Thermal Behaviour of Silica Waste from a Geothermal Power Station and Derived Silica Ceramics

The silica waste originating from a geothermal power plant in Mexico was investigated with the aim of finding its applicability as a raw secondary material for ceramics production. The thermal behaviour of the original silica waste (containing NaCl and KCl from marine brine) and of the purified silica was characterized by means of DTA/TG, emanation thermal analysis (ETA) and thermodilatometry (TD). The reactivity of the purified silica waste mixed with CaCO₃ (1.8 mass%) was characterized by means of ETA, DTA and TG. The microstructures and phase compositions of the final products prepared by heating in air were tested by means of X-ray diffraction and of scanning electron microscopy coupled with electron probe X-ray microanalysis. The thermal analysis methods allowed determination of the optimal conditions for thermal treatment of the silica waste in order to obtain partly sintered porous materials for use as refractory bricks. This revised version was published online in August 2006 with corrections to the Cover Date.     

Characterization of Some Cyclodextrin Derivatives by Thermal Analysis

Acetyl-cyclodextrins, maltosyl-β-cyclodextrin, methyl-β-cyclodextrin and hydroxypropyl-cyclodextrins were characterized from data obtained with hot stage microscopy, differential scanning calorimetry and thermogravimetry. Phase transformation processes were studied by thermomicroscopy. Enthalpy values of dehydration processes have been explained with the different chemical composition of the substituent groups of cyclodextrins. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis, Characterization and Thermal Decomposition Mechanism of Cetyltrimethyl Ammonium Tetrathiotungstate

The synthesis, characterization and thermal decomposition mechanism of cetyltrimethyl ammonium tetrathiotungstate （CTriMATT） were studied herein. The as-synthesized CTriMATT was characterized by Elemental analysis, X-ray diffraction （XRD）, Fourier transform infrared （FT-IR）, Ultraviolet visible （UV-Vis） spectra. The results showed that the as-synthesized CTriMATT had high purity and good crystallinity. The introduction of alkyl groups induced a shift of the stretching vibration band of W-S bond to lower wavenumber, while it had no influence on the position of WS4^2-. Thermogravimetric analysis （TG）, differential thermal analysis （DTA） and in situ XRD characterizations revealed that CTriMATT began to decompose at 423 K in nitrogen and was converted to WS2 eventually. In addition, the decomposition product of CTriMATT at 673 K in nitrogen was characterized by N2 adsorption （BET） and scanning electron microscopy （SEM）. The results demonstrated that WS2 with higher specific surface area, and pore volume could be obtained from the thermal decomposition of CTriMATT in nitrogen.     

Dispersion Characterization of Short Slag Fiber in Aqueous Solution

Slag fiber with desirable properties is a promising candidate for applications as fillers or reinforced materials. Its poor dispersion in bulk materials, however, becomes the major challenge. Some aspects of its physicochemical properties were focused upon in the present article. The effect of three kinds of dispersants, viz., sodium carboxymethyl cellulose (CMC), anionic polyacrylamide (APAM), and cationic polyacrylamide (CPAM), as well as their combinations on the dispersion of slag fiber in aqueous solution was investigated. The viscosities of fiber suspensions were measured and the results were correlated with the dispersion of suspensions. It was shown that the slag fiber appeared amorphous, smooth surface with high length/diameter (L/d) ratio and negatively charged in water. The dispersion of slag fiber in aqueous solution directly depended on the dispersants. The optimal uniform and stable fiber suspension could be achieved under the dispersant concentration of the combination of 2 wt% CMC and 0.25 wt% APAM. In this case, the fiber concentration was as large as 25 g/L. In addition, the plausible dispersion mechanism of slag fiber in aqueous solutions was elucidated based on the electrostatic steric stabilization.     

Thermal characterization of social vespid silk

In this paper we try to establish a link between the microclimate in the wasp nest and the structure and thermal stability of vespid silk. We suggest that there are at least two types of water that is absorbed by the silk of Oriental hornets, namely, surface water and intrinsic structural water. The release of both types of water was found to be reversible. The enthalpy values of the endothermic peaks associated with the release of water from different silk samples do not differ substantially and are in the range of 106 to 130 J g^-1 for the Vespa orientalis male larvae silk (sample #1), Paravespula germanica (yellowjacket) worker larvae silk (#3) and Vespa orientalis nest envelope(#4). For the Vespa orientalis worker larvae silk (sample #2), however, it is twice as large (228 J g^-1). This is in agreement with the increased total amount of absorbed water. The silk studied has a fibrilar structure with interconnecting surfaces overlying entire regions. It is assumed that the initial water loss stems from water evaporation from the coat of the fibers - a daily occurrence in the hornets' nest. Heating to above 70°C may result in structural changes in the silk core. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal Analysis in Studies of Technological Waste Materials to Be Subjected to Thermal Treatment

Attempt was made to evaluate the usefulness of thermoanalytical methods, combined with X-ray phase analysis and chemical analyses, for the study of thermal decomposition of waste materials to be subjected to thermal treatment. The object of the studies were petrochemical waste materials intended to be decomposed in a rotary furnace. Results are given of the studies of five selected waste materials. This revised version was published online in August 2006 with corrections to the Cover Date.     

利用铝废渣制备片状堇青石的影响因素研究

以铝厂废渣、高岭土、滑石为主要原料,采用固相法合成片状堇青石。分析了原料种类、原料配方、烧结温度、保温时间和晶核剂对合成堇青石的影响,并通过XRD、SEM进行表征。结果表明,原料的纯度越高合成的堇青石纯度越高;富含镁的配方能完全形成堇青石相;最佳烧成温度为1 380℃,保温时间为4 h,此时得到的堇青石纯度最高,且呈现片状结构,颗粒大小均匀;堇青石熟料可以起到晶核剂的作用,促进堇青石的生成。     

Thermal Characterization of Dolomites

The decomposition behaviour of dolomite samples has been carried out by simultaneous DTA-TG experiments. Dolomite samples could be classified broadly into two categories as regular and iron-bearing dolomites based on DTA decomposition temperatures. The mass% FeO of all the dolomite samples was identified by DTA and the results are confirmed by atomic absorption spectrophotometer experiments. This revised version was published online in July 2006 with corrections to the Cover Date.     

Ash and Slag Waste as a Secondary Raw Material

In the process of industrial corporation activities a lot of waste, which pollutes the atmosphere, is generated, for example ash and slag. In Tomsk region, by estimates, ash stores occupy about 600 hectares, which contain about 25 million tons by weight. In Russian thermal power-stations ash disposal areas there are about 1.3 billion tons of ash, and only 10% of it is used. That is why this problem is topical enough. In this paper the scheme of producing ash ceramic bricks and complex ash and slag waste processing is shown. Besides, profitability of the project is presented.     

Thermal transformations of titanium slag of high titania content

Titanium raw materials play important role as a source of titanium and titanium dioxide. The investigation of the rate of oxidation and phase transformation of titanium slag in static air atmosphere by use of thermogravimetry (TG) and X-ray diffractometry (XRD) were presented. The investigation were carried out for three different particle size fractions to determine influence of this parameter on rate of reaction. To estimate kinetic parameters was used the kinetic model of contracting volume. The value of kinetic parameters show that influence of heating rate and particle size on rate of reaction is not so large. The thermogravimetric investigations of the oxidation of titanium slag in air atmosphere shown that reaction proceeds in two stages. The XRD investigation shown that titanium slag has the pseudobrookite structure and its diffraction pattern is very close to the diffractogram of magnesium titanate MgTi₂O₅ and iron magnesium titanium oxide (Fe-Mg-Ti-O). At elevated temperature the structure of slag transforms to the ferric pseudobrookite structure and excess titanium dioxide forms the rutile phase. This revised version was published online in July 2006 with corrections to the Cover Date.     

Study on the In-situ Synthesis of Aluminum Titanate Sintered by Waste Aluminum Slag

Aluminum titanate was in-situ synthesized by using industrial waste-residue in the aluminum factory and TiO2 as the main raw materials and the influence of different reaction temperatures on the purity and microstructures of synthesized products were mainly discussed. The obtained Al2TiO5 was characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and relevant analytical software. The results show that elevating the sintering temperature can increase the content of aluminum titanate; and at 1420 ℃, it reaches the highest in the synthesized ceramic. When the sintering temperature continues to increase, the produced aluminum titanate will decompose resulting in the drop of its content. Therefore, the optimum sintering temperature of in-situ synthesis of aluminum titanate is determined as 1420 ℃, at which the grains of aluminum titanate grow completely, the purity of aluminum titanate is 89.3wt%., the highest density is 2.75 g/cm^3, and the porosity is 9%.     

Thermal Characterization and Physico-Chemical Properties of Fe2O3−Mn2O3/Al2O3 Systems

The effect of ferric and manganese oxides dopants on thermal and physicochemical properties of Mn-oxide/Al₂O₃ and Fe₂O₃/Al₂O₃ systems has been studied separately. The pure and doped mixed solids were thermally treated at 400–1000°C. Pyrolysis of pure and doped mixed solids was investigated via thermal analysis (TG-DTG) techniques. The thermal products were characterized using XRD-analysis. The results revealed that pure ferric nitrate decomposes into Fe₂O₃ at 350°C and shows thermal stability up to1000°C. Crystalline Fe₃O₄ and Mn₃O₄phases were detected for some doped solids precalcined at 1000°C. Crystalline γ-Al₂O₃ phase was detected for all solids preheated up to 800°C. Ferric and manganese oxides enhanced the formation of α-Al₂O₃ phase at1000°C. Crystalline MnAl₂O₄ and MnFe₂O₄ phases were formed at 1000°C as a result of solid–solid interaction processes. The catalytic behavior of the thermal products was tested using the decomposition of H₂O₂ reaction. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal and Sintering Behaviour of Basalt Glasses and Natural Basalt Powders

A study of three Spanish and one Bulgarian basaltic rock demonstrated that, after thermal treatment at temperatures higher than 800°C, crystallization of pyroxenes, anorthite and magnetic occurred. Following sintering of the original basalts and powdered original glasses, the same crystalline phases were nucleated and grown in the resulting glass-ceramics. Chemical and DTA/TG analyses suggested similar behaviour for the synthesized Canarian basalt glasses, which are located in the tephrite-basanite field, and different behaviour for the trachy-andesite Canarian and the basaltic-andesite Bulgarian basalt glass. In consequence of the high sensitivity of the specific heat to phase transformations, C_p(T) and TMA experiments allowed a distinction between the tephrite-basanite and trachy-andesite Canarian glasses on the basis of their different thermal behaviour. This revised version was published online in August 2006 with corrections to the Cover Date.     

Tannery waste solidification and stabilization

The stabilization/solidification of tannery waste containing chromium was studied as an option for its treatment and final disposal, by using a Portland cement type II and two different commercial bentonites (sodium and organophilic) as additives. Different compositions were evaluated by compressive strength analysis, porosity measurement, leaching tests and thermal analysis. The effect on the compressive strength is directly related to the resulting effect of the components present in the original paste on the hydration degree of the cement, which can be evaluated by thermogravimetric analysis from the dehydration steps of tobermorite and ettringite phases of the pastes. The results show that this process is suitable for the treatment of the tanning waste and that the best conditions of stabilization are obtained when both additives are used. This revised version was published online in August 2006 with corrections to the Cover Date.     

神府次烟煤在不同温度下的热溶产物表征

利用FT-IR、热重、GPC以及同步荧光分析等对神府次烟煤在不同温度条件下的1-甲基萘热溶物和热溶残煤进行了表征。结果表明,热溶物中含有较多的脂肪结构,灰分几乎全部转移至残煤中;热溶残煤与神府原煤的热失重特性存在明显差别;在300~360 ℃,随着温度升高,热溶物数均分子量呈增加趋势,进一步提高温度,分子量减小;热溶物缩合芳环数随着温度升高而增加。据此表明,在低于煤初始热解温度下神府次烟煤的热溶主要以溶剂化作用破坏煤中的非共价键为主,其中,酮、酯等轻质组分易于脱除;而高于煤初始热解温度的热溶过程则伴有侧链和桥键等弱共价键断裂的热解反应和自由基缩聚反应,热溶物中三环等稠环芳香结构增加。     

Thermal characterization of methyltributylammonium-smectites

A sodium smectite (NaS) with a cation exchange capacity (CEC) of 1.08 mol kg⁻¹ was intercalated with methyltributylammonium cation (MTBA⁺) with proportions equivalent to 0.2, 0.4, 0.6, 0.8 and 1.0 times the CEC. The contents of adsorbed water and intercalated MTBA⁺ in the prepared organosmectites (OSs) were determined by using the differential thermal analysis (DTA) and thermogravimetry (TG) curves. The adsorbed water of 8% in the NaS decreases greatly in OSs with the increase of the MTBA⁺ content and reduces to 2.0% for the 1.0 CEC sample. This explains the gradual change of the NaS from hydrophilic to hydrophobic character. Thermal degradation of the intercalated MTBA⁺ in OSs occurs approximately between 250–450°C. The oxidation of the formed charcoal to CO₂ occurs between 450–850°C. The intercalated MTBA⁺ content for each OS is obtained from both the TG and carbon analysis. The results do not agree exactly, but both the results tend to increase by increasing initial content of the MTBA⁺ in solution.     

Investigations on the Thermal and Elastic Properties of ZnO-Incorporated Phosphate Glasses and Glass Ceramics

Abstract

Glasses of the 45P₂O₅-(40-x)CaO-15Na₂O-xZnO system with increasing zinc oxide (ZnO) concentrations within the ranges of 3 ≤ x ≤ 12 mol% were obtained by employing the melt-quench technique. ZnO inclusions in the phosphate glass network lead to increases in its density and, conversely, a decrease in its molar volume. On the basis of the obtained thermal analysis data, the glasses underwent thermal treatment, which helped to derive their glass ceramic equivalents. The evaluations of structural and elastic properties of glasses before and after thermal treatments were made using X-ray diffraction (XRD) studies and ultrasonic nondestructive testing. The differential thermal analysis data show the reduction in the crystallization tendency and increase in thermal properties, such as crystallization temperature (T _P), thermal stability

(T _c – T _g) (where T_c is crystallization onset temperature and T _g is glass transition temperature), thermal stability parameter (S), and degree of glassification (D _g) of phosphate glasses against the progressive additions of ZnO. The XRD of glass ceramics confirmed the dominance of metaphosphate, pyrophosphate, and ZnO-related crystalline features. The measured elastic moduli, such as longitudinal (L), shear (G), Young's (Y), and bulk (K), and Vicker's microhardness values increased in both glass and glass ceramics with an increase in ZnO incorporation.     

高热稳定性介孔氧化锆的合成及表征

利用阴离子表面活性剂作模板,通过水热均匀沉淀方法成功合成了具有高热稳定性的介孔氧化锆.该方法以十二烷基苯磺酸钠(SDBS)作为介孔结构的导向剂,其含S基团在煅烧时起到了稳定剂的作用.采用透射电镜、氮气吸附-脱附、X射线粉末衍射、红外光谱测试手段对样品进行了表征.研究表明,以SD-BS为模板剂合成的介孔氧化锆具有蠕虫状介...     

纳氏试剂分光光度法测定铝灰渣浸出液中的氨氮含量

随着水土资源环境日益恶化,监测氨氮量对水土的污染程度也备受关注。为了准确测定铝灰渣浸出液中的氨氮量,实验对振荡方法、振荡时间、固液比、试液过滤方式、纳氏试剂加入量以及测定干扰因素进行了研究。确定了以翻转振荡为前处理方式,最佳振荡时间为14 h,固液比为1:10,最佳纳氏试剂加入量为1.0 mL,通过改善过滤方式,降低了空白值。由实验结果可知：在试验范围内,F^-对氨氮量的测定不产生干扰;对于浸出液中Cl^-、Al³⁺和Ca²⁺浓度高的样品,可通过移取稀释液2.00 mL,加入1.0 mL酒石酸钾钠溶液(500 g/L),即可消除其干扰。运用纳氏试剂分光光度法测定铝灰渣浸出液中的氨氮量,得到氨氮标准曲线线性相关系数为0.9998,方法检出限为0.39 mg.L^-1,RSD(n=6)<5%,回收率在94.7%～105%之间。本方法简单快速,精密度高,且具有较低的检出限,适用于大批量铝灰铝渣等固体废物浸出液中氨氮量的测定。