Advanced Materials Research Vol. 925

Abstract: Ferro-cement is a type of thin reinforced concrete made of cement-sand mortar mixture with closely spaced of relatively small diameter wire meshes. The main aim of this work was to study investigate the behavior of Ferro-cement slabs under impact loading. A total of 36 Ferro-cement slabs were constructed and tested under low velocity impact, The main parameter considered in the present investigation was number of wire mesh layers, content of (SBR) polymer and height of falling mass (falling velocity). A special testing rig was used to achieve the impact forces using a falling mass (1300 gm steel ball) dropped from (2.5, 1.2 and 0.83 m) height. (500 ×500×50 mm) slabs were used for each test. The polymer (SBR) was used as a ratio by weight of cement of 3%, 5% and 10%. The number of required blows for caused the first crack and final failure was recorded. The results exhibited that the number of blows which were required to make the first crack and failure, increased with increase of polymer content and number of wire mesh layers.

Abstract: The objective of this study was to investigate the effects of process variables on size of chitosan-alginate capsules produced through extrusion-dripping method. Chitosan-calcium chloride solution was extruded into sodium alginate to form chitosan-alginate capsules which have a defined inner core and membrane. The results showed that sodium alginate concentration, chitosan concentration, chitosan to calcium chloride concentration ratio, needle diameter, gelation time have significant effect on the diameter and membrane thickness of chitosan-alginate capsules. Under the tested condition, chitosan-alginate capsules with diameter in a range of 3.4 mm to 4.5 mm were produced. The membrane thickness of the capsules increased when the curing time increased from 5 min to 60 min. As the concentration of sodium alginate (0.3-0.9 %w/v) and chitosan (0.4-1.0 %w/v) increased, the diameter of the chitosan-alginate capsules increased. The diameter of chitosan-alginate capsules increased with decreasing the chitosan to calcium chloride concentration ratio (1:0.5-1:1.5).

Abstract: Multi-walled Carbon Nanotubes (MWCNTs) coupled with TiO₂ nanoparticles was successfully synthesized using sol-gel method at room temperature. Titanium isopropoxide and MWCNTs were selected as starting materials. The presence of anatase TiO₂ phase in the MWCNTs/TiO₂ composites was determined by XRD analysis. In addition, FTIR analysis was conducted to determine the chemical bonding of MWCNTs/TiO₂ composites. Interestingly, it was found that the shifting of absorption edges of TiO₂ nanoparticles towards to the visible-light region due to the incorporation of MWCNTs using UV-Visible spectroscopy. The photocatalytic activity of MWCNTs/TiO₂ nanocomposites was demonstrated by the Rhodamine B degradation.

Abstract: In this paper, flat sheet polysulfone (PSF) membrane and polysulfone/montmorillonite (PSF/MMT) mixed matrix membranes with different MMT contents were prepared by dry-wet phase inversion method. N-methyl-2-pyrrolidone (NMP) and deionized water were used as a solvent and coagulant, respectively. The morphology and structure of membranes were analyzed by scanning electron microscope. Thermogravimetric analysis was also performed to examine the thermal decomposition of the synthesized membrane. Results showed that MMT had a good dispersion in the PSF matrix.

Abstract: Mesoporous materials are favorable for enzyme immobilization due to their unique properties of large surface area, uniform pore system and functionalizable surfaces. Immobilization on these materials enhances enzyme stability, activity and resistance towards harsh environmental conditions such as temperature and pH. The present study deals with synthesis of mesoporous materials namely MCM-41. For that purpose, the MCM-41 was synthesized using cetyltrimethylammonium bromide (CTAB) as a template and extractable silica from rice husk ash as a silica source. The synthesis was performed under alkaline conditions to produce white fine solid particles, followed by grafting with 3-aminopropyltriethoxysilane and activation with carbodiimide before it was immobilized with lipase. Characterization of those fine particles using Nitrogen physisorption gives BET surface area, a_{s BET}, and the pore diameterto be 1184 m²/g and 2.58 nm respectively. Fourier Transform Infrared spectra show peak of SiO₂, NH₂ and COOH functional group which confirms the existence of those compounds in covalent bonding formation between amine-grafted MCM-41 and lipase enzyme. Immobilized enzyme shows an increase in pH stability when compared to free enzyme at fixed temperature of 20°C in time range from 30 to 180 minutes.

Abstract: The application of nanomaterials in cement by replacement method in concrete is becoming a trend in cement research. The utilisation of nanosilica, nanoalumina, titanium oxide and others are proven to enhance properties of concrete. The major effect of nanomaterials is its size in which it contributes to the packing theory due to increase in the surface area. nanokaolin which comes from kaolin, was tansformed to the nanoform by using high energy milling. The process of developing nanokaolin by using high energy milling is referred to process top to bottom approach in nanoprocessing technique. In this research, the nanokaolin will be used as an additive in cement by 7% weight of cement. Four (4) cement replacement materials catered by using metakaolin on weight basis from 0, 10%, 20% and 30% will also be adopted. To determine the fresh state, cement paste contains nanokaolin and metakaolin are tested its standard consistency and setting time. The effect of the inclusion of the nanokaolin as additive in cement paste that also contains metakaolin as cement replacement material will be investigated. It was found the inclusion of 7% nanokaolin increases the water demand of the cement paste level of metakaolin replacement. In addition to that, the setting time namely initial and final set was been delayed as compared to that of plain OPC. The nanoparticles of nanokaolin and also finer particles of metakaolin increase the surface area and refining the internal structure of cement paste which reduce the flow capabilities of cement paste containing nanokaolin and metakaolin.

Abstract: Ultraviolet-A (UVA) radiation is present in sunlight and have been associated with various types of human skin cancers. In this study, rubber-grade zinc oxide (ZnO) powder was used as the targeted materials to study its UVA photoresponse as well as its antibacterial function. ZnO powder was synthesized using French process. The morphological structures of the samples were investigated using field emission scanning electron microscopy and transmission electron microscopy. The dominant morphology of the sample was micro/nanoplate. The optical bandgap of the ZnO sample is 3.19 eV based on the UV-Visible measurement. Current-voltage measurement was conducted to study the effect of UVA (390 nm) illumination on the photoconductivity of the ZnO pellet. Photoconductivity was observed to increase significantly under UVA exposure due to light absorption on the surface of ZnO to raise the electrons across the bandgap. The current response of the UVA-induced also revealed the small persistent photoconductivity after the UVA light was turned off. Besides, higher voltage bias would lead to higher current flow under the same intensity of UVA exposure. According to the antibacterial test towards Staphylococcus aureus, the percentage inhibition of the bacterial after 24 h incubation increase when the concentration of ZnO suspension increases. The UVA illumination had improved the inhibition of the bacterial growth. This is due to the excitation of ZnO and increasing of free charge carriers in the solution, leading to potential distortion to the membrane surface of the bacteria. ZnO powder performed high absorption of UVA and they are not only can be used to block the UVA sunlight, but also have higher antibacterial capability under UVA excitation.

Abstract: Catalytic oxidation of alkyl substituted benzenes is an essential route for the synthesis of a number of important chemicals, perfumes, drugs and pharmaceuticals. The oxidation products of ethyl benzene are important precursors for a wide range of pharmaceuticals and synthetic materials. Acetophenone and 1-phenylethanol are two oxidation products of ethyl benzene which are the precursors of optically active alcohol, benzalacetophanones, hydrazones and so on. However, the oxidations of alkyl substituted benzenes have been remaining a challenging task. This is because of the limitations of an appropriate catalyst and requirement of corrosive chemical treatments (potassium permanganate/dichromate and ammonium cerium nitrate) which are hazardous and environmentally unfriendly. The current industrial practice in the oxidation of ethyl benzene unfortunately involves high temperature thermal autoxidation in the absence of catalysts. Although few catalysts have been tested for the oxidation of ethyl benzene, many of them found to be inefficient. For example, cobalt (II) oxide-immobilized on mesoporous silica (Co/SBA-15) was used to catalyze oxidation of alkyl benzene at high temperature (125-150°C) but only 70% conversion was obtained after prolong treatment at 150°C. Additionally, the catalyst formed mixed uncontrolled oxidation products like 1-phenylethyl hydro peroxide, benzoic acid, acetophenone and phenyl ethanol. Carbon/silica/metal oxide supported nanoporous gold is a promising green catalyst for heterogenous molecular transformation. This is because of their three dimensional open pore network structures, high surface to volume ratio, high reusability, distinct optolectronic and physio-chemical properties. Mesoporous carbon/silica/metal oxide thin film supports provide increase dispersion of metal nanocatalysts and facilitate transport of molecules, ions or electrons through the nanopores/nanochannels, enhancing product yields with minimum cost and time. This paper has reviewed various gold-skeleton green catalysts and their preparation and mechanistic schemes for the selective oxidation of alkyl substituted benzenes.

Abstract: Cholesteryl ester liquid crystal was found to be non-toxic and it was recently applied as a cell traction force sensor. The reason for the affinity of the cells to this liquid crystal is unclear and required further investigation. This paper focused on determining the surface energy of the liquid crystals. A custom built contact angle measurement system and Fox-Zisman theory was applied to determine the critical surface tension of the cholesteryl ester liquid crystal. Eight different polar probe liquids were selected to determine the contact angle of the glass slides coated with cholesteryl ester liquid crystals. We found that the critical surface tension of the liquid crystal at 37.5 mN/m characterized the surface of the liquid crystal to be moderately hydrophobic. However, as reported in our previous work that the interaction of the liquid crystal and the cell culture media could re-orientate the amphiphilic molecules of the liquid crystals leading to the formation of lyotropic layers on the bulk cholesteric phase, therefore, making the surface to be hydrophilic. This then supported the formation of the hydrophilic layers that favors cell adhesion.