Surface analysis of nanostructured ceramic coatings containing silicon carbide nanoparticles produced by plasma modulation chemical vapour deposition (original) (raw)
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Preparation of ceramic coatings from pre-ceramic precursors
Journal of Materials Science, 1994
Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) has indicated that adherent crack-free coatings of amorphous SiC and "'Si3N4//Si2N20 '" can be built up on planar alumina substrates by pyrolysis of layers of polycarbosilane (PCS) and poly(diphenyl)silazane (PDPS) precursors applied by spin-or dip-coating methods. In general, multilayers of black SiC can be prepared by pyrolysis of PCS layers at 1100 ~ in a nitrogen atmosphere while transparent coatings consisting of multiple layers of Si3N 4 are prepared by pyrolysis of either PCS or PDPS layers in a flowing atmosphere of ammonia at 1100~ The "Si3N4/Si2N20" layers prepared by pyrolysing spin-coated layers of PDPS layers are found to be superior in quality (with respect to blemishes and embedded debris) than those prepared from spin-coated layers of PCS. Microhardness tests reveal that the coatings derived from PCS and PDPS are significantly softer than would be expected for SiC and Si3N 4. X-ray photoelectron studies reveal that the surface of the PCS-derived SiC coatings consists of an Si02 layer while the surface of the PDPS-derived "Si3N4/Si2N20" coating consists of an oxygen-rich silicon oxycarbonitride. These results are also generally supported by Rutherford backscattering spectra which also indicate considerable phase mixing of silicon, carbon, oxygen and nitrogen components within the bulk of the SiC and "Si3N4//Si2N20 '' coatings on alumina.
Structure and Mechanical Properties of Ceramic Nanocomposite Coatings
ICASE/LaRC Interdisciplinary Series in Science and Engineering, 2003
• 3 wt% SrAl 12 O 19 improves the fracture toughness of alumina-zirconia ceramics. • Fragmentary structure is characteristic of the strontium hexaaluminate platelets. • The structure of SrAl 12 O 19 platelets affects the crack propagation trajectory.
Structural and functional thick ceramic coatings by electrophoretic deposition
Surface and Coatings Technology, 2005
Electrophoretic deposition (EPD) has been used in the present work to produce thick ceramic films from nanosized powders on different substrates for structural and functional applications. Hydrothermally synthesized ultra-fine (12 nm) yttrium disilicate (Y 2 Si 2 O 7) powders were used to create an effective oxidation protection layer of 90 Am thickness on bulk SiC/SiC composite and on woven SiC fibre mats by EPD using a constant voltage of 8 V for 1.5 min. EPD was also used to make lead zirconate titanate (PZT) films on Pt wires for functional applications using hydrothermally synthesized PZT powders with an average particle size of 200 nm. EPD was employed to deposit PZT films directly from the hydrothermal PZT suspensions using a deposition voltage of 4 V for 10 min, leading to the formation of a functional PZT film with a thickness of 5 Am around Pt wire. Titania films on different stainless steel substrates (plates, individual fibres, fibre mats) were also produced by EPD at constant voltage conditions. A nonaqueous suspension of TiO 2 nanoparticles in acetylacetone with iodine additions was used for optimal results, which were obtained using voltages of 10 V and deposition times of 2 min. Sintering at 800 jC for 2 h resulted in TiO 2 coatings with uniform nanoporous structure, which are interesting for biomedical and photocatalytic applications. The effect of the process parameters such as deposition time and voltage as well as the solids-loading of the colloidal suspensions on the quality, thickness and microstructure of the different ceramic films produced is discussed.
Ceramics International, 2011
bilayer anti-oxidation coating was fabricated on the surface of C/SiC composites by the chemical vapor deposition (CVD) and the combination of sol-gel and air spraying method to enhance the oxidation resistance of C/SiC composites. Results indicated that the bilayer coating can efficiently prevent the oxidation of C/SiC composites in ambient air at 1773 K for more than 100 h with slight weight loss rate of 8.12 × 10-5 g cm-2 h-1 and retained compression strength of 96.78%. Microstructure characterization revealed that the gradual densification of Yb 2 Si 2 O 7 outer coating exposed to 1773 K reduced the oxygen diffusion pathes within the Yb 2 Si 2 O 7 /SiC bilayer coating, therefore, the weight loss rate of specimens decreased as oxidation proceeded. The oxidation activation energy of bilayer coating coated C/SiC specimen was 107.73 kJ/mol during long time oxidation within the temperature range from 1573 K to 1773 K. Based on the microstructure analysis and oxidation behavior of the specimens with different exposure time of oxidation, the oxygen diffusion rate in the bilayer coating was the controlling link during the long time oxidation course.
Journal of Electronic Materials, 2005
Ceramic/self-assembled monolayer (SAM) bilayer coatings can provide adequate protection for silicon devices, or act as a multipurpose coating for other electronic applications, due to synergistic effects by forming a hybrid coating structure. The organic SAM layer acts as a "template" for the growth of the ceramic layer, while the ceramic layer can provide protection from environmental and mechanical impact. Low-temperature solution-based deposition techniques, namely, an in-situ solution method (biomimetic) and a hydrothermal method, have been employed in this study. Specifically, phosphonate-based (diethyl phosphatoethyl triethoxy silane) SAMs were used as a template to generate a zirconia ceramic layer at low temperatures. Other organic templates such as-SiCl 3- ,-OH- ,-HSO 3-, or-CH 3-terminated SAMs were also examined. The reactions to grow the ceramic film were found to be pH sensitive. The ceramic and SAM coatings were characterized by a variety of analytical techniques. A pathway for the formation of the ceramic coating is also discussed.
Three types of ceramic coating applicability in automotive industry for wear resistance purpose
Industrial Lubrication and Tribology, 2005
PurposeThe aim of the research is to investigate the influence of ceramic coating on the wear performance of machine parts.Design/methodology/approachDuctile cast iron parts were coated using ceramics. Three ceramics were used for this purpose. These coated parts were subjected to wear tests under a stable load. A pin‐on‐disc wear test apparatus was used.FindingsAs a result of this study, the following findings are reported: According to ASTM G 99‐90 pin‐on‐disc experiments, Cr2O3 was found to be best coating material with low wearing rate. Within row, Al2O3 and ZrO2 can be given. According to the previous work, motor parts for example piston ring, cylinder liner and engine valve can be coated with ceramic. In this study, it is observed that the figure of merit is increased in this study. Only wearing data is given in this research. The other results are also supporter of the results taken from the wearing experiments. As a result, due to the decrease in heat loss and coaling stabil...
Coating of non-oxide ceramics by interaction with metal powders
Materials Science and Engineering: A, 1992
Non-oxide ceramics, such as Si3N4, SiC, BN and B4C , interact at elevated temperatures with powders of metals having a high affinity for carbon and nitrogen with the formation of reaction product coatings on the ceramic surface. The diffusion of metal atoms along the ceramic surface plays an important role in the process of coating; starting temperatures for reactions with the formation of coatings correlate with surface self-diffusion rates of the corresponding metals. The coatings obtained on Si3N 4 and SiC have a layered structure and their growth is diffusion controlled. The composition of the inner layer of the coatings is in agreement with the presented thermodynamic calculations for the corresponding Si3N 4-and SiC-metal interfaces. The composition and morphology of the surface layer depend on the environment and can be modified by changing the treatment conditions. Based on the experimental observations and thermodynamic calculations, a model for the described powder immersion reaction assisted coating (PIRAC) is proposed.