Pretreatment Of Powder Research Articles

Influence of TiC Content on Microstructure and Properties of W-30Cu/TiC Composites

W-30Cu/ x TiC ( x= 0∼4, wt%) composite powders were prepared by electroless plating with simplified pretreatment. The composite powders were formed by cold compaction under 400 MPa using a tablet machine and green compactions were sintered at 1300 °C for 1 h. Micromorphology of the original W and TiC powders, simple-treated W and TiC powders, and as-received W-30Cu/ x TiC ( x= 0∼4) composite powders after electroless plating were characterized by field emission scanning electron microscopy (FE-SEM). Microstructures of the W-30Cu/ x TiC ( x= 0∼4) composites were also investigated by FE-SEM. The effect of TiC content on the properties of W-30Cu/ x TiC ( x= 0∼4) composites (such as relative density, hardness, electrical conductivity, and compressive strength) were studied. Results show that W-30Cu/TiC composite powders with uniform structure are obtained by simplified W and TiC powder pretreatment, followed by electroless copper plating. When TiC content is less than 1 wt%, the compressive strength and hardness of composite materials obviously increase and the electrical conductivity of composite materials decreases with TiC content increasing. However, the electrical conductivity of composite materials is still higher than that of the national standard value. With a certain amount of TiC content to W-30Cu/ x TiC ( x= 0∼4) composites, the composites exhibit good comprehensive performance.

Lignocellulose nanofibers prepared by ionic liquid pretreatment and subsequent mechanical nanofibrillation of bagasse powder: Application to esterified bagasse/polypropylene composites

In the present study, we examined the efficacy of choline acetate (ChOAc, a cholinium ionic liquid))-assisted pretreatment of bagasse powder for subsequent mechanical nanofibrillation to produce lignocellulose nanofibers. Bagasse sample with ChOAc pretreatment and subsequent nanofibrillation (ChOAc/NF-bagasse) was prepared and compared to untreated control bagasse sample (control bagasse), bagasse sample with nanofibrillation only (NF-bagasse) and with ChOAc pretreatment only (ChOAc-bagasse). The specific surface area was 0.83m2/g, 3.1m2/g, 6.3m2/g, and 32m2/g for the control bagasse, ChOAc-bagasse, NF-bagasse, and the ChOAc/NF-bagasse, respectively. Esterified bagasse/polypropylene composites were prepared using the bagasse samples. ChOAc/NF-bagasse exhibited the best dispersion in the composites. The tensile toughness of the composites was 0.52J/cm3, 0.73J/cm3, 0.92J/cm3, and 1.29J/cm3 for the composites prepared using control bagasse, ChOAc-bagasse, NF-bagasse, and ChOAc/NF-bagasse, respectively. Therefore, ChOAc pretreatment and subsequent nanofibrillation of bagasse powder resulted in enhanced tensile toughness of esterified bagasse/polypropylene composites.

Evaluation of the natural coagulant Moringa oleifera as a pretreatment for SODIS in contaminated turbid water

Solar Disinfection of water (SODIS) is a treatment method that traditionally exposes low turbidity water filled in clear bottles to direct sunlight up to 6 h. Typically, water should have turbidity lower than 30 NTU before solar exposure; however turbidities of water sources in communities vary and can reach higher than 200 NTU. In order to reduce turbidity, flocculating agents like Moringa oleifera (Moringa) may be used. In this study we assess the efficacy of Moringa to clear turbid water as a pretreatment for SODIS. We initially evaluate two preparations– powdered seeds and an aqueous filtrate of the seeds, to determine if these can benefit SODIS in turbid, E. coli contaminated water (Experiment 1). We show that powdered Moringa seeds reduce turbidity best and that SODIS treatment of highly turbid water was effective regardless of reduced turbidity. Overnight, however; a bio-active sludge layer formed. We then determined if 24 h Moringa pretreatment and decanting can maintain water quality over an extended period (Experiment 2). After 24 h Moringa treatment showed a 2.1 log reduction in E. coli, increasing following SODIS (6-log) E. coli without nightly recovery or sludge formation. Untreated turbid controls showed SODIS disinfection after 6 h direct sunlight; however, nightly regrowth and sludge layer formation occurred by 48 h. These results suggest that SODIS is capable of inactivating bacteria in highly turbid water at 6 h; however, active biofilm sludge layers formed by 48 h. We conclude that, for longer term water storage, we find a combination of Moringa seed powder pretreatment prior to SODIS to be optimal.

Fabrication of fine-grained spherical tungsten powder by radio frequency (RF) inductively coupled plasma spheroidization combined with jet milling

Fine-grained spherical tungsten powder with particle size from 6μm to 11μm has been fabricated by a well-designed method with two simple steps. A pretreatment of tungsten powder was carried out in the first step. Complete dispersion, effective classification and favorable shape modification have been achieved by jet milling process. Accordingly, monodisperse tungsten powders with narrow particle size distribution were obtained. On the basis of the existing calculation and simulation results, plasma spheroidization parameters have been optimized. Thus, fine-grained spherical tungsten powder with narrow particle size distribution has been prepared by subsequent radio frequency (RF) inductively coupled plasma spheroidization. Furthermore, the presented method can be useful in fabricating spherical tungsten powder of different particle size with narrow particle size distribution as well as for process control in large-scale continuous production.

Ionic liquid pretreatment of bagasse improves mechanical property of bagasse/polypropylene composites

For preparation of wood-plastic composites, pretreatment of lignocellulosic material is important to increase compatibility between matrix polymers and lignocellulosic fillers. In this study, choline acetate (ChOAc, a cholinium ionic liquid)–assisted pretreatment of bagasse powder could improve properties of chemically modified bagasse/polypropylene composites. The composites had fewer voids derived from vascular bundles of the bagasse tissue when using ChOAc-pretreated bagasse powder compared with the case when using untreated bagasse powder. The tensile strength of the composites was 20MPa, 35MPa, and 40MPa in the cases of polypropylene only, untreated bagasse powder, and ChOAc-pretreated bagasse powder, respectively. The elastic modulus was 0.7GPa, 2.0GPa, and 2.6GPa in the case of polypropylene only, the case using untreated bagasse powder, and the case using ChOAc-pretreated bagasse powder, respectively. Thus, ChOAc pretreatment of bagasse powder could enhance the blending and the tensile property of propionylated bagasse/polypropylene composites compared with those of the composites made using untreated bagasse powder.

Gamma irradiation and steam pretreatment of jute stick powder for the enhancement of dye adsorption efficiency

The aim of this study is to find out the facile and effective pretreatment technique to enhance the capacity of jute stick powder (JSP) in adsorbing dye from raw textile effluent. Hence, different pretreatment techniques, i.e., radiation treatment, alkali treatment, ammonia treatment, steam treatment and CaCl2 treatment were applied to JSP and the adsorbing performance were examined for synthetic dye solutions (Blue FCL and Red RL dye). Different gamma radiation doses were applied on JSP and optimum dye removal efficiency was found at 500 krad in removing these two dyes (50 ppm) from solutions. Among the different pretreatment techniques, gamma irradiated JSP (500 Krad) exhibits highest dye uptake capacity for RED RL dye, whereas steam-treated JSP shows highest performance in adsorbing blue FCL dye. Subsequently, we applied the gamma irradiated and steam-treated JSP on real textile effluent (RTE) and these two techniques shows potentiality in adsorbing dye from raw textile effluent and in reducing BOD5, COD load and TOC to some extent as well. Fourier transform infrared spectroscopy (FTIR) analysis also proved that dye has been adsorbed on pretreated JSP.

Fabrication, microstructures and properties of 50 vol.-% SiCp/6061Al composites via a pressureless sintering technique

ABSTRACTCommercial F500 SiC powder and 6061 Al powder were chosen to fabricate the 50 vol.-% SiCp/6061Al composites via pressureless sintering. Effects of pre-treatment of the SiC powder and sintering temperature on the microstructures and properties of the composites were studied. Densification mechanism and interfacial reaction of the composites were also investigated. The results show that the composites have a high sintering ability and a low interfacial reaction activity. The density, bending strength and thermal conductivity of the composites are all sensitive to the sintering temperature. The composites sintered at 680°C are nearly fully dense and have the following optimal properties: the relative density of 98.5%, the bending strength of 495 MPa, the TC of 153 W/(m K) and the coefficient of thermal expansion of 8.1 × 10−6/°C (50–100°C), which are superior to most of the SiCp/Al composites of the similar composition reported previously.

Permeability, strength and electrochemical studies on ceramic multilayers for solid-state electrochemical cells.

An electrochemical reactor can be used to purify flue gasses. Such a reactor can be a multilayer structure consisting of alternating layers of porous electrodes and electrolytes (a porous cell stack). In this work optimization of such a unit has been done by changing the pore former composition and the electrode powder pre-treatment. The effect on permeability, mechanical strength and electrochemical behavior was studied in this work. The effects were evaluated by measuring the pressure difference over the samples in relation to the flow through the sample, by the ball on ring method and by electrochemical impedance spectroscopy in air at temperatures between 300 and 450 °C. The resulting structures were also evaluated with scanning electron microscopy.The work showed a dependence on the pore former composition and electrode powder pre-treatment resulting in variations in porosity, strength and flow resistance. A higher porosity gives a lower backpressure. The electrochemical performance shows that both thickness and amount of pore former in the electrolyte is important, but almost no dependence of electrode composition on the polarization resistances within the tested compositions.

Effect of Particle Size and Pretreatment on the Conductivity of Glass Powder during Compaction

Abstract Physical properties of solid materials can be strongly modified by pressure treatment at elevated temperatures. This study focuses on the compaction-induced behavior of powdered amorphous solids using Li2Si3O7-glass as an example. Experiments were carried out on distinct fractions with particle sizes from <25 μm to 224–250 μm. Measurements of electrical conductivity using impedance spectroscopy were carried out in situ at pressures up to 930 MPa and at temperatures from 373 K to 667 K. Simultaneous monitoring of volume changes allows correlating conductivity and porosity of samples. To study the effect of adsorbed water on surfaces, the material was pretreated by flushing with water-bearing nitrogen before the experiment. Continuous increase of electrical conductivity upon pressurization was observed for all particle size fractions both in the brittle and in the plastic deformation regimes. The pressure derivative of DC conductivity strongly increases with grain size at low T (373 K). At high T (608–665 K) the effect is less pronounced due to the onset of welding of particles forming continuous pathways for charge transport without grain boundaries as barriers. Welding of particles occurs already at temperatures significantly below the glass transition temperature, induced by strong local forces at grain-grain contacts. No effect by pretreatment of glass powder with water vapor was observed at low temperature, while at high temperature surface modification by adsorbed water resulted in enhancement of electrical conductivity, probably caused by lowering of viscosity at grain surfaces, which facilitates welding of particles.

Area-selective Interfacial Bonding in Cu/Si Composites and Its Effect on Thermal Diffusivity

Unlike using diffusion barriers to control the severe Cu-Si reactions at elevated temperature, the area-selective interfacial reaction was achieved by a simple sol dipping pretreatment of Si powders to preserve the as-received components during the hot pressing of Cu/Si composites. The results indicate that the Cu and Si components are well preserved after hot pressing at 700 ℃ for 30 min in vacuum. In the prepared composites, the Si particle and Cu matrix bond together via Cu-Si compounds (e.g. Cu3Si) in some areas at Cu/Si interface, but separate in the other interfacial areas due to the presence of microcracks, suggesting the area-selective interfacial bonding. Furthermore, the composites possess an enhanced thermal diffusivity of 25.7 mm2/s.

Novel processing of Ag-WC electrical contact materials using spark plasma sintering

Ag-WC (60-40wt%) contact materials based on three WC particle size powders were doped with 0.1wt% Ni and processed by an appropriate powder pre-treatment followed by spark plasma sintering (SPS). The contacts produced were already bonded to a copper profile during SPS in order to eliminate additional processing steps. The SPS composites had a more homogeneous microstructure and were tougher and softer than the materials produced by conventional press-sinter-infiltration. The infiltrated contacts had a lower arc-erosion whereas the contacts produced by both processes had a similar contact resistance. The microstructure after switching confirmed that the SPS materials had a porous contact surface layer and were crack-free in contrast to their press-sinter-infiltrated equivalents.

Luminescent Er3+ doped transparent alumina ceramics

We report on successful preparation of Er3+ doped transparent alumina (0.1–0.17 at.%) exhibiting visible light photoluminescence using wet shaping method and hot isostatic pressing. The effects of dopant amount, type of doping powder and powder pre-treatment on final microstructure, real in-line transmittance and photoluminescence characteristics were studied.The real in-line transmittance ranged between 28 and 56%, depending on processing parameters. The transparency decreased with increased amount of dopant. The decrease is dependent on the type of doping powder and its pre-treatment.The photoluminescence spectra measured in both visible and NIR region showed typical emission bands due to the presence of Er3+ ions. The decay profiles of the 4S3/2→4I15/2 transition were fitted with a 2-exponential function, with faster component in the range of 360–700ns and slower component around 1.6-2.4μs. The intensity of emissions and lifetime of the 4S3/2 level decrease significantly with increasing concentration of Er3+ ions.

Rare earth element extraction from pretreated bastnäsite in supercritical carbon dioxide

Rare earth elements are a critical component in many clean energy technologies. Extraction of individual rare earth elements from natural ores or recycled material is challenging due to the very similar chemical properties across the lanthanide series. Supercritical carbon dioxide has emerged in recent years as a possible extraction medium for rare earth elements, due to its tunability and selectivity as a solvent. In this study, rare earth elements were recovered from bastnäsite concentrate using supercritical carbon dioxide extraction with nitric acid/tributyl phosphate adducts. Two bastnäsite pretreatment methods were used to render the rare earth elements amenable to recovery: 1) dry roasting of the source material at 730°C for 3h, and 2) decomposition with 50% sodium hydroxide solution at 150°C for 4h. These pretreated powder samples were extracted in supercritical carbon dioxide at 34MPa and 65°C, with kinetic samples obtained at 15–30min intervals. A range of tributyl phosphate/nitric acid adduct compositions (from 2mol/L H+ to 6mol/L H+) were used in order to determine the effect of adduct composition on recovery rate. The results showed the fastest extraction with an adduct containing approximately 4mol/L H+. Adducts with higher acidity showed reduced extraction of cerium, praseodymium, and neodymium. This could be due to the formation of aqueous droplets which dissolve rare earth elements and create an equilibrium limitation, or due to competition between the rare earth nitrates and nitric acid for coordination with tributyl phosphate. Extraction with various adduct concentrations in supercritical CO2 showed the expected increase in reaction rate with increased adduct concentration. For the 4mol/L H+ adduct at 5.0 mol% adduct concentration, roasted bastnäsite recoveries were 72% for La, 96% for Ce, 88% for Pr, and 90% for Nd after 120min. For 4mol/L H+ adduct at 5.1 mol% adduct concentration, NaOH digested bastnäsite recoveries were 93% for La, 100% for Ce, 99% for Pr, and 101% for Nd after 90min. Though further research is needed, these results are a key step in demonstrating applicability of supercritical extraction to rare earth element ores.

Antihemolytic and antioxidant properties of pearl powder against 2,2′-azobis(2-amidinopropane) dihydrochloride-induced hemolysis and oxidative damage to erythrocyte membrane lipids and proteins

Pearl powder, a well-known traditional mineral medicine, is reported to be used for well-being and to treat several diseases from centuries in Taiwan and China. We investigated the in vitro antihemolytic and antioxidant properties of pearl powder that could protect erythrocytes against 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced oxidative damage to membrane proteins/lipids. Human erythrocytes were incubated with different concentrations of pearl powder (50–200 μg/mL) for 30 minutes and then exposed to AAPH for 2–6 hours. We found that AAPH alone time dependently increased the oxidative hemolysis of erythrocytes, while pearl powder pretreatment substantially inhibited the hemolysis in a concentration-/time-dependent manner. AAPH-induced oxidative damage to erythrocyte membrane lipids was evidenced by the elevated malondialdehyde (MDA) levels. However, pearl powder remarkably inhibited the malondialdehyde formation, and the 200 μg/mL concentration showed almost similar malondialdehyde values to the control. Furthermore, pearl powder suppressed the AAPH-induced high-molecular-weight protein formation and concomitantly increased the low-molecular-weight proteins in erythrocytes. Antioxidant potential that was measured as superoxide dismutase activity and glutathione content was significantly dropped by AAPH incubation, which suggests the vulnerability of erythrocytes to AAPH-induced oxidative stress. Noteworthy, erythrocytes pretreated with pearl powder showed restored superoxide dismutase activity and glutathione levels against AAPH-induced loss. Our findings conclude that pearl powder attenuate free radical-induced hemolysis and oxidative damage to erythrocyte membrane lipids/proteins. The potent antioxidant property of pearl powder may offer protection from free radical-related diseases.

Preparation of Three Modified Natural Zeolite Powders and Antibacterial Properties of Antibacterial Paper Prepared Using them as Fillers

Natural zeolite powders, 600 meshes in size, were pretreated with three strong acids , then reacted with sodium chloride, sodium sulfate, sodium nitrate, respectively, and yielded sodium zeolite. The samples were loaded Ag++Zn2+, Ag++Cu2+, Zn2++Cu2+, and Ag++Cu2++Zn2+ ions through ion exchange to prepare the antibacterial zeolite powders. The powders were tested by MIC, SEM/EDXA and XRD. The results demonstrated that the pretreatment of zeolite powder with nitric acid could achieve a larger loading amount of metal ions compared to hydrochloric acid and sulfuric acid, and the samples loaded with Ag++Zn2+, Ag++Cu2+,Ag++Cu2++Zn2+ could attain excellent antibacterial properties with an MIC of 8 μg/ml to S. aureus Adding 5% of the aforementioned antibacterial zeolite powders to paper as filler resulted in an impressive antibacterial effect against S. aureus, as the inhibitory rate could reach to almost 100% in 1 h.

Sulfolane pretreatment of shrub willow to improve enzymatic saccharification

Pretreatment has been regarded as the most efficient strategy for conversion of lignocellulosic biomass to fermentable sugars. In this work, sulfolane pretreatment was performed to break the intricate structure of shrub willow for inhabitation of the enzymatic accessibility to holocellulose. The effects of varying pretreatment parameters on enzymatic hydrolysis of shrub willow were investigated. It was found that sulfolane was more compatible with lignin instead of carbohydrate, and the loss of carbohydrate could be attributed to water and acid generated from sulfolane. The optimum conditions leading to maximal sugar recovery from enzymatic saccharification were confirmed. After pretreatment of shrub willow powder in sulfolane at 170 °C for 1.5 h with mass ratio of sulfolane to substrate of 5, the sugar release could reach 555 mg/g raw materials (352 mg glucose, 203 mg xylose) when combining 20 FPU cellulase, 20 CBU β-glucosidase, and 1.5 FXU xylanase, representing 78.2 % of glucose and 56.6 % of xylose in shrub willow. This enhanced enzymatic saccharification was due to delignification and removal of a proportion of hemicelluloses, as confirmed by X-ray diffraction analysis, scanning electron microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, gas chromatography, and ionic chromatography. Thus, these studies prove sulfolane pretreatment to be an effective and promising approach for biomass to biofuel processing.

Effect of silicidation pretreatment with gaseous SiO on sinterability of TiC powders

Silicidation pretreatment with gaseous SiO at 1350°C for 30min is employed for chemically modifying commercially available TiC powder. Phase composition and microstructural features of the pretreated powder are discussed. Densification behavior of the pretreated TiC powder during hot pressing is studied in comparison with that of non-pretreated one. Significantly improved densification behavior and sinterability of TiC powder after silicidation pretreatment are explained by the effect of Ti3SiC2 acting as a solid lubricant. Nearly fully dense TiC-based ceramics having flexural strength of 370MPa, fracture toughness of 5.6MPam½, and microhardness of 24GPa is obtained by hot pressing under conditions as mild as 1600°C and 20MPa.

Effective reuse of electroplating rinse wastewater by combining calcined oyster shell powder with H2O2/UV process

In this study, the merits of combining the oyster shell powder (OSP) pre-treatment with H2O2/UV post-oxidation for the reuse of electroplating rinse wastewater were evaluated. The results showed that the calcined OSP was more effective in removing heavy metals than the original OSP. For the 1,000°C-calcined OSP of 0.6 g/L, the removals were 98, 94, and 99% for Fe, Ni, and Cr, respectively. That is, a small quantity of the calcined OSP could remove a large quantity of heavy metals due to the large specific surface area and the dramatically increased pH; the former resulted in a better adsorption capability and the latter induced buck precipitation. Further, after the post H2O2/UV process, the chemical oxygen demand and total organic carbon were reduced from 1,206 to 41.2 mg/L and from 252 to 12.6 mg/L, respectively, for pH of 8.0, H2O2 of 1,000 mg/L, UV of 52 W, and oxidation time of 240 min. That is, the combination of calcined OSP pre-treatment and H2O2/UV post-oxidation could not only treat the electroplating rinse wastewater to comply with the Taiwan’s effluent standard but could also satisfy the in-house water reuse criteria while resolving the issue of waste oyster shells simultaneously.

Synthesis, Sintering Behavior, Structure, and Electrical Properties of 5YSZ Electrolyte

In some applications, such as automotive oxygen sensors, 5 mol% Y2O3-stabilized zirconia (5YSZ) is generally used because its ionic conductivity and mechanical properties are excellent. In this study, fine 5YSZ powders, which contain only small aggregates with particle sizes in the 40-60 nm range, were prepared by a hydrolysis-hydrothermal method. Powder calcination behavior, ceramic sintering behavior, microstructure, and conductivity were studied. This research proved that the calcination temperature has a great influence on the size and phase composition of the powder. The sintering temperature of the 5YSZ ceramic significantly affected its final grain size and density. The results show that a powder pre-treatment temperature of 1100 °C and a sintering temperature of 1350 °C for 2 h can produce excellent 5YSZ ceramics. The grain size and microstructure of 5YSZ ceramics influence the bulk resistance, grain resistance, and grain boundary resistance; the value of grain resistance decreased and grain boundary resistance increased with increasing grain size and sintering temperature. Considering all aspects of the grain size, conductivity, density, and mechanical properties, the optimal sintering temperature was found to be 1350 °C. The highest value measured for conductivity was about 2.79 × 10−3 S/cm, measured at 700 °C.

Effects of Surfactants and Microwave-assisted Pretreatment of Orange Peel on Extracellular Enzymes Production by Aspergillus japonicus PJ01.

The effects of surfactants and microwave pretreatment of orange peel powder (OPP) on the production of pectinase, cellulase, and xylanase by Aspergillus japonicus PJ01 in submerged fermentation were investigated. The results showed that when OPP was pretreated only by microwave (630W, 9min, and liquid/solid ratio 5), the activities of exo-pectinase, carboxymethyl cellulase (CMCase), xylanase, and filter paper cellulase (FPase) were increased by 11.8, 20.6, 16.2, and 24.0%, respectively, and when OPP was pretreated by microwave at the same conditions cited above plus PEG 4000 at the concentration of 3g/L, the activities of the above four enzymes were enhanced by 40.2, 30.3, 40.4, and 40.0% after 84-h cultivation, respectively. It is suggested a synergistic effect between microwave and surfactant treatment in enhancing the multiextracellular enzymes production by OPP fermentation of A. japonicus PJ01. Chemical composition and Fourier transform infrared spectroscopy (FTIR) analysis displayed that the microwave pretreatment of OPP led to the decrease of hemicellulose and essential oil contents. Scanning electron microscope (SEM) showed that OPP surface after microwave pretreatment became porous and more susceptible to be invaded by A. japonicus. The results demonstrated that pretreatment of OPP by surfactant PEG 4000 and microwave irradiation as environment-friendly way was cost-effective in enhancing the multienzyme production from agricultural waste orange peel.