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The laser heating system for the diamond anvil cell at endstation 2 of beamline 12.2.2 of the Advanced Light Source in Berkeley, CA has been constructed and is available for in-situ high-pressure high-temperature x-ray experiments. The endstation couples a high-brilliance synchrotron x-ray source with an industrial strength laser to heat and probe samples at high pressure in the diamond anvil cell. The system incorporates an 80 watt Nd:YLF (cw) laser operated in TEM01* mode. Double-sided heating is achieved by splitting the laser beam into 2 paths that are directed through the opposing diamond anvils. X-ray transparent mirrors steer the laser beams coaxial with the x-ray beam from the superconducting bending magnet (energy range 6-35 KeV) and direct the emitted light from the heated sample into two separate spectrometers for temperature measurement by spectroradiometry. Objective lenses focus the laser beam to a size of 25 micron diameter (FWHM) in the sample region. An x-ray spot size of 10 micron diameter (FWHM) has been achieved with the installation of a pair of focusing Kirkpatrick-Baez mirrors. A unique aperture configuration has produced an x-ray beam profile that has very low intensity in the tails. The main thrust of the program is aimed at producing in-situ high-pressure high-temperature x-ray diffraction data, but other modes of operation, such as x-ray imaging have been accomplished. Technical details of the experimental setup will be presented along with initial results.

Magnesium doped Amorphous Calcium Carbonate was synthesised from precursor solutions containing varying amounts of calcium, magnesium, H2O and D2O. The Mg/Ca ratio in the resultant Amorphous Calcium Carbonate was found to vary linearly with the Mg/Ca ratio in the precursor solution. All samples crystallised as aragonite. No Mg was found in the final aragonite crystals. Changes in the Mg to Ca ratio were found to only marginally effect nucleation rates but strongly effect crystal growth rates. These results are consistent with a dissolution-reprecipitation model for aragonite formation via an Amorphous Calcium Carbonate intermediate. [ABSTRACT FROM AUTHOR]

We report the crystallite-size-dependency of the compressibility of nanoceria under hydrostatic pressure for a wide variety of crystallite diameters and comment on the size-based trends indicating an extremum near 33 nm. Uniform nano-crystals of ceria were synthesized by basic precipitation from cerium (III) nitrate. Size-control was achieved by adjusting mixing time and, for larger particles, a subsequent annealing temperature. The nano-crystals were characterized by transmission electron microscopy and standard ambient x-ray diffraction (XRD). Compressibility, or its reciprocal, bulk modulus, was measured with high-pressure XRD at LBL-ALS, using helium, neon, or argon as the pressure-transmitting medium for all samples. As crystallite size decreased below 100 nm, the bulk modulus first increased, and then decreased, achieving a maximum near a crystallite diameter of 33 nm. We review earlier work and examine several possible explanations for the peaking of bulk modulus at an intermediate crystallite size. [ABSTRACT FROM AUTHOR]

GSE_ADA/RSV is a free software package for custom analysis of single-crystal micro X-ray diffraction (SCμXRD) data, developed with particular emphasis on data from samples enclosed in diamond anvil cells and subject to high pressure conditions. The package has been in extensive use at the high pressure beamlines of Advanced Photon Source (APS), Argonne National Laboratory and Advanced Light Source (ALS), Lawrence Berkeley National Laboratory. The software is optimized for processing of wide-rotation images and includes a variety of peak intensity corrections and peak filtering features, which are custom-designed to make processing of high pressure SCμXRD easier and more reliable. [ABSTRACT FROM PUBLISHER]

Pressed for time: Amorphous calcium carbonate (ACC) undergoes a reversible amorphous–amorphous phase transition at 10 GPa, adopting an aragonite‐like local order. This result suggests a mechanism by which Mg2+—a cation with smaller ionic radius than Ca2+—modifies the local order of ACC to an aragonite‐like order by helping to decrease the molar volume of the amorphous phase. [ABSTRACT FROM AUTHOR]

The structure and elasticity of tricalcium aluminate ( C3 A) have been experimentally and theoretically studied. From high-pressure X-ray diffraction experiments, the bulk modulus of 102(6) and 110(3) GPa were obtained by fitting second- and third-order finite strain equation of state, respectively. First-principles calculations with a generalized gradient approximation gave an isotropic bulk modulus of 102.1 GPa and an isothermal bulk modulus of 106.0 GPa. The static calculations using the exchange-correlation functional show an excellent agreement with the experimental measurements. Based on the agreement, accurate elastic constants and other elastic moduli were computed. The slight difference of behavior at high pressure can be explained by the infiltration of pressure-transmitting silicone oil into structural holes in C3 A. The computed elastic and mechanical properties will be useful in understanding structural and mechanical properties of cementitious materials, particularly with the increasing interest in the advanced applications at the nanoscale. [ABSTRACT FROM AUTHOR]

The high-pressure structures of nickel monosilicide (NiSi) have been investigated to 124 GPa by synchrotron-based X-ray powder diffraction studies of quenched samples from laser-heated diamond anvil cell experiments, and the equations of state of three of these phases have been determined at room temperature. NiSi transforms from the MnP (B31) structure (space group Pnma) to the ɛ-FeSi (B20) structure (space group P213) at 12.5 ± 4.5 GPa and 1550 ± 150 K. Upon further compression, the CsCl (B2) structure (space group Pm3 m) becomes stable at 46 ± 3 GPa and 1900 ± 150 K. Thus, NiSi will be in the B2 structure throughout the majority of the Earth's mantle and its entire core, and will likely form a solid solution with FeSi, which is already known to undergo a B20 → B2 transition at high pressure. Data from the quenched (room-temperature) samples of all three phases have been fitted to the third-order Birch-Murnaghan equation of state. For the MnP (B31) structure this yields K0 = 165 ± 3 GPa with K0′ fixed at 4 and V0 fixed at 12.1499 Å3 atom−1 [ V0 from unpublished neutron diffraction measurements on the same batch of starting material; Wood (2011), personal communication]. For the ɛ-FeSi (B20) structure, K0 =161± 3 GPa and K0′ = 5.6 ± 0.2 with V0 fixed at 11.4289 Å3 atom−1. For the CsCl (B2) structure, K0 = 200 ± 9 GPa, K0′ = 4.6 ± 0.1 and V0 = 11.09 ± 0.05 Å3 atom−1. The ambient volume of NiSi, therefore, decreases by 6% at the first phase transition and then by a further 3% at the transition to the CsCl structure. Traces of additional NiSi structures predicted by Vočadlo, Wood & Dobson [ J. Appl. Cryst. (2012), 45, 186-196; part I], and labelled therein as Pbma-I, Pnma-II, and possibly also Pnma-III and P4/ nmm, have been detected. [ABSTRACT FROM AUTHOR]

Abstract: Using a diamond anvil cell, 14Å tobermorite, a structural analogue of calcium silicate hydrates (C–S–H), was examined by high-pressure synchrotron X-ray diffraction up to 4.8GPa under hydrostatic conditions. The bulk modulus of 14Å tobermorite was calculated, K o =47GPa. Comparison of the current results with previous high pressure studies on C–S–H(I) indicates that: (1) the compression behavior of the lattice parameters a and b of 14Å tobermorite and C–S–H(I) are very similar, implying that both materials may have very similar Ca–O layers, and also implying that an introduction of structural defects into the Ca–O layers may not substantially change in-plane incompressibility of the ab plane of 14Å tobermorite; and (2) the bulk modulus values of 14Å tobermorite and C–S–H(I) are dominated by the incompressibility of the lattice parameter c , which is directly related to the interlayer spacing composed of dreierketten silicate chains, interlayer Ca, and water molecules. [Copyright &y& Elsevier]

Abstract: Crystalline zeolitic materials, such as hydroxycancrinite, hydroxysodalite, herschelite and nepheline, are often synthesized from geopolymerization using fly-ash and solutions of NaOH at high temperatures. Comprised mainly of 6-membered aluminosilicate rings that act as basic building units, their crystal structures may provide insight into the reaction products formed in NaOH-activated fly ash-based geopolymers. Recent research indicates that the hydroxycancrinite and hydroxysodalite may play an important role as possible analogues of zeolitic precursor in geopolymers. Herein is reported a high pressure synchrotron study of the behavior of hydroxycancrinite exposed to pressures up to 6.1GPa in order to obtain its bulk modulus. A refined equation of state for hydroxycancrinite yielded a bulk modulus of Ko =46±5GPa (assuming =4.0) for a broad range of applied pressure. When low pressure values are excluded from the fit and only the range of 2.5 and 6.1 GPa is considered, the bulk modulus of hydroxycancrinite was found to be Ko =46.9±0.9GPa ( =4.0±0.4, calculated). Comparison with the literature shows that all zeolitic materials possessing single 6-membered rings (i.e., hydroxycancrinite, sodalite and nepheline) have similar bulk moduli. [Copyright &y& Elsevier]

Abstract: This study examines the influence of Al substitution for Si on the bulk modulus of calcium silicate hydrate I [C–S–H(I)], a structural analogue of C–S–H, by performing high-pressure synchrotron X-ray diffraction experiments in two C–S–H(I) samples: one a hydration product of alkali-activated slag and the other a synthetic C–S–H(I). The test result shows that not only the bulk modulus but also the incompressibility of the lattice parameters a, b, and c of two C–S–H(I) samples are very similar to each other, regardless of the Al substitution. This result may be due to the four-coordinated configuration of the substituted Al, which makes the dreierketten silicate chains maintain the same arrangement after the substitution. [ABSTRACT FROM AUTHOR]

Abstract: A high pressure diffraction study, from ambient to 50GPa, has been carried out on nanocrystalline TiN/amorphous BN nanocomposite materials prepared by plasma chemical vapor deposition. The compressibilities of these materials were found not to be significantly different from TiN. A large amount of biaxial and isotropic strain was found to build up on pressurization which continued to exist after depressurization and annealing indicating a permanent deformation under high pressure. This permanent deformation is located in the grain boundaries and is reduced by the presence of amorphous BN. [Copyright &y& Elsevier]

A new facility for high-pressure diffraction and spectroscopy using diamond anvil high-pressure cells has been built at the Advanced Light Source on beamline 12.2.2. This beamline benefits from the hard X-radiation generated by a 6 T superconducting bending magnet (superbend). Useful X-ray flux is available between 5 keV and 35 keV. The radiation is transferred from the superbend to the experimental enclosure by the brightness-preserving optics of the beamline. These optics are comprised of a plane parabola collimating mirror, followed by a Kohzu monochromator vessel with Si(111) crystals ( E/Δ E≃ 7000) and W/B4C multilayers ( E/Δ E≃ 100), and then a toroidal focusing mirror with variable focusing distance. The experimental enclosure contains an automated beam-positioning system, a set of slits, ion chambers, the sample positioning goniometry and area detector (CCD or image-plate detector). Future developments aim at the installation of a second endstation dedicated to in situ laser heating and a dedicated high-pressure single-crystal station, applying both monochromatic and polychromatic techniques. [ABSTRACT FROM AUTHOR]

Examines the B1 and B2 phases of potassium chloride (KCl) using an in-situ X-ray diffraction pressure-temperature. Discussion of the decrease in infrared mode frequency; Ambient-temperature compression data; Correlation of the level of cellulose nitrate and density of potassium.

Abstract: Earlier measurements of elastic moduli of nc-TiN/a-Si3N4 nanocomposites of different composition and hardness by means of vibrating reed and surface Brillouing scattering, that yield Young’s and shear modulus, as well as the Poisson’s ratio, have been confirmed by high-pressure X-ray diffraction measurements, that yield bulk modulus. It is found that elastic moduli of all measured samples are essentially the same within relatively small error of measurements, and only slightly lower than that of pure TiN. The nanocomposites are superhard thanks to their unique nanostructure with strengthened SiN x interface. [Copyright &y& Elsevier]

Abstract: This study explores the reaction products of alkali-activated Class C fly ash-based aluminosilicate samples by means of high-resolution synchrotron X-ray diffraction (HSXRD), scanning electron microscope (SEM), and compressive strength tests to investigate how the readily available aluminum affects the reaction. Class C fly ash-based aluminosilicate raw materials were prepared by incorporating Na-aluminate into the original fly ashes, then alkali-activated by 10M NaOH solution. Incorporating Na-aluminate reduced the compressive strength of samples, with the reduction magnitude relatively constant regardless of length of curing period. The HSXRD provides evidence of the co-existence of C–S–H with geopolymeric gels and strongly suggests that the C–S–H formed in the current system is C–S–H(I). The back-scattered electron images suggest that the C–S–H(I) phase exists as small grains in a finely intermixed form with geopolymeric gels. Despite providing extra source of aluminum, adding Na-aluminate to the mixes did not decrease the Si/Al ratio of the geopolymeric gel. [Copyright &y& Elsevier]

Abstract: Synchrotron X-ray diffraction data was collected from a sample of monocarboaluminate 3CaO·Al2O3·CaCO3·11H2O from ambient pressure to 4.3GPa. The refined crystal structure at ambient pressure is triclinic with parameters a=5.77(2) Å, b=8.47(5) Å, c=9.93(4) Å, α=64.6(2)°, β=82.8(3)°, γ=81.4(4)°, and space group of P1 or P . It showed some degree of perfectly reversible pressure-induced dehydration with a non-hygroscopic pressure-transmitting medium. However the dehydration effect does not critically affect a bulk modulus due to its strong framework. The isothermal bulk modulus of monocarboaluminate was found to be 53(5)GPa and 54(4)GPa with 3rd order and 2nd order Birch-Murnaghan Equation of state, respectively. That value is higher than for any other reported AFm or AFt phase. The pressure–volume behavior of the monocarboaluminate was compared with that of previous studied hemicarboaluminate. [Copyright &y& Elsevier]

Abstract: The compressibilities of two AFm phases (strätlingite and calcium hemicarboaluminate hydrate) and hydrogarnet were obtained up to 5GPa by using synchrotron high-pressure X-ray powder diffraction with a diamond anvil cell. The AFm phases show abrupt volume contraction regardless of the molecular size of the pressure-transmitting media. This volume discontinuity could be associated to a structural transition or to the movement of the weakly bound interlayer water molecules in the AFm structure. The experimental results seem to indicate that the pressure-induced dehydration is the dominant mechanism especially with hygroscopic pressure medium. The Birch–Murnaghan equation of state was used to compute the bulk modulus of the minerals. Due to the discontinuity in the pressure–volume diagram, a two stage bulk modulus of each AFm phase was calculated. The abnormal volume compressibility for the AFm phases caused a significant change to their bulk modulus. The reliability of this experiment is verified by comparing the bulk modulus of hydrogarnet with previous studies. [Copyright &y& Elsevier]

Abstract: Synthetic basic sodalite, Na8[AlSiO4]6(OH)2·2H2O, cubic, P43n, (also known as hydroxysodalite hydrate) was prepared by the alkaline activation of amorphous aluminosilicate glass, obtained from the phase separation of Class F fly ash. The sample was subjected to a process similar to geopolymerization, using high concentrations of a NaOH solution at 90°C for 24hours. Basic sodalite was chosen as a representative analogue of the zeolite precursor existing in Na-based Class F fly ash geopolymers. To determine its bulk modulus, high-pressure synchrotron X-ray powder diffraction was applied using a diamond anvil cell (DAC) up to a pressure of 4.5GPa. A curve-fit with a truncated third-order Birch–Murnaghan equation of state with a fixed K'' o =4 to pressure-normalized volume data yielded the isothermal bulk modulus, K o =43±4GPa, indicating that basic sodalite is more compressible than sodalite, possibly due to a difference in interactions between the framework host and the guest molecules. [Copyright &y& Elsevier]

Abstract: In situ synchrotron X-ray diffraction was used to observe the reaction induced by laser heating of a mixture of tantalum and boron in a diamond anvil cell. Laser heating at pressures of 12 and 24 GPa resulted in the formation of TaB2. The bulk modulus of TaB2 (B 0 = 341(7) GPa) was determined from a fit of a second-order Birch–Murnaghan equation of state to the p−V data. Density functional theory based calculations complemented the experimental observations and were used to obtain the full tensor of elastic stiffness coefficients. The choice of the most appropriate exchange-correlation functional for the description of elastic properties is discussed. [ABSTRACT FROM AUTHOR]

Abstract: X-ray diffraction from LaB6 standards document a precision of 478ppm in lattice-parameter determinations for beamline 12.2.2 at Lawrence Berkeley National Laboratory′s Advanced Light Source, a facility for characterizing materials at high pressures and temperatures using laser- and resistance-heated diamond cells. Melting of Ni, Mo, Pt and W, resistively heated at 1atm pressure in Ar, provides a validation of the beamline spectroradiometric system that is used to determine sample temperatures. The known melting temperatures, which range from 1665 to 3860K for these metals, are all reproduced to within ±80K. [Copyright &y& Elsevier]

Abstract: The increase in strength and evolution of crystalline phases in inorganic polymer cement, made by the alkali activation of slag, Class C and Class F fly ashes, was followed using compressive strength test and synchrotron X-ray diffraction. In order to increase the crystallinity of the product the reactions were carried out at 80°C. We found that hydrotalcite formed in both the alkali-activated slag cements and the fly ash-based geopolymers. Hydroxycancrinite, one member of the ABC-6 family of zeolites, was found only in the fly ash geopolymers. Assuming that the predominantly amorphous geopolymer formed under ambient conditions relates to the crystalline phases found when the mixture is cured at high temperature, we propose that the structure of this zeolitic precursor formed in Na-based high alkaline environment can be regarded as a disordered form of the basic building unit of the ABC-6 group of zeolites which includes poly-types such as hydroxycancrinite, hydroxysodalite and chabazite-Na. [Copyright &y& Elsevier]