Specimen characterization

Many early experiments on the viscoelastic behaviour of polymers were unsatisfactory because the specimens were inadequately characterized, so that like was not compared with like . 

Average moleeular mass and its distribution are both critical parameters, and all polymers eontain processing and stabilizing additives, which can sometimes have a signifieant effect on the response to stress and strain, particularly at temperatures well above that of the laboratory. 

The physieal structure of the polymer, in terms of morphology, crystallinity and molecular orientation, will also be important and should be well characterized. 

Further, a Zwick universal testing machine (Type 1474) served to measure the tensile modulus and tensile strength. This was carried out at room temperature and ambient conditions (approximately 50% humidity). The crosshead speed amounted to 1 mm/min. In addition, the broken samples were studied by scanning electron microscopy (SEM) (Jeol models JSM 5400 and JSM 6300). Thin films of dissolved samples were characterized by a Leitz transmission optical microscope. 

The resulting morphology in the different states (I)-(IV) can be made visible by cutting thin sections from (a) the bulk material before, during, and after moving the polymer 

The samples obtained by compression molding were rectangular in shape and had a geometry of approximately 50 mm in length and 4 mm in width. The samples produced by injection molding had the shape of a bone nail according to the geometry of a commercially available implant. 

The fibrils of the higher melting component possess a diameter varying from roughly 10 to 1 micrometers, and are uniformly stretched within the surroimding matrix. The latter has also experienced a certain degree of orientation, as evidenced by the oriented, stretched matrix tips formed during fracture of the oriented blend structure parallel to the fibrillation direction. 

MFC-bone nail PGA/PLA 20 80 Z = tension side D = pressure side 

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Titanium-supported Pt/Ti02 specimens characterized by cyclic voltammetry had an apparent (geometrical) area of 0.28 cm2. The measurements were carried out in an aq. 0.5 M NaHS0i,/0.5 M Na2S0t, solution kept at 20°C. The solution was saturated with Ar or CO under 1 atm. The potentials were monitored with respect to and are referred to the reversible hydrogen electrode (RHE) in the same solution. The cyclic-voltammetry procedure followed that conventionally employed with the potential swept, in general, at a rate of 0.1 V s-1. 

The Digital Material is a material description based on measurable quantities that provides the necessary link between simulation and experiment. Critical components of the Digital Material, a feature based material description with a statistical description of attributes, include 1) experimental methods that provide initial data for simulations and simulation methods to evolve the material attributes, 2) simulation tools that can be used to build virtual specimens, characterize them and compute material properties, 3) coordinated experiments to verify simulations and to supplement critical data and 4) accuracy assessment techniques for both simulation and experiment. Development of this program will itself require simulations and experiments of a fundamental nature. The output will be a model that will permit virtual experiments to be conducted on a two-phase material of previously selected and characterized microstructure. 

Many of the data published today are either erroneous or apply to inadequately characterized materials. Unrecognized systematic errors are frequently present in the measurement process, and consequently the data do not represent the property purportedly measured within the stated uncertainty. In other instances, the property measured is especially sensitive to unreported characteristics of the material. For example, the transport properties of pure metals and crystalline dielectric solids at low temperatures are determined almost entirely by the physical and chemical defects in them, rather than by their chemical or generic identification, such as copper, aluminum, etc. Great care must be exercised to characterize such materials, if reported data are to have any usefulness. Both the study of systematic errors and specimen characterization are of the utmost importance to the reliability and usefulness of data. This paper only considers the use of standard reference materials (SRMs) to reduce systematic errors in the measuring system. The problem of insufficient material characterization is an extensive subject in itself and will not be discussed further here. 

The establishment of reliable T-c phase diagrams in the R-H systems is intimately connected with an unambiguous specimen characterization and, hence, with a strict control of the preparation conditions. The lack of such a control in the past has frequently led to contradictory experimental results, in particular where non-stoichiometric compositions are concerned. It is, therefore, necessary to include in this section a relatively broad subsection on specimen preparation in order to optimize the sample quality, to determine the hydrogen concentration in the particular phase and, last but not least, to compare the data of different experiments. 

These institutes also take part in the specimen characterization by analyzing heavy metals, metalloids, and essential elements in environmental samples at the Research Centre Julich, whereas the corresponding activities at Munster comprise both the inorganic and also the organic (primarily chlorinated hydrocarbons) analysis. 

H-BEA (H-BETA) a proton exchanged BEA zeolite specimen, characterized by a three-dimensional network of pores consisting of three families of 12-ring interconnected channels [57]. The specimen here illustrated was characterized by a silica-to-alumina ratio = 4.9, corresponding to a distribution of A1 atoms per unit... 

BEA (BETA) an all-silica BEA zeolite specimen, characterized by the same three-dimensional network as H—BEA, but virtually free of A1 species in that the silica-to-alumina ratio was... 

In the following, the adsorption of CO on a H-BEA zeolite specimen, characterized by both Brpnsted and Lewis acidic sites (consisting these latter of structural defects in zeolite framework), wiU be discussed. 

A workshop was held in 2002 to discuss the structure and initial content of a possible future expert system for XPS [132]. These discussions led to many recommendations concerning instrument and specimen characterization, experimental objectives, instrument setup, acquisition and analysis of survey scans, protocols for narrow scans and analysis of results, identification of chemical state and sample morphology, and quantitative analyses. These recommendations are believed to be a valuable source of best practices as well as an educational resource for both novice and experienced users. Castle has recently designed a module for an XPS expert system that would guide corrosion scientists [133] and has shown design goals for similar applications in catalysis, adhesion science, tribology, and biomaterials [134]. 

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