Superstructure and magnetic properties of R15X9C compounds (R = rare earth; X = Si and Ge)

We report the synthesis of the new compounds R₁₅Si₉C with R = Sm, Gd-Er, Y and R₁₅Ge₉C with R = Ce, Pr and Nd. These compounds crystallize in the hexagonal La₁₅Ge₉Fe structure type (hP50, P6₃mc, Z = 2) which is an ordered superstructure of La₅Ge₃ (Mn₅Si₃-type, hP16, P6₃/mcm, Z = 2). The superstructure is absent in a single-phase R₅Ge₃C_0.33 alloy with R = Sm and Gd. The addition of interstitial carbon modifies the magnetic properties significantly as regards the magnetic transition temperature and the nature of the magnetic ordering. Carbon doping induces mostly a ferromagnetic or ferrimagnetic configuration. The preponderance of ferromagnetic interactions in the superstructure compounds, with respect to the parent phases, can tentatively be attributed to a change in the sign of the RKKY interactions. The dense Kondo lattice state of Ce in ferrimagnetic Ce₅Ge₃ is preserved in Ce₁₅Ge₉C. Large coercive fields (∼4-5 kOe) at low temperatures are observed in most compounds, which exceed ∼50 kOe in the two Sm based compound.     

Morphology and Properties of Deoiled Cake (DOC) Isolated Mixed Proteins and Low-Density Polyethylene Blends

Proteins were isolated from deoiled cakes (DOC) of soybean, castor and rapeseed. The isolated proteins were then blended with LDPE in different wt. ratios, using PEG₄₀₀ as a plasticizer. The morphology of the blends was evaluated by using a scanning electron microscope (SEM). Homogeneous blends were obtained and analyzed for various mechanical properties such as tensile strength, impact strength, hardness and % elongation and compared with properties of plastic sheets prepared from mixture of pure proteins. Results revealed that protein composition and amount of LDPE in proteins and LDPE blend, affects the mechanical properties of the plastic compositions considerably.     

CoS2/MoS2 decorated with nitrogen doped reduced graphene oxide and multiwalled carbon nanotube 3D hybrid as efficient electrocatalyst for hydrogen evolution reaction

Designing an efficient and stable electrocatalyst made of earth abundant elements to take over expensive noble metal based for Hydrogen Evolution Reaction (HER) have been focused. Cobalt disulfide-molybdenum disulfide nanocomposite supported by nitrogen doped reduced graphene oxide and multiwalled carbon nanotubes (CoS₂/MoS₂@NrGO-MWCNT) is reported as an efficient electrocatalyst for HER. CoS₂/MoS₂@N-rGO-MWCNT and ternary hybrids composed of CoS₂, MoS₂ and N-rGO/MWCNT have been investigated. The catalysts were prepared by facile hydrothermal method, and the optimal doping ratio referred to date cobalt to molybdenum as 2:1 was chosen. It is found that co-existence of CoS₂, MoS₂ brings abundant active sites and incorporation of MWCNT offered stability. Good dispersion of CoS₂ nanoparticles on graphene and MoS₂ sheets is observed. Additionally nitrogen doping on rGO sheets has been carried out to boost up the electronegativity of the catalyst as a support to enhance the catalytic activity of CoS₂/MoS₂ for refine structure and better electrical conductance. Precisely, CoS2/MoS2@N-rGO-MWCNT exhibited smaller tafel slope 73 mV dec^?1 at overpotential 281 mV for current density 10 mA cm^?2 and the substantial stability of 14 h is recorded in 0.5 M H₂SO₄ medium, results suggest that catalyst is viable alternate for HER.     

Windows malware detection system based on LSVC recommended hybrid features

To combat exponentially evolved modern malware, an effective Malware Detection System and precise malware classification is highly essential. In this paper, the Linear Support Vector Classification (LSVC) recommended Hybrid Features based Malware Detection System (HF-MDS) has been proposed. It uses a combination of the static and dynamic features of the Portable Executable (PE) files as hybrid features to identify unknown malware. The application program interface calls invoked by the PE files during their execution along with their correspondent category are collected and considered as dynamic features from the PE file behavioural report produced by the Cuckoo Sandbox. The PE files’ header details such as optional header, disk operating system header, and file header are treated as static features. The LSVC is used as a feature selector to choose prominent static and dynamic features from their respective Original Feature Space. The features recommended by the LSVC are highly discriminative and used as final features for the classification process. Different sets of experiments were conducted using real-world malware samples to verify the combination of static and dynamic features, which encourage the classifier to attain high accuracy. The tenfold cross-validation experimental results demonstrate that the proposed HF-MDS is proficient in precisely detecting malware and benign PE files by attaining detection accuracy of 99.743% with sequential minimal optimization classifier consisting of hybrid features.

     

One pot synthesis of TiO2:Eu3+ hierarchical structures as a highly specific luminescent sensing probe for the visualization of latent fingerprints

In the present work, TiO₂:Eu³⁺ (1 mol%–11 mol%) nano powders (NPs) were prepared via a facile one-pot hydrothermal method by using Epigallocatechin Gallate (EGCG) as bio-surfactant. The optimized TiO₂:Eu³⁺ (5 mol%) NPs can be used as fluorescent labeling agent for visualizing of latent fingerprints (LFPs) on various porous and non-porous surfaces. The obtained results exhibit well defined ridge details with high sensitivity, selectivity, and low background hindrance which show greater advantages as compared to conventional powders. We demonstrated the viability of high-performance security labels thorough excellent luminescence for practical anti-mimetic applications. Morphology of the prepared samples is highly dependent on pH, concentration of the bio-surfactant, temperature and time durations. Photoluminescence (PL) emission spectra exhibit intense red emission at ～ 615 nm due to electric dipole transition (⁵D₀→⁷F₂). Photometric (CIE and CCT) results clearly show the intense warm red emission of the optimized samples. Therefore, this work offers a superior and universal luminescent label, which can be applied to visualize miniature LFPs particulars for individualization and consequently display great prospective in forensic investigation.     

The effect of CO2/H2O on the formation of soot particles in the homogeneous environment of a rapid compression facility

Previous investigations show that soot particle volume fraction and number density were significantly reduced by exhaust gas recirculation (EGR) diluents CO₂ and H₂O. However, these investigations were often convoluted by their experimental flame configurations and primarily focused on soot volume fraction rather than soot inception. To isolate the effects on soot inception and the corresponding chemistry, the current study measured the reactivity of CO₂ (up to 9.5% volume fraction) for both C₂H₂ (1.00% volume fraction) and CH₄ (1.85% volume fraction) fuels in homogeneous mixtures. Computed effect of H₂O on these and other fuels are also presented. Experiments were performed at high temperature (1640 K and 1770 K) and high equivalence ratios (Φ = 55 and 75) to understand the effect of CO₂ on polycyclic aromatic hydrocarbons (PAH) and formation of nascent soot particles with negligible oxygen influence. Experimental results show that CO₂ enhanced the soot inception rate when added to C₂H₂ but had an undetectable affect on CH₄. Gas chromatography confirmed that CO₂ increases CO mole fraction and reduces C₂H₂ fuel concentration. Chemical kinetic simulations showed that the C₂H₂ was being converted to soot precursors. CO₂ enhanced the soot inception rate for C₂H₂ by producing OH radicals. Images of nascent soot particles produced in the presence of CO₂ were used to determine the size of PAH molecules in the particles and particle morphology. Both attributes were similar to particles formed without CO₂. CO₂ had little impact on the long reaction pathway from CH₄ to PAH molecules because H and CH₃ radicals propagated these reactions more readily than OH radicals.     

Observations of nascent soot: Molecular deposition and particle morphology

A complete understanding of soot particle formation is critical for accurate combustion models. Limited details are known about the molecules and physical processes involved in the formation of nascent soot. The objective of this study was to discover molecular size distribution and particle morphology from freshly nucleated particles. To accomplish this, particles created in a homogeneous, high temperature (1600–2000 K) and pressure (10 atm) environment were collected at well-resolved times throughout the early stages of soot formation and were imaged with a high-resolution transmission electron microscope (HRTEM). Image post processing revealed that the molecules deposited on both nascent and aged soot particles had a constant size distribution, and that the molecules were likely to be polycyclic aromatic hydrocarbon (PAH) molecules. Additionally, the images revealed particle morphology. At low temperatures, PAH molecules coagulated to form fairly amorphous particle cores. At high temperatures the particle cores became comprised of agglomerated 2–8 nm diameter particles. Eventually all particle cores became surrounded by layers of molecules while the small particles no longer attached as growth species. The imaged transition from small particle agglomeration at the particle core to surface growth was replicated in a coagulation model. The model quantified the increase in small particle agglomeration that was attributed to an increase in the coagulating molecule’s rate of production.     

Effect of preparation and storage of khoa on physicochemical properties of milk fat

The changes in milk fat during the preparation and storage of khoa were studied in three different seasons. Milk fat was extracted from the samples with chloroform using Soxhlet extraction. The solvent was evaporated using a vacuum evaporator followed by nitrogen flushing. The extracted fat samples were analysed for Reichert–Meissl, Polenske, saponification and iodine values, butyro‐refractometer reading at 40 °C and free fatty acids (FFAs). The study revealed an increase in the FFA content during conversion and storage of khoa, while there were small changes in other physicochemical properties of milk fat during the preparation of khoa from raw milk and its subsequent storage at room temperature.     

Synthesis, crystal structure, dielectric properties, and potential use of nanocrystalline complex perovskite ceramic oxide Ba2ErZrO5.5

A new member belongs to Ba₂REZrO_5.5 (RE = Rare-Earth) perovskites, viz. Ba₂ErZrO_5.5, is synthesized as nanocrystals using a combustion process. Unlike the other Ba₂REZrO_5.5 perovskites, which are cubic, Ba₂ErZrO_5.5 crystallizes in tetragonal structure having space group P4/mnc (#128). Phase purity and ultrafine morphology of Ba₂ErZrO_5.5 powders were examined using X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis (TGA), Fourier transform of infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) specific surface area measurements, and transmission electron microscopy (TEM). Nanocrystals of Ba₂ErZrO_5.5 was sintered at ∼1500 °C for 4 h; whereas coarse-grained powders synthesized through solid state reaction could not be sintered even at 1700 °C for prolonged duration. XRD pattern of Ba₂ErZrO_5.5 was refined for atomic coordinates, lattice parameters, occupancies, and thermal factors using Rietveld analysis of XRD. Dielectric constant (?′) of Ba₂ErZrO_5.5 at 10 MHz is 21.62 ± 2 and dielectric loss (tan δ) is 5 × 10⁻³ at room temperature. Similar to the other Ba₂REZrO_5.5 perovskites, Ba₂ErZrO_5.5 is also showed chemically stability with YBa₂Cu₃O_7−δ (YBCO) and Bi₂Sr₂Ca₁Cu₂O_x (Bi-2212) superconductors. Ba₂ErZrO_5.5 can possibly be used as a substrate for high temperature superconductor (HTS) films, or be used as an insulator in the active superconductor-insulator-superconductor (SIS) structures.     

Synthesis,characterization, and thermal properties of tris (3‐aminophenyl) phosphine oxide‐based nadimide resins

This article describes the synthesis, characterization, and thermal properties of nadimides obtained by reacting endo‐5‐norbornene‐2,3‐dicarboxylic acid anhydride (nadic anhydride) (NA), 4,4′‐oxodiphthalic anhydride (ODA), 1,4,5,8‐naphthalene tetra carboxylic dianhydride (NTDA) in glacial acetic acid/DMF. Structural characterization of the resins was done by elemental analysis, IR, ¹H‐NMR, and ¹³C‐NMR. The DSC scan showed the endothermic transition in the temperature range of 120–270°C. Multistep decomposition was observed in the TG scan of uncured resins in nitrogen atmosphere. Isothermal curing of the resins was done at 250 and 300°C for 1 h in an air atmosphere. These cured resins were stable to (350 ± 30)°C and decomposed in a single step above this temperature. This may be due to the retro Diels Alder (RDA) reaction. The char yield of the resins increased significantly on curing. The char yield was highest for P‐2N resin and this could be due to the presence of rigid skeleton i.e. naphthalene. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008