scholarly journals Chemical Preparation Routes and Lowering the Sintering Temperature of Ceramics

Ceramics ◽  
2020 ◽  
Vol 3 (3) ◽  
pp. 312-339
Author(s):  
Philippe Colomban
Keyword(s):  
Electrode Materials ◽  
Sintering Temperature ◽  
Microwave Sintering ◽  
Sol Gel ◽  
Transient Liquid Phase ◽  
Ceramic Matrix Composites ◽  
Thermomechanical Properties ◽  
Matrix Composites ◽  
Chemical Preparation ◽  
The Stability

Chemically and thermally stable ceramics are required for many applications. Many characteristics (electrochemical stability, high thermomechanical properties, etc.) directly or indirectly imply the use of refractory materials. Many devices require the association of different materials with variable melting/decomposition temperatures, which requires their co-firing at a common temperature, far from being the most efficient for materials prepared by conventional routes (materials having the stability lowest temperature determines the maximal firing temperature). We review here the different strategies that can be implemented to lower the sintering temperature by means of chemical preparation routes of oxides, (oxy)carbides, and (oxy)nitrides: wet chemical and sol–gel process, metal-organic precursors, control of heterogeneity and composition, transient liquid phase at the grain boundaries, microwave sintering, etc. Examples are chosen from fibers and ceramic matrix composites (CMCs), (opto-)ferroelectric, electrolytes and electrode materials for energy storage and production devices (beta alumina, ferrites, zirconia, ceria, zirconates, phosphates, and Na superionic conductor (NASICON)) which have specific requirements due to multivalent composition and non-stoichiometry.

Accounting for frictional contact in an anisotropic damage model based on compliance tensorial variables, illustration on ceramic matrix composites

2018 ◽  
Vol 28 (8) ◽  
pp. 1150-1169 ◽  
Author(s):  
Emmanuel Baranger
Keyword(s):  
Damage Mechanics ◽  
A Priori ◽  
Damage Model ◽  
Ceramic Matrix Composites ◽  
Inelastic Strain ◽  
Ceramic Matrix ◽  
Thermomechanical Properties ◽  
Matrix Composites ◽  
Crack Network ◽  
Evolution Laws

Ceramic matrix composites have good thermomechanical properties at high or very high temperatures. The modeling of the crack networks associated to the degradation of such composites using damage mechanics is not straightforward. The main reason is the presence of a crack network mainly oriented by the loading direction, which is a priori unknown. To model this, compliance tensorial damage variables are used in a thermodynamic potential able to account for crack closure effects (unilateral contact). The damage kinematic is initially completely free and imposed by the evolution laws. The key point of the present paper is to account for friction in such cracks that can result in an apparent activation/deactivation of the shear damage. The initial model is enriched with an inelastic strain and a friction law. The plasticity criterion is expressed only using tensorial variables. The model is identified and illustrated on multiaxial data obtained at ONERA on tubes loaded in tension and torsion.

The Stability of BN Interfacial Coatings in CFCC Systems During Oxidation and Exposure to Moisture

1997 ◽  
Vol 3 (S2) ◽  
pp. 729-730
Author(s):  
K.S. Ailey ◽  
K.L. More ◽  
R.A. Lowden
Keyword(s):  
Elevated Temperatures ◽  
Impurity Content ◽  
Chemical Vapor ◽  
Ceramic Matrix Composites ◽  
Chemical Vapor Infiltration ◽  
Forced Flow ◽  
Crystallographic Structure ◽  
Matrix Composites ◽  
Sic Composites ◽  
The Stability

The mechanical reliability of ceramic matrix composites (CMCs) at elevated temperatures in oxidative environments is primarily dependent upon the chemical and structural stability of the fiber/matrix interface. Graphitic carbon coatings have traditionally been used to control the interfacial properties in CMCs, however, their use is limited in high temperature oxidative environments due to the loss of carbon and subsequent oxidation of the fiber and matrix. Thus, BN is being investigated as an alternative interfacial coating since it has comparable room temperature properties to carbon with improved oxidation resistance. The stability of BN interfaces in SiC/SiC composites is being investigated at elevated temperatures in either flowing oxygen or environments containing water vapor. The effect of several factors on BN stability, including crystallographic structure, extent of BN crystallization, and impurity content, are being evaluated.Nicalon™ fiber preforms were coated with ≈ 0.4 μm of BN by CVD using BCl3, NH3, and H2 at 1373 K. The coated preforms were densified using a forced-flow chemical vapor infiltration (FCVI) technique developed at ORNL.

Mullite Fiber Reinforced Alumina Ceramic Matrix Composites

2008 ◽  
Vol 368-372 ◽  
pp. 710-712 ◽  
Author(s):  
Zhi Wang ◽  
Guo Pu Shi ◽  
Xiang Sun ◽  
Xian Qin Hou
Keyword(s):  
Sintering Temperature ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Alumina Ceramic ◽  
Matrix Composites ◽  
Fiber Reinforced ◽  
Sintering Aids ◽  
Original Matrix ◽  
Pull Out ◽  
Mullite Fiber

Mullite fiber reinforced alumina ceramic matrix composites (MFACC) were prepared using CaO-MgO-SiO2 (CMS) and TiO2 as sintering aids. The effects of the contents of sintering aids and mullite fiber on the density and sintering temperature of MFACC are studied. The results showed that when the CMS content is 8.0% and the TiO2 content is 1.0%, the density of the as-sintered MFACC is 98.9%. When the mullite fiber content is 15.0% and the sintering temperature is 1450 °C, the flexural strength of the resultant composite increases to 504.5MPa, 70.7% higher than the original matrix, and the relative density of the composites reaches 98.4%. The reinforcement mechanisms are fibers pull-out and sticky point.

Mechanical properties and microstructures of sol-gel derived ceramic-matrix composites

1995 ◽  
Vol 30 (11) ◽  
pp. 2769-2784 ◽  
Author(s):  
J. M. Chant ◽  
S. M. Bleay ◽  
B. Harris ◽  
R. Russell-Floyd ◽  
R. G. Cooke ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Sol Gel ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Matrix Composites

Current Status of Oxide Fibre-Reinforced Oxide Ceramic Matrix Composites for Gas Turbine Applications

2010 ◽  
Vol 434-435 ◽  
pp. 1-4
Author(s):  
Cengiz Kaya
Keyword(s):  
High Temperature ◽  
Gas Turbine ◽  
Ceramic Matrix Composites ◽  
Composite Plates ◽  
Ceramic Matrix ◽  
Thermomechanical Properties ◽  
Current Status ◽  
Oxide Ceramic ◽  
Matrix Composites ◽  
Recent Developments

Recent developments in the processing, understanding and mechanical/thermomechanical properties of oxide fibre reinforced oxide ceramic matrix composites for high temperature applications are reported. Two dimensional composite plates and uni-directional tubular composite (so called mini-composite) specimens are successfully manufactured and their microstructure, matrix/ fiber interface as well as mechanical properties are examined. It is shown that the microstructural variations, such as porosity size and interface between fibre and matrix determine the fracture behaviour and high temperature performance of the composites. The optimised components produced are considered to be suitable for gas turbine applications.

Sol-gel Elaboration of Porous Oxide Coatings as Interphase in SiC/SiC Ceramic Matrix Composites

2003 ◽  
Vol 775 ◽  
Author(s):  
M. Verdenelli ◽  
S. Parola ◽  
F. Chassagneux ◽  
S. Jacques ◽  
H. Vincent ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Sol Gel ◽  
Ceramic Matrix Composites ◽  
Matrix Composites ◽  
X Ray Diffraction ◽  
Brittle Behavior ◽  
Transmission Electron ◽  
Sol Gel Process ◽  
The Matrix ◽  
Mesoporous Oxide

AbstractCombinations of meso-, macro- and microporous coatings with a chemical composition of 90%Al2O3-10%SiO2 were elaborated on SiC Hi-Nicalon fibers using the sol-gel process. They were evaluated as porous interphase for the reinforcement of CMC. The mesoporous oxide, in contact with the fiber, allows cracks deviation whereas the macroporous one, in contact with the matrix, avoids the gaseous infiltration of the mesopores during the SiC CVD matrix process. It also prevents from oxygen diffusion during high temperature under air. The characterization of the composites was performed by SEM (scanning electron microscopy), TEM (transmission electron microscopy), X-ray diffraction, and EDS (energy dispersive spectrometry). TEM evidenced the porosity gradient as expected. A tensile test on the composites revealed brittle behavior (fracture) and no fiber debonding was observed.

Sign in / Sign up

Export Citation Format

Share Document