Zirconia Toughened Alumina Research Articles

Correction: Effect of MgO Content on the Microstructure and Properties of Zirconia-Toughened Alumina (ZTA) Ceramics by Hot Pressure Sintering

Correction: Effect of MgO Content on the Microstructure and Properties of Zirconia-Toughened Alumina (ZTA) Ceramics by Hot Pressure Sintering

Effect of MgO Content on the Microstructure and Properties of Zirconia-Toughened Alumina (ZTA) Ceramics by Hot Pressure Sintering

Effect of MgO Content on the Microstructure and Properties of Zirconia-Toughened Alumina (ZTA) Ceramics by Hot Pressure Sintering

Microstructural evolution and strengthening mechanism of TC4/ZTA composites fabricated by laser-directed energy deposition

In this study, zirconia-toughened alumina (ZTA) ceramics were prepared and used to fabricate crack-free, high-performance titanium alloy (TC4)/ZTA ceramic composites with a gradient material design through laser-directed energy deposition. The ZTA content gradients ranged from 0 wt% (0ZTA layer) to 20 wt% (20ZTA layer). During laser deposition, Ti reacted with Al2O3 in the ZTA ceramics to form TiAl2O5. Under rapid cooling in the non-preheated sample, the TiAl2O5 and ZrO2 in the 20ZTA layer underwent a phase transformation, resulting in the formation of TiAl2O5, Al2O3, and t-ZrO2. The cooling rate was lower in the preheated sample, which promoted the reaction between Ti and ZrO2, producing Ti2O. The stability of the β-Ti crystal structure was significantly affected by the presence of Al and Zr in the ZTA. First-principles calculations revealed that preheating caused a larger proportion of Al2O3 to melt, primarily destabilizing the β-phase through the action of Al. The reduction in the cooling rate also promoted the β → α phase transformation; making the α-phase dominant in the 20ZTA layer of the preheated sample. In the preheated sample, the hardness of the 20ZTA layer was 1.95 times greater than that of the 0ZTA layer, and the wear volume was reduced by 91.42 %. The strengthening mechanisms in the 20ZTA layer, in descending order, were solid solution strengthening, dislocation strengthening, load transfer, and grain refinement.

Early Biological Response to Poly(ε-Caprolactone)/Alumina-Toughened Zirconia Composites Obtained by 3D Printing for Peri-Implant Application.

The improvement of the mucosal sealing around the implant represents a challenge, one that prompted research into novel materials. To this purpose, a printable poly(ε-caprolactone) (PCL)-based composite loaded with alumina-toughened zirconia (ATZ) at increasing rates of 10, 20, and 40 wt.% was prepared, using a solvent casting method with chloroform. Disks were produced by 3D printing; surface roughness, free energy and optical contact angle were measured. Oral fibroblasts (PF) and epithelial cell (SG) tests were utilized to determine the biocompatibility of the materials through cell viability assay and adhesion and spreading evaluations. The highest level of ATZ resulted in an increase in the average roughness (Sa), while the maximum height (Sz) was higher for all composites than that of the unmixed PCL, regardless of their ATZ content. Surface free energy was significantly lower on PCL/ATZ 80/20 and PCL/ATZ 60/40, compared to PCL and PCL/ATZ 90/10. The contact angle was inversely related to the quantity of ATZ in the material. PF grew without variations among the different specimens at 1 and 3 days. After 7 days, PF grew significantly less on PCL/ATZ 60/40 and PCL/ATZ 80/20 compared to unmixed PCL and PCL 90/10. Conversely, ATZ affected and improved the growth of SG. By increasing the filler amount, PF cell adhesion and spreading augmented, while PCL/ATZ 80/20 was the best for SG adhesion. Overall, PCL/ATZ 80/20 emerged as the best composite for both cell types; hence, it is a promising candidate for the manufacture of custom made transmucosal dental implant components.

Effects of Impact Energy, Impact Frequency, and Test Time on Impact Wear Characteristics of Zirconia-Toughened Alumina Particles-Iron (ZTAp-Fe) Composites Using Response Surface Methodology

The study aimed to investigate the effects of wear parameters including impact energy, impact frequency, test time, and their interactions on the impact wear characteristics of high chromium white iron (HCWI) and zirconia toughened alumina (ZTA) reinforced HCWI composites fabricated by squeeze casting method using response surface methodology (RSM). The Box-Behnken Design (BBD) method was employed, and a linear model was developed to describe the relationship between wear loss and wear parameters, and to predict the wear behavior of the tested materials. The parameters of energy, frequency, and test time were found to be statistically significant, and positively influencing the wear behavior. Specifically, test time emerged as the most influential factor, followed by energy and frequency. The wear characteristics of HCWI are primarily characterized by shallower plowing and furrows, partial plastic deformation, surface spalling, and inserted abrasives. In contrast, the predominant wear mechanisms for ZTA/HCWI composites include slight breaking of ZTA particles, plowing, and cutting of the metal matrix; breaking and falling of ZTA particles; broken abrasive particles encrusted into the matrix; and the formation of spalling pits.

Simultaneous effect of microwave sintering and TiO2 addition on sinterability, mechanical properties, and scratch resistance of zirconia toughened alumina ceramics

This paper delves into the transformative impact of varying titanium dioxide (TiO2) content on the sinterability, physical, and mechanical properties, as well as scratch behavior, of zirconia-toughened alumina (ZTA) ceramic composites. By adjusting TiO2 content from 0 wt% to 5 wt% and employing advanced microwave sintering at 1150 °C, the study aims to lower the sintering temperature of ZTA. Microwave sintering, known for its efficiency and rapid processing, enables significant enhancements in material properties at reduced temperatures. Notably, incorporating TiO2 into ZTA yields remarkable improvements in physical and mechanical attributes, with the optimal TiO2 content determined to be 3 wt%. At this concentration, the composite achieves exceptional properties: a relative density of ∼99 %, microhardness of ∼2002 HV, and an indentation fracture toughness of ∼6.13 MPa m0.5. These enhancements represent increases of over 120 % in hardness and 61 % in toughness compared to TiO2-free ZTA. Additionally, the highest scratch resistance is observed at 3 wt% TiO2, evidenced by a minimal scratch depth of ∼7.53 μm. However, exceeding the 3 wt% solubility limit results in the formation of secondary phases, such as tialite (Al2TiO5) and zirconium titanate (ZrTiO4), which degrade the composite's properties. This research underscores the potential of TiO2 doping and microwave sintering to elevate the performance of ZTA ceramics, offering a pathway to superior materials for advanced applications.

Zirconia Ageing is related to Total Hip Arthroplasty Aseptic Loosening. A Study of 45 Retrieved Zirconia Heads

BackgroundY-TZP zirconia heads were recalled by the Food and Drug Administration (FDA) in 2001 and zirconia alone was no longer used in orthopedics. Tunnel furnace sintering was suspected of producing defects responsible for early material failure. As Zirconia Toughened Alumina (ZTA) matrices are widely used as bearing material and contain zirconia grains, there remains a need to better understand the in vivo ageing process of zirconia and its clinical implications when the material is produced by batch furnace sintering, the validated sintering process. Questions/objectivesIs there an association between the ageing of batch furnace produced zirconia and THA revision? Methods45 retrieved femoral heads, batch furnace sintered only, were analyzed. Roughness was measured by 3D profilometry, phase transfer by µRaman spectroscopy.Clinical data were compared with material characteristics. ResultsIrrespective of the cause of revision, all heads showed a crystallographic phase transition from tetragonal to monoclinic over 19.5%. A correlation was found between the phase change, roughness increase and aseptic loosening, with a threshold set at 24.5% of monoclinic phase. ConclusionsThe ageing process of zirconia may lead to aseptic loosening, which, in the absence of contrary evidence, prohibits its use as the sole component of orthopedic materials. ZTA matrices should be clinically monitored, especially in young patients, and better in vitro modelling needs to be performed. Level of evidenceIV; Case series.

Direct powder bed selective laser processing of dense alumina-toughened zirconia parts

Direct powder bed selective laser processing of dense alumina-toughened zirconia parts

Evaluation of Load on Cervical Disc Prosthesis by Imposing Complex Motion: Multiplanar Motion and Combined Rotational-Translational Motion.

(1) Background: The kinematic characteristics of disc prosthesis undergoing complex motion are not well understood. Therefore, examining complex motion may provide an improved understanding of the post-operative behavior of spinal implants. (2) Methods: The aim of this study was to develop kinematic tests that simulate multiplanar motion and combined rotational-translational motion in a disc prosthesis. In this context, five generic zirconia-toughened alumina (BIOLOX®delta, CeramTec, Germany) ball and socket samples were tested in a 6 DOF spine simulator under displacement control with an axial compressive force of 100 N in five motion modes: (1) flexion-extension (FE = ± 7.5°), (2) lateral bending (LB = ± 6°), (3) combined FE-LB (4) combined FE and anteroposterior translation (AP = 3 mm), and (5) combined LB and lateral motion (3 mm). For combined rotational-translational motion, two scenarios were analyzed: excessive translational movement after sample rotation (scenario 1) and excessive translational movement during rotation (scenario 2). (3) Results: For combined FE-LB, the resultant forces and moments were higher compared to the unidirectional motion modes. For combined rotational-translational motion (scenario 1), subluxation occurred at FE = 7.5° with an incremental increase in AP translation = 1.49 ± 0.18 mm, and LB = 6° with an incremental increase of lateral translation = 2.22 ± 0.16 mm. At the subluxation point, the incremental increase in AP force and lateral force were 30.4 ± 3.14 N and 40.8 ± 2.56 N in FE and LB, respectively, compared to the forces at the same angles during unidirectional motion. For scenario 2, subluxation occurred at FE = 4.93° with an incremental increase in AP translation = 1.75 mm, and LB = 4.52° with an incremental increase in lateral translation = 1.99 mm. At the subluxation point, the incremental increase in AP force and lateral force were 39.17 N and 38.94 N in FE and LB, respectively, compared to the forces in the same angles during the unidirectional motion. (4) Conclusions: The new test protocols improved the understanding of in vivo-like behavior from in vitro testing. Simultaneous translation-rotation motion was shown to provoke subluxation at lower motion extents. Following further validation of the proposed complex motion testing, these new methods can be applied future development and characterization of spinal motion-preserving implants.

Graphene Nanosheets along Grain Boundaries in a Zirconia-Toughened Alumina Ceramic Significantly Improve Fracture Strength

Graphene Nanosheets along Grain Boundaries in a Zirconia-Toughened Alumina Ceramic Significantly Improve Fracture Strength

Computational biomechanical study on hybrid implant materials for the femoral component of total knee replacements

Multifunctional materials have been described to meet the diverse requirements of implant materials for femoral components of uncemented total knee replacements. These materials aim to combine the high wear and corrosion resistance of oxide ceramics at the joint surfaces with the osteogenic potential of titanium alloys at the bone-implant interface. Our objective was to evaluate the biomechanical performance of hybrid material-based femoral components regarding mechanical stress within the implant during cementless implantation and stress shielding (evaluated by strain energy density) of the periprosthetic bone during two-legged squat motion using finite element modeling. The hybrid materials consisted of alumina-toughened zirconia (ATZ) ceramic joined with additively manufactured Ti–6Al–4V or Ti–35Nb–6Ta alloys. The titanium component was modeled with or without an open porous surface structure. Monolithic femoral components of ATZ ceramic or Co–28Cr–6Mo alloy were used as reference. The elasticity of the open porous surface structure was determined within experimental compression tests and was significantly higher for Ti–35Nb–6Ta compared to Ti–6Al–4V (5.2 ± 0.2 GPa vs. 8.8 ± 0.8 GPa, p < 0.001). During implantation, the maximum stress within the ATZ femoral component decreased from 1568.9 MPa (monolithic ATZ) to 367.6 MPa (Ti–6Al–4V/ATZ), 560.9 MPa (Ti–6Al–4V/ATZ with an open porous surface), 474.9 MPa (Ti–35Nb–6Ta/ATZ), and 648.4 MPa (Ti–35Nb–6Ta/ATZ with an open porous surface). The strain energy density increased at higher flexion angles for all models during the squat movement. At ∼90° knee flexion, the strain energy density in the anterior region of the distal femur increased by 25.7 % (Ti–6Al–4V/ATZ), 70.3 % (Ti–6Al–4V/ATZ with an open porous surface), 43.7 % (Ti–35Nb–6Ta/ATZ), and 82.5% (Ti–35Nb–6Ta/ATZ with an open porous surface) compared to monolithic ATZ. Thus, the hybrid material-based femoral component decreases the intraoperative fracture risk of the ATZ part and considerably reduces the risk of stress shielding of the periprosthetic bone.

Evaluation of the machinability and enhancement of biological response of ZTA-based 13-93 bio-glass composite materials

Besides the exceptional mechanical and biocompatible properties, zirconia toughened alumina (ZTA) has limited biomedical applications due to its bio-inertness properties. The present work examines the effect of 13-93 bio-glass (BG) addition on the machinability and biological responses of ZTA-containing BG composites. The ZTA–xBG (x = 0, 5, 10, 15, and 25 wt%) composites have been synthesized and sintered at 1250°C for 4 h. The machining of composite samples is done on an abrasive air-jet machine (AAJM), and their machinability is studied in terms of surface roughness (SR), material removal rate (MRR), and mechanics of material removal (MMR). The result indicates that MRR decreases and SR enhances with the addition of BG. The MMR is studied using machined surface morphology, and the results confirm that material removal is due to the large erosion crater. The relative density is decreased with enhancing the BG content except for a sample containing a high amount of BG (25 wt%). Mechanical properties such as hardness and flexural strength are enhanced by BG content up to 25 wt%. In-vitro analysis in simulated body fluid (SBF) reveals that both corrosion and bioactivity increase as BG concentrations increase. According to the in-vitro cell culture data, adding BG to ZTA improves cellular viability with BG content up to 25 wt%. The antibacterial result shows that the viability of the bacterial cells on the composites has significantly decreased with BG content. As a result, biomaterials with this architecture may be used as bone implants.

In situ carbon nanonetwork structure based on MOF-derived carbon to manufacture ceramic composites: A case study of zirconia-toughened alumina

Highly robust ceramics materials are promising materials for applications in the automobile, aerospace, and ceramic cutting tool industries. However, conventional ceramics are typically brittle, which limits their suitability for advanced applications. In this study, with zeolite imidazolium salt skeleton-8 (ZIF-8) as a carbon source, discharge plasma sintering is used to create carbon nanonetworks derived from metal-organic frameworks (MOFs) in situ on the grain boundaries of zirconia-toughened alumina (ZTA) ceramic. ZTA exhibits maximum bending strength (719 ± 20.5 MPa) and fracture toughness (7.91 ± 0.7 MPa m1/2) at MOF concentrations of 1.0 wt% and 2.0 wt%, respectively, which are 1.37 and 1.88 times higher than that of the unmodified sample. This demonstrates that the MOF-derived carbon nanonetworks significantly improve the mechanical properties of the ceramic. The finite element analysis results indicate that the carbon nanonetworks can effectively disperse the stress inside the material and transfer the concentrated stress from the internal defects to the two-phase grain boundary on the surface of the sample, thereby contributing to strengthening and toughening. Overall, this work validates that the in situ production of carbon nanonetworks from MOFs is an effective strategy to enhance the mechanical properties of ZTA ceramics. Moreover, it offers new approaches for reinforcing and toughening other ceramic materials.

Advancements in ceramic-on-ceramic bearing materials for total hip arthroplasty: Properties, challenges, and future directions

Total hip arthroplasty (THA) is a vital procedure for addressing hip injuries and end-stage arthritis, offering relief to millions annually. However, long-term issues like femoral headwear and osteolysis persist, with 25-year survival rates of around 77.6%. Material selection significantly influences THA outcomes. This article investigated five typical ceramic-on-ceramic (CoC) bearing materials, including alumina, zirconia, zirconia-toughened alumina (ZTA), delta ceramic, and sapphire. Alumina, known for hardness and wear resistance, improved with lower fracture rates, and some squeaking and zirconia ceramics addressed fractures but require impurity reduction. ZTA combines alumina and zirconia, excelling in mechanical properties but also exhibiting squeaking. Optimized with nanostructures, delta ceramic shows fracture resistance despite occasional squeaking. Sapphire offers excellent biocompatibility but requires complex manufacturing and more clinical trials. The quest for optimal THA-bearing surfaces is ongoing, demanding rigorous research and collaboration.

Mechanical evaluation of DIW-printed carbon nanofibers - alumina-toughened zirconia composites

Direct ink writing (DIW) offers cost-effective fabrication of intricate ceramic structures. However, the mechanical properties (reliability) of DIW-obtained components have been inadequate for structural applications. This study aimed to improve mechanical properties of DIW alumina-toughened zirconia (ATZ) composite filaments with and without carbon nanofibers (CNFs). Optimized debinding and sintering conditions were determined for Conventional Sintering (CS) and Spark Plasma Sintering (SPS). The influence of nozzle diameter, CNF content and sintering method on the fracture strain, Young’s modulus, flexural strength and Weibull modulus was carefully assessed via correlation analyses. CNFs, although intended to enhance properties, were often agglomerated, which negatively affected mechanical properties. Smaller nozzle diameters enhanced Young’s modulus, with CS-sintered ATZ filaments showing transformation-induced plasticity (TRIP). Mechanical properties rivaled or surpassed those of conventional techniques (e.g., cold isostatic pressing, slip casting) with a good level of mechanical reliability achieved. Overall, DIW showed promise for ceramic materials, particularly ductile Ce-TZP-based composites.

Effect of molecular weight and chemical structure of plasticizer on suspension property, binder removal, and sintered performance for zirconia toughened alumina ceramics fabricated by vat photopolymerization

Adding plasticizer is an appealing strategy to optimize binder removal for ceramic components fabricated by vat photopolymerization (VPP). However, so far the studies for effect mechanism of plasticizer on whole technological process of VPP are comparatively very limited, especially through analysis of physical and chemical properties of plasticizers. Herein, the effect of molecular weight and chemical structure of plasticizer on suspension property, binder removal, and sintered performance of zirconia toughened alumina (ZTA) ceramics was comprehensively investigated. Two types of plasticizers, namely, polyethylene glycol (PEG) and polypropylene glycol (PPG), with various molecular weights from 200 to 600 were used. Interestingly, only after adding PEG200 or PPG200, the suspensions still exhibited desired rheological and photocuring behavior, and the superior surface quality was still observed. More importantly, PPG200 proved to be the most effective plasticizer to achieve the most excellent and stable mechanical performances, as well as the highest debinding efficiency.

Characterization of a hydrothermally aged experimental alumina-toughened zirconia composite

ObjectivesTo assess the effects of different aging protocols on chemical, physical, and mechanical properties of an experimental ATZ composite compared to a zirconia. MethodsDisc-shaped specimens were obtained through uniaxial pressing of commercial powders (Tosoh), ATZ comprised of 80%ZrO2/20%Al2O3 (TZ-3YS20AB) and 3Y-TZP (3Y-SBE). The specimens of each material were divided into different groups according to the aging protocol: immediate, autoclave aging and hydrothermal reactor aging. The aging protocols were performed at 134 ºC for 20 h at 2.2 bar. Crystalline evaluations were performed using X-Ray Diffraction. The nanoindentation tests measured the elastic modulus (Em) and hardness (H). Biaxial flexural strength was performed, and Weibull statistics were used to determine the characteristic strength and Weibull modulus. The probability of survival was also determined. The Em and H data were analyzed by one-way ANOVA and Tukey test. ResultsDiffractograms revealed the presence of monoclinic phase in both materials after aging. The hydrothermal reactor decreased the Em for ATZ compared to its immediate condition; and the H for both ATZ and 3Y-TZP regarding their immediate and autoclave aging conditions, respectively. The aging protocols significantly increased the characteristic strength for ATZ, while decreased for 3Y-TZP. No difference regarding Weibull modulus was observed, except for 3Y-TZP aged in reactor. For missions of up to 500 MPa, both materials presented a high probability of survival (>99 %) irrespective of aging condition. SignificanceThe synthesized ATZ composite exhibited greater physical and microstructural stability compared to 3Y-TZP, supporting potential application of the experimental material for long-span reconstructive applications.

Preparation of ZTA composite ceramics derived from sol–gel method by DIW printing

AbstractIn this study, the dense and fine‐grained zirconia toughened alumina (ZTA) composite ceramics were efficiently prepared by 3D gel printing technology. Zirconia powder, zirconium oxychloride, and zirconium sol were introduced into boehmite gel as zirconium sources, and their effects on rheological properties, drying characteristics, microstructure, and mechanical properties of ceramics were discussed. The results showed that all gels exhibit reversible shear thinning properties. The gel with zirconia powder has a relaxation phenomenon; zirconium sol forms another gel network in the boehmite gel network, and two linear viscoelastic regions are observed. The gel with zirconia powder has the highest solid loading, small drying shrinkage, and fewer drying defects. The grain growth of ZTA ceramics with zirconium sol was inhibited, and the zirconia grains were evenly distributed, with the highest bending strength of 518 ± 103 MPa. The new gel preparation method and gel drying process offer great possibilities for manufacturing optical glasses and functional ceramics with high‐performance geometric structures, which cannot be achieved by traditional manufacturing methods.

Comparative Analysis of Osteoblastic Responses to Titanium and Alumina-Toughened Zirconia Implants: An In Vitro Study.

Osteoblastic responses play a crucial role in the success of oral implants. Enhanced proliferation of osteoblast cells is associated with reduced cell mortality and an increase in bone regeneration. This study aims to evaluate the osteoblastic responses following oral implantation. Osteoblast stem cells were harvested and subsequently cultivated using cell culture techniques. The osteoblastic phenotype of the extracted cells was confirmed by examining the extracellular matrix. Cell morphogenesis on functionalized biomaterial surfaces was assessed through indirect immunofluorescence staining. The cellular response was investigated in the presence of two types of implant materials: titanium (Ti) and alumina-toughened zirconia (ATZ). Cell viability and apoptosis were quantitatively assessed using MTT assays and flow cytometry, respectively. The survival of osteoblastic lineage cells was moderately reduced post-implantation. Viability in the Ti implant group remained at approximately 86%, while in the ATZ group, it was observed at 75%, which is considered acceptable. Moreover, there was a significant disparity in cell survival between the two implant groups (p < 0.05). Analysis of apoptosis levels at various concentrations revealed that the rate of apoptosis was 3.6% in the control group and 18.5% in the ATZ group, indicating that apoptosis or programmed cell death in the ATZ-treated group had increased nearly four-fold (p < 0.05). The findings of this study indicate a reduction in osteoblastic cell line survival following implant treatment, with titanium implants exhibiting superior performance in terms of cell survival. However, it was also noted that the incidence of apoptosis in osteoblast cells was significantly higher in the presence of zirconium-based implants.

Effect of β-spodumene additions on the phase composition, thermal, mechanical, and fracture behavior of zirconia toughened alumina composites

The fabrication of ceramic composites with low thermal expansion and excellent mechanical properties is essential for thermal barrier coating (TBC) applications. For this purpose, using the sol-gel process, novel ceramic composites were developed by combining varying weight percentages of β-spodumene (0–20 wt%) with zirconia toughened alumina (ZTA). The influence of β-spodumene addition on the densification, phase composition, microstructure, and mechanical, thermal, and fracture behavior of the studied composites was investigated experimentally and numerically. Increasing the β-spodumene content reduces the sintering temperature of the formed composites by 75 °C. Introducing 5 wt% β-spodumene to ZTA composite improves the densification process by serving as a mineralizer. X-ray diffraction (XRD) revealed that the t-m ZrO2 transformation was enhanced by increasing the β-spodumene content. The results demonstrated that composites with β-spodumene content of 5 wt% exhibited the best mechanical performance. The numerical prediction of fracture toughness agreed well with the experimental results for different composites.