Thailand National Metal and Materials Technology Center

We report a novel strategy for using gold nanoparticles capped with chitosan for sensing ions of heavy metals. Acidic anions (glutamate ions in our case) are expected to cap the nanoparticle surfaces similar to conventional methods of stabilization of gold nanoparticles by citrate ions. The polycationic nature of chitosan enables attachment of the polymer to the negatively charged gold nanoparticle surfaces through electrostatic interactions. Use of chitosan serves dual purpose of providing sufficient steric hindrance ensuring stability of the colloid and also to functionalize the nanoparticles for use as sensors. The well-documented chelating properties of chitosan and the sensitivity of the optical properties of gold nanoparticles to agglomeration have been employed to detect low concentrations of heavy metals ions (Zn2+ and Cu2+) in water. A comparison of the optical absorption spectra of the colloidal suspension before and after exposure to metal ions is a good indicator of the concentration of the heavy metal ions.

In laser material processing, understanding the laser interaction and the effect of processing parameters on this interaction is fundamental to any process if the system is to be optimized. Expanding this to different materials or other laser systems with different beam characteristics makes this interaction more complex and difficult to resolve. This work presents a relatively simple physical model to understand these interactions in terms of mean surface enthalpy values derived from both material parameters and laser parameters. From these fundamental properties the melt depth and width for any material can be predicted using a simple theory. By considering the mean enthalpy of the surface, the transition from conduction limited melting to keyholing can also be accurately predicted. The theory is compared to experimental results and the predicted and observed data are shown to correspond well for these experimental results as well as for published results for stainless steel and for a range of metals. The results suggest that it is important to keep the Fourier number of the weld much smaller than one to make it efficient. It is also discussed that the surface enthalpy could be used to prodict other effects in the weld such as porosity and material expulsion.

Abstract Nanosized TiO 2 is used extensively in sunscreen cosmetics as an inorganic UV absorber that can allow an optically transparent film to be applied to human skin. TiO 2 is known to exist in three crystal forms: anatase, brookite and rutile. The rutile phase is generally used as a component in sunscreen cosmetics because of its higher UV absorption. A surface coating can be added to nanosized TiO 2 to enhance its UV absorption by a different light diffraction mechanism. Silica‐coated nanosized TiO 2 is examined in this study for this purpose. The nanosized TiO 2 has been synthesized using hydrolysis of tetra‐isopropylorthotitanate (TIPT) as a precursor. After a calcination process, nanosized TiO 2 was formed and subsequently its surface modified by coating with tetraethoxysilane (TEOS) as the source of the silica. The same coating method was applied to nanosized commercial TiO 2 , to compare the surface characteristics. The resulting powders of coated TiO 2 were examined by transmission electron microscopy (TEM) and analyzed by energy dispersive analysis (EDS), respectively. UV‐vis spectroscopy was used to study the differences and effectiveness of the coated and uncoated TiO 2 . Copyright © 2006 John Wiley & Sons, Ltd.

The biodegradable thermoplastic poly(lactic acid) (PLA) that has restricted its application due to its high brittleness and poor crystallization behavior. Toughness properties of PLA can be developed by blending with natural rubber (NR) and epoxidized natural rubber (ENR). Blending PLA with NR and ENR were prepared at various compositions from 0-30% by weight. Morphology, crystallization behavior, thermal stability and mechanical properties of blends were investigated. The rubber phase of NR was dispersed in the continuous PLA matrix with small droplet. Increasing of NR content, the large droplet size of rubber will be resulted. However, the partially compatible between PLA and ENR was responsible for coarse surface, i.e. very fine particles of ENR dispersion. Incorporation of NR would enhance the crystallization ability of PLA better than ENR but thermal stability was decreased with both rubbers. The ductility of PLA has been significantly improved by blending with NR. The amount of NR at 10% weight seems to give optimum property. At high content of NR, it seems to suffer tensile properties. In the case of the addition of ENR, it reduced crystallization ability, thermal resistance and tensile properties of the blend.

Single-phase multiferroic BiFeO3 ceramics were fabricated using pure precipitation-prepared BiFeO3 powder. Dielectric response of BiFeO3 ceramics was investigated over a wide range of temperature and frequency. Our results reveal that the BiFeO3 ceramic sintered at 700 °C exhibited high dielectric permittivity, and three dielectric relaxations were observed. A Debye-type dielectric relaxation at low temperatures (−50 to 20 °C) is attributed to the carrier hopping process between Fe2+ and Fe3+. The other two dielectric relaxations at the temperature ranges 30–130 °C and 140–200 °C could be due to the grain boundary effect and the defect ordering and/or the conductivity, respectively.

Abstract Rice husk ash is mainly composed of silica and carbon black remaining from incomplete combustion. Both silica and carbon black have long been recognized as the main reinforcing fillers used in the rubber industry to enhance certain properties of rubber vulcanizates, such as modulus and tensile strength. In this study, two grades of rice husk ash (low‐ and high‐carbon contents) were used as filler in natural rubber. Comparison was made of the reinforcing effect between rice husk ashes and other commercial fillers such as talcum, china clay, calcium carbonate, silica, and carbon black. Fourier transform infrared spectroscopy (FTIR) analysis was employed to study the presence of functional groups on the ash surface. The effect of silane coupling agent, bis(3‐triethoxysilylpropyl)tetrasulfane (Si‐69), on the properties of ash‐filled vulcanizates was also investigated. It was found that both grades of rice husk ash provide inferior mechanical properties (tensile strength, modulus, hardness, abrasion resistance, and tear strength) in comparison with reinforcing fillers such as silica and carbon black. However, the mechanical properties of the vulcanizates filled with rice husk ash are comparable to those filled with inert fillers. The addition of silane‐coupling agent has little effect on the properties of the ash‐filled vulcanizates. This is simply due to the lack of silanol groups on the ash surface. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2485–2493, 2002

We report the synthesis of luminescent nanoparticles of manganese doped zinc sulfide (ZnS:Mn2+) with an emission peak at around 590 nm. Nanoparticles of ZnS:Mn2+ are prepared by a co-precipitation reaction from homogenous solutions of zinc and manganese salts. Based on Ostwald ripening and surface passivation, we discuss a mechanism for the formation of ZnS:Mn2+ nanoparticles. The reaction proceeds with the nucleation of ZnS crystals, which are immediately passivated by the anions in the solution. This in turn attracts cations including zinc and manganese which contribute to the growth of the crystal. These nanoparticles are sterically stabilized using polyphosphates of sodium namely sodium tripolyphosphate (STTP) and sodium hexametaphosphate (SHMP). The nanoparticles consist of particles of 60–80 nm in diameter, each containing primary crystallites that was estimated from the X-ray diffraction patterns to be at around 2.2 nm.

The prokaryotic diversity in the Bor Khlueng hot spring in Ratchaburi province, Thailand was investigated by a culture-independent molecular approach. This hydrothermal pool is located in the central part of Thailand and contains sulfide-rich mineral water that is believed to relieve muscle ache and pain. The water flow year-round with temperature ranging between 50-57 degrees C. Community DNA was extracted directly from sediment samples by coring to depth of approximately 20-30 cm. Small-subunit rRNA genes (16S rDNA) were amplified by PCR using primers specific for the domains Archaea and Bacteria. The PCR products were cloned and sequenced. For the bacterial rDNA clone library, 200 clones were randomly selected for further analyses. After restriction fragment length polymorphism (RFLP) analysis of rDNA clones and exclusion of chimeric sequences 36 phylotypes were obtained. The Bor Khlueng phylotypes spanned a wide range within the domain Bacteria, occupying eleven major lineages (phyla). Almost a quarter (23%) of the clones were classified as Acidobacteria. The other clones were grouped into the Bacteriodetes (19%), Nitrospirae (13%), Proteobacteria (12%), Deinococcus-Thermus lineage (11%), planctomycetes (6%), and Verrucomicrobia (5%). The four remaining phyla, 5% each, were assigned to Actinobacteria, Chloroflexi, Cyanobacteria, and the candidate division "OP10". For the archaeal 16S rRNA gene sequence library, 25 distinct phylotypes were obtained, 17 clones were found to be associated with Crenarahaeota and 8 clones were associated with Euryarachaeota. The findings of the molecular survey of this so far not investigated site showed that Bor Khlueng hot spring is a potential rich source of unique bacterial and archaeal species. The great majority ( approximately 80%) of the prokaryotic sequences detected in Bor Khlueng were unknown.

Use of waste as raw material for producing porous carbon was investigated in this work. Physic nut (Jatropha curcas L.) residue from oil extraction for biodiesel production was pyrolyzed at 400–800 °C with hold times of 15, 120, and 240 min to obtain char precursors. Activated carbon, with favorable Brunauer–Emmett–Teller surface area in a narrow range, was prepared by soaking these chars in concentrated KOH, H3PO4, as well as a pure CO2 gas flash activator. The maximum specific surface area of 532.30 m2 g−1 was developed for the alkaline-treated sample. The carbon fraction of activated materials was as much as 90 wt %, significantly higher than the char precursor. Mesopore of 2–50 nm and total pore volumes of the materials were also significantly enhanced by these activations. Nitrogen adsorption isotherms of physic-nut-waste-activated carbons indicated that they were mainly mesopores. Pores of char activated by KOH and H3PO4 are irregular, of different shapes and sizes, and the macropores seemed to be connected to mesopores, especially for the KOH-activated case. Surface analysis of pyrolyzed and activated char using Fourier transform infrared spectroscopy indicated main functional groups that are considerably different to those of activated materials, which may lead to greater adsorption potential of activated samples. However, functional groups on each activated carbon are quite similar even with different activation processes. According to the data obtained, physic nut residue pyrolyzed at 800 °C and followed by KOH activation could be used as a low-cost adsorbent with favorable surface properties.

The effect of polypropylene/poly(lactic acid) weight ratios on the properties of blend films compatilized with polypropylene-grafted-maleic anhydride were investigated with 100:0, 60:40, 50:50, 40:60, and 0:100 of weight ratio. The blend films were prepared by melt mixing technique and cast film extrusion. The results shown that the FTIR spectrum was confirmed the interaction between compatibilizer and polymers. Morphological investigation was distinctly seen a two phases system between polypropylene and poly(lactic acid). Increasing of PLA content from 40 to 60 wt.% resulting in decreased melting temperature and crystallinity from 158 °C to 154 °C and 38% to 31%, respectively. For tensile properties, modulus and tensile strength increased with increasing the PLA content, while elongation at break was drastically decreased from 500% (polypropylene) to less than 50% (blends). The barrier properties indicated that incorporation of poly(lactic acid) into polypropylene tend to increased water vapor permeability while oxygen permeability was decreased. From the morphology, thermal, mechanical, and barrier results, the polypropylene/poly(lactic acid) blends showed a typical immiscible polymer blend.

Giant dielectric permittivity (Li, Ti)-doped NiO (LTNO) ceramics are prepared by a simple PVA sol–gel method. The dielectric properties are investigated as a function of frequency (102–106 Hz) at different temperatures (233–473 K). The concentration of Li has a remarkable effect on the dielectric properties of the LTNO ceramics. The modified Cole–Cole equation, including the conductivity term, is used to describe the experimental dielectric spectra of a high permittivity response with excellent agreement over a wide range of frequencies (103–106 Hz) and temperatures (233–313 K). A frequency dielectric dispersion phenomenon in an LTNO ceramic is also analyzed by impedance spectroscopy. A separation of the grain and grain boundary properties is achieved using an equivalent circuit model. The grain and grain boundary conduction and the dielectric relaxation time of the Li0.05Ti0.02Ni0.93O follows the Arrhenius law associated with estimated activation energies of 0.216, 0.369 and 0.391 eV, respectively. Through the analysis by the modified relaxation model and impedance spectroscopy, it is strongly believed that the high dielectric permittivity response of the LTNO is not only contributed by the space charge polarization (Maxwell–Wagner polarization) mechanism at low frequency regions, but also by the defect-dipole polarization mechanism at high frequency regions.

We report the growth of ZnO nanowires on nonwoven polyethylene fibers using a simple hydrothermal method at a temperature below the boiling point of water. The ZnO nanowires were grown from seed ZnO nanoparticles affixed onto the fibers. The seed ZnO nanoparticles, with diameters of about 6-7 nm, were synthesized in isopropanol by reducing zinc acetate hydrate with sodium hydroxide. The growth process was carried out in a sealed chemical bath containing an equimolar solution of zinc nitrate hexahydrate and hexamethylene tetramine at a temperature of 95 °C over a period of up to 20 h. The thickness and length of the nanowires can be controlled by using different concentrations of the starting reactants and growth durations. A 0.5 mM chemical bath yielded nanowires with an average diameter of around 50 nm, while a 25 mM bath resulted in wires with a thickness of up to about 1 μm. The length of the wires depends both on the concentration of the precursor solution as well as the growth duration, and in 20 h, nanowires as long as 10 μm can be grown. The nonwoven mesh of polyethylene fibers covered with ZnO nanowires can be used for novel applications such as water treatment by degrading pollutants by photocatalysis. Photocatalysis tests carried out on standard test contaminants revealed that the polyethylene fibers with ZnO nanowires grown on them could accelerate the photocatalytic degradation process by a factor of 3.

We present a simple strategy to achieve excellent dielectric and nonlinear current–voltage properties for pure– CaCu 3 Ti 4 O 12 ceramics prepared by a modified sol–gel method with different calcining conditions. At 1 kHz and room temperature, the best CCTO ceramic can exhibit a high dielectric constant (ε′) of 9516 with a very low dielectric loss, tan δ ~0.020. The minimum value of tan δ is 0.018 at 2.5 kHz with ε′ ~9433. High breakdown field of 4032 V/cm and nonlinear coefficient of 7.05 were obtained.

This research has aims to study effect between rice husk and rice husk ash to properties of bricks. Comparative adding between rice husk and rice husk ash were varied by 0 -10% by weight. The results showed that more adding rice husk less compressive strength and density of specimens. Otherwise the porosity increases when adding rice husk. By adding 2% of rice husk ash by weight is the best of bricks properties which 6.20 MPa of compressive strength, 1.68 g/cm3 of density, and 15.20% of water absorption.

A highly sensitive and selective fluorescence sensor using N,S-GQDs for the detection of Co²⁺within 3 minutes.

In order to improve compatibility and composite properties of pineapple leaf fibers/polyamide 6 composite, alkaline and silane treatments were conducted for fiber modification. Effect of fiber surface treatment on the properties of the composites was investigated. Untreated and treated fibers were raw (R-PALF), alkaline treated (Na-PALF) and silane treated pineapple leaf fibers (Si-PALF). Fiber loading was varied in polyamide 6 based composite. Morphology and fiber-matrix interfacial adhesion, thermal and mechanical properties were examined. Surface treatments can improve interfacial adhesion between these two phases. All PALFs have enhanced thermal stability of all composites. However, thermal characteristics of the composites, i.e. Tc, Tm and crystallinity, have not been affected by PALF types. Na-PALF and Si-PALF help improving mechanical properties of the composites. Young's modulus and tensile strength have been increased whereas elongation decreased by both treated PALFs which indicates that the composites become stiffer and stronger but less flexible. From the results, it could be stated that alkali treatment is sufficient to improve compatibility and properties of the PALF/polyamide 6 composites at fiber loading of 30%wt.

In today's market environment, an aging society is recognized as one of the megatrends in the world. The demographic change in the world population age structure has driven a huge demand in healthcare products as well as services that include the technological innovation for the health and wellness of the elderly. Dysphagia or swallowing difficulty is a common problem in the elderly as many changes in swallowing function come with aging. The presence of a strong relationship between swallowing ability, nutritional status, and health outcomes in the elderly leads to the importance of dysphagia management in the population group. Modification of solid food and/or liquid is a mainstay of compensatory intervention for dysphagia patients. In this regard, texture-modified foods are generally provided to reduce risks associated with choking, while thickened liquids are recommended for mitigating risks associated with aspiration. In this review, we discuss thickened liquids and other issues including the importance of their rheological and tribological properties for oropharyngeal dysphagia management in the elderly. The review focuses on both commercial thickeners that are either based on modified starch or xanthan gum and other potential polysaccharide alternatives, which have been documented in the literature in order to help researchers develop or improve the characteristic properties of thickened liquids required for safe swallowing. Furthermore, some research gaps and future perspectives, particularly from the nutrition aspect related to the interaction between thickeners and other food ingredients, are suggested as such interaction may considerably control the rate of nutrient absorption and release within our body.

The purpose of this study was to investigate the best ratio of waste foundry sand (WFS), fly ash (FA), and electric arc furnace slag (EAF slag) for the production of geopolymer bricks. In this research study, WFS, FA, and EAF slag were mixed at the ratio of 70:30:0, 60:30:10, 50:30:20, and 40:30:30 with 8M sodium hydroxide (NaOH) and 98% purity sodium silicate (Na2SiO3) with a ratio of Na2SiO3/8M NaOH = 2.5. The mixtures were compacted in 5 cm × 5 cm x 5 cm molds and cured at an ambient temperature for 28 days. Then, their compressive strength was analyzed. The results showed that the geopolymer bricks with the highest compressive strength were those mixed at the 40:30:30 ratio, with a compressive strength of 25.76 MPa. The strongest bricks were also analyzed using the leaching test to ensure the production involved non-hazardous materials. To compare the environmental impacts of geopolymer bricks and concrete bricks, their effects on climate change, ozone depletion, terrestrial acidification, human toxicity, terrestrial ecotoxicity, and fossil fuel depletion were examined from cradle to grave using SimaPro 8.0.5.13 software. The results of the life cycle assessment (LCA) from cradle to grave showed that the environmental impact of geopolymer brick production was lower in every aspect than that of concrete production. Therefore, geopolymer brick production can reduce environmental impact and can be a value-added use for industrial waste.

A test method that measures microclimate drying time is used to compare the ability of different knit materials to dissipate moisture vapor from a saturated clothing environment to the ambient atmosphere. The performance assessment provided by this novel method is compared with those from common test methods. The latter include measures of the moisture vapor transmission rate provided by the upright cup and the evaporative thermal resistance provided by the sweating guarded hot plate procedure. Upright cup and sweating hot plate measurements are shown to be predominately influenced by fabric thickness, but microclimate drying time, or the time-dependent dissipation of accumulated moisture vapor, assessed by the new method is most influenced by the pore characteristics of the fabric. Moisture vapor transmission through fabrics is assumed to be controlled mostly by fiber, yarn, and fabric variables that determine fabric thickness and porosity. Therefore, constructional variables that lead to thin knit structures, with unobstructed interyarn pores, are shown to be important considerations for designing fabrics with optimum moisture vapor dissipation properties.

The origin of giant dielectric relaxation behavior and related electrical properties of grains and grain boundaries (GBs) of W6+-doped CaCu3Ti4O12 ceramics were studied using admittance and impedance spectroscopy analyses based on the brick–work layer model. Substitution of 1.0 at. % W6+ caused a slight decrease in GB capacitance, leading to a small decrease in the low-frequency dielectric constant. Surprisingly, W6+ doping ions have remarkable effects on the macroscopic dielectric relaxation and electrical properties of grains. X-ray photoelectron spectroscopy analysis suggested that the large enhancements of grain resistance and conduction activation energy of grains for the W6+-doped CaCu3Ti4O12 ceramic are caused by reductions in concentrations of Cu3+ and Ti3+ ions. Considering variation of dielectric properties together with changes in electrical properties of the W6+-doped CaCu3Ti4O12 ceramic, correlation between giant dielectric properties and electrical responses of grains and GBs can be described well by the internal barrier layer capacitor model. This model can ascribe mechanisms related to giant dielectric response and relaxation behavior in CaCu3Ti4O12 ceramics.