• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.152-152
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• 2017

Titanium and its alloys have been widely used for biomedical applications. However, the use of the Ti-6Al-4V alloy in biomaterial is then a subject of controversy because aluminum ions and vanadium oxide have potential detrimental influence on the human body due to vanadium and aluminum. Hence, recent works showed that the synthesis of new Ti-based alloys for implant application involves more biocompatible metallic alloying element,such as, Nb, Hf, Zr and Mo. In particular, Nb and Hf are one of the most effective Ti ${\beta}$-stabilizer and reducing the elastic modulus. Plasma electrolyte oxidation (PEO) is known as excellent method in the biocompatibility of biomaterial due to quickly coating time and controlled coating condition. The anodized oxide layer and diameter modulation of Ti alloys can be obtained function of improvement of cell adhesion. Silicon (Si) and magnesium (Mg) has a beneficial effect on bone. Si in particular has been found to be essential for normal bone and cartilage growth and development. In vitro studies have shown that Mg plays very important roles in essential for normal growth and metabolism of skeletal tissue in vertebrates and can be detected as minor constituents in teeth and bone. Therefore, in this study, Si and Mg coatings on the hydroxyapatite film formed Ti-29Nb-xHf alloys by plasma electrolyte oxidation has been investigated using several experimental techniques. Ti-29Nb-xHf (x= 0, 3, 7 and 15wt%, mass fraction) alloys were prepared Ti-29Nb-xHf alloys of containing Hf up from 0 wt% to 15 wt% were melted by using a vacuum furnace. Ti-29Nb-xHf alloys were homogenized for 2 hr at $1050^{\circ}C$. The electrolyte was Si and Mg ions containing calcium acetate monohydrate + calcium glycerophosphate at room temperature. The microstructure, phase and composition of Si and Mg coated oxide surface of Ti-29Nb-xHf alloys were examined by FE-SEM, EDS, and XRD.

• Korean Journal of Metals and Materials
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• v.48 no.4
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• pp.369-375
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• 2010

Ti-6Al-4V ELI alloy, which is commonly used as a biomaterial, is associated with a high elastic modulus and poor biocompatibility. This alloy presents a variety of problems on several areas. Therefore, the development of good non-toxic biocompatible biomaterials with a low elastic modulus is necessary. Particularly, hydroxyapatite (HA) is an attractive material for human tissue implantation. This material is widely used as artificial bone due to its good biocompatibility and similar composition to human bone. Many scientists have studied the fabrication of HA as a biomaterial. However, applications of bulk HA compact are hindered by the low strength of HA when it is sintered. Therefore, HA has been coated on Ti or Ti alloy to facilitate good bonding between tissue and the HA surface. However, there are many problems when doing this, such as the low bonding strength between HA and Ti due to the different thermal expansion coefficients and mechanical properties. In this study, a Ti-HA composite with a porous surface was successfully fabricated by pulse current activated sintering (PCAS) and a subsequent leaching process.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.386-386
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• 2010

최근 널리 보급되고 있는 치과용 임플란트는 티타늄(Ti) 또는 티타늄 합금(Ti-6Al-4V) 보철과 크라운을 연결하여 사용하고 있다. 티타늄은 생체 친화성이 우수하나, 생체 활성도가 없어 치유기간이 긴 단점이 있다. 이를 보완하기 위해 인체 경조직과 유사한 수산화아파타이트(hydroxyapatite, $Ca_{10}(PO_4)_6(OH)_2)$를 티타늄 임플란트 표면에 코팅하는 방법이 연구되고 있으나 수산화아파타이트 코팅은 티타늄과의 접착성이 나쁘기 때문에 시술 및 사용과정에서 코팅층이 임플란트로부터 박리되는 문제점이 있다. 본 연구에서는 티타늄과 수산화아파타이트 사이에서 접착력을 향상시키는 buffer layer로서 지르코니아(8YSZ, 8mol% Yttria-stabilized zirconia)를 연구하였다. 지르코니아는 고온에서 안정하며, 티타늄 합금과 수산화아파타이트 사이의 반응을 방지하며, 박막밀도와 기계적 강도가 좋은 생체세라믹스이다. 지르코니아 박막을 펄스 레이저 증착법을 이용하여 증착 온도 $600^{\circ}C$, 레이저 fluence $2\;J/cm^2$에서 산소($O_2$) 분압을 바꿔 가며 증착하였다. 그 위에 수산화아파타이트 박막을 역시 펄스 레이저 증착법으로 증착하였다. Scratch test와 Pull-off test를 통해 접착력을 평가한 결과 지르코니아 buffer layer 삽입에 의해 티타늄 합금과 수산화아파타이트 사이의 접착력이 향상되었음을 확인하였다. 또한 산소분압이 박막의 특성 및 접착력에 미치는 영향을 고찰하였다.

• Journal of Technologic Dentistry
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• v.27 no.1
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• pp.9-17
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• 2005

The use of titanium alloys as biomaterials is increasing due to their superior biocompatibility and enhanced corrosion resistance compared to conventional stainless steels and cobalt-based alloys. Ti-6Al-4V ($\alpha+\beta$type) alloy instead of pure titanium ($\alpha$type) is being widely used as biomaterials has some characteristics such as high fatigue strength, tensile strength and corrosion resistance. But it has been reported recently that the vanadium element expresses cytotoxicity and the aluminium element is related with dementia of Alzheimer type and neurotoxicity. In order to overcome their detrimental effects, $\beta$-phase stabilizer Nb was chosen in the present study. This paper was described the influence of phase changes of Ti-Nb alloys on mechanical properties. Ti-3wt.%Nb($\alpha$type),Ti-20wt.%Nb($\alpha+\beta$type) and Ti-40wt.%Nb($\beta$type) alloys were melted by vacuum arc furnace. The specimens were homogenized at 1050$^{\circ}C$ for 24hr and were then hot rolled to 50% reduction. Each alloys were solution heat treated at $\beta$ zone and $\alpha+\beta$ zone after homogenization and then were aged. The mechanical properties of Ti alloys were analysed by hardness test, tensile test, elongation test and SEM test. The results can be summarized as follows: 1) The higher hardness value of $\alpha+\beta$type alloy was obtained compared to the, $\alpha,\beta$type alloys. 2) The aged treated showed better hardness compared to the solution heat treated, homogenized. 3) In the case of solution and aging treatment at $\beta$region, the $\alpha+\beta$type alloy showed the most highest tensile strength and $\beta$type alloy showed the best elongation.

• Structural Engineering and Mechanics
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• v.35 no.6
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• pp.659-676
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• 2010

An energy-based fatigue life prediction framework was previously developed by the authors for prediction of axial and bending fatigue life at various stress ratios. The framework for the prediction of fatigue life via energy analysis was based on a new constitutive law, which states the following: the amount of energy required to fracture a material is constant. In this study, the energy expressions that construct the new constitutive law are integrated into minimum potential energy formulation to develop new finite elements for uniaxial and bending fatigue life prediction. The comparison of finite element method (FEM) results to existing experimental fatigue data, verifies the new finite elements for fatigue life prediction. The final output of this finite element analysis is in the form of number of cycles to failure for each element in ascending or descending order. Therefore, the new finite element framework can provide the number of cycles to failure for each element in structural components. The performance of the fatigue finite elements is demonstrated by the fatigue life predictions from Al6061-T6 aluminum and Ti-6Al-4V. Results are compared with experimental results and analytical predictions.

• Economic and Environmental Geology
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• v.40 no.6
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• pp.727-738
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• 2007

The present study investigation the geochemical characteristics of the stream sediments in the Unbong area was conducted to enable a understanding the natural background and a prediction the prospects of geochemical disaster as a result of that bed rocks(mylonitic granites, Kim et al., 1992). We systematically collected seventy three stream sediments samples by wet sieving along the primary channels. Major, trace and rare earth element(REE) concentrations, combined with mineralogical characteristics, were determined by XRD, XRF, ICP-AES and NAA analysis methods. Major element concentrations for the stream sediments in the Unbong area were $SiO_2\;36.94{\sim}65.39wt.%,\;Al_2O_3\;10.15{\sim}21.77wt.%,\;Fe_2O_3\;3.17{\sim}10.90wt.%,\;CaO\;0.55{\sim}5.27wt.%,\;MgO\;0.52{\sim}4.94wt.%,\;K_2O\;1.38{\sim}4.54wt.%,\;Na_2O\;0.49{\sim}3.36wt.%,\;TiO_2\;0.39{\sim}1.27wt.%,\;MnO\;0.04{\sim}0.22wt.%,\;P_2O_5\;0.08{\sim}0.54wt.%$. Trace and REE concentrations for the stream sediments were $Cu\;4.8{\sim}134ppm,\;Pb\;24.2{\sim}82.5ppm,\;Sr\;95.9{\sim}739ppm,\;V\;19.9{\sim}124ppm,\;Zr\;52.9{\sim}145ppm,\;Li\;25.2{\sim}3.3ppm,\;Co\;3.87{\sim}50.0ppm,\;Cr\;17.4{\sim}234ppm,\;Hf\;3.93{\sim}25.2ppm,\;Sc\;4.60{\sim}20.6ppm,\;Th\;3.82{\sim}36.9ppm,\;Ce\;45.7{\sim}243ppm,\;Eu\;0.89{\sim}2.69ppm,\;Yb\;1.42{\sim}5.18ppm$. According to the comparison of average major element concentrations, CaO, $Na_2O\;and\;K_2O$ contents are higher in stream sediments than in bed rocks(mylonitic granites, Kim et al., 1992) $Al_2O_3\;and\;SiO_2$ contents show good correlation both stream sediments and bed rocks(mylonitic granites, Kim et al., 1992). Yb and Eu in the stream sediments show a positive correlation with $SiO_2$. In contrast, the stream sediments display a negative correlation.

• Journal of Korea Foundry Society
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• v.26 no.2
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• pp.85-91
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• 2006

Inclusions in Ti investment castings are generally known to have detrimental effects on the performance of the castings. However, actual inclusions are infrequent and hard to be located. As a result, it is extremely difficult to obtain sufficient amount of fatigue test specimens of titanium investment castings having inclusions in the gage section. Thus, in-depth research of the adverse influence of inclusions is also hindered. To address this problem, a new casting methodology of specimens containing hard alpha inclusions was developed in this study. To guarantee successful introduction of an inclusion and casting, a carefully designed mold with 8 legs and a special tool were employed. After solidification, castings were cut, and X-ray radiography determined that the inclusions were successfully incorporated into the castings. The castings were further prepared to obtain multiple test specimens and they were fatigue-tested consecutively. Fractography analysis confirmed that fatigue cracks initiated at the hard alpha inclusion. In a nonlinear regression model, the fatigue life can be modeled as an exponential function with a negative exponent of the cross-sectional area of an inclusion. The fatigue life of Ti specimens containing inclusions is inversely proportional to the cross-sectional area of an inclusion.

• Analytical Science and Technology
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• v.20 no.1
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• pp.33-40
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• 2007

This study centered on the quantitative analysis of about 27 trace elements including toxic ones using instrumental neutron activation analysis of fine ambient particulate matter in the third and fourth industrial complex area of Daejeon city, Korea. For analytical quality control, the certified reference material (NIST, the National Institute of Standards and Technology, U.S.A., SRM 2783, air particulate on filter media) was used. The errors relative to SRM values of Sb, Mn, V, Mg, Na, K, Ti, Co, Zn, and Sm fell below 5%, while those of Cr, Fe, Ba, Th, Ce, Al, and Cu were less than 10%. From the results of the quantitative analysis, the concentration of toxic metals such as As, Mn, Se, V, and Zn were $3.26{\pm}2.72$, $9.86{\pm}4.71$, $2.18{\pm}1.25$, $4.91{\pm}2.41$, $158{\pm}78ng/m^3$, respectively. And the results of factor analysis indicated that there are no more than six factors of sources of fine ambient particulate with statistical significance in the study area.

• Korean Journal of Materials Research
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• v.21 no.7
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• pp.384-390
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• 2011

Ti-6Al-4V ELI (Extra Low Interstitial) alloy has been widely used as an alternative to bone due to its excellent biocompatibility. However, it still has many problems, including a high elastic modulus and toxicity. Therefore, nontoxic biomaterials with a low elastic modulus should be developed. However, the fabrication of a uniform coating is challenging. Moreover, the coating layer on Ti and Ti alloy substrates can be peeled off after implantation. To overcome these problems, it is necessary to produce bulk Ti and Ti alloy with hydroxyapatite (HA) composites. In this study, Ti, Nb, and Zr powders, which are biocompatible elements, were milled in a mixing machine (24h) and by planetary mechanical ball milling (1h, 4h, and 6h), respectively. Ti-35%Nb-7%Zr and Ti-35%Nb-7%Zr-10%HA composites were fabricated by spark plasma sintering (SPS) at $1000^{\circ}C$ under 70MPa using mixed and milled powders. The effects of HA addition and milling time on the biocompatibility and physical and mechanical properties of the Ti-35%Nb-7%Zr-(10%HA) alloys have been investigated. $Ti_2O$, CaO, $CaTiO_3$, and $Ti_xP_y$ phases were formed by chemical reaction during sintering. Vickers hardness of the sintered composites increases with increased milling time and by the addition of HA. The biocompatibilty of the HA added Ti-Nb-Zr alloys was improved, but the sintering ability was decreased.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.11
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• pp.937-942
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• 2008

This research investigated to find out the possibilities of applying FRPs to the AUVs. In this study, two kinds of metal materials, which is one of the popularly used materials for manufacturing AUVs, and 6 kinds of FRP materials were considered. Material properties of FRPs were derived by tensile tests and chemical analysis. Moreover, various types of AUVs were designed by 8 kinds of materials. From structural analysis, we can find out that the weights of AUV by CFRP-Autoclave could be reduced by 60% in comparison with the weights of AUV by Al 7075-T6. Also, 40% weight reduction could be expected compared to the AUV by Ti-6Al-4V. In this result, we could conclude that the material of CFRP-Autoclave have various merits and potentialities as one of the AUV materials.