Thermodynamical Calculations and Experimental Confirmation about the Mg-Al-Spinel Reaction Path in the Sol-Gel-Process

2006 ◽  
Vol 317-318 ◽  
pp. 135-138 ◽  
Author(s):  
Wilfried Wunderlich ◽  
Krupathi Vishista ◽  
Francis D. Gnanam ◽  
Daniel Doni Jayaseelan
Keyword(s):  
Thermal Analysis ◽  
Reaction Path ◽  
Sol Gel ◽  
Chemical Processing ◽  
Aluminium Isopropoxide ◽  
Spinel Formation ◽  
Sol Gel Process ◽  
Wet Chemical ◽  
Enthalpy Data ◽  
Good Agreement

The aim of this research is, to clarify which route the sol-gel-process is taking in the case of a Al-Mg-spinel slurry, in particular, whether the hydrolysis reaction or the spinel formation is faster and which of the intermediate hydroxide phases Al(OH)3, and Mg(OH)2, or MgO and Al2O3 or MgAl2O4H2O are formed during the spinel formation. The spinel-alloy was produced using the polymeric route during wet chemical processing. Aluminium-isopropoxide was hydrolyzed in order to form the boehmite-sol and then the same amount of magnesia was added and mixed. This sol precipitated as boehmite (AlOOH) and brucite (Mg(OH)2) after ageing for 12h as confirmed by differential thermal analysis (DTA), and differential thermal gravity (DTG) measurements. After that, the powders were subsequently annealed at 900oC for 3h in air and observed by TEM. Calculations using thermodynamic enthalpy data are in good agreement with the experiments and can be used to predict reaction paths in other system as well.

Luminescent Properties of Zn2SiO4:Eu3+,Dy3+ Phosphors via Sol-Gel Process

2012 ◽  
Vol 217-219 ◽  
pp. 733-736
Author(s):  
Xiu Mei Han ◽  
Shu Ai Hao ◽  
Ying Ling Wang ◽  
Gui Fang Sun ◽  
Xi Wei Qi
Keyword(s):  
Thermal Analysis ◽  
Ir Spectra ◽  
Sol Gel ◽  
Luminescent Properties ◽  
Photoluminescence Spectra ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sol Gel Process ◽  
Ft Ir

Zn2SiO4:Eu3+, Dy3+ phosphors have been prepared through the sol-gel process. X-ray diffraction (XRD), thermogravimetric and ddifferential thermal analysis (TG-DTA), FT-IR spectra and photoluminescence spectra were used to characterize the resulting phosphors. The results of XRD indicated that the phosphors crystallized completely at 1000oC. In Zn2SiO4:Eu3+,Dy3+ phosphors, the Eu3+ and Dy3+ show their characteristic red(613nm, 5D0-7F2), blue (481nm, 4F9/2–6H15/2) and yellow (577nm, 4F9/2–6H13/2) emissions.

Study on the Synthesis of Nano-Crystalline Mg2SiO4 Powders by Aqueous Sol-Gel Process

2013 ◽  
Vol 538 ◽  
pp. 142-145 ◽  
Author(s):  
X.F. Chen ◽  
J. Li ◽  
T.T. Feng ◽  
Y.S. Jiang ◽  
X.H. Zhang ◽  
...  
Keyword(s):  
Thermal Analysis ◽  
Sol Gel ◽  
Magnesium Nitrate ◽  
Metal Alkoxides ◽  
X Ray Diffraction ◽  
Calcination Process ◽  
X Ray ◽  
Nano Crystalline ◽  
Sol Gel Process ◽  
Scanning Electron

The forsterite-structure Mg2SiO4 was successfully synthesized by the aqueous sol-gel method using Si sols dioxide and magnesium nitrate as starting materials instead of expensive organic solvent and metal alkoxides. The as-prepared nanopowders were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscope (SEM), respectively. The results showed that the calcination process of gel consisted of a series of oxidation and combustion reactions, accompanied by significantly exothermal effects. Highly reactive nanosized Mg2SiO4 powders were successfully obtained at 850 °C with particle size of 60~80 nm.

Stochastic Reconstruction and Permeation of Ceramic Membranes Prepared by the Sol-Gel Method

2002 ◽  
Vol 752 ◽  
Author(s):  
E. S. Kikkinides ◽  
V. T. Zaspalis ◽  
V. N. Burganos
Keyword(s):  
Mechanical Stability ◽  
Sol Gel ◽  
Three Dimensional ◽  
Ceramic Membranes ◽  
Momentum Equation ◽  
Void Space ◽  
Sol Gel Process ◽  
Mesoporous Membranes ◽  
Permeation Properties ◽  
Good Agreement

ABSTRACTIn the present work we study the relation between structural and permeation properties of ceramic membranes made by the sol-gel process. For this purpose, we have developed γ-Al2O3 mesoporous membranes via the sol-gel route, on top of multi-layer asymmetric α-Al2O3 macroporous supports, to induce mechanical stability. Subsequently, we employ stochastic techniques to generate three-dimensional reconstructions of the membrane and the support that share the basic structural properties of the original materials determined directly from SEM and TEM studies. The permeability of each material is estimated by solving numerically the momentum equation in the void space of the reconstructed images. The very good agreement between predicted and experimentally measured permeability values, without the need to resort to any fitting parameter, renders the proposed reconstruction methodology quite promising for reliable characterization and representation of the pore structure of this type of membranes.

Chemical processing and densification characteristics of lithium aluminosilicate (LAS) gels

1992 ◽  
Vol 7 (8) ◽  
pp. 2273-2280 ◽  
Author(s):  
Hyun M. Jang ◽  
Kwang S. Kim ◽  
Chang J. Jung
Keyword(s):  
Crystallization Temperature ◽  
Condensation Reaction ◽  
Sol Gel ◽  
Processing Route ◽  
Chemical Processing ◽  
Colloidal Processing ◽  
Homogeneous Microstructure ◽  
Lithium Aluminosilicate ◽  
Temperature Range ◽  
Sol Gel Process

Two different chemical processing routes were successfully used for the fabrication of lithium aluminosilicate (LAS) specimens having dense and homogeneous microstructure with an essentially pore-free state. These are (i) sol-gel route using the hydrolysis-condensation reaction of metal alkoxides and (ii) mixed colloidal processing route. Lowering Li content in the sol-gel-derived LAS significantly enhanced densification and retarded the crystallization. The β-spodumene (∼0.8 μm) seeding in the sol-gel-derived LAS modified the sequence of phase transformations and lowered the crystallization temperature by 120 °C. Therefore, combining the epitaxial seeding with the sol-gel process, one can bring down the crystallization temperature to the sintering temperature range (∼800 °C). Similarly, the LAS gel prepared by the mixed colloidal processing route exhibited a noticeable shrinkage over a broad temperature range (600–950 °C) and produced a dense sintered body with an essentially pore-free microstructure.

Synthesis of perovskite-type BaSnO3 particles obtained by a new simple wet chemical route based on a sol–gel process

2002 ◽  
Vol 56 (3) ◽  
pp. 131-136 ◽  
Author(s):  
J Cerdà ◽  
J Arbiol ◽  
R Diaz ◽  
G Dezanneau ◽  
J.R Morante
Keyword(s):  
Sol Gel ◽  
Chemical Route ◽  
Sol Gel Process ◽  
Wet Chemical ◽  
Wet Chemical Route ◽  
Perovskite Type

Preparation of silica glass microspheres by sol-gel processing

1991 ◽  
Vol 6 (1) ◽  
pp. 168-174 ◽  
Author(s):  
J.Y. Ding ◽  
D.E. Day
Keyword(s):  
Thermal Analysis ◽  
Nuclear Magnetic Resonance ◽  
Raw Materials ◽  
Sol Gel ◽  
Porous Silica ◽  
Droplet Generator ◽  
Silica Microspheres ◽  
Glass Microspheres ◽  
Sol Gel Process ◽  
Gel Processing

A method for making glass microspheres by the sol-gel process has been developed. Porous silica microspheres were produced at temperatures as low as 500 °C and densified silica microspheres were prepared at 800 °C. The size of the microspheres was controlled by adjusting the feed rate of the raw materials and the frequency of the droplet generator so that uniform spheres were obtained. Glass microspheres prepared by this method were characterized by Nuclear Magnetic Resonance (NMR), Differential Thermal Analysis (DTA), Thermogravimetric Analysis (TGA), and optical microscopy.

Multifunctional Silica Optics

1989 ◽  
Vol 175 ◽  
Author(s):  
L. L. Hench ◽  
A. Fosmoe
Keyword(s):  
High Temperature ◽  
Intermediate Product ◽  
Sol Gel ◽  
Processing Method ◽  
Chemical Processing ◽  
Average Pore ◽  
Host Matrix ◽  
Flow Rates ◽  
Sol Gel Process ◽  
Type V

AbstractThe sol-gel chemical processing method of producing fully dense silica optics provides an intermediate product termed Type VI silica ideally suited for use in engineering multifunctional silica optics. This paper reviews the sol-gel process, the Type V dense gel-silica produced by this process and the Type VI ultraporous gel-silica intermediate product. Included is a comparison of two different porous ultrastructures with 1.2 nm and 8.0 nm average pore radii. Two uses of the porous gel-silica components as multifunctional optics are described. The first is for use in transpiration cooled windows in highspeed rocket guidance systems. Flow rates of He and N2 through the 1.2 nm and 8.0 nm ultrastructures are as high as 0.9 m/min at 0.75 MPa. High temperature UV transmission in contact with an impinging oxy-acetylene flame is demonstrated. Use of Type VI gel-silica as a host matrix for fast radiationhard scintillating detectors is also reviewed.

Sol-Gel Derived Mullite-Gahnite Composite

2014 ◽  
Vol 87 ◽  
pp. 126-131
Author(s):  
Stanislav Kurajica ◽  
Emilija Tkalčec ◽  
Vilko Mandić ◽  
Iva Lozić ◽  
Jörg Schmauch
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Powder Diffraction ◽  
Sol Gel ◽  
Intermediate Formation ◽  
X Ray ◽  
Thermal Reactions ◽  
Sol Gel Process ◽  
Crystal Phases ◽  
Crystallization Path

Mullite-gahnite composites with different phase-proportions were prepared using sol-gel process. Crystallization path was determined using differential thermal analysis (DTA). X-ray powder diffraction (XRD) was used to study the crystal phases development. The course of the thermal reactions is dominated by the intermediate formation of two spinel phases. The former phase was attributed to gahnite, while the latter to Al-Si spinel. Zn loading decreases amounts of mullite and α-alumina, while increases gahnite and amorphous phase. The observed microstructure of sintered bodies is characterized by fine gahnite particles distributed among larger mullite grains, which is highly favourable for ceramics with high mechanical requirements.

scholarly journals Sol-gel bioactive glass-ceramics Part I: Calcium phosphate silicate/wollastonite glass-ceramics

2009 ◽  
Vol 7 (3) ◽  
pp. 317-321 ◽  
Author(s):  
Lachezar Radev ◽  
Vladimir Hristov ◽  
Irena Michailova ◽  
Bisserka Samuneva
Keyword(s):  
Calcium Phosphate ◽  
Sol Gel ◽  
Glass Ceramics ◽  
Molar Ratio ◽  
Structure Evolution ◽  
Apatite Formation ◽  
Sol Gel Process ◽  
Phosphate Silicate ◽  
Good Agreement

AbstractIn this work we present experimental results about synthesis, structure evolution and in vitro bioactivity of new calcium phosphate silicate/wollastonite (CPS/W) glass-ceramics. The samples obtained were synthesized via polystep sol-gel process with different Ca/P+Si molar ratio (R). The structure of the materials obtained was studied by XRD, FTIR spectroscopy and SEM. XRD showed the presence of Ca15(PO4)2(SiO4)6, β-CaSiO3 and α-CaSiO3 for the sample with R=1.89 after thermal treatment at 1200°C/2h. The XRD results are in good agreement with FTIR analysis. SEM denotes that apatite formation can be observed after soaking in simulated body fluid (SBF).

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