Najran, Saudi Arabia
Najran, Saudi Arabia

Najran University is a state-funded public research university located in Najran, Saudi Arabia. Wikipedia.

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Sustainable buildings have an important role in achieving sustainable development by improving energy utilization and environmental performance. Buildings are considered as the biggest single contributor to world energy consumption and greenhouse gas emissions. In Saudi Arabia, the significance of the building sector can be described on the basis of per capita electricity consumption, per capita carbon dioxide emissions, and the increasing number of buildings because of economic and population growth. Therefore, the country should consider establishing energy-efficient buildings to promote sustainable development. Efforts in developing energy-efficient technologies should increase for the national energy policy. This article comprehensively describes the current challenges and opportunities of energy consumption and various energy conservation options that are viable for the Saudi building sector. Current policy efforts for improving energy efficiency in Saudi buildings have been analyzed to enhance the sustainable development in the country. The study reveals that the energy conservation policy of the country has fairly improved in the past decades. However, the country has to focus on this area and perform urgent measures to adopt energy-efficient technologies in the building sector. © 2017 Springer Science+Business Media Dordrecht

Ismail A.A.,Central Metallurgical Research and Development Institute | Ismail A.A.,Najran University | Ismail A.A.,Leibniz University of Hanover | Bahnemann D.W.,Leibniz University of Hanover
Solar Energy Materials and Solar Cells | Year: 2014

Hydrogen production from water using a catalyst and solar energy is an ideal future fuel source. The search for suitable semiconductors as photocatalysts for water splitting into molecular hydrogen and oxygen has been considered to be an urgent subject for our daily life. In this review, we aim to focus on the research efforts that have been made so far for H2 generation from water splitting by UV and visible light-driven photocatalysis. A number of synthetic modification methods for adapting the electronic structure to enhance the charge separation in the photocatalyst materials are discussed. Sacrificial reagents and electron mediators for the overall water splitting are also reviewed. The quantum efficiency of photocatalyst materials upon visible and UV illumination will be reviewed, summarized and discussed. © 2014 Elsevier B.V.

Harraz F.A.,Najran University | Harraz F.A.,Central Metallurgical Research and Development Institute
Sensors and Actuators, B: Chemical | Year: 2014

The use of porous silicon (PSi) as a sensor for detection of various analytes is reviewed. The optical or electrical properties of PSi are key sensing parameters that have been used in many chemical and biological sensing applications. PSi is a promising candidate due to ease of fabrication, large surface area, various accessible pore sizes and morphologies, controllable surface modification and its compatibility with conventional silicon processing technology. The adsorption of chemical or biological molecules into the pores modifies the electrical and/or optical properties, allowing convenient and sensitive measurement approach. In this review, we provide a critical assessment of the development of PSi as a promising material for chemical and biosensing applications. Formation procedures of PSi with various pore sizes and morphologies are firstly given. Surface properties and structural characteristics of the material are briefly described. The recent progress on utilization of such porous structures in chemical and biosensing applications is then addressed in the context of surface chemistry effects and nanostructures, measuring approaches, operating concepts and device sensitivity and stability. Finally, concluding remarks with existing challenges that hinder the material for commercial use are highlighted. © 2014 Elsevier B.V.

Al-Sayari S.A.,Najran University
Open Catalysis Journal | Year: 2013

Natural gas is catalytically converted into several bulk chemicals such as ammonia, methanol, dimethyl ether, and synthetic liquid fuels by Fischer-Tropsch synthesis and similar processes. The main step in the conversion of natural gas to these products is the production of synthesis gas with the desired composition ranging from H2/CO = 3:1 used for the production of ammonia to the 1:1 mixture preferred for production of dimethyl ether. Catalysts and catalytic processes are important in the production of synthesis gas from natural gas. In this work, relevant catalytic systems employed recently in the production of syngas by the catalytic partial oxidation of methane, as well as experimental evidences on the reaction mechanisms are examined. Differences in methane dissociation, binding site preferences, stability of OH surface species, surface residence times of active species and contributions from lattice oxygen atoms and support species are considered. The methane dissociation requires reduced metal sites, but at elevated temperatures oxides of active species may be reduced by direct interaction with methane or from the reaction with H2 and CO (or C). The comparison of elementary reaction steps on Pt and Rh illustrates the fact that a key factor to produce hydrogen as primary product is a high activation energy barrier to the formation of OH. Another essential property for the formation of H2 and CO as primary products is a low surface coverage of intermediates, such that the probability of O-H, OH-H and CO-O interactions is reduced. © Saleh A. Al-Sayari; Licensee Bentham Open.

Al-Sayari S.A.,Najran University
Ceramics International | Year: 2014

A series of MnO2-Fe2O3 with various contents of Mn (0-40% atomic ratio) was synthesized by the co-precipitation method. XRD patterns indicate that the sharp and intense peaks are related to the excellent crystal quality of α-Fe2O3 nanostructures. HR-TEM images showed that α-Fe2O3 and MnO2, were partly in close contact and the lattice fringes exhibit the typical distances, i.e., α-Fe2O3 (104) (2.7 Å) and MnO2 (310) (3.1 Å). X-ray photoelectron spectroscopy (XPS) results of the Fe 2p core-level binding energy spectrum of the α-Fe2O3 and Mn 2p, indicated the presence of Fe3+ and Mn4+. The direct synthesis of olefins from syngas was carried out over the MnO2-Fe2O3 catalysts under pressurized fixed-bed continuous flow conditions. The results showed that Mn-Fe catalyst had high catalytic activity and high olefins selectivity without the addition of any promoters at low pressure. It was found that the catalyst containing 20 at% Mn-Fe was an optimal catalyst for the conversion of synthesis gas to hydrocarbons especially light olefins. The maximum CO conversion rate was 15%, and the yield of olefins (totally about 23.77%) with a predominance of CH4 (12.24%), and C2H6 (2.80%) components. Mn-Fe catalyst can be regarded as a potential candidate for catalytic conversion of biomass-derived syngas to olefins. © 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Al-Mattarneh H.,Najran University
Construction and Building Materials | Year: 2014

Introducing steel fiber to concrete materials enhances the performance of concrete structures in terms of their flexural strength, impact load resistance and limited crack propagation. The fiber concrete performance depends on the fiber content, dispersion and orientation. No standard method is currently available to evaluate these three parameters, especially in situ. This paper describes the feasibility of using a surface electromagnetic sensor as nondestructive radio wave test system to determine the concentration, dispersion and orientation of steel fibers in the concrete. The system needs to contact the concrete material and requires only one face of the concrete material for testing. The surface electromagnetic sensor can slide on the fiber concrete surface and measure the dielectric properties at various locations to assess the fiber distribution. In addition, the sensor can rotate to polarize the electric field to various angles and evaluate the fiber orientation. The mean and standard deviation of the measured dielectric properties increase with increasing fiber content and fiber dispersion. The results indicate that the dielectric properties are maximal when the fiber is oriented in the direction of the electric field and minimal when perpendicular. A simple linear model was established to determine the fiber content and flexural strength from the measured electromagnetic properties. © 2014 Elsevier Ltd. All rights reserved.

Ismail A.A.,Central Metallurgical Research and Development Institute | Ismail A.A.,Najran University
Applied Catalysis B: Environmental | Year: 2012

Herein, we report a synthesis of mesoporous PdO-TiO 2 nanocomposites at different PdO (0-3wt%) through simple one-step sol-gel reactions. Pd 2+ ions have been immobilized into TiO 2 networks by cross-linking triblock copolymer (Pluronic F123) as the structure-directing agents to develop highly efficient PdO-TiO 2 photocatalyst. The produced PdO-TiO 2 gel were calcined at 400°C for 4h to remove organic materials. TiO 2 nanoparticles with an average diameter are 8-10nm and PdO nanoparticles are well dispersed and exhibit diameters of about 10-40nm based on the PdO content. Our prepared photocatalysts have been compared with Pd/Aeroxide TiO 2-P25 by the determination of the initial rate of HCHO formation generated by the photooxidation of CH 3OH in aqueous suspensions to calculate the corresponding photonic efficiencies. The newly prepared PdO-TiO 2 nanocomposites showed a more effective and high efficient photocatalytic activities for CH 3OH oxidation to HCHO ~4 and 2 times than TiO 2-P25 and Pd/TiO 2-P25 respectively. In the present work, the photocatalytic activities of the obtained PdO-TiO 2 nanocomposites were significantly higher than those of previously reported. To the best of our knowledge, the measured photonic efficiency ξ=19.5% of mesosporous PdO-TiO 2 nanocomposites is found to be among the highest ξ-values reported up to now. © 2012 Elsevier B.V.

Siddiqui S.A.,Najran University
Journal of Theoretical and Computational Chemistry | Year: 2012

Superhalogen properties of CoF n (n = 1 - 6) clusters have been investigated using density functional theory. These calculations reveal the unusual properties of a Cobalt (Co) atom interacting with fluorine (F) atoms. Up to six F atoms are bound to a single Co atom, which results in increase of electron affinities as successive fluorine atoms are attached, reaching a peak value of 7.43 eV for CoF 5. The large HOMOLUMO energy gap, both in neutral and anionic form, further provide evidence of their stability. These unusual properties brought about by involvement of inner shell 3d-electrons, which not only allow CoF n (n = 1 - 6) clusters to belong to the class of superhalogens but also show that its valence can exceed the nominal value of 2 or 3. © 2012 World Scientific Publishing Company.

Siddiqui S.A.,Najran University
Structural Chemistry | Year: 2012

⋯uantum chemical calculations using gradient corrected density functional theory at B3LYP level reveals the unusual properties of a chromium (Cr) atom interacting with fluorine (F) atoms. Up to seven F atoms are bound to a single Cr atom, which results in increase of electron affinities as successive fluorine atoms are attached, reaching a peak value of 7.14 eV for CrF 6. The large HOMO- LUMO energy gap, both in neutral and anionic form, further provide evidence of their stability. These unusual properties brought about by involvement of inner shell 3d-electrons, which not only allow CrF n (n = 1-7) clusters to belong to the class of superhalogens but also show that its valence can exceed the nominal value of 2. © Springer Science+Business Media, LLC 2011.

Najran University | Date: 2015-07-23

A process for the direct oxidation of methane to C_(1)-oxygenates (formaldehyde and methanol) has been developed. The process involves a gas stream, comprising methane, an oxidizing agent (such as air, or oxygen blended with an inert diluent), and a nitrogen oxide as a gas phase sensitizer at oxidation conditions to produce C_(1)-oxygenates, such as formaldehyde and methanol. A certain proportion of nitrogen oxide, which acts as a radical initiator, in the stream is crucial to achieve a high yield of formaldehyde and methanol. In addition, the temperature plays an important role in the conversion of methane and in the selectivity to C_(1)-oxygenates.

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