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).     

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。     

Rheological Properties of Quaternary Ammonium Gemini Surfactants in Aqueous Solution

The rheological properties and time effect of a quaternary ammonium salt gemini surfactant C_n‐s‐C_n?2Br solution were measured. The rheological properties were markedly different at various concentrations of the surfactant C₁₂‐2‐C₁₂?2Br solutions. When the alkyl chain of C_n‐2‐C_n?2Br solution is 14 or 16, the rheological properties of the solution exhibit fluid dilatancy very similar to C₁₂‐2‐C₁₂?2Br solutions. However, when the length of the spacer is four or six, C₁₂‐s‐C₁₂?2Br solutions exhibit Newtonian fluid behavior and are quite different from the C₁₂‐2‐C₁₂?2Br solution. A C₁₂‐2‐C₁₂?2Br solution at a high concentration shows negative thixotropy and time dependency.     

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.     

防水冲稀堵漏预处理剂HSN的研制及应用

针对含水漏失层的堵漏难题,研发了防水冲稀堵漏预处理剂HSN.HSN具有pH值降低时及与钙、镁离子作用时黏度变大的独特性质.HSN在与地层水接触后,与地层水中的钙、镁离子可发生迅速反应,使溶液黏度迅速变大,并且生成具有一定弹性的不均匀网状结构,从而使堵漏材料有效滞留.煤层气井韩5 -094井在井深605m处发生失返性漏失,堵漏9次未成功,分析认为是由含水裂缝引起的,因此采用HSN溶液并配合堵漏浆堵漏,结果使用很少堵漏材料即成功封堵.     

羧甲基瓜尔胶水溶液流变特性研究

研究了羧甲基瓜尔胶水溶液的流变特性,考察了羧甲基瓜尔胶浓度、温度、pH值及外加NaCl浓度对羧甲基瓜尔胶水溶液表观黏度的影响.结果表明,羧甲基瓜尔胶水溶液表观黏度随浓度的增加而增大,随温度的上升而降低,随NaCl浓度的增加而明显降低,稳定的pH值范围为6～8.羧甲基瓜尔胶水溶液具有剪切变稀特性,溶液表观黏度随剪切速率的变化可用Ostwald-Dewaele方程描述;零切黏度可由Spencer-Dillon经验公式外推得出,其与温度的关系符合Arrhenius公式.羧甲基瓜尔胶水溶液具有一定的触变性和黏弹性,黏弹性随浓度的增加而增强.图10表2参16     

触变成形AM608镁合金组织研究

采用OM、SEM、EDS、XRD对触变压铸AM608镁合金组织进行了分析,结果表明:触变压铸AM608镁合金组织由球状初生α-Mg颗粒(α1)与颗粒间的二次凝固组织组成.AlxMny相以颗粒状分布于二次凝固组织中.二次凝固过程主要分为三个阶段:二次凝固初生α-Mg相依附生长(α2),二次凝固α-Mg相的独立形核生长(α3)及共晶相的形成.二次凝固初生α-Mg相依附生长呈两种形态:一是形成初生α-Mg颗粒边缘不规则"锯齿"状二次凝固初生α-Mg相或"次α-Mg"(α3),二是在初生α-Mg颗粒边缘及初生α-Mg颗粒内"液池"周围形成"晕圈".α3相形成细小的等轴枝晶状,共晶反应产生显著的"骨骼"或"岛"状离异共晶β-Mg(17)Al(12)相.此外,在β-Mg(17)-Al(12)相附近还发现少量凌乱层片共晶.     

Flow behaviour of carrot puree: modelling the influence of time,temperature and potato flakes addition

Rheological properties of carrot puree were investigated in the 1–1000 s^?1 shear rate range with the objective of modelling the influence of time, temperature and addition of potato flakes on the flow behaviour. Carrot puree exhibited a shear‐thinning behaviour that was well described by the Ostwald‐de Waele (Power Law) model with a flow behaviour index of 0.34 (±0.02) at 20 °C. The time‐dependent behaviour was characterised by a second‐order Structural Kinetic Model. The decay of the structural parameter with time was found to be independent of shear rate. The Arrhenius model was used to explain the effect of temperature in the range from 4 to 60 °C. The dry matter was increased by adding potato flakes (0–5%). A power law model (for the concentration) and the Arrhenius relationship (for the temperature) were combined to simultaneously describe the effects of temperature and concentration. This study provides essential data for equipment and process design.