Spherical Zirconia Particles Research Articles

Experimental Investigation of Tribological Properties of Two Fully Formulated Engine Oils with Additional Nanoscale Spherical Zirconia Particles

Decreasing harmful emissions of vehicle engines is becoming more and more challenging due to stricter standards. A possible solution is to improve the tribological attributes of lubricants, which can be achieved through the application of appropriate additives. According to preliminary studies conducted by the authors, ZrO2 (zirconium-dioxide) nano-sized ceramic particles as lubricant additives have overwhelmingly positive tribological attributes in the presence of non-metallic superficial materials. Additive concentration, as well as cross-effects with other additives were investigated in order to determine a formulation resulting in optimal tribological attributes. In this paper, the experimental investigation of ZrO2 nano-ceramic powder as a lubricant additive is presented. The tribological performance of individually samples were experimentally investigated on a ball-on-disc translational tribometer. The experiments revealed an optimal additive content of 0.3 wt%. Increasing the quantity of additives further ruined friction and wear properties of the examined tribological system.

Effect of Porous Zirconia Coating on Human Gingival Fibroblasts and Its Mechanism.

Gingival fibroblasts play an important role in the constitution of soft tissue attachment. This study aims to investigate whether porous zirconia coating has a positive effect on promoting human gingival fibroblast attachment. The porous zirconia coating was loaded on zirconia surface by the dip coating method, surface morphology and composition were confirmed by scanning electron microscope and energy dispersive spectrometer; Tested the tensile bond strength by universal testing machine; Tested the surface roughness by roughness analyzer; Human gingival fibroblast proliferation, integrin β1 and F-actin immunofluorescence staining explored the influence of porous zirconia on the adhesion and proliferation of human gingival fibroblast. Zirconia0.2 group showed spherical zirconia particles with diameters of 3-8 μm are distributed on the surface; The bonding strength of zirconia particle coating group reached 16.1±0.1 MPa, and the surface roughness was 0.715±0.091 μm; In comparison with control group (P < 0.01), the percentage of human gingival fibroblasts adhering to zirconia was markedly higher. In zirconia group, integrin-β1 and F-actin fluoresced more obvious than in control group. Porous zirconia coating can form a porous structure on the surface and the porous structure can promote the attachment and proliferation of human gingival fibroblast, it will be more beneficial for soft tissue early sealing.

Solvothermal Synthesis of Spherical Zirconia Particles Having Meso-Macro Bimodal Pore Structures

By the thermal reaction of tetrakis(acetylacetonato)zirconium in 1,4-butanediol at 300 °C for 2 h, spherical zirconia particles with large surface areas and large pore volumes both in the meso and ...

Characterization and enhancement of physico-mechanical properties of glass ionomer cement by incorporating a novel nano zirconia silica hydroxyapatite composite synthesized via sol-gel

In restorative dentistry, there has been a growing shift towards using nanoparticles dispersed in the polymer matrix to improve properties of dental restorative materials. A new nano zirconia–silica–hydroxyapatite (nanoZrO2–SiO2–HA) was synthesized by one-pot synthesis and characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray (EDX) and dot mapping. The effect of addition of nanoZrO2–SiO2–HA to the conventional GIC (cGIC) on the compressive strength, flexural strength and surface roughness was also evaluated. The characterization studies confirmed that all particles were in the nanoscale range with spherical zirconia and silica particles embedded in the voids between rod-shaped HA crystallites. The nano particles were evenly and homogenously dispersed throughout the sample with high density patterns visible for zirconia, calcium and phosphorus. The incorporation of 5% nanoZrO2–SiO2–HA has resulted in considerable improvement in the compressive and flexural strengths of cGIC. The GIC 5% nanoZrO2–SiO2–HA exhibited an increase in compressive (144.12 ± 13.88 MPa) and flexural strength (18.12 ± 2.33 MPa) over cGIC which was statistically significant (p ≤ 0.05). It also demonstrated surface roughness profile (0.15 ± 0.029 μm) similar to that of cGIC (0.15 ± 0.019 μm). Therefore, the nanoZrO2–SiO2– HA can be a promising filler for GIC to be used as restorative dental material in high stress bearing areas

Characterization of ultralow thermal conductivity in anisotropic pyrolytic carbon coating for thermal management applications

Pyrolytic carbon (PyC) is an important material used in many applications including thermal management of electronic devices and structural stability of ceramic composites. Accurate measurement of physical properties of structures containing textured PyC layers with few-micrometer thickness poses new challenges. Here a laser-based thermoreflectance technique is used to measure thermal conductivity in a 30-μm-thick textured PyC layer deposited using chemical vapor deposition on the surface of spherical zirconia particles. Raman spectroscopy is used to confirm the graphitic nature and characterize microstructure of the deposited layer. Room temperature radial and circumferential thermal conductivities are found to be 0.28 W m−1 K−1 and 11.5 W m−1 K−1, corresponding to cross-plane and in-plane conductivities of graphite. While the anisotropic ratio of the in-plane to cross-plane conductivities is smaller than previous results, the magnitude of the smallest conductivity is noticeably smaller than previously reported values for carbon materials and offers opportunities in thermal management applications. Very low in-plane and cross-plane thermal conductivities are attributed to strong grain boundary scattering, high defect concentration, and small inter-laminar porosity. Experimental results agree with the prediction of thermal transport model informed by the microstructure information revealed by Raman spectroscopy.

Thermal oxidation of medical Ti6Al4V blasted with ceramic particles: Effects on the microstructure, residual stresses and mechanical properties

Roughening of Ti6Al4V by blasting with alumina or zirconia particles improves the mechanical fixation of implants by increasing the surface area available for bone/implant apposition. Additional thermal oxidation treatments of the blasted alloy have already shown to be a complementary low-cost solution to enhancing the in vitro biocompatibility and corrosion resistance of the alloy. In this work, the effects of oxidation treatment on a grit blasted Ti6Al4V biomedical alloy have been analysed in order to understand the net effect of the combined treatments on the alloy fatigue properties. Synchrotron radiation diffraction experiments have been performed to measure residual stresses before and after the treatments and microstructural and hardness changes have been determined. Although blasting of Ti6Al4V with small spherical zirconia particles increases the alloy fatigue resistance with respect to unblasted specimens, fatigue strength after oxidation decreases below the unblasted value, irrespective of the type of particle used for blasting. Moreover, at 700°C the as-blasted compressive residual stresses (700MPa) are not only fully relaxed but even moderate tensile residual stresses, of about 120MPa, are found beneath the blasted surfaces. Contrary to expectations, a moderate increase in hardness occurs towards the blasted surface after oxidation treatments. This can be attributed to the fact that grit blasting modifies the crystallographic texture of the Ti6Al4V shifting it to a random texture, which affects the hardness values as shown by additional experiments on cold rolled samples. The results indicate that the oxidation treatment performed to improve biocompatibility and corrosion resistance of grit blasted Ti6Al4V should be carried out with caution since the alloy fatigue strength can be critically diminished below the value required for high load-bearing components.

Processing and properties of a mica–apatite glass–ceramic reinforced with Y-PSZ particles

In this study, mica–apatite glass–ceramic was reinforced with 5, 10 and 15 wt.% partially stabilized zirconia (Y-PSZ). The composites were prepared via pressureless sintering, which was performed on the mixtures of zirconia particulates and two frits belonging to the fluoro-mica and apatite-based glasses. The sintered composites were characterized by scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS) and X-ray diffraction (XRD). Mechanical properties of the sintered samples such as bending strength, Vickers micro-hardness and fracture toughness were also investigated. The results showed that Y-PSZ dissolved in the residual glass and caused the formation of prismatic zircon crystals (ZrSiO 4) precipitated during the final stage of sintering. Spherical zirconia particles were also detected. Mechanical properties improved for composite containing 10 wt.% ZrO 2.

Ionic conductivity in directionally solidified Al 2O 3–ZrO 2(3% mol Y 2O 3) near eutectic composites

A systematic study of the relationship between microstructure, composition and conductivity of zirconia–alumina composites grown from the melt are reported in this article. Directionally solidified ZrO 2 (3 mol%Y 2O 3)–Al 2O 3 composites have been prepared with eutectic composition and enriched in zirconia. Growth conditions have been chosen to achieve homogeneous microstructures as much as possible. The shortest dimension of the zirconia particles ranged from 1 μm to below 80 nm. The total conductivity of these specimens has been measured indicating that the density of the Al 2O 3–ZrO 2 interphases is not relevant to the conductivity. The conductivity increases only slightly with growth rate and is somewhat larger than the conductivity expected for a homogeneous dispersion of spherical zirconia particles on insulating Al 2O 3, due to the preferential alignment along the growth direction. The conductivity in the eutectics (33.5 vol.% zirconia) is 1.2 × 10 − 3 Ω − 1 cm − 1 at 800 °C and can be increased 2.8 times in composites with + 12 vol.% excess zirconia when the growth conditions achieve the favorable microstructure.

Otrzymywanie i charakterystyka zywic epoksydowych napelnianych submikroskopowymi czastkami ditlenku cyrkonu

Summary — Submicron spherical zirconia particles were synthesized and used as a reinforcement for epoxy resins. In fact, recent developments indicate that a significant improvement in the thermoset polymer performance may be obtained by using submicron inorganic filler. In this paper, different composites with weight fraction of the filler in the range 1—5 % were prepared and characterized in terms of mechanical properties. A numerical model suitable for the description of such materials was set up and employed to estimate the properties as functions of the reinforcement content.

Ultrasonic Spray Pyrolysis for Synthesis of Spherical Zirconia Particles

This paper presents new findings on ultrasonic spray pyrolysis of zirconium hydroxyl acetate precursor drops whose sizes were precisely measured using laser light diffraction technique. Precursor concentration plays a predominant role in determination of product particle size. At 0.01 wt% precursor concentration, conventional spray pyrolysis at 750°C using precursor drops 5–8 μm in diameter, generated by an ultrasonic nebulizer at 2.66 MHz, yielded uniform spherical yttria‐stabilized zirconia (YSZ) particles 73 nm in diameter measured by scanning electron microscopy. The YSZ particle diameters were much smaller than those predicted by the one‐particle‐per‐drop mechanism. Under similar reaction conditions, the high‐throughput ultrasound‐modulated two‐fluid (UMTF) spray pyrolysis of larger precursor drops (28‐μm peak diameter) also yielded spherical dense particles; they were significantly smaller in size than those produced by the low‐throughput conventional ultrasonic spray pyrolysis of smaller drops (6.8‐μm peak diameter).

Making spherical zirconia particles from inorganic zirconium aqueous sols

Spherical zirconia particles were formed by coagulation of colloidal particles in zirconium aqueous sols followed by calcination. The zirconium sols were derived from zirconium oxychloride aqueous solutions by adjusting their pH values. The coagulation that resulted from reduction of dielectric permittivity of the sol medium was caused by the addition of propanol in the sols. The size of the spherical zirconia particles varied with the concentration of zirconium in the sols.

Control of Synthesis Conditions to Improve Zirconia Microspheres for Ultrafast Chromatography

Although it has been known for some time that monodisperse, micrometer‐scale spherical zirconia particles can be synthesized by the hydrolysis of zirconium alkoxides, the particles so made are frequently aggregated. Moreover, it is not clear whether they can be made nonporous without suffering aggregation; this would limit their usefulness in applications like ultrafast chromatography, which require that the particles be spherical and unaggregated (which we term “microspheres”) and that they be nonporous. Here we report that when using an alkoxide hydrolysis synthesis process, critical washing steps can eliminate irreversible aggregation and so enable reliable production of microspheres. We clarify important but practical precautions that easily ensure the reproducibility of the synthesis method. Finally, we demonstrate that the microspheres can be made nonporous with a suitable heating schedule.

Fabrication and Characterization of Spherical Zirconia Particles for Direct Force Measurement Using the Atomic Force Microscope

The spray pyrolysis technique is used to generate smooth, spherical zirconia particles, suitable as probes in direct force measurements using the atomic force microscope (AFM). Both monoclinic and tetragonal crystal structure spheres can be produced. The zirconia spheres are characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and AFM imaging. AFM measurements of the force between the zirconia probe spheres and a mica surface enable the determination of the zirconia sphere surface potential and hence the isoelectric point of the zirconia surface. A value of ca. 3.3 is found for both the monoclinic and tetragonal crystal structure spheres. The difference between this value and the higher values previously reported for colloidal systems is provisionally explained as being due to the influence, in the colloidal systems, of specific adsorption of cationic zirconium hydroxo species.

Synthesis and characterization of monodisperse spherical zirconia particles

Synthesis and characterization of monodisperse spherical zirconia particles

Synthesis and Characterization of Monodisperse Spherical Zirconia Particles

Monodisperse zirconia spherical particles are prepared by hydrolysis of zirconium propoxide in 2-methoxyethanol in presence of decanoic acid as a shape stabilizer. The powder is analyzed by computer image analysis on TEM micrographs, TG-DSC, FTIR, X-ray diffraction and nitrogen adsorption isotherms. A competition phenomenon between aggregation and individual growth of the particles during precipitation is deduced from the observations.

Synthesis of fine spherical zirconia particles by controlled hydrolysis of zirconium alkoxide in the high temperature range above 50 °C

Fine spherical zirconia particles were synthesized by controlled hydrolysis of zirconium tetrabutoxide in 1-propanol in the high temperature range above 50 °C and principally at a water molar ratio defined by [H 2O] 0/[Zr(OC 4H 9) 4] 0 equal to 3. The nucleation process was not completely separated from the particle growth process, but a coagulative nucleation and growth mechanism seemed to be operative.

Synthesis of Porous Zirconia Spheres for HPLC by Polymerization-Induced Colloid Aggregation (PICA)

Abstract Porous, spherical zirconia particles with a narrow particle size distribution, which are useful as chromatographic packing materials for high performance liquid chromatography (HPLC), were synthesized by polymerization-induced colloid aggregation (PICA) first described by Iler and McQueston (U.S. Patent 4,010,242, 1977.) and the effects of a number of crucial processing variables were examined. In this method, an aqueous zirconia sol consisting of 700 A (mean diameter) particles is mixed with urea and formaldehyde, which are polymerized by the acidic sol. Urea-formaldehyde polymer adsorbs onto the ZrO2 colloids, entraining the colloids in the precipitation of the polymer gel and thus allowing the colloids to aggregate. Features of the aggregation process are elucidated from responses of the process to variations in temperature, reaction mixture composition, and solvent polarity. Our results suggest that the aggregation process resembles those reported for the bridging flocculation of colloids by adsorbed polymers. Porous zirconia particles obtained after polymer combustion and sintering of the aggregates are 3.5 μm in diameter with a surface area of 13 m2/g, a porosity of 29% and pores ranging from

Synthesis of spherical zirconia fine particles by controlled hydrolysis of zirconium tetrabutoxide in 1-propanol

Monosized spherical zirconia particles were synthesized by controlled hydrolysis of zirconium tetrabutoxide (Zr(OBu) 4) in 1-propanol. The zirconia

Chemical control in precipitation of spherical zirconia particles

Monodisperse spherical zirconia particles are precipitated by hydrolysis of alcoholic solutions of zirconium alkoxides in the presence of long-chain carboxylic acids. The particle size can be finely tuned from 0.1 to 2.5 Μm by controlling the concentration of zirconium alkoxide, the water/zirconium ratio, the nature of alcohol from ethanol to butanol, the nature of carboxylic acid from caproic to oleic acid and its concentration. The relationships between the induction time before nucleation, the particle size and all the above parameters are tentatively explained on the grounds of the solubility of the carboxy-alkoxide derivatives and their tendency to form micelles. Calcination of precipitated powders between 300 and 600 ‡C produces mixtures of varying composition from cubic to monoclinic phases of small crystallite sizes, and brings out the loss of surface area and organic content. Different conditions of drying powders lead to variously ordered microstructures.

ChemInform Abstract: Synthesis of Solid, Spherical Zirconia Particles by Spray Pyrolysis.

AbstractIt is found that fine, spherical particles can be synthesized by conventional spray pyrolysis by limiting the initial relative solution saturation to ∼10‐2.