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The present study aims to develop a simple, non-toxic, and environmentally friendly reduced graphene oxide-silver (rGO-Ag) nanohybrid synthesis method by employing three monosaccharides which are ribose, fructose, and galactose, as the reducing agents. This study also investigated the formation and crystalline structures of the rGO-Ag formed. The resultant nanohybrids were characterised via ultraviolet-visible absorption (UV–vis), X-ray diffraction (XRD), and field emission scanning electron microscope (FESEM). The UV–vis results indicated that galactose was the most efficient reducing agent. The broadest peak recorded by the rGO-Ag reduced with galactose [rGO-Ag (Gal)] at 271 nm, while the narrowest peak observed at 423 nm corresponded to the formation of silver nanoparticles (AgNPs) on the rGO. The nanohybrids procured with the other reducing agents were also evaluated with XRD. The oxygen and carbon compositions of the samples were also analysed via FESEM equipped with energy-dispersive X-ray (EDX). The average particle size calculated based on the rGO-Ag (Gal) XRD results was the smallest (6 nm) compared to the other two monosaccharides. Furthermore, the d-spacing of the rGO-Ag (Gal) was almost identical to the XRD data, confirming the high-resolution transmission electron microscopy (HRTEM) findings. Consequently, galactose was the ideal reducing agent to synthesise rGO-ag nanohybrids. [ABSTRACT FROM AUTHOR]

With the development of 5G technology, the miniaturised and highly integrated electronic devices urgently require thermal management materials possessing high thermal conductivity and mechanical properties. In this work, isotactic polypropylene (iPP)/high-density polyethylene (HDPE)-based dielectric composites possessing ideal thermal conductivity and balanced mechanical properties were prepared via Fused Filament Fabrication (FFF). The advanced material properties were achieved by the introduction of hybrid fillers and tailored polymer crystalline structure. The highly oriented h-BN, oriented iPP crystalline and iPP/HDPE epitaxy crystalline were observed. Meanwhile, we studied the effect of the ratio of hybrid fillers on various properties of composites. The thermal conductivity of iPP/HDPE/h-BN/Al2O3 composites reach 1.802 W·m-1·K-1. The impact strength and tensile strength reach 13.23 KJ/m² and 40 MPa, respectively. In addition, the composites maintain ideal dielectric properties. This work offers a feasible strategy to fabricate dielectric and thermal conductive composites with balanced mechanical properties using semicrystalline polymer through FFF process. [ABSTRACT FROM AUTHOR]

Wood–polymer composites (WPCs) are commonly used in materials technology, and there is a reasonable amount of research for new kinds of green fillers. In this study, we have obtained the isotactic polypropylene (iPP) composites filled with native and modified xylite (brown coal fraction with a relatively high amount of cellulose). The modification of xylite has been based on processing in a mine, where the humic acids are rinsed with KOH solution for further use. The composites were subjected to a wide range of structural, thermal, functional, and mechanical characteristics. The results of the undertaken research have shown that the addition of xylite filler can be successfully used in obtaining of thermoplastic composites. The properties of those composites are similar to another types of WPCs. There also observed a strong impact of xylite filler addition into formation of β-iPP form. [ABSTRACT FROM AUTHOR]

Pasting, cooking, and digestible properties of Japonica rice with different amylose contents were investigated. Low-, medium-, and high-amylose Japonica rice (waxy, 18.8% amylose content, and 33.3% amylose content) were cooked and evaluated for water absorption, volume expansion, molecular mobility, microstructure, crystalline structure, and starch digestibility. The results showed that high-amylose rice had lower peak viscosity but higher pasting temperature and final viscosity than low- and medium-amylose rice. After cooking, high-amylose rice showed slightly higher water absorption ratio but lower volume expansion ratio than the other two rice varieties. Water was more evenly distributed in cooked low- and medium-amylose rice than in cooked high-amylose rice. After cooking, starch in low- and medium-amylose rice kernels almost lost the entire crystalline structure, but starch of cooked high-amylose rice still exhibited strong V-type crystallinity. Cooked high-amylose rice contained higher content of resistant starch than cooked rice of other two varieties. [ABSTRACT FROM AUTHOR]

In this article, BaTiO3 and Ba0.98Nd0.02TiO3 ceramics were prepared by high temperature conventional solid state reaction, followed by microwave sintering (MS) process separately. A comparative study on structural, morphological and electrical properties has been employed by powder X-ray diffraction (PXRD), Raman, scanning electron microscope and dielectric and ferroelectric measurements. PXRD and profile refinement analysis results revealed that tetragonal phase at room temperature. The Raman spectroscopy provided useful information on the presence of tetragonal symmetry. Surface morphology of the MS sample showed dramatic changes from scanning electron micrographs. Dielectric and ferroelectric behavior observed for MS sample. [ABSTRACT FROM AUTHOR]

Late-stage nitrogen (N) fertilization is an important crop management for improving rice production and also affects the quality of rice, whereas information on the influence of late N on structural and functional properties of indica rice starch is lacking. In this study, effects of various N rates (0, 60, and 120 kg ha−1 referred to as N0, N60 and N120, respectively) on structural and functional properties of grain starches from two rice cultivars (OM052 and Chaoyou1000) were investigated. Comparison of different N treatments showed that late N application exhibited strong influence on starch properties, and the sensitivity to N application varied with rice genotypes. Compared to non N rate, higher input of N (N60 for OM052, and N120 for Chaoyou1000) significantly reduced apparent amylose content (AAC), relative crystallinity (RC), gelatinization enthalpy, swelling power, solubility and degree of hydrolysis, but significantly increased the proportion of short chains with degree of polymerization 6–12 in amylopectin and gelatinization onset temperature. Further comparison and principal component analyses revealed that the variations in the starch functional properties were due mainly to the changes in RC. The solubility was positively associated with AAC. The present results can provide important information for understanding the environmental regulation of starch biosynthesis in rice grain. [ABSTRACT FROM AUTHOR]

Synthesis of a new iron(III) metalloporphyrin complex is achieved. Molecular structure, supramolecular assembly and physico-chemical properties have been explored by means of experiments and computational tools. The mean equatorial distance between the iron(III) metal center and N-pyrrolic nitrogens is appropriate for a low-spin (S = 1/2) derivative. Magnetic data confirm the low-spin state (S = 1/2) of our ferric derivative. The planarity of the porphyrin macrocycle is confirmed by the shift of the value of the half potential E1/2[Fe(III)/Fe(II)] of (I) toward more negative value in the cyclic voltammogram. Metal–ligand interactions has been also described via natural bond orbital analysis. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride)-based nanocomposite films with different loadings of PMMA-modified graphene sheets were prepared by a solution-mixing and solvent casting method. The prepared films were annealed at three different temperatures and the crystalline structures of the samples were investigated. X-ray diffraction data confirmed the PMMA-modified graphene nanosheets enhanced the preferential β-crystalline structure when increasing the annealing temperature to 90 °C, while increasing the annealing temperature to 120 °C led to a β → γ phase conversion. The tendency of the graphene sheets to restack by increasing the annealing temperature was confirmed by XRD. The PMMA-modified graphene sheets, however, didn't showa nucleating effect on the PVDF crystallizationduring DSC cooling scans. [ABSTRACT FROM AUTHOR]

In this article, a mesoporous commercial alumina was calcined in the temperature range of 600°C–1200°C. The effect of several parameters such as calcination temperature, calcination time, heating rate, and calcination steps on phase transformation and crystal size was experimentally investigated. The characterization of the commercial mesoporous alumina and samples calcined at 1000°C, 1040°C, 1070°C, 1100°C, and 1200°C by single-step and multi-step calcination was performed using XRD and N2adsorption/desorption techniques. For the commercial mesoporous alumina, TG/DTA analysis was also performed. Experimental results showed that mostly pure α-Al2O3was obtained at 1100°C. [ABSTRACT FROM AUTHOR]

N,N′-Dicyclohexyl-1,5-diamino-2,6-naphthalenedicarboxamide (NA), a highly efficient and selective β-nucleating agent for isotactic polypropylene (iPP), was synthesized and chemically supported on the surface of multiwall carbon nanotubes (MWCNTs) via an amidation reaction. The β-nucleation ability of NA, itself, is superior to the commonly used, highly efficient, and selective β-nucleating agents, e.g., commercial rare earth WBG-and aryl amide derivative TMB-5, as proved by the results of wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The effect of MWCNTs supported NA (MWCNT-NA) on the crystallization and melting behavior of iPP was investigated by means of WAXD and DSC. The results show that the MWCNTs supported NA can effectively induce the formation of β-crystals in iPP/MWCNT-NA, although the grafting degree of NA onto the surface of MWCNTs could still to be improved. [ABSTRACT FROM AUTHOR]

Microbial cellulose is a chemically pure form of plant cellulose with an ultrafine reticulated structure. In this study, microbial cellulose was biosynthesized in a static condition by acetobacter xylinium (Gluconacetobacter xylinus) of three different mono- and disaccharides, and its crystallinity structure was investigated and compared with each other and also with the crystalline structure of cellulose existing in cotton and ordinary viscose rayon fibers. According to the results, the cellulose production efficiency of monosaccharide (glucose) was higher than that of disaccharides (lactose and sucrose). The crystalline structures of all biosynthesized cellulose were cell I and their dominant allomorphs were I(alpha), contrary to native cellulose, which was I(beta). The crystallinity amount of microbial cellulose was less than 10-15% of cotton and greater than 9% of viscose. [ABSTRACT FROM PUBLISHER]

Selective laser melting (SLM) is an additive manufacturing process that enables direct manufacturing of 3D complex shape parts and internal architecture from powder materials. The SLM technology is characterised by high temperature gradients and solidification rates that have a significant effect on the microstructures and properties of final parts. The present paper aims at understanding the influence of the initial properties of various martensitic stainless steel powders on the final microstructures and mechanical properties of parts manufactured using the same optimised SLM process parameter settings. The results obtained show that for applied optimum process parameters, the thermal effects are the same for all martensitic powders used. Besides, the final microstructures and properties are different. The results clearly show the effect of the initial complex chemical composition of the martensitic precipitation hardening powder on the microstructures of final parts, and consequently, on their properties. [ABSTRACT FROM PUBLISHER]

A series of squaraine dyes, based on 2,4-bis[4-(N,N-di-n-alkylamino)-2-hydroxyphenyl] squaraine including ethyl, propyl, butyl, pentyl, hexyl and heptyl derivatives, were synthesised by condensation of the corresponding 4-(N,N-di-n-alkylamino)-2-hydroxyphenol with squaric acid. The thermal behaviour of the series was recorded using both thermogravimetic analysis and differential scanning calorimetry while their crystalline structures were elucidated via single-crystal X-ray diffraction. The length of the alkyl chain proved to have a significant effect on both the thermotropic behaviour and the crystalline structure of the squaraine series. Two derivatives, butyl and heptyl, revealed the presence of liquid crystalline mesophases, smectic and nematic, respectively, which were confirmed and characterised via polarised light microscopy and X-ray diffraction. Several of the derivatives formed H- and/or J-aggregates upon thin film formation via spin coating before and after the thermal annealing treatment as indicated by UV–vis spectroscopy. The molecular and crystal structure, aggregation and thermal behaviour provide insight into the supramolecular assembly of this important class of materials. Photophysical measurements revealed large molar absorptivity, reasonably high fluorescence quantum yields and significant fluorescence anisotropy by making these derivatives suitable candidates for a number of electro-optic and photonics applications. [ABSTRACT FROM PUBLISHER]

Titanium dioxide nanoparticles with different average diameter of particles (8, 18 and 27 nm) and different crystal structure (anatase and rutile) were used for degradation of C.I. Acid Red 88 (AR88) as a model compound. The degree of degradation of AR88 by TiO2 nanoparticles under irradiation of UV-light (254nm) with TiO2-UV100 (8 nm diameter and 100% anatase) is lower than TiO2-Merck (27 nm diameter and 95% anatase). TiO2-P25 with structure of anatase and rutile (80:20) combination shows higher photoactivity than other samples such as TiO2-UV100 and TiO2-Merck. Kinetics of removal of AR88 with all of nanosized-TiO2 particles is pseudo-first-order. The apparent reaction rate constant (kap) for removal of AR88 in the presence of different nanosized-TiO2 particles decreases with increasing of AR88 initial concentration. For TiO2-P25 and TiO2-UV100 a linear relation and for TiO2-Merck a nonlinear relation between kap and light intensity were obtained. [ABSTRACT FROM AUTHOR]

The development of crystalline morphology, structure, and impact property of isotactic polypropylene (PP) and poly(cis-butadiene) rubber (PcBR) (vol. %: 80/20) blends during mixing were investigated and compared to neat PP. It was found by polarized optical microscopy (POM) and small-angle light scatter (SALS) that the incorporation of PcBR into PP caused small and imperfect PP spherulites and more diffused spherulite boundaries, which sharply exhibited in the initial 2 min of mixing but remained almost unchanged in the rest of the mixing time. Crystalline structure of neat PP and blends was studied by wide-angle x-ray diffraction (WAXD). The addition of PcBR into PP induced formation of PP β-form spherulites. As mixing time developed, the relative degree of crystallization decreased whereas interplanar distance increased. Impact strength of PP and blends was tested. The result showed that impact strength of blends significantly improved with increase of the mixing time. [ABSTRACT FROM AUTHOR]

A series of reactor powders of ultrahigh molecular weight (UHMW) polyethylenes with different morphology was melted at 160°C for 5 min and cooled in ice water. Low‐frequency Raman spectroscopy was used to characterize the straight‐chain‐segment (SCS) length distribution of both initial and melt‐crystallized materials. A bimodal SCS length distribution was found in the melt‐crystallized sample originated from the reactor powder with a very tenuous amorphous phase. In other samples recrystallized from powders with more ordered structure, the SCS length distribution was unimodal and approximately identical. The result is explained in terms of perfection of lamellar crystals formed under limited time and thermal conditions from differently organized initial structure. [ABSTRACT FROM AUTHOR]

The effect of 975 W microwave irradiation on the crystalline structure of isotactic polypropylene (iPP) surface layer in Al/iPP/Al composite was studied by attenuated total reflection Fourier transform infrared (FTIR) and asymmetry diffraction geometry small-angle x-ray diffraction (XRD). The results show that after about 60 min irradiation, the orientated structure and crystallinity of the iPP surface layer are dropped, crystal transformation (α → β) happens. The iterative peak-fit of XRD curves indicates that the reasons for crystal transformations are: the microwave effect causes the increase of the order level of the crystal lattice, the defaults within the β-crystals are, thus, reduced. D[300] (stands for β-form phase) becomes larger, β-form iPP becomes more perfect. With microscopic distortion coefficient ε[300] and the microscopic stress of β-form becomes less attraction, the microscopic stress of the α-form goes up. This crystal transformation is useful for improving the toughness of iPP in electromagnetic shielding materials. [ABSTRACT FROM AUTHOR]

The hyperfine quadrupole interaction at probes in sites with cubic point group symmetry was measured in many perovskite-type compounds. This interaction is commonly associated to the presence of oxygen vacancies close to probes. The effect of this point defect on 181 Ta probe in BaTi x Hf 1- x O 3 for x = 0.70, 0.50, 0.30, 0.10, 0.05, and 0.01, is studied. The lattice constant of these oxides at room temperature were measured using XRD technique. The quadrupole parameters corresponding to probe-defect interaction were obtained by means of Perturbed Angular Correlation (PAC) spectroscopy as functions of both, composition and temperature. A static, asymmetric and distributed quadrupole interaction was fitted to all PAC data. This interaction was observed to be strongly composition dependent. These results and those corresponding to compositions 0.75 ≤ x < 1 were compared to the ones obtained using the point charge method for the calculation of the electric field gradient. The proposed model took into account polarized oxygen vacancies, different covalence of Ti--O and Hf--O bonds and using computational simulation for cations and oxygen vacancies lattice positions. [ABSTRACT FROM AUTHOR]

The memory effect in PA11 films is studied in close relation with the crystalline structure. In polyamide 11, [(CH2)10–CO–NH]n, the polarity of the amide group induces hydrogen bonds between chains that are crucial to the crystalline structure and are responsible for the memory effect. During the forming from the melt, the polyamides are sheared, which leads to persistent chain alignments due to hydrogen bonds. In the present work, the crystalline structure of PA11 films has been studied by differential scanning calorimetry and wide angle x-ray scattering. The crystalline structure at room temperature depends on the cooling rate. A quench leads to the smectic δ′ structure, whereas a slow cooling favors the formation of the triclinic α phase in addition to the smectic δ′ phase. This study also shows the influence of an annealing in the melt on the crystalline structure. With increasing annealing time in the melt, the δ phase develops and the δ′ phase progressively vanishes. It seems necessary to maintain PA11 above the melting point for a long time to totally erase the structural evidence of the memory effect. [ABSTRACT FROM AUTHOR]

Using powder X-Ray Diffraction and Perturbed-Angular-Correlation spectroscopy, the crystal structure and the hyperfine interaction at 181 Ta probe in Sr 0.75 Ba 0.25 HfO 3 have been studied. A tetragonal (I4/mcm) to cubic (Pm &3macr;m) phase transition was observed. A two-phase field region, where the tetragonal and cubic phases coexist, was found between 673 and 923 K. The spin precession curves were measured from room temperature up to 1373 K. A static, asymmetric and disordered electric field gradient model was used to fit these time spectra. The hyperfine parameters corresponding to the tetragonal structure changed as the temperature increases: ω T Q diminishes, η T is almost constant and δ T diminishes. This interaction was observed to be unique up to 673 K. Above this temperature, a second interaction appeared and these two phases coexist up to 923K. Above this temperature, the hyperfine parameters corresponding to the cubic structure was only observed. The tetragonal to cubic transformation is characterized by an activation energy of about 0.62 eV. [ABSTRACT FROM AUTHOR]

Experimental studies on the twin roll casting process in order to produce thin aluminum alloy strips are presented in this paper. A new twin roll caster was developed as an effective experimental tool. The caster is equipped with a complete casting system incorporating a control and measuring system using multiple sensors and various actuators. The data acquisition system of the caster can measure various process parameters including meniscus, casting speed, and temperature as well as roll gap and pressure. With this system, aluminum alloy thin strips were manufactured and the process parameters such as strip temperature, casting velocity, and pressing force of roll were investigated. Furthermore, the crystallizability, microstructure, and mechanical properties of the strip are evaluated by X-ray diffractometer, scanning electron microscope, and tensile test. The results revealed the ability of the twin roll caster to produce directly the thin strip of aluminum alloy with improved mechanical strength. [ABSTRACT FROM AUTHOR]