The chemical composition of sintered steels has been related to the physical and mechanical characteristics of the surface layers obtained by solid boronizing. Sintered samples of various composition and density were produced as bushings by mixing Hoganas powders and subsequent heating in industrial furnaces. Various conditions of temperature, time of treatment and chemical composition of the boriding agent were investigated. All the borided layers consisted of Fe//2B and FeB type borides.
IMSE
Institute of Materials Science and EngineeringPublications list
The chemical composition of sintered steels has been related to the physical and mechanical characteristics of the surface layers obtained by solid boronizing. Sintered samples of various composition and density were produced as bushings by mixing Hoganas powders and subsequent heating in industrial furnaces. Various conditions of temperature, time of treatment and chemical composition of the boriding agent were investigated. All the borided layers consisted of Fe//2B and FeB type borides.
Differential scanning calorimetry (DSC) is used in order to investigate the aging behaviour of AlCuMg alloys with different Cu:Mg ratios. Mechanism and kinetics of aging for these materials are compared with those of an (AlCuMg)-SiC composite. DSC results are in fairly good agreement with metastable AlCu and AlCuMg phase diagrams. The SiC reinforcement does not affect the precipitation path; furthermore, the activation energy for θ″ precipitation, calculated by Ozawa's method, is not appreciably different, taking into account the experimental error, for unreinforced alloy and composite.
Research groups: CeraMat
Research groups: CoatMat
La tecnologia laser texturing (LST) è una delle tecniche più promettenti nel campo delle microlavorazioni superficiali in quanto consente di ottenere un eccellente controllo della forma e delle dimensioni dei microfori prodotti ed è estremamente veloce e senza ricadute dannose per l'ambiente. Recentemente si è assistito allo sviluppo di diversi lavori nei quali il laser è stato impiegato per migliorare il comportamento tribologico di componenti meccanici in materiale metallico.
Research groups: CeraMat
The on-going research on carbon nano beads (CNBs) are focusing on applications ranging from high strength composites, catalyst carriers, lubricants, electronic devices, weather resistant materials, molecular ball bearings, drug delivery vehicles (Bio-medical), semiconductors/transistors, high-capacity batteries and Hydrogen reservoir for the automotive industry. The commercial applications of CNBs are novel and yet immature for market.
Research groups: CeraMat
The present paper reviews the current state of the art of carbon nanotubes cement-based
composites and the possible applications. The influence of carbon nanotubes additions onto cement paste
mechanical and electrical properties are discussed in detail. Though promising, several challenges have still to be
solved before the introduction of these new materials into the public sphere through civil infrastructures.
Research groups: CeraMat
This paper deals with the preparation and the characterization of ceramic porous filters whose pores were deposited with a γ-Al2O3 layer via the so-called "urea method", in order to increase their specific surface area. Once activated with a suitable catalytic principle, these filters can find a potential application in flue gas cleaning according to a combined action: mechanical particulate removal + catalytic abatement of chemical pollutants (nitrogen oxides volatile organic compounds, etc.).
The first stages of the development of a catalytic trap for diesel particulate removal from vehicle exhaust gases are addressed, ranging from catalytic trap preparation (a ceramic foam is deposited with catalysts, suitable for soot combustion, based on mixtures of KCl and different vanadates) to catalytic trap testing in a specific pilot plant (an acetylene burner is used to produce a soot laden flue gas which is then treated by the apparatus while the pressure drop buildup throughout the trap and the trap collection efficiency is measured).
The present paper deals with the preparation of catalytic filters for Diesel particulate removal by developing an in situ solution combustion synthesis method. Lanthanum chromite perovskite catalyst has been deposited on silicon carbide and cordierite honeycombs with the aim to investigate the influence of the starting solution containing catalyst precursors on the coating characteristics. SEM, XRD and EDX analyses have been carried out in order to evaluate the homogeneity and the thickness of the catalyst layer.
Research groups: CeraMat
Ceramic foams show a significant potential of development and application, essentially due to the emergence of environmental preoccupations. A brief overview of the state of the art in cellular ceramic application, preparation and characterization is presented in order to introduce some new data concerning the elaboration of mullite and PZT foams by a replication and a bubble generation method, respectively.
The application of the electrophoretic deposition (EPD) technique to the preparation of high quality electrolyte films for intermediate temperature solid oxide fuel cells (IT-SOFCs) was investigated. Films of La0.83Sr0.17Ga0.83Mg0.17O2.83 (LSGM) were deposited on Pt and La0.8Sr0.2MnO3 (LSM) substrates from suspensions in acetone/ethanol (3:1 by volume) mixture solvent and sintered at 1300 °C. Pt supported LSGM films, 10-20 μm thick, exhibited good adhesion to the Pt substrate, well-distributed microporosity and some surface roughness.
Surface layers having elevated hardness were produced by ion nitriding of titanium and α-β alloys of Ti-6wt.%Al-4wt.%V, Ti-4wt.%Al-2wt.%Sn4wt.%Mo and Ti-4wt.%Al-2wt.%Mn. The treatment was conducted at temperatures between 1073 and 1273 K for times of 4-32 h, using gaseous mixtures of nitrogen and hydrogen containing 20-80 vol.% nitrogen. X-ray diffraction, optical microscopy and microhardness were used to characterize the hardened surfaces.
TiO2 nanotube (NT) arrays with different lengths were fabricated by anodic oxidation of Ti foil and free-standing NT membranes were detached by the metal substrate and bonded on the fluorine-doped tin oxide surface implementing an easy procedure. Morphology of the as-grown material and of the prepared photoanode was investigated by means of electron microscopy, deepening the investigation on the thermal treatment effect.
Research groups: CeraMat
Co-continuous 63%Al2O3/37%Al(Si) composite, known as C4 composite, was produced by submersion of silica glass specimens in a molten metal bath. The effect of temperature and composition of the metal bath on the reactive penetration rate was investigated. An infiltration speed exceeding 2 mm/h, increasing with temperature, and suitable for practical applications, was observed above 1100 °C. Mechanical properties of C 4 specimens were measured, at room temperature, and related to composite microstructure.
Research groups: CeraMat
The fabrication of transparent polycrystalline Y3Al5O12 (YAG) is still a challenge, requiring the achievement of highly pure and fully dense, homogeneous materials. An important role is played by the powder characteristics: pure, fine and unagglomerated powders are essential for achieving full density and the required microstructural features. Keeping in mind these requirements, the aim of this work was to investigate the role of different synthesis parameters during co-precipitation, which is widely used to prepare YAG powders for transparent devices.
Research groups: AddiMat
Casting process simulation is nowadays established as a strategic tool in process optimisation to improve product quality. However, sometimes the required three-dimensional mathematical model of the casting is not available, because the original drawings are not-up-to date and parts are subjected to design changes. In these cases, reverse engineering (RE) is the most suitable method to reconstruct the geometrical model of the casting. In this paper, a RE-based procedure is proposed to obtain the three-dimensional CAD model of a casting from its physical equipment.
A K-V-I-containing catalyst for low-temperature combustion of carbonaceous materials was studied so as to check its potential in diesel particulate removal. X-ray diffraction (XRD) and scanning electron microscopy (SEM-EDS) showed that its main constituting compounds are KVO3, KI and K4O7. Differential scanning calorimetry (DSC) and temperature-programmed oxidation (TPO) tests enlightened that the catalyst is active well below 400°C (peak combustion temperature: Tp = 380°C).
Research groups: CeraMat
Several formulations of a Cusingle bondKsingle bondV catalyst supported on α-Al2O3 with different Cu:K:V atomic ratios and with different loadings of the active components on the support were prepared by impregnation with aqueous solutions of KCl, CuCl2 · 2H2O and NH4VO3, drying and calcination.
The composition of these catalysts, suitable for greatly accelerating the combustion of carbonaceous materials, was investigated by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR) and scanning electron microscopy (SEM).
Research groups: CeraMat
In Part I the chemical and microstructural nature of Cusingle bondKsingle bondV catalysts for diesel soot combustion was assessed. In this second communication the reaction mechanism of these catalysts is studied by testing their activity through either differential scanning calorimetry (DSC) or temperature-programmed oxidation (TPO), performed on catalyst-carbon mixtures.
The mechanism of combustion synthesis of lanthanum chromite was investigated by carrying out simultaneous differential thermal analysis (DTA), thermal-gravimetric analysis (TGA) and quadrupole mass spectrometry measurements (MS). The whole process was found to involve several phenomena: urea and nitrates thermal decomposition, exothermal reactions occurring directly between nitrates and urea as well as between their decomposition products, final reaction between solid oxides.
Combustion synthesis has been applied to LaMnO3 production with a view to boosting its activity towards natural gas combustion by enhancing its specific surface area. With a highly exothermic and self-sustaining reaction, this oxide can be quickly prepared from an aqueous solution of metal nitrates (oxidisers) and urea (fuel).
The favourable conditions for LaMnO3 formation were sought: only fuel-rich mixtures are effective, but carbonaceous deposits are formed when too much urea is used.
Research groups: PetroMat
In the present work the possibility to obtain large size castings of compacted graphite cast iron by inoculating ipereutectic pig iron melts with Fe-Si-Ca-Mg-Ti alloys with different calcium contents was first studied. Two alloys have been used: the first contained 4 divided by 5, 5 wt % Ca and the second less than 1 wt % of the element. The amount of inoculant alloy to be added to the melts was calculated so that the content of Mg in the casting agreed with the Sofroni equation. Casting temperatures were in the 1350-1400 degree C range.
Research groups: PetroMat
In the present work the possibility to obtain large size castings of compacted graphite cast iron by inoculating ipereutectic pig iron melts with Fe-Si-Ca-Mg-Ti alloys with different calcium contents was first studied. Two alloys have been used: the first contained 4 divided by 5, 5 wt % Ca and the second less than 1 wt % of the element. The amount of inoculant alloy to be added to the melts was calculated so that the content of Mg in the casting agreed with the Sofroni equation. Casting temperatures were in the 1350-1400 degree C range.
Research groups: CeraMat
Dry pressing is the most common industrial shaping process for ceramic pieces. Sol-gel powders are of high reactivity, but very often agglomeration-aggregation phenomena limit this advantage by inducing poor compaction behaviour. Consequently the goal of sol-gel powder research - to obtain full densification at very low sintering temperature, is not achieved. With the intention of showing the influence of sol-gel powders, specific characteristics on pressing, compaction diagrams and green body characteristics of two experimental zirconia sol-gel powders have been determined.
Research groups: CeraMat
Al2O3-YAG (50vol.%) nanocomposite powders were prepared by wet-chemical synthesis and characterized by DTA-TG, XRD and TEM analyses. Amorphous powders were pre-heated at different temperatures (namely 600◦C, 800◦C, 900◦C and 1215◦C) and the influence of this thermal treatment on sintering behavior, final microstructure and density was investigated. The best performing sample was that pre-calcined at 900◦C, which yields dense bodies with a micronic/slightly sub-micronic microstructure after sintering at 1600◦C.
Research groups: PetroMat
IRON-CHROMIUM ALLOYS PLATES WERE HEATED AT 840 K IN FUSED SALT BATHS WITH HIGH ALKALINE CYANATE CONTENTS. LONG-TERM HEAT TREATMENT UNDER THESE CONDITIONS LED TO THE FORMATION OF A(FE,CR) (C,O,N) PHASE ON THE SURFACE OF THE SPECIMEN. THE CHARACTERISTICS OF THE PHASE WERE INVESTIGATED BY X-RAY DIFFRACTION ANALYSIS, MICROPROBE DETERMINATION AND CHEMICAL ANALYSIS. THE PHASE HAS A CUBIC (NACL TYPE) UNIT CELL WITH A LATTICE PARAMETER INTERMEDIATE BETWEEN THOSE OF CRN AND WUSTITE.AS IN THE CASE OF WUSTITE, THE STRUCTURE IS IRON-DEFICIENT AND BECOMES MUCH MORE SO AS OXYGEN IS ADDED.
Research groups: PetroMat
This work presents a comprehensive investigation of the piezoresistive response of a metal-polymer composite for robotic tactile sensor application. Composite samples, based on nickel nanostructured conductive filler in a polydimetihylsiloxane (PDMS) insulating elastomeric matrix, were prepared changing several process parameters like thickness, composition of the polymer and nickel filler content. A variation of electric resistance up to nine orders of magnitude under applied uniaxial load was measured in the fabricated samples.
A wide series of carbon nanostructures (ranging from fullerenes, through carbon nanotubes, up to carbon nanofibers) promise to change several fields in material science, but a real industrial implementation depends on their availability at reasonable prices with affordable and reproducible degrees of purity. In this study we propose simple instrumental approaches to efficiently characterize different commercial samples, particularly for qualitative evaluation of impurities, the discrimination of their respective spectral features and, when possible, for quantitative determination.
Research groups: HTMat
Blocks of vertically aligned multiwall carbon nanotubes were prepared by thermal chemical vapor deposition starting from camphor and ferrocene precursors. The blocks, having a thickness of approximately 2 mm and composed of nanotubes with diameter ranging between 30 and 80 nm, were submitted to compression tests. The results were analyzed accordingly with a simple model consisting in a parallel array of nanotubes under compression and bending suffering microscopic instability and compaction.
Research groups: PetroMat
Purpose: Purpose of this paper was to apply a computer method of open porosity analysis for determination of porosity in sintered Astaloy CrL and CrM powders. Design/methodology/approach: The powders used in the present papier are pre-alloyed iron-base powders containing low amounts of chromium and molybdenum. The amount of graphite which is mixed with the iron-base powder is 0.6% and lubricant is 0.75%.
This article compares most of the three-dimensional (3D) morphometric methods currently proposed by the technical literature to evaluate their morphological informative value, while applying them to a case study of five patients affected by the malocclusion pathology. The compared methods are: conventional cephalometric analysis (CCA), generalised Procrustes superimposition (GPS) with principal-components analysis (PCA), thin-plate spline analysis (TPS), multisectional spline (MS) and clearance vector mapping (CVM).
Research groups: PetroMat
The proposed materials and the production process for particulate traps, used in order to reduce the diesel engine emissions, are reviewed. The filter regeneration principles are discussed. An overview is given on the use of catalysts for the NOx reduction or for particulate oxidation in diesel exhaust gas.
Research groups: PetroMat
The investment casting process, extensively used for the production of jewels, is made up of different phases that, for their intrinsic typology, are deeply influenced by many chemical, physical as well as metallurgical factors. Even though investment casting has been used for decades, it is absolutely not properly optimised, also in consequence of the difficulty in deeply understanding, and therefore controlling, all the different phases of the process. It is therefore evident that different, and unfortunately many, kind of defects may appear in precious art-crafts.
Research groups: CeraMat
Two α-Al2O3/YAG composite powders have been prepared by reverse-strike precipitation, starting from chlorides aqueous solutions, the former containing 50 vol% of the two phases (labelled as AY50) and the latter made of 90 vol% of alumina and 10 vol% of YAG (AY90). The as-prepared powders were characterised by DTA/TG simultaneous analysis as well as by XRD analysis performed after calcination at different temperatures.
Research groups: CeraMat