As-prepared Composite Powders Research Articles

Microstructure evolution of Ti64-TiBw composites via electron beam powder bed fusion using as-prepared composite powder as feedstock

A self-designed spherical Ti64 powder containing nanosized TiB whisker(TiBw) was developed by electrode induction melting gas atomization (EIGA), which was used as feedstock to prepare Ti64-TiBw composites by electron beam melting (EBM). Nano-scaled TiBw distributed along the grain boundaries, forming a discontinuous network structure in EBM-Ti64-TiBw composites. In order to elucidate the effect of nano-sized TiBw on microstructure and properties of EBM-Ti64-TiBw composites, heat treatment of as-fabricated EBM-Ti64-TiBw is performed from 800 to 1200 °C with interval of 100 °C, to regulate the size characteristics (diameter, aspect ratio) of TiBw, the revolution of microstructure and interface were studied in detail. The results indicate that Ti64/TiBw interface structure transforms from a semi-coherent interface to a coherent interface with increasing heat treatment temperature (HTT). Furthermore, TiBw begin to coarsen after the heat treatment above the β-transus temperature, leading to a weakening of its pinning effect on Ti64 matrix, and the discontinuous network structure disappears at 1000 °C. The growth and coarsening of TiBw are closely related to the diffusion rate of B atom in α-Ti and β-Ti phases. This work provides a theoretical foundation for size control of TiBw reinforcement and the elucidation of its evolution effect on microstructure in EBM-Ti64-TiBw composites.

High stability of silica-wrapped CsPbBr3 perovskite quantum dots for light emitting application

Encapsulating quantum dots (QDs) into other medium has been considered as an efficacious method to avoid the fluorescence degradation of QDs. Here, we proposed a facile method to embed CsPbBr3 perovskite QDs in silica matrix derived from (3-aminopropyl)triethoxysilane (APTES) at room temperature in open air. The QDs/SiO2 composite was extracted from the sol-gel solution by using a precipitation-encapsulation method assisted with APTES. As-prepared composite powder possess a high photoluminescence quantum yield (PLQY) of 68% and a full width at half maximum (FWHM) of ~23 nm. The QDs/SiO2 compounds show excellent stability after the five heating cycles (105 °C) and a continuous xenon irradiation (500 W, 70 °C). Besides, the products remain 94.3% and 98.6% photoluminescence (PL) intensity after 30 days of storage (25 °C) and 96 h of ultraviolet (UV) irradiation (λ = 365 nm) respectively. The white light-emitting diode (LED) was fabricated by coating green-emitting CsPbBr3@SiO2 composite powder and commercial red phosphors on blue chip. The fabricated white LED performed excellent light characteristics with a luminous efficacy (ηL) of 58.9 lmW-1 and a correlated color temperature (CCT, Tc) of 5829 K (current = 20 mA), it also display a wide color gamut with 126.8% of National Television System Committee (NTSC) color triangle area.

Spherical Composite Powder by Coupling Polymethyl Methacrylate and Boron Nitride via Spray Drying for Cosmetic Application.

In the present study, spherical composite powder was successfully prepared via spray drying process using polymethyl methacrylate (PMMA) and hexagonal boron nitride (h-BN) powders. The pristine and as-prepared composite powders were examined using scanning electron microscopy, a particle size analyzer, oil absorption, and specific surface area analyses. These powders were then mixed with linseed oil to prepare samples for UV-Visible-Near Infrared spectroscopy investigation to determine their light absorption ability. Blank and powder-added blemish balm creams were examined using a sun protection factor tester and a thermal conductivity tester. In addition, transmittances of these creams were also evaluated. The experimental results show that spray-dried spherical composite powder exhibited good oil absorption ability. The blemish balm cream with 10 wt.% spray-dried composite powder not only exhibited superior sunscreen protection ability, but also good thermal conductivity.

Synthesis and Photocatalytic Properties of Nitrogen Modified Titanium Dioxide

Summary Pure and nitrogen-doped titanium dioxide (N-doped TiO2) photocatalysts were prepared by non-aqueous sol-gel method by means of the reaction between titanium (IV) chloride (TiCl4) and C6H5CH2 OH (benzyl alcohol), used as precursors and urea serving as a nitrogen source. The phase formation and short-range order of the resulting particles were characterized by X-ray powder diffraction (XRD) and infrared (IR) spectroscopy. The crystallite size of as-prepared composite powders was in the range 12-35 nm. The aim of this work was to investigate the efficiency of N-doped TiO2 as a photocatalyst in degradation of model organic pollutants - dyes Reactive Black 5 (RB5) and Malachite Green (MG), under ultraviolet (UV) and visible (Vis) irradiation. 0ur results indicated that synthesized N-TiO2 nanocomposites slightly improved the photocatalytic activity under UV irradiation, compared to the pure titanium dioxide (TiO2), and had no effect under Vis light illumination.

Pretreated aluminium dross waste as a source of inexpensive alumina-spinel composite ceramic hollow fibre membrane for pretreatment of oily saline produced water

Pretreatment of produced water using ceramic membrane is considered promising due to its excellent separation performance and thermal and mechanical stabilities, however, the high cost of ceramic membranes discourages industries for large scale applications. The purpose of this work is to fabricate ceramic hollow fibre membranes from alumina-spinel composite powder synthesized from low-cost aluminium dross waste for the pretreatment of oily saline produced water. The hollow fibre membranes were prepared via phase inversion-based extrusion and sintering technique. Aluminium dross (less than 50 µm) was subjected to pre-treatment via water leaching and calcination, resulting in alumina (Al2O3) and spinel (MgAl2O4) as major constituents. Subsequently, the as-prepared alumina-spinel composite powder was used as a ceramic material in fabricating the hollow fibres. The effect of sintering temperatures on the morphology, crystalline phase, pore size and porosity, mechanical properties, and removal efficiencies of the alumina-spinel composite hollow fibre membranes were investigated. The microfiltration test of the hollow fibres was assessed using produced-water feed of 200 mg L−1 at 1 bar. The hollow fibre sintered at 1275 °C offers 92.41% rejection percentage of oil, the highest after 50 min of stable flux. Furthermore, turbidity was found to decrease from 378 NTU to 28.5 and 22.5 NTU for hollow fibres sintered at 1250 and 1275 °C after 2 h of filtration. In this work, the alumina-spinel composite hollow fibre membranes are found to be an effective tool as an alternative for the pretreatment of oily saline produced water.

Environmentally friendly wollastonite@TiO2 composite particles prepared by a mechano-chemical method

Core–shell wollastonite@TiO2 (W@T) composite particles are prepared by a mechano–chemical method (MCM) to improve the dispersion of TiO2 and reduce its dosage, and to achieve synergistic effects with the wollastonite mineral. The crystal structure, morphology, functional groups, and pigment properties of the as-prepared composite powders are determined. The W@T composite particles are formed by van der Waals force in addition to electrostatic attraction and chemical bonding. The anatase TiO2 coating is anchored on the wollastonite surface by SiOTi and CaOTi bonds. The W@T powders possess excellent characteristics such as whiteness of 96.6%, hiding power of 17.97g/m2, and oil absorption of 22.72g/100g. The properties of the W@T composite are similar to those of TiO2 and the former, which is much cheaper, can potentially substitute the latter as a white paint in many applications.

Fabrication and performance of Li4Ti5O12/C Li-ion battery electrodes using combined double flame spray pyrolysis and pressure-based lamination technique

Reduction of lithium-ion battery (LIB) production costs is inevitable to make the use of LIB technology more viable for applications such as electric vehicles or stationary storage. To meet the requirements in today's LIB cost efficiency, our current research focuses on an alternative electrode fabrication method, characterized by a combination of double flame spray pyrolysis and lamination technique (DFSP/lamination). In-situ carbon coated nano-Li4Ti5O12 (LTO/C) was synthesized using versatile DFSP. The as-prepared composite powder was then directly laminated onto a conductive substrate avoiding the use of any solvent or binder for electrode preparation. The influence of lamination pressures on the microstructure and electrochemical performance of the electrodes was also investigated. Enhancements in intrinsic electrical conductivity were found for higher lamination pressures. Capacity retention of highest pressurized DFSP/lamination-prepared electrode was 87.4% after 200 dis-/charge cycles at 1C (vs. Li). In addition, LTO/C material prepared from the double flame spray pyrolysis was also used for fabricating electrodes via doctor blading technique. Laminated electrodes obtained higher specific discharge capacities compared to calendered and non-calendered blade-casted electrodes due to superior microstructural properties. Such a fast and industrially compelling integrative DFSP/lamination tool could be a prosperous, next generation technology for low-cost LIB electrode fabrication.

Electrochemical Sensor Constructed Using a Carbon Paste Electrode Modified with Mesoporous Silica Encapsulating PANI Chains Decorated with GNPs for Detection of Ascorbic Acid

In this work, an electrochemical sensor constructed using a carbon paste electrode (CPE), modified with mesoporous silica encapsulating polyaniline (PANI) decorated with gold nanoparticles (GNPs) for the detection of ascorbic acid (AA), was presented. First of all, PANI latex was synthesized by emulsion polymerization. Then, the acid-catalyzed sol–gel solutions of tetraethyl silicate (TEOS) was prepared in the presence of d-glucose, followed by encapsulation of previously prepared PANI latex into as-prepared sol-gel solution. Upon formation of silica frameworks, electroactive composite powder was obtained. Subsequently, the as-prepared composite powder was subjected to Soxhlet extraction to remove d-glucose and the final product was denoted as PM silica. On the other hand, PGM silica was obtained by immersing PM silica in 5mL of 0.10mM HAuCl4 solution for 6h, which reduced the gold nanoparticles (GNPs) onto the surface of PANI chains located inside the nanochannels of wormhole-like mesoporous silica framework. The redox reactions that mediated between EB form of PANI and aqueous HAuCl4 solution were monitored and confirmed by FTIR spectra. The appearance of GNPs inside the PGM silica was characterized by TEM, XPS, XRD, and BET analyses. PGM silica was found to reveal higher redox capability as compared to that of PM silica based on the electrochemical CV studies.It should be noted that PGM silica-modified CPE was found to exhibit high sensitivity, a relatively low limit of detection, excellent sensing repeatability and a broader linear dynamic range for AA detection than those of bare CPE or PM silica-modified CPE. Moreover, A electrochemical sensor constructed from PGM silica-modified CPE was found to reveal better selectivity for a tertiary mixture of AA/DA/UA as compared to that of PM silica-modified CPE based on a series of studies of differential pulse voltammograms. In this work, the fabricated sensor showed reliable data in detecting AA in the tested commercially available products.

Silver nanoparticles-coated glass frits for silicon solar cells

Silver nanoparticles-coated glass frit composite powders for silicon solar cells were prepared by electroless plating. Silver colloids were used as the activating agent of glass frits. The products were characterized by X-ray diffraction, scanning electron microscopy, and differential scanning calorimetry. The characterization results indicated that silver nanoparticles with the melting temperature of 838 °C were uniformly deposited on glass frit surface. The particle size of silver nanoparticles could be controlled by adjusting the [Ag(NH3)2]NO3 concentration. The as-prepared composite powders were applied in the front side metallization of silicon solar cells. Compared with those based on pure glass frits, the solar cells containing the composite powders had the denser silver electrodes and the better silver–silicon ohmic contacts. Furthermore, the photovoltaic performances of solar cells were improved after the electroless plating.

Plasma preparation and low-temperature sintering of spherical TiC–Fe composite powder

A spherical Fe matrix composite powder containing a high volume fraction (82vol%) of fine TiC reinforcement was produced using a novel process combining in situ synthesis and plasma techniques. The composite powder exhibited good sphericity and a dense structure, and the fine sub-micron TiC particles were homogeneously distributed in the α-Fe matrix. A TiC–Fe cermet was prepared from the as-prepared spherical composite powder using powder metallurgy at a low sintering temperature; the product exhibited a hardness of HRA 88.5 and a flexural strength of 1360 MPa. The grain size of the fine-grained TiC and special surface structure of the spherical powder played the key roles in the fabrication process.

A novel TiAl3/Al2O3 composite coating on γ-TiAl alloy and evaluating the oxidation performance

A novel TiAl3/Al2O3 composite coating was prepared on γ-TiAl alloy. The process included two steps: (1) TiAl3/Al2O3 composite powders were prepared by high energy ball milling of pure Al and nano-TiO2 powders, followed by a heat-treatment; (2) the as-prepared composite powders were deposited on γ-TiAl substrate by cold spray. The cyclic oxidation was conducted at 900°C to test the performance of the composite coating. The results showed that the composite coating had good crack resistance and effectively decreased the oxidation rate of the substrate.

Fast synthesis of B4C–TiB2 composite powders by pulsed electric current heating TiC–B mixture

Abstract Synthesis of B4C–TiB2 composite powders via a carbide boronizing process was performed in a pulsed electric current sintering furnace with a specially designed graphite die/punch set-up. Pure B4C–TiB2 powders could be obtained at 1200 °C for 0 min or 1000 °C for 15 min with a total thermal cycle time of only 12–25 min. In the as-prepared B4C–TiB2 composite powders, submicrometer B4C particles were surrounded by nano-TiB2 particles with an average particle of less than 50 nm. The bulk B4C–TiB2 ceramic sintered from the as-prepared composite powders had a relative density of 96% with ultrafine microstructures.

Immobilization of silver nanoparticles onto the surface of Pb-based glass frit by a one-pot procedure involving polyol process and its application in conductive thick films

Silver nanoparticles (Ag NPs) were immobilized onto the surface of Pb-based glass frit by a fast one-pot synthetic method which only involved two reagents: AgNO3 and ethylene glycol (EG). The EG played two crucial roles in the procedure: reducing agent and reaction medium. XRD, SEM and TEM analysis revealed that Ag NPs were densely deposited onto the surface. The as-prepared composite powders were subsequently applied in conductive silver thick films. Sheet resistance was recorded by a four-point probe electrical contact method. Results showed that Ag NPs on the surface affected electrical conductivity of the films. The film from the composite powder with Ag NPs about 15 nm in diameter showed a resistance value of 5 mΩ/square as compared to 6.2 mΩ/square of that from the pure glass frit.

A simple method of synthesizing homogeneous La0.1Bi0.9FeO3–BiY2Fe5O12 composite powders

La0.1Bi0.9FeO3–BiY2Fe5O12 (abbreviated as LBFO–BYIG) composites were synthesized via a one-step sol–gel method. The synthesized composite powders were characterized using X-ray diffraction and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy. The magnetic properties of the as-prepared composite powders were investigated by a vibrating sample magnetometer. The as-prepared LBFO–BYIG composite powders show a good homogeneity of the two phases and a good crystallinity. Additionally, the magnetization of LBFO can be improved by the introduction of proper amount of BYIG.

Synthesis and characterization of WC—VC—Co nanocomposite powders through thermal-processing of a core—shell precursor

WC—VC—Co nanocomposite powders were synthesized through simultaneous reduction and carburization of a novel precursor in vacuum at 950 °C for 1 h. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The precursor consisted of nanoparticles (from 10 nm to 30 nm in diameter) with a carbon-coated core—shell structure. The as-prepared composite powders comprised spherical particles with size in the range of 40—60 nm. The effects of experimental parameters and reaction mechanism were explored. The low-temperature synthesis and short reaction time were attributed to the homogeneous chemical composition of the precursor.

Preparation of nanostructured alumina–titania composite powders by spray drying, heat treatment and plasma treatment

Nanostructured Al2O3–13wt.%TiO2 composite powders were successfully prepared by spray drying, heat treatment and plasma treatment. The as-prepared composite powders were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy, respectively. The tap density and flowability were measured by tap density instrument and hall flowmeter, respectively. The results showed that the minimum water content of the slurry suitable for spray drying was 47wt.%, and the corresponding spray dried powders had the maximum density and flowability. Spherical and porous powders had been obtained by spray drying technology. The sphericity of the particles and the pores in the particles were decreased after heat treatment, and the density of the powders was increased. The composite particles underwent fast liquid sintering process in high energy plasma flame. After plasma treatment, spherical powders with smooth surface were formed. The plasma treated composite particles were composed of a large number of nano-sized grains. The tap density of the spray dried powders was increased after heat treatment, and the tap density of the heat treated powders was further increased after plasma treatment. The flowability of the spray dried powders was decreased after heat treatment, and the flowability of the heat treated powders was significantly improved after plasma treatment.

Synthesis of uniformly dispersed carbon nanotube reinforcement in Al powder for preparing reinforced Al composites

In order to obtain homogeneously dispersed carbon nanotube (CNT) reinforcement with well structure in Al powder, a novel and simple approach was developed as a means of overcoming the limits of traditional mixing methods. This process involves the even deposition of Ni catalyst onto the surface of Al powder by impregnation route with a low Ni content (0.5 wt.%) and in situ synthesis of CNTs in Al powder by chemical vapor deposition. The in situ synthesized CNTs with well-crystallized bamboo-like structure in the composite powders can obviate the reaction with Al below 1000 °C. The feasibility of fabricating CNT/Al composites with high mechanical properties using the as-prepared composite powders was proved by our primary test, which indicated that the compressive yield stress and elastic modulus of 1.5 wt.%-CNT/Al composites synthesized by hot extrusion are 2.2 and 3.0 times as large as that of the pure Al matrix.

N-doped TiO 2/ZnO composite powder and its photocatalytic performance for degradation of methyl orange

The N-doped TiO 2/ZnO composite powder with a molar ratio of Ti to Zn of 3/1 was prepared via sol–gel process and then ammonia treated with NH 3 mass fractions of 0%, 7%, and 28% for 24 h at room temperature followed by thermal calcinations in air for 2 h at various temperatures of 500, 600, and 700 °C. The as-prepared composite powder was characterized in detail through thermo-gravimetric analyzer, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy. The results showed that the phase transformation of anatase to rutile has been successfully retarded via the ammonia treating process, leading to the presence of anatase phase in the composite. The particle crystallization of the composite powder was significantly promoted with the increase of the calcining temperature. The photocatalysis evaluation through MO degradation revealed an enhanced photocatalytic activity for the composite powder that might be related to the good crystallization, the presence of anatase phase, and the particle size reduction of the powder.

Characterization of sintered TiC–SiC composites

TiC–SiC composites were fabricated using TiC and SiC powders as starting materials at the range of 1650–2000 °C in Ar atmosphere by two-step method. In the first step, the ingots with intragranular SiC or TiC particle were prepared by arc-melting technique, subsequently, crushed and ground into TiC and SiC composite powders. In the second step, TiC–SiC composites were sintered using these as-prepared composite powders by SPS method. It was concluded that these TiC–SiC composites prepared by two-step method showed more excellent properties than that prepared by arc-melting technique. The hardness of the fabricated TiC–SiC composites was 25–27 GPa at the load of 0.98–9.8 N, which was obviously greater than that of arc-melting composites. The thermal conductivity of the TiC–SiC composites was 18–48 W K −1 m −1 at the range of 298–1273 K and slightly decreased with increasing temperature. The electrical conductivity of the composites was (2–5) × 10 5 S m −1 at the range of 298–1273 K and slightly decreased with increasing temperature.

Synthesis of fluorine-doped titania-coated activated carbon under low temperature with high photocatalytic activity under visible light

Fluorine-doped anatase titania sols were synthesized by hydrolysis of titanium- n-butoxide in the presence of abundant acidic aqueous solution and using ammonium fluoride as fluorine precursors, under mild condition. The prepared fluorine-doped titania nanoparticles were loaded on activated carbon in a rotatory evaporator under vacuum to form a composite photocatalyst. X-ray diffraction, Fourier transform infrared spectrum analysis, UV–visible spectroscopy, scanning electron microscope and Brunauer–Emmett–Teller adsorption measurement were used to characterize these as-prepared powders. The photocatalytic activity of the sample was evaluated by degrading phenol under visible light. Results showed that the composite photocatalyst was porous due to its nano–microstructure. The number of hydroxyl groups on the titania surface was enhanced after fluorine doping. Compared with pure titania–activated carbon and Degussa P25, the as-prepared composite powders exhibited much higher photocatalytic activity, although absorption response range into the visible region was not detected by diffuse reflection spectra.