• Journal of Aquaculture
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• v.16 no.4
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• pp.223-228
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• 2003

An exfoliation, the detachment of juvenile abalones from a culture substrate, is essential for selection and population density control in abalone culture. Physical instruments and anesthetics are currently available for the exfoliation but the latter is regarded as more effective in reducing physical damage to the animals. In the present study, urea ($Co(NH_2)_2$), a chemical fertilizer, was selected as a anesthetic, and its optimal concentration and sea water temperature for exfoliation of Haliotis discus were determined in order to develop an exfoliation technique which is more economical and effective. A 97% cumulated exfoliation rate was observed within 3 min at all temperatures observed when the concentration rate of urea was 9∼15%. This range of urea concentration can be ideal for both exfoliation and recovery. Also it was found that the higher concentration of urea and temperature the higher exfoliation rate, however, these conditions reduced the recovery rates of the animals tested. These results could indicate that urea is a good tool for exfoliation of various species of young abalones, and urea could substitute for all techniques and anesthetics methods currently available for abalone exfoliation.

• Korean Journal of Materials Research
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• v.23 no.12
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• pp.708-713
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• 2013

Graphene oxide has been synthesized by microwave-assisted exfoliation of graphite oxide prepared by modified Hummers method. Graphite was oxidized in a solution of $H_2O_2$ and $KMnO_4$ at $65{\sim}80^{\circ}C$, followed by 10 % $H_2O_2$ solution treatment at $80{\sim}90^{\circ}C$. The graphite oxide was exfoliated under microwave irradiation of 1 kW and was reduced to graphene effectively by hydrazine hydrate ($H_4N_2{\cdot}H_2O$) treatment. The exfoliation of graphene oxide was significantly affected by the microwave irradiation on (heating)/off (cooling) period. An on/off period of 10 s/20 s resulted in much more effective exfoliation than that of 5 s/10 s with the same total treatment time of 10 min. This can be explained by the higher exfoliation temperature of 10 s/20 s. Repetition of the graphite oxidation and exfoliation processes also enhanced the exfoliation of graphene oxide. The thickness of the final graphene products was estimated to be several layers. The D band peaks of the Raman spectra of the final graphene products were quite low, suggesting a high crystal quality.

• Journal of the korean academy of Pediatric Dentistry
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• v.4 no.1
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• pp.19-23
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• 1977

178 naturally exfoliated maxillary deciduous central incisors, 149 deciduous lateral incisors of children at exfoliation stage were studied on the degree and the tendency of the root resorption, and the age of exfoliation of the deciduous central and lateral incisors. The results were as follows; 1. The root of maxillary deciduous central and lateral incisors tended to be resorbed disto-lingually. 2. The age of exfoliation of maxillary deciduous central incisor was 7.27 year in male, 7.01 year in female, and the age of exfoliation of maxillary deciduous lateral incisor was 8.22 year in male, 7.77 year in female. 3. The exfoliation age of maxillary deciduous central and lateral incisors was earlier in female than in male.

• Journal of Power System Engineering
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• v.18 no.6
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• pp.7-12
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• 2014

The effect of various synthesis conditions in the fabrication of graphene using the exfoliation methods has been investigated. Graphite oxide and graphene fabricated by various synthesis conditions were identified by SEM and XRD. Graphite oxide was made from graphite by the chemical oxidation, and graphene was manufactured from graphite oxide by thermal exfoliation method. As a result, it is confirmed that graphite oxide was well formed from graphite, and the graphene could be obtained from graphite oxide. And it was found that the interlayer spacing between the graphene layers depended on the reaction time and particle size, regardless of the reaction temperature from $5^{\circ}C$ to $25^{\circ}C$.

• Applied Chemistry for Engineering
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• v.30 no.2
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• pp.133-140
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• 2019

Two-dimensional (2D) ultrathin molybdenum dichalcogenides $MoS_2$ has gained a great deal of attention in energy conversion and storage applications because of its unique morphology and property. The 2D $MoS_2$ nanosheets provide a high specific surface area, 2D charge channel, sub-nanometer thickness, and high conductivity, which lead to high electrochemical performances for energy storage devices. In this paper, an overview of properties and synthetic methods of $MoS_2$ nanosheets for applications of supercapacitors and rechargeable batteries is introduced. Different phases triangle prismatic 2H and metallic octahedral 1T structured $MoS_2$ were characterized using various analytical techniques. Preparation methods were focused on top-down and bottom-up approaches, including mechanical exfoliation, chemical intercalation and exfoliation, liquid phase exfoliation by the direct sonication, electrochemical intercalation exfoliation, microwave-assisted exfoliation, mechanical ball-milling, and hydrothermal synthesis. In addition, recent applications of supercapacitors and rechargeable batteries using $MoS_2$ electrode materials are discussed.

• Journal of fish pathology
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• v.25 no.2
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• pp.123-126
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• 2012

Exfoliation of fouling abalone, Haliotis discus hannai from shelters by commercial oxytetracycline (OTC) was observed in culture farms. In the present study, different components of OTC for exfoliation of abalone were investigated to understand how to work. Abalone were detached from shelter in 14,000 ppm of commercial OTC (main ingredients of OTC: OTC-hydrogen chloride (HCl), 50%; glucose, 49%; blue pigment, <1%), but not below 8,000 ppm. A 95% of exfoliation rate was observed in OTC-HCl (7,000 ppm, pH 2.8) but no exfoliation in OTC-HCl (7,000 ppm, pH 5.0), glucose (7,000 ppm) or blue pigment (140 ppm). Moreover 100% exfoliation rate was observed in HCl-seawater of pH 2.8. These results indicate that HCl is the component resulting in exfoliation of the fouling abalone. Abalone was detached in HCl solution (pH 2.5-3.2) within 2 min. However, a lower pH and longer treatment resulted in delayed recovery of the detached abalone. Thus, exfoliation of fouling abalone can be achieved by a low pH treatment with cautious handling.

• Corrosion Science and Technology
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• v.15 no.4
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• pp.159-165
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• 2016

An attempt has been made to understand the influence of retrogression and re-aging (RRA) on the exfoliation corrosion behaviour of AA 7085 alloy in comparison with the peak aged condition (PA). Immersion tests using ASTM G34 and studies involving electrochemical impedance spectroscopy showed that the RRA treated alloy provided higher resistance to exfoliation corrosion than the PA treated alloy. The improved resistance was attributed to the enhanced Cu content and the discontinuous nature of the grain boundary precipitate, which was revealed through transmission electron microscopy.

• Journal of Conservation Science
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• v.22
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• pp.121-134
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• 2008

The mechanism of stone exfoliation and its cause in relation to chemical weathering by soluble salt were studied. Chemical, mineralogical and physical analysis was performed in exfoliation samples from stone monuments. The representative salt is gypsum in the exfoliation samples. In order to understand the salt reaction, stone samples(tuff and granite) were treated with two type of the salt, gypsum and sodium sulfate, which have different solubility. The capillary water uptakes are slight increased in impregnated with Na2SO4 and weathering simulation of two rock types. It means that the rock is deteriorated in the near of the surface by $Na_2SO_4$. $CaSO_4{\cdot}2H_2O$ bring out the thicker exfoliation than $Na_2SO_4$ because it is penetrated into the deeper zone and amount of accumulated salt is more abundant in the inner part than in the near of the surface. The exfoliation was formed in the tuff by salt treatment and 30cycle of weathering simulation, but there are not significant symptoms of exfoliation in the granite by same condition. This result was caused by the different capillary water uptakes and porosity of the rocks. In the tuff, salt solutions are penetrated into the inner part due to its high capillary water uptakes and porosity but the granite, which has low value relatively, can be formed thinner exfoliation.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.290.1-290.1
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• 2016

Grapehen, a single atomic layer of graphite, has been in the spotlight and researched in vaious fields, because its fine mechanical, electrical properties, flexibility and transparence. Synthesis methods for large-area graphene such as chemical vaper deposition (CVD) and mechanical, chemical exfoliation have been reported. In particular, chemical exfoliation method receive attention due to low cost process. Chemical exfoliation method require reduction of graphene oxide in the process of exfoliation such as chemical reduction by strong reductant, thermal reduction on high temperature, and optical reduction via ultraviolet light exposure. Among these reduction methods, optical reduction is free from damage by strong reductant and high temperature. However, optical reduction is economically infeasible because the high cost of short-wavelength ultraviolet light sorce. In this paper, we make graphene-oxide and lanthanoid ion mixture aqueous solution which has highly optical absorbency in selective wevelength region. Sequentially, we synthesize reduced graphene oxide (RGO) using the solution and visible laser beam. Concretely, graphene oxide is made by modified hummer's method and mix with 1 ml each ultraviolet ray absorbent Gd3+ ion, Green laser absorbent Tb3+ ion, Red laser absorbent Eu3+ ion. After that, we revivify graphene oxide by laser exposure of 300 ~ 800 nm layser 1mW/cm2 +. We demonstrate reproducibility and repeatability of RGO through FT-IR, UV-VIS, Low temperature PL, SEM, XPS and electrical measurement.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.16 no.4
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• pp.515-520
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• 1994

Herpes Zoster is an acute viral infection characterized by the appearance of vesicles that occur on the skin and mucous membrane along the pathway of an involved sensory nerve. Although Herpes zoster is usually as benign viral infection, complications may occur especially when cranial nerves are involved. There are few reports of bony and dental complications by Herpes Zoster infection, all of which were isolated in a single quadrant. These include devitalized teeth, abnormal development of permanent teeth, internal resoption and spontaneous exfoliation of teeth with osteonecrosis of the alveolar bone. No agreement has been reached concerning the pathogenesis of osteonecrosis and tooth exfoliation associated with herpes zoster infection. We recently experienced series of maxillary osteonecrosis and spontaneous teeth exfoliation in patients with Herpes Zoster infection and present two cases with review of literature.