Ultra-High Temperature Ceramics (UHTCs) via Reactive Sintering

2007 ◽  
Vol 336-338 ◽  
pp. 1159-1163 ◽  
Author(s):  
Guo Jun Zhang ◽  
Wen Wen Wu ◽  
Yan Mei Kan ◽  
Pei Ling Wang
Keyword(s):  
Phase Composition ◽  
High Temperature ◽  
Oxidation Resistance ◽  
High Performance ◽  
Thermal Protection ◽  
Ambient Pressure ◽  
Stable Phase ◽  
Reactive Sintering ◽  
Dissociation Temperature ◽  
Monolithic Ceramics

Current high temperature ceramics, such as ZrO2, Si3N4 and SiC, cannot be used at temperatures over 1600°C due to their low melting temperature or dissociation temperature. For ultrahigh temperature applications over 1800°C, materials with high melting points, high phase composition stability, high thermal conductivity, good thermal shock and oxidation resistance are needed. The transition metal diborides, mainly include ZrB2 and HfB2, have melting temperatures of above 3000°C, and can basically meet the above demands. However, the oxidation resistance of diboride monolithic ceramics at ultra-high temperatures need to be improved for the applications in thermal protection systems for future aerospace vehicles and jet engines. On the other hand, processing science for making high performance UHTCs is another hot topic in the UHTC field. Densification of UHTCs at mild temperatures through reactive sintering is an attracting way due to the chemically stable phase composition and microstructure as well as clean grain boundaries in the obtained materials. Moreover, the stability studies of the materials in phase composition and microstructures at ultra high application temperatures is also critical for materials manufactured at relatively low temperature. Furthermore, the oxidation resistance in simulated reentry environments instead of in static or flowing air of ambient pressure should be evaluated. Here we will report the concept, advantages and some recent progress on the reactive sintering of diboride–based composites at mild temperatures.

Influences of Calcination Ambiences on Phase Composition and High Temperature Oxidation Resistance Property of Ceramic Coatings on Ti–6Al–4V Alloy by Micro-Plasma Oxidation

2007 ◽  
Vol 336-338 ◽  
pp. 2481-2483 ◽  
Author(s):  
Guo Dong Hao ◽  
Zhao Hua Jiang ◽  
Zhong Ping Yao ◽  
Heng Ze Xian ◽  
Yan Li Jiang
Keyword(s):  
Phase Composition ◽  
High Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Ceramic Coatings ◽  
Plasma Oxidation ◽  
Temperature Oxidation ◽  
Complete Decomposition ◽  
Weight Gains ◽  
High Temperature Calcination

Compound ceramic coatings with the main crystalline of Al2TiO5 (as-coated samples) were prepared on Ti-6Al-4V alloy by pulsed bi-polar micro-plasma oxidation (MPO) in NaAlO2 solution. The coated samples were calcined in Ar and air at 1000oC, respectively. The phase composition, morphology and element content of the coatings were investigated by XRD, SEM and XRF. The samples treated in Ar and the as-coated ones were calcined in air at 1000oC to study the oxidation resistance of the samples. The results showed that Al2TiO5 decomposed and transformed into corundum and rutile TiO2 during the high temperature calcination. Al2TiO5 decomposed very quickly in air and the proportion of Al2O3 to TiO2 was 44:55 after a complete decomposition. On the contrary, Al2TiO5 decomposed very slowly in argon with the final proportion of Al2O3 to TiO2 of 81:18 on the coating surface. The morphology of the ceramic coatings after the calcination was also different. The coatings calcined in argon were fined: the grains and pores were smaller than those of the coatings calcined in air. The weight gains of both coatings changed in the form of parabola law, and the weight gains of the coated samples treated in argon were comparatively lower than that of the as-coated samples. During the high temperature calcination, the samples treated in argon cannot distort easily, compared with the as-coated ones.

XRD Studies on Transformation of Calcium-Deficient Apatite to β and α TCP in Dynamic and Technological Conditions

2010 ◽  
Vol 76 ◽  
pp. 54-59
Author(s):  
Bartosz Handke ◽  
Aneta Zima ◽  
Zofia Paszkiewicz ◽  
Anna Ślósarczyk
Keyword(s):  
Phase Composition ◽  
High Temperature ◽  
Calcium Phosphates ◽  
Maxillofacial Surgery ◽  
Drug Carriers ◽  
Stable Phase ◽  
Dynamic Studies ◽  
High Temperature Xrd ◽  
Three Phase ◽  
Xrd Studies

Calcium phosphates (CaPs): hydroxyapatite (HA) and TCP are common biomaterials used in orthopedic, dental and maxillofacial surgery as bone fillers and also as drug carriers. Studies of the β→α TCP transformation and formation of mono-, bi- or three-phase CaPs materials: βTCP-αTCP-HA are of principal importance. Stability of calcium phosphate ceramics depends on many factors. Our dynamic studies by high temperature XRD measurements showed that monoclinic αTCP was a considerably stable phase after its creation completed at 1200°C. Different phase composition was obtained in technological conditions.

A Newly Developed Self-Bonded SiC Refractory

2013 ◽  
Vol 750-752 ◽  
pp. 2078-2083
Author(s):  
Long Gang Wan ◽  
Zhi Gang Huang ◽  
Shao Rong Song ◽  
Jia Ping Wang ◽  
Jie Li
Keyword(s):  
Thermal Conductivity ◽  
Phase Composition ◽  
High Temperature ◽  
Oxidation Resistance ◽  
Alkali Resistance ◽  
High Temperature Furnace ◽  
Temperature Furnace

Based on SiC aggregate, SiC powder and ultra-fine SiC powder as the main starting materials and B4C as additive, the newly-developed self-bonded SiC material was pressed and fired at 2200°C for 10 hours in Ar environment in the high-temperature furnace. The phase composition and microstructure were investigated. In the paper, traditional self-bonded SiC material and Si3N4-bonded SiC material were taken for comparison with the newly-developed self-bonded SiC material in terms of strength, thermal conductivity, cryolite resistance, molten alkali resistance and oxidation resistance etc. The results show that the newly-developed self-bonded SiC material contains 98.42% α-SiC and presents obvious higher thermal conductivity than traditional self-bonded SiC material and much better cryolite resistance, molten alkali resistance and oxidation resistance than traditional self-bonded SiC and Si3N4-bonded SiC materials.

Preparation and Property of Ceramic Matrix Coating of Anti-Oxidation for Stainless Steel at High Temperature by Slurry Method

2010 ◽  
Vol 105-106 ◽  
pp. 448-450
Author(s):  
Peng Liu ◽  
Lian Qi Wei ◽  
Shu Feng Ye ◽  
Xun Zhou ◽  
Yu Sheng Xie ◽  
...  
Keyword(s):  
Stainless Steel ◽  
High Temperature ◽  
Melting Temperature ◽  
Oxidation Resistance ◽  
High Performance ◽  
Ceramic Coating ◽  
Ceramic Matrix ◽  
Sem Images ◽  
Temperature Oxidation ◽  
Slurry Method

In this paper, the new high temperature ceramic matrix coating of anti-oxidation for stainless steel was prepared by slurry method. With the research about oxidation resistance of ceramic matrix coating formed on stainless steel, the effect of initial melting temperature, melting temperature range and thermal expansion coefficients of ceramic sintering change on protective properties of high temperature coating prepared at 1250°C is investigated, and then high temperature sintering ceramic with high-performance is gained through optimization. Through the test of TG-DTA and XRD to the coating, study on high temperature oxidation resistance of ceramic coating and the structure changing of the scale with coating from SEM images and photos, it is shown that the ceramic coating has excellent oxidation resistant properties, the weight loss with coating decrease more than 85%.

Thermal Alumina Scales on FeCrAl: Characterization and Growth Mechanism

2008 ◽  
Vol 595-598 ◽  
pp. 915-922 ◽  
Author(s):  
Sébastien Chevalier ◽  
Alain Galerie ◽  
Olivier Heintz ◽  
Remi Chassagnon ◽  
Alexandre Crisci
Keyword(s):  
Electron Microscope ◽  
High Temperature ◽  
Oxidation Resistance ◽  
Growth Mechanism ◽  
Stable Phase ◽  
Alumina Scales ◽  
Temperature Oxidation ◽  
X Ray ◽  
Transient Phases ◽  
Alpha Alumina

High temperature oxidation resistance of alumina-forming materials is connected to the growth of dense, stable and protective alumina scales. Depending on temperature, impurities present in the base alloys, presence of water vapour in the oxidizing atmosphere, the alumina scales are composed of alpha-alumina (which is the stable phase obtained for temperatures over 1000°C) or of transient alumina (γ,θ,δ obtained for lower temperatures). It is generally considered that γ- Al2O3 grows when T<850°C, that θ-Al2O3 is present for 850°C<T<1000°C and that α-Al2O3 is stable when T exceeds 1000°C. The exact role played by transient alumina formation and/or transformation on the high temperature performances of alumina-forming materials is not exactly defined. Many works proposed that transient alumina phases grew during the first steps of the oxidation process and transformed into the stable phase after further oxidation. The transformation of transient phases in the stable alphaphase is generally accompanied by a volume contraction of around 14 %. In order to get better oxidation resistance, the formation of transient alumina is not wished, because: 1) their growth rate is generally higher than that of alpha-alumina with, as a consequence, a huge Al consumption, detrimental for the material resistance after long exposures, 2) the change in volume during the transformation of transient phases into alpha-alumina can generate stresses in the oxide scale and can weaken its adherence to the underlying substrate, leading to massive spallation. The present study deals with the coupling of different characterization tools in order to precisely identify the transient phases grown on FeCrAl materials. The use of scanning electron microscope (SEM-FEG), transmission electron microscope (TEM), Photoluminscescence Spectroscopy(PLS), X-ray photoelectron spectrometry (XPS) and X-ray diffraction at different glancing angles (XRD) on model materials oxidized at two temperatures (850 and 1100°C) could help the identification of transient phases. These techniques gave a better understanding of the alumina scale growth mechanism.

scholarly journals Preparation and anti-oxidation performance of Al2O3-containing TaSi2–MoSi2–borosilicate glass coating on porous SiCO ceramic composites for thermal protection

RSC Advances ◽  
2018 ◽  
Vol 8 (24) ◽  
pp. 13178-13185 ◽  
Author(s):  
Xiafei Li ◽  
Junzong Feng ◽  
Yonggang Jiang ◽  
Hao Lin ◽  
Jian Feng
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
Borosilicate Glass ◽  
Thermal Protection ◽  
Ceramic Composites ◽  
Glass Coating ◽  
Oxidation Performance ◽  
Gas Penetration

Al2O3 improves the oxidation resistance of TaSi2–MoSi2–borosilicate glass coating through increasing the viscosity and inhibiting gas penetration into matrix at high temperature, thus prevents porous SiCO ceramic composites from being oxidized.

Microstructure Evolution of Fe-Al-Si and Ti-Al-Si Alloys during High-Temperature Oxidation

2014 ◽  
Vol 782 ◽  
pp. 353-358 ◽  
Author(s):  
Pavel Novák ◽  
Jan Kříž ◽  
Alena Michalcová ◽  
Dalibor Vojtěch
Keyword(s):  
High Temperature ◽  
Oxide Layer ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Reactive Sintering ◽  
Temperature Oxidation ◽  
Near Surface ◽  
Oxide Layers ◽  
High Temperature Mechanical Properties ◽  
Additional Protection

Alloys based on TiAl and FeAl aluminides are modern materials for high-temperature applications in automotive or aerospace industry due to low density combined with good high-temperature mechanical properties and oxidation resistance. Previous works proved that the addition of silicon to these alloys improves the oxidation resistance as well as the thermal stability. In this work, the mechanism of the silicon effect was investigated by observing the microstructure of the oxide layer and the near-surface area of the Ti-Al-Si and Fe-Al-Si alloys prepared by reactive sintering powder metallurgy. It was found that silicon improves the compactness of the oxide layers. The oxide layers on Fe-Al-Si alloys are formed by Al2O3 and small amount of iron oxide (Fe2O3) while Ti-Al-Si alloys cover by TiO2 and Al2O3 during the oxidation. Due to aluminium depletion of the alloy, a layer of silicides is formed under the oxide layer, thus acting as the additional protection against high-temperature oxidation.

Phase transformation and layer evolution in molybdenum disilicide-silicon carbide nanolayered coatings

1994 ◽  
Vol 52 ◽  
pp. 538-539
Author(s):  
H. Kung ◽  
T. R. Jervis ◽  
J.-P. Hirvonen ◽  
M. Nastasi ◽  
T. E. Mitchell ◽  
...  
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Oxidation Resistance ◽  
Elevated Temperatures ◽  
Matrix Material ◽  
Molybdenum Disilicide ◽  
High Temperature Strength ◽  
Cross Sectional ◽  
Good Oxidation Resistance ◽  
Structural Applications

MoSi2 is a potential matrix material for high temperature structural composites due to its high melting temperature and good oxidation resistance at elevated temperatures. The two major drawbacksfor structural applications are inadequate high temperature strength and poor low temperature ductility. The search for appropriate composite additions has been the focus of extensive investigations in recent years. The addition of SiC in a nanolayered configuration was shown to exhibit superior oxidation resistance and significant hardness increase through annealing at 500°C. One potential application of MoSi2- SiC multilayers is for high temperature coatings, where structural stability ofthe layering is of major concern. In this study, we have systematically investigated both the evolution of phases and the stability of layers by varying the heat treating conditions.Alternating layers of MoSi2 and SiC were synthesized by DC-magnetron and rf-diode sputtering respectively. Cross-sectional transmission electron microscopy (XTEM) was used to examine three distinct reactions in the specimens when exposed to different annealing conditions: crystallization and phase transformation of MoSi2, crystallization of SiC, and spheroidization of the layer structures.

Trends in the development of flexible thermal protection systems for modern aircraft

2020 ◽  
pp. 10-21
Author(s):  
V. G. Babashov ◽  
◽  
N. M. Varrik ◽  
Keyword(s):  
High Temperature ◽  
Thermal Protection ◽  
Heat Removal ◽  
Operating Conditions ◽  
Passive Protection ◽  
Thermal Protection Systems ◽  
Heat Protection ◽  
Protection Systems ◽  
Protected Surface ◽  
Flexible Panels

The emergence of new types of space and aviation technology necessitates the development of new types of thermal protection systems capable of operating at high temperature and long operating times. There are several types of thermal protection systems for different operating conditions: active thermal protection systems using forced supply of coolant to the protected surface, passive thermal protection systems using materials with low thermal conductivity without additional heat removal, high-temperature systems, which are simultaneously elements of the bearing structure and provide thermal protection, ablation materials. Heat protection systems in the form of rigid tiles and flexible panels, felt and mats are most common kind of heat protecting systems. This article examines the trends of development of flexible reusable heat protection systems intended for passive protection of aircraft structural structures from overheating.

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