膨润土和玄武岩纤维改性水泥砂浆的防渗抗裂性能

为解决当前水泥砂浆防渗抗裂能力较差的问题,本文研制了一种新型水泥砂浆材料。通过制备不同掺量下的膨润土和玄武岩纤维改性水泥砂浆,测试其抗渗性能和抗裂性能,并对水泥砂浆的微观机理进行分析。结果表明,在水泥砂浆中加入膨润土、玄武岩纤维后,可增强其抗渗性能和抗裂性能。当混掺4%(质量分数)膨润土和0.4%(质量分数)玄武岩纤维时,水泥砂浆抗渗压力值最大,较未掺膨润土和玄武岩纤维时可提高61.11%,抗渗等级为P8级;同时,掺入膨润土和玄武岩纤维后的水泥砂浆裂缝降低系数可以达80%以上,抗裂等级属于Ⅰ级,裂缝的特征表现为“少、细、短”。混掺膨润土和玄武岩纤维使水泥砂浆的密实度增加,裂缝和孔洞减少。膨润土和玄武岩纤维的掺入未改变水泥砂浆的水化产物种类,但使氢氧化钙的结晶度降低,促使水化硅酸钙凝胶生成。     

层状硅酸盐/橡胶纳米复合材料的结构、性能、工业化及其在轮胎工业中的应用

介绍粘土晶层水分散体/橡胶乳液共混共凝制备纳米复合材料的原理、复合材料的结构和性能以及在轮胎工业中的应用.层状硅酸盐/橡胶纳米复合材料具有优异的静态物理性能、气体阻隔性能、耐疲劳性能以及一定的阻燃性能和抗烧蚀性能,应用于轮胎内胎、工程机械轮胎胎面和输送带覆盖胶等可提高产品性能.     

复配硅酸盐与水解硅烷对混凝土抗渗性的影响

利用复配硅酸盐与水解的十二烷基三甲氧基硅烷对水泥砂浆表面进行防水处理以提高混凝土的抗渗性能.通过SEM观察微观形貌,以接触角、透气性与毛细吸水系数试验,研究了不同表面处理剂对砂浆抗渗性能的提升作用.结果表明:复配硅酸盐-硅烷复合处理可以抑制单独使用复配硅酸盐的固化开裂问题以及弥补单独使用水解硅烷难以浸渍裂缝的缺陷,提高...     

Crack Growth in Soda–Lime–Silicate Glass near the Static Fatigue Limit

The atomic force microscope (AFM) was used to explore the nature of features formed on the surfaces of cracks in soda–lime–silicate glass that were held at stress intensity factors below the crack growth threshold. All studies were conducted in water. Cracks were first propagated at a stress intensity factor above the crack growth threshold and then arrested for 16 h at a stress intensity factor below the threshold. The stress intensity factor was then raised to reinitiate crack growth. The cycle was repeated multiple times, varying the hold stress intensity factor, the hold time, and the propagation stress intensity factor. Examination of the fracture surface by optical microscopy showed surface features that marked the points of crack arrest during the hold time. These features were identical to those reported earlier by Michalske in a similar study of crack arrest. A study with the AFM showed these features to be a consequence of a bifurcation of the crack surface. During the hold period, waviness developed along the crack front so that parts of the front propagated out of the original fracture plane, while other parts propagated into the plane. Crack growth changed from the original flat plane to a bifurcated surface with directions of as much as 3° to 5° to the original plane. This modification of crack growth behavior cannot be explained by a variation in the far-field stresses applied to the crack. Nor can the crack growth features be explained by chemical fluctuations within the glass. We speculate that changes in crack growth direction are a consequence of an enhancement in the corrosion rate on the flank of the crack at stresses below the apparent crack growth threshold in a manner described recently by Chuang and Fuller.     

Effect of Atmospheric Humidity on the Fatigue Crack Propagation Behavior of Short Cracks in Silicon Nitride

The effect of the environment on crack-growth processes in silicon nitride was studied by investigating the static and fatigue crack-growth behavior of small surface cracks, as influenced by testing (i) in the ambient environment, (ii) in distilled water, (iii) under vacuum, and (iv) in toluene. A principal finding was that testing under cyclic conditions led to crack-growth rates that were much higher in air than in toluene, whereas testing under static conditions in air or toluene led to minor differences in the rate of static fatigue crack growth. This difference in sensitivity to the environment under static and cyclic loading conditions was attributed, in part, to a much-greater extent of microcracking at the surface ahead of the main crack in air under cyclic conditions, in comparison to that in other environments. This propensity for microcracking at the surface in air under cyclic conditions also was reflected in the aspect ratios of the crack shapes that developed.     

洗涤剂用硼酸盐和新型硅酸盐助剂的性能特点和趋势

综述了新型硅酸盐及硼酸盐类助洗剂的性能特点与趋势 ,其中层状硅酸盐因优良的助洗性能和易浓缩化而格外引人注目 ,其发展将取决于与沸石的价格竟争 ;硼酸盐具有独特的潜在助洗作用 ,但尚需进一步研究最佳应用组成。无论是新型硅酸盐 ,还是硼酸盐等助剂 ,都将向复配型助剂发展。     

Fatigue Crack Propagation in Ceria-Partially-Stabilized Zirconia (Ce-TZP)-Alumina Composites

Fatigue crack propagation rates in tension-tension load cycling were measured in ZrO₂-12 mol% CeO₂-10 wt% Al₂O₃ ceramics using precracked and annealed compact tension specimens. The fatigue crack growth behavior was examined for Ce-TZPs of different transformation yield stresses obtained by sintering for 2 h at temperatures of 1500°C (type A), 1475°C (type B), 1450°C (type C), and 1425°C (type D). The threshold stress-intensity range, ΔK_th, for initiation of fatigue crack propagation increased systematically with decreasing transformation yield stress obtained with increasing sintering temperature. However, the critical stress-intensity range for fast fracture, ΔK_c, as well as the stress-intensity exponent in a power-law correlation (log (da/d N ) vs log ΔK) were relatively insensitive to the transformation yield stress. The fatigue crack growth behavior was also strongly influenced by the history of crack shielding via the development of the crack-tip transformation zones. In particular, the threshold stess-intensity range, Δ K _th, increased with increasing size of the transformation zone formed in prior quasi-static loading. Crack growth rates under sustained peak loads were also measured and found to be significantly lower and occurred at higher peak stress intensities as compared to the fatigue crack growth rates. Calculations of crack shielding from the transformation zones indicated that the enhanced crack growth susceptibility of Ce-TZP ceramics in fatigue is not due to reduced zone shielding. Alternate mechanisms that can lead to reduced crack shielding in tension-tension cyclic loading and result in higher crack-growth rates are explored.     

疲劳裂纹扩展速率的统计分析及疲劳寿命的概率预测

通过对Ｐａｒｉｓ模型的分析,得到ｍ和ｌｏｇＣ的线性关系。试验结果的数据分析表明了ｍ和Ｃ分别符合正态分布及对数正态分布,并运用统计结果对疲劳寿命进行了概率预测。     

高分子/层状硅酸盐纳米复合材料的研究应用现状及发展前景

高分子/层状硅酸盐纳米复合材料因其具有优越的性能、广泛的应用前景而成为目前材料科学研究的热点。简要介绍层状硅酸盐粘土的结构与性质;总结了高分子/层状硅酸盐纳米复合材料的制备方法以及目前国内外的研究进展;综述了高分子/层状硅酸盐纳米复合材料的应用现状;展望了高分子/层状硅酸盐纳米复合材料的发展前景。     

Cyclic Fatigue Behavior of an Alumina Ceramic with Crack-Resistance Characteristics

The behavior under cyclic tension—tension loading of an alumina ceramic with pronounced crack-bridging (R-curve) characteristics is studied. Tests on disk specimens with indentation cracks reveal no failures below the static fatigue limit. Theoretical predictions of the stress-lifetime response, based on the premise that environmentally assisted slow crack growth is the sole factor determining lifetime, are consistent (within experimental scatter) with the data. The results indicate that there is no significant cyclic degradation from potential damage to the bridges, at least in the short-crack region pertinent to strength properties.     

超高分子量聚乙烯的改性及其应用

综述了超高分子量聚乙烯的改性进展,研究了层状硅酸盐对超高分子量聚乙烯加工及理化性能的影响。     

聚氨酯／层状硅酸盐纳米复合材料的研究进展

综述了近年来国内外纳米层状硅酸盐改性聚氨酯的最新研究进展状况。介绍了层状硅酸盐的结构、聚氨酯／层状硅酸盐纳米复合材料的类型及其微观结构,并对聚氨酯／层状硅酸盐纳米复合材料的制备方法及其在弹性体、涂料、泡沫方面的应用进行了阐述,展望了未来发展趋势。     

聚合物—层状硅酸盐纳米复合材料制备及应用

聚合物－层状硅酸盐（ＰＬＳ）纳米复合材料因其优异的性能是目前材料科学研究的热点,简要回顾ＰＬＳ纳米复合材料研究发展的概况,概述ＰＬＳ纳米复合材料的特点,种类,微观结构与物理力学性能,着重介绍ＰＬＳ纳米复合材料的各种制备方法和原理,并从热力学角度对插层复合过程进行了分析,讨论了层状硅酸盐的表面修饰,提出了插层剂的选择原则,展望了ＰＬＳ纳米复合材料的应用前景。     

模拟压力容器接管的新型十字试板的角裂纹疲劳扩展性能

用新型十字试板进行了双轴载荷下的角裂纹疲劳扩展性能的研究,以模拟压力容器接管处角裂纹的疲劳扩展行为。试板角裂纹尖端的应力强度因子采用三维边界元法计算,裂纹疲劳扩展的形貌变化采用降载勾线法记录。试验结果表明,裂纹疲劳扩展规律与双向载荷比及裂纹初始形状有关,裂纹沿长度方向的扩展速率可以用 Paris 公式表示,但在深度方向则不然。     

辽西膨润土提纯及活性白土制备研究

本文以辽西地区膨润土为原料,进行提纯实验,并采用干法制备活性白土.通过对原土的基本性能测试、结构分析以及实验结果分析,初步确定其制备活性白土的工艺技术路线.