14 research outputs found

    Direct Observation Of Graphene During Raman Analysis And The Effect Of Precursor Solution Parameter On The Graphene Structures

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    Controlling the precursor solution parameter in preparing active catalyst film is critical in sol-gel process. The aim of this work is to validate the precursor solution parameter that affects the structural properties of graphene. Active Co3O4 film was prepared using precursor solution from cobalt acetate tetrahydrate in two different concentrations; 0.025 M and 0.05 M. One batch of the precursor solution was directly spin coated onto the substrate's surface meanwhile the second batch was kept for 4 days aging process. The studied spin speeds were 2000 rpm and 6000 rpm, and spin coated for 60 s. The active Co3O4 film was achieved by annealing at 450 °C and the graphene was grown at 900 °C of chemical vapor deposition (CVD) processing temperature for 5 min with the presence of ethanol as the carbon feedstock. The structural properties and morphology of the as-grown graphene synthesized from active Co3O4 film were characterized by Raman spectroscopy, optical microscope, and field emission scanning electron microscope (FESEM). The results demonstrated that concentration of precursor solution and the aging process affected the performance of the as-grown graphene. Agglomerates were formed in sample with 0.05 M of Co acetate tetrahydrate, however it was found that the Raman peaks intensity increased as compared to the 0.025 M sample. The precursor with 0.05 M has an acceptable chemical stability though aged for 4 days and contributed to the graphene growth. The spin coating speed was found not to affect the graphene growth at all. For aging effect, concentration 0.025 M shows unstable condition as compared to concentration 0.05 M when the precursor solution was aged for 4 days. Nonetheless, for the quality of the as-grown graphene, the ratio of Raman 2D-band over G-band intensities was less than 1.0, indicated that the graphene was in multi-layer form

    Cyclic Voltammetry And Galvanostatic Charge-Discharge Analyses Of Polyaniline/Graphene Oxide Nanocomposite Based Supercapacitor

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    Super capacitor is an energy device that is applicable in numerous fields because of its excellent reversibility, long life and high power density. Nevertheless, its universal use is restricted by the reduced energy storage capacity and its high crossed series compared to batteries. Even with the relatively high-level output and extensive use of super capacitor, there is still substantial doubt and ambiguity as to their efficiency in general, especially when it is compared to lithium-ion batteries. The inconsistencies are attributable both to the lack of standardization of the test methods and to the certainty of the strength capacity of the super capacitor after their resistance has been identified. Therefore, in this work, graphene oxide (GO) and polyaniline(PANI)nanocomposite supercapacitor electrode was fabricated and the performance was investigated by means of cyclic voltammetry and galvanostatic charge-discharge analyses. GOwas synthesized using improve Hummers method and PANI using oxidative polymerization chemical synthesis. Three different electrode’s compositions were prepared using PANI/GO nano composite and labelled as PGO30, PGO50 and PGO70. This article will conclude the electrochemical performance of the electrode. From the results, it was found that PGO50electrode(50% PANI/50% GO) hasthe best calculated capacitance with 19.71 F/g compared to the other composite electrodes. This may be attributed from the good electrical conductivity distribution of PANI and graphene oxide. The findings of the work may significantly drive the future of supercapacitor electrode from nanocomposite related materials

    Effect Of Different Cooking Temperature And Alkalinity On Mechanical And Morphological Properties Of Composite Sheet From Durian Shell

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    Temperature and alkalinity are the critical factors that contribute to the successful of soda pulping. These factors influence the length size and interfibre bonding of the fibre. In this paper, durian (Durio zibethinus Murray) shell composite sheet were prepared by conducting chemical pulping through soda method to study the effect of different pulping temperature and % of NaOH on the mechanical and morphological characteristics of durian shell composite sheet. Six sets of composite sheet were produced from six sets of pulping. The pulping processes were conducted at 140, 160 and 170°C with 17, 19 and 21% of active alkali. The mechanical properties of the durian shell composite sheet were analyzed through few standard TAPPI analyses which are tensile, tear, burst, folding endurance and paper bulk thickness. The results show that the highest reading of paper bulk thickness, tensile, tear and burst index, and also folding endurance were achieved at the pulping condition of 170°C with 21% of NaOH with the value of 1.3366 g/cm3, 54.151 NM/g, 6.648 m.Nm2/g, 2.517 k.Pam2/g and 170 no. of fold, respectively. Scanning electron microscopic analysis showed that morphological changes took place depending on the size and arrangement of the fibres in the composites sheet

    Synthesis and characterizations of YBa2Cu3O7-5 superconductor with added AI2O3 nanoparticles via citrate-nitrate auto-combustion reaction / Mohd Shahadan Mohd Suan

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    Superconductor materials are renowned to conduct electricity at zero resistance and capable to expel magnetic flux. It can be used in developing efficient wire cables, magnetic energy storage and levitation technologies. Thus, the high temperature superconductor YBa2Cu3O7-δ with added Al2O3 nanoparticles was synthesized via citrate-nitrate auto-combustion reaction process. The novelty of this research work is the citrate-nitrate auto-combustion reaction method consumed less energy and time compared with other conventional synthesis methods for processing of composite superconductor oxides and produced well distribution of Al2O3 nanoparticles in YBa2Cu3O7-δ superconductor. The auto-combustion reaction transformed the formulated precursor citrate-nitrate gel into very fine ashes. It yielded Al2O3 and YBa2Cu3O7-δ phases after calcination process which was further heat treated to achieve superconductivity. The reactions during synthesis processes were investigated through the thermal evaluations. The effects of different concentration of Al2O3 nanoparticles on the structure, superconducting, magnetic and mechanical properties of YBa2Cu3O7-δ were investigated and appraised. The sustained orthorhombic structure in each sample contributed to consistency in superconducting transition temperature while the flux pinning forces provided by the non-superconducting nanoparticles improved the critical current density. Furthermore, the mechanical hardness of the samples was also influenced by the addition of nanoparticles. This work shows that the citrate-nitrate auto-combustion reaction is an effective method to introduce Al2O3 as nanoparticles homogeneously distributed in the YBa2Cu3O7-δ superconductor

    Synthesis Of Y1-xAlxBa2Cu3O7-δ Via Combustion Route: Effects Of Al2O3 Nanoparticles On Superconducting Properties

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    Combustion reaction was used to synthesis Al2O3 nanoparticles embedded Y1-xAlxBa2Cu3O7-δ simultaneously. The effects of Al2O3 nanoparticles with nominal molar mass (xmol) of 0.02, 0.04, 0.06, 0.08 and 0.10 towards the critical current density JC of Y1-xAlxBa2Cu3O7-δ were verified by magnetic measurement. Resulted XRD patterns revealed that the calcined samples consist of pure Al2O3 and Y1-xAlxBa2Cu3O7-δ phases which had been confirmed by EDX results. The SEM images showed that Al2O3 nanoparticles (~10 nm) were distributed in polycrystalline YBa2Cu3O7-δ grains and grain boundaries. The presence of higher concentration of Al2O3 nanoparticles has developed Al3+ rich spots which diffused within the YBa2Cu3O7-δ superconducting matrix to form Y1-xAlxBa2Cu3O7-δ and was confirmed by EDX analysis. The samples were electrically superconducting at temperature above 85 K as measured by using standard four-probe technique. The magnetic field (H) dependent magnetization (M), M-H hysteresis loops measured at 77 K for xmol ≤ 0.06 samples are significantly improved attributed to the increase of trapped fluxes in the samples. Remarkable increase of magnetic JC (H) in Al2O3 nanoparticles added samples compared to the as prepared polycrystalline YBa2Cu3O7-δ sample indicating strong pinning effect. It is suggested that well-distributed Al2O3 nanoparticles in the polycrystalline YBa2Cu3O7-δ matrix achieved via auto-combustion reaction has efficiently pin the magnetic vortex. The magnetic JC was optimized to ~6 kAcm-2 in xmol = 0.06 sample. On the other hand, insignificant magnetic JC improvement in xmol ≥ 0.08 samples is probably resulted from the agglomerated Al2O3 nanoparticles in Y1-xAlxBa2Cu3O7-δ phase

    Thermoplastic starch/beeswax blend: characterization on thermal mechanical and moisture absorption properties

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    Cassava starch has acquired many attentions owing to its ability to be developed as thermoplastic cassava starch (TPCS) where it can be obtained in low cost, making it to be one of alternatives to substitute petroleum-based plastic. An attempt was made to investigate the thermal, mechanical and moisture absorption properties of thermoplastic cassava starch blending with beeswax (TPCS-BW) fabricated using hot moulding compression method in the range of beeswax loading from 0, 2.5, 5 to 10 wt%. Addition of beeswax has significantly reduced tensile strength, elongation and flexural strength while improving tensile modulus and flexural modulus until 5 wt% beeswax. Incorporation of 10 wt% beeswax has successfully produced the lowest value of moisture absorption and water solubility among the bio-composite which might be attributed to the beeswax's hydrophobic properties in improving water barrier of the TPCS-BW bio-composite. Furthermore, the addition of beeswax resulted in the appearance of irregular and rough fractured surface. Meanwhile, fourier transform infrared (FT-IR) spectroscopy presented that incorporation of beeswax in the mixture has considerably improve hydrogen bonding of blends indicating good interaction between starch and beeswax. Hence, beeswax with an appropriate loading value able to improve the functional properties of TPCS-BW bio-composite

    Annealing effects on the properties of copper oxide thin films prepared by chemical deposition

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    Copper oxide thin films with thickness of 0.45 mu m were chemically deposited on glass substrates by dipping the microscope glass slide for 20 s each in 1 M NaOH and copper complex solutions. Temperature of NaOH solution was increased to 70 degrees C, while the copper solution was maintained at room temperature. Copper oxide thin films were annealed in air at different temperature of 200 - 400 degrees C and as-prepared sample was used as reference. The films structures were studied by XRD. The patterns showed that the films as prepared and annealed at 200 degrees C were cuprite structure with Cu(2)O composition. Films annealed at 300 degrees C consist of mixed tenorite (CuO) and cuprite (Cu(2)O) phases. Annealing the films in air at 400 degrees C completely converts these films to tenorite structure with composition of CuO. The proportion of the two forms of copper oxide varies with oxidation temperature. The surface properties were characterized using scanning electron microscopy. UV-Vis transmittance spectra confirmed the results from the XRD by a shift in the optical band gap from 2.40 to 1.73 eV. The conversion was also confirmed by the FTIR spectroscopy measurement. Photoluminescence intensity is greatly improved with the increase in annealing temperatures

    Synthesis Of a Fe2o3 Nanowires/MWCNTS Composite For Photocatalyst

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    Multi-walled carbon nanotube (MWCNTs) was decorated on nanowires iron oxide (α-Fe2O3) thin film (α-Fe2O3/MWCNTs) by spin coating method.Nanowires hematite was produced by thermal oxidation of Fe substrate at 400 °C for 120 minutes.The aim of this nanocomposite α-Fe2O3/MWCNT is to improve the photocatalytic efficiency of the α-Fe2O3 nanowires.The structural characterization of the as-prepared composites were analyzed by x-ray diffraction (XRD),raman spectra,and photoluminescence spectra (PL) to identify the structure of pure α-Fe2O3 and decorated of MWCNTs.While,the morphological observation,interaction of MWCNTs and nanowires structure on hematite phase was done by scanning electron microscopy (FESEM).It was found that,the optimization dispersion of MWCNTs in the dimethyl form amide (DMF) solvent through acid treatment with 3 Molar nitric acid (HNO₃),shows the homogenized well-decorated MWCNTs on the surface of the nanowires structure,which can eliminate the limitation of iron oxide and help in electron transfer from α-Fe2O3 to MWCNTs
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