Hydrogen storage properties of as-cast and annealed low-Co La<Subscript>1.8</Subscript>Ti<Subscript>0.2</Subscript>MgNi<Subscript>8.9</Subscript>Co<Subscript>0.1</Subscript> alloys

Low-Co La_1.8Ti_0.2MgNi_8.9Co_0.1 alloys were prepared by magnetic levitation melting followed by annealing treatment. The effect of annealing on the hydrogen storage properties of the alloys was investigated systematically by X-ray diffraction (XRD), pressure-composition isotherm (PCI), and electrochemical measurements. The results show that all samples contain LaNi₅ and LaMg₂Ni₉ phases. LaCo₅ phase appears at 1,000 °C. The enthalpy change of all hydrides is close to ?30.6 kJ·mol^?1 H₂ of LaNi₅ compound. Annealing not only increases hydrogen capacity and improves cycling stability but also decreases plateau pressure at 800 and 900 °C. After annealing, the contraction of cell volume and the increase of hydride stability cause the high rate dischargeability to reduce slightly. The optimum alloy is found to be one annealed at 900 °C, with its hydrogen capacity reaching up to 1.53 wt%, and discharge capacity remaining 225.1 mAh·g^?1 after 140 charge–discharge cycles.     

Effect of Different Shapes of the Titanium Based IrO2-Ta2O5 Coatings Anode on Electrochemical Properties

钛基IrO2-Ta2O5涂层阳极的形状分别是板状和扩张网。采用涂覆了H2IrCl6.H2O的盐酸溶液和TaCl5乙醇溶液的混合溶液再进行热分解制备得到IrO2-Ta2O5涂层。分别采用SEM,EDX,CV和加速寿命测试对电极的微观结构和电化学性能进行分析。相对板状电极而言,由于较少的活性物质IrO2在电极表面结晶析出,扩张网状电极具有更低的电化学催化活性。但是由于表面的裂纹较为细密、表面活性元素分布也较为均匀,并且其纵截面的形状更有利于电解析出的气泡排出,扩张网状电极具有更长的加速寿命。     

Thermal Spray Deposition,Phase Stability and Mechanical Properties of La<Subscript>2</Subscript>Zr<Subscript>2</Subscript>O<Subscript>7</Subscript>/LaAlO<Subscript>3</Subscript> Coatings

This paper deals with the deposition of La₂Zr₂O₇ (LZO) and LaAlO₃ (LAO) mixtures by air plasma spray (APS). The raw material for thermal spray, single phase LZO and LAO in a 70:30 mol.% ratio mixture was prepared from commercial metallic oxides by high-energy ball milling (HEBM) and high-temperature solid-state reaction. The HEBM synthesis route, followed by a spray-drying process, successfully produced spherical agglomerates with adequate size distribution and powder-flow properties for feeding an APS system. The as-sprayed coating consisted mainly of a crystalline LZO matrix and partially crystalline LAO, which resulted from the high cooling rate experienced by the molten particles as they impact the substrate. The coatings were annealed at 1100 °C to promote recrystallization of the LAO phase. The reduced elastic modulus and hardness, measured by nanoindentation, increased from 124.1 to 174.7 GPa and from 11.3 to 14.4 GPa, respectively, after the annealing treatment. These values are higher than those reported for YSZ coatings; however, the fracture toughness (K _IC) of the annealed coating was only 1.04 MPa m^0.5.     

High-pressure-torsion deformation of melt-spun Nd<Subscript>9</Subscript>Fe<Subscript>85</Subscript>B<Subscript>6</Subscript> alloy

The effect of severe plastic deformation by high-pressure torsion (HPT) at room temperature and subsequent annealing on the magnetic properties and structural transformations of the melt-spun alloy (MSA) Nd₉Fe₈₅B₆ is studied. The melt-spun ribbons in three structural states, such as nanocrystalline, mixed amorphous-nanocrystalline, and quasi-amorphous, have been subjected to deformation. In the nanocrystalline alloy, HPT leads to the decomposition of part of the Nd₂Fe₁₄B phase into the amorphous phase and α-Fe nanocrystals. The deformation of the alloy in the quasi-amorphous state leads also to the precipitation of a great amount of α-Fe nanocrystals; in this case, the amorphous matrix is depleted of iron. During the HPT of the MSA in the mixed amorphous + nanocrystaline state, both structural transformations occur. The annealing of deformed samples at above 500°C restores the two-phase (Nd₂Fe₁₄B + α-Fe) nanocrystalline state. This is accompanied by increasing magnetic hysteretic properties. The HPT has been found to suppress the formation of nonequilibrium magnetically soft phases, such as NdFe₇ and Nd₂Fe₂₃B₃, that precipitate upon annealing of the melt-spun amorphous alloy. This promotes the formation of an optimum nanocrystalline structure of the α-Fe/Nd₂Fe₁₄B composite material and an increase in its magnetic hysteretic properties because of enhancement of the intergranular exchange interaction. Compact micromagnets 6–15 mm in diameter and 0.2 mm thick, which were prepared from the Nd₉Fe₈₅B₆ alloy using HPT and subsequent annealing, exhibit the following characteristics: B _r = 11.4 kG, H _c = 5.4 kOe, and (BH)_max = 17.1 MG Oe.     

Effects of defects generated in ALD TiO<Subscript>2</Subscript> films on electrical properties and interfacial reaction in TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript>/Si system upon annealing in vacuum

Thin TiO₂ layers grown at 130°C on SiO₂-coated Si substrates by atomic layer deposition (ALD) using TTIP and H₂O as precursors were annealed, and the effects of the annealing temperature on the resulting electrical properties of TiO₂ and the interface properties between a Pt electrode and TiO₂ were examined using transmission line model (TLM) structures. The as-deposited TiO₂ thin film had an amorphous structure with OH groups and a high resistivity of 6×10³Ω-cm. Vacuum annealing at 700 °C transformed the amorphous film into an anatase structure and reduced its resistivity to 0.04Ω-cm. In addition, the vacuum-annealing of the TiO₂/SiO₂ structure at 700°C produced free silicon at the TiO₂-SiO₂ interface as a result of the reaction between the Ti interstitials and SiO₂. The SiO₂ formed on the TiO₂ surface caused a Schottky contact, which was characterized by the TLM method. The use of the TLM method enabled the accurate measurement of the resistivity of the vacuum-annealed TiO₂ films and the characterization of the Schottky contacts of the metal electrode to the TiO₂.     

Effects of H<Superscript>+</Superscript> Ion Implantation and Annealing on the Properties of CuIn<Subscript>0.75</Subscript>Ga<Subscript>0.25</Subscript>Se<Subscript>2</Subscript> Thin Films

In this paper the effects of post-deposition annealing followed by hydrogen ion-implantation on the properties of CuIn_0.75Ga_0.25Se₂ thin films have been investigated. The samples were grown by flash evaporation onto glass substrates heated at temperature between room temperature and 200 °C. Selected samples were subsequently processed under several sets of conditions, including vacuum, selenium, inert (argon) and forming gas (a 9:1 mixture of N₂:H₂) followed by hydrogen ion-implantation. A high-resolution near-infrared photoacoustic spectrometer (PAS) of the gas-microphone type was used for room temperature analysis of non-radiative defect levels in the as-grown, annealed and hydrogen implanted thin films. The absorption coefficient has been derived from the PA spectra to determine the gap energy and to establish the activation energies for several defect-related energy levels. The changes observed in the PA spectra following annealing and ion-implantation has been directly correlated with the compositional and structural properties of the samples.     

酸刻蚀处理对IrO2-Ta2O5/Ti阳极寿命的影响

通过改变腐蚀方法,研究了使用H₂C₂O₄和H₂SO₄进行钛基体表面刻蚀对金属氧化物钛阳极电化学性能和表面形貌的影响。采用扫描电子显微镜、X射线衍射仪和光电子能谱等测试方法对样品进行了结构分析。然后利用电化学工作站测试了样品的电催化活性,利用加速寿命测试研究了样品的电化学稳定性。结果表明,通过H₂C₂O₄和H₂SO₄分步腐蚀可以获得更加均匀致密的表面形貌和更好的催化稳定性。在此基础上,进一步研究了预处理对钛阳极寿命的影响原因。IrO₂-Ta₂O₅/Ti阳极的催化活性和稳定性与酸刻蚀处理的先后顺序及表面结构密切相关,并建立了预处理方法与阳极性能之间的关系。分步腐蚀使钛表面具有合适的粗糙度,因而提升了涂层附着力。在热分解过程中,经分步腐蚀形成的氢化钛在不改变表面形貌的情况下转变为金红石结构的氧化钛,有利于电子输运,从而增强涂层附着力并延长加速寿命。     

Synthetically Controlled,Carbon-Coated Co<Subscript>2</Subscript>SnO<Subscript>4</Subscript>/SnO<Subscript>2</Subscript> Composite Anode for Lithium-ion Batteries

The inherent drawbacks of Co₂SnO₄ in demonstrating the closer-to-theoretical capacity value behavior and the inadmissible volume-expansion-related capacity fade behavior have been surpassed by choosing a tailor-made material composition of Co₂SnO₄/SnO₂, prepared at two different temperatures such as 400°C and 600°C to obtain residual carbon-containing and carbon-free compositions, respectively. Among the products, carbon-coated Co₂SnO₄/SnO₂ composite exhibits better electrochemical performance compared with that of the carbon-free product mainly because of the beneficial effect of carbon in accommodating the volume-expansion-related issues arising from the alloying/de-alloying mechanism. A combination of conversion reaction and alloying/de-alloying mechanism is found to play a vital role in exhibiting closer-to-theoretical capacity values. In other words, an appreciable specific capacity value of 834 mAh g^?1 has been exhibited by Co₂SnO₄/SnO₂ anode containing carbon coating, thus, demonstrating the possibility to improve the electrochemical performance of the title anode through carbon coating, which is realized as a result of the addition of carefully manipulated synthesis conditions.     

Electrochemical properties of spinel compound LiNi_（0.5）Mn_（1.2）Ti_（0.3）O_4 as cathode materials for lithium ion batteries

The electrochemical properties of spinel compound LiNi0.5Mn1.2Ti0.3O4 were investigated in this study.The chemicals LiAc·2H2O,Mn(Ac)2·2H2O,Ni(Ac)2·4H2O,and Ti(OCH3)4 were used to synthesize LiNi0.5Mn1.2Ti0.3O4 by a simple sol-gel method.The discharge capacity of the sample reached 134 mAh/g at a current rate of 0.1C.The first and fifth cycle voltammogram almost overlapped,which showed that the prepared sample LiNi0.5Mn1.2Ti0.3O4 had excellent good cycle performance.There were two oxidation peaks at 4.21 V and 4.86 V,and two reduction peaks at 4.55 V and 3.88 V in the cycle voltammogram,respectively.By electrochemical impedance spectroscopy and its fitted result,the lithium ion diffusion coefficient was measured to be approximately 7.76 × 10?11 cm2/s.     

NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript>-based cermet inert anodes for aluminum electrolysis

Recent developments in the preparation, sintering process, mechanical properties, and thermal shock resistance of cermet inert anodes for aluminum electrolysis are reviewed in this paper. To obtain the desired technologies of low-temperature activated sintering of cermet inert anodes, the effects of material composition, sintering atmosphere, sintering temperature, and sintering aids on the densifi cation and microstructure of NiFe₂O₄-10NiO- based ceramics and cermets were studied. To obtain the toughening and strengthening technology of the cermet, the effects of material composition including ceramic and metallic phases are discussed. The cermet inert anodes with high density and mechanical properties were prepared through adjustment of material composition and sintering technology and selection of feasible sintering aids.     

Dependence of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> coating thickness and annealing conditions on microstructural and electrochemical properties of LiCoO<Subscript>2</Subscript> film

We studied the dependence of Al₂O₃ coating thickness and annealing conditions on the surface morphology and electrochemical properties of Al₂O₃ coated LiCoO₂ films. The optimum coating thickness allowing for the highest capacity retention was about 24 nm. A sample consisting of Al₂O₃ coated on annealed LiCoO₂ film with additional annealing at 400 °C had a uniform coating layer between the coating materials and cathode films. This sample showed the best capacity retention of ∼91 % with a charge-cut off of 4.5 V after 30 cycles, while the bare cathode film showed a capacity retention of ∼32 % under the same conditions. The formation of second phases such as Co-Al-O was observed in the coating films by X-ray photoelectron spectroscopy (XPS). The Co-Al-O containing samples showed a higher initial capacity because of their smaller grain size, but less capacity retention than the Al₂O₃ containing samples.     

Effect of Ga addition on the magnetic properties and microstructure of nanocrystalline Nd_（12.3）Fe_（81.7）B_（6.0） ribbons

Nd 12.3 Fe 81.7 x Ga x B 6.0 (x = 0-1.8) ribbons were prepared by melt spinning at 22 m/s and subsequent annealing treatment. The influences of Ga addition and annealing conditions on the magnetic properties and microstructure of the nanocrystalline alloys were systematically investigated. After being annealed at 620℃ for 20 min, the J r and H ci increased from 0.85 T and 582.6 kA/m for Ga-free sample to 0.97 T and 734.6 kA/m for the x = 0.9 sample, respectively. The (BH) max for the x = 0.9 sample increased by about 40% from 96.3 to 135.5 kJ/m 3 compared with that of the Ga-free one. The significant improvement of magnetic properties originated from the refinement of grains in the samples by introducing Ga, which led to a stronger exchange coupling between the neighboring grains in comparison with that in Ga-free samples. The microstructure and magnetic properties of the samples depended strongly on annealing parameters, while the sensitivity of micro-structure to annealing conditions could be significantly suppressed by the addition of Ga element.     

Influence of water vapor on the formation of pinning centers in YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript> upon low-temperature annealing

The influence of the double heat treatment (T = 300 and 930°С) on the critical parameters of highly textured YBa₂Cu₃O_6.96 and YBa₂Cu₃O_6.8 ceramics has been investigated. It has been shown that, upon low-temperature annealing in humid air, planar stacking faults are formed in these ceramics. These defects are partly retained after reduction annealing (at T = 930°С) and are efficient pinning centers in magnetic fields applied parallel and perpendicular to the c axis. Due to the absorption of water, the oxygen content is increased in the ceramics, which is accompanied by an increase in the critical temperature of superconducting transition up to 94 K for YBa₂Cu₃O_6.96 and up to 90 K for YBa₂Cu₃O_6.8. Optimal conditions of the double annealing have been established, after which the critical-current density increased to j _c ≥ 10⁴ А/сm² in an external magnetic field of up to 6 T. The low-temperature treatment in the neutral atmosphere saturated by water vapors deteriorates the current-carrying capacity of the highly textured ceramics, which is connected with the disappearance of texture due to the copper reduction and the precipitation of impurity phases.     

Surface modification of LiNi<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>O<Subscript>2</Subscript> with Cr<Subscript>2</Subscript>O<Subscript>3</Subscript> for lithium ion batteries

Cr 2 O 3-coated LiNi 1/3 Co 1/3 Mn 1/3 O 2 cathode materials were synthesized by a novel method. The structure and electrochemical properties of prepared cathode materials were measured using X-ray diffraction (XRD), scanning electron microscopy (SEM), charge-discharge tests, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The measured results indicate that surface coating with 1.0 wt% Cr 2 O 3 does not affect the LiNi 1/3 Co 1/3 Mn 1/3 O 2 crystal structure (α-NaFeO 2 ) of the cathode material compared to the pristine material, the surfaces of LiNi 1/3 Co 1/3 Mn 1/3 O 2 samples are covered with Cr 2 O 3 well, and the LiNi 1/3 Co 1/3 Mn 1/3 O 2 material coated with Cr 2 O 3 has better electrochemical performance under a high cutoff voltage of 4.5 V. Moreover, at room temperature, the initial discharging capacity of LiNi 1/3 Co 1/3 Mn 1/3 O 2 material coated with 1.0 wt.% Cr 2 O 3 at 0.5C reaches 169 mAh·g 1 and the capacity retention is 83.1% after 30 cycles, while that of the bare LiNi 1/3 Co 1/3 Mn 1/3 O 2 is only 160.8 mAh·g 1 and 72.5%. Finally, the coated samples are found to display the improved electrochemical performance, which is mainly attributed to the suppression of the charge-transfer resistance at the interface between the cathode and the electrolyte.     

Capacitance performance enhancement of TiO<Subscript>2</Subscript> doped with Ni and graphite

Nano-amorphous TiO₂ was prepared by a sol-gel method. The results of X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that the composite electrode material (TiO₂-NiO-C) is made of powder with a grain size of 36.2 nm. Doping of nickel and graphite can increase the electrical conductivity and the specific surface area of nano-amorphous TiO₂. The electrochemical properties of TiO₂-NiO-C, such as self-discharge, leakage current, and cycle life, were studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge-discharge test. With a charge-discharge current density of 500 mA/g, the specific capacity of the TiO₂-NiO-C composite material reaches 12.88 mAh/g. Also, the expense of capacity is only 3.88% after 500 cycles. The electrochemical capacitor with the electrode material of TiO₂-NiO-C shows excellent capacity and cycling performance.     

The role of Ce ions in electrochemical corrosion of 304 SS in Ce(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>.6H<Subscript>2</Subscript>O

Effects of temperature and potential on the electrochemical corrosion behavior of alloy AISI 304 (UNS S30400) Stainless steel were investigated in 3 wt.% cerium nitrate (Ce[NO₃]₃.6H₂O) solution. With an increase in electrolyte temperature from ambient temperature to 90°C, the corrosion potential of the alloy shifted towards the noble direction, and the resistance to polarization increased due to the formation of Ce-oxide on the electrode surface. The oxide films formed at the open circuit potential (OCP) and a passive potential of 0.4 V_SCE were examined by x-ray photoelectron spectroscopy (XPS). The oxide film formed at 50°C and a passive potentialof 0.4 V_SCE consists of mixed oxides of Ce and Cr, whereas that at OCP consists of only Cr oxide. The formation of Cr oxides on the electrode surface was primarily due to the nitrate (NO₃ ⁻) ions in Ce(NO₃)₃.6H₂O electrolyte.     

Effect of water intercalation on the structure and electrophysical properties of YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>6.9</Subscript>

The influence of water vapors and plastic deformation on the structure and electrophysical properties of YBa₂Cu₃O_6.9 (123) has been studied. It has been established that, at T = 200°C, the introduction of water into the structure of YBa₂Cu₃O_6.9 leads to its transition into a defect tetragonal phase of the 124 type as a result of the formation of planar stacking faults. After annealing at T = 930°C, these defects are partially retained and are efficient centers of pinning in the magnetic fields applied perpendicularly to the c axis, which makes it possible to increase (by an order of magnitude) the critical current density in the high-textured ceramics at 77 K in the external magnetic field of 5–10 T. The plastic deformation of the hydrated ceramics favors the reverse transition of the arising 124 phase to the 123 phase at T = 930°C and is accompanied by a recrystallization of the material, which leads to the appearance of a texture and an increase the critical current density.     

Microstructural and electrochemical properties of Ti-doped Al<Subscript>2</Subscript>O<Subscript>3</Subscript> coated LiCoO<Subscript>2</Subscript> films

We studied the microstructural and electrochemical properties of Ti-doped Al₂O₃ (Ti-Al₂O₃) coated LiCoO₂ thin films depending on the Ti composition. The 1.27 at.% Ti-Al₂O₃ coated films had an amorphous structure with better conductivity than that of pure Al₂O₃ films. The Ti-Al₂O₃ coating layer effectively suppressed the dissolution of Co and the formation of lower Li conductivity SEI films at the interface between the LiCoO₂ film and electrolyte. The Ti-Al₂O₃ coating improved the cycling performance and capacity retention at high voltage (4.5 V) of the LiCoO₂ films. The Ti-Al₂O₃ coated LiCoO₂ films showed better electrochemical properties than did the pure Al₂O₃ coated LiCoO₂ films. These results were closely related to the enhanced Li-conductivity and interfacial quality of the Ti-Al₂O₃ film.     

Porous Y<Subscript>2</Subscript>O<Subscript>3</Subscript> microcubes: synthesis and characterization

In this work, a facile route using a simple solvothermal reaction and sequential heat treatment process to prepare porous Y₂O₃ microcubes is presented. The as-synthesized products were characterized by X-ray powder diffraction (XRD), scanning electronic microscope (SEM), energy dispersive spectrometer (EDS), thermogravimetric analysis (TG), and differential thermal analysis (DTA). The thermal decomposition process of the Y₂O₃ precursor was investigated. SEM results demonstrated that the as-prepared porous Y₂O₃ microcubes were with an average width of about 20 μm and thickness of about 8 μm. It was found that the morphology of the Y₂O₃ precursor could be readily tuned by varying the molar ratio of S₂O₈²⁻ to Y³⁺. Y₂O₃:Eu³⁺ (6.6%) microcubes were also prepared and their photoluminescence properties were investigated.     

Effect of water vapor and low-temperature decomposition on the structure and electrophysical properties of nonstoichiometric compound Ba<Subscript>2</Subscript>YCu<Subscript>3</Subscript>O<Subscript>7 − δ</Subscript>

The effect of water vapor and decomposition into phases with different oxygen contents on the structure and electrophysical properties of the nonstoichiometric compound Ba₂YCu₃O_{7 − δ} has been studied. Both these factors were shown to lead to the formation of structural defects that can be pinning centers and improve the current-carrying capacity of materials. At the same time, the reaction with water leads to a deterioration of superconducting properties of grain boundaries. The optimum electrophysical properties of Ba₂YCu₃O_{7 − δ} can be reached by choosing appropriate heat-treatment conditions, namely, the temperature and time of annealing and the water-vapor content in the annealing atmosphere. The phase diagram of the Ba₂YCu₃O₆-Ba₂YCu₃O₇ system below 400°C is refined.