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Hydrous non-crystalline phosphates: structure, function and a new white pigment
Rosseto, Renato;Santos, ádamo C. M. A. dos;Galembeck, Fernando;
Journal of the Brazilian Chemical Society , 2006, DOI: 10.1590/S0103-50532006000800002
Abstract: hydrated non-crystalline inorganic solids are often neglected due to the limited comprehension of their complex physico-chemical and structural properties. however, these non-crystalline materials exhibit a rich and varied chemistry, interesting for scientific and technological reasons. this work reviews general aspects of formation of hydrated non-crystalline solids, with special emphasis on aluminum (poly)phosphate materials. precursors and concentration variations, temperature, ageing and reaction ph are trivial synthetic variables, but they promote the formation of a myriad of compounds adequate for many functions. amorphous aluminum phosphates are widely employed in different industrial applications, providing good examples of the potential of hydrous amorphous solids.
Technology of Porous Tantalum Production  [PDF]
Yu. Zh. Tuleushev, V. N. Volodin, Е. А. Zhakanbaev, V. N. Lisitsin, A. A. Migunova, A. S. Suleymenova
World Journal of Nano Science and Engineering (WJNSE) , 2016, DOI: 10.4236/wjnse.2016.62006
Abstract: Ion-plasma sputtering and codeposition of ultrafine Ta and Cd particles on a moving substrate were used to prepare the solid solutions, in particular, the alloys with up to 66.2 at.% Cd in the form of coatings. In vacuum heat treatment cadmium evaporates at 700°C from cadmium based solid solutions resulting in formation of a porous tantalum with a highly developed surface. The prepared tantalum-based materials assume the technological application of the investigation results.
Preparation and Characterization of Hydrous Zirconium Oxide Formed by Homogeneous Precipitation
Silva, G.L.J.P. da;Silva, M.L.C.P. da;Caetano, Tatiana;
Materials Research , 2002, DOI: 10.1590/S1516-14392002000200011
Abstract: this paper reports on the preparation, characterization and study of the ion exchange behavior of hydrous zirconium oxides formed by homogeneous precipitation from zirconium oxychloride. the precipitants used were obtained by thermal decomposition of urea, sodium nitrite or ammonium carbonate. seven compounds were prepared and characterized by thermal analysis, x-ray diffractometry and by surface area measurements. amorphous forms were obtained in each case, a result that agrees with those obtained by conventional gel precipitation methodology. all these materials present surface area values of >148 m2.g-1, determined after heat treatment at 50 °c. the ion exchange behavior of each hydrous zirconium oxide prepared was studied using k+ as the exchanged species and the results compared with those obtained for hydrous zirconium oxide originally precipitated by the sol gel method.
Preparation and Characterization of Hydrous Zirconium Oxide Formed by Homogeneous Precipitation
Silva G.L.J.P. da,Silva M.L.C.P. da,Caetano Tatiana
Materials Research , 2002,
Abstract: This paper reports on the preparation, characterization and study of the ion exchange behavior of hydrous zirconium oxides formed by homogeneous precipitation from zirconium oxychloride. The precipitants used were obtained by thermal decomposition of urea, sodium nitrite or ammonium carbonate. Seven compounds were prepared and characterized by thermal analysis, X-ray diffractometry and by surface area measurements. Amorphous forms were obtained in each case, a result that agrees with those obtained by conventional gel precipitation methodology. All these materials present surface area values of >148 m2.g-1, determined after heat treatment at 50 °C. The ion exchange behavior of each hydrous zirconium oxide prepared was studied using K+ as the exchanged species and the results compared with those obtained for hydrous zirconium oxide originally precipitated by the sol gel method.
Preparation and Formation Mechanism of Fibrous Hydrous Zirconia
ZHAI Lin-Feng,SHI Tie-Jun,WANG Hua-Lin
无机材料学报 , 2007, DOI: 10.3724/sp.j.1077.2007.00223
Abstract: Hydrous zirconia was prepared at low pH values with ZrOCl2 ¤8H2O as raw material, H2O2 as hydrolysis promoter and ethanol as solvent. FT-IR, TG and XRD were applied to study the components, structure and heat-stabilization of hydrous zirconia. Light microscope and FESEM were used to analyze the microcosmic structure of hydrous zirconia, its formation mechanism was also discussed. The results show that the molecular formula of hydrous zirconia is Zr(| OH)2(OH)2 ¤2H2O. The hydrous zirconia is amorphous, and as the treating temperature rising, it will turn from metastable tetragonal phase to monoclinic phase. The hydrous zirconia is fiber cluster composed of small short fibers via hydrogen bonds.
Melioidosis Vaccines: A Systematic Review and Appraisal of the Potential to Exploit Biodefense Vaccines for Public Health Purposes  [PDF]
Sharon J. Peacock equal contributor,Direk Limmathurotsakul equal contributor ,Yoel Lubell,Gavin C. K. W. Koh,Lisa J. White,Nicholas P. J. Day,Richard W. Titball
PLOS Neglected Tropical Diseases , 2012, DOI: 10.1371/journal.pntd.0001488
Abstract: Background Burkholderia pseudomallei is a Category B select agent and the cause of melioidosis. Research funding for vaccine development has largely considered protection within the biothreat context, but the resulting vaccines could be applicable to populations who are at risk of naturally acquired melioidosis. Here, we discuss target populations for vaccination, consider the cost-benefit of different vaccination strategies and review potential vaccine candidates. Methods and Findings Melioidosis is highly endemic in Thailand and northern Australia, where a biodefense vaccine might be adopted for public health purposes. A cost-effectiveness analysis model was developed, which showed that a vaccine could be a cost-effective intervention in Thailand, particularly if used in high-risk populations such as diabetics. Cost-effectiveness was observed in a model in which only partial immunity was assumed. The review systematically summarized all melioidosis vaccine candidates and studies in animal models that had evaluated their protectiveness. Possible candidates included live attenuated, whole cell killed, sub-unit, plasmid DNA and dendritic cell vaccines. Live attenuated vaccines were not considered favorably because of possible reversion to virulence and hypothetical risk of latent infection, while the other candidates need further development and evaluation. Melioidosis is acquired by skin inoculation, inhalation and ingestion, but routes of animal inoculation in most published studies to date do not reflect all of this. We found a lack of studies using diabetic models, which will be central to any evaluation of a melioidosis vaccine for natural infection since diabetes is the most important risk factor. Conclusion Vaccines could represent one strand of a public health initiative to reduce the global incidence of melioidosis.
Refinement of the equation of state of tantalum  [PDF]
Agnes Dewaele,Paul Loubeyre,Mohamed Mezouar
Physics , 2004, DOI: 10.1103/PhysRevB.69.092106
Abstract: The volume of tantalum versus pressure has been accurately measured up to 101 GPa by single-crystal x-ray diffraction, with helium as pressure transmitting medium. Slight deviation from previous static determinations is observed. Discrepancy with reduced shock-wave and ultrasonic data supports recent doubts about the calibration of the ruby pressure scale. Finally, first principle calculations of the literature show a positive curvature in $P(V)$ relative to the experimental data, even with a modified pressure scale.
Studies on adsorption behaviour of Cr(VI) onto synthetic hydrous stannic oxide
Saswati Goswami, Uday Chand Ghosh
Water SA , 2005,
Abstract: Hydrous stannic oxide (HSO) was synthesized in the laboratory and its systematic Cr (VI) adsorption behaviour was studied by means of batch experiments. The particle size of HSO used was in the range of 140 to 290μm. The variable parameters viz. the effects of pH, concentration of Cr (VI) and time of contact etc. are here reported. The optimum pH and time of contact required for maximum adsorption was found to be 2.0 and nearly 90 min, respectively. The experimental equilibrium adsorption data are tested for the Langmuir, Freundlich, Temkin and Redlich-Peterson equations. Results indicate the following order to fit the isotherms equations: Redlich- Peterson > Temkin > Freundlich > Langmuir. Different kinetic models have been applied to fit the experimental kinetic data. The results are compared, and indicated that the best fit is obtained with the Lagergren or pseudo first-order and the power-function models. A discussion on the adsorption mechanism with respect to the thermodynamic parameters leads to two possible interpretations: One is the exothermic nature of the adsorption process and the other is the ion-ion type electrostatic interaction between the adsorbent and adsorbate ion.
Plasma electrolytic oxidation of tantalum  [PDF]
Petkovi? Marija,Stojadinovi? Stevan,Vasili? Rastko,Bel?a Ivan
Serbian Journal of Electrical Engineering , 2012, DOI: 10.2298/sjee1201081p
Abstract: This paper is a review of our research on the plasma electrolytic oxidation (PEO) process of tantalum in 12-tungstosilicic acid. For the characterization of microdischarges during PEO, real-time imaging and optical emission spectroscopy (OES) were used. The surface morphology, chemical and phase composition of oxide coatings were investigated by AFM, SEM-EDS and XRD. Oxide coating morphology is strongly dependent on PEO time. The elemental components of PEO coatings are Ta, O, Si and W. The oxide coatings are partly crystallized and mainly composed of WO3, Ta2O5 and SiO2.
Compositon of Tantalum Nitride Thin Films Grown by Low-Energy Nitrogen Implantation: A Factor Analysis Study of the Ta 4f XPS Core Level  [PDF]
A. Arranz,C. Palacio
Physics , 2004, DOI: 10.1007/s00339-004-3182-0
Abstract: Tantalum nitride thin films have been grown by in situ nitrogen implantation of metallic tantalum at room temperature over the energy range of 0.5-5keV. X-ray photoelectron spectroscopy (XPS) and Factor Analysis (FA) have been used to characterise the chemical composition of the films. The number of the different Ta-N phases formed during nitrogen implantation, as well as their spectral shape and concentrations, have been obtained using principal component analysis (PCA) and iterative target transformation factor analysis (ITTFA), without any prior assumptions. According to FA results, the composition of the tantalum nitride films depends on both the ion dose and ion energy, and is mainly formed by a mixture of metallic tantalum, beta-TaN0.05, gamma-Ta2N and cubic/hexagonal TaN phases.
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