Antonio Marigo

Influence of substrate on structural properties of TiO2 thin films obtained via MOCVD

Abstract Among the techniques developed for depositing thin films, metal-organic chemical vapor deposition is one of the most promising. In the present work, the deposition of TiO2 thin films on stainless steel, titanium, barium borosilicate glass and alumina substrates, using titanium tetraisopropoxide as a precursor, was investigated. The films were deposited at 420 °C. The resulting film phase, checked by X-ray powder diffraction, was found to be polycrystalline anatase and was oriented with the a axis perpendicular to the substrate surface, except for alumina substrates where titania films were randomly oriented. Some considerations on texture and crystallite size as a function of film thickness are reported. Annealing up to 1100 °C induced the complete anatase-rutile transformation on alumina substrates.

Forensic differentiation of paper by X-ray diffraction and infrared spectroscopy

The possibility to discriminate between sheets of paper can be of considerable importance in questioned document examinations. 19 similar types of office paper were characterized by infrared spectroscopy and X-ray diffraction to individuate the most discriminating features that could be measured by these techniques. The discriminating value associated to them was also assessed. By using a sequence of these two techniques, all the samples could be differentiated.

The activation of MgCl2-supported ziegler-natta catalysts: A structural investigation

Abstract A mathematical procedure for the investigation of the lattice disorder by stacking faults in polycrystalline solids has been used in studying samples of MgCl2 activated by ball milling for various times in the presence of TiCl4. These samples have been investigated by X-ray diffraction and by measurements of surface area, crystallite dimensions, Ti content after washing and catalytic activity in the polymerization of ethylene. A good relationship has been confirmed between activation time and activity; furthermore, the structural variations introduced by ball milling are mainly associated with rotational disorder of the Cl-Mg-Cl triple layers. Nevertheless, the analysis by X-ray diffraction is not unequivocal about the relationships between structure and activity: other significant parameters, such as the surface area and the porosity, are probably very important.

Small-angle X-ray scattering from high-density polyethylene: lamellar thickness distributions

Abstract Small-angle X-ray diffraction patterns were recorded for a number of high-density polyethylene samples and were successively analysed by a fit with the calculated patterns corresponding to certain theoretical models. The parameters determined by the above fits were as follows: long-period, crystallinity, mean dimensions of the crystalline lamellae, amorphous thickness, crystallinity and lamellar dimension distributions. Regarding the latter, two mathematical functions were used for the fits, i.e. a symmetrical and an asymmetrical type, and for all of the samples examined the function was determined which gives the best results. Finally, a correlation is suggested between the polymer molecular weight and lamellar dimension distributions.

The Discrimination Potential of Ultraviolet‐Visible Spectrophotometry, Thin Layer Chromatography, and Fourier Transform Infrared Spectroscopy for the Forensic Analysis of Black and Blue Ballpoint Inks

Abstract:  The knowledge of the discriminating power of analytical techniques used for the differentiation of writing inks can be useful when interpreting results. Ultraviolet‐visible (UV‐VIS) spectrophotometry, thin layer chromatography (TLC), and diffuse reflectance Fourier transform infrared spectroscopy (FT‐IR) were used to examine a population of 21 black and 12 blue ballpoint writing inks. Based on corroborative results of these methods, the discrimination power for UV‐VIS, TLC, and FT‐IR was determined to be 100% and 98% for the black and blue inks, respectively. Generally, TLC and UV‐VIS can be used to differentiate the colorant components (i.e., dyes and some pigments) found in inks. As FT‐IR can be utilized to identify some of the noncolorant components, it was determined to be an excellent complementary technique that can be implemented into an analytical scheme for ink analysis.

Phase transition II → I in isotactic poly-1-butene: wide- and small-angle X-ray scattering measurements

Phase transition II → I in isotactic poly-1-butene was studied by wide- and small-angle X-ray scattering in order to follow the change of crystallinity and of the characteristic parameters of the lamellar stacks over time. Small-angle X-ray scattering experimental patterns were analyzed by a fitting method with the profiles calculated from some theoretical distribution models of the lamellar thickness. The mathematical evaluation of small-angle X-ray scattering patterns provided crystallinity values which were compared with those obtained by wide-angle X-ray scattering, in order to obtain information on the lamellar stacks organization. The transition nucleation seems to be localized on lamellar distortion points and the transition itself involves the rearrangement of lamellae and of lamellar stacks.

Synthesis methods of fluorinated polyurethanes. 1. Effects on thermal and dynamic-mechanical behaviours

Abstract Fluorinated polyurethanes (FPUs) were synthesised from 4,4′-methylenebis(phenylisocyanate) (MDI), 1,4-butandiol (BDO), as a chain-extender, and soft perfluoropolyetheric block (ZDOLTX), by a two-step polymerisation technique, following specific procedures to obtain chains with a regular-segmented structure or polymers characterised by having high hard (MDI–BDO) segment polydispersity. Calorimetric and dynamic mechanical data, reported in this first part of our work, show that, independently of the synthesis method, the polymers are always characterised by a heterogeneous structure. This is true not only at molecular level but also at a macroscopic scale, in which the continuous soft phase contains different populations of crystalline hard domains. However, the crystallinity degree decreases on increasing the weight fraction of the soft phase. The so-called ‘regular synthesis’ seems to favour the MDI–BDO–MDI sequence, which is the largest constitutive part of the hard phase, but the macrostructure is less regular than that present in the other FPUs.

Structure-property relationship in polyethylene reinforced by polyethylene-grafted multi-walled carbon nanotubes.

Polyethylene-grafted multiwalled carbon nanotubes (PE-g-MWNT) were used to reinforce polyethylene (PE). The nanocomposites possessed not only improved stiffness and strength, but also increased ductility and toughness. The effects on the structure and morphology of composites due to pristine multiwalled carbon nanotubes (MWNT) and PE-g-MWNT were studied and compared using small angle X-ray scattering (SAXS), wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The SAXS long period, crystalline layer thickness and crystallinity of polymer lamellar stacks were found to decrease significantly in MWNT composites, while the decreases were much smaller in PE-g-MWNT composites. PE-g-MWNT allowed a more efficient and unhindered crystallization at a lamellar level, while MWNT disrupted the order of lamellar stacks, probably because of their tendency to aggregate. The SAXS crystallinity and the mechanical properties of the composites showed similar trends as a function of MWNT content. This suggested that the improvement of the interfacial strength between polymer and carbon nanotubes was a result of synergistic effects of better dispersion of the filler, better stress transfer, due to the grafting of polymer and MWNT, and the nucleation of a crystalline phase around MWNT. The latter effect was confirmed by measurements of kinetics of non-isothermal crystallization.

Synthesis methods of fluorinated polyurethanes. 2. Effects on morphology and microstructure

Abstract A series of fluorinated polyurethanes, characterized by a segmented structure containing hard segments based on 4,4′-methylenebis(phenylisocyanate) (MDI) and 1,4-butandiol (BDO), were analyzed by small- and wide-angle X-ray scattering and transmission electron microscopy (TEM) in order to study the influence of the synthesis and of the soft and hard segments length on the structure. Theoretical models of lamellar morphology were used to fit calculated small-angle scattering patterns to the experimental ones. TEM and small-angle X-ray scattering analysis shows that these polymers are characterized by a heterogeneous structure, not only at the molecular level, but also at a macroscopic scale.

The activation of MgCl2-supported ziegler-natta catalysts—II: Correlation between activity and structural disorder

Abstract The properties have been examined for Ziegler-Natta catalysts comprising TiCl4 (Ti contents 2.0, 3.4 and 4.2%) supported on MgCl2 activated by dry ball-milling up to 250 hr. The samples have been investigated by measurements of catalytic activity in polymerization, of surface area and of some structural parameters related to the crystal disorder introduced by ball-milling. It is shown that the TiCl4 content affects the activation; a relationship has been found between the crystal disorder of the MgCl2 support and the catalytic activity.