共查询到20条相似文献,搜索用时 15 毫秒
1.
Mo-Y_2O_3阴极发射机理研究 总被引:3,自引:1,他引:2
采用热重分析、X射线衍射、扫描电镜及光电子能谱等方法对Mo Y2 O3阴极中钇的价态进行了研究 ,探讨了该阴极的发射机理。Y2 O3与Mo2 C在 1173K以上发生化学反应。Y2 O3与Mo2 C混合物经 1873K高温处理后 ,产物中含有两种价态的Y :Y0 和化合态的Y3 。Mo Y2 O3阴极的发射可用原子膜机理解释 ;在阴极工作过程中 ,Mo2 C将Y2 O3还原成单质钇 ,钇覆盖在钼基体表面 ,降低了基体钼的逸出功 ,促进了阴极的发射。 相似文献
2.
稀土镧在La-Mo合金粉中的存在形式及对钼粉性能的影响 总被引:1,自引:1,他引:0
通过对添加硝酸镧的二氧化钼在不同温度还原后钼粉的X射线衍射检测分析,研究了稀土镧在La-Mo合金粉中的存在形式;对La-Mo合金粉的粒度、氧含量、SEM照片等结果与纯钼粉对比分析,研究了稀土镧对La-Mo合金粉性能的影响。结果表明:随着还原的进行,稀土镧由以La2O3和钼酸镧的形式存在,逐渐转化为以唯一的La2O3形式存在;稀土镧强烈地抑制了钼粉颗粒的长大;由于稀土镧的加入,钼粉氧含量增加;La-Mo合金粉形貌为规则的多面体,分布不均匀。 相似文献
3.
镧钼合金在电火花切割加工中的应用研究 总被引:1,自引:0,他引:1
进行了镧钼丝与纯钼丝作电火花切割电极丝的对比试验,试验结果显示;在合理控制镧钼丝加工工艺的条件下,镧钼丝具有较高的抗拉强度和高温强度,其线切割使用寿命明显高于纯钼丝,试验数据显示提高50%左右,实践表明,在电火花线切割加工行业,用镧钼丝代替纯钼丝作电极丝,可有效降低切割成本,极具推广应用价值。 相似文献
4.
Masahiro Kitajima Masatoshi Okada Ryoji Watanabe 《Metallurgical and Materials Transactions A》1980,11(10):1645-1655
Secondary ion analysis was applied to the study of the carburization behavior of a superalloy by using the ion microprobe
mass analyzer (IMMA). The corrosion test of Inconel 617 was carried out for 1000 h under an environment of methane-doped impure
helium gas at 1000 °C. 20 KeV O
2
+
and N
2
+
were used as primary ions. IMMA showed that C, O, Al, Si, Ti and Mo were enriched near the surface. The chemical states of
the scale and the precipitates were determined from chemical shifts of X-ray emission spectra. It was confirmed that silicon
carbide and molybdenum carbide were coprecipitated in the same areas: in the scale, in the matrix at a depth of 10 μm to about
40 μm below the scale, and at grain boundaries. Aluminum and titanium were found to exist as oxides near the surface. It was
shown that carburization was limited near the surface, and the grain boundary precipitation of carbides in the bulk was due
to aging at high temperatures. The concentration profiles of silicon and molybdenum in (Si,Mo)-carbide were obtained by using
standard carbide samples assuming that the concentration of implanted oxygen atoms of the specimen was equal to that of the
standard sample. The ratio, (Si)/(Mo), was increased from about 0.1 in bulk to 2.4 ∼ 3.8 near the surface. This result indicates
that silicon is carburized much more preferentially than molybdenum. 相似文献
5.
6.
通过固体火箭发动机地面热试车实验获得烧蚀后的钼镧喷管试样,对比分析了烧蚀前后试样的金相组织,在常温和1000℃条件下进行了钼镧材料的力学性能实验。结果表明:对于工作时间2.1 s的固体火箭发动机中搭载使用的钼镧喷管,内型面形状完整,尺寸无明显变化,抗烧蚀性能表现良好;烧蚀前后金相组织对比显示晶粒发生再结晶,特别是喷口及喷管中部工作温度高的位置,形貌变化明显,由细长的纤维状变为等轴晶趋势。镧的氧化物粒子对钼起到了韧化作用,合金试样1000℃高温和常温下断口出现颈缩和韧窝,高温下韧窝深浅差异更大,抗拉强度和伸长率有所下降。 相似文献
7.
镧热还原氧化钐过程镧的非平衡扩散的研究 总被引:1,自引:1,他引:0
运用化学分析法和热重法对镧热还原氧化钐的反应产物镧渣进行分析,得到坩埚不同部位镧渣的镧的扩散量△La和实际反应物料的Sm2O3∶La的比值,并把理论反应物料的Sm2O3∶La和实际的比值相比较。结果表明:真空高温条件下,还原剂金属镧在反应过程中发生了有固定方向的扩散迁移。金属镧从反应物料中的由内向外的非平衡扩散,造成金属镧在反应物料中的分布不均,表面富集而芯部贫乏,降低了还原剂金属镧利用率及产物金属钐收率。 相似文献
8.
通过固体火箭发动机地面热试车实验获得烧蚀后的钼镧喷管试样,对比分析了烧蚀前后试样的金相组织,在常温和1000℃条件下进行了钼镧材料的力学性能实验。结果表明:对于工作时间2.1 s的固体火箭发动机中搭载使用的钼镧喷管,内型面形状完整,尺寸无明显变化,抗烧蚀性能表现良好;烧蚀前后金相组织对比显示晶粒发生再结晶,特别是喷口及喷管中部工作温度高的位置,形貌变化明显,由细长的纤维状变为等轴晶趋势。镧的氧化物粒子对钼起到了韧化作用,合金试样1000℃高温和常温下断口出现颈缩和韧窝,高温下韧窝深浅差异更大,抗拉强度和伸长率有所下降。 相似文献
9.
纯金属钼存在低温脆性、再结晶脆性、抗高温氧化能力较差等明显缺点,极大限制了其应用范围,通过在钼基体中添加第二相(稀土氧化物(La_2O_3、Ce_2O_3、Y_2O_3)和碳化物(TiC、ZrC、HfC))形成的钼合金因具有良好的高温性能、较低的韧脆转变温度、较高的再结晶温度受到了国内外学者的广泛关注。本文对三种钼合金制备工艺(固–固掺杂、固–液掺杂和液–液掺杂)进行了总结,并对其发展趋势做出了展望,结果表明采用液–液掺杂工艺能显著提高材料的均匀性和力学性能。 相似文献
10.
LaNialoyasoneofcandidatesforhydrogenstoragewasfirstpreparedin1970[1].Sincethenlotsoffundamentalandpracticalworkshavebeenpub... 相似文献
11.
12.
13.
The lanthanum carbide alloy was induction melted in vacuum induction melting furnace from lanthanum and graphite with the mass ratio of 89:11. Lanthanum hydroxide (La(OH)3) nanopowders were prepared by a simple hydrolysis of lanthanum carbide at room temperature under normal atmospheric pressure without any surfactant. X-ray diffraction (XRD) showed that the nanoparticles were with a hex-agonal structure. The effect factors such as reaction time,reaction temperature and the mass ratio of lanthanum carbide p... 相似文献
14.
15.
16.
分别采用固-固、液-固和液-液掺杂方式向钼粉中引入Al2O3,然后用粉末冶金法制备出掺杂钼粉,经压制、烧结制成Al2O3颗粒增强钼基复合材料.对掺杂钼粉及钼坯进行SEM形貌观察,并测定复合材料的密度和显微硬度.结果表明,液-液掺杂能够制备出粉末颗粒小、密度及硬度高的Al2O3/Mo复合材料,其掺杂Al2O3颗粒细小且分布较均匀. 相似文献
17.
以Li2B4O7-Li BO2-Li F为混合熔剂,饱和Li Br溶液为脱膜剂,对熔融制片条件进行了实验,包括样品质量和氧化剂用量、预氧化温度及时间、高温熔融温度及时间等条件实验。该文采取钼精矿国家标准样品与钼矿石国家标准样品相结合的方法,同时提高样品称样量,降低熔剂和样品的稀释比,加入Li NO3作为氧化剂,在1 050℃下熔融制片,建立了XRF测定钼精矿的工作曲线;对钼精矿标准样品和东北某大型矿山钼精矿样品中的主体元素Mo以及Cu、Pb、Zn、Mg、Ca等伴生元素进行了分析测定,其测定结果与国家标准分析法一致性良好。该方法的精密度(RSD)为0.52%~5.19%,可满足日常生产的分析质量控制要求。 相似文献
18.
试验研究了掺杂La2O3、Y2O3、CeO2稀土氧化物颗粒对钼合金的粉末物性、烧结进程、制品的烧结致密度及压力加工丝材的室温力学性能的影响规律。试验结果表明,掺杂稀土氧化物粒子细化了钼粉的粒度,降低了松装密度和粒度分布范围,同时导致粉末团聚现象增多;稀土氧化物粒子延迟了钼合金的烧结进程,降低了烧结制品的致密度,同时细化了烧结体晶粒尺寸。稀土氧化物粒子以弥散强化和细晶强化的形式,提高了钼合金丝的室温强度。CeO2显著提高了钼合金丝的室温韧性,La2O3、Y2O3则降低了钼合金丝的室温韧性。 相似文献
19.
The effects of molybdenum alloying additions to niobium on the carbide phases and their precipitation behavior were investigated.
The experimental alloys included Nb-0.1C, Nb-15Mo-0.1C, and Nb-30Mo-0.1C. After selected heat treatments the microstructural
changes were determined by metallography and the carbide phases were extracted and identified by X-ray diffraction and chemical
analysis. The results are essentially in agreement with recent phase diagram determinations. Additions of 30 wt pct Mo appears
to slightly increase the solubility of carbon in niobium at temperatures around 1650°C. The solubility of molybdenum in Nb2C is very small. Discontinuous precipitation of β-Nb2C was found to occur in the Nb-30Mo-0.1C alloy during annealing at 1200°C. The important, overall effect of molybdenum in
Nb-C alloys is to decrease the rate of niobium carbide precipitation so that appreciable carbon supersaturation can be achieved
even after comparatively slow furnace cooling. 相似文献