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。     

Perforative silica microsphere-modified phenolphthalein-based poly(arylene ether sulfone) composites: tensile and thermal properties

Perforative silica microspheres (PSMs) were prepared by an emulsion method coupled with sol–gel technology and phase separation. Next, phenolphthalein-based poly(arylene ether sulfone)/PSM composites (PES-C/PSM) were fabricated. PSM was characterized by scanning electron microscopy (SEM) and the Brunauer–Emmett–Teller (BET) method. The as-synthesized PSM exhibited a spherical shape with an external diameter of 2–10 µm, surface area of 166.5 m²/g and pore volume of 1.35 cm³/g. SEM and energy-dispersive spectroscopy (energy-dispersive spectroscopy) were used to characterize the morphology and the composition of the composite, respectively. Both SEM and energy-dispersive spectroscopy results revealed that the PES-C polymer chains penetrated into the PSM pores. In addition, the effect of PSM weight content on the mechanical properties and thermal stability of the composites was characterized by tensile tests and thermal analysis, respectively. A 19% increase in tensile strength and a 29% increase in breaking elongation of PES-C were achieved by the addition of 0.50 wt% PSM. Moreover, the thermal oxidative stability of PES-C was remarkably improved with the incorporation of PSM. Compared with pristine PES-C, the final degradation temperature was enhanced by 42 °C at 1.0 wt% PSM loading. Our studies have indicated that PSM is a kind of promising reinforcement for improvement of tensile and thermal properties of engineering plastics.     

径向柱塞泵配流轴受力平衡性分析

考虑高压油对配流轴所产生的侧倾力矩条件下,进行径向柱塞泵配流轴的平衡性分析.根据配流轴径向受力分析,运用Pro/E和MSC.Patran仿真软件辅助进行配流轴的对称平衡油槽设计.结果表明,配流轴的侧倾力矩直接影响到配流副的正常工作,增大对称平衡油槽的宽度能阻止配流副的摩擦磨损.     

新钢业公司耐侯窄带钢质量缺陷及改进

新钢业采用提钒后的半钢进行耐候窄带钢生产，在炉机不匹配、缺乏精炼手段、轧机能力小、除鳞设施简单和缺少控冷手段的情况下，通过工艺优化、技术改进，将冷弯弯裂、强度偏低、表面麻点等产品缺陷逐一解决，成功试制出符合用户要求和标准的产品。     

Fabrication and properties of degradable poly(amino acid)/nano hydroxyapatite bioactive composite

Poly(amino acid)/nano hydroxyapatite (PAA/n-HA) bioactive composite was prepared by in situ melting polymerization. The composition, structure and morphology as well as glass transition temperature (T_g), dynamic mechanical properties of the PAA/n-HA composite were characterized by infrared spectrometer, X-ray diffractometer, X-ray photoelectron spectroscopy, scanning electron microscope, differential scanning calorimeter, and dynamic mechanical analyzer. The results indicated that the n-HA particles were uniformly distributed into PAA matrix and some interactions were found at the interface between PAA and n-HA, and the crystallinity of PAA in the composite decreased with the increase of n-HA content. The T_g and storage modulus of the composite increased with increasing n-HA content, demonstrating that the n-HA content had obvious effects on the crystallization kinetic parameters and thermo properties of the PAA/n-HA composite. In addition, the n-HA amount had evident effects on the degradation of the PAA/n-HA composite in phosphate buffered saline (PBS), and the weight loss ratio of the composite decreased with the increase with n-HA content. The pH value of the medium was stable around 7.40 after the composite immersion into PBS for 8 weeks. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

温度传感器在高可靠性力矩电动机保护中的应用

主要介绍了为保证力矩电动机的可靠性,KTY84-130及PTC-130型温度传感器在高可靠性力矩电动机保护中的应用.