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Abrasive jet machining (AJM) process is commonly used for cutting and drilling of brittle materials in which the phenomenon of material removal can be considered as mechanical erosion by the impingement of high-velocity abrasives. The focus of this research is to compare the performance and economic benefits of recently developed hot abrasive jet machining (hot-AJM) with traditional AJM techniques when machining zirconia ceramic using silicon carbide (SiC) grain particles. The modified AJM employed abrasive air jet (combination of hot abrasive and compressed air) to strike on the work surface for material erosion. Briefly, the cutting performance is investigated by comparing the technological characteristics like material removal rate, machining cost, and taper angle of the developed hole. Abrasive grain size, nozzle pressure, and stand-off distance are considered as the variable factors for machining trials in accordance with the design of experiments. The usage of hot abrasives in AJM improved the material erosion owing to the occurrence of plastic deformation followed by deep chipping on the machined surfaces. From the results, it was observed that the hot-AJM outperformed the normal AJM with regard to improved material removal, reduced dimensional deviation of hole and minimal machining cost. According to the findings of the cost assessment, the machining of zirconia ceramic using hot-AJM was more cost-effective than using normal AJM since it resulted 25% reduction in the total cost of production. The overall machining cost expenditure per unit in hot-AJM was lower (INR 123.12) than expenditure in traditional AJM (INR 153.47). Machining with hot-modified AJM, compared to normal AJM, offers a more techno-economically viable solution for enhancing machinability.

The friction and wear of silicon nitride (Si₃N₄) against silicon nitride (Si₃N₄) and zirconia (Y–TZP) and chilled cast iron and Alumina sliding under dry friction at room temperature conditions were investigated with pin-on-disk tribometer at sliding speed of 0.56ms^-1 and normal load of 50N, 80N, respectively. Based on the variety regulation of the wear maps, the wear mechanisms of the two couples were analyzed. Get the result of friction coefficient and maps of wear Rate of the Pin and the Disk. The results of comparing this couple is Si₃N₄/ chilled cast iron < Si₃N₄/ ZrO₂< Si₃N₄/ Si₃N₄< Si₃N₄/ Al₂O₃.

Amorphous zirconium oxide (a-ZrO₂) thin films were prepared onto fuzzed quartz substrates by ion beam sputtering deposition (IBSD) method in (Ar +O₂) gas mixture. Optical parameters of the films were evaluated by laser ellipsometry (λ = 632.8 nm) and optical transmission measurements. Structural parameters were studied by XRD measurements. Variation of refractive index and film thickness have been defined as a function of time of high-temperature annealing at T = 900°C. Formation of monoclinic zirconium oxide (m-ZrO₂) nanocrystals with diameter of ~60 nm embedded into a-ZrO₂ matrix has been found by XRD analysis after long-time annealing.

Zirconium oxynitride films have recently received much attention because their properties may gradually be changed by varying the concentration of N, O and Zr constituents during processing. Here, we reported zirconium oxynitride films prepared by RF reactive magnetron sputtering technique. The films were deposited by different targets: ZrO₂ and ZrN with the variation of nitrogen and oxygen flow rate. To explore whether the N content could be gradually incorporated into the films, two series of samples were prepared: one was prepared by the ZrO₂ target with the variation of the nitrogen flow rate; the other was prepared by the ZrN target with the variation of the oxygen flow rate. The composition and structure of the films were investigated by XPS, EDS and XRD techniques. XPS results show that when the ZrO₂ material was used as target the concentration of N was highly dependent on the flow rate of nitrogen, while the Zr concentration gradually decreased with the increase of N concentration; ZrO${}_x$N${}_y$ and ZrO were formed. However, for ZrN used as target, the fresh film of the sample comprised of O and Zr elements without N detected. When the N₂ was introduced as reactive gas with oxidized ZrN target, ZrO${}_x$N${}_y$ film with a certain content of N was formed.

Thermal barrier coatings (TBC) are finding increasing applications in aeronautical, chemical, metallurgy industries, etc. As a ceramic material, ZrO₂ is one of the most widely used for TBCs owing to its excellent shock resistance, low thermal conductivity and relatively high coefficient of thermal expansion (CTE). In this paper the thermomechanical properties of ZrO₂ and the evolution of ZrO₂-TBCs are reviewed. The failure mechanism of TBCs and corresponding methods for lengthening the lifetime of TBCs are discussed. The advantages and disadvantages of graded thermal barrier coatings (GTBC) as well as the problems to be solved in fabricating advanced TBCs are elucidated.

Surface composites are developed on Mg RZ 5 alloy by friction stir processing. During FSP, hard reinforcements are introduced into the matrix of RZ 5 alloy and dispersed uniformly by mechanical stirring action. The reinforcements dispersed were boron carbide, carbon nanotubes (multi-walled) and an 80:20 mixture of zirconia and alumina particles. Dynamic recrystallization and grain boundary pinning action by reinforcement particles resulted in the generation of fine-grained surface composites. Corrosion characteristics of the base material and the surface composites are studied by potentiodynamic polarization technique. The corrosion rates estimated for the surface composites are found to be far lesser than the base material while their polarization resistances were higher than the base material. Among all surface composites, B₄C particle reinforced surface composites exhibited the lowest corrosion rate of $\sim$15 mpy. Reduction in the corrosion rate of the surface composites is influenced by fine-grained microstructure and presence of harder reinforcement particles.

Zirconia and zirconia toughened alumina (ZTA) are widely used for biomedical applications. Owing to the superior mechanical and bio-compatible properties of ZTA, it is now gaining more importance over zirconia, as it has the profound strength of zirconia and alumina. This study examines the tribological behavior of Zirconia and ZTA balls sliding against a Ti6Al4V disc using the Ball-on-disc (BOD) Tribometer. The effect of loads and bio-lubricants influencing the tribological behavior is investigated for a sliding distance of 2km using BoD Tribometer. The friction and wear coefficients are examined under these loading and lubrication conditions. Five bio-lubricants considered for the tribological study of biomaterials include ringer’s solution, phosphate buffer saline (PBS), distilled water, NaCl 0.9% saline solution and sesame oil. The result showed that ZTA had a lower coefficient of friction (CoF) value of 0.34 for NaCl bio-lubricant. The ZTA and zirconia exhibited the least wear coefficient values under sesame oil lubrication. Overall, ZTA had better CoF under high loads for PBS, distilled water and sesame oil bio-lubricants. However, zirconia exhibited a better wear coefficient under all loads and lubrication conditions.

The influence of alumina addition on mechanical behavior and fracture properties of all-ceramics zirconia dental materials was evaluated. Samples containing 0, 5, 10, 15 wt.% Al₂O₃ particles were prepared by cold isostatic pressing (200 MPa) and sintered at 1500°C for 5 h. Commercial powders were investigated by bulk density and phase formation using Archimedes principle and X-ray diffraction (XRD). Bending strength and fracture load were determined at room temperature by three-point bending test. In order to study the fracture, we took points on the crack path under microscope, plotted points on coordinates and used software "Origin" to general fitting curves. Scanning electron microscopy (SEM) and atomic force microscope (AFM) were introduced to estimate the particle size of powders and observe the fracture surfaces. No density difference was observed for a given alumina content. The majority phases of ceramics were t-zirconia and α-alumina before breaking while m-zirconia, t-zirconia and α-alumina coexisted on the cross section of cracked samples. Zirconia containing 10% alumina had the best mechanical properties, the most tortuous crack propagation and the least obvious crack distribution. This observation may provide a reference for the materials selection, shape design and production process of all-ceramic crown and bridge.

Plastic deformation and wear of the ultra-high molecular weight polyethylene (UHMWPE) insert have been pointed out as major issues relating to the long-term stability of an orthopaedic implant. The deposition of protective hard, tough and well-adhered zirconia (ZrO₂) thin films directly on the surface of the UHMWPE component via the Pulsed Plasma Deposition (PPD) technique has been already demonstrated to be a feasible way to approach this problem. In the current study, the tribo-mechanical properties of ZrO₂-coated UHMWPE with respect to pristine UHMWPE were investigated in detail. Specifically, strength to local plastic deformation, indentation work portioning and creep behavior were evaluated through nanoindentation and micro-scratch tests. Further, preliminary wear data (i.e., rate and volume) were obtained by tribology tests mating coated and pristine UHMWPE with an alumina ball under dry conditions. The results of the mechanical tests evidenced a strong reduction of plastic deformation under both normal and tangential local loads and a drop of the 80% of the creep phenomenon for coated UHMWPE compared to pristine UHMWPE. Despite tribological tests showed similar wear data for coated and pristine UHMWPE, a different wear mechanism was detected between the two groups. The reported results supported the possibility to pursue this novel approach of depositing ZrO₂ thin film to protect the UHWMPE insert and enhance the long-term stability of the orthopaedic implants.

Wear of bearing couples is one of the major concerns in artificial hip implantation. To minimize the wear of hip bearing surfaces, several new materials have been introduced and tested including metal-on-metal, ceramic-on-ceramic and hard-on-hard combinations. The present study involves prediction of wear on ultra-high molecular weight polyethylene (UHMWPE) cup against Co–Cr, alumina and zirconia femoral head by applying the three-dimensional (3D) physiological loads as well as angular motions on these bearing couples to calculate the contact pressure using finite element concepts. The linear and volumetric wear of bearing surfaces increase with increase in gait cycles. Overall, the Zirconia–UHMWPE combination showed least wear, when compared with Alumina–UHMWPE and Co–Cr–UHMWPE combinations. The present study also revealed that the Zirconia–UHMWPE combinations showed less volumetric wear than the Alumina–Alumina bearing which is at present used in artificial hip resurfacements.

Cubic or tetragonal zirconia thin films of transparent and 100 nm thickness were selectively formed on a quartz glass substrate by heat-treating the molecular precursor films involving Zr(IV) complexes of nitrilotriacetic acid, at 500${}^{\circ }$C in air for 1 h. A precursor solution was prepared by a reaction of the ligand and zirconium tetrabutoxide in alcohol under the presence of butylamine. By the addition of H₂O₂ or H₂O into the solution, the spin-coated precursor films were converted to cubic zirconia thin films by the abovementioned procedure. Further, the identical phase was produced also in the case of the electro-sprayed precursor film which was formed by an addition of H₂O₂ into the solution. On the other hand, the tetragonal zirconia thin film was obtained from a precursor film formed by using a solution dissolving the original Zr(IV) complex of the ligand, without H₂O₂ nor H₂O. The crystal structure of all thin films was determined by using both the X-ray diffraction (XRD) patterns and Raman spectra. Thus, the zirconia thin films of both crystals could be facilely and selectively obtained with no use of hetero-metal ion stabilizers. The XPS spectra of the thin films show that the O/Zr ratio of the cubic phase is 1.37 and slightly larger than tetragonal one (1.29), and also demonstrate that the nitrogen atoms, which may contribute to stabilize these metastable phases at room temperature, of about 5−7 atomic% was remained in the resultant thin films. The adhesion strengths of cubic zirconia thin film onto the quartz glass substrate was 68 MPa and larger than that of tetragonal one, when the precursor films were formed via a spin coating process. The optical and surface properties of the thin films were also examined in relation to the crystal systems.

We have systematically studied the composition dependence of the dielectric properties of Zr_1-xAl_xO_2-x/2 and Zr_1-xSi_xO₂. An essentially linear variation of the static dielectric constant, ε_s, was observed as a function of composition, x, for compositions rich in the p-block element, i.e., x > 0.4, for both chemical systems. However an abrupt change in ε_s is found near x ≈ 0.35, associated with the onset of crystallinity in as-deposited films. Breakdown fields do not show a comparable composition dependence. Measurements of the index of refraction at optical frequencies, combined with a simple Clausius–Mossotti interpretation, indicates that low-frequency (ionic) contributions to the polarizability exhibit systematic deviation with respect to values linearly interpolated from the endmembers. These trends are not consistently affected by the presence of crystalline order, but are related to changes associated with heterogeneous local oxygen coordination and bonding.

Conventional and nanostructured zirconia coatings were deposited on In-738 Ni super alloy by atmospheric plasma spray technique. The hot corrosion resistance of the coatings was measured at 1050°C using an atmospheric electrical furnace and a fused mixture of vanadium pent oxide and sodium sulfate respectively. According to the experimental results nanostructured coatings showed a better hot corrosion resistance than conventional ones. The improved hot corrosion resistance could be explained by the change of structure to a dense and more packed structure in the nanocoating. The evaluation of mechanical properties by nano indentation method showed the hardness (H) and elastic modulus (E) of the YSZ coating increased substantially after hot corrosion.

In this paper, a method of electronic conductivity measurement is presented. It combines two well known methods of electrochemistry: cyclic voltammetry and chronoamperometry. This DC technique uses the Hebb–Wagner approach to block ionic conduction (when steady state conditions are reached) and allows electronic conduction of solid electrolytes to be determined. In order to get short diffusion times, a micro contact is used as an ion blocking electrode. However, as the electronic conduction in electrolytes is and should be very low, the current is also very low, typically some tens of nanoamps. Thus, the heating system inevitably generates noise problems that are solved using a median filter. As opposed to other related work, our system allows the determination of the conductivities without any preliminary smoothing or fitting of the curves (since the noise is strongly reduced). Some results with oxygen ion conductors are also given.

Solid-oxide electrolytes develop electrical potential when their two opposite electrodes are exposed to the different oxygen potential. When an electrolyte is exposed to the same ambient gas, a potential may develop due to the different catalytic behavior of two electrodes to ambient gas. Such a sensor is called as a non-equilibrium e.m.f.-type sensor or mixed potential sensor. In this study, to improve the sensitivity of the sensor to reducing gases (CO, H₂), transition metal oxide (T.M.O.) was added to one of two SnO₂ electrodes of the sensor. T.M.O. addition was expected to change the catalytic behavior of the electrode and to change e.m.f. values. The Co addition increased the e.m.f. of working electrode (T.M.O.-added SnO₂) in air, implying the enhanced oxygen adsorption. Fe addition showed the reverse effect. The addition of T.M.O. to SnO₂ was also effective in changing the e.m.f. values in H₂ balanced by air. Fe and Ni addition exhibited decreased e.m.f. in H₂ from that in air. Thus, Fe and Ni addition improved the catalytic activity for H₂ oxidation. On the other hand, the catalytic activity for H₂ oxidation was suppressed by Co addition. However, no appreciable change in CO sensitivity was obtained with the T.M.O. addition.

Alumina + zirconia (PRD-166) and Saphikon fibers reinforced glass matrix composites with and without a SnO₂ interphase were prepared by slurry infiltration and their mechanical characteristics were evaluated. Longitudinal bend strength increased with volume fraction of fibers in both PRD-166/glass and PRD-166/SnO₂/glass matrix composites. PRD-166/glass matrix composites failed in a brittle manner whereas PRD-166/SnO₂/glass matrix composites exhibited non-planar failure with crack deflection and fiber bridging as major toughening mechanisms. Saphikon/SnO₂/glass matrix composites failed in a tough manner with extensive fiber pullout. The difference in the failure mode between PRD-166/SnO₂/glass and Saphikon/SnO₂/glass matrix composites was due to fiber roughness.

A method of fabricating ZrO₂-mullite composites based on plasma spraying of alumina and zircon mixtures has been proposed and developed (3Al₂O₃+2ZrSiO₄ = 2Al₂O₃·2SiO₂ +2ZrO₂). The feedstock is prepared by a combination of mechanical alloying which allows formation of fine grained, homogeneous solid solution mixtures and following plasma spheroidization that yields rapid solidified microstructures and enhanced compositional homogeneity. The homogeneity is further realized when the plasma spray coatings are formed at last, and mullite formation temperature is expected to decrease by the unique preparation technique adopted in this study. Microstructure of the coatings were studied using the transmission electron microscope (TEM), and the mechanical properties such as hardness and fracture toughness of the coatings were measured with the indentation technique. The relationship between the mechanical properties and microstructure were investigated.

To evaluate the effect of silica coating with Sol-Gel processing on the bonding strength between dental high-strength ceramic and composite resin. Method: 80 zirconia ceramic discs were randomly divided into four groups (n=20 in each group), and received different surface treatments, then the shear bonding strength of the ceramics and composite resin were calculated. Results: The three groups with silica coating had a higher bonding strength than the un-coated group with a significant difference (P<0.05); group C had the highest bonding strength (P<0.05). There were no significant differences between group B and group D (P>0.05). Conclusion: Silica coating followed by silane coupling agent treatment can significantly increase bonding strength between dental ceramic and composite resin; 30% silica sol may be more effective.

Ceramic bearing surfaces have been used over the last 25 years as a clinical solution to the polyethylene wear debris which has been attributed as the major cause of aseptic loosening in total hip arthroplasties. Research has continued over the last 15 years to transpose the technology from the hip to the knee. Monolithic ceramic knee devices have been implanted, mainly in Japan, but the problem of the femoral fixation has remained. The improvement in the polyethylene materials, coupled with the more congruent knee designs, has focused the major issue to wear particle generation as opposed to fatigue or delamination.

The focus of the Brite EuRam project “Advanced Metal to Ceramic Joining Techniques To Optimise low-friction knee prostheses” was to address the issue of fixation in conjunction with the optimum ceramic bearing surface. This was achieved by the development of a biocompatible active alloy braze for joining medical grade Y-TZP zirconia to titanium alloy. Through optimised chemistry and processing conditions a high strength active alloy braze joint was obtained that satisfied all biological and mechanical requirements.

Extensive Finite Element analysis, mechanical, fatigue, wear and compression strength testing were performed to validate the new concept.

To examine the friction and wear characteristics of ceramic materials under thin film mixed lubrication for ceramic-on-ceramic artificial hip joints, uni-directional wear tests of ceramic-on-ceramic sliding pairs lubricated with distilled water were carried out by the roller-on-flat tester. The friction and wear in the rubbing pairs of alumina of the high purity and tetragonal zirconia polycrystals (Y-TZP) were examined in the combination of the same materials and different materials. The rubbing tests under higher sliding speed of 94 mm/s showed very low friction and wear even under high contact pressure conditions, probably due to the protection by the hydrodynamic film formation. In the contrary, under slow speed of 19 mm/s, the significant adhesive wear with high friction was observed. The sliding of Y-TZP against itself exhibited the higher wear than the alumina against itself. The combinations of alumina and Y-TZP showed the intermediate wear behavior. Furthermore, it is noticed at medium speeds that some wear with removal or fracture of grains was observed particularly on the stationary specimens for alumina-on-alumina pair. The influence of operating conditions and material combinations on friction and wear behavior is discussed from the viewpoint of wear and friction maps.