Plane Spacing Research Articles

Correlation of Reduced Interlayer Charge Transfer with Antiphase Boundary Formation in BixSn1–xSe–NbSe2 Heterostructures

Heterostructures of alloyed BixSn1–xSe layers, 0 ≤ x ≤ 1.0, interleaved with NbSe2 monolayers, were prepared by using the modulated elemental reactants technique to investigate the occurrence of antiphase boundaries as a function of Bi concentration. A Rietveld refinement of the c‐axis structure of the x = 0.50 compound revealed a reduced gap distance between the Bi plane in the BixSn1–xSe layers and the Se plane in the NbSe2 layers and an increased internal Se–Se plane spacing within the BixSn1–xSe layers relative to the end member compounds, suggesting increased interaction between the layers at this composition. High‐angle annular dark‐field scanning transmission electron microscopy (HAADF STEM) images showed no antiphase boundary formation in the BixSn1–xSe layers for x = 0.24, some antiphase boundary formation when x = 0.50, and increased antiphase boundary formation for x = 0.73. Correlated with the absence of antiphase boundary formation for values of x < 0.50 and the increasing presence of antiphase boundaries for x ≥ 0.5, electrical transport measurements showed interlayer charge transfer initially increased with x, then decreased as x was increased to 0.50 and beyond.

Nanoscale η-NiSi formation via ion irradiation of Si/Ni/Si

Nickel monosilicide (NiSi) has emerged as an excellent material of choice for source-drain contact applications below 45 nm node complementary metal-oxide-semiconductor technology. We have investigated the formation of nanoscale NiSi by ion irradiation of Si (∼5 nm)/Ni(∼15 nm)/Si, grown in an ultrahigh vacuum environment. Irradiation was carried out at room temperature with 1 MeV Si+ ions. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were employed for analysis. With increasing ion fluence, ion beam mixing occurs and more and more Si is incorporated into the Ni layer, and this layer gets amorphized. At an even higher fluence, a recrystallized uniform nickel monosilicide (η-NiSi) layer is formed. Several planar spacings of different Miller indices of η-NiSi have been observed in XRD and TEM. Additionally, an interesting amorphization and recrystallization behavior has been observed in the substrate Si with increasing ion fluence. To our knowledge, this has never been observed in ion irradiation of bare Si in decades of work in this area. This kind of amorphization/recrystallization in Si is apparently Ni-induced. Irradiation displaces Ni and produces a distribution of Ni in amorphized Si. Irradiation at a higher fluence produces two recrystallized Si bands in amorphous Si with concomitant accumulation of Ni at the amorphous/crystalline interfaces. On a further increase in irradiation fluence, the recrystallized Si bands again pass through amorphization and recrystallization. The total thickness of recrystallized, as well as amorphous Si, shows an oscillatory behavior as a function of ion fluence.

Microstructural Information Mapping of a Plastic-deformed α-iron Plate during Tensile Tests using Pulsed Neutron Transmission

The spatial-dependent lattice spacing and microstructure of an α-iron plate with two notches was measured during tensile tests using a pulsed neutron transmission method to ascertain changes depending on the load. Changes in microstructural parameters such as macrostrain, microstrain, crystallite size and texture are interesting during the transition from the elastic to plastic deformation region, especially over a relatively wide field of view to see propagation of the change. The method has the capability to show changes in the position-dependence of microstructural information simultaneously over a wide area in the bulk material. Transmission spectra around the Bragg-edge regions of the neutron total cross section of α-iron were obtained, and the microstructural parameters, {110} plane spacing and its distribution, texture coefficient and crystallite size were analyzed. The spatial-dependent distributions (images) of these parameters show sample shape effects including strain concentration around the notches and the effect of dislocations being multiplied during the plastic deformation. The spatial dependence of the microstructural parameters visualized herein provides useful information for evaluating the inhomogeneous progress of deformation of the bulk engineering material.

A High-speed <italic>In Situ</italic> Measuring Method for Inner Dimension Inspection

Inner dimensional measurement techniques are difficult to improve because of the tight working space and complex inside measuring environment. In this paper, a high-speed, in situ measuring method is proposed for inner dimension by using revolved double laser beams. First, two laser beams with the inclined angle of 180° are used to construct the measuring line. The relative position between two laser beams is then calibrated before measurement. Second, the two laser beams are revolved consecutively to get collections of data samples during the measurement. The data samples contain the information concerning the geometrical features of measured workpiece. Finally, by fitting the measured data, inner dimensions can be extracted from the statistical characteristic of measured workpiece. The proposed approach is validated by using a developed measuring head installed on the spindle of a numerical control machine. Inner diameter and planar spacing measurements are taken as examples to showcase the efficacy and efficiency of the method proposed.

Influence of oxidant to fuel ratio on the structural and optical properties of In2O3 nanoparticles synthesized by auto-combustion method

The effect of fuel (Glycine, G) to oxidant (metal Nitrates, N) ratio on the formation of nano-sized powders by the self-propagating auto-combustion technique is reported. Nano-crystalline single phase In2O3 was synthesized at different G/N mole ratio. 0.5 to 2.5. The powders obtained by auto-combustion were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and diffuse reflectance UV/Vis/NIR spectrometer. The crystallite size of as synthesized powder was found to be around 11 nm for fuel lean composition. The optical studies by Kubelka–Munk analysis exhibited the variation of band gap from 2.92 eV to 3.26 eV. The lattice parameters, stress and inter planar spacing were also evaluated. Thus the G/N ratio is important for successful preparation of nano-crystalline indium oxide.

LITERATURE REVIEW ON PREPARATION OF GRAPHINE

Graphene is the world thinnest, stronger then diamond, much lighter, flexible and stiffest material which exhibits a number of outstanding electrical, excellent conductors of heat and mechanical properties that makes them very attractive for micro and nanotechnology application. The thinnest layer of graphite is called Graphene, when oxidising agents reacting with graphite the inter planar spacing between the layers of graphite is increased. The complete oxidised compound Ca then dispersed in the Base solution then Graphene is formed. Graphene is intrinsically gap less; it is lighter, thinner, transparent and stronger then diamond. It is 5%higher the denser of the steel, 10times stronger then steel.

Superconductivity in (NH3)yNaxFeSe0.5Te0.5

Na-intercalated FeSe0.5Te0.5 was prepared using the liquid NH3 technique, and a superconducting phase exhibiting a superconducting transition temperature (T-c) as high as 27 K was discovered. This can be called the high-T-c phase since a 21 K superconducting phase was previously obtained in (NH3)(y)NaxFeSe0.5Te0.5. The chemical composition of the high-T-c phase was determined to be (NH3)(0.61(4))Na-0.63(5) Fe0.85Se0.55(3) Te-0.44(2). The x-ray diffraction patterns of both phases show that a larger lattice constant c (i.e., FeSe0.5Te0.5 plane spacing) produces a higher T-c. This behavior is the same as that of metal-doped FeSe, suggesting that improved Fermi-surface nesting produces the higher T-c. The high-T-c phase converted to the low-T-c phase within several days, indicating that it is a metastable phase. The temperature dependence of resistance for both phases was recorded at different magnetic fields, and the critical fields were determined for both phases. Finally, the T-c versus c phase diagram was prepared for the metal-doped FeSe0.5Te0.5, which is similar to that of metal-doped FeSe, although the T-c is lower.

Preparation of ZnO from 2 D nanosheets to diverse 1 D nanorods and their structure, surface area, photocurrent, optical and photocatalytic properties by simple hydrothermal synthesis

Two–dimensional (2 D) ZnO nanosheets and one–dimensional (1 D) bud−like, grenade−like, prism−like, bamboo−like, brush−like, arrow−like, pencil−like, drip pipe−like, baseball bat−like, gear−like, walking stick−like, taper−like, shuttle−like, and/or hollow tower−like ZnO nanorods (nanotubes) with various tips were synthesized by a simple hydrothermal route from the system of CO(NH2)2N2H4. All the samples exhibit the wurtzite structure of ZnO. With the increase of the amount of N2H4 or decrease of CO(NH2)2, the interplanar spacing of different planes of ZnO increases or decreases simultaneously. FTIR shows that except the nanosheets of S1, all other samples are pure. The average reflectance of S8 reaches about 85% in the wavelengths ranging from 450 to 550 nm, and the reflectance of S3 is about 75%. The Eg values of ZnO from S1–S8 are 3.234, 3.215, 3.223, 3.215, 3.230, 3.243, 3.230 and 3.234 eV respectively. Raman spectra of S1 and S2 are obviously different from those of S3–S8. PL spectra of the ZnO samples exhibit a dominant UV luminescence peak of S1–S7, especially that of S1, S2 and S4. The addition of N2H4 can suppress the defects on the ZnO surface. However, the decrease of CO(NH2)2 introduces the defect. The BET surface area shows that except S1 (55.3 m2/g), S5 is a center of symmetric distribution of surface areas of S2–S8. From above discussion, the density, PL intensity of UV emission, and BET surface area of the ZnO nanorods can be easily tuned by controlling the concentrations of N2H4 and CO(NH2)2. The average values of photocurrent density of S1−S8 are 0.059, 0.170, 0.137, 0.184, 0.215, 0.091, 0.465 and 0.152 μA/cm2, respectively. S4, S2 and S7 possess the rapid photocatalytic activities and decompose 65%, 55% and 50% of MB within 50 min respectively. The order of the average diameters of S3, S4, S5, S6, and S7 agrees with that of photocatalytic efficiency, indicating that the polar (002) plane and/or the nanorod tips affect the photocatalytic activity. The decrease of the amount of CO(NH2)2 introduces the defects, which affects the photocatalytic activity of S8.

Performance of the EUDET-type beam telescopes

Test beam measurements at the test beam facilities of DESY have been conducted to characterise the performance of the EUDET-type beam telescopes originally developed within the EUDET project. The beam telescopes are equipped with six sensor planes using MIMOSA26 monolithic active pixel devices. A programmable Trigger Logic Unit provides trigger logic and time stamp information on particle passage. Both data acquisition framework and offline reconstruction software packages are available. User devices are easily integrable into the data acquisition framework via predefined interfaces. The biased residual distribution is studied as a function of the beam energy, plane spacing and sensor threshold. Its standard deviation at the two centre pixel planes using all six planes for tracking in a 6\,GeV electron/positron-beam is measured to be $(2.88\,\pm\,0.08)\,\upmu\meter$.Iterative track fits using the formalism of General Broken Lines are performed to estimate the intrinsic resolution of the individual pixel planes. The mean intrinsic resolution over the six sensors used is found to be $(3.24\,\pm\,0.09)\,\upmu\meter$.With a 5\,GeV electron/positron beam, the track resolution halfway between the two inner pixel planes using an equidistant plane spacing of 20\,mm is estimated to $(1.83\,\pm\,0.03)\,\upmu\meter$ assuming the measured intrinsic resolution. Towards lower beam energies the track resolution deteriorates due to increasing multiple scattering. Threshold studies show an optimal working point of the MIMOSA26 sensors at a sensor threshold of between five and six times their RMS noise. Measurements at different plane spacings are used to calibrate the amount of multiple scattering in the material traversed and allow for corrections to the predicted angular scattering for electron beams.

Real time investigation of the effect of thermal expansion coefficient mismatch on film-substrate strain partitioning in Ag/Si systems

We have used X-ray diffraction (XRD) to investigate strain partitioning between an epitaxial layer and the substrate as a function of temperature, where the substrate (Si) and the epilayer material (Ag) have large thermal expansion coefficient (α) mismatch. The Ag/Si(111) system undergoes morphological changes upon heating, and the larger and taller islands are formed exposing more substrate surfaces. Sample heating was carried out under nitrogen flow. At >300 °C, the Si(111) diffraction peak splits into three. One of these components conforms to the thermal expansion of bulk Si. The other two components correspond to a highly nonlinear decrease and increase of Si-d(111) planar spacing. The decreasing component has been associated with strained Si under Ag and the increasing component with strained Si under SiO2, which has been formed partly prior to the XRD experiment and partly during sample heating. The opposite trends of these two Si-d(111) components are because of the larger value of α for Ag (7 times) and smaller for SiO2 (1/5th) compared to Si. The out-of-plane strain partitioning has been such that at room temperature, the Si substrate is unstrained and the strain in Ag is ∼0.3%. At 800 °C, Ag is practically relaxed, while Si under Ag is ∼−0.7% strained. A temperature dependent strain partitioning factor has been introduced to fit the data.

Cr doping-induced structural phase transition, optical tuning and magnetic enhancement in BiFeO3 thin films

BiFe1−xCrxO3 (xBFCO, x=0, 0.03, 0.06 and 0.09) polycrystalline films have been prepared on quartz substrates by a sol–gel technique. X-ray diffraction clearly reveals the crystal structure of xBFCO thin films transforms from rhombohedral to orthorhombic, moreover, inter planar spacing and grain size of xBFCO are reduced slightly. Scanning electron microscopy shows that Cr doping can improve surface morphology and reduces the average grain size of the films. The photoluminescence (PL) spectra of xBFCO thin films at room temperature show a strong emission in the blue region. With increasing x from 0.00 to 0.09, the band gap (Eg) of xBFCO films decreases and can be expressed by Eg=(2.58−0.67x)eV. Compared with BiFeO3 film, the saturation magnetization of xBFCO (x=0.03, 0.06 and 0.09) films is significantly enhanced, which provides potential applications in information storage.

Organic functionalization of thermally reduced graphene oxide nanoplatelets by adsorption: structural and morphological characterization

Adsorption of chlorinated poly(ethylene-co-vinyl acetate)-g-maleic anhydride copolymer and in situ-generated polyaniline (PANI) on thermally reduced graphene oxide (TRGO) platelets was studied in the current study. The adsorption was characterized structurally and morphologically through thermogravimetric analysis, differential scanning calorimetry (DSC), elemental analysis, infra-red and Raman spectroscopy, X-ray diffraction and microscopy. The amount of copolymer adsorption reached a plateau of 0.22 g per g of TRGO, when the initial copolymer to TRGO weight ratio of 1 was used. In the case of PANI modification, much higher extent of adsorption of 0.92 g/g of TRGO (without reaching plateau) was observed due to in situ polymer synthesis and the absence of any steric hindrance to the chains. Shift in the DSC melting transition temperatures of copolymer also indicated that some change in the polymer chain morphology took place after immobilization of polymer on TRGO. PANI modification led to significant reduction in peak melting point from 175C to 140 °C owing to the hindrance in polymer crystallization. The basal plane spacing in the TRGO platelets increased the copolymer adsorption as the 0 0 1 basal plane diffraction shifted from 27° 2Θ for pristine TRGO to 22.5° 2Θ for modified TRGO. For the PANI modified TRGO, no diffraction signal corresponding to TRGO was observed due to extensive adsorption of polymer on the surface. A much thicker polymer phase wrapping the TRGO platelets was observed for PANI modified TRGO. This was also observed through EFTEM and EDX, where the presence of Cl and N (along with other atoms) indicated layer of copolymer and PANI, respectively on the surface of the platelets. EELS analysis also confirmed the semi-crystalline nature of the modified TRGO resulting from the adsorption of semi-crystalline polymers on TRGO. The adsorption approaches used in the study demonstrate successful generation of the functional nanomaterials with tunable extent of surface coverage and potential of employing diverse surface modifications.

Hydrogen Absorption of Palladium Thin Films Observed by in Situ Transmission Electron Microscopy with an Environmental Cell.

A window type of the environmental cell system for a high-voltage electron microscope was developed and applied to in situ observation of a palladium (Pd) thin film. For in situ hydrogenation of Pd thin films, the distances of the lattice fringes were 0.20 and 0.23 nm, which correspond to the lattice d spacings of β-phase (200) and (111) planes. Expansion of the Pd lattice happened as a result of phase transformation from the α phase to the β phase. In particular, the lattice fringes were clearly distinguished, and the dislocation behavior during Pd hydrogenation was easily recognized according to the corresponding inverse fast fourier transform images. Furthermore, significant growth in the number of dislocations was observed at the grain boundary during increasing hydrogen pressure in the cell.

Preparation and inhibition properties of molybdate intercalated ZnAlCe layered double hydroxide

ZnAlCe layered double hydroxide intercalated by molybdate (ZnAlCeMoO4 LDH) was successfully synthesized by using co-precipitation method, and the morphology, structure of ZnAlCeMoO4 LDH were observed and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) techniques. The inhibition behavior of ZnAlCeMoO4 LDH for Q235 steel in 3.5%NaCl solution was determined by polarization curves, electrochemical impedance spectroscopy (EIS), inductively coupled plasma mass spectrometer (ICP-MS) and X-ray photoelectron spectrometer (XPS) methods. The results shows that the synthesized ZnAlCeMoO4 LDH has a lamellar structure with a particle size of 0.1–2.0 μm, an average thickness of 30 nm, and a basal plane spacing of 0.898 nm. Compared with the addition of ZnAl layered double hydroxide intercalated by nitrate (ZnAlNO3 LDH) and ZnAl layered double hydroxide intercalated by molybdate (ZnAlMoO4 LDH) in 3.5% NaCl solution, Q235 steel in 3.5%NaCl + ZnAlCeMoO4 LDH solution has a lower corrosion current density, larger polarization resistance and a higher inhibition efficiency. The addition of ZnAlCeMoO4 LDH will reduce the chloride concentration in 3.5% NaCl solution by the anion exchanged with molybdate, and improve the corrosion resistance of Q235 steel owing to the formation of passive film with the composition of ferrous or iron molybdate and deposition film with zinc and cerium hydroxides.

Correlation of superconductivity with crystal structure in (NH3)yCsxFeSe

The superconducting transition temperature T-c of ammoniated metal-doped FeSe (NH3)(y)MxFeSe (M: metal atom) has been scaled with the FeSe plane spacing, and it has been suggested that the FeSe plane spacing depends on the location of metal atoms in (NH3)(y)MxFeSe crystals. Although the crystal structure of (NH3)(y)LixFeSe exhibiting a high T-c (similar to 44 K) was determined from neutron diffraction, the structure of (NH3)(y)MxFeSe exhibiting a low T-c (similar to 32 K) has not been determined thus far. Here, we determined the crystal structure of (NH3)(y)Cs0.4FeSe (T-c = 33 K) through the Rietveld refinement of the x-ray diffraction (XRD) pattern measured with synchrotron radiation at 30 K. The XRD pattern was analyzed based on two different models, on-center and off-center, under a space group of 14/mmm. In the on-center structure, the Cs occupies the 2a site and the N of NH3 may occupy either the 4c or 2b site, or both. In the off-center structure, the Cs may occupy either the 4c or 2b site, or both, while the N occupies the 2a site. Only an on-center structure model in which the Cs occupies the 2a and the N of NH3 occupies the 4c site provided reasonable results in the Rietveld analysis. Consequently, we concluded that (NH3)(y)Cs0.4FeSe can be assigned to the on-center structure, which produces a smaller FeSe plane spacing leading to the lower T-c.

Synthesis of hierarchical MoS2 microspheres composed of nanosheets assembled via facile hydrothermal method as anode material for lithium-ion batteries

A hierarchical MoS2 architecture composed of nanosheet-assembled microspheres with an expanded interplanar spacing of the (002) planes was successfully prepared via a simple hydrothermal reaction. Electron microscopy studies revealed formation of the MoS2 microspheres with an average diameter of 230 nm. It was shown that the hierarchical structure of MoS2 microspheres possesses both the merits of nanometer-sized building blocks and micrometer-sized assemblies, which offer high surface area for fast kinetics and buffers the volume expansion during lithium insertion/deinsertion, respectively. The micrometer-sized assemblies were found to contribute to the enhanced electrochemical stabilities of the electrode materials. The mentioned advantages of the MoS2 electrode prepared in this work allowed enhanced cyclability and high rate capability of the material. Along with this, the material delivered a high initial discharge capacity of 1206 mAh g−1 and a reversible discharge capacity of 653 mAh g−1 after 100 cycles at a current density of 100 mA g−1. Furthermore, the material delivered a high reversible capacity of 480 mAh g−1 at a high current density of 1000 mA g−1.

Self-templated formation of tremella-like MoS2 with expanded spacing of (002) crystal planes for Li-ion batteries

Tremella-like MoS2 consisting of ultrathin nanosheets (~7 nm in thickness) is prepared via a one-pot hydrothermal reaction without using any surfactants and templates. The reaction involves transforming precursor MoO3 to polyhedral intermediate (K2NaMoO3F3 and K3Mo2O4F5) through its reaction with Na+, K+, and F− ions in the initial stage of hydrothermal reaction. Then the polyhedral intermediate acting as the sacrifice template reacts with the S2− released from a hydrolysis process of SCN− ion and transforms to tremella-like MoS2. The obtained MoS2 product exhibits expended spacing of the (002) crystal plane, which can facilitate faster lithium ions intercalation behavior. This tremella-like MoS2 used as an anode material for lithium-ion batteries shows a very high reversible capacity of 693 mA h g−1 after 50 cycles, good rate capability, and high cyclic capacity retention. Even cycled at a high current density of 4800 mA g−1, the tremella-like MoS2 still can deliver a high capacity of 252 mA h g−1. The secondary hierarchical microstructures consisting of ultrathin nanosheets are beneficial to greatly improved electrochemical performance of the MoS2 electrode.

Tailoring of cholesteric plane spacing, dielectric relaxation and optical properties of high temperature chiral nematic phase by UV irradiation

The effect of Ultra Violet (UV) irradiation on the high temperature chiral nematic (N*) mesophase has been investigated. The controlled UV exposure produced bending in rod shape molecules. The bending of molecules affects their long molecular axis; therefore, the relaxation mode associated with the rotation of molecules along the long molecular axis shifts toward the higher frequency. The UV irradiation also increases the cholesteric plane spacing of N*LC molecules. The a.c. conductivity of N*LC has been increased enormously after UV irradiation. The efficiency of opto-dielectric effect has also been evaluated with the variation of bias voltage in the present investigation.

TENSILE DEFORMATION BEHAVIOR OF HYDROGEN CHARGED ULTRAHIGH STRENGTH STEEL STUDIED BY IN SITU NEUTRON DIFFRACTION

The tensile deformation behavior and the axial lattice strain response of 1250 MPa ultrahigh strength steels with and without hydrogen charging were comparably investigated using time-of-flight neutron diffraction together with the fracture morphology and microstructure observation. Before tensile loading, the axial (110) lattice plane spacing of hydrogen charged specimen was found larger than that of noncharged specimen while the axial (200) lattice plane spacing of the former was smaller than that of the latter, suggesting that the hydrogen atoms occupied the tetrahedral site promoted the increment of axial (110) lattice plane spacing while the balanced internal stress resulted in the proper decrement of axial (200) lattice plane spacing. The necking and ductile fracture after approaching the 1250 MPa tensile strength occurred in the non-charged specimen, while the brittle *收到初稿日期: 2014-09-30,收到修改稿日期: 2015-07-18 作者简介:徐平光,男, 1973年生,研究副主干,博士 DOI: 10.11900/0412.1961.2014.00541 第1297-1305页 pp.1297-1305

Structural and optical properties of Ni substituted CaCu3Ti4 − xNixO12

Ni2+ doped CaCu3Ti4−xNixO12 (x=0.0, 0.08, 0.12, and 0.20) [CCTO] ceramics were synthesized by solid-state reaction route method and their structural properties were investigated. X-ray diffraction along with the Rietveld refinement showed no change in crystal structure from cubic (Im-3) to any other with enhanced divalent Ni2+ ion concentration. It has been observed that the lattice parameter increases with increasing Ni concentration and is attributed to the difference in ionic radius of Ni2+ (0.69Å) is larger than the ionic radii of Ti4+ (0.60Å). Furthermore, there is a good agreement between observed and calculated interplanar spacing (d-values) of hkl planes. From FT-IR spectroscopy, it have been notice that the CCTO phase present resonance absorptions at 560, 522 and 446cm−1 which are associated to TiO and TiOTi.