Thermal analyses of bulk amorphous oxides and silicates of zirconium and hafnium

2002 ◽  
Vol 745 ◽  
Author(s):  
S. V. Ushakov ◽  
C. E. Brown ◽  
A. Navrotsky ◽  
A. Demkov ◽  
C. Wang ◽  
...  
Keyword(s):  
Crystallite Size ◽  
Thermal Analyses ◽  
Sol Gel ◽  
Tetragonal Zirconia ◽  
Interface Energy ◽  
Silica Content ◽  
Scanning Calorimetry ◽  
Amorphous Oxides ◽  
Hafnium Silicate ◽  
Crystallization Onset

ABSTRACTAmorphous pure and Y-doped ZrO2 and HfO2 were prepared by precipitation with ammonia or hydrazine. Amorphous zirconium and hafnium silicates with SiO2 content from 10 to 90 mol % were prepared by sol-gel. Crystallization was studied by differential scanning calorimetry (DSC) at 20 °C/min and crystallite size after crystallization was determined from XRD data. ZrO2 crystallized into the tetragonal phase with ΔH -21 ±2 kJ/mol and HfO2 into the monoclinic phase with ΔH -31 ±2 kJ/mol. Doping with 20 at.% Y decreased crystallite size after crystallization. Crystallization temperatures for pure and Y-doped ZrO2 samples were in the range 420–440 °C. Crystallization temperatures for pure and Y-doped HfO2 samples varied from 470 to 570°C and correlate with surface area. Crystallization onset temperature in silicates increased with silica content from about 650 to 950 °C for ZrO2·SiO2 and from 740 to 1030 °C for HfO2·SiO2. Tetragonal zirconia and hafnia were the only crystalline phases formed below 1100 °C in all zirconium silicates and in hafnium silicates with more than 10 mol% SiO2. Crystallite size after crystallization decreased with increase in silica content. In hafnium silicate, a decrease in HfO2 crystallite size from 5 to 2.5 ±1 nm corresponds to a crystallization enthalpy change from -22 to -15 ±2 kJ/mol. The tetragonal HfO2/amorphous SiO2 interface energy can be calculated from calorimetric data as ∼0.25 J/m2. The critical particle size for the tetragonal to monoclinic transformation of HfO2 in HfO2-SiO2 system is about 6 nm. We predict that tetragonal HfO2 will be stabilized in films thinner than 2 nm.

scholarly journals Synthesis and physico-chemical characterization of fluoride (F)- and silver (Ag)-substituted sol-gel mesoporous bioactive glasses

2019 ◽  
Vol 5 (1) ◽  
pp. 185-192 ◽  
Author(s):  
Saeid Kargozar ◽  
Francesco Baino ◽  
Sara Banijamali ◽  
Masoud Mozafari
Keyword(s):  
Electron Microscopy ◽  
Tissue Engineering ◽  
Glassy State ◽  
Thermal Analyses ◽  
Sol Gel ◽  
Scanning Calorimetry ◽  
Dental Tissue ◽  
Bioactive Glasses ◽  
Early Results ◽  
Doped Glasses

Abstract Synthesis and use of novel compositions of bioactive glasses (BGs) for hard tissue engineering are of important significance in the biomedical field. In this study, we successfully synthesized a series of 58S-based BGs containing fluoride (F−) and silver (Ag+) ions through a sol-gel method for possible use in bone/dental regeneration and antibacterial strategies. Characterizations of samples were performed by using thermal analyses (thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC)), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), textural analysis (N2 adsorption-desorption), and morphological observations by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The obtained data revealed that the fabricated BGs are in a glassy state before incubation in the Kokubo’s simulated body fluid (SBF), and an apatite-like layer is formed on their surface after 7 days of immersion in SBF. The size of the glass particles was in the nano-range (about 100 nm or below), and their pore size was in the mesoporous range (15-25 nm). These early results suggest that the F- and Ag-doped glasses show promise as multifunctional bioactive materials for bone/dental tissue engineering.

Phase structure and thermal evolution in coating films and powders obtained by sol-gel process: Part II. ZrO2–2.5 mole% Y2O3

1997 ◽  
Vol 12 (10) ◽  
pp. 2594-2601 ◽  
Author(s):  
R. Caruso ◽  
E. Benavídez ◽  
O. de Sanctis ◽  
M. C. Caracoche ◽  
P. C. Rivas ◽  
...  
Keyword(s):  
Tetragonal Phase ◽  
Phase Structure ◽  
Thermal Evolution ◽  
Thermal Analyses ◽  
Sol Gel ◽  
Tetragonal Zirconia ◽  
Fast Diffusion ◽  
Coating Films ◽  
Angular Correlations ◽  
Heating And Cooling

Powders and coatings of zirconia doped with 2.5 mole% yttria have been produced via the sol-gel route. The phase structure and subsequent thermal evolution in heating and cooling cycles have been investigated using mainly perturbed angular correlations spectroscopy. Thermal analyses and XRD as a function of temperature have also been performed to obtain complementary information. Upon heating, the amorphous gels crystallized into the tetragonal structure and showed the same hyperfine pattern and thermal behavior as observed in tetragonal zirconia obtained by the ceramic route: the two configurations of vacancies around zirconium ions denoted as t1 and t2 forms and their mutual t1 → t2 transformation. While the powder sample exhibited an incipient thermal instability above 1000 °C and underwent completely the t2 form to m–ZrO2 transition during subsequent, gradual cooling below 500 °C, the coating retained the tetragonal phase within the whole temperature range investigated. Hyperfine results suggest that the tetragonal phase stabilization is favored by the highly defective nature of the t1 form and consequently hardened by the availability of oxygen. The PAC derived activation energy for the fast diffusion of the oxygen vacancies inherent to the t2 form was determined as 0.54 ± 0.14 eV.

scholarly journals Photocatalytic Activity of Nanocoatings Based on Mixed Oxide V-TiO2 Nanoparticles with Controlled Composition and Size

Catalysts ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1457
Author(s):  
Miguel Sanchez Mendez ◽  
Alex Lemarchand ◽  
Mamadou Traore ◽  
Christian Perruchot ◽  
Capucine Sassoye ◽  
...  
Keyword(s):  
Mixed Oxide ◽  
Thermal Analyses ◽  
Sol Gel ◽  
Orthorhombic Phase ◽  
Vanadium Content ◽  
Pure Tio2 ◽  
X Ray Diffraction ◽  
Composition Control ◽  
Cell Parameters ◽  
Crystallization Onset

V-TiO2 photocatalyst with 0 ≤ V ≤ 20 mol% was prepared via the sol–gel method based on mixed oxide titanium–vanadium nanoparticles with size and composition control. The mixed oxide vanadium–titanium oxo-alkoxy nanonoparticles were generated in a chemical micromixing reactor, coated on glass beads via liquid colloid deposition method and underwent to an appropriate thermal treatment forming crystallized nanocoatings. X-ray diffraction, Raman, thermogravimetric and differential thermal analyses confirmed anatase crystalline structure at vanadium content ≤ 10 mol%, with the cell parameters identical to those of pure TiO2. At a higher vanadium content of ~20 mol%, the material segregation began and orthorhombic phase of V2O5 appeared. The crystallization onset temperature of V-TiO2 smoothly changed with an increase in vanadium content. The best photocatalytic performance towards methylene blue decomposition in aqueous solutions under UVA and visible light illuminations was observed in V-TiO2 nanocoatings with, respectively, 2 mol% and 10 mol% vanadium.

scholarly journals Different approaches to obtain functionalized alumina as additive in polymer electrolyte membranes

2021 ◽  
Author(s):  
Lucia Mazzapioda ◽  
Mirko Sgambetterra ◽  
Akiko Tsurumaki ◽  
Maria Assunta Navarra
Keyword(s):  
Fuel Cell ◽  
Aluminum Oxide ◽  
Thermal Analyses ◽  
Sol Gel ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Composite Electrolyte ◽  
Fuel Cell Performance ◽  
Operation Temperature ◽  
Electrolyte Membranes

AbstractA series of sulfated aluminum oxides (S-Al2O3), investigated as an electrolyte additive in Nafion membranes, was synthesized via three different methods: (i) sol–gel sulfation starting from an aluminum alkoxide precursor, (ii) room temperature sulfation of fumed aluminum oxide, and (iii) hydrothermal sulfation of fumed aluminum oxide. Through the characterization of the synthesized S-Al2O3 by means of X-ray diffraction (XRD), thermogravimetric analysis (TGA), and infrared (IR) spectroscopy, a higher sulfation rate was found to be achieved via a hydrothermal sulfation, and the coordination state of sulfate groups was identified as monodentate. By using this hydrothermally synthesized S-Al2O3 as additive, a composite Nafion-based membrane was realized and compared to plain Nafion, by means of thermal analyses and fuel cell tests. Although higher hydration degree was found for the undoped membrane by differential scanning calorimetry (DSC), improved retention of fuel cell performance upon the increase of operation temperature was observed by using the composite electrolyte, confirming the stabilizing effect of the acidic inorganic additive.

PLGA+HA/βTCP scaffold incorporating simvastatin: a promising biomaterial for bone tissue engineering

2020 ◽  
Author(s):  
Mariane Beatriz Sordi ◽  
Ariadne Cristiane Cabral da Cruz ◽  
Águedo Aragones ◽  
Mabel Mariela Rodríguez Cordeiro ◽  
Ricardo de Souza Magini
Keyword(s):  
Tissue Engineering ◽  
Bone Tissue Engineering ◽  
Bone Tissue ◽  
Thermal Analyses ◽  
Chemical Properties ◽  
Biological Properties ◽  
Scanning Calorimetry ◽  
Evaporation Technique ◽  
Porosity Analysis ◽  
Biphasic Ceramic

The aim of this study was to synthesize, characterize, and evaluate degradation and biocompatibility of poly(lactic-co-glycolic acid) + hydroxyapatite / β-tricalcium phosphate (PLGA+HA/βTCP) scaffolds incorporating simvastatin (SIM) to verify if this biomaterial might be promising for bone tissue engineering. Samples were obtained by the solvent evaporation technique. Biphasic ceramic particles (70% HA, 30% βTCP) were added to PLGA in a ratio of 1:1. Samples with SIM received 1% (m:m) of this medication. Scaffolds were synthesized in a cylindric-shape and sterilized by ethylene oxide. For degradation analysis, samples were immersed in PBS at 37 °C under constant stirring for 7, 14, 21, and 28 days. Non-degraded samples were taken as reference. Mass variation, scanning electron microscopy, porosity analysis, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetry were performed to evaluate physico-chemical properties. Wettability and cytotoxicity tests were conducted to evaluate the biocompatibility. Microscopic images revealed the presence of macro, meso, and micropores in the polymer structure with HA/βTCP particles homogeneously dispersed. Chemical and thermal analyses presented very similar results for both PLGA+HA/βTCP and PLGA+HA/βTCP+SIM. The incorporation of simvastatin improved the hydrophilicity of scaffolds. Additionally, PLGA+HA/βTCP and PLGA+HA/βTCP+SIM scaffolds were biocompatible for osteoblasts and mesenchymal stem cells. In summary, PLGA+HA/βTCP scaffolds incorporating simvastatin presented adequate structural, chemical, thermal, and biological properties for bone tissue engineering.

scholarly journals Sulbactam pivoxil powder attributes and compatibility study with excipients

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Loreana C. Gallo ◽  
Noelia L. Gonzalez Vidal ◽  
Fabio F. Ferreira ◽  
María V. Ramírez-Rigo
Keyword(s):  
Thermal Analyses ◽  
Oral Route ◽  
Endothermic Peak ◽  
Compatibility Study ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Thermogravimetric Curve ◽  
Almost All ◽  
Potential Interactions ◽  
Lactamase Inhibitor

Abstract Background Sulbactam pivoxil is an irreversible β-lactamase inhibitor that can be used with β-lactam antibiotics to improve antibacterial therapy by the oral route. Relevant properties of this drug for pharmaceutical manufacturing are not available in the open literature. In this work, a solid-state characterization of sulbactam pivoxil at the molecular, particle, and bulk levels was performed. Results Particles exhibited a mean diameter of about 350 μm, irregular shape crystals, and good flow properties. This work presents for the first time the crystal structure of this β-lactamase inhibitor obtained by X-ray diffraction analysis. Fourier-transform infrared results showed the characteristic bands of aliphatic hydrocarbons and ester groups. The differential scanning calorimetry curve exhibited a sharp endothermic peak at 109 °C corresponding to sulbactam pivoxil melting. The thermogravimetric curve revealed a mass loss at 184 °C associated with a decomposition process. This powder showed a moisture content of 0.34% and a water activity of 0.463. Potential interactions between sulbactam pivoxil and common pharmaceutical excipients were evaluated by thermal analysis. The endothermic peak and the enthalpies of melting were preserved in almost all the analyzed mixtures. Conclusion The powder was constituted by micro-sized crystals of sulbactam pivoxil that had suitable physicochemical properties for processing in controlled humidity environments. Thermal analyses suggested that sulbactam pivoxil is compatible with most of the evaluated excipients. The information obtained in the present study is relevant for the development, manufacturing, and storage of formulations that include sulbactam pivoxil.

scholarly journals Performance Improvement of ZnSnO Thin-Film Transistors with Low-Temperature Self-Combustion Reaction

Electronics ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 1099
Author(s):  
Ye-Ji Han ◽  
Se Hyeong Lee ◽  
So-Young Bak ◽  
Tae-Hee Han ◽  
Sangwoo Kim ◽  
...  
Keyword(s):  
Thin Film ◽  
Photoelectron Spectroscopy ◽  
Large Scale ◽  
Low Cost ◽  
Thermal Analyses ◽  
Thin Film Transistor ◽  
Sol Gel ◽  
Annealing Temperatures ◽  
Zinc Tin Oxide ◽  
Thermal Limitation

Conventional sol-gel solutions have received significant attention in thin-film transistor (TFT) manufacturing because of their advantages such as simple processing, large-scale applicability, and low cost. However, conventional sol-gel processed zinc tin oxide (ZTO) TFTs have a thermal limitation in that they require high annealing temperatures of more than 500 °C, which are incompatible with most flexible plastic substrates. In this study, to overcome the thermal limitation of conventional sol-gel processed ZTO TFTs, we demonstrated a ZTO TFT that was fabricated at low annealing temperatures of 350 °C using self-combustion. The optimized device exhibited satisfactory performance, with μsat of 4.72 cm2/V∙s, Vth of −1.28 V, SS of 0.86 V/decade, and ION/OFF of 1.70 × 106 at a low annealing temperature of 350 °C for one hour. To compare a conventional sol-gel processed ZTO TFT with the optimized device, thermogravimetric and differential thermal analyses (TG-DTA) and X-ray photoelectron spectroscopy (XPS) were implemented.

scholarly journals The Effect of Crystallization and Phase Transformation on the Mechanical and Electrochemical Corrosion Properties of Ni-P Coatings

Coatings ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 447
Author(s):  
Martin Buchtík ◽  
Leoš Doskočil ◽  
Roman Brescher ◽  
Pavel Doležal ◽  
Jiří Másilko ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Crystallite Size ◽  
Electrochemical Corrosion ◽  
Az91 Magnesium Alloy ◽  
Scanning Calorimetry ◽  
Corrosion Properties ◽  
High Phosphorus ◽  
P Content ◽  
Az91 Magnesium ◽  
Increasing Temperature

This paper deals with the study of the crystallization and phase transformation of Ni-P coatings deposited on AZ91 magnesium alloy. Prepared samples were characterized in terms of surface morphology and elemental composition by means of scanning electron microscopy with energy-dispersive spectroscopy analysis. The results of X-ray diffraction analysis and differential scanning calorimetry suggested that increasing the phosphorus content caused Ni-P coatings to develop an amorphous character. The crystallization of Ni was observed at 150, 250, and 300 °C for low-, medium- and high-phosphorus coatings, respectively. The Ni crystallite size increased with increasing temperature and decreasing P content. Conversely, the presence of the Ni3P phase was observed at a maximum peak of 320 °C for the high-phosphorus coating, whereas the crystallization of the Ni3P phase shifted to higher temperatures with decreasing P content. The Ni3P crystallite size increased with increasing temperature and increasing P content. An increase in microhardness due to the arrangement of Ni atoms and Ni3P precipitation was observed. The deposition of as-deposited Ni-P coatings led to an improvement in the corrosion resistance of AZ91. However, the heat treatment of coatings resulted in a deterioration in corrosion properties due to the formation of microcracks.

Interpretation of Alumina/Yttrium-Aluminum Garnet Orientation Relationships by Geometric Criteria

1990 ◽  
Vol 209 ◽  
Author(s):  
R.S. Hay ◽  
L.E. Matson
Keyword(s):  
Structural Unit ◽  
Yttrium Aluminum Garnet ◽  
Sol Gel ◽  
Interface Energy ◽  
Interface Structure ◽  
Invariant Line ◽  
Directionally Solidified ◽  
Orientation Relationships ◽  
Yttrium Aluminum

ABSTRACTGeometric criteria for low interface energy and interface structure were tested for the cubic-rhombohedral system YAG/alumina. Orientation relationships near (111){110}a // (112){110}y and facets on (111)a(112)y were observed in both sol-gel derived composites and directionally solidified eutectic composites. The ΣYAG=12 near-CSL of 2{111}, {110}, {112} was inferred to be the preferred structural unit. Dislocations with b=1/3{111}a and b=1/2{110}a were observed and inferred to accomodate deviation from the structural unit, respectively. The {110}a,y direction met some of the criteria for an invariant line. Although the OR was explained by geometric criteria it would have been difficult to predict it with such criteria

Mechanical and microstructural properties of polystyrene based composites: positron lifetime spectroscopic and DSC studies

2011 ◽  
Vol 31 (2-3) ◽  
Author(s):  
Abdullah Mohammed Ali Mohammed Altaweel ◽  
Jaya Madhu Raj ◽  
Malalvalli Nagarajaiah Chandrashekara ◽  
Puttegowda Ramya ◽  
Parthasarathy Sampathkumaran ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Free Volume ◽  
Positron Lifetime ◽  
Tensile Modulus ◽  
Silica Content ◽  
Scanning Calorimetry ◽  
Dsc Studies ◽  
Microstructural Property ◽  
Calcium Aluminosilicate

Abstract Polystyrene (PS) based composites respectively with cenosphere (CS) and calcium aluminosilicate (CAS) as fillers were studied using the positron lifetime technique to reveal the correlation between free volume, a microstructural property, and mechanical properties of the composites (tensile strength and tensile modulus). The thermal stability of the composites was determined using differential scanning calorimetry. The results showed that addition of CAS filler lead to a significant improvement in the mechanical properties of the composite, whereas addition of CS resulted in improvement in tensile modulus only. Both PS/CAS and PS/CS composites showed enhancement in thermal stability compared with that of the pure PS matrix. The positron results showed that the average free volume size for the PS/CAS composite (at 40 phr CAS) was reduced significantly compared with that of the pure PS. These results are understood in terms of the influence of silica content, filler-matrix interaction, and particle size.

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