X-ray free electron laser observation of ultrafast lattice behaviour under femtosecond laser-driven shock compression in iron.

Over the past century, understanding the nature of shock compression of condensed matter has been a major topic. About 20 years ago, a femtosecond laser emerged as a new shock-driver. Unlike conventional shock waves, a femtosecond laser-driven shock wave creates unique microstructures in materials. Therefore, the properties of this shock wave may be different from those of conventional shock waves. However, the lattice behaviour under femtosecond laser-driven shock compression has never been elucidated. Here we report the ultrafast lattice behaviour in iron shocked by direct irradiation of a femtosecond laser pulse, diagnosed using X-ray free electron laser diffraction. We found that the initial compression state caused by the femtosecond laser-driven shock wave is the same as that caused by conventional shock waves. We also found, for the first time experimentally, the temporal deviation of peaks of stress and strain waves predicted theoretically. Furthermore, the existence of a plastic wave peak between the stress and strain wave peaks is a new finding that has not been predicted even theoretically. Our findings will open up new avenues for designing novel materials that combine strength and toughness in a trade-off relationship.

Synthesis of Pd-Ru solid-solution nanoparticles by pulsed plasma in liquid method.

We have synthesized solid-solution nanoparticles (Pd : Ru = 1 : 3, 1 : 1 and 3 : 1) in an immiscible Pd-Ru system by the pulsed plasma in liquid method using Pd-Ru mixture bulk electrodes. The particle sizes of the floated and sedimented samples were measured to be <10 and <20 nm, respectively, via high-resolution transmission electron microscopy (HR-TEM). The lattice parameters of nanoparticles followed the Vegard's law, and the energy-dispersive X-ray spectroscopy (EDX) results almost coincided with those obtained for the starting bulk mixtures. The solid-solution structures and local structure were confirmed via HR-TEM, X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure spectroscopy (XAFS).

Homogeneously alloyed nanoparticles of immiscible Ag-Cu with ultrahigh antibacterial activity.

Immiscible bimetallic Ag-Cu system has been synthesized by the pulsed plasma in liquid method with a graph of one pulse duration. Herein, by combining X-ray power diffraction, K-edge X-ray absorption near edge structure and high-resolution transmission electron microscopy, our results indicate that homogeneously alloyed Ag-Cu nanoparticles (Ag-Cu NAs) have the average diameter about 2.1 nm, composed by 48.5 at% Ag and 51.5 at% Cu with chemical analysis and the estimated lattice parameter was 3.873 Å. The antibacterial property of Ag-Cu NAs was detected against E. coli and S. aureus strains according to the colony formed abilities of bacteria on agar plates covered with the nanoparticles. With very short incubation period, Ag-Cu NAs completely inhibited the E. coli and S. aureus growth at an ultralow concentration. The mechanism of antibacterial property of Ag-Cu NAs was performed by the inductively coupled plasma-atomic emission spectrometry and the plane wave pseudopotential method implemented in the CASTEP package based on the density functional theory. The Ag+ dissolution is correlated with antibacterial activity for Ag-Cu NAs-assisted antibacterial treatment. These findings obtained revealed that our Ag-Cu NAs could be served as a containing material of numerous bacteria-free products in order to avoid their bacterial contamination.

Synthesis of Pd-Fe System Alloy Nanoparticles by Pulsed Plasma in Liquid.

We synthesized Pd-Fe series nanoparticles in solid solution using pulsed plasma in liquid with Pd-Fe bulk mixture electrodes. The Pd-Fe atomic percent ratios were 1:3, 1:1, and 3:1, and the particle size was measured to be less than 10 nm by high-resolution transmission electron microscopy (HR-TEM). The nanoparticles showed face-centered cubic structure. The lattice parameter increased with increasing Pd content and followed Vegard's law, and energy-dispersive X-ray spectra were consistent with the ratios of the starting samples, which showed a solid solution state. The solid solution structure and local structure were confirmed by HR-TEM and X-ray absorption fine structure.

Modulating the Work Function of Graphene by Pulsed Plasma Aided Controlled Chlorination.

Chlorine on graphene (G) matrices was doped by pulsed plasma stimulation on graphite electrode submerged in organochlorine solvents (CH2Cl2, CHCl3, CCl4). The study of work function by Kelvin probe force microscopy (KPFM) measurement clearly indicates that Cl-doped G behave like semiconductor and GG@CHCl3 exhibits the lowest value for the work function. We propose that this report not only represents a new route for tuning the semiconductivity of G but also indicates that doping level of halogen on G based carbon framework can be controlled by pulsed plasma treatment of carbon materials on various organohalogen derivatives.

The vanadate garnet Ca2NaCd2V3O12: a single-crystal X-ray diffraction study.

Single crystals of the vanadate garnet Ca2NaCd2V3O12 (dicalcium sodium dicadmium trivanadate) were synthesized using the floating-zone method and the crystal structure was investigated using single-crystal X-ray diffraction. We considered the effectiveness of substitution of the Y-site cation with reference to previous structural studies of vanadate garnets. The structures of vanadate garnets are subject to geometric constraints similar to those of silicate garnets. These constraints force the tetrahedral-dodecahedral shared edge length in vanadate garnets to become shorter than the unshared dodecahedral edge length, as in ugrandite (uvarovite, grossular and andradite) garnets. However, the vanadate garnet Ca2NaCd2V3O12 exhibits the normal structural feature, similar to pyralspite (pyrope, almandine and spessartine) garnets, namely that the dodecahedral-dodecahedral shared edge length is shorter than the unshared dodecahedral edge length. With increasing ionic radius of the Y-site cation, the atomic coordinates x, y and z of oxygen adopt values which satisfy Pauling's third rule.

High-temperature single-crystal X-ray diffraction study of tetragonal and cubic perovskite-type PbTiO3 phases.

A high-temperature single-crystal X-ray diffraction study of a synthetic PbTiO3 perovskite was carried out over the wide temperature range 298-928 K. A transition from a tetragonal (P4mm) to a cubic (Pm \bar 3 m) phase has been revealed near 753 K. In the non-centrosymmetric P4mm symmetry group, the difference in relative displacement between Pb and O along the c-axis is much larger than that between Ti and O. The Pb and Ti cations contribute sufficiently to polarization being shifted in the opposite direction compared with the shift of O atoms. Deviation from the linear changes in Debye-Waller factors and bonding distances in the tetragonal phases can be interpreted as a precursor phenomenon before the phase transition. Disturbance of the temperature factor Ueq for O is observed in the vicinity of the transition point, while Ueq values for Pb and Ti are continuously changing with increasing temperature. The O site includes the clear configurational disorder in the cubic phase. The polar local positional distortions remain in the cubic phase and are regarded as the cause of the paraelectricity. Estimated values of the Debye temperature ΘD for Pb and Ti are 154 and 467 K in the tetragonal phase and decrease 22% in the high-temperature phase. Effective potentials for Pb and Ti change significantly and become soft after the phase transition.

Variable-temperature single-crystal X-ray diffraction study of tetragonal and cubic perovskite-type barium titanate phases.

A variable-temperature single-crystal X-ray diffraction study of a synthetic BaTiO3 perovskite has been performed over the temperature range 298-778 K. A transition from a tetragonal (P4mm) to a cubic (Pm3m) phase has been revealed near 413 K. In the non-centrosymmetric P4mm symmetry group, both Ti and O atoms are displaced along the c-axis in opposite directions with regard to the Ba position fixed at the origin, so that Ti(4+) and Ba(2+) cations occupy off-center positions in the TiO6 and BaO12 polyhedra, respectively. Smooth temperature-dependent changes of the atomic coordinates become discontinuous with the phase transition. Our observations imply that the cations remain off-center even in the high-temperature cubic phase. The temperature dependence of the mean-square displacements of Ti in the cubic phase includes a significant static component which means that Ti atoms are statistically distributed in the off-center positions.

Synthesis of Hollow Carbon Nano-Onions Using the Pulsed Plasma in Liquid.

We synthesized carbon nano-onions (CNOs) using a low-voltage spark discharge in a liquid and studied the effects of liquid type and pulse duration. By the pulsed electric discharge between two graphite rods of 120 mm length and 6 mm diameter submerged into a 200 ml toluene or ethanol, hollow CNOs with diameters ranging from 10 to 30 nm were produced. CNOs produced using toluene grew more carbon shells than does the sample produced using ethanol. The sample that was synthesized using pulsed plasma with pulse duration of 5 µs showed more carbon shells (10-30) than the sample prepared by 12 µs (2 to 10). High performance liquid chromatography (HPLC) and high resolution transmission electron microscopy analyses confirmed that the sample produced at 12 µs pulsed plasma contains fullerene C60, while the sample prepared at 5 µs does not.

Synthesis of novel CoCx@C nanoparticles.

CoC(x) nanoparticles encapsulated in carbon shells were synthesized using a pulsed plasma in liquid ethanol. This is the first time that monolithic cubic phase cobalt carbide nanoparticles have been obtained. X-ray diffraction refinement of the nanoparticles showed that the lattice parameter of prepared cubic phase cobalt carbide is larger than that of CoC(x) (44-0962) and cubic phase Co (15-0806 and 01-1259). The x-ray absorption fine structure spectra near the Co K-edge of the synthesized sample indicated differences from commercial metallic cobalt and cobalt oxide samples. High resolution transmission electron microscopy revealed that a thin carbon coating covered the surface of the nanoparticles. These carbon layers might isolate core CoC(x) material from the outside environment, and allow functionalization by carboxyl groups for the further purpose of targeted drug delivery. The obtained CoC(x)@C particles, with a crystallite size of about 10 nm confirmed by the electron microscope, aggregate into 20-40 nm secondary particles in distilled water as shown by dynamic light scattering, and possess high saturation magnetization of about 120 emu g(-1). The sodium 3'-[1-(phenylaminocarbonyl)-3,4-tetrazolium]-bis(4-methoxy-6-nitro)benzene sulfonic acid hydrate assay and defragmentation of deoxyribonucleic acid on MCF-7 cells after incubation with particles indicate relatively low cytotoxicity of CoC(x)@C nanoparticles, compared with micro-sized and nano-sized metallic cobalt particles and commonly used iron oxides. For the small sized CoC(x)@C particles, the release of cobalt ions was checked by a chelation method with ethylenediaminetetraacetic acid solution to be at a very low level compared with other reference materials.

Wurtzite-type ZnS nanoparticles by pulsed electric discharge.

The synthesis of wurtzite-type ZnS nanoparticles by an electric discharge submerged in molten sulfur is reported. Using a pulsed plasma between two zinc electrodes of diameter 5 mm in molten sulfur, we have synthesized high-temperature phase (wurtzite-type) ZnS nanocrystals with an average size of about 20 nm. The refined lattice parameters of the synthesized wurtzite-type ZnS nanoparticles were found to be larger than those of the reported ZnS (JCPDS card no 36-1450). Synthesis of ZnMgS (solid solution of ZnS and MgS) was achieved by using ZnMg alloys as both cathode and anode electrodes. UV-visible absorption spectroscopy analysis showed that the absorption peak of the as-prepared ZnS sample (319 nm) displays a blue-shift compared to the bulk ZnS (335 nm). Photoluminescence spectra of the samples revealed peaks at 340, 397, 423, 455 and 471 nm, which were related to excitonic emission and stoichiometric defects.

Synthesis of blue amorphous TiO2 and Ti(n)O(2n-1) by the impulse plasma in liquid.

Synthesis of blue amorphous TiO2 and Ti(n)O(2n-1) by the impulse plasma in dielectric liquid is presented. The impulse plasma in liquid enables us to quench from plasma state, by which we can synthesize nanomaterials, metastable materials, etc. By the impulse plasma between titanium rods submerged into water, we have synthesized blue colored amorphous TiO2 nanoparticles suspended in water and black titanium monoxide at the bottom. Different types of titania oxides like Ti3O, TiO, Ti2O3, Ti4O7 were produced by the impulse plasma in different water temperatures (3, 30, 60, and 90 degrees C respectively). High Resolution Transmission Electron Microscopy analysis showed that the amorphous TiO2 contains anatase nanocrystals with less than 10 nm. UV-vis absorption spectra of the blue TiO2 nanoparticles showed higher absorbance of visible light than the commercially available pure anatase nanoparticles.

Development of special rotor for centrifugal separation of isotopes in solid pure metals.

A prototype rotor with two grooves for the multistage centrifugal isotope separation in solid state was developed to test a new idea. This idea is based on the sedimentation of constitutional atoms in solid. In the performance test using indium specimen, it is verified that the developed rotor can receive all injected molten-indium droplets from an automatic raw-material feeding system even at the high rotational speed of 97,000 rpm without the loss of rotational stability, and the received indium specimens can be transferred in/between two grooves through the plastic flow under the influence of strong centrifugal force even in the solid state. The isotope ratio of centrifuged indium specimens was analyzed employing the secondary ion mass spectrometry, and it is confirmed that intended isotope separation by the centrifugation is realized in the solid state. The developed rotor can be used to perform the isotope separation on at least solid metals under the conditions of up to 400 degrees C in specimen temperature and 0.4x10(6)g in centrifugal force field.

Synthesis method of nanomaterials by pulsed plasma in liquid.

A new synthesis method of nanomaterials using pulsed plasma in liquid by the low voltage spark discharge is presented. The fullerene C60 and TiO nanopowder were for the first time synthesized by electric discharge method in liquid. The purity of C60 was >99%, which is much higher than those by the conventional arc plasma in inert gas methods (less than 80% C60 and 20% C70 and other fullerenes). Copper nanoparticles prepared by this method were smaller than those by arc method by a factor of >5. The pulsed plasma in liquid enables us to quench from plasma state, by which we can synthesize nanomaterials, metastable materials, etc. In addition, the applied power is 100 times smaller than those of arc discharge.