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

The demand for aggregates for civil engineering construction is high in the market. The broad adoption of fly ash for producing fly ash aggregate is the best sustainable solution to fulfill aggregate demand and utilization of unused fly ash. Crushing is an essential step for producing angular-shaped aggregate. In this paper, an experimental study using a laboratory-scaled impact crusher was carried out to investigate the effect of crushing process parameters (feed block size, crusher speed and outlet sieve size) on the quality (particle size distribution, flakiness-elongation index and mechanical properties) of angular-shaped fly ash aggregates produced after crushing high-strength fly ash blocks. Particle size distribution and flakiness-elongation index were found to be changed with crushing parameters. Higher crushing speed resulted in small-size fly ash aggregates. Better particle size distribution of crushed fly ash aggregate was produced using a 60 mm outlet sieve compared to a 30 mm one. Well-graded fly ash aggregates with good particle shape (less flaky and less elongated) for the subbase layer of the road were obtained after crushing fly ash blocks of one-third feed size in a laboratory-scaled impact crusher at a crushing speed of 527 rpm and an outlet sieve of 60 mm. Mechanical properties (impact, crushing and abrasion values) of the fly ash aggregate were not much affected by crushing process parameters. The findings of this study will help in optimizing the crushing operation of the industrial impact crusher to produce high-quality angular-shaped fly ash aggregate on a large scale.

Among the high-tech industries like automotive, aerospace, electronics, etc., aluminum matrix cast composites (AMCCs) are widely applied for the fabrication of accountable and especially acute pieces. During the present study, hybrid aluminum base composites containing Mg2Si and Al3Ni particles were fabricated successfully in casting moods and their structural characteristics were evaluated under different solidification conditions. A variety of microstructural measurements were performed on the composite microstructure in this study, including X-ray diffraction (XRD), optical microscope (OM) and scanning electron microscope (SEM). Furthermore, a hardness test was conducted to evaluate the mechanical properties of the material. Results indicate that increasing the cooling rate during solidification reduces the average size of the Mg2Si initial phases, improves their distribution uniformity and increases their final amount, whereas the average size of the Al3Ni particles decreases greatly but their content remains the same. In comparison to base alloys, hybrid composite with Mg2Si and Al3Ni particles shows the highest hardness.

In the present study, four series of Al-6061/SiC composites synthesized via powder metallurgy technique were used to investigate the impact of the matrix grain size and/or the size of reinforcing particles on enhancing the compressibility of powder mixtures and hardness of the composites. In two series, the as-received Al powders have micron-sized grains mixed with either nano-sized or micron-sized SiC particles. For the other two series, the Al powders were initially milled to convert their grain size to nano-scale before mixing with either nano-sized or micron-sized SiC particles. The powder mixtures containing 1, 2, and 3 vol.% of SiC particles were cold pressed and hot extruded. The decreased compressibility in all of the four series of Al/SiC powder mixtures with increased SiC content attributed to the enhanced portion of the hard and non-deformable SiC particles in the powder mixtures resulting in a reduced degree of plastic deformation. Increment the SiCn content from 0% to 3% resulted in a significant increase in the microhardness of 20h planetary ball milled powders accompanied with decrease compressibility of powders. The composites were subjected to Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and X-ray diffraction (XRD) studies as well as density and hardness measurements. Metallographic studies and density measurements confirmed significant densification with no indication of voids in the samples’ microstructures after hot extrusion. The results revealed that matrix microstructure, as compared with the size of the reinforcing particles, was more influential in enhancing the powder compressibility and composite hardness.

The hyperbolic non-linear elastic constitutive model for idealization of non-cohesive soil has been commonly used by researchers in numerical modeling. The hyperbolic model includes parameters (HMP) such as modulus number ‘K’, exponent ‘n’, angle of internal friction ‘φ’ and failure ratio ‘Rf’, which are evaluated using laboratory shear test. The parameters ‘K’, ‘n’ and ‘Rf’ are evaluated from transformed stress-strain curve whereas ‘φ’ is directly evaluated from normal and shear stress. When the samples are in large numbers, the process becomes very tedious and there will be no correlation for evaluation of such parameters. These parameters are highly dependent on particle size, moisture content and density. In this paper, box shear test has been performed on coarse, medium and fine sand as well as on fine gravels with varying densities. The tests have been conducted in dry and moist conditions. Based on the experiments performed, the HMP have been evaluated. The correlations have been established for every parameter based on particle size, moisture content and density. These correlations will be useful in direct evaluation of model parameters.

In this study, aluminum chips were milled in a planetary ball mill at different times and ball-to-powder weight ratios (BPRs). The resulting optimum powder was reinforced with 1 wt% and 2 wt% of multi-walled carbon nanotubes (MWCNTs). The effects of alloying time, BPR, and MWCNTs percentage on the morphology, distribution, and composition of the Al7075-MWCNT powder were investigated. The results showed that smaller particles with a limited size distribution can be obtainable by increasing BPR and decreasing mechanical milling time. A uniform dispersion of reinforcement (2 wt%) was achieved at lower alloying times (15 and 30 min) and a higher BPR (20:1). Using XRD analysis, it was revealed that the carbon peaks are more clearly in 2%-MWCNT powders than 1%-MWCNT ones. The addition of MWCNTs led to reducing the particle size; this is confirmed by the data obtained from the XRD patterns and their analysis with the Williamson-Hall model. Machining chips were converted into composite powder by cost-effective mechanical milling and alloying method with a uniform distribution of MWCNTs, which is unique.

In this study effect of active material particle size distribution (PSD) on TiNb2O7 electrodes and their performance were evaluated. To determine the effect of PSD, have focused on the performance of the electrode, which is mainly affected by the performance of individual particles and their interaction. For this purpose, TiNb2O7 was successfully synthesized by mechanochemical method and post-annealing, as an anode material for lithium-ion batteries. Phase identifications and microstructure characterization was carried out by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) to identify the phases and evaluate the morphology of the synthesized samples. The charging and discharging tests were conducted using a battery-analyzing device for evaluating the electrochemical properties of the fabricated anodes. Eventually, at faster charging rates, the electrochemical performance was found to be improved when smaller active material particle size distribution was used. Differences in particles size distributions resulted in variable discharge capacities so that the sample with particle size higher than 25 microns (>25 μm) showed a capacity of 19 mAh/g after 179 cycles, which had a lower capacity than their sample with particle size less than 25 microns (<25 μm). The final capacity of the sample with a particle size less than 25 microns is 72 mAh/g.

The present requirement of automobile industry is seeking lightweight material that satisfices the technical and technological requirements with better mechanical and tribological characteristics.  Aluminium matrix composite ( AMC ) materials meet the requirements of the modern demands. AMCs are used in automotive applications as engine cylinders, pistons, disc and drum brakes. This paper investigates the effect of particle size and wt% of Al2O3/SiC reinforcement on mechanical and tribological properties of hybrid metal matrix composites (HMMCs). AA2024 aluminium alloy is reinforced with Al2O3/SiC different particle sizes (10, 20 and 40 µm) and weight fractions (upto 10 wt %) were fabricated by using squeeze casting technique. HMMCs were characterized for its properties such asX-ray diffraction (XRD), density, scanning electron microscope ( SEM ), hardness, tensile strength, wear and coefficient of friction. AA2024/5wt%Al2O3/5wt%SiC with 10 μm reinforced particle size showed maximum hardness and tensile strength 156.4 HV and 531.43 MPa and decrease in wear rate was observed from from 0.00307 to 0.00221 for 10N. Hybrid composites showed improved mechanical and wear resistance suitable for engine cylinder liner applications.

In present research, the foam glass-ceramic composites fabricated by window glass, steel slag and SiC, CaCO3 foaming agents were investigated by press–sintering method. The optimum sintering temperature was obtained at 1200°C with a 3-minutes holding time and 20°C/min heating rate. The optimum pressure level of 80 MPa for achieving the 70 % of relative density was selected. The effect of particle size distribution of starting materials on the green and fired density of resulted glass-ceramics composites was evaluated. The composite's green density was 1.7g/cm3 obtained using the following particle size (49 wt. % 150μm, 21wt. % 85μm, 21wt. % 65μm, 9wt. % 45μm). It was shown that using medium-fine grade of the slag powder, the compaction and green densities of samples were increased up to 16% while in the case of slag/glass composites (due to the high hardness of the glass powder), the compaction of composite was  increased 11% compared to the coarse grade particles bearing samples. It was observed that finer particle sizes (below 75 μm) significantly cause more foaming and lower density (about 80 wt.% porosity). This can be due to the faster coalescence process and gases trapping which was arisen from the decomposition of foam agent.

Nanoparticles are widely used in different applications such as cancer cell treatment and antibacterial agents. SnO2 nanoparticles were synthesized successfully by hydrothermal method and subsequent calcination using Tin (II) chloride- dihydrate, Sodium hydroxide, in presence of Hexadecyltrimethylammoniumn bromide (CTAB) as Surfactant. These nanoparticles were characterized by using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD pattern showed that all diffraction peaks were assigned to the pure tetragonal phase of SnO2 and SEM image of pure SnO2 showed that the nanoparticles are homogeneous with uniform particle size. In this research SnO2 nanoparticles were successfully synthesized.

Nanocomposite of ZrO2/ZnO was prepared under ultrasonic irradiation by sol gel process from directly mixing Zirconium and Zinc gels, and the mixture was placed under ultrasonic irradiation for 2 hours then aging time the filtrated composite gel was calcinated at 500°C for 3h in furnace. The precursor sol of zirconium was prepared from an aqueous solution of ZrCl4 and zinc acetate dihydrated was dissolved in de-ionized water. The FT-IR analysis and the XRD study were exhibited that the crystal structure and purity of the ZrO2/ZnO nanocomposite FESEM images was indicated the morphology and the average size of the NPs. The average size of the ZrO2/ZnO nanocomposite was determined 37 nm.

TiO2/ZrO2 nanocomposite was obtained by the sonochemical technique. In this method, two separate gels containing zirconium and titanium were prepared and mixed together. The precursor sol of zirconium was prepared from an aqueous solution of ZrCl4. The precursor titanium tetra isopropoxide (TTIP) dissolved in isopropanol. Mixing of Titanium and Zirconium gels was resulted in a yellow TiO2/ZrO2 gel. The precipitate was calcinated in the furnace. The obtained nanopowder characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and Fourier transform infra-red spectroscopy (FT-IR).

The morphological and microstructural changes during mechanical milling of Al powder mixed with 2.5, 5 and 10 wt.% Al2O3 particles were studied. The milling was performed in a planetary ball mill for various times up to 20h. The produced composite powders were investigated using X-ray diffraction pattern (XRD) to elucidate the role of particle size, secondary phase content and milling time on grain size and lattice strain of Al matrix. The aluminum crystallite size estimated with broadening of XRD peaks by Williamson–Hall formula. The morphological changes were studied by SEM technique. The results show that the addition of hard Al2O3 particles accelerates the milling process, leading to faster work hardening rate and fracture of the aluminum matrix. Furthermore, Al becomes smaller crystallite size during ball milling of Al powder in the presence of Al2O3 particles. The results revealed that the grain size of milled powders was about 45nm with a noticeable presence of agglomerates. Uniform distribution of nano-sized Al2O3 particles in the Al matrix could be achieved with increasing milling time.