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1.
Phase transformations, particle breakdown, and partial decomposition occur in hydroxyapatite (HA) powder feedstock during
plasma spraying. The biological responses of the coatings consequently change from the bioactive nature of the starting material
to a less biocompatible one. This paper investigates the influence of powder characteristics on the phase composition and
microstructure of plasma sprayed HA coatings. The raw HA was prepared by chemically reacting calcium hydroxide with orthophosphoric
acid. Subsequently, HA was either calcined and crushed, flame spheroidized, or spray dried. These three types of HA powders
were plasma sprayed on steel substrates to form coatings. A previous study showed that the calcined HA powder suffered from
particle breakdown in the plasma. The plasma sprayed HA powders contained other calcium phosphate phases (amorphous and crystalline)
apart from hydroxyapatite. The flow properties and stability of spheroidized HA were better than calcined HA and spraydried
HA. Standard metallographic preparation of the cross sections of the coatings revealed different microstructural features
among the coatings. The HA coatings prepared from calcined HA were highly porous and lacking in intimate lamellar contact.
The spheroidized HA powders produced the coating with the lowest porosity. Characterization of the powders and coatings was
carried out using x-ray diffraction (XRD), scanning electron microscopy (SEM), and optical microscopy. 相似文献
2.
The major problems with plasma sprayed hydroxyapatite (HA) coatings for hard tissue replacement are severe HA decomposition
and insufficient mechanical properties of the coatings. Loss of crystalline HA after the high-temperature spraying is due
mainly to the loss of OH− in terms of water. The current study used steam to treat HA droplets and coatings during both in-flight and flattening stages
during plasma spraying. The microstructure of the HA coatings and splats was characterized using scanning electron microscope,
Raman spectroscopy, Fourier transform IR spectroscopy, and x-ray diffraction. Results showed that a significant increase in
crystallinity of the HA coating was achieved through the steam treatment (e.g., from 58 to 79%). In addition, the effects
were dependent on particle sizes of the HA feedstock, more increase in crystallinity of the coatings made from smaller powders
was revealed. The Raman spectroscopy analyses on the individual splats and coatings indicate that the mechanism involves entrapping
of water molecules by the individual HA droplets upon their impingement. It further suggests that the HA decomposition has
already taken place before the impingement of the droplets on precoating or substrate. The improvement in crystallinity and
phases, for example, from tricalcium phosphate and amorphous calcium phosphate to HA, was achieved by reversing the HA decomposition
through providing extra OH−. Furthermore, the steam treatment during the spraying also accounts for remarkably increased adhesion strength from 9.09
to 23.13 MPa. The in vitro testing through immersing the HA coatings in simulated body fluid gives further evidence that the
economic and simple steam treatment is promising in improving HA coating structure.
This article was originally published inBuilding on 100 Years of Success, Proceedings of the 2006 International Thermal Spray Conference (Seattle, WA), May 15–18, 2006, B.R. Marple, M.M. Hyland, Y.-Ch. Lau, R.S. Lima, and J. Voyer, Ed., ASM International, Materials
Park, OH, 2006. 相似文献
3.
Low-pressure plasma-sprayed (LPPS) bioceramic coatings with improved adhesion strength and resorption resistance 总被引:1,自引:0,他引:1
Prespray annealing of commercially available hydroxyapatite (HAp) plasma-spray powder at 1300 °C for 1 h in air leads to substantial
densification without noticeable thermal decomposition. The resulting HAp coatings, low-pressure plasma sprayed onto Ti-6A1-4V
substrates, show a dense microstructure, im-proved adhesion strength, and higher résorption resistance when treated for 7
days in simulated body fluid (Hank’s balanced salt solution). 相似文献
4.
5.
Roman Jaworski Lech Pawlowski Francine Roudet Stefan Kozerski Agnès Le Maguer 《Journal of Thermal Spray Technology》2008,17(1):73-81
The study aimed at optimizing the suspension plasma spraying of TiO2 coatings obtained using different suspensions of fine rutile particles in water solution onto aluminum substrates. The experiments
of spraying were designed using a 23 full factorial plan. The plan enabled to find the effects of three principal parameters, i.e. electric power input to plasma,
spray distance, and suspension feed rate onto microstructure of coatings, content of anatase phase and size of anatase crystals
in the coatings. The microstructure of deposits was observed with scanning electron microscope (SEM) and optical microscope
and their composition was characterized using energy dispersive spectrometry (EDS). The observations were made on the coatings
surface and their cross-sections. The latter made it possible to determine the coatings thicknesses to be in the range from
8 to 33 μm.
相似文献
Lech PawlowskiEmail: |
6.
以CaHPO4为初始粉料,采用等离子喷涂一水热合成复合技术在Ti-6Al-4V基体上制备了羟基磷灰石(HA)涂层。用SEM,EDX和XRD分析涂层的形貌和组成,用电子拉伸机测定涂层的结合强度。并与等离子喷涂HA涂层做对比,研究了涂层的微观结构和结合强度及其在生理盐水中浸泡后的变化。结果表明:喷涂CaHPO4涂层由β-Ca2P2O7和α-Ca3(PO4)2组成,经水热合成,转化为高纯度和高结晶度的HA涂层;在生理盐水中浸泡1周~4周后,该HA涂层的溶解性和结合强度退化程度均低于等离子喷涂HA涂层,呈现较高的组织和力学稳定性。 相似文献
7.
P. Pei S. G. Malghan S. J. Dapkunas P. H. Zajchowski 《Journal of Thermal Spray Technology》1996,5(3):343-351
The correlation between the performance of plasma spray coatings and feedstock powder properties is not fully understood.
To demonstrate this correlation, eight spray-dried zirconia powders containing a mass fraction of 20% Y2O3 (yttria) were characterized with respect to their physical, bulk chemical, and surface chemical properties. The same powders
were plasma spray deposited as coatings, and their relative performance was evaluated using a thermal rupture test developed
by Pratt and Whitney. The specific powder properties studied were chemical composition, binder content, particle size distribution,
powder morphology, interface chemistry, thermogravimetry, phase composition, and specific surface area. Among the characterization
data, the binder-related properties of the powder correlated most strongly with the thermal rupture test data. Specifically,
higher binder contents were associated with poor thermal rupture test performance. 相似文献
8.
1 INTRODUCTIONAtpresent ,thehydroxyapatite (HA )andtheHA basedcompositecannotbeusedforheavyload bearingapplicationsashardtissuereplacementim plantsbecauseoftheirpoormechanicalproperties[1] .Ontheotherhand ,theHAcoatingsusedtoimprovethesurfacebioactivityofTia… 相似文献
9.
X-ray diffraction characterization of crystallinity and phase composition in plasma-sprayed hydroxyapatite coatings 总被引:2,自引:0,他引:2
Paul S. Prevéy 《Journal of Thermal Spray Technology》2000,9(3):369-376
Orthopedic and dental implants consisting of a metallic substrate plasma spray coated with hydroxyapatite (HA) are currently
used in reconstructive surgery. The crystalline phases present in the calcium phosphate ceramic and the degree of crystallinity
must be controlled for medical applications. X-ray diffraction (XRD) is routinely employed to characterize the phase composition
and percent crystallinity in both biological and sintered HA. However, application of the same XRD methods to plasma-sprayed
coatings is complicated by the potential presence of several crystalline contaminant phases and an amorphous component.
To overcome the complexities of characterizing plasma-sprayed HA coatings, an external standard method of XRD quantitative
analysis has been developed that can be applied nondestructively. Data collection and reduction strategies allowing separation
of intensity diffracted from commonly occurring phases and the amorphous fraction are presented. The method is applied to
coating samples, and detection limits and sources of error are discussed. Repeability and accuracy are demonstrated with powder
mixtures of known composition. 相似文献
10.
采用微束等离子喷涂方法,分别选用工业纯氩气和含50%氦气的氦氩混合气体为工作气体,在Ti-6Al-4V基体上制备羟基磷灰石涂层.通过SEM和XRD对涂层形貌、相组成和结晶度进行研究.结果表明,两种工作气体均可以制备杂质相含量少且不产生TTCP(磷酸四钙)和CaO等杂质相的涂层,结晶度高于70%,对植入体在体内的稳定性有利.采用氦氩混合气体为工作气体的微束等离子弧热焓值高于氩气工作气体,前者涂层中的结晶相主要以再结晶的为主,后者结晶相以大量未熔HA内核为主. 相似文献
11.
Calcium phosphate materials such as hydroxyapatite (HA) have biocompatible properties that can promote osteogenesis or new
bone formation. Thermal spraying is an economical and effective process for coating the hydroxyapatite onto metal. It has
been reported that plasma spraying changes the degree of crystallinity as well as the phase composition of the HA. This article
reports the preparation and characterization of HA powders and coatings by two thermal spray processes (plasma and combustion
flame) and suggests that the state of the starting powder adversely affects the coating characteristics. The raw HA powders
are synthesized through a chemical reaction involving calcium hydroxide and orthophosphoric acid. Phase analysis using an
X- ray diffractometer revealed that the synthesized powder consists of predominantly the HA phase. Calcined and crushed HA
powders of various size ranges were fed into the plasma jet to produce HA coatings on metallic substrates. In addition, some
HA powders were sprayed into distilled water by plasma spraying and combustion flame spraying to study powder melting characteristics.
Other samples were plasma sprayed onto a solid rotating target to study atomization and impact behavior. The morphology of
the rapidly solidified powders and thermal sprayed coatings were examined by scanning electron microscopy (SEM). An X- ray
sedimentation particle size analyzer, laser diffraction particle size analyzer, and image analyzer performed the particle
size analysis. Preliminary results indicate that particle cohesion, size range, and thermal treatment in the plasma affect
the phase and structure of the as- sprayed coating, and some post- spray treatment may be necessary to produce a dense and
adherent coating with the desired biocompatible properties. 相似文献
12.
Zircon, ZrSiO4, is a natural mineral used for various applications as a refractory bulk material. It is an excellent feedstock for the plasma
spraying of protective coatings and free-standing bodies. Zircon decomposes on spraying into t-ZrO2 and glassy SiO2, which can be preserved in deposits by fast cooling. This combination of zirconia and silica exhibits properties such as
a high thermal shock resistance, good corrosion resistance, low wettability, etc. The final properties of deposits can be
further enhanced by the addition of other materials such as alumina. For instance, alumina-zircon plasma-sprayed free-standing
pipes have a low gas permeability. Several technical applications are discussed. 相似文献
13.
羟基磷灰石生物活性梯度涂层材料的界面特点 总被引:6,自引:0,他引:6
用透射电子显微镜对钛合金基体等离子喷涂羟基磷灰石 (HA)生物活性梯度涂层的界面进行了观察与分析。结果表明 :经热处理后生物活性梯度涂层的结晶程度明显提高 ,涂层中存在HA晶体、β Ca3(PO4 ) 2 晶体以及中间相CaTiO3 晶体。涂层和基体的界面结合为冶金化学结合 ,HA涂层和基体Ti间存在过渡相ZrO2 ,过渡相ZrO2 的存在有利于提高涂层和基体之间的界面结合力。 相似文献
14.
Plasma spraying of functionally graded yttria stabilized zirconia/NiCoCrAlY coating system using composite powders 总被引:1,自引:0,他引:1
Pre-alloyed and plasma spheroidized composite powders were used as the feedstock in the plasma spraying of functionally graded
yttria stabilized zirconia (YSZ)/NiCoCrAlY coatings. The ball milling parameters of the composite powders and the plasma spraying
parameters for preparing functionally graded materials (FMGs) coatings were optimized to obtain the best performance for the
thermal barrier coatings (TBCs). Microstructure, physical, mechanical, and thermal properties of YSZ/NiCoCrAlY FGMs coatings
were investigated and compared with those of traditional duplex coatings. Results showed that the advantages of using pre-alloyed
composite powders in plasma spraying were to ensure chemical homogeneity and promote uniform density along the graded layers.
Microstructure observation showed the gradient distribution of YSZ and NiCoCrAlY phases in the coating, and no clear interface
was found between two adjacent different layers. Oxidation occurred during plasma spray and the resultant aluminum oxide combines
with YSZ in a wide range of proportions. The bond strength of functionally graded coatings was about twice as high as that
of the duplex coatings because of the significant reduction of the residual stresses in the coatings. The thermal cycling
resistance of functionally graded coating was much better than that of duplex coating. 相似文献
15.
Victor K. ChampagneJr. Dennis Helfritch Phillip Leyman Scott Grendahl Brad Klotz 《Journal of Thermal Spray Technology》2005,14(3):330-334
The objective of this article is to present microstructural evidence of a bonding mechanism between copper, which has been
deposited by the cold spray process, and an aluminum substrate. Deposition conditions are varied to determine their effects
on the nature of the bond. Mechanical measurements, such as adhesion strength and hardness, as well as visual methods are
used to characterize the process. A ballistic model is proposed to explain the process. 相似文献
16.
To testify to the advantage of large ceramic powder spraying, numerical simulations and experimental studies on the behavior
of large yttria-stabilized zirconia (YSZ) powder in a high-power hybrid plasma spraying process have been carried out. Numeric
predictions and experimental results showed that, with the high radio frequency (RF) input power of 100 kW, the most refractory
YSZ powder with particle sizes as large as 88 μm could be fully melted and well-flattened splats could be formed. A large
degree of flattening (ξ) of 4.7 has been achieved. The improved adhesive strength between the large splat and the substrate
was confirmed based on the measurement of the crack density inside of the splats. A thick YSZ coating >300 μm was successfully
deposited on a large CoNiCrAlY-coated Inconel substrate (50×50×4 mm in size). The ultradense microstructure without clear
boundaries between the splats and the clean and crack-free interface between the top-coat and the bond-coat also indicate
the good adhesion. These results showed that highpower hybrid plasma spraying of large ceramic powder is a very promising
process for deposition of highquality coatings, especially in the application of thermal barrier coatings (TBCs). 相似文献
17.
晶化处理对HA/(HA+TiO2)涂层组织结构的影响 总被引:2,自引:0,他引:2
用X射线衍射仪(XRD)、电子探针(EPMA)等检测手段,以晶化处理对大气等离子喷涂法在纯钛表面制备的HA/(HA+TiO2)复合涂层为研究对象,探讨了晶化处理对HA/(HA+TiO2)涂层组织结构和成分分布的影响。结果表明:晶化处理后HA/(HA+TiO2)涂层结晶度明显提高;(HA+TiO2)过渡层中交替分布的HA和TiO2结合致密;涂层表面裂纹比对应纯HA涂层细小,涂层内部结合致密,证实TiO2的加入具有缓和应力的作用。 相似文献
18.
Examination of a grit-blasting process for thermal spraying using statistical methods 总被引:1,自引:0,他引:1
An experimental study was conducted to develop an understanding of how the grit blasting process, prior to plasma spray coating,
affects various properties of the substrate and coatings. A statistical design of experiment approach was used and the results
were analyzed using both the linear regression method and average response of factors calculations. The following process
variables were studied: grit size (20, 36, 54), blasting pressure (20, 35, 50 psi), blasting duration (4, 6, 8 passes), blasting
distance (4, 6 in.), and blasting angle (45°, 90°). Properties such as bond strength, grit contamination, surface roughness,
and substrate distortion were evaluated and correlated to the process variables. Based on multiple linear regression results,
it was shown that the bond strength can be improved by increasing all of the parameters within the range studied here. No
relationship between the surface roughness and bond strength was observed. Grit contamination is mostly influenced by grit
size, blasting pressure, and number of blasting passes. The average response method provided indications to the direction
of modifying the required properties as a function of process variables. While the average response method agreed mostly with
the linear regression predication, some differences are further discussed in the study. 相似文献
19.
等离子喷涂SrAl_2O_4涂层的发光性能 总被引:1,自引:0,他引:1
把发光材料稀土铕、镝掺入铝酸锶为喷涂材料,用等离子喷涂法, 将材料喷涂在钢板上.利用X射线衍射、扫描电子显微镜等分析手段对铝酸锶涂层的微观结构进行研究.通过发光光谱对铕、镝掺杂的铝酸锶涂层的发光性能进行表征,并对涂层的发光机制做初步探讨. 相似文献
20.
Tribological properties of TiC-Fe coatings obtained by plasma spraying reactive powders 总被引:1,自引:0,他引:1
Titanium carbide-based coatings have been considered for use in sliding wear resistance applications. Carbides embedded in
a metal matrix would improve wear properties, providing a noncontinuous ceramic surface. TiC-Fe coatings obtained by plasma
spraying of spray-dried TiC-Fe composite powders containing large and angular TiC particles are not expected to be as resistant
as those containing TiC particles formed upon spraying. Coatings containing 60 vol% TiC dispersed in a steel matrix deposited
by plasma spraying reactive micropellets, sintered reactive micropellets, and spray-dried TiC-Fe composite powders are compared.
The sliding wear resistance of these coatings against steel was measured following the test procedure recommended by the Versailles
Advanced Materials and Standards (VAMAS) program, and the inherent surface porosity was evaluated by image analysis. Results
show that, after a 1-km sliding distance, TiC-Fe coatings obtained after spraying sintered reactive powders exhibit scar ring
three times less deep than sprayed coatings using spray-dried TiC-Fe composite powders. For all coatings considered, porosity
is detrimental to wear performance, because it generally lowers the coating strength and provides cavities that favor the
adhesion of metal. However, porosity can have a beneficial effect by entrapping debris, thus reducing friction. The good wear
behavior of TiC-Fe coatings manufactured by plasma spraying of sintered reactive powders is related to their low coefficient
of friction against steel. This is due to the microstructure of these coatings, which consists of 0.3 to 1 μm TiC rounded
particles embedded in a steel matrix.
Presented at the International Conference on Metallurgical Coatings and Thin Films, ICMCTF-92, Apr 6–10, 1992, San Diego. 相似文献