• 공업화학
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• 제31권5호
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• pp.581-584
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• 2020

The effect of a chemical pretreatment on the surface carbon was investigated using a scanning electron microscope (SEM) and electrochemical methods. Primitive carbon has a reducing power likely due to incompletely oxidized functional groups on the surface. We aim to control this reducing power by chemical treatment and apply for the spontaneous deposition of nanoparticles (NPs). Highly ordered pyrolytic graphite (HOPG) was initially treated with a reducing agent, NaBH4 or an oxidizing agent, KMnO₄, for 5 min. Subsequently, the pretreated carbon was immersed in a platinum (Pt) precursor. Unexpectedly, SEM images showed that the reducing agent increased spontaneous PtNPs deposition while the oxidizing agent decreased Pt loading more as compared to that of using bare carbon. However, the amount of Pt on the carbon obviously decreased by NaBH₄ treatment for 50 min. Secondly, spontaneous reduction on pretreated glassy carbon (GC) was investigated using the catalytic hydrogen evolution reaction (HER). GC electrode treated with NaBH4 for a short and long time showed small (onset potential: -640 mV vs. MSE) and large overpotential for the HER, respectively. Although the mechanism is unclear, the electrochemistry results correspond to the optical data. As a proof-of-concept, these results demonstrate that chemical treatments can be used to design the shapes and amounts of deposited catalytic metal on carbon by controlling the surface state.

• Korean Chemical Engineering Research
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• 제48권6호
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• pp.673-678
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• 2010

본 연구에서는 탄소지지체로 활성탄소를 주요재료로 사용하고 여기에 그라파이트 나노섬유(graphite nanofibers)를 함량별로 혼합시킨 후, 백금전구체를 포함하는 용액에 분산시키고, 화학적인 환원반응을 통해서 백금입자를 담지하여 제조하였다. 첨가하는 GNF의 함량을 조절하면서, 백금입자의 결정 크기와 담지함량을 제어할 수 있었다. GNF 함량이 15 wt%인 혼합지지체를 사용한 백금입자의 경우, 최대의 전기활성 특성을 나타내었다. 또한, GNF 함량을 0%에서 15%로 증가시킴에 따라 전기전도도가 $10^{-4}S/cm$에서 $10^{-1}S/cm$로 증가하였다. 첨가제 GNF를 10%까지 도입한 경우, 백금입자의 전기활성은 크게 증가하는 경향을 보이지만, 15%에서는 그 증가경향이 작아져서 포화되는 현상이 보였다. 이런 결과는 전기활성도의 변화가 혼합지지체의 전기전도도 변화와 백금이 담지된 함량, 그리고, 담지형태와 관련성이 있음을 알 수 있었다.

• 한국전기전자재료학회논문지
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• 제13권4호
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• pp.312-317
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• 2000

Ferroelectric S $r_{0.9}$/B $i_{2.1}$/T $a_{2}$/ $O_{9}$ solutions were synthesized using sol-gel process in which strontinum ethoxide bismuth ethoxide trantalum ethoxide were used a s startring materials. SBT thin films were coated on Pt/Ti/ $SiO_2$/Si substrates by spin-coating. rapid thermal annealing (RTA) was used to promote crystallization. Thin films were annealed at $700^{\circ}C$ for 1 hr in an oxygen atmosphere. This temperature is about 10$0^{\circ}C$ lower than the usual annealing temperature for SBT thin films. Pt top-electrode was deposited by sputtering and thin films were post-annealed at $700^{\circ}C$ for 30 min. to enhance electrical properties. As the RTA temperature increased the higher 2 $P_{r}$ values were obtained. At RTA temperature being 78$0^{\circ}C$ remanent polarization of S $r_{0.9}$/B $i_{2.1}$/T $a_{2}$/ $O_{9}$ thin film was 7.73 $\mu$C/cm $_2$ and the leakage current density was 1.14$\times$10$^{-7}$ A/c $m^2$ at 3 V. As RTA temperature increased the breakdown voltage was decreased. It is considered that the low-field breadown is caused by the rough surface of SBT films and forming bismuth metal in SBT thin films.films.lms.

• 한국재료학회지
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• 제23권11호
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• pp.661-665
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• 2013

We investigated the characteristics of electroless plated Cu films on screen printed Ag/Anodized Al substrate. Cu plating was attempted using neutral electroless plating processes to minimize damage of the anodized Al substrate; this method used sodium hypophosphite instead of formaldehyde as a reducing agent. The basic electroless solution consisted of $CuSO_4{\cdot}5H_2O$ as the main metal source, $NaH_2PO_2{\cdot}H_2O$ as the reducing agent, $C_6H_5Na_3O_7{\cdot}2H_2O$ and $NH_4Cl$ as the complex agents, and $NiSO_4{\cdot}6H_2O$ as the catalyser for the oxidation of the reducing agent, dissolved in deionized water. The pH of the Cu plating solutions was adjusted using $NH_4OH$. According to the variation of pH in the range of 6.5~8, the electroless plated Cu films were coated on screen printed Ag pattern/anodized Al/Al at $70^{\circ}C$. We investigated the surface morphology change of the Cu films using FE-SEM (Field Emission Scanning Electron Microscopy). The chemical composition of the Cu film was determined using XPS (X-ray Photoelectron Spectroscopy). The crystal structures of the Cu films were investigated using XRD (X-ray Diffraction). Using electroless plating at pH 7, the structures of the plated Cu-rich films were typical fcc-Cu; however, a slight Ni component was co-deposited. Finally, we found that the formation of Cu film plated selectively on PCB without any lithography is possible using a neutral electroless plating process.

• 한국재료학회지
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• 제11권5호
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• pp.398-404
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• 2001

SiC 보강재 표면에 도금된 Cu금속층이 Al/SiC복합재료의 젖음성에 미치는 영향을 검토하였다. 보강재에 대한 금속층의 도금은 무전해도금법을 이용하였으며, Al/SiC 복합재료의 제조는 텅스텐 발열체 진공로의$ 670^{\circ}C$~$900^{\circ}C$에서 제조하여 보강재와 기지간의 접촉부위를 촬영하여 젖음성을 측정하였다 젖음성 측정 결과 보강재에 도금된 Cu층은 젖음성을 향상시켰고, 젖음성의 개선은 보강재에 도금된 금속층과 기지간의 반응에 의해 계면에너지를 변화시킴으로서 나타난 결과이며. 반응을 통한 산화피막의 배제도 영향을 미친 것으로 판단된다

• 한국재료학회지
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• 제9권11호
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• pp.1148-1152
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• 1999

본 연구에서는 기존에 알려진 구리 전구체와 새롭게 개발된 전구체인 hfac (hexafluoroacetylacetonate) Cu(I) DMB (3,3-dimethyl-1-butene)를 비교 평가해보았다. (Hfac)Cu(I) (DMB)의 증가압은 $40^{\circ}C$에서 3 torr 정도로 기존에 잘 알려진 (hfac)Cu(I) vinyltrimethylsilane (VTMS) 보다 10배 정도 높은 것으로 나타났으며 그럼에도 불구하고 상당히 안정하여 $65^{\circ}C$에서 일주일 이상 가열하여도 변하지 않았다. 이 전구체로 100-$280^{\circ}C$에서 구리 박막을 증착할 수 있었으며 150-$250^{\circ}C$온도 범위에서 2.0$\mu\Omega$-cm의 순수한 구리 박막을 얻었다. 구리 박막의 증착 속도는 기존의 전구체보다 7~8배 정도 높은 것으로 나타났다.

• 한국재료학회지
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• 제19권8호
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• pp.437-442
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• 2009

This paper describes an improved strategy for controlling the adhesion force using both the antiadhesion and adhesion layers for a successful large-area transfer process. An MPTMS (3-mercaptopropyltrimethoxysilane) monolayer as an adhesion layer for Au/Pd thin films was deposited on Si substrates by vapor self assembly monolayer (VSAM) method. Contact angle, surface energy, film thickness, friction force, and roughness were considered for finding the optimized conditions. The sputtered Au/Pd ($\sim$17 nm) layer on the PDMS stamp without the anti-adhesion layer showed poor transfer results due to the high adhesion between sputtered Au/Pd and PDMS. In order to reduce the adhesion between Au/Pd and PDMS, an anti-adhesion monolayer was coated on the PDMS stamp using FOTS (perfluorooctyltrichlorosilane) after $O_2$ plasma treatment. The transfer process with the anti-adhesion layer gave good transfer results over a large area (20 mm $\times$ 20 mm) without pattern loss or distortion. To investigate the applied pressure effect, the PDMS stamp was sandwiched after 90$^{\circ}$ rotation on the MPTMS-coated patterned Si substrate with 1-${\mu}m$ depth. The sputtered Au/Pd was transferred onto the contact area, making square metal patterns on the top of the patterned Si structures. Applying low pressure helped to remove voids and to make conformal contact; however, high pressure yielded irregular transfer results due to PDMS stamp deformation. One of key parameters to success of this transfer process is the controllability of the adhesion force between the stamp and the target substrate. This technique offers high reliability during the transfer process, which suggests a potential building method for future functional structures.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 1994년도 제3회 학술강연회논문집
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• pp.21-26
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• 1994

Conventional electroexplosive devices (EED) commonly use a very small metal bridgewire to ignite explosive materials i.e. pyrotechnics, primary and secondary explosives. The use of semiconductor devices to replace “hot-wire” resistance heating elements in automotive safety systems pyrotechnic devices has been under development for several years. In a typical 1 amp/1 watt electroexplosive devices, ignition takes place a few milliseconds after a current pulse of at least 25 mJ is applied to the bridgewire. In contrast, as for a SCB devices, ignition takes place in a few tens of microseconds and only require approximately one-tenth the input energy of a conventional electroexplosive devices. Typically, when SCB device is driven by a short (20 $\mu\textrm{s}$), low energy pulse (less than 5 mJ), the SCB produces a hot plasma that ignites explosive materials. The advantages and disadvantages of this technology are strongly dependent upon the particular technology selected. To date, three distinct technologies have evolved, each of which utilizes a hot, silicon plasma as the pyrotechnic initiation element. These technologies are 1.) Heavily doped silicon as the resistive heating initiation mechanism, 2.) Tungsten enhanced silicon which utilizes a chemically vapor deposited layer of tungsten as the initiation element, and 3.) a junction diode, fabricated with standard CMOS processes, which creates the initial thermal environment by avalanche breakdown of the diode. This paper describes the three technologies, discusses the advantages and disadvantages of each as they apply to electroexplosive devises, and recommends a methodology for selection of the best device for a particular system environment. The important parameters in this analysis are: All-Fire energy, All-Fire voltage, response time, ease of integration with other semiconductor devices, cost (overall system cost), and reliability. The potential for significant cost savings by integrating several safety functions into the initiator makes this technology worthy of attention by the safety system designer.

• 전기화학회지
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• 제3권3호
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• pp.178-181
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• 2000

본 실험에서는 리튬 이차 박막전지의 음극물질로 주석 산화물 박막을 RF magnetron sputter을 이용하여 증착하였다. RF power와 공정 압력을 각각 $2.5W/cm^2$와 10mTorr로 고정시키고 박막 중의 산소량을 조절하기 위해 산소 분압을 $0\~100\%$까지 조절하여 실험하였으며, 산소량을 더 줄이기 위해 주석 금속 칩을 사용하여 조절하였다. 산소량을 줄여 줌으로써 비가역적으로 형성되는 리튬산화물의 량을 줄이고 고용량의 $SnO_x$음극 박막을 제조하였다. 그 중 $SnO_{1.43}$일 때 가장 큰 가역용량(약$ 500{\mu}Ah/cm^2{\mu}m$) 얻었다.

• 한국군사과학기술학회지
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• 제6권3호
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• pp.54-61
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• 2003

$SnO_2$ gas sensor for the detection DMMP, simulant of nerve gas was fabricated and its characteristics were examined. Sensing materials were $SnO_2$ added by TEX>$\alpha$-$Al_{2}O_{3}$ with 0∼20wt.% and $In_{2}O_{3}$ with 0∼3wt.% and were physically mixed each material. They were deposited by screen printing method on alumina substrate. The sensor was consisted of sensing electrode with interdigit(IDT) type in front and a heater in back side. Its dimension was 7$\times$10$\times$0.6$\textrm{mm}^2$. Crystallite size 8t phase identification, specific surface area and morphology of fabricated $SnO_2$ powders were analyzed by X-ray diffraction(XRD), surface area analyzer(BET) and by a scanning electron microscope(SEM), respectively. Sensor was measured as flow type and sensor resistance change was monitored as real time using LabVIEW program. The best sensitivities were 75% at adding 4wt.% TEX>$\alpha$-$Al_{2}O_{3}$, operating temperature $300^{\circ}C$ and 87% at adding 2wt.% $In_{2}O_{3}$, operating temperature $350^{\circ}C$ to DMMP 0.5ppm. Response and recovery times were about 1 and 3 min., respectively. Repetition measurement was very good with $\pm$3% in full scale. As a result, operating temperature was lower TEX>$\alpha$-$Al_{2}O_{3}$ than $In_{2}O_{3}$, but sensitivity was higher $In_{2}O_{3}$ than $\alpha$-$Al_{2}O_{3}$.