IMSE
Institute of Materials Science and EngineeringPublications list
Research groups: PetroMat
Research groups: CeraMat
In the last years, bioactive glasses and glass-ceramics drew the attention for their application in the production of implants. Among them, Bioglass® 45S5 is the most commonly used in terms of bioactivity, but its sintering behavior and the related glass-ceramics strongly depend on the followed synthesis process. For these reasons, this paper reports a comparison of the properties and the thermal behavior of bioactive 45S5 glasses produced by a conventional melting process starting from suitable solid precursors or an innovative sol-gel procedure.
Research groups: CeraMat
Assessment of facial soft tissues could be implemented using only anatomical landmarks. These points are so significant in the medical context because are able to provide significant information about the human face morphology and dimensions. At present their detection and location is made by expert physicians using palpation. Even if this procedure normally provides reliable information, the reliability of the results is proportional to the expertise of the physician.
Research groups: CeraMat
The conservation of the historical finishes represents a difficult issue, due to their aesthetical and functional roles. In particular, the investigation on surfaces (external o internal) with wall paintings represent a typical case where researchers has some difficulties to apply non invasive diagnostic technique about the detachment of these surfaces. The method here described is aimed at the definition of a scientific method for the evaluation of the adhesion between the fresco and the wall.
Research groups: CeraMat
The activation energy of carbon combustion catalysed by alkali vanadates or alkali vanadates/chlorides mixtures is assessed by the Ozawa method. The most active catalyst, Cs4V2O7, entails more than 50% decrease of the activation energy compared to non-catalytic combustion (from 157 down to 75 kJ/mol). The catalyst performance is enhanced when the catalyst is dissolved in a eutectic liquid (e.g., AgCl + CsCl), which likely improves the catalyst/carbon contact conditions.
Research groups: PetroMat
A sensor for measuring small convective heat flows (<0.2 W/cm^2) from micro-structured surfaces is designed and tested. This sensor {exploits the notion of thermal guard and is purposely designed} to deal with metal samples made by additive manufacturing, {such as} direct metal laser sintering (DMLS).
Research groups: HTMat
An epoxy coating modified by PDMS hydroxyl terminated is presented in this paper in order to evaluate its potential use as a protective of a stone surface. With a view to its use in restoration sites, visible and long-wavelength photoinitiated cationic polymerization is proposed here. The system investigated is based on a crosslinking mechanism which shows remarkable advantages for stone protection, such as the low toxicity of the products and facility of mixture preparation.
Research groups: PetroMat
The work is intended to focus the attention on different aspects of sinterhardening, starting from the main reason to use such a process to the final characterisation of produced samples. Sintehardening allows the production of high apparent hardness parts; the process is rather attractive for components difficult to be quenched because of their dimensions. Admixed alloys, diffusion alloyed mixes, prealloyed ones or hybrid alloys can be used as starting powders, each having positive and negative aspects.
Research groups: PetroMat
Research groups: PetroMat
New polyaniline (PANi) synthesis was performed starting from non-toxic N-phenil-p-phenylenediamine (aniline dimer) using reverse addition of monomer to oxidizing agent, the synthesis allows to produce highly soluble PANi. Several types of doped PANi were prepared to be used on electromechanical active actuators. Different techniques were used to include carbon nanoparticles such as carbon nanotubes and graphene. Bimorph solid state ionic actuators were prepared with these novel nanocomposites using a variety of supporting polymers.
Research groups: AddiMat
In contemporary society we observe an everlasting permeation of electron devices, smartphones, portable computing tools. The tiniest living organisms on Earth could become the key to address this challenge: energy generation by bacterial processes from renewable stocks/waste through devices such as microbial fuel cells (MFCs). However, the application of this solution was limited by a moderately low efficiency.
Research groups: AddiMat
In this chapter a large description of additive manufacturing techniques for obtaining Al alloys and Al matrix composites is given. Results on mechanical properties, roughness and microstructure achievable with such fabrication route on Al alloys are reported
Si-SiC open cell foams with porosity >87% and high pore sizes (4-7 mm) are commonly employed as active zone in porous burners for heat radiation applications. In a porous burner, the solid porous body let the heat recirculate from the hot combustion products to the incoming reactants. The result is that the flame is confined within the foam, meaning high thermomechanical loadings on its constituent material. A set of commercial Si-SiC foams from the same production batch was aged with flat porous burners.
Research groups: CeraMat
Wet chemical synthesis of precursor oxide ceramics is a method to obtain small particulate powders. Such powders are far more prone to ageing in air than more traditional precursors. Thermogravimetric analysis is used to highlight the species responsible for the ageing of ceramic precursors. Indeed water and carbon dioxide are observed to evolve from aged powders. Ceramics obtained from aged precursors can reach a very low final density with respect to the theoretical value.
An Al2O3/5 vol%·ZrO2/5 vol% Y3Al5O12 (YAG) tri-phase composite was manufactured by surface modification of an alumina powder with inorganic precursors of the second phases. The bulk materials were produced by die-pressing and pressureless sintering at 1500 °C, obtaining fully dense, homogenous samples, with ultra-fine ZrO2 and YAG grains dispersed in a sub-micronic alumina matrix.
Research groups: CeraMat
The employment of non-dolomitic calcareous aggregates in the composition of concrete may serve to cause degradation if the mother rock contains sufficiently disordered silicates in the form of finely dispersed microinclusions. This paper reports the observation of fissures due to the formation of gel as a result of ASR in aggregates with less than 4% of microinclusions and even when this value was less than 1%.
Research groups: CeraMat
Doping of commercial alumina nanopowders by using aqueous solutions of metal salts was exploited to prepare alumina-based nanocomposites.
The same procedure was applied to produce a composite made of immiscible phases, that is an alumina–zirconia material, by doping an α-alumina powder with a zirconium chloride solution, as well as to produce an alumina–YAG (yttrium aluminium garnet) system by doping alumina with a yttrium chloride solution and promoting YAG formation by solid-state reaction at high temperature.
For this latter case, the difference in reactivity between two commercial po
Research groups: CeraMat
Al2O3/YAG composite powders have been synthesised by reverse strike precipitation. The powders were characterised by DTA/TG simultaneous analysis; the phase evolution was studied by XRD analysis, while the crystallite formation and growth were followed by TEM observations. A fully dense, homogenous material was obtained by sintering 900°C pre-treated powders at 1600°C for 3 h. For limiting grain growth, both a doping with 500 ppm MgO followed by a free sintering and a fast sintering procedure involving a high heating rate (50°C/min) were performed.
Nanostructured zirconia toughened alumina composite has been prepared by solution combustion synthesis. Urea has been used as sacrificial fuel and metal nitrates as precursor reagents. A traditional composition for the final ceramic–ceramic composite has been chosen: 20 vol.% of t-zirconia partially stabilized with 3 mol% of yttria dispersed in alumina matrix.
Research groups: PetroMat
Components in the field of automotive application produced by a modified squeeze casting process have been considered. This innovative process has been oriented toward the manufacturing of high resistance and high toughness automotive parts using A380 alloys and they have been subjected to T6 heat treatment. Standard samples have been machined directly from real automotive components for tensile properties evaluation and hardness values determination. Superior mechanical characteristics have been obtained thanks to the low porosity content and to the particular microstructure features.
An acrylic latex filled with ZnO by miniemulsion polymerization are developed for stone protection. The main latex chemical properties are determined through dynamic light scattering and differential scanning calorimetry measurements. Contact angle determination, capillary water absorption, scanning electron microscopy observations, and colorimetric measurements are also used to evaluate the coating. The accelerated photo-aging of the dried films are monitored by infrared spectroscopy.
In this work contact angle measurements have been carried out on different carbon nanotube-based materials. Thin layers of entangled carbon nanotubes have been considered, together with thick mats of vertically aligned carbon nanotubes. Pressed single-walled carbon nanotubes and graphite have also been considered, for comparison.
In particular, the properties of the as-grown thick carpets have been compared to those of the oxidized material.
The fabrication and characterization of TiO2 nanotube (NT) arrays and their integration in front-side illuminated Dye-sensitized Solar Cells (DSCs) are reported. Vertically oriented TiO2 NTs were obtained by anodic oxidation of titanium foil and not-curling free-standing NT membranes were easily separated from the metal without the formation of cracks. Stoichiometry, crystalline phase and morphology of the films were investigated, evidencing the formation of a highly ordered 1D NT array, with a pure anatase crystalline structure.
Research groups: PetroMat
The present work investigates the possibility of using powder metallurgy processing for producing a metal matrix composite. Materials were prepared from AlSi5Cu2 chips with reinforcement of 10, 15, 20 wt. % silicon carbide. Aluminum alloy chips were milled with SiC powder in a high-energy ball mill by 40 hours. Mechanical alloying process lead to obtain an uniform distribution of hard SiC particles in the metallic matrix and refine the grain size. The consolidation of composite powders was performed by vacuum hot pressing at 450°C, under pressure of 600 MPa by 10 min.
Research groups: CeraMat
Well-dispersed nano-crystalline transition alumina suspensions were mixed with yttrium chloride aqueous solutions, with the aim of producing by spray-drying Al2O3–Y3Al5O12 (YAG) composite powders of increasing YAG vol.%. Two samples were prepared, with different Y content, corresponding to 5 and 20 YAG vol.%, respectively. Both samples were then treated at either 600 or 1150 °C.
Varallo Sacred Mountain was realized at the end of the fifteenth century on initiative of the Franciscan Father Bernardino Caimi as a place of prayer, meditation and evocation of the Christian faith and has been included in the UNESCO World Heritage List since 2003. Some of its buildings show at the moment manifold maintenance, conservation and restoration problems. Therefore, in the frame of a detailed program of interventions, a research cooperation has been launched, aiming at singling out the existent materials and, as much as possible, their working techniques.
Research groups: CeraMat
This paper reports on a study of two organic-inorganic hybrid materials used as consolidants. Both formulations were synthesized from an inorganic precursor (Tetraethoxysilane, TEOS) added in different percentages (up to 60% per hundred resin) to a polysiloxane epoxy formulation (TEGO RC 1411) and to a cycloaliphatic epoxy resin (3,4 Epoxyciclohexylmethyl -3,4-epoxyciclohexane carboxylate), and cured in the presence of ytterbium as acid catalyst. The film properties and the formation of silica clusters were investigated.
Research groups: CeraMat
Research groups: HTMat
In this article an investigation has been carried out on different austempering cycles conducted on samples of the most diffused hot-work tool steel: AISI H 11. The laboratory tests have been addressed to the examination of the structure and to the evaluation of its mechanical properties: the hardness, the impact strength and the thermal fatigue.
Research groups: CeraMat
Various compositions of barium-doped hematite between pure hematite (α-Fe2O3) and pure barium hexaferrite (BaFe12O19) were synthesized by solid state reaction. The XRD analyses confirmed the progressive evolution of the two crystalline phases. Tests as humidity sensors show that the electrical resistance of samples containing high proportions of hexaferrite phase is strongly influenced. Electrochemical impedance spectroscopy (EIS) analyses under air or argon revealed an intrinsic semiconducting behavior for hematite and samples doped with 3 and 4 wt % equivalent BaO.
Research groups: PetroMat
A study has been made of the preferential distribution between the phases (M', M″)2B and (M M″)B present in the two-phase fields of the M'-M″-B systems for the transition metals with atomic numbers between 24 and 28. It has been ascertained that the metal with the smaller atomic number is systematically concentrated in the phase richer in boron.
Acid functionalization has been considered as an easy way to enhance the dispersion and biodegradation of carbon nanotubes (CNT). However, inconsistencies between toxicity studies of acid functionalized CNT remain unexplained. This could be due to a joint effect of the main physicochemical modifications resulting from an acid functionalization: addition of surface acid groups and purification from catalytic metallic impurities. In this study, the impact on CNT biotoxicity of these two physiochemical features was assessed separately.
The aim of this work was to ascertain if the alloying elements in steels influence the diffusion mechanism of the boron during boriding treatment and to relate the characteristics of the borided layer with the chemical composition of the matrix. Steels, Armco iron and some ferrous alloys containing Cr and/or Ni were borided for 7-24 hours at 1173-1223K using powders of composition B//4C equals 20 30%, KBF//4 equals 5%, SiC equals 65 75%. The borided samples were analysed by an X-ray diffractometer, electron microscope, EDS spectrometer, optical microscope and Vickers microdurometer.