Yeon-Hum Yun

Functionally graded Ti/HAP coatings on Ti–6Al–4V obtained by chemical solution deposition

Graded Ti100−x/HAPx (x=0 – 100%) films were prepared on Ti–6Al–4V implants by chemical solution deposition using a titanium-isopropoxide chelated by acetylacetone, calcium nitrate and phosphoric acid as starting materials. Ti/HAP solutions with variable HAP contents from 0 to 100% at 10% intervals were spin coated on the substrates and prefired at 500 °C. X-ray diffraction and field emission-scanning electron microscope analysis showed that Ti/HAP coatings were obtained with a dense interface between coating and substrate by final annealing at 500 °C and higher. The effectiveness of the functionally graded HAP/Ti coatings was discussed based on the analysis of the variation of Ca and P contents in simulated body fluid as a function of annealing temperature.

Waste fluorescent glass and shell derived glass-ceramics

We prepared glass-ceramics by using fluorescent glass and waste shell as starting materials to recycle waste fluorescent glass containing harmful Hg to human body and waste shell, and to resolve environmental problems. Pressed specimens after quenching and grinding were heat treated at 800°C, 900°C and 1000°C for 1 h, respectively. β-wollastonite, gehlenite and sodium calcium silicate were observed by X-ray diffraction studies. Surface morphology and chemical composition were evaluated by field emission-scanning electron microscopy and energy dispersive X-ray spectrometer.

Preparation of epitaxial and polycrystalline bismuth titanate thin films on single crystal (100) MgO by chemical solution deposition

Abstract Epitaxial and polycrystalline Bi 4 Ti 3 O 12 thin films were prepared on single crystal (100) MgO substrates by a chemical solution deposition process using metal naphthenates as starting materials. Pyrolyzed films (at 500°C) were annealed for 30 min in air at 650, 700, 750 and 800°C, respectively. The effects of annealing temperature on the crystallinity, epitaxy and surface morphology of the films were investigated by X-ray diffraction θ-2θ scans, pole-figure analysis, and atomic force microscopy (AFM). Epitaxially grown films annealed at 700 and 750°C, respectively, showed growth of three-dimensional needle-shaped grains. During annealing at 800°C, grain growth of Bi 4 Ti 3 O 12 may be suppressed by the formation of a titanium-rich phase such as Bi 2 Ti 2 O 7 owing to Bi volatilization, resulting in lower root mean square roughness than that of film annealed at 750°C.

Glass-ceramics prepared by waste fluorescent glass

To prepare glass-ceramics reinforced by β-wollastonite, fluorescent glass and calcium carbonate were used as starting materials. β-Wollastonite, gehlenite and sodium calcium silicate were observed by X-ray diffraction analysis, and surface morphology and chemical composition were evaluated by field emission-scanning electron microscopy and energy dispersive X-ray spectrometer.

Preparation of Yttria-Stabilized Tetragonal Zirconia Ceramics for Optical Ferrule

Yttria-stabilized zirconia ceramics are considered to be one of the most important ceramic materials for use in structural applications, because of the high strength and toughness of yttria-stabilized tetragonal zirconia polycrystals. In this work, in order to prepare dense and compact yttria-stabilized tetragonal zirconia body after sintering at 1400°C, we used various raw materials with different particle properties, such as crystallinity, particle size distribution, and particle shape. Crystallinity and tetragonal percentage of the sintered samples were analyzed by X-ray diffraction. Microstructure of the sintered samples was evaluated by field emission-scanning electron microscopy.

Physical properties and photocatalytic activity of chitosan-based nanocomposites added titanium oxide nanoparticles

In this study, nanocomposite films were prepared by using chitosan (CHS), poly(vinyl alcohol) (PVA), titanium oxide (TiO2) nanoparticles, sulfosuccinic acid (SSA) as a crosslinking agent, and sorbitol (SO) and citric acid (CA) as plasticizers. The CHS/PVA nanocomposite films were characterized by X-ray diffraction (XRD), Fourier transform IR spectrophotometry (FTIR), and scanning electronic microscopy (SEM). The results of the XRD and FTIR analysis verified that TiO2 characteristic peaks existed in the prepared nanocomposite films. In addition, the intensity of TiO2 characteristic peaks increased with the increase of TiO2 contents. The physical properties such as tensile strength (TS), elongation at break (%E), swelling behavior (SB), and solubility (S) were investigated. The results indicated that compared with films without added TiO2, the mechanical properties and water resistance were enhanced up to 1.42-1.50 times with the addition of TiO2. The photocatalytic degradability of the prepared films containing TiO2 was evaluated using bisphenol A (BPA) and methyl orange (MO) as photodegradation targets. In addition, the photocatalytic degradation kinetics were evaluated using the pseudo-first-order Lagergren equation.

Calcium phosphate forming ability of thermally oxidized titanium implant

Commercially pure titanium disks as-received and heat treated at 600°C in air for 10 min were used to investigate differences in calcium phosphate forming ability. Crystallinity and surface morphology were analyzed by X-ray diffraction and field emission scanning electron microscopy. Energy dispersive X-ray spectrometry and Fourier transform infrared reflection spectroscopy were used to collect information on chemical composition and chemical surface structure. TiO2 layers with a heterogeneous structure produced by heat treatment showed highin vitro calcium phosphate forming ability in contact with Eagle’s minimum essential medium.

Growth mechanism of chemical solution derived PZT films on MgO(100) substrate

PZT (Zr : Ti = 0.53 : 0.47) thin films were fabricated by chemical solution deposition with metal naphthenates used as starting materials. Effect of final annealing temperature on epitaxy and surface morphology of the films were investigated. PZT films prefired at 200°C were crystallized to be highly (00l)/(h00)-oriented at final annealing temperatures of 750°–800°C. The film annealed at 750°C was smooth and no distinct texture was exhibited, while the rosette-type microstructure caused by lead volatilization was observed in the films after annealing at 800°C.

Crystallinity and surface morphology of chemical solution derived epitaxial Bi4Ti3O12 thin films on (100)LaAlO3

Bi4Ti3O12 thin films were prepared on single-crystal (100)LaAlO3 substrates by chemical solution deposition using metal naphthenates as starting materials. Precursor films were pyrolyzed at 500°C for 10 min in air and finally annealed at 650, 700, 750 and 800°C for 30 min in air, followed by rapid cooling. Crystallinity and in-plane alignment of the thin films were investigated by X-ray diffraction θ–2θ scans and pole-figure analysis. A field emission-scanning electron microscope and an atomic force microscope were adopted for characterizing the surface morphology and the surface roughness of the films. Epitaxially grown thin films annealed at 650 and 700°C exhibited extremely flat surfaces. On the contrary, with the increase in annealing temperatures to 750 and 800°C, the columnar grain size and width of the films uniformly increased.

Calcium phosphate formation on nanocrystalline ZrO2 thin film prepared by using a zirconium naphthenate.

To investigate the calcium phosphate forming ability of ZrO2 thin film, we prepared ZrO2/Si structure by a chemical solution deposition with a zirconium naphthenate as a starting material. Precursor sol was spin-coated onto the cleaned Si substrate and prefired at 500 °C for 10 min in air, followed by final annealing at 800 °C for 30 min in air. Surface morphology and surface roughness of the annealed layer were characterized by field emission-scanning electron microscope and atomic force microscope. After soaking for 5 days in a simulated body fluid, formation of the calcium phosphate on nanocrystalline ZrO2 layer annealed at 800 °C was observed by energy dispersive X-ray spectrometer. Fourier transform infrared spectroscopy revealed that carbonate was substituted into the calcium phosphate.