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Papers by Karnwalee Pangza

Radiation Protection Dosimetry, 2012

The naturally occurring radioactive materials (NORMs) distributed in products, by-products and wa... more The naturally occurring radioactive materials (NORMs) distributed in products, by-products and waste produced from Thai mineral industries were investigated. Samples were analysed for radioactivity concentrations of two principal NORM isotopes: (226)Ra and (228)Ra. The enrichment of NORM was found to occur during the treatment process of some minerals. The highest activity of (226)Ra (7 × 10(7) Bq kg(-1)) was in the scale from tantalum processing. The radium concentration in the discarded by-product material from metal ore dressing was also enriched by 3-10 times. Phosphogypsum, a waste produced from the production of phosphate fertilisers, contained 700 times the level of (226)Ra concentration found in phosphate ore. Hence, these residues were also sources of exposure to workers and the public, which needed to be controlled.

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Materials, Aug 26, 2022

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Materials

A systematic investigation of the changes in structural and optical properties of a semi-insulati... more A systematic investigation of the changes in structural and optical properties of a semi-insulating GaAs (001) wafer under high-energy electron irradiation is presented in this study. GaAs wafers were exposed to high-energy electron beams under different energies of 10, 15, and 20 MeV for absorbed doses ranging from 0–2.0 MGy. The study showed high-energy electron bombardments caused roughening on the surface of the irradiated GaAs samples. At the maximum delivered energy of 20 MeV electrons, the observed root mean square (RMS) roughness increased from 5.993 (0.0 MGy) to 14.944 nm (2.0 MGy). The increased RMS roughness with radiation doses was consistent with an increased hole size of incident electrons on the GaAs surface from 0.015 (0.5 MGy) to 0.066 nm (2.0 MGy) at 20 MeV electrons. Interestingly, roughness on the surface of irradiated GaAs samples affected an increase in material wettability. The study also observed the changes in bandgap energy of GaAs samples after irradiation...

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Materials Today: Proceedings, 2018

Abstract Portland cement is considered as an important basic material used for building construct... more Abstract Portland cement is considered as an important basic material used for building construction. One of the main concern is that people spend more than 80% of their time indoors and they are eventually exposed to the cement or its raw materials for a long time. Therefore, assessment of natural radioactivity levels and radiological hazards associated with these materials is necessary. In this study, a total of 25 samples of five Portland cement brands favorably used in Thailand were analyzed by using gamma-ray spectrometry technique. The observed specific activities of 226 Ra, 232 Th and 40 K together with the radium equivalent activities were compared with the reported data for other countries and the world recommended levels proposed by the UNSCEAR–all obtained values were found within the acceptable limits. Additionally, for evaluation of radiological risk, six hazard parameters were considered. The estimated values of absorbed dose rate, external and internal hazard indexes, gamma and alpha indexes, annual effective dose equivalent, and excess lifetime cancer risk, all of them were found below the international standard of the maximum acceptable limits. Therefore, these studied results primarily confirm that all five brands of Thai Portland cement type I are radiologically safe to be used as construction materials with no significant impact of radiological hazards provided.

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Journal of Bioactive and Compatible Polymers, 2016

Gamma irradiation was used to fabricate crosslinked poly(vinyl alcohol)/sericin hydrogels with di... more Gamma irradiation was used to fabricate crosslinked poly(vinyl alcohol)/sericin hydrogels with different sericin concentrations, and the physicochemical and biological properties of the gamma-irradiated poly(vinyl alcohol)/sericin hydrogels were characterized. Following gamma irradiation, the hydrogels had a high gel fraction (80%–95%), implying a high degree of crosslinking. Fourier transform infrared spectra confirmed the crosslinking bonds within the hydrogels, as seen by the characteristic shift in the peak. Furthermore, a low tensile modulus together with a high elongation percentage indicated that the hydrogels were easy to handle. We also showed that all hydrogels released sericin simultaneously. The poly(vinyl alcohol)/sericin hydrogels with high sericin content released more sericin, possibly due to less crosslinking of the hydrogels. When L929 cells were cultured with the hydrogel extracts, the cells were viable and could proliferate, particularly for the cells cultured wi...

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Journal of Radioanalytical and Nuclear Chemistry, 2014

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Engineering Journal, 2011

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Journal of Radioanalytical and Nuclear Chemistry, 2014

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Radiation Protection Dosimetry, 2012

The naturally occurring radioactive materials (NORMs) distributed in products, by-products and wa... more The naturally occurring radioactive materials (NORMs) distributed in products, by-products and waste produced from Thai mineral industries were investigated. Samples were analysed for radioactivity concentrations of two principal NORM isotopes: (226)Ra and (228)Ra. The enrichment of NORM was found to occur during the treatment process of some minerals. The highest activity of (226)Ra (7 × 10(7) Bq kg(-1)) was in the scale from tantalum processing. The radium concentration in the discarded by-product material from metal ore dressing was also enriched by 3-10 times. Phosphogypsum, a waste produced from the production of phosphate fertilisers, contained 700 times the level of (226)Ra concentration found in phosphate ore. Hence, these residues were also sources of exposure to workers and the public, which needed to be controlled.

Bookmarks Related papers MentionsView impact

Materials, Aug 26, 2022

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Materials

A systematic investigation of the changes in structural and optical properties of a semi-insulati... more A systematic investigation of the changes in structural and optical properties of a semi-insulating GaAs (001) wafer under high-energy electron irradiation is presented in this study. GaAs wafers were exposed to high-energy electron beams under different energies of 10, 15, and 20 MeV for absorbed doses ranging from 0–2.0 MGy. The study showed high-energy electron bombardments caused roughening on the surface of the irradiated GaAs samples. At the maximum delivered energy of 20 MeV electrons, the observed root mean square (RMS) roughness increased from 5.993 (0.0 MGy) to 14.944 nm (2.0 MGy). The increased RMS roughness with radiation doses was consistent with an increased hole size of incident electrons on the GaAs surface from 0.015 (0.5 MGy) to 0.066 nm (2.0 MGy) at 20 MeV electrons. Interestingly, roughness on the surface of irradiated GaAs samples affected an increase in material wettability. The study also observed the changes in bandgap energy of GaAs samples after irradiation...

Bookmarks Related papers MentionsView impact

Materials Today: Proceedings, 2018

Abstract Portland cement is considered as an important basic material used for building construct... more Abstract Portland cement is considered as an important basic material used for building construction. One of the main concern is that people spend more than 80% of their time indoors and they are eventually exposed to the cement or its raw materials for a long time. Therefore, assessment of natural radioactivity levels and radiological hazards associated with these materials is necessary. In this study, a total of 25 samples of five Portland cement brands favorably used in Thailand were analyzed by using gamma-ray spectrometry technique. The observed specific activities of 226 Ra, 232 Th and 40 K together with the radium equivalent activities were compared with the reported data for other countries and the world recommended levels proposed by the UNSCEAR–all obtained values were found within the acceptable limits. Additionally, for evaluation of radiological risk, six hazard parameters were considered. The estimated values of absorbed dose rate, external and internal hazard indexes, gamma and alpha indexes, annual effective dose equivalent, and excess lifetime cancer risk, all of them were found below the international standard of the maximum acceptable limits. Therefore, these studied results primarily confirm that all five brands of Thai Portland cement type I are radiologically safe to be used as construction materials with no significant impact of radiological hazards provided.

Bookmarks Related papers MentionsView impact

Journal of Bioactive and Compatible Polymers, 2016

Gamma irradiation was used to fabricate crosslinked poly(vinyl alcohol)/sericin hydrogels with di... more Gamma irradiation was used to fabricate crosslinked poly(vinyl alcohol)/sericin hydrogels with different sericin concentrations, and the physicochemical and biological properties of the gamma-irradiated poly(vinyl alcohol)/sericin hydrogels were characterized. Following gamma irradiation, the hydrogels had a high gel fraction (80%–95%), implying a high degree of crosslinking. Fourier transform infrared spectra confirmed the crosslinking bonds within the hydrogels, as seen by the characteristic shift in the peak. Furthermore, a low tensile modulus together with a high elongation percentage indicated that the hydrogels were easy to handle. We also showed that all hydrogels released sericin simultaneously. The poly(vinyl alcohol)/sericin hydrogels with high sericin content released more sericin, possibly due to less crosslinking of the hydrogels. When L929 cells were cultured with the hydrogel extracts, the cells were viable and could proliferate, particularly for the cells cultured wi...

Bookmarks Related papers MentionsView impact

Journal of Radioanalytical and Nuclear Chemistry, 2014

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Engineering Journal, 2011

Bookmarks Related papers MentionsView impact

Journal of Radioanalytical and Nuclear Chemistry, 2014

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