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Article
Publication date: 10 July 2017

Alaa Mohamed, Mohamed Hamdy, Mohamed Bayoumi and Tarek Osman

This work describes the fabrication of composite nanogrease based on carbon nanotubes (CNTs) as an additive at different volume concentrations 0, 0.5, 1, 2 and 3 Wt.% and…

Abstract

Purpose

This work describes the fabrication of composite nanogrease based on carbon nanotubes (CNTs) as an additive at different volume concentrations 0, 0.5, 1, 2 and 3 Wt.% and investigates the correlation between CNTs and grease rheological behaviour. In addition, study the influence of shear thinning rate at various temperatures and investigates the thermal conductivity of nanogrease. The results demonstrated that grease behaves like a Newtonian viscoelastic material with a narrow linear domain. The thermal conductivity of nanogrease was enhanced by about 31.58 per cent, and the thermal and mechanical stabilities improved. Moreover, the apparent viscosity and dropping point increased by about 93 and 27 per cent, respectively.

Design/methodology/approach

Grease was dissolved in chloroform (10 Wt.%), at 25°C for 1 h. In parallel, functionalized CNTs with different volume concentrations (0.5, 1, 2 and 3 Wt.%) were dispersed in N,N-dimethylformamide; the dispersion was stirred for 15 min, and then sonicated (40 kHz, 150 W) for 30 min. Grease solution was then added to the CNTs. The nanofluid was magnetically stirred for 15 min and then sonicated for 2 h. This ensured uniform dispersion of nanoparticles in the base fluid.

Findings

Inexpensive and simple fabrication of nanogrease. Thermal conductivity of nanogrease was typically enhanced compared to other reported studies. Apparent viscosity and dropping point increases with the increase the volume concentration.

Originality/value

This work describes the inexpensive and simple fabrication of nanogrease for improving properties of lubricants, which improve power efficiency and extend lifetimes of mechanical equipment.

Details

Industrial Lubrication and Tribology, vol. 69 no. 4
Type: Research Article
ISSN: 0036-8792

Keywords

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Article
Publication date: 9 April 2018

Alaa Mohamed, Mohamed Hamdy, Mohamed Bayoumi and Tarek Osman

To enhance the tribological properties of nanogrease, one of the new technologies was used to synthesize a nanogrease having carbon nanotubes (CNTs) nanoparticles (NPs…

Abstract

Purpose

To enhance the tribological properties of nanogrease, one of the new technologies was used to synthesize a nanogrease having carbon nanotubes (CNTs) nanoparticles (NPs) with different concentrations. The microstructures of the synthesized NPs were characterized and evaluated by x-ray diffraction spectroscopy (XRD) and transmission electron microscopy (TEM). Tribological properties of the nanogrease were evaluated using a four-ball tester. The worn surface of four steel balls was investigated by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX).

Design/methodology/approach

Grease was dissolved in chloroform (10 Wt.%), at 25 °C for 1 h. In parallel, functionalized CNTs with different volume concentrations (0.5, 1, 2 and 3 Wt.%) were dispersed in N, N-dimethylformamide. The mixture was stirred for 15 min and then sonicated (40 kHz, 150 W) for 30 min. After that, the mixture was added to the grease solution and magnetically stirred for 15 min and then sonicated for 2 h.

Findings

The results suggested that CNTs can enhance the antiwear and friction properties of nanogrease at 0.5 Wt.% CNTs to about 57 and 48 per cent, respectively. In addition, the weld load of the base oil containing 0.5 Wt.% CNTs was improved by 17 per cent compared with base grease.

Originality/value

This work describes the inexpensive and simple fabrication of nanogrease for improving the properties of lubricants, which improve power efficiency and extend lifetimes of mechanical equipment.

Details

Industrial Lubrication and Tribology, vol. 70 no. 3
Type: Research Article
ISSN: 0036-8792

Keywords

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Article
Publication date: 12 March 2018

Mohamed Ashour, Alaa Mohamed, Abou Bakr Elshalakany, Tarek Osman and Aly Khatab

The purpose of this paper is to investigate the rheological characteristics of graphene nanoplatelets (GNPs) and hybridized nanocomposite consisting of multi-walled carbon…

Abstract

Purpose

The purpose of this paper is to investigate the rheological characteristics of graphene nanoplatelets (GNPs) and hybridized nanocomposite consisting of multi-walled carbon nanotubes (MWCNTs) and GNPs as an additive on lithium-based grease. The experiments of nanogrease are examined in different values of shear stress, apparent viscosity, temperature and shear rate using Brookfield Programmable Rheometer DV-III ULTRA and characterized by high-resolution transmission electron microscope (HRTEM) and X-ray diffraction (XRD).

Design/methodology/approach

First, GNPs was mixed well with lithium grease using mechanical stirring at 3,500 rpm for 15 min at room temperature to form a homogenous composite at different concentrations (0.5, 1, 1.5, 2 and 2.5 Wt.%). Afterwards, MWCNTs and GNPs are mixed and dispersed well in the lithium grease using a sonication path for 30 min and mechanical stirring at 3,500 rpm for 15 min at 28°C to form a homogenous nanocomposite.

Findings

The results indicated that 1 Wt.% of GNPs is the optimum concentration. Subsequently, the weight percentage of additives varying between MWCNTs and GNPs are tested, and the result indicate that the grease containing GNPs had a 75 per cent increase in shear stress and 93.7 per cent increase in apparent viscosity over ordinary grease.

Originality/value

This work describes the inexpensive and simple fabrication of nanogrease for improving properties of lubricants, which improve power efficiency and extend lifetimes of mechanical equipment.

Details

Industrial Lubrication and Tribology, vol. 70 no. 2
Type: Research Article
ISSN: 0036-8792

Keywords

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Article
Publication date: 21 May 2021

Tahra Elobeid, Vijay Ganji, Sara Al-Saeedi, Alaa Abdelmonem Mohamed, Hana Mohamed Dahir, Hassan Hassan, Layal Karam and Grace Attieh

The purposes of this study were to analyze fruits, vegetables, water and soil for organochlorine pesticide (OCP) residues and to assess the food exposure of these…

Abstract

Purpose

The purposes of this study were to analyze fruits, vegetables, water and soil for organochlorine pesticide (OCP) residues and to assess the food exposure of these pesticides in Qatar.

Design/methodology/approach

Pesticides were quantified in dates, leafy vegetables, fruiting vegetables, water and soil samples using a gas chromatography-electron capture detector and gas chromatography-mass spectrometry. These pesticides were α-benzene hexachloride (BHC), ß-BHC, heptachlor, aldrin, g-chlordane, endosulfan I, α-chlordane, dieldrin, endrin and methoxychlor. Additionally, food exposure risk assessment was performed by estimating daily intakes of OCP.

Findings

Most analyzed samples contained at least one OCP residue. Endosulfan was the only pesticide that was not detected. The concentrations of OCP in samples were below the maximum residue level (MRL) except endosulfan. Among all the samples analyzed, ˜18% of those exceeded the MRL with respect to the concentrations of methoxychlor and heptachlor. Only intake of methoxychlor (0.018 mg/day) exceeded the MRL (0.01 mg/day). Dates and fruiting vegetables were likely to pose a higher risk than leafy vegetables because they contained heptachlor, endrin and methoxychlor. Leafy vegetables might pose a greater risk than dates and fruiting vegetables because of the presence of β-BHC and dieldrin.

Originality/value

Eight out of ten OCPs that were measured were found to be below the MRL. These pesticides should be eliminated from the food supply based on the Qatar National Implementation Plan of the Stockholm Convention in 2010. Based on the intake risk assessment, overall, the intake of OCP may not pose a major risk to human health as the concentrations of OCP were below MRL, except methoxychlor. Water and soil are the potential sources of contamination of OCP in foods that were tested in Qatar. To limit the health risks associated with OCPs, there is a need for close monitoring of food and agricultural practices and the types of pesticides imported into Qatar.

Details

British Food Journal, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0007-070X

Keywords

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Article
Publication date: 12 September 2016

Bahaa M. Kamel, Alaa Mohamed, M. El Sherbiny and K.A. Abed

The purpose of this paper is to fabricate composite nanogrease for tribological applications. Multi-walled carbon nanotubes (MWCNTs) with a size 10 nm average diameter and…

Abstract

Purpose

The purpose of this paper is to fabricate composite nanogrease for tribological applications. Multi-walled carbon nanotubes (MWCNTs) with a size 10 nm average diameter and 5 μm in length were used as additives to calcium grease.

Design/methodology/approach

The tribological four-ball machine was used to evaluate calcium grease with carbon nanotubes (CNTs) as an additive. The interaction between CNT and calcium grease (nanogrease) were studied by transmission electron microscopy and X-ray diffraction.

Findings

MWCNTs composite nanogrease was manufactured for tribological applications. The effectiveness of the fabricated grease in improving the tribological performance at different concentrations and under different loads was tested. The results are summarized as follows. CNT nanoparticle additive dispersed in calcium grease significantly improve its anti-wear performance, reducing friction, increasing load-carrying capacity and extreme pressure (EP) property. The friction is reduced by about 50 per cent, the wear scar diameter (WSD) decreased to 32 per cent and the EP properties increases about 38 per cent, with only 3 wt.%. The modified grease with CNTs additives of 3 wt.% showed the most favorable results. Energy dispersive x-ray (EDX) analysis shows that C was present on the worn scar surface, with atomic concentration of about 22 per cent. The presence of C suggests that a lubricating film is likely formed because of the presence of CNTs and very likely prevented the steel-to-steel direct contact.

Originality/value

The results indicated that a 3 wt.% of MWCNT nanogrease is an excellent antiwear, with EP and low friction coefficient. It was also found that the friction coefficient was reduced to about 50 per cent, the WSD decreased by about 32 per cent and the EP properties increased about 38 per cent. The mating surfaces were investigated with scanning electron microscopy and EDX. The results show that a boundary film mainly composed of CNTs, Cr and Fe was formed on the rubbed surfaces.

Details

Industrial Lubrication and Tribology, vol. 68 no. 6
Type: Research Article
ISSN: 0036-8792

Keywords

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Article
Publication date: 16 August 2019

Ahmed Mobasher, Alaa Khalil, Medhat Khashaba and Tarek Osman

The purpose of this paper is to evaluate the influence of nanoparticles as an additive on the tribological properties of calcium grease.

Abstract

Purpose

The purpose of this paper is to evaluate the influence of nanoparticles as an additive on the tribological properties of calcium grease.

Design/methodology/approach

The nano additives in this research are with different concentration of multi carbon nanotubes (MWCNTs) and Talc powder (1, 2, 3, 3 and 5 per cent). The ratio of MWCNTs to Talc powder is 1:1. The tribological properties of hyper MWCNTs/Talc powder to calcium grease were evaluated using a pin-on-disk wear testing. The results show that the nano additives MWCNTs/Talc to calcium grease exhibit good performance in anti-wear and friction reduction. The action mechanism was estimated through analysis of the worm surface with x-ray diffraction and transmission electron microscope.

Findings

The result indicates that boundary film mainly composed of MWCNT and Talc powder, and other organic compound was formed on the worm surface during the friction test. In addition, the wear rate and coefficient of friction of nanogreases have shown excellent improvement about 80.62 and 63.44 per cent, respectively, at 4 Wt.% of MWCNTs/Talc powder. Moreover, the thermal conductivity of nanogrease increased about 51.72 per cent.

Originality/value

This study describes the inexpensive and simple fabrication of nanogrease for improving properties of lubricants, which improve power efficiency and extend lifetimes of mechanical equipment.

Details

Industrial Lubrication and Tribology, vol. 72 no. 1
Type: Research Article
ISSN: 0036-8792

Keywords

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Article
Publication date: 17 May 2021

Hamza Kamel Qawqzeh, Mohamed Mahmoud Bshayreh and Alaa Wasel Alharbi

This study aims to investigate the effect of the ownership structure types on the indicators of the external audit quality, in the light of the weak legal protection of…

Abstract

Purpose

This study aims to investigate the effect of the ownership structure types on the indicators of the external audit quality, in the light of the weak legal protection of the shareholders.

Design/methodology/approach

This study used the panel data of 94 listed Jordanian companies from 2009–2018 and the fixed-effect method.

Findings

The results revealed a significant relationship between the directors’ ownership, family and institutional ownership with the audit quality. By contrast, the managerial ownership had an insignificant influence on audit quality.

Research limitations/implications

The results show the important role played by the directors’ and institutions’ ownership in ensuring the audit quality in Jordan. The results have implications for the policymakers in Jordan, to encourage and support the participation of such types of the investors and provide an effective monitoring over other types of ownership in the Jordanian capital markets.

Social implications

This study suggests that the ownership structures are an essential and effective determinants of the external audit quality, which ultimately affects the performance and financial statements.

Originality/value

These results are consistent with prior studies, which have indicated a significant relation between ownership structure and the demand of the audit quality, even in a setting where legal protection of the shareholders plays essentially no role. To the best knowledge of the researchers, this study is one of the few studies that separates the ownership by the directors into two separate types. Further, this is the first study that used several indicators to measure the audit quality at the same time.

Details

Journal of Financial Reporting and Accounting, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1985-2517

Keywords

Content available
Article
Publication date: 19 October 2017

Ramzi M. Hakami, Mohamed S. Mahfouz, Abdulrahman M. Adawi, Adeebah J. Mahha, Alaa J. Athathi, Hadi H. Daghreeri, Hatim H. Najmi and Nuha A. Areeshi

Although social anxiety disorder (SAD) is a common mental disorder, it is often under diagnosed and under treated. The aim of this study is to assess the prevalence…

Abstract

Although social anxiety disorder (SAD) is a common mental disorder, it is often under diagnosed and under treated. The aim of this study is to assess the prevalence, severity, disability, and quality of life towards SAD among students of Jazan University, Saudi Arabia. A cross-sectional study was conducted among a stratified sample of 500 undergraduate students to identify the prevalence of SAD, its correlates, related disability, and its impact on the quality life. All participants completed the Social Phobia Inventory, Leibowitz Social Anxiety Scale, Sheehan Disability Scale, and the WHO Quality of Life – BREF questionnaire. Of 476 students, 25.8% were screened positive for SAD. About 47.2% of the students had mild symptoms, 42.3% had moderate to marked symptoms, and 10.5% had severe to very severe symptoms of SAD. Students who resulted positive for SAD reported significant disabilities in work, social, and family areas, and this has adversely affected their quality of life as compared to those who screened negative for SAD. Students reported several clinical manifestations that affected their functioning and social life. Acting, performing or giving a talk in front of an audience was the most commonly feared situation. Blushing in front of people was the most commonly avoided situation. Since the present study showed a marked prevalence of SAD among students, increased disability, and impaired quality of life, rigorous efforts are needed for early recognition and treatment of SAD.

Details

Mental Illness, vol. 9 no. 2
Type: Research Article
ISSN: 2036-7465

Keywords

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Article
Publication date: 9 December 2020

Noha El-Bassiouny and Ehab K.A. Mohamed

Exam administration during the COVID-19 pandemic represents a challenge for most schools. This paper aims to document the experience of a business school in a developing…

Abstract

Purpose

Exam administration during the COVID-19 pandemic represents a challenge for most schools. This paper aims to document the experience of a business school in a developing country context.

Design/methodology/approach

This paper is conceptual in its approach highlighting how exam administration was handled during the COVID-19 pandemic.

Findings

Notably, exams were replaced by research assessments. This paper presents best practices and lessons learnt in this domain.

Originality/value

This practice paper represents one of the few research studies that highlighted the mechanisms underlying the replacement of exams with research projects during the course of the COVID-19 pandemic.

Details

Journal of Islamic Marketing, vol. 12 no. 3
Type: Research Article
ISSN: 1759-0833

Keywords

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Book part
Publication date: 11 March 2021

Abstract

Details

Corporate Success Stories in the UAE: The Key Drivers Behind Their Growth
Type: Book
ISBN: 978-1-80043-579-7

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