Thermal Properties Of Metals Research Articles

Materials and technologies to achieve better energy efficiency of buildings

The article will discuss the aspects of the possibilities of improving the energy efficiency of buildings. In particular, the author will analyze innovative technologies in the field of improving the thermal insulation of external partitions and improving the efficiency of underfloor heating. The author will present the results of research on the thermal properties of metal and wooden frame structures, as well as innovative veneer floor panels. Frame structures are increasingly used in single-family housing, and veneer floor panels are used in underfloor heating. Innovative solutions of building partitions are to improve the energy efficiency of newly constructed buildings, and thus reduce the emission of greenhouse gases into the atmosphere.

The Effect of Cryogenic Cooling and Drill Bit on the Hole Quality when Drilling Magnesium-based Fiber Metal Laminates

The interest on fiber metal laminates has increased significantly in recent years as a consequence of the request of lighter and more functional aerospace and automotive components. In such parts, drilling is essential for assembly purposes. Nevertheless, drillability of fiber metal laminates is a critical issue due to the heterogeneous mechanical and thermal properties of metals and composites. The current research work aims at understanding how to improve the hole quality after drilling of magnesium-based fiber metal laminates. To this aim, dry and cryogenic cooling was applied as well as the adoption of three different drill bits, namely uncoated drill bits, coated drill bits and spur drills. Hole size, cylindricity, roughness, entry burr height, exit delamination and fiber pull-out are considered as experimental outcomes to characterize the hole surface quality. Results show that both spur drills and cryogenic cooling can significantly improve hole quality. The process parameters combination capable to guarantee the highest surface quality is finally provided.

Modelisation of Calorific Capacity by the Debye and Brillouin Functions for the Formalization of the Magnetothermal Problem

In the induction heating, in the calculation of the electric machines losses, in the mechanical engineering, in the calculation of the thermal field distribution, the equations of Maxwell and heat equation are required. Those utilize the magnetic permeability and the calorific capacity at constant volume which strongly depends on the temperature and the temperature of Debye, which is a constant for each metal.The Physics of the Solid State,through the study of the acoustic and thermal properties of metals, establishes a formula giving the calorific capacity at constant volume by an integral which one can calculate only numerically.That is due to the form even of the function of distribution of Debye. The purpose of this work is to propose an analytical formulation of the calorific capacity at constant volume by analogy with the Brillouin's function largely used in ferromagnetism.This formulation has the advantage to put at the disposal of the Engineer specific concepts to the Physicist. Another advantage is the facility of ‘’to keep’’ this new formulation by functions which come under the domain of Numerical Analysis, such spline function or other.This same formulation will also allow finding an analytical formulation of internal energy whereas it was given by an integral which one can calculate only numerically.

Spectral, thermal and optical properties of metal(ІІ)–azo complexes for optical recording media

A novel ligand, (Z)-1,5-dimethyl-4-(2-(3-methyl-5-oxo-1-phenyl-1H-pyrazol-4(5H)-ylidene)hydrazinyl)-2-phenyl-1,2-dihydropyrazol-3-one] and its metal(II)–azo complexes were synthesized and characterized using elemental analyses, proton NMR, electrospray ionization mass spectrometry, FT-IR and UV–visible absorption. Smooth thin films of the metal(II)–azo complexes were prepared using spin-coating, and the absorption spectra of the films were measured. The thermal properties of the metal(ІІ)–azo complexes were investigated using TGA and DSC. The optical constants (complex refractive index N = n + ik) of the films on single-crystal silicon were determined using variable-angle scanning ellipsometry from which the complex dielectric function ( ɛ) and absorption coefficient ( α) were calculated. The photostabilities of the metal(II)–azo complex films were also investigated.

Synthesis, spectral and thermal properties of some transition metal(II) complexes with a novel ligand derived from thiobarbituric acid

Four novel metal(II) complexes, Ni(L)2, Co(L)2, Cu(L)2, and Zn(L)2 (L = 5-(2-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)hydrazono)-1,3-diethyl-2-thioxo-dihydropyrimidine-4,6(1H,5H)-dione), were synthesized using the procedure of diazotization, coupling and metallization. Their structures were identified by elemental analyses, 1H NMR, ESI-MS and FT-IR spectra. The effect of different central metal(II) ions on absorption bands of the metal(II) complexes was researched. The thermal properties of the metal(II) complexes were investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC). Furthermore, the thermodynamic parameters, such as activation energy (E*), enthalpy (∆H*), entropy (∆S*) and free energy of the decomposition (∆G*) are calculated from the TG curves applying Coats–Redfern method. The results show that the metal(II) complexes have suitable electronic absorption spectra with blue-violet light absorption at about 350–450 nm, high thermal stability with sharp thermal decomposition thresholds.

Optical and thermal properties of metals, ceramics, and CVD diamond films upon high-temperature laser heating

A complex optical method for simultaneous determination of optical and thermal properties of solids (true temperature, reflectance, transmittance, absorbance, extinction, specific heat capacity, thermal conductivity, and diffusivity) in a wide temperature range (800–2700°C) was proposed and experimentally demonstrated. The developed setup is characterized by a high processing rate (the time taken for measuring all parameters is from milliseconds to tens of seconds). It allows the study of rather small samples (about several milligrams), which is a significant advantage as applied to new or expensive materials. New and widely used materials (AlN, Al2O3, Si3N4, SiC, and Al2O3/SiC ceramics; C45, 16MnCrS5, 115CrV3, X5NiCr18 9, X12CrNi17 7, Sd, and Satellite 6 steels; E-Cu, CuSn, AlMgSi1, and AlCuMgPb copper and aluminum alloys; as well as chemical vapor deposition (CVD) diamond films) were studied at heating rates of 103−104K·s−1 in various atmospheres (air and argon at pressures of 1 and 10−3 atm). This study demonstrated high efficiency and informativity of the proposed method. The data obtained can be used to develop theoretical models describing the solid structure and properties at high temperatures in oxidizing, neutral, or regenerative atmospheres.

Investigation of metal–glaze structures with photoacoustic and infrared methods

This article presents methods of investigation of thermal properties of metal–insulator joints. The thermal parameters of joined materials and interlayer were determined based on photoacoustic contrast images and neural network computations. Possibilities of visualization of the quality of adhesion between glaze and metal using infrared detection with induction heating also is presented.

Issues concerning shock temperature measurements of iron and other metals

Determining the melting temperature of iron at the Earth's inner and outer boundary near 3 Mbar is an important problem in geophysics. A knowledge of the pressure, volume, temperature, and internal energy of solid and molten iron at megabar pressures and several thousand degrees provides a critical constraint for modeling the Earth's core. An optical method measuring the thermal radiation from the thin metal film deposited on an optically transparent window material is described. Issues which need to be addressed to obtain accurate thermodynamic shock temperatures of metals from the thermal radiation measured are discussed. These issues include characteristics of metal films, thermal conduction occurring at the metal/window interface, optical and thermal properties of metal and window material, and characteristics of the radiation measured.

Investigation of correlation between physicochemical properties of metals and their toxicity to the water flea Daphnia magna Straus

Twenty-three metal ions were tested and ranked in terms of decrease in immobilization (EC 50) of Daphnia magna Straus. The 48-hr EC 50 values (mg/liter) of metal ions were Hg 2+, 0.0052; Ag 1+, 0.01; Cu 2+, 0.093; Zn 2+, 0.56; Co 2+, 1.49; Cr 6+, 1.79; Cd 2+, 1.88; Be 2+, 2.82; Pb 2+, 3.61; As 3+, 6.23; Fe 2+, 7.20; Ni 2+, 7.29; Mn 2+, 8.28; Sn 2+, 21.56; Ba 2+, 32.00; Al 3+, 59.60; W 6+, 89.39; Sr 2+, 94.00; K 1+, 141.46; Mg 2+, 343.56; Na 1+, 420.60; and Sb 3+, 423.45. The 48-hr EC 50 values of 23 metal ions were transformed to their corresponding negative logarithms of molarity (as p M). Correlation coefficients ( r) for more than 35 physicochemical properties of metals or metal ions and acute toxicity values (as p M) were examined by linear regression analysis. The negative logarithm of the solubility product constant of metal sulfide (p K sp), equilibrium constants of amino acids and of EDTA, nucleotide base, electronegativity, electrode potential, melting point, thermal properties of metals, and other physicochemical parameters were significantly correlated with toxicity for D. magna. The order of toxicity of metal ions has been presented and discussed. Correlation between toxicity and physicochemical properties of inorganic substances may be useful in predicting toxicity to various biologically important organisms.

Theoretical and Experimental Investigations of the Dynamic Molten Bridge

It was theoretically demonstrated and experimentally confirmed that molten bridges can be categorized into two types; first, static bridges where the velocity of separation is sufficiently low that the volume of the molten metal is independent of the velocity, and second, the dynamic bridge where the velocity of separation is sufficiently high that the volume,of the molten metal is dependent on the velocity. The critical velocity, which divides two types of bridges, is determined solely by the contact current and thermal properties of metals. The experiment was carried out by Pd and stainless steel contacts by using an arrangement allowing contacts to be operated at high controlled velocity of separation.

The formation and rupture of molten metal bridges in electrical contacts

The bridge of molten metal which is formed between the electrodes of an electrical contact is of considerable interest from a fundamental physical point of view. It is also of practical importance as the cause of erosion and failure of such contacts, which is due to the transfer of metals from one electrode to the other after repeated operations of the contact. The theory of the formation, development and rupture of contact bridges is discussed, and an experimental study of the properties of bridges between slowly opening contacts is described. Observations have been made on bridges in the ordinary atmosphere andin vacuo. The method of producing bridges for visual examination in air andin vacuo has been applied to an investigation of bridges of the noble metals, and of the readily oxidizable base metals. The temperature in a bridge can reach very high values, approaching the boiling point of the metal, with a potential difference of only one to two volts between the electrodes. Theoretical predictions of the shape of molten metal bridges as controlled by the temperature distribution and by surface tension and electrodynamic forces are compared with the shapes actually observed. Photographs of bridges showing the agreement between theory and experiment are given. The potential difference between the electrodes when the rupture of the bridge takes place, — the rupture voltage, has been measured for a number of metals: Pt, Pd, Ag, Au, Cu, Fe, Ni, W, Mo and Sn. The results are discussed in relation to theories of the cause and the mode of rupture and to the electrical and thermal properties of metals at high temperatures.

Effects of band shape on the magnetic and thermal properties of metals and alloys

The temperature variations of the electronic contributions to the paramagnetic susceptibility, χ , and specific heat C , of metals are calculated for various forms of electronic energy bands. The band shapes considered are those corresponding to density of states relations of the form d ν /d ε = ν ' = 2 a n ε n for n = 1, 2, 3 and ν ' = 2( a 0 + a 3 ε 3 ) for a range of values of ( a 3 / a 0 ). The variations of χ and C are presented graphically for effectively the whole temperature range in each case. It is shown, in particular, that with ν ' = 2 a n ε n , χ decreases monotonically with increasing temperature, T , but that with ν ' = 2( a 0 + a 3 ε 3 ) the χ , T curve may have a maximum for a certain range of values of ( a 3 / a 0 ). The effects of band closure and band overlap are also considered, and results are presented graphically for χ and C as functions of temperature for ( a ) a single closed rectangular band, ( b ) two overlapping infinite rectangular bands and ( c ) two overlapping closed rectangular bands. The status of the collective electron treatment of metals, on which the present work is based, is briefly discussed with respect to the more general theory of metals. A short discussion is also given of the theoretical results in relation to the relevant experimental results, and, in particular, in relation to the properties of palladium and of some of its alloys with silver.

Diamagnetism due to free electrons

According to the electron theory of the electrical and thermal properties of metals, these bodies contain a large number of negative electrons, which move about between the metallic atoms like the molecules of a gas. This theory explains satisfactorily several of the fundamental facts, such as the emission of electrons from hot metals, Ohm’s law, and Wiedemann and Franz’s law, but fails in its simple form to account for the different values of the Hall effect and other phenomena. More elaborate forms of the electron theory, based on the quantum hypothesis, enable some of these difficulties to be removed.