Ceria-stabilized Tetragonal Zirconia Research Articles

In-situ Laue micro-diffraction during compression tests on Ce-TZP single crystal micropillars

The widespread use of ceramics faces challenges due to their limited ductility, stemming from a lack of dislocation-induced plasticity. This study focuses on ceria-stabilized tetragonal zirconia a ceramic that benefits from its unique tetragonal-to-monoclinic phase transformation under stress, leading to transformation-induced plasticity (TRIP). Employing a micro-scale in-situ approach, the study aims to understand the mechanisms governing TRIP, particularly focusing on crystallographic features of the transformation. In-situ compression tests using synchrotron light source and Laue micro-diffraction were conducted on single crystal micropillars with various orientations. Results show that crystal orientation significantly affects the mechanical behaviour, with transformation being most likely when the resolved shear stress on {100} planes of the double-cell and along the <010> direction is highest. The martensite theory validates the correspondences obtained experimentally. This research provides insights into enhancing the mechanical properties of ceramics by leveraging the TRIP mechanisms.

Novel zirconia ceramics for dental implant materials

Ceria-stabilized tetragonal zirconia (Ce-TZP) has become an interesting alternative for the widely used yttria-stabilized zirconia (Y-TZP), whereas efforts are needed to control its microstructure in order to improve the strength of Ce-TZP ceramics. In this work, CaO was used to co-dope Ce-TZP ceramics. More specifically, 0.2–2.0 mol% Ca(NO3)3·4H2O precursor-based CaO was used to dope 10 mol% ceria-stabilized zirconia. Sintering was performed at 1300, 1350, or 1400 °C, which is lower than the temperatures commonly applied for zirconia ceramics. The microstructure and mechanical properties were investigated and correlated, revealing that 0.2 mol% CaO-doped CeO2-stabilised zirconia sintered at 1350 °C exhibited a fully dense fine-grained tetragonal ZrO2 microstructure with high toughness (10.4 MPa m1/2) and biaxial bending strength (1210 ± 43 MPa), and a narrow strength distribution (weibull modulus of 32.5). 1.5 and 2.0 mol% CaO-doping resulted in excellent biaxial bending strength but wider strength distribution and lower fracture resistance. The homogeneously distributed Ca(NO3)3·4H2O precursor prevented cubic zirconia-phase formation for CaO-doping up to 2.0 mol%. CaO-doped (≥ 0.2 mol%) 10Ce-TZP sintered at 1350 °C also highly resisted hydrothermal degradation. Furthermore, CaO-doping enabled to make Ce-TZP ceramics as translucent as different commercially available 3Y-TZP ceramics, opening possibilities to use Ce-TZP for dental restorations.

Tough and damage-tolerant monolithic zirconia ceramics with transformation-induced plasticity by grain-boundary segregation

Conventional ceria-stabilized tetragonal zirconia (Ce-TZP) with modest flexural strength has rarely been used as compared to yttria-stabilized zirconia, even though it has excellent hydrothermal stability and high toughness. Ce-TZP-based composites were recently developed, being tough and remarkably in combination with transformation-induced plasticity. However, distinct from the widely applied composite approach to improve the strength of Ce-TZP, in this study, a simpler and easily tailorable method was proposed by doping aliovalent oxides that are able to segregate at the zirconia-grain boundaries. 0.2–1 mol% divalent oxides with different cation size (Mg2+, Ca2+, Ba2+ and Sr2+) were selected to dope 10 mol% ceria-stabilized zirconia. CaO and MgO dopants were able to enter the tetragonal Ce-TZP lattice and showed a grain-boundary segregation effect, thereby tailoring the microstructure and transformation behavior. At a higher dopant concentration of 1 mol% MgO or CaO, the ceramics were strong but brittle with a typical elastic linear fracture behavior, whereas at a low dopant concentration of 0.1–0.2 mol% CaO or 0.2–0.4 mol% MgO doping, the ceramics deformed in-elastically to a certain degree without changing the Young’s modulus. At the transition between both fracture behaviors, the best combination of toughness (>10 MPa m1/2), biaxial strength (≥1200 MPa), reliability (Weibull modulus up to 30) and damage-tolerance was obtained. In-situ fracture testing revealed that transformation in such tough and deformable zirconia ceramics took place well before crack initiation with a large transformation zone of ∼100 µm ahead of the crack tip having been formed before failure.

Four-Point Bending Fatigue Behavior of Al2O3-ZrO2 Ceramic Biocomposites Using CeO2 as Dopant

This work investigated the effect of adding ceria-stabilized tetragonal zirconia (Ce-TZP) on the fatigue behavior of alumina-based ceramic composites. Alumina powder (control group) and mixtures containing 5 wt.% (group A) and 20 wt.% (group B) of a commercial m-ZrO2/Al2O3/CeO2 powder mixture were milled/homogenized, compacted, sintered at 1600°C-2h, and submitted to hydrothermal degradation. The samples were characterized by relative density, microstructure, crystalline phases, and static mechanical properties. The cyclic fatigue strength was determined using the modified staircase method in 4-point bending tests. The results indicate that adding the m-ZrO2/Al2O3/CeO2 powder mixture to the Al2O3-matrix increases the tetragonal-ZrO2 grains (Ce-TZP) content, presenting 2.9 wt.% of Ce-TZP and 11.9 wt.% of Ce-TZP for group A and group B, respectively. Furthermore, the addition of Ce-TZP improves densification (98.5% → 99.1%) with a slight reduction in hardness and modulus of elasticity and a significant KIC increase of the composite (KIC = 6.7 MPa.m1/2, group B) when compared to monolithic alumina (KIC=2.4 MPa.m1/2). The fatigue strength limit of the control group was around 100 MPa, while the composites (groups A and B) presented the values ​​of 279 MPa and 239 MPa, respectively. The results indicated that the incorporation of Ce-TZP significantly improves the fracture toughness of alumina-based ceramics. On the other hand, regarding the fatigue behavior, there was an increase in fatigue resistance in group A, resulting from the benefits of the t→m Ce-TZP grains transformation, which occurs during cyclic loading, producing a zone shielding that involves the tip of the crack, slowing its growth. The increase in the amount of Ce-TZP (group B) leads to an increase in the internal residual stresses between the phases due to anisotropy and difference in the thermal expansion coefficients, which accelerates the phase transformation and formation of microcracks at grain boundaries, reducing the fatigue strength of composites of group B.

Synthesis and Properties of Novel Calcia-Stabilized Zirconia (Ca-SZ) with Nano Calcium Oxide Derived from Cockle Shells and Commercial Source for Dental Application

Various oxides are used to stabilize zirconium oxide (ZrO2), but their superior hardness causes wear of the machining tool. Calcia-doped zirconia has been studied but reports on properties suitable for dental application are lacking. Therefore, this study aimed to fabricate and characterize zirconia stabilized by calcium oxide (CaO) derived from cockle shells and compare it with zirconia stabilized by commercial CaO, sintered at different temperatures. In this study, 176 pressed pellets of zirconia mixed with CaO either derived from cockle shells or commercial CaO were sintered between 1200 and 1500 °C to produce calcia-doped zirconia. Characterizations were made with SEM and XRD. Specimens were subjected to density, compressive and flexural strength, and Vickers hardness testing. Data were analyzed using the independent t-test and one-way ANOVA. XRD revealed the zirconia was stabilized into tetragonal and cubic phases (Ca-SZ). Ca-SZ cockle shells (CS) and Ca-SZ commercial (CC) have average particle sizes of 267 nm and 272 nm, respectively, with similar surface roughness. At 1400 °C sintering temperature, flexural strengths were 1165 and 1152 MPa, compressive strengths were 4914 and 4913 MPa, and Vickers hardness were 977 and 960 MPa for Ca-SZ(CS) and Ca-SZ(CC), respectively. Both Ca-SZ materials showed no significant difference in most properties (p &lt; 0.05) when sintered at different temperatures. The fully sintered Ca-SZ is less hard compared to the ceria-stabilized tetragonal zirconia polycrystal (Ce-TZP) available on the market. Thus, Ca-SZ may be used as an alternative to the current zirconia available on the market for dental application.

Cortical bone response toward nanosecond-pulsed laser-treated zirconia implant surfaces.

Two type of partially stabilized zirconia, namely yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) and ceria-stabilized tetragonal zirconia polycrystals including aluminum oxide nanocomposite (Ce-TZP), were irradiated by nanosecond-pulsed Nd:YAG laser and the regular structure with concave and convex of each 30 μm width and 30 μm depth were prepared on both surfaces. In the case of Ce-TZP, the surface was changed to be black after laser irradiation. EDX measurement revealed the reduction of more amounts of oxygen atoms on Ce-TZP compared to Y-TZP. Laser irradiated zirconia implants were inserted into the bone defects of rat femur during 4 weeks. As a control, large grid sandblasted and acid etching (blastedHF) implant was used. Laser treatment for Y-TZP provided greater degree of bone-implant contact ratio than blastedHF treated Y-TZP (p<0.05). In the case of Ce-TZP, however, laser treatment showed no clear effect on bone response.

Influence of additives on the purity of tetragonal phase and grain size of ceria-stabilized tetragonal zirconia polycrystals (Ce-TZP)

A comprehensive study on the influence of typical additives on zirconia (ZrO2) crystallization was presented. Zirconium nitrate pentahydrate (Zr(NO3)4·5H2O) and cerium(III) nitrate hexahydrate (Ce(NO3)3·6H2O) were employed as reagents, ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) or glycerol were adopted as additives, and ammonia water was adopted as pH regulator. The ZrO2 powders were prepared by hydrothermal method. The crystal phase purity, grain size and micro morphology of the ZrO2 powders were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS) to investigate the influence of EDTA-2Na, glycerol and Ce4+ content on the purity of tetragonal phase and the grain size of ceria-stabilized tetragonal zirconia polycrystals (Ce-TZP). It was found that EDTA-2Na could decrease the purity of tetragonal phase and alter the grain size of Ce-TZP nonlinearly, while glycerol could not decrease the purity of tetragonal phase and the grain size of Ce-TZP, and the grain size was not linear with the amount of glycerol; Doping Ce4+ could increase the purity of tetragonal phase of zirconia but could not decrease the grain size, and the grain size was not linear with the Ce4+ content; In addition, it was indicated that EDTA-2Na and glycerol could not improve the distribution uniformity of Ce4+. This study is expected to have provided a novel path to achieve tailored ZrO2 crystals with reduced low-temperature degradation.

Effect of thickness of zirconia framework on fracture strength and fracture mode of ceria-stabilized tetragonal zirconia polycrystals/alumina ceramic restoration on resin tooth abutment

Effect of thickness of zirconia framework on fracture strength and fracture mode of ceria-stabilized tetragonal zirconia polycrystals/alumina ceramic restoration on resin tooth abutment

Evaluation of five primers and two opaque resins for bonding ceria-stabilized zirconia/alumina nanocomposite

The purpose of this study was to evaluate the effect of five primers [Super-Bond C&B Monomer (SB), Clearfil Ceramic Primer, Alloy Primer, M.L. Primer, and AZ Primer] and two undercoating opaque resins [Super-Bond C&B (S-opaque) and Ceramage Pre-opaque (C-opaque)] on the bonding of a resin composite veneering material to a ceria-stabilized tetragonal zirconia polycrystals/alumina nanocomposite (Ce-TZP/Al2O3). Disk-shaped specimens of Ce-TZP/Al2O3 were sandblasted with alumina and primed. The undercoating opaque resins and resin composites were subsequently applied to the specimen, and then light cured. After 5000 thermocycles at 4°C and 60°C, shear bond strengths were determined. Data were analyzed using analysis of variance, Tukey–Kramer honest significant difference test, and Student t test (n = 10, α = 0.05). With the exception of SB/S-opaque, all S-opaque groups exhibited significantly higher bond strengths than C-opaque groups. The use of S-opaque resin is recommended when veneering frameworks made of Ce-TZP/Al2O3.

Effect of Coloring on Mechanical Properties of Dental Zirconia

Pre-sintered blocks of three kinds of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) and one ceria-stabilized tetragonal zirconia polycrystal (Ce-TZP)/alumina nanocomposite were stained with six kinds of coloring liquid (three ivory, two violet, and one pink). The crystal phases of the baking powder of the coloring liquids fired at 1100°C for 30 min were characterized by X-ray diffractometry (XRD) and their constituent elements were detected by wavelength dispersive X-ray spectroscopy (WDS). The three ivory liquids contained mainly Fe ions, the two violet liquids mainly contained Co ions, and the pink liquid contained Er and Nd ions. After the final sintering, the color differences (ΔE) were determined with a chroma meter. Three-point flexural strengths were determined at a span length of 16 mm according to ISO 6872. Fracture toughness was determined by an indentation method in terms of Palmqvist cracks. The color difference of the nanocomposite was smaller than those of three Y-TZPs due to high light scattering. The three ivory liquids for the nanocomposite led to small ΔE values. The sintered zirconia stained with the pink liquid containing Er and Nd ions showed significant decreases in flexural strength and fracture toughness. An XRD study revealed that most of the crystal phase of the zirconia stained with Er and Nd was cubic. In contrast, the three ivory and two violet liquids led to no significant change in the flexural strength and fracture toughness of the zirconia.

HRTEM observation of bonding interface between Ce-TZP/Al2O3 nanocomposite and porcelain.

The surface of a ceria-stabilized tetragonal zirconia polycrystal (Ce-TZP/Al2O3) nanocomposite was sandblasted by alumina particles and veneered with feldspathic porcelain via a conventional condensation method. The part of each specimen containing the interface layer was sliced to ultrathin sections with an argon ion slicer, and these sliced sections were observed using high-resolution transmission electron microscopy (HRTEM). For both interfaces, Ce-TZP/porcelain and Al2O3/porcelain, no transition layers due to abrupt changes in atomic distributions were observed. Besides, the porcelain layers of both interfaces consisted of homogeneous amorphous phases. These results suggested that both Ce-TZP and Al2O3 could be directly bonded to porcelain by Van der Waals forces arising from the close contact between them.

Effect of thickness of zirconia-ceramic crown frameworks on strength and fracture pattern

The aim of the present study was to evaluate the fracture load and fracture mode of thin Ceria-stabilized tetragonal zirconia polycrystals/Al(2)O(3 )nanocomposites (Ce-TZP/A) and Yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) crown frameworks. Artificial maxillary second premolars were prepared for metal-ceramic crown and all-ceramic crown restorations and Co-Cr tooth analogs were duplicated. 10 standard (0.5 mm overall thickness) zirconia-ceramic crown frameworks (Y-TZPs) for all-ceramic crown preparation and 10 modified (a 0.3-mm-thick framework increased in thickness by adding a 1.0-mm-thick palatal margin with a height of 2.0 mm) zirconia-ceramic crown frameworks (Y-TZPm, Ce-TZP/Am) for metal-ceramic crown preparation were fabricated. The frameworks were cemented to the Co-Cr tooth analog and loaded vertically until fracture. The fracture load of Y-TZPs (180.0 N) and Ce-TZP/Am (183.7 N) were significantly higher than that of Y-TZPm (133.7 N). There was a significant difference in fracture mode between Y-TZPm and Ce-TZP/Am. Within the limitation of this study, Ce-TZP/Am provide sufficient strength for clinical application.

Preparation and Characterization of Ceria Stabilized Tetragonal Zirconia Polycrystals(I) : Effect of CeO2 Contents on the Mechanical Properties of Ce-TZP

The usual ceramic process of mixing and milling in state of oxides <TEX>$ZrO_2$</TEX> and <TEX>$CeO_2$</TEX> was adopted in this study in a wet process to manufacture Ce-TZP. <TEX>$CeO_2$</TEX>-<TEX>$ZrO_2$</TEX> ceramics containing 8~20 mol% <TEX>$CeO_2$</TEX> were made by heat treatment at <TEX>$1250\sim1500^{\circ}C$</TEX> for 5hr. The maximum dispersion point of every slurry manufactured with a mixture of <TEX>$ZrO_2$</TEX> and <TEX>$CeO_2$</TEX> was neat at pH10. A stable slurry with average particle size of 90 nm can be manufactured when it is dispersed with the use of ammonia water and polycarboxylic acid ammonium. The sintered Ce-TZP ceramics manufactured with the addition of <TEX>$CeO_2$</TEX> in a concentration of less than 10 mol% progressed to the fracture of the specimen due to the existence of a monoclinic phase of more than 30% at room temperature. More than 99% of the tetragonal phase was created for the sintered body with the addition of <TEX>$CeO_2$</TEX> beyond 18 mol%, but the degradation of the mechanical properties on the entire specimen was brought about due to the <TEX>$CeO_2$</TEX> existing in a percentage above 3%. Consequently, the optimal Ce-TZP level combined in the oxide state was identified to be 16 mol% of <TEX>$CeO_2$</TEX> contents.

Evaluation of a High Fracture Toughness Composite Ceramic for Dental Applications

The introduction of yttrium partially stabilized zirconia polycrystals (Y-TZP) has pushed the application limits of all-ceramic restorations. The mechanical properties of these materials can be further improved by the addition of a secondary dopant phase. The aim of this work was to evaluate the properties of a new nano-composite ceramic used as a dental framework material. The properties of a new ceria-stabilized tetragonal zirconia polycrystal co-doped with alumina (Ce-TZP-Al) were investigated. Y-TZP was used as control. Sixty bars (20 x 2.5 x 1.5 mm(3)) from each material were prepared by cutting CAD/CAM milling blocks. Twenty specimens were used to measure the 4-point flexural strength and the modulus of elasticity of the tested materials. The remaining specimens were used to measure the fracture toughness using indentation strength (IS), single edge notched beam (SENB), and fractography (FR). The thermal expansion coefficient (TEC) was measured using temperature expansion diagrams. The bond strength of the two framework materials to two esthetic veneer ceramics was tested using the microtensile bond strength test (MTBS). Finally, scanning electron microscopy (SEM) and energy dispersive X-ray microanalysis (EDX) were used to analyze the internal structure of the materials. One- and two-way analysis of variance (ANOVA) and Bonferroni post hoc tests were used to analyze the data (alpha= 0.5). The flexural strength and modulus of elasticity of Ce-TZP-Al (856 MPa, 170 GPa) were significantly weaker (p < 0.001) than those of Y-TZP (1003 MPa, 215 GPa). The (IS) fracture toughness of the former (19.02 MPa m(1/2)) was significantly higher (p < 0.001) than SENB (12.6 MPa m(1/2)) or FR (12.8 MPa m(1/2)) values. These values were significantly higher (p < 0.001) than the fracture toughness of Y-TZP (7.4 MPa m(1/2)), which showed statistically similar values using the same three techniques. The measured TEC for the two materials was relatively similar, 10.1 microm/ degrees C and 10.4 mum/ degrees C, respectively. Regarding MTBS values, Ce-TZP-Al had significantly lower bond strength values (p < 0.001) and a higher percentage of interfacial failure than Y-TZP, which failed completely cohesively with the two used veneer ceramics. SEM analysis revealed zirconia grains pull out and structural defects at the core-veneer interface for Ce-TZP-Al material, which explained its weak bond to the two used veneers. Despite the promising mechanical properties of Ce-TZP-Al nano-composite ceramic, its very low bond strength to esthetic veneers leaves such layered restorations highly susceptible to delamination and chipping under function. Further studies are needed to enhance the surface stability of this high fracture toughness ceramic.

Bone‐bonding ability of a hydroxyapatite coated zirconia–alumina nanocomposite with a microporous surface

Using a combination of hydroxyapatite (HA) coating and microporous surface treatment, bone-bonding ability was given to composites of ceria-stabilized tetragonal zirconia and alumina (CZA), which possesses excellent mechanical and wear properties and phase stability. Four types of CZA plates (2 x 10 x 15 mm3) were prepared for this study, which were CZA with a polished surface (group 1), a microporous surface prepared by hydrofluoric acid and heat treatment (group 2), a microporous surface with a submicron HA coating prepared by alternately soaking the plate from group 2 in aqueous CaCl2/HCl and Na2HPO4 solutions (group 3), and a microporous surface with a 4-microm HA coating prepared by the biomimetic method, where the plates from group 3 were soaked in simulated body fluid (group 4). Plates were implanted into rabbit tibia, and after 4, 8, and 16 weeks, tensile testing and histological examination of the bone-implant interface were conducted. At 4 weeks, group 4 had superior bone-bonding ability compared with other implants, which was maintained at the later postimplantation times. This HA-coated CZA with a microporous surface has the possibility of clinical use as a bearing material in cementless joint prostheses or as a load-bearing bone substitute.

Piezo-spectroscopic behavior of the emission bands of ?-alumina in the 13900?14250 cm? 1 spectral range

The emission spectrum of α-alumina in the spectral range between 13900 and 14250 cm−1 is characterized by several bands which are much weaker than the two intense and sharp R1 and R2 bands appearing at 14400 and 14430 cm−1, respectively; these latter are known as Ruby lines and they are the emission bands used in the Ruby laser. Furthermore these bands shift in frequency with stress (Piezo-Spectroscopic effect). In this paper, for the first time, the stress-dependent peak frequency of the weaker bands in the 13900–14250 cm−1 range is calibrated, and the results are presented as Piezo-Spectroscopic coefficients. The calibration is performed by reporting the frequency shift of each investigated band as function of varying stresses. The stresses, residual in nature, are obtained by fabricating composite materials where α-alumina is mixed in various amounts with (i) Ceria-Stabilized Tetragonal Zirconia Polycrystals (Ce-TZP) and (ii) silicon carbide, SiC. The composite materials are prepared at high temperature (1500°–1800°C); due to the difference in thermal expansion, upon cooling to room temperature α-alumina develops compressive and tensile stresses, when mixed with Ce-TZP and SiC, respectively. The stress values necessary for the calibration are obtained from the frequency shift of the R2 band, using its well-established Piezo-Spectroscopic coefficient (7.6 cm−1/GPa). Then the newly obtained Piezo-Spectroscopic coefficients of the bands in the 13900–14250 cm−1 range are tested to retrieve the stresses in two sets of composites; finally the stress values are compared with those obtained in the same samples from the frequency shift of the R2 band. The comparison shows a very good agreement, thus providing evidence that the bands in the 13900–14250 cm−1 range can be used to monitor stresses in α-alumina-based materials.

Bone-Bonding Ability of Ce-TZP/Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Nanocomposite with a Microporous Surface and Calcium Phosphate Coating

The nano-composite of a ceria-stabilized tetragonal zirconia polycrystals (Ce-TZP) and alumina (Al2O3) polycrystals (Ce-TZP/Al2O3) is attractive as a load-bearing bone substitute because of its mechanical properties and phase stability. We have developed a new method of hydrofluoric acid and heat treatment (HFT) to give a microporous structure to the surface of this Ce-TZP/Al2O3 nanocomposite ceramic. Bone-bonding ability of a microporous surface and calcium phosphate coating on Ce-TZP/Al2O3 composite has been investigated through in vivo detaching model. Thin calcium phosphate coating layer was added by alternate soaking process, and thick CaP layer was produced by soaking in simulated body fluid for 5 days. HFT treated Ce-TZP/Al2O3 composite showed high bone-bonding ability compared with the control group. Thick and thin CaP coating accelerated bone-bonding ability in early post-implantation period. The submicron microporous surface was beneficial for achieving mechanical interlocking between the ceramic and surrounding bone. These results suggest the possibility of using a Ce-TZP/Al2O3 nanocomposite ceramic with microporous surface and calcium phosphate coating as the bearing material for uncemented total joint replacements.

Synthesis and Magneto-mechanical Properties of Ce-TZP/La M-Type Hexaferrite Composite

An in situ composite composed of ceria-stabilized tetragonal zirconia polycrystals (Ce-TZP) and La{Co 0.5 Fe 0.5 (Fe 0.9 Al 0.1 ) 11 }-O 19 was synthesized from a powder mixture of Ce-TZP, La(Fe 0.9 Al 0.1 )O 3 , Fe 2 O 3 , Al 2 O 3 , and CoO. The dense Ce-TZP dispersed with platelike La{Co 0.5 Fe 0.5 (Fe 0.9 Al 0.1 ) 11 }O 19 crystals as a second phase were formed after sintering from 1250° to 1350°C. The saturation magnetization of the in situ composite Ce-TZP/La(Co 0.5 Fe 0.5 (Fe 0.9 Al 0.1 ) 11 }O 19 was proportional to the mass fraction of the hexaferrite second phase in Ce-TZP. The coercivity of the composite with a 20 mass% of second phase decreased from 9.14 to 2.52 kOe (from 728 to 201 kA/m) after the pulverization of the composite. The susceptibility (x) increased by 15%-25% under uniaxial stress on the composite. The change of the susceptibility (ΔX/X) value increased with decreasing the mass fraction of the second phase in the composite. The ΔX was found to increase linearly with applied stress and abruptly change on cracking, which is expected for the application in fracture sensing of the composite.

Apatite-forming ability of a zirconia/alumina nano-composite induced by chemical treatment.

Induction of an apatite-forming ability on a nano-composite of a ceria-stabilized tetragonal zirconia polycrystals (Ce-TZP) and alumina (Al2O3) polycrystals via chemical treatment with aqueous solutions of H3PO4, H2SO4, HCl, or NaOH has been investigated. The Ce-TZP/Al2O3 composite is attractive as a load-bearing bone substitute because of its mechanical properties. The chemical treatments produced Zr-OH surface functional groups, which are known to be effective for apatite nucleation in a body environment. The composite, after chemical treatment, was shown to form a bonelike apatite layer when immersed in a simulated body fluid containing ion concentrations nearly equal to those in human blood plasma. This implies that it may form apatite in the living body and bond to living bone through the apatite layer. This type of bioactive Ce-TZP/Al2O3 composite is therefore expected to be useful as a bone substitute, even under load-bearing conditions.

Coating of Hydroxyapatite Films on Ceria-Stabilized Tetragonal Zirconia by a Spray-Pyrolysis Technique and Its Evaluation of Biocompatibility by Osteoblastic Cells

Coating of Hydroxyapatite Films on Ceria-Stabilized Tetragonal Zirconia by a Spray-Pyrolysis Technique and Its Evaluation of Biocompatibility by Osteoblastic Cells