Effect of Al3+ on Tobermorite Crystallinity

The difference between the systems of CaO-SiO2,-H2O and CaO-SiO2-Al(OH)3,-H2O, was studied, especially the effect of Al3+on the crystallinity of tobermorite was focussed. As a result, in the system of CaO-SiO2-H2O, tobermorite formed early, however, withreaction time forward, tobermorite was replaced by xonotlite. So far as CaO-SiO2-Al(OH)3,-H2O was concemed, hydrothermal reactionwas cdried out under the same condition as CaO-SiO2-H2O to study the morphological changes of tobermorite crystals. It was found thatAl3+ accelefated the crystal growth of tobermorite to some extent and was in faVor ofplaty crystals. Moreovef, with the Al3+ content in-creasing in the starting material, the morphology of tobermorite did not change magnificently, but platy crystals became more and moreeminent. As soon as the Al2O3 content was over 15.6%, synthetic mineral greatly changed in smicthe and haled into hibschite differentfrom 1 .1 nm tobermorite. Obviously, xonotlite was not apt to form in the presence of Al3+.     

Hydration products of cement-silica fume-quartz powder mixture under different curing regimes

Composition, morphology, and structure of hydration products in hardened pastes of three kinds of blended cement(cement-silica fume, cement-quartz powder and cement-silica fume-quartz powder) hydrated under different curing regimes(standard curing, 90 ℃ steam curing, 200 ℃ and 250 ℃ autoclave curing) were investigated by X-ray diffraction and field emission scanning electron microscope equipped with EDAX system. Results showed that the main hydration products in three kinds of hardened pastes under standard curing condition are all C-S-H gels, CH, and AFt. Under 90 ℃ steam curing condition, the main hydration products of cement-silica fume and cement-silica fume-quartz powder are C-S-H gels, whereas those of cement-quartz powder are C-S-H and CH. Under 200 or 250 ℃ autoclave curing condition, no obvious crystallized CH phase is found in hardened pastes of three kinds of blended cement, and C-S-H gels are transformed into one or more crystalline phases such as tobermorite, jennite, and xonotlite. The chemical composition and morphology of these crystalline phases depend on the composition of mixture and autoclave temperature.     

Preparation of Ultra-light Xonotlite Thermal Insulation Material Using Carbide Slag

Using carbide slag as the calcareous materials, xonotlite thermal insulation material was successfully prepared via dynamic hydrothermal synthesis. The experimental results show that the xonotlite thermal insulation material is made up of large numbers of chestnut bur shape particles. Optimum conditions of calcination temperature of carbide slag, synthesis reaction temperature and time, stirring rate, CaO/SiO2 mol ratio, water/solid weight ratio, amount of fiberglass, molding pressures, dryness temperatures...     

Preparation of ultra-light xonotlite thermal insulation material using carbide slag

Using carbide slag as the calcareous materials, xonotlite thermal insulation material was successfully prepared via dynamic hydrothermal synthesis. The experimental results show that the xonotlite thermal insulation material is made up of large numbers of “chestnut bur shape” particles. Optimum conditions of calcination temperature of carbide slag, synthesis reaction temperature and time, stirring rate, CaO/SiO₂ mol ratio, water/solid weight ratio, amount of fiberglass, molding pressures, dryness temperatures and the presence of dispersant (glycol and polyvinyl alcohol) favor the preparation of xonotlite thermal insulation material. The evaluation of xonotlite thermal insulation material reveals that the product is ultra-light and excellent in physical performances. Such a little amount of impurities in carbide slag has no effect on the phase, morphology, stability at high temperature and physical performances of products.     

Synthesis and microstructure analysis of autoclaved aerated concrete with carbide slag addition

Synthesis of autoclaved aerated concrete （AAC） has been carried out with carbide slag addition, and the carbide slag could be used as a main material to produce the AAC with the compressive strength about 2 MPa and the density below 0.6 g.cm-3. In this study, quartz sand acted as frame structure phase in the matrix, and quartz addition also influenced the Si/Ca of starting material. Tobermorite and CSH gel were formed readily at 62%, which seemed to enhance the compressive strength of samples. Curing time seemed to affect the morphology of phase produced, and specimen with the plate-like tobermorite formed at 10 h appeared to have a better compressive strength development than the fiber-like one at 18 h. The higher curing temperature seemed to favor the tobermorite and CSH gel formation, which also exerted a significant effect on the strength development of the samples. On the micro-scale, the formed CSH gel was filled in the interface of the matrix, and the tobermorite appeared to grow in internal-surface of the pores and interstices. The tobermorite or/and CSH formation seemed to densify the matrix, and therefore enhanced the strength of the samples.     

Hydrothermal synthesis of zeolites-calcium silicate hydrate composite from coal fly ash with co-activation of Ca(OH)2-NaOH for aqueous heavy metals removal

Coal fly ash is a typical secondary aluminum/silicon resource. The preparation of zeolite-type absorbent is a potential way for its value-added utilization, while the purity and adsorption property of zeolite are limited due to the occurrence of side reactions in the synthesis process. In this study, a designated composite consisted of crystalline zeolites and amorphous calcium silicate hydrate was selected, which was direct synthesized from fly ash under conditions of a Ca/Si molar ratio of 0.8, an initial NaOH concentration of 0.5 mol/L, a hydrothermal temperature of 170 ℃ and a liquid–solid ratio of 15 mL/g. The results indicated that this composite had superior adsorption property for a variety of heavy metals, which was based on the exchange of calcium and sodium ions in zeolites and calcium silicate hydrate. Its adsorption capacities for Pb²⁺, Ni²⁺, Cd²⁺, Zn²⁺, Cu²⁺ and Cr³⁺ attained 409.4, 222.4, 147.5, 93.2, 101.1 and 157.0 mg/g, respectively, in single solution with a pH of 4.5. After regulating the synthesis conditions, the transformation of amorphous calcium silicate hydrate into crystallized tobermorite weakened the adsorption capacity of the composite. Besides, due to the competitive adsorption in a multiple ions solution, the adsorption capacities for these heavy metals had a reduction.     

Low-cost oriented preparation of ultra fine xonotlite fibers

Nanometer-sized xonotlite fibers have great potential application in many fields. The traditional method of preparing ultra fine xonotlite fibers uses the ultra fine and highly active silica as the major raw materials, which is not only expensive but also difficult to prepare the xonotlite fibers with diameters around 100 nm. In this study, the ultra fine xonotlite fibers with diameters around 100 nm were prepared by an autoclaving method. The preparation was low-cost oriented by using natural powder quartz and lime as the major raw materials. The intergrowth of the fibers formed thin shell hollow balls or ellipsoids, namely the secondary particles.The length of the nanometer-sized xonotlite fibers was around several microns. The fibers and their secondary particles were produced at 216℃ for 6 h with a continuous stirring of 300-500 r/min. Zirconium oxychloride was used as an additive. The experiments show that zirconium oxychloride has an enormous effect on the growing habit of xonotlite crystals and plays an important role in controlling the diameter of the xonotlite fibers.     

Characterization and growth dynamics of barium titanate crystallite on nanometer scale

Barium titanate powder on nanometer scale was synthesized by means of co-precipitation. The thermal mass loss, crystal grain growth and phase transition of the barium titanate nanometer powder were investigated by TG (Thermogravimetric)-DTA (Differential scanning calorimetric) and XRD (X-ray powder diffractometer) at different heat treatment temperatures. The results show that amorphous barium titanate powder can transfer into tetragonal symmetry structure after heat treatment. When the heat treatment temperature is below 900℃, the grains grow rapidly because the activation energy at low temperature is greatly less than that at high temperature. By controlling the heat treatment temperature, the optimization of the barium titanate crystallite size and formation of tetragonal phase can be realized.     

水热活化前驱物对制备Li4Ti5O12晶相的影响

采用溶胶-凝胶法制备出Li4Ti5O12前驱物,分别在温度为160℃、180℃、200℃的水热条件下活化前驱物,并进行煅烧。通过热分析、XRD、SEM测试手段对样品进行表征,结果表明：前驱物水热活化条件为180℃、10h,煅烧条件为800℃、8h,可以制备出纯度较高的Li4Ti5O12晶相,其纯度大于95％;制备的Li4Ti5O12粉体分散性好且为球形颗粒,颗粒尺寸分布比较均匀,平均粒径约为0．65μm．     

硬硅钙石型硅钙材料的研究与应用

在窑炉、高温管道保温材料中，硬硅钙石型硅钙材料具有最佳性能价格比。作采用活化工艺、使其容重降低，强度提高，耐性显增长，中对其材料，配比，工艺参数优化实验作了介绍，比较了中试产品与传统中试产品的性能。结合扫描电镜和Ｘ射线衍射分析结果对其优化机理了探讨。     

Hydration Characteristics and Humidity Control Performance of Calcium Silicate Board Prepared from Mine Tailing and Diatomite

The feasibility of utilizing molybdenum tailing and diatomite as siliceous materials to prepare calcium silicate board was explored. The influences of molybdenum tailing/diatomite proportion on hydration characteristics, thermal conductivity, water absorption, flexural strength and moisture adsorption-desorption property of calcium silicate board were investigated in detail. The experimental results reveal that molybdenum tailing is environmentally friendly to prepare building materials. The main hydration products in calcium silicate board under autoclaved condition are C-S-H with low crystallinity and tobermorite. Molybdenum tailing is favorable to the formation of tobermorite. The flexural strength and bulk density of the calcium silicate board gradually increase when the content of molybdenum tailing increases. Netlike C-S-H is formed with the increase of diatomite content during autoclaved curing process, resulting in the enhancement of moisture adsorptiondesorption performance and the reduction of thermal conductivity. The optimal content of molybdenum tailing is 20%, furthermore, the flexual strength and thermal conductivity of calcium silicate board at this content meet the Chinese standard JC/T564.1-2008.     

硅系相变材料的研究进展

阐述了硅系相变材料的研究热点和应用前景.通过原位变温X线衍射(XRD)检测技术,揭示了硅系相变材料在变温过程中的物相结构变化.升温时,硅系相变材料由非晶态转化为晶态,电导性增加;降温时,由晶态转化为非晶态,电导性下降,这对相变储存器存储与擦除技术的实现起关键作用.     

温度对C/C复合材料表面HAp涂层的影响

采用水热电沉积法在碳／碳（C／C）复合材料表面制备了羟基磷灰石（HAp）涂层，用XRD、SEM等测试手段对涂层进行表征，重点研究了水热温度对HAp涂层晶相和显微结构的影响以及HAp涂层的沉积动力学机理。结果表明：随着温度的升高，HAp衍射峰有所增强，结晶程度变好，涂层更加致密和均匀；涂层的沉积速率随着温度的升高而增加，涂层的沉积活化能为25．89kJ／mol。     

Novel spin glasses by mechanical milling

Novel spin-glass alloys were synthesized by milling intermetallic compounds and also by milling mixtures of crystalline elemental powder in a high-energy ball mill.Spin glass behaviour was found in amorphous Co2Ge,which was amorphised by milling in mechanically disordered crystalline GdAl2 in ball-milled crystalline and amorphous CoZr,and in mechanically alloyed Co-Cu,which formed a supersaturated f.c.c.solid solution.All these materials are binary alloys and tlie concentration of the magnetic element is high,which makes them novel types of spin glasses.It is shown that ball milling may not only lead to structural metallic glasses,but can also generate the magnetic pendant of a structural glass,namely the spin glass.     

微/纳米ZnO的水热合成及其光学性质

以醋酸锌和氢氧化钠为原料,在低温下联用沉淀法和水热法合成了未掺杂的ZnO,考察了pH和温度等条件对ZnO晶体的影响,通过X射线衍射仪(XRD)、扫描电镜(SEM)、荧光光谱仪(PL)对产物进行了表征。结果表明:沉淀法制得的前躯体在低温下水热反应6h后可以生成晶型较好的六方晶系ZnO晶体。当反应条件变化时,ZnO呈现为微/纳米级的多种形态。130℃下制备的ZnO在380～700nm之间存在多条荧光发射峰,而且发光强度随着pH的增加而增大。     

Enhancing the crystalline degree of carbon nanotubes by acid treatment, air oxidization and heat treatment

Three approaches of treating carbon nanotubes (CNTs) including acid treatment, air oxidization and heat treatment at high temperature were studied to enhance the crystalline degree of carbon nanotubes. High temperature heat-treatment elevates the crystalline degree of carbon nanotubes. Acid treatment removes parts of amorphous carbonaceous matter through its oxidization effect.Air oxidization disperses carbon nanotubes and amorphous carbonaceous matter. The treatment of combining acid treatment with heat-treatment further elevates the crystalline degree of carbon nanotubes comparing with acid treatment or heat-treatment. The combination of the three treatments creates the thorough effects of enhancing the crystalline degree of carbon nanotubes.     

Mechanism of boron oxide as a phase regulator for modification of manganese slag

The current research focused on adjusting the low hydration activity of the metallurgical slag by phase reconstruction technique. Boron oxide was used as a phase regulator to improve the amorphous phase composition of the manganese slag, consequently enhancing its hydraulic activity. The effects of boron oxide dosage and calcination temperature on the manganese slag amorphous phase content were investigated. XRD and DTG were performed to analyze the hydration mechanism of the manganese slag powder and cement. Results show that, when boron oxide dosage is 15%, calcination temperature is 1 300 ℃, and holding time for 1 hour, the amorphous content of the modified manganese slag reaches 95% and its 28-day activity index reaches 81.7%. The manganese slag powder can then be used as cement or concrete admixtures for the building materials industry.     

废催化剂合成无磷洗涤助剂的工艺研究

以废弃氧化铝催化剂为原料,通过添加晶化导向剂,在水热合成条件下,合成无磷洗涤助剂4A沸石。实验考察了废催化剂的氧化铝转化率、合成4A沸石的晶化导向剂加入量、成胶时间、陈化时间、晶化时间对钙离子交换度的影响,确定了最佳的工艺条件,经X射线衍射检测,晶化产物结晶度高,4A沸石离子交换度在310mg(CaCO3)/g(沸石)以上。该工艺降低了原料成本,提高了产品质量,缩短了反应时间,得到了优质洗涤剂用4A沸石。     

Simulation of the cracking and ablation behavior of ferro-siliceous and siliceous nuclear sacrificial concretes

We investigated the simulation of the cracking and ablation behavior of ferro-siliceous and siliceous nuclear sacrificial concretes. To this end, four type of sacrificial concretes were fabricated, i e, the ferro-siliceous (F) and siliceous (S) plain concretes, and the polypropylene fiber reinforced concretes of the above two (FF, SF). The cracking and ablation behaviors of the sacrificial concretes were investigated by simulation tests, and the simulated elevated temperature was obtained by means of thermite powder. The number and the width of the cracks were compared and the pore size distribution of sacrificial concretes was measured. In addition, the interface and chemical composition of melt at different positions were analyzed, and the ablation depth of the sacrificial concrete crucibles was also measured. It was found that the siliceous concrete shows to be more prone to cracking than the ferro-siliceous concrete due to the higher content of fly ash and lower water to binder ratio; though the ablation depth of siliceous concrete is found to be slightly larger, no clear difference can be detected for the basemat ablation rate.     

Preparation of ITO nano-powders by hydrothermal-calcining process

1 INTRODUCTIONSn-doped In2O3(ITO) is one kind of n-typesemiconductor material[1].It has excellent electro-optical properties , such as electrical conductivityand high transparency under visible light[2],andiswidely used in electronic , transparent electrode ,solar cells and electro-irradiance , especially inscreen display[3 ,4].Recently nearly half of the met-al indium has been used to prepare ITO materialsin the developed countries[5], such as Japan, A-merica ,France and so on.So the…