• Restorative Dentistry and Endodontics
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• v.28 no.5
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• pp.363-368
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• 2003

The purpose of this study is to evaluate the effect of additional enamel etching with phosphoric acid on the microleakage of the adhesion of self-etching primer system. Class V cavity($4mm{\times}3mm{\times}1.5mm$) preparations with all margins in enamel were prepared on buccal surface of 42 extracted human upper central incisor teeth. Prepared teeth were randomly divided into 3 groups. Group 1：no additional pretreatment with 37% phosphoric acid (NE). Group 2：additional pretreatment with 37% phosphoric acid for 10 seconds (E10s). Group 3：additional pretreatment with 37% phosphoric acid for 20 seconds (E20s). The adhesives(Clearfil SE $Bond^{\circledR}$, Kuraray, Osaka, Japan) and composite resins(Clearfil $AP-X^{\circledR}$, Osaka, Kuraray, Japan) were applied following the manufacturer's instructions. All the specimens were finished with the polishing disc(3M dental product, St Paul, MN, USA), thermocycled for 500 cycles between $5^{\circ}C$ and $55^{\circ}C$ and resected apical 3-mm root. 0.028 stainless steel wire was inserted apically into the pulp chamber of each tooth and sealed into position with sticky wax. Surrounding tooth surface was covered with a nail varnish 2 times except areas 1mm far from all the margins. After drying for one day, soaked the samples in the distilled water. Microleakage was assessed by electrochemical method(System 6514, $Electrometer^{\circledR}$), Keithley, USA) in the distilled water. In this study, the microleakage was the lowest in group 1 (NE) and the highest in group 3(E20s)(NE

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.741-744
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• 2001

This paper described on the fabrication of microstructures by DRIE(Deep Reactive Ion Etching). SOI(Si-on-insulator) electric devices with buried cavities are fabricated by SDB technology and electrochemical etch-stop. The cavity was fabricated the upper handling wafer by Si anisotropic etch technique. SDB process was performed to seal the fabricated cavity under vacuum condition at -760 mm Hg. In the SDB process, captured air and moisture inside of the cavities were removed by making channels towards outside. After annealing(1000$^{\circ}C$, 60 min.), the SDB SOI structure was thinned by electrochemical etch-stop. Finally, it was fabricated microstructures by DRIE as well as a accurate thickness control and a good flatness.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1888-1891
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• 2003

In this paper, we proposed a new method to control the length of carbon nano tube in the single CNT probe. A single CNT probe was composed of a tungsten tip made by the electrochemical etching and carbon nano tube which was grown by CVD and prepared through the sonication. The two components were attached with the carbon tape. Since the length of CNT can not be controlled during the manufacturing, the post process is needed to shorten the CNT. In this paper, we proposed the method of electrochemical process. The process was done under the optical microscope and the results were checked by SEM. The diameter of the carbon nano tube used in this paper was about 130nm because the above process had to be done with the optical microscope. Using the method proposed in this paper, we can control the length of the nano tube tip.

• Journal of Integrative Natural Science
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• v.2 no.2
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• pp.82-85
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• 2009

Distributed Bragg reflector (DBR) porous silicon (PSi) was generated by an electrochemical etching a bragg structure into a silicon wafer through electrode current in aqueous ethanolic HF solution. DBR PSi exhibiting unique reflectivity was successfully obtained by an electrochemical etching of silicon wafer using square current waveform. The multilayered photonic crystals of DBR PSi exhibited the reflection of a specific wavelength with high reflectivity in the optical reflectivity spectrum. In this work, we have developed a method to create refractive index in Si substrate through intensity of an electric current. The electrochemical process allows for precise control of the structural properties of DBR PSi such as thickness of the porous layer, porosity, and average pore diameter. The number of reflection peak of DBR PSi and its pore size increased as the intensity of electric current increased. This might be a demonstration for the fabrication of specific reflectors or filters.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.423-426
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• 1998

Piezoresistive pressure sensors have fabricated using electrochemical etch-stop technique. Si diaphragm having thickness of n-epi. layer was fabricated and used to detect pressure range from 0 to 1 kg/$\textrm{cm}^2$. Piezoresistors were diffused 3${\times}$10$\^$18/ cm$\^$-3/ and placed at diaphragm edge for maximum pressure detection. The characteristics of electrochemical etch-stop in TMAH/lPA/pyrazine solution were also discussed. I-V curves of n and p-type Si in TMAH/lPA/pyrazine solution were obtained. Etching rate is highest at optimum etching condition, TMAH 25wt.%/IPA 17vo1.%/pyrazine 0.1/100m1, thus the elapsed time of etch-stop was reduced.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.6
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• pp.172-178
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• 2004

Tungsten carbide microshaft can be used as various micro-tools for MEMS because it has high hardness and high rigidity. In this study, experiments are performed to produce tungsten carbide micro-shaft using electrochemical etching. H$_2$SO$_4$ solution is used as electrolyte because it can dissolve tungsten and cobalt simultaneously. Optimal electrolyte concentration and machining voltage satisfying uniform shape, good surface quality, and high MRR of workpiece are experimentally found. By controlling the various machining parameters, a straight micro-shaft with 5 ${\mu}{\textrm}{m}$ diameter, 3 mm length, and 0.2$^{\circ}$taper angle was obtained.

• Journal of Photoscience
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• v.10 no.3
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• pp.257-261
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• 2003

We have systematically studied the evolution of the photoluminescence(PL) tuning of porous silicon(PS) by electrochemical etching in various mixed electrolytes. The electrolytes employed as an etchants were mixtures of HF:CH$_3$COOH:HNO$_3$:C$_2$H$\_$5/OH solutions where the composition ratios (%) were varied from 10:1.98:0:88.02 to 10: 1.98:8.4:79.62 under constant concentration of HF and CH$_3$COOH with a total volume of 100 ml. Changes in the surface morphology of the samples caused by variations in the etching process were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). After samples are etched in various mixed electrolytes, FTIR analyses show that there is the non-photoluminescent state and the photoluminescent state simultaneously. The PL spectra show the PL tuning in the ranging from 560 to 700 nm with the increase of HNO$_3$ concentration. An analysis of the subsequent PL relaxation mechanism was carried out by time-correlated single photon counting (TCSPC) method. Based on experimental results, it is assumed that a red shift of the main PL peak position is related to the HNO$_3$ activated formation of silicon oxygen compounds. Therefore, the use of electrolyte mixtures with composition ratios can be obtained adequate and reproducible results for PL tuning.

• Journal of the Korean Electrochemical Society
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• v.2 no.4
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• pp.190-194
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• 1999

Etched Nafion membrane and electrode assemblies were fabricated and those performances were observed in PEMFC. Adhesion of membrane to electrode increased with abrasion of membrane surface. Membrane surface ething results in reduction of hot pressing temperature, as a consequence, in improving of cell performance. It was found that Nafion etching was effective in painting method. The optimum content of electrode catalyst should be selected according to etching intensity.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.11
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• pp.1686-1690
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• 1989

Using the anisotropic etching characteristics of N2H4-H2O solutions, Si diaphragm was fabricated for the integrated sensors. The optimal composition and temperature of the etching solution in (100) Si etching process was established to be 50mol% N2H4 in H2O at 105\ulcorner\ulcorner for both higher etch rate (=2.6\ulcorner/min) and better surface quality of etched (100) planes. Based on the above optimal etching condition, the electrochemical etch-stop technique was employed to form n-type Si diaphragm having a thickness of 20\ulcorner and the thickness of diapragm could exactly be controlled to 20\ulcorner\ulcorner.

• Applied Chemistry for Engineering
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• v.24 no.5
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• pp.562-565
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• 2013

The high purity Al foil, which has an enlarged surface area by electrochemical etching process, has been used as an anode for an aluminum electrolytic capacitor. Etch pits are randomly distributed on the surface because of the existence of surface irregularities such as impurity and random nucleation of pits. Even though a large surface area was formed on the tunnel-etched Al, its applications to various fields were limited due to non-uniform tunnel morphologies. In this work, the selective electrochemical etching of aluminum was carried out by using a patterned mask fabricated by photolithographic method. The formation of etch pits with uniform distribution has been demonstrated by the optimization of experimental conditions such as current density and etching solution temperature.