Director Standard Reference Materials : Homogeneity Characterization of NBS Spectrometric Standards IV : Preparation and Microprobe Characterization of W-20 % Mo Alloy Fabricated by Powder Metallurgical Methods
A significant problem of the National Bureau of Standards Standard Reference Materials program is the provision of standards suitable in homogeneity for use with microanalytical techniques such as the spark source mass spectrograph and the electron probe microanalyzer. An interim approach to the problem has been the extended homogeneity characterization of selected existing standards. This paper describes the preparation and evaluation of the first NBS standard tested specifically from the beginning for application to electron probe microanalyzers. The standard designated SRM 480 is a tungsten-20 weight percent molybdenum alloy prepared by a powder metallurgy process. Based on the results of about 1500 determinations for both tungsten and molybdenum by electron probe microanalysis, the material was found to be of high homogeneity at about the micrometer level of spatial resolution. The coefficient of variation for molybdenum was 2.5% and that for tungsten 1.5%. Correction of relative intensity ratios to obtain concentrations is discussed in terms of input parameter uncertainties such as mass absorption coefficients, and electron backscatter factors. The result of studies for atomic number correction and effects on operating voltage on the microprobe absorption correction., will be given. It is concluded that SRM 480 should be a valuable addition to any microprobe laboratory doing quantitative analysts.
The loss of X-ray intensity due to backscattering of electrons in microanalyser targets
SummaryThe loss of X-ray intensity caused by the rediffusion of electrons in microanalyser targets has been determined from published experimental data on the energy distribution of backscattered electrons and from a simple relationship between the electron energy and the X-ray intensity. The calculation involves a numerical integration which has been performed on a computer. The data obtained can be used directly to make corrections in quantitative microanalysis.ZusammenfassungDer Verlust an Röntgenstrahlenintensität bei der Elektronenstrahl-Mikroanalyse, der entsteht, wenn Elektronen vom Target zurückgestreut werden, wurde bestimmt. Dazu wurden Literaturangaben über die Energieverteilung der Rückdiffusionselektronen und eine einfache Beziehung zwischen der Elektronenenergie und der Röntgenstrahlenintensität benutzt. Die Berechnung besteht aus einer numerischen Integration, die mittels einer elektronischen Rechenmaschine durchgeführt wurde. Die gewonnenen Werte können für Korrekturen bei der quantitativen Mikroanalyse verwendet werden.RésuméOn a déterminé, dans le cas de micro-analyses avec rayonnement électronique, la perte d'intensité du rayonnement X se produisant quand les électrons se trouvent diffractés en retour par la cible. On a utilisé pour cela les données bibliographiques sur le partage de l'énergie des électrons provenant de la diffusion en retour et une relation simple entre l'énergie des électrons et l'intensité des rayons X. Le calcul repose sur une intégration numérique que l'on a effectuée à l'aide d'une machine à calculer électronique. Les valeurs obtenues peuvent être utilisées pour des corrections en micro-analyse quantitative.
The measuriment of ferromagnets magnetic characteristics using Labview software
The digital method of measurement and registration of dynamic loops hysteresis family of magneto-soft materials where, along with known analogues from electro-technical steel, magnetic materials with considerably smaller specific magnetic losses such as amorphous alloys on the basis of iron, is offered. Tests of magnetic properties of materials are carried out on the base of the hardware-software measuring complex in which along with the standard established electric equipment and USB oscillograph for realization of a digital method, the software for the personal computer developed in the environment of visual programming of Borland Delphi 7.0, connected through the ActieveX technology with the Labview 7.0 environment, is applied. The software allows carrying out input of basic data concerning geometry of prototypes of cores from magnetic materials and numbers of rounds of the magnetizing and measuring windings located on their surface. Experimental data on voltage at measuring winding terminals are processed by means of the virtual integrator in a Labview package. The developed software provides the possibility of saving the obtained hysteresis loop in the form of a text file, and creation of the hysteresis loops family on the virtual oscillograph screen.