Diffraction Curves Research Articles

Локализация моноклинной фазы в насцентных частицах сверхвысокомолекулярного полиэтилена

Annotation The X-ray analysis of a virgin particle taken directly from the synthesis products of an ultra-high molecular weight polyethylene (UHMWPE) and not subjected to any external stresses was carried out using nanofocus beamline ID13 European Synchrotron Radiation Facility (ESRF, Grenoble,France). In the X-ray diffraction curves obtained by scanning an arbitrarily selected portion of a particle with a size of (100 x 20) μm2 by a microbeam (0.3 x 0.3) μm2 with a step of 2 μm horizontally and 0.5 μm vertically, along with reflections from the orthorhombic phase, reflexes from the metastable monoclinic phase were observed. It is believed that the cause of its occurrence may be stresses that develop during specific structure formation in slurry synthesis and persist when cooled to room temperature and the solvent evaporates. The possibility of localization of the monoclinic phase in various morphological formations is discussed.

Characterization of Fe5(AsO3)3Cl2(OH)4·5H2O, a new ferric arsenite hydroxychloride precipitated from FeCl3–As2O3–HCl solutions relevant to arsenic immobilization

Tooeleite (Fe6(AsO3)4SO4(OH)4·4H2O) is widely precipitated for direct As(III) removal from sulfate-rich industrial effluents. However, whether or not Fe(III)–As(III)–Cl(-I) precipitate is produced in chloridizing leaching media for As immobilization is almost unknown. This work founded the existence of ferric arsenite (hydroxy)chloride as a new mineral for As(III) removal. Its chemical composition and solid characterization were subsequently studied by using scanning electron microscope with an energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), infrared (FT-IR), Raman spectroscopy and thermogravimetric (TG) curve. The results showed the formation of a yellow precipitate after 3-days reaction of Fe(III)/As(III) with molar ratio ≈ 1.7 in chloride solution at pH 2.3 neutralized with NaOH. Compared with tooeleite, chemical analysis and solid characterization indicated that Cl(-I) replaces SO4(-II) producing ferric arsenite hydroxychloride with formula Fe5(AsO3)3Cl2(OH)4·5H2O. This new plate shaped solid showed better crytallinity than tooeleite, although it has similar morphology and characteristic bands to tooeleite. The FT-IR bands at 628, 964 cm−1 and the Raman bands at 448, 610, 961 cm−1 were assigned to Fe–O or As(III)–O–Fe or As(III)–O bending/stretching vibration, indicating that both arsenite and chloride substituted for the position of sulfate for ferric arsenite hydroxychloride produced due to the lack of the SO42− vibrations. Cl-(I) also contributed to increase As removal efficiency in aqueous sulfate media under acidic pH conditions via the probable formation of sulfate-chloride ferric arsenite.

Long Wavelength Type II InAs/GaSb Superlattice Photodetector Using Resonant Tunneling Diode Structure

We report on a long wavelength type-II InAs/GaSb superlattice photodetector using resonant tunneling diode (RTD) structure. The linewidth of the satellite peak of the x-ray diffraction curve of the as-grown sample is only 15.7 arcsec showing a very high structural quality. The response maximum wavelength of the RTD detector is $7.5~\mu \text{m}$ and the 50% cutoff wavelength is $9.6~\mu \text{m}$ at 77 K. The measured QE is 147% at $7.5~\mu \text{m}$ when the applied bias voltage is 1.45 V and the corresponding responsivity is 8.9 A/W. This unusual QE is attributed to a large gain achieved when the device is under a resonant tunneling condition. The corresponding shot noise limited detectivity D* is $1.2\times 10^{10}\text {cm}\cdot \sqrt {Hz}/W$ at 1.45 V at 77 K.

Structural Properties of 300 Å of Iron Films Grown on Polycrystalline Substrate

In this manuscript, the structural properties such as the distance inter-reticular of samples is studied, In the fact, four samples were used symbolized as follows: E tAg(Å), the only difference is the thickness of the Silver buffer layer (tAg= 0, 50, 100 and 150 Å) to find out how the thickness of this layer depends on the structural characteristics of the Iron thin layer, all samples are deposited using molecular beam epitaxy (MBE) at room temperature onto Si (100) substrate. The structural properties of all samples examined using X-ray diffraction method at small and high angles. The small angles X-Ray diffraction curves confirmed to us that there is a clear difference between the surface structure of the samples by varying the number of Kiessig Fringes, Also high angles X-Ray diffraction curves assured us this difference through the clear variation in the angular positions of the peaks of Bragg and the distances inter-reticular values from a sample to the other.

Controllable synthesis and morphology evolution of hierarchical LiFePO4 cathode materials for Li-ion batteries

Hierarchical LiFePO4 crystals self-assembled with subunits were successfully synthesized via a simple hydrothermal method. The X-ray diffraction (XRD) curve indicates the highly crystalline nature of the prepared samples. The field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images reveal that with increased KOH concentrations, the LiFePO4 products evoluted from microspheres self-assembled with microwires to spindle-like structures self-assembled with micro-needles and eventually to flower-like hierarchical nanostructures self-assembled with nanorods. The crystal growth mechanism could be explained by the synergetic effect of pH value and the surface-adsorbed K+ ions. The OH– anions represent pH value dominate the hierarchical morphology under both low and high KOH concentration, while K+ ions play the major role in synthesizing monodispersed LiFePO4 nanorods under medium KOH concentration. Moreover, charge–discharge curves and CV measurements demonstrated good reversible capacities and stable cycle performances of the LFP/C samples.

Realization of color-tunable emission via energy transfer in novel single-phase K3YB6O12:Bi3+, Eu3+ phosphors

Nowadays, Bi3+→Eu3+ energy transfer behavior is a hot research topic in phosphor-converted white light emitting diodes, because it can simultaneously realize the efficient sensitization of red emission of Eu3+ and emission color adjusting. Herein, we report a series of novel Bi3+ singly doped and Bi3+/Eu3+ co-doped K3YB6O12 phosphor materials synthesized by conventional high-temperature solid-state reaction. The structural and photoluminescence properties of the as-prepared phosphors were investigated by X-ray diffraction, photoluminescence spectra and decay curves. K3YB6O12:Bi3+ phosphors exhibited a single ultraviolet-blue emission band excited by ultraviolet that corresponded to the characteristic 3P1 → 1S0 transition of Bi3+ ions and reached the highest emission intensity with the Bi3+ doping concentration of 15%. By introducing Eu3+ into K3YB6O12:0.015Bi3+ phosphor, the Bi3+ → Eu3+ energy transfer phenomenon was induced in the K3YB6O12:Bi3+, Eu3+ phosphors that resulted in broad excitation characteristic in ultraviolet region. With the Eu3+ contents increase, the Bi3+ → Eu3+ energy transfer becomes more and more efficient that leads to the color-tunable emission from ultraviolet-blue to red. In addition, the efficiency and mechanism of Bi3+ → Eu3+ energy transfer were also investigated in detail, as based on theoretical evaluations. Our results implied that the as-prepared K3YB6O12:Bi3+, Eu3+ phosphors could be suitable to be applied in white light emitting diodes.

Realization of color tunable via energy transfer in Ba1.2Ca0.8SiO4:Tb3+, Mn2+ phosphor

A detailed investigation on photoluminescence properties and energy transfer mechanism of Tb3+/Mn2+ singly doped and co-doped T-phase orthosilicate Ba1.2Ca0.8SiO4 (BCS) phosphors, synthesized by conventional solid state reaction, is provided. All the samples were investigated by X-ray diffraction (XRD), photoluminescence spectroscopy and fluorescence decay curve. The Mn2+ emission intensity of BCS:Tb3+, Mn2+ is 28 times stronger than that of BCS:Mn2+. In addition, the emission color of BCS:Tb3+, Mn2+ phosphors can be tuned from green to orange-red by varying Mn2+ concentration. The efficient energy transfer from Tb3+ to Mn2+ is responsible for these phenomena. By employing the Inokuti–Hirayama model and Dexter's energy transfer theory, the dipole–dipole interaction is confirmed as the predominant multipolar effect in controlling this energy transfer process.

Preparation of CdS nanorods on silicon nanopillars surface by hydrothermal method

Cadmium sulfide (CdS) nanorods are fabricated on Silicon (Si) nanopillars surface via hydrothermal reaction method for the first time. To optimize the growth condition, the thickness of CdS seed film, temperature and time of hydrothermal reaction are researched in this work. It is found that 30–60 nm seed layer at the 180 °C for 5 h is the optimal condition for CdS nanorods growth on Si nanopillars surface. The energy dispersive spectroscopy results show that Cd and S elements with a ratio of 1:1.02 is in agreement with the stoichiometric composition of CdS. The X-ray diffraction curves indicate that the CdS nanorods are well crystallized on Si nanopillars substrate. The CdS nanorods can reduce the reflection and increase the absorption of the incoming light obviously. And the CdS nanorods-Si nanopillars structure has obvious photosensitive effect, which has great potential in the field of photoelectric.

Impact of gallium concentration in the gas phase on composition of InGaAsN alloys grown by AP-MOVPE correlated with their structural and optical properties

This work presents the epitaxial growth and material properties of InGaAsN epilayers obtained by atmospheric pressure metal organic vapour phase epitaxy. The main goal was to obtain InGaAsN quaternary alloys lattice-matched to GaAs in order to apply them as an intrinsic thick absorber in p-i-n solar cells. It allows improvement of their photovoltaic parameters (e.g. short circuit current, open circuit voltage) by reducing the density of misfit dislocations. To overcome the main difficulties connected with achieving InGaAsN composition with In/N ratio of ~ 3, which guarantees a lattice matching to GaAs, epitaxial processes were carried out with different concentration of gallium source in the gas phase. Diffraction curves, measured using HRXRD, indicated that the main aim of this work was achieved for the gas molar ratio Ga/(Ga + In) = 0.935. The optical quality and surface morphology of the investigated structures examined by PL, CER and AFM methods are also presented and discussed.

Efficient energy transfer induced tunable emission in Ce3+ and Eu2+ co-doped Ba1.2Ca0.8SiO4 phosphor

A series of Ce3+ and/or Eu2+ doped T-phase orthosilicate Ba1.2Ca0.8SiO4 (BCS) phosphors were synthesized by conventional solid state reaction. The as-synthesized samples were investigated by X-ray diffraction (XRD), photoluminescence spectroscopy, and fluorescence decay curve. The red shifts of emission peak were observed in Ce3+ and/or Eu2+ doped BCS phosphors. The possible rationalization for the red shift was discussed. The emission color for BCS:Ce3+, Eu2+ phosphors can be turned from deep blue to bluish green by varying Eu2+ concentration. The efficient energy transfer from Ce3+ to Eu2+ is responsible for this phenomenon. The energy transfer mechanism was validated and demonstrated to be a resonant type via a dipole–dipole interaction by using Inokuti–Hirayama model and Dexter's energy transfer theory. In addition, the thermal stability of the phosphors is also investigated. Furthermore, the quantum efficiency (QE) of Ba1.15Ca0.8SiO4:0.02Ce3+, 0.02Na+, 0.01Eu2+ phosphor was found to be 38.77%. Finally, to explore the practical applications of obtained compounds for indoor illumination, a white light-emitting-diode (LED) device which contained a n-UV chip, prepared phosphors, and green emitting and red emitting phosphors was packaged. The packaged white LEDs device can emit dazzling white light with satisfied color coordinate of (0.350, 0.335), Ra (84), and correlated color temperature (4744 K).

Influence of Yb2O3 on the 1.53 μm spectroscopic properties in Er3+/Ce3+ co-doped TeO2-WO3-Na2O-Nb2O5 glasses

The Yb2O3 component was introduced into the Er3+/Ce3+ co-doped tellurite glasses with the composition of TeO2-WO3-Na2O-Nb2O5 to study the effect of Yb3+ on the 1.53 μm spectroscopic properties of Er3+. The X-ray diffraction (XRD) curve and Raman spectrum were measured to investigate the structure nature of synthesized tellurite glasses. The absorption spectrum, upconversion emission spectrum and fluorescence spectrum were measured to evaluate the improved effect of Yb3+ concentration on the 1.53 μm band fluorescence of Er3+. Results of the measured 1.53 μm band fluorescence intensity show a significant improvement with the increase of Yb3+ concentration, while the total quantum efficiency reveals a similar increasing trend. The results of the present work indicate that Er3+/Ce3+/Yb3+ tri-doped tellurite glass has good prospect as a promising gain medium applied for the 1.53 μm broadband amplifier.

Microstructure and Microwave Absorption Properties of Cement-Based Material Reinforced with Reduced Graphene Oxide and Nanoparticles

Microwave absorption properties of paste reinforced with well-dispersed reduced graphene oxide, ferroferric oxide and nickel nanoparticles were investigated. The effect of nanofiller on the fluidity, mechanical properties and pore structure of the paste was studied. The microstructure of the composite is examined by scanning electron microscopy, its groups and hydration products are analyzed with infrared spectra and X-ray diffraction curves. A small nanofiller load is shown to significantly reduce the paste fluidity, but its pore structure is improved so that its mechanical properties are enhanced. Microscopic examination demonstrates that the nanofiller fosters the development of flower-like crystals, which promotes the paste compaction. A minimum reflectivity of -14.7 dB is in the range of 1–18 GHz and the effective bandwidth of 14.4 GHz is obtained when the reflectivity is less than -5 dB. The new method of preparing cement-based absorbent materials is proposed.

Enhanced removal of As(Ⅲ) and As(Ⅴ) from aqueous solution using ionic liquid-modified magnetic graphene oxide

In this study, ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6])-modified magnetic graphene oxide (MGO-IL) was prepared for the first time, and was used to adsorb and remove arsenic (As(Ⅲ) and As(V)) ions from aqueous solution. MGO-IL was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and magnetization curves. Effects of ionic liquid type, solution pH, initial arsenic concentration and contact time on the adsorption performance of MGO-IL for As(Ⅲ) and As(V) were studied. The experimental results showed that the adsorption equilibrium was achieved within 30 min, with maximum adsorption capacities of 160.65 mg g−1 for As(Ⅲ) and 104.13 mg g−1 for As(V), respectively, and MGO-IL could be rapidly isolated from solution by applying a magnetic field. MGO-IL was reused for 5 times, without marked decrease in its adsorption capacities. Moreover, common coexisting anions did not interfere with the absorption of As(Ⅲ) and As(V). Compared with MGO, the sorption quantities of MGO-IL for As(Ⅲ) and As(V) were greatly enhanced, and the equilibrium time was significantly reduced. Therefore, MGO-IL can potentially serve as an excellent adsorbent for the simultaneous separation and removal of As(Ⅲ) and As(V) from water.

Broadening of X-ray reflections and inhomogeneous strain distribution in PbZrO3/SrRuO3/SrTiO3 epitaxial heterostructures

Antiferroelectric thin film heterostructures are important in energy storage technology and have prospective applications in domain wall nanoelectronics. The improvement of functional properties of this kind of material is directly connected with the effect of epitaxial strain. Thus, the investigations of strain distribution in the antiferroelectic films volume are on demand. In this work we have studied the distribution of orientational domain states and the condition of near-interface layer in a set of PbZrO3 films with different thickness grown on SrRuO3/SrTiO3 substrate. The analysis of X-ray diffraction curves shows that only the relatively narrow near-interface part of PbZrO3 film experiences significant strain along the normal to the surface, which decays very quickly on moving away from the interface. The out-of-plane strain profiles are strongly similar in films of different thickness above d=50 nm. The inhomogeneous out-of-plane strain is surprisingly of compressive character, which we attribute to the effects of hydrostatic-like compression associated with the presence of edge dislocations. In the films of higher thickness, we observe unusual broadening of the Bragg reflections, which is also tentatively associated with relaxation through the formation of dislocations.

Ultra-broadband 1.0 μm band emission spectroscopy in Pr3+/Nd3+/Yb3+ tri-doped tellurite glass.

Tellurite glasses doped with trivalent Pr3+, Nd3+ and Yb3+ ions were prepared using conventional high-temperature melt-quenching technique and their optical absorption, near-infrared emission, X-ray diffraction (XRD), Raman spectrum, and differential scanning calorimeter (DSC) curve were measured. Upon excitation at 488 nm, an ultra-broadband near-infrared emission extending from 800 to 1120 nm was found to appear owing to the overlapping of the emission bands centered at 900 and 1035 nm of Pr3+, 880 and 1060 nm of Nd3+ as well as 978 nm of Yb3+, respectively. The energy transfer mechanism among Pr3+, Nd3+ and Yb3+ ions which was responsible for the observed ultra-broadband near-infrared emission was investigated to understand the luminescent phenomena. In addition, Judd-Ofelt theory was applied to predict the radiative properties of doped rare-earth ions, and some important radiative parameters such as radiative transition probability, branching ratio and radiative lifetime were derived. Meanwhile, the structural information of amorphous nature and vibrational units was revealed by the XRD pattern and Raman spectrum. Also, the DSC curve displayed the good thermal stability to resist thermal damage for studied tellurite glass with high glass transition temperature. The results indicate that Pr3+/Nd3+/Yb3+ tri-doped tellurite glass is a promising material for ultra-broadband fiber lasers operating around 1.0 μm near-infrared band.

Growth of Germanene on Al(111) Hindered by Surface Alloy Formation

Obtaining pure group IV 2D films on well-behaved substrates is at present a major goal in materials science and of great interest for the associated industries. This goal still represents a challenge in surface science because often these materials tend to form alloys. As a consequence, some of the proposed 2D films resulted in topics of controversy regarding the top-layer elemental composition and interpretation of the honeycomb patterns measured by STM. Very recently, germanene on Al(111) was proposed to be a system having a larger gap than silicene and a quantum-spin Hall effect. This system was studied by several techniques including scanning tunnel microscopy, low-energy electron diffraction, photoemission, and density functional theory. None of the techniques used until now have the capability to detect unambiguously the presence of substrate atoms within the ultrathin film (i.e., separated from the corresponding substrate), thus leaving open the question of the composition or purity of the layer. Here we follow previous guidelines to grow a Ge film on Al(111) with the expected 3 × 3 arrangement that was assumed to be characteristic of germanene, and then we study in situ the properties of the films with ion scattering and recoiling spectrometry, a technique particularly suited for determining the elemental composition of the last surface layer. Our results unambiguously show the formation of a mixture of well-ordered Ge and Al atoms for all of the temperatures and conditions tested, in clear disagreement with the pure single germanene layer proposed in previous works. These conclusions led us to investigate by DFT calculations other possible structures compatible with our present results and the previously reported ones. The most favorable alloyed structures obtained by DFT were then compared with new I–V low-energy electron diffraction curves, and from this comparison, a top surface model composed of five Ge atoms and three Al atoms is proposed to replace the germanene model.

Growth of high-quality organic single crystal of 2-aminopyridinium 4-nitrophenolate 4-nitrophenol (2AP4N) by a novel Rotational Sankaranarayanan–Ramasamy (RSR) method

The good quality 2-aminopyridinium 4-nitrophenolate 4-nitrophenol (2AP4N) single crystals have been grown by (i) Sankaranarayanan–Ramasamy (SR) method and (ii) Rotational Sankaranarayanan–Ramasamy (RSR) method. The effect of rotation on unidirectional crystal growth method (RSR) has been reported for the first time. The apparatus was specially designed and developed for the growth of high-quality crystals by slow cooling under rotational conditions. The high-quality crystals have been achieved under forced convection and the quality of the crystal is compared to the crystals grown under free convection conditions. The crystal structure was analyzed by single crystal X-ray diffraction (SXRD) measurement. The grown crystal was subjected to the powder X-ray diffraction (PXRD) analysis to confirm the growth direction along (0 0 1) plane. The optical quality of the grown crystals has been analyzed by UV–Vis NIR spectrophotometer. It confirms that the grown crystal is highly transparent in the visible and near IR region. The photoluminescence behaviour was recorded in the wavelength region between 450 and 700 nm. It confirms that the grown crystal has emission at 500 nm. The electro-optical properties of the grown crystal were analyzed by photoconductivity measurement and it has positive photoconductivity nature. The grown crystal has less dislocation densities as confirmed by chemical etching analysis. The mechanical strength was investigated by Vickers microhardness tester. The frequency dependent dielectric properties of the crystals were investigated. The laser damage threshold (LDT) was measured for both SR and RSR method grown crystals. The full-width at half maximum (FWHM) of high-resolution X-ray diffraction (HRXRD) curves indicate that the grown crystal has high crystalline perfection. The results obtained from the SR and RSR method grown 2AP4N crystals were compared. The RSR method grown crystal has higher optical transparency, higher photoluminescence, higher photoconductivity, higher mechanical strength, higher laser damage threshold, higher crystalline perfection, less dislocation density, low dielectric loss and low full with at half maximum (FWHM). The second harmonic generation (SHG) of 2AP4N was analyzed by Kurtz-Perry powder technique. The SHG efficiency was found to be 4.5 times that of reference KDP material. The above studies reveal that the RSR method grown crystals are more useful for device applications.

Adsorption, Reclaim, and Regeneration of Cd by Magnetic Calcium Dihydrogen Phosphate Nanoparticles

In order to improve the adsorption-separation of Cd2+ in water treatment, magnetic Fe3O4 coated Ca(H2PO4)2 nanoparticles (NMCDP) were developed by coprecipitation. The properties of these nanoparticles were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and magnetization curves. Experiments were carried out to investigate the effect of adsorption, reclaiming, and regeneration. The results showed that NMCDP was a stable material with a particle size of 60 nm and a saturation magnetization of 30.9 emu·g-1. The adsorption rate of Cd2+ by NMCDP was fast, and adsorption equilibrium could be achieved within 1 hour. The kinetic data were well fitted by a pseudo-second-order model, and the isotherm adsorption data agreed with the Langmuir and Freundlich model, with a maximum adsorption capacity of 142.50 mg·g-1. The adsorption capacity of Cd2+ was affected by the pH and increased when the pH was increased from 2 to 3, while with continued increase of the pH of the solution, the adsorption capacity gradually became stable. The coexisting ions in the solution had an effect on the adsorption of Cd2+, especially the divalent cation Cu2+. The NMCDP could be regenerated by using 0.01 mol·L-1 HCl and EDTA-Na2, and the results indicated that it could be recycled with a desorption rate of 68% by EDTA-Na2 solution.

Comparison of Single/Compound Plasticizer to Prepare Thermoplastic Starch in Starch-Based Packaging Composites

There is a recrystallization problem with natural corn starch, the major raw material of new bio-degradable starch-based composites. To improve the adhesive properties between the starch and the fibers in composites, this paper took formamide, urea, glycerol, and glycol as plasticizers to plasticize corn starch each with the proportions (starch: plasticizer) of 10:2, 10:2.5, 10:3, 10:3.5, and 10:4. Analysis of the FTIR spectra showed that the plasticizers plasticized corn starch through the intermolecular hydrogen bonding. The results from this study showed that the hydrogen bonding between the plasticizer and the starch had the strongest bond and the plasticizing performance was the best when the proportion of starch to plasticizer was 10:3. Study of X-ray diffraction curves showed that the crystallinity of formamide-urea plasticized thermoplastic starch was 1.5 %, lower than that of other plasticizers. The SEM investigation showed that starch plasticization promoted a good 3-D network structure.

Mechanism and modelling of CO2 corrosion on downhole tools.

The conditions surrounding oil and gas exploration are becoming more hazardous, especially in oil and gas fields with a high quantity of corrosive components such as CO2. CO2 causes localized corrosion of tools made from metal, rubber and other materials in humid environments; this leads to corrosion failure in metal equipment and downhole tools such as drills pipes, casings and oil pipes, thereby reducing their service life. In this study, the composition, lattice and crystalline forms of corrosion products and corroded materials were analysed using scanning electron microscopy, energy spectrum analysis, X-ray diffraction and polarization curves, in order to investigate the corrosion mechanisms and influential factors for several common tool materials. A CO2 corrosion model was established for two materials and the results were verified with optimal prediction values.