Suraya Abdul Rashid

Dispersion and stabilization of photocatalytic TiO 2 nanoparticles in aqueous suspension for coatings applications

To produce titanium dioxide (TiO2) nanoparticle coatings, it is desirable that the nanoparticles are dispersed into a liquid solution and remain stable for a certain period of time. Controlling the dispersion and aggregation of the nanoparticles is crucial to exploit the advantages of the nanometer-sized TiO2 particles. In this work, TiO2 nanoparticles were dispersed and stabilized in aqueous suspensions using two common dispersants which were polyacrylic acid (PAA) and ammonium polymethacrylate (Darvan C). The effect of parameters such as ultrasonication amplitude and type and amount of dispersants on the dispersibility and stability of the TiO2 aqueous suspensions were examined. Rupture followed by erosion was determined to be the main break up mechanisms when ultrasonication was employed. The addition of dispersant was found to producemore dispersed andmore stabilized aqueous suspension. 3wt.% of PAA with average molecular weight (Mw) of 2000 g/mol (PAA 2000) was determined to produce the best and most stable dispersion. The suspensions were then coated on quartz glass, whereby the photocatalytic activity of the coatings was studied via the degradation of formaldehyde gas under UV light. The coatings were demonstrated to be photocatalytically active.

Polysulfone–Chitosan blend ultrafiltration membranes: preparation, characterization, permeation and antifouling properties

Biocompatible and naturally occurring chitosan was used as an additive for the preparation of a polysulfone ultrafiltration membrane. Two different compositions of polysulfone in N-methylpyrrolidone (NMP) and chitosan in 1% acetic acid were blended to prepare PSf–CS ultrafiltration membranes by the diffusion induced phase separation (DIPS) method. The proper blending of polysulfone and chitosan in PSf–CS membranes was confirmed by ATR-IR analysis. The surface and cross-sectional morphology of the membranes was studied by scanning electron microscopy (SEM). The membrane hydrophilicity was determined by water uptake and contact angle measurements. The PSf–CS membrane showed an enhanced hydrophilicity compared to a PSf ultrafiltration membrane. The time dependent permeation studies revealed the improved flux of PSf–CS membranes. PSf–CS membranes were subjected to bovine serum albumin (BSA) protein rejection studies. An improved antifouling property was observed for PSf–CS blend membranes as compared to pristine PSf ultrafiltration membranes. Both the permeation and antifouling properties of PSf–CS membranes increased with an increase in chitosan composition.

Investigations on the development of the permeability properties of binary blended concrete with nano-SiO2 particles

Water permeability of cement-based concrete has been recognized as a critical intrinsic property highly affecting the durability of reinforced concrete. An experimental study was done, designed to examine the water permeability and setting time of Portland cement mortar with nano-SiO2 admixed at 0.5, 1, 1.5, and 2 wt% of cement. The percentage, velocity, and coefficient of water absorption tests results showed that the incorporation of nano-SiO2 particles improved the water penetration resistance of the binary-blended concrete. Such improvements were especially significant when using 2 wt% of nano-SiO2. The experimental results revealed that the admixing of nano-SiO2 particles not only led to denser cement mortar but also changed the morphology of cement hydration products. Mechanisms were proposed to explain the physicochemical changes induced by the nano-SiO2 particles and the specific surface area of them is demonstrated as one of the key factors. Considering the higher strength and durability is promising their use in binary-blended concrete.

Fe-Doped TiO 2 nanoparticles produced via MOCVD: synthesis, characterization, and photocatalytic activity

Iron (Fe)-doped titanium dioxide (TiO2) nanoparticles were produced via the metallorganic chemical vapour deposition (MOCVD) method at 700°C. Different amounts of ferrocene as the Fe dopant source (0.001-0.05g) were introduced inside the reactor together with the titanium precursor in order to synthesize different Fe dopant concentrations of TiO2 nanoparticles. Nitrogen (N2) adsorption results showed that increasing the Fe dopant concentration caused a slight increase in the surface area of the nanoparticles due to the decrease in nanoparticle size. The UV-diffuse reflectance spectra demonstrated an absorption shift in Fe-doped TiO2 nanoparticles to longer wavelengths, thus showing an enhancement of the absorption in the visible spectrum. Bandgap energy values determined from the UV-diffuse reflectance spectra data decreased with an increase in the Fe dopant concentrations. The photocatalytic activity of Fe-doped TiO2 nanoparticles was investigated via degradation of methylene blue under UV and fluorescent light. It was found that Fe doping reduced the photocatalytic activity of the samples. Based on X-ray photoelectron spectroscopy (XPS) results, it is believed that this is due to the unfavourable location of Fe3+ inside the interior matrix of the TiO2 nanoparticles rather than on the exterior surface, which would affect photocatalytic behaviour.

Dynamic response of tapered optical multimode fiber coated with carbon nanotubes for ethanol sensing application.

Ethanol is a highly combustible chemical universally designed for biomedical applications. In this paper, optical sensing performance of tapered multimode fiber tip coated with carbon nanotube (CNT) thin film towards aqueous ethanol with different concentrations is investigated. The tapered optical multimode fiber tip is coated with CNT using drop-casting technique and is annealed at 70 °C to enhance the binding of the nanomaterial to the silica fiber tip. The optical fiber tip and the CNT sensing layer are micro-characterized using FESEM and Raman spectroscopy techniques. When the developed sensor was exposed to different concentrations of ethanol (5% to 80%), the sensor reflectance reduced proportionally. The developed sensors showed high sensitivity, repeatability and fast responses (<55 s) towards ethanol.

Effects of the surface modification of carbon fiber by growing different types of carbon nanomaterials on the mechanical and thermal properties of polypropylene

The potential usage of different types of carbon nanoparticles in the herringbone, tubular and sheet structures of graphene plates, such as carbon nanofibers (CNF), carbon nanotubes (CNT) and graphene (G) flakes and also CNF–G and CNT–G on the carbon fiber (CF) surface as fillers in composite materials, is discussed in this paper. The combination of 2D graphene of high charge density and 1D CNTs or CNFs of large surface areas generates a versatile 3D hybrid network with synergic properties. A one-step process, chemical vapour deposition technique has been applied to synthesis these carbon nanoparticles (1D, 2D and 3D structures) by use of bimetallic catalyst (Ni/Cu). The morphology and chemical structure of the fibers, which have an effect on the polymer properties, were characterized by means of scanning electron microscopy, transmission electron microscopy, and specially Raman spectroscopy. These techniques were used to identify carbon nanoparticles, access their dispersion in polymers, evaluate filler/matrix interactions and detect polymer phase transitions. Compared with the neat CFs, the synthesized hybrid fibers led to an increase of the BET surface area from 0.7 m2 g−1 to 46 m2 g−1. Besides that, polypropylene (PP) composites with different carbon-based fillers, such as G on CF (CF–G), CNF on CF (CF–CNF), CNT on CF (CF–CNT) and also CF–CNF–G and CF–CNT–G were prepared by the melt mixed method, and the effects of these particles on the mechanical and thermal properties were analyzed. The mechanical results were confirmed by a mathematical model that state the mechanical reinforcement of the resultant composites strongly depends on the type of filler used. Noteworthy, composites based on combination of G and CNT presented the highest mechanical and thermal properties than those based on other carbon nanoparticles.

Particle size effect on the permeability properties of nano-SiO2 blended Portland cement concrete

In this study, nano-SiO2 has been used as a high reactive pozzolan to develop the microstructure of the interfacial transition zone between the cement paste and the aggregate. Mechanical tests of blended cement-based concretes exposed that in addition of the pozzolanic reactivity of nano-SiO2 (chemical aspect), its particle grading (physical aspect) also revealed considerable influences on the blending effectiveness. It was concluded that the relative permeability reduction (relative to the control concrete made with plain cement) is higher for coarser nano-SiO2 after 90 days of moisture curing. However, finer nano-SiO2 particles showed better effects in early ages. These phenomena can be due to the free spacing between mixture particles that was associated with the global permeability of the blended cement-based concretes. This article presents the results of the effects of particle size ranges involved in nano-SiO2 blended Portland cement on the water permeability of concrete. It is revealed that the favorable results for coarser nano-SiO2 reflect enhanced particle packing formation accompanied by a reduction in porosity and particularly in particle spacing after 90 days.

Effect of postdeposition heat treatment on the crystallinity, size, and photocatalytic activity of TiO 2 nanoparticles produced via chemical vapour deposition

Titanium dioxide (TiO2) nanoparticles were produced using chemical vapour deposition (CVD) at different deposition temperatures (300-700°C). All the samples were heat treated at their respective deposition temperatures and at a fixed temperature of 400°C. A scanning electron microscope (SEM), a transmission electron microscope (TEM), and X-ray diffraction (XRD) were used to characterize the nanoparticles in terms of size and crystallinity. The photocatalytic activity was investigated via degradation of methylene blue under UV light. The effects of post deposition heat treatment are discussed in terms of crystallinity, nanoparticle size as well as photocatalytic activity. Crystallinity was found to have a much larger impact on photocatalytic activity compared to nanoparticle size. Samples having a higher degree of crystallinity were more photocatalytically active despite being relatively larger in size. Surprisingly, the photocatalytic activity of the samples reduced when heat treated at temperatures lower than the deposition temperature despite showing an improvement in crystallinity.

Bulk Production of High-Purity Carbon Nanosphere by Combination of Chemical Vapor Deposition Methods

A simple method to produce pure carbon nanosphere (CNS) in high yield using continuous chemical vapor deposition (CVD) technique (combination of floating catalyst CVD and fluidized bed CVD) is proposed. Carbon fiber substrate, acetylene precursor, and Fe catalyst are employed to produce CNS. X-ray diffraction (XRD) and energy dispersive X-ray (EDX) spectrometry confirm the formation of a high percentage of hexagonal carbon. The scanning electron microscopy images reveal spheres that confirm uniform structures. Thermal gravimetric analysis implies that the CNS are free from the carbon fiber substrate as they start to decompose at a lower temperature compared to that of carbon fiber substrate. Under the optimal conditions of 700°C in ambient pressure at 60 min of reaction time and 300 mL/min of acetylene flow rate, CNS with an average diameter of less than 200 nm, 98% purity and yield of 3.07 mg/mg is obtained.

Influence of 15 and 80 nano-SiO2 particles addition on mechanical and physical properties of ternary blended concrete incorporating rice husk ash

This study demonstrates the effects of SiO2 nanoparticles as additives with two different sizes of 15 and 80 nm on compressive strength and porosity of rice husk ash (RHA) blended concrete. Up to 20% of ordinary Portland cement (OPC) was replaced by RHA with average particle size of 5 micron. Also, SiO2 nanoparticles were added to the above mixture at four different weight percentages of 0.5, 1.0, 1.5 and 2.0 and cured in lime solution. The results indicated that compressive strength of Portland cement–nano SiO2–rice husk ash (PC–NS–RHA) ternary blended concrete was considerably increased. Moreover, the total amount of porosity decreased to a minimum with respect to the control concrete. This improvement was observed at all the curing ages and replacement levels, but there was a gain in the optimal point with 20% of RHA plus 2% of 80 nm SiO2 particles at 90 days of curing.