氮化烧结V(C,N)颗粒增强铁基复合材料的研究

用热力学计算证明了氮化反应的可行性，用DTA确定了VN反应的温度范围。通过XRD和SEM比较了两种烧结气氛（真空和氮气）制备的颗粒增强复合材料烧结体的相组成、颗粒大小和形态分布。实验表明，由于V与N的亲合力大于V与C的亲合力，这导致了压坯的增强相由V6C5、V4C3向VN的转变；同时在1200℃（α-Fe→γ-Fe的相变为剩余的C的固溶创造了条件。     

碳氮化钒颗粒增强铁基复合材料微观组织的研究

以钒铁粉、石墨粉、铁粉和氮气为原料,采用粉末冶金技术合成了V(C,N)颗粒增强铁基复合材料,从热力学、热分析、致密化和微观结构等方面对该复合材料进行了研究.结果表明,在烧结温度范围内,发生了FeV+C+N2=V(C,N+Fe反应,合成了V(C,N)硬质相;制备的复合材料在1200℃烧结时,其密度达到最大值;复合材料主要相为V(C,N)和γ-Fe,所合成的硬质相V(C,N)颗粒细小,在铁基体中分布均匀.     

反应烧结合成碳化钒颗粒增强铁基复合材料

以铬铁粉、钼铁粉、钒铁粉、铁粉和碳黑为原料.原位反应合成了VC-Fe基复合材料,并用扫描电镜、X射线衍射等测试方法对试样进行了组织结构分析.结果表明:在真空中烧结后,反应合成的复合材料主要相组成为V_8C_7,和α-Fe;在氮气中烧结后,复合材料主要相组成为V(C,N)和γ-Fe;与VC相比,硬质相V(C,N)分布更均匀,颗粒形状趋于球形.     

原位合成V8C7颗粒增强铁基复合材料的制备

采用铸渗和热处理原位反应工艺相结合的方法,将准1 mm的钒丝与灰铸铁进行复合,制成钒丝-灰铸铁复合预制体,并对其进行热处理,使钒丝中的钒原子与铸铁中的碳原子原位反应生成V8C7颗粒,制备出V8C7颗粒增强铁基复合材料。用SEM、XRD对该复合材料的显微组织和物相组成进行分析。结果表明,生成的V8C7颗粒均匀分布于铁基体中,且生成物与基体有很好的冶金结合,反应区主要由α-Fe和V8C7颗粒组成;应用热力学原理对原位合成V8C7颗粒的反应机理进行分析,表明用此方法制备的V8C7增强相在热力学上是可行的。     

V(C,N)颗粒增强铁基复合材料的研究

采用粉末冶金和原位合成相结合的方法合成V(C,N)颗粒增强铁基复合材料,用扫描电镜、X射线衍射等测试方法对试样进行了组织结构分析,并探讨了原位合成V(C,N)的机理.结果表明,石墨与氮气的存在降低了σ-FeV相的稳定性,使其分解为崮溶大量V的Fe,C、N与V发生反应生成V(C,N);原位合成的复合材料主要相组成为V(C,N)和γ-Fe,所合成的硬质相V(C,N)颗粒细小,在铁基体中均匀分布.在重载十滑动摩擦条件下,V(C,N)颗粒增强铁基复合材料显示出良好的耐磨性.     

固相反应生成VC颗粒增强铁基复合材料

用粉末冶金方法,使(Fe-V合金 石墨)反应体系在较低温度的固态条件下进行碳化反应和烧结致密化,发现石墨的存在降低了σ-(FeV)相的稳定性,促使其在800℃就分离出少量α-Fe相和金属V,并且该体系在950℃即可进行固相反应,生成由马氏体基体和大量亚微米级的V8C7球状颗粒组成的铁基复合材料,在重载干滑动磨损条件下该复合材料显示了很好的耐磨性能.     

(Ti,V)C颗粒增强铁基复合材料显微组织的研究

采用粉末冶金与原位合成相结合的方法制备了不同V/Ti原子比的（Ti，V）C／Fe基复合材料，用X射线衍射（XRD）、扫描电镜（SEM）研究了该复合材料的物相结构和显微组织。研究结果表明：原位合成的（Ti，V）C增强相颗粒细小，大部分小于2μm，在α-Fe基体中均匀分布。随着V，Ti比的提高，（Ti，V）C晶格常数减小，且呈线性下降，（Ti，V）C增强相颗粒形态由不规则状趋于球形。     

碳化钛钒增强铁基复合材料的微观组织与机理研究

采用粉末冶金与原位合成相结合的方法制备了(Ti,V)C/Fe基复合材料,用X射线衍射、扫描电镜研究了该复合材料的物相结构和显微组织.结合热分析和高温X射线衍射,对Fe-Ti-V-C体系的反应机理进行研究.结果表明:反应合成的复合材料的相组成为(Ti,V)C和α-Fe,细小的球状(Ti,V)C颗粒均匀分布在珠光体基体上.Fe-Ti-V-C体系的反应机理为,首先在765.7℃发生Fe的同素异构转变,即α-Fe→γ-Fe,以及钒的碳化反应FeV+C=VC+Fe;其次在1058.5℃,Ti与Fe共熔而形成低共熔体Ti2Fe;在1140.4℃,C与Ti2Fe反应生成TiC;最后,随着温度的继续升高,TiC和VC形成了(Ti,V)C固溶体.     

原位生成Ti(C、N)/Fe基复合熔覆层的微观结构

用高能集中横流式的二氧化碳激光束作为诱导热源,在铸钢表面进行改性处理,形成了含有碳氮化钛增强粒子的铁基熔覆层。利用X射线衍射仪(XRD)、电子探针(EPMA)、扫描电镜(SEM)、能谱仪(EDX)、透射电镜(TEM)和选区电子衍射花样(SAED)等手段对复合熔覆层的微观结构及它们中第二相粒子的成分、形貌和尺寸进行了分析和研究。试验结果表明:先前加入的颗粒状TiN与石墨粉在激光熔覆过程中发生了化合反应,原位生成了新的颗粒状Ti(C0.3N0.7)强化相。复合熔覆层的基体组织由树枝胞状晶α-Fe和Ti(C0.3N0.7)颗粒硬质相共同组成,新相Ti(C0.3N0.7)颗粒的形貌特征多呈不规则形状,大小在0.1~6.0μm之间,它们较均匀地弥散分布在熔覆层α-Fe基体上。硬质相颗粒Ti(C0.3N0.7)与熔覆层基体α-Fe之间结合紧密,界面干净光滑。     

原位烧结合成(Ti,V)C/Fe复合材料的组织及形成机理

以钛粉、铁粉、钒铁粉、铬铁粉、钼铁粉及石墨粉为原料,通过原位烧结制备了(Ti,V)C/Fe复合材料.利用X射线衍射(XRD)、扫描电镜(SEM)和能谱EDS分析了材料的组织结构.结合差示扫描量热法分析(DSC)和高温x射线衍射分析研究了Fe-Ti-V-C体系原位烧结的动力学过程.结果表明:(Ti,V)C/Fe复合材料致密化程度高.增强相(Ti,V)C的形态比TiC更规则,TiC颗粒中存在富Mo的"环形结构",而(Ti,V)C中没有"环形结构".合成(Ti,V)C/Fe复合材料的动力学过程为:在770℃左右发生钒的碳化反应生成VC,1140.4℃时发生Ti的碳化反应生成TiC,随着温度升高,VC和TiC发生固溶反应形成(Ti,V)C固溶体.在1400℃烧结时,硬质相(Ti,V)C(或TiC)在液相中根据Gibbs-Thomson效应,按照小颗粒不断溶解,大颗粒相应粗化的模式长大.     

Vanadium recovery from clay vanadium mineral using an acid leaching method

A technique including direct acid leaching,vanadium precipitation with alkaline,sodium hydroxide releaching,impurity removing by adjusting pH value,precipitation vanadium with ammonium chloride,and vanadium pentoxide by roasting steps was proposed according to the characteristic of Xichuan clay vanadium mineral.The factors influencing leaching vanadium such as temperature and the concentration of sulfuric acid were investigated and optimized.The experimental results indicate that the extract ratios of V2O5 can reach 94% and 92% at a sodium chlorate ratio of 3% and a manganese dioxide ratio of 3%,respectively.A completely chemical precipitation method was adopted to decontaminate and enrich the vanadium in the acid leaching solution.The X-ray diffraction (XRD) pattern and the purity analysis of vanadium pentoxide indicate that the purity of final vanadium pentoxide can reach 99% and meet the standard specifications.The total recovery can reach about 75%.The technique has the characteristics of simplicity,less investlnent,and more environment safety as compared with the traditional salt roasting method.     

Behavior of vanadium during reduction and smelting of vanadium titanomagnetite metallized pellets

The effects of CaO content, MgO content and smelting temperature on the vanadium behavior during the smelting of vanadium titanomagnetite metallized pellets were investigated. The thermodynamics of reduction and distribution of vanadium was analyzed and the high-temperature smelting experiments were carried out. The thermodynamic calculations show that the distribution ratio of vanadium between the slag and the hot metal decreases with the increments of CaO and MgO content in the slag as well as the increase of the smelting temperature. The smelting experiments demonstrate that the vanadium content in iron and the recovery rate of vanadium in pig iron increase as the CaO content, MgO content and smelting temperature increase, whereas the vanadium distribution ratio between the slag and iron tends to decrease. Moreover, the recovery rate of vanadium in pig iron has a rising trend with increasing the optical basicity of the slag. The addition of MgO in the slag to increase the slag optical basicity can not only improve the vanadium reduction but also promote the formation of magnesium-containing anosovite, which is beneficial to following titanium extraction.     

超细V_8C_7和Cr_3C_2粉末的制备方法

制备V8C7和Cr3C2粉末的传统方法是将V(Cr)氧化物与固体碳球磨混合﹑二次碳化而成,此方法存在碳化温度高﹑粉末粒度粗等缺点。本文介绍了几种国外制备超细V8C7和Cr3C2粉末的制备方法。     

Recovery of vanadium from vanadium slag by composite roasting with CaO/MgO and leaching

A novel process of composite roasting with CaO/MgO and subsequent acid leaching was proposed to improve the recovery rate of vanadium from Linz–Donawiz (LD) converter vanadium slag. The effects of the MgO/(CaO+MgO) molar ratio and the roasting and leaching parameters on the recovery of vanadium were studied. The results showed that the leaching efficiency of vanadium decreased from 88% to 81% when CaO was replaced completely by MgO; however, it could be improved by roasting with the composite of CaO/MgO. The maximum vanadium leaching efficiency of 94% was achieved under the optimum MgO/(CaO+MgO) mole ratio of 0.5:1. The results from X-ray diffractometry (XRD) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM−EDS) confirm that the formation rate of acid-soluble vanadates can be enhanced during roasting with the composite of CaO/MgO and that the leaching kinetics can be accelerated owing to the suppression of calcium sulfate precipitation.     

热电池用锂钒氧化物正极材料的放电模式

合成V2O5-V2O3-Li2O体系的3种化合物LiV3O8、γ-LiV2O5和VO2,并以其作为热电池正极活性物质、锂硼合金为负极、LiCl-KCl为电解质进行500℃、100 mA/cm^2的放电实验,研究该正极活性物质在放电中的物相转变过程,同时对V2O5、β-Li0.3V2O5、VnO2n＋1和VnO2n？1的放电反应进行分析。结果表明,LiV3O8、γ-LiV2O5和VO2均进行分解式放电反应,生成LiV2O5、Li3VO4、V2O3和LiVO2等物相。分析认为V2O5和β-Li0.3V2O5可能出现嵌入反应直至转变为γ-LiV2O5,再由γ-LiV2O5进行放电,VnO2n＋1和VnO2n-1放电最终也将生成Li3VO4和V2O3。γ-LiV2O5和VO2放电过程中V4^＋歧化反应产生Li3VO4相和V2O3相,Li3VO4相较差的电子导电性使正极材料失去快速放电能力。     

钒钛磁铁矿提钒尾渣浸取钒

采用硫酸氢氟酸次氯酸钠组合浸出体系浸取钒钛磁铁矿提钒尾渣中的钒,研究浸出过程中试剂浓度、浸出液固比、浸出温度、浸出时间、物料粒度对钒浸出率的影响。结果表明:钒的浸出率随试剂浓度、液固比、温度和时间的升高而增大;当矿物粒度小于0.20 mm时,钒浸出率有随矿物粒度变小而减小的趋势。在物料粒度0.15~0.25 mm、初始硫酸浓度150 g/L、初始氢氟酸浓度30 g/L、次氯酸钠加入量为矿量1.5%、矿浆液固比6:1、浸出温度90℃、浸出时间6 h、搅拌速度500 r/min的条件下,钒的浸出率可达85%以上。     

常压下碳热还原制备碳化钒(V_8C_7)粉末的研究

为了实现小批量连续化制备碳化钒粉末,以工业级V2O5和纳米碳黑为原料,在常压下氩气保护的碳管炉中高温反应得到了V8C7。采用X射线衍射仪(XRD)、扫描电镜(SEM)、LECO碳氧分析仪对反应产物进行了分析。结果表明:碳化温度为1 450℃时,可得到有序V8C7,但是杂质含量较高;提高温度有利于粉末纯度的提高,而不利于粉末的细化;最终在1 600℃保温4 h的条件下,制备出游离碳质量分数为0.31%、氧质量分数为0.69%、平均粒径为2μm的V8C7粉末。     

钒及钒基合金金相试样的制备方法

介绍了一种钒及钒基合金金相试样的常规制样方法,即试样的机械磨光,机械化学抛光,化学侵蚀等技术和经验。