草酸钴沉淀工艺对钴粉粒度影响的研究

对草酸钴沉淀的工艺条件进行了试验 ,并分别就该工艺对钴粉粒度的影响进行了分析和讨论 ,总结出钴粉粒度变化的规律     

类球形草酸钴沉淀粉末的制备研究

草酸钴是制备钴粉的重要前驱体,其常见的沉淀产物呈长条棒状,而工业上急需球状或类球状的颗粒。本研究提出了一种新颖的方法,控制钴离子/草酸根的化学计量比远离1.0和温度在80℃以上时,能成功地将草酸钴沉淀形貌从晶须状改变成类球形。研究认为,在钴离子过量或草酸根离子过量的情况,会影响草酸钴成核基团及晶核表面的荷电状态,而80℃以上高温作用可能显著改变晶核表面液膜层内出现紊流传质现象,使得晶核各个晶面上生长速度差异变小,最终形成类球形颗粒草酸钴。本研究结果,将为草酸钴沉淀形貌调控及类球形草酸钴的生产提供重要指导。     

草酸钴还原过程的相变研究

利用电子探针扫描研究了制取钴粉的两个不同过程产物的相变。结果表明:由草酸钴(CoC2O4·2H2O)直接通过氢气还原制取钴粉,其钴粉的分散性和流动性差,不利于进一步生产优质硬质合金;由草酸钴(CoC2O4·2H2O)先在空气中煅烧为氧化钴(Co2O3),然后再用煅烧所得的氧化钴(Co2O3)通过氢气还原制取钴粉,其钴粉分散性和流动性好,利于进一步生产优质硬质合金。     

二水草酸钴在氩气中热分解过程及其形貌演变的研究

通过TG-DSC和SEM对二水草酸钴在氩气中热分解过程进行分析,研究结果表明:二水草酸钴在氩气中的热分解过程经历了两个阶段,一是在150℃～275℃之间二水草酸钴失去结晶水生成了CoC2O4;二是从300℃～450℃之间CoC2O4热分解为了金属钴。与此同时,二水草酸钴在氩气中热分解温度为347.7℃时并保温10 min,其热分解产物中有细球形颗粒物质生成。在500.0℃时并保温10 min,其热分解产物钴粉由原来的单个球形颗粒因热分解温度较高使得它们烧结连接在一起。因此,适当地控制二水草酸钴500.0℃时在氩气中的热分解条件可以获得球形钴粉颗粒。     

一种碳化硅粉体的处理及其沉淀行为

以一种日本产β-SiC粉体为原料，采用煅烧、酸洗和碱洗的方法对粉体表面进行处理，然后用相同的工艺配制出原始粉体和3种处理粉体的酸性（pH=3）、中性（pH=7）和碱性（pH=10）水料浆，通过料浆中分界面高度随时间的变化研究各料浆的沉淀行为，同时测量几种粉体的Zeta电位，并进行红外光谱分析。结果表明，当pH值为3和7时，4种料浆的沉淀行为相似；而当pH值为10时，3种处理粉体表现出与原始粉体截然不同的沉淀行为。红外光谱分析显示，原始粉体表面含有游离碳和碳氢化合物等杂质，因而料浆稳定性差，碱洗和酸洗可有效去除这些杂质，显著改善料浆的稳定性，而碱洗和酸洗的效果更优于煅烧。     

Co-Ni-Fe-Mn配合-沉淀体系的平衡热力学

根据质量守恒和同时平衡原理,以Me(Co、Ni、Fe、Mn)为金属元素,建立Me-OH-、Me-OH--CO32-、Me-OH--S2-、Me-OH--NH3和Me-OH--NH3-CO32-等多个配合-沉淀体系的热力学平衡模型。结果表明:Fe3+可以在Me-OH-、Me-OH--NH3体系中通过调节pH=3预先沉淀分离,而Co、Ni、Mn仅在Me-OH--NH3-CO32-体系中有分离效果。Me-OH--NH3-CO32-体系热力学计算表明:Co、Ni、Mn在溶液中的行为受pH值、配合剂、沉淀剂浓度共同影响,碳酸根初始总浓度[C]增大和氨初始总浓度[N]减小有利于Co、Ni、Mn形成沉淀。当[C]=1 mol/L、[N]=2 mol/L、pH值为9～10时,大部分Ni以高级氨配离子[Ni(NH3)42+]、[Ni(NH3)52+]、[Ni(NH3)62+]的形式保留在溶液中,而Co、Mn以MnCO3、CoCO3的形式沉淀出来。Co可在Me-OH--S2-体系中通过调节pH<6从溶液中与Mn分离。研究结果可为钴镍二次资源综合回收钴镍、制备钴镍产品提供理论指导。     

Cu—Ce—O,Cu—Ce—S,Cu—Ce—O—S溶液体系热力学及其沉淀图

本文采用铜液与反应产物直接平衡法,并用固体电解质氧浓差电池和低温无水电解分离反应产物等技术,在1200℃研究了Cu—Ce-O,Cu—Ce-S,Cu—Ce-O—S溶液体系热力学得到了铜液中铈的脱氧、脱硫,脱硫氧常数和平衡产物Ce_2O_3,CeS,Ce_2O_2S的Gibbs标准生成自由能,Ce与S的活度相互作用系数以及Ce的标准溶解自由能和自作用系数与温度的关系式绘制了铜液中[Ce]-[S]-[O]平面沉淀图,确定了铜液中Ce_2O_3,CeS,Ce_2O_2S稳定存在的热力学条件,为预测Ce的夹杂物生成的先后次序及类型提供了理论依据     

合金沉淀过程相场法模拟研究进展

通过简单介绍研究合金的一些方法,综述了相场法的界面模型、动力学模型、常用的求解方法以及目前国内外运用微观相场法模拟合金沉淀过程的研究进展,提出了微观相场模型在模拟合金沉淀机制中的一些成功及不足之处,以及今后的研究方向.     

镍基合金粗化过程中共格沉淀相的形貌演变

基于微观相场模型,研究了镍基合金粗化过程中沉淀颗粒在弹性应变能作用下的微观组织变化。结果表明,镍基合金在粗化过程中,弹性应变能的大小通过改变颗粒中心沿[10]方向和[11]方向的溶质浓度分布,影响共格沉淀相的形貌变化。     

由草酸钴热分解制备Co3O4及其物性表征

根据草酸钴的热重/差热分析曲线,利用热分解法,在不同条件下由草酸钴制备了各种Co3O4微粉,并对其进行了X射线衍射分析和扫描电镜表征.结果表明:在低温下制得了具有标准Co3O4晶形结构的树枝状Co3O4;在高温下,尤其是采用两段升温制得了具有标准活性Co3O4晶形结构的球形Co3O4,其中位粒径为1.35μm,松装密度为0.83 g/cm3,并由此获得了由草酸钴热分解制备活性球型Co3O4的分解条件.     

Thermodynamic equilibrium calculation on preparation of copper oxalate precursor powder

According to the principles of simultaneous equilibrium and mass balance, a series of thermodynamic equilibrium equations of Cu^2＋-C2O4^2--NH3-NH4^＋＋-H2O system at ambient temperature were deduced theoretically and the logarithm concentration versus pH value （lg[Cu^2＋]T--pH） diagrams at different solution compositions were drawn. The results show that when pH is below 5.0, copper ion reacts with C2O4^2- directly and the morphology of copper precursor powder is of pie-shape, when pH is above 5.0, copper ion coordinates with ammonia, and the precipitation proceeds slowly accompanying with the release of copper ions fi＇om the multi-coordinated Cu（NH3）n^2＋（n =1, 2,…, 5） and the morphologies of copper precursor powder are respectively of rod aggregation shape （when 5.0〈pH〈8.0） and of rod-shape （when pH〉8.0）. Some experiments were performed to confirm the relation between the total concentration of copper ion and pH value. It is shown that the thermodynamic mathematical model is correct and the calculated values are basically accurate.     

Thermodynamic analysis on preparation of fibrous NiO precursor powders with oxalate precipitation process

According to the principles of simultaneous equilibrium and mass balance, a series of thermodynamic equilibrium equations of Ni（ Ⅱ）-C2 O4^2--NH3-NH4^＋-H2O system at ambient temperature are deduced theoretically and the logarithm concentration versus pH value（lg[Ni^2＋ ]r-pH） diagrams at different solution compositions are drawn. The results show that when pH is above 8.0, nickel ions coordinate with ammonia, the precipitation proceeds slowly accompanying with the release of nickel ions from the multi-coordinated Ni（NH3）n^2＋ （n= 1, 2,…, 6） and the morphology of NiO powder precursor is fibrous; when pH is below 8.0, nickel ion directly reacts with C2O4^2- and the morphology of NiO powder precursor is of cubic-shape. Some experiments were made to confirm the relation between the total concentration of nickel ion and pH. It is shown that the thermodynamic mathematical model is correct and the calculated values are basically accurate.     

一种具有较低烧结温度的超细钴粉的制备及表征

目前国内金刚石工具及钴粉生产,采用碳酸氢铵为沉淀剂,通过沉淀-热分解-还原工艺制备超细钴粉。研究了沉淀过程中温度、pH值等工艺参数的影响,制备得到Fsss粒度0．5～1μm的超细钴粉。采用SEM对超细钴粉进行了形貌观察,通过热压烧结制备了40mm×8mm×3．2mm样片,对样片的硬度及抗弯强度进行了表征。与传统草酸沉淀还原生产钴粉相比,本工艺制备的钴粉具有细晶球形的形貌,活性更高。此种超细钴粉的热压烧结样片在较低温度即可获得较高的硬度,在不同的温度范围内其抗弯强度表现出了良好的稳定性,并且降低了生产成本。     

Preparation of spherical cobalt carbonate from cobalt sulfate solution

A precursor of cobaltous dihydroxycarbonate was firstly prepared by precipitation reaction of cobalt sulfate solution and ammonium carbonate solution, and then a hydrothermal process for the precursor was conducted to obtain the spherical cobalt carbonate with low sulfur content. The experimental results show that the feeding method, final pH value of the precipitation reaction slurry and the concentration of the cobalt sulfate solution have obvious effects on the sulfur content, morphology and particle size distribution of the precursor. The sulfur content of the precursor is 0.0115 wt.% under the optimized conditions. The hydrothermal treatment with temperatures of 125−150 °C can transform the precursor of cobaltous dihydroxycarbonate into spherical cobalt carbonate and decrease the sulfur content to 0.0030 wt.% in the obtained product.     

Preparation of Cobalt Nanofibres by Means of Mild Thermal Precipitation and Thermal Decomposition Process

以CoSO3和(NH4)2C2O4·H2O为原料,通过65℃的温热沉淀反应和温热陈化过程,控制合成了水合草酸钴纳米棒.以水合草酸钴纳米棒为前驱体,在Ar气氛中于360℃下,通过热分解过程制备纳米金属钴纤维.实验样品采用AAS,OEA,FT-IR,TGA-DTG,XRD和SEM测试技术进行分析.测试结果表明:温和液相沉淀法制备的样品为水合草酸钴,其化学式可写为CoC2O4·3H2O.制备的草酸钴纳米棒直径为0.2～0.4 μm,长度为1.0～5.0μm;热分解制备的金属钴纳米纤维的直径约0.2 μm,长度为1.0～5.0 μm.     

铝酸钠溶液添加活性晶种分解过程颗粒的演变

以碳酸氢钠诱导铝酸钠溶液分解制备活性晶种,研究了添加极少量该活性晶种铝酸钠溶液分解过程中的颗粒演变规律。结果表明:随着分解过程的进行,产品粒度先增大而后减小,其拐点对应于铝酸钠溶液过饱和度变化速率由快变慢的转折点。种分初期,产品中拜耳石含量高,并存在数量较多的附聚体,拜耳石为粘结相。种分后期,拜耳石被较高苛性比的铝酸钠溶液溶解,导致附聚体解体而使产品细化。研究结果可为研究铝酸钠溶液添加活性晶种分解过程的粒度控制技术提供借鉴。     

Effect of cobalt on chemical segregation and solution process in Re-containing single crystal superalloys

The effect of cobalt on chemical segregation and solution process in three nickel base single crystal superalloys was investigated. Three alloys containing the mass fi＇action of cobalt of 12% （named Alloy 1 ）, 3% （named Alloy 2） and 0 （named Alloy 3）, respectively were studied, in which the contents of other elements were same. The results show that the segregation extent of W, Re, Ta, Al between dendrite and interdendritic region rises with the increase of cobalt content. The incipient melting points decrease by 10 ℃ and 20 ℃ respectively when the content of cobalt increases from 0 through 3% to 12%. During solid solution at 1 340 ℃, the solid solution of large gamma prime in interdendritic region and the dissolution of eutectic in alloy 1 become easier than in other two alloys. After heat-treatment at 1 340℃ for 8 h, the segregation extent of elements in alloy 1 decreases dramatically, while in alloy 2 and alloy 3, the segregation ratios decrease slowly. It suggests that the higher content of cobalt can accelerate the diffusion process at high temperature.