用于悬浮浸渗法制备短GF／PP复合材料的PVA型悬浮液性的研究

发展了一种用悬浮浸渗法制备短玻璃纤维增强聚丙烯复合的新工艺方法，研究了以ＰＶＡ为稳定剂的悬浮液中各组分对悬淳液稳定性影响，给出了描述稳定剂尝试与悬浮液分怪时间之间函娄绵经验公式。     

直写成型用悬浮液的设计

直写成型技术是一种新型的三维复杂结构的制备方法。本文综述了直写成型用悬浮液的研究进展: 根据直写成型悬浮液的固化特点, 将之划分为自固化悬浮液和外固化悬浮液; 分析了自固化悬浮液的流变性能要求与设计准则, 综述了典型的自固化悬浮液; 分析了外固化悬浮液的要求与固化方式, 并总结了典型的外固化悬浮液与固化方式; 探讨了直写成型用悬浮液的发展方向。     

相变微胶囊悬浮液传热性能的研究进展

相变微胶囊悬浮液作为一种潜热型功能流体,其独特的性能使其受到科研工作者的关注。在回顾了现有相变微胶囊悬浮液传热性能的研究进展,对相变微胶囊悬浮液的导热性能、对流传热特性分别进行介绍。讨论了悬浮液的体积浓度、雷诺数(Re)、斯蒂芬数(Ste)、努塞尔数(Nu)及无量纲过冷度等因素对相变微胶囊悬浮液换热能力的影响,以及相变微胶囊悬浮液管内换热特性。本文针对相变微胶囊悬浮液中添加纳米粒子(纳米Al_2O_3,纳米Fe,纳米TiO_2)和磁性材料对其导热系数和强化传热的提升情况进行了讨论,并指出了目前研究存在的问题和今后研究的发展方向。     

重悬浮液的回收净化系统与密度自动控制

本文主阐述了重悬浮液的回收净化系统、悬浮液密度的自动控制等问题。     

高浓度悬浮液声学特性的探讨

关于低浓度悬浮液的声学特性，过去已有很多文献进行过讨论，本文着重于高浓度悬浮液的讨论。文中根据波长远大于粒径（ｋａ＜＜１）条件下悬浮液小体元内固、液二部分应力相等的假设，以及粘滞流体与团体颗粒之间发生相对运动时的附加质量和粘滞阻力的概念，探讨了悬浮液在粘滞性作用下的声学特性。 本文的结果显示了超声技术应用于悬浮液参数测量方面的前景。     

相变微胶囊悬浮液的对流换热特性研究进展

相变微胶囊悬浮液是既具有流动性又兼具蓄热能力的功能性流体。相变微胶囊悬浮液在工作过程中涉及复杂的流体流动与传热以及储热过程,近年来成为国内外学者研究的热点。对相变微胶囊悬浮液在圆管、小(微)通道内的对流换热特性进行了综述,重点阐述了国内外学者对于相变微胶囊悬浮液是否能强化对流换热存在的分歧,并提出了自己的分析与看法。分析了圆管与小(微)通道对流换热机理的区别,最后概述了强化相变微胶囊悬浮液对流换热的方法。     

相变微胶囊悬浮液的研究进展

相变微胶囊悬浮液是集储热与强化传热功能于一体的新型工质,在建筑与空调节能、太阳能利用以及航空等领域有广阔的应用前景。对相变微胶囊的制备方法、相变微胶囊乳化剂、相变微胶囊悬浮液稳定性以及流变特性的研究进展进行了综述。总结了相变微胶囊悬浮液的应用研究进展,通过分析相变微胶囊悬浮液的应用实例,提出了今后的研究方向。     

磷酸锆碟片粒径对提高二氧化钛悬浮液分散稳定性的影响

制备纳米二氧化钛(TiO_2)分别和729.6,1 004.5,1 168.5nm 3种粒径的磷酸锆碟片(ZrP)混合纳米悬浮液,研究了混合悬浮液的分散稳定性。运用稳定性性分析仪,沉降实验和紫外-可见分光光度计综合分析了纳米悬浮液的分散稳定性,并测量了混合悬浮液的粘度。结果表明,加入ZrP碟片后,TiO_2悬浮液的粘度增大,稳定性提高;3种混合纳米悬浮液的粘度相近,但ZrP粒径最小的混合悬浮液,其分散稳定性最好。通过分析发现,3种混合纳米悬浮液中,ZrP粒径越小,颗粒团聚粒径和团聚速度越小,其原因可能是ZrP碟片的粒径越小,相同质量浓度条件下碟片数目浓度越大,对TiO_2的空间位阻作用越强。     

固液密度比对PMMA/HDPE悬浮液粘度的影响

固液密度比是影响悬浮液粘度的重要参数,准确预测悬浮液的粘度对材料分选具有重要意义.本工作基于实验方法,采用不同密度的PM-MA/HDPE颗粒组成两种悬浮液,研究了固液密度比对悬浮液粘度的影响.结果表明:在相同固体体积分数下,悬浮液的粘度随固液密度比的增加而降低;在不同固液密度比下,低固体体积分数下悬浮液的粘度增长速度低于高固体体积分数下的粘度增长速度;颗粒粒径越小,悬浮液的粘度随固液密度比的增加降低得越快.在实验条件范围内,对PMMA/HDPE两种悬浮液分别采用Batchelor模型和Leighton模型,建立了相应的修正模型,并验证修正模型的准确性.     

用于电泳沉积的TiO2悬浮液分散性能研究

为了制备适合电泳沉积用的稳定悬浮液,在TiO2水基悬浮液中添加了聚乙烯亚胺(PEI)作为分散剂,对TiO2水基悬浮液进行Zeta电位、黏度、粒径以及稳定性测试,研究了PEI分散剂对TiO2分散性能的影响.结果表明通过添加相对于悬浮液中TiO2粉体质量分数0.6%～3.0%的分散剂可以获得高稳定、高分散、低黏度的悬浮液.     

Surface-charge density and potential of coal-liquid mixtures and control of their stability and fluidity

The preparation conditions of concentrated (>70%) aqueous suspensions of coal were optimized, as were the surface charge density and the surface potential of the coal-water suspensions. The theoretical study showed that (1–3) or (2–3) electrolytes such as Na₂SO₄ or Na₅P₃O₁₀, greatly increase the surface charge density and the surface potential of the coal particles in water. This study has led to the interesting result that thinners and stabilizing agents of concentrated clay suspensions, such as lignosulphonates, tripolyphosphates, polynaphtalene sulphonates, etc., must also be good thinners and stabilizing agents for ground coal-water suspensions. Two parameters were controlled: the stability and the fluidity of the suspensions. A penetrometry technique revealed the importance of the resistance coefficient,C _r that can be used as a criterion for the evaluation of coal-water mixture stability and fluidity. Concentrated coal suspensions (about 75% of solid by weight) were prepared in water by using different additives, for instance sodium tripolyphosphate (NaTPP) and surfactants like lignosulphonates (by coupling of the dispersion and stabilizing effects) with the optimum concentration ratio of these two products equal to 1.9. The stability of the suspensions was then greater than 2 months and the viscosity was 1900 cP.     

A novel approach of developing micro crystalline cellulose reinforced cementitious composites with enhanced microstructure and mechanical performance

This paper reports a novel approach of preparing aqueous suspensions of microcrystalline cellulose (MCC) for fabrication of cementitious composites. MCC was dispersed homogeneously in water using Pluronic F-127 as a surfactant with the help of ultrasonication process and the aqueous suspensions were added to cement/sand mixture to prepare cementitious composites. A commonly used stabilizing agent for MCC, carboxy methyl cellulose (CMC) was also used for the comparison purpose. The prepared suspensions were characterized through visual inspection, UV-Vis spectroscopy and optical microscopy. The developed composites were characterized for their bulk density, flexural and compressive properties as well as microstructure. The influence of Pluronic and CMC concentration, superplasticizer, dispersion technique and dispersion temperature on mortar's mechanical performance was thoroughly studied to find out the optimum conditions. Overall, Pluronic (with Pluronic: MCC ratio of 1:5) led to better MCC dispersion as well as dispersion stability as compared to CMC. The best mechanical performance was achieved with Pluronic in combination with superplasticizer using ultrasonication process, resulting in improvement of 106%, 31% and 66% in flexural modulus, flexural strength and compressive strengths, respectively (highest values reported till date). The bulk density and hydration of cementitious composites also improved significantly with the addition of MCC.     

Stabilization of water suspensions of metal powders

Sedimentation stability of water suspensions of dispersed metal powders with water-soluble high-molecular compounds (HMC) added is investigated by a method of analyzing the kinetics of their sedimentation. When stabilizing by polyvinyl alcohol (PVA) the concentration regions of sedimentation stability for the suspensions are determined. The stabilization is explained according to the model of formation of coagulation HMC layers on metal particles. The dependence of the coagulation layer thickness on the concentration of PVA in the solution is estimated.Republican Engineering-and-Technical Center of Powder Metallurgy, Perm'. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 64, No. 5, pp. 583–587, May, 1993.     

Characterization of the porosity of thin zirconium oxide coatings prepared at low temperatures

In this work we investigated the possibilities to reduce the porosity of thin protective zirconium oxide films deposited with the sol-gel technique at low temperatures. Electrochemical investigations showed that the concentration of the stabilizing agent acetylacetone is a crucial parameter for the protection performance of the zirconium oxide films and that it is possible to run the deposition process at much lower temperatures with the optimum stabilizer concentration. This allows the application of the process to sensitive substrates that cannot be treated at high temperatures and reduces energy costs as well. Characterization of the film structure with secondary ion mass spectrometry revealed that the stabilizing agent is responsible for the formation of a mixed oxide layer at the interface of substrate and coating. The thickness of this layer can be tuned with the concentration of the stabilizing agent.     

碳纤维表面化学镀铜工艺研究

传统的化学镀铜以甲醛作还原剂,污染环境.以环保型还原剂次亚磷酸钠代替甲醛,加入各种不同的稳定剂在碳纤维表面进行化学镀铜,获得了具有一定厚度、均匀、光亮的铜镀层.研究了镀液pH值、温度及还原剂、配位剂、稳定剂用量对化学镀铜溶液稳定性和碳纤维增重率的影响,确定了新的镀铜配方.用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、能谱、冷热循环处理等手段,分析了化学镀铜层的微观形貌、结构及成分.结果表明,通过此新型的环保镀液配方和工艺条件,可获得光亮、致密、均匀及含铜量较高的镀层.     

Effect of different aqueous synthesis parameters on the size of CdSe nanocrystals

The variation of CdSe nanoparticle size as a function of synthesis conditions is presented. Cadmium sulphate (CdSO₄), cadmium chloride (CdCl₂) and sodium selenosulphate (Na₂SeSO₃) solutions were used as precursors. Nanoparticles were synthesized by aqueous chemical methods. The synthesis parameters studied were pH, Cd:Se ratio and the type of stabilizing agent. Three different stabilizing agents were used, thioglycolic acid, mercaptoethanol and poly(vinyl pyrrolidone). Fourier transform infrared spectroscopy results confirmed the presence of the stabilizing agent on the surface of the nanoparticles. Ultraviolet visible and X-ray powder diffraction measurements were used to estimate the trend of size variations of the particles with different synthesis parameters, which agreed fairly by both techniques and the crystal structure. Additionally, the size of the nanoparticles was obtained by transmission electron microscopy measurements. Whilst the effect of pH was different for each of the different stabilizing agents due to the different chemical groups in the thiol compounds and the size of the nanoparticles varied with the used stabilizing agents, the effect of Cd:Se ratio in the size of nanoparticles showed the same tendency for the several stabilizing agents.     

微米α-Al_2O_3粉体的细化及其悬浮液的分散稳定性

在微米α-Al2O3粉体悬浮液中分别加入无机电解质类分散剂六偏磷酸钠、阳离子型表面活性剂十六烷基三甲基氯化铵、阴离子型表面活性剂油酸和非离子型表面活性剂异丙醇胺,并对悬浮液进行球磨分散,研究分散剂加球磨复合分散下的最优分散剂及最佳球磨参数;引入超声分散,对比分析在加入分散剂的情况下,先球磨再超声和只进行球磨时的分散效果。结果表明,采用十六烷基三甲基氯化铵为分散剂,先球磨2 h再超声分散15 min的分散效果最好,沉降24 h后的悬浮率为62%左右,平均粒径为243 nm。     

The influence of dispersing and stabilizing of indium tin oxide nanoparticles upon the characteristic properties of thin films

Stable suspensions of indium tin oxide nanoparticles were prepared by dispersing for 1 h in ethanol and stabilizing with 2-[2-(2-Methoxyethoxy)ethoxy]acetic acid. Particle size, morphology, and structure were characterized by a combination of dynamic light scattering, high resolution transmission electron microscopy, and X-ray diffraction. Spin coating of the stable suspensions resulted in densely packed films with a high transparency. Dispersing times exceeding 1 h led to a significant “overdispersing” effect, i.e. an increasing aggregate size of the suspensions was observed. Zeta-potential, pH, and X-ray photoelectron spectroscopy measurements were conducted to achieve a detailed understanding of the effect of “overdispersing”. With an increasing time of dispersion, i.e. with a decreasing stability of the suspensions, the thin films fabricated by spin coating displayed an increasing pore size distribution and surface roughness. In addition a strong decrease in transmittance and in conductivity was observed.     

Preparation of platinum nanoparticle and its catalytic activity for toluene oxidation

Colloidal Pt nanoparticles are prepared using H2PtCl6 as a precursor, polyvinylpyrrolidone (PVP: molecular weight = 10,000 and 40,000) and hydrogen as a stabilizing agent and a reducing agent, respectively. The amounts of the precursor and the stabilizing agent and the molecular weight of PVP have an effect on the formation of Pt nanoparticles. Supported Pt catalyst (CSPt) is prepared from colloidal Pt nanoparticles and y-Al2O3. Another supported Pt catalyst (ISPt) is prepared by using the conventional incipient wetness impregnation method with an aqueous H2PtCl6 solution and gamma-Al2O3. The catalytic activities of CSPt and ISPt catalysts are compared for VOC (toluene) oxidation. Transmission Electron Microscopy (TEM), UV-vis, X-ray diffraction (XRD) and temperature programmed reduction (TPR) are used to characterize CSPt and ISPt catalysts. The experimental results reveal that the catalytic activity of CSPt is superior to that of ISPT.     

Rheological properties of aqueous alumina suspensions

The aim of the present work was to investigate rheological behaviour of alumina suspensions, considering different amounts of polyvinyl alcohol (PVAL) as a binder. Three different aqueous suspensions were prepared, containing 60, 70 and 80 wt.% of alumina powder. Spinel was added as a sintering agent and Darvan 821‐A as a dispersant, in an amount of 0.08 and 0.4 wt.% of dry powder weight, respectively. The alumina suspensions flow curves were recorded and fitted satisfactorily to the power law, Herschel‐Bulkley and Bingham models. Obtained results indicate that apparent viscosity of alumina suspensions increases with increasing Al₂O₃ and polyvinyl alcohol amount.