Oxide Composite Powders Research Articles

Microstructural evolution during densification process of neodymium-doped indium zinc oxide ceramic targets and application for high mobility films

Oxide targets are crucial materials for transparent conducting oxide (TCO) thin films used in optoelectronic devices. In this study, neodymium-doped indium zinc oxide (NdIZO) ceramic targets were prepared using an advanced pressureless oxygen atmosphere sintering process. By optimizing the experimental conditions, the best sintering parameters were obtained, resulting in dense, fine-grained, and uniformly microstructured NdIZO targets. The influence mechanism of different Nd doping concentrations on the phase composition, microstructure evolution, and electrical properties of the targets during the process of oxide composite powder, green body shaping, and sintering densification was analyzed in detail. The results showed that the pretreatment of the composite powder improved its dispersibility, and sintering activity. The NdIZO-2 target with an atomic ratio of Nd:In:Zn = 0.02:1:1, fabricated under optimal conditions, exhibited high density of 99.8 %, low resistivity of 5.2 mΩ cm, and an average grain size of about 3.9 μm, thereby demonstrating the best comprehensive performance. Moreover, the sputtered films prepared using NdIZO-2 targets also showed excellent properties with transmittance (T) of 88.1 %, electron mobility (μe) of 31.5 cm2/Vs, and resistivity (ρ) of 7.5 × 10−3 Ω cm. This work provides theoretical support for the preparation of high-quality indium zinc oxide (IZO) ceramic targets and their application in high-performance optoelectronic thin film devices.

Fabrication of ZnO@Fe2O3 superhydrophobic coatings with high thermal conductivity

Efficient thermal management materials are an integral part of electronic devices and can quickly contribute to their heat dissipation, thereby greatly improving their reliability, stability and service life. However, the inherent hygroscopicity of the film surface sets obstacles to the reliability and structural stability of electronic devices. To address these issues, a bionic structural design was obtained by spraying a polyurethane/stearic acid/zinc oxide‑iron oxide composite powder (TPU/STA/ZnO@Fe2O3) on the surface of graphene composite films. At the same time, the graphene composite film has a high in-plane thermal conductivity (up to 533 W−1·m−1·K−1) and is able to reduce the film surface temperature to room temperature within 5 s due to its highly ordered layered design and strong hydrogen bonding interactions. In addition, the composite film offers a range of advantages such as good hydrophobicity and electrical conductivity. With a water contact angle of up to 159.5 ± 2° and an electrical conductivity of up to 3 × 103 S/m in steady state, the results show that the superhydrophobic graphene composite film has good physical, chemical and mechanical stability, as well as self-cleaning capabilities. It also retains good flexibility and reliability under 350 bending cycles. In this regard, the development of graphene composite films with high thermal conductivity, high superhydrophobicity, good electrical conductivity and flexibility is expected to be used as thermally conductive materials, opening up a new path in the field of thermally conductive heat dissipation materials for electronic components.

Effect of Polyaniline and Graphene Oxide Composite Powders on the Protective Performance of Epoxy Coatings on Magnesium Alloy Surfaces

Composite fillers are often used to improve the protective properties of coatings. To obtain a high protective performance of epoxy coatings for magnesium alloys, polyaniline (PANI) and graphene oxide (GO) composite powders were selected because of their corrosion inhibition and barrier performance, respectively. The paper mainly focuses on the effect of the preparation methods of the composite powders on the protective performance. PANI and GO composite powders were prepared by in situ polymerization and blending, respectively. First, the composite powder was characterized by X-ray diffractometer, Fourier transform infrared spectroscopy, and scanning electron microscopy. Then, the different composite powders and pure PANI powder were dispersed uniformly in epoxy resin, and the coating was prepared on the surface of the AZ91D magnesium alloy and studied by an electrochemical impedance test, adhesion strength test and physical properties test. The results show that the impedance value of the coating with the added PANI and GO composite powders by in situ polymerization was 4 × 109 Ω·cm2 and higher than that with the added pure PANI (4 × 109 Ω·cm2) and PANI and GO mixed powders (1 × 109 Ω·cm2) after 2400 h immersion in a 3.5% NaCl solution; the former also had better flexibility, ss impact resistance, and adhesion strength. Compared with the direct blending method, the PANI and GO polymerization powders can exert the shielding effect of GO and PANI corrosion inhibition better and achieve a better protective effect on the magnesium alloy.

Exploring hydroxyapatite/graphene oxide/zinc oxide composite powders for the preparation of bioactive-antibacterial coatings by HVOF

Exploring hydroxyapatite/graphene oxide/zinc oxide composite powders for the preparation of bioactive-antibacterial coatings by HVOF

Explosion characteristics and mechanism of aluminum-reduced graphene oxide composite powder

Aluminum-based fuel in energetic formulations has favorable ignition and combustion characteristics, but it is also prone to an explosion. To ensure safe production and prevent accident, explosion characteristics and the mechanism of aluminum-reduced graphene oxide (Al-RGO) composite were investigated. Thermal analysis showed that after adding RGO, the activation energy of Al dust in the initial oxidation stage decreased from 241.5 kJ/mol to 90.0 kJ/mol. With the addition of 5 wt% RGO, PTFE, and Ni inclusions, the minimum explosible concentration increased by 40%, 10%, and 25%, the maximum explosion pressure increased by 20.8%, 13.8%, and 7.5%, respectively. Moreover, the addition of RGO could significantly improve the flame propagation speed and oxidation efficiency of aluminum but with a slight effect on the burning time of single Al particles. XPS results revealed that the major explosion product of Al-RGO is Al2O3. Based on these results, the explosion mechanism of Al-RGO was discussed in-depth.

Recovery and Reuse of Spent ITO Targets through Electrochemical Techniques

Indium is a strategically scarce metal with excellent conductivity and light transmittance that is widely used to prepare ITO targets. In this work, an electrolysis method was exploited to recover and reuse spent ITO (s-ITO) targets to provide a novel way to recycle valuable resources. The electrochemical behaviors of indium tin oxide were studied first by cyclic voltammetry in CaCl2 at 850 °C. A reduction peak corresponding to the simultaneous reduction of indium tin oxide was found at −0.5 V vs Pt. Then, indium-tin alloy was recovered by electrolysis of s-ITO particles in CaCl2 at −2.8 V and 850 °C. The mass ratio of In and Sn in the alloy obtained by electrolysis is almost the same as that in the initial s-ITO before electrolysis. In addition, oxide composite powders were obtained by electrolysis of the alloy in NH4Cl aqueous solution, which can be used to synthesize ITO targets. The particle size of the composite powders was between 20 nm and 60 nm, and the distribution of each element was uniform.

Effect of high-energy attrition milling and La2O3 content on the microstructure of Mo-La2O3 composite powders

Mo-La2O3 composites are potential high-temperature materials for future technology devices operating at temperatures above 1300 °C because of their excellent thermal stability, high mechanical properties and good creep resistance. In this study, we focused on the preparation of Mo-matrix/lanthanum oxide (La2O3) composite powders using high-energy attrition milling. The effects of rotational milling speed (350 and 800 rpm) and La2O3 content (2.5 and 10 vol. %) on the microstructural evolution, phase composition, morphology, and distribution of the second phase in the produced composite Mo-La2O3 powders were investigated in details. The results show that the most interesting composite powder was Mo-10 vol.% La2O3 produced using a rotational speed of 800 rpm, which exhibited better distribution, smaller particle size and higher amount of ceramic phase introduced in the interiors of the Mo grains.

Hierarchical porous Fe3O4/RGO nanocomposite powders as high performance microwave absorbers

Fe3O4/reduced graphene oxide (RGO) composite powders were prepared by solution combustion synthesis method. The effects of fuel type; glycine and urea; on the structure, microstructure, magnetic, and microwave absorption properties were characterized by modern methods. A mixture of α-Fe2O3 and Fe3O4 phases was obtained by the urea fuel, while the glycine fuel led to the pure Fe3O4 phase. The scanning and transmission electron microscopy showed the Fe3O4 nanoparticles were distributed on the ultrathin RGO sheets. With the addition of RGO, the saturation magnetization increased up to 84 emu/g due to the higher amounts of the magnetite phase. The Fe3O4/RGO composite powders synthesized by the urea fuel showed a reflection loss (RL) of −28 dB with effective bandwidth of 1.4 GHz in the C1 band at the matching thickness of 3.7 mm. However, the pristine Fe3O4 powders prepared by the glycine fuel had higher absorption properties, including higher RL of −33 dB and broader bandwidth of 3 GHz in the Ku band at the matching thickness of 1.2 mm. In addition to the higher magnetic and dielectric losses, the higher microwave absorption performance was attributed to the better impedance matching property caused by the porous microstructure.

Solution combustion synthesis of nickel sulfide/reduced graphene oxide composite powders as electrode materials for high-performance supercapacitors

Nickel sulfide/reduced graphene oxide composite powders were prepared by solution combustion method using nickel nitrate and graphene oxide as oxidants together with thioacetamide, either alone or admixed with glycine, as fuel. Graphene oxide was in-situ reduced during combustion process. Phase, structure, and microstructure of the combusted powders were tuned by proper use of the type and amount of fuels. With the increase of glycine as an auxiliary fuel, bulky microstructures of sintered particles were appeared. The nickel sulfide/reduced graphene oxide composite powders showed the pseudocapacitive behavior with a high specific capacitance of 305 F g−1 at a current density of 1.1 A g−1. The high conductivity of reduced graphene oxide and distribution of nickel sulfide nanoparticles on reduced graphene oxide sheets led to the high capacity retention of 91% after 3000 cycles.

Characteristics of hydroxyapatite-reduced graphene oxide composite powders synthesized via hydrothermal method in the absence and presence of diethylene glycol

The synthesis of nanocomposites containing hydroxyapatite and graphene sheets has received much attention recently. Therefore, strategies that improve their properties will be useful. The aim of this study was to investigate the effect of diethylene glycol on the characteristics of hydroxyapatite-reduced graphene oxide powders synthesized by a hydrothermal method (180 ​°C, 5 ​h) and the nanocomposites obtained by spark plasma sintering (950 ​°C, 50 ​MPa). Graphene oxide, calcium nitrate tetrahydrate and diammonium hydrogenphosphate were used as precursors. The characterization methods included electron microscopy, X-ray diffraction, Raman spectroscopy, and indentation technique. Obtained results have shown that the presence of diethylene glycol reduced the average size of hydroxyapatite crystallites from 27 to 16 nm, reduced the particle size distribution, and increased the graphene oxide reduction rate. The presence of diethylene glycol during the synthesis process increased the elastic modulus (from 116.4 ​± ​4.9 to 125 ​± ​3.8 ​GPa), hardness (from 4.08 ​± ​0.7 to 6.32 ​± ​0.4 ​GPa), and fracture toughness (from 1.66 ​± ​0.7 to 1.87 ​± ​0.9 ​MPa ​m0.5) of the composite.

Preparation and characterization of Cr-doped tungsten oxide by liquid-liquid doping precursor

The tungsten oxides with uniformly grain growth inhibitor elements can significantly improve the distribution of inhibitors in the subsequent WC powders, and finally enhanced the properties of ultra-fine grained cemented carbides. Thus, a new liquid-liquid doping method was used to prepare the tungsten oxide composite powders with grain growth inhibitor elements by spray drying-calcining process. The microstructure and phase transition of Cr-doped and undoped tungsten oxide composite powders were studied by TG/DSC, XRD, SEM, and XPS. The results showed that Cr doping has little effect on the morphology of the precursor powders after spray drying. However, the existence of ammonium chromate had a significant effect on the properties of the calcined tungsten oxide. The volume expansion of ammonium chromate could reduce the decomposition temperature of ammonium tungstate precursor powders. Additionally, the formation of thermodynamic instability Cr-O-W compound could be the reason for the exothermic peak appeared at 486.3 °C. Moreover, the ‘liquid-liquid’ doping method guaranteed the uniform distribution of Cr2O3, which was favourable for the stable existence of hexagonal metastable h-WO3. The tungsten oxide powders calcined at 600 °C have a flaky morphology due to the uniform distribution of Cr2O3, and the uniform distribution of Cr2O3 in the powder can also prevent the grain growth of WO3.

Synthesis of Porous Cu-Co using Freeze Drying Process of Camphene Slurry with Oxide Composite Powders

Synthesis of Porous Cu-Co using Freeze Drying Process of Camphene Slurry with Oxide Composite Powders

Synthesis and characterization of nanocrystalline CuO/ZnO composite powders with enhanced photodegradation performance under sunlight irradiation

In the present work, the sol–gel auto-combustion method has been used to synthesize nanocrystalline copper-zinc oxide composite powders with different weight ratios using diethanolamine (DEA) as fuel. The structural, morphological, optical, and magnetic properties including the local atomic structure of each calcined sample were systematically characterized by means of XRD, SEM, UV-DRS, VSM, and synchrotron XANES measurements. The XRD results revealed the complete formation of CuO/ZnO nanocomposites, composed of monoclinic CuO and hexagonal wurtzite ZnO structures without any impurity phases. The observation of XANES spectra confirms that both Zn and Cu ions in all samples exhibit only fourfold coordination with oxygen atoms. UV-DRS analysis demonstrated that CuO-rich composites exhibited strong absorption in visible light with moderate infrared reflection efficiency as compared to the pure ZnO sample, but ZnO-rich composites show distinctive absorption in infrared region. According to magnetic measurements, both paramagnetism and ferromagnetism can simultaneously arise as the CuO content increases within the CuO/ZnO composites. The photocatalytic activity of CuO/ZnO composites was evaluated by the decomposition of four types of pollutants: phenol rhodamine B (RhB), heteropolyaromatic methylene blue (MB), azoic methyl orange (MO), and methyl red (MR) under sunlight irradiation. In comparison with pure ZnO, those CuO/ZnO samples for which the ratio has been optimized exhibit enhanced photocatalytic degradation in all organic dyes, reaching 90–96% within a period of 150 min. From these results, it can be argued that CuO/ZnO composites show considerable potential for the harvesting of solar energy as well as environmental remediation.

Effects of Milling Time, Zirconia Addition, and Storage Environment on the Radiopacity Performance of Mechanically Milled Bi2O3/ZrO2 Composite Powders.

Mineral trioxide aggregate (MTA) typically consists of Portland cement (75 wt.%), bismuth oxide (20 wt.%), and gypsum (5 wt.%) and is commonly used as endodontic cement. Bismuth oxide serving as the radiopacifying material reveals the canal filling effect after clinical treatment. In the present study, bismuth/zirconium oxide composite powder was prepared by high energy ball milling of (Bi2O3)100−x (ZrO2)x (x = 5, 10, 15, and 20 wt.%) powder mixture and used as the radiopacifiers within MTA. The crystalline phases of the as-milled powders were examined by the X-ray diffraction technique. The radiopacities of MTA-like cements prepared by using as-milled composite powders (at various milling stages or different amount of zirconia addition) were examined. In addition, the stability of the as-milled powders stored in an ambient environment, an electronic dry box, or a glove box was investigated. The experimental results show that the as-milled powder exhibited the starting powder phases of Bi2O3 and ZrO2 and the newly formed δ-Bi7.38Zr0.62O2.31 phase. The longer the milling time or the larger the amount of the zirconia addition, the higher the percentage of the δ-Bi7.38Zr0.62O2.31 phase in the composite powder. All the MTA-like cements prepared by the as-milled powder exhibited a radiopacity higher than 4 mmAl that is better than the 3 mmAl ISO standard requirement. The 30 min as-milled (Bi2O3)95(ZrO2)5 composite powder exhibited a radiopacity of 5.82 ± 0.33 mmAl and degraded significantly in the ambient environment. However, storing under an oxygen- and humidity-controlled glove box can prolong a high radiopacity performance. The radiopacity was 5.76 ± 0.08 mmAl after 28 days in a glove box that was statistically the same as the original composite powder.

Excellent Tribological Properties of Lower Reduced Graphene Oxide Content Copper Composite by Using a One-Step Reduction Molecular-Level Mixing Process.

Reduced graphene oxide (RGO) composite copper matrix powders were fabricated successfully by using a modified molecular-level mixing (MLM) method. Divalent copper ions (Cu2+) were adsorbed in oxygen functional groups of graphene oxide (GO) as a precursor, then were reduced simultaneously by one step chemical reduction. RGO showed a distribution converting from a random to a three-dimensional network in the copper matrix when its content increased to above 1.0 wt.% The tribological tests indicated that the friction coefficient of the composite with 1.0 wt.% RGO decreased markedly from 0.6 to 0.07 at an applied load of 10 N, and the wear rate was about one-third of pure copper. The excellent tribological properties were attributed to a three-dimensional and uniform distribution, which contributes to improving toughness and adhesion strength.

Synthesis and characterization of Co3O4/SnO2 composite powders by microwave assisted sol-gel method

Cobalt oxide (Co3O4)/tin oxide (SnO2) composite powders were synthesized by microwave-assisted sol-gel method. The Co3O4/SnO2 composite powders were treated with microwave power of 300W for 10 min and calcined at 1000 °C for 4 hr in air. The XRD patterns show both of Co3O4 and SnO2 phases. The SEM images reveal that Co3O4/SnO2 composite powders exhibit the agglomerated particles with particle size of 0.5-2 µm in range. The optical properties of the samples show absorption bands range of 230-350 nm and 520 – 750 nm.

Aerosol synthesis of molybdenum diselenide–reduced graphene oxide composite with empty nanovoids and enhanced hydrogen evolution reaction performances

MoSe2–reduced graphene oxide (rGO) composite powders with unique structures containing empty nanovoids and excellent hydrogen evolution reaction (HER) performances were prepared using a pilot-scale spray-drying process. One-step post-treatment of the spray-dried powders produced the macroporous MoSe2–rGO composite with empty nanovoids through an intermediate MoO3–Se–GO composite. Ultrafine MoSe2 nanocrystals, which consisted of a few layers and were several nanometers in size, were uniformly dispersed on the surfaces of the MoSe2–rGO composite powders with the optimal rGO contents. The MoSe2–rGO–M composite (20wt% rGO) had the optimized porous structure with a uniform distribution of MoSe2 nanocrystals and enough the rGO content for a fast electron transport, and thus exhibited the highest HER activity. The MoSe2–rGO–M composite powders exhibited a current density of 10mAcm−2 at a small overpotential of 0.21V, which was lower than that of bare MoSe2 (10mAcm−2 at 0.31V). The Tafel slopes for bare MoSe2 and MoSe2–rGO–M composite powders were 120 and 57mVdec–1, respectively. The synergistic effects of rGO sheets and MoSe2 nanocrystals and the unique porous structure resulted in outstanding HER performance with a small Tafel slope and overpotential.

Electrochemical properties of WO3-reduced graphene oxide composite powders prepared by one-pot spray pyrolysis process

In this work, we report the preparation of WO3-reduced graphene oxide (rGO) composite powders by spray pyrolysis process using a stable graphene oxide colloidal solution with ammonium tungstate. The ultrafine WO3 nanocrystals below 10 nm in size are dispersed within the rGO matrix. The bare WO3 powders prepared from the aqueous spray solution of ammonium tungstate are spherical and do not aggregate. The bare WO3 and WO3-rGO composite powders show monoclinic and cubic crystal structures, respectively. The initial discharge capacities of the bare WO3 and WO3-rGO composite powders at a current density of 100 mA g−1 are 771 and 941 mA h g−1, respectively, and their initial Coulombic efficiencies are 67 and 65%, respectively. The discharge capacities of the bare WO3 and WO3-rGO composite powders at the 300th cycle are 282 and 546 mA h g−1, respectively.

Na-ion Storage Performances of FeSe(x) and Fe2O3 Hollow Nanoparticles-Decorated Reduced Graphene Oxide Balls prepared by Nanoscale Kirkendall Diffusion Process.

Uniquely structured FeSex-reduced graphene oxide (rGO) composite powders, in which hollow FeSex nanoparticles are uniformly distributed throughout the rGO matrix, were prepared by spray pyrolysis applying the nanoscale Kirkendall diffusion process. Iron oxide-rGO composite powders were transformed into FeSex-rGO composite powders by a two-step post-treatment process. Metallic Fe nanocrystals formed during the first-step post-treatment process were transformed into hollow FeSex nanoparticles during the selenization process. The FeSex-rGO composite powders had mixed crystal structures of FeSe and FeSe2 phases. A rGO content of 33% was estimated from the TG analysis of the FeSex-rGO composite powders. The FeSex-rGO composite powders had superior sodium-ion storage properties compared to those of the Fe2O3-rGO composite powders with similar morphological characteristics. The discharge capacities of the FeSex- and Fe2O3-rGO composite powders for the 200th cycle at a constant current density of 0.3 A g−1 were 434 and 174 mA h g−1, respectively. The FeSex-rGO composite powders had a high discharge capacity of 311 mA h g−1 for the 1000th cycle at a high current density of 1 A g−1.

One-Pot Synthesis of CoSex -rGO Composite Powders by Spray Pyrolysis and Their Application as Anode Material for Sodium-Ion Batteries.

A simple one-pot synthesis of metal selenide/reduced graphene oxide (rGO) composite powders for application as anode materials in sodium-ion batteries was developed. The detailed mechanism of formation of the CoSe(x)-rGO composite powders that were selected as the first target material in the spray pyrolysis process was studied. The crumple-structured CoSe(x)-rGO composite powders prepared by spray pyrolysis at 800 °C had a crystal structure consisting mainly of Co0.85 Se with a minor phase of CoSe2. The bare CoSe(x) powders prepared for comparison had a spherical shape and hollow structure. The discharge capacities of the CoSe(x)-rGO composite and bare CoSe(x) powders in the 50th cycle at a constant current density of 0.3 A g(-1) were 420 and 215 mA h g(-1), respectively, and their capacity retentions measured from the second cycle were 80 and 46%, respectively. The high structural stability of the CoSe(x)-rGO composite powders for repeated sodium-ion charge and discharge processes resulted in superior sodium-ion storage properties compared to those of the bare CoSe(x) powders.