• Journal of Powder Materials
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• v.29 no.3
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• pp.207-212
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• 2022

Nanosized rutile titanium dioxide (TiO₂) is used in inorganic pigments and cosmetics because of its high whiteness and duality. The high quality of the white pigments depends on their surface coating technique via the solgel process. SiO₂ coatings are required to improve the dispersibility, UV-blocking, and whiteness of TiO₂. Tetraethyl orthosilicate (TEOS) is an important coating precursor owing to its ability to control various thicknesses and densities. In addition, we use Na₂SiO₃ (sodium silicate) as a precursor because of its low cost. Compared to TEOS, which controls the pH using a basic catalyst, Na₂SiO₃ controls the pH using an acid catalyst, giving a uniform coating. The coating thickness of TiO₂ is controlled using a surface modifier, cetrimonium bromide, which is used in various applications. The shape and thickness of the nanosized coating layer on TiO₂ are analyzed using transmission electron microscopy, and the SiO₂ nanoparticle behavior in terms of the before-and-after size distribution is measured using a particle size analyzer. The color measurements of the SiO₂ pigment are performed using UV-visible spectroscopy.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.2
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• pp.109-115
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• 2022

The demand for metal 3D printing technology is increasing in various industries. The materials commonly used for metal 3D printing include aluminum alloys, titanium alloys, and stainless steel. In particular, for applications in the aviation and defense industry, aluminum alloy 3D printing parts are being produced. To improve the corrosion resistance in the 3D printed aluminum alloy outputs, a post-treatment process, such as chromate coating, should be applied. However, powdered materials, such as AlSi7Mg and AlSi10Mg, used for 3D printing, have a high silicon content; therefore, a suitable pretreatment is required for chromate coating. In the desmut step of the pretreatment process, the chromate coating can be formed only when a smut composed of silicon compounds or oxides is effectively removed. In this study, suitable desmut solutions for 3D printed AlSi7Mg and AlSi10Mg materials with high silicon contents were presented, and the chromate coating properties were studied accordingly. The smut removal effect was confirmed using an aqueous desmut solution composed of sulfuric, nitric, and hydrofluoric acids. Thus, a chromate coating was successfully formed. The surfaces of the aluminum alloys after desmut and chromate coating were analyzed using SEM and EDS.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.3
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• pp.399-407
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• 1998

The infrared reflection coatings with pigment can be used to protect the surfaces of combustible materials exposed to fire. To obtain high reflectivities in the infrared range (0.5-10.mu.m) important to fire, several dielectric pigments, such as titanium dioxide, iron oxide, and silicon, can be synthesized to polymer coatings. The theoretical analysis shows that the coating design with particles diameter in the 1.5 to 2.5.mu.m range and volume fraction in the 0.1 to 0.2 range is estimated to be optimal. In the analysis of the radiation, the dependent scattering, absorption by polymeric binder, and the internal interface reflection are considered. In addition, the temperature distribution in the semi-transparent coating layer and an opaque substrate (PMMA) is also presented.

• Korean Journal of Materials Research
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• v.18 no.1
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• pp.22-25
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• 2008

In this study, calcium titanate $(CaTiO_3)$ gel was prepared by mixing calcium nitrate and titanium isopropoxide in 2-methoxy-ethanol. $CaTiO_3$ gel was single-layer coated on Ti-6Al-4V using a sol-gel dip-coating technique. The coating was calcined at $750^{\circ}C$ in air by utilizing a very slow heating rate of $2^{\circ}C/min$. The crystalline phases of the coating were characterized by x-ray diffraction using a slow scan rate of $1^{\circ}/min$. The morphology of the coating was analyzed by scanning electron microscopy. The corrosion behavior of Ti-6Al-4V samples coated with $CaTiO_3$ films were tested in an artificial saliva solution by potentiodynamic polarization and were quantified by the Tafel extrapolation method. The electrochemical parameters showed a considerable increase in the corrosion resistance for the $CaTiO_3$-coated Ti-6Al-4V samples compared to bare substrates.

• Journal of Surface Science and Engineering
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• v.52 no.4
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• pp.187-193
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• 2019

Electroless Ni-P coatings are widely used in the chemical, mechanical, and electronic industries because of their excellent wear and abrasion resistance. In this study, the effect of $TiO_2$ particles of composite coating was investigated. To improve the corrosion resistance, electroless $Ni-P-TiO_2$composite coating was studied by varying the $TiO_2$ content. The morphology and phase structure of $Ni-P-TiO_2$ composite coatings were analyzed by scanning electron microscopy(SEM), X-ray diffractometry(XRD) and X-ray photoelectron spectroscopy(XPS). The result showed that $Ni-P-TiO_2$composite coating is composed of Ni, P, Ti and O. It exhibits an amorphous structure, high hardness and good corrosion resistance to the substrate. $Ni-P-TiO_2$ composite coatings have higher open circuit potential than that of the substrate, which obtained at $TiO_2$ content of 5.0 g/L optimal integrated properties.

• Journal of the Korean Vacuum Society
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• v.14 no.3
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• pp.165-170
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• 2005

There is an increasing interest in developing novel coating to improve the blood compatibility of medical implants. Diamond-like carbon(DLC) and titanium nitride(TiN) films have been proposed as potential biomedical coatings due to their chemical k physical properties and moderate biocompatibility. To study the correlation between blood compatibility and physical properties of the films, the fibrinogen adsorption on the surface as well as morphology & wettability were investigated. The quantity of fibrinogen adsorption are Tower for TiN than DLC, which correlates with a higher hydrophilicity of TiN film. To reduce the quantity of fibrinogen adsorption on the film, plasma treatment and furnace annealing were performed, respectively. With the use of oxygen plasma and furnace annealing, the amount of fibrinogen adsorption on TiN film was remarkably reduced, while there was no decrease of the quantity with DLC.

• Molecular & Cellular Toxicology
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• v.4 no.3
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• pp.192-198
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• 2008

A variety of titanium (Ti) and its alloys are used in the clinical procedures of bone regeneration for periodontal and dental implant therapies. This study was performed to determine the effect of different surface dental implant materials on biologic responses of a MG-63 human osteoblast-like cell line. MG-63 cells were cultured on Ti coated with hydroxyapatite (HA), calcium metaphosphate (CMP), anodized (A), which compared with non-coated Ti (control). The appearances of surface of dental implant materials and the morphology of these cells were assessed by scanning electron microscopy (SEM). The gene expression profiles of MG-63 cells cultured on Ti were examined by human cDNA microarray (1,152 elements). The expression of several genes was up- and down-regulated by different surfaces of dental implant materials. Interesting, the genes correlated with cellular adhesion and extra cellular matrix (ECM) formation were enhanced, in accordance surface morphology of the dental implant materials used.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.5
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• pp.84-90
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• 2015

Titanium alloys has been received an attention due to their excellent specific strength and many other superior properties in the application of components of flying subjects. In this study, Ti-6Al-4V (Ti64 alloy) has been selected in order to evaluate oxidation and degradation behaviors under the exposure of high temperature flame. The alloy has been coated with Al diffusion coating routes. The coated alloys showed an improved oxidation and degradation behaviors. The oxidation and degradation mechanism for the coated and uncoated alloys has been discussed in terms of microstructural observations.

• Steel and Composite Structures
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• v.23 no.2
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• pp.153-160
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• 2017

It is extremely important to be aware of the ballistic performances of engineering materials in order to be able to choose the lightest armor providing full ballistic protection in civil and military applications. Therefore, ballistic tests are an important part of armor design process. In this study, ballistic performance of plates made of carbon steel and cold worked tool steel against 7.62 mm AP (armor-piercing) bullets was examined experimentally and numerically in accordance with NIJ standards. Samples in different sizes were prepared to demonstrate the effect of target thickness on ballistic performance. Some of these samples were coated with titanium nitride using physical vapor deposition (PVD) method. After examining all successful and unsuccessful samples at macro and micro levels, factors affecting ballistic performance were determined. Explicit non-linear analyses were made using Ls-Dyna software in order to confirm physical ballistic test results. It was observed that the ballistic features of steel plates used in simulations comply with actual physical test results.

• Journal of Surface Science and Engineering
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• v.23 no.1
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• pp.16-26
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• 1990

The standrd electrolyte for the electrodeposition of chromium were preparwith reagent grade chromic acid(200g/L), sulfuric acid(pH=1.8)and oxalic acalic acid(640g/L)as additive. Carbon content in chromium plating varied about2.0-3.8 wt% with current density and temperatures of the bath. The hardeness of chromium platings incresed with increasing the annealing temperatures and showed maximum value of about Hv 1700 after annealing at$ 700^{\circ}C$for 60min. But, decreased it as annealing at above $700^{\circ}C$. The reason for varing thee hardness of chromium codeposited with carbon gradually foumed chromium carbide(Cr7C3), but that changed to Cr23C6 as annealing temperature at above $^700{\circ}C$. The X-ray diffraction pattern indicated that chromium carbides, such as Cr7C3 or Cr3C2, formed at formed at above $300^{\circ}C$. titanium coating sputtered on the on surface of chromium plating had performed and determined the hardness after annealing at 500, 600, $700^{\circ}C$ for 60min. the maximum hardeness was about Hv 2400 as annealing at $700^{\circ}C$. The titanium carbide formed in layer was identified by X-ray diffraction. It was confirmed that chromium and titanium carbide has effect of increasing the hardness.