Effect of A-Site Ionic Radius on the Structure and Microwave Dielectric Characteristics of Sr1+xSm1−xAl1−xTixO4 Ceramics

SrSmAlO₄ microwave dielectric ceramics were modified by Sr/Ti cosubstitution for Sm/Al. The effects of radius difference of A-site ions on the microwave dielectric characteristics were investigated together with the structure. Sr_1+xSm_1−xAl_1−xTi_xO₄ (x=0, 0.05, 0.10, and 0.15) ceramics were prepared by a solid-state reaction approach. X-ray diffraction studies revealed a single-phase K₂NiF₄-type solid solution with corresponding peaks shifting to lower 2θ as x increased. Minor inhomogeneous grain morphology for x=0.05 and a trace amount of second phases for x=0.10, 0.15 were detected by backscattered-electron microscopy and energy-dispersive X-ray analysis. With increasing Sr/Ti cosubstitution, the dielectric constant ɛ_r increased from 18.4 to 20.4, and the temperature coefficient of resonant frequency τ_f was adjusted from −1.8 to 7.4 ppm/°C almost linearly. However, the Q×f value decreased from 74,500 GHz at x=0–53,000 GHz at x=0.15. The internal stresses caused by the decreased tolerance factor and the large ionic radii difference between Sr²⁺ and Sm³⁺ should be the predominant reasons for such a decrease in the Q×f value. The high-resolution transmission electron microscopic results revealed an increase in the lattice distortion with increasing Sr/Ti cosubstitution, and subsequently supported the above conclusion upon the increased internal stresses.     

Synthesis,Characterization, and Reaction of Divinyl‐substituted Laddersiloxanes

Silicon - Silsesquioxanes with well-defined structures have been of great interest recently because of their superior properties. Among them, laddersiloxanes (ladder-type silsesquioxanes with...     

Synthesis,Characterization and Curing of o-Cresol – Furfural Resins

Polycondensation of o-cresol (OC) with furfural (F) was carried out under various reaction conditions. The resultant resin samples designated as OCFs were characterized by elemental analysis, spectral studies, viscometric measurement of solution in 1,4-dioxane and by the estimation of the number – average molecular weight. Thermogravimetric analysis (TGA) of selected resin samples has been carried out. The curing kinetic reaction of selected OCF resin samples was studied by differential scanning calorimetry (DSC). Hexamethylenetetramine (Hexamine) has been used as curing reagent.     

Synthesis and Characterization of Nanoscale Mullite Powder

Nanoscale mullite powder were synthesized via solgel-SCFD and middle temperature treatment by using AIP (aluminum-isopropoxde)and TEOS(tetraethyl orthosilicate) as starting materials.Both of the binary aerogel of alumina-silica and calcined nanoscale materials were investigated by using TG-DSC(thermogravimetry-differential scanning calorimeter),TEM(transmission electron microscope),XRD(X-Ray diffractometer)and specific surface area and porosimetry.TG-DSC indicated the removal of most of the volatiles,i.e.15.98% up to about 700℃,and in the DSC curve,existence of two exothermic peak at about 445℃ and 1015℃ may be due to the crystallization of Si-O-Al-O in diphasic gels and mullitization and a small endothermic peak at about 805℃ indicated the decomposition of structural water molecules.On the colligation of the results of TG-DSC,XRD and TEM,the beginning temperature of mullitization in Al2O3-SiO2 aerogel system can be confirmed at about 1015℃.XRD results also showed the formation of mullite at the range 1100-1200℃.TEM and surface area and porosimetry results showed that the nanosized mullite were calcinated at 1100 and 1200℃ exhibited size 30nm and 50nm,specific surface area 138.91m^2/g and 95.81m^2/g.     

Synthesis,Characterization and Ion–Exchanging Properties of Novel Ion-Exchange Resin,Part 1

A polyamine (PA) was prepared by condensation of 1,4-bischloromethyl benzene and 1,2-ehanedeamine. The PA was then treated with cyanuric chloride at 0°C followed by reaction with sulfanilic acid in THF in concentration. NaOH (PH 9–10) at room temperature for 8 h. The resultant polymer, designated as polyamine-s-triazine-sulfanilic acid (PATS), was characterized by elemental analysis, IR spectral studies, and thermogravimetry. The PATS sample was monitored for its ion-exchanging properties by batch equilibrium method.     

Single-crystalline LaxPr1−xB6 nanoawls: Synthesis,characterization and growth mechanism

Lanthanum–praseodymium hexaboride (La_xPr_1−xB₆) nanoawls have been fabricated via a simple flux-controlled method using lanthanum (La) powders, praseodymium (Pr) powders and boron trichloride (BCl₃) gas as starting materials at 1050 °C. Scanning electron microscopy (SEM) shows that the tapered nanoawls have a length of 2–10 μm and a diameter ranging from 50 to 300 nm at the roots and 10–80 nm at the tips. Transmission electron microscopy (TEM) reveals that the nanoawls are single crystalline with the preferred growth direction along [110]. Raman spectra indicate that the T_1u mode splitting effect occurs in this ternary rare-earth hexaboride. In addition, a concentration gradient is necessary to create these awl-like structures where the combination of self-catalyzed and vapor–solid growth is responsible for the growth of tapered La_xPr_1−xB₆ nanoawls.     

Synthesis and Spectroscopic Studies of DGEBA–Grafted Polyaniline

N-grafted polyaniline with diglycidyl ether bisphenol A (DGEBA) was synthesized via anionic copolymerization technique. Metalation reaction was performed to cause grafting to occur between DGEBA with emeraldine salt polyaniline (PANI-ES) and leucoemeraldine base polyaniline (PANI-LEB), respectively. Fourier transform infrared (FTIR), ¹³C-nuclear magnetic resonance (NMR), and ¹H-NMR spectroscopies and gel permeation chromatography (GPC) were performed to characterize the PANI-EB-g-DGEBA and PANI-ES-g-DGEBA copolymers. The gel content of the resultant copolymers was determined by Soxhlet extraction. Results of spectroscopic studies showed that grafting took place together with the side reaction, cross-linking, and DGEBA homopolymerization. Oxidation states of PANI were found to influence the gel content and molecular weight distribution of copolymers produced.     

Microwave dielectric properties of (1−x)ZnTa2O6−xMgNb2O6 ceramics

Single phase MgNb₂O₆ and ZnTa₂O₆ powders were synthesized by solid-state method, and the high quality factor composite ceramics of (1?x)ZnTa₂O₆?xMgNb₂O₆ (x=0, 0.05, 0.10, 0.15, 0.20, 0.25 and 1.0) were prepared using the as-synthesized powders. The microwave dielectric properties, microstructure, phase transition and sintering behavior of the composite ceramics were investigated. The X-ray diffraction analysis revealed that solid solution between ZnTa₂O₆ and MgNb₂O₆ phases appeared in the composite ceramic. SEM results show that the grain sizes of the composite ceramics increased with increasing x values. The temperature coefficient of resonant frequency of (1?x)ZnTa₂O₆?xMgNb₂O₆ composite ceramics reaches near-zero of 1.02 ppm/°C with ε_r=35.58 and a high quality factor of 65500 GHz when x=0.20 and sintered at 1350 °C for 2 h.     

LaCo1−x Pd x O3 Perovskite-Type Oxides: Synthesis, Characterization and Simultaneous Removal of NO x and Diesel Soot

A series of naometric perovskite catalysts LaCo_1?x Pd _x O₃ (x = 0, 0.01, 0.03) were prepared via a solution combustion synthesis route using metal nitrates as oxidizers and urea as fuel. It is essential to add a certain amount of ammonia aqueous solution to Pd²⁺ ions solution in the catalyst preparation process. Homogeneous nanoparticles LaCo_1?x Pd _x O₃ catalysts with the sizes in the range of 68–122 nm were obtained and characterized by using of XRD, BET, H₂-TPR, XPS, SEM and TEM. Pd was successfully introduced into the LaCoO₃ perovskite lattices. Further information was obtained by using XPS upon the LaCo_0.97Pd_0.03O₃ (with NH₄OH) sample after H₂-TPR. The results revealed that surface Pd was reduced to the metallic state at the end of the first step in the H₂-TPR experiment, and some surface Co could be reduced to metallic Co simultaneously. The catalytic properties were investigated for simultaneous NO _x -soot removal reaction. The performance of LaCo_1?x Pd _x O₃ catalysts were greatly improved by the partial substitution of Pd. The maximum NO conversion into N₂ and the ignition temperature of soot are 32.8% and 265 °C, respectively.     

Synthesis,structural and electrical properties of Bi1−xDyxFeO3 multiferroic ceramics

Polycrystalline ceramic samples of dysprosium (Dy³⁺) doped bismuth ferrite of general formula Bi_1?xDy_xFeO₃ (x=0.00, 0.01, 0.05 and 0.1) have been prepared by standard solid state reaction method. Powder X-ray diffraction (XRD) analysis reveals that all the samples crystallize in the rhombohedral structure with noncentrosymmetric R3c space group. The refined lattice parameters decrease with the increase of Dy concentration within the same structure symmetry. The bond lengths among atoms for all the compounds were calculated by the Rietveld analysis. The frequency and temperature dependent dielectric constants (real and imaginary parts) have been measured. The real part of dielectric constant reveals that the Neel temperature decreases with the increase of Dy-substitution down to ～200 °C for 10% substitution to the Bi site.     

Electropolymerization and Impedance Spectroscopic Characterization of Thiophene Derivatives with η6-aryl-η5-cyclopentadienyliron hexaflourophosphates

Esterification reaction of organoiron complex with terminal carboxylic group with hydroxymethyl EDOT(3,4-ethylenedioxythiophene) and 2-(3-Thienyl) ethanol produced EDOT and thiophene monomers. The electrochemical polymerization of these monomers led to new polymeric materials with the conjugated system as a backbone and the iron moieties pendant to the backbone. The polymer behaved as a conductive support and the metal group acted similarly to an un-tethered complex. The modified electrode surfaces were characterized via electrochemical impedance spectroscopy to explore the capacitive properties of polymers. Further morphological characterization proved the thin film formation on the electrode surface.     

Synthesis and Characterization of the Inclusion Complex of β-cyclodextrin and Azomethine

A β-cyclodextrin (β-Cyd) inclusion complex containing azomethine as a guest was prepared by kneading method with aliquot addition of ethanol. The product was characterized by Fourier Transform Infrared (FTIR) spectrometer, ¹H Nuclear Magnetic Resonance (¹H NMR) and Thermogravimetric Analyzer (TGA), which proves the formation of the inclusion complex where the benzyl part of azomethine has been encapsulated by the hydrophobic cavity of β-Cyd. The interaction of β-Cyd and azomethine was also analyzed by means of spectrometry by UV-Vis spectrophotometer to determine the formation constant. The formation constant was calculated by using a modified Benesi-Hildebrand equation at 25 °C. The apparent formation constant obtained was 1.29 × 10⁴ L/mol. Besides that, the stoichiometry ratio was also determined to be 1:1 for the inclusion complex of β-Cyd with azomethine.     

Synthesis and Characterization of Dicyclopentadiene – cresol Epoxy Resin

Summary Starting from cresol, the synthesis of dicyclopentadiene (DCPD) – cresol epoxy resin was conducted. DCPD-containing phenol resin (DPR) was prepared via Friedel–Crafts alkylation, whereas DCPD-containing epoxy resin (DER) was prepared via epoxidation of DPR with epichlorohydrin. The chemical structure was characterized with FTIR and ¹HNMR. Cure behaviors and glass transition temperature (T_g) of the resulting polymers were studied by differential scanning calorimeter (DSC). The results clearly indicated that cured polymer with a mixture of DCPD-cresol epoxy resin and diglycidyl ether of bisphenol A (E51) had higher T_g comparing with E51.     

Microwave Dielectric Properties of (Mg1−xNix)2TiO4 (x=0.02–0.1) Ceramics

Low-loss ceramics in the system (Mg_1−xNi_x)₂TiO₄ (x=0.02–0.1) have been prepared using the conventional solid-state ceramic route. The formation of (Mg_1−xNi_x)₂TiO₄ (x=0.02–0.1) solid solutions was confirmed by the EDX analysis and the lattice parameters measured, which linearly varied from Mg₂TiO₄ (a=b=c=8.4410 Å) to (Mg_0.9Ni_0.1)₂TiO₄ (a=b=c=8.4335 Å). The X-ray diffraction analysis also confirmed the coexistence of a cubic-structured (Mg_1−xNi_x)₂TiO₄ and an ilmenite-structured second phase (Mg_1−xNi_x)TiO₃. By increasing x, not only could the Q×f of the (Mg_1−xNi_x)₂TiO₄ solid solution be considerably increased from 150,000 GHz at x=0 to a maximum 238,000 GHz at x=0.05, the highest ɛ_r∼16.43 could also be obtained simultaneously. This was mainly due to the uniform grain morphology and the highest density of the specimen. A good combination of microwave dielectric properties (ɛ_r∼16.43, Q×f∼238,000 GHz at 9.8 GHz, and τ_f∼−55 ppm/°C) can be achieved for a specimen using (Mg_0.95Ni_0.05)₂TiO₄ sintered at 1400°C for 4 h.     

Synthesis, Characterization and HDS Activity of Carbon-Containing Ni–Mo Sulfide Nano-Spheres

Ni-promoted tetramethylammonium tetrathiomolybdate precursor was prepared by the aqueous solution precipitation method using (NH₄)₂MoS₄, (CH₃)₄NBr and NiCl₂.6H₂O as raw materials. Carbon-containing Ni–Mo sulfide nanospheres, namely Ni/C₁–MoS₂, were obtained by ex situ thermal decomposition of the precursor under N₂ atmosphere. Energy dispersive X-ray spectroscopy (EDS), low temperature N₂ adsorption (BET method), X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) techniques were employed to characterize these as–synthesized sulfide particles. The results showed that the average size of solid Ni–Mo sulfide nanospheres, with surface composition MoNi₀.₄₀S₀.₇₃C₁.₄₃, is 75 nm and the solid structure leads to low surface area of Ni/C₁–MoS₂. In addition, the introduction of methyl chain improved the dispersion of nickel phases and resulted in C/Mo ratio, 1.4. By comparison with catalytic performance of the Ni/MoS₂ catalyst counterpart, Ni/C₁–MoS₂ revealed lower HDS activity but higher direct desulfurization (DDS) selectivity. Lower stacking number of MoS₂ slabs (5 layers) and shorter slabs length of MoS₂ slabs (6 nm) explained higher DDS selectivity satisfactorily. The formation of carbon-containing Ni–Mo sulfide nanospheres was possibly due to surfactant effect of tetramethylammonium cations and the potential measure to increase their surface area was discussed as well in this work.     

Green Synthesis,Structural Characterization and Photocatalytic Activities of Chitosan-ZnO Nano‐composite

Journal of Inorganic and Organometallic Polymers and Materials - Chitosan was isolated from chitin, a direct derivative of snail shell, and further used to form a heterostructure with ZnO...     

Synthesis, Characterization and Surface Properties of Cross-linked Polyurethane Dispersions Modified by Organosiloxane

A series of cross-linked polyether-polyester polyurethane dispersions modified with organosiloxane were prepared based on hydroxyl-terminated polydimethylsiloxane (HTPS) as hydrophobic component and 3-aminopropyl-triethoxysilane (APTS) as cross-linker as well as a bridge between polyurethane (PU) and polysiloxane (PSIL). It was discovered that polydimethylsiloxane segments were incorporated into PU chains chemically and organosiloxane was preferentially oriented toward the surface layer of the film by making a comparison of attenuated total reflection (ATR) spectra between the copolymer and the blend of PU and PSIL, which was further confirmed by investigation of electron spectroscopy for chemical analysis (ESCA). The relationships between surface properties of the film formed from polyurethane dispersion and organosiloxane content were also studied. The results showed that water contact angle of the film increased with the increase of organosiloxane content. Interestingly, it was also found that water contact angle of PUS film increased firstly and then decreased when film-forming temperature varied from 25℃ to 55℃.     

Synthesis,Characterization and Effect of a Solvent Mixture on the CMC of a Thio-Based Novel Cationic Surfactant Using a UV–Visible Spectroscopic Technique

A novel thio-based cationic surfactant has been synthesized by a new method. It was characterized by different techniques such as NMR, FTIR and its critical micelle concentration was determined by a UV–Visible spectroscopic technique. It is soluble in polar solvents like ethanol and partially soluble in water due to its thio-based functionality. The detailed study of the compound 4-chloro-N-((dodecanoyl(ethyl)ammonio)carbonothioyl)-N-ethylbenzenaminium bromide (4CDTB) was done using a UV–Visible spectrophotometric technique. The effect of solvent mixtures of different ratios was investigated. On the basis of solvent–solvent interaction the compound showed different results. The critical micelle concentration varied with solvent mixture ratios. The CMC of 4CDTB decreased as the ratio of water increased in the mixture of the ethanol–water system. The decrease in critical micelle concentration with the solvent mixture ratio has been discussed on the basis of solvent properties, structures, and their hydrophilic and hydrophobic interactions.