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At least 793 records · Page 44

Mechanical and Thermal Properties of Green Thermoplastic Elastomer Vulcanizate Nanocomposites Based on Poly (vinyl chloride) and Nitrile Butadiene Rubber Containing Organoclay and Rice Straw Natural Fibers

Green thermoplastic elastomer vulcanizates (GTPV) nanocomposites using poly (vinyl chloride) (PVC) and nitrile butadiene rubber (NBR) containing 5 wt% Cloisite 30B as an organoclay and various concentrations of rice straw natural fibers were made by melt mixing process and compression molding. The effect of used organoclay and various loadings of rice straw was monitored through using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), tensile tests and rheological measurements. The morphological investigations revealed that the GTPV nanocomposites reinforced by rice straw natural fiber show a more rough fracture surfaces indicated the existence of some interactions between the natural fiber and polymer matrix. Thermal decomposition measurements revealed a higher thermal stability for GTPV nanocomposites containing higher rice straw natural fibers. The tensile test analysis suggested that there is an optimum value for the weight fraction of rice straw to enhance the Young’s modulus and tensile strength of the prepared GTPV nanocomposites up to 9 MPa and 35 MPa, respectively. The effect of rice straw loading on the Young’s modulus of the PVC/NBR/organoclay GTPV nanocomposites was predicted through using the parallel and series equations of modified Ji’s model. The results show that the theoretical model can precisely predict the variation of Young’s modulus with respect to the rice straw loading.

36 MATERIALS SCIENCE↗

Transmission Properties of One-Dimensional Magneto-Optical Photonic Crystals Containing Graphene Nanolayers

Photonic crystals containing graphene nanolayers have been attracting increasing attention due to their distinctive properties. In this paper, we present a theoretical analysis on the transmission properties of magneto-photonic crystals containing graphene nanolayers by using the transfer matrix method. The investigation shows that unidirectional defect modes with high transmittance can be achieved in the proposed structure, and broad flat-top photonic conduction bands (PCBs) can also be found between the graphene-induced photonic band gap and the Bragg gap. Furthermore, the study on the PCBs indicates that the relationship between the number of PCBs (n) and the period number of the structure (N) can be expressed as n = N − 1(N = 2,3,4…). And, new and unexpected photonic band gaps among PCBs are observed. The effects of chemical potential of graphene, thickness of defect layer, and incident angle on transmission properties are also discussed. The research results may provide a valuable reference for the design and fabrication of optical communication devices, such as isolators, switches, multichannel filters, and so on.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

Total Mercury Analysis of Radioactive Waste Containing Multiple Mercury Species

In this work, a direct mercury analyzer (DMA) was used to analyze total mercury in radioactive waste samples containing methylmercury and other forms of mercury including Hg o (elemental) together with inorganic ionic mercury species and complexes. These samples were also analyzed using Cold Vapor Atomic Absorption Spectroscopy (CVAAS) and/or Inductively Coupled Plasma Mass Spectroscopy (ICMS). Comparative statistical evaluation of the results from spike solutions/simulants, liquid radioactive waste samples, and interlaboratory performance test samples demonstrated that the various methods generated accurate and/or equivalent total mercury data and equivalent precision (2σ ± < 20%). Triplicate total mercury analysis of an exemplar radioactive waste resulted in an average value of 54.1 mg/L (as Hg) using CVAAS, 55.1 mg/L using ICPMS and 56.0 mg/L using DMA. A primary advantage of the DMA in a radioactive environment is avoiding multi-step, labor-intensive, time-consuming and waste-producing sample preparation protocols needed for CVAAS and ICPMS. DMA was determined to be the preferred method for measuring total mercury in the Savannah River National Laboratory (SRNL) radioanalytical laboratory based on analytical performance combined with ease of use in a radiological containment unit.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

Characterization of terbium containing cubic zirconia crystal for high power laser applications

A magneto-active terbium containing cubic zirconia crystal is an attractive material for creating Faraday isolators thanks to a high value of its Verdet constant and low absorption coefficient. The optical anisotropy parameter of this crystal which shows the distribution of orientations of the axes of thermally induced birefringence in a thermally loaded optical element has negative value. It means that there exists a dedicated orientation of crystallographic axes, at which the axes of thermally induced birefringence are arranged in the one direction and thermally induced depolarization may be reduced substantially. For assessing potential of this crystal for high-power applications we have investigated its temperature dependence of the Verdet constant that proved to correspond to the paramagnetic behavior. Thermo-optical characteristics are also of principal importance when operating with high-power laser radiation. We present results of measurements of thermo-optical characteristics Q and P which determines values of polarization and phase distortions of passing laser radiation. Measured values can be used to determine the characteristics of Faraday isolators based terbium containing cubic zirconia crystals in various implementations of their optical schemes for various parameters of laser radiation.

36 MATERIALS SCIENCE↗

High-Temperature Corrosion of Chromia-Forming Ni-Based Alloys in CO 2 Containing Impurities

Future technologies require structural materials resistant to environmental degradation in high-temperature CO 2 -rich environments. In this work, we exposed several commercially available Ni-based alloys (230, 263, 282, 617, 625, and 740H) to atmospheric pressure gases intended to simulate the compositions expected in future direct-fired supercritical CO 2 power cycles. The alloys were exposed to 95% CO 2 + 4% H 2 O + 1% O 2 and the same gas containing 0.1% SO 2 at temperatures of 600, 650, 700, 750, and 800 °C for 2500 h. With minor exceptions, chromia scales formed on all alloys at all temperatures in the SO 2 -free gas, yielding parabolic growth rates that followed an Arrhenius temperature dependence. Behavior in the SO 2 -containing gas was more complex. Generally, the alloys performed well at temperatures of 650, 750, and 800 °C. While some alloys further performed relatively well across the whole temperature range, several of the alloys experienced chromia failure resulting in non-protective duplex oxide scales and high oxidation rates, at temperatures of 600 and 700 °C. Deviation from protective behavior was associated with internal sulfide formation and, additionally for the case of 600 °C, external sulfate formation. Extensive carburization accompanied growth of the non-protective duplex oxide scales, which made it more difficult for the alloy to recover after initiation of the sulfur-induced accelerated corrosion process. The thermodynamic and kinetic factors influencing the accelerated corrosion in the presence of sulfur are discussed. The results suggest that caution is required when assessing compatibility of Ni-based alloys for CO 2 -based systems when sulfur-based impurities are expected.

36 MATERIALS SCIENCE↗

A cis -regulatory module activating transcription in the suspensor contains five cis -regulatory elements

Little is known about the molecular mechanisms by which the embryo proper and suspensor of plant embryos activate specific gene sets shortly after fertilization. We analyzed the upstream region of the Scarlet Runner Bean ( Phaseolus coccineus ) G564 gene in order to understand how genes are activated specifically in the suspensor during early embryo development. Previously, we showed that a 54-bp fragment of the G564 upstream region is sufficient for suspensor transcription and contains at least three required cis-regulatory sequences, including the 10-bp motif (5'-GAAAAGCGAA-3'), the 10 bp-like motif (5'-GAAAAACGAA-3'), and Region 2 motif (partial sequence 5'-TTGGT-3'). Here, we use site-directed mutagenesis experiments in transgenic tobacco globularstage embryos to identify two additional cis-regulatory elements within the 54-bp cis-regulatory module that are required for G564 suspensor transcription: the Fifth motif (5'-GAGTTA-3') and a third 10-bp-related sequence (5'-GAAAACCACA-3'). Further deletion of the 54-bp fragment revealed that a 47-bp fragment containing the five motifs (the 10-bp, 10-bp-like, 10-bp-related, Region 2 and Fifth motifs) is sufficient for suspensor transcription, and represents a cis -regulatory module. A consensus sequence for each type of motif was determined by comparing motif sequences shown to activate suspensor transcription. Phylogenetic analyses suggest that the regulation of G564 is evolutionarily conserved. Lastly, a homologous cis-regulatory module was found upstream of the G564 ortholog in the Common Bean (Phaseolus vulgaris), indicating that the regulation of G564 is evolutionarily conserved in closely related bean species.

59 BASIC BIOLOGICAL SCIENCES↗

Modern level for properties prediction of iodine-containing organic compounds: the halogen bonds formed by iodine

The modern concepts on specific features of anisotropy of the electron density of valence shells of bound atoms and chemical bonds providing the successful description of the properties of halogen bonds formed by the iodine molecule in compounds with useful physicochemical properties are generalized in the review. The prognoses of basicity by the diiodine basicity scale for the nitrogen-containing compounds are illustrated. The regularities and peculiarities of shifting bands in Raman spectra of iodine-containing organic crystals are considered. The methodical and specific problems of modeling appeared when the electronic characteristics of the iodine compounds are estimated and briefly discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Ferrocene-containing tri- and tetranuclear cyclic copper(I) and silver(I) pyrazolates

New tri- and tetranuclear macrocyclic silver(I) and copper(I) 3-ferrocenyl-5-(trifluoromethyl)pyrazolates were prepared: [{(3-((η"5-C_5H_4)Fe(η"5-C_5H_5))-5-(CF_3)-Pz}M]{sub 3} (M = Cu (1), Ag (2)) and [{(3-(( η"5-C_5H_4)Fe(η"5-C_5H_5))-5-(CF_3)-Pz}Cu]{sub 4} (3). The structures of compounds were established by X-ray diffraction analysis. In the crystalline state, a planar trinuclear silver-containing macrocycliс pyrazolate and a saddle-shaped tetranuclear copper-containing macrocycle are formed. The introduction of a bulky substituent, ferrocene, into the pyrazole ligand results in complete shielding of the acidic metal sites, which precludes the coordination of base molecules.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Zinc-containing derivatives of 2-aminopyrimidine

A platform containing three anticancer components is proposed. The components are a radioactive {sup 69}mZn isotope and zinc complexes, where both zinc and ligand exhibit anticancer properties. Two zinc-containing complexes, namely (2-AP){sub 2}ZnCl{sub 2} and (2-AP){sub 2}Zn(Sal){sub 2} (AP is 2-aminopyrimidine, Sal is salicylate) were synthesized and characterized. Their cytotoxicity with respect to some leukemia cell lines is demonstrated. Their stability in physiological solution and percentage of apoptosis (by flow cytometry) are investigated. Stable complexes of compounds with the isotope {sup 69}mZn were characterized by TLC and autoradiography.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Biological activity of some sulfur- and selenium-containing spiro compounds

Cytotoxicity to K-562 leukemia cell line of two spiro compounds containing selenium or sulfur atom in their structure were compared. 4-Fluorophenyl-(1-thia-3-azaspiro[5.5]undec-2-en-2-yl]amine hydrobromide was synthesized and characterized for the first time. It was found that the introduction of a sulfur atom is more promising for this biological model, since it leads to a 3-fold increase in the therapeutic index in the case of the sulfur-containing compound.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

New magnetic nanomaterials based on ferrocene-containing polymers synthesized under ultrasonic irradiation

A new magnetic nanomaterial was obtained based on soluble ferrocene-containing poly-phenylene synthesized under ultrasonic irradiation at room temperature. The maximum magnetization of the nanomaterial containing magnetite nanoparticles was 23 G cm{sup 3} g{sup −1} in a magnetic field of 2.5 kOe. According to transmission electron microscopy results, the average size of the magnetic nanoparticles was 19 nm.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

Synthesis and pharmacological activity of a silicon—zinc—boron-containing glycerohydrogel

A new pharmacologically active nanostructured silicon—zinc—boron-containing glycerohydrogel was synthesized by the sol—gel method using silicon, zinc, and boron glycerolates as biocompatible precursors. The hydrogel composition and structural features were investigated by transmission electron microscopy, powder X-ray diffraction, IR spectroscopy, atomic emission spectrometry, and elemental analysis; a structural model was proposed. It was found that the 3D framework of the gel is formed by the products of hydrolysis and subsequent (co)condensation of silicon- and boron-containing precursors. Meanwhile, the major part of zinc monoglycerolate does not undergo hydrolytic transformations during gelation, being present in the 3D framework cells as amorphous nano-sized particles. The dispersion medium of the gel is an aqueous glycerol solution of silicon and boron glycerolates, products of their hydrolytic transformations, and water-soluble products of hydrolytic transformations of zinc monoglycerolate. The silicon—zinc—boron gel is nontoxic and possesses wound-healing and antimicrobial activities; it can be considered as a nanostructured dispersed system promising for biomedical applications, which is prepared in a simple and cost-effective way without using catalysts or toxic organic solvents.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Close structural relationship of the O-antigens of various Cronobacter species containing 3-deoxy-D-manno-oct-2-ulosonic acid

Some O-polysaccharides (O-antigens) of the lipopolysaccharides of bacteria of the genus Cronobacter contain 3-deoxy-D-manno-oct-2-ulosonic acid. O-Polysaccharides of Cronobacter turicensis G3874 and Cronobacter muytjensii G3886 containing this unit were found to be structurally related to each other and to those of Cronobacter dublinensis HPB 3169 and Cronobacter sakazakii G2706 (serotype O5) studied earlier. The O-polysaccharides differ in the N-acyl group on a 3-amino-3,6-dideoxy-D-glucose residue [(R)-3-hydroxybutanoyl vs. acetyl] or in the presence or absence of the O-acetyl group on an L-rhamnose residue only. Structures of the new O-antigens were established by chemical methods and by 1D and 2D {sup 1}H and {sup 13}C NMR spectroscopy applied to polysaccharides and pentasaccharides obtained by mild alkaline O-deacylation and mild acid hydrolysis of the isolated lipopolysaccharides, respectively.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Optimization of Mold Flux for the Continuous Casting of Cr-Contained Steels

To compensate the negative effect caused by the absorption of chromium oxide inclusions during the casting process of Cr-contained steels, a new mold flux system has been designed and investigated. The melting temperature range of the newly designed mold flux system is from [1124 K to 1395 K (851 °C to 1122 °C)]. The viscosity at 1573 K (1300 °C) and the break temperature increase with the addition of MnO and Cr{sub 2}O{sub 3} but decrease with the addition of B{sub 2}O{sub 3}. The crystalline fraction of mold flux decreases from 81 to 42.1 pct with the addition of MnO and Cr{sub 2}O{sub 3}, and then further decreases to 25.3 pct with the addition of B{sub 2}O{sub 3}; however, it improves from 54.4 to 81.5 pct when the basicity increases. Besides, the heat-transfer ability of mold flux is inverse to the crystallization ratio of the slag. The comprehensive study of the properties for the four designed mold fluxes suggests that the mold flux with 1.15 basicity-3.01 pct B{sub 2}O{sub 3}-1.10 pct MnO-2.10 pct Cr{sub 2}O{sub 3} shows the best properties for the continuous casting of Cr-contained steels.

36 MATERIALS SCIENCE↗

Interaction Between Liquid Steel and AlN Substrate Containing Al-Y-Oxides

Reactions between molten iron, molten silicon steel, and ceramic materials are of great importance from the perspective of the corrosion of refractory material in the steelmaking and continuous casting processes. Reactions between liquid steel and aluminum nitride (AlN) substrate containing Al-Y-oxides were investigated using the sessile drop method at 1833 K (1560 °C). The liquid–substrate interface was observed with the increasing holding time, and the reaction mechanism was studied. In the case of the liquid iron and the silicon steel on the AlN substrate containing Al-Y-oxides, the reaction products on the steel side of the interface between the steel and the substrate were Al-rich Al-Y-oxides and Al{sub 2}O{sub 3} particles. For silicon steel and pure AlN substrate, Al{sub 2}O{sub 3} particles were the main products. Contact angles were lower for liquid iron than for silicon steel due to the higher oxygen content in iron. In addition, the solid–liquid interfacial tension and the work of adhesion between AlN and steel were measured.

36 MATERIALS SCIENCE↗

Tribological Performance of Ni{sub 3}Al Matrix Self-Lubricating Composites Containing Multilayer Graphene Prepared by Additive Manufacturing

In order to improve tribological performance of Ni{sub 3}Al-based alloy, Ni{sub 3}Al matrix composites containing 1.5 wt.% multilayer graphene (MLG) are prepared through additive manufacturing (AM) and spark plasma sintering (SPS), which are denoted as NMAM and NMSPS, respectively. Tribological behaviors of NMAM and NMSPS against Si{sub 3}N{sub 4} balls are researched under constant speed (0.2 m/s) and varied loads (from 4 to 16 N) for evaluating the tribological properties of NMAM and NMSPS. The results present that NMAM exhibits the excellent tribological properties [low friction coefficients (0.26-0.40) and considerable wear resistance (2.8-4.6 × 10{sup −5} mm{sup 3} N{sup −1} m{sup −1})] as compared to NMSPS, which attributes to the uniform enrichment of MLG with properties of high tensile strength and being easily sheared off on the worn surfaces. Owing to the use of spherical prealloyed powder containing multilayer graphene and the characteristics of layer by layer depositing in the AM process, NMAM has a more compact and uniform substrate, which persistently provides a source of the formation of continuous and stable frictional layer. Due to the characteristics of AM rapid solidification, NMAM has the small grain size and well-compacted microstructure, which can effectively reduce the probability of spalling wear and lead to the increase in wear resistance of materials. The research can offer the reference for self-lubricating materials prepared by AM technology.

36 MATERIALS SCIENCE↗

Enhanced Strength of 304 SS-Ti6Al4V Laser-Welded Joints Containing Composite Interlayers

This paper investigates the microstructural characterization of the fracture propagation edge during laser beam welding of Ti6Al4V and 304 stainless steel using Cu, V, and Ni interlayers as a single Cu interlayer and composite interlayer structures with different Cu interlayer thicknesses. This study attempts to increase the Ti-SS joint strength through the use of the composite interlayers. X-ray diffraction characterization based on a 0.5-mm-thick Cu interlayer showed that the SS/Cu/Ti joint contained considerable brittle IMCs; however, the fracture surface of the SS/Cu-V/Ti composite interlayer sample did not contain any Fe-Ti IMCs or Cr{sub 2}Ti. EBSD observation indicated that the crack propagated transgranularly from solidified CuTi in the interdendritic regions of the FeTi compounds in the composite interlayer sample; however, the crack propagated intergranularly along Fe{sub 2}Ti grain boundaries in the single interlayer sample. The investigation based on a 1-mm-thick Cu interlayer showed that the SS/Ni-Cu1/Ti sample was stronger than the SS/Cu1/Ti sample due to a lack of CuTi at 3.5 kW. The tensile strength of the SS/Cu1-V/Ti joint was greater than that of the SS/Ni-Cu1/Ti joint due to the formation of ductile NiTi instead of brittle NiTi{sub 2}. The microstructures of the fracture edges after tensile testing illustrated that the eutectic CuTi + CuTi{sub 2} fractured at the SS/Cu1/Ti joint after tensile testing, while CuTi{sub 2} and eutectoid αTi + CuTi{sub 2} compounds fractured during the tensile experiment at the SS/Ni-Cu1/Ti and SS/Cu1-V/Ti joints, respectively. Investigations based on both the 0.5- and 1-mm-thick Cu interlayers showed that the tensile strength and elongation of the composite interlayer joints at a laser power of 3.5 kW were greater than those of the single interlayer joints.

36 MATERIALS SCIENCE↗

Improved High-Temperature Aluminum Alloys Containing Cerium

A common rare earth (cerium) when added to aluminum in compositions up to the eutectic compositions of around 10 wt.% improves the high-temperature performance of aluminum alloys. In the early 1980s, some promising research and development efforts focused on powder metallurgy revealed that aluminum alloys containing 4 wt.% cerium exhibit high-temperature mechanical properties exceeding those of the best commercial aluminum casting alloys then in production. Those compositions, which also included high levels of iron, were difficult to process. Recently, magnesium replaces iron to reduce density and improve processing. Cerium oxide is an abundant rare earth oxide that is often discarded during the refining of more valuable rare earths such as Nd and Dy. Therefore, the economics are compelling for cerium as an alloy additive. In this review, we report results obtained during an investigation of the processing and properties of aluminum-cerium alloys produced via casting, extrusion and additive manufacturing. The results show mechanical properties are retained at higher temperatures than other aluminum alloys and show complete recovery of mechanical properties at room temperature when exposed to elevated temperatures as high as 500 °C for 1000 h. Alloys containing cerium also have superior corrosion properties when compared to most aluminum alloys.

36 MATERIALS SCIENCE↗