The use of infrared spectroscopy has shown that even the order involving a few unit cells can affect the crystalline solid reactivity. In the case of monocalcium aluminate hydration in the presence of a calcareous filler, it was possible to observe that an increase of carbonate lattice disorder caused a decrease of induction time and an increase of hydration rate of CA* * Cement Chemists' Notations: A = Al2O3; C = CaO; C = CO2; H = H2O - CaCO3 mixture and a change of developed phases mutual ratios.
IMSE
Institute of Materials Science and EngineeringPublications list
Research groups: CeraMat
Research groups: PetroMat
In this paper characteristics of an AlMg/AlN composite produced "in-situ" and processed in a flowing N2 atmosphere is investigated. Some critical parameters such as the manufacturing process temperature, the percentage of the magnesium consumed, the flowing reactive gas flow and the time for completing the manufacturing are considered as variables for the parametric investigation. Moreover, the effect of different amount of Mg employed has been also investigated, since Mg acts as a catalyst at the surface both for the gas/liquid and solid/liquid systems.
Research groups: CeraMat
Nanosized powders of La0.80Sr0.20Fe0.95Cu0.05O3−w were investigated in terms of structural, morphological, chemical and surface properties by using several characterization techniques. The XPS and IR measurements showed the presence of surface hydroxide and carbonates species. After calcination of the powders at 900 °C the amount of carbonates decreased but was still significant.
Research groups: PetroMat
Al-based alloy, produced by a patented, namely Liquid forging, process is studied for automotive application. The patented procedure leads to produce high resistance and high toughness components with the possibility to realise T6 heat treatment. The influence of some process parameter (filling rate and time) on the alloy properties is investigated. The benefits of T6 heat treatment on the performance of Al-based components is considered. The alloy morphological and mechanical characterization has been realised in different conditions and a comparison of these data has been carried out.
Zirconia toughened alumina (ZTA) nanocomposites are attractive structural materials which combine the high hardness and Young's modulus of the alumina matrix with an additional toughening effect by the zirconia dispersion.
In this study two approaches to prepare ZTA are compared. For the first approach, an ultrafine alumina powder was coated with 5 vol% zirconia by a wet chemical method. For the second one, the reference material was prepared by intensively mixing and milling the same alumina with nanoscale zirconia powder.
Co-continuous metal/ceramic composites were obtained by the Reactive Metal Penetration (RMP) method. With the aim of components cost reduction, commercial cordierite preforms and standard aluminium infiltrating alloys (1050, 2011 and 7075) were used in the process. Kinetics of the infiltration reaction, microstructure and mechanical properties of the composites were found to be influenced by both quantity and type of alloying elements.
n the present work, milled carbon fibre with high mechanical properties was used to reinforce silicon carbide, and Csf/SiC multilayer composites were prepared by tape casting and pressureless sintering. The milled C fibres were firstly dispersed in solvents with the aid of dispersant (Triton X-100) and then mixed with SiC slurry to make green Csf/SiC tapes to limit fibre breakage.
Silicon carbide multilayer composites containing short carbon fibres (Csf/SiC) were prepared by tape casting and pressureless sintering. The C fibres were dispersed in solvents with dispersant (Triton X-100) firstly and then mixed with the SiC slurry to make green Csf/SiC tapes. Fibres were homogeneously distributed in the tape and tended to align fairly well along the tape casting direction. The addition of short C fibre hindered the shrinkage in the plane containing the fibres as well as the grain growth of SiC during sintering.
Advances in gas turbine technology place an increasing demand on thermal protection systems of nickel-base superalloys in turbine blades. Current strategies for performance improvements are focused on thermal barrier coatings (TBC).
Research groups: CeraMat
A novel cost-effective alternative in the form of nano/micro carbonized particles produced from waste bagasse fibers has been explored to modify the mechanical properties and fracture pattern of the resulting cementitious composites. Carbonized bagasse particles were produced at Politecnico di Torino and characterized by Raman spectroscopy and scanning electron microscopy. When added with cement paste up to 1 wt% in six different proportions, the carbonized bagasse particles were found effective in significant enhancement of mechanical strength as well as fracture toughness.
Research groups: CeraMat
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the production of coarse recycled aggregates (RA), the fine fraction is involuntarily produced, representing a large amount of the weight of the crushed C&D waste. In this work the mortar has been analyzed, by replacing standardized sand (SS) with recycled sand (RS) and by using a fixed w/c ratio equal to 0,5. The most relevant problem has been occurred during the mixing phase: in fact, RS induced a high water demand which made the mechanical properties worst.
In this investigation multilayered MoSi2 was processed by tape casting, stacking of layers, debinding and pressureless sintering. The debinding treatment was optimized by means of thermogravimetric analysis and the effect of the sintering temperature on both microstructure and properties of the laminate was studied.
Tape casting combined with layer stacking, debinding and sintering proved to be a suitable technique for processing SiC-based multilayers to be used as thermal protection system for space vehicles. In this paper two methods have been evaluated in order to decrease the thermal conductivity through the thickness of the material: the insertion of layers containing a pore forming agent able to leave residual porosity; the deposition of an external insulating coating made of yttria-partially stabilized zirconia (YPSZ). Both techniques contribute to the reduction of thermal conductivity.
Two types of laminated multilayer silicon carbide plates were processed by tape casting, de-binding and pressureless sintering. The specimens were subject to thermal re-entry testing under conditions as derived from the HERMES study: up to 100 combined thermal and air pressure cycles were performed. After the first cycle, all samples lost about 1.5% of their initial mass. This was caused by burn-off of the carbon added as sintering aid or left after thermal decomposition of binder and plasticizer used in the tape casting process.
Research groups: CeraMat
WO3 and WO3-based materials in the form of thin films, either as bulk or as nanostructures, have been widely used for the detection of a variety of gases, such as NO2, H2, NH3 and Cl2. The purpose of this study was to prepare materials from the WO3-ZnO-Nd2O3-Al2O3 system containing high amount of WO3 for applications in environmental monitoring by applying the melt quenching method. Homogenized batches of the starting oxides were melted for 20 min at 1,240 °C in platinum crucibles in air atmosphere.
Research groups: CeraMat
Research groups: PetroMat
Metal nanoparticles (NPs) have recognized a growing importance in chemistry, electronics, optics, physics, and biology in the last decades. The possibility of tuning their unique properties varying dimension and morphology widely extends the range of possible applications. Several innovative chemical routes have been investigated to design shape-controlled synthesis to combine high-yield production with controllable and repeatable morphology.
Research groups: PetroMat
Pt–Co alloys prepared by high energy ball milling synthesis were tested as electrocatalysts for hydrogen fueled Polymer Electrolyte Membrane Fuel Cells (PEMFC). In the present contribution we report on the first results regarding the electrochemical behaviour of two samples of Pt–Co alloys. One sample contains 20 wt.% alloy Pt:Co in the molar ratio 0.25:0.75 and C 80 wt.% and the second one Pt:Co in the molar ratio 0.75:0.25 and C 80 wt.%.
Materials having nanometric dimensions are able to improve their functional properties, which allow their exploitation in highly performing sensors.
Materials with at least one dimension smaller than 100 nm are classified as nanostructured.
The aging response at room temperature of aluminium alloy 6061 was compared with that of its composites containing SiC whiskers or particles. Materials were solutionized for 2 h at two different temperatures (529 and 557°C), quenched in cold water and naturally aged for up to 90 days. The improvement in mechanical characteristics was checked by means of hardness measurements. The microstructural features of aged samples were studied by differential scanning calorimetry. Both aluminium alloy and its composites showed the same aging sequence.
Research groups: CeraMat
In the present work, carbon nano/micro-particles obtained by chemical vapor depostion (CVD) process and controlled pyrolysis from polyethylene beads (CNBs) and coconuts choir (CCNs) are presented. These materials were characterized by Raman spectroscopy, thermogravimetry and field emission-scanning electron microscopy (FE-SEM). FE-SEM observations evidenced that CNBs particles proved to be spherical and interconnected, while the CCNs were irregular in shape, as the result of the grinding step.
Heat recovery from waste gas is a major key process for increasing efficiency of thermal processes. The aim of the present work is to increase heat transfer coefficients of ceramic heat exchangers of recuperative burners using highly structured surface elements created from a textile precursor. The paper describes the chosen geometries and their thermal behavior, the ceramization process and the preliminary design of the new recuperative burners.
Research groups: PetroMat
The continuous increase in demand for light alloys in different applications involves manufacturing high integrity and superior performance components using cost-effective and safety processes. In this direction, the research communities together with manufacturing industries are focusing their attention to develop new products using innovative procedures, i.e., Semi-Solid Metal (SSM) processing routes. The central issue is the technological transfer to industry for affordable mass production.
This paper concerns with the optimisation of the innovative rheocasting process to produce a new generation of brake callipers, characterised by very high reliability and strength. The attained very promising properties favoured their use on a very high performance car and the presented technique can be further extended for other important challenging applications. The prototype components are produced using T6 heat treated A357 alloy. Results on the samples machined directly from the produced callipers are in detail described and analysed.
Alkaline (lithium, potassium, rubidium) and alkaline-earth (magnesium, barium) doped hematite materials were studied for NO2 sensing application. The synthesized materials were characterized by laser granulometry, X-ray diffraction and scanning electronic microscopy. A temperature of 1300 °C was chosen as the optimal heat treatment in order to obtain the densest material.
NiAl(Si)/Al2O3 composites with co-continuous structure were prepared by a double reactive metal penetration technique. Silica preforms were in a first step immersed in an Al bath, obtaining an Al(Si)/Al2O3 composite, then a reactive penetration of Ni was performed, bringing to the substitution of Al with NiAl. The obtained composites present both phases continuous, and the whole process is a near-net-shape one. Various tests were performed, showing that the composites present high hardness and melting point and good modulus.
Research groups: PetroMat
Wear resistant hard surfaces and shock resistant cores enhance the life of mechanical components such as gears, shafts and cams. Low carbon steels can provide the core properties that such parts need while the surface characteristics can be created by the process of nitriding and nitrocarburizing. M. Rosso, G. Scavino and G. Ubertalli of the Department of Materials Science and Chemical Engineering, Polytechnic of Turin, Italy, use experimental results from research into nitrocarburizing to show the effect it has on sintered materials.
Research groups: PetroMat
Samples of UNI 39 NiCrMo 3 and 38 CrAlMo 7 steels have been nitrocarburized with two different proprietary processes, namely the Degussa's Tenifer-TF1 and the Hydromecanique and Frottement's Sur Sulf salt bath treatments. With the former process two different melt compositions were adopted, keeping the CN** minus ions content either at the 0. 5 or at the 4 wt pct level (treatments Tenifer-TF1 A and B). The top surface layer constitution, as determined by X-ray diffraction analysis, is reported for the two steels heat-treated in the Tenifer-TF1 baths in figs.
Research groups: CeraMat
NASICON powders having the Na3Zr2Si2PO12 composition were prepared using a sol-gel method. All the reagents used were alkoxides. The precursor solution was rapidly hydrolized in order to get a precipitate, or slowly gelated under exposure to low atmospheric humidity. The slow hydrolysis process was studied using nuclear magnetic resonance (NMR) spectroscopy in liquid phase. 1H, 13C, and 31P NMR spectra were performed. NMR allowed us to identify the advancement of the reaction and the degree of polymerization.
Research groups: PetroMat
Research groups: AddiMat
Purpose - The aim of this research is to reach a deep understanding on the effect of the process parameters of Direct Metal Laser Sintering process (DMLS) on macroscopic properties (hardness and density) of AlSi10Mg parts and resulting microstructure.
Design/methodology/approach - A full factorial design of experiment (DOE) was applied to determine the most significant process parameter influencing macroscopic properties of AlSi10Mg parts manufactured by DMLS process.
Research groups: CeraMat
The possible chemical interactions which occur between sodium (as sulphite), iron and cerium (as oxides) coming from pollutants or additives, and the materials which make up three commercial filters, in the working temperature of a Diesel soot filter, were considered. The commercial filters were respectively a cordierite monolith filter, a wound-fiber filter made by continuous Al2O3-B2O3-SiO 2 fibers, and a sintered Chrome-Nickel stainless steel filter plate.
Research groups: PetroMat
During carbonitriding of iron-manganese alloys employing liquid salt baths with high alkaline cyanate content, the presence of an unknown phase, identified as an iron-manganese carboxinitride of the (Fe, Mn) (C, N, O,) type, was observed on the sample surfaces. This phase forms easily and in considerable amounts on treating alloys containing more than 20 wt. % of manganese at temperatures of about 850 K and for times higher than 10 hours.
Research groups: CeraMat
The Laser Granulometer is an efficient instrument for detecting the reactivity of cement clinkers components in contact with water. Results are satisfactorily comparable with those obtained by means of different analysis techniques. Further applications are suggested.
Research groups: PetroMat
The evolution of friction and wear of Fe-2Mn-0.85Mo-0.5C steels sintered under two different conditions was investigated during dry sliding tests. Irregular behaviour of the friction coefficient was observed and analysed by means of fractal geometry methods. It was proven that the friction coefficient traces had the property of fractal curves. In general, the fractal dimension of friction coefficient trace tended to increase with increasing wear rate.
Optimal microstructural design of a catalytic premixed FeCrAlloy fiber burner for methane combustion
Research groups: PetroMat
New catalytic FeCrAlloy premixed fiber burners for natural gas combustion in domestic applications were developed according to an accurate microstructural design consisting of subsequent optimized steps: (i) optimal preoxidation of the FeCrAlloy fiber mat so as to develop the best possible Al2O3 layer for simultaneous prevention of deeper fiber oxidation at high temperature and optimal catalyst anchoring over the fiber surface, (ii) deposition via the either spray-pyrolysis or wash-coating technique of a previously developed perovskite catalyst (LaMnO3â 17MgO), and (iii) extensive testing of t
Research groups: PetroMat
This work aims at studying the possibility of optimising the heat treatment cycles of parts produced using the New Rheocasting process in order to reduce the total cost of the operation, attaining good mechanical properties for high performance parts. The mechanical properties and the microstructure features of the considered A 356 alloy and the relative produced parts have been analysed and studied on samples machined both from the as cast and from the heat treated compomnents.
Spray drying is widely used for producing granulated feed materials for compaction process, which is the current industrial method for manufacturing alumina-zirconia femoral heads. The optimization of the granules compaction behavior requires the control of the slurry rheology. Moreover, for a dual-phase ceramic suspension, the even phase distribution has to be kept through the atomization step. Here we present two approaches addressing the key issues involved in the atomization of a composite system.
Research groups: PetroMat
Preliminary results on Pt-based electrocatalysts prepared with CMK3 mesoporous carbons are presented. The electrocatalytic performance towards the oxygen reduction reaction (ORR) was compared to that of commercial Pt/C-Vulcan catalysts with the same Pt content. Polarisation tests were carried out with a single PEM fuel cell containing the Pt/OMC cathodes. The analysis of these tests, based on a semi-empirical determination of the various polarisation terms, showed an interesting catalytic activity for ORR for the cathodes prepared with mesoporous carbon supports.
Research groups: CeraMat
Organic-inorganic materials to be used as hydrophobic consolidants for plasters were synthesized starting from an inorganic precursor (Tetraethoxysilane [TEOS]), added to a polysiloxane epoxy formulation and thermally cured with Ytterbium as acid catalyst. The TEOS reduces the viscosity of the resin, contributing to the mechanical properties of the film, without causing cracking. Solvents, that are harmful for workers and environment and show some drawbacks in the practice of restoration, were not used. The film properties and the formation of silica clusters were investigated.
Research groups: PetroMat
Si–SiC–ZrB2 are produced by the reactive infiltration with molten silicon in porous SiC–C–ZrB2 preforms. It is observed that oxidized Si–SiC–ZrB2 ceramics present a layered structure composed of an outer layer of silica and a borosilicate glass intermediate layer with ZrO2 particles and the unoxidized bulk material. The graphs show that the passivation is very effective already after 5 min of oxidation. The thermograms do not vary significantly when the oxidation times are increased.
SiC–ZrB2 ceramic laminates with different SiC:ZrB2 ratios were prepared by tape casting, binder burnout and pressureless sintering at 2200 °C in view of their application in thermal protection systems. Their oxidation behavior in air was investigated by TGA up to 1600 °C and by long term oxidation tests at 1500 and 1600 °C. Both microstructure and mechanical features of laminates were compared, before and after oxidation.
The oxidation behaviour of a FeCrAl alloy with little rare earth content (Y = 0.01 wt.%) was investigated. Specimens of this alloy were submitted to long-term oxidation treatments (up to 30 days) at 900 and 1200 °C, under gaseous atmospheres containing 21, 10 and 2 vol.% of O2. The weight gain for unit area was measured vs. oxidation time. The alumina scale growth was found to occur, at least during the first days of treatment, according to Wagner's parabolic law. Afterwards, the layer rate growth decreases down to that expected on the basis of this law.