共查询到17条相似文献,搜索用时 125 毫秒
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本文研究了热处理对急冷Al-11.3at%Si合金的微观结构及超导电性的影响,结构分析表明,液态淬火的样品由两相组成:过饱和α-Al(Si)固溶体晶体相和Al,Si原子按统计分布的非晶相,经100℃/50小时热处理后,α-Al(Si)固溶体贫化,非晶相中析出Si的小颗粒,经200℃/100小时热处理的样品已趋向平衡态结构,测量了样品的临界温度,在研究磁场中的超导-正常转变时发现了反常的磁阻效应,它可以用样品中存在两个超导相的模型予以解释。
关键词: 相似文献
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本文研究了热处理对急冷Al-8.3at%Si-8.5at%Ge合金的微观结构及超导电性的影响。结构分析表明,液态淬火的样品由两相组成:过饱和α-Al(Si,Ge)固溶体基体和Al,Si,Ge的非晶球体,后者在基体中相互连接,构成连续通路。经过100℃/50h热处理后,非晶球体尺寸缩小,不再构成连续通路,并在其中析出弥散的Si(Ge)微晶。热处理后的样品的电阻-温度及电阻-磁场转变曲线上均出现两次正常-超导转变。它可以用样品中存在两个超导相的模型予以解释。
关键词: 相似文献
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本文用X射线多晶衍射方法和差热分析方法研究了LaNi5-xSix(x≤1.25)的相关系,用排水取气法测量了样品的吸H2性能,LaNi5,的固溶体和新的三元化合物LaNi4Si形成共晶体系,共晶温度1170℃,共晶点x=0.96,在单相区中LaNi5,相点阵常数随Si替代量增加,a减小,c增大,三元化合物LaNi4Si属正交晶系,点阵常数a=8.382?,b=5.210?,c=3.989?。测量密度D0=7.59g/cm3,每单胞含两个化合式单位,可能的空间群为D2h5,C2v2和C2v4,它具有可逆的吸放H2性能,吸H2后形成氢化物LaNi4SiH3.6。La1-ySiyNi,系列样品吸H2量随Si含量增加而很快下降,LaNi5-xSix系列样品吸H2量随Si含量的增加稍略下降,平台压力也下降,LaNi4.8Si0.2的生成自由能为476cal/molH2,固溶体氢化物的稳定性比LaNi1高。
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本文对Ge/An,Ge/Ag,双层膜和Ge-An,Ge-Ag合金膜的退火过程进行了透射电子显微镜观测,对Ge/多晶Au(或Ag)还进行了加热过程的原位观测。观测表明,多晶Au和单晶Au膜的存在使非晶Ge的晶化温度Tc的下降显著不同,可由晶界三叉点等处为非晶Ge的有利形核位置来解释,双层膜的缩聚区中由于局域优先晶化的影响,不仅Tc(=100℃)比非缩聚区中(Tc=150℃)低,而且形成直径为1—2μm的Ge大晶粒,而Ge/多晶Ag和Ge/单晶Ag膜的Tc均约为280℃,合金膜中金属含量较低时(CAu<17at%,CAg<18at%),Tc高于相应的Ge/多晶Au(Ag)膜;金属含量较高时,Tc低于Ge/多晶Au(Ag)膜。这说明过饱和金属原子的存在使得非晶Ge的晶化势垒大大降低。
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本文用X射线和差热分析方法对BaO-Li2O-B2O3三元系中的两个截面:BaB2O4-Li2B2O4和BaB2O4-Li2O作了研究。在BaB2O4-Li2B2O4赝二元系中发现了一个新的化合物4BaB2O4·Li2B2O4。化合物在930±3℃由包晶反应形成,并与Li2B2O4形成共晶反应。共晶温度为797±3℃,共晶点组分为79mol%Li2B2O4。在BaB2O4-Li2O截面中也存在化合物4BaB2O4·Li2B2O4,其包晶反应温度从930±3℃随Li2O含量增加下降到908±3℃。在组分60mol%Li2O处形成另一个新的化合物2BaB2O4·3Li2O。该化合物在630±3℃也是由包晶反应形成,并与Li2O和Li2CO3分别形成共晶反应,共晶温度分别为400±3℃和612±3℃。在BaB2O4-Li2B2O4和BaB2O4-Li2O体系中都没有观察到固溶体。用计算机程序分别对化合物4BaB2O4·Li2B2O4和2BaB2O4·3Li2O的X射线粉末衍射图案进行了指标化,其结果:4BaB2O4·Li2B2O4的空间群为Pmma,a=13.033?,b=14.630?,c=4.247?,每个单胞包含两个化合式单位;2BaB2O4·3Li2O的空间群为Pmmm,a=4.814?,b=9.897?,c=11.523?,每个单胞也含有两个化合式单位。
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D. L. Khalyapin P. D. Kim J. Kim I. A. Turpanov A. Ya. Beten’kova G. V. Bondarenko T. N. Isaeva I. Kim 《Physics of the Solid State》2010,52(9):1787-1796
This paper reports on a study of multilayer Co/Cu films with an effective thickness of the Co layer of ~3.5 Å, which were prepared by magnetron sputtering. The samples prepared have been found to have a metastable multiphase structure. An analysis of the data obtained by structural and, primarily, by magnetic methods has revealed that the main phases are the Co/Cu supersaturated solid solution (alloy) with a Co concentration of about 30 at %, the superparamagnetic phase, and the paramagnetic phase, which is accounted for by the presence of small (a few atoms at most) Co clusters embedded in the Cu matrix. A clearly pronounced maximum in the temperature dependences of the low-field magnetoresistance has been found, which is associated with the temperature of the magnetic phase transition of the supersaturated Co-Cu alloy. 相似文献
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A Ni-P solid solution phase was obtained by quenching of melts under a pressure of 4.5 GPa. This was considered as a metastable high pressure phase. Despite the lack of thermodynamic parameters for Ni80, P20 alloy under pressure, the degree of undercooling, nucleation frequency and crystal growth velocity were calculated. We conclude that metastable phases with the same composition as the melting phase, such as supersaturated solid solution phase and amorphous phase, are easily prepared by high-pressure quenching. 相似文献
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Jürgen Jung Michael Fricke Gabriele Hampel Jürgen Hesse 《Hyperfine Interactions》1992,68(1-4):275-278
Among the three possible phase structures (bcc, fcc and hep) of iron rich Fe100-cMn c alloys (c Mn <40 at%), the two closed packed structures, fcc and hep, produce poor resolved and similar Mössbauer spectra. Therefore the evaluation of spectra collected on a sample (nominalc Mn =35 at%) with coexisting fcc and hep phases only was possible with the help of the Afans’ev/Tsymbal method of “Mössbauer lines sharpening” introduced recently/1,2,3/. A comparison of the hyperfine field vs. temperature with an FeNi-Invar alloy (c Ni =35 at%) shows a surprising similarity. 相似文献
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在Ag38.5Cu33.4Ge28.1三元共晶合金的深过冷实验中,获得的最大过冷度为175 K(0.22TE). XRD分析表明,不同过冷条件下其共晶组织均由(Ag),(Ge)和η(Cu3Ge)三相组成. 在小过冷条件下,三个共晶相协同生长,凝固组织粗大.随着过冷度的增大,共晶组织明显细化,(Ge)相与其他两相分离,以初生相方式生长,而(Ag)相与η相始终呈二相层片共晶方式共生生长. 当过冷度超过80 K时,初生相(Ge)由小过冷时的块状转变为具有小面相特征的枝晶方式生长. 部分小面相(Ge)枝晶出现规则的花状,花瓣数介于5—8之间,并且过冷度越大(Ge)相越容易分瓣. 花状(Ge)枝晶的晶体表面为{111}晶面簇,择优生长方向为〈100〉晶向族.
关键词:
三元共晶
晶体形核
深过冷
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