scholarly journals Structural Changes of Hydroxylapatite during Plasma Spraying: Raman and NMR Spectroscopy Results

Coatings ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 987
Author(s):  
Robert B. Heimann
Keyword(s):  
Plasma Spraying ◽  
Structural Changes ◽  
Plasma Jet ◽  
Biological Properties ◽  
Atmospheric Plasma Spraying ◽  
Atmospheric Plasma ◽  
Decomposition Reactions ◽  
Laser Raman ◽  
Hot Plasma ◽  
Crystallographic Symmetry

Functional osseoconductive coatings based on hydroxylapatite (HAp) and applied preferentially by atmospheric plasma spraying to medical implant surfaces are a mainstay of modern implantology. During contact with the hot plasma jet, HAp particles melt incongruently and undergo complex dehydration and decomposition reactions that alter their phase composition and crystallographic symmetry, and thus, the physical and biological properties of the coatings. Surface analytical methods such as laser-Raman and nuclear magnetic resonance (NMR) spectroscopies are useful tools to assess the structural changes of HAp imposed by heat treatment during their flight along the hot plasma jet. In this contribution, the controversial information is highlighted on the existence or non-existence of oxyapatite, i.e., fully dehydrated HAp as a thermodynamically stable compound.

Integrated Simulation of the Atmospheric Plasma Spraying Process

1998 ◽  
Author(s):  
S. Kundas ◽  
A. Kuzmenkov ◽  
E. Lugscheider ◽  
U. Eritt
Keyword(s):  
Plasma Spraying ◽  
Experimental Verification ◽  
Computer Experiments ◽  
Plasma Jet ◽  
Atmospheric Plasma Spraying ◽  
Atmospheric Plasma ◽  
Temperature Dependent ◽  
Integrated Simulation ◽  
Plasma Spraying Process ◽  
Spraying Process

Abstract The main purpose of this work is the development of mathematical and computer models for the integrated simulation of all stages of the atmospheric plasma spraying process (APS) with temperature dependent thermophysical and mechanical properties of the used materials and gases and experimental verification of the simulated results. The following mathematical models of APS were created: particle heating and movement in the plasma jet; coating structure formation; heat transfer and residual stresses in the coating-substrate system. The computer realization of these models enables us to model all stages of APS (integrated or separately). Databases of coating, substrate and plasma-gas substances include the temperature dependent properties. The model of APS is divided in 3 parts, which are connected by continuous data interface. Two dimensional approximation of plasma-gas velocity and temperature in the free plasma jet was used for computation of particle velocity, trajectory and temperature. This information was created with a special Graphic program module and included in database. Computer experiments for plasma spraying of Ah03 and ZrO2+8%Y2O3 in Ar/H2 plasma were carried out. The experimental verification of developed models with High-Velocity-Pyrometry (HVP) and Laser-Doppler- Anemometry (LDA) have shown the satisfactory precision of simulated results.

A model of the interface between plasma jet simulation and the simulation of coating formation during atmospheric plasma spraying (APS)

2004 ◽  
Vol 120 ◽  
pp. 373-380
Author(s):  
E. Lugscheider ◽  
R. Nickel ◽  
N. Papenfuß-Janzen
Keyword(s):  
Heat Transfer ◽  
Plasma Spraying ◽  
Substrate Surface ◽  
Fem Analysis ◽  
Software Tool ◽  
Plasma Jet ◽  
Atmospheric Plasma Spraying ◽  
Atmospheric Plasma ◽  
Barrier Coating ◽  
Coating Formation

The atmospheric plasma spraying (APS) process can be divided into sub-processes, which are simulated by different numerical methods. The balance equations of momentum, mass and energy of the plasma jet are solved numerically by applying the finite volume method (FVM) using a CFD (Computational Fluid Dynamics) software tool. On the other hand the solution of the thermo-mechanical problem of the coating formation on the substrate is estimated using the finite element method (FEM). The movement of the plasma jet above the surface of the substrate during the spraying process causes a time dependent boundary condition for the FEM-analysis. The heat transfer from the plasma jet to the substrate has to be taken into account. There is also a mass and heat transfer of heated particles to the substrate surface, which is responsible for the formation of the coating. Not only the plasma jet influences the boundary conditions of the coating formation, but the substrate is also a boundary for the plasma jet. This has to be considered during the plasma jet simulation, as well. This article describes the physical and mathematical background of the plasma jet/substrate heat transfer interface model, the implementation in the overall simulation process and its use in the simulation of the formation of a thermal barrier coating (TBC) made of partially yttria stabilized zirconia on a turbine blade during atmospheric plasma spraying.

Effect of binary rare earth oxide on the properties of plasma sprayed Al2O3/TiO2 coatings

2017 ◽  
Vol 69 (5) ◽  
pp. 808-814
Author(s):  
Qingjun Ding ◽  
Bo Tian ◽  
Gai Zhao ◽  
Feng Wang ◽  
Huafeng Li ◽  
...  
Keyword(s):  
Rare Earth ◽  
Plasma Spraying ◽  
Adhesion Strength ◽  
Rare Earth Oxide ◽  
Atmospheric Plasma Spraying ◽  
Atmospheric Plasma ◽  
Micro Hardness ◽  
Content Type ◽  
Melting Degree ◽  
Binary Rare Earth

Purpose This study systematically investigated the effect of the binary rare earth oxide of La2O3 and Sm2O3 on the properties of the Al2O3/TiO2 (AT) coating, including phase transform, wear behavior, etc. Design/methodology/approach AT coatings mixed with different components of binary rare earth oxides of La2O3 and Sm2O3 are prepared by atmospheric plasma spraying. The adhesion strength, micro-hardness, phase transition and tribological behavior of coatings are systematically investigated. Findings The X-ray diffraction (XRD) analysis shows that phase transformation is obvious after spraying, and a-Al2O3 is almost translated into γ-Al2O3 when La2O3 and Sm2O3 are doped together. Meanwhile, solid solution generated between rare earth oxide and Al2O3/TiO2 coatings results in disappearance of TiO2 and rare earth oxide phase. The photos under the scanning electron microscope (SEM) indicate that binary rare earth oxide could increase the melting degree of powder and decrease porosity of coatings.The increasing of Sm2O3 rarely affect micro-hardness and adhesion strength, and the coating with 4 per cent Sm2O3 and 1 per cent La2O3 exhibits the best wear resistance and lowest friction coefficient among all the samples. Originality/value AT coatings mixed with different components of binary rare earth oxide of La2O3 and Sm2O3 are prepared by atmospheric plasma spraying. Binary rare earth oxide could increase the melting degree of powder and decrease porosity of AT coatings.

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