The Melting Point of Palladium Using Miniature Fixed Points of Different Ceramic Materials: Part I—Principles and Performances

Fifteen miniature fixed-point cells made of three different ceramic crucible materials (\(\hbox {Al}_{2}\hbox {O}_{3},\, \hbox {ZrO}_{2}\), and \(\hbox {Al}_{2}\hbox {O}_{3} (86\,\%)+\hbox {ZrO}_{2}\) (14 %)) were filled with pure palladium and used for the calibration of type B thermocouples (Pt30%Rh/Pt6%Rh). The melting behavior of the palladium was investigated by using different high-temperature furnaces usable in horizontal and vertical positions. It was found that the electromotive forces measured at the melting temperature of palladium are consistent with a temperature equivalent of ±0.25 K when using a furnace with an adequate temperature homogeneity (±1 K over a length of 12 cm), independent of the ceramic crucible materials. The emfs measured in the one-zone furnaces with larger temperature gradients along the crucibles are sensitive related to the position of the crucibles in the temperature gradient of these furnaces. This is caused by higher parasitic heat flux effects which can cause measurement errors up to about \(\text {-}\)(1\(\text {-}\)2) K, depending on the thermal conductivity of the ceramic material. It was found that the emfs measured by using crucibles with lower thermal conductivity \((\hbox {ZrO}_{2})\) were less dependent on parasitic heat flux effects than crucibles made of material of higher thermal conductivity \((\hbox {Al}_{2}\hbox {O}_{3})\). The investigated miniature fixed points are suitable for the repeatable realization of the melting point of palladium to calibrate noble metal thermocouples without the disadvantages of the wire-bridge method or the wire-coil method.     

Several Theoretical Perspectives of Ferrite-Based Materials—Part 1: Transmission Line Theory and Microwave Absorption

A theoretical model for microwave absorption from both forced non-resonance oscillation and resonance is constructed using the transmission line theory familiar to microwave engineers. The model covers both the single-phase ferrite and its composites of interest to material scientists, and can be applied to a variety of different absorption mechanisms. The transmission line theory is also shown to be consistent with the band theory of solids, a relationship that has not been revealed previously. The work bridges the gap between the interests of microwave engineers and material scientists.     

Microstructural development and solidification cracking susceptibility of Cu deposits on steel: Part II—use of a Ni interlayer

The tool and die industry is interested in depositing Cu onto steel using direct metal deposition techniques in order to improve thermal management of mold dies manufactured from steel alloys. However, Cu is a known promoter of solidification cracking in steel. Ni, however, is known to improve weldability of Cu containing alloys and steel. The goal of this work was to identify the range of Ni concentrations necessary to eliminate solidification cracking in Steel–Cu deposits and understand the cracking susceptibility through analysis and modeling of microstructural development. A wide range of Steel–Ni–Cu deposits, containing up to 75 wt% Ni, and Ni–Cu deposits were fabricated using the Gas Tungsten Arc Welding (GTAW) process with cold wire feed. The Ni–Cu and Fe–Ni deposits were found to be crack free over the entire concentration range. However, Ni concentrations of up to 75 wt% were insufficient to eliminate cracking when subsequent layers of Cu were deposited. Therefore, to ensure crack free deposition of Cu onto Steel, the concentration of the interlayer must be 100 wt% Ni. The resultant microstructures were characterized by various microscopy techniques to understand the influence of Ni and Cu on solidification cracking of Steel. Additionally, solidification modeling was undertaken to determine the amount of terminal Cu rich liquid and solidification temperature range that would form under non-equilibrium solidification conditions.     

Requirements for and factors affecting high temperature capability: Part A of ‘The Requirements for the Limitations of Materials at High Temperatures’

Examples where high temperature technology is important are given. Aspects such as melting temperature, crystal structure, deformation, creep and fatigue are covered. Environmental effects such as oxidation, corrosion, erosion and wear are also considered.     

Analysis of symm≐tric cross-ply laminated elastic plates using a higher-order theory: Part I—Stress and displacement

A simple theory for bending of composite anisotropic plates that are laminated symmetrically about their mid-plane is presented. This theory incorporates transverse shear deformation and transverse normal stress as well as the higher-order effects and fulfills the static conditions on the external boundary planes. Further on, by using Lévy-type solutions considered in conjunction with the state space concept, the state of stress and displacement of rectangular plates for a variety of edge conditions is determined and the results are compared to their first-order shear deformation and classical counterparts, obtained by using the same state-space technique.     

Dynamics of Polymeric Fluids: Part II The Molecular Theory of Die Swell: Correlation of Ultimate Die Swelling Effect to the Molecular Parameters and the Operational Variables

A general expression for the correlation of the simple shear (tan(?)) to the molecular parameters and the shear rate (γ) was deduced. It shows that the simple shear (tan(?)) may be resolved into free recoil (recoverable strain) and viscous heating (unrecoverable strain). The magnitudes of the simple shears for recoil (tan(?)E) and (tan(?)V) for viscous heating not only depended on the molecular parameters and the operational variables, but also on the exponential fractions of the recoverable (1-Wγ) and unrecoverable (W-γ) conformations for recoil and viscous heating. Therefore the magnitudes of the simple shears (tan(?)E) for recoil and (tan(?)V) for viscous heating are, respectively, expressed as the partition function to the (1-Wγ)th power and the partition function to the (Wγ)th power. Thus correlations of the total recoil and the ultimately recoverable strains to the molecular parameters [n', a,η0, GN0 and (1-Wγ)] and the operational variables (γ, (L/D) and tr) were deduced respectively, which show that at very different shear rates (0≤γ≤∞) the polymeric liquids may exhibit a very different viscoelastic behaviors. After introducing the uniform two-dimensional extension, the definition of swelling ratio and the ratio of L to D [De=(L/D)], two expressions for the ultimate die swelling effect and the ultimate extrudate swelling ratio BEVT5 to the molecular parameters [n', a,η0, GN0 and (1-Wγ)] and the operational variables (γ, (L/D) and tr) were obtained. The two correlation expressions were verified by the experimental data of high-density polyethylene (HDPE) which shows that the two correlation expressions can be used to predict the correlations of the ultimate extrudate swelling behaviors of polymeric liquids to the molecular parameters and the operational variables.     

Wood—a 45th anniversary review of JMS papers. Part 1: The wood cell wall and mechanical properties

The first part of a comprehensive review of the literature on wood published in the Journal of Materials Science since its inception in 1966 is presented. Papers are reviewed by subject ranging from the determination of the microfibril angle in the wood cell wall through to the evaluation of fatigue life. The role of moisture content in determining mechanical properties of wood is explored and mechanical properties are reported including creep, fatigue and fracture. It is concluded that JMS has played a key role in disseminating state of the art literature on new developments in the understanding of the structure-related properties of wood.     

Chemical Equilibrium and Critical Phenomena: The Solubilities of Iron(III) Oxide and Cobalt(II,III) Oxide in Isobutyric Acid + Water Near the Consolute Point

The solubilities of iron(III) oxide, formula Fe₂O₃, and cobalt(II,III) oxide, formula Co₃O₄, have been determined in the liquid mixture, isobutyric acid + water, along the critical isopleth at temperatures above the upper critical solution temperature near 299 K. When plotted in van’t Hoff form with ln s versus 1/T, the measurements of solubility, s, lie on a straight line for values of the temperature, T, in kelvin, which are sufficiently in excess of the critical solution temperature, T _c. The sign of the slope, (? ln s/?(1/T)), indicates that in the case of both oxides, the dissolution reaction is endothermic. When the temperature is within 1K of T _c, however, the slope departs from its constant value and appears to diverge toward negative infinity. The principle of critical-point universality predicts that a divergence in (? ln s/?(1/T)) is to be expected for T near T _c in those cases where the stoichiometry of the dissolution reaction involves both components of the solvent; moreover, the Gibbs–Helmholtz equation predicts that, if the heat of solution is endothermic, the sign of the divergence should be negative. Both of these predictions are confirmed by the solubilities of Fe₂O₃ and Co₃O₄ measured as a function of temperature along the critical isopleth of isobutyric acid + water.     

Wetting behaviour of SiC ceramics: Part II—Y2O3/Al2O3 and Sm2O3/Al2O3

Wettability is the most significant phenomenon in SiC liquid phase sintering. The wetting of Y₂O₃/Al₂O₃ and Sm₂O₃/Al₂O₃ on SiC was analysed by the “Sessil drop” method. The wetting of liquid on solid during liquid phase sintering is very important. The behaviour of the additive on the SiC plate was observed using an imaging system with a CCD camera, and the contact angle measurements were analysed by Qwin Leica software. The samples were cut transversally and characterized by scanning electron microscopy and X-ray spectrometry (SEM/EDS). The wetting was found to be strongly influenced by the temperature; the SiC/additive contact angle decreased with increasing temperature. The YA and SA additives presented low contact angle values, indicating their good wetting on SiC in the argon atmosphere. The contact angle could not be measured when the test was performed in the nitrogen atmosphere because bubbles formed in the liquid during the test. The best atmosphere for this sintering was found to be argon, which allows uniform spreading.     

Reactions of alcohols with hydrogen sulfide over zeolites: Part V. The role of Brönsted acid sites in thiols formation — A comparative study of zeolites and heteropoly acids

The activity and selectivity of Me²⁺ NaX zeolites (Me = Cd, Zn, Ni, Co) and free and supported heteropoly acids (HPA) for hydrosulfurization of n- and i-PrOH have been investigated. The influence of concentration and strength of Brönsted acid centers on the yield of thiols is discussed on the basis of comparative measurements carried out on zeolites and HPA. The effect of H₂S chemisorption on the selectivity of hydrosulfurization process is considered.