水基纳米TiN流体介质颗粒分散性研究

由纳米TiN颗粒、水基液以及分散剂可制备得一种水基纳米TiN流体的溶液,并针对不同制备条件下溶液中纳米颗粒在水基液中的分散稳定性进行了研究.通过改变实验制备过程中机械搅拌和超声波分散时间、分散介质水基液的种类、分散剂的质量分数,制备出不同分散程度的溶液,然后采用沉降稳定性分析和流变特性分析对得到的溶液进行分散稳定性的评价分析.结果表明,上述因素均会对溶液的分散稳定性有一定程度的影响.过短的搅拌分散时间不利于纳米TiN流体介质中颗粒的分散;在不同分散介质中分散时,去离子水的分散效果最佳;适量质量分数的分散剂可以改善纳米流体的分散稳定性.基于上述分析提出了纳米TiN颗粒在水基液中的分散理论.     

非离子表面活性剂对有机染料水分散体的稳定化机制研究

<正>本文对非离子表面活性剂(作为分散剂)对C.I.分散蓝79水分散体的稳定化机制进行了研究.实验对这些分散体的稳定参量(沉降度)、动电性质以及表面活性剂在染料颗粒表面的吸附等温线进行了成功的关联.结果表明非离子表面活性剂对分散体的稳定化必须通过吸附来完成;活性剂吸附层可能对颗粒双电层结构产生影响.存在一个活性剂浓度的最佳值对应活性剂的吸附量极值和分散体的最佳稳定性.     

纳米TiC粉末在无水乙醇中的分散性

通过沉降观察和粘度测定，探讨了pH和分散剂聚乙烯亚氨（PEI）对纳米TiC粉末分散性的影响，借助FTIR和Zeta电位测定，测定了颗粒的表面成分和带电性质。结果表明：pH和pEI浓度对粉末的分散性有极大影响，pH和分散剂添加量存在一最佳值，对应的料浆分散性最好；PEI是有效的分散剂，pH=10．07，添加量为0．1181wt％时，能够制得分散稳定的料浆；纳米TiC粉末在无水乙醇中的分散，遵循静电稳定机制。     

水性体系pH值对炭黑分散的影响

本文在测定了三种不同炭黑的表面酸碱性的基础上,分别考察了分散剂结构、炭黑的表面性质对炭黑粒子与分散剂之间锚接强度的影响以及pH值对炭黑粒子间电斥力的影响。研究发现以离子型聚合物分散剂分散炭黑时,粒子间主要靠分散剂吸附层产生的位阻斥力达到分散稳定;而以非离子表面活性剂为分散剂时,由炭黑粒子表面酸性官能团解离所产生的电斥力对分散体系中粒子的分散稳定起着重要的作用。水性分散体系中,体系pH值的增加有利于炭黑表面酸性官能团和分散剂盐基亲水端的解离,从而增加粒子间的电斥力,提高炭黑的研磨效率和分散稳定性。     

纳米TiO2在水基体系中分散的研究

研究了不同体系、表面活性剂、分散剂、pH等因素对纳米材料分散的影响;通过不同手段对纳米材料和涂料的性质进行表征,从而改善了纳米TiO2在水基体系中的分散性.     

水性体系pH值对炭黑分散的影响

本文在测定了三种不同炭黑的表面酸碱性的基础上，分别考察了分散剂结构，炭黑的表面性质对炭黑粒子与分散剂之间锚接强度的影响以及pH值对炭黑粒子间电斥力的影响，研究发现以离子型聚合物分散剂分散炭黑时，粒子间主要靠分散剂吸附层产生的位阻斥力达到分散稳定，而以非离子表面活性剂为分散剂时，由炭黑粒子表面酸性官能团解离所产生的电斥力对分散体系中粒子的分散稳定起着重要的作用，水性分散体系中，体系pH值的增加有利于炭黑表面酸性官能团和分散剂盐基亲水端的解离，从而增加粒子间的电斥力，提高炭黑的研磨效率和分散稳定性。     

悬浮液中TiO2微粒分散性研究

研究了TiO2微粉在水介质中的分散行为。考察了不同pH值、分散剂和分散方式对TiO2粉体在水中的分散稳定性影响。利用粒度分析仪分析了分散剂对TiO2颗粒团聚行为以及稳定性的影响。并利用稳定机理对水溶液中TiO2分散稳定性作了解释。     

聚乙烯亚胺对纳米SiO2空心颗粒分散行为的影响

采用在制备过程中添加聚电解质型分散剂聚乙烯亚胺(PEI)和在制备好的纳米SiO2空心颗粒水悬浮液中添加PEI并球磨这两种方法对纳米SiO2空心颗粒进行分散,并对这两种方法进行了比较,最后采用以PEI作为分散剂,利用球磨工艺,对已制备的纳米SiO2空心颗粒水悬浮液进行分散的方法,研究了PEI在纳米SiO2空心颗粒表面的吸附行为及水悬浮液的分散稳定性.结果表明,PEI在纳米SiO2空心颗粒表面的吸附提高了颗粒间的排斥势能,改善了纳米SiO2空心颗粒的团聚问题及其悬浮液的稳定性.并阐明了加入PEI后纳米SiO2空心颗粒表面ζ电位的变化趋势、不同pH值下PEI在纳米SiO2空心颗粒表面的吸附量与其加入量的关系等.     

纳米Cu分散稳定性能影响因素及作用机理研究

鉴于粉体分散对纳米流体强化传热具有重要意义,通过测定纳米Cu-水悬浮液的Zeta电位和吸光度,探讨了不同pH值、不同分散剂种类及质量分数对纳米Cu-水悬浮液分散稳定性的影响,并分析其作用机理。结果表明:Zeta电位绝对值与吸光度有良好的对应关系,Zeta电位绝对值越高,吸光度越大,则体系分散稳定性越好;pH值、分散剂种类及加入量是影响纳米Cu-水悬浮液分散稳定性的主要因素。pH值为9.5左右时,体系Zeta电位绝对值和吸光度较高,相应分散稳定性较好。CTAB和SDBS能显著提高水溶液中Cu表面Zeta电位绝对值,增大了颗粒间静电排斥力,改善了悬浮液稳定性,而TX-10通过空间位阻在颗粒表面形成良好的水化膜,提高了Cu在水溶液中的分散稳定性。在质量分数为0.1%的纳米Cu-水悬浮液中,TX-10,CTAB,SDBS 3种分散剂加入质量分数分别为0.43%,0.05%,0.07%时,均能得到分散稳定的悬浮液体系。     

纳米二氧化硅水悬浮液的稳定性研究

本文采用胶体“电空间稳定机制”,以聚羧酸盐为分散剂,研究了纳米S iO2粉体在水中的分散行为和表面化学特性,讨论了pH值、分散剂种类及用量对体系的悬浮稳定性及流动特性的影响。在最佳pH值和分散剂加入量条件下制备了高固含量、稳定性和分散性好的纳米S iO2浆料。     

纳米氧化锌在水介质中的分散性能研究

纳米粉体的分散性能对提高分散体系的导热性能具有重要意义,试验选用纳米粒子在水介质中的Zeta电位和水合粒径来表征体系的分散稳定性,探讨不同分散剂种类及其浓度以及不同pH条件对ZnO水悬浮液稳定性的影响,并分析其作用机理.结果表明:Zeta电位与水合粒径有良好的对应关系,Zeta电位绝对值越高,水合粒径越小,表明体系分散稳定越好.pH值、分散剂种类及加入量是影响纳米ZnO水相体系分散稳定性的主要因素,不同的分散剂最佳分散条件不同.在 0.1% ZnO-H2O纳米流体中,在 pH=11.4,加入 0.05%十二烷基苯磺酸钠(SDBS)分散剂,悬浮液的稳定性最佳.     

Ultrafine comminution of dental glass in a stirred media mill

A systematic study on the comminution of amorphous glass particles with complex composition (seven constituents) to produce nanoparticles has been performed in a high-energy stirred media mill. The influence of solids loading, dispersion stabilisation via pH and addition of dispersants on particle size was investigated in aqueous suspensions. Further, the effect of using 2-propanol and benzyl alcohol as dispersion media on the particle size and morphology is presented and compared to the aqueous system. The specific surface area of the product powder was analysed by the BET method, the secondary particle size was determined by static light scattering and the morphology was investigated by SEM and TEM. Dispersion viscosity and stability was measured using rotational viscosimetry and zeta-potential measurements, respectively. The results show that the solids loading plays a central role in the comminution efficiency, where lower loadings lead to finer particles after a given milling time. Stabilisation of the aqueous powder dispersion by adjusting the pH or by adding a dispersant did not result in an enhanced milling efficiency in terms of fast reduction of the particle size. The smallest glass nanoparticles with a primary particle size were achieved by a two-step comminution process. The particles were irregularly shaped when milled in water, however, when processed in 2-propanol and benzyl alcohol, they had a plate-like geometry.     

分散剂用量对碳化硅浆料流变性能的影响

使用四甲基氢氧化铵(TMAH)作为分散剂,研究了分散剂用量对SiC浆料流变性能的影响,并分析了其原因。结果表明：TMAH能够显著提高SiC粉体的zeta电位,降低浆料粘度,从而显著优化浆料的流变性能。在pH为10左右,加入质量分数为0．3％和o．6％NTMAH后zeta电位分别提高了11.7mV和21mV。实验中,在不同体积分数SiC浆料中,加入0．6%TMAH时能够达到最优性能,浆料粘度都达到最低。过量的分散剂则会增加浆料中的离子浓度而导致双电层厚度减小,从而恶化浆料的流变性。     

Dispersion and rheological properties of concentrated silicon aqueous suspension

This work focuses on the optimization of the rheological properties of silicon suspensions by changing the concentration of a dispersant and the pH value of the dispersing medium. The zeta potential and rheological properties of silicon suspensions as a function of tetramethyl ammonium hydroxide (TMAH) concentration were carried out. The results show that the isoelectric point of the silicon particles was at pH 1.6. A silicon suspension with 46 vol.% particles displayed a minimum viscosity at pH 9.6. The results also show that TMAH is an efficient dispersant by enhancing the absolute value of the zeta potential of silicon particles. The optimum dosage of the dispersant was 0.4 wt.% of silicon particles.     

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].     

Membrane dispersion precipitation method to prepare nanopartials

In this paper, a new method for preparing nanoparticles with membrane dispersion technology was developed by integrating direct chemical precipitation and membrane emulsification. Barium sulfate nanoparticles were prepared with the new method in a membrane dispersion module with a plate microfiltration membrane as dispersion medium. Barium chloride solution and sodium sulfate solution with pure water or 20% ethyl alcohol in water as solvents were selected as the reactants. The influences of the reactant concentrations, two-phase flow rate and membrane pore size were investigated. The morphology of the nanoparticles was characterized by TEM images, and the particle-size distribution was measured. The results showed that the spheric nanoparticles of barium sulfate could be prepared with the new method. The average size was in the range of 20-200 nm. The particles prepared by the new method were much more uniform, compared with those by direct precipitation method. The average size of barium sulfate nanoparticles was decreased with an increase of the concentration and the flow rate of sodium sulfate solution quickly. However, those of barium chloride solution had little influence on barium sulfate nanoparticles. The decreasing of the membrane pore size resulted in the decrease of the average size of barium sulfate nanoparticles. And by changing 20% ethyl alcohol in water as solvent instead of pure water, the nanoparticle size was decreased from 70 to 20 nm.     

复合分散体系对聚氯乙烯树脂颗粒特性的影响

以三氯乙烯模拟氯乙烯(VC),考查聚乙烯醇(KH20)/羟丙基甲基纤维素(60SH50)复合分散剂的分散能力和保胶能力,发现分散能力和保胶能力均随分散剂用量的增加而提高;复合分散剂中KH20比例增大,分散能力下降而保胶能力增强。以此为基础进行VC悬浮聚合,研究分散剂对聚氯乙烯(PVC)树脂颗粒特性的影响。发现适量的分散剂可同时提高PVC树脂的表观密度和增塑剂吸收量;增大KH20的比例可提高PVC树脂的表观密度,同时使粒度分布变窄,但是增塑剂吸收量有所下降。     

Dispersion of Boron Nitride Powders in Aqueous Suspensions with Cellulose

The dispersion of nitride and carbide ceramic particles in water is difficult, due to the absence of hydroxyl groups on their surface. Boron nitride (BN) is not an exception and despite its numerous applications, no effective dispersant has been identified so far. We demonstrate here the dispersion properties of two cellulose derivatives for hexagonal BN powders, hydroxyl ethyl cellulose and methyl cellulose. The effect of particle size and cellulose concentration was investigated. The adsorption of cellulose onto the surface of the BN particles was confirmed by isotherm adsorption. Zeta potential measurements show a charge screening effect of the cellulose The suspensions obtained were highly loaded and stable versus pH, and thus could lead to homogeneous codispersion of BN particles and sintering additives.     

飞龙掌血提取物抑菌作用初步研究

选择蒸馏水、无水乙醇、乙酸乙酯、石油醚4种提取剂,采用冷浸、加热回流两种方法萃取飞龙掌血,比较提取物对枯草杆菌、痢疾杆菌、啤酒酵母菌的抑菌效果。结果表明,冷浸 72 h 和加热回流 5 h 的飞龙掌血提取物对该3种菌的抑菌作用无显著差异,无水乙醇、乙酸乙酯提取物较水提物有显著差异;生药质量浓度为 0.25 g/mL 的乙醇提取物对3种菌都有极显著的抑菌效果,适宜抑菌生药质量浓度为 0.5 g/mL;pH值对该提取物的抑菌效果影响较大,3个菌种适宜抑菌的pH值不同。