Selection of Nanostructured Zirconium Dioxide Crystals under Dry Friction against Molybdenum

The article considers the issues of contact interaction of nanostructured zirconium dioxide crystals with molybdenum coating on titanium-based alloy ВТ9. The following statement is substantiated: the best mechanical properties of crystals correspond to the total amount of 2.8% additives of stabilizing and doping rare earths elements. Antifriction properties of crystals under dry friction against molybdenum are investigated. Tribological testing was performed on a reciprocating friction gauge simulating the operation of a plunger in a cylinder. The high scoring resistance of the friction couple under study was experimentally proved; the friction coefficient did not exceed 0.07. On the basis of the study performed, the friction couple is defined as promising for increasing the lifetime and reliability of friction units for hydraulic equipment and fuel pumps.

Ceramic Restorations Based on Zirconium Dioxide for Orthopedic Dentistry

Currently, ceramics based on solid solutions of zirconium dioxide tetragonal structure are common biomedical materials. In commercially common ceramics of orthopedic dentistry based on zirconium dioxide, the stabilization of the tetragonal shape is achieved by the introduction of yttrium or cerium cations. As a result of this scientific work, a ceramic material based on nanopowders of a system of zirconium dioxide and ytterbium oxide with high strength parameters has been developed. The results of the conducted research allow us to recommend the new Yb–TZP ceramics as an alternative to Y–TZP ceramic materials for restorations in orthopedic dentistry.

RADIATION STIMULATION OF THE CATALYTIC ACTIVITY OF ZIRCONIUM DIOXIDE NANOPARTICLES DURING THE CONVERSION OF HYDROCARBONS

The comparison of the catalytic activity of the initial and activated by bremsstrahlung -radiation on a high-current electron accelerator of zirconium dioxide nanoparticles on the nature of the conversion of ethanol. The used -activation parameters contributed to the formation of a more perfect crystal structure of ZrO2 nanoparticles. It was shown that when using -activated ZrO2 nanoparticles as a catalyst, the yield of hydrocarbon products during the conversion of ethanol was several times higher than the yield of the same products in the case of using the initial ZrO2 nanoparticles. The mechanism of such a conversion of ethanol can be associated with the synergism of large ionization losses of Auger electrons and the effect of highly reactive products involved in heterogeneous catalysis.

Enhanced Photocatalytic Activity of Ficus elastica Mediated Zinc Oxide-Zirconium Dioxide Nanocatalyst at Elevated Calcination Temperature: Physicochemical Study

The photocatalytic degradation of Rhodamine 6G dye was achieved using a Ficus elastica (F. elastic) leaf extract mediated zinc oxide-zirconium dioxide nanocatalyst (ZnO-ZrO2 NC) under stimulated solar light, resulting in a substantial increase in photocatalytic activity at the highest calcination temperature. The crystal phase and crystallite size were determined using an X-ray diffractometer (XRD), and the degree of crystallinity was observed to rise with increasing calcination temperature. Energy dispersive X-ray (EDX) was used to investigate the elemental composition and purity of ZnO-ZrO2 NC. Scanning electron microscopy (SEM) was used to investigate the surface morphology, and the morphological characteristics were altered when the calcination temperature was varied. For the ZnO-ZrO2 NC calcined at 100, 300, 600, and 900 °C, the average grain size determined from SEM images is 79.56 nm, 98.78 (2) nm, 54.86 (2) nm, and 67.43 (2) nm, respectively. Using diffuse reflectance spectroscopy (DRS) data, the optical band gap energy was calculated using a Tauc’s plot. The ZnO in ZnO-ZrO2 NC calcined at 100, 300, 600, and 900 °C had band gap energies of 3.31, 3.36, 3.38, and 3.29 eV. Similarly, ZrO2 in ZnO-ZrO2 NC calcined at 100, 300, 600, and 900 °C had band gap energies of 3.96, 3.99, 3.97, and 4.01 eV, respectively. Fourier transform infrared (FTIR) spectroscopy was used to identify the presence of various functional groups. The photocatalytic activity was also examined in relation to calcination temperature, pH, starting concentration, and catalyst dosage. Enhanced photocatalytic activity was observed at pH 11 and 15 ppm initial concentration with a catalyst dose of 25 mg. The photocatalytic activity of the sample calcined at 900 °C was the highest, with 98.94 percent of the dye mineralized in 330 min at a degradation rate of 0.01261/min.

Endodontic Management of Endo-Perio Lesions

An endo-perio lesion is one of the more common tooth-related problems. An association between the presence of apical and marginal periodontitis is known in the literature and has been observed in 5.7% of individuals aged 40–45 years old. The purpose of the present article is to present three case reports describing the successful retreatment of endo-perio lesions. In each of these cases, we used a biologically active bioceramic root canal sealer, GuttaFlow Bioseal, which is a bioactive root canal filling material composed of gutta percha, polydimethylsiloxane, platinum catalyzer, zirconium dioxide, and bioglass. All cases were followed up clinically and radiographically for a period of at least 11 months.

$ZrO_{2}$ electronic properties

The improvement of electronic and optical properties of the Zirconium dioxide $ZrO_{2}$ is very significance for the industrial applications. Here, we apply the first-principles calculations to study the influence of noble metals on the electronic and optical properties of the monoclinic $ZrO_{2}$

One-step combustion synthesis of undoped c-ZrO2 for Cr(VI) removal from aqueous solutions

The active practical application of materials based on cubic zirconium dioxide (c-ZrO2) for catalysis, luminescence, and sorption of heavy metals demands the development of methods for its preparation in a nanostructured form. In this work, nanoparticles of undoped cubic zirconia were obtained by solution combustion method, the features of their structure and morphology were investigated, and the efficiency of their use as a basis for sorbents for the removal of hexavalent chromium Cr(VI) from aqueous solutions was evaluated. Based on XPS, it was established that the stabilization of the high-temperature cubic phase of c-ZrO2 occurred due to multiple oxygen vacancies which were formed during the synthesis by glycine-nitrate combustion. The results of PXRD and Raman spectroscopy confirmed the cubic structure of the obtained zirconium dioxide nanoparticles, the average crystallite size was approximately 2 nm. Adsorption structural analysis and SEM indicated aggregation of c-ZrO2 nanocrystals into primary (45-95 nm) and secondary (submicron) agglomerates. The specific BET surface of the nanocrystals was 25.4 m2/g, the pore volume was 0.1670 cm3/g, the major part of which is associated with interparticle porosity. Using kinetic pH-metry, it was found that on the surface of synthesized c-ZrO2, rapidly hydrated aprotic Lewis acid centers predominated, and the point of zero charge (PZC) was 6.33. The results of Cr(VI) sorption from aqueous solutions with concentrations varying from 0.25 to 1.25 mmol/L were described by the Freundlich isotherm (R2 = 0.971), which corresponds to the multilayer adsorption. The maximum adsorption capacity according to Langmuir was 33 mg/g or 1.34 mg/m2 per unit area. These results allow us to consider the obtained undoped zirconium dioxide as a promising base for sorbents of heavy metals.