High-pressure Samples Research Articles

Magnetic Resonance Imaging of gas hydrate formation and conversion at sub-seafloor conditions

The production of natural gas from sub-seafloor gas hydrates is one possible strategy to meet the world’s growing demand for energy. On the other hand, climate warming scenarios call for the substitution of fossil energy resources by sustainable energy concepts. Burning natural gas from gas hydrates could be emission neutral if it was combined with a safe storage of the emitted CO2. Laboratory experiments, that address corresponding strategies, need to be performed under high pressures and low temperatures to meet the thermodynamic conditions of the sub-seafloor environment. In this paper, we present a high-pressure flow-through sample cell that is suitable for nuclear magnetic resonance (NMR) experiments at realistic marine environmental conditions, i.e. pressures up to 15 MPa and temperatures from 5 to 20°C, and we demonstrate its suitability in applied gas hydrate research.

High-pressure mafic oceanic rocks from the Makbal Complex, Tianshan Mountains (Kazakhstan & Kyrgyzstan): Implications for the metamorphic evolution of a fossil subduction zone

The Makbal Complex in the western Tianshan Mountains of Kazakhstan and Kyrgyzstan consists of HP/UHP metasedimentary host rocks which enclose various HP mafic blocks or boudins. These mafic rocks comprise rare eclogites (sensu stricto and sensu lato), garnet amphibolites (retrograded eclogites) and a newly discovered glaucophanite (glaucophane–garnet–omphacite bearing rock).So far the Makbal Complex has been interpreted to predominantly consist of continental lithologies and the mafic rocks were considered as dismembered dikes intruding continental metasediments. This interpretation is mainly based on the geological relationship and bulk rock chemistry of the different rock types. It was further suggested that the continental lithologies of the Makbal Complex underwent eclogite-facies metamorphism in a former subduction zone.In the present study we combined conventional geothermometry, P–T pseudosection modeling and major and trace element whole rock geochemistry for different mafic samples (glaucophanite and eclogites (sensu lato)) in order to shed light on both the metamorphic evolution and the protoliths of the mafic HP rocks in the Makbal Complex.Prograde to peak-pressure clockwise P–T paths of glaucophanite and eclogites (sensu lato) were modeled using garnet isopleth thermobarometry. The results show that the glaucophanite and eclogite (sensu lato) samples experienced similar prograde P–T paths and slightly different peak metamorphic conditions at ~560°C at 2.4GPa for the former and between ~520°C at 2.2GPa and ~555°C at ~2.5GPa for the latter, corresponding to burial depths between 70 and 85km.Whole rock major and trace element analyses and petrological evidence imply that the various rock types at the Makbal Complex most likely originated from different precursor rocks. Eclogites (sensu lato) are believed to represent strongly retrogressed former eclogite-facies rocks that had never been eclogites (sensu stricto, i.e. >70 vol.% garnet and omphacite) due to an unfavorable alkali-poor bulk composition (Na2O <1wt.%). The four high-pressure mafic samples investigated in this study originated from oceanic crust (Zr/Hf ratio of 33 to 35) which contradicts all previous studies suggesting a continental protolith for all mafic HP/UHP rocks at Makbal.The present study indicates that the mafic high-pressure rocks represent incoherent segments of exhumed oceanic crust. Juxtaposition of different mafic oceanic (this study) and continental rocks is suggested to be due to buoyancy-driven exhumation of the metasedimentary host rock in the subduction channel where dismembered fragments of the subducted oceanic crust were captured in different depths.

Coherent diffraction imaging of nanoscale strain evolution in a single crystal under high pressure

The evolution of morphology and internal strain under high pressure fundamentally alters the physical property, structural stability, phase transition and deformation mechanism of materials. Until now, only averaged strain distributions have been studied. Bragg coherent X-ray diffraction imaging is highly sensitive to the internal strain distribution of individual crystals but requires coherent illumination, which can be compromised by the complex high-pressure sample environment. Here we report the successful de-convolution of these effects with the recently developed mutual coherent function method to reveal the three-dimensional strain distribution inside a 400 nm gold single crystal during compression within a diamond-anvil cell. The three-dimensional morphology and evolution of the strain under pressures up to 6.4 GPa were obtained with better than 30 nm spatial resolution. In addition to providing a new approach for high-pressure nanotechnology and rheology studies, we draw fundamental conclusions about the origin of the anomalous compressibility of nanocrystals.

Effects of Filling Fraction on Magnetic Properties of Filled SkutteruditeRFe4Sb12(R= La, Ce) Synthesized under High Pressure

We report the results of the 121,123 Sb-nuclear quadrupole resonance (NQR) measurements on the filled skutterudite R Fe 4 Sb 12 ( R = La, Ce) synthesized under high pressure (HP), and compare them with those for the sample synthesized under ambient pressure (AP) in order to understand the effects of the R -site filling fraction on magnetic properties. The NQR spectra for the HP samples are much sharper than those for the AP samples, suggesting that the R -site filling fraction is high close to unity and the electronic states around Sb nuclei become uniform. In LaFe 4 Sb 12 -HP, the nuclear spin–lattice relaxation rate divided by temperature, 1/ T 1 T , exhibits the Curie–Weiss temperature dependence 1/ T 1 T = C /( T +θ) with the Weiss temperature θ=12 K above 30 K, indicating the development of ferromagnetic fluctuations. The magnitude of θ for the HP sample is smaller than that for the AP sample, which suggests that the system becomes close to the vicinity of ferromagnetic instability as the La-site fil...

Identification of Vacancy Formation Sites in LaNi5Cu During Hydrogenation Using in Situ Coincidence Doppler Broadening Technique

To study the formation mechanism of lattice defects introduced during hydrogenation, we developed equipment that can measure in situ positron lifetime and coincidence Doppler broadening (CDB) simultaneously with pressure–composition (P–C) isotherms at room temperature. The equipment, which consisted of a high-pressure sample holder, reduced the intensity of the background signals in the relatively high momentum region of the Doppler broadening spectrum by more than 2 orders of magnitude in comparison to the background shown by conventional Doppler broadening equipment. Further, the quality of data obtained by our instrument was similar to that obtained from ex situ CDB equipment without a high-pressure sample holder. The substitution effect on the positron annihilation behavior was observed from the ratio curves of CDB spectra for LaNi5Cu and LaNi5-xAlx. In addition, using the equipment we developed, we attempted to identify the vacancy formation sites introduced in LaNi5Cu during hydrogenation. Changes i...

Facilitating analysis of trace impurities in hydrogen: Enrichment based on the principles of pressure swing adsorption

A laboratory-scale gas sampling and impurity enrichment device (GSIED) based on the principles of pressure swing adsorption (PSA) has been designed, fabricated, and tested to show that such a device provides an effective method to enrich trace impurity species in hydrogen by a factor of 10 or more. With the availability of a high pressure sample gas at the hydrogen refueling stations, the device uses only a pressure sequence to enrich the impurities without need of a temperature cycle. Enrichment of the impurities allows the use of simpler and less expensive analytical instruments for hydrogen quality monitoring and certification purposes. A series of experiments was conducted using activated carbon as the PSA sorbent for impurity enrichment in a hydrogen gas containing N2, CO, CH4, and CO2. The enrichment factor varied for the different species according to their affinity of adsorption. The measured impurity enrichment factors agreed well with theoretical analyses, and are functions of the pressure ratio (adsorption/desorption pressures) and adsorption affinity relative to hydrogen (selectivity). Depending on the species of interest and the volume of the enriched sample needed for analysis, the device can be designed to enrich the impurities in hydrogen in 40 min or less.

High pressure sample cell for total internal reflection fluorescence spectroscopy at pressures up to 2500 bar

Total internal reflection fluorescence (TIRF) spectroscopy is a surface sensitive technique that is widely used to characterize the structure and dynamics of molecules at planar liquid-solid interfaces. In particular, biomolecular systems, such as protein adsorbates and lipid membranes can easily be studied by TIRF spectroscopy. Applying pressure to molecular systems offers access to all kinds of volume changes occurring during assembly of molecules, phase transitions, and chemical reactions. So far, most of these volume changes have been characterized in bulk solution, only. Here, we describe the design and performance of a high pressure sample cell that allows for TIRF spectroscopy under high pressures up to 2500 bar (2.5 × 10(8) Pa), in order to expand the understanding of volume effects from the bulk phase to liquid-solid interfaces. The new sample cell is based on a cylindrical body made of Nimonic 90 alloy and incorporates a pressure transmitting sample cuvette. This cuvette is composed of a fused silica prism and a flexible rubber gasket. It contains the sample solution and ensures a complete separation of the sample from the liquid pressure medium. The sample solution is in contact with the inner wall of the prism forming the interface under study, where fluorescent molecules are immobilized. In this way, the new high pressure TIRF sample cell is very useful for studying any biomolecular layer that can be deposited at a planar water-silica interface. As examples, high pressure TIRF data of adsorbed lysozyme and two phospholipid membranes are presented.

Small-Angle X-ray Scattering Measurements of Ionic Liquids Pressurized with Carbon Dioxide Using Titanium Sample Holder: 1-Butyl-3-methylimidazolium Bis(trifluoromethylsulfonyl) Amide Mixtures up to 22 MPa

A high-pressure sample holder made entirely of titanium and a titanium alloy was constructed for small-angle X-ray scattering (SAXS) measurement of ionic liquids pressurized with CO2. It is designed to vary the path length precisely and perform stable operation at high temperature and pressure, while retaining a constant path length. An in situ beam-monitoring detector for the transmitted X-rays was redesigned and used. SAXS experiments were carried out for an imidazolium-based ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide, pressurized and saturated with CO2. Zero angle scattering intensities, I(0), which directly relate to the mesoscale structural fluctuation, are evaluated from the obtained SAXS intensities. Values of I(0) meaningfully change with the CO2 solubility. By using the constructed apparatuses, the anomalous behavior of CO2 dissolution into ionic liquids is clarified from the viewpoint of the mesoscale structural change of ionic liquids that fluctuated by dissolved CO2. The present system for SAXS measurement is widely applicable to investigations on structural fluctuations of liquids, solutions including phase separated systems, which are the same as the ionic liquids and CO2 mixtures, and amorphous solids under extreme conditions.

Small-Angle X-ray Scattering Measurements of Ionic Liquids Pressurized with Carbon Dioxide Using Titanium Sample Holder: 1-Butyl-3-methylimidazolium Bis(trifluoromethylsulfonyl) Amide Mixtures up to 22 MPa

A high-pressure sample holder made entirely of titanium and a titanium alloy was constructed for small-angle X-ray scattering (SAXS) measurement of ionic liquids pressurized with CO2. It is designed to vary the path length precisely and perform stable operation at high temperature and pressure, while retaining a constant path length. An in situ beam-monitoring detector for the transmitted X-rays was redesigned and used. SAXS experiments were carried out for an imidazolium-based ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide, pressurized and saturated with CO2. Zero angle scattering intensities, I(0), which directly relate to the mesoscale structural fluctuation, are evaluated from the obtained SAXS intensities. Values of I(0) meaningfully change with the CO2 solubility. By using the constructed apparatuses, the anomalous behavior of CO2 dissolution into ionic liquids is clarified from the viewpoint of the mesoscale structural change of ionic liquids that fluctuated by dissolved CO2. The present system for SAXS measurement is widely applicable to investigations on structural fluctuations of liquids, solutions including phase separated systems, which are the same as the ionic liquids and CO2 mixtures, and amorphous solids under extreme conditions.

About diffusion mechanism in silica liquid under pressure

We perform a molecular dynamic simulation to study the diffusion mechanism in silica liquid under pressure up to 25GPa and at temperature of 3000K. We find that total O―Si―O angle distribution can be expressed by a simple relation between partial O―Si―O angle distribution and fractions of units SiOx. Specifically, we demonstrate that these liquids consist of identical units SiO4, SiO5 and SiO6 and have common partial O―Si―O angle distribution. We also show that each particle undergoes a series of stages where the particle locates in unchanged unit SiOx, x=3, 4, … 7 or OSiy, y=1, 2, 3, 4. The diffusivity strongly depends on the rate of transitions Siξ→Siξ±1 and Oζ→Oζ±1 which is significantly different between low- and high-pressure samples. For low-pressure sample the transitions Si4→Si5, Si5→Si4, O2→O3 and O3→O2 are dominant, meanwhile for high-pressure sample there are transitions Siξ→Siξ±1 with ξ=4, 5, 6 and Oζ→Oζ±1 with ζ=2, 3, 4. This finding may be common for diffusion in all network-forming liquids. The simulation also reveals the spatially heterogeneous dynamics in low-pressure liquid where a large cluster of immobile particle exists for the time that a number of particles move over several inter-particle distances.

An improved procedure for low‐temperature embedding of high‐pressure frozen and freeze‐substituted plant tissues resulting in excellent structural preservation and contrast

Here we describe refinements in the processing of high-pressure frozen samples of delicate plant tissues for immuno-electron microscopy. These involve: shortened freeze-substitution schedules, lower temperatures during processing and polymerisation, the avoidance of temperature fluctuations and the optimisation of heat transfer from the specimens using small disposable aluminium containers. The application of these modifications leads to very good structural preservation and selective membrane contrast. As a result, the versatility of the method is increased since not only immuno-electron microscopical studies can be performed but often the quality is also quite suitable for structural investigations.

High pressure treatments on the inactivation of Salmonella Enteritidis and the physicochemical, rheological and color characteristics of sliced vacuum-packaged dry-cured ham

The effect of high pressure (HP) on Salmonella Enteritidis in sliced dry-cured ham stored under temperature abuse (8°C) during 60d was investigated. After treatment, reductions of S. Enteritidis were 1.06, 2.54 and 4.32 log units in ham treated at 400, 500 and 600MPa for 5min at 12°C, compared to non-pressurized samples. After 60d, counts of S. Enteritidis in ham treated at 400 and 500MPa were 2.56 and 2.66 log units lower than in non-treated ham, whereas the pathogen was only detected after enrichment in ham treated at 600MPa. Lipid oxidation increased with storage and pressurization, whereas total free amino acid contents were similar in HP and control samples after 60d. Dry-cured ham treated at the highest pressures exhibited lower shear resistance, whereas the maximum force to compress the sample was slightly changed. Color (L*, a* and b*) varied with pressurization and storage. Changes induced by HP in dry-cured ham were attenuated during storage.

Comparing different preparation methods to study human fibrin fibers and platelets using TEM

For the study of cellular ultrastructure, the sample needs to be stabilized by fixation, with the ultimate aim to preserve the native tissue organization and to protect the tissue against later stages of preparation. Chemical and freezing fixation are most used, and chemical fixation employs agents that permeate tissues and cells by diffusion and covalently bind with their major biochemical constituents to fix them. Most widely used chemical fixatives are aldehydes, e.g., formaldehyde and glutaraldehyde, which are noncoagulating, crosslinking agents. Cryofixation methods for ultrastructural studies are also popular, and high-pressure freezing immobilizes all cell constituents and arrests biological activity by removing the thermal energy from the system. In the current research, we used platelet-rich plasma (PRP) to study expansive fibrin fibers and platelet ultrastructure to compare the two fixation techniques. We also used thrombin and calcium chloride as a clotting agent to determine the technique most suitable for the formation of extensive fibrin networks. Chemically fixated fibrin fibers were more compact and condensed and also showed a banding pattern on longitudinal sections. High-pressure frozen samples were more dispersed while platelets fixated showed better preserved cellular membranes and organelle structure. PRP coagulated by addition of CaCl(2) showed blood platelets that are noticeably more activated compared with PRP; however, with thrombin, a sharp ultrastructure was seen. We conclude that PRP mixed with thrombin, and freeze substituted, is the most suitable method for the study of extensive fibrin fibers as well as platelets.

ChemInform Abstract: Structure and Magnetic Properties of BiFe0.75Mn0.25O3 Perovskite Prepared at Ambient and High Pressure.

AbstractBiFe1‐xMnxO3 (0.0 ≤ x ≤ 0.4) solid solutions are prepared from stoichiometric mixtures of Bi2O3, Fe2O3, and Mn2O3 at 1143 K for 2 h (ambient pressure samples), and at 6 GPa and 1400 K for 90 min (high pressure samples).

Nanostructures in metastable GeBi2Te4obtained by high-pressure synthesis and rapid quenching and their influence on physical properties

We report on a new metastable modification of GeBi${}_{2}$Te${}_{4}$ obtained by high-pressure high-temperature synthesis. It crystallizes in the CuPt type; different nanostructures are induced by various temperature programs under a constant pressure of 12 GPa. The particle size changes from 10 nm in quenched samples to &gt;100 nm for melts slowly crystallized under high pressure. The smaller the domains the more random is their orientation distribution. The nanostructure has a high impact on the temperature characteristics of the electrical resistivity. The domain size determines whether the compounds are metallic or semiconducting. In the latter case the semiconducting behavior is due to the scattering of electrons at domain and/or grain boundaries. Intermediate behavior that starts off metal-like and changes to semiconducting at higher temperature has been observed for samples thermally quenched from the solid state at high pressure. Resistivity measurements of the high-pressure samples involving multiple heating and cooling sequences lead to a significant reduction of internal stress and finally approach a state which is characterized by \ensuremath{\rho}($T$) hysteresis. Our results show the large influence of the domain size and the grain boundary concentration on the properties of the materials and reveal how properties like the thermoelectric figure of merit ($ZT$) depend on the preparation technique. By the microstructuring of stable GeBi${}_{2}$Te${}_{4}$, the $ZT$ value drops by one order of magnitude.

Metamorphic P–T path and implications of high-pressure pelitic granulites from the Jiaobei massif in the Jiao-Liao-Ji Belt, North China Craton

High-pressure pelitic granulites have recently been found from the Jiaobei massif in the southern segment of the Jiao-Liao-Ji Belt (JLJB), which separates the Eastern Block of the North China Craton into the Longgang and Langrim Blocks. Petrological evidence from these high-pressure pelitic granulites indicates three distinct metamorphic stages (M1–M3). The pre-peak (M1) stage is represented by a mineral assemblage of garnet (core)+inclusion-type minerals within the garnet (biotite+kyanite+muscovite+plagioclase+quartz+ilmenite). The peak (M2) stage is marked by a mineral assemblage of garnet (mantle)+K-feldspar+kyanite+plagioclase+biotite+rutile+ilmenite+quartz. The post-peak (M3) stage is featured by a mineral assemblage of garnet (rim)+sillimanite+plagioclase+biotite+ilmenite+quartz. Using the THERMOCALAC technique, the NCKFMASHTO system has been applied to construct pseudosections for a representative high-pressure pelitic granulite sample. P–T conditions for the M1, M2 and M3 stages are constrained at 9.3–10.7kbar/645–670°C, 14.8–16.2kbar/860–890°C, and 6.3–8.5kbar/710–740°C, respectively. The mineral assemblages and P–T conditions of the high-pressure pelitic granulites define a clockwise P–T path involving decompression and cooling following the peak high-pressure granulite facies metamorphism. This suggests that the high-pressure pelitic granulites experienced the initial crustal thickening (M1 and M2), followed by exhumation and cooling (M3), which implies that the southern segment of the JLJB must have been involved in subduction- or collision-related tectonic processes. Therefore, the JLJB may represent another Paleoproterozoic collisional belt along which the Longgang and Langrim Blocks amalgamated to form the Eastern Block.

Multipurpose high-pressure high-temperature diamond-anvil cell with a novel high-precision guiding system and a dual-mode pressurization device

A novel diamond-anvil cell (DAC) design has been constructed and tested for in situ applications at high-pressure (HP) operations and has proved to be suitable even for HP sample environments at non-ambient temperature conditions. The innovative high-precision guiding mechanism, comparable to a dog clutch, consists of perpendicular planar sliding-plane elements and is integrated directly into the base body of the cylindrically shaped DAC. The combination of two force-generating devices, i.e., mechanical screws and an inflatable gas membrane, allows the user to choose independently between, and to apply individually, two different forcing mechanisms for pressure generation. Both mechanisms are basically independent of each other, but can also be operated simultaneously. The modularity of the DAC design allows for an easy exchange of functional core-element groups optimized not only for various analytical in situ methods but also for HP operation with or without high-temperature (HT) application. For HP-HT experiments a liquid cooling circuit inside the specific inner modular groups has been implemented to obtain a controlled and limited heat distribution within the outer DAC body.

Morphology and mechanical property of high-density polyethylene parts prepared by gas-assisted injection molding

The crystal morphology, melting behavior, and mechanical properties of high-density polyethylene (HDPE) samples obtained via gas-assisted injection molding (GAIM) under different gas pressures were investigated. Moreover, the non-isothermal crystallization kinetics of HDPE under different cooling rates was also studied. The obtained samples were characterized via differential scanning calorimetry, two-dimensional wide-angle X-ray scattering (2D-WAXS), tensile testing, dynamic mechanical analysis (DMA) and scanning electron microscopy techniques. It was found that the properties were intimately related to each other. Macroscopically, the flow-induced morphology of the various HDPE samples was characterized with a hierarchical crystalline structure, possessing oriented lamellar structure, shish–kebab structure, and common spherulites in the skin, sub-skin, and gas channel region, respectively. The 2D-WAXS results demonstrated that the degree of orientation of the high gas pressure sample was larger than that of the low pressure sample at the corresponding layer. The tensile testing results of GAIM parts showed that the mechanical properties of the GAIM parts were improved with an increase of the gas pressure. Furthermore, the DMA was utilized to obtain the dynamic mechanical properties of the GAIM samples, and the results indicated that significant improvement of the orientation was observed with an increase of the gas pressure.

Extreme structural inhomogeneities in high-pressure torsion samples along the axial direction

Structural inhomogeneities along the axial, and not only the radial, direction are shown to occur in Zr 3Al deformed by high-pressure torsion (HPT) at room temperature. Scanning and transmission electron microscopy reveal a structure of nanocrystalline and coarse crystalline banded regions parallel to the shear plane. This contradicts the accepted equation describing microstructural evolution that is derived from the geometry of HPT. Surface treatment of one set of samples prior to deformation allows a systematic study as it leads to the localization of a refined nanocrystalline structure at the sample surface. Once a ∼50 μm wide nanocrystalline banded layer is formed (10 turns), the residual structure remains coarse grained up to the highest deformations studied (80 turns). In the narrow interface region between coarse structure and nanocrystalline structure, the grain size decreases by three orders of magnitude within less than 10 μm. This is accompanied by a change in texture, indicating the transition from a dislocation-mediated deformation mechanism to a grain-boundary-mediated one. The results of the structural study are explained in terms of the occurrence of work softening, as confirmed by microhardness measurements. Once a nanocrystalline layer—softer than the coarse structure—has formed, the vast majority of strain is accommodated by that layer: this leads to extreme inhomogeneities, a large strain gradient along the axial direction and huge deviations of the actual local shear strain from the calculated strain.

EXPO, an Exocyst-Positive Organelle Distinct from Multivesicular Endosomes and Autophagosomes, Mediates Cytosol to Cell Wall Exocytosis inArabidopsisand Tobacco Cells

The exocyst protein complex mediates vesicle fusion with the plasma membrane. By expressing an (X)FP-tagged Arabidopsis thaliana homolog of the exocyst protein Exo70 in suspension-cultured Arabidopsis and tobacco (Nicotiana tabacum) BY-2 cells, and using antibodies specific for Exo70, we detected a compartment, which we term EXPO (for exocyst positive organelles). Standard markers for the Golgi apparatus, the trans-Golgi network/early endosome, and the multivesicular body/late endosome in plants do not colocalize with EXPO. Inhibitors of the secretory and endocytic pathways also do not affect EXPO. Exo70E2-(X)FP also locates to the plasma membrane (PM) as discrete punctae and is secreted outside of the cells. Immunogold labeling of sections cut from high-pressure frozen samples reveal EXPO to be spherical double membrane structures resembling autophagosomes. However, unlike autophagosomes, EXPOs are not induced by starvation and do not fuse with the lytic compartment or with endosomes. Instead, they fuse with the PM, releasing a single membrane vesicle into the cell wall. EXPOs are also found in other cell types, including root tips, root hair cells, and pollen grains. EXPOs therefore represent a form of unconventional secretion unique to plants.