聚甲醛纤维增强砂浆的力学性能和干燥收缩试验研究

本文研究了不同长度聚甲醛(POM)纤维单掺和混掺对砂浆流动度、抗折强度、抗压强度、弯曲韧性及干燥收缩的影响,并通过扫描电镜观测了其微观结构。研究发现,砂浆流动度随POM纤维长度和掺量增大而下降,混掺纤维比单掺对砂浆流动度的影响更小。POM纤维能有效提高砂浆的抗折强度,但掺量超过0.6%(体积分数,下同)时增强效果减弱,与未掺纤维试样相比,0.6%掺量的6 mm纤维对试样28 d抗折强度提升最高,为14.67%,抗压强度随纤维掺量增加而降低。12 mm纤维比6 mm及混掺对试样弯曲韧性提升更明显,最大提高49.43%。纤维的掺入可显著降低试样的干燥收缩率,且随纤维掺量增加,试样90 d干燥收缩率先减小后增大。与未掺纤维试样相比,0.6%掺量的6 mm纤维试样90 d干燥收缩率下降最多,为27.39%。混掺POM纤维在掺量0.6%以上时仍可显著提升砂浆的抗折强度并减小干燥收缩率。     

尼龙纤维增强水泥砂浆性能的试验研究

本文分析了尼龙纤维的不同体积掺量(0.05％,0.1％,0.2％,0.3％)及不同纤维长度(6 mm,12 mm,15 mm,19 mm)对水泥砂浆的抗折强度、抗压强度、韧性(折压比)及干缩性能的影响.结果表明,尼龙纤维的掺入能有效提高砂浆的抗折强度、折压比及降低同龄期下的自由干缩率,但抗压强度变化不很明显,甚至有一定程度的降低.     

海泡石纤维增强高石粉含量机制砂砂浆性能的研究

以高石粉含量机制砂砂浆为研究对象,分析了海泡石纤维体积掺量和长度的变化对砂浆力学性能和干燥收缩的影响规律,并使用压汞仪和扫描电子显微镜研究了砂浆内部孔结构和微观形貌的变化特征。结果表明:适宜体积掺量的短海泡石纤维可显著改善砂浆的抗压强度、抗折强度和抗干燥收缩能力。与空白组相比,长度为1 mm的纤维体积掺量为1.5%时,试件28 d抗压强度和抗折强度分别提高98.9%和36.2%;长度为1 mm的纤维体积掺量为2.0%时,28 d自然干燥收缩值降低72.1%。海泡石纤维试件内部形成了大量针棒状钙矾石和片状氢氧化钙晶体,有效提高了砂浆硬化体系的密实性,砂浆总孔隙率与纤维掺量成反比。     

硅酸盐水泥对脱硫石膏基砂浆物理力学性能的影响

研究了硅酸盐水泥掺量变化对脱硫石膏基砂浆的稠度、体积密度、抗压强度、抗折强度、软化系数、黏结拉伸强度、干燥收缩性能等物理力学性能的影响规律.结果表明,硅酸盐水泥能显著提高脱硫石膏基砂浆稠度,增大流动性,使得新拌砂浆体积密度和硬化砂浆体积密度略微增大;显著提高脱硫石膏基砂浆的抗压强度、抗折强度和软化系数,尤其是后期强度;能明显提高黏结拉伸强度,显著降低干燥收缩率,改善干燥收缩性能,甚至使得砂浆早期具有微膨胀特点;硅酸盐水泥在脱硫石膏基中的掺量宜控制在20％以内.     

改性聚丙烯纤维砂浆和混凝土的性能试验

试验采用P.P.Kraai提出的砂浆及混凝土干燥收缩裂缝测试方法、混凝土力学性能试验、抗冻等耐久性能试验方法,研究了改性聚丙烯纤维对砂浆和混凝土性能的影响。结果表明,在混凝土中掺入一定量的改性聚丙烯纤维,混凝土的抗压强度略有下降;纤维在混凝土中形成的乱向支撑体系,产生了有效的增强效果,减少了裂缝的产生,提高了混凝土的抗折、抗拉强度,从而改善了混凝土抗裂、抗渗、抗冲击和抗冻等性能。     

不同养护条件下内养护补偿收缩砂浆性能研究

研究了28 d干燥、保湿7d后干燥、密封三种干燥条件下复掺高倍吸水树脂(SAP)与MgO膨胀剂对砂浆性能的影响.研究结果表明:在以上三种条件下,复掺均能降低砂浆的收缩变形、提高砂浆7d和28 d的抗折强度、抗压强度和抗冻性.复掺在每种干燥条件下对砂浆性能影响不同,密封条件的收缩变形最小,保湿7d后干燥的抗折强度与抗压强度最大、抗冻性最好.复掺氧化镁膨胀剂掺量为8％时减缩效果最好,强度与抗冻性较单掺SAP砂浆有所提高.     

杨木纤维对砂浆流动度、力学性能和自收缩的影响

本文采用控制变量法设计试验,探究了杨木纤维尺寸、体积分数对砂浆流动度、力学性能(抗压、抗折强度)及自收缩的影响。研究发现：与杨木纤维尺寸相比,杨木纤维体积分数对砂浆流动度的影响更为显著,当杨木纤维体积分数自1.0%增至3.0%时,砂浆流动度降低49.56%;增加杨木纤维尺寸和体积分数均会降低砂浆的抗折强度,而增加杨木纤维的体积分数有利于提高砂浆的抗压强度;杨木纤维体积分数比其尺寸对砂浆的减缩作用更显著,添加3.0%长度为0.30～1.25 mm的杨木纤维使砂浆72 h自收缩降低45.6%。     

短切玄武岩纤维对矿渣粉煤灰混凝土力学性能和微观结构的影响

以聚丙烯纤维为参照,研究了不同长度(12 mm、18 mm)和体积掺量(0.50％、0.10％、0.20％和0.30％)的短切玄武岩纤维对矿渣粉煤灰混凝土工作性能、抗压强度、劈裂抗压强度和抗折强度的影响,并采用扫描电镜(SEM)和压汞法(MIP)对纤维混凝土的微观形貌和孔结构进行了分析.结果表明:掺入玄武岩纤维可以显著提高矿渣粉煤灰混凝土的抗折强度和劈裂抗拉强度,但对抗压强度的改善并不明显,且以长度为18 mm的玄武岩纤维,体积掺量为0.20％时,对混凝土的抗压、抗折和劈裂抗拉强度的增强效果最为显著.SEM和MIP分析结果显示:一定掺量范围内,玄武岩纤维与基体界面黏结性能良好,能够有效抑制裂纹扩展,且玄武岩纤维的掺入能够降低混凝土中有害孔的比例,改善孔结构.     

矿渣微粉对脱硫石膏基砂浆物理力学性能的影响

研究了矿渣微粉掺量变化对脱硫石膏基砂浆的稠度、体积密度、抗压强度、抗折强度、软化系数、粘结拉伸强度、干燥收缩性能等物理力学性能的影响规律。结果表明,矿渣微粉对脱硫石膏基砂浆物理力学性能具有显著影响,能显著提高脱硫石膏基砂浆稠度、新拌砂浆体积密度和硬化砂浆体积密度,降低脱硫石膏基砂浆的抗压强度、抗折强度和软化系数,尤其是早期强度;但能明显提高粘结拉伸强度,显著降低干燥收缩率,改善干燥收缩性能;矿渣微粉掺量不超过20%时,其对脱硫石膏基砂浆上述物理力学性能的改善效果较佳。     

复掺陶瓷抛光砖粉与聚丙烯纤维对砂浆性能的影响

以陶瓷抛光砖粉为辅助胶凝材料,通过单掺及复掺陶瓷抛光砖粉和聚丙烯纤维,研究了不同掺量的聚丙烯纤维及陶瓷抛光砖粉对砂浆稠度、抗压强度、抗折强度、干缩率和抗冻性的影响.研究结果表明:在单掺条件下,随陶瓷抛光砖粉掺量的增加,砂浆稠度变大;随聚丙烯纤维掺量的增加,砂浆稠度变小.在复掺条件下,当聚丙烯纤维掺量达到1.5 kg/m3时,纤维掺入所导致的粘聚性增大成为主导因素.陶瓷抛光砖粉的掺入能够提高砂浆力学性能,且随其掺量增加,砂浆抗压强度与抗折强度增大;砂浆抗折强度随聚丙烯纤维掺量的增加而增加呈上升趋势,但砂浆抗压强度随纤维掺量的增加呈先降后增趋势.陶瓷抛光砖粉和聚丙烯纤维均能有效抑制砂浆的干缩,降低砂浆经冻融循环后的抗压强度损失率,提高砂浆的抗冻性能.     

乙苯,苯乙烯的生产及合成乙苯,苯乙烯催化剂的研究进展

苯乙烯是重要的石油化工原料。本文介绍了国内外苯乙烯生产的发展概况，合成乙苯，苯乙烯所用的催化剂种类，并就苯乙烯生产及催化剂的发展趋势提出了自己的观点。     

Synthesis and characterization of homopolymers and copolymers of various acrylates and acrylonitrile

Various homopolymers and copolymers of methyl acrylate, ethyl acrylate, butyl acrylate, and acrylonitrile in different feed ratios were synthesized. These were characterized by IR, ¹³C-NMR, DSC, DTA, and TGA. Spectroscopic characterization helped in differentiating copolymers of different mol ratios. Thermal analysis revealed different degradation patterns for homopolymers and copolymers. The temperature and energy changes associated with various phase transitions were dependent on the chemical composition of homo- and copolymers, as expected. © 1993 John Wiley & Sons, Inc.     

生物质气化及生物质与煤共气化技术的研发与应用

总结了生物质原料的特点及生物质单独气化的缺点;介绍了国内外生物质气化技术及生物质与煤共气化技术的研发与应用现状;分析了在此领域国内外的发展趋势与前景;概括了开展生物质与煤共气化技术研发的意义。     

Electronic structures and reactivities of monometallic and bimetallic clusters of Au and Cu

The variation of the Au 4f binding energy of Au clusters with the cluster size has been established by measuring the binding energies of clusters whose size distributions were independently determined by HREM and STM. The binding energy increases significantly when the cluster size is less than 2 nm. Au-Cu bimetallic clusters of the composition Cu₃Au have been deposited for the first time on carbon substrates. The shifts in the core level binding energies of the bimetallic clusters show the effect of alloying in the case of large clusters, but show effects of both alloying and cluster size in the case of the small clusters. The interaction of CO with Cu₃Au clusters is stronger than with a bulk Cu metal. The interaction of CO with small Cu clusters also seems to be stronger than with bulk Cu or with large Cu clusters.     

钾盐资源及钾肥供需情况分析及预测

阐述了国内外钾盐资源及钾肥生产现状,对国内外钾盐的供需形势进行了分析及预测,从资源、原材料、国际市场三方面提出了解决我国钾盐短缺的措施。     

Kinetics and Mechanism of Oxidation of Mono- and Polyacetals

Abstract

Kinetics and mechanisms of oxidation of 6 acetals by molecular oxygen and ozone in liquid phase have been studied. Reaction with molecular oxygen (70°C, 15–16 hr) leads to the formation monoethers of the corresponding glycols with 68–90% selectivity. Salts of metals and complexes with crown-ethers have increased the reaction rate significally. Ozone have reacted with acetals with formation similar products. The mechanisms of intermediate stages have been proposed.     

Comparison of the Adhesion and Cohesion of Triblock and Random Copolymers of Styrene and Butadiene

A substantially greater detachment energy is required to strip a polyethylene tereph-thalate (Mylar) film from a styrene-butadiene-styrene (SBS) triblock copolymer compared to that for peeling from a random styrene-butadiene (SBR) copolymer. This is true even though the intrinsic interaction between the Mylar and each elastomer is expected to be similar because of their virtually identical chemical composition. It is proposed that this difference in peel strength (between the SBS and SBR) is a consequence of the much higher dissipative capacity of the former elastomer. Another manifestation of this is the higher cohesive tear strength of the SBS compared to the SBR. Extents of energy dissipation within each elastomer during detachment of the Mylar adherend are consistent with the hypothesis that the average maximum stress experience before detachment is some similar fraction of each elastomer's tensile strength.     

Wetting properties of homopolymers and copolymers of pentafluorostyrene and methylacrylate and homopolymer blends

Polypentafluorostyrene (PPFS), polymethylacrylate (PMA), and poly(pentafluorostyrene-co-methylacrylate), poly(PFS-co-MA) were prepared and the wetting characteristics of polymer blends of PPFS and PMA were compared with that of poly(PFS-co-MA) via contact angle measurements. The critical surface tension of polypentafluorostyrene was found to be 22.6 dyne/cm, which is comparable to the value reported for polytrifluoroethylene (22 dyne/cm). The critical surface tension of poly(PFS-co-MA) is not linearly related to its composition. The polymer blends of PPFS and PMA exhibit significant surface enrichment of the fluoropolymer. The harmonic-mean method¹ was employed to determine surface tensions of these polymers and many known polymers. It is found that the method produces useful surface tension data provided the contact angle values are derived from testing liquids of dissimilar polarity.     

责任和责任心的涵义与结构

责任是人应主动承担的角色义务和对其因过失所造成后果应承担的责罚.有两层涵义:一是义务;二是后果.责任心是个体自觉做好分内事务和履行道德义务的心理倾向,是个性心理品质成分中自我特征维度上的重要内容.责任心具有两个方面的涵义:一是角色分内职责;二是角色道德义务.责任心是一种通过责任认知、责任个性和责任适应的动态形式表现出来的静态品质,责任心是责任心过程结构与责任心关系结构相互制约、相互影响的统一体.     

二甲基二烯丙基氯化铵和丙烯酰胺的合成及应用

用复合引发体系(过硫酸盐-偶氮类引发剂)和脂肪胺类氧化还原体系引发,在实验室获得了单体转化率≥98%,特性粘数高于13.6 dL/g的阳离子共聚物PDA,探讨了控制聚合物分子量的影响因素.