Mohammad Hafizuddin Hj Jumali

Characterization of multilayer graphene prepared from short-time processed graphite oxide flake

Multilayer graphene has been prepared by thermal reduction of graphene oxide film. The graphite oxide flake was first synthesized by using modified Hummers method with a relatively small amount of oxidizing agent and short-time processing at ambient temperature. The graphite oxide flake was dispersed in deionized water and deposited on quartz substrates to form graphene oxide film. The red shift of absorption peak and decrease of interlayer distance as interpreted from the X-ray diffraction spectrum indicate the formation of multilayer graphene. The resultant multilayer graphene has been successfully used as counter electrode in FTO/ZnO nanorods/electrolyte/multilayer graphene dye sensitized solar cell.

A Mini Review: Can Graphene Be a Novel Material for Perovskite Solar Cell Applications?

Perovskite solar cells (PSCs) have raised research interest in scientific community because their power conversion efficiency is comparable to that of traditional commercial solar cells (i.e., amorphous Si, GaAs, and CdTe). Apart from that, PSCs are lightweight, are flexible, and have low production costs. Recently, graphene has been used as a novel material for PSC applications due to its excellent optical, electrical, and mechanical properties. The hydrophobic nature of graphene surface can provide protection against air moisture from the surrounding medium, which can improve the lifetime of devices. Herein, we review recent developments in the use of graphene for PSC applications as a conductive electrode, carrier transporting material, and stabilizer material. By exploring the application of graphene in PSCs, a new class of strategies can be developed to improve the device performance and stability before it can be commercialized in the photovoltaic market in the near future.

Carbon/Carbon Nanotubes (CNTs) Composites from Green Pellets Contain CNTs and Self‐adhesive Carbon Grains from Fibres of Oil Palm Empty Fruit Bunch

Nano composites green pellets (GPs) were prepared from the mixtures of carbon nanotubes (CNTs) at varying percentage (0, 2, 4, 6, 8 and 10%) and self‐adhesive carbon grains (SACG) from fibres of oil palm empty fruit bunch. These GPs were carbonized and CO2 activated to produce activated carbon/CNTs composites in the form of pellets (ACPs). It was found that the density (ρ) and electrical conductivity (σ) of the ACPs varied nonlinearly with CNTs content; as for the CNTs content of 3–5%, we observed the peak values of ρ and σ at 1.3781 gcm−3 and 3.4146 (Ωcm)−1 respectively. The presence of the agglomerated and individual particles of CNTs in the pores of the ACPs was clearly shown by the micrograph of the Field Emission Scanning Electron Microscope (FESEM). The nitrogen adsorption isotherm data showed the decrease in surface area, volume and diameter of pores due to the effect of CNTs. The effect of CNTs on the electrochemical behavior of the ACPs were investigated from the supercapacitor cells fabricated u...

Structure, humidity sensitivity and magnetic properties of Ce substituted magnesium ferrite

The effect of Ce ions substitution at Fe ions site on the microstructure, humidity sensing and magnetic properties of magnesium ferrite was investigated. MgCexFe2-xO4 ceramics with x = 0.00, 0.02 and 0.04 were prepared using sol-gel auto combustion technique. X-ray diffraction analysis confirms the formation of cubic spinel structure of magnesium ferrite for all samples. However a second phase of CeO was also present in samples with Ce substitution. Scanning electron images show porous structures with irregularly shaped grain. Sample with composition x = 0.04 has the highest percentage of porosity and smallest grain size. This sample also has the highest sensitivity towards humidity. Magnetic hysteresis loops show a soft magnetic material behavior with low coercive force for all samples. The magnetization decreases while the coercive field increases with Ce substitution.

Photoluminescence study of Poly (9,9-di-n-octylfluorenyl-2,7-diyl)/Flourol 7GA/Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] blends

The aim of this work is to study the photoluminescence characteristics of Poly (9,9-di-n-octylfluorenyl-2,7-diyl) (PFO)/ Flourol 7GA (F7GA)/ Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) blends for potential application as white OLEDs. In this work the PFO/F7GA acted as donor while the MEH-PPV acted as acceptor. The F7GA content was fixed at 0.5 wt% of PFO while concentration of MEH-PPV was varied between 0 and 7 wt%. All three polymers were mixed using solution blending method followed by deposition onto glass substrate using spin coating technique. It was observed that the intensity of PFO/F7GA emissions systematically reduced before completely quenched at the highest MEH-PPV content. In contrast, MEH-PPV recorded enhanced PL emission and achieved maximum intensity at the highest wt%. This observation indicates the efficient energy transfer has taken place, suggesting the shortening of Forster radius between the donor and acceptor.

Influence of the spinning rate on the β-phase formation in poly(vinylidene fluoride) (PVDF) films

In this work, the effect of rotational speed on the β-phase formation in PVDF films is investigated. The rotational speeds use in this work are 500, 1000, 2000 and 4000 rpm. All films are left to dry at room temperature. FTIR and XRD technique are employed to determine the phase formation while SEM is used to investigate the morphology of the films. The FTIR and XRD measurements confirm that the main phase formed in all PVDF films is β-phase. However, the β-phase contents vary with the spinning rate and the highest content is observed approximately 83% for 500 rpm film. SEM micrographs show the surface of all samples is porous structure and rough.In this work, the effect of rotational speed on the β-phase formation in PVDF films is investigated. The rotational speeds use in this work are 500, 1000, 2000 and 4000 rpm. All films are left to dry at room temperature. FTIR and XRD technique are employed to determine the phase formation while SEM is used to investigate the morphology of the films. The FTIR and XRD measurements confirm that the main phase formed in all PVDF films is β-phase. However, the β-phase contents vary with the spinning rate and the highest content is observed approximately 83% for 500 rpm film. SEM micrographs show the surface of all samples is porous structure and rough.

Influence of the substrate on the crystalline phase and morphology of poly (vinylidene fluoride) (PVDF) thin film

The effect of substrate on the crystalline phase and morphology of the poly (vinylidene fluoride) (PVDF) thin film has been investigated. The solution of PVDF/Hexamethyl phosphoramide (HMPA) was deposited on four different substrates, namely, silicon (Si), glass (SiO2), indium tin oxide (ITO) coated glass and silver (Ag) coated glass respectively by using the spin coating technique. The crystalline structure was investigated using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) techniques. The morphology was determined using scanning electron microscopy (SEM). XRD demonstrated that the structure of PVDF thin films on each substrate is β-phase with different orientations of the molecular chains. FTIR results confirmed XRD that the samples contain β-phase. SEM shows spherulites structure, which is rough and porous, besides, the size of spherulites and the porosity are different for each sample. The size of spherulites is in average diameter range (1–6μm) and this range is attributed to the β-phase. The nucleation process of β-phase on the various substrates attributed either to the match of polymer-substrate or to the electrostatic interaction. Among the substrates used, the ITO substrate exhibited a greater tendency for β-phase formation.

Enhanced optophysical properties of poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)] via addition of TiO2 nanoparticles

This work investigated the effect on 5 wt% addition of TiO2 nanoparticles (NPs) on the optical absorption characteristics of Poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)] (F8BT). Both materials were mixed using solution blending method and then spin coated onto ITO-coated glass substrate at 1000 rpm for 30s. The optical properties of the nanocomposite were determined using UV-Vis spectroscopy. Compares to pristine film, the absorption peak of the nanocomposite film improved and shifted to longer wavelength indicating reduction in the direct and indirect band gaps. Better optophysical properties of F8BT/TiO2 nanocomposites is believed due to compatible band structures and efficient charge trapping effect displayed by the NPs.

Effect of duration on pore widening of one-step anodized aluminum oxide template

This work investigated the effect of pore widening for fabrication of anodized aluminum oxide (AAO) template. AAO template was fabricated using one-step anodization method. The influence of H3PO4 on the widening of pore of AAO was investigated. The morphology of AAO was analyzed using FESEM. Result shows that by widening the pores at 25°C can help to protect the neighbouring pores from any damage. Single, well separated, straight without any tilt or branches, well aligned and controllable pore diameter could be obtained using this technique.

Structural and electrical evaluation of KNN ceramic

The aim of this study is to determine the effect of temperatures on structures and piezoelectric properties of Ka0.5Na0.5NbO3 (KNN) ceramic. The KNN sol was prepared using sol-gel method. The xerogels was annealed at 800 °C for 1.5h to form KNN powders. 10wt% of silicate glass was added to assist densification of KNN pellets. The pellets were sintered at different temperatures ranging from 800 °C to 1000 °C for 6h. XRD analysis confirmed the formation of KNN ceramics in all samples with monoclinic structure. However, minor impurities of KNbO3 were detected for samples sintered at 900oC and 1000oC signifying that different sintering temperatures affect the microstructure of the samples. SEM image indicates that the KNN have agglomerated granules and sintering temperature affect the densification properties. Impedance analysis showed the resistances, RT increased with the increments of sintering temperature while the piezoelectric constant, d33 of the prepared samples were in the range of 22–31 pC/N.The aim of this study is to determine the effect of temperatures on structures and piezoelectric properties of Ka0.5Na0.5NbO3 (KNN) ceramic. The KNN sol was prepared using sol-gel method. The xerogels was annealed at 800 °C for 1.5h to form KNN powders. 10wt% of silicate glass was added to assist densification of KNN pellets. The pellets were sintered at different temperatures ranging from 800 °C to 1000 °C for 6h. XRD analysis confirmed the formation of KNN ceramics in all samples with monoclinic structure. However, minor impurities of KNbO3 were detected for samples sintered at 900oC and 1000oC signifying that different sintering temperatures affect the microstructure of the samples. SEM image indicates that the KNN have agglomerated granules and sintering temperature affect the densification properties. Impedance analysis showed the resistances, RT increased with the increments of sintering temperature while the piezoelectric constant, d33 of the prepared samples were in the range of 22–31 pC/N.