Abstract: Micropore and nanotube formation on the Ti oxide are important to improve the cell adhesion and proliferation in clinical use. In this study, nanotube and micropore of Ti alloy for biocompatibility have been investigated using FE-SEM and XRD. Ternary alloys were prepared by using high purity sponge Ti Ta, Zr and Nb sphere (99.95% wt.%). Two-step anodizing was used for surface modification of the titanium alloys. Micropore formation was first performed using a potentiostat in 1 M H3PO4 electrolyte and nanotube formation was performed in 1M H3PO4 + 0.8wt% NaF solution by using a potentiostat. The two-step anodizing process is an efficient method for forming micropores and nanotubes on the surfaces of ternary titanium alloys, and the morphology of micropore and nanotube is dependent on the alloying element and composition of ternary alloy.
2061
Authors: Han Cheol Choe, William A. Brantley
Abstract: Effects of TiN, ZrN and tooth-ash coatings on the surface phenomena of Ti-(Nb, Zr, Ta,
Hf) dental implant alloys with low elastic modulus has been researched by using electrochemical
methods. Ti-(Nb, Ta, Zr, and Hf) alloys were fabricated and surface-coated with TiN, ZrN and
tooth-ash (hydroxyapatite) using the RF-sputtering. The electrochemical behaviors of the TiN, ZrN
and HA-coated dental implant fixtures were investigated using techniques such as potentiodynamic
polarization analysis in 0.9% NaCl solution, as well as examine the detailed structure of these
coated alloys using SEM and XRD. From potentiodynamic test of Ti-(Nb, Zr, Ta, Hf) alloy, the
corrosion resistance of TiN/ZrN/tooth-ash composite coated Ti-(Nb, Zr, Ta, Hf) alloy were higher
than those of the non-coated Ti-(Nb, Zr, Ta, Hf) alloy.
825
Authors: Won Gi Kim, Han Cheol Choe, Yeong Mu Ko
821
Authors: Mi Young Oh, Han Cheol Choe, Yeong Mu Ko
Abstract: In this study, AC impedance behaviors of Ti-Zr binary alloys for biomaterials have been
investigated using by electrochemical impedance spectroscopy. Ti-10wt%, 20wt%, 30wt%, and
40wt% Zr alloys were prepared by arc melting and homogenized for 24 hr at 1000 °C in argon
atmosphere. Phase constitutions and microstructure of the specimens were conducted by using XRD,
OM and SEM. The corrosion properties of the specimens were examined through potentiodynamic
test (potential range of -1500 ~ 2000 mV), AC impedance spectroscopy(100kHz~10mHz) in artificial
saliva solution by potentiostat (EG&G Co, PARSTAT 2273. USA). In as-cast and homogenized
Ti-xZr alloys, α-phase was identified by XRD. Microstructures were changed from lamellar structure
to needle-like structure as Zr content increased. From the results of polarization behavior in the
Ti-xZr alloys, it was found that the corrosion resistance was increased with increasing Zr content.
From results of AC impedance spectroscopy, passive film resistance value of homogenized Ti-40Zr
specimen(1.60×106 Ωcm2) showed higher than that of as-cast specimen.
817
Authors: Yong Hoon Jeong, Han Cheol Choe, Su Jung Park, Yeong Mu Ko
Abstract: The Ti-Hf alloy system forms α-β isomorphous system and does not form any
intermetallic compounds, which is also beneficial for good mechanical properties. And in order to
avoid the release of materials, surface modifications are generally carried out to form a TiN and
ZrN layer on the surface. Electrochemical properties of TiN and ZrN coated Ti-Hf alloy by RFsputtering
has been researched using various electrochemical methods.
Ti-10wt%, 20wt%, 30wt%, and 40wt% Hf alloys manufactured by non consumable vacuum arc
melting furnace. All the specimens were heat treatment at 1000°C for 24hr in Ar atmosphere
followed by furnace cooling, respectively. The specimens were coated with TiN and ZrN
respectively, by RF-magnetron sputtering method. The microstructures were conducted by using
OM, EDX and SEM. The corrosion tests were carried out using potentiodynamic(PARSTAT 2273,
EG&G, USA) and potentiostatic test in 0.9% NaCl solution at 36.5 ±1 °C. Microstructure clearly
observed that lamellar structure translated to needle-like structure with increased Hf contents. From
the analysis of TiN and ZrN coated layer analysis, TiN and ZrN coated surface showed columlar
structure with 600nm and 100nm thickness, respectively. The corrosion resistance of TiN and ZrN
coated Ti alloys were higher than those of the non-coated Ti-alloy in 0.9%NaCl solution, indicating
better protective effect.
813
Authors: Chae Heon Chung, Han Cheol Choe, Hee Jung Kim, Jin Sup Kim, William A. Brantley
Abstract: To investigate mechanical fitness of abutment/fixture screw interface in the internal dental implant
system, internal connection type implants from AVANA(Osstem®), Bioplant(Cowell-Medi®), Dio(DIO®),
Neoplant(Neobiotech®), systems were used in this study. Each group was acquired 2 fixtures at random. Two
piece type abutment and one piece type abutment for use with each implant system were acquired. Screw was
respectively used to hold a two piece type abutment to a implant fixture. All samples were cross-sectioned
with grinder-polisher unit and all specimens were analyzed the interface phenomena between implant
fixture/abutment/screw contact interfaces by using field emission scanning electron microscope(FE-SEM).
Implant fixture/abutment/screw connection interfaces of internal connection systems made in Korea were in
good condition. The results of the above study showed that materials and mechanical properties and quality of
milling differed depending on their manufacturing companies.
1417
Authors: Han Cheol Choe, Chae Heon Chung, William A. Brantley
Abstract: The abutment screw loosening of dental implant system has been remained problem in
restorative practices. Surface treatment of screw plays a role of preventing screw from loosening in
implant screw mechanism. The purpose of this study was to investigate surface characteristics of ZrN
and TiN coated dental gold-screw and Ti-screw by ion-plating method and to evaluate wear resistance,
surface roughness, and film adhesion on the screw surface using field emission scanning electron
microscopy(FE-SEM), energy dispersive x-ray spectroscopy(EDX), micro-diamond scratch tester,
vickers hardness tester, and surface roughness tester. The surface of gold screw and GoldTite is more
smoothly than ones of other kinds of non coated screw. The ZrN and TiN coated surface is more
smoothly than ones of other kinds of screw. The hardness of TiN and ZrN coated
surface showed higher than that of non coated surface. The TiN coated titanium screw and ZrN coated
gold screw have a good wear resistance and adhesion on the surface. The surface of ZrN coated screw
showed low surface roughness compared with the surface of TiN coated screw.
1201
Authors: Hee Jung Kim, Han Cheol Choe, Chae Heon Chung, William A. Brantley
Abstract: To evaluate the mechanical deformation phenomena of dental abutment screw after
tightening and loosening, five species of abutments were selected (3i-three, Avana- two) respectively
by two pieces. The abutment screws were repeatedly tightened and removed 20 times with a digital
controller. Field emission scanning electron microscope (FE-SEM) was used to observe changes of
each part caused by repeatedly tightening and loosening experiment. As the number of tightening and
loosening was increased, the wear or distortion of hexed or squared slot that contacted with the driver
tip was more severely progressed. Wear or distortion of hexed slot was more severe than that of
squared slot and it was more remarkable in the titanium screw than in the gold screw. All the tested
screws showed that the width in the crest of their screw thread decreased gradually as the test was
proceeded.
13
Authors: Joo Ho Lee, Jung Il Lee, Young Ho Kim, Il Ho Kim, Kyung Wook Jang, Soon Chul Ur, Han Cheol Choe, Gon Seung Yang
Abstract: The Arc melting technique was employed to synthesize the type I clathrate of Ba8Al16Si30
compound. Phase transformations during synthesis and homogenization treatment were investigated
using X-ray diffraction (XRD) and thermal analysis (TG/DSC). Thermoelectric properties as
functions of temperature and homogenization treatment time were evaluated in this study.
Maximum ZT was 0.14 at 590K for homogenized at 1173 K for 168hrs specimen and it is strongly
expected to show higher value above 600K.
275
Authors: Han Cheol Choe, S.J. Park, S.W. Eun, Yeong Mu Ko
Abstract: In order to investigate the intergranular and pitting corrosion behavior of Fe-25Al-6Cr
intermetallic compounds containing Mo, Nb and B, 11 kinds of Fe-25Al were prepared by arc
melting in Ar gas, using high purity aluminum and iron. The fabricated materials were heat treated
for homogenious structure and stabilization of the iron aluminides. The electrochemical methods
were used for interganular and pitting corrosion. Effects of Mo, Cr, Nb and B on the repassivation
current density(Ir) and the active current density(Ia) of Fe-25Al-6Cr were recorded in the following
order: MoCr>Nb>B, from the highest to the lowest respectively.
1583