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Leaching of toxic or reactive chemicals from polymeric materials can adversely affect the quality and safety of biopharmaceuticals. It was therefore the aim of the present study to analyze leachables from a disposable clinical administration syringe using a polysorbate-containing surrogate solution and to assess their chemical reactivity. Analytical methods did include (headspace) GC-MS, Fourier-transform-infrared spectroscopy, a ferrous oxidation-xylenol orange assay, and nuclear magnetic resonance analysis. In the syringe leachables solution, the carcinogenic 1,1,2,2-tetrachloroethane (TCE) was detected in concentrations above the ICH M7-derived analytical evaluation threshold. TCE was shown to be an oxidation product of dichloromethane used during sample preparation. Since TCE was only isolated from incubations with the contained rubber stopper, we hypothesized that a stopper-derived leachable acted as a reactive oxidant promoting this chemical reaction. Subsequently, the leachable was identified to be the polymerization initiator Luperox® 101. Combining different analytical approaches led to the structural elucidation of a chemical reactive oxidant, which has the potential to interact and alter drug products. We conclude that chemically reactive compounds, such as the newly identified rubber stopper leachable Luperox® 101, may be of concern and therefore should be routinely considered if a prolonged exposure of polymers with drug products can be anticipated.

International audience; Formation and evolution of defect levels in the electronic structure of silicon nitride with cubic spinel structure, -Si 3 N 4 , after the irradiation with He + ions was investigated using spectroscopic techniques. Strong changes of cathodoluminescence (CL), photoluminescence (PL), photoluminescence excitation (PLE) and Raman spectra were detected. In particular, excitonic PL was significantly inhibited and a new near-IR band appeared with the band gap excitation h≥E g =5.05 eV. This was explained by an effective trapping of photoinduced electrons and holes by charged defects. The spectral shift of PL with the excitation photon energy indicated heterogeneous nature of the defect sites. The energetic position of near-IR and visible PL bands correlate, suggesting an interaction with the common cation defect to be an origin. The visible PL of exciton bound to a neutral defect Si  was red shifted, which was attributed to the permutations between empty and occupied octahedral and tetrahedral sites, inherent to the spinel structure, after collisions with He + ions. The positively charged cation sites in the spinel structure are compensated by V N ''' anion vacancies. The local deformation of the spinel lattice affects PL intensity of the self-trapped exciton at 4.35 eV.

International audience; Cubic solids such as NaCl, crystalline argon, or H 2 O-ice VII exhibit significant elastic anisotropy strongly increasing upon compression. As earlier recognized for solid argon and H 2 O-ice (both exhibiting Zener ratio A>1), longitudinal sound velocities of their polycrystals, V Lav , measured using Brillouin light scattering (BLS) or pulse-echo ultrasonics are much closer to V L111 than to V L100 , the V L-extremes in any cubic single crystal. Here, we experimentally confirm, using the technique of time-domain Brillouin scattering, the same tendency for NaCl exhibiting the opposite anisotropy type, A

This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 and 2019-2020 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. Support from Estonian Research Council grant PUT PRG 619 is gratefully acknowledged. The multi-anvil experiments at LMV were supported by the French Government Laboratory of Excellence initiative no ANR-10-LABX-0006, the Région Auvergne and the European Regional Development Fund (ClerVolc Contribution Number 478)., Electronic band structure in germanium nitride having spinel structure, γ-Ge3N4, was examined using two spectroscopic techniques, cathodoluminescence and synchrotron-based photoluminescence. The sample purity was confirmed by x-ray diffraction and Raman analyses. The spectroscopic measurements provided first experimental evidence of a large free exciton binding energy De≈0.30 eV and direct interband transitions in this material. The band gap energy Eg = 3.65 ± 0.05 eV measured with a higher precision was in agreement with that previously obtained via XES/XANES method. The screened hybrid functional Heyd–Scuseria–Ernzerhof (HSE06) calculations of the electronic structure supported the experimental results. Based on the experimental data and theoretical calculations, the limiting efficiency of the excitation conversion to light was estimated and compared with that of w-GaN, which is the basic material of commercial light emitting diodes. The high conversion efficiency, very high hardness and rigidity combined with a thermal stability in air up to ~ 700 °C reveal the potential of γ-Ge3N4 for robust and efficient photonic emitters. © 2021, The Korean Institute of Metals and Materials. Published under the CC BY license., Euratom research and training programme 2014-2018 633053; Eesti Teadusagentuur ANR-10-LABX-0006, PUT PRG 619; ERDF; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2.

International audience; Biocompatible polymerized 2-(hydroxyethyl) methacrylate (pHEMA) is a very popular material for medical applications. Despite different studies, realised recently, there are still many questions to be answered concerning the polymerisation processes of HEMA upon compression, which does not require an initiator [1]. For this reason, the application of non-destructive contactless laser ultrasonic techniques to the evaluation of HEMA properties looks very promising. In this work, we present the measurements of longitudinal sound velocity in HEMA in a diamond anvil cell (DAC), using well known sub-nanosecond experimental setup. First results obtained using picosecond ultrasonics are also presented. These results are compared then for a validation.

Context.The Extreme Ultraviolet Imager (EUI) is part of the remote sensing instrument package of the ESA/NASA Solar Orbiter mission that will explore the inner heliosphere and observe the Sun from vantage points close to the Sun and out of the ecliptic. Solar Orbiter will advance the “connection science” between solar activity and the heliosphere.Aims.With EUI we aim to improve our understanding of the structure and dynamics of the solar atmosphere, globally as well as at high resolution, and from high solar latitude perspectives.Methods.The EUI consists of three telescopes, the Full Sun Imager and two High Resolution Imagers, which are optimised to image in Lyman-αand EUV (17.4 nm, 30.4 nm) to provide a coverage from chromosphere up to corona. The EUI is designed to cope with the strong constraints imposed by the Solar Orbiter mission characteristics. Limited telemetry availability is compensated by state-of-the-art image compression, onboard image processing, and event selection. The imposed power limitations and potentially harsh radiation environment necessitate the use of novel CMOS sensors. As the unobstructed field of view of the telescopes needs to protrude through the spacecraft’s heat shield, the apertures have been kept as small as possible, without compromising optical performance. This led to a systematic effort to optimise the throughput of every optical element and the reduction of noise levels in the sensor.Results.In this paper we review the design of the two elements of the EUI instrument: the Optical Bench System and the Common Electronic Box. Particular attention is also given to the onboard software, the intended operations, the ground software, and the foreseen data products.Conclusions.The EUI will bring unique science opportunities thanks to its specific design, its viewpoint, and to the planned synergies with the other Solar Orbiter instruments. In particular, we highlight science opportunities brought by the out-of-ecliptic vantage point of the solar poles, the high-resolution imaging of the high chromosphere and corona, and the connection to the outer corona as observed by coronagraphs.

Time-domain Brillouin scattering uses ultrashort laser pulses to generate coherent acoustic pulses of picoseconds duration in a solid sample and to follow their propagation in order to image material inhomogeneities with sub-optical depth resolution. The width of the acoustic pulse limits the spatial resolution of the technique along the direction of the pulse propagation to less than several tens of nanometres. Thus, the time-domain Brillouin scattering outperforms axial resolution of the classical frequency-domain Brillouin scattering microscopy, which uses continuous lasers and thermal phonons and which spatial resolution is controlled by light focusing. The technique benefits from the application of the coherent acoustic phonons, and its application has exciting perspectives for the nanoscale imaging in biomedical and material sciences. In this study, we report on the application of the time-domain Brillouin scattering to the 3D imaging of a polycrystal of water ice containing two high-pressure phases. The imaging, accomplished via a simultaneous detection of quasi-longitudinal and quasi-shear waves, provided the opportunity to identify the phase for individual grains and evaluate their crystallographic orientation. Monitoring the propagation of the acoustic waves in two neighbouring grains simultaneously provided an additional mean for the localisation of the grain boundaries., Comment: 20 pages, 9 figures

Polysorbates are critical stabilizers in biopharmaceutical protein formulations. However, they may degrade in drug substance (DS) or drug product (DP) during storage. Degradation catalyzed by lipases present in host cell proteins (HCPs) is one suspected root cause. The purpose of this study was to develop an assay to detect lipolytic activity in biopharmaceutical DS and DP formulations. The assay is based on the hydrolysis of the lipase substrate 4-methylumbelliferyl oleate to yield the fluorescent product 4-methylumbelliferone. First, the assay components and their concentrations (buffer salts and pH, solvent and inhibitor Orlistat) were established and optimized using a model lipase (Porcine pancreatic lipase) and cell culture harvest fluid that exhibited lipolytic activity. The assay was then successfully applied and thereby qualified in protein formulations and at lipase concentrations possibly encountered in actual biopharmaceutical DS and DP formulations. The lipase assay can be used to detect lipolytic activity in intermediate and final DS, for example during process optimization in downstream purification, to better and specifically reduce the level, or deplete, lipases from HCPs. The assay is also suitable to be applied during root cause investigations related to polysorbate degradation in biopharmaceutical DP.

Aims. Metis is the first solar coronagraph designed for a space mission and is capable of performing simultaneous imaging of the off-limb solar corona in both visible and UV light. The observations obtained with Metis aboard the Solar Orbiter ESA-NASA observatory will enable us to diagnose, with unprecedented temporal coverage and spatial resolution, the structures and dynamics of the full corona in a square field of view (FoV) of ±2.9° in width, with an inner circular FoV at 1.6°, thus spanning the solar atmosphere from 1.7R⊙to about 9R⊙, owing to the eccentricity of the spacecraft orbit. Due to the uniqueness of the Solar Orbiter mission profile, Metis will be able to observe the solar corona from a close (0.28 AU, at the closest perihelion) vantage point, achieving increasing out-of-ecliptic views with the increase of the orbit inclination over time. Moreover, observations near perihelion, during the phase of lower rotational velocity of the solar surface relative to the spacecraft, allow longer-term studies of the off-limb coronal features, thus finally disentangling their intrinsic evolution from effects due to solar rotation.Methods. Thanks to a novel occultation design and a combination of a UV interference coating of the mirrors and a spectral bandpass filter, Metis images the solar corona simultaneously in the visible light band, between 580 and 640 nm, and in the UV H ILyman-αline at 121.6 nm. The visible light channel also includes a broadband polarimeter able to observe the linearly polarised component of the K corona. The coronal images in both the UV H ILyman-αand polarised visible light are obtained at high spatial resolution with a spatial scale down to about 2000 km and 15 000 km at perihelion, in the cases of the visible and UV light, respectively. A temporal resolution down to 1 s can be achieved when observing coronal fluctuations in visible light.Results. The Metis measurements, obtained from different latitudes, will allow for complete characterisation of the main physical parameters and dynamics of the electron and neutral hydrogen/proton plasma components of the corona in the region where the solar wind undergoes the acceleration process and where the onset and initial propagation of coronal mass ejections (CMEs) take place. The near-Sun multi-wavelength coronal imaging performed with Metis, combined with the unique opportunities offered by the Solar Orbiter mission, can effectively address crucial issues of solar physics such as: the origin and heating/acceleration of the fast and slow solar wind streams; the origin, acceleration, and transport of the solar energetic particles; and the transient ejection of coronal mass and its evolution in the inner heliosphere, thus significantly improving our understanding of the region connecting the Sun to the heliosphere and of the processes generating and driving the solar wind and coronal mass ejections.Conclusions. This paper presents the scientific objectives and requirements, the overall optical design of the Metis instrument, the thermo-mechanical design, and the processing and power unit; reports on the results of the campaigns dedicated to integration, alignment, and tests, and to the characterisation of the instrument performance; describes the operation concept, data handling, and software tools; and, finally, the diagnostic techniques to be applied to the data, as well as a brief description of the expected scientific products. The performance of the instrument measured during calibrations ensures that the scientific objectives of Metis can be pursued with success.

International audience; Solid argon, crystallizing above 1.3 GPa in the face-centered cubic (fcc) structure, is considered as the archetype of a simple classical solid [1] due to a highly symmetric distribution of electron density in the atoms having completely filled electron shells. For this reason, its behavior at high pressures was intensively investigated, also by theory, aiming understanding of evolution of solids upon a strong density increase. Symmetric electron shells and cubic structure of solid argon imply elastic isotropy of its crystals which, however, was not confirmed experimentally. Accordingly, a significant and growing-with-compression contribution of non-central interaction between the Ar-atoms was hypothesized as an explanation. Also, solid argon (as well as other solidified noble gases such as neon or helium) is extremely compressible and produces a quasi-hydrostatic environment, as has been concluded on the basis of sharpness of its X-ray diffraction peaks measured up to ~8 GPa [2]. However, the degree of its hydrostaticity at higher pressures was a subject of recent controversial discussions [3,4]. Due to a strong change of its lattice parameter with pressure, solid argon was also suggested and used as an internal pressure standard [5-7]. In the present work, we have measured the maximal and minimal values of the product of the refractive index n(P) with the longitudinal sound velocity V L (P), n(P)·V L (P), in single crystals of solid argon up to 64 GPa (Figure 1). For solid argon having cubic structure, the maximal sound velocity corresponds to that along the 111 direction in a single crystal, V L111 , and the minimal sound velocity to that along the 100 direction, V L100. The observed in this work strong deviation of V L111 (P) from V L100 (P) with pressure increase (Figure 1) indicated a strong elastic anisotropy of this solid, which deserves a special attention because, at the maximal pressure, the density of solid argon is more than twice higher than that just after its solidification at P=1.2 GPa [6]. It should be mentioned here that the detected strong elastic anisotropy of solid argon could not be falsified by the presence of the hcp phase, potentially coexisting with the main fcc phase at high pressures [8]. This is because our theoretical calculations showed that the hcp phase could not contribute to the measured-by-us strong deviation of the maximal and minimal n(P)·V L (P) values (Figure 1). In the present work we used the technique of time-domain Brillouin scattering (TDBS) [9] permiting 3D-scanning of the n·V L distribution in transparent samples with sub-μm resolution along the DAC axis, in addition to the micrometric lateral resolution [10-12]. Important is to mention that the spatial resolution of the TDBS technique did not degrade with pressure. These capabilities of the TDBS technique permitted us to pitch on the extremes of the n·V L values in the polycrystalline samples of fcc argon compressed in a DAC and to closely approach the n·V L111 and n·V L100 values up to the highest pressure of our work of 64 GPa (Figure 1). Calculation of the refractive index of the fcc argon as a function of pressure n(P) was another part of the work which allowed to derive V L (P) values from the the products n(P)·V L (P) obtained directly from the oscilating TDBS signals S(t). To obtain the reliable axially resolved data, we applied the same demanding time-frequency analysis of the raw TDBS signals S(t) as described in detail earlier [11]. Figure 1. Our experimental and theoretical data on longitudinal sound velocities of solid argon at high pressures. The experimental datapoints in terms of the product n·V L , obtained using the TDBS technique, are represented by triangles pointing up and down corresponding to n(P)·V L111 (P) and n(P)·V L100 (P), respectively. They are compared with the same theoretically-calculated values for the fcc phase (solid red lines) and hcp phase (dashed violet lines) Using the envelope method and our theoretical n(P) for the fcc phase we determined, with a high degree of confidence, pressure dependences of the fastest and

Single-crystal elastic moduli ${C}_{ij}$, shear modulus $G$, and Zener anisotropic ratio $A$ of solid argon having the face-centered cubic (fcc) structure were determined at high pressures between 12 and 64 GPa using a combination of experimental and theoretical approaches. The experimental data, namely, the maximal and minimal values of the product of the longitudinal sound velocity and refractive index $n\ifmmode\cdot\else\textperiodcentered\fi{}{V}_{L}$, were obtained from the 3D scanning of elastic inhomogeneities in compressed samples of argon using the technique of time-domain Brillouin scattering. These inhomogeneities, caused by elastic anisotropy of solid argon, were revealed to be about twice as strong as those reported in the earlier experiments using classical Brillouin light scattering (BLS). To derive the ${V}_{L}$ values, we used the refractive index obtained here from ab initio calculations which also permitted us to rule out any contribution to the amplitude of the observed elastic inhomogeneities of the hexagonal close-packed phase of argon, proposed to coexist with the fcc phase at high pressures. From the measured ${C}_{ij}(P)$, we derived pressure dependence of shear modulus of the fcc argon ${G}_{H}(P)$ using the Voigt-Reuss-Hill approximation and found a very good agreement with the earlier $G(P)$ obtained from shear sound velocities in the classical BLS measurements. Our results agree very well with the earlier predictions based on a relatively simple many-body model employing the Buckingham pair potential. Finally, our measurements show a much weaker change of the Cauchy discrepancy $({C}_{12}\ensuremath{-}{C}_{44}\ensuremath{-}2P)$ of the fcc argon with pressure than reported in all earlier experimental and theoretical works.

Organic polymerization remains a limiting step in the preparation of organic-inorganic hybrid materials with a strong concentration of the inorganic component. In this work, a high-pressure-ramp process was applied to achieve pHEMA-TiO2 nanoparticulate solids with an unprecedentedly high concentration (12 mol l-1) of the inorganic component, which is four times higher than that obtained after radical polymerization induced thermally or by photons. The inorganic nanoparticles underwent morphological and structural changes with an increase of Ti concentration above 1.5 mol l-1: they slightly coarsen and crystallize into an anatase polymorph. The material possesses a strong photochromic response related to the electron-hole separation at the organic-inorganic interface and can store 1e- per 5 Ti atoms. The electron storage capacity of the titania nanoparticles decreases upon crystallization.

Vickers indentation testing was applied to examine an additive-free monolithic sample of tantalum sesquinitride having orthorhombic U 2 S 3 type structure, η-Ta 2 N 3 , synthesised at high pressures and temperatures. Crystallisation of η-Ta 2 N 3 in form of elongated crystals and a high bulk to shear modulus ratio of 2.3–2.6, considered as a qualitative criterion of malleability, suggest elevated fracture toughness for this ceramic material. Here we measured Vickers hardness, H V , indentation size effect, and fracture toughness, K Ic-if , as well as their dependences on the surface self-healing (densification) due to mechanical polishing for a sample with the residual porosity of p =0.14. H V of η-Ta 2 N 3 was found to exhibit a moderate indentation size effect and approach, for the porous sample, H V (1)=16(1) GPa at the maximal load. K Ic-if was measured to be 4.6(2) MPa m 1/2 , comparable with the values reported for hexagonal Si 3 N 4 and SiC.

We report on a successful room-temperature polymerization of 2-(hydroxyethyl)methacrylate (HEMA) under high pressure. The polymerization is observed in a limited range of pressures 0.1 to 1.6 GPa without the use of any initiator. When the compressed sample is irradiated at 488 or 355 nm by a laser, the polymerization reaction rate is increased by a factor of 10 or 30, respectively. Moreover, the shift of the laser wavelength to the UV improves the polymerization yield of the recovered sample to 84%. The catalysis of the polymerization process by light results from a one-photon-assisted electron transfer to π* antibonding states of the monomer molecule. The observed polymerization is irreversible and almost complete, which makes this synthesis process suitable for applications.

Water ice is a molecular solid whose behavior under compression reveals the interplay of covalent bonding in molecules and forces acting between them. This interplay determines high-pressure phase transitions, the elastic and plastic behavior of H 2 O ice, which are the properties needed for modeling the convection and internal structure of the giant planets and moons of the solar system as well as H 2 O-rich exoplanets. We investigated experimentally and theoretically elastic properties and phase transitions of cubic H 2 O ice at room temperature and high pressures between 10 and 82 GPa. The time-domain Brillouin scattering (TDBS) technique was used to measure longitudinal sound velocities (V L) in polycrystalline ice samples compressed in a diamond anvil cell. The high spatial resolution of the TDBS technique revealed variations of V L caused by elastic anisotropy, allowing us to reliably determine the fastest and the slowest sound velocity in a single crystal of cubic H 2 O ice and thus to evaluate existing equations of state. Pressure dependencies of the single-crystal elastic moduli C ij (P) of cubic H 2 O ice to 82 GPa have been obtained which indicate its hardness and brittleness. These results were compared with ab initio calculations. It is suggested that the transition from molecular ice VII to ionic ice X occurs at much higher pressures than proposed earlier, probably above 80 GPa.

Electronic band structures of two novel semiconducting nitrides of the group-IV elements of Th3P4-type crystal structure, c-M3N4, where M[DOUBLE BOND]Zr or Hf, is investigated using an element specific soft X-ray spectroscopy for the first time. From the pairs of N 1s X-ray absorption and N 2p [RIGHTWARDS ARROW] 1s resonant X-ray emission spectra partial densities of states (PDOS) of nitrogen, predicted to be strongly hybridized with those of the metals, are obtained for both compounds. From these data the electronic band gaps of oxygen bearing c-Zr3N4 and of c-Hf3N4, predicted before to be direct or nearly direct, are derived to be Eg = 1.6 eV and Eg = 1.8 eV, respectively. While the experimentally determined Eg for c-Hf3N4 agrees with the theoretical one obtained using the local density approximation (LDA) method, the Eg measured for oxygen bearing c-Zr3N4 is significantly higher than those calculated using both the LDA and the generalized gradient approximation method. The examined compounds, having high hardness, elastic moduli and oxidation resistance, appear to be multifunctional materials suitable also for applications as (opto)electronic materials. Band gap evolution in c-M3N4 nitrides as a function of the cation type, Zr or Hf.

Cerium phosphide undergoes a unit-cell volume discontinuity without any structural phase transitions upon application of a high pressure of ∼10 GPa. This phenomenon is attributed to a change in the electronic charge distribution of the cerium in CeP, but to date no direct experimental verification for this hypothesis has been presented. Here, we report a Ce L3-edge X-ray absorption spectroscopy study under pressure, which provides direct compelling evidence of an electronic transition associated with the above-mentioned isostructural volume discontinuity. The present results should be relevant to the understanding of the phenomenon of pressure induced isostructural transitions involving unit-cell volume collapse.

International audience; Picosecond laser ultrasonics is an all-optical experimental technique based on ultrafast high repetition rate lasers applied for the generation and detection of nanometric in length coherent acoustic pulses. In optically transparent materials these pulses can be detected not only on their arrival at the sample surfaces but also all along their propagation path inside the sample providing opportunity for imaging of the sample material spatial inhomogeneities traversed by the acoustic pulse. Application of this imaging technique to polycrystalline elastically anisotropic transparent materials subject to high pressures in a diamond anvil cell reveals their significant texturing/structuring at the spatial scales exceeding dimensions of the individual crystallites.

Among binary compounds, there is a high potential for discovery of novel members (polymorphic phases or compounds) of the nitrides of transition metals group due to a pronounced dependence of the oxidation state of the metals (M) on pressure. The power of high pressure–high temperature (HP-HT) route for synthesis of binary nitrides has already been demonstrated by the discovery of cubic nitrides of the group 4 and 14 elements, of crystalline polymorphs of P3N5, and by reports on formation of four noble metal nitrides. It is anticipated that such HP products exhibit, in addition to enhanced elastic and mechanical behavior, other functional properties making them interesting for industrial applications. Here, HP–HT synthesis research is extended to nitrides of group 5 elements, resulting in the discovery of a novel hard tantalum nitride, exhibiting U2S3 structure: η-Ta2N3 (Pbnm, a = 8.1911(17) A, b = 8.1830(17) A, c = 2.9823(3) A). The stoichiometry is supported by two independent means, verifying that η-Ta2N3 is the first thermodynamically stable transition metal nitride with a N:M ratio exceeding 4:3. Due to its high hardness and peculiar texture (needle-like and granular crystallites), η-Ta2N3 may find practical applications as a hard fracture resistant material.

This paper presents our recent results on synthesis and properties of high-pressure cubic zirconium(IV)- and hafnium(IV) nitrides having Th3P4-type structure, c-M3N4 (M = Zr or Hf). c-M3N4 were first synthesized in microscopic amounts in a laser-heated diamond anvil cell (LH-DAC) at pressures above 15 GPa and temperatures above 2500 K. Further, macroscopic amounts of c-Hf3N4 and of a new oxygen-bearing zirconium nitride, c-Zr2.86(N0.88O0.12)4, were synthesized at 12 GPa and about 1900 K using a multi-anvil apparatus. The lattice parameter of c-Hf3N4 was determined to be a0 = 670.2(1) pm. The a0 of c-Zr2.86(N0.88O0.12)4 of 675.49(1) pm was found to be slightly larger than that of c-Zr3N4 (674.0(6) pm). The bulk moduli, B0, of 219 GPa for c-Zr2.86(N0.88O0.12)4 and of 227 GPa for c-Hf3N4 were obtained from compression measurements. Combining the compression and indentation data we determined for c-Zr2.86(N0.88O0.12)4 its isotropic shear modulus G0 = 96 GPa. Finally, Vickers microhardness, indentation fracture toughness and thermal expansion of c-Zr2.86(N0.88O0.12)4 were measured.

(Figure Presented) Extreme chemistry: The carbon nitride imide C 2 N 2 (NH) is synthesized from the single-source precursor 1-cyanoguanidine under high-pressure and high-temperature conditions in a laser-heated diamond-anvil cell. Characterization of single crystals recovered at ambient conditions reveals that the new compound adopts a defect wurtzite structure (see picture). © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.

The time-domain Brillouin scattering technique, also known as picosecond ultrasonic interferometry, allows monitoring of the propagation of coherent acoustic pulses, having lengths ranging from nanometres to fractions of a micrometre, in samples with dimension of less than a micrometre to tens of micrometres. In this study, we applied this technique to depth-profiling of a polycrystalline aggregate of ice compressed in a diamond anvil cell to megabar pressures. The method allowed examination of the characteristic dimensions of ice texturing in the direction normal to the diamond anvil surfaces with sub-micrometre spatial resolution via time-resolved measurements of the propagation velocity of the acoustic pulses travelling in the compressed sample. The achieved imaging of ice in depth and in one of the lateral directions indicates the feasibility of three-dimensional imaging and quantitative characterisation of the acoustical, optical and acousto-optical properties of transparent polycrystalline aggregates in a diamond anvil cell with tens of nanometres in-depth resolution and a lateral spatial resolution controlled by pump laser pulses focusing, which could approach hundreds of nanometres.

Since the discovery of spinel nitrides in 1999, there has been a lot of effort in basic science to further develop advanced nitrides and electronic nitrides. The aim and scope of the research in this field is to synthesize novel nitrides for structural and functional applications. Silicon-based spinel nitrides combine ultrahigh hardness with high thermal stability against decomposition in different environments, suggesting potential applications as cutting tools. These materials are also expected to show interesting optoelectronic properties, which may lead to applications in light-emitting diodes. The synthesis of spinel silicon and germanium nitrides at ultrahigh pressures and temperatures, as well as the successful synthesis of tin nitride at ambient pressure, has created an enormous impact on both the basic science and technological development of advanced nitrides. Moreover, the discovery of novel phases of transition metal nitrides, such as Zr3N4 and Hf3N4 with a Th3P4 structure, as well as the recently reported nitrides of Pt and Mo, demonstrates the scientific potential of highpressure synthesis techniques in the field of materials science. Here, the state of the art in the field of novel hard materials based on nitrides synthesized reproducibly under high pressure is reviewed.

Pressure dependence of the specific volume, V ( P ) , of the recently discovered high-pressure compound Hf3N4 having cubic Th3P4-type structure (c- Hf3N4) has been measured at room temperature up to 43.9 GPa in a diamond anvil cell using energy-dispersive X-ray powder diffraction combined with synchrotron radiation. A least-square fit of the Birch–Murnaghan equation of state to the experimental V ( P ) -data yielded for c- Hf3N4 the bulk modulus of B 0 = 227 ( 7 ) GPa and its first pressure derivative of B 0 ′ = 5.3 ( 6 ) . For B 0 ′ fixed at 4 the bulk modulus of c- Hf3N4 was determined to be B 0 = 241 ( 2 ) GPa . The obtained B 0 -value is only insignificantly below that estimated in preliminary measurements. Existing theoretical predictions for B 0 scatter around the present experimental data. The observation of a high bulk modulus of c- Hf3N4 supports the suggestion that this compound could have high hardness.

The stability of methane (CH4), ethane (C2H6), octane (C8H18), decane (C10H22), octadecane (C18H38), and nonadecane (C19H40) were studied in a CO2-laser heated diamond anvil cell at pressures up to 25 GPa and temperatures up to about 7300 K. Methane and ethane were found to decompose to form hydrogen and diamond. Substantially greater yields of diamond were obtained from the longer chain alkanes.

A simple process to synthesize Zr3N4 and nitrogen-rich Hf3N4 powders via ammonolysis of metal dialkylamides, i.e. Zr(NEt2)4 and Hf(NEt2)4, at temperatures below 700 °C is presented. The obtained nitrides have a rhombohedrally distorted NaCl-type structure, which has previously been reported only for nitrogen-rich films of these nitrides. Regardless of the atmosphere (N2 and He), the Zr3N4 starts to decompose above about ∼ 650 °C and achieves the highest decomposition rate at about 900 °C, finally yielding the mononitride ZrN. Both Zr3N4 and Hf3N4 powders are nanocrystalline with the crystal size of about 2 nm.

A spectroscopic study of cubic silicon nitride (γ-Si3N4) at cryogenic temperatures of 8 K in the near IR - VUV range of spectra with synchrotron radiation excitation provided the first experimental evidence of direct electronic transitions in this material. The observed photoluminescence (PL) bands were assigned to excitons and excited "Equation missing" and "Equation missing" centers formed after the electron capture by neutral structural defects. The excitons are weakly quenched on neutral "Equation missing" and strongly on charged "Equation missing" defects. The fundamental band-gap energy of 5.05 ± 0.05 eV and strong free exciton binding energy ~0.65 eV were determined. The latter value suggests a high efficiency of the electric power transformation in light in defect-free crystals. Combined with a very high hardness and exceptional thermal stability in air, our results indicate that γ-Si3N4 has a potential for fabrication of robust and efficient photonic emitters.

The bulk and shear moduli of dense polycrystalline oxygen-bearing c-Zr3N4 were determined to be B0 = 217(20) GPa and G0 = 163(9) GPa, respectively, using laser ultrasonic technique combined with a numerical analysis of the sample porosity. While the obtained B0 is in excellent agreement with the earlier high-pressure compression measurements, the G0 value is 70% higher than the previous estimate. Since both G0 and hardness of the dense c-Zr3N4 exceed those of γ-Si3N4, c-Zr3N4 vies for the rank of the third hardest material after diamond and cubic BN. Our results also support the suggestion that shear modulus is a robust predictor of hardness. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The third known polymorph of silicon nitride, which is cubic and was only recently discovered, has been prepared from two further, different precursors—Si2N2(NH) and a-Si3N4—in a high-pressure, high-temperature synthesis using multi-anvil presses. The synthesis and characterization of the products is described, which included a structural determination by Rietveld refinement of powder X-ray diffraction data. Spinel-type c-Si3N4 is significantly harder than the α and β phases and may possibly find applications as an ultrahard material.

The two known phases of germanium nitride (Ge3N4) have hexagonal and trigonal symmetries and consist of three-dimensional networks of corner-connected Ge–N tetrahedra. A new cubic spinel phase (space-group Fd3m, a0=8.3 A, Z=8, ρ=6.36 g/cm3) containing Ge–N octahedra and tetrahedra in a 2:1 ratio was synthesized from elemental germanium and molecular nitrogen starting materials in a laser-heated diamond-anvil cell above 14 GPa. This phase is isostructural to the recently discovered cubic spinel phase of Si3N4.

The high abundance of both nickel and cobalt and the chondritic Ni/Co ratio found in samples derived from the Earth's mantle are at odds with results from laboratory-based partitioning experiments conducted at pressures up to 27 GPa (refs 1,2). The laboratory results predict that the mantle should have a much lower abundance of both Ni and Co and a considerably lower Ni/Co ratio owing to the preferential partitioning of these elements into the iron core. Two models have been put forward to explain these discrepancies: homogeneous accretion3,6 (involving changes of the Ni and Co partition coefficients with oxygen and sulphur fugacities, pressure and temperature) and heterogeneous accretion7,9 (the addition of chondritic meteorites to the mantle after core formation was almost complete). Here we report diamond-cell experiments on the partitioning of Ni and Co between the main lower-mantle mineral ((Mg,Fe)SiO3-perovskite) and an iron-rich metal alloy at pressures up to 80 GPa (corresponding to a depth of ∼1,900 km). Our results show that both elements become much less siderophilic with increasing pressure, such that the abundance of both Ni and Co and the Ni/Co ratio observed in samples derived from the Earth's mantle appear to indeed be consistent with a homogeneous accretion model.

The stability field of Mg3Al2Si3O12-pyrope was examined for the first time under hydrostatic pressure conditions in a CO2-laser heated diamond cell in the pressure range 21–30 GPa between 2300 and 3200 K. The phases were characterized using Raman and fluorescence spectroscopy. With increasing pressure pyrope transforms to an ilmenite phase above ∼21.5 GPa, to perovskite plus ilmenite above ∼24 GPa, and to perovskite above 29 GPa. The pressures of the first occurrence of perovskite in this study are about 2 GPa above the corresponding phase boundary between end-member MgSiO3-ilmenite and perovskite. A small amount of Al2O3 coexists with perovskite up to 43 GPa, as evident from fluorescence spectra resembling those of ruby, but above 43 GPa the entire Al2O3 content of the pyrope starting material is accommodated in the perovskite structure.

Melting temperatures of CaSiO3 perovskite were measured between 160 and 430 kbar in a diamond anvil cell under hydrostatic, inert conditions using CO2-laser heating. The melting temperatures are higher than those obtained in previous YAG-laser heating experiments [Shen and Lazor, 1995], where chemical reactions of the sample with rhenium might have caused a lowering in the melting temperatures. The melting temperatures of CaSiO3 perovskite are slightly higher than those of (Mg,Fe)SiO3 perovskite [Zerr and Boehler, 1993], thus making the two major minerals of the lower mantle Mg-Si-perovskite and magnesiowusite the low-melting components. First in-situ measurements of the eutectic melting temperatures of these two minerals are presented. The data suggest that eutectic melting depression in the lower mantle may be insignificant. An alternate solution for the extrapolation of the measured melting temperatures to higher pressures, based on recent observations on the highly compressible alkali halides, yields melting temperatures at the bottom of the lower mantle below 6000 K.

PtAs2 appears to be the least compressible known arsenide with a bulk modulus of 220(5) GPa and a shear modulus of between 64 and 77 GPa. PtAs2 has a hardness of 11(1) GPa, which is remarkably high for an arsenide. These elastic and mechanical properties in combination with the known chemical inertness and the small indirect band gap add interest to the use and occurrence of PtAs2 at Pt-GaAs contacts in transistors. We note the modest fracture toughness of 1.1–1.6 MPa m1/2 of PtAs2.

In this Letter using experimental and theoretical methods, we show that the solid solutions of group 14 nitrides having spinel structure ($\ensuremath{\gamma}\mathrm{\text{\ensuremath{-}}}{M}_{3}{\mathrm{N}}_{4}$ where $M=\mathrm{Si}$, Ge, Sn) exhibit mainly direct electronic band gaps with values that span the entire visible wavelength region, making these hard and thermally stable materials suitable for optoelectronic devices and, in particular, lighting applications. Using the simulated band structure, we also calculate the exciton binding energy. The combination of large exciton binding energies and the tunable electronic band gaps in the visible range makes these binary spinel nitrides and their solid solutions a new class of multifunctional materials with optoelectronic properties that can be engineered to suit the desired application.

Seismic anomaly structures at the bottom of the lower mantle may be interpreted in terms of large temperature variations based on new laboratory data at very high pressure: (1) sound velocity measurements at mantle pressures show an increase in (∂lnϱ/∂lnν)P with depth (this and the strong decrease in the thermal expansion coefficient yield thermal anomalies δT of > 1000 K using the seismically measured lateral velocity variations); (2) high melting gradients in Fe and FeO compounds measured at core pressures yield a temperature increase across the core-mantle boundary in excess of 1300 K; (3) melting temperatures of (Mg,Fe)SiO3 perovskite measured to deep mantle conditions extrapolate to > 7500 K at the bottom of the mantle and result in TTm-values between 0.3 and 0.4 (this may strongly decrease the temperature dependence of viscosity if the average temperature profile of the lower mantle is nearly adiabatic, and if the viscosity systematics found at low pressure are applicable at lower mantle conditions); and (4) for dry conditions, MgSiO3, in contrast to MgO, does not react with molten iron at pressures of the core-mantle boundary (this suggests, that chemical interactions between the mantle and the core play a minor role).

The coesite-stishovite phase boundary in the temperature range 2300–2630°C was examined in a CO2-laser heated diamond anvil cell using argon as a pressure medium. Phase identification was provided by Raman spectroscopy of the temperature quenched samples at pressure. Our results suggest a coesite-stishovite phase boundary curve described by P(GPa) = 8.1 + 0.001T(°C) in good agreement with Yagi and Akimoto's (1976) estimate at lower temperatures. The slope of this curve is less than one half that determined recently by Zhang et al. [1993, 1994] in a multi-anvil press.

The evolution of X-ray diffraction patterns in FeBO3 under high pressures up to 63 GPa has been investigated at room temperature in a diamond anvil cell. A structural phase transition at a pressure of 53±2 GPa was found for the first time. The transition is of the first-order type with a hysteresisless drop of the reduced unit cell volume of about 8.6%. Apparently, the transition is isostructural. At pressures below the transition, the equation of state for FeBO3 was fitted. In the third-order approximation of the Birch-Murnagan equation of state, the bulk modulus K and its first pressure derivative K′ were found to be 255±25 GPa and 5.0±1.2, respectively.

The third known polymorph of silicon nitride, which is cubic and was only recently discovered, has been prepared from two further, different precursors—Si2N2(NH) and a-Si3N4—in a high-pressure, high-temperature synthesis using multi-anvil presses. The synthesis and characterization of the products is described, which included a structural determination by Rietveld refinement of powder X-ray diffraction data. Spinel-type c-Si3N4 is significantly harder than the α and β phases and may possibly find applications as an ultrahard material.

International audience; In addition to pressure and temperature effects, shear strain has been proposed to play an important role in the initiation and decomposition mechanisms of energetic materials. To study the effect of shear strain in more detail, a shear diamond anvil cell has been developed. In this paper, we present a Raman spectroscopy study of the effects of shear strain on the high-pressure behaviour of nitromethane (NM). Two major effects are observed in our experiments. The first one is a lowering of the pressures at which the different structural modifications of NM occur. The second one is observed at 28 GPa, where the sample decomposes suddenly just after shear application. Examination of the black residue showed that it is composed of carbon, as indicated by the Raman spectrum.