A database of new zeolite-like materials

We here describe a database of computationally predicted zeolite-like materials. These crystals were discovered by a Monte Carlo search for zeolite-like materials. Positions of Si atoms as well as unit cell, space group, density, and number of crystallographically unique atoms were explored in the construction of this database. The database contains over 2.6 M unique structures. Roughly 15% of these are within +30 kJ mol(-1) Si of α-quartz, the band in which most of the known zeolites lie. These structures have topological, geometrical, and diffraction characteristics that are similar to those of known zeolites. The database is the result of refinement by two interatomic potentials that both satisfy the Pauli exclusion principle. The database has been deposited in the publicly available PCOD database and in www.hypotheticalzeolites.net/database/deem/.     

Survey of reference materials for trace elements, nuclides and organic microcontaminants

The International Atomic Energy Agency (IAEA), in co-operation with the United Nations Environment Programme (UNEP), has recently prepared a survey on internationally available analytical reference materials for trace elements, nuclides and organic contaminants in biological, environmental and related matrices. The purpose is to help analysts to select reference materials for quality assurance that match as closely as possible, with respect to matrix type and concentrations of the measurands of interest, the “real” samples that are to be measured. The present version of the survey, which is available in the form of two cost-free printed volumes [1], contains over 10,000 certified and information values in 650 reference materials from 27 different producers. The 455 measurands listed include trace elements, major and minor elements, organic contaminants, organometallic compounds, radionuclides and stable isotopes. Currently, the database from which the survey has been produced is being modified and extended so as to make the data available in electronic form via the Internet. Received: 11 June 1997 / Revised: 7 July 1997 / Accepted: 9 July 1997     

The updated IAEA database of natural matrix reference materials

The International Atomic Energy Agency (IAEA) maintains a database of biological and environmental reference materials of natural origin (human and animal tissues, foods, plants, soils, sediments, etc.) for trace elements, radionuclides, stable isotopes, organic contaminants and other related measurands. The purpose is to help analysts to select reference materials for quality assurance purposes that match as closely as possible (i.e., with respect to matrix type and concentrations of the measurands of interest) the real samples that are to be analyzed. Former versions of this database were prepared in co-operation with the United Nations Environment Programme (UNEP), and provided as hardcopies free of charge. The latest version was from 1995. More recently the database has been updated by the IAEA so that it now contains more than 22,500 values (mass fraction or concentration) for 660 different measurands and 1,705 reference materials developed by 56 producers from 22 countries. This paper gives an overview of the structure and content of the database and of the two ways it may be browsed. Emphasis is given to reference materials that are intended to verifying analysis for radioanalytical measurements. The database is soon accessible on-line, cost-free, via the internet.     

Design of electroceramic materials using artificial neural networks and multiobjective evolutionary algorithms

We describe the computational design of electroceramic materials with optimal permittivity for application as electronic components. Given the difficulty of large-scale manufacture and characterization of these materials, including the theoretical prediction of their materials properties by conventional means, our approach is based on a recently established database containing composition and property information for a wide range of ceramic compounds. The electroceramic materials composition-function relationship is encapsulated by an artificial neural network which is used as one of the objectives in a multiobjective evolutionary algorithm. Evolutionary algorithms are stochastic optimization techniques which we employ to search for optimal materials based on chemical composition. The other objectives optimized include the reliability of the neural network prediction and the overall electrostatic charge of the material. The evolutionary algorithm searches for materials which simultaneously have high relative permittivity, minimum overall charge, and good prediction reliability. We find that we are able to predict a range of new electroceramic materials with varying degrees of reliability. In some cases the materials are similar to those contained in the database; in others, completely new materials are predicted.     

Luminescence database I--minerals and materials.

A luminescence database for minerals and materials has been complied from the literature, the aim being to create a resource that will aid in the analysis of luminescence spectral of ionic species in minerals and materials. The database is based on a range of excitation techniques and records both major and minor lines, and their activators. The luminescence techniques included in the database are cathodoluminescence, ion luminescence, and photoluminescence. When combined with other traditional X-ray measurements collected on the same region, use of the luminescence database will give additional insight into the chemistry of minerals and materials.     

Certification of standard reference materials containing bitter orange

A suite of three dietary supplement standard reference materials (SRMs) containing bitter orange has been developed, and the levels of five alkaloids and caffeine have been measured by multiple analytical methods. Synephrine, octopamine, tyramine, N-methyltyramine, hordenine, total alkaloids, and caffeine were determined by as many as six analytical methods, with measurements performed at the National Institute of Standards and Technology and at two collaborating laboratories. The methods offer substantial independence, with two types of extractions, two separation methods, and four detection methods. Excellent agreement was obtained among the measurements, with data reproducibility for most methods and analytes better than 5% relative standard deviation. The bitter-orange-containing dietary supplement SRMs are intended primarily for use as measurement controls and for use in the development and validation of analytical methods. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Diffusion studies in non-oxide ceramics: analytical aspects of the use of ion implanted stable tracers and SIMS

The physical and chemical properties of complex non-oxide ceramic materials require advanced methods of diffusivity determination. In this study, we present a method based on the high-dose ion implantation of stable tracers in combination with secondary ion mass spectroscopy for depth profiling. The analytical basics, advantages and problems of the method are discussed for two examples of complex materials, the Si-B-C-N precursor ceramics and the Ti-based transition metal diborides. We demonstrate that is possible to measure the temperature dependence of diffusivities, especially for ceramic systems with low diffusivities, for systems that contain elements for which no suitable radioactive tracers exist for extended measurements.     

Oxide ion diffusion in optimised LAMOX materials

A series of optimised materials in the family with parent compound La(2)Mo(2)O(9) have been studied using the isotope exchange depth profile technique and SIMS analysis. The data collected indicate that the oxide ion diffusion coefficients in both the parent compound and optimised materials are significantly higher than those reported for any of the fluorite structured electrolyte materials, with a peak value for the La(1.7)Gd(0.3)Mo(2)O(9) composition of 1.41 x 10(-6) cm(2) s(-1) at 800 degrees C. Further, it was found that the substitution of isotopic oxygen into the ceramic was limited in dry atmospheres but significantly enhanced in a H(2)(18)O/(16)O atmosphere, in common with recent reports on the diffusion/exchange behaviour of the BIMEVOX class of oxide ion conductors.     

Characterization of a suite of ginkgo-containing standard reference materials

A suite of three ginkgo-containing dietary supplement Standard Reference Materials (SRMs) has been issued by the National Institute of Standards and Technology (NIST) with certified values for flavonoid aglycones, ginkgolides, bilobalide, and selected toxic trace elements. The materials represent a range of matrices (i.e., plant, extract, and finished product) that provide different analytical challenges. The constituents have been determined by at least two independent analytical methods with measurements performed by NIST and at least one collaborating laboratory. The methods utilized different extractions, chromatographic separations, modes of detection, and approaches to quantitation. The SRMs are primarily intended for method validation and for use as control materials to support the analysis of dietary supplements and related botanical materials. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Silicon Oxycarbide Glasses Derived from Polymer Precursors

This paper describes a new predictive model to estimate compositions of ceramic materials from the structure of the preceramic polymer. The polymers are prepared by sol-gel methods and have M and T silicone functionality. The ceramic predictive model works well for highly branched silsesquioxanes, which are some of the most common ceramic precursors. This report describes the control of ceramic SiOC compositions which in turn make the materials useful as: (1) matrices for ceramic matrix composites and; (2) anodes for rechargeable lithium ion batteries.     

Characterization of metallic and ceramic high-temperature materials for energy systems

For the development of metallic and ceramic high temperature materials used, for example, in heat exchanger components, in turbine blades for stationary gas turbines, in ceramic industrial products and fusion reactor components, modern physico-chemical characterization methods are required. The formation stability of naturally formed protective scales is of prime importance in the successful application of metallic materials at high temperatures in aggressive atmospheres. For the characterization and investigation of the growth mechanisms of such surface scales, the main emphasis is placed on such modern spectroscopical methods as SIMS, SNMS, GDOS, EPMA and RBS. The morphology and composition of oxide scales have been investigated by imaging and diffraction techniques. The thermal and mechanical damage behaviour of high-temperature materials for application in fusion reactor components is of importance. Damage behaviour has been simulated by electron beam and laser irradiation experiments, especially by means of in situ techniques in a scanning electron microscope. By such techniques the material erosion, crack formation and crack propagation were studied for ceramic high temperature materials as a function of load parameters. The erosion and the crack formation processes are superim-posed by a redeposition of vaporized material and by thermally activated creep of the binder phases. The application potential for all methods discussed is outlined and available results are presented.     

A review of the radiation stability of ion exchange materials

A comprehensive literature survey on the radiation stability of ion exchangers resulted in the publication of an extensive data compilation on the effects of ionizing radiation on synthetic organic ion exchangers in this journal (Vol. 97, No. 1). This paper is a brief review of the majorfindings of this literature survey along with similar information on synthetic inorganic ion exchangers. The primary goal of this literature survey is to review present knowledge on the effects of ionizing radiations on synthetic ion exchange materials used in radiochemical processing. Although there are gaps in our knowledge of the mechanisms of radiolytic changes in ion exchangers, the information available in the literature shows some general trends and similarities in observed qualitative effects by different types of organic and inorganic ion exchange materials. These trends and observations have been formulated into a set of qualitative and semi-quantitative statements that can be useful to potential users of ion exchange materials in nuclear material processing and radioactive waste management. Present knowledge, of the behavior of ion exchangers under the influence of ionizing radiations is too limited to justify quantitative predictive modeling.     

Certified reference materials for inorganic and organic contaminants in environmental matrices

Chemical measurements often constitute the basis for informed decision-making at different levels in society; sound decision-making is possible only if the quality of the data used is uncompromised. To guarantee the reliability and comparability of analytical data an intricate system of quality-assurance measures has to be put into effect in a laboratory. Reference materials and, in particular, certified reference materials (CRMs) are essential for achieving traceability and comparability of measurement results between laboratories and over time. As in any other domain of analytical chemistry, techniques used to monitor the levels and fate of contaminants in the environment must be calibrated using appropriate calibration materials, and the methods must be properly validated using fit-for-purpose matrix-matched CRMs, to ensure confidence in the data produced. A sufficiently large number of matrix CRMs are available for analysis of most elements, and the group of chemicals known as persistent organic pollutants, in environmental compartments and biota. The wide variety of analyte/level/matrix/matrix property combinations available from several suppliers enables analysts to select CRMs which sufficiently match the properties of the samples they analyse routinely. Materials value-assigned for the so-called emerging pollutants are scarce at the moment, though an objective of current development programmes of CRM suppliers is to overcome this problem.     

The need for new SI-traceable magnesium isotopic reference materials

Recent measurements revealed that commercial magnesium standard solutions showed isotopic abundance variations, which cannot clearly be distinguished from each other by calibrating against the only available isotopic reference material, SRM 980, or reference materials made from SRM 980 like IRMM-009. Therefore new SI-traceable magnesium isotopic reference materials are required.     

Reference materials: global harmonization and the assurance of data quality

Summary The need for reference materials, and the problems of locating information about them, are discussed. The first steps in the construction of a database on reference materials are described. The term reference materials was taken to mean any substance used to give a baseline or reference value for a measurement. A broadly-phrased questionnaire was sent out to 264 different organizations. So far 67 replies have been received representing a wide range of manufacturers, suppliers, and users of reference materials from 23 different countries. These replies have been compiled to form a Survey of Institutions, Organizations and Laboratories Manufacturing, Supplying, or Using Reference Materials, which will soon be available in printing form. The first edition will serve as a basis for defining user needs more precisely, and developing a more detailed questionnaire. The information will be included in digitized form as a part of the HEM metadatabase information system HEMIS.     

Availability of reference materials: COMAR the database for certified reference materials

COMAR is the international database for certified reference materials. A new user-friendly web-based version, COMAR², has been developed by BAM and CONET Consulting AG which will be available in December 2002. The advantages of COMAR² are briefly explained.Presented at the International ILAC/IAF Conference on Accreditation in Global Trade, 23-25 September 2002, Berlin, Germany     

Reflection spectroscopy of optically active materials

Theoretical and experimental results are presented to determine under what conditions it is possible to obtain the optical constants of an optically active material by reflection techniques. Experimental results axe given for absorbing and non-absorbing materials. Typical examples include liquids, thin-films, and isotropic crystals. It is concluded that it is necessary to separate the back and front surface reflections. The front surface reflection contains information that is generally within the sensitivity of available spectropolarimeters. The back surface reflection contains recoverable data and is similar to the data found by transmission methods. Experimental verification of the front surface effect is presented for one highly absorbing amino acid, tryptophane.     

Reference materials and certified reference materials for spectrometry in Romania

Several reference materials (RMs) and certified reference materials (CRMs) are widely used in Romania as measurement standards in different spectrochemical measurements. Among them, single element standard solution certified for their mass concentration play a key role in ensuring the required traceability of results expressed in this measurement unit. A short review of the locally available elemental RMs and CRMs used in atomic spectrometry or in other analytical techniques where aqueous standard solutions are required (usually called RMs or CRMs for spectrometry) is given. The experience of the INM in preparation and certification of such materials is described. Some aspects regarding their use for ensuring the accuracy and for confirmation of the traceability of analytical measurements, especially through calibration and metrological validation of main instrument performances, are discussed.     

Reference materials and certified reference materials for spectrometry in Romania

Several reference materials (RMs) and certified reference materials (CRMs) are widely used in Romania as measurement standards in different spectrochemical measurements. Among them, single element standard solution certified for their mass concentration play a key role in ensuring the required traceability of results expressed in this measurement unit. A short review of the locally available elemental RMs and CRMs used in atomic spectrometry or in other analytical techniques where aqueous standard solutions are required (usually called RMs or CRMs for spectrometry) is given. The experience of the INM in preparation and certification of such materials is described. Some aspects regarding their use for ensuring the accuracy and for confirmation of the traceability of analytical measurements, especially through calibration and metrological validation of main instrument performances, are discussed.