• Title/Summary/Keyword: SI7

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Design of a 1V 5.25GHz SiGe Low Noise Amplifier (1V 5.25GHz SiGe 저잡음 증폭기 설계)

  • 류지열;노석호;박세현;박세훈;이정환
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2004.05b
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    • pp.630-634
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    • 2004
  • This paper describes the design of a two stage 1V power supply SiGe Low Noise Amplifier operating at 5.25 GHa for 802.lla wireless LAN application. The achieved performance includes a gain of 17 ㏈, noise figure of 2.7㏈, reflection coefficient of 15 ㏈, IIP3 of -5 ㏈m, and 1-㏈ compression point of -14㏈m. The total power consumption of the circuit was 7 mW including 0.5mW for the bias circuit.

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Characteristics of Elastic Wave Generated by Wear and Friction of SiCf/SiC Composites (SiCf/SiC 복합재의 마모 및 마찰에 의해 발생된 탄성파 특성)

  • Moon, Chang-Kwon;Nam, Ki-Woo
    • Journal of the Korean Society for Nondestructive Testing
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    • v.34 no.1
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    • pp.23-30
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    • 2014
  • The wear characteristics of $SiC_f$/SiC composites were evaluated according to the alignment direction of the fibers, and the elastic wave-generated friction was detected and analyzed in wearing. The friction coefficient and wear loss were similar in the longitudinal and the transverse direction of the fibers. However, these values were lower in the vertical direction of the fibers because of the brittle nature of the fiber. The friction coefficient and the wear loss were directly proportional to each other. The dominant frequencies were 58.6 kHz for monolithic SiC and 117.2 and 136.7 kHz for $SiC_f$/SiC composites, respectively.

Selective Epitaxial Growth of Si and SiGe using Si-Ge-H-Cl System for Self-Aligned HBT Applications (Si-Ge-H-Cl 계를 이용한 자기정렬 HBT용 Si 및 SiGe의 선택적 에피성장)

  • 김상훈;박찬우;이승윤;심규환;강진영
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.16 no.7
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    • pp.573-578
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    • 2003
  • Low temperature selective epitaxial growth of Si and SiGe has been obtained using an industrial single wafer chemical vapor deposition module operating at reduced pressure. Epitaxial Si and heteroepitaxial SiGe deposition with Ge content about 20 % has been studied as extrinsic base for self-aligned heterojunction bipolar transistors(HBTs), which helps to reduce the parasitic resistance to obtain higher maximum oscillation frequencies(f$\_$max/). The dependence of Si and SiGe deposition rates on exposed windows and their evolution with the addition of HCl to the gas mixture are investigated. SiH$_2$Cl$_2$ was used as the source of Si SEG(Selective Epitaxial Growth) and GeH$_4$ was added to grow SiGe SEG. The addition of HCl into the gas mixture allows increasing an incubation time even low growth temperature of 675∼725$^{\circ}C$. In addition, the selectivity is enhanced for the SiGe alloy and it was proposed that the incubation time for the polycrystalline deposit on the oxide is increased probably due to GeO formation. On the other hand, when only SiGe SEG(Selective Epitaxial Growth) layer is used for extrinsic base, it shows a higher sheet resistance with Ti-silicide because of Ge segregation to the interface, but in case of Si or Si/SiGe SEG layer, the sheet resistance is decreased up to 70 %.

Characterization of Ca Precipitation in Al-Mg Alloys Containing a Trace of Ca During Homogenization

  • Seong-Ho Ha;Young-Chul Shin;Bong-Hwan Kim;Young-Ok Yoon;Hyun-Kyu Lim;Sung-Hwan Lim;Shae K. Kim
    • Archives of Metallurgy and Materials
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    • v.66 no.4
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    • pp.959-962
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    • 2021
  • In this study, precipitation of Ca in Al-Mg alloys containing a trace of Ca during homogenization was investigated using a transmission electron microscope (TEM) and calculated phase diagrams. TEM result indicated that the Ca-based particles found in the examined sample are Ca7Mg7.5Si14. From the calculation of Scheil-Gulliver cooling, it was found that the Ca was formed as Al4Ca and C36 laves phases with Mg2Si and Al13Fe4 from other impurities phase during solidification. No Ca-Mg-Si ternary phase existed at the homogenization temperature in the calculated phase diagram. From the phase diagram of Al-Al4Ca-Mg2Si three-phase isothermal at 490℃, it was shown that Ca7Mg6Si14 phase co-exists with Al, Mg2Si and Al4Ca in the largest region and with only Al and Mg2Si in Al4Ca-poor regions. It was thought that the Ca7Mg6Si14 ternary phase was formed by the interaction between Mg2Si and Al4Ca considering that the segregation can occur throughout the entire microstructures.

Simultaneous Synthesis and Densification of NiSi2 and NiSi2-20vol.%Nb Composite by Field-Activated and Pressure-Assisted Combustion (가압통전 활성연소에 의한 치밀한 NiSi2와 NiSi2-20vol.%Nb 복합재료 제조)

  • Kim, H.C.;Shon, I.J.;Park, C.D.
    • Journal of the Korean Society for Heat Treatment
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    • v.14 no.1
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    • pp.1-7
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    • 2001
  • A method to simultaneously synthesize and consolidate the silicide $NiSi_2$ and the composite $NiSi_2$-20vol.%Nb from powders of Ni, Si, and Nb was investigated. Combustion synthesis was carried out under the combined effect of an electric field and mechanical pressure. The final density of the products increased nearly linearly with the applied pressure. Highly dense $NiSi_2$ and $NiSi_2$-20vol.%Nb with relative densities of up to 97% were produced under the simultaneous application of a 60MPa pressure and a 3000A current on the reactant powders. The respective Vickers microhardness values for these materials were 6.0 and 5.8 GPa. From indentation crack measurements, the fracture toughness values for $NiSi_2$ and $NiSi_2$-20vol.%Nb were calculated to be 3.3 and 4.7 $MPa{\cdot}m^{1/2}$, respectively.

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Effect of Si on the Corrosion Properties of Mg-Li-Al Light Alloy (경량화 Mg-Li-Al합금의 내식성에 미치는 Si의 영향)

  • 김순호
    • Resources Recycling
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    • v.7 no.5
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    • pp.52-57
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    • 1998
  • Effect of Si in the electrochemical corrosion characteristics of Mg-Li-Al light alloy has been investigated by means of potentiodynamic polarization study. The elecrochemical behaviors were evaluated in 003% NaCl solution and the solution buffered with KH$_{2}PO_{5}{\cdot}$NaOH at room temperature. It was found that the addition of very small quantity of Si (0.48 wt%) in Mg-Li-Al light alloy increased corrosion rates and amount of corrosion products and decreated the pitting resistance of the alloy. From the results it was concluded that Si which is added to increase the strength of Mg-Li-Al alloy is harmful to corrosion properties of the alloy.

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Microstructure and Mechanical Properties of Ni-Cr-Mo Based Dental Cast Iron for Porcelain-Fused-to-Metal Firing (도재소부용 Ni-Cr-Mo계 치과용 합금의 미세조직 및 기계적성질)

  • Choi, D.C.
    • Journal of Korea Foundry Society
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    • v.27 no.3
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    • pp.120-125
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    • 2007
  • The microstructure, mechanical properties and melting range of Ni-Cr-Mo based alloys were investigated to develop Be-free Ni-Cr-Mo base dental alloys for Porcelain-Fused-to-Metal Firing(PFM). All as-cast alloys showed dendritic structure. Rockwell hardness of 20Cr7Mo was increased with addition of Si and Ti. On the contrary, it was decreased with addition of Co. The duplex alloying elemental addition such as 3Co + xTi, 2Si + xCo and 2Si + xTi to 20Cr7Mo resulted in much increase of hardness. Rockwell hardness and compressive strength for 20Cr3CoSiTi or 17Cr6CoSiTi alloy that add Si-Ti had similar values compared to the commercial alloys. Melting range for 20Cr3CoSiTi and 17Cr6CoSiTi alloy that add Si-Ti showed similar or lower than commercial alloys. In conclusion, 20Cr3CoSiTi and 17Cr6CoSiTi alloys can be applied for commercial use.

Effects of Si Addition on the Microstructure and Properties of Cr-Al alloy for High Temperature Coating (고온 코팅용 Cr-Al합금의 미세조직 및 특성에 미치는 Si 첨가의 영향)

  • Kim, Jeong-Min;Kim, Il-Hyun;Kim, Hyun-Gil
    • Korean Journal of Materials Research
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    • v.29 no.1
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    • pp.7-10
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    • 2019
  • Cr-Al alloys are attracting attention as oxidation resistant coating materials for high temperature metallic materials due to their excellent high temperature stability. However, the mechanical properties and oxidation resistance of Cr-Al alloys can be further enhanced, and such attempts are made in this study. To improve the properties of Cr-Al alloys, Si is added up to 5 wt%. Casting specimens with different amounts of Si content are prepared by a vacuum arc remelting method and isothermally heated under steam conditions at $1,100^{\circ}C$ for 1 hour. The as-cast microstructure of low Si alloys is mainly composed of only a Cr phase, while $Al_8Cr_5$ and $Cr_3Si$ phases are also observed in the 5 % Si alloy. In the high Si alloy, only Cr and $Cr_3Si$ phases remain after the isothermal heating at $1,100^{\circ}C$. It is found that Si additions slightly decrease the oxidation resistance of the Cr-Al alloy. However, the microhardness of the Cr-Al alloy is observed to increase with an increasing Si content.