• Journal of the Korean institute of surface engineering
• /
• v.29 no.2
• /
• pp.109-119
• /
• 1996

In order to improve adhesion of electroless copper deposits on alumina substrates, some stabilizers such as 2-Mercapto Benzothiazole, thiourea and NaCN were added over a wide range of concentrations. The adhesion tests of the deposits were performed by using the cellophane tape and the push-pull scale. With the minor addition of the stabilizers, 2-MBT having a large molecular size gives poor adhesion, together with a finer grain structure, whereas Thiourea and NaCN show a high mechanical strength of the deposits. The high mechanical strength is supposed to be due to the easy desorption of hydrogen gas generated from the electroless reactions. A large amount of the three stabilizers decreases the adhesion for all the cases, resulting from strong adsorption of the stabilizers to the substrates.

• Journal of the Korean institute of surface engineering
• /
• v.16 no.4
• /
• pp.160-172
• /
• 1983

티오요소류, 폴리에테르류, 염료와 같은 유기화합물이 첨가된 황산동 전기도금욕에서 석출된 구리의 광택, 평활력효과를 무첨가욕과 기존 광택제가 첨가된 도금욕에서와 각각 비교하여 이들 유기첨가제가 구리의 석출상태와 음극분극에 미치는 영향을 Hull cell 실험과 현미경관찰, 전기화학적 측정방법에 의해 고찰하였다. 황산동 전기도금욕에서 thiourea, 2-mercapto-2-imidazoline, 1-acetyl-2-thiourea와 같은 유기 황화합물은 비교적 고전류 밀도 범위에서 결정성장이 억제되고 입자가 미세한 구리석출을 일으켜 양호한 광택효과와 평활력을 가져오나, 특히 저전류밀도에서는 해로운 줄무늬가 발생한다는 점에서 많은 개선의 여지가 필요하다. 그러나 이들 유기 황화합물에 1,3-dioxolane polymer와 소량의 염소 이온을 혼합 첨가할 것 같으며 넓은 전류밀도 범위에서 양호한 광택과 평활력이 있는 동석출을 얻을 수 있었다.

• Journal of the Korean Applied Science and Technology
• /
• v.14 no.3
• /
• pp.47-53
• /
• 1997

• Elastomers and Composites
• /
• v.57 no.2
• /
• pp.55-61
• /
• 2022

In this work, we report a highly deformable covalent adaptable-liquid crystal elastomer (CA-LCE) comprising dynamic thiourea bonds that enable macromolecular network rearrangement at elevated temperatures. The exchange of chain network is verified through stress-relaxation analyses and follows Arrhenius-type behavior. The unique capability of rearranging the chain network in the CA-LCE provides useful properties, such as welding, melt reprocessing, and shape reprogramming, that cannot be achieved by the conventional LCE comprising permanent crosslinks. Reversible actuation is further demonstrated by reprogramming the polydomain CA-LCE into a monodomain via mechanical stretching at elevated temperatures.

• Applied Chemistry for Engineering
• /
• v.26 no.1
• /
• pp.99-103
• /
• 2015

We conducted reduction reactions of graphene oxide (GO) using three selected reductants. The conductivity and solubility of three kinds of the reduced graphene oxides (RGOs) were examined based on the degree of reduction. When the ethylene glycol (EG) was used as a reductant, the reduction reaction did not sufficiently progress and as a result the conductivity of RGOs was observed to be relatively low. For RGOs made by hydrazine (HZ) and thiourea dioxide (TU), we observed no significant differences in the degree of the reduction, conductivity and dispersity in water. However, RGO prepared by TU showed an exceptionally good solubility in N-methylpyrrolidone, and the solution was stable for more than 4 months.

• Analytical Science and Technology
• /
• v.13 no.6
• /
• pp.781-788
• /
• 2000

Tellurium in simulated nuclear spent fuels (SIMFUEL) has been determined by hydride generation-inductively coupled plasma atomic emission spectrometry (HG-ICP-AES). Parameters such as concentrations of HCl and $NaBH_4$, flow rate of HCl and $NaBH_4$ were optimized and then the effects of U, Mo, Pd, Rh and Ru on the Te intensity were investigated. A thiourea as a masking agent was used to eliminate or minimize such interferences specially caused by palladium. Tellurium was measured by HG-ICP-AES and ICP-MS after separation of tellurium from SIMFUEL with cation exchange chromatography. The relative deviation between direct measurement and separation method was less than 6% based on the data by ICP-MS.

• Journal of Life Science
• /
• v.22 no.6
• /
• pp.778-787
• /
• 2012

The influence of salicylic acid (SA) on growth, chlorophyll, and rubisco/rubisco activase and effect of denaturator on rubisco/rubisco activase activity were studied in tobacco plants grown in vitro with cadmium (Cd) treatment. In order to find out the optimum concentration of SA, tobacco plants treated with $10^{-6}$ mM - $10^2$ mM of SA were grown in MS medium for 9 weeks, respectively. The most pronounced effect on in vitro growth was found at $10^{-4}$ mM SA. Among the control (not treated with Cd and SA), SA, Cd, and Cd + SA, the growth and content of chlorophyll were in the sequence of Cd < Cd + SA < control < SA, and significantly higher at SA compared with others. Similar results were also observed in the content and activity of rubisco and rubisco activase. These data suggest that inhibitory effect by Cd was reversed by SA. These results also indicate that SA has a positive effect on Cd. The effect of denaturants on rubisco activity showed in the sequence of Cd < Cd + SA < control < SA. Rubisco activity was promoted by L-cysteine and ${\beta}$-mercaptoethanol, not by urea, thiourea, and guanidium-HCl. These data suggest that urea, thiourea, and guanidium-HCl are able to act as denaturator, and L-cysteine and ${\beta}$-mercaptoethanol are not. None of the five denaturants affected the activity of rubisco activase.

• Journal of Life Science
• /
• v.24 no.5
• /
• pp.558-566
• /
• 2014

Growth induced by cadmium (Cd) and ethylsalicylic acid (ESA) and the effect of ESA on rubisco/rubisco activase were studied in tobacco. The effect of denaturants on rubisco/rubisco activase was also investigated. In order to determine optimal concentration of ESA for growth of tobacco, tobacco was treated with $10^{-6}$-10 mM. It was found that its growth was the highest at $10^{-4}$ mM ESA. In the experiment using control, Cd treated group, ESA treated group, and Cd and ESA mixture group, ESA alone showed the highest growth and Cd showed the lowest growth. Cd treated group was the lowest in both rubisco/rubisco activase content and activity. ESA reduced the rubisco/rubisco activase content, but increased their activity. The activity of rubisco was inhibited by treating L-cysteine, urea, thiourea, ${\beta}$-mercaptoethanol, and EDTA other than guanidine-HCl in control group. L-cysteine, urea, thiourea, and guanidine-HCl treatments showed no change, but ${\beta}$-mercaptoethanol and EDTA increased rubisco activase activity. In conclusion, ESA inhibited the content of rubisco and promoted its activity, whereas promoted the content of rubisco activase and inhibited its activity. In addition, the content and activity of rubisco and rubisco activase inhibited by Cd were recovered by ESA. The activity of rubisco and rubisco activase by Cd and ESA was inhibited by the denaturant and the recovery of ESA inhibited by Cd was lost by the denaturant.

• Economic and Environmental Geology
• /
• v.53 no.2
• /
• pp.159-166
• /
• 2020

In this research, we investigate the effect of microwave pretreatment on the recovery of gold from the gold concentrates by thiourea leaching. The changes in mineral phases by decomposition of pyrites in the gold concentrates using microwave were observed, and the result of microwave irradiation showed that the temperature of the irradiated sample increases with increasing irradiation time. With the reaction of temperature increases, Sulfur (S) in pyrites was converted to sulfur dioxide (SO₂), and then the content of S in the sample was reduced. The analytical results of XRD and SEM-EDS showed that pyrites are converted to magnetite and hematite, and its surfaces are changed to a porous shape where micro-cracks are developed. The Au leaching efficiency from the irradiated gold concentrates using thiourea-mixed solvent increased with the increases of irradiation time and solvent concentration. The experimental results considering leaching parameters indicate that the mechanism of microwave irradiation increases the maximum leaching efficiency and leaching rate of the gold concentrates, and the solvent does a role for the increasing of leaching rate constant.

• Bulletin of the Korean Chemical Society
• /
• v.29 no.3
• /
• pp.663-665
• /
• 2008