Direct Process Metal Alkoxides as Ceramic Precursors

1986 ◽  
Vol 73 ◽  
Author(s):  
R. J. Ayen ◽  
J. H. Burk
Keyword(s):  
Surface State ◽  
Great Promise ◽  
Oxide Ceramic ◽  
Metal Alkoxides ◽  
Direct Process ◽  
Precision Casting ◽  
Ceramic Precursors ◽  
Judicious Choice ◽  
Molecular Doping ◽  
Tetraethyl Silicate

ABSTRACTMetal alkoxides have great promise as oxide ceramic precursors. Direct manufacture from the metal and the alcohol permits the production of high purity materials and of those alkoxides which cannot be easily obtained by other routes. Examples which are of great interest to ceramics are the alkoxides of silicon, aluminum, magnesium and yttrium.Currently, only tetraethyl silicate is produced in large volumes by the direct route, employing a catalytic continuously fed process, yielding a distilled product. The reactivity of silicon, aluminum, magnesium and yttrium is governed by the metal surface state and activation and varies with different catalysts and alcohol chain length and branching.The major use of tetraethyl silicate is in partially hydrolyzed form as binder for precision casting molds and zinc-rich primer coatings. Judicious choice of alkoxide ligands allows the manufacture of soluble or liquid Si, Al, Mg, and Y derivatives. These are especially suitable for molecular doping and mixing in the manufacture of yttriastabilized zirconia, mullite, spinel, cordierite and other oxide ceramic precursors.

Research of Calcium Oxide Based Ceramic Cores in Titanium Casting

2012 ◽  
Vol 531-532 ◽  
pp. 266-271 ◽  
Author(s):  
Xiao Qing Xu ◽  
Peng Gao ◽  
Tie Tao Zhou
Keyword(s):  
Internal Structure ◽  
Calcium Oxide ◽  
Oxide Ceramic ◽  
Bend Strength ◽  
Sintering Process ◽  
Precision Casting ◽  
Ultimate Properties ◽  
And Performance ◽  
Casting Industry ◽  
Sintering Shrinkage

Ceramic cores are playing a more and more important role in the modern precision casting industry system; it could influence the internal structure and performance of the castings. Especially in the precision casting field, the internal structure directly influenced the ultimate properties. This paper investigated the calcium oxide ceramic cores used in titanium precision casting fields through changing the ratio of aggregate sizes and sintering process. The main properties as bend strength, sintering shrinkage, casting reaction layer and microstructure are performed using SEM, XRD and other measurement method. Results of this research showed that the calcium oxide ceramic cores could be used in titanium precision casting, provide a stable casting property and nearly without reaction pollution to the titanium castings.

Synthesis of Non-Oxide Ceramic Fine-Powders from Organic Precursors

2008 ◽  
Vol 403 ◽  
pp. 269-272 ◽  
Author(s):  
Toshiyuki Nishimura ◽  
S. Ishihara ◽  
Yoshiki Yoshioka ◽  
Hidehiko Tanaka
Keyword(s):  
Carbothermic Reduction ◽  
Phenolic Resin ◽  
Oxide Ceramic ◽  
Metal Alkoxides ◽  
Ceramic Powders ◽  
Metal Source ◽  
Fine Powders ◽  
Argon Flow ◽  
Organic Precursors ◽  
And Control

Synthesis of titanium carbide ceramic powders and control of particle size were tried by carbothermic reduction of a precursor, comparing synthesis of silicon carbide from a precursor. Metal alkoxides were used as a metal source and phenolic resin was done as a carbon source. Homogeneous sol-like mixture was obtained by mixing ethylsilicate and phenolic resin with alcohol. Gel-like precursor was formed by drying the sol-like mixture. Precipitation was formed by mixing titanium(IV) tetraisopropoxide and phenolic resin. The precursor was amorphous and ceramization occurred by heat treatment in argon flow. Growth of particles and phase formation were investigated.

Preparation of Aluminum Oxide Ceramic Precursors by Dispersion of Aluminum Alloy D16

2015 ◽  
Vol 56 (1) ◽  
pp. 11-13 ◽  
Author(s):  
F. Z. Badaev ◽  
V. P. Tarasovskii ◽  
R. A. Novoselov ◽  
A. Kh. Khairi ◽  
A. V. Reznichenko
Keyword(s):  
Aluminum Alloy ◽  
Aluminum Oxide ◽  
Oxide Ceramic ◽  
Ceramic Precursors ◽  
Aluminum Oxide Ceramic

Crystallization sequence of an A1N-Y2O3-SiO2 glass-ceramic

1986 ◽  
Vol 44 ◽  
pp. 446-447
Author(s):  
T.R. Dinger ◽  
G. Thomas
Keyword(s):  
High Temperature ◽  
Glass Ceramic ◽  
Crystallization Behavior ◽  
High Stress ◽  
Crystallization Sequence ◽  
Sio2 Glass ◽  
Structural Applications ◽  
Ceramic Precursors

The use of Si3N4, alloys for high temperature, high stress structural applications has prompted numerous studies of the oxynitride glasses which exist as intergranular phases in their microstructures. Oxynitride glasses have been investigated recently in their bulk form in order to understand their crystallization behavior for subsequent Si3N4 applications and to investigate their worth as glass-ceramic precursors. This research investigates the crystallization sequence of a glass having a normalized composition of Y26Si30Al11 ON11 and lying in the A1N-Y2O3-SiO2 section of the Y-Si-Al-O-N system. Such glasses exist as intergranular phases in the technologically important Y2O3/Al2O3-fluxed Si3N4 alloys.

The crystallization of thin-film ceramics

1992 ◽  
Vol 50 (1) ◽  
pp. 338-339
Author(s):  
J.M. Schwartz ◽  
L.F. Francis ◽  
L.D. Schmidt ◽  
P.S. Schabes-Retchkiman
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Sol Gel ◽  
Processing Route ◽  
Small Areas ◽  
Ceramic Thin Films ◽  
Complex Shapes ◽  
Sol Gel Process ◽  
Ceramic Precursors ◽  
Crystalline Ceramic

Ceramic thin films and coatings are of interest for electrical, optical, magnetic and thermal barrier applications. Critical for improved properties in thin films is the development of specific microstructures during processing. To this end, the sol-gel method is advantageous as a versatile processing route. The sol-gel process involves depositing a solution containing metalorganic or colloidal ceramic precursors onto a substrate and heating the deposited layer to form a crystalline or non-crystalline ceramic coating. This route has several advantages, including the ability to create tailored microstructures and properties, to coat large or small areas, simple or complex shapes, and to more easily prepare multicomponent ceramics. Sol-gel derived coatings are amorphous in the as-deposited state and develop their crystalline structure and microstructure during heat-treatment. We are particularly interested in studying the amorphous to crystalline transformation, because many key features of the microstructure such as grain size and grain size distribution may be linked to this transformation.

Are HOLZ lines kinematic in off-zone-axis orientation?

1993 ◽  
Vol 51 ◽  
pp. 692-693
Author(s):  
J. M. Zuo ◽  
A. L. Weickenmeier ◽  
R. Holmestad ◽  
J. C. H. Spence
Keyword(s):  
Structure Determination ◽  
Standard Procedure ◽  
High Order ◽  
Zone Axis ◽  
Great Promise ◽  
Line Position ◽  
Measured Intensity ◽  
Constant Intensity ◽  
Axis Orientation ◽  
Diffraction Condition

The application of high order reflections in a weak diffraction condition off the zone axis center, including those in high order laue zones (HOLZ), holds great promise for structure determination using convergent beam electron diffraction (CBED). It is believed that in this case the intensities of high order reflections are kinematic or two-beam like. Hence, the measured intensity can be related to the structure factor amplitude. Then the standard procedure of structure determination in crystallography may be used for solving unknown structures. The dynamic effect on HOLZ line position and intensity in a strongly diffracting zone axis is well known. In a weak diffraction condition, the HOLZ line position may be approximated by the kinematic position, however, it is not clear whether this is also true for HOLZ intensities. The HOLZ lines, as they appear in CBED patterns, do show strong intensity variations along the line especially near the crossing of two lines, rather than constant intensity along the Bragg condition as predicted by kinematic or two beam theory.

Development of the UHV-STM

1990 ◽  
Vol 48 (1) ◽  
pp. 322-323
Author(s):  
M. Iwatsuki ◽  
S. Kitamura ◽  
A. Mogami
Keyword(s):  
Surface Science ◽  
Real Space ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Great Promise ◽  
Force Microscopy ◽  
Atomic Force ◽  
Stm Image ◽  
Surface Construction ◽  
Very High

Since Binnig, Rohrer and associates observed real-space topographic images of Si(111)-7×7 and invented the scanning tunneling microscope (STM),1) the STM has been accepted as a powerful surface science instrument.Recently, many application areas for the STM have been opened up, such as atomic force microscopy (AFM), magnetic force microscopy (MFM) and others. So, the STM technology holds a great promise for the future.The great advantages of the STM are its high spatial resolution in the lateral and vertical directions on the atomic scale. However, the STM has difficulty in identifying atomic images in a desired area because it uses piezoelectric (PZT) elements as a scanner.On the other hand, the demand to observe specimens under UHV condition has grown, along with the advent of the STM technology. The requirment of UHV-STM is especially very high in to study of surface construction of semiconductors and superconducting materials on the atomic scale. In order to improve the STM image quality by keeping the specimen and tip surfaces clean, we have built a new UHV-STM (JSTM-4000XV) system which is provided with other surface analysis capability.

Behavioral Genetics: Concepts for Research and Practice in Language Development and Disorders

1995 ◽  
Vol 38 (5) ◽  
pp. 1126-1142 ◽  
Author(s):  
Jeffrey W. Gilger
Keyword(s):  
Language Development ◽  
Behavioral Genetics ◽  
State Of The Art ◽  
Genetic Research ◽  
Great Promise ◽  
Behavioral Genetic ◽  
Fine Grained ◽  
Future Goals ◽  
Current State ◽  
Research Designs

This paper is an introduction to behavioral genetics for researchers and practioners in language development and disorders. The specific aims are to illustrate some essential concepts and to show how behavioral genetic research can be applied to the language sciences. Past genetic research on language-related traits has tended to focus on simple etiology (i.e., the heritability or familiality of language skills). The current state of the art, however, suggests that great promise lies in addressing more complex questions through behavioral genetic paradigms. In terms of future goals it is suggested that: (a) more behavioral genetic work of all types should be done—including replications and expansions of preliminary studies already in print; (b) work should focus on fine-grained, theory-based phenotypes with research designs that can address complex questions in language development; and (c) work in this area should utilize a variety of samples and methods (e.g., twin and family samples, heritability and segregation analyses, linkage and association tests, etc.).

Sign in / Sign up

Export Citation Format

Share Document