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Porous ceramics prepared by the foam replication technique have a high porosity and low mechanical stability. It has been reported that coating such porous ceramics with gelatin allows for an improved compressive strength. Little details regarding the influence of important gelatin parameters such as concentration, temperature and drying conditions as well as bloom number which is a measure of the gel rigidity, on this toughening effect are available. This paper investigates the influence of these parameters on compressive strength of gelatin coated porous hydroxyapatite ceramics. It was found that concentration in the gelatin sols has a marked impact whereas sol temperature, bloom number and differing conditions during subsequent drying have only little influence on the compressive strength of the coated ceramics.
Simple procedures for specifying and checking the performance of energy dispersive X-ray spectrometers (EDS) have been since 2002 available in form of the international standard ISO 15632:2002 [1]. When specifying their spectrometers all major EDS manufacturers refer meanwhile to this standard. Main spectrometer parameters such as energy resolution can be determined as recommended in there. Just several years ago the Si-Li detector has been the mostly widespread type of detector. Since four-five years, silicon drift detector (SDD) EDS providing comparable (in many cases even better) energy resolutions at much higher count rates than the conventional Si-Li’s have got the breakthrough on the market.
It is a latent wish of any SEM/EDS (scanning electron microscope with an energy dispersive spectrometer) analyst to “see more” of the analyzed specimen, i.e. to improve the existing analytical figures of merit.
One key issue are the relatively poor limits of detection (not below 0.1 mass-%) provided by energy dispersive X-ray spectrometry (EDX) with the conventional electron excitation (ED-EPMA). This is a consequence of relatively low peak-to-background ratios and reduced energy resolution when compared to wavelength dispersive spectrometry (WD-EPMA). Recent technological developments make possible to equip the SEM with a wavelength dispersive spectrometer (WDS), so that
significantly better energy resolution can be attained. Also a relative new product that can be easily attached to a SEM/EDS system is a micro-focus X-ray source. Hence, it is possible to perform (micro-focus) X-ray fluorescence spectrometry (μ-XRF) and take advantage of the enhanced peak-to-background ratios (well suited for trace analysis). However, there are also some disadvantages: an increased measurement time and excitation with a high current in the 10s of nA range are usually required for WDS. μ-XRF provides more bulk information and poor limits of detection for light elements. By combining the advantages of these analytical techniques “seeing more” becomes possible.
CCQM (Consultative Committee for Amount of Substance - Metrology in Chemistry) is an international body of the Meter Convention (BIPM) established as a framework of National Metrology Institutes running inter-laboratory of comparisons to demonstrate the international comparability of chemical measurements, with traceability to international or national reference standards. In 2003 the surface analysis working group (SAWG) was established at CCQM and since then several inter-laboratory comparisons in the field of EPMA have been carried out. In many cases the EPMA results deviated significantly from each other and the expanded uncertainties were greater than expected. Both methods EDS and WDS were employed. However, light elements such as carbon and nitrogen were the major elements analyzed and it is known that the corresponding lowenergy characteristic X-ray lines are more challenging to quantify by EPMA than the higher energy lines of elements with higher atomic numbers. Moreover, the standards selected and their qualities were variable, the quantification models were different, and the acquisition parameters were not specified sufficiently in the analysis instructions.
A microfocus X-ray source mounted on the analysis chamber of an SEM was used to excite X-ray fluorescence spectra and to detect chemical elements with concentrations below the detection limit of the electron-excited X-ray spectra conventionally measured with SEM/EDS. An aluminium alloy and a hard material ceramics were analysed as representative examples. It is demonstrated that the combination of the three analytical methods: (1) SEM imaging for surface morphology characterisation; (2) electron-excited X-ray spectroscopy with its high spatial resolution for element analysis of inclusions or precipitates; and (3) X-ray fluorescence for the detection of elements with concentrations below 0.1 mass% considerably improves the performance of SEM/EDX analyses.
A systematic series of measurements has been carried out with monochromatic X-ray excitation with synchrotron radiation in order to check a physical model on X-ray scattering. The model has recently been successfully tested for the case of polychromatic, unpolarised excitation emitted by an X-ray tube. Our main purpose is the modelling of a physical background in X-ray fluorescence spectra, so that improved quantitative results can be achieved especially for strongly scattering specimens. The model includes single Rayleigh and Compton scattering in the specimen, the effect of bound electrons, the challenging Compton broadening and the polarisation degree. Representative specimens, measurement geometries and excitation energies have been selected with synchrotron monochromatic light at BAMline/BESSY II. Monte-Carlo simulations have been also carried out in order to evaluate the quality of the results achieved with the model.
The accurate knowledge of the properties of polycapillary X-ray semi-lenses has a significant influence on the quantitative results in a widespread field of applications involving microfocus X-ray beams. A routine procedure for the characterisation of a polycapillary X-ray semi-lens with a scanning electron microscope (SEM) having attached an energy dispersive spectrometer (EDS) is presented in this paper. A key issue of the procedure consists of fitting the semi-lens in front of the EDS for spectra acquisition. Relevant semi-lens parameters such as focal distance, full width at half maximum (FWHM) of the acceptance area, and transmission are determined in parallelising mode of the semi-lens. Special attention has been paid to the calculation of the transmission.