Now showing 1 - 8 of 8
  • Publication
    Progression in the growth of cylindric nanostructures: carbon nanotubes (CNTs) and carbon nanofibers (CNFs) on graphene
    ( 2022-12) ; ;
    H.A. Hanafi
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    Mishthafiyatillah
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    ; ;
    Mohamad Nazri Abdul Halif
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    ;
    A.F. Abd Rahim
    The combination of carbon nanotubes (CNTs) and graphene produce a CNTs-graphene hybrid material with excellent electrical and mechanical properties that improved from their single form. This CNTs-graphene hybrid material has the potential to be used as electrodes and interconnects as it has better properties compared to copper (Cu). This work intended to grow CNTs on graphene using a CVD technique. The growth process used graphene on a Cu substrate with ferrocene as the catalyst, acetone as the carbon precursor and reactor temperature of 800oC. However, the process has unintentionally grown carbon nanofibers (CNFs). To observe the progression in the growth of CNTs and CNFs on graphene, the effect of growth reaction time is crucial. Hence, this work investigates the growth progression of the CNTs and CNFs on graphene based on different reaction times of 10 min, 20 min, 30 min and 60 min. It was found that the agglomeration of carbon is incomplete at 10 min reaction time and produced cylindric nanostructures. A further reaction time of 20 min and 30 min has significantly changed the size of the cylindric nanostructures into CNTs and CNFs with a very slight difference in the size, density, and coverage. The 30 min reaction time produced denser CNTs and CNFs with more uniform size and coverages. A longer reaction time of 60 min led to very long CNFs with an average length of 120 μm. In conclusion, meticulous fine-tuning of the reaction time is required to control the formation of CNTs and CNFs on graphene.
  • Publication
    A review: synthesis and mechanism of growth of the carbon nanotubes (CNTs) – graphene hybrid material and its application as electrodes
    The CNTs–graphene hybrids have many advantages and potential for use in a wide range of electronic applications as electrodes. The CNTs–graphene hybrid structure outperforms the structure of each material in terms of characteristics and performance. There are several methods to grow CNTs. This paper reviews the chemical vapor deposition (CVD) method used to synthesize CNTs–graphene hybrid material. This paper discusses the processes and growth parameters of the synthesis of the CNTs-graphene hybrid. This paper also discusses the growth mechanism and kinetics of CNTs. In addition, the potential and performance of CNTs–Graphene hybrid material as electrodes in batteries are also reviewed.
  • Publication
    Correlation between crystal structure and thermal reaction of TiOâ‚‚ - Graphene Oxide
    TiO₂ - Graphene oxide (GO) (GO = 0-1.0wt %) powders were synthesised using sol-gel method and annealed at 500°C. The samples were then characterised using X-ray diffraction (XRD). The additional of GO gave significant influence on the crystal structure of TiO₂. The lattice parameter of TiO₂ were increased with decreasing GO concentration. The unit cell volume of TiO₂-GO annealed in N2 decreased with the oxygen occupancy. In contrary, the TiO₂-GO annealed in O₂ has an increase in O₂ occupancies in the lattice that was nearly proportional to its unit cell volume. A continuous weight loss was recorded by TGA at a temperature range of T= 30 - 1000°C that were associated with H2O, C-H and C-O species. It is concluded that the Ti-O-C and Ti-C bonds were formed for samples annealed in O₂ and N2 respectively. The weight loss of TiO₂-GO annealed in O₂ is lesser than that annealed in N2 for same concentration additional GO into TiO₂.
  • Publication
    A controlled growth of carbon nanofibers (CNFs) on graphene
    ( 2023-12)
    Mishtha Fiyatillah
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    ; ;
    L K Wisnu Kita
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    ; ;
    A F Abd Rahim
    Carbon nanofibers (CNFs) have superior properties such as high conductivity, good mechanical strength, high specific surface area, and chemical stability. CNFs-graphene hybrid material can be used as a high-quality electrode in electronics applications. In the CNFs on graphene synthesis, the growth parameters must be well controlled. This work observes the evolution of the CNF's growth on graphene on Ni at reaction temperatures of 800oC and 860oC and at different reaction times of 30 min, 60 min, and 120 min. This research aims to find suitable conditions for obtaining controllable growth of CNFs on graphene. Based on the SEM measurement, it was found that the 860oC reaction temperature at 60 min and 120 min reaction time led to longer and smaller widths of CNFs with high coverage and distribution on graphene. The CNFs on graphene formation were confirmed by the XRD analysis.
  • Publication
    Phase reduction and thermodynamic analysis of Ilmenite Ore by carbothermal-iodination using different carbon reductants
    ( 2023-12)
    N. A. Nasrun
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    ; ; ;
    N. Takahiro
    ;
    S. A. Rezan
    The present study is on the combination of carbothermal reduction and iodination reaction (carboiodination) process for the phase reduction of ilmenite ore (FeTiO3). The aim is to understand the phase reduction and thermodynamic reaction analysis of ilmenite ore by a combined method of carbothermal-iodination using different carbon reductants (graphite and palm char). Graphite was used as a standard carbon reductant while palm char as a renewable carbon reductant was prepared via the pyrolysis technique. Ilmenite was mixed with carbon reductants and then first reduced by using a carbothermal reduction process at 1550℃. Then, the reduced samples were further investigated with iodination reaction in different temperature ranges of 900-1000 °C using a vertical tube furnace with mixed argon and iodine gas (0.2 L/min). The proximate and ultimate analyses of carbon reductants were analysed by CHON analyser and their microstructure by using SEM, while XRF and XRD were used for analyzing the chemical compositions and the phase reductions of raw ilmenite ore and reduced samples, respectively. The thermodynamics of possible reactions during carbothermal-iodination reactions were calculated by HSC Chemistry 6.0 software. By comparing graphite and palm char, palm char had an amorphous structure, with porous and high carbon content showing high potential for usage as a reductant in titanium extraction from ilmenite ore. The phases of ilmenite ore were ilmenite, rutile, and anatase transformed into rutile, pseudobrookite, and titanium oxide detected by XRD. Further reduction was performed by palm char where more rutile (TiO2) and titanium oxide (Ti3O5) developed from the iodination reaction at the highest temperature compared to graphite due to better properties and amorphous structure. The rutile and titanium oxide were found as stable phases from the thermodynamic analysis and confirmed with XRD. From the findings, the combination of carbothermal-iodination of ilmenite ore was possible and promising for rutile (TiO2) production in mineral extractions.
  • Publication
    Investigation on phase evaluation of ilmenite ore by carbothermal reduction and carboiodination reaction
    ( 2023-12)
    A. A. Adel
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    ; ;
    L. I. G. Togang
    This article presented the thermochemical calculation and experimental investigation on the phase evaluation of ilmenite ore (FeTiO3) via carbothermal reduction and carboiodination reaction for titanium production using graphite as a reducing agent. The carbothermal reduction and carboiodination reactions were performed in two different furnaces. The carbothermal reduction was evaluated at a temperature of 1550°C with inert argon gas utilizing a horizontal tube furnace. The carboiodination reactions were evaluated in temperatures ranging from 900°C, 950°C, and 1000°C using a vertical tube furnace with mixed iodine gas with argon gas. XRF and XRD were used for analyzing the chemical compositions and the phase evolutions of raw ilmenite ore and the reduced samples, respectively. The findings showed that the Perak ilmenite ore predominantly has a greater concentration of TiO2 (71.27wt%), Fe2O3 (18.85wt%), and some other oxides like aluminum oxide and quartz. In addition, XRD revealed that the ilmenite phase was converted into rutile (TiO2) titanium oxide (Ti3O5, Ti2O3), titanium carbide (TiC), and iron (Fe) phases, after the carbothermal reduction process. However, after the carboiodination reaction, the ilmenite and rutile phases remained at temperatures 900°C, 950°C, and 1000°C. The HSC Chemistry software was used in the determination of the thermochemical calculation and the possible reactions during the reaction which play an important role in shortening the reduction process. The results revealed the carboiodination process is a promising process that can reduce energy consumption and shorten the titanium production processes, and it needs more studies.
  • Publication
    Prediction of maximum spreading time of water droplet during impact onto hot surface beyond the Leidenfrost temperature
    ( 2021-12-01) ; ;
    Rahim Y.A.
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    ; ;
    Ismail K.A.
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    Ani M.H.
    When a water droplet impacts on a heated surface in the film boiling regime, it will spread, recede, and finally bounce off from the heated surface. These unique liquid-solid interactions only occur at high surface temperatures. Our main objective in this research is to measure the maximum spreading and residence time of the droplet and the findings were compared to theory. We focused our study in the film boiling regime. Brass material was selected as the test surface and was polished until it became a mirror polished surface. The temperature range for this experimental work was between 100 °C up to 420 °C. Degassed and distilled water was used as the test liquid. The high speed video camera recorded the images at the rate of 10,000 frames per second (fps). As a result, it was found that the experimental value of maximum spreading and residence time agreed closely with the theoretical calculation. A new empirical formula that can be used to predict the maximum spreading time in the film boiling regime is also proposed.
  • Publication
    Phase transformations of Langkawi ilmenite ore during carbothermal reduction using palm char as renewable reductant
    ( 2022-02-01)
    Mohammed A.I.
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    ; ;
    Nur Hazira Najmi
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    ;
    Nomura, Takahiro
    The phase transformations of carbothermal reduction of Langkawi ilmenite ore by palm char were studied in reduction temperatures ranging from 1200 °C, 1300 °C, and 1400 °C using a horizontal tube furnace with inert argon gas. The palm shells as renewable carbon reductant for carbothermal reduction of ilmenite ore were converted into palm char using pyrolysis techniques to improve and increase the surface area and carbon content. The present study aims to reduce oxides in ilmenite ore from our local mining to produce titanium oxides by carbothermal reduction process and recycled agricultural waste from palm shell as renewable reductant. The phase and chemical compositions of ilmenite ore and reduced samples were analyzed by XRD and XRF. It was found that ilmenite ore mainly contained titanomagnetite, hematite, and titanium dioxide phases. After carbothermal reduction, the titanomagnetite phase from ilmenite ore was transformed into titanium dioxide, iron titania, iron, and titanium carbide at the highest reduction temperature (1400 °C) via XRD analysis. The phase transformation revealed the porous structure with wider pore size distribution and high carbon from palm char was able to reduce the oxides in ilmenite ore. According to XRF analysis, the TiO2 amount was increased with the temperature; from 25.7 wt.% at 1200 °C up to 50.8 wt.% with the extent of reduction of TiO2 was 78.56% at 1400 °C. The carbothermal reduction of ilmenite ore using palm char as a renewable reductant was possible and promising in mineral ore extractions.