metallurgy materials and mechanical properties

... How Do We Arrive at Properties That We Want? • Crystal Structure: • diamond vs graphite • Composition • silicon vs germanium ... drag term, i.e the electrons have many collisions during drift 1/τ represents a ‘viscosity’ in mechanical terms 3.225 © E.A Fitzgerald-1999 10 Mean-free Time Between Collisions, Electron Mobility ... electrons crossing plane in time dt = n(dxA) = n(vddtA) • # charges crossing plane per unit time and area = j ( ) j = n v d dtA (− e ) dtA = − nevd = (ne 2τ m )E • Ohm’s Law: j = σ E ⇒ σ = (ne...

Ngày tải lên: 11/08/2014, 14:20

... E F =  m*   * + kbT ln h   me  Eg Since me* and mh* are close and in the ln term, the Fermi level sits about in the center of the band gap ( ) − Eg  k T 2 * * p or n = ni = 2 b  me ... are generated, the Fermi level is approximately in the middle of the band gap • The law of mass action describes the electron and hole populations, since the total number of electron states is fixed ... similar to a chemical reaction, where Eg is the barrier NCNV is the density of the reactants, and n and p are the products N C NV  → e′ + h • Eg − Eg n np =ekT = i N C NV N C NV b • • • Thus,...

Ngày tải lên: 11/08/2014, 14:20

... Temp:360C, H2, CO, NH3 (10, 50 and 100 ppm), NO2 (0.2, 0.4, and ppm) [ Pfad: \ alpha missy Messungen messplatz_1 ] 3.225 M Jägle / 27.02.2001 © H.L Tuller-2001 11 MicroElectroMechanical Systems - MEMS ... sensing a change in environment and responding without need for a microprocessor A device has both gas sensing and actuating function by integration of semiconducting oxide and piezoelectric thin films ... Chemically inert • Abrasion resistant Wide band gap semiconductor/insulator 3.225 © H.L Tuller-2001 17 Photo Electro-chemical Etching - PEC Features: • materials versatility e.g Si, SiC, Ge, GaAs,...

Ngày tải lên: 11/08/2014, 14:20

... Traditionally admired for their stability • Mechanical • Chemical • Thermal • Exhibit other key functional properties • Electrical, Electrochemical, Electromechanical • Optical • Magnetic 3.225 20 ... (Pb0.98La0.02(Zr0.7Hf0.3)1-xTixO3 AFE­ FE System (C Heremans and H.L Tuller, J Euro Ceram Soc., 19, 1139 (1999).) Atmosphere dependent conductivity (I Kosacki and H.L Tuller, Sensors & Actuators B 24-25, 370 ... stability … 3.225 23 Sensor Materials Chemical Environmental Stimulus Gas Sensor Electrical Signal compatible with Microprocessor System Requirements of Gas Sensor Materials • • • • • • • • 3.225...

Ngày tải lên: 11/08/2014, 14:20

... absorb energy and contribute to properties TF~104K (Troom~102K), EF~100Eclass, vF2~100vclass2 3.225 © E Fitzgerald-1999 Effect of Temperature (T>0): Coupled electronic-thermal properties in conductors ... variable α = ∫ ψ *α op ψ dV v 3.225 © H.L Tuller-2001 19 Time and Spatial Dependence of ψ Assume ψ (x,y,z,t) separable into ψ(x,y,z) and φ(t) Applying separation of variables: − h ∇ 2ψ h ∂φ +V ... Model Traveling wave picture L Standing wave picture Ψ ( x) = Ψ ( x + L) L e ikx = e ik ( x + L ) e ikx = 2πn k= L Just having a boundary condition means that k and E are quasi-continuous, i.e...

Ngày tải lên: 11/08/2014, 14:20

... Means to Create Internal Potentials: Heterojunctions • Different semiconductor materials have different band gaps and electron affinity/work functions Internal fields from doping p-n must be superimposed ... Joining p and n p n Ec EF Ev Carriers flow under driving force of diffusion until EF is flat - - + + + + Holes diffuse Electrons diffuse 3.225 © E Fitzgerald-1999 13 Space Charge, Electric Field and ... increases depletion region, and no current flows ideally Forward Bias Reverse Bias np np eVbi-e|Va| nn nn eVbi-e|Va| pp Solve minority carrier diffusion equations on each side and determine J at depletion...

Ngày tải lên: 11/08/2014, 14:20

... Fiber 3.225 Colors Produced by Chromium Above: alexandrite, emerald, and ruby Center: carbonate, chloride, oxide Below: potassium chromate and ammonium dichromate 3.225 © H.L Tuller, 2001 Chromium ... five 3d orbitals in a tetrahedral and an octahedral ligand field Note: When the element is a mid-gap dopant, transitions within this element lead to absorption and/ or emission via luminescence ... electronic and orientational polarizability ε r = + χe + χo = n2 + N α DC 3ε o (1 − iωτ ) ωτ

Ngày tải lên: 11/08/2014, 14:20

... promoted from the valence band to the conduction band E Ec near band gap E=hν k Creates a ‘hole’ in the valence band Ev near band gap 3.225 © E Fitzgerald-1999 Holes and Electrons • • Instead ... 1,000,000 Remember that: 3.225 µ= eτ m* and 1 ∂2E = m * h ∂k 2 Metals and Insulators • EF in mid-band area: free e-, metallic • EF near band edge – EF in or near kT of band edge: semimetal – EF in gap: ... ionic, MP and Eg increase while ao tends to decrease 3.225 © H.L Tuller-2001 Trends in III-V and II-VI Compounds Larger atoms, weaker bonds, smaller U, smaller Eg, higher µ, more costly! Band Gap...

Ngày tải lên: 11/08/2014, 14:20

... MKS: B = µ0(H+M) = µ0nI + µ0M µr = B/ µ0H = + (M/H) = + χm 3.225 © E Fitzgerald-1999 Maxwell and Magnetic Materials • Ampere’s law ∫ H ⋅ dl = I = • For a permanent magnet, there is no real current ... I A L e- What is µ? For θ=0, E = − µH ≈ −Φ B I since energy ~ LI and for loop L = ΦB I Φ B = ∫ ∫ H ⋅ dS ~ HA ∴ µH = Φ B I = HAI and ∴ µ = IA e ω A = πr c 2π e µ = − ωr 2c I =− 3.225 © E Fitzgerald-1999 ... Magnetic Materials • The inductor Φ B = LI (Q = CV) ∂B (CGS) c ∂t ∂ ∂Φ ∫ ∫ ∇ × EdS = − c ∂t ∫ ∫ BdS = − c...

Ngày tải lên: 11/08/2014, 14:20

... Hall Results on Metals • Valence=1 metals look like free-electron Drude metals • Valence=2 and 3, magnitude and sign suggest problems 3.225 © E.A Fitzgerald-1999 25 13 Response of Free e- to AC Electric ... Fitzgerald-1999 Complex Representation of Waves sin(kx-ωt), cos(kx-ωt), and e-i(kx-ωt) are all waves e -i(kx-ωt) is the complex one and is the most general imaginary A θ Acosθ iAsinθ real e iθ=cosθ+isinθ ... (ω>>1/τ) p p (ω

Ngày tải lên: 11/08/2014, 14:20

... 80.4 Electronic, ionic, and molecular polarisation Polarization that is active depends on material and frequency 3.225 © E Fitzgerald-1999 Microscopic Frequency Response of Materials • Bound charge ... polarization (E-field may distort ion positions and temporarily create dipoles) – electronic polarization (bound electrons around ion cores could distort and lead to polarization) • • Except for the ... E-M waves travel in insulating materials: What is the response of the material (εr) to these waves? 3.225 © E Fitzgerald-1999 Wave Eqn with Insulating Material and Polarization r r ∂B ∇xE = −...

Ngày tải lên: 11/08/2014, 14:20

... successful and illustrate the potential for composite materials in various aspects of mechanical engineering 9.5.1 Aerospace and Defense Composites are baseline materials in a wide range of aerospace and ... Offshore and Onshore Oil Exploration and Production Equipment Oil exploration and production equipment requirements place severe demands on materials To function successfully in these environments, materials ... in design and analysis These programs are used to predict laminate properties and to define laminate response and layer stresses and strains resulting from applied loads, moments, and changes...

Ngày tải lên: 26/12/2013, 01:18

... chemical, and mechanical properties of the bamboo species Phyllostachys pubescens The effects of plant age, horizontal layer, and vertical height location on physical, chemical, and mechanical properties ... fiberboard and evaluate water soaking, modulus of elasticity (MOE), modulus of rupture (MOR), and internal bond (IB) properties of the panels and compare the age effect on the physical and mechanical properties ... five year old bamboo and determine the correlation between SG and bending properties, and (5) compressive strength of bamboo at different ages and heights 3.2 Materials and Methods The bamboos...

Ngày tải lên: 22/02/2014, 09:20

... Berkeley, California Carl Zweben Devon, Pennsylvania Mechanical Engineers’ Handbook MATERIALS PART Mechanical Engineers’ Handbook: Materials and Mechanical Design, Volume 1, Third Edition Edited ... range of properties and characteristics BIBLIOGRAPHY Handbooks ASM Metals Handbook, Properties and Selection: Irons, Steels and High Performance Alloys, Vol 1, 10th ed., ASM International, Materials ... second edition of the Mechanical Engineers’ Handbook and the Handbook of Materials Selection, a number of chapters—on Six Sigma, TRIZ, and STEP—are new additions to this family of handbooks Contributors...

Ngày tải lên: 27/06/2014, 23:20

... crystallisation NR also had shown excellent improvements in mechanical properties, thermal properties, barrier properties and flame-retardant properties when compounded with organoclays.7–11 In this ... min–1 RESULTS AND DISCUSSION 3.1 Cure Characteristics Figures and and Table show the results for the scorch time, t2, and cure time, t90, for both organoclay-filled NR nanocomposites and organoclayfilled ... values of the minimum and maximum torques 3.2 Mechanical Properties Figure and Table show the effect of organoclay loading on the tensile strength of organoclay-filled NR and ENR nanocomposites...

Ngày tải lên: 07/08/2014, 14:20

... diversity and to measure the physical and mechanical properties in the tension wood sector as compared to the opposite wood sector, on specimen corresponding to the standard methods MATERIAL AND METHODS ... bending and in compression (MPa), Tangential, radial and longitudinal shrinkage (%), tangential/radial shrinkage ratio (TS/RS) and transversal + radial shrinkage for opposite wood (OW) and tension ... saturated and anhydrous states on the dimension in the saturated state Initial dimensions of the specimens are 20 × 20 × 50 mm3 (RTL) for longitudinal shrinkage and 20 × 20 × 10 mm3 (RTL) for radial and...

Ngày tải lên: 07/08/2014, 16:21

... between wood density or mechanical properties and growth rate in P deltoides × nigra The objective of this study is to evaluate the variability in selected physical and mechanical properties of new ... characteristics for selected trees and total stand; mean radial increment and radial increment of last 10 years (cm), circumference at BH (cm) and total tree height (m) with standard deviations Clone Beaupré ... proportion and the slower decrease of heartwood proportion with height in ’Hoogvorst’, the increase in density is less pronounced The relation between density and mechanical properties (MOE and MOR)...

Ngày tải lên: 07/08/2014, 16:21

... The results of physical and mechanical characterisation of Atlas cedar wood from Southern Italy are summarised on table IV Table V refers about physical and mechanical properties found on the ... libani and Cedrus atlantica, with a lot of ornamental cultivars, frequently giving origin to hybrids The Atlas cedar can reach 50 m height and 1.50 m DBH The species is light demanding and cannot ... Molise, Calabria, Sardinia and Sicily Table I Performed tests, dimensions of utilised samples and standard followed for the tests Test type Sample dimension (cm) Standard reference long × transerve...

Ngày tải lên: 08/08/2014, 14:20

... reviewing the properties, structures and applications of metallic glasses and phase-change materials, respectively The current difficulties in understanding the physics of these two classes of materials, ... investigate the stresses and density changes upon crystallization in amorphous thin films Two classes of materials with distinct properties and significant scientific and technological interest ... of a material xxiv Chapter Background and motivations: metallic glasses and phase-change materials- two classes of amorphous materials of great scientific and technological interests Amorphous...

Ngày tải lên: 11/09/2015, 09:16

... consisting of mechanical consolidation, sintering and extrusion Mechanical testing however often exhibits controversial results and the understanding on deformation behavior of fine grained/nc materials ... microscope (FESEM) and transmission electron microscope (TEM) Physical properties such as thermal properties, electrical resistivity, coefficient of thermal expansion and mechanical properties such ... Mg-5wt%Al reinforced with 1wt% of in-situ formed AlN via mechanical milling and power metallurgy techniques Study of microstructures and mechanical properties of Mg MMCs at different ball milling durations...

Ngày tải lên: 14/09/2015, 14:10