High magnetic and ferroelectric properties of BZT-LSM multiferroic composites at room temperature

In this research, the effects of La_0.7Sr_0.3MnO₃ additive on the phase evolution, microstructure, dielectric, ferroelectric and magnetic properties of BaZr_0.07Ti_0.93O₃ ceramics were systematically investigated. The (BaZr_0.07Ti_0.93O₃)/x(La_0.7Sr_0.3MnO₃) or BZT/xLSM (where x?=?0, 5, 10 and 20?mol%) ceramics were prepared via a solid state reaction method. A pure perovskite phase is observed for the samples of x?≤?10?mol%. The M-H hysteresis loops also show an improvement in the magnetic behavior for higher LSM content samples as well as the modified ferroelectric properties. However, the 5?mol% sample exhibited the optimum ferroelectric and ferromagnetic properties with remnant magnetization (M_r) and remanent polarization (P_r) of 2.38?emu/g and 10.5?µC/cm², respectively. The dielectric-temperature curves show that the two phase-transition temperatures as observed for the unmodified BZT ceramic merges into a single phase-transition temperature for the 5?mol% sample and then become flat curves for the 10?mol% sample. In addition, the mechanical properties i.e. Knoop hardness and Young's modulus values increase with increasing LSM content, where Knoop hardness and Young's modulus values for the 20?mol% sample are increased by ~ 45% and ~ 104%, respectively, as compared to the unmodified sample.     

Mechanical,hygroscopic, and thermal properties of metal particle and metal evaporated tapes and their individual layers

Mechanical and thermal properties of magnetic tapes and their individual layers strongly affect the tribology of magnetic head–tape interface and reliability of tape drives. Dynamic mechanical analysis, longitudinal creep, lateral creep, Poisson's ratio, the coefficient of hygroscopic expansion (CHE), and the coefficient of thermal expansion (CTE) tests were performed on magnetic tapes, tapes with front coat or back coat removed, substrates (with front and back coats removed), and never‐coated virgin films of the substrates. Storage modulus and loss tangent values were obtained at a frequency range from 0.016 to 28 Hz, and at a temperature range from ?50 to 150 or 210°C. Longitudinal creep tests were performed at 25°C/50% RH, 40°C/25% RH, and 55°C/10% RH for 50 h. The Poisson's ratio and lateral creep were measured at 25°C/50% RH. CHE was measured at 25°C/15–80% RH. CTE values of various samples were measured at a temperature range from 30 to 70°C. The tapes used in this research included two magnetic particle (MP) tapes and two metal evaporated (ME) tapes that were based on poly(ethylene terephthalate) and poly(ethylene naphthalate) substrates. The master curves of storage modulus and creep compliance for these samples were generated for a frequency range from 10^?20 to 10¹⁵ Hz. The effect of tape manufacturing process on the various mechanical properties of substrates was analyzed by comparing the data for the substrates (with front and back coats removed) and the never‐coated virgin films. A model based on the rule of mixtures was developed to determine the storage modulus, complex modulus, creep compliance, and CTE for the front coat and back coat of MP and ME tapes. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1319–1345, 2004     

The role of Pb and annealing temperature on the structural,magnetic, optical and dielectric properties of W-type hexaferrite nanostructures

In this paper, W-type Sr_1-xPb_xCo₂Fe₁₆O₂₇ nanostructures were synthesized by auto-combustion sol-gel method. Then, the effects of annealing temperature and Pb contents on the structural, magnetic, optical, and dielectric properties of Sr_1-xPb_xCo₂Fe₁₆O₂₇ nanostructure were investigated. First, a gel of metal nitrates with a specific molar ratio with x different was prepared and then the gel was annealed at different temperatures for 4?h. To determine the annealing temperature of the samples, the prepared gel was examined by thermogravimetric analysis and differential thermal analysis. The morphology and crystal structure of the prepared samples were characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction pattern (XRD). The results of XRD patterns indicated that the annealing temperature of synthesized Sr_1-xPb_xCo₂Fe₁₆O₂₇ was reduced by increasing Pb contents. In addition, FESEM images showed that the microstructure of the samples was homogeneous and uniform, but since the samples have a magnetic property, the particles were aggregated. Fourier transform infrared analysis (FT-IR) was used to confirm the phase formation. The FT-IR results of the samples indicated that the tetrahedral and octahedral sites, which are the important attributes of hexaferrites, were formed. The magnetic properties of the samples were measured by vibrating sample magnetometer (VSM). The VSM results of the samples showed that because of increasing Pb content, the amount of saturation magnetization and that of magnetic coercivity decreased from 81.29 to 10.23?emu/g and 2285–477?Oe, respectively. The optical properties of the samples were investigated by ultraviolet–visible spectroscopy, which revealed that the energy gap decreases and the absorption peaks move towards longer wavelengths by increasing Pb content. The dielectric properties of the samples were investigated by the LCR meter. It was found that by increasing frequency, the dielectric constant (ε^′) and the dielectric loss (?) of the samples were decreased.     

Critical current density and mechanical performance of MgB2 superconductors prepared with different magnesium sources

In this study, the critical current density and mechanical performance of MgB₂ superconductors prepared using different magnesium sources (Mg and MgH₂ with 99.9% and 96.5% purities, respectively) were analyzed. When the samples were characterized structurally and electrically, we found that the grain sizes were about 40?nm and transition temperature was around 30?K being lower than the literature. Critical current densities of all samples were calculated using Bean's model and our calculations yielded critical current density values higher than 10⁶?A?cm^?2 in self-field. The highest critical transition temperature value belongs to M800 (Mg with 99.9% purity) sample and when the critical current density and transition temperature values of this sample are considered, this sample appears to have the potential for practical use. Vicker's microhardness measurements were performed and yield stress (Y), elastic modulus (E), brittleness (B_i), ductility (D) and fracture toughness (K_IC) were calculated. All samples exhibited Indentation Size Effect (ISE) and microhardness measurements were compared with some microhardness models with were compatible with ISE behavior.     

Porous cordierite-based ceramics processed by starch consolidation casting – Microstructure and high-temperature mechanical behavior

Porous cordierite-based ceramics with different microstructural features and mechanical behavior were formed by starch consolidation casting (SCC) using native potato and corn starches and sintered at 1275, 1300 and 1330 °C. The composition and microstructure of the ceramic materials were investigated via quantitative phase analysis using X-ray diffraction (with Rietveld refinement), the Archimedes method, mercury porosimetry, scanning electron microscopy and optical microscopy with stereology-based image analysis. The mechanical behavior of samples was evaluated by diametral compression tests at room temperature, 1000 and 1100 °C. The type of starch used and the sintering temperatures were the main factors determining the characteristics of the developed porous microstructures. Materials prepared with corn starch achieved the lowest porosity and the lowest values of mean chord length, mean pore distance and pore throat size. Because of these features, these materials thus presented, in general, higher values of apparent Young's modulus, elastic limit and mechanical strength than those prepared with potato starch. Despite the presence of a silicate glassy phase, both porous materials, mainly those prepared with corn starch, still enhanced the basic mechanical properties at high temperature, in particular, the mechanical strength and the apparent Young's modulus due to the special combination of the porous microstructure features.     

Structural,magnetic and elastic properties of Mn0.3−xMgxCu0.2Zn0.5Fe3O4 nanoparticles

In this paper, Mn_0.3?xMg_xCu_0.2Zn_0.5Fe₃O₄ (x?=?0.00, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30) nanoparticles were prepared by the nitrate-citrate technique at low temperature. The structural, microstructural, magnetic and elastic properties of the samples were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy, Transmission electron microscopy, field emission-scanning electron microscopy and vibrating-sample magnetometer at room temperature. Rietveld refinement of the XRD patterns indicated the formation of the single phase cubic spinel structure (space group Fd-3m) without any detectable impurity phase in all the samples that also was confirmed by FTIR studies. The lattice parameter is found to increase non-monotonically with an increase in Mg ion concentration. Also, the bond lengths and bond angles (A and B sites) of the studied ferrites were calculated by the refining of the XRD data. The values of the crystallite size decrease with increasing micro-strain (and conversely) and both of them reach extremum at x?=?0.15. The low remanence and coercivity values confirmed the formation of the superparamagnetic ferrites nanoparticles. The saturation magnetization of the samples gradually grows with Mg substitution and reach extremum at x?=?0.15. Variation of saturation magnetization with Mg content can be mainly attributed to change of cation distribution, and Yafet-Kittel angle occurred between magnetic moments on B-site in the samples. The values of Young's modulus, Debye temperature, bulk modulus, rigidity modulus of the samples were determined by the values of elastic constant and wave velocities obtained from the force constants. The improvement of the elastic properties of sample x?=?0.05 could be explained regarding the smaller values of the lattice parameter (a), the bond length and angle and the smaller crystallite size.     

In vitro bioactivity,physical and mechanical properties of carbonated-fluoroapatite during mechanochemical synthesis

Mechanochemical synthesis method has been used to prepare nanocrystalline B-type carbonated fluoroapatite (B-CFA). Fourier transform infrared (FTIR) spectroscopy along with X-ray diffraction (XRD) technique was carried out to investigate the effect of milling time on the preparation of B-CFA. In vitro bioactivity of FA during synthesis was examined also by FTIR spectroscopy after soaking in simulated body fluid (SBF). Furthermore, the mechanical properties including hardness, fracture toughness, compressive strength, longitudinal modulus, Young's modulus, shear modulus and bulk modulus of the sintered samples, at 1000 and 1200?°C, for different milling times were measured by ultrasonic non-destructive technique. Furthermore, theoretical model is presented for FA according to the formula Ca₁₀(PO₄)₆F₂·18H₂O. The QSAR properties including log P, total energy, heat of formation, energy gap, dipole moment, ionization potential, polarizability, molar refractivity and molecular weight were calculated. FTIR and XRD results revealed that single phase B-CFA was successfully formed after 9?h of milling. Moreover, the results also pointed out that the total energy of FA is much more than hydroxyapatite (HA) indicating that the structure of FA is more stable than HA. These results are in agreement with XRD ones for the sintered samples where they did not undergo decomposition reflecting its thermal stability.     

Dynamic mechanical analysis of magnetic tapes at ultra‐low frequencies

A custom, ultra‐low frequency, dynamic mechanical analyzer (ULDMA) has been developed to study the correlated effects of temperature and frequency on the viscoelastic behavior of magnetic tapes. It has been used to acquire data needed for the development of future magnetic tapes that require an archival life of up to 100 years. A range of elevated temperatures is used to simulate real‐world storage environments, which enables the investigation of how the viscoelastic characteristics of tape samples influence the extent to which the tape deforms. The experiments and subsequent analysis examine the influence of the molecular structure on the viscoelasticity of magnetic tapes. Experiments were performed on a variety of magnetic tapes, including poly(ethylene terephthalate) (PET), poly(ethylene naphthalate) (PEN), metalized PET (M‐PET), and metalized Spaltan (M‐SPA). Additional experiments examined PEN and PET substrates by removing the front and back magnetic layers from the tape sample. Because of the viscoelastic behavior of the tapes, a time delay was present between the strain and stress signals, which was determined using a Fourier transform program. The elastic modulus (E), storage modulus (E′), loss modulus (E″), and loss tangent (tan δ) were obtained from the time delay for each of the ULDMA experiments at 25, 50, and 70°C over the frequency range of 0.0100–0.0667 Hz. Plots of these mechanical characteristics demonstrate the ability of frequency and temperature to affect trends associated with mechanical and thermal properties. Finally, some samples displayed an initial relaxation during the ULDMA experiments, which, when modeled using Maxwell's viscoelastic model, provided an insight into the relaxation characteristics of the samples. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Microstructure, magnetic and mechanical properties of Ni-Zn ferrites prepared by powder injection moulding

Nowadays, the electronic industry demands small and complex parts as a consequence of the miniaturization of electronic devices. Powder injection moulding (PIM) is an emerging technique for the manufacturing of magnetic ceramics. In this paper, we analyze the sintering process, between 900 °C and 1300 °C, of Ni-Zn ferrites prepared by PIM. In particular, the densification behaviour, microstructure and mechanical properties of samples with toroidal and bar geometry were analyzed at different temperatures. Additionally, the magnetic behaviour (complex permeability and magnetic losses factor) of these compacts was compared with that of samples prepared by conventional powder compaction. Finally, the mechanical behaviour (elastic modulus, flexure strength and fracture toughness) was analyzed as a function of the powder loading of feedstock. The final microstructure of prepared samples was correlated with the macroscopic behaviour. A good agreement was established between the densities and population of defects found in the materials depending on the sintering conditions. In general, the final mechanical and magnetic properties of PIM samples were enhanced relative those obtained by uniaxial compaction.     

Dielectric,magnetic, and mechanical properties of composites consisting of biopolymer chitosan matrix and hybrid spinel/cellulose filler

The composites consisting of a biopolymer chitosan matrix and hybrid spinel/cellulose filler were prepared by solvent casting method whereas the spinel CoFe₂O₄ was obtained by mechanical synthesis followed by thermal annealing. Incorporation of cellulose to the spinel – chitosan composite significantly modified dielectric, magnetic and mechanical properties of a composite consisting of the biopolymer with hybrid filler. In dielectric response the presence of the filler in the chitosan matrix hindered the molecular motion. The lowering of the activation energy and the cooperativity of the motion was observed. According to the magnetic properties, addition of cellulose to the filler enhanced coercivity field H_c in comparison to the pure spinel powder from value 0.1453 to 0.2033?T. In mechanical properties incorporation of the filler resulted in improvement of Young's modulus and tensile strength in comparison to unfilled chitosan. For composites with nanocellulose filler tensile strength was over two times higher than for chitosan.     

Ageing behavior of acrylic polyurethane varnish coating in artificial weathering environments

Polyurethane-based coatings reinforced by ZnO nanoparticles (about 27 nm) were prepared via solution blending. The ZnO/PU films and coats were fabricated by a simple method of solution casting and evaporation. The mechanical properties of the films were investigated by a universal material test, and the abrasion resistance of the prepared coats was evaluated by a pencil-abrasion-resistance tester. It was found that significant improvement of the PU films in Young’s modulus and tensile strength was achieved by incorporating ZnO nanoparticles up to 2.0 wt%, and that the abrasion resistance of the PU coats was greatly enhanced due to the addition of ZnO nanoparticles. Moreover, the antibacterial property test was carried out via the agar dilution method and the result indicated that PU films doped with ZnO nanoparticles showed excellent antibacterial activity, especially for Escherichia coli.     

Heat resistance and thermomechanical behaviour of ultralow and zero cement castables

Abstract

Knowledge of relative heat resistance as well as thermo-mechanical behaviour of refractory castables is very important for their use as linings in high temperature furnaces and refining vessels in the metallurgical, cement, and petrochemical industries. The present work aims at studying these properties for different types of refractory castable. Two classes of castable were prepared, namely ultralow and zero cement, containing either high alumina cement or hydratable alumina as bonding agent. For each class, two different castable systems were prepared, one containing an alumina-silica mixture in its matrix and the other containing magnesia-alumina. In all castables studied, calcined alumina was used as aggregate. The prepared castable samples were subjected to firing temperatures up to 1500°C. Relative heat resistance, bending strength before and after thermal cycling, hot modulus of rupture, and creep deformation were measured according to international standard specifications. It was concluded that a limited content of cement (ultralow cement castables) is beneficial with the magnesia-alumina mix in the matrix owing to the formation of calcium hexaluminate-magnesium aluminate-corundum (matrix advantage system) that results in excellent relative heat resistance as well as thermome-chanical properties. Zero cement castables on the other hand are recommended for use with the alumina-silica mixture, since the absence of cement improves the chances of mullite formation without glassy phases, thereby enhancing the properties of such refractory castables.     

Dielectric,mechanical and thermal properties of some chlorinated poly (p-phenylene oxide)s in the solid state

The dielectric, mechanical and thermal properties were investigated for poly(2,6-dichloro-1,4-phenylene oxide) (PDCPO), poly(2-chloro-6-methyl-1,4-phenylene oxide) (PCMPO) and poly(2,6-dimethyl-1,4-phenylene oxide) (PDMPO). PDCPO exhibited two dielectric secondary relaxations designated as β and γ processes around 160 and 100K, respectively. The γ process was assigned to the motion of a trace of chloroform included in the PDCPO film. A blend film PDMPO/PCMPO ($\text{9}\text{1}$ mixing ratio) exhibited dielectric relaxation around 330K and the process was assigned to the rotation of phenyl group with respect to oxygen-phenyl-oxygen axis. No dielectric relaxation was observed for the PDMPO film dried carefully, while the PDMPO film kept under an atmosphere of water vapour exhibited dielectric relaxation due to the motion of the water molecules at about 180K. Tensile stress at break measured on PDCPO prepared by Stamatoff's method was 38 MPa and was much higher than that for PDCPO prepared by the method reported by Blanchard et al. Temperature dependence of the dynamic Young's modulus for PDCPO measured at 110 Hz exhibited no appreciable loss peak in the range below 480K. Glass transition temperatures for PDCPO, PCMPO and PDMPO were determined to be 490, 445 and 500K, respectively, by differential scanning calorimetry.     

Mechanical properties of hybrid computer-aided design/computer-aided manufacturing (CAD/CAM) materials after aging treatments

The purpose of this study was to evaluate and compare the changes in the various mechanical properties of hybrid and conventional CAD/CAM materials after accelerated aging using hydrothermal processes.Five kinds of hybrid and ceramic CAD/CAM blocks were selected. A total of 225 specimens were prepared with highly polished surfaces, in the form of round discs (diameter 12?mm, thickness 1.2?mm), and were divided into three groups (the control group, thermal cycling group, and autoclave group [n?=?15, each]). The nanoindentation hardness and Young's modulus (nanoindenter), biaxial flexural strength (ball-on-ring test system), surface roughness (atomic force microscopy), surface texture (scanning electron microscopy (SEM)), and elemental concentrations (energy dispersive spectroscopy) were evaluated. The Kruskal–Wallis test and Mann–Whitney U test were used to determine statistical significance (P?<?0.05).The nanoindentation hardness and Young's modulus of the hybrid CAD/CAM materials were lower than those of ceramic materials, and they decreased after autoclave treatment. Among the hybrid CAD/CAM materials, Vita Enamic alone showed no significant difference in the Young's modulus after autoclave treatment; it also exhibited the highest nanoindentation hardness and modulus. There were significant changes in the biaxial flexural strength of hybrid CAD/CAM materials after aging. However, there was no change in the biaxial flexural strength of ceramic materials. The surface roughness of all materials, except CeraSmart, changed after aging. The SEM observations indicated a loss of filler particles in Lava Ultimate and morphological changes in IPS e.max ZirCAD, after aging.The ceramic CAD/CAM materials are superior to hybrid CAD/CAM materials in terms of the mechanical properties. The accelerated aging procedure induced changes in the mechanical properties of some hybrid CAD/CAM materials. Therefore, when using hybrid CAD/CAM materials, it is important to understand the behaviors of the various properties of each material as time progresses, and long-term follow up is necessary.     

Physical,structural, morphological,magnetic and electrical properties of Co0.5-xNixZn0.5Fe2O4 nanocrystalline ferrites

A series of Co_0.5-xNi_xZn_0.5Fe₂O₄ (x?=?0–0.25 insteps of 0.05) nano crystalline ferrites were synthesized in combustion method using citric acid as fuel. Densities and porosities were calculated using the lattice constant and Archimedes's principle. A linear increase in experimental density and a decrease in porosity were observed with increase in nickel concentration. Cationic distribution was proposed on the basis of theoretical lattice constant and it was correlated with the variation in magnetic and electrical properties of all samples. TEM image of the sample with nickel concentration x?=?0.15 indicated the existence of nano-metric range particles and the sample was characterized with the help of inter-planar spacing(s) from SAED pattern. Morphological and surface analysis was studies using Scanning Electron Microscopy and well developed nearly spherical grains were observed with increase in nickel concentration. Energy Dispersive Spectroscopic (EDS) analysis was performed for all nickel substituted samples and all displayed stoichiometric proportions of ions in the samples as per the chemical composition. Elemental mapping was done for all samples using EDS data. Curie temperature was dropped nearly 90?°C at the end of the series. Initial permeability showed slight variation with an increase in nickel concentration and it remained nearly constant with frequency up to 3?MHz. Magnetic loss was observed to be constant for all samples after 100?kHz. DC Electrical resistivities of all samples were measured and all samples displayed resistivity in the order of 10⁸ Ω-cm. AC resistivity and dielectric studies were conducted from 100?Hz to 5?MHz for all samples. Dielectric constant and losses of all samples exhibited very low values compared to that of conventional ferrites. The electrical properties of all samples were discussed with the help of temperature variation of resistivity, activation energy, grain size, density and porosity.     

Measurement of nanoindentation properties of polymers considering adhesion effects between AFM sharp indenter and material

Abstract

Nanomechanical properties of polymer samples were calculated using an adhesive contact model appropriate for AFM indentation problems. A series of Polydimethylsiloxane (PDMS) samples were indented by the sharp indenter in the air by using an AFM, and dozens of the force–displacement curves of each sample were obtained. An adhesive contact model suitable for sharp indentation with adhesion was established based on the same assumptions of the JKR model which is only suitable for spherical indentation at small penetration depth. Differences between sharp indentation problems with and without adhesion were discussed, and the limitations of the traditional adhesion model were given. The elastic modulus was obtained by fitting experimental force–displacement curves with theoretical ones, and results were compared to those macroscopic values in literature. The adhesion energy between the indenter and the sample surface was accurately calculated using the adhesion model based on the calculated elastic modulus. The influence of the indenter tip angle on the calculation results of the elastic modulus was also discussed theoretically. In this study, the mechanical properties of polymer samples were calculated at the nanoscale considering the adhesion effect.     

Dynamic mechanical and thermal analyses of magnetic particle and metal evaporated tapes and their individual layers

The mechanical and thermal properties of magnetic tapes and their individual layers strongly affect the tribology of the magnetic head–tape interface. Dynamic mechanical analysis and thermomechanical analysis tests were performed on magnetic tapes, tapes with front coat or back coat removed, substrates (with front and back coats removed), and never‐coated virgin films of the substrates. Storage modulus and loss tangent were obtained at a frequency range from 0.016 to 28 Hz, and at a temperature range from ?50 to 150 or 210°C. Coefficients of thermal expansion (CTE) of various samples were measured at a temperature range from 30 to 70°C. The tapes used in this research include two magnetic particle (MP) tapes and two metal evaporated (ME) tapes based on poly(ethylene terephthalate) and poly(ethylene naphthalate) substrates. The master curves of storage modulus for these samples were generated for a frequency range from 10^?20 to 10¹⁵ Hz. The effect of the tape manufacturing process on the dynamic mechanical properties of substrates was analyzed by comparing the data for the substrates (with front and back coats removed) and the never‐coated virgin films. A model based on the rule of mixtures was developed to determine the storage modulus, complex modulus, and CTE for the front coat and back coat of MP and ME tapes. To validate the procedure, data for these individual layers were then used to calculate the corresponding properties of the finished tape. The predicted results were compared with the experimental measurements. The data obtained in the study are also discussed in light of previously published lateral contraction, Poisson's ratio, CTE, and CHE (coefficient of hygroscopic expansion) data. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 548–567, 2003     

高模量沥青混凝土添加剂研究

针对南方和北方的不同气候特点,以回收聚烯烃为原料制备了AM系列高模量沥青混凝土添加剂,对所制备样品进行了红外(FTIR)和差示扫描量热分析(DSC).同时对高模量添加剂进行高温车辙试验、冻融劈裂试验和低温弯曲试验,并与基质沥青和市场样进行了对比,结果表明,高模量添加剂的加入可有效改善沥青混合料的高温性能和抗水损害性能.与市场样相比,所制备AM高模量添加剂使沥青混合料具有更好的抗水损害性能、高温和低温稳定性能.其中,AM-1更适合于南方地区路面的应用,而AM-2更适合于北方地区路面的应用.     

A correlation of Young's modulus with yield stress in oriented poly(vinyl chloride)

The variations of tensile and compressive yield stresses and of Young's modulus of oriented poly(vinyl chloride) sheet with direction and with degree of orientation, represented by birefringence, are shown. Young's modulus was calculated from elastic stiffness constants measured by an ultrasonic pulse method at 5MHz with estimated strain and strain rate amplitudes of 2 × 10^?5 and 100s^?1. Yield strains were about 5 × 10^?2 measured at strain rates of about 2 × 10^?2s^?1. Although the measuring conditions were so different there was found to be a close correlation between tensile yield stress and Young's modulus, the two quantities being connected by a simple linear relationship, as direction of measurement and degree of orientation were varied. Compressive yield stress did not correlate with Young's modulus, and changed little with direction or degree of orientation by comparison with tensile yield stress. The empirical linear relationship between tensile yield stress and Young's modulus, difficult to account for theoretically, might form the basis of a method for determining tensile yield stress ultrasonically.     

Studies of composites made by impregnation of porous bodies. 1. Sulphur impregnant in portland cement systems

Porous bodies formed by autoclaving portland cement-silica mixtures and by normally curing portland cement were characterized by measuring Young's modulus, microhardness and porosity. These bodies were impregnated almost completely with molten sulphur. The bodies were characterized again. It was found that the mechanical properties of the composites could be described by a form of Reuss' mixing law. Equations relating the improvement of the mechanical properties of the composite to the properties of the porous body were derived for both Young's modulus and microhardness.