Kinetics and thermodynamics of hydrogen absorption in the Zr(Al0.1Fe0.9)2 intermetallic compound

Thermodynamic and kinetic characteristics of hydrogen absorption in Zr(Al_0.1Fe_0.9)₂ were investigated at pressures up to 80 atm of H₂ and temperatures between 248 K and 270 K. The heat and entropy of formation of the Zr(Al_0.1Fe_0.9)₂ hydride are estimated to be −24.7 kJ/(mole H₂) and −120 J/(K^*mole H₂), respectively. Small, well-defined samples were utilized for the kinetic research. The experimental kinetic data fit a shrinking core (sc) model, in accord with a visual examination of partly hydrided samples. The pressure dependence of the rate constants indicates an interface-controlled phase transition as the hydride formation rate-determining step. The activation energy for the hydriding process is estimated from Arrhenius plots of the reaction rates to be 0.30 eV/H atom. The kinetic data are discussed in view of similar results for additional intermetallic compounds.     

种子层(Ni0.81Fe0.19)1-xCrx成分及厚度对Ni0.81Fe0.19薄膜磁性和微结构的影响

用直流磁控溅射方法制备了性能优良的以(Ni0.81Fe0.19)1-xCrx为种子层的Ni0.81Fe0.19薄膜,研究了种子层成分及厚度对薄膜磁性和微结构的影响,结果表明当种子层(Ni0.81Fe0.19)0.63Cr0.37厚度为5.5 nm时,Ni0.81Fe019(20.0 nm)薄膜的各向异性磁电阻(AMR)值为(2.53±0.06)%;当Cr的含量为0.36时,Ni0 81Fe0.19(60.0 nm)薄膜的AMR值为(3.35±0.06)%.AFM及XRD研究表明不同厚度缓冲层(厚度分别为2.8,5.5和8.3 nm)的Ni0.81Fe0.19(20.0 nm)薄膜表面平均晶粒尺寸基本都为35.2 nm,但其111织构相差很大,AMR值最大时,对应的111衍射峰最强;不同Cr含量(分别为0.28,0.36和0.41)的Ni0.81Fe0.19(60.0 nm)薄膜表面平均晶粒尺寸和111衍射峰相差都很明显,AMR值最大时,对应地薄膜表面平均晶粒尺寸最大,Ni0.81Fe0.19111衍射峰也最强.     

Ni-Al-Fe系中NiAl(Fe)金属间化合物的析出强化

研究Ni-Al-Fe系中B2型金属间化合物NiAl(Fe)的硬度随时效时间的变化,同时测定时效处理后含析出相的NiAl(Fe)金属间化合物的屈服强度随温度变化。结果表明,在所有实验温度区域内,NiAl(Fe)化合物的屈服强度均远高于单相NiAl;析出相为体心立方结构的α-Fe相;在时效初期α-Fe相呈球状,过时效之后变成平行于有序基体{100}晶面的板条状。通过透射电镜观察还确定变形过程中位错滑移矢量为111。虽然α-Fe析出相的硬度低于NiAl(Fe)基体,但由于α-Fe析出相对运动位错有较强的钉扎作用而使基体得到强化。     

Mg-Y体系金属间化合物扩散生长行为的计算模拟

Mg-Y基稀土合金体系中,金属间化合物在基体中的析出和生长动力学与合金性能密切相关,研究金属间化合物的扩散生长行为具有重要意义。本工作针对已有ε-Mg₂₄Y₅和δ-Mg₂Y金属间化合物形成和生长的扩散偶实验数据,采用数值反演方法计算得到了Mg-Y基稀土合金体系中,固溶体相和金属间化合物相的互扩散系数随成分和温度的变化关系。结果表明,ε-Mg₂₄Y₅的扩散系数约为δ-Mg₂Y的扩散系数的4倍。同时,采用计算的扩散系数可以定量模拟出实验所测量的元素扩散分布、扩散通量以及金属间化合物层的生长厚度随时间和温度的变化关系。     

Corrosion behavior of Fe(Ni)CrAIX alloys in an HCl−H2O−H2 gas mixture at 800°C

The high-temperature-corrosion behavior of a series of Fe(Ni)CrAlX-type alloys (where X=Zr and Hf, e.g.) has been studied in a gas mixture of 50% HCl-10% H₂O–H₂ at 800°C. The experimental results obtained indicated that Ni-base alloys had superior corrosion resistance to Fe-base alloys in this gas mixture. While the exposed Ni-base alloys showed weight gains due to the formation of oxides (e.g., Al₂O₃, Cr₂O₃) as well as CrCl₂, the Fe-base alloys exhibited substantial weight losses resulting from the formation and subsequent evaporation of FeCl₂. This study also demonstrated that Fe(Ni)Cr8AlX-type alloys, which contained high aluminum, had better chloridation resistance than Fe(Ni)25CrAlX-type alloys, which had high chromium. The improved performance of Fe(Ni)Cr8AlX-type alloys was due to the presence of a high level of aluminum which promoted formation of protective Al₂O₃. Although the presence of chromium in the alloys promoted the formation of Cr₂O₃, the high level of chromium adversely affected the chloridation resistance of Fe(Ni)25CrAlX-type alloys, due to the development of chloride (CrCl₂) at the interface of the oxide scale and alloy substrate.     

95W-5（Ni／Fe／Co）合金高温变形及影响因素

通过温度、应变速率对95W-5（Ni／Fe／Co）合金流变应力曲线的影响，分析了该合金的变形特点。结果表明：该合金在200℃～600℃温度范围内变形时，初始加工硬化十分显著。宏观上表现为合金的屈服强度较高。95W-5（Ni／Fe／Co）合金在700℃～1300℃的流变应力曲线有一明显的特点就是曲线的斜率变小，而且出现短暂稳定态的流动。这是由于粘结相发牛动态回复的结果。此外该合金的高温塑性亦随应变速率的增大而增加。扫描电镜分析结果从微观上验证了该合金高温塑性变化的原因。     

Ni对Al-5％Fe合金中初生Al3Fe相形貌的影响

采用普通熔铸方法研究了Ni对Al-5％Fe合金铸态组织的影响。结果表明，Ni可明显改善合金中初生Al3Fe相形貌。不加Ni时，合金中的初生Al3Fe相大多为针状、针片状；加入0．2％～1．0％Ni时，Al3Fe相转变为细小针状，针点状和花朵状；Ni含量超过1．0％时，组织开始粗化，出现粗大的长针状Al3Fe相。     

乙醇-水体系电沉积制备Ni(OH)2超级电容器正极材料的研究

采用电化学共沉积技术在泡沫镍基体上制备了掺杂Co的Ni（OH）2电极,研究了乙醇与水体积比为3：7,1：1和7：3及水溶液情况下,C／Ni（OH）,超级电容器的容量特性。XRD分析表明,所得产物为掺杂Co的a—Ni（OH）2;电池测试表明在乙醇与水体积比为1：1时,能获得最好的电化学充放电特性,在小电流4mA／cm^2充放电下,比容量达850F／g;在大电流32mA／cm^2充放电下,比容量可达600F／g,其比容量数值随循环次数增加逐渐趋于稳定。扫描电镜观察表明,乙醇与水体积比为1：1时所得电沉积Ni（OH）2呈细小的蜂窝状三维结构,增大了活性物质与电解液接触的比表面积,使电化学反应更加充分,提高了活性物质的利用率和放电比容量。     

稀土La在纳米晶（W, Ni, Fe, La）复合粉末烧结过程中的作用机理

采用溶胶-喷雾干燥法制备纳米晶(W,Ni,Fe,La)复合粉末,研究了粉末在烧结过程中La对抑制鼓泡和晶粒长大的作用机理,通过XRD与SEM分析了La在烧结过程中的相转变规律和在合金中的存在形式,讨论了稀土La对合金液相烧结过程中扩散的影响。结果表明:稀土La在纳米复合粉末中主要以La2WO6与La4W2O15的形式存在。经液相烧结后,稀土La主要以二次相颗粒的形式分布于粘结相中,生成高温下能稳定存在的La4W2O15相,该相对杂质元素Ca、O具有很好的亲和力,起到晶界净化和晶内净化的作用。同时二次相颗粒存在于粘结相中,抑制了W在粘结相中的扩散,降低了W在粘结相中的溶解度,使得液相烧结溶解-析出过程减慢,从而抑制液相烧结阶段的晶粒长大和鼓泡现象。     

Surface Modification of Li1.6(Fe0.2Ni0.2Mn0.6)O2.6 by V2O5- Coating

在采用低温共沉淀-水热-煅烧法合成锂离子电池Fe-Ni-Mn体系正极材料Li1.6(Fe0.2Ni0.2Mn0.6)O2.6的基础上,对合成的材料Li1.6(Fe0.2Ni0.2Mn0.6)O2.6进行V2O5的包覆改性研究,以提高材料Li1.6(Fe0.2Ni0.2Mn0.6)O2.6的首次放电比容量和循环性能。用XRD、SEM、TEM、ICP光谱和恒流充放电测试研究包覆材料的结构和电化学性能。结果表明,V2O5包覆并没有改变材料的晶体结构,只存在于材料的表面,与未包覆的材料相比,V2O5包覆后的材料具有更好的首次放电容量和容量保持率。50周循环后,添加质量分数3%V2O5样品Li1.6(Fe0.2Ni0.2Mn0.6)O2.6的放电比容量可以维持在200.3 mAh/g,大于未添加V2O5样品Li1.6(Fe0.2Ni0.2Mn0.6)O2.6的194.0 mAh/g。CV测试表明,包覆层的存在有效抑制了材料层状结构的转变及电极与电解液的负反应。     

碱性溶液环境中CrSi(Ni,Al)电阻薄膜的电学稳定性及劣化机理

研究磁控溅射法制备的Cr-Si-Ni和Cr-Si-Ni-Al电阻薄膜在模拟的碱性环境（NaOH溶液）中,介质溶液浓度和温度对薄膜电学稳定性的影响及其机理。结果表明：经热处理后呈纳米晶结构的2种薄膜在低温低浓度的碱性溶液中具有较好的电学稳定性和耐腐蚀性能,但是,随着溶液浓度和温度的增大其电学稳定性和耐腐蚀性能急剧下降,特别是在高温高浓度的碱性溶液中薄膜在很短时间内就出现性能劣化现象;2种薄膜在低温低浓度的碱性溶液中能够迅速地在膜层表面形成稳定的钝化保护层,从而有效地抑制溶液离子对薄膜内层的进一步腐蚀;而在高温或高浓度的碱性溶液中薄膜表面难以形成稳定的钝化保护层。     

磁一级相变La(Fe,Si)13基化合物的研究进展

对NaZn13型La(Fe,Si)13化合物在磁性、相变特性及磁熵变规律和制备方法等方面的研究进展进行总结和论述.低Si含量的La(Fe,Si)13化合物具有良好的软磁特性,表现出特殊的磁相变特征:在居里温度处的热诱导一级磁性转变和高于居里温度时的磁场诱导巡游电子变磁性转变,并伴随着巨大的磁熵变和磁致伸缩.随Si含量增高,化合物的这种特殊磁相变特征逐渐减弱,呈现二级相变特征.总结了元素替代和添加对La(Fe,Si)13化合物性能的影响,一定的合金化可以改变居里温度并保持巨大的磁熵变,这对于近室温磁致冷有着重要意义.快速凝固技术的应用解决了化合物合成困难的问题,降低了材料的制造成本,使得NaZn13型La(Fe,Si)13化合物成为最有应用前景的近室温磁致冷工质之一.本文还探讨了这种化合物用做磁致伸缩材料的可能性.     

Formation of the Fe(II)-Fe(III) hydroxysulphate green rust during marine corrosion of steel

Rust layers formed on steel sheet piles immersed 1 m above the mud line for 25 years were analysed by Raman spectroscopy, scanning electron microscopy and elemental X-ray mappings (Fe, S, O). They consist of three main strata, the inner one mainly composed of magnetite, the intermediate one of iron(III) oxyhydroxides and the outer one of hydroxysulphate green rust GR(SO₄²⁻). Simulations of GRs formation in solutions having large [Cl⁻]/[SO₄²⁻] ratios revealed that the hydroxysulphate GR(SO₄²⁻) was obtained instead of the hydroxychloride GR(Cl⁻), as demonstrated by X-ray diffraction and transmission Mössbauer spectroscopy analyses. Measurements of the [S], [Fe] and [Cl] concentrations allowed us to establish that GR(SO₄²⁻) formed along with a drastic impoverishment of the solution in sulphate ions; the [Cl⁻]/[SO₄²⁻] ratio increased from 12 to 240. The GR, acting like a “sulphate pump”, may favour the colonisation of the rust layers by sulphate reducing bacteria.     

Microstructure evolution in Ni and Ni-superalloy based metallic-intermetallic laminate (MIL) composites

Pure nickel and Nickel Alloy-X based Metallic-Intermetallic Laminate (MIL) composites were fabricated and investigated for their microstructure evolution, growth kinetics and microhardness distribution across the intermetallic/metal interfaces. Multi-phase layer structure with parabolic growth kinetics is shown in the nickel-based MIL composites. A two-phase eutectic layer along with a uniform layer form in the Alloy-X based MIL composites, which shows a mixed growth kinetic mechanism. The microhardness distribution across the intermetallic/metal interface of the two MIL composites was investigate with respect to the effects of texture and microstructure of the intermetallic phases. A simple intermetallic growth model is developed and validated for predicting the phase formation in binary or ternary reactions for synthesis of these MIL composites.     

Crystal structure of (TiHf)Ni phase formed in a 20Ti−50Ni−30Hf (at.%) alloy

The crystal structure of the (TiHf)Ni phase formed in a 20Ti−50Ni−30Hf (at.%) alloy was investigated by means of transmission electron microscopy and X-ray diffraction, and was found to be rhombohedral whose lattice parameters were a=0.4887 nm and α=83.3°. The atomic positions of the Ti(Hf) atoms in the rhombohedral structure of the precipitates were assumed to be Ti=0 0 0, × 1/2 0, × 0 1/2, × 1/2 1/2, and those of the Ni atoms were known to be Ni=1/2 1/2 1/2, 0 0 1/2, 0 1/2 0, 1/2 0 0.     

Nd3（Fe,Mo）29化合物及其氮化物的磁结构和内禀磁性

制备了具有Nd3（Fe,Ti）29型单斜结构的单相铁基金属间化合物Nd3（Fe,Mo）29及其氮化物,详细研究了：其在4．2K～300K之间的磁结构;磁晶各向异性;居里温度Tc,饱和磁化强度σs等内禀磁性。研究结果表明：Nd3（Fe,Mo）29金属间化合物氮化后仍保持母相结构,氮化后的晶胞体积,居里温度Tc和饱和磁化强度σs分别比氮化前提高了5．9％,70．9％,6．6％;N3d（Fe,Mo）29金属间化合物在230K左右存在自族重取向,温度低于230K时,其磁晶各向异性为锥面,温度高于230K时,其磁晶各向异性为易面;氮化后自族重取向消失。     

电极材料非晶态氢氧化镍的电化学活性

通过快速冷冻沉淀法制备非晶态氢氧化镍粉体，微粒形状不规则，具有较小粒度分布和较大比表面积。经测量，发现其样品粉体拉曼光谱（Raman）峰较多，差热分析（DSC）发现其分解温度较低，为295．18℃，结果分析表明活性较高。将所制备的非晶态Ni（OH）2粉体作为活性物质合成正极材料，并组装成MH—Ni碱性模拟电池，在恒流50mA／g下充电8h，25mA／g下放电，终止电压为1．0V时，其放电工作电压平稳且时间长，放电平台为1．26v。放电比容量可达333．22mAh／g，高于β-Ni（OH）2的理论比容量289mAh／g，循环伏安曲线的测试结果表明，可逆性能较好，在碱性电解液中结构稳定。     

双氧水水热处理泡沫镍制备 Ni(OH) 2 自集流超级电容器电极材料

目的寻找一种简便、价廉、对环境友好的方法制备具有高比容、长寿命的Ni(OH)2自集流超级电容器电极材料。方法采用水热法(15%(质量分数)的H2O2溶液,180℃,24 h)直接在泡沫镍集流体上原位生长Ni(OH)2,并对其形貌、组成以及电化学性能进行研究。结果通过双氧水水热处理,可以在泡沫镍集流体上原位生长出边长400~600nm、厚度约200nm的Ni(OH)2六边形片,此为六方晶的β-Ni(OH)2。该电极材料在2mol/LKOH溶液中的最高比容为2534F/g(扫速1mV/s),且循环1000圈后,比容值仍保持在91%以上(扫速为50mV/s)。结论该制备方法简单价廉,对环境友好,制得的电极材料具有自支撑、自集流的特点,且具有优异的电化学性能和良好的循环稳定性。     

Fe/Cr比对Zr(Fe,Cr)2吸氢性能的影响

参照锆合金中的第二相成分,熔炼2种不同Fe/Cr比的Zr(Fe,Cr)2(Fe/Cr=2和0.5)和ZrCr2(Fe/Cr=0)3种试验合金,对它们进行压力-成分-温度(P-C-T)测试和吸放氢动力学测试。同时用XRD对360℃吸氢前后的样品进行物相分析。实验结果表明,这3种合金在50,200,360℃3个温度下,均有吸氢量随Fe/Cr比值的降低而增加的现象。另外,在360℃,4MPa氢气气氛中测试时,这3种不同合金的可逆吸放氢量和吸放氢速度随Fe/Cr比的降低而增加。XRD测试表明,在360℃吸氢后并没有氢化物生成。