Si-Al-Zr-O系非晶晶化过程研究

借助DSC、XRD、SEM和TEM等技术探讨了Si-Al-Zr-O(SAZ)系非晶的原位受控晶化过程. 结果表明, SAZ系非晶在900℃左右存在分相, 形成富Si区和富Zr、Al区. 在920~950℃间, 开始成核析出初晶相四方氧化锆, 并从富Al区形成Al-Si尖晶石相. 当温度升高至1000℃时, 莫来石晶相开始生成. 温度进一步升高, Al-Si尖晶石相消失, 四方氧化锆、莫来石成为主晶相, 同时生成了方石英. 其中, 莫来石是通过过渡相Al-Si 尖晶石与非晶二氧化硅反应得到.     

污水污泥页岩陶粒的烧成工艺与性能

为制定合理的污水污泥页岩陶粒烧成工艺及揭示污水污泥对陶粒性能的影响,研究了污水污泥掺量对陶粒烧胀性能的影响以及预热、焙烧的温度和时间等因素对陶粒性能的影响,采用扫描电镜观察了污水污泥和烧成工艺对陶粒结构的影响.结果显示,含水率80%左右的污水污泥掺量30%时,可获得表观密度700 kg/m3左右的轻质陶粒;适当降低预热温度、缩短预热时间、提高焙烧温度和延长焙烧时间有利于获得轻质污泥页岩陶粒.掺加污水污泥有利于页岩陶粒烧胀性能提高,但需要控制合适的烧成工艺.     

污泥陶粒制备工艺烧结温度影响研究

为明确陶粒制备工艺的烧成温度范围,考察焙烧机制,进行了不同温度污泥烧制页岩陶粒的实验研究。结果表明,工艺控制参数耐火度:Al2O3/+SiO2Fe2O3+CaO+MgO+Na2O+K2O可以表征混合料烧成开始温度;1000℃以下烧制陶粒的孔径分布为单峰曲线,1050～1100℃烧制陶粒的孔径呈现双峰结构,焙烧机制对陶粒孔隙分布有如下影响:提高焙烧温度,峰值孔径增大,延长焙烧时间,峰值孔径相对位置增加;XRD分析表明,陶粒主要晶相为石英和蓝晶石,在1050℃以上烧结,孔分布出现双峰曲线,可能与氧化铁分解有关。     

微沸法合成纳米莫来石及活化能的研究

以硝酸铝和硅溶胶为原料,采用微沸法对合成纳米莫来石及其活化能进行研究,并用热重差示扫描热量计(TGDSC)、X射线衍射仪(XRD)和扫描电子显微镜(SEM)对合成莫来石的粒度、相组成和形貌进行分析.结果表明:在原料中的铝硅摩尔比为3∶1的条件下,温度为854℃时莫来石开始形成,温度为920℃时Al Si尖晶石开始转变为莫来石,温度为1200℃时莫来石化完成,合成莫来石的活化能为(634.52±28.90)kJ·mol-1.经过1200℃煅烧后,莫来石含Al2O3的摩尔分数为59.8％,平均粒度约为31.7nm,形状为针状,并由这些针状莫来石构成连续的网络结构.随着铝硅摩尔比的增加,合成莫来石的温度降低,活化能降低.当铝硅摩尔比增加至6∶1,合成莫来石的活化能降至(514.73±14.40)kJ·mol-1.     

非晶晶化法制备 Si-Al-Zr-O系超微细晶复相陶瓷

在1650-1700℃下制备了Si—ANZr-O（SAZ）溶胶，经快速冷却获得均匀致密的SAZ系非晶体，经梯度热处理得到SAZ系超微细晶复相陶瓷．结合示差扫描量热分析（DSC）、红外光谱（IR）、X射线衍射（XRD）和扫描电镜（SEM）等技术以及Vicker压痕法，研究了相关超微细晶复相陶瓷结构和性能随热处理温度的变化．结果表明，SAZ系非晶体在950℃时开始析出四方氧化锆，1100℃时晶化基本完成，主晶相为莫来石和四方氧化锆，晶粒尺寸为10-40nm：温度升高至1200℃，晶粒迅速长大至0．5μm左右，部分四方氧化锆向单斜氧化锆的转变．样品的显微硬度和断裂韧性经1150℃热处理后均达到最大，分别为12．6GPa和4．32MPa-m1／2．     

硫酸钠熔盐法微硅粉制备莫来石晶须

以微硅粉和Al2(SO4)3为反应原料,硫酸钠为反应介质,反应混料分别在800℃、900℃、1000℃和1100℃下煅烧保温1h后,经溶解、过滤、烘干后得到莫来石晶须。利用XRD和FESEM对合成粉体进行物相分析和显微形貌观察,结果表明:1000℃为莫来石晶须最佳的合成温度,样品在经NaOH溶液碱处理后得到的莫来石晶须长度约为3~4μm,直径约为10~30nm。同时对合成莫来石晶须形成机理进行了探讨。     

蓝晶石制备莫来石晶须的研究

为了降低莫来石晶须的合成温度及生产成本,研究了以蓝晶石为主要原料烧结制备莫来石晶须的影响条件,通过烧结实验发现,原料的粒度、升温速率和催化剂添加量对莫来石晶须的制备有较大影响,影响顺序为：原料粒度〉催化剂添加量〉升温速率。晶须的最佳合成条件为：原料粒度为-325-＋400目,混合样（蓝晶石和氧化铝）与A1F3比例为10：4．0,以1150℃作为成核温度,保温lh,以1250℃作为晶化温度,保温4h,烧结过程中的升温速率为5E／rain,莫来石晶须的产率可以达到64％。     

ZrSiO4／Al2O3制备氧化锆-莫来石复相陶瓷的反应烧结机制

以ＺｒＳｉＯ４和α－Ａｌ２Ｏ３为原料,采用反应烧结方法制备了氧化锆－莫来石复相陶瓷 材料．研究了反应烧结过程中致密化和莫来石的形成机制,重点讨论了莫来石晶种的引入对莫 来石形成机制的影响．结果表明,在莫来石形成之前,非晶态的粘滞性流动是主要的致密化机 制．晶种的添加使莫来石的形成方式发生了变化,对反应烧结有一定促进作用．添加 ３ｗｔ％晶 种的试样在１６００℃保温８ｈ相对密度可达９７％左右．     

烧成温度对合成莫来石陶瓷膜的影响

以正硅酸乙酯、硝酸铝和氟化铝为原料,采用溶胶一凝胶法在多孔莫来石陶瓷载体上原位反应烧结合成了晶须状多孔莫来石陶瓷膜.考察了在1 200,1 300,1 400,1 500℃烧成温度、保温2 h后对莫来石相及其膜层表面微观结构的影响.结果发现:在烧成温度为1 300℃时出现了莫来石相,并随着烧成温度的升高,莫来石相的特征峰增强;在氟化铝质量分数为10%、1 500℃保温2 h条件下,膜层表面生长出长为2.5μm、宽为0.5 μm、长径比(长/宽)为5的莫来石晶须,并且此时形成的莫来石晶须比较均匀,莫来石陶瓷膜平均孔径为0.75μm左右,纯水通量为725 L/(m2·h).     

ZrSiO4/Al2O3制备氧化锆-莫来石复相陶瓷的反应烧结机制

以ＺｒＳｉＯ４和α－Ａｌ２Ｏ３为原料,采用反应烧结方法制备了氧化锆－莫来石复相陶瓷材料,研究了反攻结过程中致密化和莫来石的形成机制。重点讨论了莫来石晶种的引入对莫来石形成机制的影响。结果表明,在莫来石形成之前,非晶态的粘滞性流动是主要的致密化机制,晶种的添加使莫来石的形成方式发生了变化,对反应烧结有一定促进作用,添加３ｗｔ％晶种的试样在１６００℃保温８ｈ相对密度可达９７％左右。     

Effect of sintering temperature on the characteristics of sludge ceramsite

In order to investigate the effect of sintering temperature on the characteristics of sludge ceramsite and find an optimal sintering temperature, dried sewage sludge, clay, and water glass were mixed at ratios of dried sewage sludge/clay=33% and water glass/clay=15%. Then these mixtures were heated to 850, 900, 950, 1000, 1100, and 1200 degrees C for production of sludge ceramsite. The sludge ceramsite were characterized by DTA-TGA, SEM-EDS, XRD, and XRF. The results indicate that the differences in thermal behaviours are caused by the compositional and structural variations; the ceramsite sintered at 1000 degrees C has more uniformly distributed finer pores (0.5 microm相似文献   

Paper pulp waste— a new source of raw material for the synthesis of a porous ceramic composite

A synthetic porous ceramic composite material consisting of the mullite, cordierite and cristobalite phases is produced from a mixture of paper pulp waste and clay by reaction sintering at 1400°C. Physicomechanical properties such as bulk density, porosity, cold crushing strength and cold modulus of rupture have been studied. The presence of mullite, cordierite, cristobalite and quartz as major phases and montellecite, tatanite, forsterite and anorthite as minor phases have been confirmed by X-ray diffraction pattern. SEM studies revealed the presence of well developed needle shaped mullite and quartz crystals. The paper also discusses the possible uses of this type of porous composite material.     

Evolution of microstructure in flyash-containing porcelain body on heating at different temperatures

15 wt% flyash (a calcined byproduct of thermal power plant) was incorporated in a normal triaxial kaolin-quartz-feldspar system by replacing equivalent amount of quartz. The differences in microstructural evolution on heating the compact mass of both normal and flyash-containing porcelain at different temperatures (1150–1300°C) were examined using scanning electron microscopy (SEM) operating in secondary electron image (SEI) mode. Microstructure of normal porcelain did not show the presence of mullite and quartz grains at 1200°C and the viscosity of silica-rich glass restricted the growth of mullite crystals at 1250°C. Flyash porcelain, on the other hand, shows the presence of primary mullite aggregates in the clay relict and a significant growth of mullite crystals in a low viscosity glassy matrix at 1200°C itself. At 1300°C, both the bodies show a larger region of more elongated (> 1 μm) secondary mullite along with clusters of smaller sized primary mullite (< 1 μm). Small primary mullite crystals in the clay relict can be distinguished from elongated secondary mullite crystals in the feldspar relict in their size. Primary mullite aggregates remain stable also at higher temperatures. XRD studies were carried out for quantitative estimation of quartz, mullite and glass, which supported the SEM observations. An attempt was also made to correlate their mechanical strength with the constituent phases.     

用竹炭和硅藻土为原料制备含炭建筑材料

采用竹炭、硅藻土和粘土为原料,通过干压成型-高温烧成法制备出一种用于内墙装饰的含炭建筑材料,分析了竹炭/硅藻土质量比及烧成温度对含炭建筑材料的物化性能、物相组成及显微结构的影响规律。研究结果表明,竹炭、硅藻土和粘土三种原料复合可以制备较高气孔率、较高强度的含炭建筑材料,其物相主要为石英相与莫来石相,呈现规则孔道结构;在竹炭/硅藻土质量比为15/60,烧成温度为1150℃时,含炭建筑材料具有较好的综合性能,其破坏强度可达459.7N,吸水率10.55%,显气孔率18.4%,达到国标GB/T 4100-2006附录L中对BⅢ类陶质砖的性能要求,而且该材料的比表面积达到34.86m2/g,远红外辐射率达到0.904,具备远红外及吸附等功能,有望成为一种新型的室内功能装饰材料。     

Effect of size of fly ash particle on enhancement of mullite content and glass formation

Quartz is widely replaced by fly ash in traditional porcelain composite. Increased strength and stability of the fly ash-mixed composite depends on the quantity and crystallinity of the mullite phase in the fly ash. Our aim in this investigation is to increase the formation of mullite in nanocrystalline form and study the effect of temperature. Quantitative estimation of mullite and residual quartz content were done by X-ray diffraction (XRD) and nanostructure and crystallization were studied using differential thermal analysis (DTA), field effect scanning electron microscopy (FESEM), XRD and Fourier transform infrared (FTIR) spectroscopy. The results show that fly ash sieved through 250 holes/cm² mesh contain more mullite initially and growth of mullite as well as glass formation was faster in this sample compared to coarse fly ash. The maximum mullite in these samples was formed at 1600°C. Transformation of quartz and cristobalite phases into glassy phase was also faster for smaller particle sizes of fly ash.     

A comparative study of synchronous treatment of sewage and sludge by two vermifiltrations using an epigeic earthworm Eisenia fetida

Reduction and stabilization of sewage sludge during the clarification of municipal wastewater was synchronously shown to be improved significantly in a pilot-scale vermifiltration using an epigeic earthworm Eisenia fetida. The present study aimed to select a better filter media suited to vermifiltration performance by the comparisons of sludge yields, the characteristics of the by-products of vermifiltration-vermicast and the abrasions of earthworms between ceramsite and quartz sand. It was observed that the sludge yield of the CVB (Ceramsite Vermibed) ranged from 0.07 to 0.09 kg SS/kg COD(removed) at ambient temperature of 4-29 °C, representing 81% and 50% lower than that of the SVB (Quartz Sand Vermibed) and other reduction systems mentioned in this study. In addition, the sludge morphology variations described that the vermicast sludge from the CVB was more completely digested by earthworm than that of the SVB. The abrasions of the body wall of the earthworms in the CVB depicted less injured than that of in the SVB. So the ceramsite as filter media was better suited for the vermifiltration than the quartz sand.     

莫来石含量对钙长石/莫来石复相多孔陶瓷组织结构与性能的影响

以CaCO₃、SiO₂、α-Al₂O₃为原料, 采用泡沫注凝法制备了不同莫来石含量的钙长石/莫来石复相多孔陶瓷, 研究了莫来石含量对复相多孔陶瓷的体积密度、气孔率、抗压强度、热导率及微观组织和结构的影响. 结果表明, 莫来石含量对气孔率有很大的影响, 烧结过程中液相出现引起的收缩是气孔率下降的主要原因; 在气孔率相近的情况下, 莫来石含量较高试样的抗压强度和热导率也较高, 致密的孔壁、长柱状的莫来石晶粒使得复相多孔陶瓷的抗压强度提高. 所制备的钙长石/莫来石复相多孔陶瓷的开口气孔率介于60.8%~75.2%, 抗压强度为12.94~36.95 MPa, 热导率为0.30~1.33 W/(m·K).     

Role of hydrolysis water-alcohol mixture on mullitization of Al2O3-SiO2 monophasic gels

Two kinds of monophasic gels were synthesized from silicon ethyl ester (TEOS) and aluminium nitrate mixture by varying the water-alcohol content of the system. The mullitization reaction paths of the two gels were studied by differential thermal analysis (DTA) and X-ray diffraction techniques. The first kind of monophasic gel exhibited cubic mullite (Si-Al spinel) on the 980 °C exotherm and a further two more broad exotherms at 1150 and 1243 °C. This phenomenon resembles the DTA thermogram of a kaolinitic clay. The later two exotherms have been explained as due to the formation of mullite by two different reaction paths from the two phases appearing in the 980 °C exotherm. Nucleation and crystallization of mullite from amorphous alumino silicate phase takes place at 1150 °C, and transformation of cubic mullite to orthorhombic mullite takes place at 1245 °C. The second kind of monophasic gel exhibited only one exotherm and produced exclusively tetragonal mullite at 980 °C. The results suggest that pure mullite formation is possible when water induced hydrolysis of TEOS is avoided during the gelation process.     

Urea effect on the mechanism of mullite crystallization

Mullite is an excellent structural material due to its physical and mechanical properties. In this study, mullite was obtained by the sol–gel process, using silicic acid, aluminum nitrate, and urea. The urea effect was studied by evaluating samples obtained from urea/Al³⁺ ratio equal to 0, 1, and 3. The kinetic study was conducted using the isoconversional, non-isothermal, Flynn–Wall–Ozawa method. The sample prepared without urea, which is the least homogeneous one, formed spinel and α-alumina at 1150 °C, and Al-poor mullite together with α-alumina, at 1200 °C. The Al-poor mullite crystallization process from this sample showed the lowest yield. The sample prepared with urea/Al³⁺ ratio equal to 1, which has an intermediate behavior, formed spinel at 1100 °C, Al-poor mullite at 1150 °C, and α-alumina together with Al-poor mullite at 1250 °C. However, the sample prepared with urea/Al³⁺ ratio equal to 3, the most homogeneous, formed spinel and Al-rich mullite at 1100 °C. This sample formed Al-poor mullite at 1200 °C with the highest yield. Moreover, the sample synthesized without urea showed a higher porosity and a greater amount of hexacoordinated aluminum at 350 °C. All samples showed the same kinetic model, Šesták and Berggren (SB) for Al-poor mullite crystallization. The samples synthesized with urea crystallized mullite through the same kinetic parameters and constant values of the activation energy, but the sample prepared without urea followed different kinetic parameters and values of activation energy which changed over the course of the crystallization.