El Oualid Mokhnache - Academia.edu (original) (raw)

Papers by El Oualid Mokhnache

Materials today communications, Jun 1, 2022

Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, Oct 10, 2014

B 4 C-TiB 2-SiC composites were fabricated via hot pressing using ball milled B 4 C, TiB 2 , and ... more B 4 C-TiB 2-SiC composites were fabricated via hot pressing using ball milled B 4 C, TiB 2 , and SiC powder mixtures as the starting materials. The impact of ball milling on the densification behaviors, mechanical properties, and microstructures of the ceramic composites were investigated. The results showed that the refinement of the powder mixtures and the removal of the oxide impurities played an important role in the improvement of densification and properties. Moreover, the formation of the liquid phases during the sintering was deemed beneficial for densification. The typical values of relative density, hardness, bending strength, and fracture toughness of the composites reached 99.20%, 32.84 GPa, 858 MPa and 8.21 MPa m 1/2 , respectively. Crack deflection, crack bridging, crack branching, and microcracking were considered to be the potential toughening mechanisms in the composites. Furthermore, numerous nano-sized intergranular/intragranular phases and twin structures were observed in the B 4 C-TiB 2-SiC composite. 2. Experimental 2.1. Materials Commercially available B 4 C powder (D 50 = 2.5 μm, Jingangzuan Boron Carbide Co., Ltd., Mudanjiang, China), TiB 2 powder (D 50 = 8.0 μm, Dandong Chemical Research Institute Co., Ltd., Dandong, China) and SiC powder (D 50 = 0.5-0.7 μm Shanghai Aladdin Biochemical Technology Co., Ltd., Shanghai, China) were used as the raw materials. The characteristics of the raw material powders, including mean particle size, specific surface area, oxygen content and certain metal impurities content are shown in Table 1.

Materials Today Communications

Journal of Composite Materials

The thermal, the electrical conductivity, and electromagnetic shielding properties of low cost hi... more The thermal, the electrical conductivity, and electromagnetic shielding properties of low cost high-performance expanded graphite (EG)-filled polybenzoxazine matrix nanocomposites produced by a solution blending and compression molding technique were investigated. At 2.26 vol.% EG, a percolation threshold was detected, at which the electrical conductivity increased by nine orders of magnitude in comparison to the unfilled matrix. The electrical conductivity values increased from 1.35 S.cm−1 to 28.3 S.cm−1 by increasing the EG ratios in the nanocomposites from 7 wt.% and 15 wt.%. In addition, the morphological analysis results revealed good nanofiller dispersion and the formation of 3D-conductive pathways of EG into the polybenzoxazine matrix, which are responsible for the electrical conductivity improvement. Moreover, the electromagnetic interference (EMI) shielding efficiencies, in the X-band, of these nanocomposites have been significantly improved, reaching 57.2 dB at a 15 wt.% E...

Metallurgical and Materials Transactions B, 2014

Three in situ formed Al2O3/Al-Si composites with a different volume fraction of 10, 20, and 30 vo... more Three in situ formed Al2O3/Al-Si composites with a different volume fraction of 10, 20, and 30 vol pct were fabricated using low energy ball milling and reaction hot pressing. The effect of reinforcement volume fraction on the microstructure and mechanical properties were studied. When the volume fraction was 30 vol pct, a massive primary Si (~130 µm) along with an increase of Al2O3 (~2 µm) was observed. The YS, UTS, and Brinell hardness of the composites were significantly higher than the aluminum matrix. Mechanisms governing the tensile fracture process are discussed.

Plastics, Rubber and Composites: Macromolecular Engineering, Feb 7, 2016

A new kind of polymer composite, produced from the typical polybenzoxazine and 0–30 wt-% native a... more A new kind of polymer composite, produced from the typical polybenzoxazine and 0–30 wt-% native and silane-treated aluminium nitride (T-AlN), was investigated. The mechanical tests revealed a significant increase in the microhardness and flexural properties upon adding the T-AlN particles compared to that obtained from the untreated ones. By adding 0–30 wt-% T-AlN, the tensile moduli were accurately reproduced by the Halpin-Tsai and Nielsen models. At 30 wt-% T-AlN, dynamic mechanical analysis showed a significant increase in the storage moduli and the glass transition temperature (Tg), reaching 3.2 GPa and 217°C, respectively. The thermal stability of these materials was significantly improved upon the addition of the T-AlN fillers. These improvements are attributed to the high thermal and mechanical properties of the fillers and their good dispersion and adhesion in and to the matrix as revealed by a morphological analysis.

Novel kinds of nanocomposites based on bisphenol A-aniline based polybenzoxazine matrix P(BA-a) a... more Novel kinds of nanocomposites based on bisphenol A-aniline based polybenzoxazine matrix P(BA-a) and 0 wt.%–20 wt.% boron carbide (B4C) nanoparticles were produced and their properties were evaluated in terms of the nano-B4C content. The thermal conductivity of the P(BA-a) matrix was improved approximately three times from 0.18 W/m K to 0.86 W/m K at 20 wt.% nano-B4C loading, while its coefficient of thermal expansion (CTE) was deceased by 47% with the same nanofiller content. The microhardness properties were significantly improved by adding the B4C nanoparticles. At 20 wt.% of nano-B4C content, dynamic mechanical analysis (DMA) revealed a marked increase in the storage modulus and the glass transition temperature (Tg) of the nanocomposites, reaching 3.9 GPa and 204°C, respectively. Hot water uptake tests showed that the water-resistance of the polybenzoxazine matrix was increased by filling with nano-B4C nano-filler. The morphological analysis reflected that the improvements obtain...

The effects of aluminum nitride (AlN) loading and size on the thermal conductivity of bisphenol A... more The effects of aluminum nitride (AlN) loading and size on the thermal conductivity of bisphenol A-aniline-based polybenzoxazine resin were studied. The experimental data of the thermal conductivity, CTE, and dielectric constants of these hybrids were compared with those predicted using various models. The morphological analysis revealed the formation of AlN conductive chains in the polybenzoxazine matrix. The thermal conductivity values of these hybrids gradually increased as the AlN fillers content increased and their sizes decreased. The highest thermal conductivity value reached 7.89 W m−1 K−1 at 60 vol% of 50 nm AlN. At the maximum AlN loading, the CTE values of these hybrids were reduced by 75 %, while their dielectric constants are raised by almost 45 %. The TG results showed significant improvements in the thermal degradation properties of these composites by adding the AlN filler; moreover, the Agari semiempirical model well-fitted the thermal conductivity experimental data ...

A new kind of thermally-conductive polymer nanocomposite was produced by reinforcing the typical ... more A new kind of thermally-conductive polymer nanocomposite was produced by reinforcing the typical polybenzoxazine matrix P(BA-a) with silane-treated Si 3 N 4 nanoparticles using a compression molding technique. By adding 0 to 70% nano-Si 3 N 4 , the nanocomposite׳s thermal conductivity was enhanced from 0.18 to 5.78 W/m K. Based on the analyzed morphology, the Si 3 N 4 nanoparticles tend to form continuous conductive chains within the polybenzoxazine matrix, which are responsible for the improved thermal conductivity of the polybenzoxazine resin. Also, these new nanocomposites exhibited improved dielectric, coefficient of thermal expansion, and flexural properties. The thermal stability of these materials significantly improved upon the addition of the nano-Si 3 N 4 fillers. Their unique thermal and dielectric properties make them suitable for microelectronic packaging applications.

The in-situ Al-based composites with different SiO 2 /C/Al molar ratios were fabricated by reacti... more The in-situ Al-based composites with different SiO 2 /C/Al molar ratios were fabricated by reaction hot pressing. The dry sliding wear characteristics of the composites were investigated using a pin-on-disc wear tester. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to investigate the surface composition and its morphology. The results show that when the SiO 2 /C/Al molar ratio is 3:6:9, more in-situ synthesized Al 2 O 3 and SiC along with Si particles are produced, and Al 4 C 3 is prevented completely from the Al–SiO 2 –C system. Thereby, a significant improvement of wear resistance is obtained. When the sliding velocity increases from 0.4 to 1.6 m/s, the wear loss decreases gradually. With increasing the normal load, the wear loss increases as well. Ploughing, craters and micro-grooving are observed as dominant abrasive wear mechanisms. Whereas, when a high velocity is employed, only the oxidation mechanism controls the wear behavior of...

Acta Metallurgica Sinica, Oct 10, 2014

In situ (Al 2 O 3-Si)/Al composites with a reinforcement volume fraction of 10% were synthesized ... more In situ (Al 2 O 3-Si)/Al composites with a reinforcement volume fraction of 10% were synthesized from the Al-SiO 2 system using low energy ball milling and reaction hot pressing. Differential thermal analysis was used to investigate the reaction mechanisms between SiO 2 and Al. X-ray diffraction results revealed that the reaction between Al and SiO 2 took place completely at 900°C with a holding time of 2 h, thereby forming Al 2 O 3 and Si. Scanning electron microscopic, energy dispersive X-ray spectroscopic, and transmission electron microscopic (TEM) results showed that the in situ synthesized Al 2 O 3 and Si particles, whose sizes are less than 2 lm, were polygonal in shape and dispersed uniformly in the matrix. Moreover, Al 2 O 3 particle size showed a tendency to increase from *2 to *6 lm when the synthesis temperature was increased. Furthermore, TEM observation showed that the interface between the reinforcements and Al matrix is clean. The yield strength, ultimate tensile strength, and Brinell hardness of the in situ (Al 2 O 3-Si)/Al composite was significantly higher than the aluminum matrix. Mechanisms governing the tensile fracture process are discussed.

International Journal of Minerals, Metallurgy, and Materials, 2015

In situ (α-Al 2 O 3 +ZrB 2)/Al composites with network distribution were fabricated using low-ene... more In situ (α-Al 2 O 3 +ZrB 2)/Al composites with network distribution were fabricated using low-energy ball milling and reaction hot pressing. Differential thermal analysis (DTA) was used to study the reaction mechanisms in the Al-ZrO 2-B system. X-ray diffraction (XRD) and scanning electron microscopy (SEM) in conjunction with energy-dispersive X-ray spectroscopy (EDX) were used to investigate the composite phases, morphology, and microstructure of the composites. The effect of matrix network size on the microstructure and mechanical properties was investigated. The results show that the optimum sintering parameters to complete reactions in the Al-ZrO 2-B system are 850°C and 60 min. In situ-synthesized α-Al 2 O 3 and ZrB 2 particles are dispersed uniformly around Al particles, forming a network microstructure; the diameters of the α-Al 2 O 3 and ZrB 2 particles are approximately 1-3 μm. When the size of Al powder increases from 60-110 μm to 150-300 μm, the overall surface contact between Al powders and reactants decreases, thereby increasing the local volume fraction of reinforcements from 12% to 21%. This increase of the local volume leads to a significant increase in microhardness of the in situ (α-Al 2 O 3-ZrB 2)/Al composites from Hv 163 to Hv 251.

Advanced Materials Research, 2015

The dry sliding characteristics of three in situ Al2O3/Al-Si composites fabricated with volume fr... more The dry sliding characteristics of three in situ Al2O3/Al-Si composites fabricated with volume fraction of 10, 20 and 30 vol.% were investigated. The effect of sliding parameters on the wear properties was investigated. As the sliding velocity increases the wear loss decreases systematically. When the volume fraction increased to 20 vol.%, an improvement of wear resistance was obtained. However, when the volume fraction was 30 vol.%, a further decrease of wear resistance was observed. In case of low volume fraction (10 vol.%), an extensive plastic deformation by plowing out the ductile Al matrix along with narrow grooves was observed. As the volume fraction increased to 20 vol.%, the abrasive wear by micro grooving is dominant as well as the low load is used. Whereas, when the volume fraction increased to 30 vol.%, besides the effect of large pores, the embedded Al2O3 in the massive Si blocks formed a weaker interface thereby behaving as source of crakes initiation and propagation. ...

JOM, 2015

In situ Al-based composites with different SiO2/C/Al molar ratios were fabricated by reaction hot... more In situ Al-based composites with different SiO2/C/Al molar ratios were fabricated by reaction hot pressing. Differential scanning calorimetry (DSC) was used to investigate the reaction mechanisms in the Al-SiO2-C system. X-ray diffraction results revealed that no new resultant phase was observed below the melting temperature of aluminum except the SiO2, C and Al phases. Heating at different synthesis temperatures showed that, up to 1000°C with a holding time of 1 h, the reactions in the Al-SiO2-C system took place completely, where the final products were Al2O3, SiC, Al4C3 and Si. Microstructural observation showed that the in situ synthesized Al2O3, SiC, Al4C3, and Si were dispersed uniformly and had fine sizes less than 2 µm. The formed interfaces between the reinforcements and Al matrix are clean and free from any interfacial phase. During cooling, the synthesized Si formed a multilayer growth in the (111) direction. When the SiO2/C/Al molar ratio was (6/3/9), more Al2O3 and Si w...

Metallurgical and Materials Transactions B, 2014

Materials today communications, Jun 1, 2022

Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, Oct 10, 2014

B 4 C-TiB 2-SiC composites were fabricated via hot pressing using ball milled B 4 C, TiB 2 , and ... more B 4 C-TiB 2-SiC composites were fabricated via hot pressing using ball milled B 4 C, TiB 2 , and SiC powder mixtures as the starting materials. The impact of ball milling on the densification behaviors, mechanical properties, and microstructures of the ceramic composites were investigated. The results showed that the refinement of the powder mixtures and the removal of the oxide impurities played an important role in the improvement of densification and properties. Moreover, the formation of the liquid phases during the sintering was deemed beneficial for densification. The typical values of relative density, hardness, bending strength, and fracture toughness of the composites reached 99.20%, 32.84 GPa, 858 MPa and 8.21 MPa m 1/2 , respectively. Crack deflection, crack bridging, crack branching, and microcracking were considered to be the potential toughening mechanisms in the composites. Furthermore, numerous nano-sized intergranular/intragranular phases and twin structures were observed in the B 4 C-TiB 2-SiC composite. 2. Experimental 2.1. Materials Commercially available B 4 C powder (D 50 = 2.5 μm, Jingangzuan Boron Carbide Co., Ltd., Mudanjiang, China), TiB 2 powder (D 50 = 8.0 μm, Dandong Chemical Research Institute Co., Ltd., Dandong, China) and SiC powder (D 50 = 0.5-0.7 μm Shanghai Aladdin Biochemical Technology Co., Ltd., Shanghai, China) were used as the raw materials. The characteristics of the raw material powders, including mean particle size, specific surface area, oxygen content and certain metal impurities content are shown in Table 1.

Materials Today Communications

Journal of Composite Materials

The thermal, the electrical conductivity, and electromagnetic shielding properties of low cost hi... more The thermal, the electrical conductivity, and electromagnetic shielding properties of low cost high-performance expanded graphite (EG)-filled polybenzoxazine matrix nanocomposites produced by a solution blending and compression molding technique were investigated. At 2.26 vol.% EG, a percolation threshold was detected, at which the electrical conductivity increased by nine orders of magnitude in comparison to the unfilled matrix. The electrical conductivity values increased from 1.35 S.cm−1 to 28.3 S.cm−1 by increasing the EG ratios in the nanocomposites from 7 wt.% and 15 wt.%. In addition, the morphological analysis results revealed good nanofiller dispersion and the formation of 3D-conductive pathways of EG into the polybenzoxazine matrix, which are responsible for the electrical conductivity improvement. Moreover, the electromagnetic interference (EMI) shielding efficiencies, in the X-band, of these nanocomposites have been significantly improved, reaching 57.2 dB at a 15 wt.% E...

Metallurgical and Materials Transactions B, 2014

Three in situ formed Al2O3/Al-Si composites with a different volume fraction of 10, 20, and 30 vo... more Three in situ formed Al2O3/Al-Si composites with a different volume fraction of 10, 20, and 30 vol pct were fabricated using low energy ball milling and reaction hot pressing. The effect of reinforcement volume fraction on the microstructure and mechanical properties were studied. When the volume fraction was 30 vol pct, a massive primary Si (~130 µm) along with an increase of Al2O3 (~2 µm) was observed. The YS, UTS, and Brinell hardness of the composites were significantly higher than the aluminum matrix. Mechanisms governing the tensile fracture process are discussed.

Plastics, Rubber and Composites: Macromolecular Engineering, Feb 7, 2016

A new kind of polymer composite, produced from the typical polybenzoxazine and 0–30 wt-% native a... more A new kind of polymer composite, produced from the typical polybenzoxazine and 0–30 wt-% native and silane-treated aluminium nitride (T-AlN), was investigated. The mechanical tests revealed a significant increase in the microhardness and flexural properties upon adding the T-AlN particles compared to that obtained from the untreated ones. By adding 0–30 wt-% T-AlN, the tensile moduli were accurately reproduced by the Halpin-Tsai and Nielsen models. At 30 wt-% T-AlN, dynamic mechanical analysis showed a significant increase in the storage moduli and the glass transition temperature (Tg), reaching 3.2 GPa and 217°C, respectively. The thermal stability of these materials was significantly improved upon the addition of the T-AlN fillers. These improvements are attributed to the high thermal and mechanical properties of the fillers and their good dispersion and adhesion in and to the matrix as revealed by a morphological analysis.

Novel kinds of nanocomposites based on bisphenol A-aniline based polybenzoxazine matrix P(BA-a) a... more Novel kinds of nanocomposites based on bisphenol A-aniline based polybenzoxazine matrix P(BA-a) and 0 wt.%–20 wt.% boron carbide (B4C) nanoparticles were produced and their properties were evaluated in terms of the nano-B4C content. The thermal conductivity of the P(BA-a) matrix was improved approximately three times from 0.18 W/m K to 0.86 W/m K at 20 wt.% nano-B4C loading, while its coefficient of thermal expansion (CTE) was deceased by 47% with the same nanofiller content. The microhardness properties were significantly improved by adding the B4C nanoparticles. At 20 wt.% of nano-B4C content, dynamic mechanical analysis (DMA) revealed a marked increase in the storage modulus and the glass transition temperature (Tg) of the nanocomposites, reaching 3.9 GPa and 204°C, respectively. Hot water uptake tests showed that the water-resistance of the polybenzoxazine matrix was increased by filling with nano-B4C nano-filler. The morphological analysis reflected that the improvements obtain...

The effects of aluminum nitride (AlN) loading and size on the thermal conductivity of bisphenol A... more The effects of aluminum nitride (AlN) loading and size on the thermal conductivity of bisphenol A-aniline-based polybenzoxazine resin were studied. The experimental data of the thermal conductivity, CTE, and dielectric constants of these hybrids were compared with those predicted using various models. The morphological analysis revealed the formation of AlN conductive chains in the polybenzoxazine matrix. The thermal conductivity values of these hybrids gradually increased as the AlN fillers content increased and their sizes decreased. The highest thermal conductivity value reached 7.89 W m−1 K−1 at 60 vol% of 50 nm AlN. At the maximum AlN loading, the CTE values of these hybrids were reduced by 75 %, while their dielectric constants are raised by almost 45 %. The TG results showed significant improvements in the thermal degradation properties of these composites by adding the AlN filler; moreover, the Agari semiempirical model well-fitted the thermal conductivity experimental data ...

A new kind of thermally-conductive polymer nanocomposite was produced by reinforcing the typical ... more A new kind of thermally-conductive polymer nanocomposite was produced by reinforcing the typical polybenzoxazine matrix P(BA-a) with silane-treated Si 3 N 4 nanoparticles using a compression molding technique. By adding 0 to 70% nano-Si 3 N 4 , the nanocomposite׳s thermal conductivity was enhanced from 0.18 to 5.78 W/m K. Based on the analyzed morphology, the Si 3 N 4 nanoparticles tend to form continuous conductive chains within the polybenzoxazine matrix, which are responsible for the improved thermal conductivity of the polybenzoxazine resin. Also, these new nanocomposites exhibited improved dielectric, coefficient of thermal expansion, and flexural properties. The thermal stability of these materials significantly improved upon the addition of the nano-Si 3 N 4 fillers. Their unique thermal and dielectric properties make them suitable for microelectronic packaging applications.

The in-situ Al-based composites with different SiO 2 /C/Al molar ratios were fabricated by reacti... more The in-situ Al-based composites with different SiO 2 /C/Al molar ratios were fabricated by reaction hot pressing. The dry sliding wear characteristics of the composites were investigated using a pin-on-disc wear tester. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to investigate the surface composition and its morphology. The results show that when the SiO 2 /C/Al molar ratio is 3:6:9, more in-situ synthesized Al 2 O 3 and SiC along with Si particles are produced, and Al 4 C 3 is prevented completely from the Al–SiO 2 –C system. Thereby, a significant improvement of wear resistance is obtained. When the sliding velocity increases from 0.4 to 1.6 m/s, the wear loss decreases gradually. With increasing the normal load, the wear loss increases as well. Ploughing, craters and micro-grooving are observed as dominant abrasive wear mechanisms. Whereas, when a high velocity is employed, only the oxidation mechanism controls the wear behavior of...

Acta Metallurgica Sinica, Oct 10, 2014

In situ (Al 2 O 3-Si)/Al composites with a reinforcement volume fraction of 10% were synthesized ... more In situ (Al 2 O 3-Si)/Al composites with a reinforcement volume fraction of 10% were synthesized from the Al-SiO 2 system using low energy ball milling and reaction hot pressing. Differential thermal analysis was used to investigate the reaction mechanisms between SiO 2 and Al. X-ray diffraction results revealed that the reaction between Al and SiO 2 took place completely at 900°C with a holding time of 2 h, thereby forming Al 2 O 3 and Si. Scanning electron microscopic, energy dispersive X-ray spectroscopic, and transmission electron microscopic (TEM) results showed that the in situ synthesized Al 2 O 3 and Si particles, whose sizes are less than 2 lm, were polygonal in shape and dispersed uniformly in the matrix. Moreover, Al 2 O 3 particle size showed a tendency to increase from *2 to *6 lm when the synthesis temperature was increased. Furthermore, TEM observation showed that the interface between the reinforcements and Al matrix is clean. The yield strength, ultimate tensile strength, and Brinell hardness of the in situ (Al 2 O 3-Si)/Al composite was significantly higher than the aluminum matrix. Mechanisms governing the tensile fracture process are discussed.

International Journal of Minerals, Metallurgy, and Materials, 2015

In situ (α-Al 2 O 3 +ZrB 2)/Al composites with network distribution were fabricated using low-ene... more In situ (α-Al 2 O 3 +ZrB 2)/Al composites with network distribution were fabricated using low-energy ball milling and reaction hot pressing. Differential thermal analysis (DTA) was used to study the reaction mechanisms in the Al-ZrO 2-B system. X-ray diffraction (XRD) and scanning electron microscopy (SEM) in conjunction with energy-dispersive X-ray spectroscopy (EDX) were used to investigate the composite phases, morphology, and microstructure of the composites. The effect of matrix network size on the microstructure and mechanical properties was investigated. The results show that the optimum sintering parameters to complete reactions in the Al-ZrO 2-B system are 850°C and 60 min. In situ-synthesized α-Al 2 O 3 and ZrB 2 particles are dispersed uniformly around Al particles, forming a network microstructure; the diameters of the α-Al 2 O 3 and ZrB 2 particles are approximately 1-3 μm. When the size of Al powder increases from 60-110 μm to 150-300 μm, the overall surface contact between Al powders and reactants decreases, thereby increasing the local volume fraction of reinforcements from 12% to 21%. This increase of the local volume leads to a significant increase in microhardness of the in situ (α-Al 2 O 3-ZrB 2)/Al composites from Hv 163 to Hv 251.

Advanced Materials Research, 2015

The dry sliding characteristics of three in situ Al2O3/Al-Si composites fabricated with volume fr... more The dry sliding characteristics of three in situ Al2O3/Al-Si composites fabricated with volume fraction of 10, 20 and 30 vol.% were investigated. The effect of sliding parameters on the wear properties was investigated. As the sliding velocity increases the wear loss decreases systematically. When the volume fraction increased to 20 vol.%, an improvement of wear resistance was obtained. However, when the volume fraction was 30 vol.%, a further decrease of wear resistance was observed. In case of low volume fraction (10 vol.%), an extensive plastic deformation by plowing out the ductile Al matrix along with narrow grooves was observed. As the volume fraction increased to 20 vol.%, the abrasive wear by micro grooving is dominant as well as the low load is used. Whereas, when the volume fraction increased to 30 vol.%, besides the effect of large pores, the embedded Al2O3 in the massive Si blocks formed a weaker interface thereby behaving as source of crakes initiation and propagation. ...

JOM, 2015

In situ Al-based composites with different SiO2/C/Al molar ratios were fabricated by reaction hot... more In situ Al-based composites with different SiO2/C/Al molar ratios were fabricated by reaction hot pressing. Differential scanning calorimetry (DSC) was used to investigate the reaction mechanisms in the Al-SiO2-C system. X-ray diffraction results revealed that no new resultant phase was observed below the melting temperature of aluminum except the SiO2, C and Al phases. Heating at different synthesis temperatures showed that, up to 1000°C with a holding time of 1 h, the reactions in the Al-SiO2-C system took place completely, where the final products were Al2O3, SiC, Al4C3 and Si. Microstructural observation showed that the in situ synthesized Al2O3, SiC, Al4C3, and Si were dispersed uniformly and had fine sizes less than 2 µm. The formed interfaces between the reinforcements and Al matrix are clean and free from any interfacial phase. During cooling, the synthesized Si formed a multilayer growth in the (111) direction. When the SiO2/C/Al molar ratio was (6/3/9), more Al2O3 and Si w...

Metallurgical and Materials Transactions B, 2014