石膏基自流平砂浆耐磨性能研究

本工作从原材料以及表面修饰材料等探究了石膏基自流砂浆表面的耐磨性能。研究了可再分散性乳胶粉、石膏缓凝剂、普通硅酸盐水泥和固化剂对石膏基自流平砂浆耐磨性的影响,分析了砂浆流动度和抗压强度以及胶凝材料对石膏基自流平砂浆耐磨性的影响。结果表明,可再分散性乳胶粉对石膏基自流平砂浆的耐磨性有提高的作用。石膏缓凝剂会增加砂浆的离析沉降程度,从而导致石膏基自流平砂浆耐磨性降低。在以石膏为主的自流平砂浆中,适量增加石膏和普通硅酸盐水泥的加入量都有提高石膏基自流平砂浆耐磨性的作用。在自流平砂浆表面涂刷渗透性固化剂可提高其表层的密实度和耐磨性能,颜色有所差异,这说明固化剂种类品质对石膏基自流砂浆平表面颜色差异影响较大。     

水泥对石膏基自流平材料性能的影响

研究了硅酸盐水泥和铝酸盐水泥对石膏基自流平材料流动度、凝结时间、力学性能和耐水性能的影响,通过X射线衍射仪、量热仪、压汞仪和环境扫描电子显微镜微观测试方法对水化产物、水化热、孔结构、微观形貌等进行分析表征。结果表明,随着硅酸盐水泥掺量的增加,初始流动度增大,30min流动度损失减小,凝结时间缩短,掺加铝酸盐水泥对流动度、凝结时间规律与硅酸盐水泥相似;随着硅酸盐水泥掺量的增加,力学性能和耐水性能呈先增加后降低趋势,当掺量为8%时,达到最优;28d抗折强度和耐水性能随着铝酸盐水泥掺量的增加,波动比较大,在13%掺量时出现最低点,抗压强度随着铝酸盐水泥掺量的增加呈稳步上升趋势;掺入硅酸盐水泥和铝酸盐水泥均出现钙矾石的微弱衍射峰。     

缓凝剂对脱硫石膏性能的影响及预测分析

针对脱硫石膏凝结硬化快的特点，研究了不同掺量柠檬酸、骨胶配合使用下脱硫石膏的物理性能，利用BP神经网络建立了柠檬酸、骨胶掺量与石膏凝结时间、强度关系的神经网络模型。结果表明，柠檬酸和骨胶复合使用可以延长凝结时间，减小强度损失；神经网络预测脱硫石膏物理性的准确性较高，对缓凝剂复合使用有很好的指导作用。     

不同类型缓凝剂对建筑石膏的缓凝作用

研究了麦蛋白水解液石膏缓凝剂、柠檬酸、六偏磷酸钠对脱硫石膏的凝结时间、强度损失等的影响,同时也对不同水化环境pH值条件下的缓凝作用的凝结硬化特征进行了分析,并结合XRD和SEM对建筑石膏强度损失的原因和缓凝剂的缓凝机理进行了分析。对比结果表明:凝结时间相近的情况下,麦蛋白水解液对石膏的强度影响最小,而六偏磷酸钠影响最大;麦蛋白水解液对pH值环境适用范围最广,有良好的适应性,并在弱碱条件下缓凝效果最佳,而柠檬酸和六偏磷酸钠分别在酸性和中性条件下缓凝效果最佳;麦蛋白水解液对二水石膏晶体形貌基本没有影响,而六偏磷酸钠和柠檬酸使明显而完整的二水石膏针片状晶体减少。     

环氧树脂缓释激发剂对碱-矿渣水泥性能的影响

碱-矿渣水泥目前常用缓凝剂延长凝结时间,但缓凝剂存在用量不宜控制、缓凝效果受温度影响较大、影响早期强度等问题。本研究采用一种缓释型碱激发剂对其凝结时间进行调节。实验采用不同总质量的环氧树脂包覆处理水玻璃,得到不同厚度的环氧树脂覆膜,研究了不同覆膜厚度的激发剂对碱-矿渣水泥凝结时间、力学性能、微观性能的影响。实验表明,使用环氧树脂覆膜于激发剂表面后,能显著延长碱-矿渣水泥的凝结时间,其中100%包裹组将初凝时间延长了90%;环氧树脂的加入提高了水泥的1 d强度,75%包裹组1 d强度提高了54.02%;环氧树脂对28 d的抗压强度贡献不大,但能提高试件的韧性,25%包裹组的压折比降低了10.18%;环氧树脂以覆膜形式加入碱-矿渣水泥中较直接以外加剂加入更能促进基体的水化进程。     

利用熟料岩相分析提高熟料强度

水泥强度的影响因素主要来自水泥熟料的矿物组成和形态,以及水泥的颗粒组成、颗粒形貌和细度等方面.就熟料矿物而言,硅酸盐相是影响水泥强度的主要因素,硅酸盐矿物的含量是决定水泥强度的主要因素.一般来说,熟料抗压强度越高,抗折强度也越高,在矿物组成对强度的影响方面,往往较多地研究其对抗压强度的影响,本文通过实例对熟料岩相分析提高熟料强度做了简单的分析.     

仿真技术在媒晶剂对石膏晶体转晶作用中的应用

为了研究媒晶剂在石膏晶体转晶过程中的作用,同时探讨计算机模拟在研究过程中的应用,本文利用吸附能模型计算了石膏晶体晶型以及主要晶面的附着能,同时模拟了柠檬酸、乙二胺四乙酸和苯基甘氨酸3种媒晶剂与石膏晶面(1 2-1)和(0 1 1)反应,得出了媒晶剂与石膏晶面的吸附能及媒晶剂的最佳组合方式.利用扫描电子显微镜对实验所得石膏晶型进行了分析,并测得不同媒晶剂作用下磷石膏抗折抗压强度.研究发现,实验结果与计算机模拟结果基本一致,磷石膏最大抗折抗压强度分别为3.64和7.35 MPa.     

硫铝酸盐复合水泥体系水化特征研究

通过正交试验研究了硫铝酸盐复合水泥中不同掺量的普通硅酸盐水泥、石膏、硅灰及粉煤灰对其强度、自收缩以及水化热的影响。结果表明:普通硅酸盐水泥及石膏的掺入显著改变了硫铝酸盐复合水泥水化进程,硅灰及粉煤灰是影响后期强度的主要因素;自收缩试验结果表明普通硅酸盐水泥和石膏是影响硫铝酸盐复合水泥水化早期自收缩的主要因素;水化热测试结果表明粉煤灰和普通硅酸盐水泥在水化前6 h起到显著作用,粉煤灰降低了水化放热,而普通硅酸盐水泥增加水化放热;硅灰及石膏对6~24 h水化放热影响显著。结合XRD及SEM测试结果,表明普通硅酸盐水泥和石膏的存在加速了硫铝酸盐复合水泥水化早期钙矾石生成,随着石膏浓度的下降,发生转晶(AFm),随着后期硫铝酸盐水泥中β-C₂S的水化以及硅灰、粉煤灰的火山灰反应产生C-S-H凝胶,使得体系致密化。     

环境湿度对玻璃纤维增强水泥力学性能的影响

通过开展在不同龄期、不同环境湿度下玻璃纤维增强水泥(GRC)试件的抗折强度、抗压强度试验和基体pH值测定,研究了环境湿度对掺加粉煤灰和硅灰等活性矿物掺合料的GRC试件力学性能的影响。结果表明:环境湿度对GRC试件的抗折强度有重要影响,相对湿度越大,随着龄期增加, GRC试件抗折强度降低越严重;在温度60℃、相对湿度95%条件下,经过56 d龄期后,掺有40%粉煤灰和10%硅灰的GRC试件抗折强度比未掺加粉煤灰和硅灰的GRC试件的抗折强度提高48.5%、抗压强度提高23.6%, GRC基体pH值降低6%。在相同的湿度条件下,掺有粉煤灰和硅灰试件的pH值在各个龄期都低于普通硅酸盐水泥试件,说明粉煤灰和硅灰的掺入能降低水泥水化液相的碱度,进而延缓了纤维受侵蚀的速度,显著改善了GRC试件的力学及耐久性能。通过对试验结果进行分析,利用MATLAB软件建立了GRC试件抗折强度和抗压强度与水泥砂浆基体pH值及时间的关系式。      

细菌纤维素增强水泥复合材料的制备及性能

对细菌纤维素增强水泥复合材料进行研究,探讨细菌纤维素含量、长度对水泥基复合材料抗折、抗压强度的影响以及细菌纤维素对水泥凝结时间和水化过程的影响。结果表明:细菌纤维素的加入能明显改善水泥基复合材料力学性能,细菌纤维素质量分数为0.02%是实验最佳掺量,材料抗折、抗压强度分别提高了20%和8%;过长细菌纤维素将导致分散不均,使浆体结构疏松;细菌纤维素对水泥浆体pH值和凝结时间无明显影响;细菌纤维素促进水化过程中CaO-SiO2-H2O凝胶生成。     

缓凝剂对掺UNF-5高C3S水泥水化的调控

采用流动度、电阻率和水化热等实验方法,研究了缓凝剂对掺定量UNF-5高C3S水泥浆初始水化历程的调控,着重研究了3种缓凝剂与UNF-5的叠加效应在高C3S水泥浆初始水化历程中产生的主要现象,以及这些现象对改善UNF-5与高C3S水泥的相容性的影响.实验表明:在浆体流动性方面,葡萄糖酸钠和多聚磷酸钠与UNF-5叠加时存在一个最佳掺量,柠檬酸出现负效应.在一定的温度范围内,叠加前后水泥浆体的流动度均随温度的增加而增大.缓凝剂对早期C3A水化的作用效应显著影响含UNF-5水泥浆体的流动度与早期电阻率之间的关系.缓凝剂的参与延缓水泥浆体结构的形成,放热峰削弱且得以宽化,有效解决放热集中的问题.对水泥浆体结构形成的延缓能力,葡萄糖酸钠最强,多聚磷酸钠次之,而柠檬酸相对最弱.     

Density and strength characteristics of foamed gypsum

This paper deals with the effect of substances producing and assisting gas and foam formation on the properties of gypsum density and strength. The gas-based foaming method utilises aluminium sulphate, potassium alum or ammonium bicarbonate for the chemical production of gas bubbles in gypsum paste. The second method obtains foamed gypsum by means of air entrainment in wet gypsum paste. The foaming agents chosen were sodium lauryl sulphate and nonyl phenol ethoxylate that are widely employed in detergent production. Five different foaming techniques are obtained with these additives required for gas and foam production. Citric acid, as retarder, and carboxyl methyl cellulose (CMC), as viscosity increasing agent, were used for promoting foam and gas formation during the foaming experiments. Aluminium sulphate was discovered to be the one that achieves the most foaming in gypsum. The techniques utilising potassium alum, sodium lauryl sulphate and ammonium bicarbonate reduced the density of gypsum products by values varying between 30% and 35%. Foaming with nonyl phenol ethoxylate had an insignificant effect on density. The addition of citric acid and carboxyl methyl cellulose assisted with density reduction. Besides regulating the hardening time, citric acid supported density reduction by releasing gas through a reaction with marble powder. However, an addition of CMC above 0.1% or 0.2% causes a density increase by preventing bubbles to expand and merge with each other. The compressive strength of low-density gypsum products falls well below 10 Mpa, stipulated by TS 370 for building gypsum.     

助磨剂组分对缓凝剂作用效果的影响及其机理探究

分别掺加3种常用助磨剂组分三乙醇胺(TEA)、丙三醇(PG)和多聚磷酸钠(STPP)进行水泥粉磨试验,控制出磨水泥的比表面积在(375±5)m2/kg范围内,测试了各水泥试样的凝结时间和粒径分布等基本性能。选用常用缓凝剂组分葡萄糖酸钠(PN),探究了3种助磨剂组分对缓凝剂作用效果的影响,通过水化热分析、X射线衍射(XRD)分析和缓凝剂分子吸附量分析揭示了助磨剂组分对缓凝剂作用效果的影响机理。结果表明:TEA和PG对缓凝剂的作用效果存在明显的负面作用,而STPP显著改善了缓凝剂的作用效果;一方面,助磨剂通过自身的早强(或缓凝)作用影响缓凝剂的作用效果,另一方面,助磨剂组分也会影响缓凝剂分子的吸附量进而改变缓凝剂的作用效果。     

Effect of fuel type on microstructure and electrical property of combustion synthesized nanocrystalline scandia stabilized zirconia

Nanocrystalline 10 mol% scandia stabilized zirconia (10ScSZ) powders were prepared by combustion synthesis using three different types of fuels (urea, glycine and citric acid). The influence of nature of fuel on phase formation, particle size and morphological characteristics was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The effect of fuel type on electrical conductivity was also evaluated. The 10ScSZ prepared by urea and glycine was fully crystalline whereas citric acid resulted in amorphous form. The powder turned crystalline on calcination at 800 °C. Urea resulted in highly agglomerated powder whereas porous and loose agglomerates were formed with glycine and citric acid as fuels. The powder processed with urea showed higher crystallite size compared to powders processed with glycine and citric acid. The ScSZ electrolyte pellet processed with glycine and citric acid exhibited better conductivity and lower activation energy compared to the electrolyte processed with urea.     

The crystallinity of calcium phosphate powders influenced by the conditions of neutralized procedure with citric acid additions

Calcium phosphate powders with nano-sized crystallinity were synthesized by neutralization using calcium hydroxide and orthophosphoric acid with the assistance of citric acid. The influence of processing parameters, such as free or additive citric acid, synthetic temperature and ripening time, on the crystallinity of hydroxyapatite were investigated. The results of X-ray diffraction and microstructure observations showed that the crystallinity and morphology of nano-sized hydroxyapatite particles were influenced by the presence or absence of citric acid. It was found that the crystallinities and crystallite sizes of hydroxyapatite powders prepared with the additive citric acid increased with increasing synthetic temperature and ripening time. Especially, the crystallinities of (h k 0) planes were raised and more homogeneously grown particles were obtained with increasing synthetic temperature.     

柠檬酸/PVA抗菌薄膜性能的研究

目的研究柠檬酸添加量对聚乙烯醇薄膜性能的影响。方法将柠檬酸颗粒溶解到质量分数为10%的PVA母液中,通过流延法制备柠檬酸/PVA抗菌薄膜。结果添加柠檬酸可降低薄膜吸水性和溶解性,随着柠檬酸质量分数的增加,透湿系数减小。观察扫描电镜表明,柠檬酸在聚乙烯醇中溶解均匀。以大肠杆菌和金黄色葡萄球菌为指标的抗菌性能测试表明,柠檬酸对大肠杆菌和金黄色葡萄球菌均有较强的抑制作用。结论柠檬酸的添加可降低PVA薄膜的吸水性、溶解性和水蒸气透过系数,并使薄膜具有抗菌性。     

石膏的直写成型：可打印石膏浆料的研制

石膏是雕像、建筑和铸造模具(合金和陶瓷)的常用材料。采用直写成型(Direct Ink Writing, DIW)打印石膏可避免其他3D打印技术(如Binder Jetting, PBBJ等)中存在水化反应不充分等问题, 获得高强度3D打印石膏。为了延缓水化反应获得充足的打印操作时间, 本研究通过添加缓凝剂和增稠剂, 研制了一种适用于直写成型的石膏浆料, 并打印了多种石膏三维结构(如蜘蛛网和木材堆积结构等)。结果表明, 质量分数为0.6%柠檬酸(Citric Acid, CA)的缓凝效果最好, 极大地减少了石膏流动性的经时损失。质量分数为0.3%羟丙基甲基纤维素(Hydroxypropyl Methylcellulose, HPMC)的增稠效果最好, 使石膏浆料具有良好的打印性能。CA的选择性吸附使得石膏晶体定向生长, 延长水化反应时间, 但一定程度降低石膏强度。HPMC加速石膏浆料中絮凝结构形成, 导致其粘度和剪切弹性模量升高。直写成型3D石膏件的抗压强度约为20 MPa, 远高于PBBJ等方法制备的石膏件的抗压强度。     

Structural,Magnetic, Optical,and Catalytic Properties of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles by the Sol-Gel Method

This article was aimed to extend a simple procedure for the preparation by a sol-gel method by using iron nitrate and polar solvent (e.g., water) as the starting materials from the viewpoint that they are of low cost. A study of the effect of chelating agents such as citric acid weight ratio on the structure of Fe₃O₄ was reported. The synthesized product was characterized by powder X-ray diffraction (XRD), high-resolution scanning electron microscopy (HR-SEM), high-resolution transmission electron microscopy (HR-TEM), photoluminescence (PL) studies, and vibrating sample magnetometer (VSM). Magnetic analysis revealed that the Fe₃O₄ nanoparticles had a ferromagnetic behavior at room temperature with a saturation magnetization of 20.83 emu/g. Furthermore, Fe₃O₄ nanoparticles prepared by the sol-gel method using citric acid were tested for the catalytic activity towards the oxidation of benzyl alcohol.     

Synergistic effect of rare earth salt and organic acid in the anodization of aluminum in phosphoric acid

The effect of rare-earth element (cerium salt) and organic acid (citric acid) on the anodic oxide film obtained in phosphoric acid and their synergistic mechanism in the anodizing process were studied. The results show that the synergistic effect of cerium salt and citric acid in anodization of phosphoric acid can reduce surface defects, improve its microstructure and properties of the anodic oxide film. With the analysis of EDAX and XPS, the hydroxide of cerium salt was deposited on the film surface. It is deduced that cerium salt takes part in the formation of oxide film directly on the synergistic effect of citric acid.