Biological interface study of HA/ZrO2 graded composite in a dog lumbar vertebra bone defect model

This study compared bony fusion in autologous bone grafting with HA/ZrO₂ graded composite in terms of mineral depositions, histological characteristics, and biomechanical properties of bonding interface. Twenty-four beagle dogs were established four places of bone defect in two adjacent lumbar vertebral bodies (L4 and L5) and were successively implanted with HA/ZrO₂ graded composite (group A), HA/ZrO₂ unilayer composite (group B), pure ZrO₂ (group C), and pure HA (group D). After operation, lumbar vertebral specimens were respectively harvested per time at week 6, 12, and 16. Then, the bony fusion interface was evaluated by fluorescence microscope and computer image analysis system to measure mineral apposition rates (MAR). Histological analysis of specimen was used to determine bone bonding rates (BBR) and possible foreign body reactions associated with each groups. And interface bonding force between implant and autogenous bone was quantified with biomechanical push-out test. Compared with other groups, group A led to significantly higher MAR from week 6 to 12 (p < 0.05). Histologically, new bony tissue and hyaline cartilage were seen around the HA/ZrO₂ graded composite, accompanied by mild chronic inflammation. And the BBR of HA/ZrO₂ graded composite were the highest (p < 0.05), while reaching (90.3 ± 3.8) % at week 16. Moreover, the biomechanical push-out tests revealed that the maximum interface shear strength of group A was respectively (2.64 ± 0.16) MPa, (2.95 ± 0.19) MPa, and (3.45 ± 0.23) MPa at week 6, 12, and 16, which all possessed significantly statistical differences with other three groups (p < 0.05).     

Stability of La2O3 and GeO2 passivated Ge surfaces during ALD of ZrO2 high-k dielectric

La₂O₃ grown by atomic layer deposition (ALD) and thermally grown GeO₂ are used to establish effective electrical surface passivations on n-type (1 0 0)-Ge substrates for high-k ZrO₂ dielectrics, grown by ALD at 250 °C substrate temperature. The electrical characterization of MOS capacitors indicates an impact of the Ge-surface passivation on the interfacial trap density and the frequency dependent capacitance in the inversion regime. Lower interface trap densities can be obtained for GeO₂ based passivation even though a chemical decomposition of the oxidation states occur during the ALD of ZrO₂. As a consequence the formation of a ZrGeO_x compound inside the ZrO₂ matrix and a decline of the interfacial GeO₂ are observed. The La₂O₃ passivation provides a stable amorphous lanthanum germanate phase at the Ge interface but also traces of Zr germanate are indicated by X-ray-Photoelectron-Spectroscopy and Transmission-Electron-Microscopy.     

Fabrication and Characterization of Bioglass-Modified HA–ZrO2 Biocomposites

Hydroxyapatite (HA) being the main mineral constituent of human hard tissues is highly bioactive. Good chemical bonds can be generated between HA and natural bone. However, the low strength and inherent brittleness of HA restrict its application usually to non-load-bearing conditions. In this work, production of a new kind of HA–ZrO₂ composite by hot-press sintering method is described. Bioglass which has been widely used in reconstruction of damaged or diseased tissues was added into HA–ZrO₂ composites. Comparing with pure HA ceramic, this type of composite possesses better mechanical strength and retains the bioactivity of HA as well. The liquid phase generated by bioglass has been effective in improving the sintering process of HA–ZrO₂ composites. The phase composition of HA composite was characterized by XRD and their fracture surfaces were observed by SEM. The XRD results show that introducing a small amount of bioglass into HA–ZrO₂ composite cannot enhance decomposition of HA. The SEM images show that there were fewer pores on the fracture surfaces of HA–ZrO₂–bioglass composite than in the HA–ZrO₂ composite. The flexural strength and toughness of HA–ZrO₂ composite containing 2 wt% bioglass were 157 MPa and 1.63 MPa·m^1/2, respectively.     

Multi-scale theoretical study of support effect on sintering dynamics of Pt

The capability of theoretical durability studies to offer an efficient alternative methodology for predicting the potential performance of catalysts has improved in recent years. In this regard, multi-scale theoretical methods for predicting sintering behavior of Pt on various catalyst supports are being developed. Various types of Pt diffusions depending on support were confirmed by the micro-scale ultra accelerated quantum chemical molecular dynamics (UA-QCMD) method. Moreover, macro-scale sintering behavior of Pt/γ-Al₂O₃, Pt/ZrO₂ and Pt/CeO₂ catalysts were studied using a developed 3D sintering simulator. Experimental results were well reproduced. While Pt on γ-Al₂O₃ sintered significantly, Pt on ZrO₂ sintered slightly and Pt on CeO₂ demonstrated the highest stability against sintering.     

Characterization and corrosion behavior of hydroxyapatite/zirconia composite coating on NiTi fabricated by electrochemical deposition

NiTi alloy is used as biomaterial due to its unique properties, but the high content of Ni (about 50 at.%) in biomedical NiTi is concerned. Hydroxyapatite and hydroxyapatite/zirconia composite coatings were directly electrodeposited on NiTi alloy surface. The coated samples were characterized using X-ray diffraction, scanning electron microscopy, infrared spectroscopy, bonding strength test, polarization and EIS. Results showed that when ZrO₂ was added into the electrolyte, morphology of HAP was changed from thin flake-flower-like crystals to needle-flower-like crystals, and coating was denser. Besides, HAP crystal grains in the coating were preferentially arranged in the [0 0 1] direction. Addition of ZrO₂ could improve the bonding strength between the coating and the substrate. Corrosion resistance of NiTi in the simulated body fluid at 37 °C was significantly improved by almost 60 times by electrodeposition of the hydroxyapatite/zirconia composite coating.     

Stabilization of a very high-k crystalline ZrO2 phase by post deposition annealing of atomic layer deposited ZrO2/La2O3 dielectrics on germanium

The impact of the ZrO₂/La₂O₃ film thickness ratio and the post deposition annealing in the temperature range between 400 °C and 600 °C on the electrical properties of ultrathin ZrO₂/La₂O₃ high-k dielectrics grown by atomic layer deposition on (1 0 0) germanium is investigated. As-deposited stacks have a relative dielectric constant of 24 which is increased to a value of 35 after annealing at 500 °C due to the stabilization of tetragonal/cubic ZrO₂ phases. This effect depends on the absolute thickness of ZrO₂ within the dielectric stack and is limited due to possible interfacial reactions at the oxide/Ge interface. We show that adequate processing leads to very high-k dielectrics with EOT values below 1 nm, leakage current densities in the range of 0.01 A/cm², and interface trap densities in the range of 2-5 × 10¹² eV⁻¹ cm⁻².     

Manipulating Bonding at a Cu/(0001)Al2O3 Interface by Different Substrate Cleaning Processes

Growth of Cu films on (0001)Al₂O₃ substrates can result in metallic Cu—Al or ionic-covalent Cu—O bonds at atomically abrupt interfaces. The type of bonding depends on the substrate cleaning procedure prior to film growth. Cu films deposited on Ar⁺-ion sputter-cleaned substrates exhibit interfacial Cu-L_2,3, Al-L_2,3 and O-K energy-loss near-edge structures that indicate the formation of metallic Cu—Al bonds at the Cu/Al₂O₃ interface. In contrast, growth on chemically cleaned -Al₂O₃ substrates results in interfacial energy-loss near-edge structures that suggest Cu—O bonding at the interface. The experimental electron energy-loss spectroscopic results are compared to calculated spectra, and the mechanisms causing the changes in the atomic and electronic structure are addressed.     

Adhesion at a heterophase interface: First-principles study of Mo(001)/MoSi2(001)

The bonding characteristics, interfacial energetics, and electronic structure associated with adhesion at the Mo-MoSi₂(001) heterophase interface are investigated using the first-principles, self-consistent local orbital method. We found both the adhesive energy and peak interfacial strength for the interface to be 10%-15% smaller than the respective values for cleavage along the (001) planes in crystalline Mo and MoSi₂. The equilibrium interlayer separation between Mo and MoSi₂ is found to lie between the interplanar spacings of crystalline Mo and MoSi₂. The interfacial adhesive bonding is attributable to the combination of a nearly uniform band of charge accumulation at the interface and directional charge accumulation between atoms across the interface. These first-principles calculations demonstrate that the universal-binding-energy relation can be extended to describe adhesion between dissimilar materials.     

ZrO2 coating of LiNi1/3Co1/3Mn1/3O2 cathode materials for Li-ion batteries

ZrO₂-coated LiNi_1/3Co_1/3Mn_1/3O₂ materials were prepared by hydroxide precipitation. The structure and electrochemical properties of the ZrO₂-coated LiNi_1/3Co_1/3Mn_1/3O₂ were investigated using X-ray diffraction, scanning electron microscope, and charge–discharge tests, indicating that the lattice structure of LiNi_1/3Co_1/3Mn_1/3O₂ were unchanged after the coating but the cycling stability was improved. As the coating amount increased from 0.0 to 0.5 mol.%, the initial capacity of the coated LiNi_1/3Co_1/3Mn_1/3O₂ decreased slightly; however, the cycling stability increased remarkably over the cut-off voltages of 2.5~4.3 V and the capacity retention reached 99.5% after 30 cycles at the coating amount of 0.5 mol.%. ZrO₂ coating also improved the cycling stability of LiNi_1/3Co_1/3Mn_1/3O₂ over wider cut-off voltage of 2.5~4.6 V.     

Preparation and characterization of SiO2/ZrO2/Ag multicoated microspheres

A new type of multicoated silica/zirconia/silver (SiO₂/ZrO₂/Ag) core-shell composite microspheres is synthesized in this paper. In the process, ZrO₂-decorated silica (SiO₂/ZrO₂) core-shell composites were firstly fabricated by the modification of zirconia on silica microspheres through the hydrolysis of zirconium precursor. Subsequently, on SiO₂/ZrO₂ composite cores, silver nanoparticles were introduced via ultrasonic irradiation and acted as “Ag seeds” for the formation of integrate silver shell by further reduction of silver ions using formaldehyde as reducer. The resulting samples were characterized by transmission electron microscopy, X-ray diffraction, Fourier-transform infrared, energy-dispersive X-ray, and UV-vis spectroscopy, indicating that zirconia and silver layers were successfully coated on the surfaces of silica microspheres.     

Intermediate temperature solid oxide fuel cell using (La,Sr)(Co,Fe)O3-based cathodes

Anode-supported SOFCs involving LSCF (La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ)-based cathodes are fabricated utilizing GDC interlayer on 8YSZ electrolyte for intermediate temperatures. The GDC interlayer between the LSCF cathode and YSZ electrolyte is used to prevent formation of insulating phases such as SrZrO₃ or La₂Zr₂O₇. The cell performance with the GDC interlayer was ten times better than the one without GDC at operating temperature of 750 °C. However, the observed power density (370 mW/cm²) was lower than the value reported in the literature. This can be attributed to an imperfect GDC interlayer in the present study. The GDC interlayer was porous and non-uniform, so that adverse interfacial reactions could not be completely prevented. The chemical incompatibility at the interface was evaluated by SEM and EPMA, which explains the dependence of cell performance on sintering temperatures of the GDC interlayer.     

Effect of spin contamination error on surface catalytic reaction: NO reduction by core-shell catalysts

ABSTRACT

The effects of spin contamination errors on the activation barriers of catalytic NO reduction by TiO₂/Ag and ZrO₂/Cu core-shell catalyst models were investigated using an approximate spin projection method and an unrestricted density functional theory calculation with the plane-wave basis set. The estimated barrier of the TiO₂/Ag system increased (0.03?eV), whereas that of the ZrO₂/Cu system decreased (0.04?eV) after the correction of the spin contamination error. This difference in the estimated barriers of the two systems can be attributed to the difference in their surface structures. The error obtained for the TiO₂/Ag system was larger than that obtained for the gas phase, i.e. the spin contamination error was induced by the molecule/surface interaction. Moreover, the error correction also changed the rate-determining step of ZrO₂/Cu. These results demonstrate the importance of the correction of spin contamination errors for the detailed investigation of catalytic reactions.     

Texture development and magnetic properties of [ZrO2/CoPt]n/Ag nanocomposite films

The L1₀ CoPt films with (0 0 1) preferred orientation are achieved by fabricating on the glass substrates and post annealing at 600° C for 30 min. The preferred orientation of [ZrO₂/CoPt]_n/Ag films dependence of the Ag underlayer thickness, ZrO₂ and CoPt interlayer thickness is investigated. A large perpendicular magnetic anisotropy and a nearly perfect L1₀ CoPt (0 0 1) texture are obtained in the [ZrO₂ (3 nm)/CoPt (5 nm)]₃/Ag (10 nm) film. The existence of ZrO₂ plays an important role in reducing the intergranular interactions and in determining the size of CoPt grains. Magnetic reversal in textured CoPt films are close to a Stoner-Wolfarth rotation.     

Surface phenomena of HA/TiN coatings on the nanotubular-structured beta Ti-29Nb-5Zr alloy for biomaterials

Surface phenomena of HA/TiN coatings on the nanotubular-structured beta Ti-29Nb-5Zr alloy for biomaterials have been investigated by several experimental methods. The nanotubular structure was formed by anodizing the Ti-29Nb-5Zr alloy in 1 M H₃PO₄ electrolytes with 1.0 wt.% NaF at room temperature. Hydroxyapatite (HA)/titanium nitride (TiN) films were deposited on Ti-29Nb-5Zr alloy specimens using a magnetron sputtering system. The HA target was made of human tooth-ash by sintering at 1300 °C for 1 h, and the HA target had an average Ca/P ratio of 1.9. The HA/TiN depositions were performed, using the pure HA target, on Ti-29Nb-5Zr alloy following the initial deposition of a TiN buffer layer coating. Microstructures and nanotubular morphology of the coated alloy specimens were examined by FE-SEM, EDX, XRD, and XPS. The Ti-29Nb-5Zr alloy substrate had small grain size and preferred orientation along the drawing direction. The HA/TiN coating was stable with a uniform morphology at the tips of the nanotubes.     

XPS investigation of diffusion of two-layer ZrO2/SiO2 and SiO2/ZrO2 sol–gel films

Two-layer ZrO₂/SiO₂ and SiO₂/ZrO₂ films were deposited on K9 glass substrates by sol–gel dip coating method. X-ray photoelectron spectroscopy (XPS) technique was used to investigate the diffusion of ZrO₂/SiO₂ and SiO₂/ZrO₂ films. To explain the difference of diffusion between ZrO₂/SiO₂ and SiO₂/ZrO₂ films, porous ratio and surface morphology of monolayer SiO₂ and ZrO₂ films were analyzed by using ellipsometry and atomic force microscopy (AFM). We found that for the ZrO₂/SiO₂ films there was a diffusion layer with a certain thickness and the atomic concentrations of Si and Zr changed rapidly; for the SiO₂/ZrO₂ films, the atomic concentrations of Si and Zr changed relatively slowly, and the ZrO₂ layer had diffused through the entire SiO₂ layer. The difference of diffusion between ZrO₂/SiO₂ and SiO₂/ZrO₂ films was influenced by the microstructure of SiO₂ and ZrO₂.     

Effect of Si addition on the stability of Al-10Ti-5Cu-xSi alloy/SiC interface

The effect of Si addition on the interfacial stability of Al-10Ti-5Cu-xSi (x = 0, 5, 10, 15) alloy/SiC is investigated. SiC and the Al-10Ti-5Cu-xSi alloys were compacted to obtain a stable interface with 10 wt% Si. Analysis of the processing conditions and the microstructures indicated that an excellent Ti₃SiC₂ phase had been formed and the deleterious Al₄C₃ phase had been eliminated successfully by the addition of 10 wt% Si to the Al-10Ti-5Cu alloy. Formation of Ti₃SiC₂ increased at first and then decreased, while the formation of Al₄C₃ was gradually inhibited with increasing Si content. Ti₃SiC₂ possesses good chemical stability, and flexibility. However, Al₄C₃ degrades within few days, in composites exposed to ambient conditions. The presence of Ti₃SiC₂ at the interface and the elimination of Al₄C₃ together ameliorate the bonding of Al-10Ti-5Cu-xSi alloy to SiC, thereby improving the interfacial stability of Al-10Ti-5Cu-xSi/SiC.     

Excellent stability of plasma-sprayed bioactive Ca3ZrSi2O9 ceramic coating on Ti-6Al-4V

In this work, novel zirconium incorporated Ca-Si based ceramic powder Ca₃ZrSi₂O₉ was synthesized. The aim of this study was to fabricate Ca₃ZrSi₂O₉ coating onto Ti-6Al-4V substrate using atmospheric plasma-spraying technology and to evaluate its potential applications in the fields of orthopedics and dentistry. The phase composition, surface morphologies of the coating were examined by XRD and SEM, which revealed that the Ca₃ZrSi₂O₉ coating was composed of grains around 100 nm and amorphous phases. The bonding strength between the coating and the substrate was 28 ± 4 MPa, which is higher than that of traditional HA coating. The dissolution rate of the coating was assessed by monitoring the ions release and mass loss after immersion in the Tris-HCl buffer solution. The in vitro bioactivity of the coating was determined by observing the formation of apatite on its surface in simulated body fluids. It was found that the Ca₃ZrSi₂O₉ coating possessed both excellent chemical stability and good apatite-formation ability, suggesting its potential use as bone implants.     

Structural-phase transformations at annealing of highly reflective mirrors based on aluminum and silver

Multilayered prototypes of Al and Ag total reflection mirrors with a protective coating of amorphous ZrO₂ oxide were analyzed using transmission electron (cross-sectional method), optical, and scanning (with electron probe microanalysis) microscopes. The prototypes’ reflectivity was measured by the recording of reflection spectra in the wavelength range 200–1100 nm. The structure of the mirrors was studied by X-ray diffraction reflection. High temperature annealing (8 h) did not change the stoichiometric composition of the protective coating. The reflectivity of the Al mirrors in the wavelength range 700–1100 nm and the Ag mirrors in the wavelength range of 500–1100 nm remained unchanged in spite of recrystallization of the polycrystalline metal films and the incipient process of amorphous ZrO₂ crystallization. The mass of the crystalline oxide after annealing was several percent of the total amorphous oxide mass. At the same time annealing led to the occurrence of local voids on the aluminum/upper oxide interface. Such defects were not observed on the Ag mirrors. As a whole, the Ag mirrors turned out to be more stable to heating as compared to those made of Al.     

Preparation of sol-gel ZrO2-SiO2 highly reflective multilayer films and laser-induced damage threshold characteristic

Sol-gel (ZrO₂/SiO₂)¹² ZrO₂ films were prepared by spin coating method. The reflectivity spectrum of the films was measured with a Lambda 900 spectrometer. In order to investigate laser-induced damage threshold (LIDT) characteristic of highly reflective films, one-layer ZrO₂ and SiO₂ films, two-layer ZrO₂/SiO₂ and SiO₂/ZrO₂ films were also prepared by spin coating method. LIDT of each film was measured. Damage morphology after laser irradiation was characterized by optical microscopy (Nikon E600K). The experimental results showed that the reflectivity of (ZrO₂/SiO₂)¹² ZrO₂ film at 1064 nm and 355 nm wavelength is 99.7%. The LIDT results decreases as the number of layer of films increases. All the films have similar damage morphology. The experimental results are explained by the different temperature profiles of the films.     

Swift ion irradiation effect on high-k ZrO2- and Al2O3-based MOS devices

This paper describes the heavy ion-induced effects on the electrical characteristics of reactively sputtered ZrO₂ and Al₂O₃ high-k gate oxides deposited in argon plus nitrogen containing plasma. Radiation-induced degradation of sputtered high-k dielectric ZrO₂/Si and Al₂O₃/Si interface was studied using 45?MeV Li³⁺ ions. The devices were irradiated with Li³⁺ ions at various fluences ranging from 5?×?10⁹ to 5?×?10¹²?ions/cm². Capacitance–voltage and current–voltage characteristics were used for electrical characterization. Shift in flat band voltage towards negative value was observed in devices after exposure to ion radiation. Post-deposition annealing effect on the electrical behavior of high-k/Si interface was also investigated. The annealed devices showed better electrical and reliability characteristics. Different device parameters such as flat band voltage, leakage current, interface defect density and oxide-trapped charge have been extracted.The surface morphology and roughness values for films deposited in nitrogen containing plasma before and after ion radiation are extracted from Atomic Force Microscopy.