Herbert Ipser

Bio: Herbert Ipser is an academic researcher from University of Vienna. The author has contributed to research in topics: Ternary operation & Phase diagram. The author has an hindex of 25, co-authored 199 publications receiving 2527 citations.

Transition metal-chalcogen systems viii: The CrTe phase diagram

Abstract: The CrTe phase diagram was investigated in the composition range 30–100 at.% Te using differential thermal analysis and powder diffraction methods. Six NiAs-related phases were characterized between 52.4 and 62 at.% Te. Two of them, hexagonal Cr 1− x Te (52.4–53.5 at.% Te) and monoclinic Cr 3 Te 4 -h (53.5–59.3 at.% Te), are high temperature phases. At lower temperatures monoclinic Cr 3 Te 4 -l (56.4–59.2 at.% Te) and trigonal Cr 2 Te 3 (59.5–60.0 at.% Te) are stable. Two phases, monoclinic Cr 5 Te 8 -m (59.6–61.5 at.% Te) and trigonal Cr 5 Te 8 -tr (61.5–62.0 at.% Te), were found on the tellurium-rich side of this phase system. At 75 at.% Te monoclinic CrTe 3 , a novel polytelluride, is formed in a peritectic reaction at 753 K. There are also indications of the formation of another tellurium-rich phase at about 70 at.% Te and 734 K.

Magnetic order and defect structure of Fe x Al 1 − x alloys around x = 0.5 : An experimental and theoretical study

Abstract: High-field ${}^{57}\mathrm{Fe}$ M\"ossbauer investigations up to 13.5 T on a series of ${\mathrm{Fe}}_{x}{\mathrm{Al}}_{1\ensuremath{-}x}$ alloys around $x=0.5$ and magnetic measurements on a 51.8% sample are performed between 4.2 and 295 K. The experimental results are complemented with augmented spherical-wave (ASW) and linear augmented plane-wave (LAPW) band structure as well as thermodynamic model calculations. For ideally ordered FeAl $(B2$ structure) both types of band-structure calculations yield ${\ensuremath{\mu}}_{\mathrm{Fe}}=0.71{\ensuremath{\mu}}_{B}.$ The ferromagnetic ground state is 0.7 mRy per formula unit below the nonmagnetic state. In experiment it was found that only approximately 25% of the Fe atoms carry a magnetic moment. This discrepancy can be explained if noncollinear spin ordering is allowed and a high density of defects is taken into account, which is typical for real alloys and destroys translational periodicity. Experimentally magnetic moments are only observed for Fe antistructure atoms and their eight Fe neighbors. This nine-atom cluster has a mean moment of $0.4{\ensuremath{\mu}}_{B}$ per atom, which is in fair agreement with the results from supercell (16 and 54 atoms) calculations $(0.6{\ensuremath{\mu}}_{B}).$ For the M\"ossbauer analysis four subspectra are used, which are allocated to (i) Fe in the completely ordered $B2$ structure, (ii) Fe antistructure atoms, and (iii) their nearest Fe neighbors, as well as (iv) Fe atoms around a vacancy in the Fe sublattice. This analysis allows us to obtain simultaneously the concentration of both the Fe vacancies and the Fe antistructure atoms. The derived temperature dependence for both defect types corresponds well with thermodynamic model calculations, which account for all possible kinds of point defects.

The AI-Ali8Mo3 section of the binary system aluminum-molybdenum

Abstract: The constitution of the partial system Al-Al8Mo3 is investigated using differential thermal analysis (DTA) and X-ray diffraction data. Ten (10) intermetallic phases are observed, and their stability ranges with respect to composition as well as temperature are determined. The crystal structures of Al12Mo, Al5Mo(h), Al4Mo(h), and Al8Mo3 are corroborated, confirming literature data. The crystal structures of the phases Al5Mo(ht), Al5Mo(r), Al3+xMo1-x(h), and Al3Mo(h) are newly determined. For the phases “Al22Mo5” and “Al17Mo4,” powder diffraction patterns are obtained. The revised phase diagram Al-Mo (up to 28 at. pct Mo) is presented.

Nanoscaled metal borides and phosphides: recent developments and perspectives

Abstract: and Perspectives Sophie Carenco,†,‡,§,∥,⊥ David Portehault,*,†,‡,§ Ced́ric Boissier̀e,†,‡,§ Nicolas Meźailles, and Cleḿent Sanchez*,†,‡,§ †Chimie de la Matier̀e Condenseé de Paris, UPMC Univ Paris 06, UMR 7574, Colleg̀e de France, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France ‡Chimie de la Matier̀e Condenseé de Paris, CNRS, UMR 77574, Colleg̀e de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05, France Chimie de la Matier̀e Condenseé de Paris, Colleg̀e de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05, France Laboratory Heteroelements and Coordination, Chemistry Department, Ecole Polytechnique, CNRS-UMR 7653, Palaiseau, France

Brittle intermetallic compound makes ultrastrong low-density steel with large ductility

Abstract: Although steel has been the workhorse of the automotive industry since the 1920s, the share by weight of steel and iron in an average light vehicle is now gradually decreasing, from 68.1 per cent in 1995 to 60.1 per cent in 2011 (refs 1, 2). This has been driven by the low strength-to-weight ratio (specific strength) of iron and steel, and the desire to improve such mechanical properties with other materials. Recently, high-aluminium low-density steels have been actively studied as a means of increasing the specific strength of an alloy by reducing its density. But with increasing aluminium content a problem is encountered: brittle intermetallic compounds can form in the resulting alloys, leading to poor ductility. Here we show that an FeAl-type brittle but hard intermetallic compound (B2) can be effectively used as a strengthening second phase in high-aluminium low-density steel, while alleviating its harmful effect on ductility by controlling its morphology and dispersion. The specific tensile strength and ductility of the developed steel improve on those of the lightest and strongest metallic materials known, titanium alloys. We found that alloying of nickel catalyses the precipitation of nanometre-sized B2 particles in the face-centred cubic matrix of high-aluminium low-density steel during heat treatment of cold-rolled sheet steel. Our results demonstrate how intermetallic compounds can be harnessed in the alloy design of lightweight steels for structural applications and others.

Impurity and alloying effects on interfacial reaction layers in Pb-free soldering

Abstract: The objective of this review is to study the effect of minor alloying and impurity elements, typically present in electronics manufacturing environment, on the interfacial reactions between Sn and Cu, which is the base system for Pb-free soldering. Especially, the reasons leading to the observed interfacial reaction layers and their microstructural evolution are analysed. The following conclusions have been reached. Alloying and impurity elements can have three major effects on the reactions between the Sn-based solder and the conductor metal: Firstly, they can increase or decrease the reaction/growth rate. Secondly, additives can change the physical properties of the phases formed (in the case of Cu and Sn, ɛ and η). Thirdly they can form additional reaction layers at the interface or they can displace the binary phases that would normally appear and form other reaction products instead. Further, the alloying and impurity elements can be divided roughly into two major categories: (i) elements (Ni, Au, Sb, In, Co, Pt, Pd, and Zn) that show marked solubility in the intermetallic compound (IMC) layer (generally take part in the interfacial reaction in question) and (ii) elements (Bi, Ag, Fe, Al, P, rare-earth elements, Ti and S) that are not extensively soluble in IMC layer (only change the activities of species taking part in the interfacial reaction and do not usually participate themselves). The elements belonging to category (i) usually have the most pronounced effect on IMC formation. It is also shown that by adding appropriate amounts of certain alloying elements to Sn-based solder, it is possible to tailor the properties of the interfacial compounds to exhibit, for example, better drop test reliability. Further, it is demonstrated that if excess amount of the same alloying elements are used, drastic decrease in reliability can occur. The analysis for this behaviour is based on the so-called thermodynamic–kinetic method.