熔盐分解制备氧化锌纳米晶

以新制的乙酰丙酮合锌为前驱体,添加NaCl助剂,在650℃熔盐分解制得了六棱柱形结构的ZnO纳米晶。用X-射线衍射分析(XRD)、能量色散X射线分析(EDX)和场发射扫描电子显微镜(FESEM)对粉体进行了表征。结果表明,ZnO为六棱柱形纳米晶,属六方纤锌矿结构,结晶性好,平均长度约90nm,平均直径约60nm,长径比约为1.5∶1。通过与不添加NaCl的对比试验,简单探讨了六棱柱形ZnO纳米晶的生长过程。

熔盐法从提钒尾渣中制取白炭黑的研究

以提钒尾渣为原料,NaOH为熔盐,NaF为氧化剂,研究熔盐法提取硅的实验过程。以浸取硅酸钠溶液作为硅源,利用化学沉淀法制备无定型白炭黑。结果表明:硅浸出率随着碱渣比、煅烧温度及煅烧时间的增大而先增大后减小;通过正交试验对实验数据进行分析,对硅浸出率的影响由大到小为:碱渣比>煅烧温度>煅烧时间;最佳试验条件为碱渣比3∶1、反应温度550℃、反应时间3h,此条件下硅浸出率可达到96%以上。对制备白炭黑样品进行XRD、红外光谱、SEM表征和粒度分析,结果表明:白炭黑为无定形结构,粒子呈球形,粒径大小均一,平均粒径为200nm。

Kinetics analysis of decomposition of vanadium slag by KOH sub-molten salt method

A novel process was developed for the decomposition of vanadium slag using KOH sub-molten salt under ambient pressure, and the effects of reaction temperature, alkali-to-ore mass ratios, particle size, and stirring speed on vanadium and chromium extraction were studied. The results suggest that the reaction temperature and KOH-to-ore mass ratio are more influential factors for the extraction of vanadium and chromium. Under the optimal reaction conditions （temperature 180 °C, initial KOH-to-ore mass ratio 4：1, stirring speed 700 r/min, gas flow 1 L/min, and reaction time 300 min）, vanadium and chromium extraction rates can reach up to 95% and 90%, respectively. Kinetics analysis results show that the decomposing process of vanadium slag in KOH sub-molten salt can be well interpreted by the shrinking core model under internal diffusion control. The apparent activation energies for vanadium and chromium are 40.54 and 50.27 kJ/mol, respectively.

Identification of Superoxide O2^- during KNO3-NaNO2-NaNO3 Salt by Electron UV-Vis Absorption Spectroscopy Thermal Decomposition of Molten Paramagnetic Resonance and

On account of excellent thermal physical properties, molten nitrates/nitrites salt has been widely employed in heat transfer and thermal storage industry, especially in concentrated solar power system. The thermal stability study of molten nitrate/nitrite salt is of great importance for this system, and the decomposition mechanism is the most complicated part of it. The oxide species O2^2- and O2^- were considered as intermediates in molten KNO3-NaNO3 while hard to been detected in high temperature molten salt due to their trace concentration and low stability. In this work, the homemade in situ high temperature UV- Vis instrument and a commercial electron paramagnetic resonance were utilized to supply evidence for the formation of superoxide during a slow decomposition process of heat transfer salt （HTS, 53 wt% KNO3/40 wt% NaNO2/7 wt% NaNO3）. It is found that the superoxide is more easily generated from molten NaNO2 compared to NaNO3, and it has an absorption band at 420-440 nm in HTS which red shifts as temperature increases. The band is assigned to charge-transfer transition in NaO2 or KO2, responsible for the yellow color of the molten nitrate/nitrite salt. Furthermore, the UV absorption bands of molten NaNO2 and NANO3 are also obtained and compared with that of HTS.

Decomposition kinetics of zircon sand in NaOH sub-molten salt solution

Sub-molten salt was applied to the decomposition of zircon sand(ZrSiO4).The kinetics of the decomposition of zircon sand and the effects of reaction temperature,reaction time,NaOH content,agitation speed,and the NaOH/ore mass ratio on the decomposition rate of zircon sand in NaOH sub-molten salt were investigated.The results indicate that the decomposition rate of zircon sand increases with the increase in the reaction temperature,reaction time,and NaOH content.The shrinking-core model with surface chemical reaction-controlled process is the most applicable for the decomposition of zircon sand,with the apparent activation energy of 77.98 kJ/mol.The decomposition product is sodium zirconium silicate(Na2ZrSiO5),and the decomposition rate is higher than 99%under the optimal conditions.

Thermodynamic analysis on the direct preparation of metallic vanadium from NaVO_3 by molten salt electrolysis

A novel and environmentally friendly route to directly prepare metallic vanadium from NaV03 by molten salt electrolysis is proposed. The feasibility about the direct electro-reduction of NaV03 to metallic vanadi- um is analyzed based on the thermodynamic calculations and experimental verifications. The theoretical decomposition voltage of NaV03 to metallic vanadium is only 0.47 V at 800 ℃ and much lower than that of the alkali and alkali earth metal chloride salts. The value is slightly higher than that of low-valence vanadium oxides such as V203, V305 and VO. However, the low-valence vanadium oxides can he further electro-reduced to metallic vanadium thermodynamically. The thermodynamic analysis is verified by the experimental results. The direct preparation of metallic vanadium from NaV03 by molten salt electrolysis is feasible.