Thermoelectric Properties of CexCo4Sb12 Prepared by MA-SPS

Starting with elementary powders, thermoelectric materials CexCo4Sb12 were prepared by mechanical alloying and spark plasma sintering (MA-SPS). XRD analyses reveal that the expected major phase, named skutterudite was formed in MA process and was kept after SPS. The thermoelectric properties of MA-SPS samples including resistivity, Seebeck coefficient, power factor, thermal conductivity and the dimensionless figure of merit (ZT) were studied by varying Ce content and temperature. Depending on Ce levels, both P and N types of thermoelectric semiconductors were obtained. MA-SPS sintered Ce1.0Co4Sb12 exhibits the highest ZT in the range of 100-500℃ and the maximum ZT is found at x=1.0 and 400℃.     

Rapid Preparation and Thermoelectric Properties of NdxCo4Sb12 Compounds

ratory of Advanced Functional Materials, Ministry of Education, Beijing University of Technology,Beijing 100022, China )     

Thermoelectric Properties of （Ce, La）yFe1.0Co3.0Sb12 Compounds Syntiesized by Solid State Reaction

The filled Skutterudite compounds (Ce,La)yFexCo4-xSb12 with x= 1.0 and y=0-0.3 were synthesized by solid state reaction and Spark PlasmaSintefing (SPS) using powders of Co, Sb, Fe and rare earth Ce, La as starting materials. The thermoe-lectric properties of the compounds were also studied.It is shown that the almost single phase Skutterudite compounds (Ce, La)yFex Co4-xSb12 are synthesized at900-1000K and all samples show p-type.     

Thermoelectric properties of Yb x Co_4 Sb_（12） system

Yb x Co 4 Sb 12 polycrystals were fabricated by vacuum melting combined with hot-press sintering.The effect of Yb-filling on thermoelectric property of unfilled skutterudite CoSb 3 was investigated,which indicated the enhancement of the power factor of the material.Transport properties of materials changed from semi-conductor to semi-metal during the measurement of electrical conductivity,which indicated the change of electronic band structure.The maximum value of electrical conductivity was about 190000 S/m at 300 K for all samples.On the basis of Yb-filling,power factor of Yb 0.2 Co 4 Sb 12 reached 5-6 mW/(m·K) during the measurement temperature.Thermal conductivity decreased with increase of Yb content,and the thermal conductivity of Yb 0.2 Co 4 Sb 12 reached 3.2 W/(m·K) at 600 K.The ZT value of Yb 0.2 Co 4 Sb 12 reached 1.16 at 700 K due to positive contribution from high power factor and low thermal conductivity.     

Characterization of α-Fe-Free Heteroepitaxial NdFe12−x Ti x Thin-Film Materials with a Novel Cubic Laves Fe2Ti Phase

Thin films with compositions of NdFe₁₂ and NdFe₁₁Ti₁ were fabricated on W-buffered MgO(001) substrates of varying roughness. In this study, X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the films microstructurally, chemically, and crystallographically. This study revealed successful heteroepitaxial synthesis of the tetragonal NdFe₁₂ and NdFe_12−x Ti _x phases in the Ti-free and Ti-containing films, respectively, both with surface-normal c-axis orientation. It also revealed the presence of other phases within the magnetic layer. The NdFe₁₂ films contained many α-Fe particles, which preferentially precipitated at locally rough regions of the W-buffer interface. The NdFe₁₁Ti₁ film showed the ubiquitous presence of an Fe₂Ti phase, which covered most of the buffer thereby preventing the formation of α-Fe. This phase was determined to have a novel Cu₂Mg-type cubic Laves (C15) crystal structure with fourfold interfacial symmetry, good coherency, and a low mismatch with the W-buffer, thus rendering itself as being an ideal interface for the heteroepitaxial synthesis of NdFe_12−x Ti _x crystals. It is proposed that successful application of a cubic Fe₂Ti underlayer on W can contribute to the development of a fabrication strategy for NdFe₁₂ thin films without the presence of soft magnetic α-Fe.

     

聚苯胺/Co0.5Zn0.5La0.1Fe1.9O4复合材料的表征及电磁损耗

采用原位聚合法制备聚苯胺（Pani）/复合材料,使用X射线衍射仪（XRD）、扫描电子显微镜（TEM）和紫外可见吸收光谱（UV-vis）对复合材料进行了表征。XRD结果表明样品为纯Pani和Pani/Co0.5Zn0.5La0.1Fe1.9O4复合材料,SEM照片可知,纯Pani和Pani/Co0.5Zn0.5La0.1Fe1.9O4粒子的平均粒径分别约为150 nm和500 nm,UV-vis光谱表明Pani/Co0.5Zn0.5La0.1Fe1.9O4苯环上的π-π＊和n-π＊分别红移了13 nm和10 nm.在8.2-12.4GHz测试频率范围内,Pani/Co0.5Zn0.5La0.1Fe1.9O4复合材料的介电损耗角正切（tgε）在0.22-0.34之间,磁损耗正切（tgμ）在0.27-0.35之间.     

Synthesis and Thermoelectric Properties of Ca2.6Nd0.4 Co4O9 Compound

Atemperaturedifferenceappliedacrossasolidgeneratesanelectromotiveforce ,characterizedbythethermoelectricpowerofthesolid .ThisphenomenonisnamedSeebeckeffect .Metaloxidematerialswithhighthermoelectricpropertiesaregoodcandidatesforappli cationtothermoelectricpowergenerationbecausefig ureofmeritZ ,definedasZ =S2 σ/κwhereS ,σ ,κaretheSeebeckcoefficient ,electricalconductivityandthermalconductivity ,respectively ,canevaluatetheperformanceofthermoelectricmaterials .Severalsystemshavebeeninvesti…     

纳米颗粒Ag2Te掺杂p-(Ag2Te)x(Bi0.5Sb1.5Te3)1-x的快速热压制备和热电性能表征

通过溶剂热法制备出六方相Bi2 Te3纳米粉体,采用真空封管熔炼法得到Sb掺杂的Bi0.5Sb1.5Te3合金.采用溶剂热法合成粒度为40 nm的Ag2 Te纳米粉体,并通过高能球磨工艺将其掺入Bi0.5Sb1.5Te3合金,从而得到p-(Ag2 Te)x(Bi0.5 Sb1.5 Te3)1-x合金(x为Ag2 Te摩...     

Effect of Mn Substitution on Microstructure Evolution and Magnetic Phase Transition in La(Fe1−x Mn x )10.8Co0.7Si1.5 Compounds

The influences of Mn substitution for Fe on microstructures of La(Fe_1?x Mn _x )_10.8Co_0.7Si_1.5 (x = 0, 0.01, 0.02, 0.03) alloys in both the as-cast state and the annealed state have been studied. The results show that Mn substitution promotes the fining of the as-cast microstructure and increases the formation of 1:13 phase significantly when annealed. An almost single 1:13 phase is obtained for x = 0.01 when annealed at 1373 K (1100 °C) for 3 days, while a large amount of impurity phases is still present for x = 0. By increasing the amount of Mn to x = 0.02, a more purified annealed microstructure can be obtained. However, further substitution of Mn up to x = 0.03 is harmful for the formation of 1:13 phase. The Curie temperature T _C of the annealed La(Fe_1?x Mn _x )_10.8Co_0.7Si_1.5 (x = 0, 0.01, 0.02, 0.03) varies monotonously with Mn content x, decreasing from ~279 K (6 °C) for x = 0 to ~236 K (?37 °C) for x = 0.03. When x = 0.01, a higher maximum entropy change (?ΔS)_max of 5.3 J/(kgK) and relative cooling power (RCP) of 166 J/kg can be obtained under a magnetic field of 2T. Further substitution of Mn (x = 0.02) results in a slight decrease of (?ΔS)_max, whereas a larger RCP can still be kept.     

Characterization of an Al-Y-Zn Intermetallic Particle Phase in Extruded Mg96−x Al x Zn2Y1.9La0.1 Alloys

This study focuses on extruded Mg_96?x Al _x Zn₂Y_1.9La_0.1 alloys, which contain the long period stacking ordered Mg₁₂ZnY phase. The presence of Al results in the precipitation of Al-Y-Zn precipitates, the crystal structure of which is not adequately described by ternary Al-Y-Zn phases reported in the literature. Therefore, the purpose of this investigation is to characterize the precipitates morphologically, chemically, and crystallographically. After casting, the precipitates exist as complexly shaped micron-scale clusters within the microstructure. After extrusion, the phase appears as slightly faceted particles with a plate-like morphology. The crystal structure is hexagonal and its space group is $ P6_{3} /mmc $ . For the specific composition of Mg_95.50Al_0.50Zn₂Y_1.9La_0.1, the lattice parameters of this ternary phase are a ≈ 8.98 Å and c ≈ 7.1 Å and the stoichiometry is near equiatomic. However, with decreasing Al content of the alloy, the c parameter, degree of atomic ordering, and Zn content of the phase are all observed to increase. Specifically, for Mg_95.75Al_0.25Zn₂Y_1.9La_0.1, c ≈ 7.3 Å, and the stoichiometry is approximately AlYZn₂.     

Magnetic Properties of Melt-Spun Nanocomposite PrloFe74-x Co10＋x C4B4（x=0,2,4,6,8） Ribbons

Phase evolution and magnetic properties of melt-spun Pr10Fe74-xCo10 xC4B4(x=0,2,4,6,8 ) alloy ribbons were investigated. Increasing the Co content is found to promote the generation of the 2: 14:1 phase, which results in a significant increase of coercivity and remanence.     

Effect of Nb Content on Mechanical Behavior and Structural Properties of W/(Zr55Cu30Al10Ni5)100−x Nb x Composite

In the present study, (Zr₅₅Cu₃₀Al₁₀Ni₅)_100−x Nb_(x=0,1,2,3) bulk metallic glass matrix/tungsten wire composites were fabricated by infiltration process. Structural studies were investigated by scanning electron microscopy and X-ray diffraction method. Also, mechanical behaviors of the materials were analyzed using quasi-static compressive tests. Results indicated that the best mechanical properties i.e., 2105 MPa compressive ultimate strength and 28 pct plastic strain before failure, were achieved in the composite sample with X = 2. It was also found that adding Nb to the matrix modified interface structure in W fiber/(Zr₅₅Cu₃₀Al₁₀Ni₅)₉₈Nb₂ since the stable diffusion band formation acts as a functionally graded layer. Finally, the observation of multiple shear bands formation in the matrix could confirm the excellent plastic deformation behavior of the composite.

     

Influence of annealing on spin state of cobalt ions in La1-xSrxCoO3（0≤x≤0.5） system

Perovskite oxide La1-xSrxCoO3 (0≤x≤0.5) series were prepared and effect of oxygen annealing on crystal structure and magnetic susceptibility were studied. High-temperature susceptibility could be well fitted by Curie-Weiss law for all Sr-doped samples. Weiss constant and effective magnetic moment were determined, and their variations with Sr doping and oxygen annealing condition were obtained. The result suggested that by assuming that the Co3+ ions were in the intermediate-spin (IS) state, most of the Co4+ ions in the as-prepared samples might be in the high-spin (HS) state, but both the Co3+ and Co4+ ions might be in the IS state after oxygen annealing, which indicated that annealing in flowing oxygen could cause transition of the spin state of Co4+ ions from the HS state to IS state.     

Preparation of binary single-phase line compounds via diffusion couples: The subnitride phases η-Hf3N2−x and ζ-Hf4N3−x

It is shown that diffusion couples allow the preparation of pure line compounds, i.e. compounds with a very narrow homogeneity region, which are otherwise difficult or even impossible to prepare in single-phase form. With appropriate reaction conditions even a line compound forms a relatively large core in a symmetric diffusion couple of “finite” plane-sheet diffusion geometry due to the formation of a flat diffusion profile in the centered phase. The core of such a diffusion couple can then be isolated to obtain single-phase (and compact) material. This was shown for the phases η-Hf₃N_2−x and ζ-Hf₄N_3−x, which have a homogeneity region of only 2.5 at.% and <1 at.% N, respectively, in the temperature range of 1200–1700°C. The diffusion process was characterized by computational simulation, metallography, EPMA and XRD. By means of powder XRD and chemical nitrogen analysis it was possible to obtain more precise data on the two subnitride phases. η-Hf₃N_2−x has hexagonal lattice parameters of a = 0.32124(1) and c = 2.32790(10)nm for [N]/([Hf] + [Zr]) = 0.58(1) and 2.5 wt%Zr, and ζ-Hf₄N_3−x has hexagonal lattice parameters of a = 0.32084(1) and c = 3.10800(9)nm for [N]/([Hf] + [Zr]) = 0.62(1) and 3.1 wt%Zr. By this technique a single-phase sample of a ζ-phase, ζ-Hf₄N_3−x, could be prepared for the first time.     

Synthesis, Structure and Ionic Conductivity of La2／3-x Li3x MoO4

AlargenumberofM0 .5A0 .5M′O4 (M :rareearthion ,Bi3+,Fe3+,Cr3+,etc .A :alkaliion ,Cu+,Ag+,etc .M′ :Mo ,W )withtetragonalscheelite typestructurehavegoodcatalyticproperties .Aslumines centsubstrates ,theyhaveexcellentsensitizationtolu minescenceofrareearthion .Manyresearchesontheirstructure ,catalytic ,magneticandluminescentproper tieshavebeenmadesince 196 0s[1～ 10 ] .Thegeneralformulaforcompoundswiththetetragonalscheelite typestructureisAM′O4 wherethecationM′istetrahe drallycoordinat…     

Magnetic Transition of La0.8Sr0.2Mn1-xCoxO3（x =0, 0.3, 0.5, 1.0）

A series of rare earth compound oxides with the formula of La0.8Sr0.2Mn1-xCoxO3（ were prepared by the method of citric acid. Structures, figures and magnetic properties of the x=0.0, 0.3, 0.5, 1.0） samples were analyzed by means of XRD, SEM and SQUID. Experiment results prove that all the samples are hexagonal, but their figures and magnetic properties are different. La0.8Sr0.2MnO3 is ferromagnetic. La0.8Sr0.2Mn0.7CO0.3O3 and La0.8Sr0.2Mn0.5Co0.5O3 are ferrimagnetic. La0.8Sr0.2CoO3 is antiferromagnetic. SEM results indicate that the structure of the first three are three-dimensional reticulations which are made up of some small ellipsoids which link up at the head and the end. The fourth sample looks like some dispersed small balls.     

Evaluation of Mechanical and Tribological Behavior of Al–4 %Cu–x %SiC Composites Prepared Through Powder Metallurgy Technique

This article presents characterization of 99.85 % pure aluminum with 4 % copper, reinforced with varying proportions of silicon carbide. Al–Cu–SiC metal matrix composite (MMC’s) are prepared by powder metallurgy route for 0, 2.5, 5, 7.5, 10, 12.5 and 15 % of SiC addition. To investigate the effects of adding SiC particles, microstructural analysis and mechanical properties by micro-hardness, compression, wear and thermal conductivity are studied. Scanning electron microscope image shows uniform distribution of particulates. Results show that upon increasing addition of SiC particles, micro-hardness and compression strength increases, whereas thermal conductivity decreases. Wear rate increases till 7.5 % SiC addition, with further addition of SiC, wear rate increases due to the un-bonding of SiC particles from the MMC, aiding in the increase of wear rate. Addition of SiC up to 7.5 % play an important role in improving wear resistance, thermal and mechanical properties of Al–Cu–SiC MMC.     

Dependence of the lattice parameter of {\gamma '} iron nitride,Fe4N1−x,on nitrogen content; Accuracy of the nitrogen absorption datairon nitride,Fe4N1−x,on nitrogen content; Accuracy of the nitrogen absorption data

Pure iron foils were converted into { \(\gamma ' - Fe_4 N_{1 - x} \) } foils of various compositions by means of nitriding in selected NH₃/H₂ gas mixtures at 803 and 843 K. The lattice parameter and the linear thermal expansion coefficient of { \(\gamma ' - Fe_4 N_{1 - x} \) } nitride and the surrounding gas atmosphere.