• Korean Journal of Materials Research
• /
• v.13 no.8
• /
• pp.531-536
• /
• 2003

The electromagnetic properties and microstructures of the ferrites based on ($Ni_{0.2}$ $Cu_{0.2}$ $Zn_{0.6}$)$_{1.085}$($Fe_2$$O_3$)$_{0.915}$ were investigated by changing the amount of additive SnO$_2$and CaO and the sintering temperatures. Addition of $SnO_2$caused pores in the specimen. There was no variation of grain size by changing the amount of additives. Total loss was reduced when ($Ni_{0.2} $Cu_{0.2}$ $Zn_{ 0.6}$)$_{1.085}$ ($Fe_2$$O_3$)$_{0.915}$ composition was sintered at $1150^{\circ}C$ rather than $1300^{\circ}C$. Addition of CaO was useful to reduce the total loss because it increased the sintering density. The lowest total loss was obtained when 0.06 wt% $SnO_2$and 0.4 wt% CaO were added at the same time.

• Journal of the Microelectronics and Packaging Society
• /
• v.30 no.4
• /
• pp.91-97
• /
• 2023

Electrochemical (EC) CO₂ reduction is a promising method to convert CO₂ into valuable hydrocarbon fuels and chemicals ecofriendly. Here, we report on a facile method to synthesize surface-controlled SnO₂/Cu(OH)₂ nanowires (NWs) and its EC reduction of CO₂ to HCOOH and CO. The SnO₂/Cu(OH)₂ NWs (-16 mA/cm²) showed superior electrochemical performance compared to Cu(OH)2 NWs (-6 mA/cm²) at -1.0 V (vs. RHE). SnO₂/Cu(OH)₂ NWs showed the maximum Faradaic efficiency for conversion to HCOOH (58.01 %) and CO (29.72 %). The optimized catalyst exhibits a high C1 Faradaic efficiency stable electrolysis for 2 h in a KHCO₃ electrolyte. This study facilitates the potential for the EC reduction of CO₂ to chemical fuels.

• Transactions of Materials Processing
• /
• v.7 no.5
• /
• pp.465-473
• /
• 1998

The effect of alloying elements of Ag-Cu-Zr-X brazing alloy on the microstructure and the bond strength of $Al_2O_3/Ni-Cr$ brazed steel joint was investigated. The reaction layer, $ZrO_2$ (a=5.146 ${\AA}$ , b=5.213 ${\AA}$ , c=5.311 ${\AA}$ )was formed at the interface of $Al_2O_3/Ni-Cr$ steel joint by the redox reaction between alumina and Zr. The addition of An and Al to the Ag-Cu-Zr brazing alloy gave rise to changes in the thickness of the reaction product layer and the morphology of the brazement. Sn caused the segregation of Zr was decreased b Al the $ZrO_2$ layer formed at the Ag-Cu-Zr-Al alloy was thinner than that of $ZrO_2$ formed at the Ag-Cu-Zr-An alloy. The fracture shear strength was strongly dependent on the microstructure of the brazement. Brazing with Ag-Cu-Zr-Sn alloy resulted in a better bond strength than with Ag-Cu-Zr or Ag-Cu-Zr-Al alloy.

• Journal of the Korean Magnetics Society
• /
• v.1 no.2
• /
• pp.15-21
• /
• 1991

The magnetic properties of the $Y_{1}Ba_{2}Cu_{3-x}Sn_{x}O_{7-y}$ superconductor were studied as a function of Sn concentration by utilizing both the vibrating sample magnetometer (VSM) and torque magnetometer. Unlike the cases where Fe and Co were substituted for Cu, the superconducting transition temperature was maintained above 90 K until x reached the value of 0.36. The lower critical field $H_{c1}(T)$ and upper critical field $H_{c2}(T)$ are measured as a function of temperature and external magnetic field, respectively. By aid of these results, $H_{c1}(0)$.($H_{c2}(0)$), the coherence length ${\varepsilon}_{0}$, the penetration depth ${\lambda}_{0}$, and the Ginzburg-Landau parameter k were oqtained. Flux pinning was also observed in the sample.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.5
• /
• pp.81-86
• /
• 2019

Metal oxide/graphene composites have been known as promising functional materials for advanced applications such as high sensitivity gas sensor, and high capacitive secondary battery. In this study, tin dioxide ($SnO_2$) nanostructures were grown on chemically synthesized graphene nanosheets using a two-zone horizontal furnace system. The large area graphene nanosheets were synthesized on Cu foil by thermal chemical vapor deposition system with the methane and hydrogen gas. Chemically synthesized graphene nanosheets were transferred on cleaned $SiO_2$(300 nm)/Si substrate using the PMMA. The $SnO_2$ nanostuctures were grown on graphene nanosheets at $424^{\circ}C$ under 3.1 Torr for 3 hours. Raman spectroscopy was used to estimate the quality of as-synthesized graphene nanosheets and to confirm the phase of as-grown $SnO_2$ nanostructures. The surface morphology of as-grown $SnO_2$ nanostructures on graphene nanosheets was characterized by field-emission scanning electron microscopy (FE-SEM). As the results, the synthesized graphene nanosheets are bi-layers graphene nanosheets, and as-grown tin oxide nanostructures exhibit tin dioxide phase. The morphology of $SnO_2$ nanostructures on graphene nanosheets exhibits complex nanostructures, whereas the surface morphology of $SnO_2$ nanostructures on $SiO_2$(300 nm)/Si substrate exhibits simply nano-dots. The complex nanostructures of $SnO_2$ on graphene nanosheets are attributed to functional groups on graphene surface.

• Journal of the Korean institute of surface engineering
• /
• v.51 no.1
• /
• pp.47-53
• /
• 2018

Sn-based lithium-ion batteries have low cost and high theoretical specific capacity. However, one of major problem is the capacity fading caused by volume expansion during lithiation/delithiation. In this study, 3-dimensional foam structure of Cu-Sn alloy is prepared by co-electrodeposition including large free space to accommodate the volume expansion of Sn. The Cu-Sn foam structure exhibits highly porous and numerous small grains. The result of EDX mapping and XPS spectrum analysis confirm that Cu-Sn foam consists of $SnO_2$ with a small quantity of CuO. The Cu-Sn foam structure electrode shows high reversible redox peaks in cyclic voltammograms. The galvanostatic cell cycling performances show that Cu-Sn foam electrode has high specific capacity of 687 mAh/g at a current rate of 50 mA/g. Through SEM observation after the charge/discharge processes, the morphology of Cu-Sn foam structure is mostly maintained despite large volume expansion during the repeated lithiation/delithiation reactions.

• Tribology and Lubricants
• /
• v.37 no.3
• /
• pp.83-90
• /
• 2021

In this study, an ultrasonic nanocrystal surface modification (UNSM) was used to improve the mechanical properties, scratch resistance and tribological performance of Cu-based bimetals, which are usually used to manufacture sliding bearings and bushings for internal combustion engines (ICEs). Two different Cu-based bimetals, namely CuPb10Sn10 and CuSn10Bi7, were sintered onto a low carbon steel substrate. The mechanical properties and dry tribological performance using a tensile tester and micro-tribo tester were evaluated, respectively. The scratch resistance was assessed using a micro-scratch tester at an incremental load. The tensile test results showed that the yield strength (YS) and ultimate tensile strength (UTS) of both Cu-based bimetals increased after UNSM. Furthermore, the scratch and tribological tests results revealed that the scratch resistance and tribological performance of both Cu-based bimetals were improved by the application of UNSM. These improvements were mainly attributed to the eliminated pores, increased hardness and reduced roughness after UNSM. CuSn10Bi7 demonstrated better mechanical properties, scratch resistance and tribological performance than CuPb10Sn10. It was found that the presence of Bi in CuSn10Bi7 formed a Cu₁₁Bi₇ intermetallic phase, which is harder than Cu₃Sn. Hence, CuSn10Bi7 demonstrated higher strength and wear resistance than CuPb10Sn10. In addition, a CuSn10Bi7 formed both SnO₂ and Bi₂O₃ that prevented adhesion and improved the tribological performance. It can be expected that under dry tribological conditions, ICEs can utilize UNSM bearings and bushings made of CuSn10Bi7 instead of CuPb10Sn10 under oil-lubricated conditions.

• Journal of the Korean Ceramic Society
• /
• v.50 no.1
• /
• pp.87-91
• /
• 2013

The doping effect of Sn on the microstructure evolution and dielectric properties was studied in $CaCu_3Ti_{4-x}Sn_xO_{12}$ polycrystals. Samples were produced by a conventional solid-state reaction method. Sintering was carried out at $1115^{\circ}C$ for 2-16 h in air. The dielectric constant and loss were examined at room temperature over a frequency range between $10^2$ and $10^6$ Hz. The microstructure was found to evolve into three stages. Addition of $SnO_2$ led to an increase in density and advanced formation of abnormal grains. The formation of coarse grains with a reduced thickness of the boundary brought about an enhanced dielectric constant and a lower dielectric loss below ~1 kHz. EDS data showed the Cu-rich phase along the grain boundary, which should contribute to the improved dielectric constant according to the internal barrier layer capacitor model. After all, $SnO_2$ was an effective dopant to elevate the dielectric characteristics of $CaCu_3Ti_{4-x}Sn_xO_{12}$ polycrystals as a promoter for abnormal grain growth.

• Textile Coloration and Finishing
• /
• v.12 no.6
• /
• pp.389-395
• /
• 2000

A natural colorants was extracted from cherry by 10wt% aqueous acetic acid solution as an extractant. Silk and cotton fabrics were dyed with the cherry extract in the temperature range of $40-80^\circ{C}$ and for the time range of 30-60min. by pre- and post-mordanting with various mordants, their dyeability and fastness were investigated. The natural cherry extract prepared in this study has a maximum absorbance at 520nm. It was found that the optimum dyeing temperature and time were $40^\circ{C}$ and 50min, respectively. The pre-mordanting method was more effective than post-mordanting. All mordants except $SnCl_2\cdot{2H}_2O\;and\;FeSO_4\cdot{7H}_2O$ were effective for silk fabrics. However, the dyeability on cotton fabrics increased in the order of $CrK(SO_4)_2\cdot{12H_2O>(CH_3COO)_2Cu\cdot{H}_2O>CuSO_4\cdot{5H}_2O>AlK(SO_4)_2\cdot{12H}_2O>FeSO_4\cdot{7H}_2O>SnCl_2\cdot{2H}_2O$ among the mordants used in this study Fastness(light, water, washing, perpspiration fastness) on the silk and cotton fabrics increased with using mordants. The post-mordanting using mordant$(CH_3COO)_2Cu\cdot{H}_2O$ among the various mordants in this study gave the best fastness.

• 한국초전도학회:학술대회논문집
• /
• v.14
• /
• pp.38-38
• /
• 2004