Papers by Keyword: Zirconium Oxide

Abstract: The formation energies of point defects in zirconium-doped yttrium oxide were calculated using density functional theory (DFT). Both substitutional zirconium defects (Zr_Y) and their complexes with native point defects in Y₂O₃ were considered. The results show that zirconium predominantly incorporates into yttrium oxide as Zr⁴⁺ ions, creating positively charged substitutional defects that are compensated by interstitial oxygen ions (O_i²⁻). A considerable fraction of zirconium ions form bound complexes with interstitial oxygen, such as Zr_Y–O_i pairs and Zr_Y–O_i–Zr_Y ternary defects. These defects are predicted to reduce the lattice parameter, in agreement with experimental observations.

Abstract: PMMA is used in dentistry as the main matrix for denture manufacture. Dentures are a substitute for natural human teeth which must have mechanical properties and are biocompatible to withstand mastication in the oral cavity. However, PMMA has poor mechanical properties, so it is necessary to add filler to the PMMA matrix. In this study zirconium oxide (ZrO₂) was used as a filler because it has good mechanical properties and aesthetics. The aim of this study was to study the effect of adding ZrO₂ filler on the hardness and compatibility of denture composites at concentrations ( 0%, 1%, 3%, 5%, and 7%). The bulk composite polymerization method used in the manufacture of dental composites is by mixing powdered materials in the form of PMMA, BPO as an initiator, and ZrO₂ filler which has been silanized with liquid materials in the form of MMA monomer and cross-linking agent Ethylene Glycol Dimethacrylate (EGDMA). Mixing powder liquid in this method uses hand mixing in a stainless steel container until it reaches the dough phase and is packed into a mold according to ASTM for Vickers hardness tests. Heat cured polymerization technique was used for the curing process in a water bath at 74°C for 90 minutes and continued at 100°C for 30 minutes. The results obtained in this study, the addition of ZrO₂ filler to a concentration of 5% showed an increase in the hardness value up to 37.6 VHN. Keywords: Denture Teeth, Composite Bulk Polymerization, Heat cured Polymerization, Zirconium Oxide

Abstract: One of factor causing the failure of Ti-6Al-4V Extra Low Interstitial (ELI)-based material implants, does not have bioactive properties in the implantation process, thus not supporting the osseointegration process in the body. For this reason, coating with hydroxyapatite (HA) suspension is necessary. This research used the dip-coating method and added Zirconium Oxide (ZrO₂) into nanosized commercial HA to be suspensions (17%wt and 20%wt) to strengthen the adhesion of the coating. The specimens were heated at 800, 900, and 950°C to densify the layers. Bioactivity increased along with the increasing calcium/phosphate (Ca/P) ratio of the HA layers in the test specimens. The specimens were immersed in Simulated Body Fluid (SBF), namely Hank’s Solution, for 1, 2, 3, and 4 weeks. ZrO₂ added to the HA suspensions of Ti-6Al-4V ELI can increase the Ca/P ratio from 1.51 in the first immersion week to 1.62 in the fourth. The bioactivity level is also proven by the accumulation of calcium and phosphate on the surface of the coating. The Ca/P value close to the Ca/P ratio of HA of 1.67 is good for improving the osseointegration process in the body.

Abstract: The scope of the work covers the development of the relationship between the chemical composition of surface-modified aluminium and its mechanical properties. This article presents the impact of laser alloying with ZrO powder on the microstructure and mechanical properties of pure aluminium. In order to study the phenomena occurring during the laser alloying process, microstructural studies were carried out using optical microscopy. Additionally, the properties of the obtained alloy were tested - abrasion resistance and hardness measured at low load force. As a result of the alloying process, three distinct zones were identified: the remelting zone (RZ), the diffusion zone (DZ) and the heat affected zone (HAZ). The surface modification resulting from laser alloying increases the hardness and abrasion resistance of the material.

Abstract: The method for synthesis of zirconium oxide nanopowder in low-pressure arc plasma was developed. The physicochemical properties of the nanopowder were studied. The estimation was carried out by means of X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). The sequence and kinetics of structural transformations occurring in the specified time-temperature heating regimes have been examined using differential thermal analysis. It was shown that the particles have a nanometer size, a narrow particle size distribution and an amorphous-crystalline structure. The maximum specific surface area detected by the method of sorption of surfactants was 470 m²/g. The issues of crystallization were discussed. From comparison between the results of experimental studies from earlier works with the results obtained for zirconium oxide, it is concluded that the proposed method for producing NPs in a low-pressure arc discharge plasma is universal.

Abstract: In this paper, zirconium tungstate ceramic with negative thermal expansion coefficients was prepared from zirconium oxide and tungstic acid by solid phase synthesis and high temperature quenching technique with a sintering temperature of 1200 °C. The phase structure of the material was determined by X ray and the thermal expansion coefficient was measured by dilatometer, while the TG-DTA analysis of the prepared material was also carried out. The results showed that zirconium tungstate with high purity could be obtained by rapid chilled while fired at 1200 °C. The coefficient of thermal expansion at 300 °C was minus 8.5413 × 10^-6K^-1, which is identical with the theoretical value. The thermal expansion coefficient of the material was negative fired lower than 750 °C, while it was positive fired higher than 750 °C, and this indicates that the decomposition temperature of zirconium tungstate is about 750 °C.

Abstract: Polyaniline-Zr(IV) tungstovanadate and Polyaniline-Zirconium oxide nanocomposite ion -exchangers were synthesized and physico-chemical characterization done by FT-IR-UV spectral studies, XRD, SEM and TGA. These composites are having high mechanical strength, good electrical conductivity and stability than their individual components. The organic polymeric component of the composites provides mechanical as well as chemical stability whereas the inorganic component supports the ion-exchange behavior and thermal stability. Both the inorganic and organic parts are jointly responsible for their improved electrical conductivity. They have more promising ion exchange capacity towards alkali metal halides and have selective adsorption towards Pb(II) ion and these can be used as powerful candidates for water softening

Abstract: Conventional WC-Co hardmetals are widely used in various applications due to their excellent properties. High hardness can be achieved using compositions with little to no content of cobalt or nickel. These binder metals are hazardous to health, making a substitution not only desirable because of availability and cost reasons. A new possibility to manufacture such hard materials is the combination of tungsten carbide with oxides such as Al₂O₃ and ZrO₂. In this way the binder metal content can be replaced. Furthermore the content of the also expensive WC can be reduced. Such metal carbide – oxide composites with oxide contents between 16 vol% and 40 vol% were manufactured. The completely dense composites feature high hardness values of 2000 HV10 to 2400 HV10 while also having an acceptable fracture toughness of up to 7 MPa⋅m^1/2. The improved mechanical properties make the replacement of WC-Co hardmetals and binder free WC ceramics in special areas possible.

Abstract: Nanostructured Fe–ZrO₂ composite powders with homogeneous distribution of zirconia were synthesized by thermochemical process. The synthesis procedures are (1) preparation of precursor powder by spray-drying of solution made from water-soluble iron and zirconium nitrates, (2) air heat treatments to evaporate volatile components in the precursor powder and synthesis of nanostructured Fe₂O₃ +ZrO₂, and (3) Fe₂O₃ reduction by hydrogen into pure Fe. In order to find phase containing Zr the powder was treated with 15% hydrochloric acid to dissolve iron particles. The size of the particles is less than 50 nm. Fe–ZrO₂ composite powders can be used as filler for cored welding wire. Shown that particles zirconium oxide well affect the final structure of the weld.

Abstract: In work investigated effects of zirconium oxide (ZrO₂), spinel (MgAl₂O₄) and mullite (Al₆Si₂O₁₃) nanosized powders on the base oil tribological properties. The nanosized (30-40nm) powders manufactured by plasma chemical synthesis method. Tribological experiments used on ball-on-disc type tribometer, measured coefficient of friction and determined metalic disc wear. Base oil used selectively purified mineral oil (conform SAE-20 viscosity) without any functional additives. Nanosized powders dispersed in base oil at 0.5; 1.0; 2.0; wt.%. At work cocluded, that the adition nanoparticles in base oil, possible reduced friction pair wear and friction coefficient. As the main results include spinel (MgAl₂O₄) nanoparticles 0.5 and 1.0 wt. % concentration ability reduced friction coeffiecient value.