bluuebunny/crossref_metadata_2025 huggingface dataset:
3-D Static and Time-Depending Modelling of DC and RF Thermal Plasmas for Industrial Applications
Authors: Colombo Vittorio , Ghedini Emanuele , Sanibondi Paolo
Published: October 2010

Thermal plasma processes play nowadays a key role in many industrial applications, such
as powder densification and spheroidization, synthesis of nano-powders, treatment of waste
materials and spraying of thin coatings. Although many of these applications have been fully
implemented industrially for many decades, modelling plays an important factor in their continued
development and improvement. 3-D simulation of the behaviour of commercial inductively coupled
(RF) plasma can be useful tool to predict the main features of plasma assisted treating and
processing of injected raw materials. The effects of changing coil current frequency, the hydrogen
mixing in argon primary gas and the flow patterns and temperature distributions have been
investigated. 3-D time-dependent modelling DC non-transferred arc plasma torch for plasma
spraying operating at atmospheric pressure can allow the prediction of particle trajectories and
thermal history, the analysis of the influence of the plasma jet cold gas entrained eddies on particle
behaviour and the mechanisms that can lead to a fluctuating and non homogeneous heating of the
particle stream. All computations have been performed using a customized version of the CFD
commercial code FLUENT©.
Damping Properties of Hard Coatings for Engine Applications
Authors: Torvik Peter J.
Published: October 2010

Although blade coating materials dissipate vibratory energy while acting as thermal barrier coatings or protecting the substrate against corrosion or erosion, the inherent nonlinearity of these materials complicates the determination of the necessary material parameters. While plasma-sprayed ceramics alone do not appear to provide the desired levels of dissipation, notable increases in damping have been found to result from the inclusion of small amounts of viscoelastic materials. With proper selection of the added component, the resulting coating may be tailored for high damping in a specific temperature range. Vacuum infiltration of polymeric components into plasma-sprayed ceramics raise the dissipation to desired levels for temperatures of 93-135 oC; co-spraying mixtures of ceramics and glass frits leads to extremely high damping in the transition range of the glass, typically 550-800 oC.
Mechanical and Surface Properties of Chemical Vapor Deposited Protective Aluminium Oxide Films on TA6V Alloy
Authors: Samélor D. , Aufray Maelenn , Lacroix Loic , Balcaen Yannick , Alexis Joel , Vergnes H. , Poquillon Dominique , Béguin Jean Denis , Pébère Nadine , Marcelin Sabrina , Caussat B. , Vahlas Constantin
Published: October 2010

Mechanical, barrier and surface properties of aluminium oxide films were investigated by nanoindentation, microscratch and micro tensile tests, by isothermal oxidation and voltammetry, and by contact angle measurement. The films were grown on TA6V substrates by a low pressure MOCVD process from aluminium tri-isopropoxide. Modelling of local gas flow, gas concentration and deposition rate profiles was performed using the CFD code Fluent on the basis of an apparent kinetic law. Films grown at 350 °C are amorphous AlO(OH), the one at 480 °C is amorphous Al2O3 and the one at 700 °C is nanocrystalline -Al2O3. Scratch tests and micro tensile tests resulted in adhesive failure on the two films grown at low temperature whereas cohesive failure was observed for the high temperature growth. Sample processed at 350 °C presents significantly lower oxidation kinetics in dry air than the bare substrate. Contact angle changes approximately from 100 to 50 degrees for films processed at 350-480 °C and 700 °C, respectively. Concerning the electrochemical behavior in NaCl environment, polarization curves revealed that amorphous alumina coatings improved the corrosion resistance by comparison with the others oxide films. These consolidated results reveal promising combination of properties for the films grown at different temperatures with regard to the targeted applications.
Miniature Ceramic Antennas for Wireless Applications
Authors: Milosavljevic Zlatoljub D.
Published: October 2010

This paper explores the use of high-permittivity ceramic substrates in producing novel miniature ceramic chip antenna designs. Single- and dual-band antennas for non-cellular applications have been presented. Another aspect presented in the paper is creating a compact switchable ceramic chip antenna for cellular application. The measured results of all antennas are given. It is shown that presented antenna structures have very good impedance and radiation properties, features that are of interest in many mobile applications.
Electric Field Breakdown of Polymer Based Nano-Composite at Room and Cryogenic Temperatures
Authors: Rodrigo Horatio , Heller George H. , Ingrole Aniket , Liang Z.R. , Crook Danny G. , Ranner Steve L.
Published: October 2010

Electrical breakdown field measurements on Polymethylmethylacrylate (PMMA) and a nano-composite of PMMA/Barium Titanate (BTA) by 10% wt are presented. The measurements were made using uniform field electrode configuration under high voltage DC. The electrodes were made of stainless steel, each having a Bruce profile, and diameter 25 mm. The measurements were made at room temperature (293 K) and liquid Nitrogen temperature (77 K). Using Weibull statistics it shows that both PMMA and the nano-composite have breakdown electrical field strengths much higher at 293 K than at 77 K. It has been shown that there was very marked improvement in the reliability of results for both compounds at 77 K over those at 293 K. The SEM micrographs have shown very distinct differences in the behavior of the nano-compound between 293 K and 77 K, PMMA also exhibit some clear differences.
Electrical Properties of Nb-Doped and Nb-Mn-Codoped BaTiO3-(Bi0.5Na0.5)TiO3 Lead-Free PTCR Ceramics
Authors: Li Guo Rong , Leng Sen Lin , Zheng Liao Ying , Zeng Jiang Tao , Xu Zhi Jun , Chu Rui Qing
Published: October 2010

Nb-doped and Nb-Mn-codoped (1-xmol%)BaTiO3-xmol%(Bi0.5Na0.5)TiO3 (BBNTx) lead-free positive temperature coefficient of resistivity (PTCR) ceramics were prepared by the conventional solid state reaction method. The XRD patterns indicated that all BBNTx samples formed a single perovskite structure with tetragonal phase. 0.25 mol% Nb doped BBNT1 ceramic, sintered at 1330°C for 1h in air, had low room-temperature resistivity (ρ25) of 80 Ω•cm and a high resistivity jump (maximum resistivity [ρmax]/minimum resistivity [ρmin]) of 4.2 orders of magnitude with Tc about 152°C. The Nb-doped BBNTx (10≤x≤60) ceramics also showed distinct PTC effect with Tc between 185 and 232°C by sintering in N2, which was shut off when samples were cooled to a low temperature. In addition, The Nb-Mn-codoped BBNT1 ceramics exhibited higher resistivity jump than the single Nb-doped ones, with increasing the room-temperature resistivity.
High Performance Varactor
Authors: Testino Andrea
Published: October 2010

A multi-components multi-layer co-fired ceramic varactor with superior performance is
here presented. The concept combines a tunable capacitor with optimized properties in a restricted
temperature range with PTCR layers to control the overall device temperature. Different prototypes
are produced as demonstrator units; one of them is described in detail. The device may be tuned by
a primary bias voltage applied to the capacitor and by a secondary voltage applied to the PTCR to
set the working temperature. By proper choice of materials, bias voltage and working temperature,
the varactor is optimized to the requested figure of merit for a specific application. The prototype
here described has shown a tunability >83% @ 2.75 V//m (Patent Pending)
Coexistence of Superconductivity and Magnetism in Ruthenocuprates
Authors: Cuoco Mario , Gentile Paola , Gombos Marcello , Vecchione Antonio , Noce Canio
Published: October 2010

The layered ruthenocuprate materials RuSr2LnCu2O8 and
RuSr2(Ln1+xCe1-x)Cu2O10, with Ln=lanthanide or Y for both structures,
consist of pairs of CuO2 planes alternating with perovskite-like sheets of
vertex sharing RuO6 octahedra. Samples of Ru-1212 and Ru-1222 materials
were known to show both superconducting and magnetic transitions. Here,
we discuss the problem of the coexistence, considering a model which
includes two types of carriers responsible separately for the ordered phases.
By considering the interplay between a hybridization mechanism and the
direct exchange coupling between these carriers, we look at the stability of
the coexisting phase assuming an inhomogeneous superconducting phase.
Manipulating Electronic Structure by Laser Pump-Photoemission Probe in Oxides
Authors: Mizokawa Takashi
Published: October 2010

We report on photoemission studies of SrTiO3, Pr0.55(Ca1-ySry)0.45MnO3 (PCSMO, y=0.25,0.40), and Ti1-xCoxO2-δ (x=0.05, 0.10) under laser illumination and discuss the origins of the unusual electronic structure changes induced by optical excitation at the surfaces of these transition-metal oxides. The present study shows that photoemission spectroscopy is a powerful tool to explore novel photo-induced electronic states which can open up possibilities of new optical devices.
Effect of DC Poling Field on Domain Behavior in Lead-Free Piezoelectric Ceramics
Authors: Ogawa Toshio , Furukawa Masahito , Tsukada Takeo
Published: October 2010

Poling characteristics, especially DC poling field (E) dependence of dielectric and piezoelectric properties were investigated to evaluate the domain behavior in lead-free ceramics such as alkali niobate and alkali bismuth titanate ceramics. The domain switching was confirmed by the E to realize minimum dielectric constant (εr), minimum electromechanical coupling factor (k) and maximum frequency constant (fc), because of domain clamping. On the other hand, the domain rotation occurred at the E to obtain maximum εr and minimum fc. These phenomena are observed in the lead-free ceramics as well as PZT ceramics.
Diffuse Phase Transition and Ferroelectric Properties of Ceramic Solid Solutions in New SrTiO3-BiScO3 System
Authors: Ivanov Oleg , Danshina Elena , Tuchina Yulia , Sirota Viacheslav
Published: October 2010

Ceramic solid solutions of (1-x)SrTiO3-(x)BiScO3 system with x=0, 0.05, 0.1, 0.2, 0.3, 0.4 and 0.5 have been for the first time synthesized via solid-state processing techniques. Both of end compounds in this system are not ferroelectric materials. X-ray diffraction analysis revealed that at room temperature the samples under study at x=0.2, 0.3, 0.4 and 0.5 consist of mixture of center-symmetric cubic Pm3m phase and polar tetragonal P4mm phase. Anomalous behaviour of dielectric permittivity and dielectric losses for these samples is found to be specific one for ferroelectrics with diffuse phase transitions. Furthermore, examination of the polarization hysteresis behavior revealed weakly nonlinear hysteresis loops in the ferroelectric phase.
Magnetostrictive Galfenol Torque Sensor Devices for Smart by-Wire Steering System in Automobile Technology
Authors: Furuya Yasubumi , Okazaki Teiko , Saito Chihiro , Shimada Munekatsu
Published: October 2010

Polycrystalline Galfenol (Fe-Ga-X, X=Al, C, Zr etc.) alloys were fabricated as a bulk sample from rapid-solidified powders or ark-melted and annealing process method for enhancing various engineering applicabilities of this magnetostrictive alloy. Especially, (Fe-Ga0.15-Al0.05)99.0-Zr0.5-C0.5 [at.%] sample showed a maximum magnetostriction of λmax=90ppm to 150ppm as well as a tensile stress over σ=800MPa. This large magnetostriction is mainly caused by non-precipitating of the ordered A2 phases without the excessive precipitation of ordered phases such as fcc ordered L12, bcc ordered D03 phases and the remained [100] oriented strong textures by a heat treatment. Based on the improvements of these properties in the developed bulk Galfenol alloys, secondarily, we will introduce an application as a smart torque sensor by utilizing Galfenol-ring around the shaft for steering-by-wire system of automobile. A torque sensing system by using the magnetostrictive ring of Galfenol alloy was developed and magnetic flux leakage from the ring attached on the rotating shaft was experimentally measured by using differential Hall probe sensor. The sensitivity of this type of torque-sensor shows a strong dependency of metallurgical microstructure and the residual stress (i.e.hoop-stress) in the ring due to sensor shows a strong dependency of the residual stress (i.e.hoop-stress) in the ring due to the fitting level. A promising result on ring-type and single-structured inverse magnetostrictive torque sensor will be presented.
Fast Firing of Glazed Tiles Containing Paper Mill Sludge and Glass Cullet
Authors: Tonello Gabriele , Furlani Erika , Minichelli Dino , Bruckner Sergio , Maschio Stefano , Lucchini E.
Published: October 2010

The present paper reports on the results of some experiments on the progress of a previous research and describes the production, in single fast firing, of tiles containing 30 wt% of a natural red clay and a mixture of 42 wt% of paper mill sludge and 28 wt% of glass cullet which were coated with a commercial “matt white” glaze. Fired materials were characterized as a function of the top temperature (1090 or 1140 °C) reached during the fast sintering process made in an industrial roller kiln. It is observed that tiles fired at 1090 °C display the best overall performances since the matt glaze well covers the substrate concurring to maintain in line with the official standard for production the mechanical and physical properties of the tiles.
Kinetics Study on Controlled Crystallization of a Ca2ZnSi2O7 Phase in Materials Obtained from Vitrification of Metallurgical Slag and Recycled Soda Lime Glass
Authors: Cedillo González Erika Iveth , Ruiz Valdés Juan Jacobo , Álvarez Méndez Anabel
Published: October 2010

Non isothermal kinetics of a glass obtained from a mixture of 59 wt % of metallurgical slag and 41 wt % of soda lime recycled glass was studied by differential thermal analysis (DTA), x-ray diffraction (XRD) and scanning electron microscopy (SEM). The curves of differential thermal analysis revealed the presence of two exothermic peaks, a major peak at 810 °C and a minor peak at 1085 °C. DRX revealed that the first exothermic peak corresponds to the formation of hardystonite, Ca2ZnSi2O7 and aegirine, NaFe3+Si2O6, while the second minor peak corresponds to the formation of zinc ferrite, ZnFe2O4. The activation energy of the crystallization, Ea, was calculated with the Kissinger equation from DTA data, obtained at different heating rates. In addition, the particle size effect on the kinetics of crystallization was studied. The Avrami factor, n, was calculated with Augis-Bennett method. The values of obtained Ea increase with bigger particle sizes and also the value of n, indicating that for small particles the superficial crystallization mechanism is predominant, while bulk mechanism is preferential on large particles. Obtained materials are suitable for some structural applications.
Effect of Nanosized TiO2 on Nucleation and Growth of Cristobalite in Sintered Fused Silica Cores for Investment Casting
Authors: Casarano Giuseppe , Licciulli Antonio , Chiechi Antonio , Diso Daniela , Bardaro Danilo , Bene Pasquale , Di Foggia Michele
Published: October 2010

Sintered fused silica is often used for making sacrificial cores in investment castings of Ni superalloys. Their usage is fundamental in the manufacture of precise superalloy gas turbine components with complex internal cooling passages.
In this study SiO2/ZrSiO4/TiO2 cores were prepared from fused silica powders with different grain size and zircon and TiO2 content by slip casting method. Green samples were sintered at 1230°C at various soaking time: from 0,5 to 10 hours.
Thermomechanical and microstructural properties of optimized silica obtained by add of 1,5%wt of TiO2 to SiO2/ZrSiO4 composition have been investigated by three point bending tests, XRD and Hg porosimetric analysis. The influence of cristobalite content on thermal stability at high temperature was studied by an optical dilatometer.
At temperature below 1200°C TiO2 appears to act as a phase transformation inhibitor reducing the transformation rate of fused silica to cristobalite at high temperatures. At higher temperature it speeds up the formation of cristobalite.
A comparison with commercial silica cores made by injection moulding has been performed.
A prototype core was obtained and an investment casting was performed on that.
Almost Complete Nitridation of Mesoporous Silica to Mesoporous Silicon (Oxy)Nitride with Ammonia
Authors: Hayashi Fumitaka , Iwamoto Masakazu
Published: October 2010

Mesoporous silicon oxynitride and nitride were prepared through nitridation of various
mesoporous silica, MCM-41, -48, and SBA-15 with ammonia in a plug flow reactor. The nitrogen
contents were dependent on the reaction temperature and the amount of ammonia supplied per sample
weight. The appropriate nitridation temperature was 1273 K and the maximum contents of nitrogen
were 35-39 wt % which correspond to 88-98% of that of Si3N4. Various physicochemical
characterization of the resulting silicon (oxy)nitiride indicated that the pore structures were not
changed upon the nitridation though the lattice constants and the pore diameters decreased and the
wall thickness increased. The nitridation mechanism was discussed on the basis of 29Si MAS NMR
and XPS experiments.
Simple Rheological Tests and Protocols for SME Ceramic Producers
Authors: Gardini Davide , Galassi Carmen
Published: October 2010

The rheological behaviour of ceramic suspensions affects the quality of the products and
the yield of the processes. Therefore, rheology control is needed to obtain materials with enhanced
properties and to reduce energy consumption. The importance of rheology control in slip casting,
spray-drying, screen-printing, ink-jet printing, glazing, and so on, either for Quality Control (QC)
aims or for system formulation, has been acknowledged from many years. As in these control
procedures the determination of the rheological behavior is a critical issue, this work is focused on
the assessment of viscosity (flow behavior) and its dependency on time (usually, thixotropic
behavior). Most of ceramic factories still use simple and cheap instruments to investigate
rheological behaviors (or something related to it). However, the information provided by such
instruments is not completely satisfactory. Therefore, optimization of the procedures is important to
improve reproducibility and precision. Suggestions about simple tests and protocols applicable to
viscometers ordinarily available in ceramic factories are given. Protocols consider besides a precise
description of the tests, all other factors that can affect the results, such as the thermo-mechanical
history of the samples before testing.
Consolidation of Sand by Alkaline Silicate Solution
Authors: Lucas Sandrine , Tognonvi Monique Tohoué , Soro Julien , Rossignol Sylvie , Gelet Jean Louis
Published: October 2010

Progress of fuse technology to reduce cost and to protect environment requires the understanding of physicochemical phenomena that govern the consolidation of the sand with alkaline silicate solution. In this context, this work concerns the agglomeration behaviours of sand with alkaline silicate solution. The effects of sand particles size and concentration of solutions are investigated at various temperatures. The main objective is to understand the interactions between sand and this alkaline solution during the impregnation of sand with sodium silicate solution and the drying leading to the consolidated materials. Various investigations were performed, thermogravimetrical and differential thermal analysis (TG/DTA), gravimetric analysis of wet sample, scanning electron microscopy (SEM) and compressive strength test on dry samples. The results show that agglomeration is affected by silica grains size distribution and temperature. Bonds strength between the grains increase with decreasing grain size and increasing temperature.
Development of Photochromic Coatings on Ceramic Tiles
Authors: Atay Burcak , Gurbuz Mevlut , Kucuk Ali , Goktas Aydin , Dogan Aydin
Published: October 2010

Photochromic materials are sensitive to light when such a material exposed to the sunlight or UV irradiation, it can change color very quickly and turn back to its original uncolored form by removing light resource. Photochromic powder at different ratios in polymeric gel were prepared and coated on ceramic surfaces by using spray technique. This coating technique provided to form homogeneous layer structure on surface. By using polymeric gel, photochromic coatings were occurred at low temperatures with good adhesion. After heat treatment fast response photochromic coatings were achieved. Surface morphology of coatings on ceramic surfaces were investigated by scanning electron microscopy (SEM), the photochromic effect and optical characterization of coatings were analyzed by using Minolta 3600-d spectrophotometer.
Formation of Tetra-Coordinated Aluminum in the Low Temperature Ashes
Authors: Straka Pavel
Published: October 2010

Formation of tetra-coordinated aluminum in low temperature coal ashes was investigated.
Coal samples were intensively air-oxidized at 350oC for 160 hours, then 27Al MAS NMR spectra of
obtained ashes were acquired and compared against those for initial coals, a reference ash and Al
standards. It was found that chemical shift at 4 ppm with coals corresponds to that for triaquohydroxo-
diphenoxido-aluminum(III) complex and the shift at 72 ppm with resulting coal ashes
agrees with that for Al tetra-coordinated with oxygen. So, in the presence of coal organics the tetracoordinated
Al is formed under low temperature conditions. Formation of this form of Al can be
elucidated as follows. Probably, Al in coal originates from kaolinite, as this mineral is very frequent
in coal. Mentioned Al-complex was formed through the long-term reactions of kaolinitic hexacoordinated
Al with phenols/polyphenols as prevailing oxygen-contaning components in coal
substance. During this process the octahedral structure of hexa-coordinated Al was retained, but
ligands coordinated around the central Al atom changed. At first, delamination of a kaolinitic
structure through the effect of coal organics proceeded and separation of the Al gibbsite octahedral
and silica tetrahedral layers occurred. Then, two oxygens in the Al octahedron were substituted with
two phenoxide groups while OH groups were preserved. As result, Al-tetrahydroxo-diphenoxide
ion was formed, further stabilized in a water environment as Al(H2O)3(OH)(C6H5O)2. During low
temperature ashing this complex was transformed to Al tetra-coordinated with oxygen only at
350oC.
Development of Building Materials through Alkaline Activation of Construction and Demolition Waste (CDW) - Resistance to Acid Attack
Authors: Gonçalves Rapazote Joana , Laginhas Cristóvão , Teixeira-Pinto Amândio
Published: October 2010

Construction and demolition waste (CDW) is a by-product of construction and demolition activity. It consists mostly of inert and non-biodegradable material such as concrete, plaster, metal, wood, plastics etc. CDW is priority waste in the E.U. due to the increased quantities and volumes that are produced. While retrievable items such as brick, wood and metal wires are recycled, concrete, masonry tile and ceramic waste, accounting for more than 60% of CDW, are not being currently recycled.
The main objective of this study is to develop a process for obtaining new building materials from CDW using low temperature geopolymerisation in alkaline environment.
The two major fractions of the CDW which are not currently being recycled are concrete, mortars, masonry and rubbles for one side and ceramic tile, mosaic and bricks for the other. The major constituents of the first fraction are SiO2 and CaO along with minor concentration of Al2O3 and Fe2O3, mostly crystalline. The major constituents of the latter are SiO2 and Al2O3 and comprise crystalline as well as glassy constituents.
The aluminosilicate fraction of both fractions will actively participate in the reaction and for the obtaining of ASH gel (A= Al2O3, S = SiO2, H = H2O), which is the main binding phase. Any deficiency (quantity) in chemical constituents will be compensated by addition of suitable material, e.g., Al2O3 can be compensated with a source of alumina which will be added for alkaline activation reaction. The remaining non aluminosilicate portions such as iron oxide and others will act as filler material. The final product is a very hard ceramic like product. These products can be used for civil engineering applications such as pavement blocks, precast concrete blocks, retaining walls, in general the same use as plain concrete.
Chemical and Biological Characterization of Geopolymers for Potential Application as Hard Tissue Prostheses
Authors: Catauro Michelina , Bollino Flavia , Lancellotti Isabella , Kamseu Elie , Leonelli Cristina
Published: October 2010

In this study different geopolymers have been investigated and characterized as
potential biomaterials. The work presents exhaustive FT-IR, SEM/EDS and X-Ray studies of two
geopolymer formulations, where water content, water to solid content and curing conditions have
been varied during mixing stage, maintaining constant the ratios among Na-Al-Si. The amorphous
matrix is typical of sodium aluminosilicates, as shown by the FT-IR spectra. The presence of
zeolitic phases has been observed by XRD at the surface of the material while the main matrix was
characterized by amorphous aluminosilicate phases. The compressive strength of all the
compositions was higher than 50 MPa. In order to study their bioactivity, samples of the studied
materials were soaked in a simulated body fluid (SBF). The bioactivity of the synthesized
geopolymers was shown by the formation of a layer of hydroxyapatite on the surface of the
materials by using the SEM.
Geopolymer Development by Powders of Metakaolin and Wastes in Thailand
Authors: Tippayasam Chayanee , Boonsalee Sansanee , Sajjavanich Suvimol , Ponzoni Chiara , Kamseu Elie , Chaysuwan Duangrudee
Published: October 2010

Geopolymer has been developed as an alternative material to Portland cement. Geopolymer is based on the polymerization of alkaline activation and oxide of silicon and aluminium. These oxides can be found in many pozzolanic materials such as metakaolin and the wastes from industries and agricultures in Thailand, e.g., fly ash, bagasse ash and rice husk ash.
Pozzolanic materials were selected as source materials for making geopolymers into 4 different types. Sodium hydroxide concentration of 10 Molar (10MNaOH) and sodium silicate (Na2SiO3) solutions were used as alkaline activators by the mass ratio of Na2SiO3/NaOH at 1.5. The mixtures were cast in 25×25×25 mm. cubes. After casting, the geopolymers were cured at 80๐C for 24 hrs. in an oven and then at room temperature for 7 days. The pozzolanic materials effects, the Si/Al molar ratio and the Na/Al molar ratio were studied and characterized.
An X-ray fluorescence (XRF) was chosen to determine the percentages of silica and alumina in order to verify the proper ratio of the fly ash, Rice husk ash, Bagasse ash and Metakaolin.The study also included the impact on mechanical and physical properties such as compressive strength, water absorption, density and porosity.
Thermal Schock Criteria of Refractory Ceramics: Limitations of Conventional Analyses and Some Numerical Approaches to Improve the Prediction of the Resistance to Thermal Schock
Authors: Schmitt Nicolas
Published: October 2010

Significant advances in the mechanical design of ceramic parts were realized since the
pioneer works of Kingery and Hasselman to define thermal shock resistance. But for high
heterogeneous refractories and contrasted local phase properties the use of these criteria is not
always convincing because the assumptions made are too simplicist.
First, we underline how thermal shock resistance parameters helped to improve the global
performance of ceramics and make some comments on their limitations for refractory materials.
Then we show how numerical tools are useful for the design of refractory structures at high
temperatures through several approaches we have developed for refractory structures: prediction of
macroscopic thermal shock resistance of heterogeneous refractories using multi-scale analysis, finite
element methods applied to a specific structure considering either a two-scale approach to describe
the thermo-elastic quasi brittle behavior of heterogeneous materials, at the macroscopic scale
approach considering homogeneous microstructure.
Sizing of Refractory Castable Gas-Burner Using Thermomechanical Simulations
Authors: Nazaret Fabien , Cutard Thierry , Barrau Olivier
Published: October 2010

Damage is a crucial characteristic of refractory castables and has to be considered to
simulate correctly the behaviour of refractory structures. But, damage modelling by finite element
simulations remains difficult. Indeed, the use of a continuum damage model with softening leads to
strain localization phenomena. Numerical results depend on the mesh. Several numerical methods
allow solving this meshing dependence by introducing an internal length in the material constitutive
laws. In this paper, a regularization method has been applied with the damage plasticity model,
considering a scalar value for damage. This model enables to take into account permanent strains
due to plasticity and damage before and after the peak stress in tension and compression.
Thermomechanical simulations are performed with this model to predict damage in a gas-burner.
The damage level is evaluated after a thermal simulation generating high temperature gradients.
Interests to take into account damage in the refractory structures are discussed. Sensitivity of results
to material properties is studied. This work gives an example of using thermomechanical
simulations to improve the design of refractory castable structures and to help in the material
choice.
A New Generation of Refractories to Enable Gasifier Fuel Flexibility
Authors: Bennett James P. , Kwong Kyei Sing , Thomas Hugh , Krabbe Rick
Published: October 2010

Gasification is used by industry to convert low cost carbon into materials for producing electricity
and chemical products such as fertilizer, plastics, and Fischer-Tropsch liquids. It is considered a
critical technology in the success of the DOE’s Near Zero Emissions Advanced Fossil Fuel Power
Plants, could play a key role in defining long-term energy security in both power and liquid fuels,
and is considered a leading candidate for H2 production in a hydrogen based economy. Molten slag
originating from mineral impurities in the carbon feedstock is of concern to slagging gasifier
operation, with some gasifiers generating over 100 tons per day. Molten slag attacks and wears
away the internal lining of the gasifier vessel by two major mechanisms, chemical dissolution and
spalling. The main component in current refractory linings is chrome oxide. NETL is researching
new types of refractory materials as an alternative to the high chrome oxide refractories currently
used, with the goal of improving performance and providing a predictable service life. It has
previously developed and patented the use of phosphate additives to improve the wear and spalling
resistance of high chrome oxide refractories, and is exploring chrome and non-chrome oxide
materials through laboratory testing and the use of thermodynamic modeling. In this paper, the
results of a different additive (carbon) was evaluated by laboratory testing and found to improve
slag penetration resistance. Data on this evaluation will be presented, and is proposed as a means of
improving the molten slag wear resistance of the refractory. The use of it as a means of improving
refractory service life in the field is patent pending.
Thermal Shock Behavior of Zircon Based Refractories
Authors: Rendtorff Nicolás , Suárez Gustavo , Bruni Yesica , Garrido Liliana , Aglietti Esteban Fausto
Published: October 2010

In service refractory materials are submitted to local temperature gradients that originate
thermal stresses causing a thermal shock (TS) damage to the material. Practical tests for evaluating
the thermal shock resistance (TSR) determine the variation or change of some characteristic
property of the test sample like E (elastic module) or the strength before and after quenching. In this
work, the microstructure and thermal shock behavior of Zircon based refractories are analyzed.
Several compositions (eight), from pure Zircon to 70 % of Zircon were studied. The main structural
and mechanical properties of the refractories were characterized, as modulus of rupture, elastic
modulus, porosity, and microstructure. The dynamic elastic modulus E of the refractories was
measured by the excitation technique. The TS behavior was evaluated by measuring the decrease in
E and the modulus of rupture, before and after a quenching test. The influence of the presence of
other phases was also analyzed. Refractories showed Zircon as the main crystalline phase. In some
materials, m-ZrO2 appears coming from Zircon dissociation. The thermal shock behavior of
refractory of high Zircon content is typical of the brittle ceramic materials. Materials showed a
relation between elastic module and strength. Dynamic elastic modulus measurements have shown
to be suitable for evaluation the TSR for these materials.
Exploitation of Ceramic Wastes by Recycling in Alumina-Mullite Refractories
Authors: Mazzanti Francesca , Brentari Alida , Burresi Emiliano , Coglitore Antonino , Labanti Martino , Martelli Stefano , Mingazzini Claudio , Ricci Antonio , Sangiorgi Sergio , Scafè Matteo , Villa Matteo
Published: October 2010

Alumina-mullite (AM) refractories are widely used as liners in gas turbines for power production, because of their peculiar properties, appropriate for the thermal insulation of combustion chambers, characterized by turbine inlet temperature around 1400 °C. The typical tiles are made with a mixture of alumina and mullite with different granulometries, including a coarse fraction. In this work the feasibility of recycling of ceramic wastes, which come from other industrial processes, into AM refractories was assessed. The effects of their addition on phase composition, microstructure and thermomechanical properties of AM refractories were investigated. MOR and Young’s modulus were determined at room temperature and up to 1500 °C by four point flexural tests; thermal shock resistance was evaluated by MOR measurements after quenching tests. The comparison with a typical AM refractory used as liners shows that thermomechanical properties and thermal shock resistance were not significantly compromised by ceramic waste additions up to 20%, and, on the contrary, were improved.
Modelling Infiltration of Fibre Preforms From X-Ray Tomography Data
Authors: Vignoles Gerard L. , Ros William , Szelengowicz Ivan , Mulat Christianne , Germain Christian , Donias Marc
Published: October 2010

The production of high-quality Ceramic-Matrix Composites often includes matrix
deposition by Chemical Vapour Infiltration (CVI), a process which involves many phenomena such
as gas transport, chemical reactions, and structural evolution of the preform. Control and
optimization of this high-tech process are demanding for modelling tools. In this context, a
numerical simulation of CVI in complex 3D images, acquired e.g. by X-ray Computerized
Microtomography, has been developed. The approach addresses the two length scales which are
inherent to a composite with woven textile reinforcement (i.e. inter- and intra-bundle), with two
numerical tools. The small-scale program allows direct simulation of CVI in small intra-bundle
pores. Effective laws for porosity, internal surface area and transport properties as infiltration
proceeds are produced by averaging. They are an input for the next modelling step. The second
code is a large-scale solver which accounts for the locally heterogeneous and anisotropic character
of the pore space. Simulation of the infiltration of a whole composite material part is possible with
this program. Validation of these tools on test cases, as well as some examples on actual materials,
are shown and discussed.
SA-Tyrannohex-Based Composite for High Temperature Applications
Authors: Ishikawa Toshihiro
Published: October 2010

To modify the relatively low fracture toughness of monolithic ceramics, the incorporation
of long ceramic fibre within a matrix material has been extensively performed. In this case, as
cracks form in the matrix material and approach the fibres, they will be deflected at the interface
between the fibre and the matrix. We developed another approach toward improving the toughness
of ceramics involving the creation of a textured internal structure within the ceramic itself, similar
in some respects to the fibrous structure of wood. Actually, we developed a tough ceramic, which
consists of a highly ordered, close-packed structure of very fine hexagonal columnar fibres with a
thin interfacial carbon layer between fibres. The interior of the fibre element was composed of
sintered beta-silicon carbide crystal. This concept is fundamentally different from that described
previously, in that it is extremely difficult to distinguish separate “fibre” and “matrix” phases in the
traditional composite sense. The toughness of the material in this case derives from the tremendous
amount of interface area created within the internal structure through the close packing of the
hexagonal columnar fibres. Furthermore, this ceramic also achieved the excellent high temperature
properties, high thermal conductivity and low density. These properties will make it very attractive
for replacement of heavy metal super alloy components.
Irradiation of a Polypropilene-Glass Fiber Composite
Authors: de Miranda L.F. , Silveira L.H. , Andrade e Silva Leonardo Gondim , Munhoz Jr. Antônio Hortêncio
Published: October 2010

The use of composite materials, mainly reinforced thermoplastic has increased on the polymer industry, mainly the polypropylene resins (PP) reinforced by glass fibers (GF). The ionizing radiation can promote alterations in the polymeric chains by scission and crosslinking reactions. The objective of this work is to study the effect of the ionizing radiation in the properties of the polypropylene long fiber glass reinforced thermoplastic. Pellets with 1,3 cm of length, contend 15wt% of the unidirectional long glass fiber were obtained by extrusion and, subsequently, the samples were molded by injection, irradiated and submitted to thermal and mechanical tests. The mechanical (tensile and impact) properties and thermal (HDT and Vicat softening temperature) of irradiated and non irradiated reinforced thermoplastic were determined. The doses of the irradiation of the samples were 30, 50 and 100 kGy in a source of 60Co. The results showed a reduction in the thermal and mechanical performances indicating a degradation of the polymeric matrix.
Opal-Type Photonic Crystals: Fabrication and Application
Authors: Chiappini Andrea , Alombert-Goget Guillaume , Armellini Cristina , Berneschi Simone , Boulard Brigitte , Brenci Massimo , Cacciari Ilaria , Duverger-Arfuso Claire , Guddala Sriram , Ferrari Maurizio , Moser Enrico , Rao D. Narayana , Righini Giancarlo C.
Published: October 2010

We report on fabrication and characterization of two different opal-like structures: (i) crystal exhibiting mechanochromism, i.e. change of colour when subjected to mechanical stress, composed of closely packed colloidal polystyrene particles (CPCP) embedded in a poly-dimethylsiloxane (PDMS) elastomeric matrix; (ii) metallo-dielectric systems (MDCS), based on the realization of inverse silica opal and following attachment of gold nanoparticles on the silica network of the inverse colloidal structure. Optical measurements, performed on the two structures, have demonstrated that: (i) when an horizontal strain is applied on the CPCP embedded in PDMS, a blue shift of the diffraction peak occurs as a function of the applied strain and (ii) MDCS have unique optical properties that combine the localized surface plasmon resonance (LSPR) of gold nanoparticles (Au NPs) with the photonic band gap features of colloidal crystal structures. Finally, preliminary results on MDCS used as SERS substrate evidence a higher increase of the Raman signal in respect to that observed for others metallic structures.
Si-C-O Fibres in Gas Reactive Atmospheres
Authors: Brisebourg Mathieu , Mazerat Stephane , Puyoo Geraldine , Plaisantin Herve , Dibandjo Philippe , Soraru Gian Domenico , Chollon Georges
Published: October 2010

The aim of the present work was to investigate the high temperature reaction between Si-
C-O fibres and Cl2, and to correlate the carbon layer growth kinetics with their initial composition
and structure. Large disparities have been observed between the various materials reaction rates. If a
large amount of mixed silicon atom environments increases the reactivity of Si-O-C materials with
Cl2, this sole feature does not explain all the experimental results. Traces of heteroelements (Ti, Zr,
Al…) or percolated free carbon both appear to bear on the reaction rate. For a better understanding
of the fibres reaction behaviour, this study was extended to other model materials (oxycarbide
glasses, oxygen-free Si-C fibres, SiC).
Design and Preparation of Laminated Composites
Authors: Jiang Dong Liang
Published: October 2010

Active researches have been conducted to seek the application of ceramics as structural
components. However, the lack of damage tolerance ability has been a critical problem. Laminated
composites as one of the main way for improving the brittleness of ceramics are getting more and
more attention from the biomimetic point of view.
In the present paper, three laminated composites, SiC/TiC, Al2O3/Ni and ZrB2-SiC/ZrB2 with
intentionally introduced surface compressive stress were presented. The finite element method
(FEM) was used to simulation the stress distribution and to optimize the layered structure for the
development of more reliable materials. Based on FEM analysis, the laminated structure was
realized by aqueous tape casting and hot pressing. The dependence of mechanical properties
(fracture strength and toughness) on the structural parameter (the composition of layers, the
thickness ratio between layers, number of layers) was investigated. The calculated mechanical
properties were in agreement with the tested ones to some extent.
Long-Term Stabilization of Creep-Resistant Ferritic Steels for Highly Efficient Ultra-Supercritical Power Plants
Authors: Abe Fujio
Published: October 2010

Alloy-designing of high-strength ferritic heat resistant steels has been investigated for application to highly efficient, low emission ultra-supercritical power plant with maximum steam temperature of 700 oC. Ferritic heat resistant steels can be applied to the next highest temperature components and are strongly desired to expand their temperature range up to 650 oC in order to minimize the requirement of expensive nickel base superalloys. A dispersion of nanometer size MX nitrides along boundaries and the addition of boron significantly improve long-term creep strength. Newly alloy-designed 9Cr-3W-3Co-0.2V-0.05Nb steel with 160 ppm boron and 85 ppm nitrogen exhibits excellent creep strength of base metal and no degradation in welded joints at 650 oC. The protective Cr2O3-rich scale forms on the surface of 9Cr steel by pre-oxidation treatment in Ar gas, which significantly improves the oxidation resistance in steam at 650 oC.
Proton Vibrations in Lithium Imide and Amide Studied through Incoherent Inelastic Neutron Scattering
Authors: Colognesi Daniele , Pietropaolo Antonino , Ramírez-Cuesta Aníbal Javier , Catti Michele , Nale Angelo Claudio , Zoppi Marco
Published: October 2010

Lithium imide (Li2NH) and amide (LiNH2) belong to the Li-H-N system, which has been recently considered for on-board hydrogen storage applications. However the imide low-temperature crystal structure is still highly controversial, with at least six options compatible with the diffraction experimental findings. A complementary study on low-temperature Li2NH and LiNH2 has been recently accomplished by the authors using neutron spectroscopy (with energy transfer in the 3-500 meV range). The rationale of these measurements was that crystal structures (especially their proton arrangements) affect in a strong way the neutron scattering spectra, so that a combined use of computer ab-initio simulations and inelastic neutron scattering could be a stringent validation method for the various models. Data analysis has pointed out broad and almost featureless proton-projected phonon densities of states for lithium imide, with large differences in the data sets derived from forward scattering and backscattering detector banks. On the contrary, a sharp phonon spectrum and much less discrepancy was found applying the same analytic procedure to lithium amide. This Li2NH peculiarity has been interpreted as an effect of the fast proton jump diffusion among the available lattice sites, which smears out the phonon vibrational excitations in a momentum transfer-dependent way.
Metal Hydride-Based Composite Materials with Improved Thermal Conductivity and Dimensional Stability Properties
Authors: Pentimalli Marzia , Frazzica Andrea , Freni Angelo , Imperi Enrico , Padella Franco
Published: October 2010

To address the issues of poor thermal conductivity and fragmentation of metal hydride particles undergoing hydriding/dehydriding reactions, a metal hydride-based composite material was developed. The active metal phase was embedded in a silica matrix and a graphite filler was incorporated by ball milling. A set of compact pellet samples at different composition were prepared and tested. Experimental data obtained from the thermal conductivity measurements shown that using powder graphite produced a quite linear increase in the thermal conductivity of the metal hydride – silica composite. Ongoing studies include composition optimization as well as long-term testing upon cycling of such metal hydride composites to evaluate their potentiality in technological hydrogen storage applications.
Simple and Binary Hydrogen Clathrate Hydrates: Synthesis and Microscopic Characterization through Neutron and Raman Scattering
Authors: Celli Milva , Colognesi Daniele , Giannasi Alessandra , Ulivi Lorenzo , Zoppi Marco , Garcia Sakai Victoria , Ramírez-Cuesta Aníbal Javier
Published: October 2010

The search for efficient hydrogen-storage materials has led to an increasing interest in hydrogen clathrate hydrates, since it has been demonstrated that an appreciable amount of molecular hydrogen can be stored in the water cages and released at melting. Different synthetic routes have been followed to maximize the quantity of trapped hydrogen and to speed up the kinetics of the clathrate formation.
Here, we describe two different synthetic routes for the production of hydrogen clathrate hydrates. Then we present the results of inelastic neutron scattering and Raman light scattering experiments on simple (i.e. containing only hydrogen) and binary (i.e. with a second guest molecule) clathrates. For each class of compounds, we have obtained spectroscopic information on the motion of hydrogen inside the cages, on the occupancy of the cages by hydrogens, and on lattice dynamics. Finally, we have investigated the clathrate crystal stability and the hydrogen release as a function of temperature by means of neutron diffraction.