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1.
研究了分别以Mg,Al为还原剂,还原K2HfF6制备金属铪粉的可能性。利用X射线衍射(XRD)、扫描电镜(SEM)、能谱分析(EDS)等测试方法分析了产品的物相、形貌,研究了NaCl-KCl熔盐体系对铪粉形貌和杂质含量的影响。实验结果表明:Mg(过量20%)为还原剂,反应温度900℃、时间3 h可以还原铪氟酸钾得到金属铪粉,但产物中含有大量的无法除去的杂质MgF2;Al(过量20%)为还原剂,反应温度900℃、时间3 h制备的铪粉纯度达到98.75%,粒径为3μm左右,杂质含量较低,其中极少量的铝是以铪铝金属间化合物的形式存在的。研究表明,在以铝为还原剂的还原体系中添加NaCl-KCl熔盐由于添加的熔盐使铪和铝更易和杂质形成以氟络盐的形态存在的复杂化合物,导致铪粉中杂质的含量增加,同时由于添加熔盐使体系引入相当数量的电子,有利于铪氟酸钾的还原,在均相反应过程中呈现局部的电中性,使得制取的铪粉尺寸倾向于降低。  相似文献   

2.
研究了LiF-LaF3体系下,以La-Ni合金和La金属作可溶性阳极,以Ta为阴极,熔盐电解精炼镧过程中不同工艺条件对槽电压、沉积物形貌、产物杂质含量的影响。采用扫描电镜(SEM)对电解精炼所得La沉积物形貌进行观察,采用电感耦合等离子体质谱法(ICP-MS),辉光放电质谱法(GD-MS),高频燃烧-红外法与惰气脉冲-红外热导法进行最终产品金属La的成分分析。结果表明:槽压与电流之间的线性关系受到接触压降、熔盐性质等因素的影响,控制较高电解温度、使用La-Ni合金代替金属La作阳极时槽压较低;沉积物均为枝晶形貌,电流密度增大导致沉积物的形貌由三维多面体转变为二维片状,电解温度升高导致颗粒几何规则性减弱,低电流密度下沉积物生长机制应为阶梯状生长;金属杂质中W,Ta可由50~100μg·g-1降至2~3μg·g-1,使用La阳极的实验所得精炼产物金属镧纯度为99.867%(分析77个杂质元素)。  相似文献   

3.
熔盐电解法制备高纯钛粉   总被引:2,自引:0,他引:2  
以海绵钛作可溶阳极,纯钛板为阴极,NaCl-KCl-TiClx混合熔盐作电解质,在电解温度为900~980℃、阴极电流密度为0.1~0.6A/cm2、初始可溶钛浓度2%~8%的条件下,电解24h制备高纯钛粉,研究初始可溶钛浓度对钛粉中杂质元素含量的影响,以及电流密度和初始可溶钛浓度对电流效率及钛粉形貌的影响。结果表明,钛粉杂质含量完全达到高纯钛粉的标准,提高初始可溶钛浓度可降低杂质含量;在较高的阴极电流密度以及高的初始可溶钛浓度下电解效率较高;在阴极电流密度较高时钛粉为细小的树枝状晶体,而在阴极电流密度较低时得到较粗大均匀的结晶粉体。  相似文献   

4.
电解法制备高纯钛的研究   总被引:1,自引:0,他引:1  
以海绵钛为可溶阳极,纯钛板为阴极,NaCl-KCl-TiClx混合熔盐作电解质,在900~980℃温度范围内进行熔盐电解,研究了加料温度、电解温度、可溶钛浓度以及阴极电流密度等因素对阴极产品杂质含量的影响。结果表明,在较高温度下加料并电解可获得杂质含量低的产品,通过控制可溶钛浓度和阴极电流密度可获得不同形貌和纯度的阴极产品。  相似文献   

5.
本文报道了由氯氟氧化物熔盐电解精炼制取粗结晶钨粉的试验室及半工业试验结果,电解熔盐成份为:60%NaCl、15%NaF、25%WO_3。D_K=0.4~1.0A/cm~2,D_a≤0.1A/cm~2,t=830~930℃,密封多阴极电解槽。 阴极电流密度、温度、电解时间、阳极材料的  相似文献   

6.
熔盐电解法制备硼粉的研究   总被引:1,自引:0,他引:1  
研究了在KCl-KBF4体系和KCl-KBF4-B2O3体系中熔盐电解法制备硼粉的工艺条件。对KCl-KBF4体系采用正交试验法研究了熔盐配比、温度、阴极电流密度和电解时间对硼粉纯度及电流效率的影响,得到的最佳实验条件为:KCl∶KBF4为5∶1,温度750℃,阴极电流密度1.5A.cm-2,电解时间3h。该条件下能得到纯度95%以上的球形非晶态硼粉,电流效率可达到80%以上。KCl-KBF4-B2O3体系熔盐电解得到超细球形硼粉,但电流效率低,产品难以收集,杂质含量较高。  相似文献   

7.
研究了不同配比的NaCl-K2ZrF6熔盐体系的熔点,K2ZrF6:NaCl=3:7的熔点较低为721℃.在此基础上,研究了熔盐配比、阴极电流密度、电解温度等因素对NaCl-K2ZrF6熔盐体系电解精炼电流效率的影响,结果表明阴极电流密度、电解温度均与电流效率成反比.采用XRD及元素含量分析等方法研究了电解精炼产品质量.较佳的工艺条件为K2ZrF6:NaCl为3:7(%,质量分数),温度800℃,阴极电流密度1 A·cm-2,在此条件下,电流效率可达84%以上.阴极锆为合格的工业级锫产品,产品中Fe,Ni,Cr,Mn等杂质分别由2700×10-6,540×10-6,350×10-6,400×10-6降低到30×10-6,10×10-6,18 ×10-6,100×10-6以下,产品纯度达到99%以上.  相似文献   

8.
NaCl-Na_2WO_4-WO_3系熔盐电解法制备超细钨粉的研究   总被引:3,自引:1,他引:2  
在NaCl Na2 WO4 WO3熔盐体系中 ,对熔盐电解法电解氧化钨制取高纯超细钨粉进行了实验研究。在该电解质体系中 ,在电解温度为 780℃、阴极电流密度为 32 0mA/cm2 的条件下 ,可以制得平均粒度为 0 96 1μm的超细钨粉。在低电流密度时 ,阴极的电解反应为W6 在阴极放电 ,三氧化钨直接还原得到钨粉 ;而在高电流密度时 ,阴极电解反应分为两步 ,首先是Na 在阴极放电 ,生成金属钠 ,然后是金属钠还原三氧化钨得到钨粉。另外 ,还对电解槽温度、阴极电流密度和电解质中WO3的浓度对电流效率的影响进行了测定与研究  相似文献   

9.
NaCl—Na2WO4—WO3系熔盐电解法制备超细钨粉的研究   总被引:6,自引:0,他引:6  
在NaCl-Na2WO4-WO3熔盐体系中,对熔盐电解法电解氧化钨制取高纯超细钨粉进行了实验研究。在该电解质体系中,在电解温度为780℃、阴极电流密度为320mA/cm^2的条件下,可以制得平均粒度为0.961μm的超细钨粉。在低电流密度时,阴极的电解反应为W^6 在阴极放电,三氧化钨直接还原得到钨粉;而在高电流密度时,阴极电解反应分为两步,首先是Na^ 在阴极放电,生成金属钠,然后是金属钠还原三氧化钨得到钨粉。另外,还对电解槽温度、阴极电流密度和电解质中WO3的浓度对电流效率的影响进行了测定与研究。  相似文献   

10.
在CaCl_2熔盐体系中,以金属钙为还原剂,在不同的温度下进行还原制备铪粉,再经酸洗、水洗、烘干后,铪粉的产率可达92%以上。通过热力学研究确定实验的最佳温度,分析了不同温度下铪粉粒度、形貌及成分的变化,研究了钙热还原氧化铪的反应过程。结果表明:反应的适宜温度为1 000℃左右,制备的铪粉中主要物相为Hf,同时有少量的ZrO_2存在;在950℃下,铪粉中还有CaHfO_3存在,说明钙热还原氧化铪的反应分两步进行。随着反应温度的升高,铪粉粒度增大,形貌由颗粒状与枝状转变为块状,氧含量降低。  相似文献   

11.
YBa2Cu4O8/La2/3 Ca1/3 MnO3/YBa2Cu4O8 ( Y-124/LCMO/Y- 124) heterostructure was prepared by facing-target sputtering technique. The oscillatory superconducting transition temperature was observed when the thickness of LCMO d L is larger than critical thickness d L^CR. The metal-insulator transition temperature can only be detected at d L 〉 d L^CR. The dependence on the spacer layer in LCMO/Y-124 systems suggests strongly the interplay of ferromagnetic and superconducting couplings.  相似文献   

12.
The crystalline materials Ca3Sc2Si3O12 and Ca3Y2Si3O12 were characterized by different crystal structures, as the former is a cubic garnet, while the latter is an orthorhombic compound. We investigated the optical spectroscopy of these materials doped with several trivalent lanthanide ions and compared the results for the two hosts. Polycrystalline samples were prepared by solid state reaction, both undoped and doped with the trivalent lanthanide ions Eu3+, Tb3+ and Sm3+. Emission, excitation and Raman spectra of these materials were measured at temperatures ranging from 300 to 10 K. The optical spectra were assigned and discussed, and the effects of the crystal structure of the host on the spectroscopic behaviour were addressed. The technological potential of these compounds in the field of optical materials and devices was discussed.  相似文献   

13.
采用CaO-SiO2-Na2O-CaF2-Al2O3-MgO渣系,通过测定熔渣的粘度和Al2O3吸收速率,研究连铸保护渣的Al2O3吸收速率与粘度及化学成分之间的关系。在一定条件下,当CaO/SiO2为1.2左右时,粘度达到最小值,Al2O3吸收速率达到最大值,分别为0.10?Pa*s、8.403×10-4?kg*m-2*s-1。随着渣中Na2CO3含量、CaF2含量和MgO含量的增加,粘度减小,Al2O3吸收速率增大。随着渣中Al2O3含量的增加,粘度增大,Al2O3吸收速率减小。粘度为Al2O3吸收速率的主要控制因素。随着熔渣粘度的增加,连铸保护渣的Al2O3吸收速率逐渐减小。  相似文献   

14.
CaO-La2O3-B2O3-Eu2O3转光玻璃的合成及荧光性质   总被引:1,自引:1,他引:1  
《稀土》2004,25(4):1-5
X射线衍射研究表明CaO-La2O3-B2O3-Eu2O3体系的玻璃化温度在1025℃附近.荧光光谱和ESR谱研究表明,在CaO-La2O3-B2O3-Eu2O3玻璃体系中存在着Eu2+和Eu3+两种价态离子. 316, 360, 379, 394, 413, 462和532nm锐线激发峰和592,616和650红区发射峰分别对应Eu3+的f-f激发跃迁和5D0-7FJ (J=1,2,3)跃迁发射;351nm和427nm宽带激发峰和蓝区发射分别对应Eu2+的5d-4f激发跃迁和发射.  相似文献   

15.
The interplay between chemical composition, plastic behavior, and fracture modes of Cu46.5Zr46.5Al7 and Cu46.5Zr41.5Al7Y5 bulk metallic glasses (BMGs) was investigated by compression tests and fracture surfaces analyses. The aim was to explore the possibility of coupling physical, chemical, and hardness properties, with adequate macroscopic compressive plasticity. Cylindrical test samples, having a height-to-diameter ratio equal to 2, were machined and ground from as-cast bars and were tested in compression between lubricated plates, the displacement being measured by a clip-gage inserted between the plates. Y free BMG engineering stress-strain curves show a plastic behavior consisting of successive sudden stress drops and linear reloading segments. A detailed analysis of these features was performed to yield a correlation between the plastic deformation steps and the released elastic energy associated with each serration.  相似文献   

16.
项南  郭玉峰  郭兴敏 《工程科学学报》2017,39(11):1669-1673
钒钛磁铁矿是烧结矿重要的原料之一,Ca3TiFe2O8作为钒钛烧结矿中矿物被发现之后,其生成机理尚不明确.本文采用X射线衍射分析、元素能谱分析和TG-DSC分析相结合的方法,研究了Ca3TiFe2O8的生成机理以及不同温度、CaO与TiO2含量下Ca3TiFe2O8的生成规律.实验结果表明,Ca3TiFe2O8由Ca2 Fe2O5和CaTiO3反应生成,即CaO和Fe2O3反应生成Ca2 Fe2O5;其后,与CaTiO3反应生成Ca3TiFe2O8.反应时间越长,Ca3TiFe2O8的生成量越大,但反应温度对Ca3TiFe2O8生成的影响并不明显.另外,还发现CaO含量越高,Ca3TiFe2O8越易于生成,而且等摩尔Fe2O3和CaO下只要存在TiO2,就会有Ca3TiFe2O8生成.   相似文献   

17.
18.
Ce0.67Zr0.33O2-Al2O3 solid solution was prepared by the co-precipitation method. Fe2O3-based catalysts supported on the solid solution were obtained by the impregnation method. The article revealed that the optimal loading amount of Fe2O3 on Ce0.67Zr0.33 O2-Al2O3 in our experimental condition for catalytic combustion of methane was 8% ( mass fraction). The prepared catalysts were characterized by BET, TPR, XRD analyses, and their catalytic activity was investigated after being calcined at 873 K and after being aged in water gas at 1273 K. When the loading amount of Fe203 was 8% ( mass fraction), the catalyst held the highest activity, and the best temperature speciality and thermal stability. The complete-conversion temperature of methane for fresh and aged sample was 788 and 838 K, respectively. The range between the light-off temperature and the complete-conversion temperature was only 15 K. The characterization results of XRD indicated that Fe2O3 was well dispersed on the Ce0.67Zr0.33O2-Al2O3 matrix. The results of BET and TPR were in good harmony with the catalytic activity results.  相似文献   

19.
在对Al2O3-V2O5体系相图、热力学数据以及晶体结构数据进行综述与评估的基础上,采用相图计算方法对Al2O3-V2O5体系进行热力学优化.液相采用修正的似化学模型进行描述,利用对近似处理液相中存在的短程有序.将液相模型的最大短程有序设置在AlVO4处,将VO43-当作液相中V2O5的基本组成单元.体系中AlVO4相看作线性化合物.计算结果很好的重现了选定的实验数据,获得了一套合理、可靠、自洽的模型参数用来描述体系中各相的热力学性质,为Al2O3负载V2O5型催化剂催化性能的提高打下坚实的基础.   相似文献   

20.
Magnetocaloric Effect of Ni56Mn18.8Ga24.5 Gd0.7 Alloy   总被引:1,自引:0,他引:1  
Inrecent years materials with high magnetocaloriceffect (MCE) have attracted considerable attention ow-ingto its potential application as a magnetic refriger-ant .Many material systemsthat underwentthefirst-or-der magnetic transition have been found to exhibit agiant MCE. Their typical representatives areGd5(SixGe1 -x)4[1 ,2]and La (FexSi1 -x)13[3 ,4]alloys .Ni MnGa is aferromagnetic shaped memory alloy whichundergoes a reversible first-order structural phase tran-sition (SPT) with the …  相似文献   

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