Abstract: Calcium silicate was successfully synthesized using agricultural byproduct such as rice husk ash and shell of snail namely Pomacea canaliculata by solid state reaction. Chemical composition of silica in rice husk ash and calcium oxide in shell were 91.50 and 98.25%, respectively by X-ray fluorescent determination. The rice husk ash and shell in molar ratio of 1:1 were milled for 5-8 hr and calcined at 800-1000 °C for 2 hr. The Fourier transforms infrared spectra and X-ray diffractometry pattern were confirmed the formation of calcium silicate as the milling time increased.
Abstract: The aim of this study was to develop a pH-sensitive ternary system of chitosan, κ-carrageenan, and carboxymethylcellulose sodium salt (CMC) that can serve as a controlled release system. Encapsulation of curcumin in chitosan was achieved by transforming the present colloidal suspension into hydrogels via cryotropic gel formation. The frozen hydrogel specimens (cryogels) were freeze-dried for preservation and investigation. It was reported that, when the ratio of κ-carrageenan to NaCMC was kept constant, the cooling rate was found to determine the type of release between burst type and controlled first-order-rate type . The microstructural morphology of freeze-dried specimens was observed with a Scanning Electron Microscope (SEM) to be affected by the cooling rate. The faster cooling rate produced specimens with slightly larger pore size and, as a result, higher amount of curcumin released at 2 days. Swelling tests of the hydrogels in buffer solutions of different pH values showed that acidic media had a pronounced effect on swelling compared to the neutral and alkaline media. The faster cooling rate produced specimens that had higher structural strength against swelling despite the fact that the specimens had larger pore size and faster controlled release rate.
Abstract: Gas sensor array based on polymer/multi-walled carbon nanotubes (polymer/MWCNTs) composites prepared by screen printing technique was examined for rice aroma detection. The sensor array consists of two sets of three different sensors, i.e., MWCNTs dispersed in the matrix of poly (2-Acrylamido-2-methyl-1-propanesulfonic acid-co-acrylonitrile (S1-S2), polyvinyl alcohol (S3-S4) and poly (styreneco-maleic acid) partial isobutyl/methyl mixed ester (S5-S6). Sample temperature, which is one of the important parameters, has been found to influence the releasing rate of the volatiles from rice grain when needed to operate on the electronic nose system. In this case, the fabricated sensor array installed within a lab-made electronic nose system with optimum sample temperature at 70°C could provide rapid and best responses to the volatiles released from the milled rice sample. Moreover, the responsive signals could be recovered to original state as well within four minutes by only purging with fresh air at room temperature. Based on the principal component analysis (PCA) pattern recognition, it was shown that the electronic nose can discriminate six rice samples based on the content of aroma.
Abstract: The magnetic nanoparticles of cobalt-and nickel-iron oxide have been extensive interest due to their superparamagnetic properties and their potential applications in many fields. The iron, cobalt and nickel can stay in many oxidation states and are easily oxidized especially in ambient air therefore the composition and oxidation states of these oxides can be unintentionally modified. Usually, the composition and oxidation states in these magnetic nanoparticles are determined by various experimental techniques required a sample in solid phase. This may lead the nanoparticles to directly contact with air and change the state. In this study, the magnetic nanoparticles in colloidal phase with concentration of 24mg/ml, derived from co-precipitation process, were directly injected to liquid cell for X-ray absorption near-edge structure (XANES) measurement. The iron-, cobalt-or nickel-iron oxide nanoparticles were prepared by dissolving CoCl2/FeCl3 or NiCl2/FeCl3, respectively, in deionized water with various atomic ratios. The average iron oxide nanoparticle size obtained by dynamic light scattering is about 4.2 nm with polydispersity of 0.987. Spherical shape with some stabilizer layer was observed by transmission electron microscope. The iron content in various composition nanoparticles was estimated in liquid phase by the ratio between the Fe edge peak and Co or Ni edge peak. The oxidation states of metal ions were also derived from the linear fitting of standard compounds at particular oxidation states. The shifts of peak positions were examined to indicate the variation of oxidation state as well.
Abstract: This research aims to study the effect of addition of microsilica and nanoalumina on compressive strength and products of high calcium fly ash geopolymer with low NaOH concentration. Microsilica and nanoalumina were added in the mixture in order to adjust the Si/Al ratios which resulted in the change of product form of geopolymer pastes. Geopolymer was synthesized using high calcium fly ash and 2 molar sodium hydroxide (NaOH). Microsilica and/or nanoalumina were added as additional sources of silica and alumina in the mixtures. Compressive strengths of pastes were investigated at the age of 7, 28 and 60 days. The products of geopolymer pastes were characterized by FTIR and salicylic acid with methanol (SAM leaching test). The results showed that the mix (2Si10Al0) with additional 10% of microsilica gave the highest compressive strength of 14 MPa at the age of 60 days. The products of geopolymer pastes were CSH gel, CASH gel, NASH gel and zeolite which were characterized by FTIR and SAM leaching test.
Abstract: Formation of ZrO2-5 wt.% Y2O3 nanostructured powders in glycine-nitrate combustion synthesis was investigated and the effect of "glycine-to-NO3-" ratio and heating method on the reaction product composition and particle morphology studied. Urea and ammonium nitrate additives were used to optimize the regime of the process. The effect of these reagents on gas generation required for the dispersion of particles, and on the process temperature was investigated.
Abstract: In this work, conducting polyaniline (PANI) nanofibers were fabricated by electrospinning technique. PANI (emeraldine-based) and polyvinyl alcohol (PVA) were used as the starting precursors for electrospinning technique and their concentrations were kept at 0.01 and 0.08 g/ml respectively. The effects of electrospinning conditions including volume ratio of polymer solution, operating voltage and injection rate at constant electrospinning distance on the morphologies and size distribution of the fibers were investigated. Scanning electronmicroscopy (SEM) and Fourier transforms infrared (FT-IR) were utilized to characterize morphologies and physical properties of the fibers. The optimized conditions with PVA:PANI (27;3, v/v), 20 kV voltage, 0.8 ml/hr injection rate to fabricate well-defined PVA/PANI nanofibers was acknowledged.
Abstract: Zinc aluminate (ZnAl2O4) nanopowders were synthesized by co-precipitation method using zinc chloride and aluminum chloride as starting precursors. The crucial preparation factors including pH and calcination temperature were varied and their influence on relevant physical properties of the product is investigated. Structural properties of as-synthesized nanoparticles were investigated by X-ray diffraction, scanning electron microscope and Raman spectroscopy. XRD results suggested that ZnAl2O4 in spinel structure with high crystallinity could be obtained by this process after calcination beyond specific temperature. Meanwhile, SEM images revealed that surface morphologies and structure of ZnAl2O4 were in spherical structure with average size of few hundred nanometer range at high pH condition. Raman result indicated the correlated chemical bonding relating to the formation of ZnAl2O4 structure.
Abstract: Photoresponse characteristic from efficient exciton dissociated heterojunction based on copper phthalocyanine (CuPc) and fullerene (C60) layers was observed the different spectrum responses under positive and negative biases. The nanostructures of CuPc and C60 thin films were fabricated between transparent indium tin oxide (ITO) and aluminum (Al) electrodes. The 100 nm thick of CuPc and C60 layers were deposited on patterned ITO glass substrates by thermal evaporation with quartz thickness monitor. Photoresponses of the fabricated devices were investigated by current measuring as a function of wavelength in range of 400 to 700 nm. Measured current in Al/C60/CuPc/ITO structure when applied negative voltage to ITO electrode is higher than that of positive voltage case. Under monochromatic light, the photoresponse characteristic of Al/C60/CuPc/ITO structure under negative bias shows dominate response current peak at around 450 nm and double peaks in range of 500-700 nm originated from C60 and CuPc layers, respectively. These two response characteristics can be described by the combination of responses from Al/C60/ITO and Al/CuPc/ITO structures. The response current characteristics of Al/C60/ITO and Al/CuPc/ITO structures also agree with the optical absorptions of C60 and CuPc layers, respectively. By applying positive bias to Al/C60/CuPc/ITO structure, the photoresponse characteristic has only one peak at about 450 nm that is similar to the response in Al/C60/ITO structure only. This indicates that under positive bias, the photocurrent only from C60 layer can be observed.