bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface chemistry in tribology
Authors: Gellman A. J. , Spencer N. D.
Published: January 2003

Surface chemistry is key to the understanding of tribological phenomena in the absence of a thick lubricant film. Progress in the development of surface analytical techniques has opened a new window into tribochemical phenomena and holds the promise of a better understanding of many critically important tribological processes. In this review the areas in which surface chemistry has played an important role in enhancing tribological understanding are surveyed. These include boundary lubrication, surface-additive interactions, the anomalous tribological behaviour of quasicrystals and the lubrication of hard disks.
Multi-scale representation of tribological surfaces
Authors: Podsiadlo P , Stachowiak G. W.
Published: January 2003

Many numerical surface topography analysis methods exist today. However, even for the moderately complicated topography of a tribological surface these methods can provide only limited information. The reason is that tribological surfaces often exhibit a non-stationary and multi-scale nature while the numerical methods currently used work well with surface data exhibiting a stationary random process and provide surface descriptors closely related to a scale at which surface data were acquired. The suitability of different methods, including Fourier transform, windowed Fourier transform, Cohen's class distributions (especially the Wigner-Ville distribution), wavelet transform, fractal methods and a hybrid fractal-wavelet method, for the analysis of tribological surface topographies is investigated in this paper. The method best suited to this purpose has been selected.
Synthesis of Copper Sulfide Nanowhisker via Sonochemical Way and its Characterization
Authors: Xu Changqi , Zhang Zhicheng , Ye Qiang , Liu Xiong
Published: January 2003

An ultrasonic irradiation route (USI route) is developed to synthesize whisker-like copper sulfide (Cu9S8) nanocrystals via the reaction between copper sulfate pantahydrate (CuSO4·5H2O) and thioacetamide (CH3CSNH2) in an aqueous solution at room temperature under ambient pressure. XRD, TEM, UV–vis and PL spectra are used to characterize the obtained product. A possible reaction process is suggested in the end of this paper.
Emission Spectrum of the C2 Radical Embedded in Superfluid Helium around 1.5 K
Authors: Wada Akira , Aratono Yasuyuki
Published: January 2003

The C2 d3Πg-a3Πu (v′−v″) Swan band emission spectrum induced by the laser ablation of graphite in the superfluid helium around 1.5 K, was observed. Only the vibrational progression of Δv=v′−v″, where Δv less than 0 are observed, indicating fast (τ<100 ns) vibrational relaxation in superfluid helium. This result also indicates a unique characteristic of superfluid helium as a circumstance of chemical processes.
Synthesis, Structure, and Preliminary Magnetic Studies of a Cluster Polymer with a Hexacopper(II) Barrel Portion
Authors: Wang Li-Yan , Igarashi Satoshi , Yukawa Yasuhiko , Hashimoto Takeshi , Shimizu Kunio , Hoshino Yoshimasa , Harrison Andrew , Aromí Guillem , Winpenny Richard E P
Published: January 2003

The synthesis and characterization of a new cluster polymer with a sodium centered hexacopper(II) barrel portion, catena-[Na⊂Cu2{Cu(hpro)2}4(ClO4)4](ClO4)·4H2O (hpro = 4-hydroxy-l-prolinato) are described. The central sodium ion in the barrel portion is surrounded by eight carboxylate oxygen atoms from hpro ligands, which link the central metal to the copper atoms of four [Cu(hpro)2] units. These units are in turn connected to two further apical CuII centers. The central alkali ion is therefore octahedrally surrounded by six copper atoms. The hydroxyl oxygen atoms of two hpro groups are coordinated to the axial copper atoms of two neighboring barrel portions, so that a chain complex forms. Magnetic studies indicate weak ferromagnetic coupling between copper(II) ions within the complex leading to a high spin multiplicity in the ground state.
Characterization of effective primary voice therapy for dysphonia
Authors: Sellars Cameron , Carding Paul N. , Deary Ian J. , MacKenzie Ken , Wilson Janet A.
Published: January 2003

Despite advances in the development of voice outcome measures, there is no methodology to define and quantify the elements of the complex process of speech therapy. The components of therapy given by one therapist to the intervention limb of a controlled trial werecharacterized according to a list of five minutes. The intervention was of proven benefit compared with a control period of observation. Indirect approaches comprised two thirds of therapy time. The types and duration of intervention were assessed but no treatment category seemed moreassociated with a favourable outcome. The design shows that it is possible to perform a prospective, structured analysis of the components of voice therapy. The method appears viable for thefuture comparison of the widely varying techniques current in voice therapy practice.
A New Design Conception for Large Span Deployable Flat Grid Structures
Authors: Wujun Chen , Gongyi Fu , Jinghai Gong , Yanli He , Shilin Dong
Published: January 2003

The deployable flat grids, consisting of only hinged pantographic units, usually have low structural stiffness, and the bending moment constitutes a great part of internal forces. This results in structural inefficiency, especially for large span grids. Diagonals (web struts) and lower chords are added herein to enhance the structural stiffness. The newly added web struts must be compatible with the deployable geometry. Cables or foldable bars can be used as lower chords. The statical determinacy characteristics are analysed for the newly proposed grid system. On the basis of this concept, several flat grids are firstly developed for potential applications. And a joint conception also developed. The structural performances are investigated for a series of deployable flat grids. Steel quantities and deflections are compared for four different grids. The results indicate that the newly proposed conception has fairly high economic scale, structural efficiency and promising potential application field.
Full Dynamic Analysis of Large Concrete Cooling Towers: Soil-Structure Interaction
Authors: Horr A. M. , Safi M.
Published: January 2003

Based on the complex spectral element method and the theory of fractional calculus, a hybrid complex damped spectral element method is developed. The new method is capable of making accurate predictions of the full dynamic behaviour of reinforced concrete cooling tower structures including soil-structure interaction effects. The dynamic soil-structure interaction of large space shell structures can be analysed using hybrid spectral-finite element method where the seismic wave propagation in the soil media has been modelled using the spectral element method. The frequency-dependent damping characteristic of soil materials can also be modelled accurately using the fractional derivative model. It is shown that the proposed method can be extended to develop a frequency domain dynamical method to analyse damped large space structures under earthquake excitation. The soil-structure dynamical solution is shown graphically, and the consistency of method is investigated. Using a computer program, the proposed formulation has been used to derive the dynamic response of a large concrete cooling tower with the soil media.
Logic, Optimization, and Constraint Programming
Authors: Hooker John N.
Published: February 2003

Because of their complementary strengths, optimization and constraint programming can be profitably merged. Their integration has been the subject of increasing commercial and research activity. This paper summarizes and contrasts the characteristics of the two fields; in particular, how they use logical inference in different ways, and how these ways can be combined. It sketches the intellectual background for recent efforts at integration. It traces the history of logic-based methods in optimization and the development of constraint programming in artificial intelligence. It concludes with a review of recent research, with emphasis on schemes for integration, relaxation methods, and practical applications.
Extending an Algebraic Modeling Language to Support Constraint Programming
Authors: Fourer Robert , Gay David M.
Published: February 2003

Although algebraic modeling languages are widely used in linear and nonlinear programming applications, their use for combinatorial or discrete optimization has largely been limited to developing integer linear programming models for solution by branch-and-bound procedures. Yet much of a modeling language's underlying structure for expressing integer programs is equally useful for describing more general combinatorial optimization constructs.

Constraint programming solvers offer an alternative approach to solving combinatorial optimization problems, in which natural combinatorial constructs are addressed directly within the solution procedure. Hence the growing popularity of constraint programming motivates a variety of extensions to algebraic modeling languages for the purpose of describing combinatorial problems and conveying them to solvers.

We examine some of these language extensions along with the significant changes in solver interface design that they require. In particular, we describe how several useful combinatorial features have been added to the AMPL modeling language and how AMPL's general-purpose solver interface has been adapted accordingly. As an illustration of a solver connection, we provide examples from an AMPL driver for ILOG Solver.
Spare-Capacity Assignment For Line Restoration Using a Single-Facility Type
Authors: Balakrishnan Anantaram , Magnanti Thomas L. , Sokol Joel S. , Wang Yi
Published: February 2003

The network restoration problem is a specialized capacitated network design problem requiring the installation of spare capacity to fully restore disrupted network flows if any edge in a telecommunications network fails. We present a new mixed-integer programming formulation for a line restoration version of the problem using a single type of capacitated facility. We examine two different models, for distinct and integrated spare-capacity systems, reflecting technologies used in synchronous transfer mode (STM) and asynchronous transfer mode (ATM) networks. The problem is NP-complete in the strong sense. We study the problem's polyhedral structure to identify strong valid inequalities that tighten the problem formulation. Our computational results on several real and randomly generated problems show that these inequalities considerably reduce the integrality gap from an average of 10% to an average of under 1%. These results indicate that strong cutting planes combined with branch-and-bound can provide efficient algorithms for solving a class of real-world problems in the telecommunications industry.
The Access-Control Problem on Capacitated FIFO Networks With Unique O-D Paths is Hard
Authors: Erera Alan L. , Daganzo Carlos F. , Lovell David J.
Published: February 2003

This paper is concerned with the performance of multicommodity capacitated networks in a deterministic but time-dependent environment. For a given time-dependent origin-destination table, this paper asks if it is easy to find a way of regulating the input flows into the network to avoid queues from growing internally, i.e., to avoid capacity violations. Problems of this type are conventionally approached in the traffic/transportation field with variational methods such as control theory (if time is continuous) and with mathematical programming (if time is discrete). However, these approaches can only be expected to work well ifthe set off easible solutions is convex.

Unfortunately, it is found in this paper that this is not the case. It is shown that continuous-time versions of the problem satisfying the smoothness conditions of control theory can have a finite but very large number off easible solutions. The same happens for the discrete time case. These difficulties arise even with the simplest versions of the problem (with unique origin-destination paths, perfect information, and deterministic travel times).

The paper also shows that the continuous-time feasibility problem is NP-hard, and that if we restrict our attention to (practical) problems whose data can be described with a finite number ofbits (e.g., in discrete time), then the problem is NP-complete. These results are established by showing that the problem instances of interest can be related to the Directed Hamiltonian Path problem by a polynomial transformation.
Knowledge Networks: Explaining Effective Knowledge Sharing in Multiunit Companies
Authors: Hansen Morten T.
Published: February 2003

This paper introduces the concept of knowledge networks to explain why some business units are able to benefit from knowledge residing in other parts of the company while others are not. The core premise of this concept is that a proper understanding of effective interunit knowledge sharing in a multiunit firm requires a joint consideration of relatedness in knowledge content among business units and the network of lateral interunit relations that enables task units to access related knowledge. Results from a study of 120 new product development projects in 41 business units of a large multiunit electronics company showed that project teams obtained more existing knowledge from other units and completed their projects faster to the extent that they had short interunit network paths to units that possessed related knowledge. In contrast, neither network connections nor extent of related knowledge alone explained the amount of knowledge obtained and project completion time. The results also showed a contingent effect of having direct interunit relations in knowledge networks: While established direct relations mitigated problems of transferring noncodified knowledge, they were harmful when the knowledge to be transferred was codified, because they were less needed but still involved maintenance costs. These findings suggest that research on knowledge transfers and synergies in multiunit firms should pursue new perspectives that combine the concepts of network connections and relatedness in knowledge content.
Knowledge as a Contingency Variable: Do the Characteristics of Knowledge Predict Organization Structure?
Authors: Birkinshaw Julian , Nobel Robert , Ridderstråle Jonas
Published: February 2003

This paper examines the validity of knowledge as a contingency variable. Building on recent advances in thinking about the dimensions of knowledge assets (Winter 1987, Zander and Kogut 1995), we argue that such dimensions might have an important influence on organization structure. More specifically, we focus on two dimensions of knowledge—observability and system embeddedness—and their influence over the level of unit autonomy and interunit integration in an international network of R&D units. Statistical analysis of questionnaire responses from 110 R&D unit managers show strong association between the dimensions of knowledge and organization structure. It also indicates partial support for the “fit” hypothesis in contingency theory.

The paper makes two important contributions to the knowledge management literature. First, we find support for the contingency logic, suggesting that effective organization design has to take into account the underlying characteristics of the firm's knowledge base. Second, we shed light on a relatively neglected dimension of knowledge that we call system embeddedness. This is the extent to which knowledge is a function of the social and physical system in which it exists. In the statistical analysis it emerges as a strong predictor of organization structure. Moreover, it also appears to be conceptually distinct from the tacit-articulate dimension that is normally emphasized. This allows us to speculate on four generic forms that a firm's knowledge might take, that we label integrated, isolated, opaque, and transparent. These are discussed using examples from the data.
Action and Possibility: Reconciling Dual Perspectives of Knowledge in Organizations
Authors: Hargadon Andrew , Fanelli Angelo
Published: February 2003

At times knowledge can be seen as the source of organizational innovation and change—at other times, however, it can be the very constraint on that change. This conflicted role offers insights into why the phenomenon of organizational knowledge has been interpreted by researchers in multiple and possibly conflicting ways. Some theories depict knowledge as an empirical phenomenon, residing in action and becoming “organizational” in the acquisition, diffusion, and replication of those actions throughout the organization. Others consider it a latent phenomenon, residing in the possibility for constructing novel organizational actions. This paper argues that while each of these qualities—empirical and latent—are intrinsic to knowledge in organizations, our understanding of organizational phenomena is essentially incomplete until the relationship between them is considered. Building on structuration theory, we propose a complementary perspective that views organizational knowledge as the product of an ongoing and recursive interaction between empirical and latent knowledge, between knowledge as action and knowledge as possibility. We ground this complementary model of knowledge in evidence from the field study of two firms whose innovation practices provide unique insights into how knowledge simultaneously enables and constrains behavior in organizations. We then discuss how a complementary perspective avoids the reification of knowledge by depicting it instead as an ongoing and social process and offers an alternative distinction between individual and collective knowledge.
Islands of Shared Knowledge: Specialization and Mutual Understanding in Problem-Solving Teams
Authors: Postrel Steven
Published: February 2003

Where should the boundaries of knowledge between economic actors be located in order to maximize the efficiency of their interactions? In particular, what circumstances determine whether it makes sense for adjacent stages in the value chain to invest in the development of common understanding, and when does it make sense for them to operate in mutual ignorance? To address these questions, it is necessary to construct a kind of production function which takes different forms of knowledge—specialist capability and trans-specialist understanding—as inputs and relates them to problem-solving output.

Using a simple model of product design as a template, it is possible to derive such a production function. One can then use its properties in conjunction with plausible assumptions about the cost of acquiring different kinds of knowledge to develop general principles that explain when efficiency requires costly learning across specialties and when it is better to allow specialties to operate in mutual ignorance of one another's domains. The derived production function, contrary to some intuition and previous literature, implies that specialist capability can substitute for knowledge shared across specialties. This result in turn implies that the nature of learning costs, rather than the shape of knowledge benefits, plays the predominant role in determining when mutual ignorance is a good idea.

The analysis also helps resolve the following paradox: The economy depends for its efficiency upon a drastic separation of knowledge across individuals and organizational units, yet studies of product development find that greater knowledge commonality is associated with better firm performance. An implication of the substitutability of specialized and trans-specialty knowledge is that situations where learning across specialties is desirable seem relatively rare in the economy as a whole. These situations are disproportionately common, however, in those areas where important managerial activity takes place. A key role of management is to attend to the strategic, operational, and governance needs of these “islands of shared knowledge in a sea of mutual ignorance.”
Coexistence of Two Polytypic Groups in Cronstedtite From Lostwithiel, England
Authors: Kogure Toshihiro , Hybler Jiří , Yoshida Hideto
Published: February 2003

Cronstedtite from Lostwithiel, Cornwall, England, in which two polytypic groups (A and C) are present within the same crystal, has been investigated using various techniques to reveal the distribution of the two groups and the relationship between polytypic structure and chemical composition. X-ray precession photographs from cleaved fragments of pyramidal crystals revealed the variable proportions of the two groups from the top to the base. Near the top, the crystal consists entirely of group C, with 1Tas the dominant polytype. Near the base, both groups A and C are present. Back-scattered electron images from cross-sections parallel to the pyramidal axis showed mosaic contrast near the base, suggesting that two compositionally-different domains of several tens of microns in size are present, whereas the contrast was uniform near the top. Electron microprobe chemical analysis indicated the compositions<mml:math xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:mnf="http://cambridge.org/core/manifest" xmlns:cup="http://contentservices.cambridge.org" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://cambridge.org/core/metadata" xmlns:core="http://cambridge.org/core" xmlns:c="http://cambridge.org/core/content">(Fe2.312+Fe0.693+)(Si1.31Fe0.693+)O5(OH)4and<mml:math xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:mnf="http://cambridge.org/core/manifest" xmlns:cup="http://contentservices.cambridge.org" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://cambridge.org/core/metadata" xmlns:core="http://cambridge.org/core" xmlns:c="http://cambridge.org/core/content">(Fe2.162+Fe0.843+)(Si1.16Fe0.843+)O5(OH)4. Electron back-scattered patterns (EBSPs) confirmed that the domain with Si-rich composition belongs to group C and that with Si-poor composition to group A. This is the first evidence that specific chemical compositions are related to the polytypic structures in cronstedtite. Transmission electron microscopy revealed that intergrowth of groups A and C at the monolayer level is also present as stacking disorder in both domains near the base, whereas such intergrowth was not observed in the region near the top.
Crystallization of Layered Double Hydroxides by Ultrasound and the Effect of Crystal Quality on Their Surface Properties
Authors: Seida Yoshimi , Nakano Yoshio , Nakamura Yasuo
Published: February 2003

The ultrasound technique was applied to the synthesis of layered double hydroxides. The use of ultrasound in the synthesis of these compounds was studied in terms of its effect on their crystal qualities and surface properties. The crystal qualities of the compounds synthesized with ultrasound were compared with those of compounds synthesized without ultrasound to elucidate the effect of the ultrasound on the synthesis. The effect of crystal quality (crystallite size) on the adsorption behavior of humic substances was examined. The compounds synthesized under ultrasonic conditions showed a larger crystallite size and a larger adsorption capacity for humic substances than those synthesized without ultrasonic treatment. The degree of adsorption correlated well with crystal quality.
Hydraulic Performance of Untreated and Polymer-Treated Bentonite in Inorganic Landfill Leachates
Authors: Ashmawy Alaa K. , El-Hajji Darwish , Sotelo Nestor , Muhammad Naim
Published: February 2003

Short- and long-term exposure to inorganic solutions can cause significant degradation of the hydraulic properties of bentonite clay used in geosynthetic clay liners (GCLs). In particular, the increase in hydraulic conductivity due to cation exchange when Na-montmorillonite is subjected to leachates rich in Ca and Mg has caused problems in incinerator ash landfill liners located in wet environments, where large quantities of leachates are generated. Experimental results are presented to evaluate the immediate change in hydraulic conductivity of seven types of GCL clays upon permeation with leachate generated from three ash landfills. The composition of the ash, which is a by-product of the incineration of municipal solid waste (MSW), in turn influences the composition of the resulting leachate. Falling head permeability tests were performed on flexible-wall permeameter specimens, with back-pressure saturation. Chemical analysis shows that the three leachate products contain high, medium, and low concentration Ca and Mg cations. The clay component of GCL materials tested in this study consists of regular and polymer-treated bentonite. Polymer treatment is believed to render the clay non-reactive to many organic and inorganic chemicals. The results of this study indicate that: (1) polymer treatment is generally more beneficial if the clay is first saturated with water and not directly with the leachate; (2) high swell potential of the bentonite is more advantageous than polymer treatment, especially when low hydraulic conductivity is required in the short term and if the clay is pre-hydrated. Experiment setup and special specimen preparation procedures are also discussed.
Micro-Structure and Hydraulic Conductivity of Simulated Sand-Bentonite Mixtures
Authors: Abichou Tarek , Benson Craig H. , Edil Tuncer B.
Published: February 2003

This paper describes the relationship between the micro-structure and hydraulic conductivity of simulated sand-bentonite mixtures (SSBMs) prepared with powdered and granular bentonite. Glass beads were used to simulate sand grains because of their superior optical properties. The micro-structure of SSBMs was observed using optical micrography and scanning electron microscopy. For mixtures prepared with powdered bentonite, the indications are that bentonite coats the particles. As the bentonite content increases, the thickness of bentonite coating increases and reduces the area available for flow. For mixtures containing granular bentonite, the dry bentonite granules occupy the space between the particles and then swell to fill the void space. As the bentonite content increases, the number of granules increases, leading to more void spaces being filled with bentonite. At higher bentonite content (>8%), flow paths devoid of bentonite are unlikely, and the hydraulic conductivity appears to be controlled by the hydraulic conductivity of bentonite. The changes in micro-structure that were observed are consistent with the decrease in hydraulic conductivity that occurs with increasing bentonite content. However, the relationship between hydraulic conductivity and bentonite content differs depending on whether a mixture contains powdered or granular bentonite.
Early Stages of Volcanic Tuff Alteration in Hydrothermal Experiments: Formation of Mixed-Layer Illite-Smectite
Authors: de la Fuente Sandra , Cuadros Javier , Linares José
Published: February 2003

Volcanic tuff from the Cabo de Gata region in Almería, southeastern Spain, was altered under hydrothermal conditions at different temperatures (60 to 180°C), reaction times (60 to 360 days), and reacting solutions (deionized water and NaCl and KCl solutions with Na/K ratios from 0.01 to 100, and a total salt concentration of 0.1 to 1 M).

X-ray diffraction (XRD) patterns of the reacted samples revealed a very weak, broad peak at ∼13 Å that migrated to 17 Å upon glycolation. Comparison between simulated (NEWMOD) and experimental XRD patterns indicated that the neoformed phase is a random mixed-layer illite-smectite (I-S) with 75% expandable layers. Fourier transform infrared (FTIR) spectroscopy showed that I-S formation was most extensive for high pH (8–9) solutions, corresponding to dilute solutions and, especially, to deionized water. Analytical electron microscopy (AEM) analyses of isolated I-S particles showed that most of them are smectite-rich I-S regardless of the experimental conditions, in agreement with XRD results. The I-S particles had a wide range of octahedral Mg contents. The pH and Na, K, Ca and Mg concentrations in the final solutions suggested cation (including H+) exchange as a major process in the alteration experiments. Analysis of aqueous activity diagrams (log aK/aHvs. log <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:c="http://cambridge.org/core/content" xmlns:core="http://cambridge.org/core" xmlns:m="http://cambridge.org/core/metadata" xmlns:cup="http://contentservices.cambridge.org" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:mnf="http://cambridge.org/core/manifest">aSiO2) showed that some solution compositions are consistent and some are inconsistent with I-S formation. These results, combined with complementary electron microscopy analyses (de la Fuente et al., 2000a), are interpreted to be due to direct transformation of the glass into I-S in a process controlled by glass composition.
Origin of Allophane and Retardation of Pebble Weathering in Quaternary Marine Terrace Deposits
Authors: Jeong Gi Young , Bae Jin Han , Cheong Chang Sik
Published: February 2003

Quaternary marine terrace deposits consisting of gravels interbedded with thin sandy gravel layers have been subjected to subaerial weathering. Restricted to the sandy gravel layers, allophane gel either replaced bytownite sands to form a pseudomorph or coated the pebbles. The allophane has an average Al/Si atomic ratio of 1.5 with 45% H2O. The sandy gravels were originally rich in bytownite (av. An86) sands derived from underlying Tertiary basaltic lapilli tuff. The highly soluble and aluminous bytownite favored the formation of allophane. In the sandy gravel layers, pebbles coated with allophane gel were almost fresh whereas those in the gravel layers were highly weathered to form halloysite-rich clays. Allophane gels acted as a somewhat impermeable geochemical barrier impeding a mineral-water reaction in the bytownite-rich sandy gravel layers and thus significantly retarding pebble weathering, while prolonged weathering in the gravel layers resulted in the severe decomposition of pebbles. Bytownite protected the pebbles against weathering, implying that minor soluble minerals might be one of the factors in the natural variation of the weathering rates of rocks and sediments.
The Nature of Soil Kaolins From Indonesia and Western Australia
Authors: Hart Robert D. , Gilkes Robert J. , Siradz Syamsul , Singh Balwant
Published: February 2003

Purified soil kaolins from Indonesia and Western Australia were characterized using analytical TEM, XRD, TGA and chemical analysis. The Indonesian kaolins, formed from tuff, consist of a mixture of tubular kaolin crystals with relatively low Fe concentrations and platy kaolin crystals with higher Fe concentrations. Western Australian kaolins also contained tubular and platy crystals but showed no systematic relationship of crystal morphology with Fe content. The coherently scattering domain (CSD) size of the Indonesian samples (5–6 nm for 001,i.e. caxis dimension) is remarkably consistent and is approximately half of the value for the Western Australian kaolins (9.7–13.4 nm), and both are much smaller sizes than values for the reference kaolins (15.6–27.8 nm). Coherently scattering domain sizes derived from the Scherrer equation are approximately twice the values obtained from the Bertaut-Warren-Averbach Fourier method but the results show the same pattern of variation. For the Indonesian, Western Australian and reference kaolins, the N2-BET surface area ranges 59–88, 44–56 and 5–28 m2/g; the dehydroxylation temperatures range 486–499, 484–496 and 520–544°C, the mean cation exchange capacities (CEC) are 9.4, 5.0 and 3.5 meq 100 g−1and the surface densities of charge range 0.10–0.14, 0.08–0.10 and 0.04–0.12 C/m2. The properties of the Western Australian kaolins and Indonesian kaolins differ substantially, but kaolins within each group have similar properties. These results suggest that soil kaolin properties may be characteristic of a particular pedoenvironment and that a systematic study of kaolins in different pedoenvironments is required.
Thermal Evolution of Fluorine From Smectite and Kaolinite
Authors: Chipera Steve J. , Bish David L.
Published: February 2003

The fluoride ion is crystal chemically very similar to the hydroxyl ion, substituting for hydroxyl in many minerals in which hydrogen bonding is not important. Fluoride substitutions are particularly common in 2:1 layer silicates, such as micas, illites and smectites. The brick and tile industries, which use naturally occurring clays as their primary raw materials, have devoted considerable effort to understanding fluorine evolution during firing of the raw materials due to increasingly stringent fluorine emission regulations. In order to understand fluorine evolution from ceramic raw materials, we have studied a number of phyllosilicate materials used in making bricks. X-ray powder diffraction and fluorine analyses were combined with heating experiments and thermogravimetric analysis to evaluate the chemical and structural changes taking place on heating. Fluorine remained in 2:1 layer silicates to higher temperatures than did hydroxyl, but it behaved identically to hydroxyl in the kaolinite studied. In all cases, fluorine evolution coincided with structural breakdown of the clay host. These results show that fluorine evolution will consistently occur during firing of clay raw materials, and the problems of fluorine emission cannot be readily solved by simple variations of firing temperatures or times.
High-Temperature X-Ray Diffraction, Differential Thermal Analysis and Thermogravimetry of the Kaolinite-Dimethylsulfoxide Intercalation Complex
Authors: Franco F. , Ruiz Cruz M. D.
Published: February 2003

The intercalation complex of a kaolinite from Cornwall, UK, with dimethylsulfoxide (DMSO) was studied by high-temperature X-ray diffraction (HTXRD), differential thermal analysis (DTA) and thermogravimetry (TG). The X-ray pattern obtained at room temperature indicated that intercalation of DMSO into kaolinite caused an increase of the basal spacing of kaolinite from 7.14 to 11.19 Å. Heating between 25 and 300°C caused the removal of the DMSO, which occurred over several stages. In a first stage (25–125°C), an expansion (from 11.19 to 11.28 Å) followed by a contraction (from 11.28 to 11.19 Å) is observed, at the same time as the intensity of the basal reflection decreased and was replaced by a broad band extending from ~11 to ~7 Å. In a second stage (125–200°C), the loss of DMSO did not lead to changes in the HTXRD patterns; and finally, in a third stage, the loss of DMSO caused an important increase in intensity and sharpening of the basal reflections of the kaolinite. These stages were also shown by the DTA-TG curves for the complex. The TG curve indicated that the loss of ~15% of the intercalated DMSO occurs below 150°C, and caused the disruption of the structure. The remaining molecules, forming stronger bonds with the kaolinite surfaces, were lost between 150 and 300°C.
Weathering of Chlorite: II. Reactions and Products in Microsystems Controlled by Solution Avenues
Authors: Aspandiar Mehrooz F. , Eggleton Richard A.
Published: February 2003

Weathering of chlorite adjacent to macro- and micro-passages (fissures) in regolith units has been studied to determine the alteration mechanisms and products and compare them to those that prevail at a distance from the open passages. The micro-fissures in the saprolith units evolve as a function of weathering with an increase in micro-fissure density and their infilling with ferriargillans corresponding to an increase in weathering intensity. In the saprock and saprolite units, goethite-rich bands with surrounding reddish haloes invade the chlorite adjoining the micro-fissures. In the reddish haloes surrounding the goethite bands and fissures, the phyllosilicates alter to an intimate mixture of goethite, kaolinite, feroxyhyte and halloysite with the possible nanoscale presence of other fine-grained iron aluminosilicates such as hisingerite and smectite. In the fine saprolite, the weathering products after original chlorite adjoining the micro-fissures bearing ferriargillans, alter directly to ferriargillan products — kaolinite and goethite. The lack of orientation of the products with the parent phyllosilicates indicates the operation of a dissolution-precipitat ion mechanism which is in contrast to the topotactic alteration mechanism functioning at a distance within the phyllosilicate grain assemblage. The differences in alteration mechanisms and products of chlorite weathering in different microsites suggest the rate of weathering of chlorite can differ in microsites within individual regolith units. The presence of fine-grained metastable products in the form of feroxyhyte and halloysite adjoining the fissures suggests an Ostwald Step Rule sequence during alteration of phyllosilicates with rapid oxidation of Fe and the presence of Si in the microsite considered the main factor favoring fine-grained metastable products.
Transmission Electron Microscopy Evidence for Experimental Illitization of Smectite in K-Enriched Seawater Solution at 50°C and Basic pH
Authors: Drief A. , Martinez-Ruiz F. , Nieto F. , Velilla Sanchez N.
Published: February 2003

Experimental illitization of smectite was studied by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Experiments were performed on the <2 µm fraction consisting entirely of smectite separated from a soil formed on subvolcanic rock located in the External Zone of the Betic Cordilleras (southern Spain). Amounts of 0.25 g were added to different solutions: seawater, and three K-enriched seawater solutions prepared by adding KOH to seawater whose final [K] values were 0.1, 0.5 and 1 M, respectively. The experiments were performed at 50°C over a period of 30 days. The XRD patterns showed no mineralogical changes in residues from seawater or from the 0.1 M [K] solution. With increasing pH and K molarity, the smectite peak, initially at 1.4 nm, became broader. This change in the smectite peak was more significant in the residue from the 1 M [K] solution. The appearance of a small shoulder at 1.0 nm in the residue from a 0.5 M [K] solution showed the beginning of illite formation. However, its appearance was clearer in XRD patterns of the residue corresponding to the 1 M [K] solution. The XRD data from air-dried, glycolated, and heated samples from the 1 M [K] solution indicated the presence of smectite, disordered interstratified illite-smectite (I-S) and illite.

The TEM/AEM studies were performed on the residue corresponding to the 1 M [K] experiment. The HRTEM images revealed that smectite and illite occurred as separated packets with a ferroan lizardite, as a by-product of the smectite-to-illite reaction, interstratified and intergrown with illite. Smectite occurs both as ‘rims’ on the illite packet and in its core. The presence of smectite in the core of illite packet indicates that the lateral transition from smectite to illite was incomplete, taking place by direct replacement of smectite layers as a whole through a dissolution-precipitation mechanism. The experimental study shows that smectite may transform in a wide range of geological and artificial environments involving high-pH K-rich solutions.
Chemical Disaggregation of Kaolinitic Claystones (Tonsteins and Flint Clays)
Authors: Triplehorn Don M. , Bohor Bruce F. , Betterton William J.
Published: February 2003

The coarse, non-clay fraction of many flint-like kaolinitic claystones often contains mineral grains diagnostic of the claystone's origin and, in the case of tonsteins (altered volcanic ashes), may also provide minerals suitable for radiometric dating. Separation of the non-clay mineral fraction is often difficult because flint clays and flint-like clays resist slaking in water and thus are difficult to disaggregate. Chemical disaggregation of resistant kaolinitic claystones may be achieved by immersion in either hydrazine monohydrate or DMSO for periods ranging from one day to several weeks. Generally, hydrazine monohydrate works more quickly and efficiently than DMSO to disaggregate most kaolinitic claystones and flint clays.
Formation of Sepiolite-Palygorskite and Related Minerals from Solution
Authors: Birsoy Rezan
Published: February 2003

Most of the world's sepiolite-palyg orskite precipitates in lacustrine and perimarine environments. Although these minerals can transform from precursor minerals, the most common formation mechanism involves crystallization from solution. In this study, equilibrium activity diagrams are calculated for sepiolite-palygorskite in the seven component system MgO-CaO-Al2O3-SiO2-H2O-CO2-HCl, employing available thermodynamic data for related minerals, aqueous species and water. Stability fields are illustrated graphically on plots of log <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:c="http://cambridge.org/core/content" xmlns:core="http://cambridge.org/core" xmlns:m="http://cambridge.org/core/metadata" xmlns:cup="http://contentservices.cambridge.org" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:mnf="http://cambridge.org/core/manifest">[aMg2+/(aH+)2]vs. log <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:c="http://cambridge.org/core/content" xmlns:core="http://cambridge.org/core" xmlns:m="http://cambridge.org/core/metadata" xmlns:cup="http://contentservices.cambridge.org" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:mnf="http://cambridge.org/core/manifest">[aH4SiO4o], using the activities for log <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:c="http://cambridge.org/core/content" xmlns:core="http://cambridge.org/core" xmlns:m="http://cambridge.org/core/metadata" xmlns:cup="http://contentservices.cambridge.org" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:mnf="http://cambridge.org/core/manifest">[aAl3+/(aH+)3] defined by an arbitrarily chosen value and the approximate saturation limits of pyrophyllite + amorphous silica, kaolinite + amorphous silica, kaolinite + pyrophyllite, pyrophyllite + quartz and gibbsite. The formation of sepiolite-palygorskite from solution is more favored in the presence of amorphous silica than quartz. Lower aqueous aluminum activities favor the non-aluminum phases sepiolite and kerolite relative to the aluminum-containing phases palygorskite and saponite. The stability ranges of worldwide associations of magnesite and dolomite with sepiolite and palygorskite are also illustrated as a function of aluminum activity.
Transmission and Analytical Electron Microscopy Evidence for High Mg Contents of 1M Illite: Absence of 1M Polytypism in Normal Prograde Diagenetic Sequences of Pelitic Rocks
Authors: Peacor Donald R. , Bauluz Blanca , Dong Hailiang , Tillick David , Yan Yonghong
Published: February 2003

The normal prograde diagenetic and low-grade metamorphic sequence of dioctahedral clay minerals including illite-rich I-S and illite, as observed by TEM, proceeds from a partially disordered 1Md stacking sequence to 2M1; i.e. 1M does not normally occur as an intermediate polytype. Examples of 1M illite stacking sequences have been studied, however, from the Golden Cross gold deposit, New Zealand, the Broadlands-Ohaaki geothermal system, New Zealand, the Potsdam Sandstone, New York, and the Silverton Caldera, Colorado. Specific clay-mineral packets identified by TEM techniques as 1M illite were found to have anomalously high Mg contents. The Broadlands illite provides the most definitive data, as separate packets of 1M and 2M1 illite coexist. Average compositions for 1M and 2M1 illite are (K1.66Ca0.04)Σ1.70(Al3.32Fe0.31Mg0.57Mn0.06)Σ4.26(Si6.43Al1.57)Σ8O20(OH)4 and (K1.57Na0.31Ca0.03)Σ1.91(Al3.58Fe0.05Mg0.29Mn0.01)Σ3.93(Si6.70Al1.30)Σ8O20(OH)4, respectively. In addition, 1Mdillite, which is the polytype occurring in the common 1Mdto 2M1 prograde sequence, is relatively Mg poor, but coexists with Mg-rich illite in the Silverton Caldera sample.

These data confirm that 1M stacking is caused by compositional anomalies, and thus explain the lack of the 1M stacking sequence in normal diagenetic sequences in pelitic rocks, as most illite in such environments has a relatively small phengitic component. The parameter Δz, a measure of the corrugation of the oxygen sheets, may be the key parameter reflecting the polytypic state of dioctahedral and trioctahedral micaceous minerals. Such composition-determined relations may be related to the occurrence of 1M polytypism in glauconite and celadonite, both dioctahedral 2:1 clay minerals having large Mg or Fe octahedral-cation components, and in trioctahedral micas. Insofar as the 1M stacking sequence does not have the same composition as 2M1 material, these data confirm that the different varieties of illite are not polytypes, sensu stricto.
Diagenesis and Rheology of a Recent-Pleistocene Volcanogenic Sedimentary Sequence, Mexican Basin
Authors: de Pablo-Galán Liberto , de Pablo Juan J. , de Lourdes Chávez-García M.
Published: February 2003

Diagenesis of the Holocene-Pleistocene volcanogenic sediments of the Mexican Basin produced, in strata of gravel and sand, 1H2O- and 2H2O-smectite, kaolinite, R3-2H2O-smectite (0.75)-kaolinite, R1-2H2O-smectite (0.75)-kaolinite, R3-kaolinite (0.75)-2H2O-smectite and R1-1H2O-smectite (0.75)-kaolinite. Smectite platelets were formed from volcanic glass by loss of Si4+. Partially-formed platelets have Si4+ between 4.55−4.10 a.p.f.u., Mg+Mn and the interlayer charge are relatively uniform while VIAl+Fe3++Ti varies between 0.98 and 1.63 a.p.f.u. Almost fully transformed platelets have Si4+ of 4.08−4.04 a.p.f.u.; Mg+Mn and the interlayer charge decrease proportionally to increasing VIAl+Fe3++Ti. Smectite-kaolinite mixed layers have octahedral occupancies of 2.01–2.15 a.p.f.u., IVAl3+ 0.09–0.55 a.p.f.u. and interlayer charges about half that of smectite; structural formulae corresponding to smectite (0.75–0.80)-kaolinite indicate octahedral occupancy of 2.50 a.p.f.u., tetrahedral replacement 0–0.31 a.p.f.u., and interlayer charge 0.24–0.51 equivalents, some indicating interstratifications of beidellite. Kaolinite is presumed to have formed from K-feldspar; smectite-kaolinite interstratifications sustain the transformation of kaolinite to smectite in an increasingly siliceous high-cation environment. In the mudstones of low-hydraulic conductivity and practically stagnant alkaline fluids, glass was transformed to 2H2O-smectite lamellae of IVAl between 0 and 0.47 a.p.f.u., octahedral occupancy 1.70–2.00 a.p.f.u. and interlayer charge of 0.23–1.21 equivalents, some corresponding to beidellite. The interlayer charge increases with IVAl and decreasing occupancy of the octahedral sheet; the abundance of Mg+Mn is inverse to that of VIAl+Fe3++Ti.

Clay suspensions containing 1H2O- and 2H2O-smectite, kaolinite and R3-2H2O-smectite (0.75)-kaolinite lead to low-energy edge-to-edge particle associations, non-Newtonian pseudoplastic behavior, and maximum apparent viscosity of 180 Pa s at 0.008 s−1 followed by rapid descent. Clay fractions with slightly larger 2H2O-smectite contents and smaller kaolinite contents reach maximum viscosity of 3611 Pa s at a shear rate of 0.0018 s−1 and of 3300 Pa s at 0.0024 s−1. They denote two high-energy face-to-face particle associations, followed by slow descent of the apparent viscosity under viscous flow. Suspensions change from elastic to viscous behavior at shear stresses of 1.03 and 5.91 Pa, respectively. Clay suspension vibrated at a frequency of 1 Hz develops a shear storage dynamic modulus greater than the shear dynamic loss modulus or the energy is preferentially stored, whereas at 5 Hz more energy is dissipated than stored.