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Due to their large bandgaps, multiferroic oxides, the promising candidates for overcoming the disadvantages of metal-halide perovskites as light absorbers, have so far very limited use in solar cell applications. Previous investigations demonstrate that high pressure represents an efficient tool for tuning the bandgap of multiferroic Mn3TeO6 (MTO). However, the underlying mechanism of the giant bandgap reduction discovered in MTO remains unclear, which critically prevents the design of next-generation light absorbers. In this study, we performed in situ x-ray diffraction analyses on the structure evolution of MTO upon compression and decompression, discovering a sequence of irreversible phase transitions R 3 ¯ →C2/c→P21/n. The experimental results, supported by electronic structure calculations, show the shortening of Mn–O–Mn bonding, and, to a lower extent, the decrease in connectivity of octahedra across the phase transition, explain the giant bandgap reduction of MTO. These findings will facilitate the design and synthesis of next-generation light absorbers in solar cells. [ABSTRACT FROM AUTHOR]

Bi2NiTiO6 compound which shows both magnetic (TM = 58 K) and ferroelectric properties (TC = 513 K) was synthesized under high pressure of 5 GPa and temperature of 1273 K. The crystal structure, as determined by X-ray powder diffraction and neutron powder diffraction, is a distorted A(B1B2)O3 type perovskite with space group Pn21a. Structural evolution of multiferroic Bi2NiTiO6 shows that there are two isostructural phase transitions at ∼2 GPa and ∼15 GPa under high pressure and at room temperature and indicates that isostructural phase transitions occurred with temperature higher than 823 K under ambient condition. All the isostructural phase transitions come from the Bi ion discontinuous shift, which identifies the phase transition at ∼15 GPa and at temperature higher than 823 K are the same. Using a modified high-T Birch-Murnaghan equation of state and a thermal-pressure approach, we have derived the thermoelastic parameters of high pressure phase Bi2NiTiO6, including the ambient bulk modulus K0, temperature derivative of bulk modulus at constant pressure, volumetric thermal expansivity, pressure derivative of thermal expansion, and temperature derivative of bulk modulus at constant volume. [ABSTRACT FROM AUTHOR]

The pressure-induced structural transformations of CdS have been investigated using synchrotron x-ray diffraction in a diamond anvil cell up to 104 GPa and the density functional theory calculations. The x-ray diffraction experiments show that CdS is stable with the wurtzite-type structure at ambient conditions. The wurtzite-type phase transforms to NaCl-type structure at 3 GPa, which is followed by a second phase transition at 52.3 GPa. In the diffraction patterns, the peak-splitting is observed, indicating that the high-pressure phase appearing at 52.3 GPa is the Pmmn structure, rather than the Cmcm phase reported earlier. With increasing pressure, the lattice parameter a of the Pmmn phase increases abnormally, contrary to decrease of b and c axes. Our calculations reveal that the abnormal change of the a-axis could be related to the pressure-induced crystal structural change. The bulk modulus (B0), is 64.3(9) GPa for wurzite-type phase, 105(2) GPa for NaCl-type phase, and 54(4) GPa for the Pmmn phase, respectively. [ABSTRACT FROM AUTHOR]

The structural stability of cubic Ho2O3 under high pressure has been investigated by angle-dispersive x-ray diffraction (ADXD) in a diamond anvil cell up to 63.0 GPa at room temperature. The diffraction data reveal two structural transformations on compression. The structural transformation from a cubic to a monoclinic structure starts at 8.9 GPa and is complete at 16.3 GPa with a ∼8.1% volume collapse. A hexagonal phase begins to appear at ∼14.8 GPa and becomes dominant at 26.4 GPa. This high-pressure hexagonal phase with a small amount of retained monoclinic phase is stable up to the highest pressure of 63.0 GPa in this study. After release of pressure, the hexagonal phase transforms to a monoclinic structure. A third-order Birch-Murnaghan fit yields zero pressure bulk moduli (B0) of 206(3), 200(7) and 204(19) GPa and their pressure derivatives (B0') of 4.8(4), 2.1(4), 3.8(5) for the cubic, monoclinic and hexagonal phases, respectively. Comparing with other rare-earth sesquioxides, it is suggested that the transition pressure from cubic to monoclinic phase, as well as the bulk modulus of the cubic phase, increases with the decreasing of the cation radius of rare-earth sesquioxides. [ABSTRACT FROM AUTHOR]

In situ X-ray diffraction and Raman scattering experiments using a diamond anvil cell revealed that Im-3-type KSbO3 remains stable up to 40.5 GPa with a bulk modulus K0 = 101.6 (7) GPa. Rietveld structure refinements and mode Grüneisen parameters suggested that the stability mechanism of this three-dimensional cubic tunnel structure was attributed to the isotropic compression for all types of Sb-O bonding in the unit of SbO6 octahedron. Isotropic structure adjustment with external pressure reflected the nature that Im-3-type KSbO3 model structure has a high ionic tolerance with a change in the chemical pressure in the isomorphous substitutions. [ABSTRACT FROM AUTHOR]

The thermal reaction properties of the aluminum nanoparticles/copper (II) oxide nanoparticles/poly(vinylidene fluoride) (Al-NPs/CuO-NPs/PVDF) nanocomposite (mass ratio of Al-NPs/CuO-NPs/PVDF = 20/60/20) were investigated by means of thermogravimetry-differential scanning calorimetry-mass spectrometry (TG/DSC-MS) and X-ray diffraction (XRD) analysis. Al-NPs/PVDF (mass ratio of Al-NPs/PVDF = 50/50) and CuO-NPs/PVDF (mass ratio of CuO-NPs/PVDF = 75/25) nanocomposites were also prepared as a comparison. It is observed that PVDF in the Al-NPs/PVDF nanocomposite acts as an oxidizer. The fluorine ions/fluorinated gases formed at elevated temperatures react with the AlO shell leading to the formation of aluminum fluoride (AlF). The oxide shell is degraded from the reaction between fluoride ions and AlO, leaving the core Al available for reaction with fluorine ions/fluorinated gases. H ( m/z = 2), OH ( m/z = 17), HO ( m/z = 18), HF ( m/z = 20), CF ( m/z = 31) and CHF ( m/z = 33) fragments were detected in the gaseous products. For CuO-NPs/PVDF nanocomposite, oxygen was released due to the decomposition of CuO to CuO and then Cu metal, oxidizing hydrocarbon groups in PVDF. Species of OH ( m/z = 17), HO ( m/z = 18), CO ( m/z = 44), CHF ( m/z = 45) and HF ( m/z = 20) were detected in the gaseous products. The final reduction product of CuO is Cu metal. It is observed that PVDF in the Al-NPs/CuO-NPs/PVDF nanocomposite acts as both oxidizer and reducer in the thermal decomposition. Below 550 °C, PVDF is oxidized by CuO-NPs and oxidizing Al-NPs at the same time, resulting mass reduction. After 550 °C, the remaining Al-NPs and copper (I)/copper (II) oxide will proceed the exothermic solid-state thermite reaction. OH ( m/z = 17), HO ( m/z = 18), CO ( m/z = 44), CHF ( m/z = 45) and HF ( m/z = 20) were the main products of the decomposition of Al-NPs/CuO-NPs/PVDF nanocomposite. [ABSTRACT FROM AUTHOR]

The high pressure behaviour of a cubic dense inorganic–organic framework [DABCOH22+][K(ClO4)3] (DABCOH22+ = diazabicyclo[2.2.2]octane-1,4-diium) has been systematically studied via synchrotron X-ray powder diffraction, over the range of 0–3.12 GPa. The framework [DABCOH22+][K(ClO4)3] shows a more rigid response, with a bulk modulus of 30(1) GPa and an axial compressibility of 7.6(4) × 10−3 GPa−1, compared with ZIF-8 and the dense hybrid solar cell perovskite CH3NH3PbI3. Density functional theory calculations reveal that the structural change in [DABCOH22+][K(ClO4)3] is attributed to the contraction of the KO12 polyhedra, which consequently results in the rotation of the perchlorate linkers and synergistic movement of the DABCOH22+ guest. Further extensive theoretical calculations of full elastic tensors give full mapping of the Young's moduli, shear moduli and Poisson's ratios of [DABCOH22+][K(ClO4)3], which are in the range of 31.6–36.6, 12.3–14.6 GPa and 0.2–0.32, respectively. The Young's and shear moduli of [DABCOH22+][K(ClO4)3] are larger than those of cubic MOF-5, ZIF-8 and CH3NH3PbI3. In addition, the narrow range of Poisson's ratios in [DABCOH22+][K(ClO4)3] indicates its very isotropic nature in response to biaxial stress. [ABSTRACT FROM AUTHOR]

ZnS nanotetrapods synthesized via a solvothermal route have a octahedral core with a zincblende (ZB) structure and four hexprism-shaped arms consisting of alternately stacking ZB and wurtzite (WZ) phases, where the WZ phase has a higher volume percentage.In situangular-dispersive X-ray diffraction (ADXRD) measurements were carried out to study the structural behavior of ZnS nanotetrapods under high pressure up to 41.3 GPa. The initial WZ structure exhibits a very high mechanical stability to ∼11.3 GPa. Both the WZ and ZB structures transform to the rocksalt (RS) structure at ∼15.4 GPa. The bulk moduli of the WZ (148.2 ± 8.9 GPa) and RS (165.6 ± 9.9 GPa) phases are both larger than the previously reported values. These phenomena are discussed based on the alternating epitaxial growth of the WZ and ZB phases in the arms of nanotetrapods. Our study suggests that the internal structure of nanomaterials could also greatly affect their stability and transition behavior. [ABSTRACT FROM PUBLISHER]

VF3-type FeF3 is generally considered as a perovskite with a completely vacant A site. The high-pressure structural evolution of FeF3 has been studied by both X-ray diffraction and theoretical simulation up to 62.0 GPa. Experimental and theoretical results demonstrate that VF3-type FeF3 is stable up to 50 GPa. The structural evolution presents three features at different pressure ranges. At P < 10 GPa, the volume reduction is dominated by the FeF6 octahedral rotation, and a small octahedral strain develops upon compression, which represents an elongation of FeF6 octahedra along the c axis. Between 10 and 25 GPa, the volume reduction is mainly attributed to the Fe-F bond length decreasing, and the octahedral strain gradually disappears. Between 25 and 50 GPa, an octahedral elongation along the a axis quickly develops, resulting in a substantial structural distortion. Structural instability is predicted at P > 51 GPa on the basis of a soft mode occurring in phonon calculations. The pressure-volume relationship is described by a third-order Birch-Murnaghan equation-of-state with B0 = 14 (1) GPa, B0′ = 17 (1) by experiment and B0 = 10.45 (1) GPa, B′10 = 12.13 (1) by calculation. [ABSTRACT FROM AUTHOR]

PbTe has been investigated using synchrotron X-ray diffraction (XRD) in a diamond anvil cell under quasi-hydrostatic pressures up to 50 GPa. Upon compression to 6.6 GPa, the initial NaCl phase transforms to an intermediate phase, which is confirmed to be an orthorhombic structure with a space group Pnma. At 18.4 GPa, the intermediate Pnma phase undergoes a phase transition to the CsCl structure. The systemic analysis of the crystal structures between the NaCl and intermediate phases indicates that the structure of the Pnma phase could be derived from the distortion of the NaCl structure. The bulk modulus of the CsCl phase isB0=52(2) GPa withV0=60.8(4) Å3andB′0=4.0 (fixed), slightly larger than the NaCl phase (B0=44(1) GPa) and the intermediate phase (B0=49(3) GPa). [ABSTRACT FROM AUTHOR]

High-pressure single-crystal diffraction experiments often suffer from the crushing of single crystals due to the application of high pressure. Consequently, only diffraction data resulting from several particles in random orientations is available, which cannot be routinely indexed by commonly used methods designed for single-crystal data. A protocol is proposed to index such diffraction data. The techniques of powder pattern indexing are first used to propose the possible lattice parameters, and then a genetic algorithm is applied to determine the orientation of the reciprocal lattice for each of the particles. This protocol has been verified experimentally. [ABSTRACT FROM AUTHOR]

BaWO4-II has been synthesized at 5 GPa and 610°C. Its high pressure behavior was studied by in situ synchrotron X-ray diffraction measurements at room temperature up to 17 GPa. BaWO4-II retains its monoclinic structure. Bulk and axial moduli determined by fitting a third-order Birch–Murnaghan equation of state to lattice parameters are: K 0=86.2±1.9 GPa, K 0(a)=56.0±0.9 GPa, K 0(b)=85.3±2.4 GPa, and K 0(c)=146.1±3.2 GPa with a fixed K′=4. Analysis of axial compressible modulus shows that the a-axis is 2.61 times more compressible than the c-axis and 1.71 times more compressible than the b-axis. The beta angle decreases smoothly between room pressure and 17 GPa from 93.78° to 90.90°. [ABSTRACT FROM AUTHOR]

Ternary Zr49Cu44Al7 metallic glass matrix composite rods with CuZr nano-phase, exhibiting an elastic strain of 1.6% and a high strength of 1.78 GPa, have been manufactured. The structural evaluation of the ternary metallic glass matrix composite under high pressure has been investigated using angle dispersive X-ray diffraction with a synchrotron radiation source. The investigation shows that the amorphous matrix structure is stable under pressures up to 40.8 GPa at room temperature. No pressure induced CuZr nano-phase disappearing or growing was detected. According to the Bridgeman equation of state, the bulk modulus B0 =115.2 GPa has been obtained. [ABSTRACT FROM AUTHOR]

Investigations of the equation of state of tungsten tetraboride (WB4) have been performed under nonhydrostatic compression to 85.8 GPa using radial x-ray diffraction techniques in a diamond anvil cell at room temperature. The hexagonal structure of WB4 is found to be stable up to the highest pressure of 85.8 GPa. The radial x-ray diffraction data yield a bulk modulus K0 = 319(5) GPa with K0′ = 4.1(0.2) at ψ = 54.7°. With a fixed K0′ of 4, the derived K0 is 323(1) GPa. The bulk modulus obtained from fits of diffraction data at ψ = 0° and 90° is 196(6) GPa and 507(13) GPa, respectively. The values gradually increased from ψ = 0° to 90°, showing the compressibility of the sample strongly depends on the stress environment. In addition, the compressibility of the unit cell axes (a- and c-axes) of WB4 demonstrates an almost isotropic nature with pressure increasing. [ABSTRACT FROM AUTHOR]

The pressure-induced phase transition of the hexagonal manganite ErMnO3 has been investigated using the synchrotron x-ray diffraction technique up to 57.6 GPa in a diamond anvil cell. The hexagonal structure exhibits anisotropic compression behavior. The bulk modulus (B0) is 168(3) GPa with B0′ = 4.0 (fixed). At room temperature, ErMnO3 undergoes a hexagonal-to-orthorhombic phase transition at ∼20.2 GPa, but coexists with the orthorhombic phase up to the highest pressure of 57.6 GPa. When laser-heated to 1500-2000 K, the hexagonal ErMnO3 transforms to a denser orthorhombic perovskite structure completely at ∼17 GPa, accompanied by ∼11% volume reduction. The distortion and tilts of the octahedra MnO6 in the orthorhombic structure decrease with increasing pressure. The bulk modulus of the orthorhombic structure is 214(4) GPa with B0′ = 4.0 (fixed), larger than that of the hexagonal structure. The orthorhombic structure ErMnO3 is stable at least up to ∼45 GPa and can be quenched. [ABSTRACT FROM AUTHOR]

Fluorite phase CeO2 is compressed non-hydrostatically up to 27 GPa using a diamond anvil cell until the transition to α-PbCl2 phase occurred. The compressive strength (t) of CeO2 as a function of pressure is determined by the line width analysis of the high pressure angle dispersive x-ray diffraction patterns. The strength of CeO2 increases quickly below 3.30 GPa and reaches a plateau region at high pressures. A procedure combined the line width analysis and the line shift analysis together, based on the non-hydrostatic data to obtain the corresponding lattice parameter under hydrostatic pressures, is proposed and applied to the case of CeO2 sample. The bulk modulus and its pressure derivative of fluorite phase CeO2 (K0 = 235 (18) GPa, K0′ = 3.67) are obtained by fitting the P-V results into Vinet equation of state. A discussion of the pressure dependence of α, which determines the relative weights of the isostress and isostrain conditions across the grain boundary in an actual case, is presented. [ABSTRACT FROM AUTHOR]

The structural stability of hexagonal Nd2O3 under pressure has been investigated by in situ synchrotron angle dispersive x-ray diffraction and Raman spectroscopy up to 53.1 GPa and 37.0 GPa, respectively. Rietveld analysis of the x-ray diffraction data indicate that the hexagonal Nd2O3 undergoes an isostructural phase transition in the pressure range from 10.2 to 20.3 GPa, accompanied by anomalous lattice compressibility and pressure-volume curve. A third-order Birch-Murnaghan fit based on the observed Pressure-Volume data yields zero pressure bulk moduli (B0) of 142(4) and 183(6) GPa for the low and high pressure hexagonal phases, respectively. Raman spectroscopy confirms this isostructural transition, the pressure dependence of the Raman modes display noticeable breaks in the pressure range of 9.7-20.9 GPa, which is consistent with the change of Nd-O bond length. The pressure coefficients of Raman peaks and the mode Grüneisen parameters of different Raman modes were also determined. [ABSTRACT FROM AUTHOR]

Negative linear compressibility (NLC), a rare and important mechanical effect with many application potentials, in a crystal of α-BiB3O6 (BIBO) is comprehensively investigated using first-principles calculations and high-pressure synchrotron X-ray diffraction experiments. The results indicate that the BIBO crystal exhibits the second largest NLC among all known inorganic materials over a broad pressure range. This unusual NLC behaviour is due to the rotation and displacement of the rigid [BO3] and [BO4] building units that result in hinge motion in an umbrella-like topology. More importantly, the parallel-polar lone-pair electrons on the Bi3+ cations act as 'umbrella stands' to withstand the B-O hinges, thus significantly enhancing the NLC effect. BIBO presents a unique example of a 'collapsible umbrella' mechanism for achieving NLC, which could be applied to other framework materials with lone-pair electrons. [ABSTRACT FROM AUTHOR]

The effectiveness of Cu-ZnO-ZrO 2 (CZZ) catalysts is largely influenced by the cooperative interaction between the three components. This study involved the preparation of various CZZ catalysts by altering the molar ratio of Cu/Zn to adjust the ternary synergy of Cu-ZnO-ZrO 2 , with the aim of examining its impact on the hydrogenation of CO 2 to methanol. The characterization results including XRD, Raman, TEM, SEM, and XPS confirmed that the formed CuZn alloy over catalyst surface and the intimate Cu-ZnO x interface were the main reasons for the good activity. In-situ DRIFTS showed that CO 2 hydrogenation primarily followed the formate pathway on CZZ catalysts. The interactions between ZnO and ZrO 2 greatly enhanced the generation of oxygen vacancies, improved the adsorption and activation of CO 2 , and further stabilized the formate species which formed on ZnO-ZrO 2 interfaces. Copper species played a vital role in H 2 dissociation and formate intermediates to methoxide. [Display omitted] • CuZn alloy and the intimate Cu-ZnO x interface over Cu-ZnO-ZrO 2 catalyst were the main reasons for the good activity. • The relatively high content of Cu+ showed higher activity. • The CO 2 hydrogenation to methanol over Cu-ZnO-ZrO 2 followed the formate intermediate pathway. • Interactions between ZnO and ZrO 2 enhanced the generation of oxygen vacancies, and stabilized the formate species. • Copper species played a vital role in H 2 dissociation and promoted formate intermediates to methoxide. [ABSTRACT FROM AUTHOR]

Abstract The order-disorder transition has long been viewed as an important key to study materials structures and properties. Especially, pressure-induced ordering attracted the intense research interest in the recent years. In the present work, the pressure-induced ordering phase transition (disordered-fcc to ordered-fcc structures) in a CoCrCuFeNiPr high-entropy alloy (HEA) was found by employing the in situ high-pressure energy-dispersive X-ray diffraction (EDXRD) technique. It is interesting to note that there exists a pressure-induced fast ordering transition at the pressure ranging from 7.8 GPa to 16.0 GPa, followed by a slow transition with the pressure increase up to 106.4 GPa. We suggest that this phenomenon is caused by the presence of some short-range-order (SRO) local structures in the CoCrCuFeNiPr HEA. These SRO structures can be regarded as embryos, which will develop into the ordered phase with increasing the pressure in the prototype materials. This pressure-induced ordering may provides a new technique for tuning structures and properties of HEAs. Highlights • The in situ high-pressure X-ray diffraction technique was used and the maximum applied pressures were up to 106.4 GPa. • The pressure-induced ordering phase transition was found in CoCrCuFeNiPr high-entropy alloy. • The elastic anisotropy of the ordering-fcc phase can be well described with the pressure-dependence of the lattice strain. [ABSTRACT FROM AUTHOR]

A new type of nanothermite composed of n-Al (metal fuel) and FeF 3 (oxidizer) was investigated in this paper. The thermal behavior and combustion properties of the n-Al/FeF 3 nanothermite were compared with that of n-Al/Fe 2 O 3 nanothermite by TG/DSC-MS, XRD, SEM and high-speed camera. The results showed that the decomposition of FeF 3 begins at 300 °C and releases free F ions. The F ions react with Al 2 O 3 shell covered on the surface of aluminum. The start and exothermic peak temperatures of the major reaction of n-Al/FeF 3 are at 415 °C and 520 °C respectively, which are 95 °C and 34 °C lower than those of n-Al/Fe 2 O 3 . Furthermore, the FeF 3 will be reduced to Fe completely at 700 °C. However, the Fe 2 O 3 could only be converted to Fe 3 O 4 . It demonstrates that the reaction of n-Al/FeF 3 is completely, but only a part of n-Al/Fe 2 O 3 reacts at 700 °C. The n-Al/FeF 3 has larger, brighter flame and shorter burning time than n-Al/Fe 2 O 3 in open air. [ABSTRACT FROM AUTHOR]

The elastic properties and thermal expansion behavior of lead-free halide double perovskite, Cs 2 AgBiBr 6 , were studied first with the aid of first principles calculations, which were followed by experimental characterization. The calculated full elastic constants enable the complete mapping of Young’s and shear moduli, and Poisson’s ratios of Cs 2 AgBiBr 6 along all crystallographic orientations. Results show that significant anisotropy in them despite the fact that Cs 2 AgBiBr 6 possesses cubic symmetry. Detailed structural analysis and a spring model were utilized to rationalize the observed anisotropy. Further, the theoretical results were validated by recourse to nanoindentation and high-pressure synchrotron powder X-ray diffraction experiments. The superior mechanical behavior of Cs 2 AgBiBr 6 over the hybrid bromide analogues, MAPbBr 3 (MA = CH 3 NH 3 + ), were attributed to the higher framework stiffness of the former, which is a result of the presence of relatively stronger Ag-Br and Bi-Br bonds in it. Variable temperature single crystal X-ray diffraction reveal linear and volumetric thermal expansion coefficients to be about 20% lower than those of MAPbBr 3 , again suggesting its higher framework rigidity. The superior stiffness, thermal expansion behavior, moisture stability, and nontoxicity of Cs 2 AgBiBr 6 make it a strong candidate for potential applications in optoelectronics and photovoltaics. [ABSTRACT FROM AUTHOR]

Abstract: The structural evolutions of Lanthanide-based metallic glasses under high pressure annealing were investigated by using X-ray diffraction, differential scanning calorimetry, in situ high pressure angle dispersive X-ray diffraction measurements with synchrotron radiation, and nanoindentation. The results show that the amorphous structure in the glasses keeps quite stable up to approximately 40GPa at room temperature. The high pressure annealing treatments reveal that pressure can inhibit the crystallization process, improve local packing efficiency, and restrain long-range atom diffusion. The thermal stability and hardness of the alloys both improved after the treatment. The approach has implications for the design of the microstructure- and property-controllable functional materials for various applications. [Copyright &y& Elsevier]

Abstract: Novel bifunctional magnetic–photoluminescent nanofibers based on Fe2O3 nanoparticles and europium complex Eu(DBM)3(Bath) (DBM=dibenzoylmethanate, Bath=bathophenanthroline) have been prepared by electrospinning. Extensive characterizations of the resulting bifunctional nanofibers have been performed using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). The influence on photoluminescence properties of bifunctional nanofibers of the addition of Fe2O3 nanoparticles has also been studied. The results indicate that due to decreased symmetry in the composite nanofibers the excitation bands of the composite nanofibers are split into two different components. Furthermore, the existence of the Fe2O3 and polymer hybrid matrixes can improve the thermal and photo stability of the europium complex and elongate the fluorescence lifetime of the europium complex. [ABSTRACT FROM AUTHOR]

• Synthetic sodium azotetrazolate was eco-friendly, hydrogen-free, thermal stable. • NaNO 3 /STZ pyrotechnics could generate 321.04 L/kg vapor-free gaseous product. • The reaction process was: i) decomposed into NaCN; generating ii) N 2 ; iii) CO 2. • NaNO 3 /STZ showed a stable combustion, better ignition delay and burning rate. • The maximum pressure of NaNO 3 /STZ produced was 1.7 times of that of NaN 3 /Fe 2 O 3. Gas-generating pyrotechnics are widely used in airbag inflator, pre-tensioner seat belt, deep-water salvage, fire extinguishing bomb, etc. However, for maintaining prolonged high-pressure, specific gas-generating pyrotechnics are required that are capable of producing water-vapor-free gaseous products to avoid the decrease of pressure caused by the condensation of water vapor. Currently, only sodium azide (NaN 3)-based gas-generating pyrotechnics can meet the demand, but its application is limited due to its toxic effects. In this work, a sodium-azotetrazolate-based (STZ-based) eco-friendly and hydrogen-free gas-generating pyrotechnics was presented. A typical STZ-based gas-generating pyrotechnics was NaNO 3 /STZ gas-generating pyrotechnics, which could generate 321.04 L/kg clean and non-toxic gas composed of N 2 and CO 2 without any water vapor. The burning characteristics, including the ignition delay, maximum pressure and burning time of NaNO 3 /STZ gas-generating pyrotechnics was determined by conducting a closed vessel test. NaNO 3 /STZ gas-generating pyrotechnics showed a stable combustion process, lower ignition delay, higher burning rate, and the maximum pressure produced is 1.7 times of that of NaN 3 /Fe 2 O 3. Thus, STZ exhibited great potential as gas-generating pyrotechnics, which could be applied, especially where a stable pressure is required for a long time. [ABSTRACT FROM AUTHOR]

Abstract: The compression behavior of a natural haüyne has been investigated to about 8.1GPa at 300K using in situ angle-dispersive X-ray diffraction and a diamond anvil cell at High Pressure Experiment Station, Beijing Synchrotron Radiation Facility (BSRF). Over this pressure range, no phase change or disproportionation has been observed. The isothermal equation of state was determined for the first time. The values of V 0, K 0, and K′0 refined with a third-order Birch–Murnaghan equation of state are V 0=751.6±0.4Å3, K 0=49±1GPa, and K′0=3.3±0.3, respectively. [Copyright &y& Elsevier]

Negative linear compressibility (NLC), a rare and important mechanical effect with many application potentials, in a crystal of α-BiB3O6 (BIBO) is comprehensively investigated using first-principles calculations and high-pressure synchrotron X-ray diffraction experiments. The results indicate that the BIBO crystal exhibits the second largest NLC among all known inorganic materials over a broad pressure range. This unusual NLC behaviour is due to the rotation and displacement of the rigid [BO3] and [BO4] building units that result in hinge motion in an umbrella-like topology. More importantly, the parallel-polar lone-pair electrons on the Bi3+ cations act as 'umbrella stands' to withstand the B-O hinges, thus significantly enhancing the NLC effect. BIBO presents a unique example of a 'collapsible umbrella' mechanism for achieving NLC, which could be applied to other framework materials with lone-pair electrons. [ABSTRACT FROM AUTHOR]