Ruhiyuddin Mohd Zaki
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Preferred name
Ruhiyuddin Mohd Zaki
Official Name
Ruhiyuddin, Mohd Zaki
Alternative Name
Ruhiyuddin, M. Z.
Mohd Zaki, Ruhiyuddin
Zaki, Ruhiyuddin Mohd
Ruhiyuddin, Mohd Zaki
Zaki, R. Mohd
Mohd Zaki, R. S.R.
Zaki, R. M.
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Scopus Author ID
55560602300

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  • Publication
    Study of thermoelectric properties of Sr₀.₉₂A₀.₀₈TiO₃ (A=Yb / Tm) perovskite oxide using density functional theory method
    (IOP Publishing, 2020)
    Akeem Adekunle Adewale
    ;
    Abdullah Chik
    ;
    Ruhiyuddin Mohd Zaki
    The first principle methods have been employed to investigate electronic and thermoelectric properties of Sr₀.₉₂Yb₀.₀₈TiO₃ and Sr₀.₉₂Tm₀.₀₈TiO₃ perovskite-oxide based molded samples. Generalized gradient approximation (GGA) with Hubbard U parameter is used by WIEN2k code for the calculations. The straight band line was observed in the band structure of both studied samples. This was generated from 4f-orbitals as shown in partial density of state diagrams. It is also noticed that Yb and Tm doped in SrTiO₃ changed the perovskite-based oxide from a wideband insulator to metallic nature. A thermoelectric power factor of Sr₀.₉₂Tm₀.₀₈TiO₃ sample is higher than that of Sr₀.₉₂Yb₀.₀₈TiO₃, this is as a result of its huge electrical conductivity. The dependent of chemical potential to temperature was revealed in the study where high value of power factor was recorded for high temperature.
  • Publication
    Electronic properties of calcium and zirconium co-doped BaTiO₃
    (Trans Tech Publications Ltd., 2020)
    Akeem Adekunle Adewale
    ;
    Abdullah Chik
    ;
    Ruhiyuddin Mohd Zaki
    Barium titanate (BaTiO₃) is a perovskite based oxides with many potential application in electronic devices. From experimental report BaTiO₃ has wide energy band gap of about 3.4 eV which by doped with Ca and Zr at A-and B-sites respectively can enhance their piezoelectric properties. Using first principles method within the density functional theory (DFT) as implement in Quantum Espresso (QE) with the plane wave pseudo potential function, the influence of the Ca and Zr doping in BaTiO₃ are studied via electronic properties: band structure, total density of states (TDOS) and partial density of states (PDOS). The energy band gap calculated was underestimation which is similar to other DFT work. Two direct band gap where observed in Ba₀.₈₇₅Ca₀.₁₂₅Ti₀.₈₇₅Zr₀.₁₂₅O₃ sample at Γ-Γ (2.31 eV) and X-X (2.35 eV) symmetry point.
  • Publication
    Thermoelectric properties of Sm doped CaMnO₃ using density functional theory method
    (Trans Tech Publications Ltd., 2020-09)
    Abdullah Chik
    ;
    Ruhiyuddin Mohd Zaki
    ;
    Akeem Adekunle Adewale
    ;
    Faizul Che Pa
    ;
    Yeoh Cheow Keat
    The electronic structure and thermoelectric properties of CaMnO₃ doped with 8% and 17% f block element Sm using first principles calculations and semi-classic Boltzmann theory were presented in this paper. The G-type AFM phase is most stable among five phases for CaMnO3, however, with 8% and 17% Sm doping, these compounds became nonmagnetic phases. CaMnO₃ calculated electronic band structure shows an indirect band gap of 0.523 eV, which is underestimated by the density functional theory (DFT) calculations but the band gap explains the semiconducting behavior. However, with 8% and 17% Sm doping, the electronic bandstructure of these compounds exhibit metallic behavior, with Sm 4f and Mn 3d electrons contributing to conduction band, increasing the magnitude of conductivity for doped compounds. All temperature dependence Seebeck coefficient plots show n-typed conduction for all compound with reduced magnitude of Seebeck coefficient for doped compounds. The temperature dependence thermal conductivity plot shows overall thermal conductivity is reduced in Sm doped compound. CaMnO₃ with 17% Sm doping exhibit much higher ZT of 0.32 at 800 K showing enhanced thermoelectric properties at high temperature and suitability or high temperature energy conversion devices.
  • Publication
    Microstructural analysis of iron aluminide fabricated from iron mill scale by powder metallurgy method
    (Universiti Malaysia Perlis (UniMAP), 2010-06-09)
    S. Nurul Syuhada
    ;
    Ruhiyuddin Mohd Zaki
    ;
    Khairel Rafezi Ahmad
    This research describes the microstructural of iron aluminide which fabricated from iron mill scale by powder metallurgy method. The raw material used consists of iron mill scale and aluminum powder. Iron mill scale is obtained from steel plant company in north Malaysia. This mill scale was milled for 4 hours with grinding media to produce a fine particle size and then the mill scale was sieved into a different size. After that, the premix of iron mill scale and aluminum powder was compacted with 5.7 ton load and the process was conducted at room temperature. The green compact were subjected to sinter in condition of nitrogen atmosphere at 500ûC with 8°C/min heating rate and soaking time was set for 30 minute. The structural characteristics of sintered sample and raw material investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) methods are presented. SEM result of the sintered sample obtained at 500ûC showed that some particle of iron mill scale do not react with aluminum powder to create bonding together. This means the temperature that used for sintering do not reached the suitable sintering temperature.
  • Publication
    Structural, electronic and thermoelectric properties of SrTiO₃ ceramic doped by lanthanum using first principles
    (IOP Publishing Ltd., 2020)
    Akeem Adekunle Adewale
    ;
    Abdullah Chik
    ;
    Ruhiyuddin Mohd Zaki
    The Sr₀.9₂La₀.₀₈TiO₃ model compound was studied by means of the first-principles method grounded on the full-potential linearized augmented plane wave with the local orbital method as implement in WIEN2k. The structures, electronic and thermoelectric properties of the model compound are examined. Geometry optimization of Sr₀.9₂La₀.₀₈TiO₃ compound structure reveals the lattice constant of 3.9451 Å, which is the same as un-doped SrTiO₃. The direct bandgap of 2.48 eV (Γ-Γ) was measured from computed electronic band structure and its displayed density of states for Sr₀.9₂La₀.₀₈TiO₃ sample. Transport properties were calculated using BoltzTraP code as implemented in the WIEN2k code. The results were analyzed as a function of the variable temperatures, the density of state and chemical potential. Temperature and density of state variation with transport properties are in the same trend. Chemical potential proves material as n-type via Seebeck coefficient. The thermoelectric performance ZT of 0.05 was obtained at room temperature, while maximum value of 3.79 was recorded at 1200 K.
      26  1
  • Publication
    Preparation & characterization of biochar from rice husk by pyrolysis method
    ( 2024-12)
    Faizul Che Pa
    ;
    Nur Nuha Ulya Norazman
    ;
    Ruhiyuddin Mohd Zaki
    In nations where rice cultivation is prevalent, the responsible management of substantial quantities of rice waste is necessary to mitigate potential environmental concerns. This study aims to produce biochar from rice husks through the pyrolysis method, specifically without using inert nitrogen gas by utilizing a low-oxygen pyrolysis technique. The study employed many experimental parameters, including the process temperature, residence time, and heating rates. The FTIR results revealed a decrease in the stretching of O-H bonds in rice husk biochar at elevated temperatures (500°C), suggesting the degradation and disintegration of cellulose, hemicellulose, and lignin. Various bands associated with hydroxyl, carboxyl, aromatic bonds, amine groups, and other aromatic compounds were observed at lower pyrolysis temperatures. The observed functional group in rice husk biochar closely resembles the outcomes obtained from commercial biochar, except for the absence of C=O stretching. It was seen that the biochar structure exhibited an increase in pore size with increasing temperature. At higher temperatures, a decrease in pore size was observed on the surface of the biochar. It has been observed that when subjected to elevated pyrolysis temperatures, commercial biochar has a greater pore size compared to rice husk biochar, albeit fewer in number than the latter. Based on the findings, it can be inferred that the most favourable conditions for the rice husk biochar production by the low oxygen pyrolysis method are attained at temperatures of 300°C for durations of 60 and 90 minutes, as well as at 400°C for 90 minutes.
      1  20
  • Publication
    Logam bukan ferus
    ( 2012)
    Ruhiyuddin Mohd Zaki
    ;
    Faizul Che Pa
    ;
    Murizam Darus
    ;
    Mohd Arif Anuar Mohd Salleh
    Umum mengetahui kepentingan bahan logam dalam kehidupan manusia seharian. Walaubagaimanapun, tidak ramai yang mempunyai pemahaman jelas berkaitan dengan bahan ini. Situasi ini mengilhamkan para penulis untuk menghasilkan buku Logam Bukan Ferus ini. Bab pertama menjelaskan berkenaan logam bukan ferus secara umum, pola penggunaan logam bukan ferus serta masa depan logam bukan ferus ini. Bab-bab lain pula memberikan fokus kepada beberapa jenis bahan bukan ferus secara spesifik seperti aluminium, zink, plumbum, kuprum, logam refraktori dan logam berharga.
      1  267
  • Publication
    DFT Study of Thermoelectric Performance of SrTiO₃ Doped by Tantalum
    (Universiti Malaysia Perlis (UniMAP), 2019-10)
    Akeem Adekunle Adewale
    ;
    Abdullah Chik
    ;
    Ruhiyuddin Mohd Zaki
    ;
    Faizul Che Pa
    ;
    Yeoh Cheow Keat
    ;
    Noorina Hidayu Jamil
    This paper deals with enhancement of thermoelectric performance of SrTiO₃ - a perovskite-based material by doping Ti-site with Ta. The electronic and the thermoelectric transport properties of doped SrTiO₃ were studied using the first principle calculation in full-potential of density functional theory. Spin-orbit coupling including Hubbard U parameter influences were observed in the investigation. Energy band structure and electron density of state were determined for electronic properties. The Seebeck coefficients, thermal conductivity, electrical conductivity as well as thermoelectric efficiency ZT were calculated for thermoelectric properties. The results of our calculations revealed that narrowing the bandgap of the material leads to the increase of thermoelectric efficiency ZT. At spin-orbit coupling with DFT+U method, ZT of 0.18 at 750 K were obtained and this is similar to the experimental data reported.
      1
  • Publication
    Asas logam
    ( 2011)
    Faizul Che Pa
    ;
    Ruhiyuddin Mohd Zaki
    ;
    Siti Hawa Mohamed Salleh
    ;
    Farah Farhana Zainal
    ;
    Mohd. Mustafa Al Bakri Abdullah
    ;
    Nurfazlin Abu Hassan
    Buku Asas Logam diterbitkan khusus untuk membimbing dan memberi panduan kepada para pelajar yang mengikuti pengajian Kejuruteraan Bahan terutamanya dalam bidang Metalurgi. Buku ini menggabungkan aspek teori dan praktikal yang wujud dalam keseluruhan pemprosesan logam. Secara keseluruhannya buku ini membolehkan pembaca memahami teori dan mengaplikasikan kejuruteraan Metalurgi di alam pekerjaan dan kehidupan harian.
      13  135
  • Publication
    Logam ferus
    ( 2011)
    Murizam Darus
    ;
    Faizul Che Pa
    ;
    Ruhiyuddin Mohd Zaki
    ;
    Mohd Arif Anuar Mohd Salleh
    Logam ferus adalah kumpulan logam dengan komposisi utamanya terdiri daripada bahan logam besi. Pengetahuan berkaitan bahan ini dapat membantu kita menghasilkan produk yang lebih berkualiti serta mengoptimakan penggunaan bahan ferus dengan lebih cekap. Bab pertama menjelaskan berkenaan logam ferus secara umum, proses penghasilan logam ferus serta piawai yang menjadi rujukan utama industri berkaitan. Bab kedua buku ini pula memberikan fokus kepada sifat-sifat logam ferus serta peranan utama bahan karbon dalam penghasilan keluli. Jenis-jenis keluli yang utama pula dijelaskan dalam bab tiga. Manakala bahagian terakhir menjelaskan proses-proses yang berkaitan dengan penghasilan produk daripada bahan logam ferus.
      2  506