共查询到20条相似文献,搜索用时 31 毫秒
1.
Min-Ho Lee Il-Song Park Kwan-Sik Min Seung-Geun Ahn Ju-Mi Park Kwang-Yeob Song Charn-Woon Park 《Metals and Materials International》2007,13(2):109-115
Titanium is widely used as an implant material for artificial teeth. Furthermore, various studies have examined surface treatment
with respect to the formation of a fine passive film on the surface of commercial titanium and its alloys and to improve the
bioactivity with bone. However, there is insufficient data about the biocompatibility of implant materials in the body. The
purpose of this study was to examine whether surface modification affects the precipitation of apatite on titanium metal.
Specimens were chemically washed for 2 min in a 1∶1∶1.5 (vol.%) mixture of 48 %HF, 60%HNO3 and distilled water. The specimens were then chemically treated with a solution containing 97%H2SO4 and 30%H2O2 at the ratio of 1∶1 (vol.%) at 40°C for 1h, and subsequently heat-treated at 400°C for 1h. All the specimens were immersed
in HBSS with pH 7.4 at 36.5°C for 15d, and the surface was examined with TF-XRD, SEM, EDX and XPS. In addition, specimens
of commercial pure Ti, with and without surface treatment, were implanted in the abdominal connective tissue of mice for 28
d. Conventional aluminum and stainless steel 316L were also implanted for comparison. An amorphous titania gel layer was formed
on the titanium surface after the titanium specimen was treated with a solution of H2SO4 and H2O2. The average roughness was 2.175 μm after chemical surface treatment. The amorphous titania was subsequently transformed
into anatase by heat treatment at 400°C for 1h. The average thickness of the fibrous capsule surrounding the specimens implanted
in the connective tissue was 47.1μm in the chemically treated Ti, and 52.2, 168.7 and 101.9μm, respectively, in the untreated
commercial pure Ti, aluminum and stainless steel 316L. 相似文献
2.
The growth and degradation of the oxide scale on modified 9Cr–1Mo ferritic steel was studied at 1123 K using a thermogravimetric
balance by employing the “transient-mass-gain method” in conjunction with the adaptation of a cyclic-oxidation procedure.
The total duration of the oxidation was 1000 h. The experiment revealed that the cracking of the scale was initiated when
the average thickness was 72 μm. Spallation occurred when the average thickness was 75 μm. The rate of spallation was found
to be enhanced as the scale thickens and attained a higher rate after 90 μm. The rate constants for the different stages of
oxidation were found to be different. The specimen was examined by SEM, EDS and XRD. The scale morphology revealed outwardly
protruded growth, a uniform adherent oxide layer and a spalled region. Four oxide phases were identified; Cr2O3, Fe2O3, (FeCr)2O3 and FeCr2O4. The spall contained more (FeCr)2O3 whereas the adherent scale was more FeCr2O4. 相似文献
3.
U. Turkan 《Surface & coatings technology》2010,205(7):1904-4783
The effect of nitric acid surface treatment on CaP deposition of an open-cell Ti6Al4V foam (60% porous and 300-500 ?m in pore size), prepared by means of the space holder method using 94 and 66 μm average particle size powders, was investigated in a simulated body fluid (SBF) solution up to 14 days. Although, nitric acid surface treatment did not change the foam flat surface roughness values significantly, it increased surface area difference greatly by introducing nano scale undulations on the surface. The increased surface area difference was found to be more pronounced in smaller particle size foam samples. A continuous relatively thin CaP coating layer formed after 5 and 14 days of SBF immersion in nitric acid surface treated small and larger average particle size foam specimens, respectively. Whereas, the cells of untreated foam specimen were observed to be filled with CaP precipitates and a continuous CaP layer development was found after 14 days of SBF immersion. These results were also confirmed with the grazing incidence XRD and FTIR analysis of SBF immersed specimens. 相似文献
4.
Jin-Hyeon Cho Young-Min Jin Dong-Yong Park Hyung-Jun Kim Ik-Hyun Oh Kee-Ahn Lee 《Metals and Materials International》2011,17(1):157-166
In this study, the manufacture of a large thickness Cu coating layer as sputtering target material via a cold spray coating
process was undertaken. The microstructure and properties of the Cu layer as the sputtering target material (before and after
the annealing heat treatment) were evaluated, compared, and analyzed. To evaluate the purity, density, grain size and uniformity,
microstructure, and properties of the Cu-coated layer as a sputtering target, X-ray diffraction, ICP analysis, SEM, EBSD,
porosity analysis, and Vickers hardness tests were performed. The result of the observation of the layer’s purity and microstructure
showed that a purity level (99.47%) similar to that of the early powder 2N5 was maintained and that the manufacture of a cold
spray deposited, ∼20 mm thick Cu coating material for the sputtering target was performed successfully. As a result of the
EBSD mapping, the average grain size near the interface and around the center measured 1.48 μm and 1.49 μm; the grains were
small and non-uniform compared with the 1.91 μm size near the surface. Note, however, that the recrystallization and grain
growth (caused by annealing) increased the grain size to 1.82 μm (near the interface), 1.83 μm (near the center), and 1.87
μm (near the surface) and improved the level of uniformity. Moreover, through post heat treatment, the overall porosity declined
(0.44 % porosity/400 °C/h heat treatment), and the grain texture became uniform. The possibility of controlling the microstructure
as a large thickness sputtering target by conducting an annealing heat treatment was also confirmed. Nonetheless, the differences
in the porosity and hardness associated with the coating thickness changes were partially maintained. Based on the aforementioned
findings, this study suggests that by using cold spray deposition, Cu coating layers with large thicknesses can be applied
as a sputtering target. 相似文献
5.
A novel electromagnetically accelerated plasma spraying technique was applied to mixtures of αSi3N4, and alumina, yttria, and silica additives to deposit thin coatings (50–100 μm) onto mirror-polished stainless steel surfaces.
The dense coatings consisted of crystalline αSi3N4 with minor amounts of β'SiAlON, traces of βSi3N4 and Y3Al5O12 as well as a quinary Si−Al−N−O−Y glass. The adhesion strengths depended on the powder particle size showing values of>77
MPa for coarse powders (median grain size 25 μm) and>67 MPa for fine powders (median grain size 8 μm). The average indentation
hardnesses were 450 HV0.025 (coarse powder) and 620 HV0.025 (fine powder); the sliding wear resistances were comparable to those of sintered Si3N4 used as counterbody in a pin-on-disc friction test. The friction coefficient showed surprisingly large values (1.0–1.1 in
water and 1.3–1.4 in air), suggesting application of such coatings as tribological high-friction surfaces. 相似文献
6.
The fatigue fracture surface of a duplex stainless steel was analyzed using x- ray fractography. A lower than average austenite
content was observed at the fracture surface due to the transformation of austenite into deformation- induced martensite.
The influence of fatigue cycling on the transformation was confined to a depth of about 30 μm below the fracture surface.
X- ray analyses of both the ferrite- martensite and the austenite phases indicated residual stresses (σr) increasing with depth from the fracture surface and reaching a maximum some tens of microns below the fracture surface.
The lower σr observed at the fracture surface has been attributed to the stress relaxation effects caused by the new fracture surfaces
created in the crack growth process. The observed decrease in full width at half maximum (FWHM) in the ferrite- martensite
phase was presumed to be due to the dynamic recovery effect that was likely to occur within the material close to the crack
tip as a consequence of fatigue cycling. 相似文献
7.
Dong Bok Lee Min Jung Kim Li Chen Sang Hwan Bak Oleh Yaskiv Iryna Pohrelyuk Viktor Fedirko 《Metals and Materials International》2011,17(3):471-477
Ti-6Al-4V alloys were nitrided through gas nitriding at 950 °C for 3 h in deoxygenated, atmospheric nitrogen gas. During nitriding,
nitrogen reacted and diffused into the alloys to form Ti2N and a meager amount of TiN in a Ti-N compound layer with a thickness of 20 μm to 25 μm. An α-Ti(N) diffusion layer with
a thickness of 40 μm to 80 μm formed below this layer. A small amount of Al was dissolved at the top of the Ti-N compound
layer because of the strong interaction of nitrogen with Ti and Al. Nitriding resulted in the dissolution of interstitial
nitrogen and the formation of nitrides. Oxidation of the nitrided Ti-6Al-4V alloys initially resulted in the formation of
a Ti-N-O layer, which later oxidized to TiO2. Above 800 °C, the nitrided alloys oxidized rapidly, accompanied by microcracking of the TiO2 surface layer. 相似文献
8.
KyuBong Jung WooJin Song Doo-Man Chun Jun-Cheol Yeo Min-Saeng Kim Sung-Hoon Ahn Caroline Sunyong Lee 《Metals and Materials International》2010,16(3):465-467
Nano particle deposition system (NPDS) is a novel method to deposit ceramic and metal powders at room temperature. Nickel
powders with a size of 3 μm in diameter were sprayed through the fabricated micro nozzle, varying stand-off distance (SoD),
which is a gap between the end of the nozzle and the substrate. Injection time for Ni powders was set to 1 min and the flow
rate of air-powder was kept to 10 l/min. When SoD was 300 μm, the average deposition thickness was measured to be 2.49 μm,
whereas the average deposition thickness was 300 nm for SoD being 500 μm. Therefore, Ni powder deposition at a SoD of 300
μm was successful compared to a SoD of 500 μm with minimal deposition. Moreover, electrical resistance of the deposited film
was measured to study its characteristics. Resistivity of the film deposited at a SOD of 300 μm was substantially lower than
that of the film deposited at a SoD of 500 μm, confirming the successful deposition at a SoD of 300 μm. Finally, heated treatment
of the deposited Ni powders to 150 °C improved the electrical conductivity significantly by lowering its resistivity to 4.4
× 10−7 Ωm. 相似文献
9.
S. R. Samarasinghe Isabel Pastoriza-Santos M. J. Edirisinghe M. J. Reece Luis M. Liz-Marzán 《Gold bulletin》2006,39(2):48-53
A dispersion containing 15nm gold particles in ethanol was subjected to electrohydrodynamic atomization, producing droplets
with an average size of ≈26μm as measured by laser diffraction. An electrohydrodynamic direct-write device was used to deposit
the dispersion onto silicon wafers with the intention of printing gold tracks. Immediately after deposition ethanol evaporated,
leaving the gold particles organised in a ≈75μm wide central region surrounded by two regions, each ≈50μm wide, at the edge
of which two further gold tracks, each ≈7μm existed. 相似文献
10.
Magnetic and dielectric loss are systematically controlled by using iron flake powders with various initial sizes (7 μm and
70 μm) as the absorbent fillers in the rubber matrix, and their noise absorbing characteristics have been investigated as
a function of frequency and sheet thickness. Flake iron particles were prepared by the mechanical forging of spherical powders
using an attrition mill. Composite sheets (thickness=0.2 mm-1.0 mm) were prepared with a mixture of iron particles and silicone
rubber. Attaching the composite sheets to a microstrip line of 50 Ω, a network analyzer was used to measure the reflection
and transmission parameters (S11 and S21, respectively). A nearly constant value of S11 (about −10 dB) was observed, irrespective of particle size. However, S21 is strongly dependent upon initial particle size. For the composites of 7 μm particles (with high magnetic loss), S21 is reduced below −20 dB in the frequency range of 1 GHz to 10 GHz, and the corresponding bandwidth of noise absorption is
not so greatly diminished by reducing the sheet thickness as low as 0.2 mm. For the composites of 70 μm particles (with high
dielectric loss), however, the bandwidth is greatly reduced with a decrease in sheet thickness. It is concluded that the attenuation
of conduction noise through the microstrip line is primarily controlled by the magnetic loss of the iron particles due to
strong magnetic field around the microstrip line. 相似文献
11.
Il Song Park Jong Jun Kim Seung Geun Ahn Min Ho Lee Kyeong Won Seol Tae Sung Bae 《Metals and Materials International》2007,13(2):117-122
This study examined the effect of fluoride on the surface characteristics of an anodized titanium implant. Commercial pure
titanium plate 20mm×10mm×2mm in size, and discs 1.5 mm thick and 1.5 mm in diameter, were used. The prepared samples were
polished with #200 to #1, 000 SiC papers and were then washed sequentially with distilled water, alcohol and acetone. Anodic
oxidation was performed using a regulated DC power supply in an electrolyte containing a mixture of 0.015 M DL-α-glycerophosphate
disodium salt hydrate (DL-α-GP) and 0.2 M calcium acetate hydrate (CA) with an electric current density of 30mA/cm2 and voltage ranging from 0 to 290 V. The specimens were divided into four groups and a fluoride treatment was carried out.
Group 1 was thermally treated in a 0.05 M TiF3 solution at 90°C, Group 2 was electrochemically treated at 150 V in a 0.05 M TiF3 solution, Group 3 was electrochemically treated at 150 V in a 0.05 M NaF solution, and Group 4 was electrochemically treated
at 150 V in a 0.05 M HF solution. A porous oxide layer containing pores 1–4 μm in size was observed on the surface treated
with anodic oxidation. The diameter of the pores was higher in the protrusion areas than in the sunken areas. A significant
amount of fluoride ions was released in the initial period, with small amounts being released continuously thereafter. The
viability of MC3T3 cells was high when the fluoride ion concentration was 10 ppm, but decreased with further increases in
the fluoride concentration. A six-week immersion test in simulated body fluid (SBF) showed dense HA crystals in the group
immersed in 0.05 M TiF3 at 90°C, which indicated good biocompatibility. 相似文献
12.
Sung-Hwan Choi Song-Yi Kim Jung-Yeul Yun Young-Min Kong Byoung-Kee Kim Kee-Ahn Lee 《Metals and Materials International》2011,17(2):301-307
This study investigated the effect of the pore size of Ni-22.4%Fe-22%Cr-6%Al porous metal on its hightemperature oxidation.
Two types of open porous metals with pore sizes of 800 μm and 580 μm were used. A 24-hour isothermal oxidation test was conducted
at three different temperatures of 900 °C, 1000 °C, and 1100 °C under a 79% N2 + 21% O2 atmosphere. The results of the BET analysis revealed that the specific surface area increased as the pore size decreased
from 800 μm to 580 μm. The high-temperature oxidation results showed that porous metals exhibited far lower levels of oxidation
resistance compared with bulk metals, and that the oxidation resistance of porous metals decreased with a decreasing pore
size. According to the microstructural observations of the oxide layers, the 900 °C and 1000 °C oxidation layer contained
Ni, Cr, and Al oxides mainly on the strut. The 800 μm porous metal strut exhibited similar oxidation behavior at 1100 °C to
that found at lower temperatures. In contrast, the 580 μm porous metal strut was found to consist of Ni and Fe oxides in the
upper layer and Ni, Cr, and Al oxides in the lower layer, representing a low oxidation resistance. For powders affixed to
the strut inside the porous metal, a different oxide-forming behavior from that of the strut was observed. In addition, the
Ni-Fe-Cr-Al porous metal high-temperature oxidation microscopic mechanism is also discussed. 相似文献
13.
A. I. Rat’ko A. I. Ivanets I. O. Sakhar D. Yu. Davydov V. V. Toropova A. V. Radkevich 《Protection of Metals and Physical Chemistry of Surfaces》2012,48(5):553-556
The retentiveness of microfiltration membranes based on crystalline silicon dioxide with an average pore size of 3 μm with respect to ferric iron ions Fe(III) is studied. A correlation between the state of Fe(III) in water solutions and the degree of retention, as well as the membrane surface origin and structural properties, is found. A comparative assessment of the retentiveness of the microfiltration ceramic and ultrafiltration polyamide membranes—with an average pore size of 7.8 nm—with respect to Fe(III) ions is made. 相似文献
14.
Gary Paul Kennedy Kwang-Young Lim Young-Wook Kim In-Hyuck Song Hai-Doo Kim 《Metals and Materials International》2011,17(4):599-605
Porous self-bonded silicon carbide (SBSC) ceramics were fabricated from SiC powders with various particle sizes (0.7 μm, 25
μm, 50 μm, 65 μm), plus Si, C and boron (as a sintering additive). The effects of submicron (0.7 μm) SiC particle incorporation
into the SBSC and the SiC particle size (25 μm, 50 μm, 65 μm) on the flexural strength and porosity of the ceramics were investigated
as a function of sintering temperature. Incorporating 0.7 μm SiC particles into the ceramic material containing 25 μm SiC
particles increased the flexural strength by 3 times, from 11.7 MPa up to 35.5 MPa after sintering at 1800 °C. Simultaneously,
the porosity was reduced by ∼5 %. Furthermore, the flexural strength of ceramic with 25 μm SiC particles was superior to that
with 65 μm SiC particles. Generally, the flexural strength of the SBSC increased as, both, a function of submicron SiC particle
incorporation along with relatively small micron-sized particles (25 μm) in the microstructure of the ceramic plus increased
sintering temperature. 相似文献
15.
Insup Lee 《Metals and Materials International》2008,14(1):77-81
Plasma nitrocarburizing and post-oxidation treatments were performed to improve the wear and corrosion resistance of S45C
steel. Plasma nitrocarburizing was conducted for 3 h at 570°C in a nitrogen, hydrogen and methane atmosphere to produce the
ε-Fe2−3(N,C) phase. It was found that the compound layer produced by plasma nitrocarburising was predominantly composed of the ∈-phase
with traces of the γ′-Fe4(N,C) phase. The thickness of the compound layer was approximately 12 μm and the diffusion layer was approximately 300 μm
in thickness. Plasma post oxidation was performed on nitrocarburized samples with various oxygen/hydrogen ratios at a constant
temperature of 500°C for 1 h. The very thin magnetite (Fe3O4) layer 1 μm to 2 μm in thickness on top of the compound layer was obtained by plasma post oxidation. It was also confirmed
that further improvement of the corrosion characteristics of the nitrocarburized compound layer was possible with an application
of the superficial magnetite layer. Finally, throttle valve shafts of S45C steel were treated under optimum plasma processing
conditions. Accelerated life time test results using a throttle body assembled with a shaft treated by plasma nitrocarburising
and post oxidation showed that plasma nitrocarburizing and plasma post-oxidation processes could be a viable technology in
the very near future in place of Cr6 plating. 相似文献
16.
Eun-A Ko Dong-Wook Kim Heon-Song Kannappan Santhakumar Jin-Soo Kim In-Hwan Lee Byung-Joon Baek Cheul-Ro Lee 《Metals and Materials International》2008,14(6):753-758
Epilayers of GaN were grown on patterned Si (111) substrates of various terrace widths by means of metal organic chemical
vapor deposition. The technique of lateral epitaxy on a patterned substrate used the growth of GaN epilayers from the periodic
and parallel stripes that form as a result of the substrate etching. Silicon substrates were patterned for various terrace
widths of 3 μm, 8 μm, and 18 μm. A low temperature AlN was used as a seed layer for the growth of a 1.5 μm thick GaN epilayer.
The as-grown samples were characterized by using double-crystal X-ray diffractometry (DCXRD), photoluminescence and atomic
force microscopy (AFM). From the DCXRD spectra, the full width at half maximum (FWHM) of the samples was found to decrease
as the terrace width decreased. This behavior indicates that there is an improvement in the crystalline quality of the GaN
epilayers as the terrace width decreases. The photoluminescence spectra reveal a decrease in the FWHM and an increase in the
peak intensity as the terrace width decreases. This behavior indicates that there is an improvement in the optical quality
of the GaN epilayer as the terrace width decreases. The atomic force micrographs reveal a dislocation-free homogeneous surface
in the trench region compared to the terrace region with defects such as pits and dislocations. The results clearly show that
GaN epilayers grown on a patterned Si substrate with a terrace width 3 μm have a good crystalline quality with minimal threading
dislocation and excellent band edge emission. 相似文献
17.
The superplastic deformation behavior of quasi-single phase Zn-0.3 wt. %Al was investigated. A series of load relaxation and
tensile tests was conducted at various temperatures ranging from RT (20 °C) to 200 °C. The recently proposed internal variable
theory of structural superplasticity was applied. The flow curves obtained from load relaxation tests were shown to consist
of contributions from interface sliding (IS) and accommodating plastic deformation. In the case of quasi-single phase Zn-0.3
wt.% Al alloy with an average agrain size of 1 μm, the IS behavior could be described as a viscous flow process characterized
by a power index of Mg=0.5. A large elongation of about 1400% was obtained at room temperature and the strain rate sensitivity parameter was about
0.4. Although relatively large-grained (10 μm) single phase alloy showed a high value of strain rate sensitivity comparable
to that of fine-grained alloy at very low strain rate range, IS was not expected from the analysis based on the internal variable
theory of structural superplasticity at room temperature. As the temperature increased above 100 °C, however, the contribution
from IS was observed at a very low strain rate range. A high elongation of ∼400% was obtained in a specimen of 10-μm-grain-size
at 200 °C under a strain rate of 2×10−4/sec.
Jointly appointed at Center for Advanced Aerospace Materials (CAAM) 相似文献
18.
In-Ha Jung Kee-Chan Song Kweon-Ho Kang Byoung-Ok Yoo Yang-Hong Jung Hyun-Soo Park Myung-Seung Yang 《Metals and Materials International》2001,7(5):513-518
A simulated DUPIC (Direct Use of Spent PWR Fuel in CANDU Reactors) fuel was irradiated at HANARO research reactor of KAERI
in 1999. Post-irradiation examinations, such as measurements of γ-scanning, profilometry, density, hardness, microstructure,
and fission product distribution were performed on the irradiated simulated DUPIC fuel. In γ-scanning, the intensity along
the axial direction was sharply decreased at the areas between the pellets. There was no significant change in the profilometry
of SEU-1.47%, but variation was detected in SEU-2.19%+F.P by 67 μm, and the peaks precisely coincided with the ridges of the
pellets. The marked difference between SEU-1.47% and SEU-2.19%+F.P pellets after irradiation was the configuration of cracks
arised in the pellets. Some large equiaxed grains of 11.1 μm were observed at the center of the SEU-2.19%+F.P pellet, while
the grain size near the surface of the pellet was remained almost the same as the original grain size of 5.58 μm. The hardness
had no tendency toward change to the direction, but average hardness was increased as much as 10% compared with a fresh simulated
DUPIC fuel.
This article is based on a presentation made in the “Symposium on Nuclear Materials and Fuel 2000”, held at the Korea Atomic
Energy Research Institute (KAERI), Taejon, Korea, August 24–25 under the auspices of the Ministry of Science and Technology
(MOST). 相似文献
19.
E. F. Dudarev R. Z. Valiev Yu. R. Kolobov A. I. Lotkov V. G. Pushin G. P. Bakach D. V. Gunderov A. P. Dyupin N. N. Kuranova 《The Physics of Metals and Metallography》2009,107(3):298-311
Mechanisms of plastic deformation have been studied in detail in the process of isothermal loading at room temperature in
a high-purity shape-memory alloy of composition Ti49.4Ni50.6. The alloy was studied in two initial states: usual coarse-grained (with an average grain size of 20–30 μm) and submicrocrystalline
(with an average grain size of 0.2–0.3 μm). It has been shown that during tensile tests there occurs a mechanically induced
martensitic transformation in the alloy at stresses corresponding to stages I, II, and III in the tensile curve and then elastic
and plastic deformation of B19′ martensite is observed at stages IV, V, and VI, respectively. Optical metallography in situ and electron microscopy have
been used to study microstructural features and mechanisms of plastic deformation of the alloy up to its failure.
Original Russian Text ? E.F. Dudarev, R.Z. Valiev, Yu.R. Kolobov, A.I. Lotkov, V.G. Pushin, G.P. Bakach, D.V. Gunderov, A.P.
Dyupin, N.N. Kuranova, 2009, published in Fizika Metallov i Metallovedenie, 2009, Vol. 107, No. 3, pp. 316–330. 相似文献
20.
The optimum parameters were determined for synthesizing ZrN-Si3N4 composite powder from zircon by carbothermal reduction-nitridation (CTRN) process. The samples were prepared by mixing the
carbon black of an average particle size less than 30 μm and the zircon of 40 μm with C/ZrSiO4 mass ratios of 0.2, 0.3, 0.4, and 0.5. The prepared samples were subjected to the CTRN process at temperatures of 1673, 1723,
1753, and 1773 K for 6, 9, and 12 h. The CTRN process was conducted in an atmosphere-controlled tubular furnace in a nitrogen
gas flow of 1.0 L/min. All the products were examined by X-ray powder diffraction to determine the transformation. The results
showed that the proper transformation of ZrN-Si3N4 occurred at 1773 K for 12 h with a C/ZrSiO4 mass ratio of 0.4. 相似文献