聚四氟乙烯填充高岭土基矿物聚合物复合材料的摩擦学性能

研究了PTFE填充量对高岭土基矿物聚合物复合材料的力学性能和摩擦磨损性能的影响,利用XRD、SEM分析了材料的微观结构和磨损表面形貌。结果表明:填充PTFE对矿物聚合物材料的力学性能会有一定程度的降低,但可以有效改善复合材料的摩擦磨损性能,当PTFE体积分数为30%时,摩擦因数和磨损率均达到最低,分别为0.429和1.22×10-5mm3/N·m;当PTFE含量较高时,磨损机理除了磨粒磨损外还有对偶件的粘着转移。     

高岭土的活化及其地质聚合物的性能研究

研究了4种高岭土在不同煅烧条件下的活化及其地质聚合物的抗压强度和H4 交换容量的变化趋势.试验结果表明:产地相同的高岭土在800℃煅烧6 h后,所合成的地质聚合物的抗压强度和NH4 交换容量达到最大值;产地不同的高蛉土经相同条件煅烧后,所合成的地质聚合物的抗压强度和NH4 交换容量差异很大,这与高岭土的化学成分没有相关性,而与煅烧高岭土在碱溶液中的硅铝溶出率有相关性.     

Effects of Na+ substitution Cs+ on the microstructure and thermal expansion behavior of ceramic derived from geopolymer

As part of a series of studies, effects of Na⁺ substitution on the thermal evolution of cesium‐based geopolymers on heating were studied. A series of sodium‐substituted cesium‐based geopolymers, Cs_(1?x)Na_xGPs (where x=0, 0.1, 0.2, 0.3, and 0.4), were prepared and treated at 1300°C for 2 hours to obtain the corresponding ceramic products. The thermal evolution process was disclosed by virtue of a variety of technical, including TG‐DTA, thermal shrinkage, XRD analysis, SEM, and TEM investigation. The results indicated that unheated Cs_(1?x)Na_xGPs was not completely amorphous after the substitution of Na⁺ and the crystallinity of Cs_(1?x)Na_xGPs gradually increased with the rise of sodium content. Meanwhile, the average particle sizes of Cs_(1?x)Na_xGPs also increased evidently with increases in sodium substitution. The final product after heat treatment mainly consisted of pollucite (CsAlSi₂O₆) and amorphous glass phase. The particle size of pollucite grain gradually decreased as more Cs⁺ were replaced maybe owing to the role of Na⁺ in the nucleation process of pollucite. Two forms of Na⁺ present in the final products: A small portion was present in the pollucite grains due to Na⁺ partial occupied the crystallographic sites of Cs⁺; and the rest were present in the amorphous glass phase among the pollucite grains. The average coefficient of thermal expansion (CTE) of resulting Cs_(1?x)Na_xGPs ceramics increased from 4.80×10^‐6 K^?1 (x=0) to 7.26×10^?6 K^?1 (x=0.4) with increases in sodium substitution, which could be due to the amorphous glass phase had a relatively higher CTE than that of pollucite.     

Influence of preheating of fly ash precursors to produce geopolymers

This study has been focused on the effect of pretreatment of FA and POFA after geopolymerization on the mechanical properties. The aim of this work was to simplify the pretreatment that it can easily industrial be applied, using existing technology. Previous work has shown that a reduction in particle size increases the mechanical properties. However, this method involves a milling process which is not applicable for a wide industrial application. Hence, FA and POFA particles have been heated to 300°C, 500°C, and 800°C but applying different pretreatments: (i) predried at 110°C (reference sample); (ii) as received; (iii) prewetted; (iv) prewetted and later quenched in cold water. It was found that during the treatment the particle size increased due to thermal stress cracking. During fast heating, trapped pore water cannot be removed as fast as it evaporates and hence the particles crack. This increase in particle size caused an increase in compressive strength. In addition, heating to 300°C and 500°C caused a dehydroxylation of FA and POFA. This dehydroxylation resulted in a higher initial reactivity, reducing the setting time and improved mechanical strength.     

地聚合物复合水泥混凝土性能研究

通过实验室的试件试验,比较了地聚合物复合水泥(GBC)混凝土与普通混凝土的物理力学性能和耐久性能.试验结果表明,GBC混凝土的干缩小于普通混凝土,抗裂性能高于普通混凝土.GBC具有较好的抗硫酸盐侵蚀性能.GBC混凝土比普通混凝土具有更强的抗氯离子扩散性能,其水溶性氯离子有效扩散系数只有普通混凝土的17%.     

Reaction kinetics of fly ash geopolymerization: Role of particle size controlled by using ball mill

Fly ash is milled for 0, 30 and 90?min and used to study the role of particle size on the kinetics of geopolymer formation. The increase in particle fineness is very prominent in the initial milling stage, and then slows down due to agglomeration effect of finer fraction. The fly ash geopolymerization kinetics and its mechanism is determined using heat of reaction data measured by isothermal conduction calorimeter. The improvement in reaction rate with milling is correlated with the median particle size of the fly ash. The apparent activation energy decreases with size reduction because finer fractions are more prone to alkali activation. Although the kinetics changes with particle fineness, but no alternation is detected in the reaction mechanism, governed by nucleation and growth. The apparent activation energy evaluated by rate method is showing three major steps of geopolymerization such as dissolution, gel formation and restructuring.     

地聚物砂浆高温后抗拉和粘结性能及退化机理

为考察地聚物砂浆在有耐高温要求的混凝土结构加固领域的应用可行性,开展了常温下和高温后地聚物砂浆的抗拉强度试验以及地聚物砂浆与普通水泥砂浆及普通混凝土基体的粘结性能试验,并与普通水泥砂浆的抗拉及粘结性能进行试验比较;通过热重分析-差示扫描量热分析(TG-DSC),探究了地聚物砂浆的高温强度退化机理.试验结果表明:地聚物砂浆与水泥砂浆及混凝土之间的常温粘结强度分别达2.15 MPa及1.7 MPa,经300℃高温后残余粘结强度仍有1.5 MPa左右,远高于普通水泥砂浆的粘结强度;超过300℃以后地聚物砂浆的强度急剧退化,这主要是因地聚物砂浆高温脱水、微观结构遭受破坏引起.基于上述试验结果,可将地聚物砂浆用于300℃以下高温环境的混凝土结构修补加固.     

煅烧高铝煤矸石-矿渣-水玻璃系地聚合物材料的研究

根据地聚合物合成原理，采用煅烧高铝煤矸石-磨细矿渣-水玻璃系合成地聚合物类材料。深入研究了高铝煤矸石-矿渣-水玻璃系统材料的制备、性能的测试评价、水化硬化机理和最优制备工艺参数选择。材料中矿渣对早期强度起主要作用，煅烧高铝煤矸石对后期强度贡献较大。在矿渣和高铝煤矸石质量比处于合理状态时，材料各龄期强度均较优。高铝煤矸石类地聚合物材料的抗压强度随水玻璃模数的减小而增大，随水玻璃掺量的增大而增大，随液胶比的减小而增大。水玻璃模数为1．049，矿渣与煅烧高铝煤矸石的配比为4：6，激发剂掺量为22％，液胶比为0．35时，复合材料28d抗压强度达到了41．7MPa。     

镍渣/偏高岭土基地聚合物的制备与表征

以工业固体废弃物镍渣和偏高岭土为原料,以水玻璃为激发剂,在相同稠度下制备镍渣/偏高岭土基地聚合物。研究了镍渣种类和掺量对地聚合物力学性能和体积变化的影响,测定了地聚合物的碱溶出情况,并利用XRD、SEM-EDS对地聚合物的矿物组成和微观形貌进行分析。结果表明:随着水淬镍渣掺量的增大,地聚合物的抗压强度先增大后降低,在镍渣掺量为50%、液固比为0.45时,地聚合物的抗压强度最大,28d达到58.8 MPa;而随着风冷镍渣掺量的增大,地聚合物的强度逐渐降低。此外,水淬镍渣/偏高岭土基地聚合物的体积变化主要表现为膨胀,而风冷镍渣/偏高岭土基地聚合物表现为收缩。     

粉煤灰地聚物反应体系下的反应影响因素分析

以粉煤灰基地质聚合物为研究对象,研究了粉煤灰在地聚物反应体系下的反应影响因素。主要研究内容有:反应时间、反应温度和反应碱浓度对反应过程及宏观强度的影响及相关反应机理。结果表明:在反应中后期,粉煤灰反应速率明显下降而此时地聚物的宏观性能反而呈现最大值。以75℃为例,反应时间从24h延长到672h的过程中,反应程度仅从20.8%增加到了32.4%,平均反应速率仅为0.0179%/h,而此时样品的抗压强度则从1.31MPa增加到了7.98 MPa;在地聚物反应体系下,反应产物为无定形的硅铝胶凝体,该物质的致密程度与地聚物宏观性能直接相关;温度的升高可有效提高粉煤灰的反应速率及地聚物的宏观性能,促进无定形胶凝体的形成和硬化。反应24h,75℃下的反应程度和抗压强度可以达到20.8%和1.31 MPa,而同期35℃下的反应程度只能达到7.8%且尚未形成宏观强度;碱浓度的变化不仅可影响反应速率和宏观性能,还可改变粉煤灰在地聚物反应体系下的最终反应程度,在反应温度为75℃和50℃时,10 mol/L体系下672h的反应程度比5 mol/L体系分别高了90%和28.6%。