جستجوی مقالات مرتبط با کلیدواژه « composite » در نشریات گروه « مواد و متالورژی »

Metal Matrix Composites (MMCs) are of great importance in the industry due to characteristics such as good corrosion resistance, superior elastic modulus, high strength-to-weight ratio, and thermal stability. Among MMCs, Hybrid Metal Matrix Composites (HMMCs), which use two or more reinforcements, offer a combination of desirable properties.

In this research, to fabricate composite samples, the surfaces of aluminum and copper sheets were first prepared by washing with acetone and brushing. WC and MoS2 powders were heated at 120°C to remove moisture. Four aluminum sheets and one copper sheet were stacked, with WC and MoS2 powders sprinkled on them. Then, these sheets were arranged in a sandwich structure consisting of four layers of aluminum, one layer of copper, and four layers of WC-MoS2, and rolled using a 30-ton rolling mill with a 65% reduction in cross-sectional area at room temperature without any lubricant. After the initial rolling, the sandwich was cut into three equal parts, and after cleaning and surface preparation, they were re-stacked into a new sandwich and rolled with a 60% reduction in cross-sectional area. This process was repeated for seven cycles, according to previous studies on the fabricated samples.

In this study, the hybrid composite Al/Cu/WC/MoS2 was fabricated using the Accumulative Roll Bonding (ARB) process over seven cycles. Structural analysis using X-ray diffraction (XRD) patterns indicated that no new phases were formed. Scanning Electron Microscope (SEM) images confirmed the desirable multilayer structure. The ARB process resulted in the proper distribution of copper metal and WC-MoS2 particles within the aluminum matrix. In the final stage of ARB, the copper metal was distributed in an island-like pattern within the aluminum matrix. Corrosion tests showed that corrosion resistance improved with an increasing number of ARB cycles. The corrosion current density in the hybrid composite produced with seven cycles was lower than in other cycles due to the minimal porosity and homogeneous distribution of MoS2 and WC particles, indicating the highest corrosion resistance. The corrosion current density in the hybrid composite produced with seven cycles was lower than in other cycles due to the least porosity and homogeneous distribution of MoS2 and WC particles, indicating the highest corrosion resistance.

In this study, a copper-silicon carbide composite consisting of SiC particulate with an average size of 7 micrometers was produced using the electroforming method. An acidic electrolyte bath containing sulfuric acid and copper sulfate with a concentration of 5 g/L was used at a temperature range of 23 to 25 degrees Celsius, and a mechanical stirrer with a speed of 250 rpm was used to prepare the samples. Silicon carbide powder was added to the bath at different concentrations between 15 to 45 g/L. The composite samples were produced after 12 hours at an optimal current density of 5.6 A/dm2 and then were examined for the amount of SiC entered into the composite matrix, microstructure, and morphology using SEM. To determine the corrosion behavior properties of the produced composites, potentiodynamic testing and electrochemical impedance spectroscopy were used. The results showed that the highest volume percentage of SiC entered into the composite sample was 30% at a concentration of 35 g/L. The corrosion resistance of the composite samples increased with an increase in SiC percentage, and protective layers were formed on the surface to prevent corrosion.

In the present research, nanoparticles based on the alumina-yttria system were synthesized using a sol-gel method. Then, the effect of heat treatment on the phase evolution and crystallite size in this composite system was investigated. The produced composite powder was characterized using X-ray diffraction and scanning electron microscopy. Scherrer equation was used to investigate the effect of temperature on crystallite sizes. The composite powder was cold isostatically pressed and subjected to a pressureless sintering process at different temperatures to evaluate its density changes. The X-ray diffraction results showed that the powder sample was initially amorphous. By increasing the temperature, the components of this composite system reacted and Alpha-Al2O3 and Y3Al5O12 phases are formed. The crystallite size of the Theta-alumina phase grew with increasing temperatures up to 1000 C. At higher temperatures, crystallite size decreased due to the decomposition of theta-alumina. The density of the samples increased by increasing the temperature up to 1600 C so that the samples reached a relative density of about 96%. The densification curve of the composite showed three different stages during sintering. Examining the hardness of the samples showed that the hardness increases with the increase of the sintering temperature, and in the sample sintered at 1600 C for 3 hours, the Vickers hardness reached about 14 GPa.

In this research, the use of composites based on bismuth oxide with impurities of Gadolinium, titanium, yttrium, tungsten, zirconium and zinc as a protective material for effective protection has been discussed. In here, the evaluation of X-ray and gamma ray shielding for selected composites has been done using the simulation tool based on Monte Carlo method of Geant4, in the photon energy range of 15 keV to 15 MeV. To investigate the performance of these selected composites, effective quantities in gamma ray attenuation such as: attenuation coefficients (total, linear and mass), mean free distance, one-tenth and half-value layers, the ratio of Compton scattering to the total attenuation coefficient have been calculated. To verify the simulation results, the simulation results are compared with the data extracted from the NIST-XCOM database, and the data extracted from the NIST-XCOM database and the simulation results are in good agreement with each other. Also, the percentage deviation (RD) between the calculated results is less than 2% in most cases. Due to the high atomic number of bismuth and Gadolinium, compound of bismuth oxide containing Gadolinium absorb and attenuate high-energy photons with higher efficiency than lead and are less toxic. Bismuth oxide compound shields with Gadolinium element can be used as absorbers of high-energy photons for various jobs in the field of medical radiation, such as doctors, dental hygienists, operating room workers, and radiologists, and can improve the health and safety of workers.

This study aims to compare the effect of graphite content (0–5 wt.%) on the mechanical and ‎tribological properties of aluminum matrix nanocomposites. The bulk samples were prepared ‎by the mechanical milling/hot pressing (temperature 420 °C/ pressure 400 MPa/ time 1h) ‎process. According to the obtained results in this work, the addition of graphite to an ‎aluminum matrix significantly improves the wear properties of aluminum (wear rate and ‎coefficient of friction). The best wear performance was obtained with the sample containing ‎‎5wt.% graphite, which showed a 62% reduction in the wear rate and a 2.5-fold reduction in ‎coefficient of friction compared to the unreinforced aluminum sample. Although increasing ‎the amount of graphite in the range of 0-5 wt.% leads to a continuous improvement in the ‎wear behavior of the composite material, it results in a simultaneous deterioration of the ‎mechanical properties (hardness and compressive strength) and the density of the Aluminum- ‎Graphite composites.‎

This research aimed to investigate the effect of nanoclay composite stabilized on chitosan surface in removing zinc, copper, iron and aluminum metals from fish meal Company effluent in 2017. Chitosan was prepared from common carp (Cyprinus carpio) skin. The amount of absorption of zinc, copper, iron and aluminum metals by chitosan-clay nanocomposite was investigated in five concentrations of 0, 0.2, 0.5, 0.8 and 1 weight percentage and at contact times of 60, 120 and 180 minutes. . In two concentrations of 0.2% and 0.5% of adsorbent and in contact times of 60 and 120 minutes, zinc and aluminum metals had the highest absorption rate compared to copper and iron metals, and in contact time of 180 minutes, iron metal had the highest absorption percentage (P<0.05). In concentrations of 0.8% and 1% of adsorbent in all three times, zinc metal has the highest removal percentage and aluminum has the lowest removal percentage (P<0.05) and two metals iron and copper rank second without any significant difference were placed (P<0.05). The results of the present study showed that the amount of metal absorption by chitosan-clay nanocomposite is related to the concentration of the adsorbent and the contact time and chitosan-clay nanocomposite can be used to remove and reduce the level of heavy metal contamination in the wastewater of fishmeal and other food factories.

One of the most important finishing operations that is usually performed as the final process when producing a part is the modification of surface properties with surface engineering operations. Many metals can be coated by the electroless-coating method. Electroless nickel-boron coatings have been widely used in the industry due to their cheap price and uniform coating capability. In this article, nickel-boron-nanodiamond electroless coating with different concentrations of nanodiamond was applied on AISI 4140 steel, and its structural properties and wear behavior were investigated. The structural properties of the coatings were investigated with the help of X-ray diffraction tests, scanning electron microscopy, and hardness test. Also, the friction coefficient and wear properties of the samples were studied using the pin-on-disc test. The results show that with the increase in nanodiamond concentration, the structure of the coating changes from amorphous to semi-crystalline. In addition, the electron microscope images and the hardness test results show that adding nanodiamonds to the electroless bath increases the hardness. Adding nanodiamonds to a concentration of 0.5 g/L improved the wear resistance and reduced the friction coefficient. However, increasing the concentration of nanodiamonds up to 1 g/L due to the agglomeration of nanodiamonds caused an increase in the specific wear rate of the coating.

In recent years, piezoelectric materials have received great attention due to their wide applications in transducers, actuators, and sensors. In the meantime, lead-based piezoelectric materials have become the most successful piezoelectric materials in practical applications due to their excellent electrical properties, but due to the toxicity of lead and its harms to human health and the environment, their use has been limited. Among lead-free piezoelectric compounds, potassium-sodium niobate compound (KNN) has shown promising dielectric, ferroelectric and piezoelectric properties. KNN-ZnO ceramic compound with high density (ρth=95%), favorable microstructure, suitable dielectric and piezoelectric properties (K=875.12, d33=125pC/N, D=0.01) was chosen as the ceramic phase for composite fabrication. On the other hand, polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) polymer with favorable piezoelectric and mechanical properties was selected as the polymer phase. To achieve special properties of the composition, ceramic-polymer composites were made, and the electrical behavior of these composites was evaluated. In this research, the cold sintering process was used to make KNN-ZnO/PVDF-HFP composites and the effect of adding different amounts of nano SnO2 on the final properties of the composites was investigated. According to the results, adding small amounts of SnO2 to the composite containing 80% by weight of KNN-ZnO increased the density and dielectric constant of the composite, but there were no specific changes in the piezoelectric properties of the composite. Among the composite samples, the sample with 1wt% of nano tin oxide had the highest values ​​of voltage coefficient and figure of merit

Electrolytic plasma oxidation coatings are one of the most important materials used to deal with the wear of aluminum parts due to their compact, sticky and hard nature. In recent years, improving the surface properties of these coatings with the help of adding reinforcement particles has attracted the attention of researchers.

Methods:

 In this study, plasma electrolytic oxidation (PEO) process was applied in two modes, normal and composite, to coat aluminum 7075. To produce the composite coating, the same electrolyte as the normal mode was used with the addition of 12 grams per liter of silicon oxide particles. Characterization of coatings was done with the help of SEM, X-ray diffraction analysis, energy dispersive spectrometer (EDS) analysis, roughness measurement and hardness measurement. The tribological behavior of coatings was investigated with the help of pin-on-disk test and the analysis of the wear mechanism of the samples was done with the help of SEM images and EDS analysis of wear surfaces.

Both coatings had a pancake structure with craters. Also, the drainage channels that lead to the porosity of the coatings were less created on the surface of the composite coating. The normal coating was an oxide coating with an amorphous/crystalline nature, but the composite coating had silicon oxide and mullite crystalline phases in addition to these two phases. The lowest weight loss (highest wear resistance) and friction coefficient were obtained for the composite coating. wear mechanism was also observed delamination wear and oxidation wear for substrate, abrasion, adhesive and oxidation  wear for PEO coating, and fine scratch mechanisms and adhesive mechanism with very little effect for composite coating.

In the present research, alumina-ceria particles were synthesized by a sol-gel method. The produced particles were characterized by X-ray diffraction and scanning electron microscopy. Then, alumina matrix composites containing 15 wt.% of ceria were densified under 80 MPa pressure at different temperatures by spark plasma sintering process. X-ray diffraction results showed that the powder produced before heat treatment has an amorphous structure, while alumina and ceria phases are formed after calcination at 800 °C. The produced particles have an average particle size of 250 nm. The effect of sintering temperature on the density of samples, grain size, and hardness of composites was investigated. The samples were densified at about 1400 °C, reaching a density of about 97% of the theoretical density. The microstructure analysis revealed that the composite grains have grown with increasing sintering temperature. The results declared that increasing the temperature and pressure in the sintering process enhances the density of the samples. The Vickers hardness of the composites increased with increasing sintering temperature, as the composite samples sintered at 1400 °C for 20 minutes at a pressure of 80 MPa had the highest Vickers hardness of about 15.3 GPa.

This study aims to improve the wear resistance of mullite ceramics as one of the most critical engineering ceramics by adding tungsten carbide (WC) particles. For this purpose, mullite-WC composites without and with adding 5, 10, and 15 % by weight of WC particles produced by Spark Plasma Sintering (SPS) method. In addition, it investigates the effect of sintering temperature on the wear resistance of mullite-WC composites applied by the SPS process at 1300 °C, 1350 °C, 1400 °C, and 1450 °C for 4 minutes under the pressure of 30 MPa. The results pin on the disk testing indicates that upon increasing the weight percentage of WC particles and increasing the sintering temperature up to 1400 °C, the wear resistance of mullite-WC composites would increase. However, increasing the sintering temperature up to the range of 1450 °C led to a decrease in the wear resistance due to the poor mechanical properties and formation of the W2C phase. The results from Scanning Electron Microscopy (FESEM) analysis are indicative of the formation of abrasive wear and surface layer structure mechanisms on the surface in mullite ceramics samples with and without WC reinforcing particles.

In this research, fused silica-zirconia composites including of 5 % by weight of zirconia stabilized yettria prepared by Spark Plasma Sintering (SPS) method. The powders were mixed by Spex (8000D, High energy ball mill) for 30 min in ethanol media. After mixing process, the ethanol removed by heating of the batches at 70 °C. The prepared samples were sintered at 1100, 1200 and 1300 °C and final pressure of 30 MPa. FESEM images demonstrated distribution of reinforcements at the fused silica matrix, also the results showed that sintered samples at 1200 °C have better properties than other samples. Relative density, flexural strength, hardness and toughness of these samples were 99.99 %, 13.4 GPa, 131 MPa and 4.46 MPa.m1/2 respectively. Also results showed that with increasing of sintering temperature to 1300 °C, due to crystallization in fused silica and as a result the formation of cracks in matrix, flexural strength decreased but the hardness and toughness increased slightly.

Compared to mechanical joining methods, adhesive bonded joints have uniform stress distribution, good fatigue performance and better weight reduction effect. Some failures in the adhesive bonded joints are caused by the presence of contamination and inappropriate roughness in the joint surfaces. In this study, the effect of different surface treatment on the mechanical behavior of the composite/aluminum adhesive joint in the mode I of fracture is investigated by using Double-cantilever beam specimen. Surface treatment has been done with three methods of Peel Ply Processing, Sanding and Laser for composite adherent and two methods of Sanding and Laser for aluminum adherent. In the laser surface treatment method, the transverse distance of the grooves and the spots diameter are fixed, and the scanning speed and power of the machine are variable. The surface roughness measurement of the adherents shows the increase of the surface roughness up to a certain value of the laser energy density, but after that the roughness has decreased due to the melting of the adherent surface. The results show an increase of 13.43% and 7.46% in the critical strain energy release rate of the mode I of fracture using the laser surface treatment method compared to the Sanding method and the Peel Ply Processing method, respectively. Also, examination of the fracture surface of the joint shows an increase in the failure mode of fiber tearing at the joint surface with the correct selection of laser parameters, which has improved the strength of the joint.

Lead-acid batteries are a significant part of the global battery market; however, due to limited life of these batteries, we are faced with major environmental challenges associated with lead-acid battery waste. One of their main components is the separator. In addition to polyethylene and silica, the separator of these batteries also contains lead compounds. In this research, lead-acid battery separator and polyethylene were used as a matrix for preparing a composite that could improve polyethylene's mechanical properties due to the presence of silica. Samples of HDPE and LLDPE with 5% to 15% lead-acid battery separator were prepared and their mechanical and thermal properties were evaluated and compared. By analyzing the DSC results, the type of polyethylene in the battery separator, HDPE, was determined. By adding the battery separator to HDPE matrix, elastic modulus increased by about 22% and bending modulus by about 55%. For LLDPE elastic modulus increased by approximately 35%. The yield strength of the sample, with HDPE matrix containing 15% separator has increased from 25.1 MPa to 28 MPa, and for the sample, with LLDPE matrix containing 15% separator, yield strength increased from 11.9 MPa to 13.7 MPa. Hardness and modulus for 15% of the separator are at maximum value. Consequently, 15 wt.% separator is an optimal value to improve samples' mechanical properties.