Refractory metals and their alloys show potential for high temperature applications, due to the elevated melting points often paired with very good creep resistance. Spark plasma sintering (SPS) as well as arc-melting is used here to prepare quaternary and quinternary Mo-9Si-8B-xAl-yGe (x is 0 or 2; y is 0 or 2, all numbers in at%) samples. All samples consist of a Mo solid solution (Mo ss ) and two intermetallic phases: Mo 3 Si (A15) and Mo 5 SiB 2 (T2). Aluminum and germanium reduce the melting point and slightly decrease the density of the material. The specimens are homogenized and coarsened by a subsequent heat-treatment in vacuum at 1850C for 24 h. The resulting microstructure is investigated using scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), and inductively coupled plasma optical emission spectrometry (ICP-OES) analysis. A vacuum creep testing device for small tensile creep specimens is presented. It is heated by graphite radiation heaters usable up to 1500 C in vacuum of 2 Á 10 -4 Pa with an oil diffusion pump. Tensile creep tests are performed at 1250 C and stresses from 50 MPa up to 250 MPa. Specimens produced by ingot metallurgy feature superior creep properties compared to powder metallurgy samples.

Mo–Si–B alloys show great potential as high temperature materials. Due to peak overlapping of B‐Kα and Mo‐Mζ, analyzing these alloys with microanalysis presents a real challenge. This paper describes the analytical methodology used to qualify and quantify the boron content in these alloys without stoichiometric reference samples by the use of a single parallel‐beam wavelength dispersive spectrometer. Characterization of boron is performed by using a coupled energy dispersive X‐ray spectroscopy—wavelength dispersive spectroscopy system in a scanning electron microscope. Self‐made pure element samples are used for calibration and quantification of the boron content.

Ueber Charakterisirung und Bestimmung der Zuckerarten sind eine ganze Anzahl von Abhandlungen erschienen, über welche wir im Anschluss an die in den letzten Bänden dieser Zeitschrift gegebenen Referate1) nachstehend berichten. Nur erwähnen können wir die Beschreibung der vereinbarten offieiellen Zuekerbestimmungsmethoden der Assoeiatiõn of agrieultural Chemists 2), die Besehlüsse der österreichisch-ungarischen Zucker-Chemiker a) und ebenso einen zusammenfassenden Artikel über Zuekerbestimmungen von W. Bish op*). Auch die Fortsetzung der Studien zur Bestimmung von Rohrzucker, Dextrose und Gä»ulose neben einander von F.G. Wi e eh-mannS), die einerseits genau das Verhalten von Lävulose, Dextrose und Invertzueker beim Kochen mit Säure unter Berücksichtigung der Stärke der Säure und der Zeitdauer erkennen lassen und andererseits eine Nethode der indirekten Analyse zur Bestimmung der drei Körper auf Grund der Polarisation, der Reduetion vor und nach der Inversion enthalten, können wir nur unter Hinweis auf das Original anführen. Die Benutzung der Phenylhydrazinverbindungen der Z u e k e r a r t e n (der sogenannten Osazone) zur Charakterisirung der einzelnen Zucker hat, wie in dieser Zeitschrift 25, 232 berichtet wurde, E m i 1 F i s e h e r vorgeschlagen. Derselbe Verfasser hat seitdem eine ganze Reihe von Arbeiten 6) über diese Osazone veröffentlicht, auf deren interessanten Inhalt wir, weil er nicht in erster Linie von analytiseher Bedeutung ist, hier nicht näher eingehen können. Nur aus der ersten der eben erwähnten Abhandlungen wollen wir die nachstehende Charakterisirung der von dem Verfasser dargestellten Osazone folgen lassen:

Refractory metals and their alloys show potential for high temperature applications due to their increased melting point and creep resistance. Mo‐Si‐B ternary alloys consisting of the phases Mo ss (molybdenum‐based solid solution)‐Mo 3 Si (A15)‐Mo 5 SiB 2 (T2), with melting points over 2000 °C, are particularly favorable for new high‐temperature materials. However these alloys show a lack of oxidation resistance in the intermediate temperature range, 650‐750 °C, and possess a relatively high density (9.6 g/cm 3 ) compared to Nickel‐Based Superalloys. The characterization of the Mo 5 SiB 2 phase with an SEM with X‐ray microanalysis analytical capabilities presents a real challenge. The B‐Kα X‐ray has an energy of 183.3 eV, but might shift slightly due to its bonding with Mo. This X‐ray line energy is very close to the Mo‐Mζ line which is at 192.6 eV. In addition, the K‐shell absorption edge of boron is at 192 eV, just below the Mo‐Mζ line. Finally the absorption coefficient of B‐Kα in Mo is very high, and is even more extreme in Si. As a result, EDS microanalysis proved to be insufficient. The EDS spectrum of the Mo 5 SiB 2 phase shows a very small peak at the B‐Kα position, but without any separation from the Mo‐Mζ line. The elemental distribution maps even showed a strong artifact: due to the higher Mo content in the Mo ss phase and the absence of a boron absorption edge the Mo‐Mζ peak is considerably higher in that phase, resulting in an incorrect increase of intensity of boron in the Mo ss phase. See figure 1. Alternatively, WDS spectrometers have a much better energy resolution and are capable of separating to a large extend the B‐Kα and Mo‐Mζ peaks. Modern parallel‐beam WDS spectromers are also very sensitive to the low‐energy part of the spectrum, and can detect small amounts of boron with very high efficiency. A careful energy scan over the B‐Kα and Mo‐Mζ peaks can be seen in figure 2. And of course creating an element distribution image for boron now indeed showed the correct boron distribution, as can be seen in figure 3. The final challenge lies with the quantitative analysis: what exactly is the weight percentage of boron in the supposed Mo 5 SiB 2 phase? The B‐Kα and Mo‐Mζ peaks still partially overlap even with WDS, and one has to be very careful in the selection of the background support points to correctly subtract the background X‐ray intensity. Using a stoichiometric Mo 5 SiB 2 standard this can still be done, and an accurate quantification can be performed. This case shows how vital it can be for certain applications to widen the range of available microanalysis tools with a parallel‐beam WDS spectrometer to perform analyses beyond the performance limit of EDS.