Study on degrees of mesomorphic zone of polymer.Ⅰ.Determination of degrees of crystallinity of Eucommia ulmoides gum and natural rubber by dynamic mechanical thermal analysis

According to the two-phase model theories of polymer crystallization, the degree of crystallinity of natural rubber (NR) induced to crystallize at −25 °C can be directly determined by dynamic mechanical thermal analysis (DMTA) by testing its tanδ peak areas of crystalline state and 100% amorphous state respectively. The degree of crystallinity is 86% when the induction time increases to 12 h. However, due to the tanδ peak area of 100% amorphous state cannot be measured by DMTA directly, the degree of crystallinity of Eucommia Ulmoides (EU) gum can only be determined indirectly with DMTA by using the tanδ peak areas of 100% amorphous state extrapolated from the linear equation (y = ax + b) which is derived from the relationship between tanδ peak areas and crosslink densities. The degree of crystallinity is 87%, which is very close to NR. The crystallization of NR can be prevented effectively by increasing slightly the crosslink density to the critical crystallization point, which is 6.20 × 10⁻⁵mol/cm⁻³ for vulcanized NR induced to crystallize at −25 °C for 4 h. However, it is very hard for EU gum to prevent the crystallization by crosslinking. Because, with increasing of the crosslink density, the EU gum will firstly show a percolation threshold, which is 53.34 × 10⁻⁵mol/cm⁻³, and the degree of crystallinity is 71.04%. Then, like NR, the degree of crystallinity of EU gum will decrease rapidly to zero by increasing the crosslink density to the critical crystallization point, which is 68.89 × 10⁻⁵mol/cm⁻³. In the end of the paper, the linear relationship of the equation is verified and the influence factors on slope a and intercept b of the linear equation are discussed as well.     

Anisotropic compressive behavior of rigid PVC foam at strain rates up to 200 s−1

The elevated strain rate compressive response of closed-cell polyvinyl chloride (PVC) foam at various densities is investigated. Two loading directions, (i.e., parallel and perpendicular to foam rise direction) were considered to investigate structural anisotropy. The elevated strain rates tests (up to 200 s⁻¹) were performed using a customized drop tower device. Engineering stress/strain behavior, energy dissipation, and maximum stress capacity were obtained for each density and compared against each other. Except for the lowest density of 45 kg/m³, strain rate effects were clearly observed through increased compressive strength and plateau stress when loading in the foam rise direction. The strain rate effect is more evident at higher densities. However, no significant strain rate effect was observed when loading perpendicular to the foam rise direction. Scanning electron microscopy (SEM) analysis showed that plastic hinges are the primary deformation mechanism for PVC foam cells. An analytical model has been calibrated using the experimental results and successfully predicted the mechanical response of the foam. Shape anisotropy has been measured employing the SEM images. The analytical approach was also able to predict the foam's anisotropic mechanical response.     

Effect of 120 MeV Au9+ ion irradiation on the structure and surface morphology of ZnO/NiO heterojunction

ZnO/NiO thin films, each of thickness 100 nm, were deposited on Si(100) substrate by pulsed laser deposition method. The resulting heterojunction, ZnO/NiO/Si, was irradiated by 120 MeV Au⁹⁺ ions and characterized by grazing incidence X‐ray diffraction (GIXRD), Raman spectroscopy, and atomic force microscopy (AFM). The GIXRD confirmed the presence of both NiO and ZnO in the samples. Ion irradiation induced suppression of crystalline nature, and the recrystallization of the same occurred at the fluence of 1 × 10¹³ ions cm⁻². The occurrence of most intense band at 302 cm⁻¹ in Raman spectra corresponds to the symmetric stretching vibration of ZnO. The linear shift of stretching mode of ZnO with ion fluence could be associated with the effect of compressive stress in the material. AFM analysis of the films indicated that the rms roughness increased when the film is irradiated at a fluence of 1 × 10¹² ions cm⁻². Beyond this fluence, the value of roughness decreased up to fluence of 1 × 10¹³ ions cm⁻² and increased thereafter. To see the effect of the stress of buffer layer on the surface layer, we calculated the stress for NiO layer with ion fluence form the lattice parameter. Comparing the stress of buffer layer with roughness of surface layer at the given fluence, we can say that the compressive stress in the buffer layer could possibly control the roughness of the surface layer.     

Mechanical,acoustical and flammability properties of SBR and SBR-PU foam layered structure

In this work a layer structure from styrene butadiene rubber (SBR) composites and PU foam with improved flame retardancy property and high sound absorption coefficient at frequency range (200–500 Hz). Different types of flame retardants; iron (acrylic-co-acrylamide) as metal chelate (MC), magnesium hydroxide (MOH) and sodium tripolyphosphate (STP) were blended with SBR. The type and loading level of flame retardant had a great effect on filler dispersion and consequently on mechanical properties of SBR. MOH exhibited the best dispersion as indicated from scanning electron microscope (SEM), and SBR/MOH samples had almost the highest crosslink density (16.04*10⁻⁵ g⁻¹ mol) and the best mechanical properties where the tensile strength was improved by 32.7% at 40 phr MOH. Horizontal burning rate of SBR composites indicated that MC and MOH reduced the rate of burning of SBR at all loading levels. TGA data presented that the addition of flame retardants to SBR increased the maximum decomposition temperature in all composites. A double and triple layer structures of SBR composite and PU foam was designed. The effect of 2.5 cm air cavity on the sound absorption coefficient of SBR-PU foam layered structure was studied. The presence of air cavity behind the layered structure improved the sound absorption in the range of (200–500 Hz) better than the existence of it between the layers. The triple-layer structure gave higher sound absorption coefficient at lower frequencies than that obtained with the double-layer structure where it reached to ≥0.98 at 315 Hz.     

Terminal end-on coordination of dinitrogen versus isoelectronic CO: A comparison using the charge displacement analysis

The metal dinitrogen bonding in a wide series of terminal end-on dinitrogen complexes is investigated with the charge displacement analysis based on natural orbitals of chemical valence (CD-NOCV). The effect of the σ donation and π backdonation on the N N bond are discussed and compared with the observations for a series of carbonyl complexes, published in 2016 by Tarantelli et al. The σ donation is relative invariant over the series of dinitrogen complexes and has no significant effect on the N N bond strength, whereas the π backdonation causes a considerable elongation of the N N bond. Some uncommon examples of weakly bound dinitrogen with blue-shifted stretching frequency compared to free N₂ (ν = 2330 cm⁻¹) are known. The dinitrogen bonding in these complexes is simulated with a point charge. Apparently, electrostatics account for the shortened N─N bond in these systems.     

Electrically rechargeable zinc-oxygen flow battery with high power density

The development of a powerful, cyclically stable and electrically rechargeable zinc-oxygen battery with a three-electrode configuration is reported. A copper foam was used as stable substrate for zinc deposition in flowing potassium hydroxide electrolyte, while oxygen reduction and evolution were accomplished by a commercial silver electrode and a nickel foam, respectively. The cell could be charged and discharged with up to 600 mA cm^− 2, delivered a peak power density of 270 mW cm^− 2, and performed for more than 600 cycles, although short circuits by dendrite formation could not yet be completely avoided. At a current density of 50 mA cm^− 2 and a temperature of 30 °C, a promising energy efficiency of 54% was achieved.     

Infrared spectral characteristics of noncyclic carbonylureas

Noncyclic diacylimides (noncyclic carbonylureas) have NH frequencies higher than cyclic diacylimides. In solid state spectra, two bands at 3240-3220 cm⁻¹ and 3140-3120 cm⁻¹, and in chloroform spectra, one band at 3480-3380 cm⁻¹ appear consistently in all compounds under discussion. Consequently, these bands could be considered as characteristic of noncyclic diacylimides, and furthermore, the occurrence of several weak bands in the region 3300–3100 cm⁻¹ along with regular NH bands may be considered as characteristic of noncyclic diacylimides. By contrast, cyclic diacylimides in the solid state show two widely separated carbonyl bands in the 1790-1720 cm⁻¹ and 1710-1670 cm⁻¹ regions, whereas in noncyclic diacylimides these bands appear as one strong band at 1670-1660 cm⁻¹ with a weak shoulder at 1690-1680 cm⁻¹. Furthermore, the compounds behave like secondary amides, as there appear amide I, II and III bands regularly. The amide II band seems to be characteristic of noncyclic diacylimides, as the band is missing in cyclic diacylimides.     

Resonance Raman studies of the coupled binuclear copper active site in met azide hemocyanin

Spectroscopic studies were performed on the met azide derivative of hemocyanin in order to probe small molecule binding to the coupled binuclear copper active site. The charge transfer spectrum shows a broad band near 380 nm in the absorption and a negative feature near 450 nm in the CD. Resonance Raman results indicate the presence of two enhanced vibrations, the copper—azide stretch at 397 cm⁻¹ and the asymmetric intraazide stretch at 2042 cm⁻¹. The 397 cm⁻¹ peak is maximally enhanced near 500 nm and the 2042 cm⁻¹ peak shows increasing enhancement into the u.v. At least three separate charge transfer transitions are needed to simultaneously fit the absorption, CD and resonance Raman profile, which requires that the azide bridges the binuclear copper active site. Mixed isotope results, using ¹⁴N¹⁴N¹⁵N, shows that the 2042 cm⁻¹ peak splits into two peaks at 2023 and 2035 cm⁻¹ and the 397 cm⁻¹ peak shifts to 393 cm⁻¹. A normal coordinate analysis was used to determine that the mixed isotopic splitting is not due to a simple mass effect but requires nonequivalence in bonding within the azide molecule. Combined with previous data, the results indicate that the azide is bound in a μ-1,3 geometry and the nonequivalence in bonding within the azide molecule is due to a strong interaction with residue(s) in the protein pocket.     

Rapeseed oil as main component in synthesis of bio-polyurethane-polyisocyanurate porous materials modified with carbon fibers

Porous polyurethane-polyisocyanurate (PUR-PIR) composites have been synthesized using two types of rapeseed oil-based bio-polyols. The bio-polyols from rapeseed oil were synthesized using two methods: (i) transesterification and (ii) epoxidation followed by oxirane ring opening. The PUR-PIR porous materials were prepared with two isocyanate indices, 150 and 250, and were modified with carbon fibres (CF) in an amount of 3 and 6 wt% of the total foam mass. The structure of the composites was examined using scanning electron microscopy. Thermal and mechanical properties of the composites were determined through a thermogravimetric analysis and measurements of the thermal conductivity, compressive strength, and Young modulus. The influence of CF on the composite flammability was analyzed using oxygen index and cone calorimeter tests. The investigations of the mechanical properties have shown that the compressive strength is the most beneficial in the case of the PUR-PIR foams modified with 6 wt % of CF. The studies have shown that the oxygen index of the composites increases with an increasing CF content and isocyanate index. An addition of CF reduces the heat rate release, especially for the materials with an isocyanate index of 250. An introduction of CF into the PUR-PIR foam structure is a way to improve the thermal stability and to decrease the flammability of final porous composites.     

The effect of apodization and finite resolution on Fourier transform Raman spectra

The effects that finite resolution and choice of apodization function have on Fourier transform (FT) Raman spectra are illustrated by the 839 cm⁻¹ (ν₁) and 914 cm⁻¹ bands of KMnO₄. FT-Raman spectra were recorded at 0.5, 1, 2, 4, 8, 16 and 32 cm⁻¹ resolution using boxcar, Norton—Beer (strong, medium and weak) and triangular apodization functions at each resolution. The results show the dramatic changes in bandshape that occur as the ratio (resolution/true full width at half height of band) increases. The changes were measured in terms of the full width at half height of the band, the height of the band, the area of the band and the bandshape (expressed as a sum of Lorentzian and Gaussian lines). At a given resolution the degree to which each of these characteristics is affected is strongly dependent on the choice of the apodization function.     

Analysis and identification of irradiated Spirulina powder by a three-step infrared macro-fingerprint spectroscopy

A three-step infrared (IR) macro-fingerprint method combining conventional IR spectra, and the secondary derivative spectra with two-dimensional infrared correlation spectroscopy (2D-IR), was developed to analyze Spirulina powder before and after gamma irradiation. In the IR spectra, most of the absorption peaks of samples irradiated at 1, 2.7, 6, and 10.4 kGy had lower intensities than the non-irradiated ones, whereas peaks at 1152, 1078, and 1051 cm⁻¹ were slightly enhanced with irradiation at 2.7, 6, and 10.4 kGy. Their second derivative spectra amplified the differences and revealed that irradiation affected the C=O band of carboxylic acid and esters, and the N–H band of proteins. The peaks at 1746 and 1741 cm⁻¹, and those at 1730 and 1725  cm⁻¹ became two broad peaks. Meanwhile, the three sharp peaks at 1548 cm⁻¹, 1544 cm⁻¹ and 1536 cm⁻¹ changed to two broad peaks at around 1547 and 1534 cm⁻¹ after irradiation at doses higher than 1 kGy. The characteristic IR bands from 1700 cm⁻¹ to 1600 cm⁻¹, which represent the C=O band in proteins, also have different shapes and intensities after irradiation. The finding indicated that irradiation affected the secondary structures of protein which was confirmed by curve fitting results. During the process of increasing the temperature from 50 to 210 °C, the ratio of amide I to II in absorption intensities in the 2D-IR spectra of the irradiated samples varied with different response for different samples. Saccharides in Spirulina powder had a higher thermostability than proteins, but the autopeaks of irradiated samples did show differences from the non-irradiated sample. The intensity of autopeaks at 1012 cm⁻¹ increased dramatically in the irradiated samples while that of peaks at 1053, 1071, and 1083 cm⁻¹ decreased after irradiation. Based on the three-step IR macro-fingerprint method, irradiated Spirulina powder samples were successfully and fast identified and discriminated.     

Ultra-lightweight paper foams: processing and properties

A methodology for producing a low density cellulose-based foam has been developed by combining a surfactant with pulp, mixing at high velocity to entrain air, and then drying in a non-restrained fashion. The structure of the foam, characterized through optical microscopy and X-ray computed tomographic microscopy, consists of pulp fibres in random orientations surrounding air bubbles along with large void spaces. Through careful design of experiments, the effect of fibre type, length distribution, surfactant, and air content on the mechanical behavior and permeability of the foam material was investigated. The results indicate that foamed cellulose materials can be produced at a strength of one-half the tensile strength of a standard handsheet, but having a relative density of only one percent. No chemical additives were used to enhance the strength of these samples as the properties of the foam material are enhanced simply through variation of the process parameters. Thus, a strong cellulose-based foam, with a density as low as 10 mg/cm³, can be fabricated using standard papermaking infrastructure and hence at low cost.     

Mechanical properties,thermal stability,sound absorption,and flame retardancy of rigid PU foam composites containing a fire‐retarding agent: Effect of magnesium hydroxide and aluminum hydroxide

Isocyanate, polyether polyol, a flame retardant (10 wt%), and aluminum hydroxide/magnesium hydroxide (0, 5, 10, 15, and 20 wt%) are used to form the rigid polyurethane (PU) foam, while nylon nonwoven fabrics and a polyester aluminum foil are combined to serve as the panel. The rigid PU foam and panel are combined to form the rigid foam composites. The cell structure, compressive stress, combustion resistance, thermal stability, sound absorption, and electromagnetic interference shielding effectiveness (EMI SE) of the rigid foam composites are evaluated, examining the effects of using aluminum hydroxide and magnesium hydroxide. Compared with magnesium hydroxide, aluminum hydroxide exhibits superior performance to the rigid foam composites. When aluminum hydroxide is 20 wt%, the rigid foam composite has an optimal density of 0.153 g/cm³, an average cell size of 0.2466 mm, a maximum compressive stress of 546.44 Kpa, an optimal limiting oxygen index (LOI) of 29.5%, an optimal EMI SE of 40 dB, and excellent thermal stability and sound absorption.     

Hybrid Transition-Metal Oxide and Nitride@N-Doped Reduced Graphene Oxide Electrodes for High-Performance,Flexible, and All-Solid-State Supercapacitors

Nanoscale composites for high-performance electrodes employed in flexible, all-solid-state supercapacitors are being developed. A series of binder-free composites, each consisting of a transition bimetal oxide, a metal oxide, and a metal nitride grown on N-doped reduced graphene oxide (rGO)-wrapped nickel foam are obtained by using a universal strategy. Three different transition metals, Co, Mo, and Fe, are separately compounded with nickel ions, which originate from the nickel foam, to form three composites, NiCoO₂@Co₃O₄@Co₂N, NiMoO₄@MoO₃@Mo₂N, and NiFe₂O₄@Fe₃O₄@Fe₂N, respectively. These as-prepared active materials have similar regular variation patterns in their properties, including better conductivity and battery-mimicking pseudocapacitance, which result in their high whole-electrode capacitance performance [2598.3 F g⁻¹ (39.85 F cm⁻²), 3472.6 F g⁻¹ (41.43 F cm⁻²) and 1907.5 F g⁻¹ (3.41 F cm⁻²) for the composites incorporating Co, Mo, and Fe, respectively]. The as-assembled flexible, all-solid-state NiCoO₂@Co₃O₄@Co₂N//KOH/PVA//NiCoO₂@Co₃O₄@Co₂N device can be easily bent and exhibits high energy density and power density of 92.8 Wh kg⁻¹ and 1670.4 W kg⁻¹, respectively. The universality of this design strategy could allow it to be employed in producing hybrid materials for high-performance energy-storage devices.     

Ambiguity in Assignment of Near Infrared Vibrational Bands for Polymerisation Monitoring of Epoxy System

The curing process of epoxy affects the chemical structure of the final network so mechanical and physical properties of the polymeric matrix for a composite may be modified according to the polymerisation conditions. This paper describes the ambiguity in assignment of reference bands to follow the cure of poly-epoxy reactive systems using a laboratory-made system which allows the coupling of dielectric analysis and Fourier Transform Near Infrared Spectroscopy (FTNIR). The dielectric measurements were obtained using interdigitated electrode. In situ monitoring of extent of reaction was carried out from room temperature up to 160 °C using fibre-optic FTNIR spectroscopy. For the DGEBA/MCDEA system the epoxy band at 6060 cm⁻¹ was chosen in preference to the band at 4530 cm⁻¹ as representative of the epoxy function evolution during polymerisation because a small unknown peak probably due to the hardener appears in the 4530 cm⁻¹ region. The bands at 4620 and 4680 cm⁻¹ assigned to aromatic combination bands and widely used as reference bands are not unique for this formulation hence the band at 5980 cm⁻¹ is used as reference. The Principal Components Analysis (PCA) shows clearly also that the bands at 4620 and 4680 cm⁻¹ vary during the polymerisation. Surprisingly, the band at 4530 cm⁻¹ is equivalent to the one at 6060 cm⁻¹ to calculate the conversion rate. It is probably due to the fact that the hardener band near 4530 cm⁻¹ follows the same behaviour as the epoxy band at 4530 cm⁻¹.     

Structural and electrical characteristics of ALD-HfO2/n-Si gate stack with SiON interfacial layer for advanced CMOS technology

We report the fabrication of an ultra-thin silicon oxynitride (SiON) as an interfacial layer (IL) for n-Si/ALD-HfO₂ gate stack with reduced leakage current. The XRD, AFM, FTIR, FESEM and EDAX characterizations have been performed for structural and morphological studies. Electrical parameters such as dielectric constant (K), interface trap density (D_it), leakage current density (J), effective oxide charge (Q_eff), barrier height (Φ_bo), ideality factor (ƞ), breakdown-voltage (V_br) and series resistance (R_s) were extracted through C-V, G-V and I-V measurements. The determined values of K, D_it, J, Q_eff, Φ_bo, ƞ, V_br and R_s are 14.4, 0.5 × 10 ¹¹ eV⁻¹ cm⁻², 2.2 × 10⁻⁹ A/cm², 0.3 × 10¹³ cm⁻², 0.42, 2.1, −0.33 and 14.5 MΩ respectively. SiON growth prior to HfO₂ deposition has curtailed the problem of high leakage current density and interfacial traps due to sufficient amount of N₂ incorporated at the interface.     

High-resolution infrared analysis of seven fundamental bands of gaseous isothiazole between 750 and 1500 cm−1

The gas phase IR spectrum of isothiazole, C₃H₃NS, between 550 and 1700 cm⁻¹ was recorded with a resolution of ca. 0.003 cm⁻¹. The rotational structure of seven fundamental bands in the region 750–1500 cm⁻¹ has been assigned and analysed by the Watson Hamiltonian model. A number of local resonances in the bands have been identified and explained qualitatively in terms of Coriolis interactions. For each band upper state spectroscopic constants, including band center, rotational constants, and quartic centrifugal distortion constants are given. From observed crossings due to resonances we locate the weak bands ν₉(A′) and ν₁₃(A′) at 1041.9(2) and 642.0(3) cm⁻¹, respectively. The anharmonic frequencies have been determined using a cc-pVTZ basis set, at the MP2 and B3LYP levels; the two theoretical methods give very similar results for rotational constants, anharmonic band center frequencies and distortion constants, and many of these are in good agreement with experiment.     

Metal—nitrogen stretching assignments in some metallophthalocyanines and μ-oxo-(Fephthalocyanine)2

Metal-isotope substitution has been employed to establish the absorptions in the i.r. spectra of some metallophthalocyanines that contain MN stretching motion. The primary MN stretching bands appear at 240.7 cm⁻¹ in ⁶⁴Znpc; 284.0 cm⁻¹ in ⁶³Cupc; 376.0 cm⁻¹ and 317.8 cm⁻¹ in ⁵⁸Nipc; and 308.4 cm⁻¹ in ⁵⁴Fepc. Assignment of the far-i.r. spectrum of u-oxo-(Fepc)₂ places the FeN stretching band at 280.2 cm⁻¹ and suggests a linear arrangement of the FeOFe with Fe atoms in the plane of the phthalocyanine ring.     

In Situ Growth of Hierarchical Ni-Mn-O Solid Solution on a Flexible and Porous Ni Electrode for High-Performance All-Solid-State Asymmetric Supercapacitors

To endow all-solid-state asymmetric supercapacitors with high energy density, cycling stability, and flexibility, we design a binder-free supercapacitor electrode by in situ growth of well-distributed broccoli-like Ni_0.75Mn_0.25O/C solid solution arrays on a flexible and three-dimensional Ni current collector (3D-Ni). The electrode consists of a bottom layer of compressed but still porous Ni foam with excellent flexibility and high electrical conductivity, an intermediate layer of interconnected Ni nanoparticles providing a large specific surface area for loading of active substances, and a top layer of vertically aligned mesoporous nanosheets of a Ni_0.75Mn_0.25O/C solid solution. The resultant 3D-Ni/Ni_0.75Mn_0.25O/C cathode exhibits a specific capacitance of 1657.6 mF cm⁻² at 1 mA cm⁻² and shows no degradation of the capacitance after 10 000 cycles at 3 mA cm⁻². The assembled 3D-Ni/Ni_0.75Mn_0.25O/C//activated carbon asymmetric supercapacitor has a high specific capacitance of 797.7 mF cm⁻² at 2 mA cm⁻² and an excellent cycling stability with 85.3 % of capacitance retention after 10 000 cycles at a current density of 3 mA cm⁻². The energy density and power density of the asymmetric supercapacitor are up to 6.6 mW h cm⁻³ and 40.8 mW cm⁻³, respectively, indicating a fairly promising future of the flexible 3D-Ni/Ni_0.75Mn_0.25O/C electrode for efficient energy storage applications.     

Room temperature processable heat‐resistant epoxy‐oxazolidone‐based syntactic foams

Syntactic foams based on oxazolidone‐modified epoxy resin using glass microballoons as reinforcing filler with varying densities were processed. The influence of various grades of microballoons and their concentration on the mechanical, thermal, thermomechanical, and flammability characteristics were investigated. The effect of temperature on the compressive strength with density was monitored in detail. By incorporating the microballoons, T_g of the syntactic foam increased from 90 °C to 115 °C. Thermal conductivity was found to decrease from (0.064 to 0.056 W/(m·K)) in conjunction with decreasing resin to filler ratio. In the case of composites filled with K25 alone, the creation of large voids due to less effective packing between the microballoons led to lower thermal conductivity. The specific heat of the different composites was in the range of 0.32 to 0.44 cal/g/°C, and the coefficient of thermal expansion was in the range of 13.2 to 17.4 × 10⁻⁶/°C with limiting oxygen index of 28% to 33%.