Search results for "POWDER"
showing 10 items of 437 documents
Phase formation in mixed TiO2-ZrO2 oxides prepared by sol-gel method
2011
Pure titania, zirconia, and mixed oxides (3—37 mol.% of ZrO2) are prepared using the sol-gel method and calcined at different temperatures. The calcined samples are characterized by Raman spectroscopy, X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption porosimetry. Measurements reveal a thermal stability of the titania anatase phase that slightly increases in the presence of 3—13 mol.% of zirconia. Practically, the titania anatase-rutile phase transformation is hindered during the temperature increase above 700 C. The mixed oxide with 37 mol.% of ZrO2 treated at 550 C shows a new single amorphous phase with a surface area of the…
"Identification of mixed bromidochloridotellurate anions in disordered crystal structures of (bdmim)2[TeX2Y4] (X, Y = Br, Cl; bdmim = 1-butyl-2,3-dim…
2013
Abstract The discrete mixed [TeBrxCl6−x]2− anions in their disordered crystal structures have been identified by using the phases prepared by the reaction of 1-butyl-2,3-dimethylimidazolium halogenides (bdmim)X with tellurium tetrahalogenides TeX4 (X = Cl, Br) as examples. Homoleptic (bdmim)2[TeX6] [X = Cl (1), Br (2)] and mixed (bdmim)2[TeBr2Cl4] (3), and (bdmim)2[TeBr4Cl2] (4) are formed depending on the choice of the reagents, and their crystal structures have been determined by single-crystal X-ray diffraction. The coordination environments of tellurium in all hexahalogenidotellurates are almost octahedral. Because of the crystallographic disorder, the mixed [TeBr2Cl4]2− and [TeBr4Cl2]2…
A biocompatible ZnNa2-based metal–organic framework with high ibuprofen, nitric oxide and metal uptake capacity
2020
Metal organic frameworks (MOFs) have received significant attention in recent years in the areas of biomedical and environmental applications. Among them, mixed metal MOFs, although promising, are relatively few in number in comparison with their homometallic analogues. The employment of benzophenone-4,4′-dicarboxylic acid (bphdcH2) in mixed metal MOF chemistry provided access to a 3D MOF, [Na2Zn(bphdc)2(DMF)2]n (NUIG1). NUIG1 displays a new topology and is a rare example of a mixed metal MOF based on 1D rod secondary building units. UV-vis, HPLC, TGA, XRPD, solid state NMR and computational studies indicated that NUIG1 exhibits an exceptionally high Ibuprofen (Ibu) and nitric oxide adsorpt…
Mesoporous iron phosphate/phosphonate hybrid materials
2014
Abstract Relatively high surface area pure mesoporous iron-phosphorus oxide-based derivatives have been synthesized through an S + I − surfactant-assisted cooperative mechanism by means of a one-pot preparative procedure from aqueous solution and starting from iron atrane complexes and phosphoric and phosphonic acids. A soft chemical extraction procedure allows opening the pore system of the parent as-prepared materials by exchanging the surfactant without mesostructure collapse. The nature of the pore wall can be modulated from iron phosphate up to hybrids involving approximately 30% of organophosphorus entities (phosphonates or diphosphonates). X-ray powder diffraction, transmission elect…
Synthesis of yttrium aluminum garnet nanoparticles in confined environment, and their characterization
2016
Abstract Nanopowders of yttrium aluminum garnet (YAG, Y3Al5O12) have been prepared by thermal treatment of hydroxides obtained by synthesis in a confined environment constituted by water/Cetyltrimethylammonium bromide (CTAB)/1-butanol/n-heptane. The phase behavior of the above system has been investigated on varying the water/CTAB molar ratio (R) at constant 1-butanol/CTAB and heptane/CTAB molar ratio. The dispersed aqueous phases were constituted by solutions of ammonia and of yttrium and aluminum nitrates, respectively. Measures of Kinematic Viscosity, Electrical Conductivity and Small Angle X-ray Scattering have been carried out. It was found that, on increasing the ammonia solution cont…
A cyano-bridged bimetallic ferrimagnet: Synthesis, X-ray structure and magnetic study
2010
Mixing of trans-[Mn(cyclam)Cl2]Cl (cyclam = 1,4,8,11-tetraazacyclotetradecane) and potassium hexacyanochromate (K3[Cr(CN)6]) aqueous solutions instantaneously yields a 1D infinite chain complex {[Mn(cyclam)(l-CN)2Cr(CN)4]� H2O}n (1). The crystal structure of 1, crystallizing in the monoclinic system with space group P21/n has been solved from X-ray powder diffraction data following direct space approach and refined by the Rietveld method. The structure analysis of 1 reveals alternating [Cr(CN)6] 3� and [Mn(cyclam)] 3+
Synthesis and structural and ionic conductivity studies of Na2ZrSi4O11
1996
The compound Na 2 ZrSi 4 O 1 1 has been prepared both by solid state synthesis and by the sol-gel technique via alkoxides. The structure of Na 2 ZrSi 4 O 11 was investigated by the Rietveld method using X-ray diffractometer data. The powder diffraction data show evidence for a triclinic distortion of the basic monoclinic structure. The ionic conductivity has been determined in the temperature interval 130-560°C using a.c. impedance measurements. The Na + ion mobility is limited, with E a =1.04 eV and σ(300°C)= 2-9 10 7 S/cm. Samples with Ta partially substituted for Zr, according to the formula Na 2-x (Zr 1-x Ta x )Si 4 O 11 with x ≤0.2, showed the same evidence for a triclinic distortion. …
Influences of atomization process and precursor material on the compaction mechanisms and metallurgical properties of parts developed by HIP
2022
Hot Isostatic pressing process is based on the densification of metals powders to near net shape parts with higher mechanicals properties than forged chemical equivalent. The precursor material can influence the parts properties. Thus the aims of this these is to understand the influence of the powder properties on the HIP parts. The particles characterization and the elements and compound monitoring during the HIP cycle allowed to understand the different oxidations phenomenons and their impact on the mechanical properties of parts. The comparison of differents powders batches with identical particles size repartition or identical chemical composition showed that the chemical composition a…
MZ-35, a new layered pentasil borosilicate synthesized in the presence of large alkali cations
2013
Abstract A new layered borosilicate has been synthesized in the presence of cesium and sodium cations and its structure has been solved by a combination of automated diffraction tomography (ADT) and X-ray powder diffraction (XRPD). MZ-35 has a composition NaCs 2 [BSi 7 O 16 (OH) 2 ](OH) 2 ·4H 2 O and features space group P-4m2. The unusually small unit cell ( a 7.3081 A, c 10.7520 A) is shared by two random-stacked configurations of the structure: a network of connected pentasil units related to the layer of RUB-18 and a bidimensional checkerboard of intersecting ladders of 4-membered rings. The two configurations are related by the simple face-sharing inversion of a hydroxyl-bearing tetrah…
Über die struktur aus 2,4,6-tri(dihydroxymethyl-amino)-1,3,5-triazin (hexamethylolmelamin) erhaltener polykondensate
1960
Die Polykondensation von Hexamethylolmelamin bei 110°C bis 150°C in Platintiegeln und im Stickstoffstrom erfolgt ohne ein Schmelzen der weisen, pulverigen Proben. Es wird hierbei der Gewichtsverlust, sowie quantitativ der abgespaltene Formaldehyd und das abgespaltene Wasser bestimmt. Aus den Elementaranalysen der Polykondensate einerseits, sowie dem Gewichtsverlust und den Spaltprodukten andererseits, lassen sich fur den durchschnittlichen Grundbaustein der Polykondensate innerhalb einer gewissen Streuung ubereinstimmende Summenformeln ableiten. Aus den Summenformeln und dem quantitativ verfolgten Polykondensationsverlauf schlieslich ergeben sich die Konstitutionsformeln der durchschnittlic…