表面包覆Al(OH)3改性石墨的研究

采用异相成核法在天然鳞片石墨水悬浮液中 ,使硫酸铝水解 ,在石墨表面包覆一层Al(OH) 3对石墨进行表面改性处理。介绍了包覆条件对石墨表面改性的影响 ,对改性后的石墨进行了形貌观察、接触角测定、差热 -热重分析。研究结果表明 :在适当的条件下 ,可在石墨表面形成Al(OH) 3包覆层 ,pH值为 4 .0时 ,包覆效果最好 ;包覆后石墨的抗氧化性及对水的润湿性均有所提高     

PCL包覆Al(OH)_3填充PLA的结构与性能

采用高速混合机将低熔点的聚己内酯(PCL)包覆在Al(OH)3表面,然后通过熔融混炼法分别制备了包覆Al(OH)3、未包覆Al(OH)3以及纯PCL填充聚乳酸(PLA)的复合材料,研究了包覆前后的Al(OH)3及其与PLA复合材料的微观形态,以及复合材料的力学性能、流变性能、热性能和降解性能。结果表明:PCL包覆Al(OH)3填充PLA可以显著提高复合材料的拉伸性能,当Al(OH)3/PCL=100/20时,在PLA中加入5phr包覆Al(OH)3后,复合材料的断裂伸长率可以提高到176%;PCL能有效改善包覆Al(OH)3颗粒在PLA中的分散性及与PLA之间的界面结合力,同时,填料表面多余的PCL能以微球粒子形式分散在PLA中,起到良好的增塑作用;少量包覆Al(OH)3能显著提高PLA的结晶度降,低其结晶温度促,进其降解。     

水热法制备氢氧化镁改性鳞片石墨

为了提高鳞片石墨的水润湿性，以无水硫酸镁和氨水为主要原料，采用水热法在鳞片石墨表面生成氢氧化镁改性层，主要研究了表面活性剂种类(十二烷基苯磺酸钠、聚丙烯酸钠),水热温度(180、190、200℃),C、Mg²⁺质量比(1∶10、2∶10、3∶10)对改性鳞片石墨水润湿性和抗氧化性的影响。结果表明：1)改性石墨表面生成了片状氢氧化镁包覆层，其水润湿性和抗氧化性提高。2)以聚丙烯酸钠为表面活性剂，采用3∶10的C、Mg²⁺质量比，在190℃水热处理12 h,制得的改性石墨的水润湿性和抗氧化性最好。     

硬脂酸对纳米Al2O3的有机表面修饰研究

为提高纳米α-Al2O3粒子在有机体系中的分散性和相容性,对纳米α-Al2O3进行了有机表面改性.首先制备了纳米α-Al2O3水分散液,然后把纳米Al2O3水分散液转移到溶有硬脂酸的正丁醇溶液中,升温到一定温度,将纳米Al2O3浆体中的水分蒸馏出去,使纳米Al2O3在有机相中进行表面改性,使得纳米Al2O3有机表面改性和防团聚处理一步完成,得到了团聚程度较小的纳米Al2O3粉体.采用红外光谱(IR)、热分析(TG-DTA)、透射电镜(TEM)、润湿性实验、分散性实验等手段对表面改性前后的纳米Al2O3进行表征.红外光谱和TEM表明,在纳米Al2O3表面包覆有硬脂酸的有机层,并且可能有硬脂酸铝的生成.热分析显示,包覆量约为16.7%.润湿性实验及分散性实验表明,经硬脂酸改性的纳米Al2O3的表面性质由亲水变为疏水.     

硬脂酸对纳米ZnO的有机表面修饰研究

利用硬脂酸对纳米ZnO进行有机表面修饰;采用红外光谱(IR)、热分析(TG-DTA)、透射电镜(TEM)、润湿性实验、分散性实验等手段对表面改性前后的纳米ZnO进行表征。红外光谱和TEM表明,在纳米ZnO表面包覆有硬脂酸的有机层;热分析显示,包覆量约为18.98%;润湿性实验及分散性实验表明,经硬脂酸改性的纳米ZnO的表面由亲水性变为亲油性。     

表面改性剂和硅油对HDPE/Al(OH)3力学性能的影响

探讨了各种表面改性剂和硅油对高填充HDPE/Al（OH)3复合材料力学性能的影响。研究表明,使用经特殊表面改性剂处理的Al（OH)3作填料并加入硅油时,可以大幅度提高HDPE/Al（OH)3复合材料的缺口冲击强度和断裂伸长率。利用扫描电镜和差示扫描量热仪研究了Al（OH)3的表面改性对硅油分布的影响,观察到硅油的两种分布类型;包覆Al(OH）3粒子和以液滴形式与Al(OH）3粒子单独分散于HDPE中,并将硅油的分布状况与材料的力学性能作了对比分析。     

HDPE-g-MAH改性氢氧化铝阻燃PP

在液相中用马来酸酐接枝高密度聚乙烯(HDPE-g-MAH)表面改性Al(OH)_3以改善其在高分子基相中的分散性。形态观察表明,用适量HDPE-g-MAH处理Al(OH)_3可改善Al(OH)_3在聚丙烯(PP)中的分散性,从而提高体系的力学性能;HDPE-g-MAH用量过多造成的Al(OH)_3粒子间桥联,该现象经熔融混合后依然存在,导致力学性能降低。偏光显微镜观察显示,适量HDPE-g-MAH处理Al(OH)_3可改善PP的结晶形态。     

两性表面活性剂及脂肪酸对联苯胺黄G的改性研究

本文以两性表面活性剂和脂肪酸对联苯胺黄G表面改性，测定了颜料的流动性、润湿性和分散性。结果表明，添加脂肪酸后，颜料的流动性和在非极性介质中的润湿性和分散性有所提高；添加两性表面活性剂后，颜料的流动性及在极性、非极性介质中的润湿性和分散性均得以改善，并随活性剂用量的增加呈递增趋势。     

改性纳米Al(OH)3粉体的制备

以铝酸钠溶液和二氧化碳气体为原料，采用碳分法制备纳米Al(OH)3粉体. 考察了原料液浓度、气液流量比、旋转填料床转速等因素对Al(OH)3粒径d50的影响. 在Al(OH)3胶体溶液中添加复合表面活性剂三乙基苄基氯化铵/磷酸钠(TEBAC/PO43-)，对Al(OH)3粒子进行防团聚研究. 利用XRD和TEM等测试方法对最终产物进行了分析表征，表明所制备的Al(OH)3粒子呈单斜晶系，具有憎水性，粒度分布均匀，平均粒径20 nm.     

Al2O3包覆石墨颗粒的制备及表征

以Al(NO3)3·9H 2O为主要原料,采用非均匀成核技术在鳞片状石墨表面包覆一层Al2O3,制备成石墨/氧化铝复合粉体.对复合粉体的制备条件、表面形貌和特性进行了研究.研究表明pH值、处理温度和覆层物质前驱体浓度是影响包覆的主要因素.TEM观察和XPS能谱检测表明,石墨颗粒表面均匀包覆有一层Al2O3.包覆后石墨表面由疏水转为亲水.     

水基纳米SiC复合料浆的流变性能和稳定性

引言 纳米复相碳化硅陶瓷是在多相复合碳化硅陶瓷基础上发展起来的-种新型碳化硅陶瓷材料,通过引人第二或第三纳米增强相来同时实现细晶结构、梯度残余应力场、裂纹桥联、自增韧等增强增韧机理,从而获得多强韧化机理协同强化碳化硅陶瓷,已成为碳化硅陶瓷的研究方向之一[1-4].其中,纳米增强相在碳化硅基体(包括料浆、复合粉体、陶瓷)中的分布是制备纳米复相碳化硅陶瓷的关键和前提之一[5].     

Reinforcing effect of graphene nanoplatelets in the electrochemical behaviour of manganese oxide-based supercapacitors produced by EPD

A simple procedure for the manufacture of metal oxide based supercapacitors consisting on the electrophoretic deposition (EPD) onto graphite paper of well-dispersed aqueous slurries of manganese oxide with graphene nanoplatelets is presented. EPD was performed using optimised slurries and depositing onto graphite paper electrodes. In order to improve manganese oxide conductivity graphene nanoplatelets (GNP) were incorporated in a concentration of 20 wt% over the MnO₂ content. The evaluation of the electrochemical properties of the so prepared deposits demonstrates that the addition of GNP improves both the capacity and specific energy, with values of 158 F g⁻¹ and 4 W h Kg⁻¹ respectively, which represents four times the values reported for the bare manganese oxide.     

Development of a technique for measuring the degree of dispersion of chrysotile fibre in aqueous systems

Chrysotile asbestos, when dispersed in an aqueous solution of a soap or a detergent by high shear mixing, results ultimately in a colloidal dispersion consisting of fibrils of approximately 30 nm in diameter and very high aspect ratio. In the intermediate stages of the dispersion process, slurries are produced which are represented by a wide range of colloidal concentrations and conversely a wide range of undispersed, macroscopic fibre concentrations. The degree of dispersion in these slurries and the dispersion mechanism cannot be assessed by existing methods of analysis. A new method capable of estimating the degree of fibre dispersion has been developed and has been termed Load Impulse Analysis. In the dispersion process, the disappearance of macroscopic fibres may be estimated and the development and destruction of a colloidal structure has been illustrated through this type of analysis. The meaning of the viscosity of a fibre dispersion measured at a low shear rate is also made clearer.     

Surface modification of ultrafine silicon nitride powders by calcination

Calcination was used for surface modification of ultrafine silicon nitride powders, which improved the flowability and dispersion stability of their slurries. Surface characteristics of the powder were investigated by X-ray photoelectron spectroscopy, which showed the generation of an oxide layer and partial elimination of amine groups on the particle surfaces. Ion analysis results suggested a drop in both ion conductivity and supernatant concentration after calcination. For the as-received powder, poor flowability and dispersion stability was caused by high-valence cations, which were detrimental to colloidal processing according to the Schulze–Hardy rule, and surface amine groups were also present; both of these were partly removed by calcination. The oxide layer formed on the particle surfaces hydrolyzes into silanol groups when the powder is dispersed in aqueous solutions, which was favorable for surface charging and formation of higher diffuse layer potential on the particles. These factors contributed to the improved flowability and dispersion stability of the slurries.     

Determination of particle size distribution of salt crystals in aqueous slurries

A method for determining particle size distribution of water-soluble crystals in aqueous slurries is described. The salt slurries, containing sodium salts of predominantly nitrate, but also nitrite, sulfate, phosphate, aluminates, carbonate, and hydroxide, occur in radioactive, concentrated chemical waste from the reprocessing of nuclear fuel elements. The method involves separating the crystals from the aqueous phase, drying them, and then dispersing the crystals in a non-aqueous medium based on nitroethane. Ultrasonic treatment is important in dispersing the sample into its fundamental crystals. The dispersed crystals are sieved into appropriate size ranges for counting with a HIAC brand particle counter. A preponderance of very fine particles in a slurry was found to increase the difficulty of effecting complete dispersion of the crystals because of the tendency to retain traces of aqueous mother liquor. Traces of moisture produce agglomerates of crystals, the extent of agglomeration being dependent on the amount of moisture present. The procedure is applicable to particles within the 2 – 600 μm size range of the HIAC particle counter. The procedure provides an effective means for measuring particle size distribution of crystals in aqueous salt slurries even when most crystals are less than 10 μm in size.     

新型高性能陶瓷成型法的研究

探讨了一种新的非化学反应直接凝聚固化成型方法。利用高分子电解质分散剂可以制备固体含量高、流动性良好的陶瓷泥浆。这种泥浆注入非多孔性模具后 ,无需生物酶催化反应 ,只需将温度升至70～80℃ ,泥浆便由分散状态转为凝聚状态 ,泥浆即达到固化成型。这种方法具有工艺简单、容易控制的特点 ,并且可以获得高致密、高均匀性的陶瓷成型体。通过对氧化铝 -高分子电解质 -水系统的吸附及流动特性进行的系统的研究 ,提出了覆盖率理论 ,解释了用经典的DLVO理论难以解释的胶体稳定性与温度敏感特性之间的关系     

8%Y2O3-ZrO2水基料浆的流变性质研究

详细研究了固含量、球磨时间、分散剂用量和pH值对8％摩尔分数Y2O3稳定ZrO2水基料浆流变性质的影响。结果表明：料浆均表现出剪切变稀行为，且为假塑性流体。确定了最佳实验参数，当pH=10，分散剂用量为2％体积分数，球磨24h的ZrO2水基料浆，稳定性好，适合于成型薄片ZrO2固体电解质材料，并最终制备出体积分数为56％，适合浇注的ZrO2陶瓷料浆。     

Processing of Concentrated Aqueous Silicon Nitride Slips by Slip Casting

The optimization of concentrated Si₃N₄ powder aqueous slurry properties to achieve high packing density slipcast compacts and subsequent high sintered densities was investigated. The influence of pH, sintering aid powder (6% Y₂O₃, 4% Al₂O₃), NH₄PA dispersant, and Si₃N₄ oxidative thermal treatment was determined for 32 vol% Si₃N₄ slurries. The results were then utilized to optimize the dispersion properties of 43 vol% solids Si₃N₄-sintering aid slurries. Calcination of the Si₃N₄ powder was observed to result in significantly greater adsorption of NH₄PA dispersant and effectively reduced the viscosity of the 32 vol% slurries. Lower viscosities of the optimized dispersion 43 vol% Si₃N₄-sintering aid slurries resulted in higher slipcast packing density compacts with smaller pore sizes and pore volumes, and corresponding higher sintered densities.     

Preparations of silica slurry for wafer polishing via controlled growth of commercial silica seeds

Silica slurry in aqueous medium for wafer polishing was prepared by sol-gel reaction of silicon alkoxide utilizing commercial silica particles as seeds that were grown stepwise through intermittent additions of tetraethylorthosilicate (TEOS) as a silica precursor. Before the growth reaction, the commercial silica particles were pre-treated in the vibratory mill partially filled with zirconia ball and the sonicator to ensure good dispersion. The alcohol left after growth reaction was removed by vacuum distillation and repeated washings with distilled water followed by centrifugations. Then, the alcohol-free silica particles were redispersed in water. The dispersion stability of the silica slurries was examined by measuring surface charge of silica particles and rheological properties. Finally, wafer-polishing performance of the prepared silica slurries was considered by measuring the polishing (or removal) rate, and RMS (root mean square) roughness of the polished wafer surface. For the polishing, MEA (monoethanolamine) and TMAH (tetramethylammonium hydroxide) were used as polishing accelerators. The polishing result showed that the removal rate was nearly independent of the concentrations of MEA and TMAH in the range of 0.3-0.5 wt% and 100-500 ppm, respectively. One of the most interesting features is that hydrothermal treatment of the prepared silica slurries in autoclave increased the removal rate as high as ten times. Although the removal rate was increased by the increased size of the abrasive particle, surface roughness of the polished wafer surface was deteriorated.