Browsing by Author "Smith, Paul"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
Item Design and characteristics of hydroxyapatites: effect of radiation(Society of Photo-Optical Instrumentation Engineers (SPIE), 2018-05-14) Bhavsar, Jayati; Tufail, Areeba; Gautam, Pooja; Arnold, Brad; Choa, Fow-Sen; Kelly, Lisa; Cullum, Brian; Smith, Paul; Su, Ching Hua; Mandal, K. D.; Singh, N. B.We have prepared silicate based hard materials and have processed it with organic flux. Because of the bioactivities of hydroxyapatites with tissues, this class of materials have attracted interest for bone applications. We have utilized low temperature processing techniques. Organic melt was used and the directional solidification method to cast the shaped sample. This organic treated material has different characteristics than coarsened oxide materials. Our approach involved low temperature processing using nano and micron sized powders of the material system Na₂OK₂O-CaO- MgO-Ga₂O₃-SiO₂, and titanates were processed by sintering and grain growth. Our results indicate that substitution of gallium and magnesium or titanium with some variation in processing methods have great potential to improve the glassy characteristics without decreasing the mechanical properties of bones. Effect of radiation on bone was studied by exposing with commercially available Cs¹³⁷ gamma ray source. It was observed that electrical resistivity increased due to radiation exposure for this system.Item Distorted perovskites for high voltage dielectric capacitors(SPIE, 2019-05-13) Gill, Puneet; Bagherzadeh, Hedyeh; Choa, Fow-Sen; Arnold, Bradley; Smith, Paul; Su, Ching Hua; Verma, Manish; Singh, Laxman; Mandal, Kamdeo; Singh, N. B.There are several mechanisms which have been proposed for the existence of colossal dielectric constant in the class of perovskite calcium copper titanate (CaCu₃Ti₄O₁₂ or CCTO) materials. Researches indicate that existence of twinning parallel to (100) (001) and (010) planes causes planar defects and causes changes in local electronic structure. This change can cause insulating barriers locally which contribute to the large dielectric values irrespective of processing. The combination of insulating barriers, defects and displacements caused by twinning have been attributed to the generation of large dielectric constant in CCTO. To examine some of these arguments some researchers replaced Ca with other elements and evaluated this concept. In this study we present the synthesis and characterization of Ga₂/₃CaCu₃Ti₄O₁₂₋ₓNₓ (GCTON) material. This provides both distortion due to atomic size difference and defects due to insertion of nitrogen. The morphology of the compound was determined to show that processing has tremendous effect on the dielectric values. The resistivity of GCTON was several order higher than CCTO and dielectric constant was higher than 10,000.Item Effect of additives: organic-metal oxide nanocomposites for γ-ray sensors(SPIE, 2018-05-23) Singh, N. B.; Su, Ching Hua; Arnold, Bradley; Choa, Fow-Sen; Cooper, Christopher; Sova, Stacey; Gill, Puneet; Dayal, Vishall; Kelly, Lisa; Prasad, Narasimha; Smith, Paul; Cullum, BrianThe transition metal oxide embodied organic composites have great promise for high energy radiation detection. The interaction of high energy radiation such as γ-rays with the organic composite can generate photoelectric responses, Compton scattering and electron hole pairs, which can provide favorable properties to enhance the radiation detectivity of the composite. These effects along with changes of oxidation state of metal oxides, provide significant change in the electrical characteristics of composites due to radiation exposure. We have developed nickel oxide (NiO₂) nanoparticles embodied urea composite (urea-NiO₂), and determined effect of γ-radiation on the current – voltage characteristics in the frequency range of 100 Hz to 100,000Hz. In this paper, we describe the results of effect of additional oxidizing agent MnO₂ (urea-NiO₂-MnO₂) on the morphology, processing and current voltage characteristics due to exposure of Cs-137 γ-radiation. It was observed that addition of MnO₂ in urea-NiO₂ composite decreases the sensitivity of detection. However, urea-NiO₂-MnO₂ composite recovers to original properties after irradiation much faster than urea-NiO₂ composite.Item Effect of additives: γ-Ray sensors based on ionizing organic nanocompositesDayal, Vishall; Cooper, Christopher; Sova, Stacey; Gill, Puneet; Su, Ching-Hua; Arnold, Bradley; Choa, Fow-Sen; Kelly, Lisa; Cullum, Brian; Smith, Paul; Singh, N. B.We have developed ionizing organic based composites which have demonstrated great promise for radiation sensing. Nickel oxide has been proven as an active material for detecting high energy radiation. The oxidation state of unusual oxides such as nickel oxide in nanocomposites of ionizing organics changes much faster than thin film or bulk, and hence increases the sensitivity for radiation sensing. The resistivity of the oxide composite increases following sequential irradiation processes because of the decrease in holes' concentration. In this paper, we will present the effect of additional oxidizing agent on the morphology, processing and sensing of γ-ray by oxides - urea based nanocomposites. It was observed that addition of MnO₂ decreases the sensitivity. However, it recovers to original properties after irradiation much faster than undoped composites.