几种碳酸盐熔融体的粘度计算

熔融碳酸盐是一种良好的热载体和反应介质。计算了Na2CO3、K2CO3、Li2CO3及其混合熔融体的粘度,结果表明,碳酸盐熔融体的粘度随温度的升高而降低,并且变化明显。摩尔比为1∶1的K2CO3,Na2CO3熔融体在1 050 K时的粘度为0.4 Pa.s,摩尔比为1∶1∶1的K2CO3、Na2CO3、Li2CO3熔融体在1 200 K时的粘度为4.4×10 2 Pa.s,这说明碳酸盐在融化以后具有良好的流动性。     

TiO2,TiN和Ti(CN)对连铸保护渣粘性特征的影响

采用旋转粘度计全面系统的研究TiO2,TiN和Ti(CN)对连铸保护渣粘性特征的影响作用机制。研究表明,TiO2可以降低连铸保护渣的粘度,但随着钙钛矿的析出,会增加凝固温度和粘度。TiN以固相质点的形式存在且会抑制渣中晶体析出,相对地降低凝固温度,但会增大粘度。Ti(CN)由于分解反应放出气体,会降低连铸保护渣的化学稳定性。     

TiN对连铸保护渣黏度的影响

采用旋转黏度计并结合XRD分析系统研究了不同碱度条件下,TiN对连铸保护渣黏度的影响。结果表明TiN可以增加连铸保护渣的黏度。TiN加入量〈5％时,对连铸保护渣的黏度影响较小。随着CaO／SiO2的增大,添加10％TIN连铸保护渣的黏度先迅速减小而后有所增大。添加10％TIN,CaO／SiO2为0．3的连铸保护渣中仅存在TiN晶体。CaO／SiO2为1．5的连铸保护渣中出现钙钛矿（CaTiO3）、硅酸二钙（Ca2SiO4）、枪晶石（Ca4Si2O7F2）、霞石（NaAlSiO4）及TiN。     

Li2CO3-Na2CO3-K2CO3相图的理论预测

熔盐是一种重要的聚光太阳能系统传热流体,多元熔盐混合是满足实际需求的有效方法,而熔盐混合物的相图是其筛选的主要因素之一.该文基于热力学原理及吉布斯自由能对Li2CO3-Na2CO3-K2CO3的相图进行预测与计算,结果显示:该熔盐混合物的共晶点为421.2℃,Li2CO3、Na2CO3和K2CO3的质量分数分别为25....     

TiO2对连铸保护渣结晶性能的影响

采用热丝法结晶性能测定仪及XRD,研究了不同冷却速率条件下TiO2对连铸保护渣结晶性能的影响。结果表明：在相同冷却速率条件下,随着TiO2加入量的增加,连铸保护渣的结晶温度和结晶化率随之增大。TiO2加入量（质量分数）为15％和20％条件下,连铸保护渣的结晶化率在不同冷却速率下都接近100％。添加少量的TiO2可以降低连铸保护渣的结晶温度和结晶化率。确定了TiO2加入量（质量分数）为20％时连铸保护渣析出晶体的种类。     

连铸保护渣配碳模式的研究

采用熔点熔速测定仪研究了连铸保护渣的熔化特性,最终得到连铸保护渣的配碳模式.结果表明:连铸保护渣的熔化过程由碳质材料控制熔化阶段和渣系成分控制熔化阶段两部分组成.保证连铸保护渣符合熔化性能的要求,确定最终的配碳模式需同时考察连铸保护渣的熔化曲线斜率和熔化时间.     

低温固体氧化物燃料电池SDC-(Li/Na)2CO3复合电解质材料优化

采用两种工艺(干法和湿法)制备了钐掺杂的氧化铈(SDC)-(Li/Na)2CO3复合电解质,其中碳酸盐的质量分数分别为20%、25%和30%.通过XRO和SEM观察了不同制备工艺和碳酸盐含量的复合电解质材料的物相结构和表面形貌.采用交流阻抗法测量了复合电解质在空气中400～600℃温度范围的电导率.采用于压法制作了基于(SDC)-(Li/Na)2CO3电解质的单电池,并在氢气/燃料中评价了该电池的输出性能.     

连铸保护渣数据库查询系统的设计开发

以Microsoft Visual Basic6.0为编译工具,查阅并检索了国内外钢铁企业现场使用的连铸保护渣相关资料,建立了连铸保护渣数据库查询系统.该查询系统可以将连铸保护渣相关数据归类存储,并通过单项和多项组合检索对其相关内容进行查询,为连铸保护渣的选择应用和设计开发提供充分的理论依据.依据此检索结果,设计开发了...     

金属基与熔融盐复合蓄热材料的制备与性能研究

采用一定的制备工艺将金属基(泡沫镍)与K2CO3,Li2CO3,Na2CO3,LiOH和NaOH等熔融盐在一定温度下进行复合,得到一种新型复合蓄热材料。用扫描电镜,X-射线以及差热-差重分析等手段对复合蓄热材料的结构与性能进行研究,测试结果表明该复合蓄热材料达到了预期的结果;进一步讨论了复合时间和复合材料中熔融盐含有率关系以及复合温度和蓄热密度之间的关系。     

不同温度条件下连铸保护渣结晶性能的研究

实验采用热丝法熔化结晶性能测定仪对连铸保护渣的结晶性能进行了研究。结果表明:不同的实验温度条件下,连铸保护渣的结晶化率和结晶时间相差很大。在实验条件下,实验温度为1 000,1 200℃时,连铸保护渣的结晶化率均达到100%,但结晶时间随着实验温度的上升而减少,分别为262,99 s。实验温度为1 300℃时,连铸保护渣没有发现晶体析出。     

Thermodynamic and experimental approach of electrochemical reduction of CO2 in molten carbonates

This work is dedicated to the feasibility of CO₂ dissolution and transformation into CO by an electroreduction process. It is first based on a predictive thermodynamic study, through the establishment of potential-oxoacidity diagrams, mainly focused on competing reduction processes (CO₂/CO, CO₂/C, H₂O/H₂, M⁺/M) relative to pure Li, Na and K carbonates, Li₂CO₃–K₂CO₃ (62–38 mol.%) and Li₂CO₃–Na₂CO₃ (52–48 mol.%) carbonate eutectics. Due to their lower melting points, only the Li–K and Li–Na eutectics are investigated experimentally by cyclic voltammetry at a gold flag or planar disk working electrode at temperatures from 575 °C to 650 °C. CO₂ reduction wave gives evidence for both eutectics, showing that CO₂/CO system is relatively slow in the present conditions. Re-oxidation of CO formed at the Au electrode only produces a very low intensity signal, indicating a lower solubility of this species. Microelectrolysis at a potential corresponding to the reduction wave of CO₂ increases the amount of CO and an oxidation wave probably corresponding to adsorbed CO can be observed. The whole electrochemical process is complex, involving both soluble and adsorbed CO₂, mostly adsorbed CO and probably other intermediate species.     

TM dopant-induced H-vacancy diffusion kinetics of sodium-lithium alanates: Ab initio study for hydrogen storage improvement

We present a hydrogen storage mechanism of the surface and bulk Na–Li–Al hydrides substituted by the transition metal (TM) dopants such as Ni, Cu, Ag, and Zn. The host hydrides of interest, namely, NaAlH₄, LiAlH₄, Na₃AlH₄, Li₃AlH₄, and Na₂LiAlH₄ are found to be stable compositions at ambient pressure. Hydrogen vacancy mechanisms of the host hydrides with the TM dopants are investigated using ab initio calculations. Remarkably, the results show the enhancement of the internal mechanism for hydrogen storage in the Na–Li–Al complex hydrides. Doping of Ni or Zn mainly reduces the energy barrier of diffusion kinetics in the host Na–Li–Al hydrides, leading to the improvement of the hydrogen storage efficiency of the host Na–Li–Al hydrides. Therefore, hydrogen vacancy diffusion kinetics in the Na–Li–Al hydrides can be induced by adding the Ni and Zn dopants.     

Carbothermal reduction of alkali hydroxides using concentrated solar energy

The reduction of hydroxides of various alkali metals (i.e., Na, K and Li with carbon) using concentrated solar radiation at high temperatures in the range of 900–1600°C results in the production of CO, H₂ and the alkali metal. These reactions are highly endothermic; for instance, C+LiOH→Li+0.5H₂+CO requires 523 kJ/mol (at 298 K). The reaction is performed in two basic stages. In the first stage, at a temperature range of 900–1300°C, the carbonate of the alkali metal is formed as an intermediate compound. In the second stage, at slightly higher temperatures in the range of 1200–1600°C, the carbonates are decomposed and reduced to the metal element and additional CO. The metal element can be reoxidized with water and then produce additional hydrogen. The hydroxide is recovered and recycled. The metal can also be used as a chemical, fuel or as an intermediate material for production of other energy-intensive metals, such as magnesium. Thermodynamic calculations and experimental results, which verify this hypothesis, are presented. Potential applications and advantages of the process are discussed.     

Spectrophotometric study of the corrosion behaviour of chromium in molten alkali carbonates

The corrosion of chromium species in molten (Li/K)₂CO₃ and (Li/Na/K)₂CO₃ are investigated by spectrophotometry. A strong charge-transfer absorption band is observed in the ultraviolet region with λ_max=372 nm, and the molar absorptivity of CrO₄²⁻ in molten (Li/K)₂CO₃ is calculated. The corrosion rates are investigated by means of increasing the concentration of CrO₄²⁻ in the melts. Under an air atmosphere, the corrosion rate is slower in molten (Li/K)₂CO₃ than in molten (Li/Na/K)₂CO₃ and Cr₂O₃ corrodes more easily in molten (Li/K)₂CO₃ than Cr. With an atmosphere of CO₂=1 atm, there is no increase in the CrO₄²⁻ concentration in the solution phase during a period of 5 h.     

A first-principles study of Li and Na co-decorated T4,4,4-graphyne for hydrogen storage

To obtain high hydrogen storage performance, Li and Na co-decorated T4,4,4-graphyne have been studied by the method of first-principles calculations in this paper. Li and Na atoms are bound on hexagonal ring and acetylenic ring included in T4,4,4-graphyne, with the average adsorption energy of 1.73 and 2.38 eV, respectively. Our calculations show that the maximum gravimetric density of H₂ uptake is 10.46 wt%, and an appropriate adsorption energy is reached. Moreover, by plotting charge density differences, it is found that the induced electric field between Li/Na and T4,4,4-graphyne can enhance the adsorption for hydrogen molecule. Furthermore, this complex is thermodynamic stable at room temperature, which is certificated by molecule dynamics simulation. Our results demonstrate that Li and Na co-decorated T4,4,4-graphyne is an alternative material for hydrogen storage.     

Tin carbide monolayers decorated with alkali metal atoms for hydrogen storage

In this work, a density-functional study of hydrogen storage in tin carbide monolayers (2DSnC) decorated with alkali metals atoms (AM) such as Li, Na, and K, is reported. The most stable adsorption site for these alkali metal atoms on the 2DSnC is above a tin atom. The results indicate that the alkali metal atoms are chemisorbed on the 2DSnC and that electronic charge is transferred from the decorating atom to the 2DSnC. In all the studied cases, the hydrogen molecules are physisorbed on the AM-2DSnC (AM = Li, Na, and K) complexes and then these systems could be used for hydrogen storage. In particular, it is found that the K-2DSnC monolayer has the highest hydrogen-storage capacity, where a single potassium atom can adsorb up to 6 hydrogen molecules, followed by Na-2DSnC with 5 hydrogen molecules and Li-2DSnC with 3 hydrogen molecules. Finally, it can be estimated that when the K, Na and Li adatom-coverings respectively attain 40%, 44% and 70%, the hydrogen-storage gravimetric capacities of AM-2DSnC could overcome the US-DOE recommended target of 5.5 wt% for onboard automotive systems.