bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and Preparation of Heterogeneous Catalysts by Controlled Chemical Reactions with Oxygen and Hydrogen
Authors: Cocke David L. , Naugle Donald G. , Hess Thomas R.
Published: April 2011

Chemical reactions of metals and strongly interacting alloys such as Cu-Mn, Ni-Ti, Ni-Hf and Ni-Zr with oxygen and hydrogen play important roles in the preparation, activation, and regeneration of many important heterogeneous catalytic systems involving supported and unsupported metals and alloys. Recent advances in the understanding of metal and alloy oxidation is bringing new insight into the reactive design and activation of bi- and multi-metallic catalysts. By surface studies of oxidation, thermal annealing and reduction of selected alloys and their thin films and reaction layers and products we have been able to delineate the factors which are most important to the oxide formation processes and the oxide reduction processes. Reaction models developed from these results are permitting the design of new catalyst systems and providing long sought understanding to explain specific aspects of well established metallic catalysts.
The Preparation and Characterization of Pt/Fe Electrocatalyst for Direct Methanol Oxidation
Authors: Ma Chaoying , Kowalak A. D. , Sung Changmo
Published: April 2011

Pt/Fe electrocatalysts (Pt/Fe) supported on Vulcan XC-72 carbon black were prepared by chemical method. The formation of Pt/Fe clusters was confirmed by transmission electron microscopy (TEM) and energy dispersive x-ray spectrometry (EDXS). The electrochemical efficiency and durability of the catalysts for direct methanol oxidation were compared with the catalyst containing Pt only (Pt) under the same reaction conditions of 1 M CH3OH in 0.1 M H2SO4 electrolyte solution. The current density for the Pt/Fe is three times of that of the Pt catalyst. Effects of various factors on the behavior of the catalysts, such as reaction time during preparation, order of the addition of the chemicals into the reaction system, methanol concentration, activation per unit Pt, scan rate for cyclic voltammograph, were examined.
Activity and Structure of Supported Molybdenum Nitride Hydrotreating Catalysts
Authors: Dolce Gregory M. , Colling Craig W. , Thompson Levi T.
Published: April 2011

Molybdenum nitrides have been shown to be active hydrotreating catalysts. We explored the hydrotreating activities of supported Mo nitrides. It was observed that the hydrodenitrogenation and hydrodesulfurization activities were inverse functions of the molybdenum loading. By using oxygen chemisorption and carbon monoxide temperature programmed desorption, we were able to characterize the particle morphology of the nitrides.
Interaction of Ni(II,III) and Sol-Gel Derived ZrO2 in Ni/ZrO2 Catalyst System
Authors: Zeng H.C. , Lin J. , Teo W.K. , Loh F.C. , Tan K.L.
Published: April 2011

NiO/ZrO2 catalyst has a selectivity for producing higher hydrocarbons, whereas NiO on classical supports gives rise to methanation of CO + H2 mixture. In this study, tetragonal and monoclinic ZrO2 gel carriers have been synthesized using sol-gel method. The interaction of nickel ions with a sol-gel derived catalyst support has been investigated using FTIR, DTA, and XPS. It is found that the nickel ions diffuses into the ZrO2 continuously over 400 to 600°C for both tetragonal and monoclinic ZrO2, and forms a thermodynamically stable Ni/ZrO2 solid solution at elevated calcination temperatures. Higher nickel surface contents are observed in tetragonal ZrO2. In addition to Ni2+, Ni3+ ions are also detected in Ni/ZrO2 system. Cation ratio of Ni2+/Ni3+ peaks at 700°C in the tetragonal ZrO2. In the monoclinic case, the ratio remains constant at different elevated temperatures. The diffusion activation energy for Ni(II,III) on both tetragonal and monoclinic in ZrO2 is 0.40 eV.
Cellular Ceramic Substrates
Authors: Williams Jimmie L. , Lachman Irwin M. , Patil M.D. , Guile Donald L.
Published: April 2011

Ceramic materials in monolithic honeycomb form offer the advantage of low pressure drop for automotive & stationary emissions control reactors, catalytic oxidation, adsorption, separation, and other applications. The ceramic materials can be extruded into cellular monoliths or coated onto a cellular ceramic substrate using conventional “washcoat” processes. Both extruded and coated ceramic substrates are prepared with a binder to promote interparticle adhesion and strength. For many applications it is advantageous to control pore structure, density, strength and surface area.

In this paper composition, fabrication and physical properties of cellular monolithic substrates will be reviewed. Emphasis will be on extruded materials used as catalytic supports for automotive, DeNOx and oxidation reactions.
Monoliths for Partial Oxidation Catalysis
Authors: Schmidt L. D. , Dietz A.
Published: April 2011

Monolith catalysts are effective for partial oxidation reactions at high temperatures at contact times between 10−4and 10−2sec. We summarize results for three reactions: (1) syngas by direct oxidation of CH4, (2) olefins by oxidative dehydrogenation of alkanes, and (3) HCN by ammoxidation of CH4, and we consider what features of monoliths create optimal selectivity with high conversions. Monoliths used are noble metal films coated on ceramic foams, extruded ceramics, ceramic fibers, and woven Pt-10%Rh gauze catalysts. Effects of metals and geometries of the ceramics are ceramics are compared to show how these factors influence activity and selectivity.
Sol-Gel Strategies for Controlled Porosity Ceramic Materials: Thin Film and Bulk
Authors: Brinker C. Jeffrey , Sehgal Rakesh , Raman Narayan K. , Prakash Sai S. , Delatire Laurent
Published: April 2011

Using sol-gel processing techniques it is possible to vary the condensation pathway over wide ranges to form primary species ranging in structure from oligomers to polymers to particles. The porosity of the corresponding dry gels depends on the size and structure of the primary species, the organization of these structures, often by aggregation, to form a gel, and the collapse of the gel by drying. This paper reviews these ideas in the context of forming thin film or bulk specimens. Several strategies are introduced to control porosity on length scales of interest for catalysis and catalytic membrane reactors: 1) aggregation of fractals; 2) management of capillary pressure; 3) surface derivatization; 4) relative rates of condensation and evaporation; 5) the use of organic templates and 6) sintering. These strategies are contrasted with the more traditional particle packing approach to preparing controlled porosity materials.
Effect of Prehydrolysis on the Textural and Catalytic Properties of Titania-Silica Aerogels
Authors: Miller James B. , Johnston Scott T. , Ko Edmond I.
Published: April 2011

A sol-gel based preparation of a mixed oxide allows considerable control over the extent of component mixing. When the reactivities of the alkoxide precursors are evenly matched, a homogeneously mixed sample can be produced; a large reactivity difference results in a segregated mixed oxide product. We have prepared and characterized two sets of mixed titania-silica aerogels, each covering the entire composition range. One set was made using silicon precursor prehydrolysis to minimize the reactivity difference and promote homogeneous component mixing; the second set was made without prehydrolysis.
Nickel Catalyzed Conversion of Activated Carbon into Porous Silicon Carbide
Authors: Moene R. , Schoonman J. , Makkee M. , Moulijn J. A.
Published: April 2011

High surface area silicon carbide (SiC) of 31 m2/g has been synthesized by the catalytic conversion of activated carbon. The thermal stability in non-oxidizing environments is shown to be excellent; no significant sintering has been observed after ageing in nitrogen for 4 hours at 1273 K. The presence of 2v% steam or the use of air results in SiC oxidation into SiO2 and considerable sintering at 1273 K. Air oxidation of SiC is shown to cause substantial SiC conversion, viz. 60 % after 10 hours at 1273 K. Complete conversion is achieved at 1080 K in about 100 days. This rate of oxidation agrees with reports on the oxidation of non-porous Acheson SiC and Chemical Vapour Deposited SiC coatings. The use of SiC based catalysts is, therefore, limited to (1) high temperature gas phase reactions operating in the absence of oxidizing constituents (O2 or H2O) and (2) liquid phase processes at demanding pH. Syntheses of highly dispersed and highly loaded Ni/SiC catalysts are feasible by applying an ion-exchange technique, resulting in supported nickel particles of 4 nm.
Synthesis of Graphite Intercalation Compounds with Donor Species
Authors: GuÉrard Daniel , Nalimova Vera A.
Published: April 2011

For 15 years, the chemistry of the intercalation of donors species into graphite has beenlargely developed and a great number of new phases were discovered : over 100 if one takes into account the various stages and stacking, which involves different properties of the compounds for a given intercalate. Four new systems and synthesis methods were developed : intercalation of metallic alloys containing an alkali metal, ionic species (alkali metal hydrides, hydroxides and, even chlorides), alkali metals with oxygen (by addition to the metal of a small quantity of its peroxide M2O2), intercalation under high pressure of the alkali metal. Those new syntheses, still in progress, lead to compounds in which the first stages exhibit a fairly high intercalate/carbon ratio : from LiC2 to MC4 (M = Na, K, Rb or Cs) instead of LiC6 or MC8 obtained by classical methods.

The increase of this ratio confers them interesting properties and possibilities of application, especially in the field of new materials for primary or secondary batteries.
The Carbon-Lithium Negative Electrode for Lithium-Ion Batteries in Polymer Electrolyte
Authors: Yazami R. , Deschamps M.
Published: April 2011

Several types of carbonaceous materials are evaluated as negative electrodes for lithium storage in polymer electrolyte based cells operated at 100ºC. The corresponding faradaic efficiencies of the spherical cycle and the achieved reversible first capacity and rate capacity will be given. A meso carbon yielded a higher capacity than the theoretical 372 mAh/g. This is tentatively explained by the necessary enhancement of the carbon/polymer interfacial properties through the formation of C-Li-O bonding at the carbon surface and by the possible formation of multilayers of lithium on the external a,b planes of disordered carbons. The formation of the passivating layer on the carbon surface will be described.

A lithium-ion type battery using coke and LiNiO2 as the negative and positive leads and POE-LiCIO4 was operated at 100ºC and cycled galvanostatically. Good reversible capacity was attained with the LiNiO2 electrode.
Transition Metal Oxides for Rocking-Chair Cells
Authors: Thackeray M. M. , Ferg E. , Gummow R. J. , Kock A. De
Published: April 2011

Transition metal oxides have been evaluated extensively in the past as cathode materials for lithium cells. The major emphasis of recent research has been to develop lithium-ion or rockingchair cells that are assembled in the discharged state with a lithiated transition metal oxide cathode and a carbon anode. Although these cells are significantly safer to use than lithium cells with metallic lithium anodes, the possibility of depositing lithium at the surface of the carbon particles at the top of charge or at high rates of charge cannot be discounted. This paper discusses some recent developments in fabricating rocking-chair cells with transition metal oxide host structures as both anode and cathode, the anode providing a relatively low voltage vs. lithium and the cathode a relatively highvoltage vs. lithium. These cells avoid the reduction and oxidation of lithium during charge and discharge and, therefore, reduce the safety hazards of lithium cells. Improved safety is gained, however, at the expense of cell voltage and specific energy.
MorphÒlogy and Properties of Vanadium Oxide Xerogels and Aerogels
Authors: Katz B. , Liu W. , Salloux K. , Chaput F. , Dunn B. , Farrington G.C.
Published: April 2011

The high redox potential and ion insertion properties of vanadium pentoxide have made this material a viable cathode for secondary lithium batteries. The use of sol-gel methods to synthesize vanadium pentoxide and other transition metal oxides has been well studied as the technique represents a relatively simple approach for preparing thin films and powders. Although it is well known that sol-gel processing may be used to prepare high surface area aerogels, the research on transition metal oxides has been largely limited to xerogels. The present paper compares the properties, structures and morphologies of vanadate xerogels and aerogels.
Monte Carlo Study of Dispersive Transport in Glassy Electrolytes
Authors: Knödler D. , Pendzig P. , Dieterich W.
Published: April 2011

A lattice-gas model is presented, where ions are diffusing in an energy landscape due to immobile, randomly placed counterions. All Coulombic interactions are taken into account.By Monte Carlo simulations we obtain the ac-conductivity, which shows strong dispersion in the form of power-laws. In a separate study we investigate a restricted model, where long-range diffusion is suppressed. These calculations suggest that the response at high frequencies can be interpreted in terms of highly correlated, local motions of dipolar character. Conductivity exponents n1 near unity or even exceeding unity arefound in that regime. We discuss the relationship of these results to experiments on ionic transport in alkali-doped network glasses.
Point Defects and Protonic Conduction in A3B'B”2O9 Compounds
Authors: Du Yang , Nowick A.S.
Published: April 2011

We have investigated the defect structure and protonic transport properties of nonstoichiometric complex perovskite-type compounds of the type A3B'1+xNb2-xO9-δ. where A and B' are both divalent ions. Protons are incorporated by treatment in H2O vapor and their presence is manifested by the appearance of an OH band in the IR spectra, as well as by the large increase in electrical conductivity to produce excellent protonic conductors, with lower activation energies. A non-classical isotope effect, in which the Arrhenius plots for D+ and H+ cross over, can be explained by a modification of the classical ART hopping theory.
Point Defects and Cation Diffusion in Cobaltous Oxide
Authors: Aggarwal Sanjeev , Dieckmann RÜdiger
Published: April 2011

The deviation from stoichiometry, δ, in Co1-δO was measured in-situ as a function of oxygen activity at temperatures between 1000 and 1400 ºC, using ahigh resolution microbalance. The experiments were conducted over the entire Co1-δO phase stability region at atmospheric pressure. The experimental results were analyzed with regard to the point defect structure and also in comparison with mass and charge transport data. Contrary to prior belief, it was found that the average mobility of the cationic defects and holes varied with their respective concentration.
Improved Oxide Ion Electrolytes
Authors: Feng Man , Goodenough John B.
Published: April 2011

Systematic experiments on anion-deficient ABO3-δ perovskites are reviewed with a view to the development of a strategy for the design of improved oxide-ion electrolytes. Ba0.6 La0.4 1nO2.7 is shown to be competitive with the best yttria-stabilized zirconia and La0.9 Sr0.1 Ga0.8Mg0.202.85 to be a superior oxide-ion electrolyte suitable for fuel-cell applications.
Bi2Sr2M'2M”O11.5 [(M' = Nb, Ta) and (M” = Al, Ga)], Synthesis and Characterization of Oxygen-Deficient Aurivillius Phases
Authors: Kendall Kurt R. , Navas Carlos J. , Zur Loye Hans-Conrad
Published: April 2011

Oxygen-deficient layered bismuth oxides, Bi2Sr2M'2M”O11.5 [(M' = Nb, Ta) and (M” = Al, Ga)] were synthesized. Powder X-ray diffraction and transmission electron microscopy were usedto characterize the new materials' structures. The ionic conductivity was measuredusing impedance spectroscopy which indicated the existence of multiple conductive states in the new oxygen-deficient materials. Arrhenius plots of the conductivity showed discontinuities which were attributed to transitions between different conductive states. At 800ºC, Bi2Sr2Nb2GaO11.5 and Bi2Sr2Nb2A1O1.5, have ionic conductivities of 2.0×10−2 S/cm and 1.2×10−2 S/cm, respectively. Differential thermal analysis showed phase transitions in the oxygen-deficient materials. These transitionsoccurred at temperatures similar to those at which discontinuities were observed in the Arrhenius plots of the conductivity and are attributed to oxygen vacancy order/disorder transitions. The transference number was calculated for some of the samples by measuring both the EMF and the conductivity as a function of oxygen partial pressure. Under atmospheric conditions the new materials are predominantly ionic conductors.
Defect Spinels in the System Li—Mn—O. Chemistry and Lithium Insertion
Authors: Cras F. Le , Bloch D. , Anne M. , Strobel P.
Published: April 2011

Spinel phases Li-Mn-C with Li/Mn ratios between 0.35 and 0.8 were synthesized. The relationships between composition, manganese valence, vacancy fraction and electrochemical capacity are described using a new composition-valence phase diagram. Electrochemical performances in lithium batteries are compared. The best materials showed constant capacit> 140 Ah/kg in the range 3.5/2 V in liquid electrolyte batteries up to 20 cycles, without the usual capacity drop observed in stoichiometric LiMn204.
Ionic Conductivities of Lithium Phosphorus Oxynitride Glasses, Polycrystals and Thin Films
Authors: Wang B. , Bates J. B. , Chakoumakos B. C. , Sales B. C. , Kwak B. S. , Zuhr R. A. , Robertson J. D.
Published: April 2011

Various lithium phosphorus oxynitrides have been prepared in the form of glasses, polycrystals, and thin films. The structures of these compounds were investigated by X-ray and neutron diffraction, X-ray photoelectron spectroscopy (XPS), and high-performance liquid chromatography (HPLC). The ac impedance measurements indicate a significant improvement of ionic conductivity as the result of incorporation of nitrogen into the structure. In the case of polycrystalline Li2.88PO3.73N0.14 with the γ-Li3PO4 structure, the conductivity increased by several orders of magnitude on small addition of nitrogen. The highest conductivities in the bulk glasses and thin films were found to be 3.0 × 10-7 and 8.9 × 10-7 S-cm-1 at 25°C, respectively.
Synthesis and Lithium Intercalation Properties of a Layered Lithiated Manganese Oxide with Rancieite Type
Authors: Leroux F. , Guyomard D. , Piffard Y.
Published: April 2011

The 2D lithiated manganese oxide with Rancieite-type structure (lithium phyllomanganate), synthesized via a soft chemistry route (T≤60ºC) is hydrated at room temperature and can be dehydrated progressively by a thermal treatment. This compound and a series of samples obtained after annealing at different temperatures were characterized and studied for their electrochemical lithium intercalation properties. They are poorly crystallized, with however the advantage of a manganese oxidation state very close to 4, a mustto get high specific capacity. Their chemical characterization was achieved after gathering results obtained from complementary techniques such as AAS, redox titration, TGA and XPS measurements. Special care was taken for the chemical characterization of electrode compositions effectively used in the electrochemical cells.

Electrochemical lithium intercalation was systematically studied for the series of samples, when starting in charge or in discharge after assembly of the Li battery. The electrochemical behavior is discussed in relation with the manganese average oxidation state and the interlayer water content. Materials of the series showing the larger specific capacities were further examined on the application point of view, for their reversibility, cyclability and high rate capability upon Li intercalation.

This work shows that the anhydrous material which is obtained at 300ºC, with the composition Li0.42MnIII0.20MnIV0.8002.11, is a promising rechargeable layered manganese dioxide material.
Non-Crystallizing Molten Salt and Ionic Rubber Electrolytes with Wide Electrochemical Windows
Authors: Xu K. , Angell C. A.
Published: April 2011

New realizations of the type of ambient temperature lithium ion conducting electrolyte introduced at this symposium two years ago are given and a 5 volt electrochemical window, absent from the earlier examples, is demonstrated. The new systems satisfy the criteria for “ionic oils” though their conductivities, - 10-3 S cm-1, are smaller than desirable.
Xafs Studies of Polymer Electrolytes
Authors: Bandara H M N , Linford R G , Latham R J , Schlindwein D W S
Published: April 2011

Because of the procedures associated with the deconvolution of the data present in an EXAFS spectrum, the experimental XAFS spectra also include both the edge and XANES regions. It is possible to obtain additional structural and chemical information from the data associated with these regions of the XAFS spectrum and in this work we have re-examined the XAFS spectra for a series of polymer electrolytes. These spectra were originally recorded for EXAFS analysis. The XANES spectra for PEOn:CaBr2 electrolytes confirm that the behaviour of calcium polymer electrolytes appears to be very different from that of other divalent based electrolytes. We have also examined the edge features for PEO8:NiBr2 samples which were subject to different thermal histories and evidence for phase separation is presented.
Lithium-7 NMR Studies of Li1−xCoO2 Battery Cathodes
Authors: Ouyang B. , Cao X. , Lin H.W. , Slane S. , Kostov S. , Denboer M. , Greenbaum S.G.
Published: April 2011

Lithium-deficient cathode materials Li1-xCoO2 where x = 0.1, 0.4 and 0.6 were prepared electrochemically from the stoichiometric parent compound (x = 0.0).The materials were observed to be air-stable, and x-ray diffraction characterization yielded good agreement with the in situ studies of Dahn and co-workers, regarding changes in lattice parameters. In addition to both static and magic angle spinning (MAS) 7Li NMR, measurements, the samples were investigated by EPR and cobalt K-edge NEXAFS. The removal of Li is accompanied by compensating electrons from the Co d-orbitals, asevidenced by both shifts in the NEXAFS peak and the observation of EPR signals due to spins localized on the Co ions. These spins, in turn, result in dramatic 7Li chemical shifts (89 ppm for x = 0.6) and line broadening. Whereas MAS analysis of Li0.9CoO2 indicates two magnetically inequivalent Li sites, the spectra becometoo broad to resolve different sites for higher values of x. Finally NMR linewidth and spinlattice relaxation measurements as a function of temperature suggest a modest increase in Li+ ion mobility for Li-deficient samples as compared to the parent compound.
The Li-Ion Technology: Its Evolution From Liquid to Plastic
Authors: Tarascon J.M. , Schmutz C. , Gozdz A.S. , Warren P.C. , Shokoohi F.K.
Published: April 2011

In 1992, Bellcore researchers demonstrated the feasibility of a liquidelectrolyte Li-ion system based on the Li1 + xMn2O4/C redox couple which presents cost and environmental advantages over the LiCoO2/C system. However, neither of these systems are free of the risk of electrolyte leakage. To address this problem, we investigated various means of trapping the liquid electrolyte in a polymer matrix and developed the first practical plastic Li-ion battery. In this paper we compare the performance and scaleability of this technology to those of its liquid Li-ion counterpart. Based on the “hybrid polymer” concept, this battery exhibits excellent cycle life (more than 2500 cycles) and good rate capabilities (the battery can deliver 95% of its total capacity at a 1C discharge rate). This technology is compatible with various positive (LiMn2O4, LiCoO2 and LiNiO2) and negative (carbon, graphite) electrode materials.
Vapor Deposition of Thin-Film Y-Doped ZrO2 For Electrochemical Device Applications
Authors: Chung Brandon W. , Brosha Eric L. , Brown David R. , Garzon Fernando H.
Published: April 2011

The growth of high-quality, pin-hole free, ytrrium doped ZrO2 thin films is of great interest for a variety of electrochemical applications such as fuel cells and oxygen gas separation devices. In the work, we have grown polycrystalline thin films of ytrrium doped ZrO2 on thick porous Al2O3 substrates in multilayer La1-xSrxMEO3/YSZ/La1-xSrxMEO3 (ME = Mn, Co) configurations using a combination of single-target RF magnetron sputtering and electron beam physical vapor deposition techniques. The structure and morphology of these films have been studied using X-ray diffraction, and Scanning Electron Microscopy techniques. The ionic conductivity of the thin films has been measured using AC impedance analysis.
Electrical Properties of Donor and Acceptor Doped Gd2Ti2O7
Authors: Kosacki Igor , Tuller Harry L.
Published: April 2011

The results of electrical conductivity measurements on Nb, W, and Mn-doped Gd2Ti2O7 are presented. A correlation between electrical conductivity, the oxygen partial pressure and type of dopants has been obtained. The source of the different PO2 dependence for Mn-doped material is discussed.
Image-Based Characterization of Fracture Surface Roughness
Authors: Abell A.B. , Lange D.A.
Published: April 2011

Analysis of images from SEM, optical and confocal microscopes provides insight into the roughness of fracture surfaces of cement-based materials. Several techniques including 3D surface reconstruction and 2-D vertical contour analysis are compared. Roughness parameters and fractal dimensions are computed to describe the degree of tortuosity of the fracture surface. The tortuosity of the surface (i.e. crack path) is an aspect that has not been adequately integrated into fracture mechanics models of cement-based materials. Topographic maps from confocal microscopy reveal orientation of the crack front throughout the fracture process, allowing analysis of mixed-mode character of nominally mode I fracture. These techniques allow quantification of microstructural parameters to be linked to material properties.
A Re-Evaluation of Hardened Cement Paste Microstructure Based on Backscatter Sem Investigations
Authors: Diamond Sidney , Bonen David
Published: April 2011

Backscattered electron imaging of polished cement paste specimens permits a re-evaluation of structural details of hydrated cement paste at the gim level. The primarily microstructural units comprise a highly porous groundmass and large distinct grains (“phenograins”) set in it. The groundmass is composed of several kinds of fine particles, with a significant content of easily detected gross pores. Phenograins are primarily large clinker grains hydrating in-situ, but may be distinct deposits of CH, or may be mineral admixture grains. Detailed EDS analyses indicated that hydrating cement in phenograins has a highly consistent composition, interpreted as C-S-H with a small but regular incorporation of sub-jim CH and calcium monosulfoaluminate. Groundmass particles are highly variable in composition, but appear to consist of C-S-H with variable and occasionally major contents of other hydration products on a sub-μm scale. Incorporation of fly ash does not appear to change the basic microstructure, but silica fume incorporated with superplasticizer drastically modifies the character of the groundmass. Some attempts at quantification of these features by application of image analysis are briefly described.
Sem Observation of the Influence of Sucrose and Koh on Formation of Sulphoaluminate Hydrates of a Cement Clinker During the Early Hydration
Authors: Peiming Wang , Peifen Xia , Zhiyuan Chen
Published: April 2011

The morphology of early hydrates of a cement clinker was studied by SEM and EDS. The hydrates were formed on thin plates cut from the clinker and immersed in a solution containing Ca(OH)2, CaSO4·2H20, and varying amounts of sucrose and KOH. The results show the different influences of sucrose and of KOH on the formation of the hydrates, in particular on the crystallization of AFt. The sucrose plays a leading role, and altered the time of primary formation of AFt and its morphology. KOH did not. In CaSO4·2H20 saturated solution without sucrose, regardless of the presence or absence of Ca(OH)2, the foil -like hydrates, CxAHy are formed as the first result of reaction of C3A with water. Then CxAHy reacts with CaSO4·2H20 to form AFt. However, in the presence of sucrose the C3A reacts directly with CaSO4·2H20 to form AFt. It is supposed that sucrose acts as a catalyst for the formation of AFt crystals. During the early stage of cement hydration, AFt crystals appear to form by both topochemical and by through-solution reaction mechanisms.
Pore Size Distributions in Hardened Cement Paste by Sem Image Analysis
Authors: Diamond Sidney , Leeman Mark E.
Published: April 2011

Technical requirements for determining the size distribution of capillary pores in hardened cement paste by SEM image analysis are discussed. Results of such measurements are reported for a set of hardened cement pastes of w:c ratio 0.40 and 0.25, and of ages ranging from 1 to 28 days. Pore size distributions based on conventional mercury intrusion porisimetry are presented for the same pastes. Estimates of pore diameters by mercury intrusion are two orders of magnitude smaller than the sizes revealed by the image analysis. Diameters of air voids are even more drastically underestimated by mercury intrusion. Typical micrographs are provided to illustrate the physical reality of the image analysis results, and the technical reasons underlying the conventional misinterpretation of MIP results for hydrated cements are reviewed.
Durability And Microstructure of Pore Reduced Cements(PRC)
Authors: Geslin N.M. , Israel D. , Lachowski E.E. , Macphee D.E.
Published: April 2011

The pore structure characteristics of cementitious materials play an important role in defining their mechanical and durability performance. The mechanical properties of pore reduced cements (PRC) have already been reported [5] as a function of the product density. This paper reports recent data on the durability of PRC and attempts to relate the pore properties of the material to its resistance against deterioration in aggressive environments.
Compressive Yield Stress of Cement Paste
Authors: Miller Kelly T. , Shi Wei , Struble Leslie J. , Zukoski Charles F.
Published: April 2011

Compressive yield stresses have been measured for pastes (0.35 ≤ w/c ≤ 0.50) of portland cement, calcium aluminate cement, and weakly and strongly flocculated alumina (Φ0 = 0.20) using the centrifuge sediment height technique. Equilibrium sediment heights are reached quickly, allowing all measurements to be taken during the cement's induction period. The compressive behavior showed little dependence on the compressive history. Compressive yield stress was, however, dependent upon initial volume fraction, decreasing as the initial volume fraction increases. This behavior was observed in both the cements and alumina suspensions, implying that strong dependencies on initial structure may be a general property of the compressive behavior of flocculated suspensions.
Optical Microscopy and Digital Image Analysis of Bond-Cracks in Cement Based Materials
Authors: Vervuurt Adri , Van Mier Jan G.M.
Published: April 2011

A new testing method is presented in which the properties of the bond zone between aggregate and matrix in concrete are investigated. The reason for starting the investigation is the improvement of the lattice model, which is developed at the Stevin Laboratory. In the lattice model the material is schematized as a lattice of beam elements. The fracture properties of the individual beam elements are purely brittle, and the use of fracture energy parameters as a material property can be avoided for simulating the non-linear fracture process. In spite of the fact that a locally brittle law is used, the global behaviourshows softening of the material. An improved optical microscopy technique in combination with image processing is adopted for investigating the fracture process during loading.
Changes Induced by PVA in the Cement Microstructure Surrounding Aggregate
Authors: Chu Un-Jen , Kim Jae-Ho , Park Cheol , Robertson Richard E.
Published: April 2011

The presence of poly(vinyl alcohol) (PVA) in portland cement during its hydration was found to induce changes in the microstructure and behavior of the paste that forms around aggregate. The microstructure was studied with scanning electron microscopy in secondary electron, backscattered electron, and EDX mapping modes and with Fourier-transform infraredspectroscopy. The adhesion between cement paste and aggregate was examined with planar aggregate surfaces. With concentrations of the order of 1% by weight of PVA based onthe weight of the cement, the deposition of calcium hydroxide on the aggregate surface was found to be diminished and the porous layer that usually surrounds the aggregate to be reduced in thickness. Also, the bond between the aggregate and cement paste was increasedenough for the bond to approach the strength of the cement.
Further Studies on Fracture Properties of Paste/Rock Interfaces
Authors: Alexander Mark G. , Stamatiou Andreas
Published: April 2011

The results of fracture tests on rocks, pastes, and paste/rock interfaces are presented. Variables included rock type (andesite, dolomite, and granite), w/c ratio (0.3 - 0.55) and age of test (3 - 91 d). The results illustrate the variability inherent in toughness measurements on naturally fractured rough rock interfaces, but also indicate that interface toughness is not necessarily intrinsically lower than that of pure paste.
Microcrack Study of Cement-Based Materials by Means of Image Analysis
Authors: Alhassani Yahia , Bascoul Alain , Ringot Erick
Published: April 2011

The relationship between microscopical damaging of concrete and its mechanical parameters such as Young's modulus and degree of reversibility is a basic issue. In the same time, transport properties and of course the durability of civil engineering and hydraulic structures are linked to the state of microcracking.

The replica technique has been developed in our laboratory in order to study microcracks with a scanning electron microscope. This non-destructive method allows observation of the imprint of the concrete surface and to follow the evolution of the alterations with time. An objective quantitative analysis requires numerous replicas and many microscopic fields within each replica.

After a brief state of the art of the automatic method of extraction of lines by image processing, we propose a specific algorithm of image analysis which allows the cleaning of the pictures and the extraction of the microcrack skeleton. Today, this procedure has been validated on cement paste samples. It has to be improved to be applied on concrete.

The measured parameters are the microcrack specific lengths and their orientation. The objective values measured by means of this procedure compare favorably to results obtained by hand drawing.
Heat Curing and Delayed Ettringite Formation
Authors: Lewis M.C. , Scrivener Karen L. , Kelham S.
Published: April 2011

This paper reports some preliminary results from a study of the effect of elevated temperature curing on mortars and the phenomenon of delayed ettringite formation (DEF). Mortars made from cements with sulphate levels of 3%, 4%, and 5% and with 5% sulphate and added alkali were cured at 20 and 90° C and subsequently stored in water. Expansion measurements showed a pessimum effect with increasing S03 content. Mortars which expanded showed a corresponding decrease in strength. X-ray diffraction (XRD) studies indicated that no ettringite is present after heat treatment but re-forms over time within the material. However, the ultimate levels of ettringite reached do not correspond to the magnitude of expansion observed. X-ray microanalysis shows that immediately after the heat treatment the aluminate species and most of the sulphate species are incorporated within the C-S-H gel. The concentrations of these species decrease during expansion, such that at the end of expansion the amounts remaining correspond to the presence of AFm phase mixed with C-S-H.
Hydrothermal Synthesis of Alumina Pillared Layered α- Zirconium Phosphate
Authors: Mérida-Robles Josefa , Olivera-Pastor Pascual , Jiménezlópez Antonio , Rodriguez-Castellón Enrique
Published: April 2011

A new strategy to prepare alumina pillared α-zirconium phosphate with enhanced surface area and narrow pore size distribution is reported. The required precursor, a highly expanded single phase intercalate, is obtained in two steps. In the first one, the oligomeric solution of aluminium, prepared by dissolving aluminium in a solution of A1C13at 95°C, is contacted with colloidal α-zirconium phosphate under reflux, in the presence of fluoride. Subsequently, the resulting intercalation compound is treated again with a diluted solution of fluoride under hydrothermal conditions at 200°C. It is thought that fluoride ions complex aluminium monomers present in the pillaring solutions, and remove aluminium from the external surface of the phosphate. The pillared materials obtained by calcination in the range 400-600°C present BET surface areas between 184-140 m2g−1and basal spacings between 17.3-15.4 Å. These results contrast with those reported using classical methods, which systematically lead to materials with BET surface areas <80m2g−1.
Porous Solids of Boron Phosphate, Aluminum Phosphate, and Silicon Phosphate
Authors: Babb K. B. , Lindquist D. A. , Rooke S. S. , Young W. E. , Kleve M. G.
Published: April 2011

Anhydrous sol-gel condensation of triethyl phosphate [(CH3CH2O)3PO] with boron trichioride (BCl3), triethyl aluminum [(CH3CH2)3Al] or silicon tetrachloride [SiCI4] in organic solvents led to rigid gels. The pore fluid of the gels was removed under supercritical conditions in a pressurized vessel to form porous solids. The condensation chemistry prior to the gel point was monitored by solution 1H, 13C, 31P, and 11B NMR. The materials were then calcined at progressively higher temperatures to produce high surface area phosphates. Nitrogen gasphysisorption was used to determine the surface areas, total pore volume, and average pore radius of the products. FT-IR was used to determine functional groups in the materials. The microstructure was also examined by scanning electron microscopy.
Nitrogen and Water Sorption Properties of Ethyl-Substituted Silica Aerogels and Xerogels
Authors: Liu Chunling , Komarneni Sridhar
Published: April 2011

High surface area ethyltrimethoxysilane (ETMS) modified silica aerogels and xerogels were synthesized by cohydrolyzing the mixtures of ETMS and tetramethylorthosilicate (TMOS). The effects of ETMS content, pH value and solvent addition were investigated. The surface area, pore structure and hydrophobicity were studied using nitrogen and water sorption measurements. By ETMS modification of TMOS gels, high surface area, density and hydrophobicity were achieved. The 25 mole% ETMS-75 mole% TMOS was found to be the best composition for both aerogel and xerogel, which are hydrophobic and have surface areas of 1221 and 832 m2/g, respectively.
Synthesis of Porous Transition Metal Oxides by the Salt-Gel Method
Authors: Stein Andreas , Fendorf Mark , Jarvie Thomas P. , Mueller Karl T. , Garcia Maurie E. , Mallouk Thomas E.
Published: April 2011

Composites of surfactants with certain transition metal oxides can be arranged into periodic arrays with giant tunnel structures. Transmission electron micrographs of these structures resemble images of mesoporous silicate molecular sieves synthesized in the presence of surfactants. However, data in this study lead to the conclusion that Keggin-ions of the type (H2W12O40)6-are formed during the hydrothermal synthesis of a cetyltrimethylammonium/tungstate composite. These cluster anions are not connected to each other. Removal of the organic template therefore results in the collapse of the tunnel structures.

A strategy has been developed which uses pre-arranged surfactant-salt structures as precursors for microporous and mesoporous framework materials. Transition metal silicates with long-range structural order have been synthesized by reacting surfactant salts of niobotungstate clusters with tetraethylorthosilicate to form a salt-gel. Infrared and solid-state NMR double resonance spectra indicate that, in addition to linkages between silicate tetrahedra, niobium-oxygen-silicon linkages have been formed in this reaction. Removal of the cationic surfactants by acid-extraction has resulted in porous structures with surface areas up to 265 m2/g.
Synthesis, Characterization and Modification of Mcm-41 Molecular Sieves
Authors: Sayari A. , Karra V.R. , Reddy J.S. , Moudrakovski I.L.
Published: April 2011

A series of crystalline mesoporous molecular sieves were prepared using alkyl hexadecyl dimethyl ammonium bromide salts (C16H33)(CnH2n + 1)(CH3)2NBr, in which the number of carbon atoms (n) in one alkyl group was varied from 1 to 12. The influence of (n) value on the nature of the final phase obtained and on its pore size was investigated. A hexagonal phase was obtained for n = 1, 3, 5 and 7, while a lamellar phase was obtained for all other templates. Vanadium and titanium modified MCM-41 molecular sieves were also prepared in the presence of C12H25(CH3)3N+ and C16H33(CH3)3N+ ions, respectively. These materials were characterized by XRD, nitrogen physisorption, FTIR, solid state NMR, XPS, UV-Vis and catalytic testing in the oxidation of 1-naphthol, 2,6-di-tert-butylphenol, norbornylene, n-hexane and propylamine. Ti-MCM-41 exhibited considerable catalytic activity only in the oxidation of aromatics, olefins and alcohols. V-MCM-41 was found to be a good catalyst in the oxidation of aromatics and alkanes.
Preparation of Hollow Shell ICF Targets Using A Depolymerizing Mandrel
Authors: Letts Stephan A. , Fearon E. M. , Buckley S. R. , Saculla M. D. , Allison L. M. , Cook R. C.
Published: April 2011

A new technique for producing hollow shell laser fusion fuel capsules was developed that starts with a depolymerizable mandrel. In this technique we use poly(alpha-methylstyrene) (PAMS) beads or shells as mandrels which are overcoated with plasma polymer. The PAMS mandrel is thermally depolymerized to gas phase monomer, which diffuses through the permeable and thermally more stable plasma polymer coating, leaving a hollow shell. We have developed methods for controlling the size of the PAMS mandrel by either grinding to make smaller sizes or melt sintering to form larger mandrels. Sphericity and surface finish are improved by heating the PAMS mandrels in hot water using a surfactant to prevent aggregation. Using this technique we have made shells from 200 μm to 4 mm diameter with 15 to 100 μm wall thickness having sphericity better than 2 μm and local surface finish better than 10 nm RMS.
Low Dielectric Constant Laminates Containing Microspheres
Authors: Japp Robert M. , Papathomas Kostas I.
Published: April 2011

As electronic devices become faster, the effective dielectric constant of the circuit packaging connecting them becomes more important. The dielectric constant of standard epoxy/glass laminates can be significantly reduced by the addition of hollow glass microspheres. However the addition of such microspheres usually results in the degradation of other physical, electrical and mechanical properties which are prerequisites for materials to be used in commercial circuit packaging. By carefully optimizing the formulation many of these undesirable effects can be avoided. These topics and others pertaining to the development and testing of a microsphere laminate are discussed.
Synthesis of Indium Oxide Microspheres for Antistatic Spacecraft Coatings
Authors: Speckman Donna M. , Jackson C. A.
Published: April 2011

Indium oxide microspheres were synthesized for potential use in novel, polymer-based antistatic coatings for exposed spacecraft surfaces. Non-agglomerating indium oxide microspheres with diameters ranging from 0.5–2.0 μm were produced using an aerosol spray pyrolysis technique. The precursor solution used to generate the aerosol droplets for pyrolysis consisted of indium acetate dissolved in water; however, the actual indium species present in solution was identified as the hydrolysis product, dihydroxy(acetato)indium. Thermogravimetric analyses of commercial indium acetate and of pure crystals of the dihydroxy(acetato)indium compound both demonstrated clean solid-state pyrolyses to generate pure indium oxide, as confirmed by x-ray diffraction and infrared spectroscopic analysis. Air was used as the carrier gas for the aerosol droplets for the spray pyrolysis experiments, and pyrolysis took place within a 2′′ tube furnace. The microspheres were characterized by x-ray diffraction and scanning electron microscopy. The non-agglomerating characteristics of the microspheres, combined with their small size, indicates that these particles are highly promising for dispersion within a polymer matrixes required for novel polymer-based antistatic films.
Porous Spherical Shells and Microspheres by Electrodispersion Precipitation
Authors: Harris Michael T. , Sisson Warren G. , Hayes Susan M. , Bobrowski Sophie J. , Basaran Osman A.
Published: April 2011

Pulsed electric fields have been used to enhance the dispersion of aqueous metal (Zr and Al) salt solutions from a nozzle and into a nonconducting liquid continuous phase that is immiscible with the aqueous phase. The diameter of the resulting microdroplets ranged in size from approximately 0.1 to 10 μm. Precipitation of hydrous metal oxides occurred as ammonia, which was dissolved in varying amounts in the continuous phase, diffused into the aqueous microdroplets. Spherical shells were formed at higher ammonia concentrations and microspheres were produced at lower ammonia concentrations. Upon drying, dimples appeared in the particles that were synthesized at higher ammonia concentrations. The latter result accords with the well known fact that under certain conditions spherical shells collapse when a fluid is extracted from the core of the particle. No dimples were observed in the microspheres that were produced at lower ammonia concentrations. Analog X-ray dot maps for aluminum and zirconium were done to determine the spatial distribution of each metal in the particles.
Formation of Solid and Hollow Spherical Particles by Spray Pyrolysis
Authors: Zhang Shi C. , Messing Gary L. , Lee Seong Young , Santoro Robert J.
Published: April 2011

Spray pyrolysis offers a number of opportunities for the synthesis of either solid or hollow spherical particles. As predicted by the evaporation model, particles with different shell thicknesses can be obtained depending on the concentration gradient at the onset of precipitation. If the precipitate shell has a sufficiently high permeability for removal of the remaining solvent, then the shell can be preserved and a hollow particle obtained. By drying at a lower temperature solid particles are readily formed from precursor salts but hollow particle formation by SP at these low temperatures imposes demanding heating rate requirements.
Solid and Hollow Micro and Nano Spherical Structures: in Polysilicon and Phosphosilicate Glass
Authors: Farooqui M. M. , Evans A. G. R.
Published: April 2011

Fabrication of three dimensional micro structures in silicon and silicon related materials is becoming increasingly important for the realisation of micro systems comprising of sensors, actuators, transducers and analytical assemblies. Fabrication of such devices so far has been mostly in form of structures defined by the crystal planes of silicon, or has involved sophisticated technologies such as ion beam machining, replication using LIGA, or micromachining techniques involving a sequence of alignment and etch stages using binary masks. Structures with circular symmetry are of great interest as micro optical components amongst others, and these are not easily amenable to microfabrication techniques commonly employed.