Pavadee Aungkavattana | National Nanotechnology Center (original) (raw)

Papers by Pavadee Aungkavattana

Journal of Applied Polymer Science, 2013

ABSTRACTPoly(butylene succinate‐co‐butylene adipate) (PBSA)/graphene oxide (GO) nanocomposites we... more ABSTRACTPoly(butylene succinate‐co‐butylene adipate) (PBSA)/graphene oxide (GO) nanocomposites were synthesized via in situ polymerization for the first time. Atomic force microscopy demonstrated the achievement of a single layer of GO, and transmission electron microscopy proved the homogeneous distribution of GO in the PBSA matrix. Fourier transform infrared spectroscopy results showed the successful grafting of PBSA chains onto GO. With the incorporation of 1 wt % GO, the tensile strength and flexural modulus of the PBSA were enhanced by 50 and 27%, respectively. The thermal properties characterized by differential scanning calorimetry and thermogravimetric analysis showed increases in the melting temperatures, crystallization temperatures, and thermal stability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4075–4080, 2013

Journal of Chemical Technology & Biotechnology, 2015

BACKGROUND: Polybenzoxazine (PBZ) membranes have received increasing attention for serving as a h... more BACKGROUND: Polybenzoxazine (PBZ) membranes have received increasing attention for serving as a high performance membrane for pervaporation processes owing to their good mechanical properties, high chemical resistance, high thermal stability, and low synthesis cost. This study aims to develop PBZ membrane and NaA-PBZ mixed matrix membrane (MMM) for purification of ethanol/water mixtures using a pervaporation process and to investigate the effects of preparation parameters on the membrane performance, including precursor concentrations, number of dippings, amount of NaA zeolite loading, temperature, and ethanol concentration. RESULTS: It was found that PBZ membrane and NaA-PBZ MMM exhibited excellent stability in all feed ethanol concentrations tested, with a low degree of swelling. The highest separation factor of the pure PBZ membrane was more than 10 000 while the NaA-PBZ MMM was even higher, up to and, in some cases, higher than 100 000 with the highest permeation flux of 1071 g m −2 h −1 when using 25 wt% PBZ precursor with 15 wt% NaA zeolite loading. The permeation flux of MMM increased with increase in temperature or a decrease in the feed ethanol concentration. Swelling increased when the ethanol concentration was increased, revealing the hydrophobic behavior of NaA-PBZ MMM. CONCLUSION: The membranes are capable of purifying ethanol over a wide feed ethanol concentration range with excellent performance and properties that promise great potential for use in bioethanol purifying applications.

Electrochimica Acta, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Ewsuk/Characterization, 2012

CERN European Organization for Nuclear Research - Zenodo, Jul 14, 2022

Toxicological & Environmental Chemistry, 2021

Abstract Since 2006, the Strategic Approach to International Chemicals Management is a policy fra... more Abstract Since 2006, the Strategic Approach to International Chemicals Management is a policy framework to promote chemical safety around the world. In 2009, safety of nanomaterials has been recognised as an Emerging Policy Issue, and awareness to it has improved in the last two decades. Various countries act as pioneers in their respective geographic regions. This article presents the Nanosafety and Ethics Strategic Plan of Thailand and its implementation since 2012, when on the third International Conference on Chemicals Management nanosafety was amended as emerging policy issue. In 2015, an intersessional process was started to negotiate a new post-2020 regime. This process was delayed by the Covid-19 pandemic, so many countries have not yet implemented nanosafety in their national legislations. Therefore, it is important to keep nanosafety in the post-2020 context of the Strategic Approach to International Chemicals Management as an issue of concern without going a second time through an elaborate evaluation process again.

The alumina grinding beads are usually formed by a pan granulator method, however it is difficult... more The alumina grinding beads are usually formed by a pan granulator method, however it is difficult to form small size beads (1-2mm diameter). This work is focused on a new forming method which uses agar as gelling agent in gelcasting. The mixtures of alumina suspension and agar solution (concentration 1.5-4wt.%) are dropped into cooled oil using a pipette. The shape of mixture becomes sphere by its surface tension. After the mixture transformed to gel, it is separated from cooled oil. Later the gelled beads are dried in air and finally sintered at 1300-1400 degrees celsius. Tellus 46 oil is the cooled oil having the proper viscosity for forming. At 1.5wt.% concentration of agar solution, the shape of drop which is just dropped from the pipette tip is almost sphere. The sphere became better when final agar content increases from 0.25 to 1.0wt.%. However, at concentration [is more than or equal to] 2wt.% the shape of drop became more and more oval with increasing of the agar content. A...

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Construction and Building Materials, 2016

h i g h l i g h t s TiO 2 promoted hydration reactions in geopolymers resulting more CÀSÀH phase.... more h i g h l i g h t s TiO 2 promoted hydration reactions in geopolymers resulting more CÀSÀH phase. The strength increased due to the formation of CÀSÀH and anatase phases in matrix. Addition of 5% TiO 2 resulted in increased by 44% strength.

Advanced Powder Technology, 2016

Metakaolin based geopolymer composites have been synthesized at room temperature by mixing metaka... more Metakaolin based geopolymer composites have been synthesized at room temperature by mixing metakaolin with NaOH and sodium silicate solutions, then adding cordierite powder from 0 to 50 wt% as a weight fraction of geopolymer matrix. Compressive strength was measured after aged 28 days. The thermal stability was analyzed by placing cube specimens in the furnace at 800°C for 2 h. The compressive strength of cordierite-metakaolin based geopolymer composites was studied in comparison with those without cordierite addition. In this study, the compressive strength showed an increase with cordierite addition (from 0 to 30 wt%), whereas the molar ratio SiO 2 /Al 2 O 3 = 3.5 and H 2 O/Na 2 O = 13, the strength increased from 45 MPa to 57 MPa. The microstructure revealed the unreacted metakaolin phase dispersed in the dense geopolymer matrix corresponding with the XRD results. It is evident that cordierite content in metakaolin based geopolymers can provide the good thermal stability at high temperature. Thermal shock resistance of 50 wt% cordierite added to geopolymers at 800°C attained 15 cycles without cracking, although, the residual compressive strength was declined. Cordierite-metakaolin based geopolymer composites could be considered as a good candidate for high temperature refractory applications.

The preparation of NaA zeolite membranes has attached much attention in recent years due to their... more The preparation of NaA zeolite membranes has attached much attention in recent years due to their potential application in many fields, especially, ethanol-water separation for gasohol production. Generally, NaA zeolite films are prepared using several techniques, but the preparation of a continuous and thin layer of the zeolite film is also concerned to obtain high performance. In this work, NaA zeolite films have been synthesised on a-Al2O3 tube by different techniques, viz. microwave heating, autoclave and electrophoresis. The effects of synthesis parameters, such as seeding and optimum conditions (temperature and time) on membrane perfection will be discussed. The continuous and thin layer of the zeolite films was observed using XRD and SEM. Moreover, the performance of the membranes was determined by pervaporation technique.

Applied Organometallic Chemistry, 2007

ABSTRACT Recently, zeolite membranes on porous supports have been extensively studied in the etha... more ABSTRACT Recently, zeolite membranes on porous supports have been extensively studied in the ethanol–water separation process for further use for gasohol production. This work focuses on a NaA membrane synthesized on an α-Al2O3 support via microwave hydrothermal treatment. Synthesis temperature and time, type of substrate, seed amount and seeding time for the layer growth of the membrane are considered. The formation of as-synthesized membranes is discussed according to observations by SEM and XRD. In addition, a preliminary study of the performance of the synthesized NaA zeolite membrane was conducted using the pervaporation technique. It was found that, for the synthesized continuous NaA membranes prepared using a 0.5 µm NaA crystal seed concentration of 3 g/l via vacuum seeding, the optimum conditions were 363 K synthesis temperature for 15–20 min via microwave heating. The flux and the separation factor obtained were 1.6 kg/m2 h and 1760.5, respectively, for the substrate without an intermediate layer. Interestingly, the substrate with an intermediate layer showed better flux and separation factor at 1.7 kg/m2 h and 6532.7, respectively. Copyright © 2007 John Wiley & Sons, Ltd.

Ferroelectrics (Print), Jan 3, 2014

The durability, the reliability and the factors leading to the degradation of PZT become more imp... more The durability, the reliability and the factors leading to the degradation of PZT become more important. The factors initiating the degradation such as crack propagation and environmental conditions were investigated. The dielectric constant and the piezoelectric coefficient, d 31 of PZT prior to degradation are 3200 and 15000 pm/V, respectively. After the degradation with crack propagation, the dielectric constant and piezoelectric coefficient, d 31 were reduced to 3100, 2400, 1400 and 12000, 11000, 349 pm/V, respectively depend on the degree of crack propagation. In addition, the effect of environmental conditions such as temperature of un-cracked and pre-cracked samples were also investigated and reported.

In the present work, transparent submicrometer grains alumina formed by gel casting using agar as... more In the present work, transparent submicrometer grains alumina formed by gel casting using agar as gelling additive was investigated. Green bodies were obtained by mixing welldispersed alumina slurries (65-75 wt.%) with agar solution (0.1-0.3 wt%) at 45°C and changed to gel on cooling. The density of green bodies ranging from 51-57 % was obtained. The density of bodies sintered at 1300 and 1350°C in air was in the range of 91-97 % of TD. After HIPing, the specimen transparent with mean grain size of 0.56 μm. The transmittance measured at 645 nm was 17%.

This work aims to investigate how compressive strength of a typical class C fly ash-based geopoly... more This work aims to investigate how compressive strength of a typical class C fly ash-based geopolymer would be changed with addition of mullite. In preparation of basic geopolymer, fly ash was collected from Mae Moh power plants, Lampang province, was alkaline activated and cured for a total period of 7 days. In making the composites, 20-60% of mullite powder was added to the basic geopolymer mixture and cured at the same condition. Porosity, density, and water absorption of the samples were determined by following ASTM C-642. The results showed that the compressive strength of the geopolymer mortar could be remarkably improved from 14 MPa to 71 MPa with mullite addition. The mechanical property variation of the composites was discussed along with their physical properties and microstructures.

The Proceedings of the Asian Symposium on Materials and Processing

Several types of ceramic membranes have been developed for a half of century, Alurnina is the mos... more Several types of ceramic membranes have been developed for a half of century, Alurnina is the most extensive advantage among different type of ceramic membranes. Many types of alumina powder with difference panicle size distributions were used as a starting material for extrusion process. The ceramic dough compositions fbr extmsion were studied. The sheet of alumina supports were fired at various sintering temperatures contained approximately 40% porosity after sintering at 14000C for 2 hour.

Materials Today: Proceedings, 2021

In this study, two processing parameters in preparation of high-strength fly ash based-geopolymer... more In this study, two processing parameters in preparation of high-strength fly ash based-geopolymer: concentrations of NaOH solution and curing regimes were reexamined. From the study of NaOH solution concentration effect, a sharp rise in compressive strength to 55.7 MPa was observed when the solution concentration was increased from 4 to 6 molar (M). Further increase in the concentration up to 12 M caused the setting time of the paste to increase continuously whereas the compressive strength was slightly improved. As for the various curing regimes, the resulting compressive strength was not significantly different. The suitable curing regime was the one at 90°C in the water-saturated atmosphere for 24 hours, then at room temperature in the water-saturated atmosphere for 72 hours and finally at room temperature in a dry normal atmosphere for 72 hours (90C24h-RT)

Advances in Materials Science and Engineering

Copper samarium co-doped ceria (CSDC) (Cu0.01Sm0.19Ce0.80O2−δ) nanoparticles were synthesized via... more Copper samarium co-doped ceria (CSDC) (Cu0.01Sm0.19Ce0.80O2−δ) nanoparticles were synthesized via a sol-gel auto-combustion of metal nitrates without a complexing agent (DI) and with tartaric acid (TA) or citric acid (CA). The solid oxide formation of CSDC/DI corresponds to the endothermic stage, whereas that of CSDC/TA and CSDC/CA matches the exothermic stage caused by the decomposition of the metal cross-linking and carbon combustion. The cross-linking occurs more extensively in the CA case as more heat is released in CA than in the TA route. The as-synthesized morphology of CSDC/DI reveals both layered structures and small agglomerated particles, whereas CSDC/TA and CSDC/CA show dense xerogel and porous xerogel, respectively. The cubic fluorite structure for calcined CSDCs was confirmed by XRD. From Raman analysis, calcined CSDC/CA has the lowest amount of copper segregation and the highest relative total oxygen vacancy concentration [ V O • • ]total, whereas calcined CSDC/DI has...

Ceramics International, 2008

In this research, solid oxide fuel cell electrolytes were fabricated by aqueous tape-casting tech... more In this research, solid oxide fuel cell electrolytes were fabricated by aqueous tape-casting technique. The basic compositions for SOFC electrolyte systems were focused on yttria-stabilized zirconia (YSZ) system. The powders used in this study were from different sources. ZrO2-based system doped with 3, 8, and 10mol% of Y2O3, and 8YSZ electrolyte tape illustrated the desirable properties. The grain size of