Study on spinel-based inert anode for aluminium electrolysis

1 IntroductionSince the Hall-Heroult process was applied in aluminium production,an inert anode was al ways thetarget that the aluminiumindustry is seeking for in the newtechnology field. The greenhouse gases CO2and the fluoride CFnemittedfromthe present carbon anodes ,give a huge pressure onthe environment .Theapplication of inert anodes will help us go through this trouble :a cell with inert anodes emits oxygen in-stead of CO2and other nocuous gases ;the newtype of cell with inert anodes …     

水泥砂浆TSA侵蚀机理及其预防技术研究

分析了碳硫硅酸盐（thaumasite）对水泥混凝土结构的破坏机理及对实际工程建筑所带来的危害。并针对其破坏产生的条件与作用机理,从水泥品种、水灰比、矿物掺合料的选择以及对环境因素的控制等方面阐述了有效的、可行的抗TSA侵蚀的技术。     

Microstructural evolution and relevant mechanical properties of Al-rich transparent magnesium aluminate ceramics

A novel phenomenon is found that the grain growth of aluminum-rich magnesium aluminate is suppressed to 5 μm, despite of high-temperature hot-isostatic-press at 1750 °C. For the transparent MgO-nAl₂O₃ (n = 1.2, 1.5, 2.0), the transmittance and strength tended to be enhanced with increasing Al₂O₃ content, having the highest values 80 % at 550 nm and 214.3 MPa for n = 2.0. This is due to the different microstructural evolution depending on the composition. When the excessive Al₂O₃ was small, the inhomogeneous microstructure with bimodal grain size and lots of rod-shaped particles were observed. However, as the Al₂O₃ amount increased, the microstructure became homogeneous with reducing the grain size and the rod-shaped particles. The microstructural and compositional analysis revealed that the rod-shaped particle were generated due to the trace potassium impurity as well as the different cationic diffusion rate, and the suppression of grain growth was induced by the severe Al segregation at the grain-boundaries.     

Rheological investigation of alginate chain interactions induced by concentrating calcium cations

Chain interactions of sodium alginate during its gelation were investigated by a new gelation method which was based on a Ca²⁺-concentrating gelling process (CCGP) produced by water evaporation of an alginate solution containing CaCl₂. For two commercially available sodium alginate samples (low viscosity (LA) and medium viscosity (MA)) having different molecular weight distributions but the same G/M blocks, the critical Ca²⁺ concentrations for their gelation were found to be 4.6 (for LA) and 4.5 (for MA) μmol/mL after evaporating water from 1% of alginate solutions containing 4 μmol/mL of CaCl₂. The CCGP gelation method for alginate under the above conditions were confirmed by rheological measurements and the observed highly ordered and uniform mesh structure of the CCGP-formed alginate gels shown in cryo-SEM images. Combinations of LA and MA at different ratios (0:4, 1:3, 2:2, 3:1, 4:0 on weight basis) were studied using the CCGP gelation method to further the understanding of the alginate chain interactions during gelation. Different LA/MA mixtures exhibited different rheological properties in either non-gelled or gelled systems, indicating that the molecular weight distributions of the sodium alginates influence the alginate chain interactions mediated by Ca²⁺. Thus, an appropriate combination of LA and MA is required for a strong alginate interchain interaction during CCGP, and alginate products with desirable characteristics can be produced by manipulating the mixing ratios of sodium alginates having different molecular weight distributions even at the same total composition and distribution of G/M blocks.     

Experimental investigation and numerical modeling of chloride penetration and calcium dissolution in saturated concrete

Chloride penetration and calcium dissolution have been investigated for a saturated concrete after exposure to a 0.5 mol/L NaCl solution for a period of up to 3150 days. Simultaneous ion transport model (SiTraM) that allows the transport of chloride and calcium ions to be simultaneously simulated in a hydrated cement system has been used to verify the experimental results.Self-compacting concrete (SCC) with a water to cement ratio of 0.3 resulted in a limited chloride penetration depth while the calcium dissolution was also reduced within the near surface zone. Increased unit water content for normal concrete resulted in higher chloride penetration depth and larger dissolution front of Ca(OH)₂ regardless of having the same water to cement ratio.It was revealed that the SiTraM can predict the profiles of chloride and calcium for self-compacting concrete. It was also found that the primary factor to control chloride penetration front and the dissolution front of Ca(OH)₂ was the pore structure characteristic of concrete.     

Reaction mechanism and size control of CaB6 micron powder synthesized by the boroncarbide method

Reaction synthesis mechanism of Calcium hexaboride (CaB₆) powder was investigated by using CaCO₃-B₄C-C system. Micron-scale CaCO₃ and B₄C powders were used as main raw materials. The synthesized powder was determined by X-ray diffraction, showing no left reactants if enough CaCO₃ was added to compensate the evaporation of calcium atoms at high temperature. The powder morphology was observed through SEM. The synthesized CaB₆ powder formed hard agglomerates which consisted of cubic CaB₆ crystallites when the reaction completely finished. Reaction process was illustrated indicating it was a solid-state reaction occurred from B₄C surface to the centre. The dry high-energy ball milling was used to investigate the influence of ball-milling time on the shape and size of powder particles. The particle granularity was measured by laser size analysis method. It is obvious that the particles were refined greatly after ball milling for 8 h. However, the CaB₆ powder could not been refined markedly after 16 h. Finally, optimized parameters for size controlling were given in this paper.     

铝酸盐水泥-粉煤灰系水泥基多孔防火隔热材料研究

以铝酸盐水泥,粉煤灰为主要原料制备水泥基多孔防火隔热材料,讨论和分析了粉煤灰掺量时抗压强度的影响,并通过高温试验时比,结果表明,粉煤灰在铝酸盐水泥中具有很好的耐高温性,X.射线衍射分析表明,高温前主要矿相为C3AH6,CAH10C2AS,CA和α-siO2,高温后主要矿相为C3AH6;C2AS,CA和α-SiO2,CAH10在高温下分解.铝酸盐水泥.粉煤灰系多孔混凝土高温后材料的力学性能优于纯铝酸盐水泥多孔混凝土,铝酸盐水泥.粉煤灰系水泥基多孔混凝土是一种低成本性能优良的防火隔热材料.     

Modelling biological and chemically induced precipitation of calcium phosphate in enhanced biological phosphorus removal systems

The biologically induced precipitation processes can be important in wastewater treatment, in particular treating raw wastewater with high calcium concentration combined with Enhanced Biological Phosphorus Removal. Currently, there is little information and experience in modelling jointly biological and chemical processes. This paper presents a calcium phosphate precipitation model and its inclusion in the Activated Sludge Model No 2d (ASM2d). The proposed precipitation model considers that aqueous phase reactions quickly achieve the chemical equilibrium and that aqueous-solid change is kinetically governed. The model was calibrated using data from four experiments in a Sequencing Batch Reactor (SBR) operated for EBPR and finally validated with two experiments. The precipitation model proposed was able to reproduce the dynamics of amorphous calcium phosphate (ACP) formation and later crystallization to hydroxyapatite (HAP) under different scenarios. The model successfully characterised the EBPR performance of the SBR, including the biological, physical and chemical processes.     

有机硅防护剂对铝酸盐水泥砂浆防护性能的影响

采用接触角测试仪、红外光谱(FTIR)仪、X射线衍射(XRD)仪、扫描电子显微镜(SEM)表征和分析了有机硅烷涂覆量对铝酸盐水泥砂浆防护性能的影响规律.结果表明:采用1次涂覆方式时,铝酸盐水泥砂浆试件的吸水率随有机硅烷涂覆量的增加先降低后趋于稳定,吸水率均降低90%以上,符合规范要求;铝酸盐水泥砂浆试件接触角随有机硅烷涂覆量的增加先增大后减小,试件表面由亲水性变为疏水性,当有机硅烷涂覆量为250g/m~2时砂浆试件接触角达142.66°;有机硅烷渗透深度随涂覆量的增加先增加后减少,当有机硅烷涂覆量为250g/m~2时其渗透深度可达10.73mm.机理分析表明,有机硅烷与铝酸盐水泥砂浆只是在毛细孔内壁发生了水解缩合反应,形成了网状硅氧烷憎水膜层,并未形成新的物质.     

热活化水化高铝水泥颗粒吸附氟化物行为研究

对水化高铝水泥颗粒(ALC)进行热活化改性,制备成活化温度t不同的吸附剂(ALCt),研究了热活化温度、pH值、共存离子和离子强度等因素对ALCt吸附氟化物性能的影响,同时利用热重分析(TGA)、X射线衍射(XRD)、傅里叶转换红外光谱(FTIR)、扫描电镜(SEM)等分析了其表面形态、内部结构特征和吸附机理.结果表明:在25℃、pH=7、初始氟浓度100mg/L条件下,热活化温度为600℃的吸附剂ALC600平衡吸附量高达17.42mg/g,且能在较宽的pH值范围(5~9)具有良好的除氟性能;共存离子Cl^-、NO3^-、SO4^2-和离子强度对ALC600的吸附效果影响不明显;ALC600的吸附过程遵循准二级动力学模型,符合Langmuir等温线模型,其理论最大吸附容量为223.72mg/g.结合吸附氟化物前后ALC600的晶体结构、化学键、表面形态的变化,确定其吸附机理是以化学吸附为主,通过内部络合和表面沉淀来实现氟离子的去除,同时也涉及离子交换和静电作用.