Friction and wear properties of ZrO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript> composite nanoparticles

In this article, the lubrication properties of ZrO₂/SiO₂ composite nanoparticles modified with aluminum zirconium coupling agent as additives in lubricating oil under variable applied load and concentration fraction were reported. It was demonstrated that the modified nanoparticles as additives in lubrication can effectively improve the lubricating properties. Under an optimized concentration of 0.1 wt%, the average friction coefficient was reduced by 16.24%. This was because the nanoparticles go into the friction zone with the flow of lubricant, and then the sliding friction changed to rolling friction with a result of the reduction of the friction coefficient.     

Preparation and properties of Fe and Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles in ZrO<Subscript>2</Subscript> matrix

Iron and magnetite nanoparticles in zirconium oxide matrix have been prepared by a heat treatment of a mixture of nanocrystalline iron oxide and zirconium oxide or zirconium hydride powders. Changes in the phase composition of the as-mixed powders during annealing in vacuum or in hydrogen were monitored using thermomagnetic curves. Structure and phase composition of the final products were characterized by X-ray powder diffraction and ⁵⁷Fe Mössbauer spectroscopy. Influence of the composition of the original mixture and quality of the annealing atmosphere on the final properties of the composites are discussed.     

A study of the structure and properties of nanostructured ZrO<Subscript>2</Subscript>-Y<Subscript>2</Subscript>O<Subscript>3</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composite powders

The correlation between temperature treatment conditions and the ratio of components in nanostructured fibrous powders with a composition of ZrO₂-Y₂O₃-Al₂O₃ and their porous crystal structure and physicochemical properties is studied. The dependences of the ratio between zirconia tetragonal and monoclynic phases on the treatment temperature and the alumina content are found to have a nonmonotonic character. The growth of zirconia crystallite size is suppressed by introduced nanocrystalline alumina in a temperature range of 600–1200°C, which is caused by the processes of ternary solid solution formation. The bulk and picnometric density values of materials are proportional to the temperature of heat treatment. The temperature dependence of the specific surface and the size of oxide grain particles has an inversely proportional character. With increasing alumina content in the powders, the specific surface increases, while the picnometric and bulk densities decrease.     

The transport and thermal properties of glassy LiPO<Subscript>3</Subscript>/crystalline Al<Subscript>2</Subscript>O<Subscript>3</Subscript> (ZrO<Subscript>2</Subscript>) composite electrolytes

Glassy LiPO₃/crystalline Al₂O₃ and glassy LiPO₃/crystalline ZrO₂ (0–12.5 vol.% of oxide fillers) composite solid electrolytes have been prepared by glass matrix softening. Their thermal and transport properties have been investigated by differential scanning calorimetry (DSC) and impedance spectroscopy methods. The addition of ZrO₂ leads to a decrease in the crystallization temperature of LiPO₃ glass. It was found that the conductivity behavior depends on the nature of the dispersed addition. In the case of the Al₂O₃ addition, the increase in the electrical conductivity is observed. The ionic conductivity of the LiPO₃/10% Al₂O₃ composite reaches 5.8 × 10^?8 S/cm at room temperature. In contrast, the conductivity in the LiPO₃/ZrO₂ composite system decreases.     

Evolution of the phase composition and physicomechanical properties of ZrO<Subscript>2</Subscript> + 4 mol % Y<Subscript>2</Subscript>O<Subscript>3</Subscript> ceramics

The evolution of the phase composition and physicomechanical properties of ZrO₂ + 4 mol % Y₂O₃ ceramics subjected to hot isostatic pressing and subsequent calcining in air is investigated. It is found that hot isostatic pressing results in the formation of an easily transformed phase T_et with a degree of tetragonality c/a=1.035, which determines high fracture toughness. After calcining in air, the phase T_et decomposes to form a nontransformed phase T′ with a degree of tetragonality c/a=1.005, which determines low fracture toughness.     

Numerical simulation of fracture of ZrO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> ceramic composites

The regular grid generation method was generalized for a 3D region based on the solid mechanics equations that describe deformation of a finite volume. Test calculations of fracture of ceramic composites with inclusions are represented which are based on the developed model of quasi-brittle media with regard to damage accumulation.     

Two-band conductivity of ZrO<Subscript>2</Subscript> synthesized by molecular beam epitaxy

Using experiments on the injection of minority carriers from n-and p-type silicon, the contribution of electrons and holes to the conductivity of ZrO₂ in the Si/ZrO₂/Al structure is determined. It is found that electrons and holes make a contribution to the conductivity of ZrO₂, so that ZrO₂ exhibits two-band conductivity.     

Luminescent characteristics of ZrO<Subscript>2</Subscript>:Pb nanopowders

ZrO₂ nanopowders doped with Pb ions are prepared by the coprecipitation method. The average size of the powders, measured by X-ray diffraction, is 4–6 nm. The emission spectra show a narrow band originating from the transition from the ¹S₀ ground state to the ³P₁ excited state of the Pb ions. A quenching of the photoluminescence is observed when the concentration of Pb²⁺ is higher than 5%. The influence of residual chlorine ions on the luminescent properties of the nanopowders is also discussed. PACS 78.55.-m; 81.05.Je; 61.72.Ww     

Thermoeletrochemical study on LiNi<Subscript>0.8</Subscript>Co<Subscript>0.1</Subscript>Mn<Subscript>0.1</Subscript>O<Subscript>2</Subscript> with in situ modification of Li<Subscript>2</Subscript>ZrO<Subscript>3</Subscript>

To improve the electrochemical performance of Nickel-rich cathode material LiNi_0.8Co_0.1Mn_0.1O₂, an in situ coating technique with Li₂ZrO₃ is successfully applied through wet chemical method, and the thermoelectrochemical properties of the coated material at different ambient temperatures and charge-discharge rates are investigated by electrochemical-calorimetric method. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests demonstrate that the Li₂ZrO₃ coating decreases the electrode polarizatoin and reduces the charge transfer resistance of the material during cycling. Moreover, it is found that with the ambient temperatures and charge-discharge rates increase, the specific capacity decreases, the amount of heat increases, and the enthalpy change (ΔH) increases. The specific capacity of the cells at 30 °C are 203.8, 197.4, 184.0, and 174.5 mAh g^?1 at 0.2, 0.5, 1.0, and 2.0 C, respectively. Under the same rate (2.0 C), the amounts of heat of the cells are 381.64, 645.32, and 710.34 mJ at 30, 40, and 50 °C. These results indicate that Li₂ZrO₃ coating plays an important role to enhance the electrochemical performance of LiNi_0.8Co_0.1Mn_0.1O₂ and reveal that choosing suitable temperature and current is critical for solving battery safety problem.     

Antireflection fianite and ZrO<Subscript>2</Subscript> coatings for solar cells

Fianite is a promising multipurpose material for new electronic technologies owing to its unique combination of physical and chemical properties. It can be used in virtually all of the main technological stages of the production of micro-, opto-, and SHF-electronics; in particular, as a bulk dielectric substrate and a material for buffer layers in heteroepitaxy; as a material for insulating, antireflection, and protective layers in device elements; and as a gate dielectric [1–3]. In this work, we consider the possibilities for using fianite and ZrO₂ as an antireflection coating for silicon solar cells (SCs) and SCs based on InGaAsP heterostructures.     

Phase composition and structure of nanocrystalline powders based on ZrO<Subscript>2</Subscript>(Y) and Al<Subscript>2</Subscript>O<Subscript>3</Subscript> obtained by plasma spray pyrolysis

It is shown that a nonequilibrium solid solution ZrO₂(3Y, Al) with tetragonal structure is formed in systems based on ZrO₂(3Y) with Al₂O₃ as a second component. A delay in the γ → α Al₂O₃ transformation and a reduction in the size of the coherently scattering domain of modifications are observed in systems based on Al₂O₃ with ZrO₂(Y) as a second component.     

Magnetic properties of nonstoichiometric Ni<Subscript>2</Subscript>MnIn Heusler alloys

Results from studies of the crystal structure, resistivity, susceptibility, and magnetization of nonstoichiometric Ni₅₀Mn_{50 − x} In _x Heusler alloys are presented. Anomalous effects discovered in temperature dependences can be interpreted as the influence of the frustrated magnetic state exhibited by manganese moments in the martensitic phase. A field-induced phase transition to the austenitic phase was observed for several concentrations around room temperature.     

Effect of ultradisperse TiO<Subscript>2</Subscript>, ZrO<Subscript>2</Subscript>, and cryolite powders on high-chromium cast iron hardening

The quantitative parameters of structural-phase state of Fe–27% Cr–2% Ni–2.8% C cast iron are determined via X-ray diffraction and transmission electron microscopy before and after adding ultradisperse TiO₂, ZrO₂ and cryolite powders. The contributions from individual physical mechanisms in increasing the yield stress of cast irons are quantitatively assessed. It is established that the main contribution to the durability of modified Fe–27% Cr–2% Ni–2.8% C cast iron come from solid-solution, dispersion, and grain-boundary mechanisms of hardening.     

Superconducting properties of molybdenum ruthenium alloy Mo<Subscript>0.63</Subscript>Ru<Subscript>0.37</Subscript>

Resistance, magnetization and specific heat measurements were performed on Mo_0.63Ru_0.37 alloy. All of them confirm that Mo_0.63Ru_0.37 becomes superconducting at about 7.0 K with bulk nature. Its upper critical field behavior fits to Werthamer-Helfand-Hohenberg (WHH) model quite well, with an upper critical field of μ₀H_c2(0) = 8.64 T, less than its Pauli limit. Its electronic specific heat is reproduced by Bardeen-Cooper-Schriffer (BCS)-based α-model with a gap ratio Δ₀ = 1.88k _B T _c , which is a little larger than the standard BCS value of 1.76. We concluded that Mo_0.63Ru_0.37 is a fully gapped isotropic s-wave superconductor, with its features are mostly consistent with the conventional theory.     

Conductivity of nanostructured India oxide films containing Co<Subscript>3</Subscript>O<Subscript>4</Subscript> or ZrO<Subscript>2</Subscript>

The effect of additives of cobalt and zirconium oxides on the conductivity of nanostructured composites based on indium oxide is studied. It is shown that addition of up to 20 wt % ZrO₂ to In₂O₃ leads to a sharp decrease in the conductivity of the composite. For the Co₃O₄?In₂O₃ system, the conductivity decreases up to a Co₃O₄ content of 60 wt %, after which it increases. At a Co₃O₄ content in the Co₃O₄?In₂O₃ system of up to 60 wt %, n-type conduction takes place, changing to p-type at 80 to 100 wt % Co₃O₄. Zirconium oxide exhibits practically no n-type conduction, so electric current in the ZrO₂?In₂O₃ system flows through In₂O₃ nanocrystals, i.e., n-type conduction takes place. Possible causes of the observed effects are considered.     

RETRACTED ARTICLE: Refractive-index tailoring and morphological evolutions in Gd<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> and ZrO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript> composite thin films

Refractive-index tailoring and morphological evolutions in two different thin film composite systems of gadolinia–silica (Gd₂O₃:SiO₂) and zirconia–silica (ZrO₂:SiO₂) deposited through reactive electron-beam codeposition processes are discussed in this research paper. For Gd₂O₃:SiO₂ the refractive-index tuning has been achieved from 1.45 to 2.18, whereas in the case of ZrO₂:SiO₂ the achieved tunable range is from 1.45 to 2.45 in the ultraviolet region. Under certain compositional mixings with lower silica fractions both the systems demonstrated relative microstructural and morphological densifications. Such evolutions were very successfully derived through phase-modulated ellipsometry and atomic force microscopy. The composition-dependent refractive-index tailoring and microstructural densifications have been investigated by adopting Tauc–Lorentz and single-effective-oscillator models. The morphological correlation functions have also very aptly supported such evolutions in these composite films. These experimental results indicate their favourable properties and applicability down to the extreme ultraviolet wavelength region of the electromagnetic spectrum. PACS 42.79.Wc; 78.66.-w; 78.20.Ci; 61.16.Ch; 42.70.-a;68.55.-a; 68.35.Bs; 81.15.Ef     

Investigation of ion transport in Li<Subscript>8</Subscript>ZrO<Subscript>6</Subscript> and Li<Subscript>6</Subscript>Zr<Subscript>2</Subscript>O<Subscript>7</Subscript> solid electrolytes

Lithium ionic conductivity and spin-lattice relaxation rates were measured in Li₈ZrO₆ and Li₆Zr₂O₇ solid electrolytes. It was found that the Li₈ZrO₆ solid electrolyte undergoes a transition to the superionic state in the temperature range 673–703 K. It was shown that Li⁺ ions are mobile in particular lattice positions of the Li₆Zr₂O₇ phase, and that ionic conductivity is monotonic at an activation energy of 79.4 kJ/mol.     

Frequency dependent smoothing of rough surfaces by laser deposition of ZrO<Subscript>2</Subscript>

The development of the surface roughness of amorphous ZrO₂ layers with different thicknesses, which were laser deposited on nanocrystalline Ag surfaces, was analyzed by atomic force microscopy. With increasing ZrO₂ layer thickness first the surface slightly roughens due to island growth, but above a layer thickness of about 30 nm it continuously smoothens. From the power spectral densities it is clear that the smoothing processes are frequency dependent. First the high-frequency surface features vanish before lower roughness frequencies are decreased. Although the starting roughness is only 1 nm, a ZrO₂ layer thickness of about 4 μm is necessary to smooth the long-wavelength surface features. From the decrease of the roughness with ZrO₂ layer thickness and the observed final spectral densities, the dominant smoothing mechanisms were identified as downhill currents, probably induced by the energetic ions impinging on the substrate surface during deposition. PACS 68.35.Ct; 68.37.Ps     

Elevated electrochemical property of LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> originated from nano-sized Mn<Subscript>3</Subscript>O<Subscript>4</Subscript>

By employment of nano-sized pre-prepared Mn₃O₄ as precursor, LiMn₂O₄ particles have been successfully prepared by facile solid state method and sol-gel route, respectively. And the reaction mechanism of the used precursors of Mn₃O₄ is studied. The structure, morphology, and element distribution of the as-synthesized LiMn₂O₄ samples are characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Compared with LiMn₂O₄ synthesized by facile solid state method (SS-LMO), LiMn₂O₄ synthesized by modified sol-gel route (SG-LMO) possesses higher crystallinity, smaller average particle size (~175 nm), higher lithium chemical diffusion coefficient (1.17 × 10^?11 cm² s^?1), as well as superior electrochemical performance. For example, the cell based on SG-LMO can deliver a capacity of 85.5 mAh g^?1 at a high rate of 5 °C, and manifests 88.3% capacity retention after 100 cycles at 0.5 °C when cycling at 45 °C. The good electrochemical performance of the cell based on SG-LMO is ascribed mainly to its small particle size, high degree of dispersion, and uniform element distribution in bulk material. In addition, the lower polarization potential accelerates Li⁺ ion migration, and the lower atom location confused degree maintains integrity of crystal structure, both of which can effectively improve the rate capability and cyclability of SG-LMO.     

Specific features of the properties of half-metallic ferromagnetic Heusler alloys Fe<Subscript>2</Subscript>MnAl,Fe<Subscript>2</Subscript>MnSi,and Co<Subscript>2</Subscript>MnAl

The structural, magnetic, and electrical properties of half-metallic Heusler alloys Fe₂MnAl, Fe₂MnSi, and Co₂MnAl have been investigated in the temperature range of 4–900 K. According to the X-ray diffraction analysis, these alloys have the B2 and L2₁ structures with different degrees of atomic order. The magnetic state of the alloys is considered as a two-sublattice ferrimagnet. The electrical resistivity and thermoelectric power have been discussed in the framework of the two-current conduction model taking into account the existence of an energy gap in the electronic spectrum of the alloys near the Fermi level for the subband with spin-down (minority) electrons.