碱式氯化镁晶须制备纳米氧化镁热分解动力学研究

采用水热法以氯化镁和氢氧化钙为原料制备了碱式氯化镁(BMC)晶须, 然后热解得到了纳米氧化镁。经透射电镜(TEM)和选区电子衍射(SAED)分析其粒径在20~40 nm之间, 暴露晶面族为{111}和{110}。通过热重差热分析(TG-DTA)、扫描电镜(SEM)、X射线衍射(XRD)以及红外光谱(FT-IR)分析确定了碱式氯化镁晶须热分解过程分四步进行, 前两步分别脱去两个结晶水, 第三步脱氯化氢, 最后脱羟基水。采用Satava法和微分法对BMC晶须的热分解机理和动力学进行了研究, 得出第一步反应热分解机理为随机成核与随后生长、第二步为二维扩散、第三步为相边界反应、第四步为一维相边界反应。     

碱式氯化镁晶须的制备与应用进展

详细论述了在碱式氯化镁晶须的制备过程中,碱试剂、氯化镁浓度、碱与氯化镁的物质的量比、反应及陈化温度和时间等因素对晶须结构与形貌的影响,并指出在当前碱式氯化镁晶须的制备研究中存在产率低、缺乏理论研究等问题.作为一种简单易得的无机晶须,目前碱式氯化镁晶须的应用还比较有限,对其进行有机改性或将其作为模板剂制备一维中空材料可以明显拓宽其应用范围.     

有机凝胶法制备微细纤维的研究

以柠檬酸、乳酸及金属盐为原料,采用有机凝胶法制备了微细金属镍纤维、氧化铝纤维和氧化镁纤维.纤维的直径可以<1μm,组成纤维的晶粒在100nm以下.通过FTIR、XRD、DSC和SEM对纤维前驱体凝胶的结构、热分解过程及热处理产物的形貌进行了表征,并对其形貌的可控性进行了初步探索.试验结果表明有机凝胶法是一种很有前途的微细纳米结构纤维制备方法.     

卤水-氨法制备纤维状碱式氯化镁

以MgCl2·H2O和NH3·H2O为原料，采用直接沉淀法合成纤维状碱式氯化镁。考察了各种因素对产物理化性能的影响，获得了最佳的工艺条件。利用XRD、SEM及化学分析方法对产品进行了表征。     

硬脂酸溶胶凝胶法制备氧化镁纳米微粒的研究

以硬脂酸为分散剂，采用溶胶凝胶法研究了制备氧化镁纳米微粒的条件，探讨了分散剂用量，反应时间，反应温度，烧结温度和时间对产物粒径与转化率的影响，取得了最佳工艺条件，分别用红外光谱（IR），X射线射末衍射（XRD），透射电镜（TEM）和比表面积（BET）测定，对该纳米微粒的结构与性能进行了表征，结果表明：Mg(NO3)2与CH3（CH2）16COOH的摩尔配比控制在1：1，于90℃反应20min，在470℃热处理3h，得到立方相氧化镁钠米微粒，形貌为椭球体，分散性好，平均粒径约为36nm.     

高纯超细氧化镁的制备工艺

以MgCl_2·6H_2O为原料,PVA与CTAB为添加剂,采用氨水直接沉淀制备氢氧化镁前驱体,再经煅烧得到高纯超细氧化镁。研究了温度、镁离子浓度、添加剂用量、原料配比和煅烧温度对氧化镁粒度的影响。确定最佳工艺条件为:反应温度40℃,Mg2+浓度1mol/L,PVA用量0.6%(质量分数),CTAB的用量1.2%(质量分数),n(NH_3·H_2O)∶n(MgCl_2·6H_2O)=3.3∶1,煅烧温度600℃,煅烧时间3h。荧光光谱分析表明,氧化镁纯度达到了99.9%以上;激光粒度和SEM结果显示,粒子分散性较好,平均粒径为190nm,粒度分布呈正态分布。     

纳米氧化镁制备技术的展望

对几种常见的制备纳米氧化铗的技术进行了详细的介绍和比较,分析了各种工艺存在的问题.液相沉淀法由于原料廉价,工艺简单使其成为最具有工业应用价值的纳米氧化镁制备技术.但该工艺中仍有诸如粒子团聚的机理、降低粒子团聚的手段等问题值得进一步研究.指出,相移、微波等新技术也应引入到纳米氧化镁的制备工艺中来.     

快速烧结法制备连续碳化硅纤维

通过熔融纺丝，不熔化处理制得连续聚碳硅烷（ＰＣＳ）不熔化纤维，采用快速烧结方法制备出性能较好的连续ＳｉＣ纤维。探讨了气封条件的选择，以及烧结速度对ＳｉＣ纤维的组成，结构及性能的影响。结果表明，快速烧结条件下，可以实现向纤维上施加张力以及纤维的无机化转变，烧结速度加快会降低纤维的Ｃ／Ｓｉ（原子比），同时有利于提高纤维的抗拉强度和热稳定性。     

制备氧化镁晶须的工艺和设备

本文对MgO晶须的应用状况作了简介，重点对MgO晶须的制备工艺和设备作了评述，为研制这种性能优良的增强材料提供了一些科学数据。     

聚四氟乙烯中空纤维膜的制备

通过聚四氟乙烯(PTFE)树脂糊料挤出和拉伸烧结成型方法,制备PTFE中空纤维膜.考察了拉伸倍数、温度和速度等拉伸工艺和烧结工艺对PTFE中空纤维膜的结构和性能的影响.实验结果表明,制膜参数中,随着拉伸倍数和温度的增加,平均孔径和孔隙率增加,泡点降低;随拉伸速度增大,膜平均孔径变小,泡点增加,拉伸速度对孔隙率的影响则呈现无规律变化;烧结可提高PTFE中空纤维膜的强度,孔径和孔隙率增加.PTFE中空纤维膜具有明显的非对称结构.     

A Novel Route to Prepare Nanocomposites in Larger Scale

A novel route to prepare nanocomposites was illustrated through preparing overbased calcium petroleum sulfonate lubricating oil detergent, where the rotating packed bed （RPB） was used as reactor in place of conventional reaction vessel. The results showed that the carbonation efficiency is improved, the raw materials consumption is reduced, and the dispersibilities, sizes and morphologies of nano-sized CaCO3 particles in overbased detergent are enhanced. It is deduced reasonably that this route can be extensively applied to nanocomposites preparation in appropriate conditions and would be a platform technology in this field.     

A Galvanic Replacement Route to Prepare Strongly Fluorescent and Highly Stable Gold Nanodots for Cellular Imaging

Fluorescent gold nanodots (GNDs) are an important kind of nanoprobes. Herein, the application of galvanic replacement for the preparation of fluorescent GNDs is reported. Using presynthesized and size‐controlled Ag nanodots (Ag NDs) as templates, the as‐prepared GNDs have strong fluorescence (quantum yields ～10%) with high stability and surface bioactivity. The resultant GNDs show excellent photoluminescence properties with high photo‐, time‐, metal‐, and pH‐stability, which are attributed to the protective surface layer of glutathione (GSH) and the presence of Au(I)–S complexes on the surface of the gold core. GSH, a naturally occurring and readily available tripeptide with carboxyl and amino functional groups, allows good dispersion of the as‐prepared GNDs in aqueous solution and favorable biocompatibility. These advantages, combined with their small size, mean that the as‐prepared GNDs have potential application in biological labeling, especially as a DNA probe for the specific detection of nucleic acids. In this study, the CAL‐27 cells are used as a model to evaluate the fluorescence imaging of GNDs.     

Solid State Shear Milling to Prepare Magnesium Hydroxide Flame-Retardant Polyamide 6 with High Performance

A novel processing method, that is, solid state shear milling (S3M), was adopted to compound high loading inorganic flame-retardant magnesium hydroxide with polyamide 6 by using our self-designed pan-mill equipment. S3M can effectively pulverize PA6, increase the interfacial interaction of the resin and magnesium hydroxide, and achieve their even blending, thus effectively controlling the state of the dispersion phase in solid state. With the co-milled composite powder as flame retardant master batch filled in original PA6 pellets, it can greatly improve the compatibility of the system, modify the distribution process of magnesium hydroxide, and decrease the dispersion phase size in the following melt processing. As a result, S3M technology can remarkably increase the melt flowability of the composite materials, and obtain obviously enhanced flame retardance and mechanical performance, thus providing an effective solution to the poor processibility and deteriorated performance of magnesium hydroxide flame-retardant PA6 obtained through direct melt processing.     

A Route Toward Smart System Integration: From Fiber Design to Device Construction

Fiber is a symbol of human civilization, being ubiquitous but obscure in society over most of history. Fiber has been revived upon the advent of fiber-based electronic devices in the past two decades. This is due to its desirable lightweight, flexible, and conformable characteristics, which enable it to play a fundamental role in the electronic and information era. Numerous fiber-based electronic devices have sprung up in energy conversion, energy storage, sensing, actuation, etc. A possibility is thereby conceived that they can be integrated into smart systems compatible with the human body, consisting of biotic fiber-based organs and tissues, which possess similar but more advanced functions. However, the design of mono-/multifibers, the construction of fiber-based devices, and the integration of these smart systems represent great challenges in fundamental understanding and practical implementation. A systematic review of the current state of the art with respect to the design and fabrication of electronic fiber materials, construction of fiber-based devices, and integration of smart systems is presented. In addition, limitations of current fiber-based devices and perspectives are explored toward potential and promising smart integration.     

Alkoxide Route to Re- and Mo-Based Metallic and Oxide Materials

The oxomethoxo complexes Re₄O₂(OMe)₁₆, Re₄O₆(OMe)₁₂, and Re_{4 –x} Mo _x O₆(OMe)₁₂ (x = 0.10, 2.82) are prepared via anodic dissolution of rhenium and molybdenum in methanol in the presence of LiCl. The phase composition of the solid products obtained by decomposing the synthesized complexes in oxidizing, inert, and reducing atmospheres is examined by x-ray diffraction. The results demonstrate that, by decomposing these complexes in the range 150–500°C, one can obtain Re-based metallic and oxide materials: ReO₃, monoclinic ReO₂, orthorhombic (Re,Mo)O₂ solid solutions, metallic Re powder, and Re–Mo alloys, including nanocrystalline powders.     

Carbon Long Fiber Reinforced Magnesium Alloys

Magnesium alloys have a high potential for reducing mass in automotive and aerospace applications due to their extraordinary low density. However, their utilization is often restricted since magnesium suffers from several material inherent deficiencies like low stiffness, poor high temperature strength, low wear and creep resistance as well as a high thermal expansion coefficient. Certain remedies have been developed in the past, e.g., extremely high in‐axis strength and stiffness values can be reached by the reinforcement of magnesium with carbon long fibers. This paper reviews the investigations at the University of Erlangen on carbon long‐fibers introduced into magnesium by a gas pressure melt infiltration technique.