The microstructural evolution and modulation of mechanical properties were investigated for a Ti65Fe35 hypereutectic alloy by addition of Bi53In47 eutectic alloys. The microstructure of these alloys changed with the additional Bi- In elements from a typical dendrite-eutectic composite to a bimodal eutectic structure with primary dendrite phases. In particular, the primary dendrite phase changed from a TiFe intermetallic compound into a β-Ti solid solution despite their higher Fe content. Compressive tests at room temperature demonstrated that the yield strength slightly decreased but the plasticity evidently increased with an increasing Bi-In content, which led to the formation of a bimodal eutectic structure (β-Ti/TiFe + β- Ti/BiIn containing phase). Furthermore, the (Ti65Fe35)95(Bi53In47)5 alloy exhibited optimized mechanical properties with high strength (1319MPa) and reasonable plasticity (14.2%). The results of this study indicate that the transition of the eutectic structure, the type of primary phases and the supersaturation in the β-Ti phase are crucial factors for controlling the mechanical properties of the ultrafine dendrite-eutectic composites.

Titanium alloys have high specific strength, excellent corrosion and wear resistance, as well as high heatresistant strength compared to conventional steel materials. As intermetallic compounds based on Ti, TiAl alloys are becoming increasingly popular in the aerospace field because these alloys have low density and high creep properties. In spite of those advantages, the low ductility at room temperature and difficult machining performance of TiAl and Ti3Al materials has limited their potential applications. Titanium powder can be used in such cases for weight and cost reduction. Herein, pre-forms of Ti-Al-xMn powder alloys are fabricated by compression forming. In this process, Ti powder is added to Al and Mn powders and compressed, and the resulting mixture is subjected to various sintering temperature and holding times. The density of the powder-sintered specimens is measured and evaluated by correlation with phase formation, Mn addition, Kirkendall void, etc. Strong Al-Mn reactions can restrain Kirkendall void formation in Ti-Al-xMn powder alloys and result in increased density of the powder alloys. The effect of Al-Mn reactions and microstructural changes as well as Mn addition on the high-temperature compression properties are also analyzed for the Ti-Al-xMn powder alloys.

Polycrystalline diamond (PCD) tools possessing high hardness and abrasive wear resistance are particularly suited for drilling of carbon fiber reinforced plastic (CFRP) composites, where tool life and consistent hole quality are important. While PCD presents superior performance when drilling CFRP, it is unclear how it performs when drilling multi-stack materials such as CFRP-titanium (Ti) stacks. This comparative study aims to investigate drilling of a Ti plate stacked on a CFRP panel when using PCD tools. The first sequence of the drilling experiments was to drill 20 holes in CFRP only. CFRP-Ti stacks were then drilled for the next 20 holes with the same drill bit. CFRP holes and CFRP-Ti stack holes were evaluated in terms of machined hole quality. The main tool wear mechanism of PCD drills is micro-fractures that occur when machining the Ti plate of the stack. Tool wear increases the instability and the operation temperature when machining the Ti plate. This results in high drilling forces, large hole diameter errors, high surface roughness, wider CFRP exit thermal damage, and taller exit Ti burrs.

Abstract Y2Ti2O7 nanoparticles (0.3 mol%) have been successfully synthesized by the co-precipitation process. The samples, adjusted to pH7 with ammonia solution as catalyst and calcined at 700~900 ℃, exhibit very fine particles with close to spherical shape and average size of 10-30 nm. It was possible to control the size of the synthesized Y2Ti2O7 particles by manipulating the conditions. The Y2Ti2O7 nanoparticles were coated on a glass substrate by a dipping coating process with inorganic binder. The Y2Ti2O7 solution coated on the glass substrate had excellent adhesion of 5B; pencil hardness test results indicated an excellent hardness of 6H. The thickness of the thick film was about 30 μm. Decomposition of MB on the Y2Ti2O7 thin film shows that the photocatalytic properties were excellent.

This paper is concerned with a test method that can be used to investigate the parameters of the Johnson-Cook constitutive model. These parameters are essential for accurately analyzing material behavior under impact loading conditions in numerical simulation. Ti-6Al-4V alloy (HCP crytal structure) was used as a specimen for the experiments. In the 10−3-103/ s strain rate range, three types of experimental methods (convention, compression and tension) were employed to compare the differences using MTS-810, SHPB and SHTB. Finite element analysis results when applying these parameters were displayed along with the experiment results.

Binary Ti-Al alloys containing 50 to 60 atomic percent aluminum are rapidly solidified by hammer anvil method under an argon atmosphere. Constituent phases in each alloy are identified by X-ray diffractometry and microstructures of the alloys are investigated using a transmission electron microscope. In alloys with aluminum content between 50 and 54 percent, a second phase exists besides TiAl(γ); this second phase is identified as Ti3Al(α2). The α2 phase is observed in two types of morphology. One is as fine lamellar alternating with γ and the other is as a particle. It is concluded that the existence of a metastable phase with the morphologies stated above should arise from a higher quenching rate attained by the hammer anvil method as compared to the conventional roll or splat-quench method. Implications of the above observation are discussed with respect to the phase relations in the Ti-Al binary system; these implications are still controversial in many respects.

Grain morphology, phase stability and mechanical properties in binary Ti-Al alloys containing 43-52 mo1% Al have been investigated. Isothermal forging was used to control the grain sizes of these alloys in the range of 5 to 350 μm. Grain morphology and volume fraction of α2 phase were observed by optical metallography and scanning electron microscopy. Compressive properties were evaluated at room temperature, 1070 K, and 1270 K in an argon atmosphere. Work hardening is significant at room temperature, but it hardly took place at 1070 K and 1270 K because of dynamical recrystallization. The grain morphologies were determined as functions of aluminum content and processing conditions. The transus curve of α and α+γ shifted more to the aluminum-rich side than was the case in McCullough’s phase diagram. Flow stress at room temperature depends strongly on the volume fraction of the α2 phase and the grain size, whereas flow stress at 1070 K is insensitive to the alloy composition or the grain size, and flow stress at 1270 K depends mainly on the grain size. The α2 phase in the alloys does not increase the proof stress at high temperatures. These observations indicate that improvement of both the proof stress at high temperature and the room temperature ductility should be achieved to obtain slightly Ti-rich TiAl base alloys.

Graphite was diffusion-bonded by hot-pressing to W-25Re alloy using a Ti interlayer. For the joining, a uniaxial pressure of 25 MPa was applied at 1600 oC for 2 hrs in an argon atmosphere with a heating rate of 10 oC min−1. The interfacial microstructure and elemental distribution of the W-25Re/Ti/Graphite joints were analyzed by scanning electron microscopy (SEM). Hot-pressed joints appeared to form a stable interlayer without any micro-cracking, pores, or defects. To investigate the high-temperature stability of the W-25Re/Ti/Graphite joint, an oxy-acetylene torch test was conducted for 30 seconds with oxygen and acetylene at a 1.3:1 ratio. Cross-sectional analysis of the joint was performed to compare the thickness of the oxide layer and its chemical composition. The thickness of W-25Re changed from 250 to 20 μm. In the elemental analysis, a high fraction of rhenium was detected at the surface oxidation layer of W-25Re, while the W-25Re matrix was found to maintain the initial weight ratio. Tungsten was first reacted with oxygen at a torch temperature over 2500 oC to form a tungsten oxide layer on the surface of W-25Re. Then, the remaining rhenium was subsequently reacted with oxygen to form rhenium oxide. The interfacial microstructure of the Ti-containing interlayer was stable after the torch test at a temperature over 2500 oC.

This study was purposed to develope a titanium alloy with low elastic modulus to be used as dental implant. The new titanium alloy was prepared as titanium alloy by adding Tantalum(Ta), Zirconium(Zr), Molybdenum(Mo) into the Ti-X-Y-Z system alloys. In designing the new titanium alloys, two physical variables bond order (Bo) and d-electron orbit energy level (Md) were varied. Mean bond order (  ) was around 2.818∼2.8784eV, and Mean d-electron orbit energy level ( ) was 2.4541~2.4747eV. In the cases of titanium alloys of T-3M and T-3Z, the XRD analysis showed β phase. On the other hand, the phase of α+ β were observed in the T-6Z and T-8Z alloys. Exhibited the highest hardness value to result in T-3Z 309.7Hv alloy Vickers hardness with respect to titanium alloy. In the resulting T-3Z alloy of measuring the elastic modulus value for a titanium alloy exhibited the smallest modulus of elasticity value to 89.81GPa. TEM analysis identified additional feature for T-3Z alloy was detected in addition to the ß-phase.

This study is performed to fabricate a Ti porous body by freeze drying process using titanium hydride (TiH2) powder and camphene. Then, the Ti porous body is employed to synthesize carbon nanotubes (CNTs) using thermal catalytic chemical vapor deposition (CCVD) with Fe catalyst and methane (CH4) gas to increase the specific surface area. The synthesized Ti porous body has 100 μm-sized macropores and 10-30 μm-sized micropores. The synthesized CNTs have random directions and are entangled with adjacent CNTs. The CNTs have a bamboo-like structure, and their average diameter is about 50 nm. The Fe nano-particles observed at the tip of the CNTs indicate that the tip growth model is applicable. The specific surface area of the CNT-coated Ti porous body is about 20 times larger than that of the raw Ti porous body. These CNT-coated Ti porous bodies are expected to be used as filters or catalyst supports.

A Ni-Ti-B alloy powder prepared by mechanical alloying (MA) of individual Ni, Ti, and B components is examined with the aim of elucidating the phase transitions and crystallization during heat treatment. Ti and B atoms penetrating into the Ni lattice result in a Ni (Ti, B) solid solution and an amorphous phase. Differential thermal analysis (DTA) reveals peaks related to the decomposition of the metastable Ni (Ti, B) solid solution and the separation of equilibrium Ni3Ti, TiB2, and τ-Ni20Ti3B6 phases. The exothermal effects in the DTA curves move to lower temperatures with increasing milling time. The formation of a TiB2 phase by annealing indicates that the mechanochemical reaction of the Ni-Ti-B alloy does not comply with the alloy composition in the ternary phase diagram, and Ti-B bonds are found to be more preferable than Ni-B bonds.

The effect of heat treatment on the microstructure and mechanical properties of cast Ti-6%Al-4%V alloy was investigated. Heat treatment of cast Ti-6Al-4V alloy was conducted by solution treatment at 950 oC for 30 min; this was followed by water quenching and then aging at 550 oC for 1 to 1440 min. The highest hardness of the heat-treated specimens was obtained by solution treatment and subsequent aging for 5 min due to precipitates of fine α that formed from retained β phase. The tensile strength of this alloy increased without dramatic decrease of the ductility due to microstructural refinement resulting from the decomposition of α' martensite into fine α and β phases, and also due to the fine α phase formed from the retained β phase by aging treatment for 5 min. In addition, this strengthening might be caused by the transformation induced plasticity (TRIP) effect, which is a strain-induced martensite transformation from the retained β phase during deformation, and which occurs even after aging treatment at 550 oC for 5 min.

Ti films were deposited on glass substrates under various preparation conditions in a chamber of two-facing-target type dc sputtering; after deposition, the electric resistivity values were measured using a conventional four-probe method. Crystallographic orientations and microstructures, including the texture and columnar structure, were also investigated for the Ti films. The morphological features, including the columnar structures and surface roughness, are well explained on the basis of Thornton’s zone model. The electric resistivity and the thermal coefficient of the resistivity vary with the sputtering gas pressure. The minimum value of resistivity was around 0.4 Pa for both the 0.5 μm and 3.0 μm thick films; the apparent tendencies are almost the same for the two films, with a small difference in resistivity because of the different film thicknesses. The films deposited at high gas pressures show higher resistivities. The maximum of TCR is also around 0.4 Pa, which is the same as that obtained from the relationship between the resistivity and the gas pressure. The lattice spacing also decreases with increasing sputtering gas pressure for both the 0.5 μm and 3.0 μm thick films. Because they are strongly related to the sputtering gas pressures for Ti films that have a crystallographic anisotropy that is different from cubic symmetry, these changes are well explained on the basis of the film microstructures. It is shown that resistivity measurement can serve as a promising monitor for microstructures in sputtered Ti films.

티타늄은 표면에 형성되는 보호성 부동태 피막 때문에 일반부식과 해수에서 내식성이 강하지만 염산, 황산, 인산 등의 산에서는 보호성 산화물 피막이 파괴된다고 알려져 있다. 본 연구에서는 Ti에 Al 및 V등을 첨가한 α+β계에 대하여 1066℃와 966℃에서 5시간 용체화 열처리를 실시하고, 이 시편을 550℃, 600℃, 및 650℃에서 각각 1시간, 4시간, 8시간 및 16시간 시효열처리한 후 마이크로비커스 경도를 측정하고, 이 시편을 1N H₂SO₄ 용액에서 전기화학적 분극법으로 부식을 계측하였으며, 분극을 마친 시편의 표면을 현미경 조직사진으로 부식상태를 검토하였다. 시험 결과 용체화열처리한 시편이 모재와 시효열처리한 시편보다 높은 내식성을 나타내며. 용체화 온도가 높고 시간이 길어질수록 내식성은 증가하였다.

목 적 : 비후성심근증 환자군에서 TI scout과 MOLLI(modified Look-Locker Inversion recovery) 시퀀스를 이용하여 심근의 T1 값을 비교하고 유용성을 평가하고자 한다. 대상 및 방법 : 50명의 비후성심근증 환자를 대상으로 심장 MRI(1.5T, Avanto scanner, Siemens, Erlangen, Germany)를 시행하였다. 좌심실의 중앙에서 SA 단면으로 조영제 주입 전과 후에 영상을 획득하였다. 조영제 주입 후 평균 10분에 TI scout(SL 8mm, Turbo factor 22-46)을 획득하고, 평균 13.5분에 MOLLI(SL 8mm, GRAPPA factor 2, 11 heart beats(4+3+2))시퀀스 영상을 획득하였다. 획득한 영상은 두명의 측정자가 Argus (Siemens medical system, Erlangen, Germany)을 이용하여 6개의 구역에 ROI를 설정하여 T1 값을 획득하였다. 통계적 분석으로는 paired t-test(SPSS, ver18.0K)를 이용하여 유용성을 평가하였고, Bland-Altman(MedCalc, ver14.12.0)를 이용하여 상관관계를 평가하였다. 결 과 : TI scout과 MOLLI는 시간에 따른 보정을 하기 전에 유의한 차이를 보였다(TI scout=233.7msec, MOLLI=245.6msec, p<0.001). 그러나 획득 시간에 따른 보정 후에는 유의한 차이를 보이지 않았다(MOLLI=230msec, p=0.17). 두 방법으로 획득한 T1 값은 Bland-Altman 그래프에서 높은 일치도를 보였다. 관찰자 간의 상관계수는 0.97이상으로 높은 일치도를 보였다. 결 론 : MOLLI를 이용한 T1 값은 TI scout과 상응하는 결과를 보여주었다. MOLLI는 심근의 섬유화를 파악하는데 도움을 주며 이를 통해 진단의 정확도를 높이는데 기여할 것으로 사료된다.

목 적 : 인체에서 질병이 있는 부위에는 관류의 변화가 발생할 수 있다. 관류(perfusion)란 모세혈관 이하의 미세한 흐름(micro flow)을 말하는데 이것을 관찰하기 위한 검사는 PET, CT, MRI 등이 있다. 이러한 검사에서 관류를 탐지하기 위하여 사용하는 동위원소나 조영제 등은 방사능 피폭이나 조영제 부작용과 같은 문제점을 안고 있다. ASL(arterial spin labeling)은 조영제 대신에 자화표지(magnetization labeling)를 이용한 MRI 관류 검사이다. ASL은 조영제를 사용하지 않아도 된다는 장점이 있는 반면, 관류대조도 및 화질이 다소 떨어진다는 단점이 있다. ASL영상은 자화표지를 시작한 순간부터 영상을 획득하기까지 시간, 즉 ASL TI(inversion time)에 영향을 많이 받는다. 따라서 적절한 ASL TI(inversion time)를 적용하면 보다 좋은 영상을 얻을 수 있을 것이다. 본 연구는 적절한 ASL TI(inversion time)를 구하기 위하여 사용한 TI scout scan의 유용성과 ASL 영상의 화질개선효과를 평가하고자 기획하였다. 대상 및 방법 : Siemens 3Tesla Verio를 사용하여 Brain MRI 검사를 예약한 환자를 대상으로 TI를 각각 달리하여 두 번의 ASL검사를 시행하였다. ASL검사 전에 사전검사로서 16단계의 inversion time이 있는 “TI scout scan”을 실시하였다. TI scout scan에서 획득한 영상 중에서 가장 적절한 ASL TI(inversion time)을 찾고 이것을 ASL 본(本)검사에 적용하였다. TI scout에서 가장 적절한 TI time을 채택하기 위한 방법으로 관능적인 평가방법과 함께 회백질 몇 군데에서 ROI를 측정하여 활용하였다. 대조군 검사로서 ASL TI를 1990ms로 고정시킨 ASL을 연구대상 모두에게 시행하였다. 본 검사와 대조군 검사의 화질을 비교·평가하기 위한 방법으로 영상선호도를 정성적인 방법으로 평가하였다. 결 과: TI를 1990ms로 고정한 ASL영상과 비교해서 TI scout을 이용한 ASL영상의 선호도가 약간 높았지만 그 차이는 크지 않았다. TI scout에서 자주 채택되는 TI time의 범위가 있었다. 결 론 : ASL 검사는 조영제 없이도 관류검사가 가능하다는 장점에도 불구하고 영상의 화질과 관류대조도 등에서 다소 미흡하다는 평가가 있다. 이러한 단점에도 불구하고 ASL 영상을 개선하기 위한 노력이 계속되고 있다. 이를 위해서는 pulse sequence와 혈류에 대해 이해하고 적용하는 것이 필요하다. TI scout을 적용해 봄으로써 적절한 관류대조도와 화질개선 효과를 확인할 수 있었다. ASL TI scout은 관류영상을 얻는 유용한 방법이다.

Titanium has many special characteristics such as specific high strength, low elastic modulus, excellent corrosion and oxidation resistance, etc. Beta titanium alloys, because of their good formability and strength, are used for jet engines, and as turbine blades in the automobile and aerospace industries. Low cost beta titanium alloys were developed to take economic advantage of the use of low-cost beta stabilizers such as Mo, Fe, and Cr. Generally, adding a trace of boron leads to grain refinement in casted titanium alloys due to the pinning effect of the TiB phases. This study analyzed and evaluated the microstructural and mechanical properties after plastic deformation and heat treatment in boron-modified Ti-2Al-9.2Mo-2Fe alloy. The results indicate that a trace of boron addition made grains finer; this refinement effect was found to be maintained after subsequent processes such as hot forging and solution treatment. This can effectively reduce the number of required manufacturing process steps and lead to savings in the overall cost as well as low-cost beta elements.

The present work reports a systematic study of using carboxymethylated cellulose (CMC) as water-bornebinder to produce Li4Ti5O12-based anodes for manufacture of high rate performance lithium ion batteries. When theLTO-to-CB-to-CMC mass ratio is carefully optimized to be 8:1:0.57, the special capacity of the resulting electrodes is144 mAh·g−1 at 10 C and their capacity retention was 97.7% after 1000 cycles at 1C and 98.5% after 500 cycles at5C, respectively. This rate performance is comparable or even better than that of the electrolytes produced using con-ventional, organic, polyvinylidene fluoride binder.

Impedancemetric NOx (NO and NO2) gas sensors were designed with a stacked-layer structure and fabricated using LaCrxCo1-xO3 (x = 0, 0.2, 0.5, 0.8 and 1) as the receptor material and Li1.3Al0.3Ti1.7(PO4)3 plates as the solid-electrolyte transducer material. The LaCrxCo1-xO3 layers were prepared with a polymeric precursor method that used ethylene glycol as the solvent, acetyl acetone as the chelating agent, and polyvinylpyrrolidone as the polymer additive. The effects of the Co concentration on the structural, morphological, and NOx sensing properties of the LaCrxCo1-xO3 powders were investigated with powder Xray diffraction, field emission scanning electron microscopy, and its response to 20~250 ppm of NOx at 400 oC (for 1 kHz and 0.5 V), respectively. When the as-prepared precursors were calcined at 700 oC, only a single phase was detected, which corresponded to a perovskite-type structure. The XRD results showed that as the Co concentration of the LaCrxCo1-xO3 powders increased, the crystal structure was transformed from an orthorhombic phase to a rhombohedral phase. Moreover, the LaCrxCo1-xO3 powders with 0 ≤ x < 0.8 had a rhombohedral symmetry. The size of the particles in the LaCrxCo1-xO3 powders increased from 0.1 to 0.5 μm as the Co concentration increased. The sensing performance of the stack-structured LaCrxCo1-xO3/Li1.3Al0.3Ti1.7(PO4)3 sensors was found to divide the impedance component between the resistance and capacitance. The response of these sensors to NO gas was more sensitive than that to NO2 gas. Compared to other impedancemetric sensors, the LaCr0.8Co0.2O3/Li1.3Al0.3Ti1.7(PO4)3 sensor exhibited good reversibility and reliable sensingresponse properties for NOx gases.