天然碱蒸发过程的相图分析与计算

利用１５０℃Ｎａ＿２ＣＯ＿３—ＮａＨＣＯ＿３—Ｎａ＿２ＳＯ＿４—ＮａＣｌ—Ｈ＿２Ｏ五元体系相图，对内蒙古两个典型天然碱液的蒸发过程进行了相图分析和相图计算，并进行了分析讨论。从而得出对天然碱蒸发法加工具有指导意义的几点结论。     

酸法加工硼镁石矿中三个三元体系溶解度测定

测定了２５℃、１００℃Ｈ３ＢＯ３－ＭｇＣｌ２－Ｈ２Ｏ,Ｈ３ＢＯ３－ＭｇＳＯ４－Ｈ２Ｏ,Ｈ３ＢＯ３－Ｍｇ（ＮＯ３）２－Ｈ２Ｏ三个体系的溶解度,并绘制了相图。     

25℃和100℃时H3BO3—Na2SO4—NaCl—H2O体系的相平衡

测定了２５℃和１００℃时,Ｈ３ＢＯ３－Ｎａ２Ｓｏ４－ＮａＣｌ－Ｈ２Ｏ体系的固液平衡数据并绘成相图,应用相图分析了ＮａＣｌ作盐析剂分离Ｈ２Ｂ作盐析剂分离Ｈ３ＢＯ３的生产过程,为硼砂硫酸酸化制取Ｈ３ＢＯ３的生产工艺改进提供了一定的理论基础。     

钾长石热分解热力学分析和ΔG°_T计算

利用热力学数据及ＣａＯ－Ａｌ２Ｏ３－ＳｉＯ２、Ｋ２Ｏ－Ａｌ２Ｏ３－ＳｉＯ２体系相图，对钾长石分别添加ＣａＯ、ＣａＳＯ４、ＣａＣｌ２、ＣａＯ＋ＣａＣｌ２和ＣａＯ＋ＣａＳＯ４下的热分解进行了热力学分析，并拟定了５２０个可能反应，在８００～１６００Ｋ范围内计算了各反应的ΔＧＴ，确定了添加ＣａＯ＋ＣａＳＯ４制取Ｋ２ＳＯ４的物料配比范围，并以此指导工艺实验。     

提高肥料利用率化工部门能做些什么？（续）

２·２对于碳铵厂碳铵中的ＮＨ４＋是与负电性弱的ＨＣＯ３－结合,对ＮＨ４＋的约束力弱。因此,碳铵中的ＮＨ４＋比其他氮肥中的ＮＨ４＋更易于被土粒所吸附,如表１０所示。碳铵被雨水流失量少。但由ＮＨ３－ＣＯ２－Ｈ２Ｏ相图可看出,ＮＨ４ＨＣＯ３属不相称溶解化合...     

内蒙古天然碱液四元体系的相图研究──150℃Na_2CO_3—NaHCO_3—

本文测定了１５０℃ＮａＨＣＯ＿３─ＮａＣｌ—Ｈ＿２Ｏ、ＮａＨＣＯ＿３—Ｎａ＿２ＳＯ＿４—Ｈ＿２Ｏ两个三元体系及１５０℃Ｎａ＿２ＣＯ＿３—ＮａＨＣＯ＿３—Ｎａ＿２ＳＯ＿４—Ｈ＿２Ｏ、Ｎａ＿２ＣＯ＿３—ＮａＨＣＯ＿３—ＮａＣｌ—Ｈ＿２Ｏ和ＮａＨＣＯ＿２—Ｎａ＿２ＳＯ＿４—ＮａＣｌ—Ｈ＿２Ｏ三个四元体系的相平衡数据，结合前人工作，绘制了上述各体系的相图，并对各相图的构成进行了分析讨论。     

钢水的钙处理与连铸用耐火材料发展的新趋势

用化学热力学和相图原理，分析了ＣａＳｉ处理钢水中钙对连铸用Ａｌ_２Ｏ_３－Ｃ质耐火材料的化学蚀机理；指出在Ａｌ_２Ｏ_３－Ｃ质控制元件的关键部位用ＭｇＯ－Ｃ质材料进行复合，是钙处理钢水连铸用耐火材料发展的新趋势。     

CaO-Al2O3-P2O5三元系统富铝区水硬活性的研究

首次研究了ＣａＯ－Ａｌ２Ｏ３－Ｐ２Ｐ５三元相图中Ｃ１２Ａ１７－Ｐ２Ｏ５连线附近富铝区域组成的水硬活性,讨论了高场强阳离子Ｐ＾５＋极化作用形成［ＰＯ４］＾３－四面体对体系相组成,进而对其水硬活性的影响。由所研制的磷铝酸盐水泥中,得到了新化合物－三元磷铝酸钙。通过ＸＲＤ、ＩＲ和电子探针微区分析（ＥＰＭＡ）等手段,证实了α－Ｃ３Ｐ和ＣＡ矿相在结构上的变化。由于三元磷铝酸钙化合物与改性α－Ｃ３Ｐ（３ＣａＯ     

制备α—氧化铁过程水解反应研究

采用简易的奥氏仪测定ＦｅＣＯ３－Ｆｅ（ＯＨ）２体系水解过程产生的ＣＯ２体积以推算悬浮液中ＣＯ＾２－３浓度,并以ＣＯ＾－３浓度建立水解率的定义式,定量研究温度,起始浓度等因素对不解反应速度与水平衡浓度的关系。     

298K时Li~+,Na~+,K~+/CO_(-3)~2H_2O四元体系相图和液相物化性质测定

用等温溶解平衡法研究了四元体系Ｌｉ＋ , Ｎａ ＋ , Ｋ＋ ／ＣＯ２ －３ Ｈ２ Ｏ２９８Ｋ 时盐类的溶解度及饱和溶液的物化性质（ 密度、折光率、粘度、电导率、ｐＨ 值） , 研究表明： 该四元体系２９８Ｋ 溶解度相图由两个无变量点、五条溶解度曲线和四个结晶区构成。四个结晶区分别对应于组分Ｌｉ２ ＣＯ３ , Ｎａ２ ＣＯ３·１０Ｈ２ Ｏ, Ｋ２ ＣＯ３·３／２Ｈ２ Ｏ 及复盐Ｎａ２ ＣＯ３·Ｋ２ ＣＯ３·Ｈ２ Ｏ。复盐Ｎａ２ ＣＯ３·Ｋ２ ＣＯ３·Ｈ２ Ｏ２９８Ｋ 时为不相称溶解化合物     

Phase diagram of the Al2O3–ZrO2–La2O3 system

The phase diagram of the Al₂O₃–ZrO₂–La₂O₃ system was constructed in the temperature range 1250–2800 °C. The liquidus surface of the phase diagram reflects the preferentially eutectic interaction in the system. Three new ternary and two new binary eutectics were found. The minimum melting temperature is 1665 °C and it corresponds to the ternary eutectic LaAlO₃ + T-ZrO₂ +  La₂O₃·11Al₂O₃. The solidus surface projection and the schematic of the alloy crystallization path confirm the preferentially congruent character of phase interaction in the ternary system. The polythermal sections present the complete phase diagram of the Al₂O₃–ZrO₂–La₂O₃ system. No ternary compounds or regions of remarkable solid solution were found in the components or binaries in this ternary system. The latter fact is the theoretical basis for creating new composite ceramics with favorable properties in the Al₂O₃–ZrO₂–La₂O₃ system.     

Thermodynamic modeling of the CaO-SiO2-ZrO2 system coupled with key phase diagram experiments

Thermodynamic modeling coupled with key phase diagram experiments of the ternary CaO-SiO₂-ZrO₂ system was carried out. The isothermal phase diagram of the CaO-SiO₂-ZrO₂ system at 1873 K was established by using a classical phase equilibration and quenching technique followed by EPMA phase analysis. The Gibbs energy of each phase was optimized through critical evaluation of all available thermodynamic properties and phase diagram data in literature with new experimental data. The discrepancies between experimental phase diagram data and possible errors in the existing thermodynamic data were resolved in this study.     

Phase diagram of the pseudobinary system Bi–Co–O

Samples with different ratios of Bi₂O₃ and Co₂O₃ were prepared by ceramic route. Based on the results of differential thermal analysis, X-ray powder diffraction, SEM–EDXA and FactSage database the phase diagram of the Bi–Co–O diagram in air atmosphere was assessed and calculated using the FactSage software. The sillenite structure of Bi₂₄Co₂O₃₉ was identified and the single phase homogeneity range of Bi₂₄Bi_2?xCo_xO₃₉, x = 0.9–2.0 was determined by Rietveld analysis and SEM–EDXA. To verify the composition in the various parts of the phase diagram at elevated temperatures, a number of high-temperature annealing experiments was performed followed by rapid quenching to room temperature.     

Phase and melting relationships of β, α and α′-Ca3(PO4)2 polymorphs in the Ca3(PO4)2-Zn3(PO4)2 system

In order to provide an exact knowledge of the phase transitions and melting relationships of Ca₃(PO₄)₂ (TCP) in the presence of zinc, a revisited version of the rich-Ca₃(PO₄)₂ region of the phase diagram of the system Ca₃(PO₄)₂-Zn₃(PO₄)₂ has been established in the present work. Experimental determination of this diagram was carried out by solid-state reactions of samples prepared from pure NH₄H₂PO₄, CaCO₃ and ZnO raw materials. X-ray Diffraction, Differential Thermal Analyses and Field Emission Scanning Electron Microscopy studies allowed to revise the α, β, α + β-TCP phase stability fields, delimitating for the first time the biphasic α + α′-TCP field and the melting relationships in the high temperature region of the system. The results allowed to determine two peritectic invariant points, at ≈1400 °C for 95 mol% Ca₃(PO₄)₂ and at ≈1490 °C for ≈99.5 mol% Ca₃(PO₄)₂.     

Thickness-dependent phase evolution and bonding strength of SiC ceramics joints with active Ti interlayer

A robust solid state diffusion joining technique for SiC ceramics was designed with a thickness-controlled Ti interlayer formed by physical vapor deposition and joined by electric field-assisted sintering technology. The interface reaction and phase revolution process were investigated in terms of the equilibrium phase diagram and the concentration-dependent potential diagram of the Ti-Si-C ternary system. Interestingly, under the same joining conditions (fixed temperature and annealing duration), the thickness of the Ti interlayer determined the concentration and distribution of the Si and C reactants in the resulting joint layer, and the respective diffusion distance of Si and C into the Ti interlayer differentiated dramatically during the short joining process (only 5 min). In the case of a 100 nm Ti coating as an interlayer, the C concentration in the joint layer was saturated quickly, which benefited the formation of a TiC phase and subsequent Ti₃SiC₂ phase. The SiC ceramics were successfully joined at a low temperature of 1000 °C with a flexural strength of 168.2 MPa, which satisfies applications in corrosive environments. When the Ti thickness was increased to 1 μm, Si atoms diffused easily through the diluted Ti-C alloy (a dense TiC phase was not formed), and the Ti₅Si₃ brittle phase formed preferentially. These findings highlight the importance of the diffusion kinetics of the reactants on the final composition in the solid state reaction, particularly in the joining technique for covalent SiC ceramics.     

Low-valued raw materials challenge the common eligibility criteria for triaxial ceramics

In this work, two low-valued natural raw materials were used, namely a low plasticity and high iron content clay and a powdered rock waste generated during crushing of igneous rocks to produce construction aggregates. After characterization (chemical, mineralogical, thermal and granulometric), mixtures containing up to 75 wt% of rock powder were prepared and extruded closely following industrial practice, and fired for 60 min from 900 to 1100 °C. Property development was evaluated on as-extruded, dried and fired pieces. The results obtained were interpreted based on chemical compositions, the estimates from the Al₂O₃–SiO₂–CaO phase diagram and presumed reaction kinetics. Such interpretation showed that physical characteristics dominate not only during shaping and drying, but also during low temperature firing (slow reaction kinetics), when rock additions act as inert material; at high firing temperatures, however, the rock promotes liquid phase development after first melting (fluxing effect) and thermodynamics prevail. The dominant fluxing effect results in improved fired properties, which were shown to depend almost linearly on the liquid phase content, predicted by the phase diagram and determined by the chemical composition. These results enabled the identification of behavioural composition ranges to best exploit the materials’ industrial use potential and demonstrate that current paradigms in raw material evaluation and processing in traditional ceramics industries need a re-assessment.     

Fabrication of transparent ceramics through melt solidification of near eutectic compositions in HfO2–Al2O3–GdAlO3 system

Solidification of eutectic melts in multiple oxide systems can produce directionally solidified eutectic composites by slow cooling, while rapid cooling would give the formation of amorphous phases as super cooled liquids. We have successfully fabricated an amorphous bulk ceramics in the ternary system HfO₂–Al₂O₃–GdAlO₃ for the first time. It has the near eutectic composition of HfO₂ (14 mol%), Al₂O₃ (63 mol%) and Gd₂O₃ (23 mol%) and highly transparent, >85%, in the visible region after the cooling of around 200–500 K/s for 2–5 mm Ø globules. The sample had kept amorphous up to 1073 K but crystallized above 1273 K then lost the transparency. The formation of an amorphous phase could be discussed by the equilibrated temperature (T₀) lines in meta-stable phase diagram. The present study suggests possible formation of transparent bulk ceramics by the melt-solidification of eutectic melts in various ternary or multiple phase systems.     

Experimental determination of the liquidus line in the high Bi2O3 region in the TiO2–Bi2O3 system

Liquidus line in the high-Bi₂O₃-containing region of the TiO₂–Bi₂O₃ system was determined experimentally. The equilibrating and quenching technique with subsequent electron probe microanalyser (SEM-EDS) microanalysis were employed. Based on the data, liquidus line was constructed between 60 and 92 mol% Bi₂O₃. The current results showed a higher solubility of Bi₂O₃ in the liquid phase in equilibrium with the Bi₄Ti₃O₁₂ compound compared with the existing phase diagram. In addition, differential scanning calorimetry (DSC) was used to estimate the transformations covering the composition range from 60 to 95 mol% Bi₂O₃. Further, the phase diagram of the TiO₂–Bi₂O₃ system was calculated using a quasichemical model for the liquid phase. The thermodynamic properties of the intermediate compounds were estimated from the data of TiO₂ and Bi₂O₃ pure solids.     

Solubility of tungsten in zirconium diboride solid solution

Zirconium diboride (ZrB₂) is arguably one of the most important ceramic materials for applications involving extreme high temperatures and oxidizing environments such as those encountered in re-entry vehicles and hypersonic aircraft, among others. Accordingly, enhancing the creep resistance of ZrB₂ is of critical importance. A viable approach to achieve the latter is through the addition of substitutional atoms such as tungsten. In this work, using a combination of quantum mechanics based first-principles simulations and thermodynamic modeling; we present the essential elements of the W-ZrB₂ phase diagram to enable the design of enhanced creep-resistant ultra-high temperature ZrB₂-alloys. In the course of the assessment, we estimate the Gibbs free energy of WB₂, nonexistent in the literature to date, and based on the developed phase diagram, conclude that the solubility of tungsten in ZrB₂ does not occur below ∼1380 °C and that temperatures above ∼1700 °C are needed to dissolve 1 mol% of W in ZrB₂.