₃ and dielectric permittivity ε₃₃ of the textured PMN-28PT ceramics were further enhanced around 5–8%. It is believed that the advantages of high electromechanical properties, low cost, and easy mass production of textured PMN-28PT ceramic will make it a promising candidate for advanced electromechanical devices.     

反渗透膜污染原因分析及清洗技术在电厂的应用

反渗透膜污染常见于电厂锅炉补给水处理系统.针对某电厂2套反渗透装置发生的污堵,分析了污堵情况,体现在一段压差增大和流量下降;利用探针试验和化学测定的方法确定了污染物类型,主要为微生物污染、金属氧化物和胶体污染,并分析了污染原因.采用非氧化性杀菌剂清洗和碱洗相结合的清洗方法,对反渗透膜进行了化学清洗.详细描述了清洗流程及工艺控制要点,对清洗前后数据进行分析,清洗后一段压差下降至清洗前的50％,恢复至0.08～0.11 MPa,进水流量和产水流量分别提高了26％和27.5％,达到了理想的清洗效果.     

臭氧氧化动力学模型及反应器建模研究进展

臭氧化技术可以实现对有机污染物的有效去除,同时兼具绿色环保、工艺流程简单等特点而被广泛应用,而臭氧化模型的构建可以实现对污染物减排的有效预测,对于臭氧化处理污水的工程应用意义重大。本文介绍了臭氧化技术的基本原理,并着重综述了臭氧氧化的动力学模型和反应器建模的研究进展。在臭氧氧化模型的建立中,臭氧的传质和反应是两个最重要的因素。本文首先讨论了臭氧的传质过程,并对其气液两相模型进行了阐述。然后针对忽略臭氧传质的液-液或液-固体系,并根据反应机理,分别总结了常规臭氧氧化、均相催化臭氧氧化和非均相催化臭氧氧化的动力学模型。在充分研究了臭氧氧化的动力学模型后,将其应用到具体反应器的建模中,并总结出模型建立的基本假设。最后指出现有模型存在的一些问题并给出相关的建议,提出臭氧化模型构建的出处是优化工业反应器,实现工程应用。     

烷基铝/氢化铝锂还原体系还原液体端羧基氟橡胶

采用两种还原体系二异丁基氢化铝（DIBAl-H）/氢化铝锂（LiAlH4）和三异丁基铝[Al（i-Bu）3]/LiAlH4,将液体端羧基氟橡胶（LTCFs）还原得到液体端羟基氟橡胶（LTHFs）。傅里叶转换红外光谱、核磁共振氢谱和核磁共振氟谱分析均表明,两种还原体系均能将LTCFs中的碳-碳双键和羧基分别还原成碳-碳单键和和羟基。进一步对比两种还原体系的还原能力发现,DIBAl-H/LiAlH4更适合还原LTCFs,且在反应温度为60 ℃、反应时间为8 h、羰基/LiAlH4/DIBAl-H物质的量比为1/1/2的最优条件下LTCFs的还原率可达到88%。与传统强还原剂LiAlH4相比,DIBAl-H/LiAlH4可降低反应温度,且减小还原剂用量。     

MAX7219在带清零与置数功能的增量式光电码盘中的应用

介绍了用高性能八位串行接口LED驱动芯片MAX7219,实现带置数与清零功能的增量式光电码盘静态显示。机上系统采用AT89C51实现码盘清零与置数功能,软件设计实现分、秒的六十进制压缩BCD码加、减运算;机下系统采用AT89C2051控制MAX7219串行驱动7位共阴极数码管,显示从串行接口接收到的码盘位置检测角度值。     

基于 FPGA 的多通道温度采编装置设计

针对飞行试验中对设备温度测量的需求,设计了一种适用于飞行测试的高精度多通道温度采编装置。设计以FPGA构建信号采集处理系统,采用AD8227和AD590来实现信号的调理和温度冷端补偿,通过标准RS422协议实现16路温度信号传输,并采取线性拟合的方式对输出进行非线性校正,提高了系统准确率和稳定性。测试结果表明,测温电路全量程内最大测量误差为±0.083%F.S.。经过测试验证,该方案传输过程无丢帧零误码,系统运行高效、可靠。     

基于时效性的Web页面个性化推荐模型的研究

Internet的快速增长导致了对个性化服务需求急剧增加。该文通过分析个性化挖掘的特点,提出了基于时效性的Web页面个性化推荐模型。该模型的挖掘算法在FP-Tree的存储结构上加入时效价值系数,并进行增量挖掘。通过实验证明,该模型挖掘出来的信息,能够更好地符合用户的真实需求。