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Optimization of ethanolic extraction of asiaticoside and asiatic acid: A stability study and correlation of dielectric constant
(2025-06-01)
Chysirichote, Teerin
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Wattanasiriwit, Waewwan
;
Uraipong, Chatchaporn
This study optimized the extraction of asiaticoside and asiatic acid from Centella asiatica using an ultrasonic-assisted extraction method. The research focused on ethanol concentration, extraction temperature, and extraction duration to maximize yield efficiency. In addition, the stability of the extracted compounds was assessed under different temperature and pH conditions for practical applications. The highest asiaticoside yield was achieved using 53.7 % ethanol at 50.0 °C for 35 min., whereas asiatic acid extraction was most efficient using 63.3 % ethanol at 64.3 °C for 28 min. A significant correlation was observed between the dielectric constant of the extraction conditions, which was affected by solvent concentration and temperature, and extraction efficiency. Stability tests showed that temperature had a more pronounced impact than pH, with degradation accelerating at higher temperatures. The findings emphasize the importance of maintaining processing conditions below 70 °C and within an acidic to neutral pH range. These results provide valuable insights for industrial applications in pharmaceutical, cosmetic, and nutraceutical sectors, underscoring the necessity of controlled conditions to preserve the bioactive properties of Centella asiatica extracts.
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Non-destructive determination of coconut oil using microwave dielectric constant sensing
(2019-01-01)
Suwalak, R.
;
Phongcharoenpanich, C.
Coconut oil demand for food, medical and cosmetic uses is increasing. Analyses of quality using non-destructive tools would be useful, and therefore, wireless sensing using high frequency to determine the percentage of coconut oil has been tested. The proposed sensing is based on the wireless power transmission and the penetration of the ultrahigh frequency wave. The system operates with the microwave transceiver that generates wireless power and receives the backscatter power from a sensor placed on a coconut. A transceiver at microwave frequency of 920-925 MHz with low power level was used to avoid affecting coconut quality. Wireless microwave dielectric constant sensing was used with reasonable accuracy to determine the percentage of the coconut oil.
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Optical and dielectric properties of nano-sized tricalcium aluminate hexahydrate (C3AH6) cement
(2018-08-10)
Phrompet, Chaiwat
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Sriwong, Chaval
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Maensiri, Santi
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Chindaprasirt, Prinya
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Ruttanapun, Chesta
The present study investigates the optical and dielectric properties of nano-sized C3AH6 cement hydrates. A cement product was fabricated via a simple hydration process using a derivative of a C12A7 cement precursor reacting with de-ionized water while raising the reaction temperature to 100 °C. A crystalline phase of the C3AH6 cement product was characterized and confirmed using an XRD technique. Its morphology was also evaluated using TEM and SEM techniques. It was found that nano-sized C3AH6 (in size 10–50 nm) was successfully derived via this process. This cement product was thermodynamically stable over the range of room temperature to 300 °C. The optical direct gap was 4.1 eV and the indirect energy gap was 2.45 eV. Over the range of 20 Hz to 2 MHz, the observed capacitance was 10<sup>−10</sup> F–10<sup>−11</sup> F and the dielectric constant varied from 20 to 150. The dielectric properties were enhanced over those of general cement compounds. This effect was due to its complex structure in which –O–H bonding appeared in the structure and the formation of nano-sized structures from this process. These results suggested that the nano-C3AH6 hydrated particles were transparent to visible light and exhibited a high frequency electrical response. This implies an important role for these cement-based materials as potential candidates having optical and dielectric properties appropriate for applications such as smart building materials in the form of transparent electrode windows, smart wall capacitors, triboelectric devices and supercapacitors.
1
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Dielectric properties of Palmyrah palm juice at microwave frequencies
(2014-03-25)
Kanahna, Rachen
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Keowsawat, Panisa
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Promwong, Sathaporn
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Phongcharoenpanich, Chuwong
The dielectric properties of Palmyrah palm juice with different total soluble solid (TSS) of 16-32° Brix were measured by open ended coaxial probe at three different frequencies of 915, 1800, and 2450 MHz. The dielectric constant was increased with increasing TSS and vice versa for the dielectric loss factor. At 2450 MHz, the dielectric constant and loss factor were higher than 915 M Hz along the entire ranges of TSS. There are the distinctions of dielectric constant and loss factor between the pure and impure palm juice.
1
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The effects of solvents on the properties of ultra-thin poly (methyl methacrylate) films prepared by spin coating
(2013-11-01)
Tippo, T.
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Thanachayanont, C.
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Muthitamongkol, P.
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Junin, C.
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Hietschold, M.
Poly (methyl methacrylate) (PMMA) is extensively used as an insulating layer in organic electronic devices. In this study, spin coating method was used to cast thin layers of PMMA for dielectric application from solutions in three different solvents, namely dimethylformamide (DMF), n-butyl acetate and toluene. The solvent's vapor pressure causes the solvent to vaporize at different rates leading to layer's distortion and different surface roughnesses. Preparation of suitable surface morphologies, for example, pinhole-free and crack-freewas studied. A step profilometer was used to measure the film thicknesses. Alternatively an equation correlating final film thickness to spin speed and solution concentration was proposed. A metal/insulator/metal parallel plate capacitor structurewas fabricated and the current density dependence on the applied electric fieldwas measured. The resulting low surface roughness, low leakage currents, high breakdown voltage, and high dielectric constant were obtained for the 100 nm-thick PMMA film prepared with DMF. © 2013 Elsevier B.V.
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Use of the combustion technique for the preparation of Ba(Ti 0.70Zr0.30)O3 ceramics
(2010-12-01)
Phungjitt, N.
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Panya, P.
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Vittayakorn, N.
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Bongkarn, T.
The preparation conditions for barium titanate zirconate [Ba(Ti <inf>0.70</inf>Zr<inf>0.30</inf>)O<inf>3</inf>] ceramics by the combustion method were studied. The X-ray diffraction pattern indicated that the calcined powders belonged to a cubic phase. The maximum percentage of the cubic perovskite phase was found in the sample calcined at 850°C. A pure cubic crystal structure was found in all ceramic samples. The average grain size increased with increasing sintering temperatures. The dielectric constant-temperature plots showed a maximum peak value of 5800 from ceramic sintered at 1350°C. The densities of samples corresponded to the dielectric constant. A diffuse phase transition was also observed.
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Effect of annealing time on electrical and mechanical properties of 0.7(Pb(Zr1/2Ti1/2)O3) - 0.3(Pb(Zn 1/2Nb2/3)O3 ceramics
(2009-12-01)
Rujijanagul, G.
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Vittayakorn, N.
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Nabunmee, S.
The solid solution between the normal ferroelectric and relaxor ferroelectric of 0.7(Pb(Zr1/2Ti1/2)O3) - 0.3(Pb(Zn1/2Nb2/3)O3 was synthesized by the columbite method. After sintering, the ceramics were investigated as a function of annealing time. Properties of the ceramics were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), dielectric spectroscopy, and hardness tester. The results indicated that dielectric constant of the annealed samples was enhanced. In addition, hardness values of the annealed samples were also improved. Copyright © Taylor & Francis Group, LLC.
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