ZrO2-based Composites Research Articles

Influence of the Thickness of Titanium Foils on the Deformation Pattern in ZrO2-Based Metalceramic Composites

Influence of the Thickness of Titanium Foils on the Deformation Pattern in ZrO2-Based Metalceramic Composites

Zirconia-Based Ceramics Reinforced by Carbon Nanotubes: A Review with Emphasis on Mechanical Properties

This review outlines the state of the art, processing techniques, and mechanical testing methods of zirconia (ZrO2)-based composites reinforced by carbon nanotubes (CNTs). The use of CNTs as a secondary phase in a zirconia matrix is motivated by their outstanding crack self-healing ability, the possibility to tailor the desired nano-structural properties, and their exceptional wear behavior. Therefore, a detailed investigation into CNT features has been provided. The debate of using the different Vickers indentation fracture toughness equations to estimate the resistance of crack propagation was critically reviewed according to crack characteristics. Finally, this review particularly highlights the exceptional role of ZrO2-based composites as a promising material owing to their outstanding tribo-mechanical properties.

Carbothermal reduction of ZrSiO4 for in situ formation of ZrO2-based composites using spark plasma sintering

In the present study, ZrO2 based composites were synthesized in-situ and sintered by the novel RSPS-assisted carbothermal reduction of ZrSiO4 (Z) in the presence of graphite (G) and Activated Carbon (AC). The RSPS process was performed using a vacuum furnace at different temperatures of 1400–1600°C for 5–15 min under an external pressure of 30 MPa. The thermodynamic analysis was conducted on the synthesis process by FactSage software. The microstructure development and mechanical properties of RSPS-ed ZrO2-based composites were investigated. The Phase evolution and phase content, as functions of temperature, were characterized using x-ray diffraction and FESEM/EDS analysis. The XRD studies showed that all primary ZrSiO4 was decomposed into ZrO2, ZrC, SiC, and SiO2 phases. The unreacted graphite or activated carbon was also identified in the samples. Finally, the hardness and flexural strength of the composites were examined by Vickers hardness and 3-point bending strength tests. The results indicate that the SPS-ed ZrSiO4 + Activated Carbon composite (ZAS-3) has the best mechanical properties. A density of 2.87 ± 0.05 g/Cm3, an open porosity of 0.02%, a bending strength of 132.4 ± 11.2 MPa and a hardness of 9.86 ± 1.1 GPa were estimated for the SPS-ed ZrSiO4 + Activated Carbon mixture of powders at 1600°C.

Influence of HAP on the Morpho-Structural Properties and Corrosion Resistance of ZrO2-Based Composites for Biomedical Applications

In the present work, ZrO2-based composites were prepared by adding different amounts of antibacterial magnesium oxide and bioactive and biocompatible hydroxyapatite (HAP) to the inert zirconia. The composites were synthesized by the conventional ceramic processing route and morpho-structurally analyzed by X-ray powder diffraction (XRPD) and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS). Two metallic dental alloys (i.e., Ni–Cr and Co–Cr) coated with a chitosan (Chit) membrane containing the prepared composites were exposed to aerated artificial saliva solutions of different pHs (i.e., 4.3, 5, 6) and the corrosion resistances were investigated by electrochemical impedance spectroscopy technique. The obtained results using the two investigated metallic dental alloys shown quasi-similar anticorrosive properties, having quasi-similar charge transfer resistance, when coated with different ZrO2-based composites. This behavior could be explained by the synergetic effect between the diffusion process through the Chit-composite layer and the roughness of the metallic electrode surface.

Structure, phase composition and properties of vacuum pressureless sintered ZrO2-based composites reinforced with carbon nanotubes

In this work, composites based on 3 mol. % yttria-stabilized zirconia (3YSZ) with additives of 1, 5 and 10 wt. % multi-walled carbon nanotubes (MWCNT) were investigated. Samples were obtained by cold pressing followed by vacuum pressureless sintering at a temperature of 1500 °C. It was found that MWCNTs retain their structure after high-temperature sintering, they are located along the zirconia grain boundaries and they lead a grain refining effect for zirconia matrix. Nanotubes can significantly affect the phase composition of composites. Additives 5 wt. % and 10 wt. % MWCNT partially limits the monoclinic-tetragonal phase transition of ZrO2 and leads to the formation of a new phase of zirconium carbide. An increase of MWCNTs content in composites leads to a smooth decrease of the relative density from 99.2 % to 81.2 %. To obtain fully dense 3YSZ/MWCNT composites, longer sintering at higher temperatures is required compared to the conditions for sintering 3YSZ ceramics without additives.

Nanocrystalline Powders in ZrO2–Y2O3–CeO2–Al2O3–CoO System for Microstructural Design of ZrO2-Bazed Color Composites

The changes in the physical–chemical properties of ZrO2–Y2O3–CeO2–Al2O3–CoC nanocrystalline powders, produced by hydrothermal synthesis combined with mechanical mixing, are investigated. It is found out that, in the presence of cobalt compounds, the temperatures of phase transformations of ZrO2-based solid solution decrease. The powders are characterized by increased activity to sintering. AMIS software is used for processing the research results on the powder morphology. The flame atomic absorption spectrometry is used to confirm that the probability of cobalt wash-out from ZrO2–Y2O3–CeO2–Al2O3–CoO composites does not exceed 0.2 mg/l. The research results will be used for the microstructural design of blue ZrO2-based composites.

Fabrication of ZrO2-based nanocomposites for transuranic element-burning inert matrix fuel

Abstract ZrO2-based composites reinforced with 6.5 vol.% of carbon foam, carbon fiber, and graphite were fabricated using spark plasma sintering, and characterized using scanning electron microscopy and X-ray diffractometry. Their thermal properties were also investigated. The microstructures of the reinforced composites showed that carbon fiber fully reacted with ZrO2, whereas carbon foam and graphite did not. The carbothermal reaction of carbon fiber had a negative effect on the thermal properties of the reinforced ZrO2 composites because of the formation of zirconium oxycarbide. Meanwhile, the addition of carbon foam had a positive effect, increasing the thermal conductivity from 2.86 to 3.38 W m−1 K−1 at 1,100°C. These findings suggest that the homogenous distribution and chemical stability of reinforcement material affect the thermal properties of ZrO2-based composites.

Comparative studies on zirconia and graphene composites obtained by one-step and stepwise electrodeposition for deoxyribonucleic acid sensing

In this paper, the comparison of two kinds of electrochemically reduced graphene oxide (ERGNO) and zirconia composites, obtained by one-step (ZrO2–ERGNO) and stepwise (ZrO2/ERGNO) electrodeposition for DNA sensing, is systematically studied. The resulting composites were characterized by scanning electron microscopy, cyclic voltammetry, and differential pulse voltammetry. The results indicated that the ZrO2–ERGNO presented fine globular nanostructure. However, ZrO2/ERGNO presented agglomerate massive microstructure due to the absence of the oxygen-containing groups of graphene oxide, confirming the oxygen-containing groups provided a better affinity for the deposition of ZrO2. Due to the strong binding of the phosphate groups of DNA with the zirconia film, DNA probes were attached on the ZrO2-based composites. ZrO2–ERGNO/Au owning fine nanostructure presented larger surface area than microstructured ZrO2/ERGNO/Au. Moreover, compared with microstructured ZrO2/ERGNO, the nanostructured ZrO2–ERGNO provided more accessible space for immobilized DNA probe hybridization with target sequence, which consequently resulted in higher hybridization efficiency. Therefore, the ZrO2–ERGNO was chosen for fabricating DNA sensor with a limit of detection 1.21×10−14molL−1.

Two-D Analysis of the Thermo-Mechanical Properties of ZrO2-Based Composites

In this paper, a fast and efficient tool for predicting a set of physical and mechanical composite properties such as thermal expansion coefficients, thermal and electrical conductivity, stiffness, and thermal residual stress is developed based on the analysis of a representative volume of ZrO2-based composite. Such an analysis allows an engineer to assess the mechanical and physical properties to design an optimum composite composition in terms of advantageous mechanical properties and at the same time a good electrical discharge machining performance. Thermal residual stresses in the constituent phases and thermal and electrical conductivity of ZrO2-based composites are assessed by a Finite Element (FE) model using 2 dimensional SEM micrographs. The FE models are verified by comparing numerically calculated results with experimentally measured data.

Impact of wire-EDM on dry sliding friction and wear of WC-based and ZrO2-based composites

Abstract Linearly reciprocating sliding wear experiments on WC-Co and WC-Ni cemented carbides and ZrO2-WC, ZrO2–TiCN and ZrO2–TiN composites with different surface finishes corresponding to sequential wire-EDM or grinding/polishing have been performed using an ASTM G133 system with WC-6 wt%Co cemented carbide as counter body. The WC-based alloys contained 6 up to 12 wt% of binder, whereas the amount of secondary phase for the ZrO2-based composites was 40 vol.% pin-on-plate testing was carried out in unlubricated circumstances at constant oscillating frequency with fixed displacement amplitude and normal contact loads ranging between 15 and 35 N. 3D topography mapping and volumetric quantification of the wear tracks was obtained by surface profilometry. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy were employed to observe morphological and chemical features of worn surfaces and wear debris. The identified wear mechanisms are discussed. The highest wear resistance was encountered with the WC-Ni alloy, whereas the ZrO2–TiN composite displayed the lowest wear resistance. Wire-EDM surfaces displayed higher friction and wear compared to their ground/polished equivalents, especially during running-in. The inferior wear resistance of wire-EDM’ed samples could be correlated to 3-point bending tests, revealing a considerable decrease in flexural strength compared to ground samples.

Impact of Wire-EDM on Tribological Characteristics of ZrO2-based Composites in Dry Sliding Contact with WC–Co-Cemented Carbide

The effect of surface conditions and secondary phase addition on the dry sliding friction and wear characteristics of five yttria-stabilized ZrO2-based composites with 40 vol% WC, TiCN or TiN was investigated using an ASTM G133 pin-on-flat sliding contact configuration. WC–6wt%Co-cemented carbide pins were used as mating material. The friction and wear level were higher for wire-EDMed ZrO2-based composites compared to their equivalent ground specimens. This finding could be correlated to flexural strength measurements, revealing strong discrepancy between wire-EDMed and ground surfaces. The most favorable tribological characteristics were encountered with ZrO2–WC composites compared to ZrO2–TiCN and ZrO2–TiN grades.

Tribological behavior of wire-EDM’ed ZrO2 composites and cemented carbides

Five ZrO2-based composites (ZrO2-WC, ZrO2-TiCN and ZrO2-TiN grades) and five WC-Co cemented carbide grades were machined by wire-EDM and tested on a linearly reciprocating sliding pin-on-flat tribometer PLINT TE77 in dry conditions against WC-6wt%Co pins. Measurement of friction coefficient and penetration depth due to wear was performed continuously. The results revealed a strong influence of the secondary phase, surface finish, chemical and mechanical properties on the tribological characteristics of the ZrO2-based composites and cemented carbides. WC10Co(Cr/V) displayed superior wear resistance compared to the other grades. The lowest coefficient of friction was encountered with ZrO2-WC.

Y2O3 and Nd2O3 co-stabilized ZrO2-WC composites

Y2O3 + Nd2O3 co-stabilized ZrO2-based composites with 40 vol% WC were fully densified by pulsed electric current sintering (PECS) at 1350 °C and 1450 °C. The influence of the PECS temperature and Nd2O3 co-stabilizer content on the densification, hardness, fracture toughness and bending strength of the composites was investigated. The best combination of properties was obtained for a 1 mol% Y2O3 and 0.75 mol% Nd2O3 co-stabilized composite densified for 2 min at 1450 °C under a pressure of 62 MPa, resulting in a hardness of 15.5 ± 0.2 GPa, an excellent toughness of 9.6 ± 0.4 MPa.m0.5 and an impressive 3-point bending strength of 2.04 ± 0.08 GPa. The hydrothermal stability of the 1 mol% Y2O3 + 1 mol% Nd2O3 co-stabilized ZrO2-WC (60/40) composites was compared with that of the equivalent 2 mol% Y2O3 stabilized ceramic. The double stabilized composite did not degrade in 1.5 MPa steam at 200 °C after 4000 min, whereas the yttria stabilized composite degraded after less than 2000 min. Moreover, the (1Y,1Nd) ZrO2-WC composites have a substantially higher toughness (~9 MPa.m0.5) than their 2Y stabilized equivalents (~7 MPa.m0.5).

Influence of electrical discharge machining on tribological behavior of ZrO 2–TiN composites

ZrO 2-based composites containing electro-conductive secondary phases have successfully proven their feasibility for electrical discharge machining (EDM) in demineralised water. Samples of ZrO 2–TiN composites with 40 vol.% TiN were self-developed and manufactured by wire-EDM. The effect of the surface finishing condition on the tribological characteristics was investigated by comparing the reciprocative sliding friction and wear response of polished and fine wire-EDM’ed flat samples against WC–Co cemented carbide pins using a Plint TE77 tribometer. The experimental results revealed that the surface finishing operation exhibits a significant impact on wear resistance and frictional behavior of the ZrO 2–TiN composites. Correlations between wear volume, wear rate and coefficient of friction on the one hand and surface conditions on the other hand were derived.

EDM machinability and frictional behavior of ZrO2-WC composites

Zirconium dioxide (ZrO2)-based composites with WC addition are demonstrated to be suitable for electrical discharge machining (EDM) in deionized water. ZrO2-based composites with 40 vol. % WC, obtained from distinctive WC powder sources, were produced in order to derive correlations between material removal rate (MRR), surface finish, wire EDM parameters and material properties. Dry reciprocating sliding experiments on wire-electrical discharge machined ZrO2-WC composite samples against WC-Co cemented carbide, performed using a pin-on-plate testing rig, revealed a significant influence of the microstructure of the secondary WC-phase on wire EDM behavior and frictional characteristics.

Sliding Wear of Electrically Conductive ZrO2−WC Composites Against WC–Co Cemented Carbide

ZrO2-based composites with WC addition can be successfully machined by electrical discharge machining (EDM) in demineralised water. ZrO2 composites with 40 vol.% WC were produced from nanocrystalline and micrometre sized WC starting powders in order to compare their tribological behaviour. Friction and wear data are obtained on wire-EDM’ed ZrO2–WC composite flats sliding against a WC–Co cemented carbide pin using a small-scale pin-on-plate testing rig. Correlations between wear volume, wear rate and friction coefficient on the one hand and material properties and test conditions on the other hand were elucidated. The experimental results revealed that the grain size of the electro-conductive WC-phase exhibits a strong influence on the friction and wear behaviour of the ZrO2-based composite.

Production and characterization of ZrO2 ceramics and composites to be used for hip prosthesis

Tetragonal ZrO2 polycrystalline (TZP) ceramics with varying yttria and ceria content (2–3 mol%) and distribution (coated or co-precipitated), and varying second phase content Al2O3 were prepared and investigated by means of microstructural analysis, mechanical properties, and hydrothermal stability, and ZrO2-based composites with 35–60 vol% of electrical conductive TiN particles were developed. The effects of stabilizer content and means of addition, powder preparation, sintering conditions, and grain size have been systematically investigated. Fully dense Y-TZP ceramics, stabilized with 2–3 mol% Y2O3, 2 wt% Al2O3 can be achieved by hot pressing at 1,450 °C for 1 h. The hydrothermal stability increased with increasing overall yttria content. The jet-milled TiN powder was used to investigate the ZrO2–TiN composites as function of the TiN content. The experimental work revealed that fully dense ZrO2–TiN composites, stabilized with 1.75 mol% Y2O3, 0.75 wt% Al2O3, and a jet-milled TiN content ranging from 35 to 60 vol% could be achieved by hot pressing at 1,550 °C for 1 h. Transformation toughening was found as the primary toughening mechanism. The decreasing hardness and strength could be attributed to an increasing TiN grain size with increasing TiN content, whereas the decreasing toughness might be due to the decreasing contribution of transformation toughening from the tetragonal to monoclinic ZrO2 phase transformation. The E modulus increases linearly with increasing TiN content, whereas the hydrothermal stability increases with addition of TiN content.

ZrO<sub>2</sub>-TiN Composites

1.75 mol % Y2O3-stabilized ZrO2-based composites with 35-95 vol % TiN were fully densified by hot pressing for 1 hour at 1550°C under a load of 28 MPa. The TiN grain size was found to increase with increasing TiN content, resulting in a decreasing hardness and strength. The best mechanical properties, i.e., an indentation toughness of 5.9 MPa.m1/2 in combination with a Vickers hardness of 14.7 GPa and an excellent bending strength of 1674 MPa were obtained for the composites with 40 vol % TiN. The active toughening mechanisms were identified and their contribution to the overall composite toughness is discussed. Transformation toughening was found to be the primary toughening mechanism in all investigated composites.

Microstructure and mechanical properties of sinter-HIPed ZrO2–ZrB2 composites

Abstract In the area of the advanced materials, there exists a persistent need to develop tougher, stronger and harder ceramics. In the present work, we report the microstructure and properties of hard and tough ZrO2 composites reinforced with 30 vol.% ZrB2 particulates, processed using sinter-HIPing (Hot Isostatic Pressing) route. The influence of ZrO2 matrix composition (Y2O3 content) on the microstructure and mechanical properties of the sinter-HIPed composites is investigated. While the presintering was carried out in argon at 1400 °C, subsequent HIPing of presintered samples was carried out at 1400 °C for 1 h under 110 MPa argon pressure. The fully dense sinter-HIPed microstructure is characterized by the dispersion of ZrB2 particles (1–3 μm) in submicron ZrO2 matrix. An important outcome of the present work is that an excellent combination of hardness (upto ∼20 GPa) and toughness (upto ∼18 MPa m1/2) is measured, for the first time, in ZrO2-based composites. The microstructure-property correlation is discussed with particular importance to understand the underlying microstructural reasons for the enhanced mechanical property. The measurement of fracture surface m-ZrO2 content indicates that the transformation toughening phenomenon is an active mechanism for toughness enhancement. Additionally, crack deflection toughening by ZrB2 particulates also contribute to toughening of the composite.

Rapid Rate Sintering of Nano-grained ZrO2-based Composites Using Pulse Electric Current Sintering Method

Rapid Rate Sintering of Nano-grained ZrO2-based Composites Using Pulse Electric Current Sintering Method