• Title/Summary/Keyword: metallic structure

Search Result 548, Processing Time 0.023 seconds

Electronic Structure and Bonding in the Ternary Silicide YNiSi3

  • Sung, Gi-Hong;Kang, Dae-Bok
    • Bulletin of the Korean Chemical Society
    • /
    • v.24 no.3
    • /
    • pp.325-333
    • /
    • 2003
  • An analysis of the electronic structure and bonding in the ternary silicide YNiSi₃is made, using extended Huckel tight-binding calculations. The YNiSi₃structure consists of Ni-capped Si₂dimer layers and Si zigzag chains. Significant bonding interactions are present between the silicon atoms in the structure. The oxidation state formalism of (Y3+)(Ni0)(Si3)3 for YNiSi₃constitutes a good starting point to describe its electronic structure. Si atoms receive electrons from the most electropositive Y in YNiSi₃, and Ni 3d and Si 3p states dominate below the Fermi level. There is an interesting electron balance between the two Si and Ni sublattices. Since the π orbitals in the Si chain and the Ni d and s block levels are almost completely occupied, the charge balance for YNiSi₃can be rewritten as (Y3+)(Ni2)(Si2)(SiSi)+, making the Si₂layers oxidized. These results suggest that the Si zigzag chain contains single bonds and the Si₂double layer possesses single bonds within a dimer with a partial double bond character. Strong Si-Si and Ni-Si bonding interactions are important for giving stability to the structure, while essentially no metal-metal bonding exists at all. The 2D metallic behavior of this compound is due to the Si-Si interaction leading to dispersion of the several Si₂π bands crossing the Fermi level in the plane perpendicular to the crystallographic b axis.

B20 Crystal Structure and Electromagnetic Property of MnGe and MnSi (B20 결정구조와 MnGe와 MnSi의 전자구조 및 자기적 특성)

  • Jeong, Tae Seong
    • Korean Journal of Materials Research
    • /
    • v.29 no.8
    • /
    • pp.477-482
    • /
    • 2019
  • The magnetic properties and electronic structures of the B20 crystal structure MnGe and MnSi were investigated using the density functional theory with local density approximation. The low symmetry of the B20 crystal structure plays a very important role to make electromagnetic characteristics of these materials. The important result of the calculations is that it can be observed the appearance of a pair of gaps in the density of states near the Fermi level in both compounds. These features are results from d-band splitting by the low symmetry of the crystal field from B20 crystal structure. It can be seen that there is half-metallic characteristics from the density of states in both compounds. The calculation shows that the value of magnetic moment of MnGe is 5 times bigger than that of MnSi even though they have same crystal structure. The electronic structures of paramagnetic case have a very narrow indirect gap just above the Fermi level in both compounds. These gaps acquire some significance in establishing the stability of the ferromagnetic states within the local density approximation. Calculation shows that the Mn 3d character dominates the density of states near the Fermi level in both materials.

A Study of WLAN Switch Stucture using DGS (DGS 구조를 이용한 WLAN용 스위치 구조 연구)

  • An Ka-Ram;Park Jun-Seok;Kim Hyung-Seok;Cho Hong-Goo
    • 한국정보통신설비학회:학술대회논문집
    • /
    • 2004.08a
    • /
    • pp.295-297
    • /
    • 2004
  • A double-role double through switch with defected ground structure (DGS) is Proposed. The equivalent circuit for the proposed switch structure is derived based on equivalent circuit of newly proposed DGS unit structure. The equivalent circuit parameters of DGS unit are extracted by using the circuit analysis method The on/off operation of the proposed switch Is obtained by varying the capacitance in the ground metallic plane The experimental results show excellent insertion loss characteristic at on state and isolation characteristic at off state.

  • PDF

A Study on the Machinability Progress by the Structure Improvement of Materials for Automobile's Piston (자동차 피스톤 소재의 조직 개질에 의한 절삭성 향상)

  • 채왕석;김동현
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • 2003.06a
    • /
    • pp.573-576
    • /
    • 2003
  • In this paper the following conclusions were obtained after examining and analyzing data through the various experiments by adopting automobile's piston as the experimental materials among the automobile materials which are being commercialized. The various experiments have been carried out with the object of presenting the selection of rational. economic materials and criterion according to the improvement of machining characteristics by grasping the strength and weakness of existing various materials and using the effects of metallic structure variables as well as satisfying the required conditions.

  • PDF

Development of the injection mold structure for internal gears (내측기어 성형용 사출성형 금형구조의 개발)

  • Kwon, Y.S.;Jeong, Y.D.
    • Journal of Power System Engineering
    • /
    • v.12 no.6
    • /
    • pp.78-82
    • /
    • 2008
  • Plastic gears are more and more widely used in many industrial machine elements. Plastic gear has higher properties such as light weight, wear resistance, and vibration absorbing ability than metallic gears. But, in case of using an inaccurate plastic gear, its tooth breakage happen and fatigue life is shortened due to increase of applying load and temperature rising on the tooth flank. Inaccuracy of plastic gears such as pitch circle roundness and tooth profile generates vibration and noise. In this study, an internal plastic gears which is molded by a new injection mold structure are developed. The new mold structure is called the HR3P(hot runner type 3plate mold) that has an improved runner system in order to have good filling balance. As a result from this study, an internal gear with very accurate roundness was developed by using design of experiment.

  • PDF

Antireflection Structures and Optical Recording Properties of Te-based Alloy Thin Films (Te계 합금 박막의 Antireflection 구조와 광기록 특성)

  • Lee, Hyun-Yong;Choi, Dae-Young;Lee, Young-Jong;Chung, Hong-Bae
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • 1988.05a
    • /
    • pp.74-77
    • /
    • 1988
  • This paper reports the properties of antireflection structure and hole formation of Te-based systems. The optical-recording characteristics of metallic recording media are enhanced significantly by incorporating the metal(Al) layer into an antreflection trilayer structure. Due to the interface condition inherent in the design of the trilayer structure, reflectivity from holes is ranked low fraction (<10%). The hole formation is carried by Ar+ Laser(488nm). For 20nsec pulse duration, hole opening power(threschold) of (Te86Se14)50Bi50 trilayer is lower than that of monolayer that used in this experiment. Hole shapes of the whole sample were clean.

  • PDF

Effect of Melting and Pouring Conditions on Structures of Leaded Tin Bronze Castings (연청동주물(鉛靑銅鑄物)의 조직(組織)에 미치는 용해(熔解) 및 주입조건(鑄入條件)의 영향(影響)에 관한 연구(硏究))

  • Lee, W.W.;Choi, C.O.
    • Journal of Korea Foundry Society
    • /
    • v.7 no.1
    • /
    • pp.45-52
    • /
    • 1987
  • The effects of melting and casting conditions on cast structures of Cu-Sn-Pb alloys were studied. Specimens were prepared at different pouring temperatures of 1100C to 1260C with use of various kind of molds, green sand mold, CO2 sand mold, shell mold, furan sand mold and metallic mold. (1) The transition of equiaxed to columnar structure greatly influenced by adding elements and mold binders. (2) The change of equiaxed structure according to pouring temperatures were expressed by separation theory. Lower pouring temperature and rapid cooling rate increase hardness and it's further increase was shown in the region of columnar structure. (3) Proper controls of pouring temperature, cooling rate and mold binder were important factors to improve wear properties of Cu-Sn-Pb alloys castings.

  • PDF

Materials Flow Analysis of Metallic Cobalt and Its Powder in Korea

  • Hon, Hyun Seon;Kang, Lee-Seung;Kang, Hong-Yoon;Suk, Han-Gil
    • Journal of Powder Materials
    • /
    • v.21 no.3
    • /
    • pp.235-240
    • /
    • 2014
  • The basis of the cobalt demand analysis by use was established via the investigation and analysis of the cobalt materials flow, and the overall cobalt metal material and parts industry structure in Korea was examined to determine the cobalt material flow. The markets of the cobalt material for machinery were studied, including their interrelations, via market and study trends, and relevant plans were examined. The results of the study indicated that the advanced core technology for advanced industry and technology-intensive industry development is required to structurally innovate the parts materials and basic materials industries and to upgrade the catch-up industry structure to the new frontier structure.

The Effects of Cell Sizes on Compression and Bending Strength of Aluminum Material (알루미늄 소재의 미세 기공 크기가 압축 및 굽힘 강도에 미치는 영향)

  • 전용필;강충길
    • Transactions of Materials Processing
    • /
    • v.11 no.8
    • /
    • pp.701-709
    • /
    • 2002
  • Aluminium foam material is highly porous material, which has the complicated cellular structure defined by randomly distributed pores in metallic matrix. This structure gives the characteristic properties which cannot be achieved by any other conventional processes. As the properties of aluminium foam material significantly depend on its porosity, a desired profile of properties can be tailored by changing the foam density. But various defects lead to undesirable effects on the mechanical properties. Mechanical properties are dependent on cell sizes and aspect ratios. Therefore, this paper presents the effects of various processing parameters of various parameters on the mechanical properties. For the sake of this, combined stirring was used to fabricate aluminum foam materials by the parameters. Compression and bending tests were performed to investigate the effects of cell sizes and aspect ratios on the mechanical properties.

The fire-risks of cost-optimized steel structures: Fire-resistant and hot-rolled carbon steel

  • Garcia, Harkaitz;Cuadrado, Jesus;Biezma, Maria V.;Calderon, Inigo
    • Structural Engineering and Mechanics
    • /
    • v.78 no.1
    • /
    • pp.67-75
    • /
    • 2021
  • This work studies the behaviour of a steel portal frame selection under fire exposure, considering both span lengths and fire exposure times as variables. Such structures combine carbon steel (S275), fireproof micro-alloyed steel (FR), and coatings of intumescent paint with variable thicknesses, improving thereby the flame retardant behaviour of the steel structure. Thus, the main contribution of this study is the optimization of the portal frames by combining both steels, analysing the resulting costs influence on the final dimensions. Besides, the topological optimization of each steel component within the structure is also defined, in accordance with the following variables: weather conditions, span, paint thickness, and cost of steel. The results mainly confirmed that using both FR and S275 grades with intumescent painting is the Pareto optimum when considering performance, feasibility and costs of such portal frames widely used for industrial facilities.