Phase Transformations During Li-Insertion into V<Subscript>2</Subscript>O<Subscript>5</Subscript> at Elevated Temperature

Recent interest in developing cathode materials for an elevated temperature operation of Li-ion batteries has motivated researchers to explore the possibility of using layered V₂O₅ as a potential candidate because of its high capacity and cyclic stability. Despite a wide lithiation voltage window of V₂O₅ (between 1.0 V and 4.0 V), compositional fluctuations, metal dissolution, and so on contribute to capacity loss at high temperatures. A first discharge of V₂O₅ to voltages below 2.0 V has been observed to be associated with a series of phase transformations at both room temperature and high temperature and has been characterized here. From structural characterization of harvested electrodes post–first discharge, a new Li-rich phase was observed to be formed at 120°C and the composition was estimated.     

Na<Subscript>2</Subscript>SO<Subscript>4</Subscript>-Deposit-Induced Corrosion of Mo-Containing Alloys

Disk alloys used in advanced gas turbine engines often contain significant amounts of Mo (2 wt% or greater), which is known to cause corrosion under Type I hot corrosion conditions (at temperatures around 900 °C) due to alloy-induced acidic fluxing. The corrosion resistance of several model and commercial Ni-based disk alloys with different amounts of Mo with and without Na₂SO₄ deposit was examined at 700 °C in air and in SO₂-containing atmospheres. When coated with Na₂SO₄ those alloys with 2 wt% or more Mo showed degradation products similar to those observed previously in Mo-containing alloys, which undergo alloy-induced acidic fluxing Type I hot corrosion even though the temperatures used in the present study were in the Type II hot corrosion range. Extensive degradation was observed even after exposure in air. The reason for the observed degradation is the formation of sodium molybdate. Transient molybdenum oxide reacts with the sodium sulfate deposit to form sodium molybdate which is molten at the temperature of study, i.e., 700 °C, and results in a highly acidic melt at the salt alloy interface. This provides a negative solubility gradient for the oxides of the alloying elements, which results in continuous fluxing of otherwise protective oxides.     

Microstructure and Thermomechanical Properties of Atmospheric Plasma-Sprayed Yb<Subscript>2</Subscript>O<Subscript>3</Subscript> Coating

In this study, a Yb₂O₃ coating was fabricated by the atmospheric plasma spray technique. The phase composition, microstructure, and thermal stability of the coating were examined. The thermal conductivity and thermal expansion behavior were also investigated. Some of the mechanical properties (elastic modulus, hardness, fracture toughness, and flexural strength) were characterized. The results reveal that the Yb₂O₃ coating is predominantly composed of the cubic Yb₂O₃ phase, and it has a dense lamellar microstructure containing defects. No mass change and exothermic phenomena are observed in the thermogravimetry and differential thermal analysis curves. The high-temperature x-ray diffraction results indicate that no phase transformation occurs from room temperature to 1500 °C, revealing the good phase stability of the Yb₂O₃ coating. The coefficient of thermal expansion of the Yb₂O₃ coating is (7.50-8.67)?×?10^?6 K^?1 in the range of 200-1400 °C. The thermal conductivity is about 1.5 W m^?1 K^?1 at 1200 °C. The Yb₂O₃ coating has excellent mechanical properties and good damage tolerant. The unique combination of these properties implies that the Yb₂O₃ coating might be a promising candidate for T/EBCs applications.     

Improvement of electrochemical and electrical properties of LiFePO<Subscript>4</Subscript> coated with citric acid

LiFePO₄ was synthesized using hydrothermal method and coated with different amounts of citric acid as carbon source.The samples were characterized by X-ray powder diffraction（XRD）,scanning electron microscopy（SEM）,transmission electron microscope（TEM）,surface area measurement—Brunauer–Emmett–Teller（BET）,discharge capability,cyclic voltammetry（CV）,and electrochemical impedance spectroscopy（EIS）.The results show that the quality and thickness of the carbon coating on the surface of LiFePO₄ particles are very important.The optimum carbon content（about 30 wt%）can lead to a more uniform carbon distribution.Electrochemical results show that the samples containing 20 wt%,30 wt%,40 wt%,and50 wt% carbon deliver a discharge capacity of 105,167,151,and 112 mAhg^-1,respectively,at the rate of 0.1C.The increase of carbon content leads to the decrease of discharge capacity of LiFePO₄/C,owing to the fact that excess carbon delays the diffusion of Li⁺ through the carbon layers during charge/discharge procedure.The LiFePO₄/C with low carbon content exhibits poor electrochemical performance because of its low electrical conductivity.Therefore,the amount of carbon must be optimized in order to achieve excellent electrochemical performance of LiFePO₄/C for its application in a lithium ion battery.     

Phase Equilibria and Ternary Intermetallic Compound with L1<Subscript>2</Subscript> Structure in Co-W-Ga System

Phase equilibria and stabilities of intermetallic phases appearing in the Co-rich portion of the Co-W-Ga ternary alloys were investigated and isothermal section diagrams at 1200, 1100, 1000, and 900 °C were determined. A fine cuboidal phase with an L1₂ structure was observed at 900 and 800 °C, where the composition of the new ternary compound obtained by aging at 900 °C for the Co-7.4W-12.0Ga alloy was Co-11.2W-11.4Ga (at.%). It was confirmed that this compound is metastable at 900 °C but is more stable at 800 °C. These results mean that the thermodynamic stability of the metastable Co₃W L1₂ phase, especially in the low temperature region, increases by the addition of Ga.     

Recovery of V<Subscript>2</Subscript>O<Subscript>5</Subscript> from Bayer liquor by ion exchange

A new technology was developed to recover V2O5 from Bayer spent liquor by ion exchange.The experimental results show that in the conditions of 105°C and 0.20-0.25 mass ratios between CaO in lime and Al2O3 in spent liquor, the precipitation rate of vanadium in Bayer liquor is more than 85%.The vanadium-bearing precipitation is leached by NaHCO3 solution.The leaching rate of vanadium can reach 85% in the conditions of 95°C, 40 g·L-1 of NaHCO3 concentration, and ventilating of CO2.The 201 × 7 type of resin has...     

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 carbon-coated LiFePO<Subscript>4</Subscript> and LiFe<Subscript>0.98</Subscript>Mn<Subscript>0.02</Subscript>PO<Subscript>4</Subscript> cathode materials synthesized by solid-state reaction

Olivine structured LiFePO4/C (lithium iron phosphate) and Mn2+-doped LiFe0. 98Mn0. 024/C powders were synthesized by the solid-state reaction. The effects of manganese partial substitution and different carbon content coating on the surface of LiFePO4 were considered. The structures and electrochemical properties of the samples were measured by X-ray diffraction (XRD), cyclic voltammetry (CV), charge/discharge tests at different current densities, and electrochemical impedance spectroscopy (EIS). The electrochemical properties of LiFePO4 cathodes with x wt. ％ carbon coating (x=3, 7, 11, 15) at γ=0. 2C, 2C (1C=170 mAh·g-1) between 2. 5 and 4. 3 V were investigated. The measured results mean that the LiFePO4 with 7 wt. ％ carbon coating shows the best rate performance. The discharge capacity of LiFe0. 98Mn0. 02PO4/C composite is found to be 165 mAh·g 1 at a discharge rate, γ=0. 2C, and 105 mAh·g-1 at γ=2C, respectively. After 10cycles, the discharge capacity has rarely fallen, while that of the pristine LiFePO4/C cathode is 150 mAh·g-1 and 98 mAh·g-1 at γ=0. 2 and 2C, respectively. Compared to the discharge capacities of both electrodes above, the evident improvement of the electrochemical performance is observed, which is ascribed to the enhancement of the electronic conductivity and diffusion kinetics by carbon coating and Mn2+-substitution.     

Magnetic anisotropy induced by stress annealing,its thermal stability,and structure of the Fe<Subscript>5</Subscript>Co<Subscript>72</Subscript>Si<Subscript>15</Subscript>B<Subscript>8</Subscript> alloy

The efficiency of the magnetic-anisotropy induction in the Fe₅Co₇₂Si₁₅B₈ amorphous alloy during its thermomechanical treatment and the thermal stability of the anisotropy are shown to depend on the structural state of the alloy. Structural inhomogeneities (microinhomogeneities and preprecipitates) formed in the structure of the amorphous alloy upon annealing at 350–430°C increase both the efficiency of the magnetic-anisotropy induction in the course of subsequent heat treatment at 290°C combined with tensile deformation and the thermal stability of the anisotropy.     

Formation of Cr<Subscript>2</Subscript>O<Subscript>3</Subscript> Diffusion Barrier Between Cr-Contained Stainless Steel and Cold-Sprayed Ni Coatings at High Temperature

A novel approach to prepare a coating system containing an in situ grown Cr₂O₃ diffusion barrier between a nickel top layer and 310SS was reported. Cold spraying was employed to deposit Ni(O) interlayer and top nickel coating on the Cr-contained stainless steel substrate. Ni(O) feedstock was prepared by mechanical alloying of pure nickel powders in ambient atmosphere, acting as an oxygen provider. The post-spray annealing was adopted to grow in situ Cr₂O₃ layer between the substrate and nickel coating. The results revealed that the diffusible oxygen can be introduced into nickel powders by mechanical alloying. The oxygen content increases to 3.25 wt.% with the increase of the ball milling duration to 8 h, while Ni(O) powders maintain a single phase of Ni. By annealing the sample in Ar atmosphere at 900 °C, a continuous Cr₂O₃ layer of 1-2 μm thick at the interface between 310SS and cold-sprayed Ni coating is formed. The diffusion barrier effect evaluation by thermal exposure at 750 °C shows that the Cr₂O₃ oxide layer effectively suppresses the outward diffusion of Fe and Cr in the substrate effectively.     

Structure and Electrochemical Properties of Rapidly Quenched Mm0.3Ml0.7Ni3.55Co0.75Mn0.4Al0.3 Hydrogen Storage Alloy

The as-cast Mm_0.3Ml_0.7Ni_3.55Co_0.75Mn_0.4Al_0.3 alloy has been treated using rapid-quenching technique at different quenching speeds to improve the electrochemical hydrogen storage properties of the alloys. The morphologic and microstructural characterizations of alloys were studied using x-ray diffraction and transmission electron microscopy. It is observed that the quenched alloy is composed of two main phases, LaNi₅ and LaNi₃, and one minor phase of La₂Ni₃. The microstructures of the alloys vary with the quenching speeds, as well as contain microcrystalline, nanocrystalline, and amorphous structures. The electrochemical hydrogen storage properties were measured using a battery test system. The results indicate that the discharge capacity of the alloy increases initially and then decreases with the rising quenching speeds. The quenched alloy at a speed of 15 m/s exhibits the maximum discharge capacity (388 mAh/g), which is much higher than that of the AB₅-type rare earth-based hydrogen storage alloy reported in previous studies. However, the stability of the electrochemical cycle of the quenched alloy exhibits inverse trends compared with the discharge capacity. The best electrochemical cyclic stability of the quenched alloy can be obtained at a speed of 25 m/s.     

Thermal behavior analysis of a pouch type Li[Ni<Subscript>0.7</Subscript>Co<Subscript>0.15</Subscript>Mn<Subscript>0.15</Subscript>]O<Subscript>2</Subscript>-based lithium-ion battery

Since lithium-ion battery with high energy density is the key component for next-generation electrical vehicles,a full understanding of its thermal behaviors at different discharge rates is quite important for the design and thermal management of lithium-ion batteries（LIBs）pack/module.In this work,a 25 Ah pouch type Li[Ni_0.7Co_0.15Mn_0.15]O₂/graphite LIBs with specific energy of200 Wh kg^-1were designed to investigate their thermal behaviors,including temperature distribution,heat generation rate,heat capacity and heat transfer coefficient with environment.Results show that the temperature increment of the charged pouch batteries strongly depends on the discharge rate and depth of discharge.The heat generation rate is mainly influenced by the irreversible heat effect,while the reversible heat is important at all discharge rates and contributes much to the middle evolution of the temperature during discharge,especially at low rate.Subsequently,a prediction model with lumped parameters was used to estimate the temperature evolution at different discharge rates of LIBs.The predicted results match well with the experimental results at all discharge rates.Therefore,the thermal model is suitable to predict the average temperature for the large-scale batteries under normal operating conditions.     

Microstructure and Thermophysical Properties of SrZrO<Subscript>3</Subscript> Thermal Barrier Coating Prepared by Solution Precursor Plasma Spray

Strontium zirconate (SrZrO₃) thermal barrier coatings were deposited by solution precursor plasma spray (SPPS) using an aqueous precursor solution. The phase transition of the SrZrO₃ coating and the influence of the aging time at 1400 °C on the microstructure, phase stability, thermal expansion coefficient, and thermal conductivity of the coating were investigated. The unique features of SPPS coatings, such as interpass boundary (IPB) structures, nano- and micrometer porosity, and through-thickness vertical cracks, were clearly observed evidently in the coatings. The vertical cracks of the coatings remained substantially unchanged while the IPB structures gradually diminished with prolonged heat treatment time. t-ZrO₂ developed in the coatings transformed completely to m-ZrO₂ phase after heat treatment for 100 h. Meanwhile, the SrZrO₃ phase in the coatings exhibited good phase stability upon heat treatment. Three phase transitions in the SrZrO₃ coatings were revealed by thermal expansion measurements. The thermal conductivity of the as-sprayed SrZrO₃ coating was ~1.25 W m^?1 K^?1 at 1000 °C and remained stable after heat treatment at 1400 °C for 360 h, revealing good sintering resistance.     

Facile Synthesis of Anatase TiO<Subscript>2</Subscript> Nanospheres as Anode Materials for Sodium-Ion Batteries

Anatase TiO₂ nanospheres (ATNSs) were successfully prepared through a facile solvothermal method followed by a thermal treatment. The sample was characterized by scanning electrons microscopy, transmission electron microscopy, x-ray diffraction, Raman spectrum and nitrogen adsorption techniques. When tested as an anode material for sodium-ion batteries, the electrode of ATNSs delivered a large discharge capacity of 208 mAh g^?1 after 100 cycles at a current density of 50 mA g^?1, indicating excellent cycling performance. This could be attributed to the uniform structure of the nanospheres with large surface area and porous nature, providing more active sites, buffering volume change, and facilitating the sodium ion intercalation as well as rapid diffusion during the charge/discharge process. Cyclic voltammetry demonstrated that the sodium storage mechanism is mainly controlled by pseudocapacitive behavior, resulting in a large capacity and outstanding cycling stability.     

Ascorbic Acid-Assisted Eco-friendly Synthesis of NiCo<Subscript>2</Subscript>O<Subscript>4</Subscript> Nanoparticles as an Anode Material for High-Performance Lithium-Ion Batteries

We have synthesized NiCo₂O₄ nanoparticles (NCO NPs) using an ascorbic acid-assisted co-precipitation method for the first time. When NCO NPs are used as an anode material for lithium-ion batteries, the cell exhibits superior lithium storage properties, such as high capacity (700 mA h g^?1 after 300 cycles at 200 mA g^?1), excellent rate capabilities (applied current density range 100–1200 mA g^?1), and impressive cycling stability (at 1200 mA g^?1 up to 650 cycles). The enhanced electrochemical properties of NCO NPs are due to the nanometer dimensions which not only offers a smooth charge-transport pathway and short diffusion paths of the lithium ions but also adequate spaces for volume expansion during Li storage. Hence, this eco-friendly synthesis approach will provide a new strategy for the synthesis of various nanostructured metal oxide compounds, for energy conversion and storage systems applications.     

The Effects of KCl,NaCl and K<Subscript>2</Subscript>CO<Subscript>3</Subscript> on the High-Temperature Oxidation Onset of Sanicro 28 Steel

The present study investigates the early stages in the oxidation process of Sanicro 28 (Fe31Cr27Ni) stainless steel when exposed to an alkali salt (KCl, NaCl or K₂CO₃) for 2 h at 450 and 535 °C. After the exposure, the oxidized samples were analyzed with a combinatory method (CA, XPS and SEM–EDX). It was found that all three salts were corrosive, and the overall oxidation reaction rate was much higher at 535 °C than at 450 °C. There were clear differences in terms of the impact of cations (Na⁺, K⁺) and anions (Cl^?, CO₃ ^2?) on the initial corrosion process at both temperatures. When focusing on the cations, the presence of potassium ions resulted in a higher rate of chromate formation than in the presence of sodium ions. When studying the effect of anions, the oxidation of iron and chromium occurred at higher rates in the presence of both chloride salts than in the presence of the carbonate salt, and chloride salts seemed to possess higher diffusion rate in the gas phase and along the surface than carbonate salts. Moreover, at the higher temperature of 535 °C, the formed chromate reacted further to chromium oxide, and an ongoing oxidation process of iron and chromium was identified with a significantly higher reaction rate than at 450 °C.     

Synthesis and electrochemical performances of LiCoO<Subscript>2</Subscript> recycled from the incisors bound of Li-ion batteries

A new LiCoO₂ recovery technology for Li-ion batteries was studied in this paper. LiCoO₂ was peeled from the Al foil with dimethyl acetamide (DMAC), and then polyvinylidene fluoride (PVDF) and carbon powders in the active material were eliminated by high temperature calcining. Subsequently, Li₂CO₃, LiOH·H₂O and LiAc·2H₂O were added into the recycled powders to adjust the Li/Co molar ratio to 1.00. The new LiCoO₂ was obtained by calcining the mixture at 850°C for 12 h in air. The structure and morphology of the recycled powders and resulting samples were studied by XRD and SEM techniques, respectively. The layered structure of LiCoO₂ synthesized by adding Li₂CO₃ is the best, and it is found to have the best characteristics as a cathode material in terms of charge-discharge capacity and cycling performance. The first discharge capacity is 160 mAh·g⁻¹ between 3.0–4.3 V. The discharge capacity after cycling for 50 times is still 145.2 mAh·g⁻¹.     

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.     

Formation of high-density TiN/Ti<Subscript>5</Subscript>Si<Subscript>3</Subscript> ceramic composites using preceramic polymer

The formation, microstructure and properties of high-density TiN/Ti₅Si₃ ceramic composites created by the pyrolysis of preceramic polymer with filler were investigated. Methylpolysiloxane was mixed with TiH₂ as filler and ceramic composites prepared by pyrolysis at 1200°C to 1600°C under N₂, Ar and vacuum were studied. When a specimen with 70 vol.% TiH₂ was pyrolyzed up to 1600°C in a vacuum after a preheat treatment at 850°C in a N₂ atmosphere and subsequently heat-treated at 1600°C for 1 h under Ar at a pressure of 2 MPa, a ceramic composite with full density was obtained. The microstructure of the ceramic composite was composed of TiN and Ti₅Si₃ phases. Under specific pyrolysis conditions, a ceramic composite with a density of 99.2 TD%, a Vickers hardness of 18 GPa, a fracture toughness of 3.5 MPam^1/2, a flexural strength of 270 MPa and a electrical conductivity of 6200 ohm⁻¹·cm⁻¹ was obtained.     

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.