Kinetochemical and morphological differentiation of ettringites by the Le Chatelier-Anstett test

In this research, former XRD experiments have been verified by Le Chatelier-Ansttet (L-A) test. For this purpose, 28 cements consisting of 7 Portland cements and 21 blended cements containing 20%, 30% and 40% metakaolin have been submitted to the Le Chatelier-Anstett (L-A) test for 2 years. With all these cements, L-A specimens were manufactured and a direct parameter was measured for these specimens: increase in diameter, Δ∅, or diameter growth. Other complementary determinations were chemical analysis, XDA patterns and SEM of ettringites and specific properties of some cements tested. The experimental results have borne out that the formation rate of the ettringite formed from the reactive alumina, Al₂O₃^r−, present in pozzolans must be considerably higher than the formation rate of the ettringite from C₃A and much higher than the ettringite from C₄AF, both present in OPC. Owing to this, these ettringites were proposed being named “rapid formation” (ett-rf), “slow formation” (ett-lf) and “very slow formation” (ett-vlf) ettringites, respectively. On the other hand, these experimental results have also shown that the ett-rf has a much smaller size than the ett-lf (this is a direct consequence of the aforementioned conclusion); that almost all the alumina, Al₂O₃, present in M pozzolan must be regarded as being “reactive,” Al₂O₃^r−, or at least, the greatest part; that the detrimental effects derived from gypsum attack are shown much earlier in these POZC than in their plain OPC and, to such an extent, that this aggressive action can be described as rapid gypsum attack; and that none of the 21 POZC tested can be described as high nor moderate sulphate resistant cements according to L-A test.     

Synthesis mechanism of AlN–SiC solid solution reinforced Al2O3 composite by two-step nitriding of Al–Si3N4–Al2O3 compact at 1500 °C

The in-situ controllable synthesis of AlN–SiC solid solution reinforcement in large-sized Al–Si₃N₄–Al₂O₃ composite refractory by two-steps nitriding sintering was examined. In the first step, a dynamic Al@AlN structure was constructed in the composite by pre-nitriding at 580 °C. During the subsequent sintering process, it cracked above ∼900 °C, and micronized Al cluster (mixture of droplets and vapor) was extracted out gradually. As a result, multiple AlN mesophases were formed through different reaction paths, including i) initial AlN shell formed by solid Al with N₂, ii) reaction of Al cluster with N₂, and iii) reaction of Al cluster with Si₃N₄ from 900 °C to 1500 °C. The Si₃N₄ precursor serves as both a solid nitrogen source and an active Si source, and the controllable reaction between Al and Si₃N₄ leading to uniformly distributed AlN and Si mesophases. AlN–SiC solid solution is significantly formed when liquid Si appears. The shell, granule and whisker SiC–AlN solid solution were observed mainly depending on the dynamic AlN mesophase. The SiC–AlN solid solution reinforced Al₂O₃ materials is a novel promising refractory for large-scale blast furnace lining.     

Advances in crack formation mechanism and inhibition strategy for ceramic additive manufacturing

Crack formation is a common problem in ceramic additive manufacturing (CAM) process. In this paper, the forming characteristics of indirect ceramic additive manufacturing (DCAM) and direct ceramic additive manufacturing (IDCAM) technologies are comprehensively compared. The morphology and spatial distribution characteristics of micro and macro cracks in CAM are summarized. The crack formation mechanisms in different process stages of IDCAM, such as forming, sintering and cooling are analyzed and in DCAM are mainly discussed from the perspectives of stress distribution and energy release. The crack inhibition methods, including process parameters, auxiliary energy fields and material components are summarized comprehensively. The challenges and possible future trends of crack research in CAM are proposed.     

Experimental Evidence of Gas-Liquid Boundary Controlled Reactions in UV-Ozone Systems

Oxalic acid is chosen as a model compound to study the UV + O₃ reactions in an heterogeneous continuous gas sparging reactor. Oxalic acid has the advantage of not reacting significantly with ozone alone, and when oxidized with O₃ + UV radiation, the reaction is of the single-step type : HOOC-COOH + O₃ (UV) = 2 CO₂ + H₂O + O₂. The reactions are of zero order as long as no additional alkalinity is introduced into the system. Evidence is that the photolysis of ozone is produced in the gas phase and that the reaction occurs in the gas-liquid boundary layer.     

Conditions Affecting Bromate Formation During Ozonation of Bottled Water

Bromate concentration, ozone lifetime and ozone exposure (CT value) measured in bottled water in full-scale runs, were in good agreement to those measured in laboratory experiments. Ozone lifetime in bottled water was high enough to result in a CT value greater than 5 even for ozone dose as low as 0.1?mgO₃/L, at a water pH of 7.6. Bromate was gradually formed during the ozone lifetime. Bormate formation and ozone exposure were significantly influenced by pH. In full-scale runs, an ozone dose of 0.15?mgO₃/L at pH=7.6 resulted in a CT of 10.3 and a bromate concentration of 13.5?µg/L, while at pH=7.25 the values of CT and BrO₃ ^? were 12.6 and 9.6?µg/L, respectively. By decreasing further the pH to 6.8, an increase of CT value to 15.8 and a reduction of bromate to 5.5?µg BrO₃ ^?/L were observed. In addition, results in full-scale runs showed that ozone exposure and bromate concentrations were linearly related to ozone dose in the working range of 0.1 to 0.25?mgO₃/L.     

沿水平井钻井液渗滤研究

在钻井过程中,如果地层孔隙中流体的压力小于钻井液液柱压力,会发生地层被钻井液侵入,引起地层污染的后果。这会大大影响油气井的产能,我们只有理解和掌握钻井液渗滤的污染机理,才能有效的进行防治。在油气井投产之前,一般会采用酸化、压裂的方法解堵,为了确保解堵措施安全高效,需要精准地确定钻井液的伤害程度和侵入深度。数值模拟在研究钻井液渗滤问题上应用非常广泛。基于有限元的数值模拟的方法研究地层渗透率,泥饼渗透率和钻井时间对钻井液渗滤的影响。通过对相关算例进行分析,系统的概括出钻井液渗滤的影响因素。结果表明:地层渗透率越低,钻井液沿水平井筒渗滤越困难;泥饼渗透率越低,钻井液的侵入深度越小,钻井时间越长钻井液沿水平井筒渗滤越多,侵入的深度越大。     

基于LS-SVM的天然气水合物生成条件预测模型建立

在天然气管线内生成的水合物会严重影响天然气的开采、运输,因而天然气水合物的预测方法和防治措施备受重视。针对天然气水合物生成条件,考虑天然气组分对水合物生成的影响,为简化计算、提高预测精度,引入一种能够很好解决复杂物理问题的最小二乘支持向量机(LS-SVM),并且通过Matlab语言编程,建立了一种包含CH4浓度、CO2浓度、H2S浓度以及水合物生成温度为输入,水合物生成压强为输出的天然气水合物生成条件预测模型,同时将实验数据作为最小二乘支持向量机训练数据并进行预测分析。结果表明,该预测模型不仅拥有较高的预测精度,而且方法简单、可行,为天然气水合物生成条件预测提供了一种新的解决方法。     

石灰竖窑结瘤原因分析和预防措施

结合生产实践,对石灰竖窑的结瘤原因进行了分析,介绍了结瘤的防范措施、结瘤的判断方法及处理方法。     

准噶尔盆地西北缘中拐地区二叠系佳二段砂砾岩体沉积期次划分

本文综合测井、钻井和地震资料,在地质背景和基准面约束原则下,通过三维地震资料进行三、四级层序地层解释,并以测井曲线小波变换时频分析为核心,对佳木河组佳二段砂砾岩体进行沉积基准面恢复。     

Predicting the Detonation Velocity of CHNO Explosives by a Simple Method

A simplified method is shown, based on a semi‐empirical procedure, to estimate the detonation velocities of CHNO explosives at various loading densities. It is assumed that the product composition consists almost of CO, CO₂, H₂O and N₂ for oxygen‐rich explosives. In addition solid carbon and H₂ are also counted for an oxygen‐lean explosive. The approximate detonation temperature, as a second needed parameter, can be calculated from the total heat capacity of the detonation products and the heat of formation of the explosive by PM3 procedure. The detonation velocities of some well‐known CHNO explosives, calculated by the simple procedure, fit well with measured detonation velocities and the results from the well‐established BKW‐EOS computer code.