Cubic Phase Research Articles

Nano-structured Bimetallic (Ni,Co) Sulphide Complex, Synthesis Characterization and Thin Film Deposition by PVD Assisted Technique

Transition metal sulfides have attracted great attention owing to their outstanding properties and varied applications in photovoltaic devices. Ternary nickel cobalt sulfides are materials that have been considered as good electrode material for high performance energy storage devices owing to their higher electrochemical activity and capacity as compared to mono-metal sulfides. NiCo2S4 compound has been synthesized by annealing of its respective metal diethyl dithiocarbamtes (Cobalt and Nickel) complexes. Furthermore the compound formed was characterized by UVVis absorption which reveals that C10H20NiN2S4 has λmax at 290 nm while C10H20CoN2S4 has λmax at 321 nm and NiCo2S4 at 291 nm, FTIR of cobalt diethyl dithiocarbamate showing bands at 1487cm-1 and 1064 cm-1 while nickel diethyl dithiocarbamate showing bands at 1519 cm-1 and 993 cm-1 and NiCo2S4 showing sulfide stretchings at 447 cm-1 and 619 cm-1, in XRD major peaks were at 2θ=18Eš, 24Eš, 31.5Eš, 33Eš, 41Eš) while SEM confirmed the cubic structure of crystals. All the results indicated the synthesis of crystalline nickel cobalt sulfide. Thin films of nickel cobalt sulfide were made using PVD technique and calculated band gap was found to be 2.4 eV. Thus it is suggested that compound formed is excellent material for use in supercapacitors and also as an electrode material.

Parameter estimation for maneuvering targets with complex motion via scaled double-autocorrelation transform

In this paper, a novel parameter estimation method is proposed for maneuvering targets with complex motion. In the proposed method, the second-order keystone transform (SOKT) and modified range cell migration correction (RCMC)/integration are jointly applied to overcome the velocity ambiguity and eliminate the envelope migration. Then, since the azimuth echoes of maneuvering targets with complex motion can be modeled as cubic phase (CP) signals after motion compensation, a new transform, namely, scaled double-autocorrelation transform (SCDCT), is defined. This transform can be essentially interpreted as the two-dimensional (2-D) Fourier transform (FT) of a scaled parametric instantaneous double-autocorrelation (PIDAC) function. By employing this derived transform, the estimated chirp rates and derivative of chirp rates of CP signals can be obtained simultaneously without searching operation and thus the computational burden can be reduced significantly. Furthermore, the characteristics of cross terms and anti-noise performance of SCDCT are theoretically analyzed. Compared with three other popular methods, product high-order match phase transform, TC-dechirp Clean and modified discrete chirp Fourier transform, the proposed SCDCT-based method is more computationally efficient and has better estimation performance in low signal-to-noise ratio (SNR) circumstance. Simulation results verify the effectiveness of the proposed SCDCT-based method.

Interpenetrating Metal-Metalloporphyrin Framework for Selective CO2 Uptake and Chemical Transformation of CO2.

Herein we report a robust primitive cubic (pcu)-topology metal-metalloporphyrin framework (MMPF), MMPF-18, which was constructed from a ubiquitous secondary building unit of a tetranuclear zinc cluster, Zn4(μ4-O)(-COO)6, and a linear organic linker of 5,15-bis(4-carboxyphenyl)porphyrin (H2bcpp). The strong π-π stacking from porphyrins and the lengthy H2bcpp ligand affords a 4-fold-interpenetrating network along with reduced void spaces and confined narrow channels. Thereby, MMPF-18 presents segmented pores and high-density metalloporphyrin centers for selective CO2 uptake over CH4 and size-selective chemical transformation of CO2 with epoxides forming cyclic carbonates under ambient conditions.

Hardness Evaluation of Dental Composite with Ceramic Fillers

In this study, new dental composites materials were developed. The two composites systems composed of zirconia (ZrO2), alumina (Al2O3) and silica (SiO2) (composites A) and zirconia (ZrO2), calcium (CaO), and silica (SiO2) (composites B) were synthesized through sol-gel method. These two systems were combined with urethane dimethacrylate and tetraethylene glycol dimethacrylate with 1% chitosan as coupling agent to build up the dental composites material. The resulting composites were subject to evaluation by microvickers hardness test and X-ray diffraction. The microvickers hardness test revealed that the hardness value for composites A and B were 24.48 and 21.9 VHN, respectively. Furthermore, the data were submitted to t-test (α=0,01) and it showed t count of both samples was 0,871 which means between the -t1-½α< t <t1-½α thus showing statistically the same average hardness value of both samples. Eventually, the new dental composites could be anticipated to apply in dental composites filler. The hardness results support the XRD result revealed that tetragonal crystal phase will help the transformation toughening mechanism and cubical crystal phase of zirconium dioxide. Both of the crystal phases were formed to stabilize the zirconia.

Effect of dysprosium concentration on thermoluminescence behavior of ZrO2:Eu3+ phosphor

This work describes the change in thermoluminescence (TL) behavior of ZrO2:Eu3+ nanoparticles due to the dysprosium co-doping synthesized by using the conventional solid state synthesis method. They were characterized by X-ray diffraction (XRD), FTIR (Fourier transform infrared spectroscopy) and transmission electron microscope (TEM). The XRD result shows a nanocrystalline material with a cubical phase along, while TEM images display particles of spherical shapes of diameters in the 25–35nm range. We report on the TL glow curves and kinetic parameters, activation energy, order of kinetics, and the frequency factor of europium, dysposium co-doped zirconium (ZrO2:Eu3+, Dy3+) phosphor under UV irradiations, The TL glow curves were recorded for different doses of UV exposure at a heating rate of 5°C/s. The kinetic parameters activation energy E, the order of kinetics b, and the frequency factor S of synthesized phosphor of ZrO2:Eu3+, Dy3+ have been calculated by using a peak shape method.

Novel Facile Technique for Synthesis of Stable Cuprous Oxide (Cu2O) Nanoparticles – an Ageing Effect

A novel facile method to synthesize stable phase of Cuprous Oxide (Cu2O) nanoparticles at room temperature is demonstrated. The structural and optical properties of (Cu2O) nanoparticles were investigated by using X-ray diffraction (XRD), UV-VIS Spectroscopy. XRD analysis has indexed nanocrystalline nature of cubical phase Cu2O with an average edge length of about 20 nm. The Scanning Electron Microscopy (SEM) measurements also ascertain the cubical morphology. The Fourier Transform Infrared Spectroscopy (FTIR) affirms the presence of characteristic functional group of Cu2O. The absorbance peak at 485 nm in UV-VIS spectra also confirms the Cu2O synthesis. Furthermore, UV-VIS absorbance spectra at different ageing time substantiate the phase stability of Cu2O nanoparticles. The ageing leads to blue shift of absorbance peak mainly due to decrease in Cu2O particle size with no additional absorbance peak in UV-VIS spectra indicating the formation of secondary phase. The reduction in particle size may be attributed to tiny conversion Cu2O to CuO. The energy band gap measurements from Tauc plots for Cu2O nanoparticles shows the increasing trend (2.5 eV to 2.8 eV) with ageing time (2 months), owing to quantum confinement effects.

Crystal engineering of a family of hybrid ultramicroporous materials based upon interpenetration and dichromate linkers.

A new family of 2-fold interpenetrated primitive cubic (pcu) networks of formula [M(L)2(Cr2O7)] n (M = Co2+, Ni2+, Cu2+ and Zn2+; L = 4,4'-azopyridine), DICRO-3-M-i, has been synthesised and their structures, permanent porosity and gas sorption properties were comprehensively characterised. Molecular simulations indicate that CO2 molecules occupy both of the two distinct ultramicropores that run through this isostructural series. The orientation of the Cr2O72- pillars is thought to contribute to high isosteric enthalpy of adsorption (Qst) towards CO2 and temperature programmed desorption experiments reveal that DICRO-3-Ni-i selectively adsorbs CO2 from gas mixtures that simulate flue gas. Performance in this context is among the highest for physisorbents measured to date and these materials are readily regenerated at 50 °C.

The Conductivity Tensor and Induced Current in the Simple Cubic Phase of the Endohedral La@C_(82) (C_(82)) Crystal

The Conductivity Tensor and Induced Current in the Simple Cubic Phase of the Endohedral La@C_(82) (C_(82)) Crystal

Re-Gauging Groupoid, Symmetries and Degeneracies for Graph Hamiltonians and Applications to the Gyroid Wire Network

We study a class of graph Hamiltonians given by a type of quiver representation to which we can associate (non)-commutative geometries. By selecting gauging data, these geometries are realized by matrices through an explicit construction or a Kan extension. We describe the changes in gauge via the action of a re-gauging groupoid. It acts via matrices that give rise to a noncommutative 2-cocycle and hence to a groupoid extension (gerbe). We furthermore show that automorphisms of the underlying graph of the quiver can be lifted to extended symmetry groups of re-gaugings. In the commutative case, we deduce that the extended symmetries act via a projective representation. This yields isotypical decompositions and super-selection rules. We apply these results to the primitive cubic, diamond, gyroid and honeycomb wire networks using representation theory for projective groups and show that all the degeneracies in the spectra are consequences of these enhanced symmetries. This includes the Dirac points of the G(yroid) and the honeycomb systems.

Predicting the Crystal Structure and Phase Transitions in High-Entropy Alloys

High-entropy alloys (HEAs) have advantageous properties compared with other systems as a result of their chemistry and crystal structure. The transition between a face-centered cubic (FCC) and body-centered cubic (BCC) structure in the Al x CoCrFeNi high-entropy alloy system has been investigated on the atomic scale in this work. The Al x CoCrFeNi system, as well as being a useful system itself, can also be considered a model HEA material. Ordering in the FCC structure was investigated, and an order–disorder transition was predicted at ~600 K. It was found that, at low temperatures, an ordered lattice is favored over a truly random lattice. The fully disordered BCC structure was found to be unstable. When partial ordering was imposed (lowering the symmetry), with Al and Ni limited specific sites of the BCC system, the BCC packing was stabilized. Decomposition of the ordered BCC single phase into a dual phase (Al-Ni rich and Fe-Cr rich) is also considered.

The ferroelectricity in perovskite K0.85Ba0.15TaO3+0.075 nanocrystallites

The perovskite K0.85Ba0.15TaO3+0.075 nanocrystallites have been synthesized by mild hydrothermal method for the first time. The powder X-ray diffraction analysis indicates that the crystallographic structure is a primitive cubic, space group Pm-3m with a unit cell edge a=4.00Å. Heavily Ba doped in K-site was achieved in the perovskite structure with excess oxygen to balance the charge. The chemical substitution changes the crystal structure and electronic structure of KTaO3, which has an impact on its polarization property and induce a ferroelectric phase. The temperature-dependent dielectric response from 300K to 600K and hysteresis loop at 300K provide direct evidence for the ferroelectric character. Its Curie temperature has been obtained from relative dielectric and thermal analysis (TC=460K).

Effect of Heat Treatment Temperature on the Spectral Properties of Cu-Ni Coating.

Cu-Ni coatings were prepared on the surface of nickel by electrodeposition method, and Cu-Ni coatings were heat-treated in 25-900 °C. Heat-treated Cu-Ni coatings were characterized with scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDAX) and X-ray diffraction (XRD) techniques, respectively. Effects of heat treatment temperature on the spectral properties of Cu-Ni coatings were studied. The surface of Cu-Ni coating is composed of the nodules. The nodules of Cu-Ni coating surface become smaller with the increase in heat treatment temperature in 25-600 °C. The nodules of Cu-Ni coating surface become smaller and the dividing line between the nodules becomes more blurred with the increase in heat treatment temperature in 600-900 °C. The contents of copper in Cu-Ni coating decrease from 82.52 at % to 78.30 at % with the increase in heat treatment temperature in the range of 25-900 °C; the contents of nickel in Cu-Ni coating increase from 17.48 at % to 21.70 at % with the increase in heat treatment temperature in the range of 25-900 °C. The crystal structure of Cu-Ni coating is Cu0:8lNi0.19 cubic crystal structure. The crystal structure of the CuO0.81Ni0.19 becomes more complete with the increase in heat treatment temperature in 25- 300 °C. Part of crystal structure of the Cu0.81AlNi0.19 can turn Cu0.8lNi0.19 cubic crystal structure into Cu3.8Ni cubic crystal structure, and is advantageous to Cu3.8Ni (311) and Cu0.81Ni0.19 (311) growth with the increase in heat treatment temperature in 600-900 °C.

Thermodynamic Parameters of PbTe Crystals: DFT-Calculations

Based on the analysis of the crystal NaCl type and electronic structure of cubic phase CdS crystals the cluster models have been built for calculation of the geometric and thermodynamic parameters. According to density functional theory (DFT) and using the hybrid valence base set B3LYP the temperature dependence of the energy ΔE and the enthalpy ΔH of formation, Gibbs free energy ΔG, entropy ΔS, specific heat at constant volume CV and pressure CP of the crystals have been found. The analytical expressions of the temperature dependences of presented thermodynamic parameters which was approximated from the quantum- chemical calculations data and with using mathematical package Maple 14 have been received.

Novel mode of 2-fold interpenetration observed in a primitive cubic network of formula [Ni(1,2-bis(4-pyridyl)acetylene)2(Cr2O7)]n.

A primitive cubic (pcu) network of formula [Ni(1,2-bis(4-pyridyl)acetylene)2(Cr2O7)]n, , has been synthesised and found to exhibit a novel type of inclined 2-fold interpenetration and an isosteric heat of adsorption (Q(st)) of 30.5 kJ mol(-1) towards CO2 at zero loading. Q(st) is relatively high in the broad context but less than that observed in related hybrid ultramicroporous materials, a feature that can be understood after studying pore structure and molecular simulations of CO2 adsorption.

The Effect of Zinc Concentration on the Structural, Morphological and Optical Properties of CdS: Zn Nanocrystalline Prepared by Chemical Bath Deposition

Undoped Cadmium sulfide (CdS) nanocrystalline thin film and doped Zinc are prepared by chemical bath deposition (CBD) technique. The characterization of the product was done by UV-VIS absorption, x-ray diffraction (XRD) and atomic force microscopy (AFM). The effect of zinc content on structural, morphological and several optical properties have been studied. The X-ray diffraction (XRD) analysis revealed that the films were polycrystalline and exhibited two phases cubic and hexagonal structure which increases the cubic phase and Zn ratio. Atomic force microscopy images show uniform, homogeneous and strong adherent to Undoped (CdS) nanocrystalline and doped Zinc over the entire glass substrate surface without any voids, pinholes or cracks. This reveals a continuous granular morphology for the films and therefore the average grain size changes which increase the zinc content and the band gap of the thin films which are found to be direct allowed transition. The optical characterizations of the as deposited and annealed films were carried out using UV. VIS transmittance spectroscopy in the wavelength range 300.1100 nm. The results show that in the visible region the transmittance of the films decreases as the containing of Zn increases. The reverse is the case with the absorbance as it was observed to be increased in the same region. The result also shows that the absorption coefficient, extinction coefficient, real and imaginary parts of dielectric constant are tending to increase with the increasing of Zn concentration.

Synthesis, characterization and time dependent phase transformation of Li0.4WO3 bronze

Abstract Lithium tungsten bronzes with a nominal composition of Li0.4WO3 were synthesized by solid state reactions in silica tubes at 973 K and various low pressures. Samples were characterized using X-ray single crystal and powder diffraction, and neutron powder diffraction. The air pressure inside the sealed quartz tubes played roles for the formation of Li0.4WO3 phases with different symmetries. Whereas using a pressure of 10–7 MPa a pure body centered cubic (Im 3 ¯ $\bar 3$ ) tungsten bronze was formed, at higher pressures (>10–7 MPa) a mixture of Im 3 ¯ $\bar 3$ and primitive cubic (Pm 3 ¯ $\bar 3$ m) perovskite tungsten bronzes were observed with pressure dependent phase fractions. While keeping the synthesized samples under open atmospheric conditions the Im 3 ¯ $\bar 3$ phase gradually transformed into a tetragonal perovskite (P4/nmm) tungsten bronze. The slow cubic into tetragonal phase transformation has been explained in terms of the mobility of lithium within two different crystallographic sites.

Structural transitions of ternary imide Li2Mg(NH)2 for hydrogen storage

Phase transitions and energetic properties of Li2Mg(NH)2 with different crystal structures are investigated by experiments and first-principles calculations. The Li2Mg(NH)2 with the primitive cubic and orthorhombic structure is obtained by dynamically dehydrogenating a Mg(NH2)2-2LiH mixture up to 280 °C under an initial vacuum and 9.0 bars H2, respectively. It is found that the obtained orthorhombic Li2Mg(NH)2 is converted to a primitive cubic structure as the dehydrogenation temperature is further increased to 400 °C or performed by a 36 h of high-energetic ball milling. Moreover, the primitive cubic phase can be converted to an orthorhombic phase after heating at 280 °C under 9.0 bars H2 for 1 h. Thermodynamic calculations show that the orthorhombic phase is the ground state structure of Li2Mg(NH)2. The mechanism for phase transitions of Li2Mg(NH)2 is also discussed from the angle of energy.

Thickness Dependent Photoelectrochemical Performance of Chemo-Synthesized Nanostructured CdS Thin Films

Abstract Thin films of cadmium sulfide (CdS) with different film thicknesses were chemo-synthesized onto soda lime glass and fluorine doped tin oxide (FTO) coated glass substrates. The synthesized CdS films were characterized by using UV-vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The XRD patterns revealed the formation of CdS with a cubic crystal structure. The variation in band gap energies was found to be in the range of 2.42–2.85 eV. An increase of 0.43 eV over the bulk band gap energy of CdS was found due to the quantum size effect in CdS thin films. The atomic force microscopy study depicted a novel egg-like morphology of CdS nanoparticles. Further, photoelectrochemical (PEC) performance of as grown CdS thin films was investigated using two electrode configurations in polysulfide electrolyte. The sample with film thickness 1389 Å showed the best PEC performance compared to other samples.

The synthesis of core-shell monodisperse P(St-MAA) microspheres and fabrication of photonic crystals Structure with Tunable Colors on polyester fabrics

The core-shell monodisperse P(St-MAA) microspheres with different diameters ranging from 200 nm to 400 nm were prepared by soap-free emulsion copolymerization, in which styrene (St) and methacrylic acid (MAA) were polymerizable monomers, and ammonium persulfate (APS) acted as initiator. The diameters and monodispersity of P(St-MAA) microspheres could be controlled by adjusting the concentrations of styrene, methacrylic acid and ammonium persulfate. The core-shell structure and chemical component distribution of the P(St-MAA) microspheres were confirmed by TEM and XPS. The photonic crystals on polyester fabrics with three-dimensionally ordered arrangement were fabricated by self-assembly of gravitational sedimentation with P(St-MAA) microspheres and exhibited brilliant structural colors without any chemical dyes and pigments. SEM, TEM and crystallographic analysis were applied to confirm a face centered cubic (fcc) structure of the photonic crystals on polyester fabrics. The versatile structural colors of the photonic crystals were dependent on the photonic band-gap which could be regulated by the spherical size of P(St-MAA) microspheres and viewing angles. This technology may provide a new strategy to color the fabrics and reduce the pollution in the current textile industry.

Tuning Photoluminescence Emission of a Cadmium–Organic Framework by Excitation

AbstractA novel three‐dimensional metal–organic framework with primitive cubic (pcu) topology exhibits interesting tunable photoluminescent emission based on the variation of excitation light at room temperature. By judicious choice of two different conjugated organic linkers incorporating in a certain framework, the contributions of distinct emission bands may be finely controlled. This work may provide a new route to explore functional luminescent materials with tunable photoluminescence.