This work focuses on the processing and deposit by suspension plasma spraying (SPS) of ZrO 2 -based ceramic materials for Thermal Barrier Coatings (TBC's) applications. The system of interest is ZrO 2 -16mol%Y 2 O 3 -16mol%Ta 2 O 5 (16YTZ). This ceramic has been reported to keep a non-transformable tetragonal phase (t'-phase), suitable to overcome the thermodynamic limits of the mostly used conventional 7-8wt.% yttria stabilized zirconia (YSZ). The research consists into evaluate the t'-phase stability and performance of the 16YTZ SPS coating. Synthesis of 16YTZ and, the evolution of the resulting microstructure in the dense ceramic and in the coating are a central part of the study. Sintering behavior in dense ceramics prepared from both precursor derived and milled powders is evaluated. Microstructural characterization by XRD, SEM and RAMAN spectroscopy of the as-deposited ceramic coating is presented and discussed.

By approaching the glass transition temperature it was possible to realize well quality metallic coatings on two different glasses using Cold Spray deposition, CS. A roughness is introduced on the glass surface and is proportional to the energy deposited. Using the thermal pressure memory effect of glass, Raman spectroscopy mapping allowed determining that the CS introduced a strong heterogeneity of the glass substrate characterized by zones with different cooling rate and residual stress. Using a simplified Eshelby's inclusion approach, it is demonstrated that the residual stress can be in first approximation explained by the introduction of local density fluctuation induced with high cooling rate of micrometric regions related with the impact of the deposited metallic particles.

In this study, hydroxyapatite, titania, and HA-TiO 2 composite layers are deposited by suspension plasma spraying on titanium substrates and assessed by means of SEM and XRD analysis, Raman spectroscopy, and acoustic emission testing. The coatings exhibited dense microstructures with low porosity and good interfacial bond strength. The main phase in the HA and composite coatings was found to be similar to the peak of the feedstock powder. In the composite and titania coatings, besides rutile and anatase, a significant percentage of thermally stable Ti 3 O 5 was observed, which is favorable for photocatalytic performance.

The thermal phase stability of plasma sprayed TBC is presented and discussed. TBC phase transformation after various isothermal heat treatment processes was studied via Xray diffraction (XRD) and Raman Spectroscopy methods. The YSZ-Gd-Yb and 20YSZ TBCs demonstrated superior thermal phase stability as compared with the high and standard purity 8YSZ TBCs, although higher purity also helps delay the tetragonal to monoclinic phase transformation. The phase transformation appears to be suppressed by cooling at higher rates. This data presents a qualitative phase stability comparison between the various coatings. However, cooling rate has to be taken into consideration in determining the extent of phase instability during the coating design of aero turbine applications.

Plasma-sprayed ceramic coatings are deposited such that flattened splats together with some nonmelted particles are present in the coatings. In this study, the nonmelted particles in plasma-sprayed alumina coatings were examined by scanning electron microscopy, confocal Raman analysis, and X-ray diffraction analysis with the aim of quantitative evaluation of the coating microstructure. Results showed that the nonmelted particles can be clearly identified from the cross-sectional microstructure due to the morphology that results from the high hardness of the nonmelted particles. The obvious gap at the interface between nonmelted particles and the surrounding splats suggests weak interface bonding. Raman analysis revealed that there was little α-Al 2 O 3 phase in the flattened splats region, which confirms that this phase in the coating appears only from nonmelted particles. Attention should be paid to the weak bonding of the nonmelted particles relative to the flattened splats during the preparation of samples for quantitative characterization of coating microstructure.

Detonation spraying provides the opportunity to produce superabrasive diamond grinding tools under atmospheric conditions. In this study, several methods are used to assess the effects of the spraying process on diamond particles, including SEM analysis, energy dispersive X-ray spectroscopy, differential thermal analysis, thermogravimetric analysis, X-ray diffraction, Raman spectroscopy, and friability and fracture force testing. It was found that under optimized conditions, the thermal and mechanical impact of the detonation can remain low enough to ensure the reliability of the diamonds with no adverse effects.

High velocity oxy-fuel (HVOF) combustion spraying has previously been shown to be a viable method for depositing polymer and polymer/ceramic composite coatings. The addition of hard particulate reinforcing phases to soft polymeric matrices should improve their durability and wear performance. Nano-sized diamond is an ideal reinforcing phase, owing to its high hardness and desirable thermal properties. Composite coatings comprising a Nylon-11 matrix reinforced with nanodiamonds have been successfully produced by HVOF. An important challenge is preserving the structure of the nanoparticles after thermal spray deposition and achieving a uniform dispersion of them within the polymeric matrix. Raman spectroscopy and X-ray diffraction confirmed the presence and retention of nanodiamonds after HVOF deposition. Understanding of the role of variables including the % loading of reinforcing phase in the matrix and powder preparation route are necessary. The coatings exhibited improved sliding wear resistance in macromechanical tests. Nanoindentation studies demonstrated an improvement in deformation behavior and recovery of the HVOF nanodiamond Nylon-11/nanodiamond composites subjected to deformation.

The monoclinic and tetragonal phase compositions and distribution in air plasma sprayed (APS) yttria-partially stabilized zirconia (YPSZ) thermal barrier coatings were studied. The coatings were produced from powders with varying phase concentrations, chemical purity and powder production processes. Both the powder and coatings were characterized using X-ray diffraction (XRD) and Raman spectroscopy. The use of environmental scanning electron microscopy (ESEM) and X-ray energy dispersive analysis (EDS) added morphological and elemental information to the study. XRD and Raman spectroscopy were shown to be powerful combined tools and shows an overall decrease in the monoclinic phase within the coatings produced from the different powders. The distribution of both the monoclinic and the tetragonal phases could be highlighted both in the coatings and the individual powder particles. This indicated changes in monoclinic concentration in the less dense areas of some of the coatings and a varying distribution across particles in some of the powders. Raman mapping over small areas also showed how phase surface distribution, on the coatings surfaces, could be assessed.

Two kind of the feedstock materials were used to produce the atmospheric plasma sprayed coatings. One is the spraying dried powder and the other is the nano-particle dispersed sol precursor. Coating properties were evaluated by the XRD, Raman spectroscopy, SEM and TEM. Also, the photodecomposition efficiency was examined by measuring the decomposition rate of the MB(methylene blue) in a water-cooled solution during the UV radiation and compared to the decomposition efficiency of the optimum coating produced using spraying dried particle. Both the anatase phase fraction and the photodecomposition rate of the coating using the sol precursor were higher than that of the optimum coating using the spraying dried powder.

Yttria Partially Stabilized Zirconia (YPSZ) coatings are used as Thermal Barrier Coatings (TBCs) because of their capability to improve gas turbine performance by allowing higher turbine inlet temperature and reduced cooling air flow. Usually, YPSZ layers are applied by plasma spray on Ni-based superalloys pre-coated with a bond coat layer of MCrAlY, where M is Co, Ni, or both. In this work we used Raman spectroscopy to study the performance of TBCs during thermal cycling at two different temperature (1273K and 1373K). Raman scattering is capable of detecting monoclinic zirconia and to analyze residual stresses of the coatings with an higher sensitivity than traditional X-ray diffraction measurements. Raman spectra were analyzed by deconvolution methods in order to study the evolution of the relative intensities and position of different bands. We found that the position of the 635 cm-1 band shifts to higher values of wave number during thermal cycling and by comparing this data with those reported in literature, it is possible to retrieve the value of residual stresses in zirconia coating. We also observed a relation between the intensities of the bands at 602 cm-1 and 635 cm-1 band and the number of thermal cycles performed.

A diameter of 30 mm polycrystalline diamond film has been deposited by magnet-enhanced DC plasma jet CVD. The diamond film was characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and surface profilograph. Results reveal that under the same depositing parameters, magnetic field can increase purity of diamond film, improve thickness uniformity of diamond film, but no influence on crystal perfection and size of microcrystal of diamond film. A discussion on magnetic effect is presented.