bluuebunny/crossref_metadata_2025 huggingface dataset:
Cobalt-Supported Clay as Catalytic Film Prepared by Electrophoretic Deposition for Hydrogen Release Applications
Authors: Chamoun Rita , Demirci Umit B. , Cornu David , Zaatar Youssef , Khoury Antonio , Miele Philippe
Published: October 2010

Shaped catalyst is much more practical than powder catalyst when the material is
intended to technological applications. Nevertheless, shaping a reactive powder catalyst is not
evident, loss in reactivity occurring by e.g. decreasing specific surface area. Addressing such
problem has been our objective. The present paper reports methods and results about the shaping of
a lab-made cobalt supported clay catalyst over a stainless steel plate (SSP) taken as substrate. The
deposition method chosen is electrophoretic deposition (EPD). Clay has been chosen owing to its
abundance and greenness. Herein, we report that it is feasible to make a Co-Clay-SSP shaped
catalyst by EPD in a two-step process. Typically, the supported Co-Clay has first to be prepared by
wet impregnation and then the as-obtained powder is deposited over the substrate by EPD. Such
shaped catalyst is intended to be used in NaBH4 hydrolysis, a well known route for on-demand
release of hydrogen.
Constrained and Non-Constrained Sintering of Plasma-Sprayed Zirconia Based Electrolytes for SOFCs
Authors: Christenn Claudia , Ansar Syed Asif
Published: October 2010

Electrolyte layers for solid oxide fuel cells (SOFCs) consisting typically of yttria-stabilized zirconia
were prepared using atmospheric plasma spraying in a first step and sintered in a second one. The
influence of particle size on sintering kinetics and microstructure development was analyzed by
comparison of nanostructured and conventional YSZ layers. Sintering of free-standing coatings
differ significantly from that of coatings on substrates.
Microstructural and Thermo-Mechanical Characterization of Yttria Ceramic Cores for Investment Casting, with and without Particulate Reinforcement
Authors: Beaulardi Leandro , Brentari Alida , Labanti Martino , Leoni Enrico , Mingazzini Claudio , Sangiorgi Sergio , Villa Matteo
Published: October 2010

Yttria is an interesting material for the production of high performance ceramic cores
for Directionally Solidified investment casting. DS casting of superalloys of the last generation
challenge conventional silica ceramic cores, because of the high temperatures and the long times
involved. Compared to silica, yttria is characterized by improved mechanical properties and higher
chemical resistance at high temperatures. Submicronic and nanometric SiC reinforcements were
tested in order to increase compression creep resistance of yttria. Oxidation resistance of both
reinforcements was tested in conditions simulating the industrial process. The experimental results
demonstrated the increase of compression creep resistance and showed that the industrial
application of yttria ceramic cores reinforced with submicronic SiC is possible with minimal
changes to current practices, thanks to a high enough oxidation resistance.
Effects of the Pin-on-Disc Parameters on the Wear of Alumina
Authors: Tedesco Nadetsa R. , Pallone Eliria M.J.A. , Tomasi R.
Published: October 2010

There is a growing interest in the application of ceramic as high wear resistance materials due to the unique properties. Although brittleness and low toughness, recent improvements in alumina processing have lessen this restrictions and suggest improvements in wear resistance which in turn have driven some research on this. Since a direct comparison between the many published works regarding this wear improvement is complicated due to the fact that wear resistance is a response of the microstructure, material and testing condition, the work herein presented aims to first do a literature review on the main parameters to be controlled in a pin-on-disc apparatus on the wear of alumina and then discuss preliminary test results and analyze the influence of critical parameters as load and sliding speed in a pin-on-disc wear test in a dense and sub micrometer grain size alumina.
Diffusion Studies Involving Nanometric and Submicrometric Based Alumina Composites with Gray Cast Iron
Authors: Tonello Karolina Pereira Santos , Hernandes Vânia Trombini , Bressiani Ana Helena Almeida , Bressiani José Carlos
Published: October 2010

Machining processes require tool materials with properties such as high hardness at elevated temperature, high fracture toughness and chemical stability with the workpiece. Advances in science and industry, as well as the development of harder materials have permitted cutting tool technology to evolve. In cutting processes, the contribution of different wear mechanisms to total wear is related to the mechanical and chemical properties of the two materials in contact. The high temperatures at tool-workpiece contact zones often result in diffusion of material from the workpiece to the cutting tool. Diffusion experiments were carried out to understand wear mechanisms involved at cutting edges of ceramic tools and the influence of microstructure on diffusion without the interference of mechanical wear processes. The chemical stability was analyzed from static interaction couple experiments at 1100°C with ceramic composite materials and gray cast iron. To investigate the influence of grain size on diffusion, sub-micrometric and nanometric alumina based composites with NbC as the second phase were used. These experiments showed that the influence of grain size on diffusion and the relative inertness of the composites in the presence of gray cast iron.
Titanium Carbide Reinforced Composite Tool Ceramics Based on Alumina
Authors: Szutkowska Magdalena , Smuk Barbara , Boniecki Marek
Published: October 2010

The present study reports some preliminary results obtained by reinforcing
Al2O3-10 wt% ZrO2 (partially stabilized with Y2O3 -Y5 and monoclinic phase m-ZrO2) composite
with TiC phase in amount of 5 wt %. Ceramic composites were prepared on the basis submicro and
nano scale trade powders. Apparent density, porosity, Vicker’s hardness, Young’s modulus and
fracture toughness (KIC) were determined. Wear resistance (Vn) very important property for tool
ceramics was specified by the speed of mass lost. Scanning electron microscopy (SEM) to
observation of the fracture surface microstructure was used. The titanium carbide reinforced
composite tool ceramics based on alumina exhibit high hardness, fracture toughness (critical stress
intensity factor KIC increase up to 5,2 MPa m1/2), high elastic moduli and higher wear resistance in
related to pure alumina. Cutting tests confirm the high performance of these ceramic composites.
Ceramic Tool Materials for High Speed Cutting Process
Authors: Górny Gabriela , Pampuch Roman , Stobierski Ludosław , Rutkowski Paweł
Published: October 2010

Frictional and mechanical properties of hot-pressed Al2O3 and Si3N4 - matrix composites
containing up to 5 vol. % hexagonal BN as a solid lubricant. A very low coefficient of friction
which is necessary for high-speed cutting has been observed. Fracture toughness remained constant
with increase of h-BN content while flexural strength changes with the hBN content have been
found to depend upon the material homogeneity. The work has been supported by EU Funds in
Poland under contract UDA-POIG.01.03-12-024/08-00.and has been realized in the frame of
scientific-industrial consortium.
Microstructure and Mechanical Properties of Rare-Earth Doped Si3N4 and Si3N4/SiC Ceramics
Authors: Tatarko Peter , Lojanová Štefánia , Chlup Zdeněk , Dusza Ján , Šajgalík Pavol
Published: October 2010

Microstructure and mechanical properties of Si3N4 and Si3N4 + SiC nanocomposites sintered with rare-earth oxide additives (La2O3, Y2O3, Yb2O3 and Lu2O3) have been investigated. The composites exhibited smaller grain diameter compared to that of monolithic materials. The aspect ratio of β-Si3N4 grains increased with a decreasing ionic radius of rare-earth elements in the Si3N4 monoliths as well as in the Si3N4-SiC nanocomposites. The hardness of both systems increased with a decreasing ionic radius of rare-earth element. The fracture toughness of the materials with coarser microstructure and higher aspect ratio was higher due to the more frequent toughening mechanisms. No significant difference between strength values of monoliths and composites was observed and the strength in the composites was determined mainly by the present processing flaws. Significantly improved creep resistance was observed in the case of composites and for materials with smaller ionic radius of RE3+.
Advanced Ceramic Tribological Layers by Thermal Spray Routes
Authors: Gadow Rainer , Killinger Andreas , Rempp Andreas , Manzat Andrei
Published: October 2010

Protective and functional coatings featuring outstanding tribological performance are of general interest for all kinds of industrial applications i.e for high performance automotive and mechanical applications. Thermal spray coating technologies play a key role in fabricating hard layers based on ceramic, metal - ceramic and further multiphase materials. Additional functionality can be achieved by combining these coatings with polymer based top coats with low friction coefficient or anti adhesive behaviour. Combined coatings feature also designed thermophysical and electrophysical properties. Several case studies will be discussed, ranging from automotive applications to paper and printing industry. Thermally sprayed coatings were applied using APS, HVOF and the newly developed HVSFS processes (High Velocity Suspension Spraying) with a special focus on nanoceramic feedstocks. In some applications polymer top coats with dispersed solid phases are applied to enhance functional properties. Special aspects in manufacturing engineering are addressed with particular importance not only of the influence of spray process parameters on coating properties but also of spray torch kinematic and robot trajectories on hardness, residual stress distributions, dimensional tolerances and porosity distributions will be discussed.
Anti-Bacteria Behaviors of TaN-Cu and TaN-Ag Nanocomposite Thin Films
Authors: Hsieh Jang Hsing , Yeh T.H. , Chiou C.S. , Huang C.T. , Li C.
Published: October 2010

TaN–Cu and TaN-Ag nanocomposite films were deposited by reactive co-sputtering on Si. The films were then annealed using RTA (Rapid Thermal Annealing) at 400 °C for 2, 4, 8, 15 minutes respectively to induce the nucleation and growth of metal particles in TaN matrix and on film surface. The samples were then tested for their anti-bacterial behaviors against Gram-negative and Gram-positive bacteria. The results were compared with the solubility of Ag and Cu in a buffer solution. Under similar ion concentrations, it is concluded that Ag ion or TaN-Ag is more effective against E. Coli (Gram-negative), while Cu ion or TaN-Cu is more effective against Staphylococcus aureus (Gram-positive).
Hydrogen Effect on Structure and Mechanical Properties of ZnO Films Deposited in Ar/H2 Plasma
Authors: Bartali Ruben , Micheli V. , Gottardi G. , Luciu I. , Laidani N.
Published: October 2010

In the present work the mechanical properties of ZnO thin films, deposited on Si (100) substrates, were studied using the nanoindentation technique. ZnO thin films were deposited by radiofrequency sputtering from a ZnO target with different H2/Ar gas mixtures. During the deposition the plasma species were in-situ monitored using optical emission spectroscopy (OES).
The results showed that the introduction of H2 in the plasma phase had a strong effect on the material’s hardness and elastic modulus. The measured elastic modulus values were then related to the material density to estimate the porosity of the ZnO films. We found an increased film porosity when H2 was added to the sputtering gas, from 6% to 18% in volume. Moreover we found that the porosity was correlated by the emission intensity ratio of atomic Argon on atomic Hydrogen.
Optimisation of the Ceramic Phase for Ceramizable Silicone Rubber Based Composites
Authors: Pędzich Zbigniew , Dul Jan
Published: October 2010

Paper describes the experiment on manufacturing of composite basing on silicone rubber
matrix filled with silica binder and kaolin and also glassy fillers. Such material is oriented on
applications connected with potential fire hazard. Investigations performed on three mixes,
differentiated in proportion of components, indicate potential simply way of composition of
ceramizable composite.
A Comparison between Conventional Thermal Treatment and Excimer Laser Irradiation Performed on Alumina/PEEK Composite Coatings
Authors: de Riccardis M. Federica , Martina Virginia , Carbone Daniela , Rotolo Paolo , Caricato Annapaola , Leggieri Gilberto , Pilloni Luciano , Tapfer Leander , Giorgi Rossella , Salernitano Elena
Published: October 2010

Poly(etherether-ketone)-alumina coating were deposited by EPD. In order to densify the
coatings, conventional thermal treatments were performed at a temperature equal or higher than the
melting point of the polymer. The samples treated at the lower temperature showed an increase in
the quality of crystallinity of the polymer. As an alternative method, an excimer laser was used to
treat the surface of the composite coatings. The laser beam irradiation did not induce any
modification in the crystalline structure of the polymer and at the same time did not produce strong
degradation of the polymer molecule, also when the laser beam fluence was higher than the ablation
limit. The most relevant modification induced by both the treatments was a change in the
morphology and the porosity.
ESR Study of Elements Added-DLC Films Deposited by PBII and RF-CVD Methods
Authors: Moolsradoo Nutthanun , Sato Hirohumi , Watanabe Shuichi
Published: October 2010

The element added diamond-like carbon films (hydrogen, fluorine, and sulfur) fabricated from C2H2:H2, C2H2:CF4 and C2H2:SF6 mixtures were used to study the effects of element contents on the spin density (ESR) and their relation to the changes in the structure of the DLC films deposited by PBII and RF-CVD method. The Raman spectroscopy was represented along with the ESR. The results indicate that the ESR spin density and g value of H-DLC, F-DLC, and S-DLC films deposited by PBII method decreases with element addition, attributed to the dangling bond was strongly observed after element addition. The Raman G peak position shifts towards higher, while the ID/IG intensity ratio increases with element addition and changes of bias voltage. For H-DLC films deposited by RF-CVD method, the spin density and g value decreases, the G peak shifts toward higher and ID/IG intensity ratio increases with hydrogen addition, that similar to H-DLC films deposited by PBII method. The ID/IG intensity ratio increases with hydrogen addition, indicating that the number of sp2 graphitic clusters of aromatic rings increases in the structure, and the decrease of spin density is correlated to the increase of the paramagnetic centers in the sp2-bonded graphite-like carbon structures, indicating to the spins originate mainly from the sp2 sites in the graphite-like carbon structures.
Development of Advanced Coatings for ITER and Future Fusion Devices
Authors: Matějíček Jiří , Chráska Pavel
Published: October 2010

Thermonuclear fusion is a potential source of cleaner and safer energy for the future. Its technological realization depends on the development of materials able to survive and function in extreme conditions, often involving a variety of loading – thermal, mechanical, chemical and irradiation. Single bulk materials are often at the edge of their properties limits; therefore, composites and coatings are intensely studied. This article reviews the development, characteristics and applications of coatings for fusion reactor materials. First, the technological objectives and material-environment interactions are briefly summarized, together with materials requirements and the role of coatings. Then, specific applications in different areas of a fusion device are reviewed, namely the plasma facing components, electrical insulation, diffusion and permeation barriers. Various coating fabrication methods are mentioned and the respective coating characteristics are compared. Selected case studies are presented, with particular focus given to ITER and to ceramic coatings.
Corrosion Resistance of Titanium Aluminide Layers on Two Phase (α+β) Ti6Al4V Titanium Alloy
Authors: Sitek R. , Kaminski Janusz , Pisarek Marcin , Matysiak Hubert , Kurzydlowski Krzysztof Jan
Published: October 2010

The paper presents results of investigations into the structure and corrosion resistance of Ti-Al
diffusion layers produced on two phase (a+b) Ti6Al4V alloy by Chemical Vapour Deposition
(CVD). The process was carried out in aluminium chloride (AlCl3) mixed with argon
atmosphere.
Surface topography and microstructure characterization of the coatings were examined by
scanning electron microscopy (SEM). The local chemical composition witch 1 μm lateral
resolution was measured via EDS. The phase content was investigated by X-ray diffraction
and analysis of the chemical composition of the surface by XPS.
Corrosion resistance was tested using the potentiodynamic method in 0.1M Na2SO4 and
0.1M H2SO4 solutions at the room temperature.
Their resistance to high temperature at atmospheric pressure was tested by 24-hours cycling
to 700°C.
The results indicate that the layers produced on the Ti6Al4V titanium alloy exhibit a very
good adhesion combined with exceptional corrosion resistance, especially high at high
temperatures.
Effects of the Co-Presence of Conflicting Magnetic Anisotropy in Ba Ferrite Particles
Authors: Bottoni Giancarlo
Published: October 2010

In Ba ferrite particles magnetocrystalline and shape anisotropies are contemporarily present and conflicting. The strength and evolution of the two anisotropies are studied, through the dependence of the anisotropy constants on temperature. While in pure Ba ferrite particles the anisotropy is uniaxial at all temperatures, since the magnetocrystalline anisotropy clearly prevails on shape anisotropy, in particles modified for employment in recording media the two anisotropies are comparable and at low temperatures the shape anisotropy result stronger than the crystalline anisotropy. Besides the irregular shape of the particles introduces further preferred directions for the magnetization. The Co/Ti-doped particles show a multiple axes anisotropy. The macroscopic magnetic properties are found in relationship with the evolution of the anisotropy. Also the influence that the presence of such multiple anisotropy has on the magnetization switching and on the thermal stability of the magnetization of the Ba ferrite particles is analyzed.
NTC Ceramics: Past, Present and Future
Authors: Feteira Antonio , Reichmann Klaus
Published: October 2010

In contrast with metals, the resistivity of ceramics decreases with increasing temperatures.
This phenomenon was first discovered in 1833 by Faraday and remained a mere scientific
curiosity until 1930, when Samuel Ruben proposed the fabrication of a pyrometer device,
which explored the negative temperature coefficient (NTC) of resistance exhibit by Cu2O.
Eight decades later, NTC ceramic thermistors constitute an important business segment for
most electroceramic manufacturers. Here, we present a review of the most significant
scientific and technological advances, which lead to the enormous commercial success of
NTC thermistors. This review concludes with an outlook into future possible applications of
NTC ceramics, providing that some current technological shortcomings (such as ageing) are
resolved.
Magnetic Properties of the Bi6Fe2Ti3O18 Aurivillius Phase Prepared by Hydrothermal Method
Authors: Bućko Mirosław M. , Polnar Joanna , Przewoźnik Janusz , Żukrowski Jan , Kapusta Czesław
Published: October 2010

The multiferroic Aurivillius phases in the Bi-Fe-Ti-O system are built from alternate (Bi2O2)2+ and (Bin-1XnO3n+1)2 layers, where X = Fe3+, Ti4+ and “n” refers to the number of perovskite-like layers between Bi2O2 layers. Detailed magnetic studies should be done to understand electromagnetic interactions and multiferroic coupling effects. In the present paper, a powder composed of the Aurivillius phase with n = 5, Bi6Fe2Ti3O18, was successfully prepared by the hydrothermal method. The powder was sintered, obtaining dense polycrystalline materials. It was stated that both powder and sintered bodies were paramagnets with a possible antiferromagnetic ordering or a spin-glass state at the liquid helium temperatures.
Electron Spin Resonance of Nickelate
Authors: Poirot Nathalie , Autret-Lambert Cécile , Souza Raquel A.
Published: October 2010

In the present study we focused on the nickelate system, which presents stable stripe order and allow a large domain of oxygen doping. More specifically, we studied the non-stoichiometric system La2NiO4 in which the oxygen excess tends to order. ESR technique has been used due to its sensibility to microscopic magnetic fluctuations. We present a systematic study of the charge and spin fluctuations in oxygen doped nickelates to get insight into the dynamic of the system using ESR. The intrinsic resonance signal of polycrystalline La2NiO4 - values 0.09 and 0.12 have been studied, in a large temperature range (10K < T < 300 K). The = 0.12 compound has been chosen as a starting point, since neutron diffraction studies in composition very close to this value have been well characterized the stripe order in this system, showing that the holes order at around TCO = 200K, while the spins order at TS = 110K. By analogy, the ESR results on this compound allowed us to interpret the results in the other compound.
Preparation and Characterization of Dielectric Behavior of A2/3Cu3Ti4O12 (A = Nd, Sm, Gd, Dy) Ceramics
Authors: Szwagierczak Dorota , Kulawik Jan
Published: October 2010

In this work perovskite materials A2/3Cu3Ti4O12 (where A=Nd, Sm, Gd, Dy) were synthesized by conventional solid state reaction and sintered at 1000-1100°C. X-ray diffraction analysis confirmed single-phase composition of the investigated ceramics. Dielectric properties of the samples were investigated in the temperature range from -55 to 300°C at frequencies 10 Hz – 2 MHz. Dielectric permittivities of the ceramics are very high, exceeding 105 at low frequencies and/or elevated temperatures (above 50°C) and 103 at higher frequencies and/or low temperatures. Two observed contributions to the dielectric response are attributed to semiconducting grains and more resistive grain boundaries. For Nd2/3Cu3Ti4O12 and Sm2/3Cu3Ti4O12 ceramics, the observed low- and high frequency plateaus are lower than those for Gd2/3Cu3Ti4O12 and Dy2/3Cu3Ti4O12. The relaxation times determined on the basis of impedance data were found to decrease with increasing atomic number of lanthanide. The analysis of the impedance spectroscopic data and the microstructure implies spontaneous formation of internal barrier layer capacitors in the investigated materials.
Quantitative Infrared Thermography (IRT) and Holographic Interferometry (HI): Nondestructive Testing (NDT) for Defects Detection in the Silicate Ceramics Industry
Authors: Sfarra Stefano , Ambrosini Dario , Paoletti Alfonso , Paoletti Domenica , Ibarra-Castanedo Clemente , Bendada Abdel Hakim , Maldague Xavier
Published: October 2010

Ceramics are inorganic materials fabricated by a high-temperature chemical reaction.
Most ceramics are oxides, but the term is also used for silicides, nitrides and oxynitrides, hybrids
and other inorganic materials. It is convenient to consider ceramics that are essentially silicates,
called traditional ceramics, separately from all of the others. In the ceramic industry testing systems
are seldom employed for detecting on-line the presence of defects in ceramic tiles. Defects in the
ceramic body are usually originated during the pressing stage due to the incorrect use of process
parameters or to the improper selection of raw materials. These defects are generally characterized
by the inclusion of heterogeneous materials or agglomerates, which decreases the structural strength
jeopardizing the final quality of the produced piece. Disagreeable repercussions on the sale market,
especially on higher-quality ceramics such as porcelain, are characterized by the lack of specific
nondestructive testing (NDT) techniques that “certify”, pre-emptive, the quality of the produced
piece. The integration of IRT and HI for the NDT of a green ceramic tile with both fabricated and
real defects (cracks caused by the natural shrinkage process), allowed us to produce a clear “defects
map”.
Testing of Photocatalytic Activity of Self-Cleaning Surfaces
Authors: Lavrenčič Štangar Urška , Kete Marko , Černigoj Urh , Ducman Vilma
Published: October 2010

Due to relatively successful application of TiO2 photocatalysis in the field of self-cleaning surfaces, a reliable and appropriate quantitative method for determining the self-cleaning efficiency of the products (photocatalyst films on different supports) should be widely recognized and established. Currently, the two standard methods are based on photobleaching of methylene blue aqueous solution in contact with thin solid catalyst layer, and on photodegradation of a solid fatty deposit (e.g. stearic acid) over catalyst layer followed indirectly by water contact angle (CA) measurements. Another method proposed recently is based on the entrapment of an organic dye in a solid polymer matrix deposited over the photocatalyst layer. Upon illumination, the dye (e.g. resazurin) is reduced by the photogenerated electrons to the form of a different colour or to the bleached form. Recently, a new method for determination of self-cleaning activity of photocatalytic surfaces was developed in our laboratory. It is based on the deposition of a transparent solid layer comprising terephthalic acid over the photocatalytic surface. When such a system is irradiated, among the other degradation products also a hydroxyterephthalic acid is formed due to a reaction between photoexcited TiO2 and terephthalic acid. Hydroxyterephthalic acid is a highly fluorescent molecule and can be easily detected by HPLC-FLD or spectrofluorimeter. Many different samples were tested using this method and using the standard method based on photodegradation of a solid fatty deposit over the catalyst layer. Regarding the sample (substrate) type, the focus was given to the self-cleaning ceramic tiles coated with TiO2-SiO2 thin films that were produced in cooperation with the major manufacturer of floor ceramic tiles in Slovenia, Martex d.o.o.. In case of self-cleaning ceramics and some other sample types, the advantages of the new method over standard methods were highlighted and critically evaluated.
Characterization of Microstructure and Crystallographic Texture of Silicate and Phyllosilicate Ceramics
Authors: Chateigner Daniel , Blanchart Philippe , Deniel Sarah , Lutterotti Luca , Wenk Hans Rudolf
Published: October 2010

We illustrate the x-ray Combined Analysis approach capabilities in characterizing silicates and phyllosilicates for samples exhibiting crystallographic textures. Two mullite composite ceramics, one elaborated under uniaxial pressure the other under centrifugation, and one uniaxially pressed montmorillonite aggregate, are studied in terms of texture, cell parameters and phase contents. Several weak texture components are present in the mullite samples, combinations of planar- and fibre-like textures. The methodology is able to take account of the amorphous silica-like matrix of the composite, and cell parameters and structure of mullite correspond to the commonly modelled used for this phase. The montmorillonite turbostratic phase is correctly reproduced with its fibre texture, eventhough minor phases are also present and modelled in the aggregate.
Novel Ceramic Pigments Based on Industrial Wastes
Authors: Hajjaji W. , Costa G. , Ribeiro M.J. , Seabra M.P. , Labrincha J.A.
Published: October 2010

We report the preparation of ceramic pigments using industrial wa stes as primary sources.
An Al-rich sludge (generated in the wastewater treatment unit of an anodising or surface coating
industrial plant), a galvanizing sludge (from the Cr/Ni plating process ), a Fe-rich sludge (generated
during steel wiredrawing), a foundry sand and a marble sawing sludge are combined to formulate
distinct pigment structures via the solid state reaction method. In particular, a black spinel and a
novel blue pigment based on the hibonite structure are detailed. A green olivine, and brown and
pink sphenes are also reported. The pigments were fully characterized, and then were tested in a
standard transparent bright ceramic glaze. Typical working conditions and colour development are
fully described.
The Role of the Kaolinite-Mullite Reaction Sequence in Moisture Mass Gain in Fired Kaolinite
Authors: Mesbah Hesham , Wilson Moira A. , Carter Margaret A.
Published: October 2010

Kaolinite (2SiO2.Al2O3.2H¬¬¬¬2O), an aluminosilicate mineral, is the most common constituent mineral in clay used in manufacturing traditional ceramics such as whitewares, some refractories and structural clay products. On firing, kaolin (mainly kaolinite) undergoes several phase transformations. Immediately following firing, kaolin starts to chemically combine with atmospheric moisture. This reaction causes a mass increase that is proportional to the fourth root of time. The consequence of this mass gain is an accompanying expansive strain. Kaolinite transformations following firing at a range of temperatures between 700 and 1200 oC were examined by XRD. Following firing, high accuracy mass gain measurements were carried out using a microbalance under precisely controlled conditions of temperature and relative humidity. It was found that the formation and development of crystalline phases increases with increasing firing temperature. This causes a reduction in the amorphous phase which, in turn, leads to reduced mass gain. Kaolin fired at 1200 oC exhibited the least reactivity with moisture and mullite was found to be the dominant crystalline phase after firing at that temperature. SEM was used to examine microstructural changes in the fired specimens. The reactivity of the ceramic with moisture is shown to be directly related to the crystallinity of the fired clay.
Lightweight Aggregate Processed from Waste Materials
Authors: Ducman Vilma , Mirtič Breda
Published: October 2010

In order to decrease the deadweight of structures and/or increase thermal and acoustic insulation properties, the most widely used material for the preparation of concrete is lightweight aggregate processed either from naturally occurring lightweight materials or waste materials. The present paper presents a methodology for the production of light-waste aggregate (LWA). Waste glass, silica sludge, clay, and polishing residue were studied as potential raw materials. There are two different mechanisms active in the process of LWA production; one is combustion of organic residue in clay matrix, resulting in porous structure, the other one is a foaming process, applicable to glassy matrix where a selected foaming agent degasses at elevated temperature, and the resulting gasses remain trapped in the glassy structure. In the presented case, paper mud served as poreforming agent whereas MnO2 and SiC were added as foaming agents. The emphasis of this study was placed on finding suitable additives for lowering the softening temperature and thus facilitating the foaming process. It was found that the addition of polishing residue from the polishing process of granite–like stone lowered the softening point of the clay and silica sludge. Depending on mixture composition and regime of firing, lightweight aggregates with densities between 0.5 and 2.0 g/cm3 were obtained and analyzed.
Status and Prospects of Research and Application of Alkali-Activated Materials
Authors: Kryvenko Pavlo V.
Published: October 2010

Beginning from 1957, a scientific school in Kiev (USSR) headed by Victor Glukhovsky has been
developing a new direction in binding/cementitious/ materials. Taken as background was discovery
of binding properties of the alkali metal compounds when they act not only as activators of
hardening but are responsible for the formation of main structural elements of the alkali- activated
cements – zeolite-like compounds of different types.
Just these hydration products, analogues to natural zeolites of the Na2О(K2О)•Al2О3 •(2-
4)SіО2•2Н2О type, were identified in the ancient concretes (Ancient Greece, Ancient Rome, Egypt,
Syria). Durability of the ancient concretes and similarity of their structure with that of the alkaliactivated
cement concretes allowed to predict their high durability. High performance properties of
the alkali- activated cement concretes are supported by over 50-year experience of service of the
structures made from them.
Comparative Study of the Consolidation Process and Properties of Clay Based Geomaterials and “Geomimetic” Lateritic Clay Based Materials
Authors: Lecomte Gisèle L. , Wattiaux A. , Lecomte G.
Published: October 2010

The present work focuses on the elaboration of low energy consuming materials and the correlation between their final properties and the fabrication route. For this purpose, geomaterials have been elaborate using a common raw clay material. Also an original route has been developed to elaborate “geomimetic” materials. The raw material consists of lateritic clay, whereas the main reactives are namely: nitric acid, fulvic acid, and calcium hydroxide in an aqueous medium. In both materials, the strengthening process and the final characteristics of the as obtained products have been investigated. Namely: the characteristic compressive strength and the resistance to water seeping and wearing. The geomaterials exhibit a good resistance towards water seeping and wearing, but the products obtained using Portland cement present a greater characteristic compressive strength than with lime. “Geomimetic” materials are also water resistant. In fact, the products elaborated using nitric acid exhibit the best characteristic compressive strength, namely 20 MPa. While with fulvic acid, an environmental friendly organic acid, a characteristic compressive strength of 12 MPa is obtained. Thus the latter appears competitive towards usual stabilized earth and concrete building materials.
Characterization of Geopolymer Materials Containing MSWI Fly Ash and Coal Fly Ash
Authors: Andini Salvatore , Cioffi Raffaele , Colangelo Francesco , Ferone Claudio , Montagnaro Fabio , Santoro Luciano
Published: October 2010

In this work three samples of MSWI ash have been stabilized in systems containing coal fly ash and able to give geopolymers through a polycondensation reaction. Monolithic products were obtained with both MSWI ashes as received and after chloride partial removal by water washing. The polycondensation products have been characterized qualitatively by means of FT-IR spectroscopy and scanning electron microscopy (SEM) and quantitatively through the determination of the amount of reacted water and silicate. Differently from traditional cement based stabilization systems, those based on geopolymerization show a chemical behaviour almost insensitive to the presence of chlorides and sulphates in the MSWI ash. On the other hand, the microstructure is strongly affected by the content of soluble salts.
Medium to Long Term Engineering Properties and Performance of High-Strength Geopolymers for Structural Applications
Authors: Sagoe–Crentsil Kwesi , Brown Trevor , Yan Shi Qin
Published: October 2010

The medium to long term engineering performance of high-strength geopolymer concrete systems are largely dependent on fluid ingress and the transport phenomena that govern permeability of structural members exposed to aggressive environments. For the purpose of analysing durability performance, both high pressure water and gas permeability testing of fly-ash geopolymer(GP) concretes have been assessed for samples cured under ambient and steam exposure conditions at 65OC. The observed mean permeability coefficient values for gas(k) and water(Kw) of steam-cured structural grade concrete was respectively 6.19E-17m2 at 300kPa gas pressure and 1.52E-10m/s at 525kPa water pressure. While mean gas permeability values were comparable to reference steam-cured ordinary Portland cement(OPC) systems, the corresponding water permeability coefficient data for geopolymer concrete was ten-fold higher. The transport properties of OPC concrete systems are typically governed by water-to-cement ratio and the degree of hydration which is linked to the level of porosity and pore interconnectivity. However, corresponding permeability of geopolymer concrete appears to be dictated by an inherent mesoporous capillary pore network structure for which transport properties appear to be partly dependent on mode of concrete curing. The Paper examines global implications of increased permeability and key durability parameters such as chloride diffusion, carbonation rates and steel reinforcement corrosion on long-term engineering and durability performance.
Bond Strengths of Geopolymer and Cement Concretes
Authors: Sarker Prabir
Published: October 2010

Geopolymer is an inorganic alumino-silicate product that shows good bonding properties. Geopolymer binders are used together with aggregates to produce geopolymer concrete which is an ideal building material for infrastructures. A by-product material such as fly ash is mixed together with an alkali to produce geopolymer. Current research on geopolymer concrete has shown potential of the material for construction of reinforced concrete structures. Structural performance of reinforced concrete depends on the bond between concrete and the reinforcing steel. Design provisions of reinforced concrete as a composite material are based on the bond strength between concrete and steel. Since geopolymer binder is chemically different from Ordinary Portland Cement (OPC) binder, it is necessary to understand the bond strength between geopolymer concrete and steel reinforcement for its application to reinforced concrete structures. Pull out test is commonly used to evaluate the bond strength between concrete and reinforcing steel. This paper describes the results of the pull out tests carried out to investigate the bond strength between fly ash based geopolymer concrete and steel reinforcing bars. Beam end specimens in accordance with the ASTM Standard A944 were used for the tests. In the experimental program, 24 geopolymer concrete and 24 OPC concrete specimens were tested for pull out. The concrete compressive strength varied from 25 to 55 MPa. The other test parameters were concrete cover and bar diameter. The reinforcing steel was 500 MPa steel deformed bars of 20 mm and 24 mm diameter. The concrete cover to bar diameter ratio varied from 1.71 to 3.62. It was found from the test results that the failure occurred by splitting of concrete in the region bonded with the steel bar, in both geopolymer and OPC concrete specimens. Comparison of the test results shows that geopolymer concrete has higher bond strength than OPC concrete. This suggests that the existing design equations for bond strength of OPC concrete with steel reinforcing bars can be conservatively used for calculation of bond strength of geopolymer concrete.
Geopolymers as Waste Encapsulation Materials: Impact of Anions on the Materials Properties
Authors: Frizon Fabia , Desbats-le-Chequer Charlène
Published: October 2010

One of the most promising applications of geopolymers is their use as waste
encapsulating matrix. These binders are indeed compatible with aqueous waste streams and capable
of activating several chemical and physical immobilization mechanisms for a wide range of
inorganic waste species. Several works have investigated the immobilization of cations, mainly
heavy metals or radioactive wastes, but very few studies are taking counterions, namely anions, into
account. The aim of this work is to experimentally investigate the impact of anions with different
valences on the materials’ properties in regard to the requirements of an industrial process at
ambient or slightly elevated temperature: among others setting time, maximum achievable
compressive strength or resistance to leaching. The modifications caused by the introduction of
monovalent and divalent anions, such as sulphate and nitrate, are also monitored in term of
mineralogy, porosity and microstructure. Their immobilization seems to be related to the
advancement of geopolymerization reaction. On another hand, depending on the alkali ions used in
the activation solution, the anionic species considered may also enhance the precipitation of some
zeolites.
Recent Development of Magnesium-Based Cements - Magnesium Phosphate Cement and Magnesium Oxychloride Cement
Authors: Li Zongjin , Qiao Fei , Chau Chung Kong
Published: October 2010

The recent development of two types of environmental friendly cementitious materials, magnesium oxychloride cement and magnesium phosphate cement, at HKUST are presented. Both of them can develop high strength without heat treatment under elevated temperature, i.e. the bonding of these cementitious materials can be achieved at low temperature through chemical reaction, as opposed to fusion or sintering at high temperature. The preparation process of the two cements can not only save a lot of energy but also emit no carbon dioxide. For magnesium oxychloride cement, our research includes parametric study of the formulation, strength development, water resistance, and also identification of phase composition in the cement paste. Magnesium phosphate cement is mainly applied as rapid repair material in civil engineering. In this paper, the formulation, mechanical properties and performance in patch repair of mortar specimen including strength, bond ability to old concrete substrate, volume stability are studied.
Physical, Mechanical and Micro-Structural Properties of F Type Fly-Ash Based Geopolymeric Bricks Produced by Pressure Forming Process
Authors: Arıöz Ömer , Kilinç Kadir , Tuncan Mustafa , Tuncan Ahmet , Kavas Taner
Published: October 2010

Geopolymer is a new class of three-dimensionally networked amorphous to semi-crystalline alumino-silicate materials, and first developed by Professor Joseph Davidovits in 1978. Geopolymers can be synthesized by mixing alumino–silicate reactive materials such as kaolin, metakaolin or pozzolans in strong alkaline solutions such as NaOH and KOH and then cured at room temperature. Heat treatment applied at higher temperatures may give better results. Depending on the mixture, the optimum temperature and duration vary 40-100 °C and 2-72 hours, respectively. The properties of geopolymeric paste depend on type of source material (fly ash, metakaolin, kaolin), type of activator (sodium silicate-sodium hydroxide, sodium silicate-potassium hydroxide), amount of activator, heat treatment temperature, and heat treatment duration. In this experimental investigation, geopolymeric bricks were produced by using F-type fly ash, sodium silicate, and sodium hydroxide solution. The bricks were treated at various temperatures for different hours. The compressive strength and density of F-type fly ash based geopolymeric bricks were determined at the ages of 7, 28 and 90 days. Test results have revealed that the compressive strength values of F-type fly ash based geobricks ranged between 5 and 60 MPa. It has been found that the effect of heat treatment temperature and heat treatment duration on the density of F-type fly ash based geobricks was not significant. It should be noted that the spherical particle size increased as the heat treatment temperature increased in the microstructure of F-type fly ash based geobricks treated in oven at the temperature of 60 °C for 24 hours.
Application of Micromechanics on Alkali-Activated Materials
Authors: Šmilauer Vit , Škvára František , Němeček Jiří , Kopecký Lubomír , Hlaváček Petr
Published: October 2010

Research of alkali-activated materials has been a traditional domain of chemists. This
paper exploits contribution of micromechanics to the subject. A new model for volumetric
evolution of chemical phases is formulated. The first homogenization level identifies elasticity on
the scale of N-A-S-H gel. Nanoindentation sensing technique yielded the intrinsic Young's modulus
of N-A-S-H gel as ~18 GPa, which was further downscaled to the solid gel particles. Percolation
theory had to be introduced to match an early-age elasticity. The second homogenization level takes
into account an unreacted fly ash. Homogenization models match well the experimental elasticity
and demonstrate stiffening of N-A-S-H gel, induced by increasing packing density of the solid gel
particles. The percolation model explains a long setting time of alkali-activated materials.
Durability of Geopolymer Concretes upon Seawater Exposure
Authors: Astutiningsih Sotya , Nurjaya Dwi Marta , Ashadi Henki Wibowo , Swastika Niken
Published: October 2010

Geopolymer concrete with designed strength of 40 Mpa has been mixed from coarse aggregates, sands and geopolymer pastes. Two kinds of pastes are synthesized from different precursors, i.e. fly ash and dehydroxylated kaolin, using sodium silicate solution as the activator. Compression test pieces of 15x15x15 cm3 of both geopolymer and ordinary Portland cement (OPC) concretes (ASTM C39) have been cast and cured. Curing was done at room temperature for 1 day while Portland cement concretes were immersed in water for 28 days to provide complete hydration. After curing, the samples were immersed in ASTM seawater (ASTM D1141-90) for 7, 28, 56 and 90 days. It is found that geopolymer concretes were in general more durable upon seawater immersion than OPC concrete, This is indicated by the compressive strength retained after immersion. Dehydroxylated kaolin geopolymers show the best performance whose strength did not decrease with time of immersion. The strength of fly ash geopolymers decreased by about 20% during 56-day immersion but did not decrease further. Calcium content is suspected to cause the decrease in strength upon immersion. Kaolin geopolymers containing no calcium showed the best performance, while OPC which consist mostly of calcium silicate hydrates as the strength contributor, showed consistent decrease in strength. It is also found from the experiment that room temperature curing of fly ash geopolymer was slow but continued to progress until 28 days both under dry condition (not immersed) and immersed in water.
Interactions between Superalloys and Mould Materials for Investment Casting of Turbine Blades
Authors: Valenza Fabrizio , Nowak Rafal , Sobczak Natalia , Passerone Alberto , Di Foggia Michele , Muolo Maria Luigia
Published: October 2010

The need of increased efficiency of industrial gas turbines comes also through the improvement of the composition of superalloys (addition of new solutes) and of the manufacturing technologies involved in the investment casting process of the turbine blades. Thus, the knowledge of the interactions between the ceramic materials used for casting and the molten superalloys must be deepened in order to minimize the formation of internal defects, to improve the casting surface and to optimize finishing and casting operations.
In this work, a study of the wetting behaviour of some Ni- or Co -based superalloys, used for the fabrication of turbine blades, has been performed with reference to the interactions of these alloys in the molten state with the silica-aluminate based ceramic materials forming the shell or the core in the casting process.
Wettability tests have been performed by means of the sessile drop method at 1500°C; the characterization of the interfaces between the molten drop and the substrates has been made on solidified sessile drop samples by SEM/EDS analysis to check the final characteristics of the interfaces. The results are discussed in terms of chemical interactions in relation to the processing parameters and as a function of the surface and interfacial energetic properties of the systems.