纳米高岭土的研究与应用

介绍了高岭土的结构、性质以及研究现状,并结合纳米基础理论和技术对高岭土的研究方向进行了探讨,综述了纳米高岭土的制备方法,总结了纳米高岭土的应用现状,同时对高岭土纳米化的前景与技术进行了展望.     

PP/POE/高岭土三元复合材料的力学及热性能

研究了高岭土和乙烯-辛烯共聚物弹性体(POE)填充聚丙烯(PP)制备的PP/POE/高岭土三元复合材料的力学和热力学性能。结果表明,POE和高岭土不能提高PP的拉伸强度,但高岭土可以显著提高PP/POE的杨氏模量。POE降低了PP的弯曲强度和弯曲模量,但PP/POE/高岭土三元复合材料的弯曲强度和弯曲模量显著高于PP/POE和PP。POE和高岭土可以显著提高PP的冲击强度,当高岭土和POE的填充份数分别为10份和5份时,PP/POE/高岭土复合材料的冲击强度最大。高岭土的添加可以提高PP的结晶温度,加快PP的结晶速率,促进PP的异相成核。合适含量的高岭土可以提高PP的熔融温度,改善PP的耐热性能。     

复掺偏高岭土对混凝土抗压强度的影响

我国高岭土资源丰富,偏高岭土应用于混凝土有将会很大前景。本文对比研究了复掺偏高岭土对混凝土抗压强度的影响。研究表明在水胶比为0．31下,偏高岭土与粉煤灰总掺量为35％（偏高岭土掺量为8％）时更能充分发挥偏高岭土的活性。合理的偏高岭土掺入对掺粉煤灰混凝土早期抗压强度有提高明显,抗压强度提高可达47％。     

硅烷偶联剂修饰高岭土对沥青物理和老化性能的影响

为改善沥青的物理和老化性能,本文采用γ-(2,3环氧丙氧)丙基三甲氧基硅烷(KH560)对高岭土进行了表面修饰,通过熔融共混法分别制备了高岭土和表面修饰高岭土改性沥青,并对其进行了薄膜加热试验(TFOT)和压力老化容器试验(PAV),测试了高岭土和表面修饰高岭土改性沥青老化前后的物理性能,并利用傅里叶变换红外光谱(FTIR)和X射线衍射(XRD)对高岭土和表面修饰高岭土及其改性沥青老化前后的结构进行了表征。FTIR和XRD分析表明,KH560成功接枝到高岭土表面,但未改变高岭土的晶体结构。相比未修饰高岭土,表面修饰高岭土对沥青软化点和黏度的提高幅度更大,对沥青低温延度的不利影响减弱,TFOT和PAV老化对沥青性能的负面影响降低,并有效抑制了沥青老化后羰基指数的增加,显著改善了沥青的抗热氧老化性能。随着表面修饰高岭土掺量的增加,沥青物理性能和抗老化性能的提升越来越明显。     

精制高岭土市场广阔

高岭土主要由小于2微米的片状、管状、叠片状等高岭石簇矿物组成,质纯的高岭土具有白度高,质软易分散悬浮于水中,具有良好的可塑性和高的粘结性、优良的电绝缘性能、良好的抗酸溶性、很低的阳离子交换量,较高的耐火度等物理化学性能,因此广泛用于造纸、陶瓷、橡胶、塑料、耐火材料、化工、医药、纺织、石油、建材及国防等部门。按工业用途,高岭土可分为造纸用高岭土、搪瓷用高岭土、橡胶用高岭土和陶瓷用高岭土等,其中造纸工业用高岭土占精制高岭土产量的一半左右。2005年世界高岭土产量约为4450万吨,其中精制高岭土产量约为2500万吨,占世界高岭土产量的60%,而未经加工的原土占总产量的40%。在精制高岭土中,造纸级高岭土产量约为1100万吨,占世界高岭土产量的四分之一。目前在世界造纸工业中,印刷与书写用纸是造纸级高岭土的主要消费领域,其中填料和涂料使用的比例为60%和40%。高岭土使用量约占纸张重量的10.15%,重钙约占10.45%,轻钙约占4.48%。在印刷与书写用纸中,铜版纸对高岭土和碳酸钙的使用量占59%,其他纸类占41%全球造纸工业2003年使用3000万吨矿物原料,其中2700万吨用于印刷和书写纸。在印刷和书写纸领域,3...     

高岭土表面改性及技术加工现状

高岭土储量丰富,价格便宜,是一种重要的化工原材料,我国是高岭土资源大国。高岭土作为聚合物的功能性填料时,不仅能降低聚合物产品的成本,还能提高其力学性能、耐热性、阻燃性。但是高岭土与聚合物两者相容性差,容易在聚合物基体中发生团聚,需要对其表面改性才能分散均匀于聚合物基体中。本文介绍了高岭土改性的方法以及改性高岭土填料的应用,提出了高岭土改性存在的问题及发展建议。     

高岭土的机械化学改性及其对聚乙烯的补强性能

采用机械研磨和表面改性的方法,制备了硅烷接枝高岭土粉体。利用粒度分析仪、红外光谱分析和沉降性能测试等进行表征。研究结果表明:机械研磨提高了硅烷与高岭土的反应活性,使其在液体石蜡中具有良好的分散稳定性,与直接改性高岭土相比,沉降体积由3.2mL提高到7.6mL。将高岭土原矿、直接改性高岭土和磨剥改性高岭土分别与聚乙烯熔融共混制备复合材料。研磨改性高岭土对聚乙烯具有良好的补强性能,并且在填充量为10份时达到最佳,材料的拉伸强度较纯聚乙烯提高了3.7MPa。     

聚苯胺-高岭土纳米复合材料的制备与表征

苯胺分子中的氨基-NH_2可与高岭土层间氧原子或羟基—OH形成更强氢键,发生插入反应而“溶胀“。过硫酸铵引发苯胺原位聚合,成功制备了聚苯胺—高岭土纳米复合粉体。经粒度分析、SEM、XRD和导电率测定等手段,表征了复合粉体的结构与性能。结果表明:当高岭土含量达50wt.%时,复合材料的体积电导率为:0.253 S/cm。表观粒度与高岭土相比有较大幅度的提高,但分布变窄。由于层状高岭土的诱导作用,使聚苯胺的结晶度提高,聚苯胺与高岭土之间不是简单的混合,存在氢键相互作用。高岭土层间受限环境和聚苯胺与高岭土之间的氢键自组装,高岭土层间羟基—OH对聚苯胺有质子掺杂作用,使聚苯胺的结构与性能发生了变化。     

环氧树脂改善固井用偏高岭土地质聚合物的力学性能与机理

针对偏高岭土地质聚合物脆性较强的问题，研究了环氧树脂对偏高岭土地质聚合物力学性能的改善效果。研究结果表明，环氧树脂掺量为偏高岭土质量分数的2%时，偏高岭土地质聚合物的7 d抗压、抗拉和抗弯强度分别提升40%、36%和28%。对环氧树脂/偏高岭土地质聚合物进行XRD、FTIR、MIP和SEM/EDS测试。结果表明，环氧树脂均匀分散在偏高岭土地质聚合物之中，填充孔隙和优化孔隙结构；环氧树脂与偏高岭土地质聚合物之间的氢键作用增强了环氧树脂对基体裂纹的阻碍和偏转能力。上述作用使得偏高岭土地质聚合物的脆性得到改善。环氧树脂可以显著改善偏高岭土地质聚合物的力学性能，这有助于拓宽偏高岭土地质聚合物的应用领域。     

高岭土径厚比对丁苯橡胶复合材料动态性能的影响研究

利用不同产地高岭土存在径厚比的差异,将7个不同产地的高岭土通过乳液共混法制备了高岭土/丁苯橡胶复合材料,研究了径厚比对高岭土在丁苯橡胶中分散形态的影响。并结合橡胶分子链-高岭土3种作用模型,研究了"连续式"和"孤岛式"两种分散形态对复合材料动态性能的影响机理。研究表明,径厚比较大的高岭土倾向于在复合材料中形成"连续式"的分散网络,径厚比较小的高岭土则倾向于"孤岛式"分散。当高岭土在橡胶基体中呈现"连续式"分散网络时,板状高岭土将丁苯橡胶基体分割成彼此相互独立的单元,同时提高了复合材料的储能模量及损失模量。     

潜望镜白光透射比测量装置的设计与实施

提出一种潜用光学系统白光透射比测量装置的设计方法，并根据该方法研制一套具有测量结果准确、功能齐全、操作方便的测量装置。用于实际测量的结果表明，该装置完全符合设计要求。     

高精度圆度仪误差分离装置研制及测量不确定度分析

介绍了一种由程控型多齿分度台和高精度圆度仪组合而成的全自动误差分离装置,该装置能够使圆度仪主轴回转误差从被测工件测量结果中可靠分离,从而极大地提高了圆度测量不确定度,本文对该装置测量不确定度进行了分析。     

多齿分度台标准装置的测量不确定度评定

分析了多齿分度台作为角度标准测量多面棱体的误差来源，从测量方式出发，建立数学模型，对标准不确定度和扩展不确定度进行评定，且给出了评定的自由度。     

Evaluation of a maintenance strategy by the analysis of the rate of repair

The evaluation of maintenance strategies is a problem which has been widely tackled. However, it remains a topic worthy of consideration since the economic stakes peculiar to this activity are huge. The work presented in this paper deals with this problem under the point of view of data feedback. A statistical analysis is made from the examination of the forms of the failure rate distribution. The laws resulting from the implementation of a given maintenance strategy inform us about the relevance of the choices representative of this strategy. The construction of these laws from a raw time of repair is a global approach which tends to hide the induced phenomenon. A decomposition of the repair process into phases allows us to better identify the influence of the strategy parameters. The analysis of each elementary phase distribution is interesting since it givesinformation about the performance of the implemented maintenance strategy. Copyright © 2003 John Wiley & Sons, Ltd.     

燃气轮机转子系统振动激励源特性研究

燃气轮机的振动一直是设备的关键问题之一,燃气轮机结构复杂,导致其振动的激励源具有复杂性、多样性等特点,传递到其机脚处的振动更是船用燃气轮机所关注的研究课题之一。在对燃气轮机转子系统进行研究的基础上,对转子振动的典型激励源及其振动特性进行梳理和分析,并对传递到支撑处的激励力进行分析,采用力的传递率探究典型激励源传递到支撑处的振动特性,得到轴承参数和力的作用点对力的传递率的影响规律,并对流场激励力的特性进行分析,得到流场激励力的频率特性。研究成果对燃气轮机的减振降噪以及前期的参数设计都具有一定的指导意义。     

Effect of defects on fatigue life of plates with fastener holes

The behavior of defects (inclusions and cavities) on fatigue life of plates with fastener holes under tensile loading has been analyzed. Special attentions have been paid on the influence of the size and location of defects on fatigue life of plates with fastener holes. Thirty‐five different finite element models of plates with different size and location of defects are established and the nominal stress method is used to estimate the fatigue lives of this models. The results show that there is a region whose center is the maximum stress point of the hole without defects. When the defect is located in this region, the influence of defects on fatigue life of plates with fastener holes is obvious. When the defects are far away form this region' center, the defects hardly influence the fatigue life of plates with fastener hole. The larger the size of the defect is, the bigger this region is. In this region, the larger the size of the defect and the shorter the distance between the defect and the region's center, the shorter the fatigue life of plates with fastener hole is.     

离散频谱多点卷积幅值修正法的理论分析

利用信号处理中的帕塞伐原理得到两个有关离散频谱特性的重要结论，在此基础上提出了离散频谱多点卷积幅值修正法，并讨论了算法中的参数选取问题，仿真计算表明该方法确实有效。理论分析还表明该方法特别适合于转速有小波动的旋转机械振动信号分析。     

Formulation of non-standard dissipative behavior of geomaterials

In this paper, fundamental mathematical concepts for modeling the dissipative behavior of geomaterials are recalled. These concepts are illustrated on two basic models and applied to derive a new form of the evolution law of the modified Cam-clay model. The aim is to discuss the mathematical structure of the constitutive relationships and its consequences on the structural level. It is recalled that non-differentiable potentials provide an appropriate means of modeling rate-independent behavior. The Cam-clay model is revisited and a standard version is presented. It is seen that this standard version is non-dissipative, which at the same time explains why a non-standard version is needed. The partial normality is exploited and an implicit variational formulation of the modified Cam-clay model is derived. As a result, the solution of boundary-value problems can be replaced by seeking stationary points of a functional.An erratum to this article can be found at .     

The theory of critical distances

The aim of this review article is to introduce the theory of critical distances, to which this special issue of the journal is devoted. The theory of critical distances (TCD) is the name which I have given to a group of theories used for predicting the effects of notches and other stress concentration features. The basic methodology is described, along with a number of variants which have developed over the years. After a brief history of the TCD, the predictive power of this group of theories is demonstrated, showing that they are capable of predicting experimental data on fracture and fatigue in a wide variety of circumstances. After some discussion regarding the fundamental scientific basis of the TCD, areas for future work in this field are suggested.     

Evolution of the Microstructure by High Velocity Impacts of Particles by Cold Spray

The cold spray technique is still in its innovation stage. This process is similar to other thermal coating techniques with the additional benefit of lower working temperature than the melting energy of the feedstock material. In this study, a new coating–substrate system is developed by using the 80%Ni–20%Cr feedstock powder sprayed by this technique on a superni 601 superalloy substrate. The coating microstructure depends upon both the substrate and coating material properties, and thus, coating obtained in this study has a unique microstructure. The coating microstructure developed and tested in this study by scanning electron microscopy/energy-dispersive x-ray spectroscopy (SEM/EDX) and X-ray diffraction (XRD) techniques is found to be suitable for boilers and incinerators.