T.A. Aljohani

T.A. Aljohani


Research Focus & Metrics

Academic Career Length

18Years (2009-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 November 2018 in Chem
Verified
Journal Article
Closed access
NWNiamh Willis-Fox
Niamh Willis-Fox
EREtienne Rognin
Etienne Rognin
TAT.A. Aljohani
T.A. Aljohani
RDRonan Daly
Ronan Daly

21 February 2021 in Metals
Verified
Journal Article
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AAAbdulrahman Alateyah
Abdulrahman Alateyah
TAT.A. Aljohani
T.A. Aljohani
MAMajed O. Alawad
Majed O. Alawad
Hassan Abd-ElhafezHassan Abd-Elhafez
Hassan Abd-Elhafez
AAAbdulrahman Almutairi
Abdulrahman Almutairi
Waleed El-GaraihyWaleed El-Garaihy
Waleed El-Garaihy
This study aims to establish the effects of equal channel angular pressing (ECAP) processing on the corrosion behavior and hardness values of the AZ31 Mg alloy. The AZ31 billets were processed through ECAP successfully at 250 °C and their microstructural evolution was studied using optical and field emission scanning electron microscopy. The corrosion resistance of the AZ31 alloy was studied before and after processing through ECAP. The homogeneity of the hardness distribution was studied using both sections cut parallel and perpendicular to the extrusion direction. ECAP processing resulted in highly deformed central regions with elongated grains aligned parallel to the extrusion direction, whereas the peripheral regions showed an ultra-fine-grain recrystallized structure. After processing, small ultra-fine secondary particles were found to be homogeneously dispersed alongside the grain boundaries of the α-Mg matrix. Regarding the corrosion properties, measurements showed that ECAP processing through 1-P and 2-Bc resulted in decreasing their corrosion rate to 67.7% and 78.3%, respectively, of their as-annealed counterpart’s. The corrosion resistance of the ECAPed Mg alloy increased with the number of processing passes. This was due to the refinement of the grain size of the α-Mg matrix and secondary phases till ultra-fine size, caused by the accumulation of strain during processing. On the other hand, ECAP processing through 2-Bc resulted in increasing the Vickers hardness values by 132% and 71.8% at the peripheral and central areas, respectively, compared to the as-annealed counterpart.

13 May 2020 in Advanced Functional Materials
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Journal Article
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NWNiamh Willis‐Fox
Niamh Willis‐Fox
EREtienne Rognin
Etienne Rognin
CBChristoph Baumann
Christoph Baumann
TAT.A. Aljohani
T.A. Aljohani
RGRobert Göstl
Robert Göstl
RDRonan Daly
Ronan Daly
Mechanical forces can drive chemical transformations in polymers, directing reactions along otherwise inaccessible pathways, providing exciting possibilities for developing smart, responsive materials. The state‐of‐the‐art test for solution‐based polymer mechanochemistry development is ultrasonication. However, this does not accurately model the forces that will be applied during device fabrication using processes such as 3D printing or spray coating. Here, a step is taken toward predictably translating mechanochemistry from molecular design to manufacturing by demonstrating a highly controlled nozzle flow setup in which the shear forces being delivered are precisely tuned. The results show that solvent viscosity, fluid strain rate, and the nature of the breaking bond can be individually studied. Importantly, it is shown that the influence of each is different to that suggested by ultrasonication (altered quantity of chain breakage and critical polymer chain length). Significant development is presented in the understanding of polymer bond breakage during manufacturing flows to help guide design of active components that trigger on demand. Using an anthracene‐based mechanophore, the triggering of a fluorescence turn‐on is demonstrated through careful selection of the flow parameters. This work opens the avenue for programmed chemical transformations during inline manufacturing processes leading to tunable, heterogeneous final products from a single source material.

6 September 2018 in Scientific Reports
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Journal Article
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ABA. G. Bhagurkar
A. G. Bhagurkar
AYA. Yamamoto
A. Yamamoto
LWL. Wang
L. Wang
MXM. Xia
M. Xia
ADA. R. Dennis
A. R. Dennis
DCD. A. Cardwell
D. A. Cardwell
The grain boundaries in superconducting MgB2 are known to form effective magnetic flux pinning sites and, consequently, bulk MgB2 containing a fine-grain microstructure fabricated from nanoscale Mg and B precursor powders exhibits good magnetic field-trapping performance below 20 K. We report here that the trapped field of MgB2 bulk superconductors fabricated by an infiltration and growth process to yield a dense, pore-free microstructure, can be enhanced significantly by carbon-doping, which increases intra-band scattering within the superconducting grains. A maximum trapped field of 4.15 T has been measured at 7.5 K at the centre of a five-sample stack of Mg(B1−xiCxi)2 bulk superconductors processed by infiltration and growth, which not only represents a ~40% increase in trapped field observed compared to undoped bulk MgB2, but also is the highest trapped field reported to date in MgB2 samples processed under ambient pressure. The trapped field is observed to decay at a rate of <2%/day at 10 K, which suggests that bulk MgB2 superconductors fabricated using the infiltration and growth technique can be used potentially to generate stable, high magnetic fields for a variety of engineering applications.

11 June 2021 in Metals
Verified
Journal Article
Open access
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AAAbdulrahman Alateyah
Abdulrahman Alateyah
TAT.A. Aljohani
T.A. Aljohani
MAMajed O. Alawad
Majed O. Alawad
SESally Elkatatny
Sally Elkatatny
Waleed El-GaraihyWaleed El-Garaihy
Waleed El-Garaihy
Magnesium (Mg) alloys have unique properties. However, their applications are limited in working environments due to their poor corrosion resistance. Plasma electrolytic oxidation (PEO) is one of the most environmentally friendly and cost-effective ways that has been promoted to treat Mg alloys. In this study, we investigated the effect of electrical parameters on the microstructure, as well as the mechanical and corrosion resistance of AM60 alloy coated with PEO. The electrical parameters studied were current mode (unipolar and bipolar), frequency and duty ratio. The microstructure evolution of the coated AM60 substrates was studied using X-ray diffraction and scanning electron microscopy. Subsequently, the mechanical properties were determined using compression tests and microhardness measurements. The potentiodynamic polarization curves indicated that the PEO-coated samples experienced a significant decrease of 99.9% in the corrosion rate compared to the base metal. The electrochemical impedance spectroscopy findings showed that PEO coating increased the corrosion resistance of the AM60 magnesium alloy by 1071870% compared to the base metal. On the other hand, the PEO coated samples showed superior adhesion to the substrate. Moreover, the PEO coating led to an improvement in the hardness value by 114% compared to base metal, coupled with insignificant change in the compressive properties.

1 May 2020 in Journal of Saudi Chemical Society
Verified
Journal Article
Open access
ADAshok Kumar Das
Ashok Kumar Das
SJSwarnabala Jena
Swarnabala Jena
Sumanta SahooSumanta Sahoo
Sumanta Sahoo
Rambabu KuchiRambabu Kuchi
Rambabu Kuchi
DKDongsoo Kim
Dongsoo Kim
JJJong-Ryul Jeong
Jong-Ryul Jeong