Norani Muti Mohamed

Integrated PV based solar insolation measurement and performance monitoring system

The focus of this project is to develop a PV monitoring system that requires the development of mathematical model to estimate the solar insolation based on PV output power. The sustainability and reliability of PV based electricity generating system depends on the solar insolation, and optimization is important to meet the demand of the load. It is important to measure solar insolation in order to obtain an optimum PV sizing and also the system must be attached to a monitoring unit. The monitoring unit will be able to give feedback, so that the performance of the system is kept at optimum level. The relationship between solar insolation and output voltage of PV module was determined by using suitable experimental set up, and the modeling equation was used to determine the level of solar insolation. Monitoring software was developed using Visualbasic.Net together with hardware package, which can transfer the voltage signal from the PV panel to the computer. The integrated system can be used by multiple users to remotely monitor the performance of the PV system via internet.

Core–Shell Vanadium Modified Titania@β-In2S3 Hybrid Nanorod Arrays for Superior Interface Stability and Photochemical Activity

Core-shell rutile TiO2@β-In2S3 and modified V-TiO2@β-In2S3 were synthesized to develop bilayer systems to uphold charge transport via an effective and stable interface. Morphological studies revealed that β-In2S3 was deposited homogeneously on V-TiO2 as compared to unmodified TiO2 nanorod arrays. X-ray photoelectron spectroscopy (XPS) and electron energy loss spectrometry studies verified the presence of various oxidation states of vanadium in rutile TiO2 and the vanadium surface was utilized for broadening the charge collection centers in host substrate layer and hole quencher window. Subsequently, X-ray diffraction, high-resolution transmission electron microscopy, and Raman spectra confirmed the rutile phases of TiO2 and modified V-TiO2 along with the phases of crystalline β-In2S3. XPS valence band study explored the interaction of valence band quazi Fermi levels of β-In2S3 with the conduction band quazi Fermi levels of modified V-TiO2 for enhanced charge collection at the interface. Photoelectrochemical studies show that the photocurrent density of V-TiO2@β-In2S3 is 1.42 mA/cm(2) (1.5AM illumination). Also, the frequency window for TiO2 was broadened by the vanadium modification in rutile TiO2 nanorod arrays, and the lifetime of the charge carrier and stability of the interface in V-TiO2@β-In2S3 were enhanced compared to the unmodified TiO2@β-In2S3. These findings highlight the significance of modifications in host substrates and interfaces, which have profound implications on interphase stability, photocatalysis and solar-fuel-based devices.

Breakdown voltage reduction by field emission in multi-walled carbon nanotubes based ionization gas sensor

Ionization gas sensors using vertically aligned multi-wall carbon nanotubes (MWCNT) are demonstrated. The sharp tips of the nanotubes generate large non-uniform electric fields at relatively low applied voltage. The enhancement of the electric field results in field emission of electrons that dominates the breakdown mechanism in gas sensor with gap spacing below 14 μm. More than 90% reduction in breakdown voltage is observed for sensors with MWCNT and 7 μm gap spacing. Transition of breakdown mechanism, dominated by avalanche electrons to field emission electrons, as decreasing gap spacing is also observed and discussed.

The Role of Al2O3 Buffer Layer in the Growth of Aligned CNTs

Carbon nanotube (CNT) can be thought of as a hexagonal network of carbon atoms that has been rolled up to make a seamless cylinder. If they are consisting of one layer, they are termed singled-walled CNTs (SWNTs) while if there are multiple walls, they are called multi-walled CNTs (MWNTs). For most functional devices application, an aligned arrangement of CNTs is desired. Aligned multiwalled carbon nanotubes (MWNTs) have been successfully grown by the inclusion of a buffer layer of oxidized Al. An Al2O3 layer has been proven to be an important contributing factor towards obtaining good quality aligned CNTs. In this work, Al is deposited onto the Si wafer using electron beam evaporation and later oxidized by heating in air. A thin layer of iron catalyst is then deposited on top of the oxidized Al layer and annealed at 400oC. The result shows an improvement in the intensity of the graphitization peak (G-band) in the Raman spectra and aligned MWNTs is observed in these samples compared to the ones that have undergone the same process parameter except the Al2O3 layer.

Effect of ferrocene concentration on the quality of multiwalled CNTs grown by floating catalytic chemical vapor deposition technique

Controllable synthesis of quality carbon nanotubes is a precondition for their broad applications. The objective of the work was to study the effect of catalyst concentration on the quality, diameter, length, alignment and crystallinity of the grown multiwalled carbon nanotubes (MWCNTs). To meet the stated objective, MWCNTs were successfully synthesized by using floating catalytic chemical vapor deposition technique. The ferrocene concentration was varied from 0.1 to 0.2 g and MWCNTs were synthesized with ethylene as a carbon precursor at reaction temperature of 850 ◦ C. The grown MWCNTs were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The obtained data revealed that an increase in concentration of the ferrocene significantly affects the diameter, crystallinity and growth of nanotubes, however, negligible effect on the CNTs forest length was noticed. The dense, uniform and meadow like patterns of grown CNTs were observed for 0.15 g ferrocene. The average diameter of the grown CNTs was ranged from 32-75 nm. Above 0.15 g ferrocene, some of the grown CNTs were found defective and few black spots were also appeared in TEM images.

Effect of different catalyst deposition technique on aligned multiwalled carbon nanotubes grown by thermal chemical vapor deposition

The paper reported the investigation of the substrate preparation technique involving deposition of iron catalyst by electron beam evaporation and ferrocene vaporization in order to produce vertically aligned multiwalled carbon nanotubes array needed for fabrication of tailored devices. Prior to the growth at 700°C in ethylene, silicon dioxide coated silicon substrate was prepared by depositing alumina followed by iron using two different methods as described earlier. Characterization analysis revealed that aligned multiwalled carbon nanotubes array of 107.9 µm thickness grown by thermal chemical vapor deposition technique can only be achieved for the sample with iron deposited using ferrocene vaporization. The thick layer of partially oxidized iron film can prevent the deactivation of catalyst and thus is able to sustain the growth. It also increases the rate of permeation of the hydrocarbon gas into the catalyst particles and prevents agglomeration at the growth temperature. Combination of alumina-iron layer provides an efficient growth of high density multiwalled carbon nanotubes array with the steady growth rate of 3.6 µm per minute for the first 12 minutes and dropped by half after 40 minutes. Thicker and uniform iron catalyst film obtained from ferrocene vaporization is attributed to the multidirectional deposition of particles in the gaseous form.

A review of nanostructured based radiation sensors for neutron

Currently radiation sensors with various mechanisms such as radio thermo luminescence, radiographic and radiochromic film, semiconductor and ionization have been used for the detection of nuclear radiation. Sensitivity, handling procedure, heating condition, energy response, nonlinearity, polarization, non-uniform electric field, high bias voltage and spatial resolution due to large physical size are some of the key issues faced by these sensors. Due to the excellent electrical and mechanical properties, nanostructured materials such as carbon nanotubes (CNTs) have been researched as sensing elements in the sensors to overcome the mentioned problems. However CNTs are found to pose different problems, arising from the uncontrolled helicity and small cross-sectional area. Therefore, alternative sensing elements are still been sought after and the possibility of using boron nitride nanotubes for sensing neutron is considered in this review.

Carbon nanotube-graphene composite film as transparent conductive electrode for GaN-based light-emitting diodes

Transparent conductive electrodes (TCE) made of carbon nanotube (CNT) and graphene composite for GaN-based light emitting diodes (LED) are presented. The TCE with 533-Ω/□ sheet resistance and 88% transmittance were obtained when chemical-vapor-deposition grown graphene was fused across CNT networks. With an additional 2-nm thin NiOx interlayer between the TCE and top p-GaN layer of the LED, the forward voltage was reduced to 5.12 V at 20-mA injection current. Four-fold improvement in terms of light output power was observed. The improvement can be ascribed to the enhanced lateral current spreading across the hybrid CNT-graphene TCE before injection into the p-GaN layer.

Sizing and designing a stand-alone photovoltaic electricity generation system using a customized simulation program

The electricity consumption in Malaysia has been rising steadily over the last decade and electricity demand has been projected to increase by 4 – 5 % per annum for the next five years. The increase in electricity demand in the years to come only means that more fuel is needed to generate the amount of electricity needed to meet demand. However, a disturbing fact is that electricity generation in our nation is still largely dependent of the combustion of fossil fuels. Concerns and issues tied to these fuels are raising interest in the utilization of alternative energy sources such as solar energy for electricity generation. The stand-alone photovoltaic electricity generation system (PVEGS) needs to be sized and designed properly prior to system set up. Since setting up a PVEGS is rather extensive and complicated, a simulation program that performed system sizing and designing prior to implementation was necessary. A simulation program was developed in MATLAB and is customized for the Malaysian context. In this paper, the sizing and designing of a stand-alone PVEGS for a small household load performed using the locally acclimatized simulation program is discussed. The site selected for this study is Ipoh. The life-cycle cost (LCC) analysis of the system is also reviewed to estimate the cost of the proposed PVEGS. The thorough sizing, designing and costing method discussed in this paper encourages the use of PVEGSs to meet our electricity needs especially for rural electrification.

Upgrading of Pyrolysis Bio-Oil to Fuel over Supported Nanomaterials - A Review

Upgrading of bio-oil obtained from pyrolysis of biomass is one the most attractive way to produce fuel both in technological and economical aspect. Development of cost-effective, long life and highly active catalyst is a major challenge in this concern. Addition of support material to the nanocatalyst not only increases the life span of the catalyst but also offers more active sites as well as reduces the cost by lowering the amount of active metal used. Moreover, selection of appropriate support favors efficient dispersion of the active phase. The main focus of this review article is to look into the development of supported nanocatalysts in the past few decades, comparing catalytic performance and deactivation rate of catalysts in the upgrading of bio-oil to produce a value-aided and efficient transportation fuel. Overall, appreciable work has been done to improve the hydrodeoxygenation reaction using different nanosized rare earth metal support materials with enhanced catalytic efficiency and finally need to be implemented in industries for upgrading of pyrolysis bio-oil.