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

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. (...