Powder Fractions Research Articles

Influence of severe plastic deformation of Cu powder and space holder content on microstructure, thermal and mechanical properties of copper foams fabricated by lost carbonate sintering method

Micro-porous copper foam with open cell structure and acceptable mechanical behavior charts a path for developing the supreme chips and integrated circuit due to its large surface area and good thermal conductivity. In this study, semi-open cell structure copper foams were successfully produced using mechanically pre-activated (milled) Cu powders by different milling durations and 50–70 vol% K2CO3 as a filler material by lost carbonate sintering (LCS) method. The effect of mechanical milling of the used powder and volume fraction of K2CO3 on the microstructure, porosity, strength, energy absorption, and the cooling rate of the produced foam was examined. Microstructural analysis showed that long-duration milled powder creates foams with small pores and homogeneous size distribution, leading to plateau stresses up to ≈170 MPa. Cu foam with increased porosity showed a reduction in yield strength, plateau stress, and energy absorption but a significant increase in its cooling rate. The foam with 70% porosity prepared using 2.5h-milled Cu powders exhibited the highest cooling rate. The results of this study show that the fabrication of Cu foams using flake Cu powder obtained from short-time milling yields improvements in the mechanical and thermal performance of the foam. Mechanical milling of the used powder for a longer time leads to a decrease in cooling rate of the produced foam.

Microstructural characterization of rapidly solidified Al-13.5 at.% Cr and Al-13.5 at.% V alloys for catalytic applications

Intermetallic compounds, due to their well-defined stoichiometry, arrangement of atoms and controlled crystal structure, are a promising alternative to expensive noble metal catalysts. In this paper, the catalytic properties of Al-13.5 at.% Cr and Al-13.5 at.% V alloys, corresponding to the quasicrystalline approximants Al45Cr7 and Al45V7, were investigated for the first time.The alloys in the form of fragmented brittle ribbons were produced by the melt-spinning. The microstructure of the ribbons, both in the as-spun state and after heat treatment (100 h at 600 °C), was characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. In the as-spun state, the ribbons showed a multiphase microstructure. In addition to the Al45Cr7 phase in the Al-Cr alloy and the Al3V phase in the Al-V alloy, they also contained α(Al) solid solution and icosahedral quasicrystalline phases. After heat treatment, the alloys became almost single phase, consisting mainly of stable monoclinic phases: Al45Cr7 or Al45V7. The catalytic performance of the phenylacetylene hydrogenation reaction was tested on as-spun and heat-treated alloys that had previously been pulverized and sieved to select a powder fraction of less than 32 µm. All the tested materials show high substrate conversion, above 80% after 1 h reaction, along with high activity rate. The homogenized powders demonstrated a slightly better properties in relation to as-spun materials. These results confirm the potential of intermetallic catalysts, including the tested alloys, in hydrogenation reactions and verify the possibility of using the metallurgical method to obtain catalytically active materials.Graphical abstract

Hepatoprotective and in vivo antioxidant effects of granulometric classes and decoction of Ficus dicranostyla Mildbread leaves powders against carbon tetrachloride-induced hepatotoxicity in Wistar rats.

Ficus dicranostyla is a plant from the Moraceae family commonly used in African countries for its nutritional value and its believed medicinal properties. Its antioxidant in vitro capacity and its richness in phenolic compounds have been previously demonstrated. This work aimed at evaluating the hepatoprotective and in vivo antioxidant activities of different granulometric fractions of the F. dicranostyla leaves against carbon tetrachloride-induced hepatotoxicity in rats. Powdery fractions (<125, 250-125, and ≥250 μm), and the unsieved powder, obtained from the F. dicranostyla leaves were water-dissolved and given orally to rats at the same dose (250 mg/kg body weight) before administering carbon tetrachloride intraperitoneally (1 mL/Kg bw). The lipid status parameters (total cholesterol, triglycerides, HDL-cholesterol, and LDL-cholesterol), hepatic toxicity through aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT) in blood plasma, and antioxidant status by measuring the malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) in liver homogenate were performed. The activities of all parameters registered a significant (p < .05) alteration in CCl4-treated rats, which were significantly recovered toward an almost normal level in coadministered with Ficus dicranostyla leaf powder samples in a particle size-dependent manner. Results suggest that the smaller particle size of the powder fraction, as well as the decoction powder of Ficus dicranostyla, may be used as hepatoprotective and antioxidant agents.

Improving functional properties of protective coatings obtained by electrophoretic deposition on steel interconnects for solid oxide cells by tuning particle size distribution

This paper analyses the effect of particle size distribution in the suspension on the quality of the resulting coating in the electrophoretic deposition of a protective coating on a steel interconnect for solid oxide cells (SOCs). Mn1.5Co1.5O4 commercial powder was subjected to grinding for 2, 4 and 18 h, and admixing it with the finest fraction was used to form thin layers on Crofer 22APU steel. The functional properties of the coatings, such as density and area-specific resistance (ASR) were evaluated over the respective temperature ranges. The resistivity of the coatings was measured in 60 and 1000 h tests. It was shown that the increase of the fine powder fractions yields a higher density layer, which contributes to slowing down the growth rate of the oxide scale and therefore can decrease ASR by 65%. The lowest resistivity was performed by the samples fabricated with the admixed powder. Post-test analysis by FIB/SEM/EDS did not reveal diffusion of chromium through the fabricated layers (after the 1000 h test), which is a key indicator of the reliability of the formed protective barrier.

Static Shear Strength of Single-Lap Joint Using Eggshell-Toughened Epoxy as Adhesive Agent

Eggshells are daily food waste disposed of in landfills, producing environmentalissues and an unpleasant odour. Eggshells were crushed to form eggshell powder and may be suitably applied as a filler in epoxy resins to improve their mechanical properties. The shear strength of toughened epoxy with eggshell powder (TEEP) wasstudied. Single-lap joint (SLJ) sheartests were conducted toinvestigate the shear strength of the SLJbonded with different volume fractionsof TEEP. For this purpose, the eggshells were dried and crushed into particles of size 150μm. The volume fraction of eggshell powder in the epoxy resin is 0%, 2.5%, 5%, and 10% by epoxy weight. The epoxy resin system was made of EPIKOTE Resin 828 and Hardener 651 with a mixing ratio of 5:2 by weight.The results show that the shearstrength greatly depended upon overlap lengthand filler volume fractions.The improvement was up to 72.7% and 39.9%,with the longest overlap length and 5% TEEP fraction.Hence, an overlap length of 38.1 mm and a 5% eggshell volume fraction gave the optimum shear strength of 5.045 kN.

Destruction mechanisms of epoxybased composite filled with metal powder under cavitation attack

The samples of epoxy compound with a powder filler and without it are tested on cavitation wear. The powder of aluminum bronze BrAZhNMts9–4–4–1 is used as a filler. The powder is obtained by filing the rod of the bronze. The composition of the epoxy compound is 100 parts of the resin K‑153 plus 12 parts of the hardener (polyethylene epolyamine). The distribution of the bronze particles in the epoxy compound follows the law close to the exponential one, the average particle size is equal to approximately 27 μm, and the volume fraction of the bronze powder in the compound is about 9,5 percent. The tests are conducted using the ultrasonic magnetostrictve vibrator UZDN‑2T in fresh water of room temperature, the frequency and amplitude of the vibrator horn end equal to 22 kHz and 28 µm respectively. The distance between the horn end and the sample surface is 0,5 mm. During the experiments the wear of the samples is evaluated by their weighting on analytical scales with step-type indication of 0,1 mg, measuring the surface roughness and the microhardness of the bronze particles in the composite is carried out as well. It has been shown that the addition of the bronze particles into the epoxy compound not only changes the kinetics of cavitation wear of the polymer but also decreases its cavitation resistance. The decrease in cavitation resistance caused by bronze particles addition is attributed to the fact, that the boundary between a metal particle and epoxy matrix is a «weak» spot, and the destruction of polymer begins from this boundary area under cavitation attack.

INVESTIGATION OF THE EFFECT OF MESH SIZE AND FRACTION VOLUME ON BENDING STRENGTH CHARACTERISTICS OF GEOPOLYMER COMPOSITE

Composite material is a material consisting of two or more type materials that have different properties, by combining macroscopically, and good interfacial bonds from one material to another. Currently, polymer composite materials are widely applied in the land, sea, and air transportation industries, moreover polymer composites with fire resistance properties have been developed with the addition of geopolymer that has the advantage of producing high performance. This study aims to determine the effect of mesh size and volume fraction of lightweight brick powder on flexural strength. The benefits of this research directly increase the economic value of lightweight brick waste and produce a tough advanced material at a low cost. The composite filling material used lightweight brick waste and sieved using a sieve with a level of 50, 100, 150, and 200 at a volume fraction of 45%, and a volume fraction of 0%, 15%, 30%, 45%, and 60% at a mesh 200. While the composite matrix used the thermoset polymer Ripoxy R-804. Based the result, addition of lightweight brick powder with variations in particle size of the lightweight brick powder and volume fraction showed a decrease in flexural strength resistance compared to those without lightweight brick powder.

Investigation of cold plasma technique as an alternative to conventional alkalization of cocoa powders

In the production of cocoa, a crucial process called “Alkalization” or “Dutching” has been used to reduce its acidity, bitterness and astringency as well as modify its solubility and color. It is a time- and energy-consuming process. It was investigated whether it is possible to replace the conventional alkalization with the cold plasma (CP) technique. We discover that atmospheric pressure plasma jet (APPJ) CP treatment is capable of reducing the lightness values, improving the solubility, and decreasing the acidic perception of natural cocoa powders as well as protecting bioactive compounds (total phenolic and flavonoid content) of natural cocoa powders, consuming ∼65% less time than the traditional method and without the need for external expenditures such as chemicals, high pressure, or aeration. Moreover, CP treatment did not increase the total ash content and thus water-holding capacity of powders unlike the conventional alkalization, which caused a 40% and 42% increase, respectively. The SEM micrographs demonstrated that CP treatment caused etching on the surface and removed the layer of protein-polyphenol-cell wall complex. FTIR spectra showed the incorporation of hydrophilic functional groups on the surface after CP treatment. CP treatment effectively reduced the acidic fractions of cocoa powder, but caused to the oxidation of cocoa butter and the formation of decomposition products of oleic and linoleic acid. Finally, this is a pioneering study for replacing an alkalization process step that has been used since the 19th century and has no alternative, and the results seem to be very promising for further detailed studies and pilot- and industrial-scale trials.

Use of Natural Flake Graphite in the Calibration of Instrumental Research Methods

The size of mosaic blocks along the graphite layers (that is, the average diameter of crystallites in the basal plane) was determined by two methods for specially made model materials based on narrow fractions of flake graphite powders and milled pyrographite with lamellar particles. The first method consisted in the calculation of mosaic block sizes from a minimum of the temperature dependence of electrical conductivity using an empirical law according to Mason; the second method based on mathematical modeling used the values of the magnetoresistance of carbon materials at temperatures of 80 and 300 K. The correspondence between the sizes of mosaic blocks calculated by these methods along the graphite layers in the considered materials was shown. A correction for the lamellar shape of graphite crystallites was determined to calculate the sizes of mosaic blocks in the direction perpendicular to the graphite layers from the 002 peak broadening in the diffraction pattern.

Study on Energy Output Characteristics of Aluminized Emulsion Explosive

In order to study the energy output characteristics of multi-component explosives mixed with aluminum powder and emulsified explosives, five groups of emulsified explosives containing aluminum with different proportions were used for underwater explosion experiments and overpressure tests in the air. The experimental data show that when the mass fraction of aluminum powder increases from 0% to 40%, the shock wave energy increases from 0.68 kJ·g-1 to 1.22 kJ·g-1, which increases by 79.41%. Bubble energy increased by 135.66% from 2.44 kJ·g-1 to 5.75 kJ·g-1; the total energy of underwater explosion increased by 123.40% from 3.12 kJ·g-1 to 6.97 kJ·g-1. The explosion overpressure in the air increased by 93.66% from 60.794 KPa to 117.734 KPa. Aluminum powder greatly increases the output level of emulsified explosives. Emulsified explosive containing aluminum has the characteristics of high working capacity and high explosive performance.

Hypolipidemic effects of microencapsulated powder fraction from Hibiscus sabdariffa. L calyx in hyperlipidic rats

The lipid-lowering activity of microencapsulated and nonmicroencapsulated Hibiscus sabdariffa L. powder fractions in rats rendered hyperlipidemic by a hyperlipid diet (HLD) was determined. Dried calyces of H. sabdariffa were finely ground and fractionated on a sieve column to retain particle sizes ϕ &lt; 315 µm, and were microencapsulated with maltodextrin (MD). Rats were randomly divided into four groups: normal control group, hyperlipid diet group (negative control groups), hyperlipid diet group supplemented with atorvastatin, non-microencapsulated (NMEPHS) and microencapsulated (MEPHS) powders from H. sabdariffa calyces groups. Rats received atorvastatin, NMEPHS and MEPHS for three weeks. Atorvastatin (10 mg/kg) and individual powders were dissolved in water and administered to rats at a dose of 250 mg/kg body weight for three weeks. Body weight, total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), aspartate transferase (AST), alanine transferase (ALT), superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) were measured. Very low-density lipoprotein cholesterol (VLDL-C), hepatosomatic index (HSI), and adiposomatic index (ASI) were calculated. Lipid profil, and MDA were increased in the negative control rat groups compared with the negative control rat group. NMEPHS and MEPHS significantly reduced body weight gain, ASI, HSI, TC, TG, LDL-C, ALT, AST, and MDA and increased HDL-C level significantly. Moreover, SOD and CAT activities were reduced with HLD and significantly increased with HSCP intake. however, the most significant activities were revealed by MEPHS. These results suggest that MEPHS exerts potent lipid-lowering effects, promotes hepatic fat breakdown, and regulates antioxidant enzymes in a more efficient manner.

EFFECT OF PARTICLE SHAPE AND SIZE OF COPPER POWDERS ON THE PROPERTIES OF SINTERED PARTS

The particle shape and size of the starting powders represent the most important physical properties, on which the quality of the compacts and final sintered products depends. Two types of powder were analyzed in the paper - electrolytic copper powder with a dendritic particle shape and water-atomized copper powder with an irregular particle shape. The starting powders were sieved through a sieve system with openings of 45 μm, 80 μm, and 120 μm. The characterization of the obtained fractions of both powders was performed by determining the shape and dimensions of the particles using SEM microscopy in combination with ImageJ software, and the apparent density and flow rate were determined using the Hall flowmeter funnel. Pressing of each powder fraction was done using a pressure of 600 MPa. The compacts were further sintered at 1000°C for 2 hours to obtain the final sintered parts. After sintering, their density, hardness, and electrical conductivity were determined and their microstructure was analyzed. The results indicate a great influence of the characteristics of the starting powders on the properties of the final parts obtained by the powder metallurgy route. The particle shape of the powders had a more pronounced influence compared to the particle size.

Improvement of rate of freezing inside a thermal storage container with use of nanomaterial for controlling the water treatment

The main target of present transient simulation is to find the best conditions in which the highest rate of solidification can be achieved. To gain this aim, nanoparticles were dispersed and various sizes were considered to obtain the best diameter in view of discharging rate. Additionally, the radiation term was added in the energy equation. As a fraction of CuO augments, solidification time decreases about 28.56 % at Rd = 0, dp = 40 nm. With the rise of Rd, impact of nano powder fraction reduces about 2.74 %. The minimum time of full discharging is 2024.8 s and obtained when φ = 0.04, Rd = 1 and dp = 40 nm. When Rd = 0, required time reduces 12.41 % with a rise of dp up to 40 while it augments about 34.82 % when dp augments greater than 40. Obtained data demonstrates that size of nano powders has a more important role when Rd is non-zero. Maximum effect of Rd on time of solidification occurs when dp = 50 nm and minimum changes occurs when dp = 40 nm. Additionally, duration reduces about 11.16 % with rise of Rd for pure H2O.

Microplotter Printing of a Miniature Flexible Supercapacitor Electrode Based on Hierarchically Organized NiCo2O4 Nanostructures.

The hydrothermal synthesis of a nanosized NiCo2O4 oxide with several levels of hierarchical self-organization was studied. Using X-ray diffraction analysis (XRD) and Fourier-transform infrared (FTIR) spectroscopy, it was determined that under the selected synthesis conditions, a nickel-cobalt carbonate hydroxide hydrate of the composition M(CO3)0.5(OH)·0.11H2O (where M-Ni2+ and Co2+) is formed as a semi-product. The conditions of semi-product transformation into the target oxide were determined by simultaneous thermal analysis. It was found by means of scanning electron microscopy (SEM) that the main powder fraction consists of hierarchically organized microspheres of 3-10 μm in diameter, and individual nanorods are observed as the second fraction of the powder. Nanorod microstructure was further studied by transmission electron microscopy (TEM). A hierarchically organized NiCo2O4 film was printed on the surface of a flexible carbon paper (CP) using an optimized microplotter printing technique and functional inks based on the obtained oxide powder. It was shown by XRD, TEM, and atomic force microscopy (AFM) that the crystalline structure and microstructural features of the oxide particles are preserved when deposited on the surface of the flexible substrate. It was found that the obtained electrode sample is characterized by a specific capacitance value of 420 F/g at a current density of 1 A/g, and the capacitance loss during 2000 charge-discharge cycles at 10 A/g is 10%, which indicates a high material stability. It was established that the proposed synthesis and printing technology enables the efficient automated formation of corresponding miniature electrode nanostructures as promising components for flexible planar supercapacitors.

Direct comparison of surface crystal growth kinetics in chalcogenide glass measured by microscopy and DSC

AbstractSurface crystallization in fine powder Se70Te30 chalcogenide glass was studied by differential scanning calorimetry (DSC) and optical microscopy. A complex kinetic analysis of these experimental data reveals that the contracting sphere mechanism (R3 model) is the rate determining step of crystal growth, and the conventional Johnson–Mehl–Avrami–Kolmogorov model cannot be used in this case. Moreover, it is clearly shown that the particle size distribution should be considered in crystallization studies. Actually, when the particle size effect is taken into account, the simulated DSC curves for the R3 model agree very well with the experimental data over the entire temperature range. The crystallization kinetics determined from the nonisothermal DSC data are consistent with previously reported isothermal crystallization data for the same powder fraction. The crystal growth rate calculated from isothermal and nonisothermal DSC data agrees very well with the microscopically measured surface and bulk crystal growth rate.

Modification of Carbon Black by Laser Irradiation

The effect of modification of Cabot Corporation SPHERON 5000 carbon black suspended in bi-distilled water by laser irradiation (CuBr2 laser with fundamental wavelength of λ = 511nm and 2 kHz repetition rate) has been studied. The carbon black suspensions were prepared by mixing 0.10 g carbon black previously treated with acetone in 100 ml bi-distilled water. Different laser beam fluencies and different irradiation times were used in order to optimize the modification process. The modified suspensions were decanted after sedimentation and dried. The powder fractions obtained were studied by scanning electron microscopy, X-ray diffraction and Raman spectroscopy.

Characteristics of Palm Kernel Shell/Alumina/Epoxy Composites as Motorcycle Brake Pad Material

Brake pads are one of the components of a motor vehicle that functions to slow down or stop the vehicle's motion. In the concept of braking, one inevitable factor is wear and tear. Wear and tear occur when two objects press against each other and create friction. Composite material is an alternative substance that can be used to replace asbestos brake pads. In this research, shell of palm oil, alumina (Al2O3) powder and epoxy was used for material of brake pad. Type of brake pads was made in this study is brake pads used for motorcycle disc brakes. Addition of volume fraction of alumina powder to 6% in composite material. The aims this study was determine the characterization of brake pad based on composite materials with addition of alumina powder in composite material. This study showed that there was increase of physical and mechanical properties with the addition of alumina powder in composites up 6% by volume fraction.

Evaluation of Mechanical Properties of Bio-degradable Hybrid Particulate Fibre Reinforced Polymer Composite

Recent interest in advancement of biomaterials and their implant applications is well known. In the last five decades, great advances have been made in the field of biomaterials, including ceramics, glasses, polymers, composites, glass-ceramics and metal alloys. A variety of bio implants are currently used in body implantation. In the present study, ISO Polymer and crab shell derived hydroxyapatite (HAp) have been selected to develop composites by hand lay-up method targeted for degradable implant applications. Composite was successfully developed with various fractions of crab shell powder (0%, 5%, 10% and 15%) &amp; e-glass fiber was composed to prepared hybrid polymer composites. HAp powder reinforced hybrid polymer composites, SEM studies and mechanical properties (hardness, tensile strength and impact strength) were determined as per ASTM standards. The higher mechanical properties were obtained at 15% Crabshell powder particulate composite. The introduced Crab Shell (HAp) enhances bio mineralization and promotes rapid healing rate in the bio medical implants applications.

Characterization of Green and Yellow Papaya (Carica papaya) for Anti-Diabetic Activity in Liver and Myoblast Cells and Wound-Healing Activity in Fibroblast Cells.

Obesity and diabetes, often characterized as "metabolic syndrome", have been recognized as two of the most important public health issues worldwide. The objective of the present research was to evaluate green and yellow papaya for anti-oxidation and anti-diabetic properties. Leaves, skin, pulp, and seed samples from papayas were freeze-dried and then extracted in water or 80% methanol. The extracts were used to determine total polyphenolic content and anti-oxidation activities, and to determine biological activities, including glucose uptake, Glut-2 expression, triglyceride reduction, and wound-healing activity. Our data demonstrated that methanol and water extracts of green and yellow papaya have similar concentrations of polyphenols in skin (10-20 mg/g dry powder), leaf (25-30 mg/g dry powder), and pulp (1-3 mg/g dry powder) fractions. However, both methanol and water extracts of seeds from yellow papaya have substantially higher concentrations of polyphenols compared to green papaya. Both water and methanol extracts of yellow papaya exhibited higher anti-oxidation activity compared to green papaya in skin (50-60%), pulp (200-300%), and seeds (10-800%). Old leaves also showed greater anti-oxidation activity (30-40%) compared to new leaves. Pulp extracts from both yellow and green papaya stimulated greater glucose uptake, but only pulp from green papaya stimulated glucose uptake in muscle cells. Similarly, pulp extract stimulated glucose transporter Glut-2 expression in liver cells. The skin, pulp, and seeds of green or yellow papaya showed triglyceride-lowering activity in liver cells by 60-80%, but samples taken from yellow papaya had a more potent effect. Seeds from both green and yellow papaya significantly stimulated the migration of fibroblasts in the wounded area by 2-2.5-fold compared to the untreated control. Consistent with these data, seeds from both green and yellow papaya also significantly stimulated collagen synthesis in fibroblast cells by almost 3-fold. In conclusion, our data indicate that different parts of papaya produce stimulatory effects on glucose uptake, Glut-2 expression, TG reduction, and wound-healing activities. This study concludes that different parts of the papaya can be beneficial for preventing diabetes and diabetes-related wound healing.

Influence of microwave sintering temperatures on mechanical and microstructural Behavior of Al/SiC/snail shell hybrid composite synthesized through powder metallurgy technique

This study emphasizes the synthesis of hybrid aluminum composite reinforced with SiC and Snail Shell (S-Shell) particles through the powder metallurgy technique. The hybrid composite corresponding to the optimized volume fraction of SiC and Snail shell powder (Al-6%SiC-6%S-Shell) was subjected to microwave-assisted sintering (MAS) by varying the sintering temperatures from 400°C to 550°C in steps of 50°C. Results concluded that microwave-sintered composites show superior mechanical characteristics than the composites sintered through conventional sintering techniques. The maximum ultimate tensile strength (U.T.S) of 316 MPa, and compression strength of 396 MPa were obtained for microwave sintered Al-6%SiC-6%Snail shell powder composite sintered at 500°C. However, increasing the sintering temperature above 500°C leads to a reduction in U.T.S and Compression strength due to the formation of coarse grains by absorbing the microwaves at higher temperatures. The U.T.S, Compression strength and Vickers hardness of the microwave sintered Al-6%SiC-6%Snail shell powder hybrid composite sintered at 500°C was enhanced by 42.08%, 42.4%, and 35.5% compared to conventionally sintered hybrid composite. The grain size was found to be increased with an increase in microwave sintering temperature due to the enhancement in the absorption capability of the microwaves with the temperature rise. The results of this study also suggest that choosing materials with a high microwave response helps to achieve improved mechanical properties for microwave-sintered composites.