超声辅助对共沉淀法制备富锂锰基正极材料Li[Li_0.144Ni_0.136Co_0.136Mn_0.544]O₂性能影响的研究

通过超声辅助共沉淀法成功制备了富锂锰基正极电极材料,研究了不同的超声时间对材料形貌、结构和电化学性能的影响。研究发现,超声辅助能够使材料颗粒更加均匀,结构更合理,有利于材料电化学性能的提升。当合成前躯体材料超声时间为8h时,复合材料的放电比容量最好,在0.1C的初始放电比容量为327.8 mAh g_-1,均高于未超声的复合材料的265.2 mAh g_-1,1C下循环50圈后放电容量为181.6 mAh g_-1,保持率为84.8%。通过循环伏安法测试和电化学交流阻抗测试,发现超声后的复合材料还原氧化峰电流更大,电荷转移阻抗更小,具有较好的倍率性能。     

Isothermal section of the Er–Fe–Al ternary system at 800 °C

Physico-chemical analysis techniques, including X-ray diffraction and Scanning Electron Microscope–Energy Dispersive X-ray Spectroscopy, were employed to construct the isothermal section of the Er–Fe–Al system at 800 °C. At this temperature, the phase diagram is characterized by the formation of five intermediate phases, ErFe_12?xAl_x with 5 ≤ x ≤ 8 (ThMn₁₂-type), ErFe_1+xAl_1?x with ?0.2 ≤ x ≤ 0.75 (MgZn₂-type), ErFe_3?xAl_x with 0.5 < x ≤ 1 (DyFe₂Al-type), Er₂Fe_17?xAl_x with 4.74 ≤ x ≤ 5.7 (TbCu₇-type) and Er₂Fe_17?xAl_x with 5.7 < x ≤ 9.5 (Th₂Zn₁₇-type), seven extensions of binaries into the ternary system; ErFe_xAl_3?x with x < 0.5 (Au₃Cu-type), ErFe_xAl_2?x with x ≤ 0.68 (MgCu₂-type), Er₂Fe_xAl_1?x with x ≤ 0.25 (Co₂Si-type), ErFe_2?xAl_x with x ≤ 0.5 (MgCu₂-type), ErFe_3?xAl_x with x ≤ 0.5 (Be₃Nb-type), Er₆Fe_23?xAl_x with x ≤ 8 (Th₆Mn₂₃-type), and Er₂Fe_17?xAl_x with x ≤ 4.75 (Th₂Ni₁₇-type) and one intermetallic compound; the ErFe₂Al₁₀ (YbFe₂Al₁₀-type).     

NaCl-KCl-NdCl3-AlCl3熔盐体系电解制备Nd-Al合金及机理

在700℃的NaCl-KCl体系中,采用循环伏安法、方波伏安法和开路计时电位法等电化学测试方法研究了钨电极上Nd(Ⅲ)的电化学行为以及与Al(Ⅲ)共沉积的电化学过程。结果表明:在低扫描速率(0.1～0.5V·s~(-1))下,NaCl-KCl-NdCl_3熔盐中Nd(Ⅲ)的还原是一步交换3个电子的准可逆过程,该还原过程由扩散步骤控制,扩散系数约为1.2×10~(-5) cm~2·s~(-1)。将AlCl_3引入NaCl-KCl-NdCl_3熔体后,循环伏安、方波伏安以及开路计时电位测试结果表明,电解过程中形成了3种Nd-Al金属间化合物(Nd_3Al_(11)、NdAl_3和NdAl_2),其形成机理为Nd在预先沉积的Al上发生欠电位沉积。通过电动势法,计算了700℃时Nd-Al金属间化合物的热力学参数,如两相共存下Nd的活度和相对偏摩尔吉布斯自由能以及Nd-Al金属间化合物的标准吉布斯自由能。在-2.3 V下进行恒电位电解5 h制备了Nd-Al合金,所得合金由Nd_3Al_(11)、NdAl_3、NdAl_2和Al4种物相组成。     

Composition dependence of magnetic properties of directly quenched Nd-Fe-Ti-Zr-B bulk magnets

Magnetic properties, phase evolution, and microstructure of directly quenched Nd_yFe_97−y−zTi_3−xZr_xB_z (x = 0-3; y = 7-10; z = 14-19) bulk magnets of 0.9 mm in diameter have been investigated. Proper Zr substitution for Ti and appropriate Nd and B contents modify the magnetic phases constitution and refine the grain size from 200-250 nm to 50-100 nm. Consequently, the magnetic properties of the rods are enhanced remarkably from _iH_c = 6.2 kOe and (BH)_max = 5.6 MGOe for Zr-free rods to _iH_c = 6.7-13.5 kOe and (BH)_max = 6.7-8.2 MGOe for Zr-substituted Nd_yFe_97−y−zTi_3−xZr_xB_z rods (x = 0.5-2; y = 8-10; z = 14-16). The optimum magnetic properties of B_r = 6.6 kG, _iH_c = 9.6 kOe and (BH)_max = 8.2 MGOe were achieved for Nd_9.5Fe_72.5Ti_2.5Zr_0.5B₁₅ alloy.     

New ternary Yb5Sb3-type R5T1−x{Sb,Bi}2+x phases (R = Y,Dy, Ho,T = Co,Ru, Rh,Pd) and their magnetic properties

Several novel R₅T_1?x{Sb,Bi}_2+x phases having the Yb₅Sb₃-type structure (space group Pnma) have been synthesized. The cell parameters are: a = 1.20668(9), b = 0.88396(7), c = 0.78745(7) nm for Y₅CoSb₂; a = 1.19939(7), b = 0.88364(5), c = 0.78283(5) nm for Dy₅CoSb₂; a = 1.19633(8), b = 0.89231(6), c = 0.78450(6) nm for Ho₅RhSb₂; a = 1.18650(6), b = 0.90455(4), c = 0.79260(4) nm for Ho₅PdSb₂; a = 1.2215(3), b = 0.8948(2), c = 0.7977(2) nm for Y₅CoBi₂; a = 1.1781(8), b = 0.9071(7), c = 0.7936(6) nm for Tm₅Co_0.5Bi_2.5; a = 1.1972(1), b = 0.92096(9), c = 0.80048(9) nm for Ho₅RuBi₂; a = 1.2082(1), b = 0.90346(9), c = 0.79413(8) nm for Ho₅RhBi₂ and a = 1.20374(5), b = 0.91076(4), c = 0.80135(4) nm for Ho₅PdBi₂, respectively. Magnetization measurements indicate ferromagnetic transitions for Dy₅CoBi₂, Ho₅RhSb₂, Ho₅RhBi₂, Ho₅PdSb₂ and Ho₅PdBi₂ at T_C = 34, 38, 28, 42 and 38 K, respectively. The Ho₅RhSb₂ and Ho₅PdBi₂ compounds show additional magnetic transitions at about 18 K, probably associated with a spin reorientation. The magnetocaloric effect of Dy₅CoBi₂ in terms of the isothermal entropy change, ΔS_m, is ?6.2 J/(kg/K) at 38 K and in terms of the adiabatic temperature change, ΔT_ad, is 2.2 K for a 5 T field change.     

Measurement of interdiffusivity for fcc_A1 Co-V-W alloys

Combining the solid-solid diffusion couples and the electron probe microanalysis (EPMA) technique, the composition profiles of 15 ternary diffusion couples within single fcc_A1 Co-V-W alloys at 1373, 1423 and 1473 K were measured in the present work. The interdiffusivities were evaluated by means of composition profiles applied to Matano-Kirkaldy method, in which the uncertainties were calculated by error propagation and the reliability was validated via thermodynamic constraints. According to the measured main interdiffusivities ${\tilde{D}}_{\mathit{VV}}^{C\mathrm{o}}$ and ${\tilde{D}}_{\mathit{WW}}^{C\mathrm{o}}$, it is found that the diffusion of V in fcc_A1 Co is faster than that of W in fcc_A1 Co. The ternary main interdiffusion coefficients of ${\tilde{D}}_{\mathit{VV}}^{C\mathrm{o}}$ and ${\tilde{D}}_{\mathit{WW}}^{C\mathrm{o}}$ at different compositions were compared with the ones for boundary binary CoV and CoW systems in the literature. A normalized ternary interdiffusivity diagram, in which the ternary interdiffusivities ${\tilde{D}}_{\mathit{VV}}^{C\mathrm{o}}$ and ${\tilde{D}}_{\mathit{WW}}^{C\mathrm{o}}$ are plotted against the normalized ration of x(W)/(x(W) + x(V)), is proposed in the present work. Meanwhile, comprehensive comparisons of main interdiffusivity ${\tilde{D}}_{\mathit{XX}}^{C\mathrm{o}}$ in fcc_A1 Co-W-X (X = Al, V, Cr, Mo) alloys and ${\tilde{D}}_{\mathit{YY}}^{C\mathrm{o}}$in fcc_A1 Co-V-Y (Y = Al, Ti, Mo, W) alloys indicate that both of the main interdiffusivities decrease with the increase of atomic number. The present work provides interdiffusivties for the establishment of a kinetic database to computationally design the multi-component cemented carbides.     

Corrosion behavior of thermoelectric clathrates α- and β-Eu8Ga16−xGe30+x in air

The corrosion of thermoelectric clathrates α- and β-Eu₈Ga_16−xGe_30+x is studied under static air (DSC/TG) up to 650 °C. Oxidation product layers with thicknesses of 10.5 μm (α-Eu₈Ga_16−xGe_30+x) and 4.5 μm (β-Eu₈Ga_16−xGe_30+x) are formed. The oxidation begins at 360 and 380 °C, respectively. XRD pattern of the β-Eu₈Ga_16−xGe_30+x oxidized layer shows Ge and four Eu₂O₃ reflections; while α-Eu₈Ga_16−xGe_30+x data (sample crushed and grinded) shows α-Eu₈Ga_16−xGe_30+x reflections (majority phase), two EuGa_2±xGe_4?x strongest reflections and Ge (minority phases). These results indicate the amount of oxides is very small or they are amorphous. High temperature powder XRD measurements on α-Eu₈Ga_16−xGe_30+x under air confirm the oxidation onset temperature determined in DSC studies.     

High-speed deposition of Y-Si-O films by laser chemical vapor deposition using Nd:YAG laser

Y-Si-O films were prepared by laser chemical vapor deposition (LCVD) with a Nd:YAG laser using TEOS (tetraethyl orthosilicate) and Y(dpm)₃ precursors. The effects of laser power (P_L), deposition temperature (T_dep) and total chamber pressure (P_tot) on the phase, microstructure and deposition rate of Y-Si-O films were investigated. At P_L < 102 W (T_dep < 1140 K), amorphous Y-Si-O films were obtained independent of P_tot. At P_tot = 0.6 kPa, mixture phase films of Y₂SiO₅ (the X1 phase) and Y₂Si₂O₇ (the α, β, δ and y phases) were obtained at P_L = 102 W (T_dep = 1210 K), while single phase X1-Y₂SiO₅ films were prepared at P_L > 139 W (T_dep > 1280 K). Y₂Si₂O₇ mixture phase films were obtained at P_tot = 3.5 kPa and Y₂Si₂O₇ and Y₂SiO₅ (the X2 phase) mixture phase films were obtained at P_tot = 7.5 kPa independent of T_dep. Amorphous Y-Si-O films showed a dense, glassy microstructure. Faceted columnar grains grew on the Y-Si-O films at P_tot = 0.6 kPa, whereas rounded cauliflower-like grains grew at P_tot = 7.5 kPa. The R_dep increased with increasing P_L and T_dep and reached a maximum of 430 μm h⁻¹ at P_tot = 0.6 kPa, P_L = 186 W and T_dep = 1310 K.     

Near room temperature magnetic entropy changes in as-cast Gd100−xMnx (x = 0, 5, 10, 15, and 20 at.%) alloys

A series of Gd_100−xMn_x (x = 0, 5, 10, 15, and 20 at.%) alloys were prepared by arc-melting. The Curie temperature (T_C) associated with the ferromagnetic-paramagnetic transitions, derived from M-T curves, show decrease in T_C for as-cast alloys (∼279 K) as compared to as-cast Gd (∼292 K). No appreciable decrease in the |ΔS_M|_max values ∼4.6 J/kg K (0-2 T) and ∼8.6 J/kg K (0-5 T) were observed upon alloying Gd with Mn up to x ≤ 15 at.%. Refrigerant capacity (q) showed negligible variation ∼195 J/kg (0-2 T) and ∼450 J/kg (0-5 T) with increasing Mn (up to x ≤ 15 at.%) content. Similar values of |ΔS_M|_max and q coupled with ∼13 K decrease in T_C for as-cast Gd_100−xMn_x (0 ≤ x ≤ 15) alloys as compared to Gd, suggests expansion of working temperature region of Gd upon alloying with Mn up to 15 at.%. Low cost, adjustable T_C, favorable magnetocaloric properties make Gd_100−xMn_x alloys potential candidates as second-order transition based magnetic refrigerants for near room temperature air-conditioning and magnetic refrigeration.     

The isothermal section of the La–Ag–Mg phase diagram at 400 °C

The whole isothermal section of the La–Ag–Mg phase diagram at 400 °C was constructed by means of phase identification and analysis on about eighty annealed ternary alloys. The tendency of Ag and Mg to reciprocally substitute in binary Ag–Mg phases reflects in the formation of several La–Ag–Mg ternary phases including solid solutions based on boundary binary phases, which show wide homogeneity regions extending at a constant La-content.Among the solid solutions, La(Ag_xMg_1-x) (0 ≤ x ≤ 1, cP2-CsCl), La(Ag_xMg_1-x)₃ (0 ≤ x ≤ 0.67, cF16-BiF₃) and La₂(Ag_xMg_1-x)₁₇ (0 ≤ x ≤ 0.30, hP42–3.64-CeMg_10.3) are the most extended. The crystal structure of La₂(Ag_xMg_1-x)₁₇ was determined from X-ray diffraction data refinement on two single crystals corresponding to x = 0 and x ≈ 0.2: a hexagonal disordered structure based on the CeMg_10.3 type structure is proposed for this solid solution (for La₂Mg₁₇: P6₃/mmc, hP42–3.64, a = 1.0387(1), c = 1.0263(2) nm, wR₂ = 0.0727, 408 F² values, 29 variables).Among the ternary compounds, the crystal structures of τ₁-LaAg_1+xMg_1-x (0 ≤ x ≤ 0.15, hP9-ZrNiAl), τ₂-La₄Ag_10+xMg_3-x (?0.15 ≤ x ≤ 0.3, oS68-Ca₄Au₁₀In₃) and τ₅-La₄Ag_10.3+xMg_12-x (?0.4 ≤ x ≤ 0.70, oS116–10.33-La₄Ag_10.3Mg₁₂) were confirmed and their homogeneity ranges established. The crystal structures of τ₄-LaAg_4+xMg_2-x (?0.15 ≤ x ≤ 0.88, tI14-YbAl₄Mo₂), τ₄’-LaAg_5+xMg_1-x (?0.1 ≤ x ≤ 0.05, tP14-LaAg₅Mg) and τ₆-La₃Ag_4+xMg_12-x (?1.6 ≤ x ≤ 1.0, hP38-Gd₃Ru₄Al₁₂) were solved and refined by X-ray powder diffraction data analysis. The phases τ₄ and τ₄’ crystallize in two strictly correlated tetragonal structures, body centered and primitive respectively; these two structures were interpreted as structural modifications of the same phase. Two more new ternary phases, τ₃-LaAg_2+xMg_2-x (0 ≤ x ≤ 0.45, oS20-LaAg₂Mg₂) and τ₇-La(Ag_xMg_1-x)₁₂ (0.11 ≤ x ≤ 0.21, tI208-La(Ag_xMg_1-x)₁₂), were also detected in this system.     

药芯组成及工艺参数对ENiCrMo3T0-4药芯焊丝气孔敏感性的影响

采用体式显微镜、优化设计软件研究了ENiCrMo3T0-4药芯焊丝中药芯组成及工艺参数对气孔敏感性的影响。结果表明:随着焊丝药芯组成中SiO_2/ZrO_2、TiO_2/ZrO_2、(TiO_2+ZrO_2+SiO_2)/MnO的减小,气孔敏感性降低;气体流量的改变对焊缝表面针眼气孔数的影响不大,但气体流量过小会产生条虫状气孔;当焊接电压25 V、焊接电流160 A、干伸长量20 mm时,焊缝金属针眼气孔数最少,焊丝气孔敏感性最低;增大固液相温度区间及氢在高温熔渣中的溶解度,可以降低焊缝金属气孔敏感性。     

On calorimetric study of the fragility in bulk metallic glasses with low glass transition temperature: (Ce0.72Cu0.28)90−x Al10Fex (x = 0, 5 or 10) and Zn38Mg12Ca32Yb18

Compared with conventional bulk metallic glasses, Ce-based and Zn-based bulk metallic glasses have received considerable attention because of their possible application as structural and functional materials. Kinetic fragility parameter m in amorphous material presents degree of deviations from the Arrhenius law above the glass transition temperature (T_g) of the material. Kinetic fragility parameter (m) and Kauzmann temperature (T_K) in (Ce_0.72Cu_0.28)_90?x Al₁₀Fe_x (x = 0, 5 or 10) and Zn₃₈Mg₁₂Ca₃₂Yb₁₈ bulk metallic glasses have been determined by differential scanning calorimetry (DSC). Results show that Zn₃₈Mg₁₂Ca₃₂Yb₁₈ presents a higher m than (Ce_0.72Cu_0.28)_90?x Al₁₀Fe_x (x = 0, 5 or 10). The activation energies E_g for glass transition are 1.51 eV (x = 0), 1.59 eV (x = 5) and 1.83 eV (x = 10) in (Ce_0.72Cu_0.28)_90?x Al₁₀Fe_x (x = 0, 5 or 10), and 3.59 eV in Zn₃₈Mg₁₂Ca₃₂Yb₁₈, respectively. The values of E_g increase with increasing the Fe content in (Ce_0.72Cu_0.28)_90?x Al₁₀Fe_x (x = 0, 5 or 10) bulk metallic glasses. Kinetic fragility parameter m of bulk metallic glasses increases with the glass transition temperature T_g of bulk metallic glasses, in agreement with previous investigations.     

Microstructure and spin polarization of quaternary Co2Cr1−xVxAl,Co2V1−xFexAl and Co2Cr1−xFexAl Heusler alloys

The microstructures, magnetic properties and spin polarization of quaternary Co₂Cr_1−xV_xAl, Co₂V_1−xFe_xAl and Co₂Cr_1−xFe_xAl alloys were investigated. Phase separation into A2 and B2/L2₁ structure occurs in Co₂CrAl and Co₂Cr_0.6Fe_0.4Al, whereas Co₂FeAl exhibits a single-phase B2 structure. The ordered L2₁ structure becomes more stable with increasing vanadium concentration (x ⩾ 0.35). The saturation magnetization measured at 5 K for Co₂Cr_1−xV_xAl alloy changes from 1.4 to 2.0 μ_B when x increases from 0.0 to 0.5 and then becomes 1.4 μ_B for x = 1.0. This behavior can be attributed to the variation in the local magnetic moment of Co atoms. The saturation magnetization of Co₂V_1−xFe_xAl and Co₂Cr_1−xFe_xAl alloys increases with increasing Fe concentration. The spin polarization decreases from 0.62 to 0.56 with increasing x for Co₂Cr_1−xFe_xAl alloy. Also, the spin polarization decreases with increasing x for Co₂Fe_1−xV_xAl and Co₂Cr_1−xV_xAl alloys. Possible reasons for the reduced spin polarization in these alloys are discussed.     

Subsolidus phase relations of the SrO–Ta2O5–CuO system at 900 °C in air

The subsolidus phase relations of the SrO–Ta₂O₅–CuO system were investigated in air. The samples were equilibrated at 900 °C. The ternary oxide Sr₃Ta₂CuO₉ compound is stable under these conditions. This phase presents a solid solution range, its actual composition being Sr₃Ta_2−xCu_1+xO_9+δ with 0.0 ≤ x ≤ 0.2. Up to about 5 at.% Cu can be incorporated in the Sr_3−xTa_1+xO_5.5+δ phase. Similarities with the SrO–Nb₂O₅–CuO system are discussed.     

Ultraviolet and violet upconversion luminescence in Ho-doped Y2O3 ceramic induced by 532-nm CW laser

Ultraviolet and violet upconversion luminescence spectra of holmium-doped Y₂O₃ were produced under the excitation of a compact continues-wave 532 nm solid-state laser. Emissions around 306, 362, 412, 390 and 428 nm can be assigned to the transitions of ³D₃ → ⁵I_J (J = 8, 7, 6), ⁵G₄ → ⁵I₈ and ⁵G₅ → ⁵I₈, respectively. Power dependence and upconversion dynamics analysis demonstrated that both the energy transfer upconversion (ETU) and the excited state absorption (ESA) processes were involved in the population of ³D₃ state via the coupled intermediate states ⁵S₂/⁵F₄. Fluorescence spectra in the visible and infrared ranges showed that ⁵G₄ and ⁵G₅ states were populated by the ESA process from ⁵I₆ and ⁵I₇ states, respectively, while the ⁵I₆ and ⁵I₇ states were radiatively populated from the excited ⁵S₂/⁵F₄ states. Upconversion mechanisms have been evaluated based on a rate equation model.     

Phase Equilibria,Crystal Chemistry and Physical Properties of Au-Ba-Ge Clathrates

In the Au-Ba-Ge system the clathrate type I solid solution, Ba₈Au _x Ge_46−x−y □ _y , extends at 800 °C from binary Ba₈Ge₄₃□₃ (□ is a vacancy) to Ba₈Au₆Ge₄₀. For the clathrate phase (1 ≤ x ≤ 6) cubic primitive symmetry (space group Pm[`3]n Pm{\bar{{3}}}n ) was confirmed by x-ray powder diffraction assisted by x-ray single crystal analyses of Ba₈Au_4.6Ge_40.3□_1.1. The lattice parameters of the solid solution show an almost linear increase with increasing gold content. Site preference from x-ray refinement shows that gold atoms preferably occupy the 6d site in random mixture with Ge and vacancies, which vanish at the solubility limit. Clathrate type ΙX (Ba₆Ge₂₅ type) has a maximum solubility of 2.7 at.% gold at 800 °C. Phase equlilibria at 800 °C are characterized by four ternary phases in the investigated region up to 33.3 at.% barium. The homogeneity range of Ba(Au_1−x Ge _x )₂ (AlB₂-type) and BaAu_1+x Ge_3−x has been established: Ba(Au_1−x Ge _x )₂ extends from BaAu_0.5Ge_1.5 to BaAu_0.9Ge_1.1 and BaAu_1+x Ge_3−x from BaAu_1.1Ge_2.9 (BaNiSn₃-type) to BaAu_2.7Ge_1.3 (Ce(Ni,Sb)₄-type). The crystal structures of two phases in the gold-rich part have been determined from single crystal x-ray data and were found to form new structure types: BaAu₃Ge with BaAu₃Ge-type (space group P4/nmm, a = 0.6459(2), c = 0.5487(2) nm) and BaAu_5+x Ge_2−x (x = 0, BaAu₅Si₂-type, space group Pnma, a = 0.8981(2), b = 0.7106(2) and c = 1.0363(2) nm), the latter revealing with increasing gold content a closely related derivative structure type (BaAu_5.3Ge_1.7, a = a_{\textBaAu5 \textSi2} ,  b = b_{\textBaAu5 \textSi2} ,  c = 2c_{\textBaAu5 \textSi2} a = a_{{{\text{BaAu}}_{5} {\text{Si}}_{2} }} ,\;b = b_{{{\text{BaAu}}_{5} {\text{Si}}_{2} }} ,\;c = 2c_{{{\text{BaAu}}_{5} {\text{Si}}{}_{2}}} ). Transport properties and particularly the thermoelectric behavior were studied for Ba₈Au₆Ge₄₀.     

Electro/magnetic shielding effectiveness of soft magnetic Fe80Nb6B14 amorphous alloy

Application of the Fe₈₀Nb₆B₁₄ amorphous alloy to electromagnetic shielding was examined in detail using different experimental techniques. For shields made of the optimized (annealing at 700 K/1 h) amorphous ribbons the shielding effectiveness b was measured versus frequency f and shield thickness h. It was shown that for h = 200 μm in the frequency range 2 MHz < f < 15 MHz (the near-zone, electric field) b decreases from 55 dB to 20 dB. In the frequency range 0.2 kHz < f < 10 kHz (the near-zone, magnetic field) b > 20 dB. The best shielding effectiveness, i.e. b > 100 dB was obtained for electromagnetic field in the frequency range 200 MHz < f < 1000 MHz (the far-zone).