Sol-gel processing of PbTiO3 and Pb(Zr0.52Ti0.48)O3 fibers

1992 ◽  
Vol 7 (4) ◽  
pp. 992-996 ◽  
Author(s):  
Ulagaraj Selvaraj ◽  
A.V. Prasadarao ◽  
Sridhar Komarneni ◽  
Keith Brooks ◽  
Stewart Kurtz
Keyword(s):  
Heat Treatment ◽  
Sol Gel ◽  
Dielectric Constants ◽  
Heat Treated ◽  
Viscous Solutions ◽  
Gel Processing ◽  
Alkoxide Precursors

Homogeneous and stoichiometric PbTiO3 and PbZr0.52Ti0.48O3 gel fibers were drawn from viscous solutions prepared by sol-gel processing of alkoxide precursors. The fibrous gels on heating at 450 and 600 °C, respectively, formed the well-crystallized phases of PbTiO3 and PbZr0.52Ti0.48O3. Fibers heat treated at 700 °C are a few centimeters long and 50 to 150 μm in diameter. PbZr0.52Ti0.48O3 fibers subjected to heat treatment at 700 °C for 1 h consisted of fully dense submicron grains (0.15 to 0.2 μm). However, PbTiO3 fibers under analogous conditions showed a few micropores with grains of ∼0.1 μm. Dielectric constants of these PbTiO3 and PbZr0.52Ti0.48O3 fibers were approximately 300 and 800, respectively.

Synthesis and Dielectric Properties of SrBi2Nb2O9 Layered Perovskite by Sol-Gel Processing

1998 ◽  
Vol 541 ◽  
Author(s):  
Y. Wu ◽  
F. S. Ohuchi ◽  
G. Z. Cao
Keyword(s):  
Heat Treatment ◽  
Sol Gel ◽  
Dip Coating ◽  
Dielectric Constants ◽  
Layered Perovskite ◽  
Condensation Process ◽  
Complexing Agent ◽  
Low Dielectric ◽  
Gel Processing ◽  
Multiple Step

AbstractFerroelectric layered perovskite strontium bismuth niobium oxide SrBi2Nb2O9(SBN) ceramics and films were made by sol-gel processing. A multiple step hydrolysis-condensation process was applied to the synthesis of the SBN sol by using inorganic salts as precursors with citric acid as a complexing agent. Single phase polycrystalline SBN was obtained after heat-treatment at 650°C. It was found that the dielectric constants of SBN ceramics were dependent on heat-treatment. SEM, XPS, TGA/DTA and XRD analyses indicated that bismuth-deficiency may contribute to the relatively low dielectric constants. While a prolonged firing time at high temperatures may lead to a lattice expansion resulting in a significant decrease of the dielectric constant. C-oriented SBN films were obtained by dip-coating onto SrTiO3 substrates and the films are dense and crack-free with a thickness of 900 nm.

Sol-gel processing of cordierite: Effect of seeding and optimization of heat treatment

1990 ◽  
Vol 5 (5) ◽  
pp. 1095-1103 ◽  
Author(s):  
Ann M. Kazakos ◽  
Sridhar Komarneni ◽  
Rustum Roy
Keyword(s):  
Heat Treatment ◽  
Single Phase ◽  
Excess Free Energy ◽  
Sol Gel ◽  
Nucleating Agents ◽  
Optimum Conditions ◽  
Nanosized Powders ◽  
Nanocomposite Gels ◽  
Powder Compacts ◽  
Gel Processing

Three series of cordierite powders were prepared by the sol-gel route: a single phase (monophasic) gel prepared from alkoxides, a nominally triphasic nanocomposite gel made with two nanosized powders and one solution phase, and a truly compositionally triphasic nanocomposite gel prepared from three nanosized powders. Crystalline α-cordierite seeds were also incorporated with the gels and their effectiveness as nucleating agents was investigated and found to lower the crystallization temperature of α-cordierite by 125–150°C. The densification behavior of powder compacts was examined and alterations made to the heat treatment until optimum conditions were found. The truly triphasic compact sintered at 1300°C for 2 h resulted in 100% of theoretical density whereas the nominally triphasic and monophasis pellets densified to 96% and 80%, respectively. The enhanced densification achieved with powder compacct prepared for triphasic nanocomposite gels is due to part to the excess free energy of the three components.

Effects of Heat-Treatment Temperature on the Properties of Negative CTE Eucryptite Ceramics

2010 ◽  
Vol 105-106 ◽  
pp. 123-125 ◽  
Author(s):  
Yong Li ◽  
Qi Hong Wei ◽  
Ling Li ◽  
Chong Hai Wang ◽  
Xiao Li Zhang ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Heat Treatment Temperature ◽  
Bending Strength ◽  
Sol Gel ◽  
Negative Thermal Expansion ◽  
Treatment Temperature ◽  
Heat Treated

In this paper, negative thermal expansion coefficient eucryptite powders were prepared by sol-gel method using silica-sol as starting material. The raw blocks were obtained by dry pressing process after the powder was synthesized, and then the raw blocks were heat-treated at 600º, 1150º, 1280º, 1380º, 1420º and 1450°C, respectively. Variations of density, porosity and thermal expansion coefficient at different heat treatment temperatures were investigated. Phase transformation and fracture surface morphology of eucryptite heat-treated at different temperatures, respectively, were observed by XRD and SEM. The results indicate that, with the increasing heat- treatment temperature, the grain size and the bending strength increased, porosity decreased, thermal expansion coefficient decreased continuously. Negative thermal expansion coefficient of -5.3162×10-6~-7.4413×10-6 (0~800°C) was obtained. But when the heat-treatment temperature was more than 1420°C, porosity began to increase, bending strength began to decrease, which were the symbols of over-burning, while the main crystal phase didn’t change.

Copper-alumina materials made by infiltration in boehmite

1995 ◽  
Vol 10 (9) ◽  
pp. 2271-2276 ◽  
Author(s):  
V. Pierre ◽  
D. Pierre ◽  
A.C. Pierre
Keyword(s):  
Thin Films ◽  
Heat Treatment ◽  
Phase Transformation ◽  
Sandwich Structures ◽  
Sol Gel ◽  
Copper Acetate ◽  
New Materials ◽  
Heat Treated ◽  
Direct Infiltration

New materials were made by infiltration of sol-gel boehmite thin films with copper acetate. The structure and phase transformation of these materials during heat treatment were studied. It was found that infiltration in the boehmite state did not end up in the same material as direct infiltration in the θ-alumina derived from boehmite, even after both types of materials were heat-treated at 900 °C. Infiltration in boehmite makes it possible to synthesize sandwich structures comprised of alternate layers of CuO and of γ-alumina.

Indium-Sensitized UV Photocatalysts Made from Alkali Titanate Microfibers

2009 ◽  
Vol 620-622 ◽  
pp. 651-654
Author(s):  
Leticia M. Torres-Martínez ◽  
Cecilia Sánchez-Trinidad ◽  
Vicente Rodríguez-González ◽  
Ricardo Gómez
Keyword(s):  
Heat Treatment ◽  
Annealing Time ◽  
Uv Light ◽  
Sol Gel ◽  
Dichlorophenoxyacetic Acid ◽  
Sem Images ◽  
Uv Light Irradiation ◽  
Heat Treated ◽  
Munk Function ◽  
Sol Gel Process

Indium-alkali microfibers doped ceramic were prepared by the sol-gel process. The gels preparation samples, were heat treated at 700°C for different length of time. The products were characterized by means of XRD, SEM-EDS and UV–Vis-DRS. The XRD showed the formation of the Na2Ti6O13 phase whose crystallinity depends on the annealing time. The band gap calculated from the UV–Vis Kubelka-Munk function shows very similar values (3.53-3.55 eV). The SEM images of the indium-alkali titanates show microfiber clumps morphologies of about 5 µm, and the EDS spectra show that In2O3 is on the Na2Ti6O13 surface. The results of the evaluation of the In-Na2Ti6O13 semiconductors in the 2, 4-dichlorophenoxyacetic acid (2, 4-D) photodecomposition under UV light irradiation, show that the photoactivity depends on the time of heat treatment of the samples.

Mechanical Properties of Sol-Gel Inorganic-Organic Hybrid Films in Nanoindentation

2006 ◽  
Vol 317-318 ◽  
pp. 317-322 ◽  
Author(s):  
J.Q. Zhang ◽  
Atsunori Matsuda ◽  
Hiroyuki Muto ◽  
Mototsugu Sakai
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Treatment Time ◽  
Sol Gel ◽  
Heat Treatment Time ◽  
Nanoindentation Test ◽  
Glass Substrates ◽  
Organic Hybrid ◽  
Elastoplastic Properties ◽  
Heat Treated

Methylsilsesquioxane films were formed on glass substrates by dropping a sol prepared from methyltriethoxysilane and then heat-treated in an oven. Nanoindentation test was performed to assess the elastoplastic properties of the films, including the relative residual depth ξr, Meyer hardness HM, work-of-indentation WI and the elastic modulus E’. The values of ξr, HM and WI were obtained by a Berkovich indenter and E’ was determined by a spherical indenter on the basis of Hertz elastic theory. ξr decreased with the increase in the heat treatment time, whereas HM , WI and E’ significantly increased with the time. The changes in the mechanical properties with the heat treatment time well reflected the evolution of the Si-O-Si network structure in methylsilsequioxane film.

Optical Properties of ATO Sol-gel Coated Carbon Fibers

2012 ◽  
Vol 1454 ◽  
pp. 221-226
Author(s):  
Brandon Richard ◽  
Norma Alcantar ◽  
Andrew Hoff ◽  
Sylvia Thomas
Keyword(s):  
Heat Treatment ◽  
Optical Properties ◽  
Carbon Fibers ◽  
Sol Gel ◽  
Functional Materials ◽  
Additional Material ◽  
Heat Treated ◽  
Ft Ir ◽  
Recent Trends ◽  
Thermal Infrared Radiation

ABSTRACTRecent trends in composite research include the development of structural materials with multiple functionalities. In new studies, novel materials are being designed, developed, modified, and implemented into composite designs. Typically, an increase in functionality requires additional material phases within one system. The presence of excessive phases can result in deterioration of individual or overall properties. True multi-functional materials must maintain all properties at or above the minimum operating limit. In this project, samples of Sb-doped SnO2(ATO) sol-gel solutions are used to coat carbon fibers and are heat treated at a temperature range of 200 – 500 °C. Results from this research are used to model the implementation of sol-gel coatings into carbon fiber reinforced multifunctional composite systems. This research presents a novel thermo-responsive sol-gel/ (dopant) combination and evaluation of the actuating responses due to various heat treatment temperatures. While ATO is a well-known transparent conductive material, the implementation of ATO on carbon fibers for infrared thermal reflectivity has not been examined. These coatings serve as actuators capable of reflecting thermal infrared radiation in mid-range and near-range wavelengths (λ). By altering the ATO sol gel thickness and heat treatment temperatures, optimal optical properties are obtained. While scanning electron microscopy (SEM) is used for imaging, electron diffraction spectroscopy (EDS) is used to verify the compounds present in the coatings. Fourier transform infrared (FT-IR) spectroscopy was performed to analyze the reflectivity in the infrared spectra and analyze the crystal structures after heat treatments.

Evolution Of Molecular Structure In Alkoxide-Derived Lithium Niobate

1990 ◽  
Vol 180 ◽  
Author(s):  
Dennis J. Eichorst ◽  
D. A. Payne
Keyword(s):  
Heat Treatment ◽  
Lithium Niobate ◽  
Structural Changes ◽  
Sol Gel ◽  
Lithium Oxide ◽  
Structural Rearrangements ◽  
Raman Spectroscopic ◽  
Amorphous Network ◽  
Niobium Ethoxide ◽  
Gel Processing

ABSTRACTStructural rearrangements during the sol-gel processing of lithium niobate were investigated by FTlR and Raman spectroscopic methods. The reaction of lithium ethoxide with niobium ethoxide resulted in the formation of a bimetallic alkoxide, LiNb(OEt)6 , which could be crystallized from solution. Single crystals were comprised of helical polymeric units consisting of niobium octahedra linked by lithium in tetrahedral (distorted) coordination. Successive crystallizations from solution allowed for the enhanced purification of the alkoxide precursor. Hydrolysis of the bimetallic alkoxide resulted in the formation of an amorphous network structure, which contained niobium-oxygen octahedral units modified by lithium. Heat-treatment facilitated structural rearrangements for the niobium environment, which allowed for the formation of the lithium niobate crystal structure. Further heat-treatment above 700°C resulted in structural changes associated with lithium oxide volatility.

Physical-Chemical Properties of TiO2 Membranes Controlled By Sol-Gel Processing

1988 ◽  
Vol 132 ◽  
Author(s):  
Qunyin Xu ◽  
Marc A. Anderson
Keyword(s):  
Primary Particle ◽  
Sol Gel ◽  
Chemical Properties ◽  
Primary Particle Size ◽  
Chemical Processes ◽  
Gel Structure ◽  
Physical Chemical ◽  
Membrane Porosity ◽  
Gel Processing ◽  
Alkoxide Precursors

ABSTRACTParticulate TiO2 membranes have been prepared by sol-gel techniques from alkoxide precursors. The degree of aggregation, which is controlled by physical chemical processes during sol preparation influences the gelling volume and gel structure. While three types of gel structures have been proposed, the porosity of the final membrane seems to be little affected by these hydrogel structures. Firing temperature is a much more critical parameter. It is concluded that the primary particle size determines the final membrane porosity in this TiO2 system.

PREPARATION AND STRUCTURE CHARACTERIZATION OF BiFeO3-SrBi2Nb2O9 THIN FILMS ON SILICON BY SOL-GEL PROCESSING

2002 ◽  
Vol 16 (28n29) ◽  
pp. 4455-4459
Author(s):  
HAOSHUANG GU ◽  
WANQIANG CAO ◽  
JUNMIN XUE ◽  
JOHN WANG
Keyword(s):  
Thin Films ◽  
Sol Gel ◽  
Precursor Solution ◽  
Monomethyl Ether ◽  
Structure Characterization ◽  
Layered Perovskite ◽  
Heat Treated ◽  
Average Grain Size ◽  
Gel Processing

A new system 0.1 BiFeO 3-0.9 SrBi 2 Nb 2 O 9 thin films have been successfully prepared by an ethanolamine-modified sol-gel technique. The precursor solution was synthesized from compounds, Bi(NO 3)3· 5H 2 O , Sr(NO 3)2, Fe(NO 3)3· 9H 2 O and Nb(OC 2 H 5)5 in solution ethylene glycol monomethyl ether. The thin films were deposited on Si single crystal by spinning coating, and heat-treated at temperatures ranging from 400°C to 700°C. Crystallization of thin films occurred at about 500 ~ 600°C and the films exhibit a pure phase of layered perovskite ferroelectric structure. The grain of films is well distributed and the average grain size of the film is about 100nm.

Sign in / Sign up

Export Citation Format

Share Document