Mechanical properties of hydroxyapatite–zirconia compacts sintered by two different sintering methods (original) (raw)
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Science and Technology of Advanced Materials, 2012
Continuously porous hydroxyapatite (HAp)/t-ZrO 2 composites containing concentric laminated frames and microchanneled bodies were fabricated by an extrusion process. To investigate the mechanical properties of HAp/t-ZrO 2 composites, the porous composites were sintered at different temperatures using a microwave furnace. The microstructure was designed to imitate that of natural bone, particularly small bone, with both cortical and spongy bone sections. Each microchannel was separated by alternating lamina of HAp, HAp-(t-ZrO 2 ) and t-ZrO 2 . HAp and ZrO 2 phases existed on the surface of the microchannel and the core zone to increase the biocompatibility and mechanical properties of the HAp-ZrO 2 artificial bone. The sintering behavior was evaluated and the optimum sintering temperature was found to be 1400 • C, which produced a stable scaffold. The material characteristics, such as the microstructure, crystal structure and compressive strength, were evaluated in detail for different sintering temperatures. A detailed in vitro study was carried out using MTT assay, western blot analysis, gene expression by polymerase chain reaction and laser confocal image analysis of cell proliferation. The results confirmed that HAp-ZrO 2 performs as an artificial bone, showing excellent cell growth, attachment and proliferation behavior using osteoblast-like MG63 cells.
Sintering of HA/Zirconia Composite for Biomedical and Dental Applications: A Review
Advanced Materials Research, 2013
Hydroxyapatite is a calcium phosphate product that being widely use in medical application due to its excellence biocompatibility. However its application has being limited due to the inferior mechanical properties, many researcher attempted to improve its mechanical properties. HA-ZrO2 composites have great potential because of their advantages from both constituent materials, such as the excellent biocompatibility of HA and the considerable mechanical strength and toughness of ZrO2. The synergy of the two materials provides a new possibility for developing a composite material with better properties than monolithic ZrO2 and HA. In this work, the stages of development, as well as the different sintering and processing methods of HA and ZrO2 such as conventional sintering, solid-state reaction, microwave sintering and hot isostatic pressing were discussed. It can be concluded that hot isostatic pressing processing yield the most satisfying result amount above method, however the use...
Zirconia–hydroxyapatite composite material with micro porous structure
Dental Materials, 2011
Objectives. Titanium plates and apatite blocks are commonly used for restoring large osseous defects in dental and orthopedic surgery. However, several cases of allergies against titanium have been recently reported. Also, sintered apatite block does not possess sufficient mechanical strength. In this study, we attempted to fabricate a composite material that has mechanical properties similar to biocortical bone and high bioaffinity by compounding hydroxyapatite (HAp) with the base material zirconia (ZrO 2), which possesses high mechanical properties and low toxicity toward living organisms. Methods. After mixing the raw material powders at several different ZrO 2 /HAp mixing ratios, the material was compressed in a metal mold (8 mm in diameter) at 5 MPa. Subsequently, it was sintered for 5 h at 1500 • C to obtain the ZrO 2 /HAp composite. The mechanical property and biocompatibility of materials were investigated. Furthermore, osteoconductivity of materials was investigated by animal studies. Results. A composite material with a minute porous structure was successfully created using ZrO 2 /HAp powders, having different particle sizes, as the starting material. The material also showed high protein adsorption and a favorable cellular affinity. When the mixing ratio was ZrO 2 /HAp = 70/30, the strength was equal to cortical bone. Furthermore, in vivo experiments confirmed its high osteoconductivity. Significance. The composite material had strength similar to biocortical bones with high cell and tissue affinities by compounding ZrO 2 and HAp. The ZrO 2 /HAp composite material having micro porous structure would be a promising bone restorative material.
Journal of Biomaterials Applications, 2011
The biological response of strontium (Sr) doped hydroxyapatite (HA) and hydroxyapatite–zirconia (HA–ZrO2) composites produced by employing sol–gel technology, minimal ZrO2 loadings, and novel microwave-sintering regimes thereby retarding decomposition, is reported. In vitro evaluations indicate that all materials induce a favorable response from rat osteosarcoma cells. In vivo evaluations show osteoconductivity and biocompatibility for both the Sr–HA and HA–ZrO2. The materials did not cause any inflammatory response in bone. The Sr–HA displays better biocompatibility which may be due to the incorporation of Sr and the formation of a surface apatite layer.
Porous Hydroxyapatite–Zirconia Composites Prepared by Powder Deposition and Pressureless Sintering
Advanced Materials Research, 2012
In the present study, hydroxyapatite was synthesized from local gypsum by microwavehydrothermal method. Different percentage amounts of zirconia (0, 20, 30 and 40 wt.%) and polymethyl methacrylate (40, 50 and 60 wt.%) mixed with hydroxyapatite (HA) for six hours. These powder mixture were deposited using deposition machine to produce specimens. These specimens were sintered at a temperature of 140 o C with holding time for 1 hour into the green parts. These green parts were sintered at temperature of 1450 o C with holding time for 2 hours. This process produces porous hydroxyapatite-zirconia composites with porosity between 62.76-73.92 percent. These composites were examined by XRD, XRF, SEM-EDX, BET analysis and compressive strength testing. Compressive strength of porous hidroxyapatite-zirconia composite decreased from 3.706 to 0.039 MPa when percentage amounts of zirconia increased up to 40 wt.%. This caused by several factors i.e. increased porosity, grain zirconia cracked, zirconia reacted with HA to produce CaZrO 3 , β-TCP and α-TCP, HA matrix cracks because of the phase change of tetragonal-zirconia into monoclinic-zirconia.
Ceramics International, 2014
Microwave sintering has emerged in recent years as a novel method for sintering a variety of materials that have shown significant advantages against conventional sintering procedures. This work involved an investigation of microwave hybrid fast firing of alumina-zirconia nanocomposites using commercial alumina powder and monoclinic nanometric zirconia. The suspensions were prepared separately in order to obtain 5, 10 and 15 vol.% of ZrO 2 in the alumina matrix. The samples were sintered in a 2 monomode microwave furnace at 2.45 GHz in air at different temperatures in the range 1200-1400 ºC with 10 min of dwelling time and 200 ºC/min of heating rate. The effect of sintering temperature in densification, mechanical properties and microstructure behaviour of the composites was investigated. Higher density, hardness and Young's modulus, excellent fracture toughness properties and homogeneous microstructure were achieved by microwave sintering in comparison to conventional heating. Microstructure analysis showed that the alumina grains had not grown significantly, indicating that the zirconia particles provided a hindering effect on the grain growth of alumina.
Effect of ZrO 2 content on the mechanical properties and microstructure of HAp/ZrO 2 nanocomposites
Ceramics International, 2018
This paper presents the effect of Zirconia (ZrO 2 = 0, 5, 10, 15, 20 and 25 wt. %) on the mechanical properties and micro structural studies of Hydroxyapatite (Ca 10 (PO 4) 6 (OH) 2) (HAp) nano composites. HAp and Zirconia nano composites of 20-40 nm were produced using High Energy Ball milling at 300 rpm for 1 h. X-ray diffraction studies showed that the crystallite and grain size gradually decreased with the increase in ZrO 2 content till 20 wt.%, after which there was a sudden raise in both parameters. A dominant ZrO 2 phase was observed in X-ray diffraction studies of sintered samples. Mechanical properties were found to significantly improve on adding 20wt. % of ZrO 2 at 1200 °C. However, the addition of 25 wt. % of ZrO 2 powder decreased the mechanical properties of HAp. The reduction could be due to the increase in grain size and dominant smaller particles of ZrO 2. The improved mechanical properties were correlated with the observed micro structural features.
Hydroxiapatite - zirconia composites for biomedical applications
Hydroxiapatite with stabilised or unstabilised zirconia ceramics were synthesised by solid state-reaction of oxide powders. Their sinterability as well as phase analysis were studied by X-ray diffraction analysis. The microstructure of sintered materials was investigated by scanning electron microscopy (SEM) and EDAX. The ceramic and some mechanical properties were investigated using a comparative approach. An interaction mechanism between zirconia and its polymorphs with calcium phosphates existing or formed after sintering is discussed.
Applying microwave technology to sintering dental zirconia
The Journal of Prosthetic Dentistry, 2012
Based on the study results, a microwave furnace, which creates a more uniform heat distribution and uses less energy, may be used to sinter dental zirconia. Statement of problem. When sintering zirconia, conventional processing may not provide uniform heating and consumes more energy than an alternative method using microwave energy. Purpose. The purpose of this study was to compare the surface quality, mechanical and physical properties, and dimensional stability obtained by sintering yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) in a conventional furnace versus a microwave furnace. Material and methods. Twenty bars of Y-TZP were prepared from Zircad blocks. Ten specimens were used for sintering in a conventional furnace. The remaining 10 specimens were sintered in a microwave furnace. The sintering temperature used for both techniques was 1500˚C. The flexural strength of all specimens was measured with the 3-point bend test with a universal testing machine with a cross head speed of 1.0 mm/min. Density was measured by applying the Archimedes method, and specimen length, width, and thickness were measured with a digital micrometer. The phase composition and average grain size of these ceramics were examined by using X-ray diffraction, and microstructure characteristics were studied with scanning electron microscopy. Data obtained were analyzed by using independent t tests (α=.05). Results. No significant difference between conventional and microwave sintering for either flexural strength, t18=0.49 (P=.63) or density, t18=0.07 (P=.95) was found. Specimens in both groups exhibited a uniform firing shrinkage of approximately 24.6% in all dimensions. The surface of selected specimens examined with a scanning electron microscope showed no visible difference in grain shape or porosity size between the 2 sintering methods. Conclusions. Under the conditions of this study, it appears that either microwave or conventional zirconia sintering may be used for processing zirconia for dental use. However, microwave energy provides uniformity of heating, allowing the use of higher heating rates, which can increase productivity and save energy.