Zirconia Toughened Alumina Ceramics 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.

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.

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

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.

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.

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.

Preparation of high-performance zirconia toughened alumina doped with Cr2O3 and SrO for artificial joints by spray granulation

Zirconia-toughened alumina (ZTA) ceramics have attracted much attention in the medical field as joint replacement materials due to their good mechanical properties and biocompatibility. However, the flexural strength of conventional ZTA is still slightly insufficient in traditional preparation techniques. In this study, by improving the slurry system, the effects of the solid content of the slurry, additives, and the pH of the slurry on the slurry system were investigated. ZTA powders with a uniform particle size distribution, high degree of sphericity and high flowability were prepared by spray granulation. The mechanical properties, microstructure and biocompatibility of the ZTA pressing were investigated after degreasing and sintering processes. The results showed that the hardness of the prepared ZTA ceramics was 1658.24 ± 28.04 HV, the fracture toughness was 4.016 ± 0.027 MPa·m1/2, and the biaxial bending strength was 501.43 ± 21.44 MPa, and the three-point bending strength reached 635 MPa. The ZTA ceramics also possessed good biocompatibility and a low haemolysis rate, which aligns with the requirements of clinical biomedical implant materials.

Study of Cu-doped zirconia toughened alumina ceramics (Cu-ZTA) subject to lubrication behaviors for arthroplasty

Zirconia-toughened alumina (ZTA) is widely applied in total hip arthroplasty (THA). However, problems with insufficient fracture toughness and lubrication remain, leading to wear, squeaking, and fracturing. In this study, the Cu doping of ZTA (Cu-ZTA) is proposed to solve these problems. To further promote the use of Cu-ZTA, the role of Cu doping on its tribological properties must be studied. In this study, the microstructure, mechanical properties, and stability capacity in a physiological environment, as well as the tribological behaviors of Cu-ZTA in phosphate-buffered saline (PBS) and bovine serum albumin (BSA), were systematically studied with varying amounts of Cu. The results demonstrated that holes and soft Cu-rich phases appeared, and grains grew after Cu doping, causing a decrease in hardness. The fracture toughness increased after Cu doping because the Cu-rich particles formed “bridges” during crack propagation and release energy. The incorporation of Cu improved the stability of ZTA in physiological environments, which enhanced the long-term stability of Cu-ZTA. The protein adsorption results indicated that a higher hydrophobicity and roughness contributed to a greater protein adsorption on the Cu-ZTA surfaces after Cu incorporation. In the BSA solution, the 5.0 wt% Cu-ZTA ceramics achieved a lower coefficient of friction (COF) and wear rate compared to ZTA, and a higher protein adsorption and formation of the denatured protein layer catalyzed by Cu ions in the wear track during friction, thus clearly improving the tribological properties of the Cu-ZTA.

Grain size distribution analysis of MgO and VC inhibited zirconia toughened alumina ceramics using digital image processing

Abnormal grain growth (AGG) of zirconia toughened alumina (ZTA) during sintering decreases phase transformability at critical temperature, leading material failure. The first-ever grain size distribution analysis using image processing in materials science identifies the impact of carbide and oxide inhibitors on tetragonality and grain refinement of ZTA ceramics. Incorporating insoluble vanadium carbide and soluble magnesium oxide inhibitor in ZTA restricts AGG, reducing average grain size of 0.5VC_ZTA by ∼ 86.84% compared to 0.5 MgO_ZTA due to Zener pinning effect of refractory carbide. The inhabitation of dehydroxylation process helps to decrease alumina crystallite size by ∼33.37% in case of VC, thereby increasing the density. Automated analysis using digital image processing makes the process less affected by user bias. A perceptible improvement in micro-mechanical properties through grain refinement of pressure-less sintered 0.5VC_ZTA confirms the structure property correlation of the matrix. This type of analysis has a beneficial aspect towards the fabrication of advanced ceramics with improved properties.

Zirconia Toughened Alumina Ceramics via Forming Intragranular Structure.

The distribution of second phase particles in the microstructure of composite ceramics affects the mechanical properties, and the intragranular structures often result in better properties compared to the intergranular structures. However, it is difficult to obtain composite ceramics with intragranular structure by conventional route. To produce composite ceramics with an intragranular structure in a simpler route. In this work, starting powders with different phase compositions were obtained by the co-precipitation method, and zirconia toughened alumina (ZTA) composite ceramics were prepared with these starting powders by spark plasma sintering (SPS). The results show that it is easier to fabricate ZTA composite ceramics with an intragranular structure by using composite powders containing amorphous or transition phase Al2O3 as starting materials. The phase composition of the powder prepared by the co-precipitation method after calcination at 1100 °C is θ-Al2O3 and t-ZrO2, and the average grain size after sintering at 1500 °C is 1.04 ± 0.28 µm, and the maximum Vickers hardness and fracture toughness of the specimens reach 19.37 ± 0.43 GPa and 6.18 ± 0.06 MPa·m1/2, respectively. The ZrO2 particles were the core of crystallization and grow together with the Al2O3 matrix, forming the intragranular structure of ZTA ceramics. This work may provide a new idea for preparing composite ceramics with intragranular structure.

Microstructure, mechanical properties, and bone cell interactions of ZTA composites reinforced with BN

Due to their remarkable mechanical properties and biocompatibility, zirconia toughened alumina (ZTA) based composites are preferred materials for dental and orthopedic uses. This study focuses on the production and characterization of hexagonal boron nitride (BN) containing ZTA ceramics. To achieve this, we formulated composite systems with a composition of 70Al2O3-(30-x)YSZ-(x)BN (in vol%, where x ranges from 1 to 5). These mixtures were densified via spark plasma sintering (SPS) at a temperature of 1350 °C under a pressure of 40 MPa, with a dwell time of 5 min. The densification, resulting microstructure, and mechanical properties, including Vickers hardness and indentation fracture toughness, were thoroughly examined. All ZTA-BN composites achieved sintering densities exceeding 98.5% of their theoretical values. Incorporating BNs into ZTA composites increased fracture toughness by ∼55% while maintaining Vickers hardness values. Notably, crack deflection mechanism played a dominant role in toughening, particularly for the composite containing 3 vol% BNs. Furthermore, in vitro biocompatibility assessment of the YZTAB3 sample demonstrated that the composite had no cytotoxic effects towards human bone cells, indicating its potential for biomedical applications.

Effect of TiO2 reinforcement on low temperature (1300 °C) sinterability of zirconia toughened alumina ceramics by correlating its structural and physico-mechanical properties

The primary goal of this research is to investigate the sinterability of zirconia toughened alumina (ZTA) at low temperature (1300 °C) utilizing two different sintering techniques: hot press and cold press. The effect of titanium oxide (TiO2) content variation (0–5 wt%) in ZTA is compared for each sintering method. The solubility limits of TiO2 in ZTA are identified to be 2 wt% and 3 wt% for hot press and cold press sintering respectively which have served exceptional physical and mechanical properties. In the case of hot press, outstanding relative density (99%) is achieved due to excellent compaction, including high microhardness of ∼2092 HV0.5, nanohardness of ∼25.05 GPa, elastic modulus of ∼371.59 GPa and indentation fracture toughness of ∼5.43 MPa·√m for 2 wt% TiO2 inclusion. Whereas in the case of cold press, 3 wt% TiO2 addition has revealed a considerable relative density (96%), alongside microhardness of ∼1975 HV0.5, nanohardness of ∼20.92 GPa, elastic modulus of ∼280.39 GPa and an indentation fracture toughness of ∼4.84 MPa·√m. However, further addition of TiO2 leads to the formation of secondary phases i.e., tialite and zirconium titanate which deteriorate the mechanical and physical properties due to the abnormal grain growth. Therefore, it has been postulated that the small additions of TiO2 have enormous capability of lowering the sintering temperature of ZTA-MgO ceramic without compromising the physical and mechanical characteristics.

The Effects of Compressive Residual Stress on Properties of Kyanite-Coated Zirconia Toughened Alumina Ceramics.

In this study, the prestressed coating reinforcement method was employed to create kyanite-coated zirconia toughened alumina (ZTA) prestressed ceramics. Due to the mismatch of the coefficient of thermal expansion (CTE) between the coating and substrate, compressive residual stress was introduced in the coating. The effects of compressive residual stress on the mechanical properties of ZTA have been demonstrated. Results show that the flexural strength of the kyanite-coated ZTA ceramics improved by 40% at room temperature compared to ZTA ceramics. In addition, the temperature dependence of mechanical properties has also been discussed. And the results show that the reinforcement gradually diminished with increasing temperature and eventually disappeared at 1000 °C. The modulus of elasticity of the material also exhibits a decreasing trend. Furthermore, the introduction of the prestressing coating enhanced the thermal shock resistance, but the strengthening effect diminished as the temperature increased and completely disappeared at 800 °C.

Zirconia-Toughened Alumina (ZTA) Nanoceramics with a Gradient Microstructure: A Comparative Study of ZTA Ceramics with Fibrous and Granular Morphology.

ZrO2-toughened Al2O3 (ZTA) ceramic composites with a porosity gradient and with improved mechanical properties have a wide range of possible applications. We fabricated nanofibrous and nanogranular Y-ZTA and Ce-ZTA composites with a gradient microstructure by creating a temperature gradient during SPS sintering, with the use of asymmetric graphite tool arrangement (ASY). In this study, we examined the morphology effect of the starting materials on the sintering process and on the final microstructure, as well as the mechanical properties of the composites. A large temperature difference was established for both the granular and fibrous samples fabricated in the ASY configuration, which resulted in gradient porosity along the ceramics bodies: the upper part of the ceramics showed a highly porous fine microstructure, while the opposite side was highly densified. The final microstructure of the composites can be tailored by varying the morphology of the starting ceramics or the graphite configuration. A highly porous skeleton-like structure was formed by sintering fibres in the ASY configuration, whereas the granular precursors resulted in a much less porous composite. The microstructure affected the mechanical properties of the composite. Improved hardness and more than 50% higher compression strength were obtained for the granular Ce-ZTA samples as compared to the fibrous sample. Gradient porosity with fibrous or granular morphology promotes the penetration of bioactive nanosized hydroxyapatite (HAp) into the pore structure. Fibrous ZTA absorbs HAp more effectively due to its higher porosity as well as its bimodal pore structure.

Mechanical properties and wear behaviors of Cu-doped zirconia-toughened alumina ceramics

Cu-doped, ZrO2-toughened alumina (ZTA) ceramics with varying amounts of Cu (0, 1.5, 3.0, and 5.0 wt%), denoted as Cu/ZTA, were prepared using a fast hot pressing sintering furnace. The microstructure, mechanical properties, tribological properties, and wear mechanism of Cu/ZTA ceramics were subsequently studied. The results showed that Cu doping can cause the formation of holes in the ZTA ceramics. The formation of holes originated from the O2 produced by CuO decomposition at high temperatures and the phase transformation of ZrO2. Cu/ZTA ceramics with 5.0 wt% Cu exhibited significantly improved toughness and tribological properties but diminished hardness. The worn surface analysis of the Cu/ZTA ceramics revealed that their wear mechanism primarily involved abrasive wear and material transfer. The ZrO2 and Cu particles were first pulled out from the wear track to form wear debris during friction. The 5.0 wt% Cu/ZTA ceramic exhibited decreased hardness and high toughness, which made it easier for the abrasive debris to adhere to the surface and holes. Additionally, the wear debris was crushed into the holes formed by Cu doping. The results indicated that a reduction in the number of wear particles at the friction interface could impede the wear of the abrasive particles. Overall, the Cu/ZTA ceramic with 5.0 wt% Cu was found to be a promising structure material with excellent tribological properties.

Material extrusion-based additive manufacturing of zirconia toughened alumina: Machinability, mechanical properties and biocompatibility

Material extrusion-based additive manufacturing (MEAM) has gained significant attention due to its versatile flexibility for fabricating a broad range of materials. In this study, fabrication of dense zirconia-toughened alumina (ZTA) ceramics with micro/nano powders of excellent mechanical and biological properties was investigated. The ZTA paste rheology was engineered to achieve appropriate rheological behavior. A novel machining scheme on MEAM produced ZTA green parts using CNC milling and high precision micro-milling was studied to investigate their effect on surface integrity and geometric accuracy. The MEAM produced ZTA ceramics show the highest relative density, Vickers hardness, bending strength, and fracture toughness of 99 %, 17.7 GPa, 422.5 MPa, and 6.2 MPa*m1/2, respectively. Biocompatibility of fabricated ZTA ceramics with different size of powders was investigated including cell adhesion, cell toxicity and cell proliferation, showing a good potential in biomedical usage. This framework provides a unique pathway for MEAM of ZTA ceramics to combine design and manufacturing freedom, multifunctionality, stability, and economical simultaneously.

Seamless joining of ZTA ceramics without the application of pressure

Seamless joining of zirconia-toughened alumina (ZTA) ceramics without the application of any external pressure was demonstrated in this work through a reaction-bonded aluminum oxide (RBAO) method. Reliable joining of ZTA ceramics in a green-state was successfully accomplished in ambient air at 1600 °C for 2 h with the use of an Al/3Y–ZrO 2 /Al 2 O 3 powder mixture as joining interlayer. The joining mechanism was discussed based on the RBAO process where the effective joining principally relies on the conversion of all Al particles to alumina. Thermogravimetry and differential thermal analysis confirmed the oxidation behavior of the milled Al particles. The joining interface exhibited excellent compositional and structural homogeneity without defects in commensurate with parent bodies. The mechanical properties of the joints were nearly equivalent to bare ZTA ceramics. This proposed simple and cost-effective joining technique can be used for the joining of other alumina-based advanced ceramics to realize large and complex-structures.

Improved ageing-resistance and fracture toughness of zirconia-toughened alumina bioceramics via composition and microstructure design

Low-temperature degradation (LTD) is the main obstacle that hinders the application of zirconia-toughened alumina (ZTA) ceramics as artificial hip joints. In this study, a new type of ZTA bioceramic with LTD resistance, high fracture toughness, and superior wear resistance was prepared by the in-situ formation of plate-like crystals and co-stabilised tetragonal phase zirconia (t-ZrO2). This new design is realised by synthesising nanocrystalline PrAlO3 through a one-step solution combustion method and introducing it into a ZTA matrix to form praseodymium hexaaluminate (Pr0.833Al11.833O19, PHA) plate-like crystals by solid-state sintering. PHA plays a key role in toughening and Y–Pr co-doped t-ZrO2 slows down the low-temperature degradation of ZTA bioceramics. After hydrothermal ageing, the combination strategies have a positive influence on the flexural strength, fracture toughness, and Vickers hardness of the ceramics. This study provides a novel direction for ensuring long-term safety of bioceramics.