G. N. Greaves

• University of Cambridge

In the version of this Review Article originally published, parentheses were misplaced and the longitudinal and transverse speeds were inverted in two expressions for Poisson’s ratio in Box 2; the expressions should have read, respectively, ν = (3B/G – 2)/(6B/G + 2) and ν = [½(Vl/Vt)² − 1]/[(Vl/Vt)² − 1].

Well‐defined density functional theory (DFT) calculations are performed as the first exploratory study for the atomic and electronic mechanism of defect mediated morphology and optical properties of CdnSen (n = 3, 10, 13, and 33) quantum dots (QDs) in inorganic amorphous matrix. The intrinsic defects of pristine CdSe QDs, and the interfacial defect...

Hybrid glasses connect emerging fields of metal-organic frameworks (MOFs) with the glass-formation, amorphization, and melting processes of these structurally diverse and chemically versatile systems. Most zeolites, including MOFs, amorphize around the glass transition, devitrifying and then melting at much higher temperatures. The relationship bet...

The development of novel contactless aerodynamic laser heated levitation techniques is reported that enable thermophysical properties of refractory liquids to be measured in situ in the solid, liquid, and supercooled liquid state and demonstrated here for alumina. Starting with polished crystalline ruby spheres, we show how, by accurately measuring...

In comparing a material's resistance to distort under mechanical load rather than to alter in volume, Poisson's ratio offers the fundamental metric by which to compare the performance of any material when strained elastically. The numerical limits are set by ½ and -1, between which all stable isotropic materials are found. With new experiments, com...

Aerodynamic levitation is an effective way to suspend samples which can be heated with CO2 lasers. The advantages of this containerless technique are the simplicity and compactness of the device, making it possible to integrate it easily in different kinds of experiments. In addition, all types of materials can be used, including metals and oxides....

The physics of critical phenomena is well established in systems as diverse as molecular fluids, crystalline alloys and magnetic materials. As the critical point is approached, the susceptibility increases anomalously and fluctuations give rise to dramatic opalescence. Evidence has recently emerged for the existence of a second critical point in th...

A Comment on the Letter by Adrian C. Barnes et al., Phys. Rev. Lett. 103, 225702 (2009). The authors of the Letter offer a Reply.

Using time resolved x-ray diffraction combined with aerodynamic levita-tion and CO 2 laser heating, we have studied the structural evolution of the fragile glass-forming liquid CaAl 2 O 4 during supercooling from the stable liquid phase to the cold glass below T g . In particular, we followed the evolution of the structure factor S(Q) and of the co...

By extending recent work on liquid-liquid transitions in supercooled yttria-alumina AYx liquids we draw attention to the compositional dependence of the structure factor of the high density liquid, arguing that this is sufficiently sensitive to discriminate between liquids at the level of a few %. Comparing structure factor differences between liqu...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Employing small angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS) combined with laser-heated aerodynamic levitation has enabled different transitions in supercooled yttrium oxide–aluminium oxide to be distinguished. These include liquid–liquid phase transitions as well as high temperature crystallization for different composition...

The development of monodisperse crystalline particles in cordierite glass doped with Cr3+ after a two-step heat treatment is elucidated by a combination of time-resolved small and wide angle x-ray scattering (SAXS/WAXS) experiments with electron microscopy. The effects of bulk and surface crystallization can clearly be distinguished, and the crysta...

In situ inelastic x-ray scattering (IXS) experiments have been used to probe heterogeneity and deformability in zeolte Y as this thermally collapses to a high density amorphous (HDA) aluminosilicate phase. The Landau-Placzek ratio RLP falls slowly as amorphisation advances, increasing in the later stages of collapse clearly showing how homogeneity...

Small angle x-ray scattering (SAXS) has been measured in the wavevector range 0.01<Q<1 angstrom(-1) for supercooled yttria-alumina melts using a laser-heated aerodynamic furnace. SAXS intensity rises gradually with temperature reflecting density fluctuations deriving from isothermal compressibility. With decreasing Q a minimum is located close to 0...

Changes in the structure factor of yttria-alumina liquids have been identified in the supercooled range. Different inter-polyhedral configurations between AlO{sub 4} and YO{sub 6} groups distinguish low density and high density liquid phases. The coexistence of phases at high temperatures have been identified in simultaneous measurements of small a...

After over a quarter of a century, the doors of the world's first synchrotron radiation source have closed. Its contribution to materials science in the past and the future should not be underestimated.

Modern levitation furnaces are enabling melting and freezing of refractory materials like Al2O3 to be studied in depth with synchrotron radiation techniques. Whilst α-Al2O3 is a close packed Debye-like solid, liquid Al2O3 has smaller coordination numbers and the structure has network-like characteristics. Under contactless conditions, substantial u...

We combine small-angle x-ray scattering (SAXS) and wide-angle x-ray scattering (WAXS) with aerodynamic levitation techniques to study in situ phase transitions in the liquid state under contactless conditions. At very high temperatures, yttria-alumina melts show a first-order transition, previously inferred from phase separation in quenched glasses...

An overview is given of recent advances in the experimental physics of supercooled liquids and glasses. These are described in the context of measurements of non-ergodicity, viscosity and low frequency dynamics. Particular attention is paid to recently reported correlations between melt fragility and the vibrational and mechanical properties of the...

The phenomenology of zeolite collapse is outlined, drawing on recent synchrotron x-ray diffraction experiments and computer simulations of low density cage structures like zeolite A and zeolite Y. Attention is drawn to the importance of polyamorphism in destabilizing this type of microporous crystal and its role in order–disorder as well as amorpho...

Phase transitions in the liquid state can be related to pressure-driven fluctuations developed in the density (i.e., the inverse of the molar volume; ρ = 1/V) or the entropy (S(T)) rather than by gradients in the chemical potential (μ(X), where X is the chemical composition). Experiments and liquid simulation studies now show that such transitions...

The authors have studied the structural evolution of the fragile glass-forming liquid CaAl2O4 during supercooling from the stable liquid phase to the cold glass below Tg. The evolution is characterized by a sharpening of the first diffraction peak and a shortening of the average nearest-neighbor bond length around 1.25Tg, indicating an increase in...

The glass-forming reactions between sodium carbonate (Na2CO3) and silica (SiO2) have been investigated by 23Na, 29Si, and 13C magic-angle spinning (MAS) NMR spectroscopy. The multinuclear MAS NMR approach identifies and quantifies reaction products and intermediates, both glassy and crystalline. A series of powdered batches of initial composition N...

The crystallization mechanism in cordierite glass (Mg2Al4Si5O18) doped with 0.34 mol% Cr2O3 has been studied in detail with in situ small angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS) and ex situ Cr X-ray absorption fine structure (XAFS). The crystalline component comprises an alumino-chromate spinel precipitating within the...

In situ experiments following the thermal amorphisation of zeolites reveal massive increases in small angle X-ray scattering (SAXS), persisting well beyond the stage where wide angle X-ray scattering (WAXS) can detect that any crystalline phase is present. This heterogeneity in the amorphised phase is attributed to the transition from a low density...

Direct SAXS measurements of soot formation from ethylene have been made using laminar pre-mixed flames for the first time. The slot burner was configured to maximise the signal from particulates. The geometry also enabled the thermal background from the surrounding hot gasses to be accurately removed. With cold flame speeds of 40 cm s−1 we have bee...

High-resolution inelastic neutron scattering was used to identify major sources of low-frequency vibrations in zeolite crystals. Dispersed and nondispersed modes were found, both of which are prominent in the early stages of compressive amorphization but decline dramatically in strength once a glass of conventional density is created. By identifyin...

The glass-forming reactions between sodium carbonate (Na2CO3) and silica (SiO2) have been investigated by 23Na, 29Si, and 13C magic-angle spinning (MAS) NMR spectroscopy. The multinuclear MAS NMR approach identifies and quantifies reaction products and intermediates, both glassy and crystalline. A series of powdered batches of initial composition N...

Zeolites collapse under modest pressure or temperature, their microporous structures transforming into glasses of conventional density. Using in situ synchrotron radiation diffraction methods we show how pressure and temperature-induced amorphization are equivalent processes and that these are mirrored by changes in the local structure of charge co...

We have designed and built a new beamline for the study of materials during processing where three synchrotron techniques; SAXS; WAXS and XAS are available simultaneously (MPW6.2). We have demonstrated that Rietveld refineable data can be collected from standard materials and from known reactions such as gypsum at high temperature on timescales of...

A new beamline (MPW6.2) has been designed and built for the study of materials during processing where three synchrotron techniques, SAXS, WAXS and XAS, are available simultaneously. It has been demonstrated that Rietveld refinable data can be collected from silicon SRM 640b over a 60° range in a time scale of 1 s. The data have been refined to a χ...

Low-density zeolites collapse to the rigid amorphous state at temperatures that are well below the melting points of crystals of the same composition but of conventional density. Here we show, by using a range of experimental techniques, how the phenomenon of amorphization is time dependent, and how the dynamics of order-disorder transitions in zeo...

A unique self-organization of optically active nanoparticles of CdS on a silicon surface forming nanoring structures (see Figure and inside cover) is presented. Tunneling luminescence mapping on these structures show that there is direct correspondence between the morphology and the light emission, suggesting that this novel nanomaterial system cou...

Time-resolved in situ small angle X-ray scattering measurements were carried out to monitor the formation of nanoparticles of cadmium sulfide, from a solution containing the corresponding acetate and thioacetamide under solvothermal conditions. Analysis of the SAXS data shows that spherical cadmium sulfide particles of ca 105 Å in radius form withi...

Recent results using a new combined small-angle/wide-angle X-ray scattering (SAXS/WAXS) beam line at the European Synchrotron Radiation Source (ESRF) will be presented. This beam line is specifically designed to be able to handle complicated sample environments required to perform time-resolved experiments mimicking processing conditions used in ma...

Time-resolved in situ SAXS and XAS measurements were carried out to monitor the formation of nanoparticles of the sulfides of cadmium and zinc, from solutions containing he corresponding acetate, and thioacetamide under solvothermal conditions. Analysis of the SAXS data shows that particles of ca 5 nm in radius form within the first few minutes of...

New Cr X-ray absorption fine structure (XAFS) data have been combined with the results of small angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS) experiments to probe in detail the crystallisation mechanism in cordierite (Mg2Al4Si5O18) glass doped with 0.34 mol% Cr2O3. By direct comparison with chromo-aluminate spinels (MgCr2xAl2...

The structural characterization of condensed matter by synchrotron radiation combined with neutron data constitutes a powerful structural tool in material science. In order to investigate refractory liquids at very high temperatures, we have developed a new analysis chamber for performing combined X-ray absorption and diffraction measurements by us...

We show how combined synchrotron X-ray techniques like SAXS/WAXS can be used to chart the collapse of low density zeolites to form rigid alumino-silicate glasses of conventional density. The exothermal character of amorphisation is stressed and directly compared to the degree of crystallinity determined from WAXS and the density contrast contained...

Characterization of zinc oxide containing zeolite Y was performed employing time-resolved in situ small angle X-ray scattering (SAXS), WAXS and EXAFS techniques. Extending procedures used previously for the preparation of CdO clusters in side zeolite cages, zinc oxide particles have been successfully prepared within the cavities of zeolite Y. The p...

High-pressure powder diffraction is used to follow the collapse of zeolite-A at ambient temperature and this is compared with the exotherms obtained from differential scanning calorimetry, when collapse at ambient pressure is induced at high temperatures Constraint theory is discussed in relation to these zeolitic densification processes and a simp...

The neutron scattering structure factor S(Q) for liquid alumina has been measured using a specially designed laser-heated aerodynamic levitation furnace. Employing the empirical potential structural refinement (EPSR) method, a model of liquid alumina has been generated where S(Q) is consistent with that determined by neutron scattering. We find few...

Molecular dynamics (MD) calculations of (B2O3)x(Na2Si2O5)(1−x) glasses have been performed using Born–Mayer–Huggins interatomic potentials together with three-body potentials and increasing B2O3 concentrations examined (x=0.3, 0.5 and 0.7). The main features in the total radial distribution functions (RDFs) are directly attributable to those found...

and magic angle spinning (MAS) NMR has been used as an atomic probe for structural characterisation of soda-lime–silicate glasses. The glasses studied are based on the composition (CaO)x(Na2Si3O7), where x is varied from x=0 to x=1, (increasing CaO from 0 to 20 mol%) finally matching the Na2O fraction. The glass network becomes increasingly depolym...

Wide-angle X-ray scattering and Si-29 NMR have been employed to investigate the medium-range structure of xK(2)O-(1- x)SiO2 glasses, with x varying in the limits 5% < x < 35%. The diffractograms show a first sharp diffraction peak (FSDP) in the 1.4 Angstrom (-1) < q < 2.2 Angstrom (-1) range. The peaks broaden below x = 20%, and at the lowest K2O f...

The neutron scattering structure factor S(N)(Q) for a 40 mg drop of molten alumina (Al2O3) held at 2500 K, using a laser-heated aerodynamic levitation furnace, is measured for the first time. A 1700 atom model of liquid alumina is generated from these data using the technique of empirical potential structural refinement. About 62% of the aluminum s...

ESA Publications p699-706 (2001)

Microstructure in silicate glasses is reviewed from the standpoint of density fluctuations, phase separation and microsegregation. Recent experiments in Brillouin Scattering and Nuclear Magnetic Resonance (NMR) spin relaxation are used to characterise the length scale, magnitude and dimensionality of density fluctuations in monophasic silicate glas...

Using a laser-produced plasma as the X-ray source, and a dispersive spectrometer, EXAFS measurements of Al foil have been made that compare favourably with data obtained using a scanning monochromator and soft X-ray synchrotron radiation. Fourier transform analysis yields a radial distribution function for metallic Al that is realistic out to 6 or...

Measurements have been made of the effects of water corrosion on the fluorescence EXAFS emission above the LIII edge of U from a flat borosilicate glass containing simulated nuclear waste with a cation concentration of about 3 wt.%. The X-rays were incident at grazing angles below the critical angle for total external reflection, limiting the penet...

Anharmonicity in the lattice vibrations of oxygens in UO2 has been examined by using EXAFS of the ULIII absorption edge. Whilst the EXAFS-determined U-U distance of 3.89 AA closely matches the crystallographic separation, the U-O distance of 2.43 AA is 0.06 AA longer. This shift is interpreted on the basis of an anharmonic lattice model in which ox...

A brief review is given of the ways in which the local structure in glass can influence the microstructure that supports ionic transport. This in turn contributes to the co-operative nature of ion dynamics and ways in which this underpins the 'mixed alkali effect' are discussed. Glass microstructure too is expected to affect glass fracture as well...

Replacement of one alkali in a glass by another is known to have a profound effect on many physical properties in that glass. In the case of electrical conductivity, there is a nonlinear variation between the values of the two relevant single-alkali glasses, with a minimum at some mixed composition. This is referred to as the mixed-alkali effect (M...

The synthesis of cadmium oxide from a gel of cadmium hydroxide has been followed in situ using unique combinations of X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) spectroscopy, and small-angle X-ray scattering (SAXS). XRD and XAFS enable the crystallography, particle size, and local structure to be quantified as the hydroxyl gel...

In situ X-ray Diffraction (XRD), X-ray Absorption Fine Structure (XAFS) spectroscopy and Small Angle X-ray Scattering (SAXS) have been used in conjunction with Diffuse Optical Spectroscopy (DOS) to characterise cadmium oxide particles nucleated within cadmium exchanged sodium zeolite Y treated with sodium hydroxide. The zeolite structure is maintai...

Starting with a hydroxyl gel, the synthesis of cadmium oxide has been charted using combinations of in situ X-ray Diffraction (XRD), X-ray Absorption Fine Structure (XAFS) spectroscopy and Small Angle X-ray Scattering (SAXS). The crystallography, particle size and local structure have been quantified from XRD and XAFS, as the gel converts into cadm...

A new high temperature chamber using aerodynamic levitation and laser heating has been used to study spheres of oxide materials at temperatures up to 2100°C. Near edge studies of Fe3O4 (MP : 1597°C) and FeO (MP 1377°C) have been performed by fluorescent XANES and in situ X-ray Diffraction (XRD). Both iron oxides reveal a shift in the Fe K-absorptio...

Alkali X-ray absorption fine structure (XAFS) spectra from KxCs(1-x)Si2O5 glasses measured at room temperature reveal changes in the Debye-Waller factors of nearest neighbour oxygen shells as the mixed alkali composition is altered. The thermal contributions have been estimated using the correlated Einstein model from the different frequencies of t...

The temperature dependence of the dc conductivity sigma of most glass-forming and crystalline ionic conductors is Arrhenius with constant activation energy, Esigma, at sufficiently low temperatures or conductivity levels. However, sigma becomes non-Arrhenius at high temperatures or conductivity levels. We have found that the product, betaEsigma, of...

Evidence for the clustering of alkalis in mixed alkali silicate glasses from recent Small Angle X-ray Scattering, X-ray Absorption Fine Structure and Molecular Dynamics experiments is discussed. As a result of clustering different types of alkali will associate in the glass structure leading to different configurations which in turn will have a dis...

X-ray small angle scattering measurements on silicate and berate glasses are described and the contrasting effects of inhomogeneities such as density fluctuations and alkali microsegregation are discussed. The consequences of microstructure for ionic diffusion, the mixed alkali effect (MAE), thermal expansion, glass fracture and polishing are consi...

The collapse and recrystallization of zinc-exchanged sodium zeolite-A has been observed in situ using combined X-ray spectroscopy and diffraction. The temperature at which this occurs is reduced by the presence of zinc, but the precipitation of NaAlSiO4 (nepheline) is blocked by the nucleation of ZnAl2O4 (gahnite), which persists to at least 1100 d...

A new single-crystal diffraction facility has been constructed on beamline 9 of the SRS at Daresbury Laboratory for the study of structural problems in chemistry and materials science. The station utilizes up to 3.8 mrad horizontally from the 5 T wiggler magnet which can be focused horizontally and vertically. The horizontal focusing is provided by...

With recent developments in solid state detectors combined with X-rays at glancing angles of incidence, Extended X-ray Absorption Fine Structure (EXAFS) experiments on arsenic ion-implanted into amorphous silicon surfaces have been obtained at dilutions down to 0.01 at%. Structural relaxation processes in both hydrogen-containing and hydrogen-free...

The chapter concerns ion implantation into amorphous semiconductors. The main issues addressed concern the ion beam technique experiments used to produce amorphous silicon and to dope plasma-deposited amorphous silicon. Moreover, the chapter focuses on the physics underlying the structural changes occurring in a target material in which irradiation...

Our previous work has concentrated on the recrystallisation of amorphous silicon with temperature and we used XAFS to follow the local order of the dopants (typically As, Ga, etc) to see them change from essentially Sfold in the amorphous state to 4-fold in the crystalline state. The main findings were that the silicon matrix recovers before the do...

Heterovalent ions substituted aluminophosphates (divalent in place of Al3+ or tetravalent for P5+) or trivalent (for eg.Al3+ or Fe3+ or Ga3+ in place of Si4+) ions in substituted zeolites[1] have been shown to be efficient catalysts for Bronsted acid catalysed reactions. Furthermore, some of the framework-incorporated divalent ions such as Co2+ or...

EXAFS data analysis using a multiple-scattering method for metal-ion substituted microporous solids are presented. It is shown that such an approach yields the best description of local structure for the first and the second shell neighbours around the central atom.

Long-timescale molecular dynamics simulations of duration 150-250 ps have been performed on alkali-metal disilicate glasses at 1400 K with the general formula M(2)Si(2)O(5) (M=Na, K, or an equiatomic mixture of the two). The simulations are long enough to analyse the diffusive behaviour of the alkali-metal ions in detail. The calculated diffusion c...

This volume comprises the proceedings of the 1995 Cardiff symposium on sieve methods, exponential sums, and their applications in number theory. Included are contributions from many leading international figures in this area which encompasses the main branches of analytic number theory. In particular, many of the papers reflect the interaction betw...

A solvate compound of rubidium bromoacetate and bromoacetic acid (1:1) was prepared and characterized. Its thermochemical reactivity was studied with thermal analysis (DSC and thermogravimetry combined with mass spectroscopy) and time-resolved in situ X-ray absorption spectroscopy at the K-edges of both bromine and rubidium. The reaction leads firs...

Hydrotalcite structures containing copper, magnesium and aluminium in the metal hydroxide layers have been investigated for their potential as precursors to the formation of catalysts for the decomposition and reduction of nitrogen oxides. These (CuMgAlIII)-Mg-II-Al-II hydrotalcites are catalytically active towards both the decomposition of nitric...

The title anion accommodated as a pillar in the interlamellar space of a Zn(II)AlIII double hydroxide(hydrotalcite-like) host is shown by X-ray absorption spectroscopy, supplemented by other studies, to possess three terminal MoO groups, in contrast to the two that exist in the dispersed, catalytically active anion.

Combinations of in situ Small Angle X-ray Scattering (SAXS) with X-ray Powder Diffraction (XRD) and X-ray Absorption Fine Structure (XAFS) have been used to follow the collapse of cadmium exchanged sodium zeolite-A (Cd/Na Z-A) to a glassy aluminosilicate and the subsequent recrystallisation processes that occur as the temperature is increased above...

The crystallization behaviour of Sr-doped lead zirconate titanate (PZT) powder obtained from an organic-gel process was investigated. The PZT gel was synthesized from organic complexes derived from nitrate solutions using EDTA as a complexing agent. Time-resolved Small Angle X-ray Scattering (SAXS) and Wide Angle X-ray Scattering (WAXS) experiments...

Quantitative kinetics for the crystallisation of Pb1-xLax(Zr0.65Ti0.35) 1-x/4O3 (x = 0.08 and 0.04) from alkoxide sol-gels have been studied in-situ by Energy Dispersive X-ray Diffraction (EDXRD) at temperatures in the range 550 - 625°C. The material shows a three stage evolution, with an amorphous precursor of a pyrochlore/fluorite intermediate to...

We have combined X-ray and neutron scattering with solid state nuclear magnetic resonance (NMR) measurements on glasses of the spodumene and analogous compositions. These glasses LiAlSi2O6, NaAlSiO6 and KAlSi2O6 are fully compensated i.e. contain equal quantities of alkali and aluminium. Q-space and R-space representations for each probe suggest co...

MCM-41 type mesoporous silicas have been prepared in which one or more of the following elements are accommodated in framework sites: titanium, iron, chromium, vanadium, manganese, boron and aluminium. XRD and FTIR are used as aids to characterisation, which is achieved chiefly — and to a degree that arrives at valence states, bond lengths and coor...

Substitutional (B, P, As and Ga) and interstitial (K) dopants have been incorporated into H‐free amorphous Si (a‐Si) films produced by ion beam amorphization of crystalline silicon material. X‐ray absorption fine‐structure, photothermal deflection spectroscopy and electronic transport measurements have been performed on these films to monitor the a...

The power of a new variant of the in situ combined XRA-XRD experiment (see ref. 12) is illustrated by tracking the inner shell environment and bonding of a CoIIion as it changes, in the gel just prior to crystallisation, from octahedral to tetrahedral coordination, the state in which it finally appears in the microporcus catalyst CoAlPO-5: the tech...

Experimental structural evidence for the microsegregation of alkali ions from network formers in alumino-silicate glasses is considered in relation to their ionic transport properties. Simple expressions for the activation enthalpies for diffusivity and electrical conductivity, that can be parameterised from the results of local structure spectrosc...