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
    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
    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
  • Publication
    The effect of Sn doping on the thermoelectric properties of SiGe using first principle technique
    (Trans Tech Publications Ltd., 2020)
    Abdullah Chik
    ;
    Haw Wei Kheng
    ;
    Ruhiyuddin Mohd Zaki
    ;
    Akeem Adekunle Adewale
    ;
    Faizul Che Pa
    ;
    Yeoh Cheow Keat
    The thermoelectric properties of hexagonal SiGe doped with Sn with doping percentage of 12.5% and 25% were investigated using linearised augmented plane wave method using the WIEN2k package and semiclassical Boltztmann Transport equation using the BoltzTraP software for the purpose of understanding the role of Sn as a dopant in the SiGe. For temperature range of 300 to 1000 K, it can be seen that by doping with Sn, there is an improvement in overall thermal conductivity of the samples with the highest improvement is in the 25% doped sample. The conductivity vs temperature for 25% Sn doped SiGe also shows higher value through temperature range from 300 K to 1000 K, however the Seebeck coefficient decreases with Sn doping percentage for the same temperature range. Due to lower Seebeck coefficient and higher thermal conductivity values, the overall thermoelectric coefficient, ZT, of the doped compound is lower than the SiGe values with highest ZT equal to 0.29 and 0.17 at 650 K for 12.5% and 25% respectively while the ZT of simulated SiGe at 650 K is 0.35. Thus 25% Sn doping actually reduce the ZT but enhanced the thermal and electrical conductivity of SiGe for temperature range of 300 to 1000 K.
      1  13