• Journal of Welding and Joining
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• v.15 no.5
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• pp.104-114
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• 1997

The microstructure and bond strength were investigated on the SiC/SiC and SiC/mild steel joints brazed by Ag-5at%Ti alloy. Ag-5at%Ti-2at%Fe and -5at%Fe brazing alloys were also used to see the effects of Fe addition on the bond strength of SiC/SiC brazed joints. Brazing temperature and brazing gap were selected and examined as brazing variables. The microstructure of SiC/SiC brazed joints was affected by Fe addition to the Ag-5at%Ti alloy, but the bond strength was not. Increasing brazing temperature also changed the microstructure of $Ti_5Si_3$ reaction layer and brazing alloy matrix of the SiC/SiC and SiC/mild steel joints, but not the bond strength. Brazing gap had a great effects on the bond strength. Decreasing brazing gap from 0.2 mm to 0.1 mm in SiC/SiC brazing increased the bond strength from 187 MPa to 263 MPa and, in SiC/mild steel brazing, from 189 MPa to 212 MPa. It was concluded that the most important parameter on the bond strength in SiC/SiC and SiC/mild steel brazing was the relative ratio between brazing gap and specimen size.

• Journal of the Korean Ceramic Society
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• v.46 no.5
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• pp.520-524
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• 2009

Porous self-bonded silicon carbide (SBSC) ceramics were fabricated at temperatures ranging from 1750 to $1850^{\circ}C$ using SiC, Si, C as starting materials and Al as an optional sintering additive. The effect of Al addition on the porosity and strength of the porous SBSC ceramics were investigated as functions of sintering temperature and Si:C ratio. The porosity increased with decreasing the Si:C ratio and increasing the sintering temperature. It was possible to fabricate SBSC ceramics with porosities ranging from 37% to 44% by adjusting the Si:C ratio and the sintering temperature. Addition of Al additive promoted densification and necking between SiC grains, resulting in improved strength. Typical flexural strengths of SBSC ceramics with and without Al addition were 44 MPa and 34MPa, respectively.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.3
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• pp.9-14
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• 2004

In this study, Si anisotropic etching characteristics of tetramethylammonium hydroxide (TMAH)/ ammonium persulfate(AP)/isopropyl alcohol(IPA) solutions were investigated to realize the optimum structure of a diaphragm for the piezoresistive pressure sensor application. Due to its low toxicity and its high compatibility with the CMOS processing, TMAH was used as Si anisotropic etchants. The variations of Si etch rate on the etching temperature, TMAH concentration, and etching time were obtained. With increasing the etching temperature and decreasing TMAH concentrations, the Si etch rate is increased while a significant non-unifonnity exists on the etched surface because of formation of hillocks on the (100) surface. The addition of IPA to TMAH solution leads to smoother etched surfaces but, makes the Si etch rate lower. However, with the addition of AP to TMAH solution, the Si etch rate is increased and an improvement in flatness on the etching front is observed. The Si etch rate is also maximized with increasing the number of addition of AP to TMAH solution per one hour. The Si square membranes of 20${\mu}{\textrm}{m}$ thickness and l00-400${\mu}{\textrm}{m}$ one-side length were fabricated successfully by applying optimum Si etching conditions of TMAH/AP solutions.

• Journal of the Korean Ceramic Society
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• v.28 no.6
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• pp.471-477
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• 1991

Effects of ZnO, PbO and SiO2 on the grain growth and magnetic properties of Sr-ferrite were investigated. (1) Addition of ZnO to Sr-ferrite increased remanence, but decreased coercivity and maximum energy product. (2) Addition of PbO up to 0.5 wt% increased (B$.$H)max of Sr-ferrite, but addition more than 0.5 wt% decreased (B$.$H)mzx (3) SiO2 addition to the 0.5 wt% PbO doped Sr-ferrite decreased remanence and increased coercivity. The coercivity increase in due to the grain refinement effect of SiO2. But addition of SiO2 more than 0.5 wt% invoked a decrease of coercivity and (B$.$H)max of Sr-ferrite due to abnormal grain growth. Sr-ferrite magnet having maximum energy product of 3.7MGOe was fabricated by using the roasting product of Pyrrhotite.

• Journal of the Korean Ceramic Society
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• v.42 no.8 s.279
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• pp.588-592
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• 2005

The effect of SiC additive on the densification behavior and microstructural change of $TiB_2$ ceramics was investigated. The infiltration and direct mixing with polycarbosilane (PCS), which was converted to SiC by pyrolysis during sintering, were used for the addition of SiC. The addition of Fe enhanced the densification of $TiB_2$, but which resulted in exaggerated grain growth. However, the addition of PCS enhanced the densification and suppressed the exaggerated grain growth of $TiB_2$. Moreover, the addition of PCS using direct mixing was more effective for suppress of grain growth as compare to the addition of PCS using infiltration.

• Journal of the Korean Ceramic Society
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• v.25 no.6
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• pp.601-608
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• 1988

The effect of SiO2 addition on sintering characteristics of 8 mole percent yttria-stabilized zirconia ceramics is investigated. As the addition of SiO2 is increased, sinterbility, microstructure, and Vickers hardness of the zirconia ceramic increased but fracture toughness and electrical conductivity are decreased. It is considered that the electrical conductivity decrease with the increase of SiO2 is due to the decrease of defect concentration of ionized oxygen. From the complex impedance measurement, it is shown that the influence of SiO2 is more dominant at the resistivity of bulk region than of grain boundary region.

• Journal of the Korean Ceramic Society
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• v.40 no.1
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• pp.69-76
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• 2003

For lithium secondary microbattery anode, the tin oxide thin films with Si addition (0, 2, 6, 10, 20 ㏖%) were prepared with R.F. magnetron sputtering at substrate temperature of 30$0^{\circ}C$ and Ar:O$_2$=7:3 atmosphere. As Si addition amount increased, Si-O bonding density increased and Sn-O bonding density decreased. The addition of optimum Si amount led the decrease of Sn oxidation state so that the irreversible capacity reduced and cycle characteristic enhanced during charge-discharge test. SnO$_2$films with 6 ㏖% Si had the highest reversible capacity of 700 mAh/g after 100 cycles.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.8
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• pp.657-662
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• 2003

This paper presents a new fabrication method of selective SiGe epitaxial growth at 650 $^{\circ}C$ on (100) silicon wafer with oxide patterns by reduced pressure chemical vapor deposition. The new method is characterized by a cyclic process, which is composed of two parts: initially, selective SiGe epitaxy layer is grown on exposed bare silicon during a short incubation time by SiH$_4$/GeH$_4$/HCl/H$_2$system and followed etching step is achieved to remove the SiGe nuclei on oxide by HCl/H$_2$system without source gas flow. As a result, we noted that the addition of HCl serves not only to reduce the growth rate on bare Si, but also to suppress the nucleation on SiO$_2$. In addition, we confirmed that the incubation period is regenerated after etching step, so it is possible to grow thick SiGe epitaxial layer sustaining the selectivity. The effect of the addition of HCl and dopants incorporation was investigated.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.5
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• pp.1042-1046
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• 2007

In this study, we investigated the mechanism responsible for the thermal stability of CoSi by addition of a foreign chemical element. Addition of W was found to increase the heat of formation of CoSi. This increase was claimed to inhibit the glass formation, which is preferred by silicide formation kinetics depicted by the maximum system energy degradation rate. In this case, there forms at the interface between CoSi and Si wafer a crystalline structure, the effective diffusion coefficient of which is much less than the self-diffusion rate provided by the glass. It was stated that the phase transition requires a higher thermal energy as the consequence, thereby enhancing the thermal stability of CoSi.

• Journal of Mechanical Science and Technology
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• v.14 no.8
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• pp.830-835
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• 2000

The thermodynamical estimation of the interfacial reaction and the impact properties of $Nb/MoSi_2$ laminate composites containing SiC, $NbSi_2$ or $ZrO_2$ particles are investigated. Laminate composites, which comprise alternating layers of $MoSi_2$ with the particle and Nb foil, were fabricated by the hot press process. It is clearly found out that the interfacial reaction of $Nb/MoSi_2$ can be controlled by the addition of $ZrO_2$ particle to the $MoSi_2$ phase. The addition of $ZrO_2$ particle increases both the impact value and the sintered density of Nb/McSij, The suppression of the interfacial reaction is caused by the formation of $ZrSiO_2$ in $MoSi_2-ZrO_2$ matrix mixture.