Noorhana Yahya

Synthesis of Carbon Nanostructures by CVD Method

The field of nanotechnology continues to develop. Carbon based materials with different structure and dimensions become increasingly important in the field. Carbon nanotubes (CNTs) are particularly promising due to their anisotropic extraordinary electrical, thermal and mechanical properties that have captured the imagination of researchers worldwide. However, the complexity involved in synthesis of nanotubes in a predictable manner has held back the development of real-world carbon nanotube based applications. In this chapter the structure and synthesis methods will be discussed of CNTs and other forms of nanostructures of carbons. Furthermore, their structuring into macroscopic assemblies, like mats and fibres will be presented as it has important role in future industrial applications of these materials.

Cobalt Ferrite Nanoparticles: An Innovative Approach for Enhanced Oil Recovery Application

This Paper Describes the Synthesis of Cobalt Ferrite (CoFe2O4) Nanoparticles and their Application in Enhanced Oil Recovery. Cobalt Ferrite (CoFe2O4) Nanoparticles Were Used as Ferrite Magnetic Feeders with Antenna to Improve the Magnetic Field Strength and Cobalt Ferrite Nanofluid to Improve Oil Recovery. Cobalt Ferrite (CoFe2O4) Nanoparticles Were Synthesized by Sol-Gel Method. these Nanoparticles Were then Characterized by Using X-Ray Diffractometer (XRD) and Field Emission Scanning Electron Microscope (FESEM). Cobalt Ferrite Nanoparticles Annealed at 600oC, the Particle Size Is 51.17nm and 26nm as Determined by XRD and FESEM, Respectively while for the Sample Annealed at 800oC, the Particle Size Is 62nm as Determined by XRD and 60 Nm as Determined by FESEM. Magnetic Measurement Results Show that Initial Permeability of Cobalt Ferrite Powder Increased and Relative Loss Factor Decreased at High Frequency. in Order to Improve the Oil Recovery, Nanoparticles Were Used in Two Different Experiments. in the First Experiment, Nanoparticles Were Used as Magnetic Feeders with an Antenna to Improve the Magnetic Field Strength. in the Second Experiment, Nanoparticles Were Used as Nanofluids. Results Show that the Antenna with Magnetic Feeders Increases the Magnetic Field Strength by 0.94% as Compared to Antenna without Magnetic Feeders in the Water, and by 5.90% in the Air. Magnitude versus Offset (MVO) Study of Antenna with Magnetic Feeders Shows an Increase in Magnetic Field Strength of 275% as Compared to Antenna without Magnetic Feeders. it Is Found that Antenna with Magnetic Feeders Was Able to Recover 29.50% and 20.82% of Original Oil in Place (OOIP) in Core Rock Samples A-1 and A-2 Respectively. the Use of Cobalt Ferrite Nanoparticles as a Nanofluid with Electromagnetic Waves Yielded a Higher Recovery of Residual Oil in Place (ROIP) which Is 31.58% as Compared to 8.70% when it Was Used as Nanofluid Alone. it Is Investigated that due to Absorption of Electromagnetic Waves by Cobalt Ferrite Nanoparticles the Oil Viscosity Reduces which Increase the Oil Recovery. it Can Be Concluded that the Synthesised Cobalt Ferrite (CoFe2O4) Nanoparticles Can Be Potentially Used for Enhanced Oil Recovery in Future.

A compact multiband hybrid meander-Koch Fractal antenna for WLAN USB dongle

There is a current upsurge for the high data rate and wide bandwidth in the communication technologies. This has posed several challenges for the researchers. These challenges include but are not limited to size reduction, high efficiency, and low-cost. The prevailing fashion in the communication system is to integrate several WLAN standards in small user equipment. The emergence of the USB dongle for WLAN has attracted the antenna design engineers to design multi band antennas. The antenna size is restricted to the small size of the USB dongle. The main challenge is to reduce the antenna size without compromising on the performance related characteristics such as; wide bandwidth, low VSWR, high gain and high radiation efficiency. In this paper a novel Koch-meander Fractal antenna has been proposed for the application of WLAN USB dongle. The proposed compact antenna is simulated in CST microwave studio. The simulation results depicts that the antenna has a −10 dB return loss bandwidth of 2.2909–2.553 GHz and 5.1406–5.8737 GHz. The minimum return loss of −28.9 dB is achieved at the lower band of 2.41 GHz. While the upper band depicts a return loss of −20.8 dB at 5.36 GHz. The proposed antenna is capable of covering the whole band required for the WLAN 802.11 a/b/g standards.

Microwave conductivity of sorted CNT assemblies.

Recent progress with tailored growth and post-process sorting enables carbon nanotube (CNT) assemblies with predominantly metallic or semi-conducting concentrations. Cryogenic and microwave measurements performed here show transport dimensionality and overall order increasing with increasing metallic concentration, even in atmospheric doping conditions. By 120 GHz, the conductivity of predominantly semi-conducting assemblies grew to 400% its DC value at an increasing growth rate, while other concentrations a growth rate that tapered off. A generalized Drude model fits to the different frequency dependent behaviors and yields useful quality control parameters such as plasma frequency, mean free path, and degree of localization. As one of the first demonstrations of waveguides fabricated from this material, sorted CNTs from both as-made and post-process sources were inserted into sections of practical micro-strip. With both sources, sorted CNT micro-strip increasingly outperformed the unsorted with increasing frequency-- illustrating that sorted CNT assemblies will be important for high frequency applications.

The Effect of Nanoparticles Crystallite Size on the Recovery Efficiency in Dielectric Nanofluid Flooding

Application of nanotechnology in enhanced oil recovery (EOR) has been increasing in recent years. After secondary flooding, more than 60% of the original oil in place (OOIP) remains in the reservoir due to trapping of oil in the reservoir rock pores. One of the promising EOR methods is surfactant flooding, where substantial reduction in interfacial tension between oil and water could sufficiently displace oil from the reservoir. In this research, instability at the interfaces is created by dispersing 0.05 wt% ZnO nanoparticles in aqueous sodium dodecyl sulfate (SDS) solution during the core flooding experiment. The difference in the amount of particles adsorbed at the interface creates variation in the localized interfacial tension, thus induces fluid motion to reduce the stress. Four samples of different average crystallite size were used to study the effect of particle size on the spontaneous emulsification process which would in turn determine the recovery efficiency. From the study, ZnO nanofluid which consists of larger particles size gives 145% increase in the oil recovery as compared with the smaller ZnO nanoparticles. In contrast, 63% more oil was recovered by injecting Al2O3 nanofluid of smaller particles size as compared to the larger one. Formation of a cloudy solution was observed during the test which indicates the occurrence of an emulsification process. It can be concluded that ultralow Interfacial tension (IFT) value is not necessary to create spontaneous emulsification in dielectric nanofluid flooding.

Current issues and challenges of MIMO antenna designs

The demand for high data rate and channel bandwidth is always the primary area of concern in modern wireless communication systems. All the modern wireless communication system applications are rapidly shifting towards multiple input multiple output (MIMO) from single input and single output (SISO) and single input multiple output (SIMO) systems, increasing the demand for the integration of multiple antennas in the users equipment. The development of MIMO antennas and its performance evaluation for the portable wireless communication terminals have attracted many researchers to improve channel capacity, bandwidth, gain, polarization diversity and reduce coupling between inter elements. Further these systems also demands that the multiple element antenna (MEA) should be minimized so that they can fit in the compact and robust user equipment, and support multiband operation for the equipment reusability in the different regions of the world. Antenna designers have ample vacuum in the development of novel antenna systems for the new generation networks by enhancing the impedance bandwidth and multiband resonance. In addition improving radiation pattern diversity reduces the correlation coefficient and increases MIMO antenna performance. This review paper is focused on the related work in the field of MIMO antenna designs. Researchers have proposed various different techniques to design antennas at a range of microwave bands of interest, where the key concern of the research is to enhance the channel capacity by reducing the correlation coefficient and increasing the isolation between multi element antennas.

Data compression technique for modeling of global solar radiation

This paper studies the use of wavelet transform and curve fitting methods for solar radiation compression and prediction-based modeling. Symlet 6 and Meyer wavelets will be utilized for analyzing the transient nature of solar radiation. The measured solar radiation data will be decomposed up to level 4. After the data has been filtered, curve fitting method will be used to derive the modeling equation to estimate the horizontal global solar radiation. The instantaneous global solar radiation received on the surface of earth in Malaysia on a clear sky day around noon time can be up to 980 W/m2. The amount of solar energy received is highly transient in nature, due to the meteorological conditions. Therefore data captured using electronic data acquisition system is quite dense, and there is a need to filter the data, in order to reduce the amount of dataset. The data is highly useful for the designing of solar energy related electricity generation systems. The accuracy of the predicted output from a photovoltaic (PV) based electricity generation system depends on the accuracy of the intercepted solar radiation. The sizing of the electricity generating system cannot be based on a single power density value. Therefore compressed time based solar radiation values serve as an important input for the designing of a PV based system during the availability of sunshine.

Hardness Improvement of Dental Amalgam Using Zinc Oxide and Aluminum Oxide Nanoparticles

Strength tests of a dental amalgam material were conducted. Zinc oxide and aluminium oxide nanoparticles were used as fillers to enhance the hardness and other mechanical properties of dental amalgam material. The zinc oxide nanoparticles were synthesized by using a sol–gel technique, the samples of which were characterized by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM) and Raman spectroscopy and then mixed with the material and compacted into cylindrical-shaped pellets for green density, compressibility and Vickers hardness evaluation. Increment of 183 % in hardness was observed with average Vickers hardness of 0.95 GPa by using 250 °C zinc oxide as nanofiller. On the other hand, the Al2O3 nanoparticles filled composite observed 1.12 GPa of average Vickers hardness with 229 % of increment as compared to without the fillers. All in all, that the application of Al2O3 nanoparticles as filler result in improved hardness. This work offers the dentistry industry a potential contender in the market place.

Application of ZnO Nanoparticles EM Wave Detector Prepared by Sol- gel and Self-Combustion Techniques

Zinc oxide (ZnO) has found many important applications such as optoelectronic devices, sensors and varistors. The challenging part however is synthesizing ZnO nanoparticles and its utilisation as EM detectors. Sol-gel and self-combustion techniques were chosen in this study due to the ability to produce single phase and nano-size samples. The starting mixture consists of 10 grams of zinc (II) nitrate, Zn(NO3)2.6H2O salt which was dissolved in 50 mL of nitric acid, HNO3.The solution was stirred at 250 rpm continuously for 1 day. The mixture was then gradually heated for every 15 minutes until it combusted at 110oC for the self-combustion technique. For the sol-gel technique, the dissolved mixture was heated at 40oC, 50oC, 60oC and 70oC until the gelatine was formed. After the drying process, the as-prepared samples were annealed at 100oC and 200 oC for 1 hour for each technique. Characterizations were performed by using X-Ray Diffraction (XRD), Raman Spectra and Scanning Electron Microscopy (SEM).The XRD analysis showed a major peak of [101] plane at 2Ө for the self-combustion technique and the sol-gel technique. Raman results for the samples prepared via sol-gel and self-combustion techniques had shown the major peak of ZnO that is located at the Raman shifts of 437.67 cm-1. Using the Scherrer equation, single crystal nano particle of ZnO was successfully obtained in the range of 38.49 nm to 50.70 nm for the sample prepared via the sol gel technique. By the self-combustion technique, the average dimension of the as-prepared sample is in the range of 34-49 nm. Further heat treatment resulted in a major change of the Raman shift corresponding to the single phase ZnO nano particles. The best samples were used as electromagnetic (EM) detectors. The EM detectors are polymer based composite which were prepared using a casting technique.

Synthesis and Characterization of Yttrium Iron Garnet (YIG) Nanoparticles Activated by Electromagnetic Wave in Enhanced Oil Recovery

Due to the geographical location and technological limitation, various novel enhanced oil recovery (EOR) methods has been proposed to recover the remaining oil from a depleted oil reservoir. Research on application of nanoparticles either on its own or coupled with other stimulating agents has been growing enormously and some of them have shown a promising future. In high temperature and high pressure reservoirs, thermal degradation will cause failure to the conventional chemicals. In this work, temperature-stable YIG magnetic nanoparticles with an electromagnetic wave has been proposed as a new candidate for reservoir stimulating agent. The purpose of nanoparticle injection is to increase the sweep efficiency in the reservoir by increasing the viscosity of displacing fluid. In this research, Yttrium iron garnet (YIG) nanoparticles have been injected into a waterflooded oil saturated porous medium to recover the remaining oil in the presence of an electromagnetic wave. At the sintering temperature 1200°C, a mixture of hematite and YIG was obtained, suggesting a higher temperature for single phase YIG. From VSM analysis, the average magnetic saturation, coercivity and remanence are 18.17 emu/g, 21.73 Oe and 2.38 emu/g, respectively. 1.0 wt% of YIG nanofluid was prepared and subsequently injected into the pre-saturated porous medium in the presence of square electromagnetic wave of 13.6 MHz. As much as 43.64% of the remaining oil in place (ROIP) was recovered following the injection of 2 pore volume of YIG nanofluid.