Bioactive effect of alkali-heat treated TiO₂ nanotubes by water or acid treatment

Kim, S.Y.,Kim, Y.K.,Jang, Y.S.,Park, I.S.,Lee, S.J.,Jeon, J.G.,Lee, M.H. Elsevier Sequoia 2016 Surface & coatings technology Vol.303 No.1

Various surface treatments are used to enhance the biological activity of titanium. Alkali and heat treatments promote the formation of hydroxyl apatite (HAp), which increases the bone-bonding ability in simulated body fluid (SBF). The sodium titanate layer is converted to the more bioactive layer, with sodium-ion removal from alkali- and heat-treated surfaces, via a water treatment. The anatase phase resulting by water treatment is effective in generating apatite nuclei in SBF. In this study, two types of surface treatment were performed to improve the bioactivity of alkali and heat-treated TiO<SUB>2</SUB> nanotubes: One is the only water treatment for 48h. Another is the combination of the acid-solution (10 and 50mM of HCl or HNO<SUB>3</SUB>) treatment for 24h and the water treatment for 24h. Each treatment was conducted after the fabrication of alkali-treated TiO<SUB>2</SUB> nanotubes via anodization and an alkali treatment in 5M NaOH. Finally, all of the treated groups were all heated at 550<SUP>o</SUP>C. The properties, bioactivity, and cytotoxicity of the alkali-heat treated TiO<SUB>2</SUB> nanotubes were determined after the water or acid treatment. In addition, histological samples were evaluated by inserting implants into bilateral rat tibia for 3 and 6weeks. The concentration of O ions and the amount of anatase phase increased after the HCl treatment. Furthermore, the apatite-forming ability was greatly enhanced with an increase in the amount of anatase phase, especially in the 50mM HCl-treated group. The surface of the water- or 50mM HCl-treated group promoted osteoblastic proliferation and differentiation, thereby allowing effective osteointegration. In the 6-week implant, the uniform new bone layer grew in the case of the HC50 group only. Therefore, we conclude that the HCl treatment constitutes the most favorable surface-modification method for improving the bioactivity of alkali- and heat-treated TiO<SUB>2</SUB> nanotubes.

The effect of silane applied to glass ceramics on surface structure and bonding strength at different temperatures

Tevfik Yavuz,Oguz Eraslan 대한치과보철학회 2016 The Journal of Advanced Prosthodontics Vol.8 No.2

PURPOSE To evaluate the effect of various surface treatments on the surface structure and shear bond strength (SBS) of different ceramics. MATERIALS AND METHODS 288 specimens (lithium-disilicate, leucite-reinforced, and glass infiltrated zirconia) were first divided into two groups according to the resin cement used, and were later divided into four groups according to the given surface treatments: G1 (hydrofluoric acid (HF)+silane), G2 (silane alone-no heat-treatment), G3 (silane alone-then dried with 60℃ heat-treatment), and G4 (silane alone-then dried with 100℃ heat-treatment). Two different adhesive luting systems were applied onto the ceramic discs in all groups. SBS (in MPa) was calculated from the failure load per bonded area (in N/mm2). Subsequently, one specimen from each group was prepared for SEM evaluation of the separated-resin–ceramic interface. RESULTS SBS values of G1 were significantly higher than those of the other groups in the lithium disilicate ceramic and leucite reinforced ceramic, and the SBS values of G4 and G1 were significantly higher than those of G2 and G3 in glass infiltrated zirconia. The three-way ANOVA revealed that the SBS values were significantly affected by the type of resin cement (P<.001). FIN ceramics had the highest rate of cohesive failure on the ceramic surfaces than other ceramic groups. AFM images showed that the surface treatment groups exhibited similar topographies, except the group treated with HF. CONCLUSION The heat treatment was not sufficient to achieve high SBS values as compared with HF acid etching. The surface topography of ceramics was affected by surface treatments.

타타늄의 열처리 조건에 따른 동전위 양극분극특성 및 표면 미세구조 변화

주동현,이용렬,정영화,양홍서,박상원,이도재,송호준,박영준 大韓齒科器材學會 2002 대한치과재료학회지 Vol.29 No.2

The corrosion resistance of metallic implants is essential for successful implant osseointegration. Moreover, the implant surface should have appropriate surface roughness for the attachment of the osteoblast and collagen fibrils. When titanium is exposed to air a thermodynamically very stable oxide film is formed at once. This oxide is very thin and yet it protects the metal from corrosion instantaneously. However, the oxide would not be ideal, and it would be supposed that the state of oxide film would be various by the different conditions when it is formed. The objective of this study was to evaluate the electrochemical properties and surface microstructural changes of titanium after passivation treatment or exposure to high heat (in vacuum or in air). ASTM grade 2 commercially pure titanium (Ti) disks of 10㎜ diameter were wet ground and polished with 240 and 600 grit SiC, and then ultrasonically cleaned with distilled water and ethanol. Cleansed as-received samples (As-R group) were passivated with 30% nitric acid solution at 50℃ for 15 minutes to make the Pas group. The Std-V samples were made by treating the Ti disks in vacuum quartz tube (10^-8 Torr) at 530℃ for 40 min for stress relieving, followed by annealing at 700℃ for 90 min, and then slow cooling to room temperature. The Std-A samples undergo identical procedure as the Std-V group except that it is done in air. For 530℃-V samples, Ti disks were heated at 530℃ for 40 minutes and slow cooled to room temperature. The 1000℃-V samples were produced by heating Std-V specimens again at 1000℃ for 2 hr, followed by cooling to room temperature. 530℃-A and 1000℃-A samples were also prepared. Potentiodynamic anodic polarization measurement, SEM, AFM and XRD analysis were performed to evaluate the effects of the various treatments. The difference in the mean values of E_corr between groups showed statistically significant difference (P<0.05), but that of I_corr did not show significance (P>0.05). When Ti surface was passivated there was a shift of corrosion potential (E_corr) in the noble direction and a lower corrosion current density (I_corr) value. Std-A samples showed most noble E_corr value among the tested groups. 530℃-V samples showed more noble E-corr than other tested groups except Std-A group. 1000℃-V samples showed more noble E-corr than those of Std-V sample. In the case of Std-, 530℃- and 1000℃-groups, -A sub-groups showed better corrosion resistant characteristics than -V sub-groups in regard to E-corr and I_corr values. In the SEM observations, the surfaces of the As-R samples showed only scratch line on smooth surface. In Pas samples, thick oxide layer covered the surface under high magnification observation. 530℃-A samples were covered by oxide granules, and Std-A samples had 25~50 nm-thick acicular oxides. The 1000℃-A samples were covered by coarse oxide crystals with a granule diameter of 0.1~0.6 μm having a gross appearance of milky white color, which was identified by XRD as a rutile. On the other hand, 1000℃-V samples showed an Widmansta¨tten structrue of which the orientation of the lattice is formed along crystallographic planes of the parent crystals. On the AFM observation, 530℃-A samples showed RMS roughness of 79.38 nm which is 5 times rougher than those of the As-R samples. Std-A sample had a roughness of 330.47 nm which is about 20-times rougher than that of the As-R sample. 1000℃-A samples were covered by coarse granular oxides and the roughness were about 0.56 μm. Vacuum sub-group samples showed a more smooth surface than air sub-group samples, and the oxide film was more dense. Due to variability of the surface treatment and heat treatment conditions, the process of the oxide formation seems to be affected thereby making the corrosion properties and surface micro-morphology different. However, more various electrochemical analysis together with surface analysis, and an investigation for the effects of those on the osteoblast cell adhesion and calcium phosphate apposition are needed for the improvement of the osseointegration rates of the titanium implants.

사포, 샌드블라스트로 표면 거칠기 처리에 따른 알루미늄 판의 방열 효율 증대

이동희(Dong-Hee Lee),이종현(Jong-Hyeon Lee) 한국산학기술학회 2019 한국산학기술학회논문지 Vol.20 No.1

최근 에너지 절감에 대한 관심도가 높아짐에 따라 에너지 소비가 높은 형광등과 백열등을 대체하는 친환경소재인 LED의 조명을 활용하는 움직임이 활발하다. 그러나, 고출력 LED의 경우 발열에 의한 열화현상 때문에 수명이 단축되는 현상이 발생하게 된다. 이에 대한, 해결방안으로 본 논문은 LED Packing중 방열판표면의 거칠기 처리를 통하여 열전달 계수를 증대시킴으로서 LED 수명연장 효과를 평가하였다. 거칠기 공정은 사포 및 샌드블라스트를 이용하여 진행하였다. 각 표면처리 공정에 따른 거칠기 및 표면적 변화를 정량적으로 평가하였으며, 열전달 계수를 측정하였다. 샌드블라스트, 사포를 이용하여 알루미늄 표면에 거칠기처리를 진행했을 경우 미 처리 시 보다 높은 대류 열전달 계수를 얻을 수 있었고, 샌드블라스트 처리 시 약 82.76%의 높은 방열 효율 향상을 얻을 수 있어, 이를 방열판에 적용할 시 큰 경제적 부담 없이 기존대비 더 높은 방열효율 증대를 통해 LED 수명을 대폭 연장 시킬 것으로 기대된다. Recently, as the interest in energy savings has increased, there has been increasing use of LED lighting, which is an eco-friendly device that replaces high energy consuming fluorescent lamps and incandescent lamps. In the case of a high output LED, however, the life time is shortened due to deterioration caused by heat generation. As a solution to this problem, this paper evaluated the LED life extension effect by increasing the convective heat transfer coefficient of the heat sink surface for LED packaging. A roughing process was carried out using sandpaper and sand blasting. The changes in surface roughness and surface area after each surface treatment process were evaluated quantitatively and the convective heat transfer coefficient was measured. When sandblasting and sandpaper were used to roughen the aluminum surface, a higher convection heat transfer coefficient was obtained compared to the untreated case, and a high heat dissipation efficiency of 82.76% was obtained in the sandblast treatment. Therefore, it is expected that the application of heat dissipation to the heat sink will extend the lifetime of the LED significantly and economically by increasing the heat efficiency.

금형재료용 주철강의 복합열처리 특성

황현태,소상우,김종도,Hwang, Hyun-Tae,So, Sang-Woo,Kim, Jong-Do 한국재료학회 2011 한국재료학회지 Vol.21 No.7

Currently, there are two main issues regarding the development of core technologies in the automotive industry: the development of environmentally friendly vehicles and securing a high level of safety in the event of an accident. As part of the efforts to address these issues, research into alternative materials and new car body manufacturing and assembly technologies is necessary, and this has been carried out mainly by the automotive industries. Large press molds for producing car body parts are made of cast iron. With the increase of automobile production and various changes of design, the press forming process of car body parts has become more difficult. In the case of large press molds, high hardness and abrasive resistance are needed. To overcome these problems, we attempted to develop a combined heat treatment process consisting of local laser heat treatment followed by plasma nitriding, and evaluated the characteristics of the proposed heat treatment method. From the results of the experiments, it has been shown that the maximum surface hardness is 864 Hv by the laser heat treatment, 953 Hv by the plasma nitriding, and 1,094 Hv by the combined heat treatment. It is anticipated that the suggested combined heat treatment can be used to evaluate the durability of press mold.

레이저 가공 기반 사출 금형강의 선택적 표면 개질 연구: 레이저 나이트라이딩에 따른 AlN 형성 및 경화 거동

천은준,박창규,박원아 대한금속·재료학회 2020 대한금속·재료학회지 Vol.58 No.1

Laser surface heat treatment and laser nitriding processes were applied using selective surface modification techniques to investigate phase transformation, microstructural evolution, and surface hardening behaviors for two types of plastic injection mold steels, AISI 1045 and P21. During laser surface heat treatment, a 245% hardness increase compared to that of the base metal (290 HV) was achieved due to martensite transformation of the AISI 1045 steel. However, for the AISI P21 steel, hardness within the heat-treated zone was largely unchanged from that of the base metal (410 HV) despite being accompanied by martensite transformation. Compared to that of the base metal, this static hardness behavior of the heat treated P21 steel was due to coarsening of Cu particles induced by the laser irradiation. To overcome the static hardness behavior of P21 steel, laser nitriding was used. The laser-nitrided specimen (at 4500 J/mm heat input) was approximately 40% (577 HV) harder than the base metal (410 HV) and was highly correlated with nitride formation. Nitrogen successfully penetrated the surface of the specimen during laser irradiation and formed a nitrided layer mainly composed of an AlN phase. Thus, the surface hardening behavior of AISI P21 steel after laser nitriding could be largely attributed to the AlN phase development.

Development of hydrophobicity and selective separation of hazardous chlorinated plastics by mild heat treatment after PAC coating and froth flotation

Thanh Truc, Nguyen Thi,Lee, Chi-Hyeon,Lee, Byeong-Kyu,Mallampati, Srinivasa Reddy Elsevier 2017 Journal of hazardous materials Vol.321 No.-

<P><B>Abstract</B></P> <P>Polyvinyl chloride (PVC) containing chlorine can release highly toxic materials and persistent organic pollutants if improperly disposed of. The combined technique of powder activated carbon (PAC) coating and mild heat treatment has been found to selectively change the surface hydrophobicity of PVC, enhancing its wettability and thereby promoting its separation from heavy plastic mixtures included polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene (PS) and acrylonitrile butadiene styrene (ABS) by means of froth flotation. The combined treatments helped to rearrange the surface components and make PVC more hydrophobic, while the remaining plastics became more hydrophilic. After the treatments at 150°C for 80s the contact angle of the PVC was greatly increased from 90.5 to 97.9°. The SEM and AFM reveal that the surface morphology and roughness changes on the PVC surface. XPS and FT-IR results further confirmed an increase of hydrophobic functional groups on the PVC surface. At the optimized froth flotation and subsequent mixing at 150rpm, 100% of PVC was recovered from the remaining plastic mixture with 93.8% purity. The combined technique can provide a simple and effective method for the selective separation of PVC from heavy plastics mixtures to facilitate easy industrial recycling.</P> <P><B>Highlights</B></P> <P> <UL> <LI> PAC coating and mild heat treatment were combined for selective wetting of PVC. </LI> <LI> The combined treatment rearranged the PVC surface and increased its hydrophobicity. </LI> <LI> Optimized froth flotation was crucial for selective separation of the treated PVC. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Control of laser-ablated aluminum surface wettability to superhydrophobic or superhydrophilic through simple heat treatment or water boiling post-processing

Ngo, Chi-Vinh,Chun, Doo-Man Elsevier BV * North-Holland 2018 Applied Surface Science Vol.435 No.-

<P><B>Abstract</B></P> <P>Recently, controlling the wettability of a metallic surface so that it is either superhydrophobic or superhydrophilic has become important for many applications. However, conventional techniques require long fabrication times or involve toxic chemicals. Herein, through a combination of pulse laser ablation and simple post-processing, the surface of aluminum was controlled to either superhydrophobic or superhydrophilic in a short time of only a few hours. In this study, grid patterns were first fabricated on aluminum using a nanosecond pulsed laser, and then additional post-processing without any chemicals was used. Under heat treatment, the surface became superhydrophobic with a contact angle (CA) greater than 150° and a sliding angle (SA) lower than 10°. Conversely, when immersed in boiling water, the surface became superhydrophilic with a low contact angle. The mechanism for wettability change was also explained. The surfaces, obtained in a short time with environmentally friendly fabrication and without the use of toxic chemicals, could potentially be applied in various industry and manufacturing applications such as self-cleaning, anti-icing, and biomedical devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Superhydrophilic/superhydrophobic Al surfaces were made by laser ablation and simple post process. </LI> <LI> Laser-ablated Al surface became superhydrophobic using heat treatment. </LI> <LI> Laser-ablated Al surface became superhydrophilic using boiling water treatment. </LI> <LI> Mechanism of wettability change to superhydrophobic/superhydrophilic was explained. </LI> <LI> The performances of superhydrophobic and superhydrophilic Al were demonstrated. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

SiC 증착층 계면의 표면조도에 미치는 흑연 기판의 표면조도 영향

박지연,정명훈,김대종,김원주 한국세라믹학회 2013 한국세라믹학회지 Vol.50 No.2

The surface roughness of the inner and outer surfaces of a tube is an important requirement for nuclear fuel cladding. When an inner SiC clad tube, which is considered as an advanced Pressurized Water Cooled Reactor (PWR) clad with a three-layered structure, is fabricated by Chemical Vapor Deposition (CVD), the surface roughness of the substrate, graphite, is an important process parameter. The surface character of the graphite substrate could directly affect the roughness of the inner surface of SiC deposits, which is in contact with a substrate. To evaluate the effects of the surface roughness changes of a substrate, SiC deposits were fabricated using different types of graphite substrates prepared by the following four polishing paths and heat-treatment for purification: (1) polishing with #220 abrasive paper (PP) without heat treatment (HT), (2) polishing with #220 PP with HT, (3) #2400 PP without HT, (4) polishing with #2400 PP with HT. The average surface roughnesses (Ra) of each deposited SiC layer are 4.273, 6.599, 3.069, and 6.401 μm, respectively. In the low pressure SiC CVD process with a graphite substrate, the removal of graphite particles on the graphite surface during the purification and the temperature increasing process for CVD seemed to affect the surface roughness of SiC deposits. For the lower surface roughness of the as-deposited interlayer of SiC on the graphite substrate, the fine controlled processing with the completed removal of rough scratches and cleaning at each polishing and heat treating step was important.

Hole Drilling 방법의 열과 표면처리에 의한 잔류응력 계산

유재석,박세만 明知大學校 産業技術硏究所 2008 産業技術硏究所論文集 Vol.27 No.-

Residual stresses deteriorate strength of materials adversely affecting quality of industrial products. A removable or a reduction of the residual stresses is an essential procedure in successful product developments. Effective and convenient methods are necessary for detection and evaluation of the residual stresses. In this investigation Hole Drilling Method is chosen for identification and a quantitative determination of the residual stresses of specimen in different groups under three heat and surface treatment conditions. The specimen in the first group is standard reference specimen without the heat treatment. The ones in the second group is carburized specimen with the surface treatment. In another group specimen is exposed to high frequency electric power to achieve the desired heat treatment condition. The residual stresses of metal alloys are evaluated subsequently with an analysis for the specimens prepared under a variety of heat and surface conditions, revealing complex effects of the treatments on the residual stresses as well as on properties of the materials. The amount of the residual stresses comes in that order of the specimen with the high frequency, with the carburized treatment and the specimen without the heat treatment. The quantitative analysis as well as experience suggests reliable and effective processes to eliminate or reduce the residual stresses. Also, during process of pipe welding a high level of residual stresses is observed to develop and its level increases non-uniformly with a depth into a hole. Based on the experimental results and the analysis, proper treatment conditions can be predicted to reduce or even completely eliminate the residual stresses, leading to an establishment of reliable methods for a control of the residual stresses.