Now showing 1 - 8 of 8
  • Publication
    Formation of bio-based derived dicalcium silicate ceramics via mechanochemical treatment: physical, XRD, SEM and FTIR analyses
    ( 2023-07)
    Siti Nur Hazwani Yunus
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    ; ; ;
    Nur Hazlinda Jakfar
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    ;
    Emma Ziezie Mohd Tarmizi
    ;
    Zainal Abidin Talib
    Beta-dicalcium silicate plays an important role in modern technology, but its tendency for polymorphic transformation results in the dusting phenomenon, is a major challenge. Therefore, mechanochemical treatment is used to reduce the particle size to retain the stability of the polymorph. In this study, pure dicalcium silicate ceramics of β-monoclinic structure with P 121/c1 space group were synthesized using calcium oxide and silicate powders derived from calcined eggshells and rice husks, respectively. The powders were mixed in a 2:1 molar ratio by mechanochemical treatment and heat-treated in the air at temperatures ranging from 900°C to 1100°C for 2 h. The results reveal that pure betadicalcium silicate formed at 1100°C without adding stabilizers. The properties of the pristine and sintered bodies were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). SEM revealed that the grain and pore sizes increase with rising sintering temperatures. FTIR spectra indicate the existence of Si-O bonds in -4 4 SiO tetrahedrons on all the samples. The sample sintered at 1000°C attains the lowest bulk density (1.2463 g/cm3), whereas the apparent porosity is the highest (62.5%). The reason for this trend is due to the decomposition of carbonate into CO2 gas. The densification onset for the sample sintered at 1100°C as the bulk density rises and grain size achieves 6.06 μm. This study further explains the effect of sintering temperatures on the physical, structural, and morphological properties of Ca2SiO4 which would also be useful for further optimization of its use.
  • Publication
    The Microstructural and Bioactivity Behavior of Magnesium Alloy Filled with Bioglass for Biomedical Application
    ( 2022-01-24) ;
    Dahlan N.F.
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    ;
    Baharom N.A.
    Magnesium alloy have known as degradable implant material due to biodegradable properties. However, by developed Mg alloy matrix composites containing a bioceramic will produced more biodegradable and does not need second surgical to remove the implants in body. Powder metallurgy route was used to fabricate the AZ91/BG composite by mixing, compacting and sintering. Mg alloy (AZ91) was reinforced with 0, 3, 6, and 9 wt% of bioglass (BG) before compact and sintered at 400°C for 2 hours. The Vickers hardness, scanning electron microscope, and x-ray diffraction are used to investigate the effect of BG particles addition on the mechanical properties and microstructure of the composite AZ91/BG. Bioactivity behaviour was studied by immersion test of AZ91/BG composite into phosphate buffered saline (PBS) solution for 72 hours. The results showed that as the addition of BG increases from 3 to 9 wt%, the hardness of AZ91/BG decrease from 43.3HV to 27.9HV. The result also showed the formation of protective layers or apatite layer on the surface of AZ91/BG composite after immersed in PBS solution for 72 hours. Phase analysis by XRD shows the presence of peak Ca10(OH)2(PO4)6 as the BG increased from 3 to 9 wt%. As a conclusion, AZ91/3BG shows the optimum composite for biomedical application based on its properties and bioactivity behaviour.
  • Publication
    Phase Analysis of Bio-Based Derived Tricalcium Disilicate From 2CaO:1SiO2 By X-ray Diffraction
    ( 2021-12-14)
    Siti Nur Hazwani Yunus
    ;
    Fhan K.S.
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    ; ;
    Jakfar N.H.
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    In this paper, tricalcium disilicate was formed from dicalcium silicate compound powder, synthesised via a mechanochemical technique using a stoichiometric 2CaO:1SiO2. Compound CaO and SiO2 were derived from the bio-waste of eggshell and rice husk at the calcination temperature of 900oC and 800oC, respectively. The dicalcium disilicate powder was sintered for 2 hours at different temperatures ranging from 1150oC to 1350oC. Using X-ray diffraction with Rietveld analysis, it was found that the amount of tricalcium disilicate with monoclinic (beta) crystal structure increases on sintering temperature at the expense of dicalcium silicate. The complete formation of single-phase tricalcium disilicate began at a sintering temperature of 1300oC. The effect of sintering temperatures on the crystallisation and phase transition of dicalcium silicate is reported. The size of crystallites depends on the sintering temperature. The finding of this study rebound to the benefit of society by reducing the risk-off pollution cause by accessive redundant bio-waste eggshell and rice husk and also reduced the amount of CaO and SiO2 used in the fabrication of Ca3Si2O7
  • Publication
    The effects of henna fillers on the properties of polyurethane foam composites
    ( 2020-01-01)
    Adnan S.A.
    ;
    Zainuddin F.
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    ;
    Zulkeply N.A.
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    ;
    Polyurethane (PU) foam were produced from polyol (PolyGreen R3110) and 4,4-diphenylmethane diisocyanate (Maskiminate 80) with distilled water as a blowing agent. Natural fibers have received more attention from researchers due to their ability to increase the properties of the polymer composites. In this work, PU/Henna foam composites were prepared by used Henna fibers at different loading of 5, 10, 15 and 20 wt. %. The effect of different Henna loading on PU foam were investigated by density, compression test, morphology and water absorption. Core density of PU/Henna foam composites increased with addition Henna compared to control PU and showed highest core density of 85.10 kgm-3 . Compressive strength decreased to 0.53 MPa after Henna addition at 5 % PU/Henna foam composites. Henna addition to 20 % PU/Henna foam composites were reduced the compressive strength to 0.97 MPa due to stiffness effect of Henna that contributed to embrittlement of the cell wall. The distorted cell wall and less uniform of cell structure were proved by SEM due to Henna addition as compared to control PU. Water absorption percentage of PU/Henna foam composites were increased with Henna addition as compared to control PU. It is because hydrophilic properties of Henna tendency to absorb moisture.
  • Publication
    Effects of Heat Treatment on the Properties of SS440C for Blades Applications
    SS440C steel is commonly used for knife blades, bearings, valve parts, and medical equipment. The composition of SS440C steels is designed to increase hardness especially in blade applications. The effect of quenching and tempering heat treatment on the properties of SS440C was investigated in this study. Quenching heat treatment is done at 1000 Â°C, followed by tempering at 150 and 500 Â°C in a muffle furnace. Microstructure of SS440C samples were studied using an optical microscope (OM) and scanning electron microscope (SEM). Properties of SS440C after heat treatment have been investigated using the Rockwell hardness test and tensile test. It was found that the sample quenched at 1000 Â°C (without temper) had the highest hardness with 58.4HRC, while the as-received annealed sample had 11.4HRC followed by sample tempered at 150 Â°C with 57.5HRC and 500 Â°C with 54.1HRC. Tensile testing reveals that quenching and tempering at 500 Â°C result in the highest maximum stress compared to other samples. Through optical microscopy observation, a sample tempered at 500 Â°C has larger size of carbide precipitate than sample that quenched and tempered at a 150 Â°C. Insufficient carbide dissolution or a more abrasive reaction is revealed by larger carbide sizes. In conclusion, SS440C temper at 500 Â°C reflects that it has better properties than the other.
  • Publication
    Heat treatment of ss 316l for automotive applications
    Stainless steel 316L (SS 316L) is a low carbon-chromium-nickel-molybdenum austenitic stainless steel. Its application in automotive industry include as exhaust housings for catalytic converters and turbocharger. In this research, the tempering heat treatment was conducted by using SS 316L samples. These steels were austenitized at 860 °C for 1 hours before doing two tempering process. Austempering was conducted at 360 °C for 15 min in the muffle furnace then air cooled while martempering was conducted at 160 °C for 15 min in a muffle furnace then quench in water. The corrosion test was carried out using 1.0 M oxalic acid solution for 30 days in room temperature. Hardness test and microstructural observation were carried out for SS 316L before and after corrosion test. Experimental result showed that untreated sample have highest hardness value before and after corrosion test which were 232 HV and 225 HV respectively. The hardness value before corrosion test is 199.7 HV for austempered sample, and 201.3 HV for martempered sample. Untreated sample shows the lowest corrosion rate (0.94×10-3 mpy), followed by austempered sample (1.89 x 10-3 mpy) and the highest corrosion rate is for martempered sample (2.36×10-3 mpy). After corrosion, under optical microscope observation, martempered steel has more pits than austempered steel. In summary, austempering is the best heat treatment for SS 316L in automotive applications that give high ductility and toughness after heat treatment with high corrosion resistance.
  • Publication
    The effect of aging time on microstructure and hardness value of AZ80 Mg Alloy
    AZ 80 Magnesium (Mg) alloy (AZ80) is the lightest structural metallic materials with good mechanical properties. However, Mg AZ80 has drawbacks which result in poor ductility and low strength where applications of Mg alloy have been restricted. The AZ80 has high aluminium content can cause the precipitation of ß-phase which is Mg17Al12 in Mg-Al alloy. It can affect the mechanical properties such as poor strengthening. This paper was discussed the effect of aging time on microstructure and hardness value of AZ80. The AZ80 samples were cut to 1cm × 1cm. Samples heat treated at 360 C for one-hour quenching in water. Then, samples aged at 170 C with different aging times (2 to 8 hours) with same quench. Optical Microscope (OM), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Vickers Microhardness machine were used to analyse the samples. As the results showed ß-Mg17Al12 phase was discontinuously distributed along the grain boundary throughout solid solution treatment. The ß-Mg17Al12 phase did not fully dissolve into the α-Mg phase and distributed along the grain boundary. The results showed that sample after 2 hours aging time with highest hardness value 62.5 HV is the optimum sample.
  • Publication
    Crystal Structure and Thermal Behaviour of Calcium Monosilicate Derived from Calcined Chicken Eggshell and Rice Husk Ash
    ( 2021-12-14)
    Jakfar N.H.
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    Fhan K.S.
    ;
    Johar B.
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    ;
    Yunus S.N.H.M.
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    This study focuses on the synthesis of synthetic calcium monosilicate ceramic from chicken eggshells and rice husks waste through the mechanochemical route that relatively straightforward without adding any binders. Synthetic calcium monosilicate was mixed using a 1:1 ratio of calcined eggshell and rice husk ash, which both materials known as rich in calcium oxide and silica sources, respectively. The mixed powder was pressed using uniaxial pressing before fired at 1100oC, 1150oC, 1200oC, 1250oC, and 1300oC for 120 minutes with a heating rate of 5oC/min. The XRD spectrum from 1100oC to 1200oC mainly consists of pseudowollastonite (ICSD: 98-005-2576), wollastonite and silicon dioxide phases. However, as the sintering temperature increases, the wollastonite phases was completely transformed into pseudowollastonite, leaving some unreacted silica.