Evolution of Globular Microstructure in New Rheocasting and Super Rheocasting Semi‐Solid Slurries

Based on the solidification theory for metal alloys, a simple recipe for the controlled processing of globular microstructures without external stirring is presented: Firstly, small solidification nuclei must be distributed homogeneously throughout a melt. In New Rheocasting (NRC) these nuclei are formed by forced homogeneous nucleation due to partial quenching of the melt, while in Super Rheocasting (SRC) the nuclei are “second phase particles” in specially designed alloys, which are grown in a controlled fashion in a certain temperature range. Potential alloy compositions for SRC are provided. Secondly, given these melts with small particles in them, globular growth can be assured by utilizing the Gibbs‐Thomson “self healing effect” and slow further cooling to allow diffusion in the melt and to suppress constitutional supercooling. This simple recipe is applicable to various ferrous and non‐ferrous alloys. If an SRC alloy is cooled more rapidly than necessary for globular growth of the primary phase, but is held sufficiently long in the SRC range for dispersoid formation, these dispersoids can act as potent grain refiners and possibly enhance elevated temperature properties. A combination of both processes by using SRC alloys in the NRC equipment may lead to pressure tight castings with low porosity and finer grain structure than can be achieved with NRC on its own, and consequently, better mechanical properties.     

胶体电解质在VRLA蓄电池中的研究

对胶体电解质的研究进展进行了综述,阐述了胶体的凝胶机理,得出了二氧化硅凝胶剂量的大小、粒径和比表面积对凝胶速度及胶体结构的形成有明显影响的结论;同时也讨论了稳定剂、盐浓度、pH值和温度对胶体性能的影响;最后提出了国内胶体蓄电池生产面临的问题、改进措施和发展方向。     

混凝土流变参数十字搅拌轴测试方法

采用十字搅拌轴剪切仪测定混凝土拌和物的流变参数（屈服应力τ0和塑性黏度η）更具准确性.通过推导给出了自制十字轴流变仪扭矩与转速关系,得出了流变参数计算公式;试验所得混凝土拌和物流变参数与已有相关理论和试验具有良好的一致性,并能量化分析混凝土触变性能,可满足施工现场连续测定混凝土工作性需求.     

超高性能混凝土流变特性及其调控研究

为了实现超高性能混凝土(UHPC)流变特性的高效调控,采用膨润土作为辅助胶凝材料并对制备的UHPC进行了性能评估,包括UHPC浆体的流动度、静态屈服应力、动态屈服应力、塑性黏度和触变性,并系统分析了不同掺量的膨润土对UHPC浆体流变性能的影响。结果表明:随着膨润土掺量增加,UHPC浆体的流动度整体表现为下降趋势,下降幅度逐渐增大;当膨润土掺量由0%增加到15.0%(质量分数)时,UHPC浆体静态屈服应力、动态屈服应力和塑性黏度均显著增大,分别提高了约17.05倍、5.78倍和1.16倍;随着膨润土掺量增加,滞回环面积和触变指数增大,触变性得到明显改善。同时,掺入膨润土后仍然满足UHPC的优异力学性能要求。     

高黏度苯丙乳液的制备

为了制备高性能的苯丙乳液,研究了乳化剂、助剂DZ-1及丙烯酸对苯丙乳液黏度及触变指数等性能的影响。研究结果表明：乳化剂用量低反应生成的凝聚物较多,用量大乳液的气泡较多。乳液的黏度和触变指数随DZ—1用置增大而大幅度提高。乳液黏度随丙烯酸用量的增加而提高,但用量超过3％后,耐水性能变差。乳化剂用量为1．0％,DZ-1用量为4．5％,酸用量为3．0％时合成的苯丙乳液黏度和触变指数较高。用该苯丙乳液配制的涂料黏度高、触变性好,耐擦洗及耐水性好,综合性能优良。     

梨膏的流变学特性及其影响因素

目的 考察人为加糖、加胶后梨膏触变性及黏度的变化。方法 以鸭梨为实验材料,通过真空浓缩方式制备鸭梨膏,采用HR-10型流变仪对其流体类型、黏度、触变性进行测定。结果 鸭梨膏属于非牛顿流体,具体细分为无限接近牛顿流体的假塑性流体,具有剪切稀化特性和正触变特性;损耗模量G″总是大于储能模量G’,表现出液体黏性性质;剪切速率与剪切力变化关系符合PowerLaw方程,拟合效果良好(r2>0.99);温度显著影响梨膏黏度,黏度随温度升高而降低,二者关系符合Arrhenius方程,拟合效果良好(r2>0.99);可溶性固形物含量(solublesolidscontent,SSC)对黏度的影响符合指数函数关系,模型拟合效果良好(r2>0.99);SSC以及人为加糖、加胶处理对梨膏触变性、黏度影响显著(P<0.05),黏度随SSC的升高而增强,人为加胶、加糖加胶会导致梨膏黏度显著升高(P<0.05);触变性随SSC的升高而增强,同时人为加糖、加胶、加糖加胶处理会导致梨膏触变性显著减弱(P<0.05)。结论 人为添加糖、胶会导致梨膏的流变学特性发生改变。本研究可为工业...     

Rheology evolution of a geopolymer precursor aqueous suspension during aging

Geopolymer-based glass-ceramic matrix composites can be processed at room temperature and a heat treatment below 100°C leads to matrix hardening thanks to the geopolymerization mechanisms. The stabilization of the matrix into glass-ceramics is achieved via a post-curing at high temperature. This paves the way of the utilization of cost-effective liquid composite molding processes, for which all the necessary equipment is already available for processing temperature ranges related to polymer matrix composites, provided that the rheological behavior of the precursor is suitable to conveniently permeate the fibrous preform. The paper describes the thixotropic rheological behavior of a reference suspension at processing temperature (10°C-20°C) and its evolution along aging at −18°C. The changes are interpreted in terms of geopolymerization mechanisms (dissolution and polycondensation) and suspension rheology (predominance of hydrodynamic effects at high shear rate). On this basis, a phenomenological modeling framework, combining two Krieger-Dougherty equations, is proposed to build a relationship between the effective viscosity of the suspension and the phenomena involved during aging (dissolution of aluminosilicate particles) and shearing (microstructure scalar variable).     

The galenic behaviour of a dermopharmaceutical excipient containing honey

This paper describes the design of an emulsion cream, obtained from a self-emulsifying base, to which lavender honey has been added. Physical, galenic and stability studies and assays, and rheological analyses, are used to describe the qualities and properties of the honeyed cream under study. The formula is presented as an ivory-coloured cream with a light lavender scent and agreeable organoleptic characteristics. From a rheological viewpoint this is very adequate for spreading and applying onto the skin because of its thixotropic behaviour. The emulsion is stable and perfectly adaptable to the requirements of this type of skin application.     

垂直型单组分聚氨酯防水涂料的研究

合成了能够在垂直立面施工的单组分聚氨酯防水涂料,研究全新的化学增稠方式,实现产品触变性,探讨聚醚种类及比例、-NCO含量、反应温度等对产品性能的影响.结果表明,通过化学反应增稠的方式,能够实现垂直面不流淌、不流挂、可1次厚涂,涂层密实.m(聚醚二元醇):m(聚醚三元醇)=1:1.5,-NCO含量3.5%,预聚温度控制80℃左右时,可得到综合性能优异的防水涂料.