TeO2 Powders Research Articles

Assessment of Elongation Percentage, Tensile, and Tear Strength of Filler Particles

Introduction: We aimed to assess how the addition of nano tellurium oxide (TeO2) filler particles affected the elongation percentage, tensile strength, and tear strength of the maxillofacial silicone elastomer. Methods: Thirty samples were created by adding nano TeO2 powder (518.9 nm) at percentages of 0%, 3%, and 5% w/w into the RTV VST-50 silicon elastomer. Elongation percentage, tensile, and tear strength were assessed according to the specifications of ISO 37:2017 using a computerized universal testing device. Data were analyzed with one-way ANOVA and Tukey’s honest significant difference test using MedCalc 20.104. Results: There were statistically significant differences regarding elongation percentage, tensile, and tear strength among study groups (P < 0.001). All of the post hoc comparisons showed statistically significant differences (P ≤ 0.002). Conclusion: The addition of 5% and 3% nano TeO2 filler particle significantly increases the elongation percentage, tensile strength, and tear strength of maxillofacial silicone in comparison with the control group, concentration-dependently.

Investigating the Leaching Rate of TiTe<sub>3</sub>O<sub>8</sub> Towards a Potential Ceramic Solid Waste Form

An important property of glass and ceramic solid waste forms is processability. Tellurite materials with low melting temperatures and high halite solubilities have potential as solid waste forms. Crystalline TiTe3O8 was synthesized through a solid-state reaction between stoichiometric amounts of TiO2 and TeO2 powder. The resultant TiTe3O8 crystal had a three-dimensional (3D) structure consisting of TiO6 octahedra and asymmetric TeO4 seesaw moiety groups. The melting temperature of the TiTe3O8 powder was 820℃, and the constituent TeO2 began to evaporate selectively from TiTe3O8 above around 840℃. The leaching rate, as determined using the modified American Society of Testing and Materials static leach test method, of Ti in the TiTe3O8 crystal was less than the order of 10-4 g·m-2·d-1 at 90℃ for durations of 14 d over a pH range of 2-12. The chemical durability of the TiTe3O8 crystal, even under highly acidic and alkaline conditions, was comparable to that of other well-known Ti-based solid waste forms.

Phosphine-free engineering toward the synthesis of metal telluride nanocrystals: the role of a Te precursor coordinated at room temperature.

A colloidal strategy offers opportunities for the rational design and synthesis of metal telluride nanocrystals (NCs) with the desired crystal structure, uniform geometry, and composition. However, it remains a challenge to use the paradigm to construct metal telluride NCs by a phosphine-free synthesis procedure for promising applications such as luminescence, photovoltaics and thermoelectricity. Here, we developed a new strategy for fabricating metal telluride nanocrystals, e.g. CdTe and PbTe NCs, by using a highly reactive phosphine-free Te precursor. The ability to reduce a TeO2 powder with dodecanethiol (DDT) has been achieved in the presence of oleylamine (OLA) to generate a soluble alkylammonium telluride at room temperature. We provide direct experimental evidence that the OLA-Te complexes were formed in an order of second magnitude kinetic process based on an in situ UV-vis absorption test. In the case of the CdTe NC system, the straightforward measurement of luminescence and the fabrication of LED devices are presented that can semiquantitatively assess the quality of preparation and the reactivity of this air-stable precursor. The proposed strategy highlights several unique features of this solution-based green chemistry that can be useful for synthesizing other metal telluride NCs to develop novel functional materials.

Synthesis and antimicrobial activity of gold/silver-tellurium nanostructures.

Gold-tellurium nanostructures (Au-Te NSs), silver-tellurium nanostructures (Ag-Te NSs), and gold/silver-tellurium nanostructures (Au/Ag-Te NSs) have been prepared through galvanic reactions of tellurium nanotubes (Te NTs) with Au(3+), Ag(+), and both ions, respectively. Unlike the use of less environmentally friendly hydrazine, fructose as a reducing agent has been used to prepare Te NTs from TeO2 powders under alkaline conditions. The Au/Ag-Te NSs have highly catlaytic activity to convert nonfluorescent Amplex Red to form fluorescent product, revealing their great strength of generating reactive oxygen species (ROS). Au/Ag-Te NSs relative to the other two NSs exhibit greater antimicrobial activity toward the growth of E. coli, S. enteritidis, and S. aureus; the minimal inhibitory concentration (MIC) values of Au/Ag-Te NSs were much lower (>10-fold) than that of Ag-Te NSs and Au-Te NSs. The antibacterial activity of Au/Ag-Te NSs is mainly due to the release of Ag(+) ions and Te-related ions and also may be due to the generated ROS which destroys the bacteria membrane. In vitro cytotoxicity and hemolysis analyses have revealed their low toxicity in selected human cell lines and insignificant hemolysis in red blood cells. In addition, inhibition zone measurements using a Au/Ag-Te NSs-loaded konjac jelly film have suggested that it has great potential in practial application such as wound dressing for reducing bacterial wound infection. Having great antibacterial activitiy and excellent biocompatibility, the low-cost Au/Ag-Te NSs hold great potential as effective antimicrobial drugs.

Synthesis of Bi0.5Sb1.5Te3 Thermoelectric Powder Using an Oxide-Reduction Process

The present study focused on synthesis of Bi0.5Sb1.5Te3 thermoelectric powder using an oxide-reduction process. The phase structure and particle size of the synthesized powders were analyzed using x-ray diffractometry and scanning electron microscopy. The synthesized powder was sintered using the spark plasma sintering method. The thermoelectric properties of the sintered body were evaluated by measuring the Seebeck coefficient, electrical resistivity, and thermal conductivity. Bi0.5Sb1.5Te3 powder was synthesized using a combination of mechanical milling, calcination, and reduction processes, using a mixture of Bi2O3, Sb2O3, and TeO2 powders. The sintered body of the oxide-reduction-synthesized Bi0.5Sb1.5Te3 powder showed p-type thermoelectric characteristics. The thermoelectric properties of the sintered bodies depended on the reduction time. After being reduced for 2 h at 663 K, the sintered body of the Bi0.5Sb1.5Te3 powder showed a figure of merit of approximately 1.0 at room temperature.

Synthesis of high purity, stoichiometric controlled, TeO2 powders

The growth of high quality TeO2 single crystals for acousto-optic devices usually requires a starting powder of relatively high purity (99.995% or better). In addition to foreign metallic impurities, even minute amounts of excess Te precipitating in TeO2 can play a role in the crystal growth behavior and in the resulting properties of the crystal. In this paper, two different approaches for the synthesis of high quality TeO2 starting material have been tested, both using 99.9995% Te as precursor. In the first case, basically a high temperature oxidation process, fine Te powder was subjected to a multi-stage oxidizing process occurring either in vapor or solid phase. In the second case, a hydro-metallurgical method, Te powder was dissolved in nitric acid and then precipitated in form of TeO2. The purity was measured by glow discharge mass spectroscopy and the tellurium fraction in TeO2 was determined by measuring the absorption at 442nm of the gas phase in equilibrium with a solid sample. This technique, used for the first time to measure free Te in TeO2, has proven to apply to this system, leading to good sensitivity and good repeatability. While high temperature oxidation (vapor phase oxidation or solid state diffusion) of 99.9995% Te powder allowed for preserving the purity of the material, the incorporation of impurities was observed when the TeO2 was synthesized through a wet chemical process, leading to a 99.999% purity. This last technique, however, offered the lowest deviation from stoichiometry.

Thermoelectric Properties of P-Type Bismuth Telluride Powders Synthesized by a Mechano-Chemical Process

P-type bismuth telluride thermoelectric (TE) powders were synthesized by a mechano-chemical process (MCP) in which a mixture of Bi sulfate, Sb chlorides, and TeO2 powders was dried, calcinated, and reduced to a powder alloy with ternary composition. The synthesized powders were a few micrometers in size, with a clear Bi0.5Sb1.5Te3 phase. The powders were consolidated into p-type bismuth telluride bulk materials that exhibited an electrical resistivity of 0.6×10−5 Ωm, a Seebeck coefficient of 140 μVK−1, and a thermal conductivity of 1.3 Wm−1K−1 at 298 K. Dimensionless figures-of-merit increased from 0.8 to 1.18 as the temperature increased from 298 K to 450 K. The results show that MCP is a promising process for the production of p-type bismuth telluride powders as raw materials for high-performance TE bulk alloys.

New limits on the β+EC and ECEC processes in 74Se and 120Te

Limits on double-beta processes in 74Se and 120Te have been obtained using a 400 cm3 HPGe detector and an external source consisting of natural Se or TeO2 powder. In particular, limit with a 90% C.L. on the 74Se half-life of 5.5 × 1018 y for ECEC(0ν) transitions to the 2+2 excited state in 74Ge (1204.2 keV) has been obtained. This transition is discussed in association with a possible enhancement of the decay rate, in this case by several orders of magnitude, because the ECEC(0ν) process is nearly degenerate with an excited state in the daughter nuclide. For other β+ EC and ECEC transitions (to the ground and excited states) obtained limits are on the level ∼ 1018 – 1019 y.

New limits on the β+EC and ECEC processes in 120Te

New limits on the double beta processes for 120Te have been obtained using a 400 cm3 HPGe detector and a source consisting of natural TeO2 powder. At a confidence level of 90% the limits are 0.19 × 1018 y for the β+EC(0ν + 2ν) transition to the ground state, 0.75 × 1018 y for the ECEC(0ν + 2ν) transition to the first 2+ excited state of 120Sn (1171.26 keV) and (0.19 − 0.6) × 1018 y for different ECEC(0ν) captures to the ground state of 120Sn.

Transparent conductive Cd3TeO6 thin films with perovskite structure

Transparent conductive Cd3TeO6 thin films were deposited by radio-frequency magnetron sputtering using a target composed of CdO and TeO2 powders, and these films’ electrical and optical properties were examined. The electrical resistivity of 1.9×10−2Ωcm and an average transmittance above 85% in the visible region (400–800 nm) were obtained after annealing the film at 500 °C. The film’s carrier density and Hall mobility were 8.7×1019cm−3 and 6.8cm2V−1s−1, respectively. The absorption edge of the films was shifted to a lower wavelength by increasing the carrier density. The maximum band gap of these films was found to be 3.69 eV.

05/02345 Monte Carlo modeling of KAMINI

The purpose of this study is to provide a detailed safety analysis of overall system and components in terms of their ability to provide optimum output from the irradiation of TeO2 in the central thimble of the 3 MW TRIGA MARK II research reactor at Atomic Energy Research Establishment (AERE), Savar, Dhaka, Bangladesh. It identifies safety issues relevant to 131I radioisotope production and ensures that safety analysis and design are consistent. It evaluates threats developed within the facility during the irradiation process and ultimately ensures establishment of in-core safety limits and conditions at all stages of 131I production. In-core irradiation safety not only ensures the safe operation of the reactor but also strengthens the production of radioisotopes (RI). This study attempts to review and modify all safety related events and aspects relating to RI production. The three-dimensional continuous energy Monte Carlo code MCNP is used to develop a versatile and accurate full-core model of the TRIGA core. The cross-section library and fission product inventory are generated by using NJOY and ORIGEN computer codes. The methodology to evaluate heat generation and other relevant parameters necessary to provide enough information for thermal hydraulic analysis are discussed. The neutron flux distribution inside the dry and water filled central thimble is determined in order to locate the highest neutron flux trapping position. The thermal hydraulic and safety analysis are performed by elaborate numerical analysis as well as by using GENGTC computer code. A mock-up facility has also been developed to supplement and verify the theoretically predicted results. The total energy generated during irradiation of 50 gm TeO2 sample in dry condition is found to be 113.84 w of which 75% energy is due to neutron heating and rest of the amount is from gamma heating. Around 11.28 w of heat energy is also generated in the quartz vial. When the total generated-heat transfer is considered through conduction and radiation mechanisms, the calculated temperature of 50 g of TeO2 reaches at 970 °C. Considering simultaneous heat transfer mechanisms, (conduction, radiation and convection) the calculated maximum temperature of the 50 g of TeO2 powder comes down at 680 °C. It may be pointed out that very high amount of heat is generated during the irradiation of TeO2 at 3 MW reactor power in dry condition which is nearly the melting point of TeO2 and may be termed as unsafe mode of irradiation.