Mehdi Shahedi Asl | Xi'an Jiaotong-Liverpool University (original) (raw)

Uploads

Papers by Mehdi Shahedi Asl

Research paper thumbnail of Nanostructural and nanoindentation characterization of ZrB2 ceramics toughened with in-situ synthesized ZrC

International Journal of Refractory Metals & Hard Materials, 2021

Research paper thumbnail of Effect of B4C content on sintering behavior, microstructure and mechanical properties of Ti-based composites fabricated via spark plasma sintering

Materials Chemistry and Physics, Sep 1, 2020

Research paper thumbnail of Microstructure–mechanical properties correlation in spark plasma sintered Ti–4.8 wt.% TiB2 composites

Materials Chemistry and Physics, Feb 1, 2019

Research paper thumbnail of Nanoindentation and nanostructural characterization of ZrB2–SiC composite doped with graphite nano-flakes

Composites Part B-engineering, Oct 1, 2019

Research paper thumbnail of TEM characterization of spark plasma sintered ZrB2–SiC–graphene nanocomposite

Ceramics International, Sep 1, 2018

Research paper thumbnail of Effects of carbon additives on the properties of ZrB2–based composites: A review

Ceramics International, May 1, 2018

Research paper thumbnail of Formation of Al–Al2O3 core–shell nanosphere chains during electron beam melting of γ-TiAl

Intermetallics, Sep 1, 2021

Abstract Several core–shell nanosphere chains were observed in the electron beam melted Ti–48Al–2... more Abstract Several core–shell nanosphere chains were observed in the electron beam melted Ti–48Al–2Cr–2Nb samples. The formation mechanism of such core–shell nanospheres, induced by Al vaporization, during the electron beam melting of γ-TiAl was investigated using the HRTEM, FESEM, STEM, and XRD analyses. The solidification of TiAl/Ti3Al lamellae, in the vicinity of the Al-diminished zones, was disclosed by microstructural studies. The core and shell of the nanospheres were characterized as porous Al and α-Al2O3, respectively. Finally, the formation of core–shell nanosphere chains in the additive manufactured γ-TiAl was schematically illustrated.

Research paper thumbnail of A novel ZrB2–VB2–ZrC composite fabricated by reactive spark plasma sintering

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, Jul 1, 2018

Research paper thumbnail of Spark plasma sintering of TiN ceramics codoped with SiC and CNT

Ceramics International, Feb 1, 2019

Research paper thumbnail of Densification improvement of spark plasma sintered TiB2-based composites with micron-, submicron- and nano-sized SiC particulates

Ceramics International, Jul 1, 2018

Research paper thumbnail of Characteristics of multi-walled carbon nanotube toughened ZrB 2 –SiC ceramic composite prepared by hot pressing

Ceramics International, 2016

Research paper thumbnail of In-situ synthesized MgO-based ceramic coatings on a novel Mg–Ca material: Morphological response to the PEO electrolyte

Research paper thumbnail of Toughening of ZrB2-based composites with in-situ synthesized ZrC from ZrO2 and graphite precursors

Journal of Science: Advanced Materials and Devices, 2021

Research paper thumbnail of Effects of SiC content on thermal shock behavior and elastic modulus of cordierite–mullite composites

Ceramics International, 2020

Research paper thumbnail of Electron microscopy study of ZrB2–SiC–AlN composites: Hot-pressing vs. pressureless sintering

Ceramics International, 2020

Abstract The impact of AlN addition on the microstructure and sinterability of ZrB2-SiC composite... more Abstract The impact of AlN addition on the microstructure and sinterability of ZrB2-SiC composites was studied. The pressureless sintering and hot-pressing techniques were used as manufacturing methods. The composites produced by hot-pressing method were sintered at 1900 °C, producing fully dense products with 1 and 5 wt% AlN. X-ray diffraction (XRD), and electron microscopy (FESEM and HRTEM) instruments were implemented to characterize the produced composites. The XRD analysis clarified the in-situ formation of graphitized carbon during the sintering. However, no Al-based compounds could be identified in the patterns. Moreover, liquid phase formation was confirmed as one of the sintering mechanisms for the all samples, creating clean interfaces in the composites produced by hot-pressing.

Research paper thumbnail of On the oxidation behavior of ZrB2–SiC–VC composites

International Journal of Applied Ceramic Technology, 2021

In this study, near‐fully dense ZrB2–SiC–VC (75‐20‐5 vol%) composite was manufactured through hot... more In this study, near‐fully dense ZrB2–SiC–VC (75‐20‐5 vol%) composite was manufactured through hot pressing at 1850°C under the pressure of 40 MPa for 60 min. Then the oxidation examination of the composite was carried out under different durations and temperatures. The microstructure and phase evolution after hot pressing and oxidation processes were examined by scanning electron microscopy, and X‐ray diffractometry. The VC addition led to the formation of ZrC and VSi2 phases, which assisted the densification of the composite by removing ZrO2 from the particles’ surface. The oxides of ZrO2, SiO2, ZrSiO4, V2O5, and VO2 formed distinct layers on the sample during the oxidation at 1700°C for 4 h with a parabolic regimen and activation energy of 177.5 kJ/mol.

Research paper thumbnail of Role of h-BN content on microstructure and mechanical properties of hot-pressed ZrB2–SiC composites

Ceramics International, 2020

Research paper thumbnail of Boron nitride-palladium nanostructured catalyst: efficient reduction of nitrobenzene derivatives in water

Nano Express, 2020

Boron nitride (BN) supported palladium (Pd) nanostructured catalyst, as an alternative support fo... more Boron nitride (BN) supported palladium (Pd) nanostructured catalyst, as an alternative support for heterogeneous reduction of nitrobenzene derivatives, was prepared by a mild reduction of a Pd precursor in water. The structural characteristics and distribution of the synthesized Pd nanoparticles (NPs) on BN support were investigated by transmission electron microscopy, scanning transmission electron microscopy, energy-dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy methods. The potential and efficiency of the BN supported Pd NPs as an active and stable nanostructured catalyst were verified in the reduction of nitroaromatics. Excellent yields of the corresponding aryl amines in water were obtained and due discussion were included about the catalytic activity of the synthesized catalyst. It was also indicated that the nanostructured catalyst can be recycled at least for six consecutive cycles in the reduction of nitrobenzene, without losing significant activity.

Research paper thumbnail of Role of hot-pressing temperature on densification and microstructure of ZrB2–SiC ultrahigh temperature ceramics

International Journal of Refractory Metals and Hard Materials, 2020

Research paper thumbnail of Influence of SiAlON addition on the microstructure development of hot-pressed ZrB2–SiC composites

Ceramics International, 2020

Research paper thumbnail of Nanostructural and nanoindentation characterization of ZrB2 ceramics toughened with in-situ synthesized ZrC

International Journal of Refractory Metals & Hard Materials, 2021

Research paper thumbnail of Effect of B4C content on sintering behavior, microstructure and mechanical properties of Ti-based composites fabricated via spark plasma sintering

Materials Chemistry and Physics, Sep 1, 2020

Research paper thumbnail of Microstructure–mechanical properties correlation in spark plasma sintered Ti–4.8 wt.% TiB2 composites

Materials Chemistry and Physics, Feb 1, 2019

Research paper thumbnail of Nanoindentation and nanostructural characterization of ZrB2–SiC composite doped with graphite nano-flakes

Composites Part B-engineering, Oct 1, 2019

Research paper thumbnail of TEM characterization of spark plasma sintered ZrB2–SiC–graphene nanocomposite

Ceramics International, Sep 1, 2018

Research paper thumbnail of Effects of carbon additives on the properties of ZrB2–based composites: A review

Ceramics International, May 1, 2018

Research paper thumbnail of Formation of Al–Al2O3 core–shell nanosphere chains during electron beam melting of γ-TiAl

Intermetallics, Sep 1, 2021

Abstract Several core–shell nanosphere chains were observed in the electron beam melted Ti–48Al–2... more Abstract Several core–shell nanosphere chains were observed in the electron beam melted Ti–48Al–2Cr–2Nb samples. The formation mechanism of such core–shell nanospheres, induced by Al vaporization, during the electron beam melting of γ-TiAl was investigated using the HRTEM, FESEM, STEM, and XRD analyses. The solidification of TiAl/Ti3Al lamellae, in the vicinity of the Al-diminished zones, was disclosed by microstructural studies. The core and shell of the nanospheres were characterized as porous Al and α-Al2O3, respectively. Finally, the formation of core–shell nanosphere chains in the additive manufactured γ-TiAl was schematically illustrated.

Research paper thumbnail of A novel ZrB2–VB2–ZrC composite fabricated by reactive spark plasma sintering

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, Jul 1, 2018

Research paper thumbnail of Spark plasma sintering of TiN ceramics codoped with SiC and CNT

Ceramics International, Feb 1, 2019

Research paper thumbnail of Densification improvement of spark plasma sintered TiB2-based composites with micron-, submicron- and nano-sized SiC particulates

Ceramics International, Jul 1, 2018

Research paper thumbnail of Characteristics of multi-walled carbon nanotube toughened ZrB 2 –SiC ceramic composite prepared by hot pressing

Ceramics International, 2016

Research paper thumbnail of In-situ synthesized MgO-based ceramic coatings on a novel Mg–Ca material: Morphological response to the PEO electrolyte

Research paper thumbnail of Toughening of ZrB2-based composites with in-situ synthesized ZrC from ZrO2 and graphite precursors

Journal of Science: Advanced Materials and Devices, 2021

Research paper thumbnail of Effects of SiC content on thermal shock behavior and elastic modulus of cordierite–mullite composites

Ceramics International, 2020

Research paper thumbnail of Electron microscopy study of ZrB2–SiC–AlN composites: Hot-pressing vs. pressureless sintering

Ceramics International, 2020

Abstract The impact of AlN addition on the microstructure and sinterability of ZrB2-SiC composite... more Abstract The impact of AlN addition on the microstructure and sinterability of ZrB2-SiC composites was studied. The pressureless sintering and hot-pressing techniques were used as manufacturing methods. The composites produced by hot-pressing method were sintered at 1900 °C, producing fully dense products with 1 and 5 wt% AlN. X-ray diffraction (XRD), and electron microscopy (FESEM and HRTEM) instruments were implemented to characterize the produced composites. The XRD analysis clarified the in-situ formation of graphitized carbon during the sintering. However, no Al-based compounds could be identified in the patterns. Moreover, liquid phase formation was confirmed as one of the sintering mechanisms for the all samples, creating clean interfaces in the composites produced by hot-pressing.

Research paper thumbnail of On the oxidation behavior of ZrB2–SiC–VC composites

International Journal of Applied Ceramic Technology, 2021

In this study, near‐fully dense ZrB2–SiC–VC (75‐20‐5 vol%) composite was manufactured through hot... more In this study, near‐fully dense ZrB2–SiC–VC (75‐20‐5 vol%) composite was manufactured through hot pressing at 1850°C under the pressure of 40 MPa for 60 min. Then the oxidation examination of the composite was carried out under different durations and temperatures. The microstructure and phase evolution after hot pressing and oxidation processes were examined by scanning electron microscopy, and X‐ray diffractometry. The VC addition led to the formation of ZrC and VSi2 phases, which assisted the densification of the composite by removing ZrO2 from the particles’ surface. The oxides of ZrO2, SiO2, ZrSiO4, V2O5, and VO2 formed distinct layers on the sample during the oxidation at 1700°C for 4 h with a parabolic regimen and activation energy of 177.5 kJ/mol.

Research paper thumbnail of Role of h-BN content on microstructure and mechanical properties of hot-pressed ZrB2–SiC composites

Ceramics International, 2020

Research paper thumbnail of Boron nitride-palladium nanostructured catalyst: efficient reduction of nitrobenzene derivatives in water

Nano Express, 2020

Boron nitride (BN) supported palladium (Pd) nanostructured catalyst, as an alternative support fo... more Boron nitride (BN) supported palladium (Pd) nanostructured catalyst, as an alternative support for heterogeneous reduction of nitrobenzene derivatives, was prepared by a mild reduction of a Pd precursor in water. The structural characteristics and distribution of the synthesized Pd nanoparticles (NPs) on BN support were investigated by transmission electron microscopy, scanning transmission electron microscopy, energy-dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy methods. The potential and efficiency of the BN supported Pd NPs as an active and stable nanostructured catalyst were verified in the reduction of nitroaromatics. Excellent yields of the corresponding aryl amines in water were obtained and due discussion were included about the catalytic activity of the synthesized catalyst. It was also indicated that the nanostructured catalyst can be recycled at least for six consecutive cycles in the reduction of nitrobenzene, without losing significant activity.

Research paper thumbnail of Role of hot-pressing temperature on densification and microstructure of ZrB2–SiC ultrahigh temperature ceramics

International Journal of Refractory Metals and Hard Materials, 2020

Research paper thumbnail of Influence of SiAlON addition on the microstructure development of hot-pressed ZrB2–SiC composites

Ceramics International, 2020