Showing 7 results for Akbari
G. H. Akbari, M. A. Sheikhi,
Volume 4, Issue 1 (winter & spring 2007 2007)
Abstract
Abstract: Ball mills are used in the last stage of ore processing for grinding raw materials. Forged
70Cr2 alloy steel and Austempered Ductile Iron (ADI) balls are materials from which grinding
balls are made for Sarcheshmeh Copper Plant (SCP) ball mills. In the present study wear and
impact properties of these two kinds of balls have been investigated. Some balls randomly were
selected as samples. They were cut to investigate the cross section under optical and scanning
electron microscopes. The microstructure of the sample balls was studied and quantitative
measurements of microstructural features were performed. The hardness of different parts of cross
sections of balls was measured. The wear resistance of the balls was measured by Pin on Disc
method. Repeated dropt test was employed to evaluate impact resistance of the balls. The
microstructure of ADI balls consisted of bianitic matrix with graphite nodules and some retained
austenite and martensite. Micro cracks and porosities in the cast structure were frequently
observed. In the case of forged steel balls the microstructure composed of tempered martensite in
outer area and bianitic structure with some tempered martensite in central areas. The wear and
impact resistance of forged steel balls were markedly higher than those of ADI balls. The
difference was consistent with the differences between the microstructures of the two kinds of balls.
Cast structure with microcracks and shrinkage porosities in ADI balls gives rise to lower impact
resistance.
M. Pirhadi Tavandashti, M. Zandrahimi, B. Akbari,
Volume 6, Issue 1 (winter 2009 2009)
Abstract
Abstract: Nanoparticles exhibit a high reactivity and strong tendency towards agglomeration. In this study, aluminum
oxide (alumina) nanoparticles were characterized by gas adsorption (BET), transmition electron microscopy (TEM)
and photon correlation spectroscopy (PCS) techniques to assess the agglomeration of the particles. There is a good
correlation between the BET and TEM measurements but PCS was larger in the mean and median size and with a
degree of agglomerates being detected. Some agglomeration was evident, but most of the particles existed as discrete
objects as observed in the (HR) TEM images which were in good agreement with the agglomeration factor.
I. Ebrahimzadeh, Gh.h. Akbari,
Volume 6, Issue 1 (winter 2009 2009)
Abstract
Abstract: Horizontal continuous casting is widely used to produce semi-finished and finished metallic products.
Homogeneity in metallurgical characteristics and mechanical properties in such products is of importance. In the
present work microstructure and mechanical properties of a horizontal continuous cast pipe have been studied.
Microstructural features were investigated by an optical microscope equipped with image analyzer and SEM was used
to characterize precipitates. Tensile behavior, impact strength and hardness variations were the mechanical properties
which were studied. Results showed that microstructure and mechanical properties had diversities in different parts of
the pipe and distinct differences were observed between upper and lower parts of the pipe. A meaningful correlation
was found in microstructure and mechanical properties in different parts of the component.
B. Akbari, M. Pirhadi Tavandashti, M. Zandrahimi,
Volume 8, Issue 2 (spring 2011 2011)
Abstract
Abstract: Most properties of nanoparticles are size-dependent. In fact, the novel properties of nanoaprticles do not prevail until the size has been reduced to the nanometer scale. The particle size and size distribution of alumina nanoparticle, as a critical properties, have been determined by transmission electron microscopy (TEM), photon correlation spectroscopy (PCS), surface area analysis (BET) and x-ray diffraction peak broadening analysis. The particle size was found to be in the range of 5-95nm. Cumulative percentage frequency plot of the data extracted form TEM images indicates that particle size distribution obeys the log-normal function. The TEM images also reveal that particles are spherical in shape and loosely agglomerated. Comparing of the XRD and TEM results shows that the particles are single-crystal. The HRTEM images also verify that the particles have a single-crystal nature. In comparison, there is a good correlation between the BET, XRD and TEM measurements other than PCS that is sensitive to the presence of the agglomerates.
Reza Mirahmadi Babaheydari, Seyed Oveis Mirabootalebi, Gholam Hosein Akbari Fakhrabadi,
Volume 18, Issue 1 (March 2021)
Abstract
Cu-based alloys have a wide range of applications in the electronics industry, communications industry, welding industries, etc. Regarding the type and percentage of the second phase, changing in the alloying elements has a significant effect on the mechanical and electrical properties of copper composites. The aim of the present work is to synthesize, investigate, and compare the micro-structure, micro-hardness, and electrical properties of different Cu-based nanocomposites. For this purpose, Cu-Al, Cu-Al2O3, Cu-Cr, and Cu-Ti were fabricated via ball milling of copper with 1, 3, and 6 weight percentages. The vial speed was 350 rpm and the ball-to-powder weight ratio was kept at 15:1. The milling process was performed at different times in Argon. Next, the prepared composites were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), and dynamic light scattering (DLS). Based on XRD patterns, crystallite size, lattice strain, and lattice constant were calculated by Rietveld refinement using Maud software. The results show a decrease of crystallite size, and an increase of the internal strain and lattice constant by rising the alloying elements in all composites. Then, the produced powders compressed via the cold press and annealed at 650˚C. Finally; the micro-hardness and the electrical resistance of the manufactured tablets were measured. The results of these analyses show that micro-hardness is increased by enhancement of the reinforcement material, due to the rising of the work hardening. Cu-6wt%Ti with 312 Vickers and Cu-1wt%Al2O3 with 78 Vickers had the highest and lowest micro-hardness, respectively. Moreover, the results of the electrical resistance indicate a dramatic rise in the electrical resistance by increasing the amount of alloying material, which Cu-1wt%Al with 0.26 Ω had the highest electrical conductivity.
Leila Taghi-Akbari, Mohammad Reza Naimi-Jamal, Shervin Ahmadi,
Volume 20, Issue 4 (December 2023)
Abstract
Two-dimensional molybdenum disulfide (MoS2) is used as a promising flame retardant and smoke suppressant nano additive in polymer composites due to its high thermal stability and layered structure. In this study, thermoplastic polyurethane (TPU) was melt-blended with MoS2 (1wt. %) and a halogen-free intumescent flame retardant (IFR) system. The IFR system consisted of ammonium polyphosphate (APP), Melamine polyphosphate (MPP), and pentaerythritol (PER), with a total amount of 25 wt. %. The TPU/IFR/MoS2 composite exhibited outstanding flame-retardant properties, achieving a UL-94 V-0 rating and a limiting oxygen index (LOI) value of 34%. Reaction-to-fire performance of the TPU/IFR/MoS2 composite was evaluated by cone calorimeter test (CCT). The CCT results indicated high flame-retardant efficiency and considerable smoke suppression performance, along with a significant decrease in the peak heat release rate (PHRR: 65.9%), peak smoke production rate (PSPR: 65.6%), and peak CO production (PCOP: 60.7%) compared to the neat TPU. The significant improvement in fire performance of TPU composite was mainly attributed to the effects of the physical barrier of MoS2 and catalytic carbonization of the IFR system. These resulted in forming an intumescent compact carbonized layer during the combustion, effectively restricting dripping. The continuous structure of the residual char was revealed by FESEM. Thermogravimetric analysis (TGA) indicated improved thermal behavior of the TPU composite in high temperatures. This work provides an effective method to improve the reaction to fire of TPU composites by incorporating traditional IFRs and MoS2, resulting in enhanced fire safety.
Marzieh Akbari, Fatemeh Dabbagh Kashani, Seyed Mohammad Mirkazemi,
Volume 22, Issue 4 (December 2025)
Abstract
CIGS solar cells are currently very high-efficiency thin-film solar cells. With regard to higher efficiency in solar cells, research is being conducted on the influence of both light scattering and plasmonic resonances due to metallic nano-structures. This article discusses the assessment of the incorporate plasmonic nanostructures on the absorber layer of a 1000 nm CIGS solar cell, in terms of light absorption and device performance. It is noted that decisions on material, size, and surface coverage (Occupied Factor) were important considerations that affected the performance. Opto-electrical assessment was used to investigate absorption, charge-carrier generation, current density-voltage response, power-voltage properties, and total efficiency. Using simulations, we discovered the aluminum nanosphere arrays (200 nm diameter, Occupied Factor 0.64) at the top of the absorber layer yielded the maximum efficiency (26.14%). This was shown by the resonances, and near-field distribution garnered from the nanospheres boost charge carrier generation, diminished recombination losses, and increased charge separation. Collectively, these raised the performance of the CIGS solar cells in this research and suggested hope for moving CIGS and potentially other photovoltaics forward using nanoscale plasmonic resonances.
