New epoxy/episulfide resin system for electronic applications. I. Curing mechanism and properties

A new epoxy/episulfide is investigated using a dicyandiamide (DICY) curing agent system. The resin exhibits better adhesion to copper, a lower thermal expansion coefficient, a lower heat of reaction, and slightly higher water absorption as compared with the standard epoxy system. The dielectric constant of the epoxy/episulfide system is almost the same as that of the standard epoxy system. The properties are due to the reaction mechanism change caused by the addition of episulfide, which is studied using a monofunctional model compound system; the amino groups in DICY initially react much more easily with the episulfide than with the epoxy ring. The S⁻ formed by this reaction reacts with the episulfide and the epoxy quickly. In the presence of copper, the episulfide and/or the S⁻ also react with copper, forming a durable bond between the copper and matrix resin that retains strength even after water boiling. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1359–1370, 2001     

Coating formation by spontaneous polymerization on aluminum: Various monomers

Spontaneous polymerization to give conformal, uniform coatings on metals has been expanded to a series of different monomers. The monomer 4‐fluoro maleimide, when copolymerized with styrene, a coupling agent, and a bis‐maleimide crosslinker, imparts very low dielectric constant (2.4) to the coating while retaining high temperature resistance. Diethyl fumarate, with the same comonomers, enhances ductility and provides an adjustable glass transition temperature. Addition of glycidyl acrylate to the monomer system provides reactivity of the coating to epoxy resins. Kinetic studies using these monomers were consistent with the free radical polymerization mechanism. The rate of reaction seemed limited by the diffusion of species to the reaction site. Extent of incorporation of the new monomers into the chain backbone was verified, and adhesion and corrosion resistance properties examined. The data illustrate the versatility of the conformal, chrome free spontaneous polymerization process. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 875–885, 2000     

Fourier transform infrared analysis of polycarbonate/epoxy mixtures cured with an aromatic amine

In our previous article, we established that polycarbonate (PC) can react with the diglycidyl ether of bisphenol-A (DGEBA) at 200°C through transesterification and addition reactions, resulting in degraded PC chains with phenolic end groups and also in PC/DGEBA copolymers. However, these reactions can be minimized or eliminated at lower temperatures, below 160°C. In this article, Fourier transform infrared analysis (FTIR) was used to study the curing kinetics of epoxies in the presence of PC. The curing agent was an aromatic amine, diaminodiphenyl methane (DDM). FTIR results showed that the presence of a small amount of PC promoted the amine–epoxide reactions, probably due to the catalytic effect of the phenolic end groups in the PC chains. However, the PC did not alter the epoxy cure reaction mechanism. Two different blending processes were used to premix the PC and DGEBA, namely, solution-blending and melt-blending processes, in order to give different extents of prereactions. If a solution-blending process was used, PC tended to undergo crystallization during an early stage of cure. When a melt-blending process was used, no melting peak was observed in the thermograms of the differential scanning calorimeter (DSC) for the modified epoxies; PC chains bonded to DGEBA during prereaction at 200°C, thus inhibiting the crystallization of PC during cure. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2395–2407, 1998     

The design and evaluation of a buffer algorithm for database machines

This paper reports on the design, development and evaluation of a buffer algorithm named RESBAL, which exploits parallelism in order to provide high query execution performance in relational database systems. The algorithm aims to provide both predictive and efficient data buffering by exploiting the use of advance knowledge of query reference behaviour. Designed to offer a high level of flexibility, RESBAL employs a multiple buffering strategy both on page fetch level and page replacement level in order to improve buffer performance. The evaluation of RESBAL has been carried out in a parallel database system environment based on a transputer architecture. The results of this performance assessment allow comparison to be made between different buffer algorithms, and demonstrate the feasibility and effectiveness of the RESBAL algorithm. © 1998 John Wiley & Sons, Ltd.     

点阵分布激光表面强化球铁材料的耐磨性检测

用经过二元光学变换后呈二维点阵(3×3 和 7×7)分布的脉冲激光束对球铁试样作了表面强化处理,并用环块磨损方法对其进行了耐磨性实验。试验表明,常规的环块磨损实验只能检测均匀材料或者是表层处理材料一定厚度内的耐磨性,而点阵分布脉冲激光表面强化球铁材料,由于其强化区沿层深度方向(激光束方向)的横截面上硬度分布的不均匀以及硬度较高的区域在月牙区的内部,因而,表层耐磨性并不能合理的表征整个强化区的耐磨性。对耐磨性检测方法和一些影响因素进行了分析和讨论,提出了耐磨性的合理测试方法。     

NaHCO3基微晶粉喷射清理技术研究

选用铝合金和高温合金零件为研究对象,以NaHCO_3基微晶粉为喷射介质,利用喷砂设备对其表面污层进行喷射清理。利用光学显微镜、扫描电镜、EDS等分析技术,对喷射清理后的表面形貌、成分进行分析;利用粗糙度仪观察清理后的表面粗糙度。结果表明:采用NaHCO_3基微晶粉喷射清理技术能有效去除零件表面积碳、油污、氧化物等污层;采用NaHCO_3基介质清理后,零件表面粗糙度仅为传统喷砂介质清理后粗糙度的10%,对零件表面损伤较小。     

丁腈-40增韧室温固化环氧结构胶

采用丁腈-40液体橡胶对环氧体系进行增韧,研究了丁腈-40液体橡胶含量、甲组分处理温度及时间对所制备环氧结构胶剪切强度的影响。结果显示:环氧树脂和橡胶的最佳质量比为10∶1;所得结构胶室温固化24h,室温剪切强度最高可达22.4 MPa,具有良好的力学性能。     

大型真空抽气系统性能测试

真空抽气系统抽气性能的好坏直接影响RH-KTB精炼的脱气、脱碳、脱氮的效果,极限真空度高低决定了钢水最终的气体含量。测试结果表明:相同负荷下真空度最终稳定在某一值。在无负荷抽真空工况下的稳定真空度(极限真空度)最大,系统稳定真空度随着负荷的增加而下降。对系统性能下降的原因进行了分析,水蒸汽的入口温度、压力、流量的变动及冷凝器的冷凝效果不佳而导致的真空泵抽气能力下降以及系统泄漏是导致系统性能下降的主要原因。     

Achieving targets for bone and mineral metabolism: the impact of cinacalcet HCl in clinical practice

Achieving the K/DOQI targets for bone and mineral metabolism has proven difficult with the use of vitamin D analogues and phosphate binders. The introduction of cinacalcet HCl provided a new tool with a novel therapeutic mechanism of action. The purpose of this study was to evaluate the effect of the introduction of combination algorithm for managing secondary hyperparathyroidism (SHPT) on phosphorus, calcium, and biointact parathyroid hormone (PTH). The 61 patients who dialyzed in the facility from January 2004 (baseline) and who remained in the facility as of April 2005 (follow-up) were included in the study. In the baseline period, 37 (61%) of the patients received paricalcitol at some time during the 3-month observation period. In the follow-up period, 19% or 31% of the patients received cinacalcet HCl. Of those not receiving cinacalcet HCl, 67% had PTH at or below target, 17% were felt to be noncompliant with oral meds, 7% had low calcium, and 10% either could not get the medication or were not switched to the combination pathway. Compared with the baseline period, the percent of patients who met the PTH target increased from 19.7% to 37.7%, p<0.05. The percent of patients meeting all 4 targets increased from 14.8% to 24.6%, although this did not reach statistical significance. The introduction of cinacalcet HCl into a treatment algorithm for management of SHPT resulted in a significant increase in the percentage of patients achieving the PTH target while maintaining the other mineral metabolism targets.     

用于酸性环境下的耐腐蚀合金涂层的开发与评价

本文介绍了一种抗硫化氢/二氧化碳的耐腐蚀合金涂层的开发和评价,该涂层可用于油气开采中的油管、套管、管线管等碳钢管件内壁,保护管件不受硫化氢、二氧化碳、氯离子等造成的腐蚀危害,保障酸性油气田安全可靠地生产。在本开发工作中,选择高等级合金钢——C276作为原材料,采用圆柱体磁控溅射技术将C276合金沉积到碳钢管材内壁,对涂层的厚度、成份、附着力等性能进行了研究,在酸性溶液中,对涂层的耐腐蚀性能及抗氢渗透性能进行了实验评价。