应用PLC对电动机自耦减压起动电路进行改造

采用耦变压器减压起动对电动机进行控制的技术,在大型电机控制中应用较多,但在控制技术上有不少地方需要改进,特别是用自耦变压器组成的起动控制箱,较容易出现超时起动和熔焊的问题.通过应用可编程控制器(PLC)对起动箱进行改造,对起动箱起动中可能存在的这些问题进行适当的处理,就可以避免故障的发生,提高自耦变压器减压起动的可靠性,使其能在实际中得到更好的应用.     

Transition Temperature of Bi_2Sr_2CaCu_2O_(8+x) Superconducting Films Prepared from Commercial Precursors

This paper have made a systematic study of the superconducting Bi-2212 phase transition temperature, which has a transition temperature (Tc) around 80-93 K, and depends on precise control of synthesis conditions, mainly including heat treatment parameters, oxygen partial pressure, and annealing temperature. Partial melting of the sample during preparation helps to raise its Tc. To elucidate the origin of this strong effect, the samples were heated with different melting process. The rapid changes in Tc valu...     

无机黏土的改性及其在硬质PVC中的应用

采用离子置换法对一种超细无机黏土进行了改性,并利用红外光谱及广角X射线衍射进行了分析。结果表明:在无机黏土表面接枝有机长链分子的同时,还实现了对无机黏土的部分插层。采用熔融共混法制备的PVC/改性无机黏土复合材料,由于改性无机黏土在基体中的均匀分散和较好的界面黏结,其性能较相同无机黏土填充量的PVC/无机黏土复合材料的性能要好。     

降低熔体造粒复合肥料缩二脲含量的实践

在塔式熔体造粒复合肥料生产过程中,影响缩二脲生成的因素主要包括混合物料加热温度、停留时间及其物料水分和含氮量.针对影响因素,给出了降低缩二脲含量的措施.改造后,效果显著,产品中的缩二脲质量分数可控制在0.9%～1.3%.     

新型家具封边用EVA热熔胶的制备

采用氢化C5石油树脂代替传统EVA热熔胶中的增黏剂,制备EVA热熔胶。通过对产品软化点、固化时间、剥离强度、熔融黏度及破坏状态等性能的分析,确定出了新型EVA热熔胶的配方。实验结果表明,以EVA树脂做为基料,加入量为50%(质量百分比,下同),调节剂的加入量为10%,填料的加入量为5%,氢化C5石油树脂加入量为35%时,最终得到的产品能广泛应用在家具封边,地板粘结等领域,并且产品性能达到了行业标准的要求。     

高熔体强度聚丙烯技术进展

高熔体强度聚丙烯(HMSPP)是聚丙烯改性的研究的重要产品之一。本文综述了高熔体强度聚丙烯的性能特点、制备方法、用途以及国内外研究和开发情况。     

氯盐类融雪剂对桥梁安全性的影响分析

结合我国桥涵设计规范和两类桥梁用钢筋腐蚀后力学性能退化的实验数据,对氯盐类融雪剂引起的钢筋腐蚀对桥梁安全性的影响进行了分析,并根据试验数据得出钢筋质量腐蚀率与钢筋力学性能退化的数值关系,得到了钢筋质量腐蚀率与桥梁安全性的初步规律,并根据试验数据及现象,提出桥梁钢筋锈蚀问题的评价标准。     

Compressive characteristics of closed-cell aluminum foams with different percentages of Er element

In the present study, closed-cell aluminum foams with different percentages of erbium(Er) element were successfully prepared. The distribution and existence form of erbium(Er) element and its effect on the compressive properties of the foams were investigated. Results show that Er uniformly distributes in the cell walls in the forms of Al3 Er intermetallic compound and Al-Er solid solutions. Compared with commercially pure aluminum foam, Er-containing foams possess higher micro-hardness, compressive strength and energy absorption capacity due to solid solution strengthening and second phase strengthening effects. Additionally, the amount of Er element should be controlled in the range of 0.10 wt.%-0.50 wt.% in order to obtain a good combination of compressive strength and energy absorption properties.     

UHTC-based matrix as protection for Cf/C composites: Original manufacturing,microstructural characterisation and oxidation behaviour at temperature above 2000 °C

In space propulsion applications, the development of new ceramic matrix composites with improved resistance to oxidation and ablation at high temperature is needed and ultra-high temperature ceramics-based ones appear the most suitable. Combination of both powder impregnation (ZrB₂, C) and liquid silicon infiltration enabled manufacturing of UHTC based matrices in C_f/C preforms with less than 10 vol% open porosity and various proportions and homogeneous distribution of C, ZrB₂, SiC and Si. Oxidation behaviour was evaluated on composite structures using an oxyacetylene torch at temperatures higher than 2000 °C. Chemical analyses and microstructural observations before and after oxidation testing evidenced the protection ability of ZrB₂-SiC-Si matrices thanks to the formation of multi-oxide scales which resisted even tested durations of 6 min and pointed the unharmful presence of residual 12 vol% silicon on the composite for use at high temperature under high gas flows.     

CPP膜专用树脂的开发

结合聚丙烯生产装置和市场的特点,有针对性地提出流延聚丙烯膜专用树脂YPF 3008的开发目标,控制熔体流动速率、树脂产品的均匀性、等规指数及灰分等,成功生产了YPF 3008。经加工厂家应用表明,该树脂能满足进口流延膜生产线的高速加工。