橡胶的红外光谱分析

本文报导了天然橡胶、合成异戊二烯橡胶、顺丁、丁苯、丁腈、丁基、氯丁和乙丙等八种橡胶的红外光谱分析。     

速度面积法中对数线性选点的合理性及适用性

本文通过理论分析计算,提出了对数线性选点在速度面积法测流量中具有较高精度,对均速管流量计的总压孔位置和速度面积法的测速点位置确定具有指导意义。     

关于1990年国际温标(ITS—90)

自1990年元旦开始,1990年国际温标(TTS-90)已取代1968年国际实用温标(IPTS-68、1975年修订版)。本文评述了制订 ITS-90的背景,以及与 IPTS-68相比它在准确性、一致性和光滑性等方面的重大改进。这里还对 ITS-90的构成进行了分析,并对它可能达到的准确度作出讨论。文章也指出了为贯彻 ITS-90所涉及到的一些问题。     

Mssbauer在测定Al—V—Fe纳米晶合金中相组成的应用

采用机械合金方法制备Al—V—Fe纳米晶合金粉末,合金粉末由纳米尺度的铝晶粒加非晶颗粒组成。利用Mossbauer测定表明合金由单铁组态、双铁组态固溶体以及非晶相组成,三者的含量分别为22.644%,16.746%,60.610%。     

增效试剂在动力学分析法中的应用研究锰(Ⅱ)—高碘酸钾—氨三乙酸—PAN—Triton X—100催化体系

本文报道了以 Triton X—100为增溶剂,高碘酸钾氧化 PAN 催化光度法测定痕量锰的新体系。方法的检出限为3.6×10~(-3)μg/mL,精密度为2.4%(n=9),线性范围为0.10～1.3μg/25mL,可用于谷物样品中锰的测定。     

福建高岭土合成赛龙(β′—Sialon)粉体的烧结性能研究

本文研究了由福建高岭土合成的赛龙(β—Sialon)粉体的烧结性能。实验表明:在常压和不加任何其它添加剂的条件下,烧结温度不低于1700℃才能获得较致密的烧结材料。烧结机理为扩散—溶解—沉析复合型机制。原料中 CaO,MgO 和 Fe_2O_3等杂质在高温烧结过程于晶界处形成低熔液相,加速了β'—Sialon 坯体烧结致密化进程。β'—Sialon 烧结体由长柱状β'—Sialon 晶体相互交织成网状骨架,并由石英,氮化硅,莫来石和少量β'—Sialon 等轴晶粒填充到骨架空隙的复合型结构。此外,烧结温度与烧结气氛中氧气含量对烧结密度和矿物组成影响也很大。     

PECVD非晶SiOx∶H薄膜的Si—O—Si键红外吸收特性研究

用傅里叶红外光谱(FT-IR)测试分析了等离子体化学气相沉积法沉积的非晶SiOx∶H(0≤x≤2.0)薄膜中的Si—O—Si伸缩振动模与氧含量x的关系。Si—O—Si伸缩振动模在1000和1150cm     

The electrochemical origins of open-circuit voltages observed during heating of metal-polymer-metal systems

A quantitative development of the electrochemical origins of the open-circuit voltages in metal-1 — polymer — metal-2 systems is presented and shown to be applicable to the large amount of systematic data available on these systems. These electrochemical considerations arise from the battery effect, and associated electrode processes, created when two dissimilar metals are connected $\text{via}$ an ionic conductor. It is pointed out that such effects would arise in general in any metal — dielectric — metal system, assuming that conditions obtain for some ionic conduction in the dielectric.The attribution of open-circuit voltages generated in metal-1 —polymer — metal-2 systems to the differences in the work functions of the metals involved is shown in some recent work to be neither conceptually nor empirically valid. Although these metal — polymer — metal sandwiches behave as galvanic cells, their internal resistance is much too high to offer any interest as batteries. The detrimental influences (and means to reduce them) of the open-circuit voltages, on the measurement of some low-field electrical properties of the polymers are discussed.The analysis presented also provides a novel method of determining the free energy changes undergone by the polymer with the change in temperature; this involves the measurement of the open-circuit voltages of the M — polymer — M system (note: the two electrodes here are similar) at the two temperatures of interest and deducing the free energy changes from the difference in the e.m.f. values of the above system at the two temperatures.     

聚碳硅烷纤维氧化交联机理的研究

对聚碳硅烷(PCS)原丝在不同氧化交联温度区间生成的逸出产物进行红外、核磁和GC-MAS分析,并结合交联丝的红外分析,推测氧化交联的机理。结果表明,PCS的氧化交联主要是其Si—H氧化生成Si—OH,后者进而彼此缩合生成Si—O—Si交联结构;氧化交联温度高于150℃时,其部分Si—CH3也开始氧化生成Si—OH并进而交联;同时,在氧化交联过程还发生PCS侧链的热裂解,所形成小分子也通过Si—OH彼此结合,形成较大分子,且其分子量随交联温度的提高而提高。因此,要及时排除氧化交联过程废气,以免逸出产物黏附在纤维表面而导致粘结。     

Vu-Khanh参数在表征高聚物共混物断裂韧性中的应用

Vu-Khanh plot作为高聚物共混物断裂韧性的表征方法,与J积分、基本断裂功相比具有显著的优点,因此逐渐受到高分子材料研究领域的广泛重视。主要介绍了Vu-Khanh plot表征聚合物断裂韧性的基本原理、参数的测试方法、在高聚物共混物研究中的应用,并且讨论了Vu-Khanh参数——裂纹引发断裂能Gi和撕裂模量Ta的影响因素和二者之间的关系。     

聚硼硅氧烷的合成及其流变性能EI北大核心CSCD

为了探究聚硼硅氧烷(PBDMSs)的物理交联网络结构对体系黏弹性的影响,将不同羟基含量的端羟基聚二甲基硅氧烷(PDMS)分别与硼酸进行反应,制备不同硼化交联密度的PBDMSs,并对合成的PBDMSs的结构、热力学及流变性能进行表征。结果表明:制备的PBDMSs中含有Si—O—Si,Si—O—B,CH_(3)—Si—CH_(3)和B—O—B结构单元;PBDMSs具有优异的耐低温性能,其玻璃化转变温度随着原料PDMS中羟基含量的增加而升高,且当原料PDMS的羟基含量较低时(1%和2%,质量分数),生成物PBDMSs具有一定的结晶能力;PBDMSs具有频率敏感性的特征,并且具有良好的抗冲击能力、优异的阻尼耗散能力和出色的回弹性能,原料PDMS的羟基含量影响生成物PBDMSs的物理交联网络结构,进而对PBDMSs的动态模量有显著影响,实际应用时可根据需求改变PDMS的羟基含量来调节PBDMSs的黏弹性。     

含铍碳化硅陶瓷先驱体聚铍碳硅烷的合成

以氢氧化铍、硫酸和乙酰丙酮为原料合成了乙酰丙酮铍(Be(acac)2).用乙酰丙酮铍和聚碳硅烷在加热的条件下反应一定时间,生成了树脂状的产物.反应中乙酰丙酮铍被消耗,生成产物熔点相对起始聚碳硅烷熔点升高.元素分析表明产物中含有铍元素,凝胶渗透色谱分析表明产物分子量相对起始聚碳硅烷向增大的方向发生变化.傅立叶红外光谱分析表明产物中主要存在如下结构:Si(CH3)2—CH2—,—Si(CH3)·(H)—CH2—.核磁共振1H-NMR分析表明反应物中Si—H键被消耗.根据分析结果推测了反应机理,Si—H键的消耗在产物的形成中起了重要作用.实验与理论分析表明先驱体产物是一种含铍聚碳硅烷,可以命名为聚铍碳硅烷(PBeCS).在1200℃的高温处理下产物作为先驱体可以转化为碳化硅陶瓷,元素分析表明碳化硅陶瓷中含有铍,是含铍碳化硅陶瓷.     

Taking Another Look at Educating African American Engineers: The Importance of Undergraduate Retention

In this paper we identify the engineering schools that either graduate large classes of African Americans or that retain relatively high percentages of African American students in engineering; point out that modest improvements in student retention would significantly affect the total number of bachelors degrees earned annually by African Americans in engineering; examine the measures implemented by some schools that are particularly effective at retaining African Americans in engineering; and present our views on the future of diversity efforts in engineering. The message we wish to emphasize is that at the very least colleges and universities should endeavor to retain those under represented minority undergraduates who have decided to pursue an engineering education. Frequently used abbreviations EWC — Engineering Workforce Commission, HBCU — historically black college or university, MEP — minority engineering program, MES — minority engineering society, MRR — minority retention rate, NACME — National Action Council for Minorities in Engineering, TWI — traditionally white institution     

DBTM—St—BA三元共聚竞聚率的测定

根据改进的欧拉公式,解得Alfrey-Goldfinger微分方程的数值积分,将单纯形调优法与数值积分法相结合,建立数学模型并编写微机程序。采用红外光谱法测定不同转化率下DBTM(顺丁烯二酸二丁基锡酯)-St(苯乙烯)-BA(丙烯酸丁酯)三元共聚体系共聚物的组成。根据三元共聚体系的起始组成、和不同转化率下共聚物的组成,应用所编制的程序,计算该三元共聚体系单体的竞聚率。     

Structural behaviour of loaded multilayer wall panels

Four precast room-height wall panels, each comprising three distinct concrete layers—the middle one being lightweight aggregate concrete serving as a thermal insulation core-were experimentally investigated. They were tested up to failure under lengthwise loads applied axially—to the core—in two of them, and eccentrically—to the bearing layer—in the other two. Results showed that the whole thickness of the walls participated in the load bearing process and that failure did not occur by buckling, but rather in the form of a vertical crack near the supports, and parallel to the layering. Transverse reinforcement should be used, in construction practice, at both ends of the panel, so as to preclude earlier splitting failure.     

聚丙烯酰胺钕配合物的研究

首次引入稀土金属钕离子,合成聚丙烯酰胺钕[PAAM—Nd(Ⅲ)]配位聚合物,并用FT—IR、XPS、元素分析及电导率等分析手段对配合物进行表征,证明了Nd(Ⅲ)与PAAM的配位作用,并测出Nd(Ⅲ)与PAAM单体单元的配位比为1∶4。     

The effect of acoustic oscillations on diffusion combustion of methane

Aspects of ecological safety related to the combustion of hydrocarbons—in particular, the demand for reducing the content of toxic compounds in combustion products—are extremely topical. In addition, there is still important task of increasing the efficiency of using all kinds of fuel, including hydroarbons. One possible mechanism of controlling combustion processes—namely, the effect of acoustic perturbations on the diffusion combustion of methane—has been considered. The influence of acoustic oscillations on the characteristics of diffusion flame has been studied, and the dependence of the concentration of nitrogen oxides in the combustion products on the acoustic signal frequency has been determined.     

烯烃聚合Ti-Mg系负载型催化剂的IR光谱

采用IR技术测试了烯烃聚合Ti-Mg系负载型催化剂制备过程形成的物种,根据Si-Ci、Ti-O、C—O和C=O键特征吸收峰的变化,表征制备过程所生成的载体Bu—O—SiCl_3与MgCl_2和催化剂“预备体”与MgCl_2·TiCl_4,IR光谱的信息与聚合反应动力学的结果一致。     

Application of the Hydrogen Diffusion Model to the Hydrogen Permeation

The model of hydrogen diffusion formerly de-veloped [1] has been applied successfully to thehydrogen permeation experiment results of threekinds of materials,α—Fe,Fe—Ti alloy and Fe—Ti—Calloy by the mathematical fitting method.From thefitting results it was shown that the model can re-fiect well the diffusion of hydrogen in the materialswith trapping.The obtained trapping parameters(αand β)can be used to explain well the diffusion ofhydrogen in the samples with trapping.