Search

This study reports on synthesis of ZnO nanostructures using Zinc chloride (ZnCl2) as precursors and Potassium hydroxide (KOH) as alkaline source in a solvothermal process with varying molar concentrations (Zn2+/OH-) of 1:1, 1:3 and 1:5 for temperatures of 30 °C and 50 °C. The synthesized nanostructures were characterized by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared (FT-IR) Spectroscopy, and Ultraviolet Visible (UV-Vis) spectroscopy. ZnO nanostructures synthesized at lower ratios (1:1) exhibited wurtzite hexagonal shapes. However, as the concentration ratios increases in both cases, spherical structures were formed with the emergence of some rod-like structures dominating, and finally aggregated to form flower-like structures at 30 °C temperature. The average crystallite size for nanostructures from XRD (30-50 °C) were in the range 15-21 nm whereas the average particle size from TEM analysis (30-50 °C) were in the range 39-76 nm. Increase in temperature and molar concentration of the alkaline source generally decreased the crystallite and particle size of the as well as a decrease in the wavelength of ZnO nanostructures as a result of blue-shifting of the absorption peak. FT-IR spectra of ZnO NSs prepared from concentration ratios of Zn2+: OH- (1:1, 1:3 and 1:5) at 30 °C and 50 °C showed characteristic peak bands at 461-467 cm-1 and 460-462 cm-1 respectively.

In this study, sorption efficiency of coated (C-) and uncoated (U-) zinc oxide nanoparticles (ZnO-NPs) in aqueous solution onto raw sago hampas (RSH) and acetylated sago hampas (ACSH) was studied. Physical and chemical characteristics of both the sorbate and sorbents were analysed using various characterization techniques. The mechanism of the sorption process was evaluated using equilibrium isotherms, kinetic and thermodynamic studies. From the study, maximum percentage removal of both sorbate ions were achieved at an equilibration time of 100 minutes with an optimum sorbate mass of 2.0 g per 50 ml. The study recorded a maximum % removal of 85.1% & 87.6% for C-and U-ZnO-NPs (< 50 nm) onto RSH and 90.0% & 91.1% onto ACSH. Langmuir isotherm fitted well for the sorption process with the highest efficiency of 0.793 mg/g recorded for C-ZnO-NPs onto RSH. Pseudo-second model best described the sorption process. An exothermic and non-spontaneous sorption process was realised in all the sorption studies except that of U-ZnO-NPs (< 50 nm) onto ACSH which became spontaneous as temperature increased. Based on the findings from the multiple approaches employed, both sorbents could be proposed as viable alternatives to act as a green sorbent in the removal of ZnO-NPs from water and wastewater.

This work reports utilised of RGO from Sengon wood biomass to support Fe–N–C noble-free catalyst (Fe–N-RGO), while also attempt to investigate the effect of pyrolysis stage on Fe–N-RGO catalysts with four different nitrogen precursors towards the ORR activity in acidic medium. One- and two-step pyrolysis were performed at 900 °C for 1 h and 2 h respectively to produce Fe–N-RGO. This work revealed that two-step pyrolysis was able to remove the volatile components and hence forming more graphitised, stable graphitic-N and Fe-Nx, synergistically improve the ORR activity with highest onset potential of 0.83 V vs RHE and limiting current density of 5.33 mA cm−2 reported on Fe-Pani-RGO 2py. An increase in the kinetic on Fe-Pani-RGO 2py with Tafel slope of 74 mV/dec operated at 80 °C was reported. The mesoporous structure on RGO increases the stability by 8% and better methanol tolerance when compared to a benchmark Pt/C catalyst.

Nitrogen-doped graphene has been prepared using the ball milling method that is known to be eco-friendly, scalable and economic. The parameters studied in the synthesis were the mass ratio of starting materials (graphite and melamine) and speed of the ball milling. To determine its structure and properties, the nitrogen-doped graphene was characterized using Field Emission Scanning Electron Microscopy with Energy Dispersive X-Ray (FESEM-EDX), RAMAN Spectroscopy and X-Ray Diffraction (XRD). Based on FESEM-EDX analysis, the doped composite exhibited nitrogen content of ~3.5%. The nitrogen-doped graphene was examined as a replacement for platinum catalysts in fuel cells. Different composite catalysts were evaluated using a Rotating Disk Electrode (RDE) to test the Oxidation Reduction Reaction (ORR) performance. Based on ORR performance comparison, the composite with highest performance was then used to fabricate a Membrane Electrode Assembly (MEA). Testing on MEA performance was conducted on a Fuel Cell Station, where Open Circuit Voltage (VOC) of 0.14 V was obtained. The results indicate that the ball milling method may produce an efficient nitrogen-doped graphene MEA electrode from graphite and melamine only. Compared with a platinum counterpart, the new composite material electrode showed soundly high current-potential characteristics and fuel conversion efficiency.

This study aimed to explore the potential application of starch nanoparticles as the nanocarriers for the controlled release of piperine. Starch nanoparticles with mean particle sizes ranging from 50 nm to 200 nm have been synthesised as nanocarriers for encapsulation of piperine. Piperine has been successfully loaded onto starch nanoparticles via the in-situ nanoprecipitation method. The loading capacity of piperine was affected by the synthesis conditions such as types and concentrations of surfactants as well as initial piperine concentrations. Under optimum conditions, starch nanoparticles exhibited a maximum piperine loading capacity of 4.74 mg mg–1. Piperine was observed to release out from starch nanoparticles in a slow and steady manner over a period of 168 h under physiological pH.

Single phase ZnO nanostructures were synthesized by simple and low temperature solvothermal process from two different alkaline sources; Potassium hydroxide (KOH) and Sodium hydroxide (NaOH) with zinc acetate dihydrate (Zn(CH3COO)2∙2H2O) as precursor. This facile and rapid synthesis technique achieve high purity of Zinc oxide (ZnO) nanostructures on large scale negating the use of complex and high temperature routes. The synthesized particles were characterized by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDX), Fourier Transform Infrared (FT-IR) Spectroscopy, Ultraviolet Visible (UV-Vis) spectroscopy and Brunauer-Emmett-Teller (BET) analysis. ZnO synthesized using KOH and NaOH exhibit wurtzite hexagonal and flake-like nanostructures with average crystallite size of 11.0 nm and 14.9 nm respectively. Surface area of 59.50 m2/g and 31.43 m2/g were determined for KOH and NaOH sources respectively. The optical absorption spectra of the two samples showed absorption bands of 367.70 and 365.30 nm. The results showed the effect of alkaline sources on the surface morphology, structural and optical properties of ZnO.

Porous mullite ceramics were produced using mullite precursor and modified cenospheres as a non-sacrificial pore-forming agent. The cenospheres used are aluminosilicate hollow spheres with high silica and alumina content, which are obtained from coal-fired power plant. In this study, the cenospheres were modified using aluminum trichloride hexahydrate (AlCl 3 ·6H 2 O), alkali/acid leaching and heat treatment. Various types and amounts of the modified cenospheres were mixed with mullite precursor to produce porous mullite ceramics for subsequent firing at 1500 °C. Graphite powder, as sacrificial pore-forming agent, was also used to prepare porous mullite ceramics by the same processing conditions for comparison. The study found that the use of graphite powder was unable to increase the porosity of the mullite ceramics as a result of excessive shrinkage. It acted more as a sintering aid rather than as sacrificial pore-forming agent. On the other hand, addition of modified cenospheres as non-sacrificial pore-forming agent leads to the increment of both total porosity and closed porosity, with the reduction of open porosity. The results showed that with the addition of 40 wt% of modified cenospheres to the mullite precursor, the resultant porous mullite ceramic has a total porosity of 50.2%, thermal conductivity of 1.28 Wm −1 K −1 , linear shrinkage of 4%, and biaxial flexural strength of 45.9 MPa. Porous mullite ceramic with majority closed pores has potential application for high temperature thermal barrier.

A novel self-heating hydrogen gas sensor based on zinc oxide nanorods coated on indium tin oxide was fabricated. This sensor utilizes Joule heating effect of indium tin oxide to generate heat, while ZnO acts as a variable resistor to regulate the amount of electric current that passes through indium tin oxide layer upon exposure to oxygen and hydrogen gas. The gas sensor was capable of detecting very low concentration of H2 in air. Hence, for the first time, a new way of gas detection based on sensor temperature variation as the sensing mode was demonstrated.

Grog is an additive material that plays important roles in ceramic making. It improves the fabrication process of green bodies as well as the physical properties of fired bodies. Few low-cost materials and wastes have found their application as grog in recent years, thus encouraging the replacement of commercial grogs with cost-saving materials. Coal fly ash, a combustion waste produced by coal-fired power plant, has the potential to be converted into grog owing to its small particle sizes and high content of silica and alumina. In this study, grog was derived from coal fly ash and mixed with kaolin clay to produce ceramics. Effects of the grog addition on the resultant ceramics were investigated. It was found that, to a certain extent, the grog addition reduced the firing shrinkage and increased the total porosity of the ceramics. The dimensional stability of the ceramics at a firing temperature of 1200 &deg, C was also not noticeably affected by the grog. However, the grog addition in general had negative effects on the biaxial flexural strength and refractoriness of the ceramics.

Pyrolysed Fe-N-C catalysts are foreseen to be promising noble-free cathode catalysts for proton exchange membrane fuel cells. Nevertheless, efforts are required to overcome active site degradation, which is influenced by the meso/macroporous composition of the catalyst and support. Reduced graphene oxide from Sengon wood is seen as a potential support for Fe-polyaniline (Pani) catalysts due to its hierarchical porous structure that depends on N/C ratio. This work reveals that the Fe-N4 moiety serves as the active site, which is confirmed by XPS and first-principles calculations. Fe-Pani-RGO 2:0.2, with the highest content of Fe-N4 and specific surface area, results in the highest ORR activity with Eonset =0.84 V, E1/2 = 0.79 V, and JD = 5.5 mA/cm2. Although micropores are important for hosting the active sites that contribute to high ORR activity, in regard to single-cell performance, the role of meso‑/macropores is crucial for achieving higher overall performance.

In this study, single phase of nickel oxides was synthesized using a feasible precipitation technique. The sample was irradiated by argon ion beams with pulsed plasma of kilojoules energy to induce microstructural changes in the materials before it was assembled on a graphene support as electrocatalyst for oxygen reduction reactions in fuel cell. Physical and electrochemical characterizations have been carried out to study the structure-property relationship of the electrocatalyst. Irradiated graphene supported nickel oxides demonstrated improved catalytic performance for the oxygen reactions due to the increased exposed surface area available as active sites resulting from the structural modification induced by the plasma radiation, apart from the high synergistic effect with graphene.

A study on the levels of uranium (U) in urban soils of Samarahan was conducted to assess the contamination of uranium in the soil. Uranium was extracted from soil samples using aqua regia and extract was analyzed using ICP-OES. Results showed that acidic soils influence the absorption of uranium in soils and the binding of uranium due to the presence of organic matter. The highest concentration of uranium obtained from UM2 with 60 mg kg-1 and the lowest from UM3 with < 0.01 mg kg-1. Based on the contamination factors (CF) and geo-accumulation index (Igeo) calculations, the locations presented from low to high contamination of uranium and fall in Class 0 to Class 3. Most of the concentrations of the studied areas are within the tolerable value which was 23 mg kg−1 for residential lands and 33 mg kg−1 for commercial lands except for UM2 based on the soil quality guidelines. In conclusion, the current U concentrations in soil of Kota Samarahan do not pose any hazardous effect towards the environment and human health.

Solvothermal synthesis has shown to have a great potential to synthesize Zinc Oxide nanoparticles (ZnO NPs) with less than 10 nm size. In this study, we present a rapid synthesis of ZnO NPs in which ZnO NPs with more uniform shape and highly dispersed were synthesized using zinc acetate dihydrate (Zn(CH 3 COO) 2 ∙2H 2 O) and potassium hydroxide (KOH) as a precursor and absolute ethanol as solvent via solvothermal method. Few techniques were exploited to characterize synthesized ZnO NPs including X-ray diffraction (XRD), transmission electron microscope (TEM), Brunauer-Emmett-Teller (BET), energy-dispersive X-ray spectroscopy (EDX), fourier transform infrared (FT-IR) spectroscopy, and ultraviolet visible (UV-Vis) spectroscopy. Synthesized ZnO NPs that were prepared via solvothermal synthesis method at 60 o C for 3 hours exhibited a wurtzite structure with a crystalline size of 10.08 nm and particle size of 7.4 ± 1.2 nm. The UV-vis absorption spectrum has shown peak at 357 nm indicate the presence of ZnO NPs. Hence, better quality with uniform size ZnO NPs can be easily synthesized with reduced amount of time via solvothermal synthesis method rather than using other complicated and lengthy synthesis methods.

In this study, we have demonstrated the humidity sensitivity of graphite pencil marks sensing material drawn on paper. The fabricated sensing devices (sensors) were characterized for their humidity sensitivity by measuring the resistance changes across the pencil marks. In order to improve the humidity sensitivity of the sensing material, ethanol chemical treatment was applied on the pencil marks to increase their surface hydrophilicity. Sensors with different levels of intrinsic resistances were also prepared and tested. Results showed that the ethanol-treated sensors have better humidity sensitivities and the intrinsic resistances of the sensors were directly proportional to their humidity sensitivity. To evaluate this carbon-based sensing material, the humidity sensing characteristics of the pencil graphite were gauged with other forms of carbon materials that have been reported in previous studies, such as carbon quantum dots film, carbon nanoparticles, carbon nanotubes, graphene oxide and graphene.

We report, for the first time, a facile, scalable, and cost-effective method for the synthesis of high-performance and monodispersed hexagonally shaped cobalt oxide platelets supported on iron oxides (Fe3O4 and α-Fe2O3) as the electrocatalyst systems for water electrolysis. The Fe3O4 was synthesized in the absence of an inert environment and organic solvent, using a modified coprecipitation procedure. Fe3O4 nanoparticles of average size 15 nm served as the best catalyst support for Co3O4, in the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). A current density of 10 mA/cm2 was achieved, at −0.36 and 1.64 V for the HER and OER [versus reversible hydrogen electrode (RHE)], respectively, for the Co3O4/Fe3O4 system, in 0.1 M KOH with low total catalyst loading of 250 μg/cm2 (or 100 μgCo3O4/cm2). Compared to those using the same total loading of unsupported Co3O4 catalyst, the overpotentials of Co3O4/Fe3O4 catalyst decreased by 0.22 and 0.06 V for the HER and OER, respectively. Despi...

The solution of poly [(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo [2,1,3] thiadiazol-4,8-diyl)] (F8BT) F8BT/TiO2 nanocomposites were prepared using solution blending methods. The TiO2 contents were fixed between 0 wt% - 35 wt%. Then, the solutions were spin coated at 1000 rpm for 30 s onto glass substrates to form thin film samples. The optical properties of the nanocomposites were determined using UV-Vis spectroscopy and photoluminescence spectroscopy. The absorption properties of the thin film increased due to existence of intermediate energy band which lead to higher space charge regions for electron insertion. Besides that, the λmax for absorption and emission spectrum were systematically shifted due to incorporation of TiO2 NPs indicating an interaction between nanoparticles and polymer matrix. Furthermore, the intensity of the emission spectrum were enhanced in the presence of TiO2 NPs. This is due to the existence of TiO2 NPs which trapped more electrons at the interface F8BT/TiO2, resulted production of higher number of exciton formation in the nanocomposirte samples.

Electrochemical route has been a favorite technique for the fabrication of ZnO as it is relatively cheap and capable of producing abundance amount of materials. In this paper, we investigate the morphologies of hydrothermally synthesized ZnO structures assisted by galvanic process on conducting Au-coated silicon substrate. To induce the galvanic process, the substrate was in contact with aluminum so that the difference in the reduction potentials between the two materials provided the driving force for the formation of the ZnO structures. The galvanic process was found to promote compact and anisotropy growth of ZnO nanorods along the (001) plane. It was also found that substrate orientations in the electrolyte solution had an important bearing on the morphologies of ZnO. Well aligned periodic hexagonal arrays of ZnO nanorods of homogeneous diameters were obtained on gold-coated Si substrate with face-down orientation in the electrolyte solution.

Kualiti membran AAO yang disediakan melalui teknik penganodan dua peringkat adalah sangat dipengaruhi oleh pra-pembentukan cekung yang dihasilkan semasa penganodan pertama. Kajian ini dijalankan untuk menentukan tempoh penganodan yang optimum bagi menghasilkan cekung yang berkualiti. Penganodan dilakukan menggunakan larutan 0.3 M H2C2O4 sebagai elektrolit dengan beza keupayaan dan suhu masing-masing ditetapkan pada 40 V dan 18°C. Proses penganodan dilakukan sehingga 6 jam. Perubahan nilai arus sepanjang tempoh penganodan direkodkan. Selepas penyingkiran lapisan oksida, kualiti cekung yang terbentuk dikaji menggunakan FESEM. Mikrograf FESEM mengesahkan pembentukan cekung berstruktur heksagon adalah seragam. Selain memperbaiki keseragaman, pertambahan tempoh penganodan telah membentuk cekung yang lebih jelas, tersusun serta kecacatan yang minimum. Keputusan kajian mendapati bahawa tempoh optimum bagi mendapatkan cekung yang seragam dan sempurna adalah antara 4 dan 6 jam. Ini kerana pertambahan tempoh penganodan seterusnya akan menyebabkan keruntuhan dinding cekung yang akhirnya menjadi punca kepada pembentukan liang yang bersentuhan antara satu sama lain. Selain itu, mekanisma penghasilan bentuk cekung turut dibincangkan.

The electrochemical processes in current fuel cell is still relying on high-loading of scarce and expensive precious metals such as Pt as electrocatalysts for device operation which hinder their commercialization Thus, there is a critical need in search of non-precious metal-based electrocatalysts to replace these precious metals. In view of its corrosion resistant advantage and low production cost, non-precious metal oxides have been recognized as the potential candidates for electrocatalysts in fuel cell. In this study, the aim was to develop a stable catalyst based on transition metal oxides using a simple and cheap modified precipitation technique. Three types of transition metal oxides, namely the cobalt oxides, nickel oxides and iron oxides, were synthesized and a systematic study on the physicochemical properties of the materials are carried out using X-ray diffraction (XRD), Raman spectroscopy and field emission scanning electron microscopy (FESEM). It was observed that cobalt oxide was grown as porous hexagonal platelets while iron oxides and nickel oxides were grown as nanosized particles. The role of the microstructural properties of these transition metals in enhancing their catalytic performance is discussed.

The aim of this study is to produce noble-metal-free oxygen reduction reaction (ORR) catalyst via irradiation. Gamma ray irradiation reduction has been utilized to produce N-doped reduced graphene oxide (rGO)-supported iron (Fe)-based catalysts, whose weight percent (wt.%) of Fe loading varies from 10% to 20%. In this study, the physicochemical properties of Fe/N-rGO with various loadings of Fe (10 wt.%, 15 wt.% and 20 wt.%) were explored through X-ray diffraction (XRD), field emission scanning electron microscopy-energy dispersive spectroscopy (FESEM-EDS), Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). XRD showed that a broad-peak nanocrystallite Fe2O3 phase formed. Raman spectroscopy revealed that Fe insertion increased the disordered GO structure. Fourier transform infrared (FTIR) demonstrated that N was functionalized into rGO. FESEM-EDX presented that Fe nanoparticles existed on the wrinkled rGO surface but their amount was low. Linear sweep voltammetry (LSV) was performed with a rotating disk electrode in 0.1 M KOH at a scanning rate of 20 mVs&minus, 1 and revolution rates of 400, 900 and 1600 rpm and the corresponding electron transfer numbers were investigated with a Koutecky&ndash, Levich model. This model indicated that the number of electron transfers of 20% Fe/N-rGO was above 2 and its performance toward ORR was higher than those of 10% Fe/N-rGO and 15% Fe/N-rGO.

In this work, both the binary BiTe and ternary BiSbTe nanowires were synthesized using template-assisted electrodeposition. Stoichiometric depositions of the nanowires were achieved via systematic study on compositional change as a function of applied potential. Electrical and thermal transport properties of the nanowires were studied using a custom-designed suspended micro-electro-thermal system. Thermoelectric test modules constructed from pairs of p- and n-types BiTe based nanowire arrays thermocouples were demonstrated to produce a power output of ∼ 0.36 nW per a pair of P-N thermocouples at a maximum temperature difference of ∼ 50 K.

The capability of zinc oxide (ZnO) as a hydrogen sensing element has been pushed to its limits. Different methods have been explored to extend its sensing capability. In this paper, we report a novel approach which significantly improves the hydrogen sensing capability of zinc oxide by applying a bias voltage to ZnO nanorods as the sensing elements. Zinc oxide in the form of aligned nanorods was first synthesized on an Au-coated Si(111) substrate using a facile method via the galvanic-assisted chemical process. The sensing performance of the zinc oxide nanorods was investigated in response to the applied biasing voltage. It was found that the sensitivity, response time and detection limit of the ZnO sensing elements were dramatically improved with increasing bias voltage. A 100% increment in sensing response was achieved for the detection of 2000 ppm hydrogen gas when the bias voltage was increased from −2 to −6 V with 70% reduction in response and recovery times. This remarkable sensing performance is attributed to the reaction of hydrogen with chemisorbed oxygen ions on the surface of the ZnO nanorods that served as the electron donors to increase the sensor conductance. Higher reverse bias voltages sweep the electrons faster across the electrodes. This shortened the response time and, at the same time, depleted the electrons in the sensor elements and weakens oxygen adsorption. The oxygen ions could then be readily removed by hydrogen, leading to a higher sensitivity of the sensors. This, therefore, envisages a way for high-speed hydrogen gas sensing with high detection sensitivities.

Palladium nanowires are good candidates for hydrogen sensing due to the many advantages. In this paper, we discuss the controlled growth of palladium nanowires into the nanopores of anodized alumina oxide (AAO) via template-assisted electrodeposition. This technique provides precise control for the dimensional growth of Pd nanowires. The potential range for electrochemical deposition of palladium nanowires was determined by Linear Sweep Voltammetry (LSV). Crystallinity and microstructural studies of the palladium nanowires were carried out using X-ray diffractometry (XRD) and scanning electron microscopy (SEM) as characterization tools. Systematic study on nanowire alignment across 3 µm-gaps between pairs of microfabricated gold electrodes was carried out using a.c. dielectrophoresis technique. Optimized conditions for good nanowire alignment were reported.

In this work, palladium surface-functionalized single-walled carbon nanotubes (SWNTs) hydrogen gas sensor was fabricated by electrodeposition and its sensing properties were systematically studied under various conditions. The diameter and density of the Pd nanoparticles were optimized by tuning the deposition voltage and time. Using a microfabricated chip consisting of a circular array of 16 individually addressable Pd-functionalised nanosensors, the gas sensing performance for each nanosensor was evaluated sequentially via a customized multiplexer-coupled electronic measurement system with Labview program control. The sensing properties were optimized for high sensitivity and short response time with respect to hydrogen detection. Sensor formed from non-connected chains of Pd particles was found to exhibit excellent sensing properties with resistance change exceeding 60% in 2000 ppm of hydrogen and lowest detection limit of 30 ppm hydrogen. The response time increased from a few minutes to tens of minutes with decreasing hydrogen concentrations.

Porous alumina films are widely used as templates for fabricating one-dimensional (1-D) nanostructures such as nanowires or nanotubes. Using a two-step anodisation process, we have successfully optimized the growth conditions for fabricating highly ordered porous alumina films with pore diameters ranging from 20 to 150 nm, to be used as templates for 1-D nanostructure synthesis. The effects of the anodisation conditions on pore structure and the formation rate of the films were systematically studied. It was found that low electrolyte temperatures and agitations decreased the growth rate of the films but favored the process of pore ordering. Removal of oxide layer formed from first anodisation process and removal of barrier oxide at pore ends had an important bearing on pore morphology. Besides the stand-alone porous alumina films, we have also fabricated porous alumina films on rod-shaped Al substrates.

Some industrial wastes are shown to be useful in the production of mullite ceramics. These industrial wastes are rich in certain metal oxides such as silica (SiO2) and alumina (Al2O3). This gives wastes the potential to be used as a starting material source for mullite ceramics preparation. The purpose of this review paper is to compile and review various mullite ceramics preparation methods that utilized a variety of industrial wastes as starting materials. This review also describes the sintering temperatures and chemical additives used in the preparation and its effects. A comparison of both mechanical strength and thermal expansion of the reported mullite ceramics prepared from various industrial wastes were also addressed in this work.

In this study, we report the fabrication of nanoporous aluminum oxide film from high purity aluminium foil via a two-step anodisation process controlled by a constant direct current potential ranging from 40 60 V from a DC power supply. The anodisation process was conducted at 20˚C in an electrochemical cell with the Al foil acting as anode, Pt as cathode and an acidic bath as electrolyte. Porous aluminium oxide films of pore diameters ranging between 30 90 nm were successfully fabricated. The morphologies and phase compositions of the anodized porous alumina films were investigated using scanning electron microscopy (SEM) and x-ray diffraction (XRD) for characterizations.

Large-area randomly-oriented silicon nanowires (SiNWs) were synthesized using Au-coated p-type Si (100) substrates via the solid-liquid-solid (SLS) process under different growth conditions. Microstructural studies on the NWs produced showed that straight crystalline nanowires of large aspect ratios were generally obtained at a growth temperature of 1000°C along with some worm-like amorphous structures. Large-area vertically aligned silicon nanowire (SiNW) arrays on p-type (001) Si substrates were also synthesized in an aqueous solution containing AgNO3 and HF by self-selective electroless etching. Diameters of the SiNWs produced from both methods varied from 50 nm to 350 nm and their lengths generally extended from several to approximately a few tens of µm depending on the growth conditions used. Te-Si and Bi2Te3-Si core-shell structures were subsequently obtained via galvanic displacement of SiNWs in acidic HF electrolytes containing HTeO2+ and Bi3+/HTeO2+ ions. The reactions were basically a nanoelectrochemical process due to the difference in redox potentials between the materials. The modified SiNWs of core-shell structures had roughened surface morphologies and, therefore, higher surface-to-bulk ratios compared to unmodified SiNWs. They should have potential applications in sensors, photovoltaic and thermoelectric nanodevices. Microstructural studies on the SiNWs and core-shell structures produced are presented using various microscopy, diffraction and probe-based techniques for characterization.

The science of biomimicry has served as a fusion point between nature and technology where one could adopt nature’s best solution for human’s use. Lotus leaf, for example, possesses self-cleaning capability due to the unique physical and chemical properties of its surface structural features. In this work, we aimed to mimic these features on glass surface using ZnO nanostructures to achieve the self-cleaning functionality. A series of ZnO films were electrochemically deposited on indium-doped tin oxide (ITO) conducting glass substrates from different aqueous electrolytes at systematically varied deposition potentials and electrolyte conditions. The surface morphology, density, orientation and aspect ratio of the ZnO micro/nanostructures obtained were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). ZnO ranging from two dimensional plate-like to one-dimensional needle-like micro/nanostructures were observed. Results from these studies show that lower electrolyte concentrations tend to favor one-dimensional growth of ZnO nanostructures that self-assembled into micron-size flower-like clusters at higher deposition temperatures. The ZnO-modified hierarchical dual-structured surface exhibits superhydrophobic property with water contact angle as high as 170o.

This paper reports on the process developed to fabricate anodic aluminum oxide (AAO) templates suitable for the fabrication of nanowires arrays. Anodization process has been used to fabricate the AAO templates with pore diameters ranging from 15 nm to 30 nm. Electrodeposition of parallel arrays of high aspect ratio nickel nanowires were demonstrated using these fabricated AAO templates. The nanowires produced were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that the orientations of the electrodeposited nickel nanowires were governed by the deposition current and electrolyte conditions.

Silicon nanowires (SiNWs) were first synthesised using Au coated p type Si (100) substrate via the solid–liquid–solid (SLS) process. The growth parameters were selectively varied to achieve various stages of growth for studying their effects on the morphology and microstructures of the nanowires (NWs). The SLS growth of SiNWs is discussed in the context of the experimental conditions used. Straight NWs of large aspect ratios, good crystallinity and morphology were generally obtained at a growth temperature of 1000°C along with some worm-like amorphous structures. Te–Si NW core–shell structures were subsequently obtained via post-growth galvanic displacement of the SiNWs in an acidic HF electrolyte containing ions. The core–shell structures obtained were decorated with Te nanoparticles. This increases the NW surface areas and should have great potential in non-reflecting, photovoltaic and thermoelectric applications. Growth study on the SiNWs and Te–Si core–shell structures is presented using vario...

Magnetic multilayered nanowires, such as NiFe/Cu and Co/Cu, exhibit perpendicular giant magnetoresistance, which has potential applications in sensors and high density data storage devices. This work focuses on the synthesis of magnetic multilayered nanowires using three-electrode cells and the potentiostatic pulse technique. Porous alumina templates with well defined pore size were used to synthesise arrays of oriented nanowires with controlled shape and size. Cyclic voltammetry experiments were first performed to optimise the deposition potentials for individual layers, and the compositions of the electrolytes were optimised to yield uniformity in composition and characteristics of the nanowires. Nanowires of good layering quality and uniformity have been successfully obtained using appropriate deposition conditions and electrolyte compositions. Characterisation of the nanowires was carried out using SEM, TEM and X-ray diffraction, and their magnetic properties were studied using a vibrating sam...

Permalloy (Ni80Fe20)/Cu multilayered nanowires (NWs) were potentiostatically electrodeposited within the nanopores of anodized alumina from sulfate baths via pulse technique. Microstructures and compositions of the nanowires were characterized using various microscopy and spectroscopy techniques. The effects of deposition potential and concentration of metal ions were optimized to reduce composition inhomogeneity and incorporation of copper in the permalloy layers. Composition of the NiFe layers was found to be close to 20% Fe with maximum 5% Cu. Our experimental observations show that individual nanowires exhibit distinct and coherent layering structure with rough and wavy interfaces. Synthesized single nanowires was also AC dielectrophoretically assembled across microfabricated gold electrodes for subsequent magnetoresistance measurement.