Markku Tammenmaa

Bio: Markku Tammenmaa is an academic researcher. The author has contributed to research in topics: Crystal structure & X-ray crystallography. The author has an hindex of 8, co-authored 21 publications receiving 142 citations.

Coordination complexes of silver(I) with tertiary phosphine and related ligands

Abstract: This paper gives an overview of the structural chemistry of silver(I) coordination complexes. The main discussion is on the halide complexes (F−, Cl−, Br−, I−) but included are also the pseudo-halides (CN−, SCN−) and the classical non-coordinating anions (NO3−, ClO4−, BF4−, PF6−) and oxy-anions (NO3−, H3CCO2−, F3CCO2−, F3CSO3−, etc.). The main focus is on complexes of these silver(I) salts with phosphine ligands, but where relevant the chemistry of other donor ligands is also reviewed. Coordination complexes of silver(I) halides show a rich variation of structural types. The type of structure depends on the stoichiometry of the ligand to silver in the reaction mixture, as well as reaction conditions. Other factors influencing the structure of these complexes include the halide or pseudo-halide ligands used as counterion and the type of solvent.

Ultra-High Temperature Materials II: Refractory Carbides I (Ta, Hf, NB and Zr Carbides)

Abstract: The work represents a thorough treatment of ultra-high temperature materials with melting points around or over 2500 °C. The second volume included physical (structural, thermal, electromagnetic, optical, mechanical and nuclear) and chemical (binary, ternary and multicomponent systems, solid-state diffusion, wettability, interaction with chemicals, gases and aqueous solutions) properties of refractory carbide materials: tantalum carbides (monocarbide TaC1–x and semicarbide a/b-Ta2±xC), hafnium monocarbide HfC1–x, niobium carbides (monocarbide NbC1–x and semicarbide a/b/c-Nb2±xC) and zirconium monocarbide ZrC1–x. It will be of interest to researchers, engineers, postgraduate, graduate and undergraduate students alike. The reader/user is provided with the full qualitative and quantitative assessment for the materials, which could be applied in various engineering devices and environmental conditions in the wide range from cryogenic to ultra-high temperatures, on the basis of the latest updates in the field of physics, chemistry, nanotechnology, materials science and engineering.

Order–disorder transformations and phase equilibria in strongly nonstoichiometric compounds

Abstract: Data on order–disorder phase transformations in strongly nonstoichiometric carbides and nitrides MXy (X=C, N) of Group IV and V transition metals at temperatures below 1300–1400 K are reviewed. The order-parameter functional method as applied to atomic and vacancy ordering in strongly nonstoichiometric MXy compounds and to phase equilibrium calculations for M–X systems is discussed. Phase diagram calculations for the Ti–C, Zr–C, Hf–C, V–C, Nb–C, Ta–C, Ti–N, and Ti–B–C systems (with the inclusion of the ordering of nonstoichiometric carbides and nitrides) and those for pseudobinary carbide M(1)C–M(2)C systems are presented. Heat capacity, electrical resistivity and magnetic susceptibility changes at reversible order–disorder phase transformations in nonstoichiometric carbides are considered.

Selective extraction of vanadium (v) from solutions containing molybdenum (vi) by ammonium salts dissolved in toluene

Abstract: Several separation schemes, involving liquid-liquid extraction procedures, were found to be theoretically feasible in order to separate Vanadium and Molybdenum based on computer simulation of the acid-base properties of these metals, where cationic and anionic (both mono and polynuclear) species are formed as the pH increases. A liquid cationic extractant (LIX 26), a basic alkylamine (Alamine 336) and a quaternary ammonium salt (Aliquat 336) were experimentally tested. Among them, the sulphate of the quaternary ammonium salt extracts V(V) selectively and quantitatively from Mo(VI) solutions in the basic range 8 < pH < 9. A close relation between the extraction of the metals and the distribution of their species in the aqueous phase has been found. The sulphate forms of Alamine 336 and Aliquat 336 extract quantitatively both metals at the pH where anionic polynuclear species are predominant.