Elasticity electrical resistance

Titanium siUcides are used in the preparation of abrasion- and heat-resistant refractories. Compositions based on mixtures of Ti Si, TiC, and diamond have been claimed to make wear-resistant cutting-tool tips (157). Titanium siUcide can be used as an electric—resistant material, in electrically conducting ceramics (158), and in pressure-sensitive elastic resistors, the electric resistance of which varies with pressure (159). 

Compound Molecula r formula Densit T g/mL Mp, °C Micro hardness a Transvers e mpture strength, N/imn Compressio n strength, N/imn Modulus of elasticity, N/imn Heat conductivity, W/(cm-K) Coefficien t of thermal expansion, /3 X 10 Electrical resistivity, //n-cm... 

Type and designation Melting range (°C) Density (kg m ) Specific heat (J kg- K- ) Mean coefficient of thermal expansion (K- ) Thermal conductivity (W m K ) Electrical resistivity (fl m) Modulus of elasticity (G Pa)... 

The presence of a few atomic percent of oxygen in tantalum increases electrical resistivity, hardness, tensile strength, and modulus of elasticity, but decreases elongation and reduction of area, magnetic susceptibility, and corrosion resistance to HF . 

Changes in electrical resistivity (V3) and mechanical properties (V3, V4) of graphite fibers upon nitration have been studied. Increases in elastic modulus, and decreases in tensile strengths, have been related to removal of boundary dislocations by the intercalation process proposed elsewhere iN4). 

Elastic prop es of glass, 13. Electrical resistance of gl s, 14 Electrodes in apparatus, 156 Electrofytic gas generator, 149 Em, 39... 

Fig. 8.4 Plots of relative change in electrical resistance against tensile deformation of a CNT/epoxy composite (a) shows the various characteristics of the piezoresistivity of nanocarbon networks linear resistance change in the elastic regime, nonlinear region after inelastic deformation and the permanent electrical resistance drop due to plastic deformation (image adapted from [30]) ...

For example, the required lower bulk electrical resistance and surface contact resistance are directly related to reducing internal power consumption in fuel cells to achieve maximum power output. The requirements of high flexural strength and flexibility (ultimate strain) are important to assure no distortion of fluid fields and no crack in a plate sustained in the large compressive loading when each unit cell is assembled together as a stack. This is particularly important when the thickness of the plate becomes thinner and thinner (can be close to or less than 1 mm [9]) and the dimension of the fluid field becomes smaller and smaller. Whether it is elastic or plastic, the large... 

Properties Density Thickness Electrical Resistivity Corrosion Current Permeability for Hydrogen Modulus of Elasticity... 

The electric properties of polymers are also related to their mechanical behavior. The dielectric constant and dielectric loss factor are analogous to the elastic compliance and mechanical loss factor. Electric resistivity is analogous to viscosity. Polar polymers, such as ionomers, possess permanent dipole moments. These polar materials are capable of storing... 

Grayish metal hexagonal close-packed crystal system, lattice constant, a=2.286 A and c=3.584 A density 1.85 g/cm permeable to x-rays highly ductile modulus to weight ratio very high, elastic modulus 44.5 x 10 at 25°C (for hot-pressed block and sheet) melting point 1,287°C vaporizes at 2,471°C sound transmission velocity 12,600 m/sec reflectivity (white hght) 55% thermal neutron absorption cross-section 0.0090 barns/atom electrode potential, Be/Be2+(aq) 1.85 V electrical resistivity 3.36 x 10-i° ohm.m (at 20°C). 

Bright, silvery-white metal face-centered cubic crystal structure (a = 0.5582 nm) at ordinary temperatures, transforming to body-centered cubic form (a= 0.4407) at 430°C density 1.54 g/cm at 20°C hardness 2 Mohs, 17 Brinnel (500 kg load) melts at 851°C vaporizes at 1,482°C electrical resistivity 3.43 and 4.60 microhm-cm at 0° and 20°C, respectively modulus of elasticity 3-4x10 psi mass magnetic susceptibility -i-1.10x10 cgs surface tension 255 dynes/cm brick-red color when introduced to flame (flame test) standard reduction potential E° = -2.87V... 

Colorless or light yellow metal at ordinary temperatures it occurs in hexagonal close-packed crystalline form, known as alpha-gadolinium alpha form transforms to a body-centered cubic allotropic form, beta-gadolinium upon heating at 1,262°C density 7.90 g/cm melting point 1,313°C vaporizes at 3,266°C vapor pressure 9.0 torr at 1,800°C (calculated) electrical resistivity 134.0 microhm-cm at 25°C Poisson ratio 0.259 modulus of elasticity 8.15x106 psi thermal neutron absorption cross section 46,000 barns insoluble in water dissolves in acid (reacts). 

Occurs as a close-packed hexagonal alpha-form and a hody-centered cubic beta modification melting point 2,233°C vaporizes at 4,602°C electrical resistivity 35.5 microhm-cm at 20°C magnetic susceptibility 0.42xlCL6 emu/g at 25°C thermal neutron absorption cross section 105 barns/atom work function 3.5 eV modulus of elasticity 20x10 psi tensile strength 58,000 psi at 25°C insoluble in water, dilute mineral acids and nitric acid at all concentrations soluble in hydrofluoric acid, concentrated sulfuric acid and aqua regia. 

Silver-white lustrous soft metal highly malleable and ductile face-centered tetragonal crystalline structure (a=4.583A, c=4.93GA) diamagnetic metal density 7.31 g/cm at 20°C melts at 156.6°C vaporizes at 2,072°C electrical resistivity 8.4 x Kh ohm-cm superconducting at 3.38°K (—269.8°C) hardness 0.9 (Brinnel) tensile strength 26.19 atm modulus of elasticity 10.8 GPa thermal neutron absorption cross-section 190 10 bams soluble in acids. 

Soft white, ductile metal high-purity metal is very ductile at ordinary temperatures occurs in three allotropic forms (i) body-centered cubic form, alpha iron stable up to 910°C, (ii) face-centered cubic form, gamma iron occurring between 910 to 1,390°C, and (iii) body-centered delta iron allotrope forming above 1,390°C. Density 7.873 g/cm at 20°C melting point 1,538°C vaporizes at 2,861°C hardness (Brinell) 60 electrical resistivity 4.71 microhm-cm at 0°C tensile strength 30,000 psi Poisson s ratio 0.29 modulus of elasticity 28.5 X 10 psi thermal neutron absorption cross-section 2.62 bams velocity of sound 5,130 m/s at 20°C. 

Silvery-white metal close-packed hexagonal structure density 1.74 g/cm at 20°C, 1.57 g/cm3 at 650 C (hquid melt) melts at 650 C vaporizes at 1,090°C vapor pressure 5 torr at 678 C and 20 torr at 763 C electrical resistivity 4.46 microhm-cm at 20 C, 28.0 microhm-cm at 650 C (hquid melt) surface tension 563 dynes/cm at 681 C modulus of elasticity 6.5x10 Ib/sq in Poisson s ratio 0.35 thermal neutron absorption cross section 0.059 bam soluble in dilute acids. 

Silvery-white lustrous metal face-centered cubic crystal structure ductile ferromagnetic density 8.908 g/cm at 20°C hardness 3.8 Mohs melts at 1,455°C vaporizes at 2,730°C electrical resistivity 6.97 microhm-cm at 20°C total emissivity 0.045, 0.060 and 0.190 erg/s.cm2 at 25, 100 and 1,000°C, respectively modulus of elasticity (tension) 206.0x10 MPa, modulus of elasticity (shear) 73.6x10 MPa Poisson s ratio 0.30 thermal neutron cross section (for neutron velocity of 2,200 m/s) absorption 4.5 barns, reaction cross section 17.5 barns insoluble in water dissolves in dilute nitric acid shghtly soluble in dilute HCl and H2SO4 insoluble in ammonia solution. Thermochemical Properties... 

Metallic appearance in massive form, black to metallic color in powdered state or in electrodeposited form hexagonal crystal system density 20.53 g/cm3 hardness (Brinell) 250 melts at 3,180°C vaporizes at 5,627°C (estimated) vapor pressure 4.6x10- torr at 2,500°C electrical resistivity 19.14 microhm -cm modulus of elasticity 67x10 psi at 20°C specific magnetic susceptibility 0.369x10 thermal neutron absorption cross section 86 barns/atom superconductivity transition temperature 1.7°K insoluble in water and hydrochloric acid soluble in dilute nitric acid and hydrogen peroxide slightly soluble in sulfuric acid. 

White metal with brdhant metaUic luster face-centered cubic crystals density 10.43 g/cm at 20°C, and 9.18 g/cm at 1,100°C melts at 961.8°C vaporizes at 2,162°C vapor pressure 5 torr at 1,500° C pure metal has the highest electrical and thermal conductive of aU metals, electrical resistivity of pure metal at 25°C 1.617x10 ohm-cm elastic modulus 71GPa (10.3x10 psi) Poisson s ratio 0.39 (hard drawn), 0.37 (annealed) viscosity of hquid silver 3.97 centipoise at 1,043°C thermal neutron absorption cross section 63 1 barns insoluble in water inert to most acids attacked by dilute HNO3 and concentrated H2SO4 soluble in fused caustic soda or caustic potash in the presence of air. 

Gray, heavy, and very hard metal malleable and ductile body-centered cubic lattice structure the density of the metal 16.65 g/cm at 20°C and that of powder 14.40 g/cm melts at 2,996°C vaporizes around 5,458°C electrical resistivity 13.1 microhm-cm at 25°C modulus of elasticity 27x10 psi Poisson s ratio 0.35 magnetic susceptibility 0.849x10 cgs units at 25°C insoluble in water, alcohol and practically all acids soluble in hydrofluoric acid... 

Grayish-white metal hody-centered cubic crystalline structure density 19.3 g/cm3 melts at 3,422°C vaporizes at 5,555°C vapor pressure 1 torr at 3,990°C electrical resistivity 5.5 microhm-cm at 20°C modulus of elasticity about 50 to 57 x lO psi (single crystal) Poisson s ratio 0.17 magnetic sus-ceptibilty +59 x 10-6 thermal neutron absorption cross section 19.2 + 1.0 barns (2,200m/sec) velocity of sound, about 13,000 ft/sec insoluble in water practically insoluble in most acids and alkabes dissolves slowly in hot concentrated nitric acid dissolves in saturated aqueous solution of sodium chlorate and basic solution of potassium ferricyanide also solubibzed by fusion with sodium hydroxide or sodium carbonate in the presence of potassium nitrate followed by treatment with water... 

A bright white metal soft and ductile body-centered cubic structure index of refraction 3.03 density 5.96 g/cm melts at 1,910°C vaporizes at 3,407°C electrical resistivity, 18.1 microhm-cm at 0°C and 20.1 microhm-cm at 25°C magnetic susceptibility 1.4x10 cgs units modulus of elasticity 18-19x10 psi shear modulus 6.73xl0 psi Poisson s ratio 0.36 thermal neutron absorption cross section 5 barns/atom insoluble in water, dilute sulfuric acid, and hydrochloric acid at all concentrations soluble in nitric acid, aqua regia, and concentrated sulfuric acid insoluble in alkalies. 

How can the actual contact surface be measured One possibility is to measure the electrical resistance between two conductors and calculate the contact area from the measured resistance and the specific resistivity of the materials. Another possibility is to use an IR sensitive microscope to measure hot spots of a transparent solid that is in contact with a hot surface. With these methods it was found that the friction force is, in fact, proportional to the actual contact area. This implies that the true contact area must increase linearly with load. To illustrate how this is possible, we consider two extreme cases. In the first case, purely elastic deformation is considered. In the second case, we assume plastic deformation of the microcontacts. 

---