111 research outputs found
MICROSTRUTTURAZIONE SUPERFICIALE IN ACCIAI PER IL MIGLIORAMENTO DELLE PERFORMANCES TRIBOLOGICHE
Nell’ambito delle tecnologie per l’ottimizzazione di contatti striscianti, una soluzione interessante è la microingegnerizzazione superficiale mediante la tecnica Laser Surface Texturing (LST). Il presente lavoro sperimentale mira a chiarire il beneficio tribologico garantito dalla micro-strutturazione laser in superfici di acciaio. I provini in acciaio sono stati micro-strutturati mediante LST creando micro-cavità circolari distribuite uniformemente sulla superficie. Sono stati effettuati test di prestazione mediante tribometri “pin-on-disk” e “ballon- disk” in regimi di “piena lubrificazione”, “scarsa lubrificazione”, e “contatto a secco” accoppiato con un rivestimento sottile in CrN cresciuto mediante deposizione da fase vapore-magnetron sputtering. A fini comparativi, sono stati contemporaneamente testati in analoghe condizioni provini in acciaio non micro-strutturati (lisci). L’analisi morfologica delle tracce d’usura è stata effettuata mediante un sistema dual beam che combina un fascio elettronico (SEM) ed un fascio ionico (FIB), ambedue ad alta focalizzazione. Nelle condizioni di contatto lubrificato, la micro-strutturazione superficiale contribuisce ad un significativo abbassamento del coefficiente d’attrito dell’acciaio. In assenza di lubrificante, la presenza di micro-cavità rallenta i processi di usura abrasiva
Amide nitrogen co-ordination of CoII and NiII in ternary 2,2′-bipyridine-containing systems. A solution and solid-state study
The ternary systems 2,2′-bipyridine (bipy)-M-amino acid [M = CoII or NiII; amino acid (H2L) = N-p-tolyl-sulfonylglycine (tsgly), -β;-alanine (ts-β-ala) or N-benzoylglycine (H2hip)] were investigated in aqueous solution by means of polarography, electronic spectroscopy and potentiometry, in order to identify the type, number and stability of complex species, as a function of pH and bipy : M : amino acid ratio. With tsgly the prevailing species are [MII(bipy)n(HL)]+ and [MII(bipy)nL] (n = 1 or 2), with pKNH for the deprotonation of sulfonamide nitrogen 7.8(2) and 7.4(2), for CoII and NiII, respectively and the crystal and molecular structure of [Co(bipy)2(tsglyNO)]·2H2O (NO indicates binding as a N,O-chelating dianion) was determined. The CoII is six-co-ordinated by four nitrogen atoms of the bipy moieties, the deprotonated sulfonamide nitrogen and one carboxylic oxygen of the tsgly dianion. On standing in air, an alkaline solution of bipy-CoII-tsgly turned from orange to wine-red in a few days, indicating the oxidation of CoII to CoIII. With ts-β-ala and H2hip metal hydrolysis prevents the formation of deprotonated complexes
Structure and spectroscopic properties of ternary complexes of copper(II) N-tosylglcinates. Crystal and molecular structure of catena-mu-aqua)bis(N-tosylglycinato)bis(4-metylpyridine) copper(II). A case of linear-chain water bridged copper(II) polymer.
Two ternary complexes of copper(II)- N-tosylaglycine with pyridine and 4-Methylpyridine were prepared and characterized by means of magnetic, EPR, electronic, and IR spectra. Forone of them, catena-(mu-aqua)bis(N-tosylglycinato)bis(4-methylpyridine)copper(II). The structure was solved by the heavy-atom technique and refined by the full-matrix least-squares method to a final R index of 0.047 for 1965 unique reflections. The copper environment consists of two centrosymmetrically related carboxylic oxygens and two 4-methylpyridine nitrogens in a square-planararrangement. Two centrosymmetric water molecules, lying on the twofold axis, complete the coordination polyhedron totetragonal bipyramid and bridge the copper atoms, forming chains running along the [001] axis. The dependence of thed-d band maximum on the Cu-O(axia1) contact (2.755 (1) A). TheEPR parameters are also consistent with a CuN204 chromophore. The infrared spectra are discussed in comparison withthose of other structurally known copper(I1)-N-tosylglycinate complexes
The factors stabilizing square-planar geometries in -bonding amine adducts: crystal and molecular structure of bis(N-tosyl--alaninato)bis(piperidine)copper(II).
A violet, air-stable, crystalline compound of empirical formula [Cu(Ts-β-ala)2(pipd)2] (Ts=4- toluene sulfonyl group, hereafter abbreviated as tosyl group, Ts-β-ala=N-tosyl-β-alaninate ion, pipd = piperidine) was synthesized and characterized by means of structural and spectroscopic measurements. The crystal structure of the compound was determined from three-dimensional diffractometric data. The crystals are triclinic, space group PView the MathML source, a = 9.305(1), b = 9.637(2), c = 12.727(2) Å, α = 61.50(2), β = 63.26(1), γ = 71.68(1)°, Z = 1. The structure was solved by the heavy atom method and refined through least-squares calculations to R = 0.032 for 2911 observed reflections. The copper atom lies on the symmetry center coordinating two piperidine and two carboxylic oxygens of N-tosyl-β-alanine in a square-planar arrangement. The second carboxylic oxygen is not involved in metal coordination. Electronic data are also discussed in comparison with those of other ternary Cu(II) carboxylate amine complexes
Coordination of 2-hydroxyhippuric acid to the copper(II) ion: A solution and solid state study
Spectroscopic, magnetic, and structural properties of diaquadimethanolbis-(N-tosylvalinato)copper(II) and its 2,2'-bipyridine adduct
Binary copper(II) compounds of N-tosylvalinate of formula [Cu(tsvalO)2(H2O)2]4H2O and [Cu(tsvalO)2(H2O)2(MeOH)2] were separated. The structure of the latter consists of discrete [Cu(tsvalO)2(H2O)2(MeOH)2] units in which the copper ion, lying on the symmetry centre, is surrounded by two carboxylic oxygens and two water molecules centrosymmetrically related. Two methanol molecules complete the co-ordination which is elongated tetragonal bipyramidal. The spectroscopic properties are consistent with a CuO6 chromophore. (...
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