ZrO2-toughened Al2O3 Research Articles

On the Preparation and Wear Properties of Ceramic Particle-reinforced High-chromium Cast Iron-based Surface Composite Material

In this study, we successfully developed a composite material that can enhance the local wear resistance of high-chromium cast iron matrix by using 203 and ZTA (ZrO2-toughened Al2O3) ceramic particles and high-chromium cast iron as the basic raw materials, using the preparation methods of melt casting infiltration and porous ceramic preform. The specific operation steps were as follows: firstly, nickel treatment was carried out on the ceramic fragments, and then the treated ceramic fragments were mixed with the preset adhesive and poured into a mold with honeycomb-shaped voids. After pressurization and heating, its texture gradually strengthened, and finally a porous ceramic preform with a honeycomb shape was formed. After that, the preform was stably placed inside the sand mold to prevent the casting from getting worn. After that, it was filled monolithically and penetrated by a high-chromium cast iron metal fluid, thus forming a composite wear-resistant layer composed of ceramics and metals.

Impact-abrasive wear property of ZrO2 toughened Al2O3 ceramic particles reinforced high manganese steel matrix composites

ZrO2-toughened Al2O3 (ZTA) ceramic particle–reinforced high manganese steel (HMS) matrix composites are a promising class of wear-resistant structural materials for various purposes such as mining. In this study, millimeter-scale ZTA/HMS composites were prepared by cast infiltration method. Using SEM, EPMA, TEM, nanoindentation, a microhardness tester, and an impact-abrasive wear machine, the microscopic characteristics of interfacial layers, work-hardening behaviors, impact-abrasive wear properties, and wear failure mechanism were investigated. The results show a smooth and continuous interfacial layer between ZTA and the matrix. This layer is dominated by an amorphous structure, and the hardness and modulus of the interfacial layer reached 6 and 200 GPa, respectively. The relative wear resistance of the composites under impact (energies of 2–5 J) was between 2.17 and 0.59, and the depth of the work-hardening layer amounted to 0.95–2.95 mm. The wear failure mechanism of the composites was as follows: at a low impact energy (2 J), micro-cutting, grooving, fatigue spalling, and wedge formation occurred. When the impact energy was increased to 5 J, the wear mechanism of the composites was dominated by the breaking and shedding of the ZTA particles. This study has practical importance because it is based on the problems and needs of composites in actual production.

Implementing Machine Learning approaches for accelerated prediction of bone strain in acetabulum of a hip joint

The Finite Element (FE) methods for biomechanical analysis involving implant design and subject parameters for musculoskeletal applications are extensively reported in literature. Such an approach is manually intensive and computationally expensive with longer simulations times. Although Artificial Intelligence (AI) based approaches are implemented to a limited extent in biomechanics, such approaches to predict bone strain in acetabulum of a hip joint, are hardly explored. In this context, the primary objective of this paper is to evaluate machine learning (ML) models in tandem with high-fidelity FEA data for the accelerated prediction of the biomechanical response in the acetabulum of the human hip joint, during the walking gait. The parameters used in the FEA study included the subject weight, number and distribution of fins on the periphery of the acetabular shell, bone condition and phases of the gait cycle. The biomechanical response has also been evaluated using three different acetabular liners, including pre-clinically validated HDPE-20% HA-20% Al2O3, highly-crosslinked ultrahigh molecular weight polyethylene (HC-UHMWPE) and ZrO2-toughened Al2O3 (ZTA). Such parametric variation in FEA analysis, involving 26 variables and a full factorial design resulted in 10,752 datasets for spatially varying bone strains. The bone condition, as opposed to subject weight, was found to play a statistically significant role in determining the strain response in the periprosthetic bone of the acetabulum. While utilising hyperparameter tuning, K-fold cross validation and statistical learning approaches, a number of ML models were trained on the FEA dataset, and the Random Forest model performed the best with a coefficient of determination (R2) value of 0.99/0.97 and Root Mean Square Error (RMSE) of 0.02/0.01 on the training/test dataset. Taken together, this study establishes the potential of ML approach as a fast surrogate of FEA for implant biomechanics analysis, in less than a minute.

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.

Variation in Centrifugal Speed and Resultant Changes in Microstructure and Properties of ZrO2-Toughened Al2O3 Particle-Reinforced Iron Matrix Composites

Variation in Centrifugal Speed and Resultant Changes in Microstructure and Properties of ZrO2-Toughened Al2O3 Particle-Reinforced Iron Matrix Composites

Study on the Penetration Power of ZrO2 Toughened Al2O3 Ceramic Composite Projectile into Ceramic Composite Armor.

This work aims to improve the penetration ability of a 14.5 mm standard armor-piercing projectile into ceramic/armor steel (Al2O3/RHA) composite armor. To this end, ZrO2 toughened Al2O3(ZTA) is prepared as the material for bullet tips, utilizing in situ solidification injection molding that is realized via ceramic dispersant hydrolytic degradation. The penetration power of ZTA ceramic composite projectile, compared with standard armor, against 15 mm armor steel (RHA) and 30 mm Al2O3/RHA composite armor, is studied by ballistics testing combined with numerical simulation. The Tate theory is optimized and then employed to calculate the penetration depth and bullet core’s residual mass when ZTA ceramic composite projectile penetrates into Al2O3/RHA composite armor. The results show that when penetrating RHA of 15 mm, the penetration area of ZTA ceramic composite projectile into RHA increases by 27.59% and the exit area by 42.93%. While the standard projectile fails to penetrate the 30 mm Al2O3/RHA composite armor, the ZTA ceramic composite armor-piercing projectile succeeds, with the mass loss reduced by 66.67% over the standard one. The ZTA ceramic composite bullet has a better performance than the standard bullet in penetrating RHA and Al2O3/RHA composite armors. The test results, simulation, and theoretical analysis are consistent. This study has practical values for engineering applications to design new ceramic composite bullets.

Preparation and characterization of Ni-Cu dual coated ZTA particles by ionic liquid-assisted electroless plating as reinforcement of metal-based composites

An ionic liquid assisted electroless plating is adopted to prepare continuous and dense Ni-Cu dual coatings on the surface of ZTA particles. The effects of l-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4) additive, NiSO4 and CuSO4 concentrations on the surface morphologies, coating thickness, and element content of Ni-Cu dual coated ZrO2-toughened Al2O3 (ZTA@Ni-Cu) particles have been characterized systematically. Results show that with incremental addition of [bmim]BF4, suspended Ni-Cu particles in plating bath can be diminished but the incubation period and plating time of Ni-Cu coatings are prolonged significantly. The addition of 20 g·L−1 [bmim]BF4 is optimum for the preparation of uniform and compact ZTA@Ni-Cu particles. Besides, the thickness of Ni-Cu coating is about 20–30 μm and the Cu element content can be controlled in the range of 14.10–60.76 at.% through adjusting Cu(II) ions concentration. Furthermore, the possible reactions and deposition sequences for the preparation of Ni-Cu coatings on ZTA surfaces are analyzed and an empirical model of the deposition process assisted with [bmim]BF4 additive is also proposed to expound the function mechanism of [bmim]BF4 additive and the formation process of Ni-Cu coatings on ZTA surfaces.

Compressive fatigue behaviour of ZTAp/40Cr steel matrix composites by three-dimensional structural toughening

Herein, the compressive fatigue behaviour of three-dimensional metal matrix composites/steel (3D-MMCs/steel) is studied. The ZrO2-toughened Al2O3 (ZTA) particle strengthens 40Cr steel composite materials (MMCs) as a reinforcement. The experimental conditions were uniaxial compression fatigue under 500 MPa and 20 Hz. The failure modes of the composites were analysed by three-dimensional x-ray microscopy. The fatigue life of the 3D-MMCs/steel composite is 9.0 × 106 cycles, and for the homogeneous ZTAp/40Cr composite material is 1.03 × 106 cycles. The analysis shows that grids of the matrix area can inhibit the propagation of a crack in the MMC area and can cause it to turn or to disappear. Toughening of the 3D-MMCs/steel composite primarily occurs because the matrix area grids protect the MMC area from tearing.In other words, the presence of the MMC grids causes the toughening of this kind of material.

Comparison of properties and impact abrasive wear performance of ZrO2-Al2O3/Fe composite prepared by pressure casting and infiltration casting process

Abstract A ZrO2-toughened Al2O3 (ZTA) particle-reinforced high chromium cast iron (HCCI) composite was prepared by pressure bonding following flow mixing (PB-FM). Its microstructure, mechanical properties, and impact abrasive wear behavior were investigated and compared with a similar commercially available composite (Xwin® composite), which is prepared by infiltration casting. The PB-FM composite exhibited better wear performances under high impact energies. The wear mechanisms of the investigated composites at low impact energies were mainly ploughing and cutting of the matrix and slight breaking of the reinforcements, whereas at high impact energies, they were dominated by the breaking and detachment of the reinforced particles, embedded abrasives, and spalling pits.

Green Preparation and Dry Sliding Wear Properties of a Macro-ZTA/Fe Composite Produced by a Two-Step Method

In this paper, a two-step method, rapid-flow mixing followed by high-pressure compositing was used to prepare a macro-ZTA (ZrO2-toughened Al2O3) particles reinforced high chromium cast iron (HCCI) matrix composite. The method is based on the squeeze casting process without general casting pollution problems. The microstructure, mechanical properties and dry sliding wear performance of the fabricated composite were investigated. The results showed that the particles were distributed uniformly throughout the iron matrix and a tightly bonded interface was obtained. Under dry sliding wear conditions, the wear resistance of the composite was significantly improved in comparison with the HCCI alloy, and the relative wear resistance was 1.8 and 2.9 times at the applied load of 300 and 900 N, respectively. When the load increased from 300 N to 900 N, the wear characteristics of the composite changed from shallow and narrow grooves and scratches to damages in the form of fragmentation of particles, transfer layer and interface cracking.

Fabrication and interaction mechanism of Ni-encapsulated ZrO2-toughened Al2O3 powders reinforced high manganese steel composites

In order to solve the cast-infiltration difficulty and low interface bonding strength of ZrO2-toughened Al2O3 (ZTA) powders reinforced high manganese steel (HMS) matrix composite, uniform and continuous Ni-encapsulated ZTA powders (ZTAp@Ni) as reinforced phase are fabricated by electroless deposition assisted with ionic liquid additive. The effects of Ethaline concentration, temperature, ZTA concentration and deposition times on the morphology of ZTAp@Ni have been investigated. Experimental results show that the thickness of Ni coating is about 7–10 μm, and there is no casting crack or shrink on the composite, so compact bonding between ceramic and matrix is obtained. In addition, the impact abrasive wear resistance testing demonstrates that the performance of ZTAp@Ni reinforced HMS composite is superior to that of matrix. On the basis of experimental analysis, a schematic illustration of the cast-infiltration process is put forward. It implies that Ni-encapsulated ZTA can be wetted with molten HMS matrix to form a ZTA/Al2NiO4-Al2MnO4/Fe interface layer through Ni diffusion and reactive wetting. The interdiffusion of Ni and other elements at ZTA interface layer can reinforce the interfacial bonding strength to form an interface layer between metal and hard phases.

Probing Cytocompatibility, Hemocompatibility, and Quantitative Inflammatory Response in Mus musculus toward Oxide Bioceramic Wear Particulates and a Comparison with CoCr.

Peri-prosthetic bone resorption and loosening of artificial joints have been widely recognized to limit the performance of the load-bearing implants. Therefore, the present study probes into the cyto-, hemo-, and histocompatibility of the small sized wear particulates of ZrO2-toughened Al2O3 (ZTA). In order to develop a comprehensive, yet clinically relevant understanding, a comparison is made with two baseline ceramics (Al2O3 and ZrO2) and metallic material (CoCr), all in particulateforms. Whilein vitro cytotoxicity assessment was carried out with mouse osteoblast cells, preclinical testing of intra-articularly injected particulates up to the concentration 25 wt % in PBS over the period of 12 weeks was performed in mouse model. Interestingly, mouse osteoblast cells, cultured in media with ZTA, Al2O3, and ZrO2 particulates of three different concentrations (0.25, 2.5, and 25 mg/mL) exhibited uncompromised cell viability and considerable cell spreading, up to the time frame of 72 h. In contrast, similar experiments with CoCr particulates demonstrated significant decrease in cellular growth with drastic change in osteoblast proliferation behavior. Furthermore, the decrease in RBC damage after contact with ZTA, Al2O3, and ZrO2 particulates at 25 mg/mL of dose level illustrated 4.4, 5.8, and 1.25% hemolysis, respectively, confirming clinically acceptable hemocompatibility. However, hematic activity of CoCr particles was reflected with 15.6% of hemolysis. In vivo, the absence of any significant effect of intra-articularly injected ceramic (Al2O3, ZrO2, ZTA) as well as metallic (CoCr) particulates on complete hemogram and serum biochemistry of Balb/C mice was recorded at all the time points up to 12 weeks. The extensive histological analysis confirmed the absence of any signature of the tissue-level toxicity at all time points. The pro-inflammatory cytokine analysis using TNF-α and IL-1β markers provided complementary evidence toward nongranulomatous and nonimmunogenic response of synovial membrane of knee joint and other vital organs of mice that were exposed to Al2O3, ZrO2, ZTA, and CoCr particulates. Taken together, our results establish the nontoxic nature of oxide ceramic particulates to bone cells, in vitro, as well as to periprosthetic tissue, in vivo.

Preparation of nickel coating on ZTA particles by electroless plating

With the aim to effectively improve the interface between ZrO2 toughened Al2O3 (ZTA) particles and metal matrix, nickel was deposited on the surface of ZTA particles by electroless plating method. Formation mechanism of nickel coating and effects of the solution pH, loading capacity of ZTA particles and temperature on the nickel deposition were investigated. Microstructures, thickness and element distributions of nickel coating were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results showed that the nickel was successfully deposited on the surface of ZTA particles by electroless plating without noticeable defects. The process of electroless nickel plating could be explained by combination of atomic hydrogen and electrochemistry theories. The interfacial nucleation of nickel is easier to form than spontaneous nucleation in the solution. Deposited Nickel has priority on the surface of ZTA particles comparing to that in solution. The optimal conditions to coat nickel on the surface of ZTA particles are: solution pH 4.7–4.8, loading capacity 15–20 g/L, and electroless plating temperature 85 °C. The ZTA particle reinforced iron matrix composites prepared by powder metallurgy could have better interfacial bonding between ZTA particle and iron matrix because of the nickel coating on the surface of ZTA particle. Nickel diffuses into the iron matrix during the sintering preparation of composite materials. The interface between ZTA particle and iron matrix presents the evidence of non-chemical bonding.

Implementing statistical modeling approach towards development of ultrafine grained bioceramics: Case of ZrO2‐toughened Al2O3

AbstractThe application of statistical modeling approach with the predictive capability of sinter density and grain size is perceived as a central theme in the development of next generation ceramics. Such computationally intensive method can be equally significant, if the predicted process conditions can be adapted experimentally to develop complex shaped ceramics with variable sizes. In the first ever attempt to address such issues for the ceramics, we have, in the present work, considered a range of factors and levels from relevant process variables (sintering temperature, sintering time) and material variables (sinter‐aid addition and reinforcement content) as input parameters to formulate data‐driven, high throughput analytical assays by response surface method (RSM). Using ZrO2 toughened Al2O3 (ZTA) as a model system, the adopted RSM approach has been used to quantitatively predict independent and interactive role of process and material variables on sinter density and grain size.

Uniaxial Compaction‐Based Manufacturing Strategy and 3D Microstructural Evaluation of Near‐Net‐Shaped ZrO2‐Toughened Al2O3 Acetabular Socket

The article presents computer‐aided design approach and discusses an integrated manufacturing protocol to fabricate ZrO2‐toughened Al2O3 (ZTA) prototype with excellent geometrical conformity. In particular, a powder mixture of 95 wt% Al2O3–5 wt% ZrO2 with 800 ppm MgO sinter aid is uniaxially compacted at 200 kN, followed by pre‐sintering‐machining‐final sintering. The finishing of ZTA socket to obtain submicron surface roughness (Ra ≈ 0.01 μm) is accomplished using polymer rheological medium with silicon carbide abrasives. Summarizing, the uniqueness of uniaxial compaction‐based processing approach is established to fabricate scalable near‐net‐shaped acetabular ceramic sockets having uniform ZrO2 distribution in 3D microstructure of ZTA, as analyzing using microcomputed tomography.

Spark Plasma Sintering and Characterization of Graphene Platelet/Ceramic Composites

AbstractThis paper reports a study on sintering and characterization of graphene platelet (GPL)‐reinforced ceramic composites. Alumina (Al2O3) and zirconia (ZrO2) toughened Al2O3 (ZTA) composites reinforced with GPLs are fabricated, respectively, using spark plasma sintering. The microstructures and mechanical properties of the sintered samples are investigated. It is found that the addition of GPLs hinders the growth of the ceramic matrix grains and help form homogenous microstructures of the ceramic matrices. Agglomeration of GPLs occurs during the fabrication process and formation of GPL aggregates is impeded when ceramic powders of smaller particle size and a shorter milling process are used. Fracture toughness of the ceramic matrices is significantly improved by introducing GPLs. Approximately, a 26.4% and a 29% improvements in fracture toughness are achieved for GPL/Al2O3 and GPL/ZTA composites, respectively. The main toughening mechanisms induced by GPLs are pull‐out and crack bridging.

Effectively Inhibiting Abnormal Grain Growth of Alumina in ZTA with Low‐Content Fine‐Sized ZrO2 Inclusions Introduced by Infiltration and In Situ Precipitation

Previous literatures have all emphasized that the successful control of microstructure homogeneity of ZTA (ZrO2 toughened Al2O3) composites can only be achieved provided that the ZrO2 particles are homogeneously distributed and the volume content exceeds 5 vol%. In this paper, we report our strategy to incorporate fine‐sized ZrO2 into Al2O3 by infiltrating presintered alumina compact using zirconium ion‐containing solution and then in situ precipitation with ammonia solution. Homogeneous microstructure without AGG can be achieved in the prepared composite at a lower ZrO2 content (2.3 vol%). Such a result might be attributed to the excellent homogeneous distribution of fine‐sized incorporated ZrO2 particles in Al2O3 matrix.

Fabrication and Characterization of Three‐Dimensional ZrO2‐Toughened Al2O3 Ceramic Microdevices

Dense three‐dimensional (3D) microdevices of ZrO2‐toughened Al2O3 (ZTA) were fabricated using microstereolithography and a subsequent sintering process. Using microstereolithography, 3D green bodies could be formed from a 40 vol% ZTA ceramic–resin paste. After sintering, the fabricated 3D devices are converted into dense ceramic devices without deformation. In this study, a gear (with a tooth edge of 25 μm) and a photonic crystal (with a lattice constant of 500 μm) were designed and fabricated. The dimensional accuracy of the fabrication process is within 20 μm and the sintering shrinkage is around 26% for these microdevices. The relative density of the sintered ZTA ceramics reached 96.5% of theoretical value. The measured hardness and toughness were about 14 GPa and 11 MPa m1/2, respectively, in both the top and side surfaces. A band gap between 320 and 420 GHz was observed in the ZTA photonic crystal. The microstereolithography process can be easily applied to other ceramic materials and devices.

Effect of cerium zirconate (Ce2Zr2O7) on microstructure and mechanical properties of Ce-ZTA

Powders for ZrO2 toughened Al2O3 (ZTA) composites containing 8, 11, 13.8 and 16.5 vol% ZrO2 (stabilized with 11.5 mol% CeO2) are prepared by a hybrid sol-gel method using Al2O3 powders and a sol formed from Zr-alkoxide and cerium nitrate. Besides ZrO2, a small amount of a Ce-zirconate phase (Ce2Zr2O7) forms when the powders are calcined in air. The zirconate phase persists in the sintered specimens and its amount increases from surface to centre of the specimen. Presence of higher amount of Ce2Zr2O7 promotes exaggerated grain growth of Al2O3. Particles of Zr rich phases are found to be trapped inside the Al2O3 grains. Composites exhibit higher fracture toughness despite lower transformability of t-ZrO2 during fracture when they contain high amount of zirconate. Crack bridging is shown to be an important mechanism contributing to enhancement in fracture toughness in these composites.

Effect of zirconia addition on the fatigue behaviour of fine grained alumina

The fatigue behaviour of fine grained Al2O3 and ZrO2 toughened Al2O3 (ZTA) compositions with 15 vol% ZrO2 (3 mol% Y2O3 stabilized: 3Y-TZP) have been investigated by using three different techniques. Primarily 4-point bending load was employed to generate tension-tension fatigue data under both static and cyclic conditions. The results clearly showed that the materials were susceptible to both the static and cyclic fatigue and the time to failure under cyclic loading was considerably shorter than the equivalent static loads. The repeated indentations at the same spot with varying loads showed a typical fatigue behaviour. In addition, both the materials were subjected to the repeated impact cycles at varying subcritical loads simulating impact fatigue. In all the cases typical fatigue curves were obtained having a progressive endurance at subcritical loads having an endurance limit. The fatigue behaviour of Al2O3 was much improved by the addition of 15 vol% 3Y-TZP, having micro-plasticity contributing towards the cyclic fatigue phenomena of these materials.