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Papers by Ali Mohammad Hadian
International Journal of Refractory Metals and Hard Materials, 2020
Multi-walled Carbon Nanotubes (MWCNTs) are added to NbC-12 vol% M2 high-speed steel to investigat... more Multi-walled Carbon Nanotubes (MWCNTs) are added to NbC-12 vol% M2 high-speed steel to investigate the effect on microstructural and mechanical properties. Powder mixtures containing small amounts of MWCNTs (0, 0.1, 0.3 and 0.9 wt%) were prepared and shaped into pellets using cold compaction. The green samples were sintered under high vacuum condition for 1 h at 1360°C. In order to study the microstructure and phase evolution of the sintered cemented carbide, field-emission scanning electron microscopy (FESEM) equipped with energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis were used. Density was measured using Archimedes method and Vickers hardness was performed to characterize the mechanical properties including hardness and fracture resistance. Results show that addition of MWCNTs from 0 to 0.3 wt% significantly increases the hardness from 1101 ± 18 to 1470 ± 22 HV. However, higher MWCNTs content causes reduction in hardness value down to 997 ± 26 for 0.9 wt%. FESEM images and density measurement reveal better densification of the cemented carbide by adding MWCNTs up to 0.3 wt%. Further microstructural investigations on indented samples showed remarkable bridging mechanism activated by the presence of nanotubes in the sample containing 0.3 wt%. Despite the toughening effects of MWCNTs, the fracture resistance slightly improved and reached the maximum value of 3.55 ± 0.08 MPa.m 0.5 for NbC-M2-0.3 wt% MWCNTs. According to XRD phase analysis, no compositional changes were detected in samples containing MWCNTs.
AIP Conference Proceedings, 2018
Fluid transmission pipes made of aluminum are widely used in petrochemical industries. For many a... more Fluid transmission pipes made of aluminum are widely used in petrochemical industries. For many applications, they have to be brazed to each other. The brazed joints, in many cases, are encountered with corrosive medias. This paper reports a part of a work to investigate the corrosion behavior of brazed AA6061 using AA4047 as filler metal with and without the use of flux under different brazing atmospheres. The samples brazed under air, vacuum, argon, and hydrogen atmospheres. The interfacial area of the joints was examined to ensure being free of any defects. The sides of each test piece were covered with an insulator and the surface of the joint was encountered to polarization test. The results revealed a significant difference of corrosion resistance. The samples that brazed under argon and hydrogen atmospheres had better corrosion resistance than other samples. The microstructure of the corroded joints revealed that the presence of defects, impurities due to use of flux and depth of filter metal penet...
Ceramics International, 2018
Yttria-stabilized zirconia (YSZ) has been widely used in dental applications due to its excellent... more Yttria-stabilized zirconia (YSZ) has been widely used in dental applications due to its excellent properties. However, chipping of fused feldspathic veneers on the zirconia cores is prone to limit the use of YSZ in allceramic dental restorations. The aim of this study was to investigate the effect of some processing parameters such as roughening the core surface and the atmosphere in which the feldspathic veneer was fused on the dental zirconia core. In order to address possible reasons of the chipping issue, the wetting behavior of a molten veneer on a zirconia core was evaluated using a sessile drop method at 990°C for 0-120 min. The results showed the nonwetting behavior of the materials as the contact angles was measured to be > 90°at conventional processing conditions. By varying some processing parameters such as surface roughening or firing atmosphere, it was found that these factors had huge effects on the wettability. The results showed that the melt veneer had little tendency to spread on the rougher zirconia surfaces. In addition, the firing of the feldspathic veneer in vacuum significantly decreased the wetting compared with that of in the air.
International Journal of Modern Physics: Conference Series, 2012
Gas atomized Al (6061) powder particles were used to synthesize nano-structured Al based composit... more Gas atomized Al (6061) powder particles were used to synthesize nano-structured Al based composite powders reinforced with 2 and 5wt.% of nano and micro sized boron carbide particles by mechanical alloying. These composite powders as well as the un-reinforced Al powders were compacted by cold uniaxial pressing. In order to investigate the effect of consolidation procedures on the properties of the resultant Al - B 4 C composites, a number of the samples were subjected to sintering at 620 °C for 2h while the others were hot extruded at 520 °C with the extrusion ratio of 8:1. The effect of percentage and size of B 4 C on the density, hardness and mechanical properties (such as yield strength, compression strength) of the composites were evaluated and compared with those of the un-reinforced alloy. The fractured surfaces of the samples were studied by scanning electron microscopy (SEM). The results of the present study revealed a higher hardness for the extruded samples as compared wit...
Advanced Materials Research, 2013
Titanium diboride (TiB2) ceramics have unique physical and chemical properties such as excellent ... more Titanium diboride (TiB2) ceramics have unique physical and chemical properties such as excellent electrical conductivity, high melting point and good corrosion resistance. But due to its relatively low sinterability, the use of this material is currently limited. The addition of Al2O3 to TiB2 can improve its fracture toughness, flexural strength, sinterability, and impact resistance. In this paper, TiB2-Al2O3 composite powders were produced by self-propagating high-temperature synthesis (SHS) method with reductive process from H3BO3-TiO2-Al system. Aluminum and magnesium were used as reductive elements to provide sufficient heat as primary driving force to obtain TiB2-Al2O3 composite. Due to the lower energy release in using aluminum as the initiator of the SHS process, finer microstructure can be achieved. Different stoichiometric amounts of aluminum as precursor were added to the mixture to examine its effect on the reaction progress. To evaluate the complete chemical conversion o...
Advanced Materials Research, 2012
ABSTRACT
Advanced Materials Research, 2013
Bismuth oxide, due to its low melting point was selected as filler for joining alumina to alumina... more Bismuth oxide, due to its low melting point was selected as filler for joining alumina to alumina using Transient Liquid Phase (TLP) method. For this purpose a thin layer of bismuth oxide was placed as an interlayer between the ceramic bodies. To study the effect of time and temperature on the mechanical properties of the joined samples, the joining tests were carried out in 900, 1000 and 1100°C for various times. The mechanical properties of the joined samples were measured using shear testing method. To investigate the microstructure of the joining area, the cross section ofthe joints were studied using scanning electron microscope (SEM) and X-ray diffraction method. The results showed that longer joining times results in higher mechanical properties of the joints. The highest joint strength of about 80 MPa was obtained for the sample joined in 900°C for 10hour.
Key Engineering Materials, 2002
IRANIAN JOURNAL OF MATERIALS SCIENCE AND …, 2005
Enhancing the properties of dental resin composites is of interest to researchers. The objective ... more Enhancing the properties of dental resin composites is of interest to researchers. The objective of the present investigation was to improve the strength and fracture toughness of dental composites via addition of silicon carbide whiskers and substitution of commonly ...
Journal of the American Ceramic Society, 2005
Ceramics International, 2014
ABSTRACT In this study, mixed hydride/alanate nano powders in the Al-Mg system were used as the i... more ABSTRACT In this study, mixed hydride/alanate nano powders in the Al-Mg system were used as the interlayer for low temperature diffusion bonding of dense alumina parts. Decomposition of hydride nanopowders at bonding temperatures in-situ formed metals and alloys nano particles with oxide free surfaces and high sinter-ability in the interlayer. Nano powders sintering behavior in the interlayer and formation of compounds in the reaction layer during diffusion bonding were studied. Mixture of 50-50 M ratio of AlH3 and Mg(AlH4)(2), as the interlayer improved bond strength of the joints. Diffusion bonding products were formed in the MgO-Al2O3 spinel system with different stoichiometries. Bond strength improved up to 202 MPa by induction hot pressing alumina parts at low bonding temperature of 400 degrees C under pressure of 20 MPa during 30 min bonding period. (c) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Advanced Materials Research, 2013
Al-Cu joints have been widely used in electronic and heat exchanger industries due to their excel... more Al-Cu joints have been widely used in electronic and heat exchanger industries due to their excellent electrical and thermal conductivity. Meanwhile, the use of Al in the Al-Cu joints can result in lower weight and cost of the final structure. The purpose of the current study is to join Al to Cu by furnace brazing using ultrafine Al-Si powder. To study the microstructure of the join area, the brazing tests were conducted in the range of 590 to 610°C for 5 to 15 minutes under inert atmosphere. The microstructure of Al/Cu joints was studied by scanning electron microscopy (SEM). The elemental analysis was conducted using an energy dispersive spectrometry (EDS) system. Experimental results show that two kinds of intermetallic compounds (IMCs) mainly Cu3Al2 and CuAl2 phases are formed near the interface of copper and in the braze layer region. The bulky prismatic structure which is formed on the side of Al substrate was found to be α-Al+CuAl2 eutectic.
International Journal of Refractory Metals and Hard Materials, 2020
Multi-walled Carbon Nanotubes (MWCNTs) are added to NbC-12 vol% M2 high-speed steel to investigat... more Multi-walled Carbon Nanotubes (MWCNTs) are added to NbC-12 vol% M2 high-speed steel to investigate the effect on microstructural and mechanical properties. Powder mixtures containing small amounts of MWCNTs (0, 0.1, 0.3 and 0.9 wt%) were prepared and shaped into pellets using cold compaction. The green samples were sintered under high vacuum condition for 1 h at 1360°C. In order to study the microstructure and phase evolution of the sintered cemented carbide, field-emission scanning electron microscopy (FESEM) equipped with energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis were used. Density was measured using Archimedes method and Vickers hardness was performed to characterize the mechanical properties including hardness and fracture resistance. Results show that addition of MWCNTs from 0 to 0.3 wt% significantly increases the hardness from 1101 ± 18 to 1470 ± 22 HV. However, higher MWCNTs content causes reduction in hardness value down to 997 ± 26 for 0.9 wt%. FESEM images and density measurement reveal better densification of the cemented carbide by adding MWCNTs up to 0.3 wt%. Further microstructural investigations on indented samples showed remarkable bridging mechanism activated by the presence of nanotubes in the sample containing 0.3 wt%. Despite the toughening effects of MWCNTs, the fracture resistance slightly improved and reached the maximum value of 3.55 ± 0.08 MPa.m 0.5 for NbC-M2-0.3 wt% MWCNTs. According to XRD phase analysis, no compositional changes were detected in samples containing MWCNTs.
AIP Conference Proceedings, 2018
Fluid transmission pipes made of aluminum are widely used in petrochemical industries. For many a... more Fluid transmission pipes made of aluminum are widely used in petrochemical industries. For many applications, they have to be brazed to each other. The brazed joints, in many cases, are encountered with corrosive medias. This paper reports a part of a work to investigate the corrosion behavior of brazed AA6061 using AA4047 as filler metal with and without the use of flux under different brazing atmospheres. The samples brazed under air, vacuum, argon, and hydrogen atmospheres. The interfacial area of the joints was examined to ensure being free of any defects. The sides of each test piece were covered with an insulator and the surface of the joint was encountered to polarization test. The results revealed a significant difference of corrosion resistance. The samples that brazed under argon and hydrogen atmospheres had better corrosion resistance than other samples. The microstructure of the corroded joints revealed that the presence of defects, impurities due to use of flux and depth of filter metal penet...
Ceramics International, 2018
Yttria-stabilized zirconia (YSZ) has been widely used in dental applications due to its excellent... more Yttria-stabilized zirconia (YSZ) has been widely used in dental applications due to its excellent properties. However, chipping of fused feldspathic veneers on the zirconia cores is prone to limit the use of YSZ in allceramic dental restorations. The aim of this study was to investigate the effect of some processing parameters such as roughening the core surface and the atmosphere in which the feldspathic veneer was fused on the dental zirconia core. In order to address possible reasons of the chipping issue, the wetting behavior of a molten veneer on a zirconia core was evaluated using a sessile drop method at 990°C for 0-120 min. The results showed the nonwetting behavior of the materials as the contact angles was measured to be > 90°at conventional processing conditions. By varying some processing parameters such as surface roughening or firing atmosphere, it was found that these factors had huge effects on the wettability. The results showed that the melt veneer had little tendency to spread on the rougher zirconia surfaces. In addition, the firing of the feldspathic veneer in vacuum significantly decreased the wetting compared with that of in the air.
International Journal of Modern Physics: Conference Series, 2012
Gas atomized Al (6061) powder particles were used to synthesize nano-structured Al based composit... more Gas atomized Al (6061) powder particles were used to synthesize nano-structured Al based composite powders reinforced with 2 and 5wt.% of nano and micro sized boron carbide particles by mechanical alloying. These composite powders as well as the un-reinforced Al powders were compacted by cold uniaxial pressing. In order to investigate the effect of consolidation procedures on the properties of the resultant Al - B 4 C composites, a number of the samples were subjected to sintering at 620 °C for 2h while the others were hot extruded at 520 °C with the extrusion ratio of 8:1. The effect of percentage and size of B 4 C on the density, hardness and mechanical properties (such as yield strength, compression strength) of the composites were evaluated and compared with those of the un-reinforced alloy. The fractured surfaces of the samples were studied by scanning electron microscopy (SEM). The results of the present study revealed a higher hardness for the extruded samples as compared wit...
Advanced Materials Research, 2013
Titanium diboride (TiB2) ceramics have unique physical and chemical properties such as excellent ... more Titanium diboride (TiB2) ceramics have unique physical and chemical properties such as excellent electrical conductivity, high melting point and good corrosion resistance. But due to its relatively low sinterability, the use of this material is currently limited. The addition of Al2O3 to TiB2 can improve its fracture toughness, flexural strength, sinterability, and impact resistance. In this paper, TiB2-Al2O3 composite powders were produced by self-propagating high-temperature synthesis (SHS) method with reductive process from H3BO3-TiO2-Al system. Aluminum and magnesium were used as reductive elements to provide sufficient heat as primary driving force to obtain TiB2-Al2O3 composite. Due to the lower energy release in using aluminum as the initiator of the SHS process, finer microstructure can be achieved. Different stoichiometric amounts of aluminum as precursor were added to the mixture to examine its effect on the reaction progress. To evaluate the complete chemical conversion o...
Advanced Materials Research, 2012
ABSTRACT
Advanced Materials Research, 2013
Bismuth oxide, due to its low melting point was selected as filler for joining alumina to alumina... more Bismuth oxide, due to its low melting point was selected as filler for joining alumina to alumina using Transient Liquid Phase (TLP) method. For this purpose a thin layer of bismuth oxide was placed as an interlayer between the ceramic bodies. To study the effect of time and temperature on the mechanical properties of the joined samples, the joining tests were carried out in 900, 1000 and 1100°C for various times. The mechanical properties of the joined samples were measured using shear testing method. To investigate the microstructure of the joining area, the cross section ofthe joints were studied using scanning electron microscope (SEM) and X-ray diffraction method. The results showed that longer joining times results in higher mechanical properties of the joints. The highest joint strength of about 80 MPa was obtained for the sample joined in 900°C for 10hour.
Key Engineering Materials, 2002
IRANIAN JOURNAL OF MATERIALS SCIENCE AND …, 2005
Enhancing the properties of dental resin composites is of interest to researchers. The objective ... more Enhancing the properties of dental resin composites is of interest to researchers. The objective of the present investigation was to improve the strength and fracture toughness of dental composites via addition of silicon carbide whiskers and substitution of commonly ...
Journal of the American Ceramic Society, 2005
Ceramics International, 2014
ABSTRACT In this study, mixed hydride/alanate nano powders in the Al-Mg system were used as the i... more ABSTRACT In this study, mixed hydride/alanate nano powders in the Al-Mg system were used as the interlayer for low temperature diffusion bonding of dense alumina parts. Decomposition of hydride nanopowders at bonding temperatures in-situ formed metals and alloys nano particles with oxide free surfaces and high sinter-ability in the interlayer. Nano powders sintering behavior in the interlayer and formation of compounds in the reaction layer during diffusion bonding were studied. Mixture of 50-50 M ratio of AlH3 and Mg(AlH4)(2), as the interlayer improved bond strength of the joints. Diffusion bonding products were formed in the MgO-Al2O3 spinel system with different stoichiometries. Bond strength improved up to 202 MPa by induction hot pressing alumina parts at low bonding temperature of 400 degrees C under pressure of 20 MPa during 30 min bonding period. (c) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Advanced Materials Research, 2013
Al-Cu joints have been widely used in electronic and heat exchanger industries due to their excel... more Al-Cu joints have been widely used in electronic and heat exchanger industries due to their excellent electrical and thermal conductivity. Meanwhile, the use of Al in the Al-Cu joints can result in lower weight and cost of the final structure. The purpose of the current study is to join Al to Cu by furnace brazing using ultrafine Al-Si powder. To study the microstructure of the join area, the brazing tests were conducted in the range of 590 to 610°C for 5 to 15 minutes under inert atmosphere. The microstructure of Al/Cu joints was studied by scanning electron microscopy (SEM). The elemental analysis was conducted using an energy dispersive spectrometry (EDS) system. Experimental results show that two kinds of intermetallic compounds (IMCs) mainly Cu3Al2 and CuAl2 phases are formed near the interface of copper and in the braze layer region. The bulky prismatic structure which is formed on the side of Al substrate was found to be α-Al+CuAl2 eutectic.