첨가 나노 입자의 크기와 형상에 따른 나노윤활유의 윤활 특성 비교

이창건(Changgun Lee),황유진(Yujin Hwang),최영민(Youngmin Choi),박민찬(Minchan Park),김경민(Kyoungmin Kim),이재근(Jaekeun Lee),최철(Cheol Choi),오제명(Jemyung Oh) 한국트라이볼로지학회 2008 한국트라이볼로지학회 학술대회 Vol.2008 No.6

본 연구에서는 산업용 기어유를 이용하여 나노 윤활유를 제작하고 첨가 입자의 형상과 크기에 따른 윤활 특성을 비교 평가하였다. 각 윤활유에 대한 윤활 특성을 파악하기 위하여 Disk-on-disk Tribotester를 이용하여 다양한 하중 조건에서의 마찰계수 및 마찰표면의 온도를 측정하였으며, SEM 분석을 통하여 그 마찰면의 마멸 특성을 파악하였다. 윤활유에 나노 입자를 첨가할 경우, 윤활 특성이 향상된다. 마찰면 사이에 나노 입자가 존재할 경우, Ball Bearing과 같은 역할을 수행하여 두 면의 접촉을 감소시킨다. 입자 형상과 관련하여 섬유상의 입자를 첨가한 나노 윤활유는 구형 입자를 첨가한 나노 윤활유에 비하여 더 높은 마찰계수 값을 가지고 윤활 특성이 나쁘며 마찰면의 마멸이 많이 발생한다. 이는 섬유상의 입자를 윤활유에 분산시킬 경우, 그 분산이 불안정하며 응집 등이 발생하여 마찰을 증가시키기 때문이다. 나노 입자의 크기도 접촉면의 마찰과 마멸을 감소시키는데 주요한 요소로 입자의 크기가 작을수록 윤활 특성이 우수하며, 입자 크기가 마이크로 크기가 되면 입자 침전으로 인해 나노 윤활유의 기능을 상실하며 마이크로 입자가 유막 형성을 방해하여 그 윤활 특성이 나빠지게 된다. Many researchers have tried to improve the tribological characteristics of the lubricants to decrease the friction coefficient and wear rate. One of the trials is simply adding additives into the base lubricant. This method has been widely applied in lubrication engineering and contributed to the increase of the ability of lubricants. Recently nanoparticles are suggested as a new kind of additives because of their size, shape and other properties. Nano lubricant is a new kind of engineering lubricant made of nano particles, dispersants and base oil. In this study, carbon-based nano particles and nano fibers such as graphite, carbon black, GNF(Graphite nanofiber) and MWCNT(Multi-walled carbon nano tube) are used to fabricate nano lubricants for enhancing the tribological properties and lubrication characteristics. The base lubricant used in this research is an industrial gear oil which has 220 cSt of kinematic viscosity at 40℃. To investigate the physical and tribological properties of nano lubricants, the friction coefficients and the temperatures were measured with disk-on-disk tribotester in the range up to 3,000 N. The friction surfaces were observed by scanning electron microscope (SEM). The results were compared on the views of the effects of the particle shape and size. The results of friction coefficient test show that the spherical particles have better lubrication characteristics than the fibrous particles. Also from the results of SEM, the tendency of wear in the case of spherical particles additives is better than of fibrous particles. To observe the size effect of nano particle additives, graphite paticles having different particles size (i.e. 55㎚, 450㎚, 5㎛) are adopted. The smaller particle additives decrease the friction coefficient and wear of the friction surfaces. But the micro scale particle additives show worse lubrication characteristics than nano scale particle additives because of the unstable dispersion and the sedimentation of particles.

Charging Effect of a Nano-Floating Gate Capacitor with Double-Layered Au Nano-Particles

김은규,이동욱,Min Seung Lee,이태희,김원목 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.3

A nano-floating gate capacitor with double-layered Au nano-particles embedded in a SiO1:3N layer was fabricated and characterized. The Au nano-particles were formed from Au thin film with a nominal thickness of 1 nm and their average size and density were about 4 nm and 2 × 1012 cm-2, respectively. After the post-annealing process at 800 ℃ for 10 s, the flat-band voltage shift of the nano-floating gate capacitor with double-layered Au nano-particles was about 9 V when the applied gate voltage was swept from -10 V to +10 V. Signicantly, the flat-band voltage shifts were improved after the post-annealing process. The double-layered Au nano-particles embedded in a SiO1:3N dielectric showed feasibility as nano-floating gate capacitors for nonvolatile memories. A nano-floating gate capacitor with double-layered Au nano-particles embedded in a SiO1:3N layer was fabricated and characterized. The Au nano-particles were formed from Au thin film with a nominal thickness of 1 nm and their average size and density were about 4 nm and 2 × 1012 cm-2, respectively. After the post-annealing process at 800 ℃ for 10 s, the flat-band voltage shift of the nano-floating gate capacitor with double-layered Au nano-particles was about 9 V when the applied gate voltage was swept from -10 V to +10 V. Signicantly, the flat-band voltage shifts were improved after the post-annealing process. The double-layered Au nano-particles embedded in a SiO1:3N dielectric showed feasibility as nano-floating gate capacitors for nonvolatile memories.

Charging Effect of WSi2 Nano-particles Embedded in SiO2 Layers

Ki Bong Seo,이동욱,Tae Hee Lee,김은규 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.3

A nano-floating gate capacitor with WSi2 nano-particles embedded in a SiO2 layer was fabricated. The WSi2 nano-particles were formed from a thin WSi2 layer during a rapid thermal annealing process, and they had a spherical shape with an average diameter of 2.5 nm. The electrical properties of the nano-floating gate capacitor with WSi2 nano-particles embedded in SiO2 dielectrics were characterized by using capacitance-voltage measurements. Then, a flat-band voltage shift of up to 3.8 V due to carrier charging of the WSi2 nano-particles appeared when the gate voltage was swept from –7 V to +7 V and from +7 V to –7 V, which showed that the WSi2 nano-particles could be applied to nonvolatile memory devices. A nano-floating gate capacitor with WSi2 nano-particles embedded in a SiO2 layer was fabricated. The WSi2 nano-particles were formed from a thin WSi2 layer during a rapid thermal annealing process, and they had a spherical shape with an average diameter of 2.5 nm. The electrical properties of the nano-floating gate capacitor with WSi2 nano-particles embedded in SiO2 dielectrics were characterized by using capacitance-voltage measurements. Then, a flat-band voltage shift of up to 3.8 V due to carrier charging of the WSi2 nano-particles appeared when the gate voltage was swept from –7 V to +7 V and from +7 V to –7 V, which showed that the WSi2 nano-particles could be applied to nonvolatile memory devices.

APS로 표면 처리한 Fe 나노 입자 촉매를 이용한 CNT의 직경제어

이선우,Lee, Sunwoo 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.6

Diameter controlled carbon nanotubes (CNTs) were grown using surface modified iron nano-particle catalysts with aminpropyltriethoxysilane (APS). Iron nano-particles were synthesized by thermal decomposition of iron pentacarbonyl-oleic acid complex. Subsequently, APS modification was done using the iron nano-particles synthesized. Agglomeration of the iron nano-particles during the CNT growth process was effectively prevented by the surface modification of nano-particles with the APS. APS plays as a linker material between Fe nano-particles and $SiO_2$ substrate resulting in blocking the migration of nano-particles. APS also formed siliceous material covering the iron nano-particles that prevented the agglomeration of iron nano-particles at the early stages of the CNT growth. Therefore we could obtain the diameter controlled CNTs by blocking agglomeration of the iron nano-particles.

Charging effect of In2O3 nano-particles embedded in polyimide layer for application as non-volatile nano-floating gate memory

김선필,이태희,이동욱,김은규,구현모,김영호,조원주 한국물리학회 2009 Current Applied Physics Vol.9 No.11

The memory charging effect of the nano-floating gate capacitor containing the In2O3 nano-particles embedded in polyimide layer was characterized. Self-assembled In2O3 nano-particles were created by chemical reaction between the polymer precursor and indium film, and then the particles size and density were about 7 nm and 5.8 × 1011 cm-2, respectively. From capacitance–voltage hysteresis originated from electrons charging in the In2O3 nano-particles through tunneling oxide from p-type Si wafer, the flat-band voltage shift was obtained up to about 3.4 V, when the sweeping gate voltage was from -6 to 6 V. The endurance ability of this capacitor showed up to 2 × 105 cycles during the programming at 5 V for 0.2 ms and erasing at -5 V for 1.8 ms processes. The memory charging effect of the nano-floating gate capacitor containing the In2O3 nano-particles embedded in polyimide layer was characterized. Self-assembled In2O3 nano-particles were created by chemical reaction between the polymer precursor and indium film, and then the particles size and density were about 7 nm and 5.8 × 1011 cm-2, respectively. From capacitance–voltage hysteresis originated from electrons charging in the In2O3 nano-particles through tunneling oxide from p-type Si wafer, the flat-band voltage shift was obtained up to about 3.4 V, when the sweeping gate voltage was from -6 to 6 V. The endurance ability of this capacitor showed up to 2 × 105 cycles during the programming at 5 V for 0.2 ms and erasing at -5 V for 1.8 ms processes.

Analysis of Mechanical Properties and Microstructure of Nano- and Micro-SiO2 Materials as Cementitious Composite Binder

김원우,문재흠 한국콘크리트학회 2024 International Journal of Concrete Structures and M Vol.18 No.1

This study evaluated the setting time, mechanical properties and microstructure of Portland cement (OPC) by adding SiO2 nano- and micro-particles. The setting time was reduced due to the pozzolanic reaction of the nano- and micro-SiO2, and the compressive strength was increased through a reduction in the porosity of the microstructure. When nano- and micro-SiO2 were used alone, micro-silica was the most effective in reduced the initial and final setting times and developing compressive strength. When two or more nano- and micro-SiO2 were used, a micro-sized binder and a small amount of nano-silica effectively improved performance as the setting time was reduced to 50–52% of that of ordinary Portland cement (OPC). It appears that a small amount of nano-silica could reduce the setting time and increase compressive strength because it caused the pozzolanic reaction and because the nanoparticles filled the pores between the silica fume and cement, which were composed of relatively large particles. This result could also be derived from compressive strength and microstructure analysis. Cement paste containing to nano- and micro-silica increased the strength by approximately 112% compared to OPC. Because nano-binders may cause a reduction in flow due to their large specific surface area, adding chemical admixture needs to be considered during mix design. In addition, the particle size distribution must be considered when nano- and micro-materials are used because an imbalance in particle size distribution can increase the pore size in the microstructure.

나노 CuO입자로 충진된 PTFE 나노복합소재의 저속 및하중 조건에서의 트라이볼로지 특성에 관한 연구

조민행,김정환 한국트라이볼로지학회 2023 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.39 No.3

This paper presents an experimental investigation of the tribological characteristics of PTFE composites filled with nano CuO particles under low sliding speed and load. All the specimens were prepared by sintering. Before sintering, the mixture of PTFE powder and CuO particles were mixed by a high-speed mixer using CuO volume fractions of 0.2 vol. % and 5 vol. %. Each mixture was sintered at 350 °C for 30 min on the steel disk. We conducted ball-on-disk sliding test an hour using a steel ball against PTFE composites, including pure PTFE. The load and sliding speed used was 2 N and 0.01 m/s, respectively. Adding nano CuO particles increases the friction coefficient because of the abrasiveness of hard nano CuO particles. The highest coefficient of frictions was obtained from 5 vol. % CuO. Conversely, the lowest wear of the composites was obtained from the 5 vol. % CuO nanocomposite. This study reveals that the addition of nano CuO particles can lower the wear of PTFE, despite an increase in the coefficient of friction. However, the coefficient friction is still moderate compared to other engineering polymers. In addition, the amount of CuO nano particles has to be optimized to reduce friction and wear at the same time.

이성분 나노유체 (NH₃/H₂O + 나노입자)의 열전달 및 흡수성능 촉진실험

이진기(Jin Ki Lee),정청우(Chung Woo Jung),강용태(Yong Tae Kang) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.9

The objectives of this paper are to examine the effect of nano-particles on the pool type absorption heat transfer enhancement and to find the optimal conditions to design a highly effective compact absorber for ammonia/water absorption system. The effect of Al₂O₃ nano-particles and carbon nanotube(CNT) on the absorption performance is studied experimentally. The experimental ranges of the key parameters are 20% of ammonia concentration, 0~0.08 vol% (volume fraction) of CNT particles, and 0~0.06 vol% of Al₂O₃ nano-particles. For the ammonia/water nanofluids, the heat transfer rate and absorption rate with 0.02 vol% Al2O3 nano-particles were found to be 29% and 18% higher than those without nano-particles, respectively. It is recommended that the concentration of 0.02 vol% of Al₂O₃ nano-particles be the best candidate for ammonia/water absorption performance enhancement.

Modeling and simulations of the removal of formaldehyde using silver nano-particles attached to granular activated carbon

Shin, SeungKyu,Song, JiHyeon Elsevier 2011 Journal of hazardous materials Vol.194 No.-

<P><B>Highlights</B></P><P>► Silver nano-particles were attached onto the surface of GAC for the simultaneous catalytic oxidation and adsorption reactions of formaldehyde. ► By the silver nano-particles, formaldehyde oxidation to carbon dioxide as expressed as pseudo-first-order. ► The nano-particle deposits reduced the available surface area of the GAC and blocked the openings of the micro-pores. ► The modified numerical model yielded an accurate prediction of the performance of the Ag-GAC. ► Depending on the surface coverage ratio, the factions of catalytic oxidation and the formaldehyde mass removed were proportionally changed.</P> <P><B>Abstract</B></P><P>A combined reaction, consisting of granular activated carbon (GAC) adsorption and catalytic oxidation, has been proposed to improve the removal efficiencies of formaldehyde, one of the major indoor air pollutants. In this study, silver nano-particles attached onto the surface of GAC (Ag-GAC) using the sputtering method were evaluated for the simultaneous catalytic oxidation and adsorption of formaldehyde. The evolution of CO<SUB>2</SUB> from the silver nano-particles indicated that formaldehyde was catalytically oxidized to its final product, with the oxidation kinetics expressed as pseudo-first order. In addition, a packed column test showed that the mass of formaldehyde removed by the Ag-GAC was 2.4 times higher than that by the virgin GAC at a gas retention time of 0.5s. However, a BET analysis showed that the available surface area and micro-pore volume of the Ag-GAC were substantially decreased due to the deposition of the silver nano-particles. To simulate the performance of the Ag-GAC, the homogeneous surface diffusion model (HSDM), developed for the prediction of the GAC column adsorption, was modified to incorporate the catalytic oxidation taking place on the Ag-GAC surface. The modified HSDM demonstrated that numerical simulations were consistent with the experimental data collected from the Ag-GAC column tests. The model predictions implied that the silver nano-particles deposited on the GAC reduced the adsorptive capacity due to decreasing the available surface for the diffusion of formaldehyde into the GAC, but the overall mass of formaldehyde removed by the Ag-GAC was increased due to catalytic oxidation as a function of the ratio of the surface coverage by the nano-particles.</P>

Retention Characteristics of Nano-Floating Gate Capacitor with SiC Nano-Particles

이동욱,이태희,김은규 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.6

A nano-floating gate capacitor with SiC nano-particles embedded in a SiO2 layer was fabricated and its electrical properties such as the capacitance-voltage hysteresis curve at various temperature, and the retention were characterized. The SiC nano-particles in the SiO2 layer were formed by magnetron sputtering of SiC and SiO2 targets and post-annealing at 900 ˚C for 3 min. They had a spherical shape with an average diameter of 3 s 5 nm and were distributed between the tunnel oxide and the control oxide layers. For the nano-floating gate capacitor with SiC nano-particles embedded in a SiO2 layer, the flat-band voltage shift decreased from 2.2 V at 25 ˚C to about 1.6 V at 85 ˚C and 0.6 V at 125 ˚C, when the gate voltages were swept from −8 V to 8 V. Also, the memory window under the programming/erasing operation at +12 V and −12 V for 700 ms appeared to be approximately 0.54 V at 25 ˚C, 0.61 V at 85 ˚C, and 0.22 V at 125 ˚C after 1 hr. A nano-floating gate capacitor with SiC nano-particles embedded in a SiO2 layer was fabricated and its electrical properties such as the capacitance-voltage hysteresis curve at various temperature, and the retention were characterized. The SiC nano-particles in the SiO2 layer were formed by magnetron sputtering of SiC and SiO2 targets and post-annealing at 900 ˚C for 3 min. They had a spherical shape with an average diameter of 3 s 5 nm and were distributed between the tunnel oxide and the control oxide layers. For the nano-floating gate capacitor with SiC nano-particles embedded in a SiO2 layer, the flat-band voltage shift decreased from 2.2 V at 25 ˚C to about 1.6 V at 85 ˚C and 0.6 V at 125 ˚C, when the gate voltages were swept from −8 V to 8 V. Also, the memory window under the programming/erasing operation at +12 V and −12 V for 700 ms appeared to be approximately 0.54 V at 25 ˚C, 0.61 V at 85 ˚C, and 0.22 V at 125 ˚C after 1 hr.