From Zirconium Nanograins to Zirconia Nanoneedles

Impact of Annealing on ZrO2 Nanotubes for Photocatalytic Application

This work aims to study the structural, optical, and photocatalytic properties of ZrO2 nanotubes (NTs) that have been synthesized using the electrochemical anodization method. The structural and morphological characteristics of unannealed and annealed (400 °C, 500 °C, and 700 °C) ZrO2 NTs were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Details of the structural and morphological results are depicted to clarify the effect of annealing temperature on the NTs. Furthermore, the reflectivity and photoluminescence of ZrO2 NTs were found to depend on the annealing temperature. The resulting bandgap values were 3.1 eV for samples annealed at 400 °C and 3.4 eV for samples annealed at 550 and 700 °C. Thus, amorphous and annealed ZrO2 NTs were tested in terms of their photocatalytic degradation of Black Amido (BA) dye. Samples annealed at 400 °C exhibited 85.4% BA degradation within 270 min compared to 77.5% for samples annealed at 550 °C and 70.2% for samples annealed at 700 °C. The anodized ZrO2 NTs that were annealed at 400 °C showed the coexistence of tetragonal and monoclinic crystalline phases and exhibited the fastest photocatalytic performance against the BA dye. This photocatalytic behavior was correlated to the crystalline phase transformation and the structural defects seen in anodized ZrO2.

Nanomechanical properties of zirconium anodized in a mixture of electrolytes with fluoride ions

The present work introduces nanostructured Zr as a possible choice of metallic implant biomaterial in competition with titanium and its new alloys. The paper reports on the preparation of anodized zirconium in a mixture of electrolytes with fluoride ions, 1 M (NH₄)2SO₄ + 0.15 M NH₄F + distilled water, at 20 V. The obtained nanostructures were investigated by SEM, EDX, XRD and AFM techniques. The SEM - EDX longitudinal and cross sectional analysis revealed the morphology of the formed oxide layers and their thicknesses, which were found to be 7.45 ± 0.18 μm. The mean nanopores' diameter was calculated as 15.8 ± 3.3 nm. The XRD investigations enabled the evaluation of crystallite sizes and texture coefficients for zirconium and zirconium oxide containing samples. The inhibition effect against Escherichia coli and Streptococcus Aureus bacteria was evaluated and discussed as well. The AFM studies revealed that the nano-porous Zr has similar hardness parameter as the uncoated Zr, but lower surface adhesion force that could be translated into improved properties in terms of antimicrobial effects, as confirmed by its inhibition index, which makes it a very promising material for bio-medical applications.

Preparation of a Novel Transplant Material, Zirconium Oxide (ZrO₂) Nanotubes, and Characterizations Research

Background

Zirconia is one of the most widely used ceramic materials for transplanting and treating caries. This study aimed to synthesize zirconium oxide (ZrO₂) nanotubes and evaluated their characteristics.

Material/Methods

Zr film was prepared using an ion plating method. Nanoarray film was constructed with anodizing. Photocatalytic properties of nnanotubes were assessed by evaluating decolorization of methyl orange. Elemental analysis and structural morphology for coatings were evaluated using x-ray analysis and scanning electron microscopy (SEM). Dimensions for layers were measured with SEM imaging. X-ray diffraction (XRD) was measured using Empyrean x-ray diffractometry.

Results

There were irregular cavities on the surface of ZrO₂ nanotubes undergoing anodizing of 30V. Anodizing voltage of 45 V (with regular nano-pore arrays and smooth nanotube walls) and anodic oxidation duration of 60 min (ZrO₂ nanotubes clearly formed atop ZrO₂-coated substrate surface) were the optimal condition for ZrO₂ nanotube formation. TEM illustrated tube length of ZrO₂ nanotubes was approximately 2.01 μm. Nanotube diameter was 51.06 nm, and wall thickness was 13 to 14 nm. Annealed nanotubes showed an obvious crystal diffraction pattern. TEM diffraction ring showed nanotube array without obvious transistor structure before annealing, but with good crystallinity post-annealing. Increased annealing temperatures result in enhanced intensity for the monoclinic phase (400–800°C). After annealing at 600°C, the decolorization effect of ZrO₂ nanotubes on methyl orange was better than that post-annealing at 400 and 800°C. ZrO₂ nanotubes demonstrated higher microshear bond strength.

Conclusions

Zirconium nanotubes were successfully synthesized and demonstrated good structural characteristics, which can be applied to transplanting and treating caries.

Ductilization of Nanoporous Ceramics by Crystallinity Control

Synthesizing ceramic materials with a significant amount of deformability is one of the most important engineering pursuits. In this study, we demonstrate the emergence of metal-like plasticity through the crystallinity control in the monolithic zirconia with the vertically aligned honeycomb-like periodic nanopore structures fabricated using the anodizing technique. The crystalline orders of the nanoporous zirconia films vary between monoclinic, tetragonal, and amorphous phases after the heat treatment and/or proton irradiation, whereas the vertical pore structures are maintained. The micropillar compression tests on those samples reveal a large amount of plasticity, more than 20% of total stains, in the as-anodized and proton-irradiated samples, both of which contain the amorphous phase. In contrast, the fully crystallized zirconia that resulted from annealing at 500 °C shows the brittle failure, the typical characteristic of conventional ceramic foams. These results offer a new opportunity for the nanoporous ceramic materials to be used in various applications, benefited from the tunable structural stability.

Properties Investigation of GO/HA/Pt Composite Thin Film

Hydroxyapatite/graphene oxide/platinum (HA/GO/Pt) nanocomposite was synthesized and electrodeposited on a pure zirconium substrate. The coated zirconium was annealed at 200, 300, 400, and 600°C in vacuum furnace in presence of argon gas. The structure and morphology of the coated samples were characterized. Biocompatibility and wear and corrosion resistances of specimens were examined. The result of corrosion tests shows that the graphene into HA/Pt composites significantly improves their corrosion resistance. The wear tests results of uncoated and coated samples before and after annealing show that coated samples annealed at 300°C had better wear resistance compared with uncoated and coated samples at other temperatures. Furthermore, the biocompatibility test shows that the coatings improved the cell attachment and proliferation compared to the pure zirconium substrate.

Controlled Synthesis of ZrO2 Nanoparticles with Tailored Size, Morphology and Crystal Phases via Organic/Inorganic Hybrid Films

In this investigation, well defined mesoporous zirconia nanoparticles (ZrO₂ NPs) with cubic, tetragonal or monoclinic pure phase were synthesized via thermal recovery (in air) from chitosan (CS)- or polyvinyl alcohol (PVA)-ZrO_x hybrid films, prepared using sol–gel processing. This facile preparative method was found to lead to an almost quantitative recovery of the ZrOx content of the film in the form of ZrO₂ NPs. Impacts of the thermal recovery temperature (450, 800 and 1100 °C) and polymer type (natural bio-waste CS or synthetic PVA) used in fabricating the organic/inorganic hybrid films on bulk and surface characteristics of the recovered NPs were probed by means of X-ray diffractometry and photoelectron spectroscopy, FT-IR and Laser Raman spectroscopy, transmission electron and atomic force microscopy, and N₂ sorptiometry. Results obtained showed that the method applied facilates control over the size (6–30 nm) and shape (from loose cubes to agglomerates) of the recovered NPs and, hence, the bulk crystalline phase composition and the surface area (144–52 m²/g) and mesopore size (23–10 nm) and volume (0.31–0.11 cm³/g) of the resulting zirconias.