Journal Volumes



Shear-Flexure-Interaction Frame Element Inclusion of Bond-Slip Effect for Seismic Analysis of Non-Ductile RC Columns
Author:Worathep Sae-Long, Suchart Limkatanyu and Nattapong Damrongwiriyanupap
Vol. Vol.49 No.1 (Special Issue I : Jan 2022) Page -

     This paper demonstrates the effect of bond-interfaces slip on the shear responses within the non-ductile reinforced concrete (RC) columns. Those columns were conducted as the flexure-shear critical members, which were commonly found in the existing RC frame structures constructed before the regulation of recent seismic codes. To represent the behaviors of those columns, the proposed model is developed within the framework of the forced-based formulation under the Timoshenko beam kinematic assumption. The axial-flexure interaction of the RC frame element is considered through the fiber-section model while the shear action couples to the flexural action through the UCSD shear-strength model within the shear constitutive model. Finally, one simulation is employed to verify the model performance to predict complex behaviors of the non-ductile RC columns for seismic analysis and to discuss the effect of bond-interfaces slip on those responses. From the results, it confirms that the proposed model is simple but accurate. Furthermore, the model can well represent several salient features of the non-ductile RC columns such as the shear-flexure interaction effect, the strength degradation in shear due to the increasing curvature ductility demand, the gradual spread inelasticity, and the weakened shear responses due to the bond-slip effect. The predicted maximum shear force is well corresponding to the value obtained from the experiment with an error of about 0.83% while the error obtained from the frame model without the bond-slip effect is about 2.58%.

Investigation of the Initiating and Catalytic Behavior of Tri-n-butyltin(IV) n-Butoxide in Ring-Opening Polymerization of ε-Caprolactone and Transesterification of Poly(L-lactic acid)
Author:Winita Punyodom, Puttinan Meepowpan, Boontharika Thapsukhon, Manita Dumklang and Wanich Limwanich
Vol. Vol.49 No.1 (Special Issue I : Jan 2022) Page -

     Tri-n-butyltin(IV) n-butoxide (nBu3SnOnBu) was successfully synthesized and utilized as a stable and homogeneous initiator for the small-scale synthesis of biodegradable polymers in our laboratory. From our previous works, the initiating performance of nBu3SnOnBu in the ring-opening polymerization (ROP) of cyclic ester monomers was completely investigated by differential scanning calorimetry (DSC). It was found that nBu3SnOnBu acted as the slow initiator in the ROP of ε-caprolactone (ε-CL) due to its high steric hindrance around the active center. Moreover, it could be used in the stereoselective ROP of racemic-lactide (rac-LA). The synthesized nBu3SnOnBu showed higher stereoselectivity than the conventional tin(II) octoate (Sn(Oct)2) system. In this present work, the effectiveness of nBu3SnOnBu in scaled-up (250 g) of the synthesis of poly(ε-caprolactone) (PCL) was further investigated comparing to small-scale polymerization (4 g). Furthermore, the catalytic performance of this nBu3SnOnBu in the transesterification of high molecular weight poly(L-lactic acid) (PLA) was also investigated for the first time. The transesterification of PLA with 0.05 M and 0.10 M of soluble nBu3SnOnBu catalyst in CHCl3 was successfully investigated by the gel permeation chromatography (GPC) technique. It was found that the molecular weight of PLA dramatically decreased with increasing time and nBu3SnOnBu concentration. From the kinetics study, nBu3SnOnBu acted as a highly active transesterification catalyst for PLA. From a mechanistic study, the transesterification mechanism of PLA with nBu3SnOnBu catalyst was proposed through intramolecular transesterification.

Limit Load Solution for Thin-Walled Cylinder with Circumferential Crack under Combined Internal Pressure, Axial Force, Bending Moment and Torsion Moment
Author:Sutham Arun, Wichaphon Fakkaew and Thongchai Fongsamootr
Vol. Vol.49 No.1 (Special Issue I : Jan 2022) Page -

This research aims to establish the limit load solution for thin-walled cylinder with circumferential crack under combined internal pressure, axial force, bending moment and torsion moment. The solution is derived based on the net-section collapse principle and the von Mises yield criterion. The material considered in this work is assumed to be elastic-perfectly plastic. The solutions obtained from this work are compared with the results from the finite element models. The comparison shows that the equations established from NSC analysis provide acceptable results for the case of cracked cylinder under combined axial force and bending moment. For the case of cylinder subjected to internal pressure or torsional moment, however, these equations can be used to predict the limit load only if np ≤ 0.40 and nT ≤ 0.6. This is because when the effects of internal pressure or torsional moment are included, the distribution of stresses on the crack plane at the yielding does not correspond to the NSC principal.

Optimization of Melt-mixing Transesterification of Polylactide by Polyethylene Glycol Employing Response Surface Methodology
Author:Narisara Jaikaew, Rafael Auras and Pakorn Opaprakasit
Vol. Vol.49 No.1 (Special Issue I : Jan 2022) Page -

A process for preparing polylactide-block-polyethylene glycol (PLA-b-PEG) copolymers has been developed and optimized by employing a transesterification reaction in a melt-mixing process. The reaction was carried out in a counter-rotating mixer unit, using polyethylene glycol (PEG) and tetrabutyl titanate (TBT) catalyst. The effects of PEG weight percentage, catalyst contents, temperatures, and rotor speeds on chemical structures of the resulting PLA-b-PEG were examined, in terms of number average molecular weight (Mn), weight average molecular weight (Mw), in-chain PEG contents (wt.% PEG), and specific mechanical energy (SME) imparted by the mixer. The process parameters were optimized using a central composite rotatable design (CCRD) response surface methodology (RSM). The CCRD was designed with four variables at three levels of variations (-1, 0, -1), four replicates center point, and a redundancy factor (α) of 2.000. The responses (Mn, Mw, wt.% PEG, and SME) from 28 experimental trials were analyzed by a multiple linear regression fitting, a second-order equation, and the RSM model. Mn and Mw of the products were determined by gel permeation chromatography (GPC). The in-chain PEG content was examined by nuclear magnetic resonance (1H-NMR) spectroscopy. The results show that the PEG weight percentage and the reaction temperature significantly affect (P< 0.05) Mw and Mn of the products, which are drastically decreased with an increase in the PEG weight percentage and temperature. A quadratic interaction is observed between the PEG weight percentage and temperature, indicating that high reaction temperature leads to lower PEG conversions, due to undesirable competing thermal-oxidative degradations of PEG in the presence of the catalyst. Optimum operating conditions on the PEG weight percentage, catalyst contents, temperatures, and rotor speed for obtaining high Mw with high wt.% PEG was identified. Although the optimal conditions are observed at the boundary level, the model serves as a platform for effective preparation of PLA-b- PEG copolymers with designed molecular weight and chemical structures. Further optimization of the model may be conducted by extending the range of independent factor levels. The resulting flexible PLA-b-PEG copolymers, with tunable structures and properties, have high potential for use as singlecomponent degradable bioplastics with excellent mechanical properties, plasticizers, or toughening agent for enhancing PLA’s toughness.

Performance of Shear Wave Speed Measurements by Using Reverberant Optical Coherence Elastography
Author:Nirawit Kunanta, Fernando Zvietcovich, Kevin J. Parker, Jannick P. Rolland and Panomsak Meemon
Vol. Vol.49 No.1 (Special Issue I : Jan 2022) Page -

      Elasticity of biological tissue is important to understand its properties, which could play important role in medical diagnosis and treatment, especially in its early stage of pathology. Optical Coherence Elastography (OCE) has been intensively developed for mapping the elasticity contrast of various biological tissues. OCE techniques based on tracking of shear vibrational wave propagation is one of the most popular techniques. The high speed of shear wave propagation in biological media leads to challenges in both data acquisition and data processing. Recently, the concept of reverberant shear wave field has been applied to OCE, called Rev3D-OCE. In this work, we experimentally investigate the performance of Rev3D-OCE to differentiate gelatin phantoms with a slight difference of elasticity. We verified that Rev3D-OCE can differentiate different shear wave speeds associated with different concentrations of gelatin phantoms, where higher shear wave speed was observed in a higher concentration of the phantom as expected. The average shear wave speed of gelatin with 3 wt% and 4 wt% concentrations were measured as 1.3 ± 0.2 m/s and 1.5 ± 0.1 m/s with about 11% and 14% of errors as compared with that obtained by standard mechanical testing, respectively. In addition, the spatial resolution of Rev3D-OCE as determined from the edge response measurement at the boundary between two gelatins of 3 wt% and 4 wt% concentrations was measured to be 0.3 millimeters.

Purification of TiO2 from Leucoxene for the Synthesis of NIR-Reflective Cr-doped CaTiO3 Pigment
Author:Kanyawee Sinmongkolkul, Pattana Rakkwamsuk, Tippaban Palathai, Sasijuta Wattanarach, Parjaree Thavorniti and Sitthisuntorn Supothina
Vol. Vol.49 No.1 (Special Issue I : Jan 2022) Page -

This work aimed to explore the possibility of producing NIR-reflective pigment from Thai leucoxene which is an abundant mineral consisting of ~89 wt.% TiO2, 6 wt.% SiO2 and 5 wt.% other oxides such as Al2O3 and Fe2O3. The leucoxene was purified by selective leaching of undesired oxides with NaOH under hydrothermal condition. Effects of NaOH concentration, hydrothermal temperature and time were investigated. The results revealed that dissolutions of the SiO2 and Al2O3 increased with an increased NaOH concentration, while that of the ZrO2 and Fe2O3 remained the same, resulting in the increased TiO2 concentration. The SiO2 dissolution also increased with an increased temperature and time. The optimum leaching condition, i.e. 4 M NaOH, 180 °C and 60 min, yielded TiO2 content of 93.94 ±0.14 wt.%. The Cr-doped CaTiO3 pigments (CaCrxTi1-xO3; x = 0, 0.025, 0.05, 0.75 and 0.1), synthesized from the purified leucoxene, CaO and Cr2O3 by solid-state reaction at 1100 °C, exhibited brown color hue and NIR reflectance in a range of 34.5−59.8% depending on the Cr content. At the Cr content of 0.05, the pigment exhibited decent brownish appearance and modest NIR reflectance of 50.7% which was close to that of the pigment synthesized from pure rutile. The glaze consisting of 10 wt.% pigment had a glossy light brown appearance, and possessed NIR reflectance of 75.0 %, indicating a promising application in a field of NIR-reflective coating.

Development of Polycaprolactone Infiltrated Anti-Tuberculosis Drug-Loaded 3D-Printed Hydroxyapatite for Localized and Sustained Drug Release in Bone and Joint Tuberculosis Treatment
Author:Faungchat Thammarakcharoen, Autcharaporn Srion, Watchara Chokevivat, Ruedee Hemstapat, Noppawan Phumala Morales and Jintamai Suwanprateeb
Vol. Vol.49 No.1 (Special Issue I : Jan 2022) Page -

     Bone and joint tuberculosis is one of extrapulmonary tuberculosis that is commonly found globally. Treatment of bone tuberculosis typically involves long term oral medication and frequently causes side effects due to its systemic administration route. In order to mitigate the side effects and to increase the performance, the use of localized medication for sustained drug release was investigated. Three first-line anti-tuberculosis drugs were loaded into three-dimensional printed hydroxyapatite (3DP HA) by vacuum infiltration and then further infiltrated by low molecular weight polycaprolactone (PCL). It was observed that PCL uniformly coated on the surface and filled the inside pores of all infiltrated samples and did not much affect the drug loading content in the samples. Rifampicin (RIF) loaded samples, either non-infiltrated or infiltrated ones, displayed longer sustained release than those of isoniazid (INH) or pyrazinamide (PZA) loaded samples, but the release of infiltrated samples could be further enhanced in terms of released content and duration. These were related to the drug solubility and diffusion distance of drugs in the samples. Bioactivity of the drug-loaded samples was also not hampered as the apatite layer was seen to grow on the surface ascertaining its role as a dual functioned bone graft.

Surface Modification of Silica Particles Taken from Waste Glass by Surfactant Treatment for Light Scattering Application
Author:Kanokthip Boonyarattanakalin, Wanichaya Mekprasart, Aphisit Manivong, Tirapat Wechprasit, Krisana Chongsri and Wisanu Pecharapa
Vol. Vol.49 No.1 (Special Issue I : Jan 2022) Page -

This work aims to modify the surface of silicon dioxide particles for high dispersion property in the host matrix. Silicon dioxide powders were obtained from wasted material as broken beaker glass and reduced its particle size by high energy milling process operating at 500 rpm for 30 min. These particles can be proposed as an effective light scatterer and applied in the transparent light planar waveguide for the improvement of light emission performance. However, the main problem of using milled silica powder is the poor dispersion in the polymer matrix. Therefore, the surface modification method is a key role to resolve this obstacle by using polymer surfactant agents as polyvinyl alcohol, polyethylene glycol, and sodium hexametaphosphate. The proper polymer surfactant in the surface modification on silica powders has been revealed. The particle size of each condition was analyzed by a particle analyzer. Modified silica particle size with polymer surfactants trended to decrease lower than 1 μm owing to good dispersion of the particles by polymer chain and interaction between silica and surfactant surface. Chemical functional groups on modified silica powders were investigated by Fourier transform-infrared (FT-IR) spectroscopy. FTIR spectra shown that main chemical components of all samples were composed of silica and borate chemical bonding. Meanwhile, the O-H stretching vibration appeared in the spectra was a key role for particle size and good dispersion of modified surface silica particles in the solution. Moreover, light scattering property and transmission of modified silica with polymer surfactants in dispersion solution were detected by luminance meter and UV-Vis spectrometer to confirm its possibility for application in light scattering material. The best polymer surface for milled silica surface modification in this work was obtained from polyvinyl alcohol, which proved that the adjustment of surface charge and physical properties on the silica surface.

Fabrication of Monetite by a Controlled Phase Transformation of Three Dimensionally Printed Calcium Sulfate Construct
Author:Autcharaporn Srion, Faungchat Thammarakcharoen and Jintamai Suwanprateeb
Vol. Vol.49 No.1 (Special Issue I : Jan 2022) Page -

     Monetite is one of the calcium phosphates that has been used for bone regeneration and repair. Comparing to the widely used hydroxyapatite, monetite displayed greater resorption at physiological pH and could induce osteoclast resorption. Fabrication of a shape-customizable monetite construct by using a powder-based three dimensional printing (3DP) technique in combination with a phase transformation at low temperature was studied. Phase transformation of 3D printed calcium sulfate-based sample was carried out in 1M disodium hydrogen phosphate solution at pH5. Various processing parameters were then varied including temperatures (37 oC, 65 oC and 100 oC), sample weight to solution volume ratios (1:20, 1:30, 1:40 and 1:50) and soaking periods (24 h, 48 h, 72 h, 96 h and 120 h). It was found that a temperature of 100 oC, a sample weight to volume ratio of 1:50 and a time greater than 48 h were needed to fully transform the as-printed sample to monophasic monetite without causing the destruction of the structure or the incomplete transformation. Consistently, the microstructure of samples changed from rod-like crystals of calcium sulfate to petal-like crystals of monetite during the transformation process. Density, compressive modulus and strength decreased with soaking times during the course of transformation, but they did not further change with times after complete transformation. In vitro resorbability showed that 3D printed resorbed without conversion to other phase and its weight loss and ions release were greater than those of 3D printed hydroxyapatite indicating its greater resorption potential.

Emissions and Performance of a Hybrid Hydrogen-gasohol E20 Fueled Si Engine
Author:Maethas Phantoun, Karoon Fangsuwannarak and Thipwan Fangsuwannarak
Vol. Vol.49 No.1 (Special Issue I : Jan 2022) Page -

     This paper has investigated the effects of an alternative hybrid hydrogen-gasohol E20 fueled spark ignition engine on engine performance and exhaust pollutants. A hydrogen mixture with gasohol E20 was performed in an external mixture formation by installing a hydrogen fuel injection kit into the intake manifold area which is responsible for injecting hydrogen fuel into the inside of the engine’s cylinder. The hydrogen energy fraction in the intake was gradually increased from 3% to 9% ignition degree in the range of 20°, 25°, 30° and 35° before top dead center were controlled by using the electronic control unit to study the optimal condition for a four-stroke single-cylinder engine. In the steady-state test condition with half-open throttle under the variable load engine at 28%, 42%, 56%, and 70% of maximum engine torque, the engine can be available satisfactorily for an average relative air-fuel ratio (λ) value of 1.2 for hybrid hydrogen-gasohol E20 fuel. The results indicated that when the increase of hydrogen volume fraction. Postponing the spark timing was closer to top dead center (TDC) at 25° BTDC, the brake power and thermal engine efficiency increases. It is also noted that postponing the spark timing also caused NOx, HC and CO emissions to decrease. NOx emissions increased as the hydrogen volume fraction increased, whereas HC and CO emissions decreased.

Comparison of Mechanical and Corrosion Properties for 17-4 PH Stainless Steel Fabricated by Metal Injection Moulding Using Varied Powder Sizes
Author:Phanuphak Seensattayawong, Pierre Métais-Lagouarde†, Sukrit Songkuea and Anchalee Manonukul
Vol. Vol.49 No.1 (Special Issue I : Jan 2022) Page -

     17-4 PH stainless steel is commonly used in several engineering applications because of the combined good mechanical properties and high corrosion resistance. Metal injection moulding (MIM) was used to fabricate 17-4 PH stainless steel specimen with three mean powder sizes (D50), which are 2.82, 4.04 and 12.65 μm. The rheology of three feedstocks were investigated using melt flow index (MFI) and viscosity analysis. Feedstocks were injected at 170 °C. Injected tensile specimens were sintered at 1325 °C for 2 h in argon atmosphere. Surface roughness (Ra) measurement, relative density measurement, tensile test and hardness test (HRC) were carried out. Corrosion properties were determined by cyclic polarisation tests. The results indicated that the relative density of sintered samples is higher than 98% (7.68-7.74 g/cm3). α-Fe (bcc-martensite), δ-Ferrite (delta ferrite) and also SiO2 were observed in all sintered samples, which were detected by scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDS). As the mean powder size of injected specimens increases, the elongation and hardness increase, whereas the ultimate tensile strength (UTS) and surface roughness decrease. Moreover, the specimens using the smallest powder (2.82 μm) have shown better corrosion resistance than the specimens using the larger powders as the higher potentials in term of E-pit (the potential of pitting) and E-rep (the potential of repassivation) and the lower potential in term of E-cor (the potential of corrosion).

Eff ect of Injection Moulding Sequences on Mechanical Properties of Two-material Metal Injection Moulding
Author:Sukrit Songkuea, Nicolas Montroussier†, Phanuphak Seensattayawong and Anchalee Manonukul
Vol. Vol.49 No.1 (Special Issue I : Jan 2022) Page -

Two-Material Metal Injection Moulding (2M-MIM) process was developed for a component that requires different properties of materials. The materials used in this study were SCM 415, Fe-2Ni and 316L stainless steel (316L SS). The tensile test specimens were injected into 2M-MIM of SCM 415-Fe-2Ni and SCM 415-316L SS. In addition, each alloy was fabricated by MIM as reference samples. The 2M-MIM processes were injected with two different injection moulding sequences, which are “sequential injection” and “simultaneous injection”. The injection process of “sequential injection” specimens is to fi ll a half of the mould with the fi rst alloy and then inject the second half of the mould with the second alloy. The “simultaneous injection” specimens utilised the co-nozzle and co-injected both alloys simultaneously from each end of tensile specimen. The weld line positions of both injection moulding sequences were controlled in the middle at the gauge length. After injection, all specimens were sintered at 1325°C for 2 hrs. The shrinkage of each single-material specimen is 12.20 ± 0.64%, 14.90 ± 1.95% and 13.84 ± 0.24% for SCM 415, Fe-2Ni and 316L SS respectively. The ultimate tensile strength of SCM 415, Fe-2Ni and 316L SS are 549.62 ± 7.87 MPa, 474.08 ± 8.1 MPa and 351.44 ± 0.42 MPa respectively and the elongation is 9.68 ± 0.71%, 23.05 ± 2.64% and 51.33 ± 3.76% respectively. For 2M-MIM, the mechanical properties of the “sequential injection” specimens are more superior than the “simultaneous injection” specimens. This is due to the difference of weld line interface of 2M-MIM. The interface of sample was investigated by SEM and OM. Cracks were observed at the weld line of SCM – Fe-2Ni using “simultaneous injection” and the sharp crack was observed near the edge of specimen all specimens. The ultimate tensile strength of SCM 415-Fe-2Ni specimens and SCM 415-316L SS specimens are 374.42 ± 13.80 MPa and 403.35 ± 31 MPa respectively for “sequential injection” and 223.87 ± 31.98 MPa and 193.75 ± 15.41 MPa respectively for “simultaneous injection”. EDS results across the weld line of SCM 415-Fe-2Ni “sequential injection” specimen show that nickel diffused from Fe-2Ni to SCM 415 while chromium diffused from SCM 415 to Fe-2Ni.

The Study of Ranong Metakaolin-Based Porous Geopolymers as Insulating Materials for Construction
Author:Pimpun Henpraserttae, Sitthisuntorn Supothina and Patthamaporn Timakul
Vol. Vol.49 No.1 (Special Issue I : Jan 2022) Page -

     An increased concern of global warming has driven an increased demand of thermal-insulating materials, particularly in a construction industry. Traditional thermal-insulating construction materials are porous ceramic and light-weight cement brick which have high porosity and heat resistance. However, the manufacturing of cement is a major carbon dioxide (CO2) emission as it has been reported that 0.73-0.85 tons of CO2 were released from every single ton of cement production. Geopolymer is one of the alternatives to replace the cement-based materials. The present study aims to improve the properties of Ranong metakaolin-based porous geopolymers prepared by mixing the metakaolin in an alkaline activator at a weight ratio of metakaolin: activator of 55:45. A 3-μm Al powder employed as pore former was added into the geopolymer mixtures, and the samples were cured at 27-60°C for 24 h followed by aging at room temperature for 28 days. The addition of 0.1-0.4 wt.% Al powder resulted in porous structures having bulk densities in a range of 0.58-0.93 g/cm3, thermal conductivities in a range of 0.172-0.390 W/m∙K and compressive strengths in a range of 3.1-22.4 MPa. The properties of the fabricated porous geopolymers satisfy the TIS 1510-2541 standard and the CIBSE Guide A, indicating potential application as green thermal-insulating materials for building and construction.

Preliminary Characterization of Mucus Crude Extracts from Mushroom Phallus indusiatus
Author:Thanyarat Saejung, Sarote Nitsawang and Patchara Punyamoonwongsa
Vol. Vol.49 No.1 (Special Issue I : Jan 2022) Page -

     Skin diseases, such as dermatitis, allergies and eczema, are one of the most leading causes of global diseases, affecting millions of people worldwide. Most of them are associated with the skin dehydration condition, caused by the loss of natural moisturizing factors (NMFs) in the corneocyte skin layer. To resolve this issue, the exogenously administered hyaluronic acid (HA) therapeutics were introduced. Nonetheless, HA sources from microbial fermentation is still expensive with potential toxicity from the toxin protein impurities. We demonstrated an alternative NMFs source from the mucus extracts of the Phallus indusiatus (P. indusiatus) mushroom. For this, the fresh mucus was partially purified by the sequential chelation (CaCl2/EDTA). A combined use of both IR and 13C-NMR spectroscopic techniques confirmed the presence of glucuronic acid (GlcA) in the crude extracts, as convinced by the presence of the IR absorption bands at 1600-1603 cm−1 (C=O stretching), 3000-3800 cm−1 (-OH stretching), and at 1402-1410 cm−1 (C-O stretching), together with the 13C-NMR resonances at 101 ppm, 79 ppm and 81 ppm. The disappearance of the NMR characteristic peaks, corresponding to the N-acetyl glucosamine (GlcNAc) at 1.9-2.0 ppm (1H-NMR) and 23-25 ppm (13C-NMR), suggested the extremely low level of the HA in the crude extracts. Nonetheless, these crude extracts showed the higher water content, comparing to the HA standard, highlighting their potential use as an alternative NMFs sources for dry skin therapeutics.

Effects of Cr Doping on Physical Properties of CuBO2 Delafossite Oxide
Author:Sornamol Traiphop, Jedsada Manyam and Teerasak Kamwanna
Vol. Vol.49 No.1 (Special Issue I : Jan 2022) Page -

     In this research work, CuB1−xCrxO2 (x = 0.00, 0.01, 0.03, 0.05, and 0.07) were synthesized by using a conventional solid-state reaction method. The effects of Cr concentration on its microstructure, optical, magnetic, and dielectric properties were investigated. X-ray diffraction (XRD) results revealed the crystal structure of all samples belongs to the R-3m delafossite structure. Besides, a second phase CuCrO2 appeared in a high Cr content sample. Scanning electron microscope (SEM) indicated that particle size of samples was about 300 nm and slightly increased with increasing the Cr content. The optical properties measured by UV-visible spectroscopy showed the absorbance peak at ~250 nm. The corresponding direct optical band gap was about 2.90 eV. The magnetic hysteresis curve measurements of all samples revealed the paramagnetic behavior at room temperature. Noticeably, the Cr-doped samples (x = 0.01−0.07) exhibited as a ferromagnetic behavior at 50 K. Furthermore, the zero-field-cooling magnetization of the Cr-doped samples shows a ferromagnetic transition temperature at ~130K. Finally, the dielectric measurement of all samples shows the colossal dielectric permittivity.

Temperature Dependence on Mechanical, Dielectric, and Electric Field-Induced Strain Properties of Lead-Free BNST Ceramics
Author:Kamonporn Saenkam, Pharatree Jaita, Parkpoom Jarupoom, Chamnan Randorn, Komsanti Chokethawai, Gobwute Rujijanagul and Tawee Tunkasiri
Vol. Vol.49 No.1 (Special Issue I : Jan 2022) Page -

In this research, temperature dependence on the phase evolution, physical, microstructure, mechanical, dielectric, and electric field-induced strain responses of the Bi0.41Na0.35Sr0.21TiO3 or BNST ceramics were investigated. The BNST ceramic was prepared by a conventional mixed oxide method and sintered at various temperatures from 1100 °C to 1175 °C in order to clarify the optimal sintering temperature for all propereties. X-ray diffraction results showed that all ceramics exhibited a single perovskite without any secondary phases. A mixed between tetragonal and rhombohedral phases were identified for all ceramics. Grain size tended to increase with increasing the sintering temperature. The mechanical improvement was related with the change in densification. The optimum relative density (95.83 %), mechanical (HV = 6.43 GPa, HK = 5.12 GPa, E = 107.57 GPa, and KIC = 2.42 MPa.m1/2), and dielectric properties (ε′ = 1752, tan δ = 0.0514, and δA = 100 K), were obtained for the ceramic sintered at 1125 - 1150 °C. In addition, the obtimum sintering temperature of 1125 - 1150 °C were also found to improve the electric field-induced strain response (Smax = 0.14 % and d*33 = 285 pm/V), and the electrostrictive coefficient (Q33 = 0.0199 m4/C2).

Author:Dr. Robert Molloy
Vol. Vol.49 No.1 (Special Issue I : Jan 2022) Page v - v

The 18 selected papers in this special issue were presented at the The 21st International Union of Materials Research Societies - International Conference in Asia (IUMRS-ICA 2020) held online from 23-26 February 2021 at the Faculty of Science, Chiang Mai University, Chiang Mai, Thailand.

The conference was co-organized by the Materials Research Society of Thailand (MRS-Thailand); Materials Science Research Center, Faculty of Science, Chiang Mai University; Office of Research Administration, Chiang Mai University; Bioplastics Production Laboratory for Medical Applications, Chiang Mai University; Center of Excellence in Advanced Nanomaterials and Characterization, Suranaree University of Technology; Center of Excellence on Advanced Functional Materials, Suranaree University of Technology; Establishment of Integrated Ecosystem for Quantum Technology Research, Suranaree University of Technology; Center of Excellence on Petrochemical and Materials Technology (PETROMAT), Chulalongkorn University; Metallurgy and Materials Science Research Institute, Chulalongkorn University; Faculty of Engineering and Industrial Technology, Silpakorn University; Naresuan University; Rajamangala University of Technology Thanyaburi; Faculty of Engineering, Kasetsart University; National Nanotechnology Center (NANOTEC); National Metal and Materials Technology Center (MTEC); Synchrotron Light Research Institute (SLRI); and Seagate Technology (Thailand) Ltd.

The conference covered all fields of materials research divided into 10 parallel symposia, namely:
- Electronic and Optical Materials
- Energy and Environment Materials
- Bioplastics, Biomaterials and Medical Devices
- Advanced Functional Materials
- Advanced Structural Materials
- Computational Materials Science, Modeling and Simulation
- Advanced Fabrication, Characterization and Devices
- Instrumentation and Materials Characterization
- Rheology
- Special Symposium on Material Enterprises and Industries

Altogether there was a total of 368 oral presentations including 6 plenary lectures, 37 keynote lectures and 84 invited lectures; and supported by 252 poster presentations. The conference was attended by a total of 859 registered participants from 25 different countries.

In publishing this special issue, the Chiang Mai Journal of Science would like to thank the organizers of IUMRS-ICA 2020 and the authors of the papers for choosing to make this select collection of papers available to the Journal for wider dissemination to the scientific community. All of the papers have been peer reviewed for which special thanks are due to the conference’s Scientific Committee.

Synchrotron Radiation Study on Ancient Burnt Rice Found at Archaeological Sites in Thailand
Author:Chatdanai Boonruang, Krit Won-in, Somchai Tancharakorn, Phakkananan Pakawanit, Kanjana Thumanu and the Pisutti Dararutana
Vol. Vol.49 No.1 (Special Issue I : Jan 2022) Page 1 - 13

Rice is the food staple for most of the world’s population especially Asians. It is also the essence of life of people in Thailand. Archaeological evidence based on the paddy rice reveals the rice planting in northeastern Thailand over 5,000 years ago. The burnt rice grains have been found in many archaeological sites in Thailand, which are involved with the religious ceremony and home prosperity. In this work, the synchrotron radiation has been applied to investigate the elemental distribution, chemical composition and bio-molecular structure, and three-dimensional segmentation of the ancient burnt rice samples from Nakorn Nayok (Ban Dong Lakon), Suphan Buri (U-Thong), and Prachin Buri (Sri Mahosot) using micro-beam XRF (SR μ-XRF), Infrared spectroscopy (SR IR), and X-ray tomographic microscopy based on synchrotron radiation (SR XTM), respectively. Field emission scanning electron microscope (FE SEM) incorporated with energy dispersive spectrometer (EDS) have been carried out in order to characterize the structure and composition of samples. It has been found that the grains are oblong in shape with a rough surface. Major elements in the grains are C, Si, Ca, and Al. Other trace elements such as Ti, Cr, Mn, Fe, Ni, Cu, and Zn are also detected. The IR spectra provide some information about molecular bonds. The tomographic investigations reveal the internal structure of ancient burnt rice.

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