• Corrosion Science and Technology
• /
• 제12권1호
• /
• pp.50-55
• /
• 2013

The purpose of this study was to investigate corrosion characteristics of Ti-xTa alloys with Ta contents. Ti-xTa alloys used as samples (x=30, 40%) were arc-melted under argon atmosphere of 99.9% purity. Ti-xTa alloys were homogenized for 12hr at $1000^{\circ}C$ and then water quenched. The surface characteristics of Ti-xTa alloys were investigated using optical microscopy (OM) and X-ray diffractometer (XRD). The anodic corrosion behaviors of the specimens were examined through potentiodynamic, potentiostatic and galvanostatic test in 0.9 % NaCl solution at $36.5{\pm}1^{\circ}C$. After corrosion test, the surface characteristics of Ti-xTa alloys were investigated using OM. The microstructure of Ti-Ta alloy showed the beta structure with Ta content. The corrosion resistance of Ti alloy was improved by increasing Ta content and the corrosion morphology of Ti-Ta alloy showed that the site attacked by chloride ion decreased from the active to passive region with Ta content. Potential of Ti-40Ta alloy increased as time increased, whereas, current density of Ti-40Ta alloy decreased as time increased compared to Ti-30 alloy.

• 한국표면공학회지
• /
• 제27권5호
• /
• pp.253-260
• /
• 1994

Ta-N films were reactively sputter deposited by dc magnetron sputtering from a Ta target with a various Ar-N, gas ratio. Electrical resistivity of pure Ta film was 150$\mu$$\Omega$cm and decreased initially with nitrogen addition, and then increased to a value of 220$\mu$$\Omega$-cm~260$\mu$$\Omega$-cm at 9%~23% nitrogen partial flow. Rutherford backscattering spectrometry(RBS) and Auger electron spectroscopy (AES) analysis show that nitrogen content in the film is increased with the nitrogen partial flow. The film contains 58at.% nitrogen at 36% nitrogen partial flow. Both the phase and the microstructure of the as-deposisted films were investigated by x-ray diffractometry(XRD) adn transmission electron microscopy (TEM) at various nitrogen content. The phase of pure Ta film is identified as $\beta$-Ta with a 200$\AA$~300$\AA$ grain size. The phase of Ta film is changed to bcc-Ta as small amount of nitrogen is added. Crystalline Ta2N film was deposited at 24at.% nitrogen content. Amorphous phase is formed over a range of nitrogen content from about 33at.% to 35at.% while crystalline fcc-TaN is observed to form at 39at.%~48at.% nitrogen content.

• 한국재료학회지
• /
• 제11권12호
• /
• pp.1080-1085
• /
• 2001

Dielectric properties and leakage current characteristics of 100 nm-thick $Ta_2O_5/Al_2O_3$multilayer thin films, which were fabricated by reactive sputtering of$Al_2O_3$and$Ta_2O_5$ successively on top of each other for total 9 layers, have been investigated with variation of the$Al_2O_3$content$(i.e,\;Ta_2O_5/Al_2O_3 \;thickness\;ratio)$.$Ta_2O_5/Al_2O_3$films were amorphous regardless of the$Al_2O_3$content. With increasing the$Al_2O_3$content from 0% to 100%, refractive index of the $Ta_2O_5/Al_2O_3$films decreased linearly from 2.03 to 1.56 and dielectric constant was lowered from 23.9 to 7.7 Variation of the dielectric constant with the$Al_2O_3$content was in good agreement with the behavior that was obtained by assuming parallel capacitors of$Al_2O_3$and Ta_2O_5$. Leakage current characteristics of $Ta_2O_5/Al_2O_3$ multilayer films were superior to those of $Ta_2O_5$ and$Al_2O_3$films. $Ta_2O_5/Al_2O_3$ films of 5% and 10%$Al_2O_3$content exhibited excellent leakage current densities which were lower than $10^{-7} A/cm^2$ at 1MV/cm.

• 한국세라믹학회지
• /
• 제35권10호
• /
• pp.1107-1112
• /
• 1998

We could obtan c-axis oriented $SrBi_2$$Ta_2$$O_9$ thin films on usual Pt(111)/Ti/$SiO_2$/Si(100) substrate using a r. f. magnetron sputtering technique. According to the increase of sputtering pressure from 250 to 300 mTorr the Bi content and degree of the c-a xis preferred orientation of $SrBi_2$$Ta_2$$O_9$ thin films were increased. By controlling Bi(or $Bi_2O_3$) loss from $SrBi_2$$Ta_2$$O_9$ thin films during post annealing and by inserting $Bi_2O_3$ layer in $SrBi_2$$Ta_2$$O_9$ thin films the effect of Bi content on the c-axis oriented growth of $SrBi_2$$Ta_2$$O_9$ thin films could be investigated without the effect of sputtering pressure. The degree of the c-axis preferred orientation of $SrBi_2$$Ta_2$$O_9$ thin films was increased with increasing with increasing Bi content by control of Bi(or $Bi_2O_3$) loss of $SrBi_2$$Ta_2$$O_9$ thin films. But the c-axis oriented growth of $SrBi_2$$Ta_2$$O_9$ thin films disappeared by the inserting of $Bi_2O_3$ lay-er in $SrBi_2$$Ta_2$$O_9$ thin films.

• 한국재료학회지
• /
• 제31권12호
• /
• pp.682-689
• /
• 2021

NbC, HfC, TaC, and their solid solution ceramics have been identified as the best materials for ultrahigh-temperature ceramics. However, their structural stability and elastic properties are mostly unclear. Thus, we investigated structure and elastic properties of (Nb_1-xTa_x)C and (Nb_1-xHf_x)C solid solutions via ab initio calculations. Our calculated results show that the stability of (Nb_1-xTa_x)C and (Nb_1-xHf_x)C increases with the increase of Hf and Ta content, and (Nb_1-xHf_x)C is more stable than (Nb_1-xTa_x)C at the same content of Hf and Ta. The lattice constants decrease with increasing of Hf and Ta content. (Nb_1-xTa_x)C and (Nb_1-xHf_x)C carbides are mechanically stable and brittle. Bulk modulus of (Nb_1-xTa_x)C increases with increasing Ta content. In contrast, bulk modulus of (Nb_1-xHf_x)C decreases with increasing Hf content. Hardness of solid solutions shows the highest values at the (Nb_0.25Ta_0.75)C and (Nb_0.75Hf_0.25)C. In particular, (Nb_0.75Hf_0.25)C shows the highest hardness for the current system. The results indicate that the overall mechanical properties of (Nb_1-xHf_x)C solid solutions are superior to those of (Nb_1-xTa_x)C solid solutions. Therefore, controlling the Hf and Ta element and content of the (Nb_1-xTa_x)C and (Nb_1-xHf_x)C Solid solution is crucial for optimizing the material properties.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2012년도 춘계학술발표회 논문집
• /
• pp.254-254
• /
• 2012

The purposed of this work was to determine surface charateristics of anodized Ti-30Nb-xTa alloys with Ta content. Samples were prepared by arc melting, followed by followed by homogenization for 12 hr at $1000^{\circ}C$ in argon atmosphere. The electrolyte for anodization treatment was prepared by mixing 465ml $H_2O$ with 35M $H_3PO_4$ and anodized at 180V to 220V. The microstructures of the alloys were examined by X-ray diffractometer (XRD) and optical microscopy (OM). Surface characteristics of anodized Ti-30Nb-xTa alloys was investigated by potentiodynamic test and potentiostatic in 0.9% Nacl solution at $36.5{\pm}1^{\circ}C$. It was observed that the changed ${\alpha}$ phase to ${\beta}$ phase with Ta content.

• 한국연초학회지
• /
• 제19권2호
• /
• pp.129-135
• /
• 1997

This study was carried out to investigate the influence of triacetin(TA) on some phisico-chemical properties of cigarette filter rods. To find the effect of TA on physical properties, we made six kinds of filters varying the TA levels(0%, 2%, 4%, 6%, 8%, 10%) and measured the hardness, resilience and roundness. The hardness of filter rods was increased from 83.2% to 94.6% with increasing the TA level hut the roundness was not affected by TA levels. After manufacturing the cigarette with the filters, we have analysed the delivery amount of phenol and TA with the content of TA. The amount of phenol was decreased from 20.6$\mu\textrm{g}$/cig. to 12.0 $\mu\textrm{g}$/cig. with increasing the TA level of the filters. The decreasing of phenol amount was thought to be caused by solution effect. Also the TA delivery of TPM was increased from 0% to 5% of TPM with increasing the amount of TA. We have found the interesting phenomena that ventilation rate was also decreasing up to 6oye with increasing TA. It seemed to be due to the encapsulated pressure drop and the reduction of the plugwrap porosity which also caused by the smear with TA on the surface of plugwrap. From this results, we could find that not only the hardness, resilience and ventilation rate but also the contents of phenol and TA in cigarette smoke was affected by the TA levels on the cigarette filter rods.

• 한국세라믹학회지
• /
• 제35권8호
• /
• pp.819-826
• /
• 1998

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.352-353
• /
• 2006

The effect of TiC content on oxidation behavior of the sintered WC-TiC-TaC alloys with 2 mass% TaC and different TiC amounts of 3-45 mass% was investigated through oxidation tests in air at 973K. As a result of the tests, it was revealed that with increasing TiC content in the alloys, mass changes caused by oxidation and thickness of the scale decreased. Thus, it is considered that the main component of the scales changed gradually from $WO_3$ to $TiO_2$ with increasing TiC content in the alloys, and oxygen diffusion through the scale to the alloys was inhibited gradually.

• 한국세라믹학회지
• /
• 제31권11호
• /
• pp.1299-1306
• /
• 1994

Effect of MgO content on microstructural evolution and microwave dielectric properties of Ba(Mg1/3Ta2/3)O3 system was investigated. MgO content was varied from 10 mol% deficiency to 10 mol% excess of stoichiometric composition, respectively. It was found that MgO-deficient specimen showed faster grain growth rate than stoichometric and MgO excess BMT system. Besides, sandwich type precipitates of Ba5Ta4O15 which was formed within the BMT grain, might lead to the anisotropic grain growth of BMT grain. On the contrary, in MgO excess specimen, BMT grain growth rate was retarded by precipitations of MgO phase in grain boundary. Besides, the Q values of MgO-deficient showed lower than MgO-excess due to precipitations of Ba5Ta4O15 within BMT grain.