Physical ageing of polypropylene in glassy state

Physical ageing behaviour of a semicrystalline polymer, polypropylene, has been studied at a pressure-temperature state (P=2.5 kbar,T=15° C) for which the amorphous region is in the glassy state. Polypropylene contains 57% crystallinity and its glass transition temperature at atmospheric condition is −20° C. The ageing behaviour was monitored by measuring the Young's modulus (E) from the stress-strain curves as a function of ageing time up to 200 h. The Young's modulus of the rapidly pressure quenched samples increased at 0.4% per ageing hour of the initial value for up to 30 h and tapered off thereafter. The glassy polypropylene also exhibited a memory behaviour when it was given a pressure perturbation.     

Study of omeprazole-gamma-cyclodextrin complexation in the solid state

The possibility of obtaining inclusion complexes between omeprazole (OME) and γ-cyclodextrin (γ-CD) by kneading, spray-drying, coprecipitation, and freeze-drying was evaluated. All these methods lead to the isolation of a true inclusion compound, as evidenced by differential scanning calorimetry (DSC), infrared spectroscopy, and X-ray diffractometry on powder (PXRD). Moreover, PXRD and scanning electron microscopy (SEM) afforded data concerning crystallinity and surface characteristics of the solid phases obtained. In all cases, a significant increase of the release rate with respect to the drug alone was found, and it was attributed to the formation of an inclusion compound. Among the solid phases obtained, the coprecipitated product presented the highest dissolution rate.     

Relevance of liquid state to solid state properties

We outline in this talk the beginning of a new programme to study physical properties of crystalline solids. It is based on considering the latter, a broken symmetry phase, in terms of the higher symmetry liquid phase. The solid is a calculable perturbation on the fluid. This is exactly opposite to the standard approach which relates mechanical properties to the behaviour of defects (mainly dislocations) etc., in an otherwise perfect crystalline solid. However, most other broken symmetry phases (e.g. ferromagnets) are discussed starting from a symmetric Hamiltonian or a free energy functional, and earlier work by one of the authors shows that the liquid-solid transition is well described, qualitatively and quantitatively, by this approach. On the other hand, defect theories of melting have a long record of nonsuccess. In the first part of the talk, the density wave theory of freezing will be outlined, and it will be shown how properties such as Debye Waller factor, entropy change of freezing etc. can be calculated with no or one free parameter. The problem of calculating shear elastic constants and dislocation core structures as well as energies in terms only of observable liquid state properties will be set up, and results presented. The method will be contrasted with zero temperature ‘atomistic’ models which obscure the essential dependence on structure and flounder in a mass of detail. The concluding part will describe further proposed applications, some suggestive experimental results extant in the literature, and some speculations. Only a summary is presented.     

Crystallinity of isotactic polypropylene films annealed from the quenched state

Quenched isotactic polypropylene films were annealed at 130, 140 and 155 °C for 24 h. The structural organization, after annealing, was analysed by wide-angle X-ray diffractograms (WAXD), differential scanning calorimetry (DSC), density and sorption of dichloromethane vapour at low activity. The comparison of the different methods used to obtain the crystallinity shows that, even at the highest annealing temperature, the transformation of the smectic phase into the monoclinic phase, is not complete. WAXD and DSC give the amount of monoclinic phase, whereas the amorphous fraction was derived from sorption of dichloromethane vapour at low activity. From the density, it was possible to derive the residual smectic fraction in the different samples. The results indicate that, at temperatures higher than 150 °C, there is an accelerated decrease of smectic phase and an accelerated increase in the crystal dimensions and perfection.     

The rotating solid disk in the fully plastic state

Subject of the investigation is the distribution of stress, displacement, and plastic strain in a rotating solid disk of elastic-plastic material with linear strain-hardening in the fully plastic state. In order to obtain a realistic model of the rotating disk one may not neglect hardening. Since the onset of plastic flow occurs at the axis of the disk the corresponding image-point lies in a corner of Tresca's hexagon. As in related cases, the plastic zone of the rotating disk is composed of two parts, the image points of the outer part lying on one side of the hexagon. It is demonstrated that the boundary between the two regions approaches a limit for unbounded growth of the angular velocity. Residual stress remaining in the disk after the standstill is discussed.     

Effect of water on monetite synthesis in the solid state

Synthesis of calcium hydrogen phosphate CaHPO₄ can be carried out with a milling apparatus into which solid calcium dihydrogen phosphate Ca(H₂PO₄)₂.H₂O and tricalcium phosphate Ca₃(PO₄)₂.1/6H₂O mixtures are introduced. The effect of water vapor pressure P_H2O on this reaction has been investigated. At a given temperature (60°C) the curves of degree of conversion as a function of milling time depend on P_H2O. Formation of brushite CaHPO₄.2H₂O during the course of reaction can be noted for a particular range of water vapor pressure.If some amounts of brushite are added to the initial mixture, the kinetics of the reaction developed under water vapor are increased. Experiments on the evolution of products after a milling treatment give evidence of the important dependence of the reaction rate on water vapor pressure.     

Micrometer-level naked-eye detection of caesium particulates in the solid state

Abstract

Large amounts of radioactive material were released from the Fukushima Daiichi nuclear plant in Japan, contaminating the local environment. During the early stages of such nuclear accidents, iodine I-131 (half-life 8.02 d) is usually detectable in the surrounding atmosphere and bodies of water. On the other hand, in the long-term, soil and water contamination by Cs-137, which has a half-life of 30.17 years, is a serious problem. In Japan, the government is planning and carrying out radioactive decontamination operations not only with public agencies but also non-governmental organizations, making radiation measurements within Japan. If caesium (also radiocaesium) could be detected by the naked eye then its environmental remediation would be facilitated. Supramolecular material approaches, such as host–guest chemistry, are useful in the design of high-resolution molecular sensors and can be used to convert molecular-recognition processes into optical signals. In this work, we have developed molecular materials (here, phenols) as an optical probe for caesium cation-containing particles with implementation based on simple spray-on reagents and a commonly available fluorescent lamp for naked-eye detection in the solid state. This chemical optical probe provides a higher spatial resolution than existing radioscopes and gamma-ray cameras.     

Elastic stiffness of crystalline cellulose in the folded-chain solid state

In previous papers the axial stiffness of crystalline native cellulose has been calculated for two proposed configurations of the cellulose chains within the elementary fibrils: an extended chain configuration, and a configuration in which the chains are folded to form a ribbon which in turn is helically wound into a rather open, spring-like structure. In the present paper two additional folded-chain configurations are treated: a more tightly wound helical configuration in which axial secondary bonds are formed between adjacent turns of the helix; and a configuration in which the chains are folded rather infrequently and remain in a fully-dense close-packed arrangement. It is shown that this last configuration is mechanically equivalent to the extended chain configuration so far as axial stiffness is concerned, and that either helical configuration has a substantially lower axial stiffness than that of the extended chain.The investigation reported in this paper (No. 69-8-64) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director.     

Gold-to-alumina solid state reaction bonding

This paper describes methods by which strong vacuum-tight bonds between gold and alumina can be fabricated in an air atmosphere. Temperature was found to be a sensitive factor in bond formation; the higher the temperature, the stronger the bond, provided that the temperature remained below the melting point of gold. Intimate contact between the bonding gold and alumina surfaces during formation of the bond was also an important consideration. This was achieved by using an optically flat and polished ceramic surface and applying a low pressure of about 1 MPa to the bonding couple. Further enhancement of the contact can be achieved by depositing an additional thin layer of gold onto the ceramic surface by evaporation or by other means, and by thorough cleaning by high temperature heat treatment prior to bonding. Good bonding occurs in the range of 1 to 100 h. Bond strengths as high as 80 MPa were achieved.     

The solid state diffusion pump

The concept of a solid state diffusion pump is discussed. In such a device, ionized atoms are injected into a membrane which separates the pumped region and a higher pressure backing region. The injected ions are not stored indefinitely in this membrane as in ion pump geometry however but are transported across the membrane by diffusion. Diffusion across the membrane is enhanced by a thermal gradient or, more practically, by producing a defect gradient in the membrane by simultaneous ion irradiation from the backing region.     

Quantum computing in the solid state: the challenge of decoherence

The current status of solid-state implementations of quantum computing is briefly described. There are numerous candidate proposals, but only comparatively recently have some of them begun to progress to the point of demonstrating coherent motion of the individual quantum bits (qubits), and the controlled coupling of more than one qubit remains a significant challenge. We also present a generalization of the fluctuation-dissipation theorem that provides a relationship between the coherent evolution entangling two spatially separated qubits, and the associated irreducible decoherence. This relationship may be used to bound the maximum attainable figures of merit in proposed two-qubit gates.     

A solid state Pomeranchuk refrigerator

Recently we have shown that YbInCu₄ and related compounds present a solid state Pomeranchuk effect. At their first order volume transition, a local moment phase coexist with a renormalized Fermi liquid in analogy with ³He at its melting curve. This structural transition can be affected by pressure and magnetic field. We show here that as in ³He the Pomeranchuk effect can be used to produce cooling. We discuss the efficiency and different ways of implementing the solid state Pomeranchuk refrigerator.     

Material state remapping in computational solid mechanics

A computational procedure for remapping material state information from one finite element mesh to another is described. The procedure is useful in connection with evolving meshes for inelastic problems, as for example occur in the context of fracture simulation and adaptive mesh refinement. The proposed method is based on weak enforcement of equality between corresponding fields on the two meshes, where piecewise‐constant fields on both meshes are generalized from the quadrature‐point values. The essential algorithmic problem is that of calculating the volume partition of an arbitrary convex region with respect to a covering set of disjoint convex regions. Instead of geometrically resolving the associated intersections, the problem is herein approximated by a constrained optimization problem, which may be readily and efficiently solved computationally. This formulation is a main contribution of the paper. Computational examples are given that illustrate the effectiveness of the proposed procedure. Copyright © 2002 John Wiley & Sons, Ltd.     

Stress-strain state of solid railway wheels

A method for the design of railway wheels, which is based on use of the semianalytical finite-element method and which makes it possible to account for both the forces of contact interaction between the wheel and rail and negative production clearance during the press fitting of wheels, is developed.Translated from Problemy Prochnosti, No. 10, pp. 75–78, October, 1990.     

Role of stacking faults in solid state transformations

This article illustrates the two different roles played by stacking faults in solid state transformations viz. (i) in accommodating part of the transformation strains as observed in the noble metal-based alloys undergoing martensitic transformations, and (ii) in providing a mechanism for changing the stacking sequence of layers in a variety of materials like SiC, ZnS, Co and its alloys, and certain steels. Diffraction patterns taken from the martensitic phases of noble-metal-based alloys as well as from SiC and ZnS crystals undergoing transformation from one close-packed modification to another reveal the presence of characteristic diffuse streaks. It is shown that from a theoretical analysis of the observed intensity distribution along streaked reciprocal lattice rows in terms of physically plausible models for the geometry and distribution of faults, one can make a choice between various possible routes for transformation. From simple computer simulation studies, it is shown that the observed arrest of transformations in SiC is essentially due to the insertion of stacking faults in a random space and time sequence leading to an irregular distribution of solitons.