氧化锆复合氮化硅陶瓷

分析了二氧化锆的性质及氧空位对二氧化锆相变的影响 ,讨论了二氧化锆韧化氮化硅陶瓷的影响因素 ,提出了二氧化锆韧化氮化硅陶瓷时避免氮化锆生成、促进复相氮化硅陶瓷烧结的途径。     

Deactivation of VMgO x Catalysts by Coke in the Process of Isobutane Dehydrogenation with Carbon Dioxide

The process of isobutane dehydrogenation in the presence or absence of carbon dioxide was carried out over VMgO _x catalysts with different vanadium loading. The performed tests show that both the reaction atmosphere and physicochemical properties of the catalysts (related to vanadium content) have a great influence on the activity decrease and the carbonaceous deposit formation. Despite small ability of carbon dioxide to remove coke in the Boudouard reaction, the amounts of carbonaceous species deposited on the catalysts after the isobutane dehydrogenation under CO₂ atmosphere were even twice greater in comparison to those deposited in helium stream. Moreover, the rate of coke deposition during the dehydrogenation in the inert gas flow was only slightly dependent on the reaction time, in contrast to the process in carbon dioxide atmosphere. The results show that the coke formation on VMgO _x is enhanced predominantly by surface acidity of the catalysts, which grows with the vanadium content and the presence of CO₂ in the feed.     

粗四氯化钛有机物精制除钒尾渣提钒技术

从四氯化钛有机物精制除钒尾渣中提钒并制备V2O5产品,研究了精制除钒尾渣焙烧温度、浸出剂加入量、液固比、浸出温度、浸出时间对尾渣中钒转化和溶出率的影响。结果表明,焙烧温度大于600℃时,可高效脱除精制除钒尾渣中的碳和氯(?0.1%),且低价钒被氧化为高价,钒主要以V2O5形式存在。对焙烧后的尾渣以Na2CO3水溶液为浸出剂,液固比6 mL/g及80℃下浸出60 min,钒浸出率为85.5%,浸出液仅含少量Si, Al, Ti杂质,以NH4+:V=2.5:1(摩尔比)直接加铵盐沉钒,得到NH4VO3,经干燥、煅烧制得V2O5产品,可满足99级粉钒指标要求,全流程钒收率为75%。     

The influence of precursors and additives on the hydrothermal synthesis of VO2: A route for tuning the metal–insulator transition temperature

Thermochromic materials have attracted the attention of scientific and technological researchers due to their ability to change color depending on the temperature. Vanadium dioxide (VO₂) is capable of considerable polymorphs and has aroused interest mainly because its metal–insulator transition (MIT) presents a thermochromic characteristic at a relatively low temperature. This work aimed to obtain vanadium oxide nanostructures using hydrothermal synthesis to tune the MIT temperature. Ammonium metavanadate or vanadium pentoxide was used as a precursor of vanadium, oxalic acid as a reducing agent, and sodium molybdate as an additive. The starting materials were homogenized and inserted in a hydrothermal reactor at 180 °C. After 24 h of synthesis, part of the resulting product was heat-treated at 400 °C for 3 h. The powders obtained were characterized by their structure, morphology, and thermal properties. The results showed a fiber/rod-shaped VO₂ (M) morphology. Distinct strategies were used to obtain the crystalline phase of interest (VO₂(M)), and the presence of a reversible change occurring at ~68 °C was evaluated according to the parameters from the VO₂ phase transition. The addition of sodium molybdate favored a 22% reduction in the MIT temperature when the precursor used was vanadium pentoxide, indicating possible doping in the structure increased the effects of smaller crystallite size and the presence of crystalline phases. This work opens new perspectives for applications of the vanadium oxides obtained, such as in thermal sensors and/or intelligent materials.     

Applications of penetration and film theories to the catalysis of gas reactions by liquid catalysts: the oxidation of sulphur dioxide

A general analysis is given, using film and penetration theories, of the reaction of two gases (e.g. SO₂ and O₂) to give a gaseous product (SO₃). The reaction is assumed to take place in solution and is catalysed by an involatile solute which can exist in oxidised and reduced forms. The implications for the industrial sulphur dioxide oxidation process in which the catalyst is an ionic melt of vanadium pentoxide in potassium pyrosulphate are considered.     

钙化提钒溶液沉钒的影响因素及沉钒动力学

用(NH4)2SO4对钒渣钙化焙烧、稀酸浸取、化学沉淀净化后的酸性含钒溶液进行沉淀富集,考察了钒浓度、初始pH值、加铵系数(NH3/V摩尔比)、沉钒温度和时间对沉钒率及V2O5含量的影响,研究了沉钒动力学,对沉钒产物进行了表征. 结果表明,在初始pH为2.00?0.05、加铵系数1.5、温度大于95℃、沉钒时间120 min、钒液中V浓度大于20 g/L的条件下,沉钒率超过96%,产品中V2O5含量大于98%,杂质含量符合98级氧化钒的国家标准. 75~99℃下的沉钒过程可由Avrami动力学方程描述,表观活化能Ea=93.23 kJ/mol,指前因子A=9.14×1011 min?1. 铵盐沉钒产物为(NH4)2V6O16?1.5H2O,高温煅烧所得V2O5晶体为柱状,平均粒径1.25 ?m,主要杂质Mn以MnV2O6形式存在.     

Producing a composite material based on zircon concentrate and nanocrystalline zirconium dioxide

The effects have been examined of adding nanocrystalline zirconium dioxide powder stabilized by yttrium oxide on the production and properties of a composite material based on zircon. It is found that the zirconium dioxide particles at the boundaries of the zircon grains slow the consolidation of the zircon matrix in sintering and zircon grain growth.     

高纯氯氧化锆和二氧化锆的制备

研究了工业氯氧化锆重结晶制备高纯氯氧化锆的过程，通过选择，确定氯氧化锆溶液浓度为160g/L，结晶酸度为5.5-6.0mol/L，煅烧过程中盛装高纯氯氧化锆匣钵为石英匣钵，从而得到产品纯度为99．9％的高纯二氧化锆。     

钒渣钠化焙烧熟料浸出液除磷工艺研究

以钒渣钠化焙烧熟料浸出后得到的含钒溶液为原料,分析了二水硫酸钙在碱性条件下对含钒溶液中磷的去除机制,研究了二水硫酸钙用量、溶液pH、反应时间、反应温度等因素对磷去除率、钒损失率以及溶液中五氧化二钒与磷质量浓度比的影响。研究结果表明：在弱碱性条件下,二水硫酸钙可有效去除含钒溶液中的磷,磷去除率达到70%以上、钒损失率小于1%、五氧化二钒与磷质量浓度比大于2 300,满足后续沉钒的要求。确定的除磷工艺条件：二水硫酸钙与磷物质的量比为5.3,溶液pH为9.0,反应时间为30 min,反应温度为25 ℃。除磷后的含钒溶液经沉钒、洗涤、煅烧得到五氧化二钒产品,沉钒率大于99%,五氧化二钒产品质量满足YB/T 5304—2011《五氧化二钒》中99级的要求。     

Porous structure formation and physicomechanical properties of SiC–C carbon-ceramic composite materials. Part 2

A study has been made of the effects of adding nanocrystalline zirconium dioxide powder stabilized by yttrium oxide on the production and properties of a composite material based on zircon. It is found that the particles of zirconium dioxide are located at the zircon grain boundaries and delay the consolidation of the zircon matrix during sintering and zircon grain growth.     

微波辐射SiO2负载磷钨酸催化合成丙酸苄酯

研究了微波辐射下,用SiO2负载磷钨酸催化剂直接催化合成丙酸苄酯的反应,考察了影响酯化收率的因素。其优化反应条件为催化剂用量0.5g(磷钨酸负载量20.2%),微波辐射功率450W、反应时间4.0min,n(丙酸)/n(苯甲醇丙酸)=1∶1,带水剂(环己烷)用量5mL,丙酸苄酯收率达83.4%。结果表明:相同条件下微波辐射-SiO2负载磷钨酸催化剂与常规加热-SiO2负载磷钨酸催化剂相比之下加快反应速度45倍,催化剂可重复使用。     

The effect of embedded vanadium catalyst on activated electrospun CFs for hydrogen storage

In this paper, the effect of embedding vanadium pentoxide in electrospun carbon fiber was investigated in relation to textural properties and hydrogen storage behavior. Electrospun carbon fibers involving vanadium were prepared from polyacrylonitrile/N,N-dimethyl formamide/vanadium pentoxide through electrospinning method and heat treatment. Chemical activation of electrospun carbon fibers was carried out in order to generate the pore by using potassium hydroxide as a chemical agent. Eventually, vanadium embedded activated electrospun carbon fibers (AECFs) with high specific surface area 2780 m²/g were prepared as a hydrogen storage medium. As the effects of vanadium pentoxide, it was found that dissociated oxygen from vanadium pentoxide in electrospun fibers would generate the ultra-micropore (0.6 nm) by forming carbon monoxide and carbon dioxide during the carbonization. Also, vanadium in electrospun carbon fibers is considered to act as a catalyst for the improved capacity of hydrogen adsorption. Vanadium embedded AECFs have the high capacity of hydrogen storage, about 2.5 wt% at room temperature and 100 bar.     

石煤灰渣酸浸提钒工艺中钒的浸出动力学

采用液-固多相反应的缩芯模型研究了石煤灰渣中V2O5的浸出动力学,考察了酸浸温度、硫酸浓度对V2O5浸出反应速率的影响. 结果表明,在实验温度范围内,V2O5的浸出过程为固膜扩散控制,浸出反应的表观活化能为29.96 kJ/mol. 当硫酸浓度小于6 mol/L时,浸出属化学反应控制过程;当硫酸浓度大于6 mol/L时,浸出过程为固膜扩散控制,其表观反应级数为1.199. 提高酸浸温度可提高V2O5的浸出率;在硫酸浓度小于6 mol/L时提高硫酸浓度,可提高V2O5的浸出率;而高于该值提高硫酸浓度对V2O5浸出率的提高无明显作用.     

硫酸生产危险性及安全对策措施分析

以硫铁矿制酸工艺为例,分析了硫酸生产中主要危险化学物质:硫酸、二氧化硫、三氧化硫及五氧化二钒,辨识了它们的危险因素和存在的部位,并针对物质的危险特性提出了一些相关安全对策措施。     

Effective Guanidine‐Catalyzed Synthesis of Carbonate and Carbamate Derivatives from Propargyl Alcohols in Supercritical Carbon Dioxide

The reactions of propargyl alcohols with carbon dioxide in supercritical carbon dioxide or in acetonitrile with gaseous carbon dioxide in the presence of organic bases as catalysts have been examined. Bicyclic guanidines are effective catalysts for the formation of α‐methylene cyclic carbonates under mild reaction conditions. Oxoalkyl carbonates, oxoalkyl carbamates or α‐methyleneoxazolidinones are obtained in high yields and good selectivities in one‐step starting from propargyl alcohols and an external nucleophile (alcohols or amines) using bicyclic guanidines as catalysts in supercritical carbon dioxide. Propargylic diols under the same reaction conditions underwent a rearrangement process instead of carbon dioxide insertion whereas in the presence of an external nucleophile the formation of oxocarbonates, oxocarbamates or cyclic carbamates was achieved in satisfactory yields.     

Some molten ionic oxides as chemical reagents

Molten ionic oxides possess important desirable properties: thermal stability, and useful chemical properties resulting from their acid or basic behaviour, i.e., from their capacity to accept or donate an oxygen ion, and, in several cases, relatively low melting points, well below 1000°c. Bismuth trioxide was found to effect a two-temperature decomposition of ammonium chloride, yielding ammonia and hydrogen chloride. Molten antimony trioxide was found to attack rock phosphate and convert part of the phosphate to a water-soluble form. Molten lead monoxide was found to dissolve calcium oxide readily, to dissolve chromic sesquioxide, to decompose chromite ore and to permit an extraction of iron-free lead chromate into an upper layer of molten alkali chloride. Addition of lead sulphide to a lead monoxide melt caused formation of elemental lead and lead sulphate. Vanadium pentoxide was found to decompose ammonium chloride, yielding first, hydrogen chloride and then, ammonia. The reaction of a vanadium pentoxide melt with rock phosphate, studied in some detail, resulted in water-solubilisation of the phosphate. The product formed in the melt is probably a calcium phosphate vanadate, from the aqueous solution of which calcium can be precipitated by ammonium carbonate; the ensuing ammonium phosphate and vanadate solution can be separated by known methods, permitting recovery of the vanadium pentoxide, and yielding ammonium phosphate.     

Fabrication and photocatalytic evaluation of functionalized chitosan decorated vanadium pentoxide nano-adsorbents for water remediation

The narrow bandgap and rapid interconversion of the oxidation states of vanadium in vanadium pentoxide makes it an extensively used photocatalyst for the degradation of organic pollutant but inadequate response towards visible spectrum and low quantum yield limits its activity. Here, functionalized chitosan decorated vanadium pentoxide nano-adsorbents are fabricated that exhibited significant sensitivity to visible light absorption and shows more efficient quantum yield by the transformation of absorbed light into radiated light. Further, they were used in the photodegradation of methylene blue under natural conditions. The characterization results demonstrated the presence of chitosan and its derivatives over the surface of nanoparticles. Decorated vanadium pentoxide nano-adsorbents exhibited enhanced surface area and better catalytic properties which increases the photodegradation by lowering the recombination rate of charge and hole. Among the decorated nano-adsorbents, chitosan-anisaldehyde decorated vanadium pentoxide (CHVD₃) possessed wedge-shaped pore that favoured the photocatalytic degradation of methylene blue followed by others synthesized nanoparticles. The degradation rate constant and half life time for CHVD₃ were 3.84 × 10^?3 min^?1 and 18.07 min respectively. Major species responsible for the degradation and the mechanism has been elucidated by taking into consideration the degradation process in absence and presence of various scavengers. The degradation performance of CHVD₃ was severely affected, reducing from 92% to 36% in the presence of the scavenger, where *O₂^? act as a major active species in degradation process.     

硝酸法常压氧化制备2-氯-6-硝基苯甲酸

以2-氯-6-硝基甲苯为起始原料,在硫酸介质中,五氧化二矾催化下,滴加硝酸,常压氧化生成2-氯-6-硝基苯甲酸。     

掺杂中孔氧化锆的合成进展

介绍中孔氧化锆的合成机理及国内外研究现状,讨论了影响合成中孔氧化锆的一些因素,特别是对掺杂中孔氧化锆合成的影响。概述了掺杂中孔氧化锆的应用并展望了其发展方向。     

Problem of evaluating the crack resistance in ceramics of Si3N4 and ZrO2

The mechanical behavior of silicon nitride and zirconium dioxide ceramics is investigated in a wide temperature range. Much attention is paid to crack resistance under the conditions of the ambient. Data obtained by different methods used for evaluating crack resistance are analyzed, and it is shown that the best results have been obtained in tests in which the concentrator was an indentation of a Vickers pyramid. The analysis was conducted using fractographic investigations of the materials and data of tests of a model material of zirconium dioxide.Translated from Ogneupory, No. 1, pp. 21 – 26, January, 1996.