Preparation and characterization of layered silicate magadiite intercalated by Cu<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> for antibacterial behavior

The purpose of this work is the synthesis of two series of layered silicate materials with different ratios (10, 30, 50, 80 and 100) of Cu(NO₃)₂, or Zn(NO₃)₂ by ion-exchange method. Several analysis techniques have been used such as X-ray diffraction, energy dispersive X-ray spectroscopy, thermogravimetric analysis, scanning electron microscope and Fourier transform infrared spectroscopy. The results revealed that ion-exchange method of copper and zinc with different ratios did not affect the structure of Na-magadiite. The gap between the theoretical and experimental ion-exchange are in agreement. Antibacterial activity test against Escherichia coli, Rhizobium sp. and Staphylococcus demonstrate that when ratio was (30, 50, 80 and 100) the antibacterial activity of the layered silicate materials showed high antibacterial activity.     

A novel SiCN@TiO2 core–shell ceramic microspheres derived from a polymeric precursor

A novel core–shell ceramic microspheres, composed of a SiCN inner core and TiO₂ nanoparticles outer shell, were prepared via emulsion technique and polymer-derived ceramics (PDCs) method. The forming process of SiCN@TiO₂ core–shell ceramic microspheres were controlled by adjusting the ratio of raw material, curing temperature and pyrolysis temperature. The morphology, chemical composition and phase transformation were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). PVSZ@TiO₂ microspheres with good spherical structure and uniform-dispersed TiO₂ surface were fabricated at 200 °C with raw material ratio of 25%. After pyrolyzed at 1400 °C, the obtained SiCN@TiO₂ core–shell ceramic microspheres retained spherical structure. The XRD showed that the products were mainly composed of rutile TiO₂, SiC and Si₃N₄ crystalline phase, which were generated by polyvinylsilazane.     

Crystallization kinetics of lanthanum monoaluminate (LaAlO3) nanopowders prepared by co-precipitation process

Lanthanum monoaluminate (LaAlO₃) nanopowders were synthesized using La(NO₃)₃·6H₂O and Al(NO₃)₃·6H₂O as starting materials by a co-precipitation method. The crystallization kinetics of the LaAlO₃ nanopowders has been investigated by using differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The XRD results and SAED patterns show that the rhombohedral LaAlO₃ nanopowders have been obtained when the precipitates as calcined at 1092 K for 10 min. The activation energy for the crystallization of the rhombohedral LaAlO₃ nanopowders is determined as 286.75 kJ/mol by a non-isothermal method. The TEM examination shows that the rhombohedral LaAlO₃ has a spherical morphology with the size ranging from 30 to 50 nm.     

Synthesis optimization, structural evolution and optical properties of hierarchical nanoporous alumina microspheres prepared by continuous soft chemistry method

In the present work, nanoporous alumina microspheres have been synthesized by sol–gel technique. Acid deficient aluminum nitrate and a mixture of equimolar HMTA-Urea were used as starting materials. The prepared sol then injected as droplets into hot oil column to give spherical shape. After calcinations the samples were characterized by scanning electron microscope, fourier transform infra-red spectroscopy, thermogravimetry–differential thermal analysis, X-ray diffraction and N₂ adsorption–desorption isotherms. With respect to the results achieved from the above analyses, it was found that nanoporous alumina microspheres with controllable size and morphology can successfully be produced through sol–gel method.     

Consolidation of mine tailings through geopolymerization at ambient temperature

Mine tailings-based geopolymers were prepared at ambient temperature. The evolution of their microstructure and the immobilization of lead were studied. Characterizations include measurements in compressive strength, scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and toxicity characteristic leaching procedure (TCLP) tests. With increasing the ratio of metakaolin from 0% to 50%, geopolymer gel in the mine tailings-based geopolymers increased from 33.92% to 79.45%, leading to the compressive strength that increased from 2 to 15.5 MPa. With addition of Pb(NO₃)₂, a three-stepped changes in the compressive strength and microstructure of the geopolymers were observed. As increasing Pb(NO₃)₂ dosage from 0% to 6%, geopolymer gel was kept constant, while lead silicate glass increased from 0% to 10.51%, and Si sites in calcium silicate hydrate (CSH) gel decreased from 20.55% to 11.3%. Pb²⁺ was effectively immobilized in the geopolymers. This study first presents the evolution of geopolymer gel, belite, lead silicate glass, and CSH gel in mine tailings-based geopolymers as the functions of metakaolin and Pb(NO₃)₂ additions.     

Synthesis of nitrogen-doped carbon coated TiO2 microspheres and its application as metal support in cinnamaldehyde hydrogenation

N-doped carbon coated TiO₂ microspheres (CNx/TiO₂) were synthesized by the carbonization of the polypyrrole (PPy) coating on the surface of TiO₂ microspheres and used as support to disperse Pt and PtCo nanoparticles for investing the selective hydrogenation of cinnamaldehyde. The support and catalysts have been characterized in terms of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). The hydrogenation results showed the conversion increased with an increase of CNx amount until the CNx coated TiO₂ microspheres completely.     

Synthesis of alumina nanofibers: Role of calcination temperature on dimethyl ether production

In this work, we present the aluminum oxide (Al₂O₃) ceramic nanofiber synthesis by means of thermal calcination of polyvinylpyrrolidone–aluminum nitrate (PVP–Al(NO₃)₃) composite nanofibers previously prepared by electrospinning; the studied calcination temperatures were: 500, 650, and 800 °C. These nanofibers were evaluated for their catalytic conversion of methanol to dimethyl ether (DME) by dehydration reaction. Thermal properties were evaluated via thermal gravimetric analysis (TGA). The results showed full calcination of the PVP polymer support and complete transformation of Al(NO₃)₃ to Al₂O₃. The chemical composition was elucidated through Fourier-transform infrared (FTIR) spectroscopy and energy-dispersive X-ray spectroscopy (EDX). Structural characteristics were obtained by X-ray diffraction (XRD) and selected-area electron diffraction (SAED), which demonstrated an amorphous-to-crystalline evolution as the calcination temperature is increased, obtaining the cubic gamma-alumina (γ-Al₂O₃) structure with a crystallite size of 6 nm at 800 °C. Scanning and transmission electron microscopies (SEM and TEM, respectively) showed a decrease of the diameter fiber from 254 to 160 nm and an increase in surface roughness as the calcination temperature is increased. The Barrett-Joyner-Halenda (BJH) and Brunauer-Emmett-Teller (BET) methods were employed to study the texture properties, and the results indicated an increase in pore volume (from 0.008022 to 0.04 cm³ g^–1), as well as surface area (from 10.22 to 37.46 g/m²) with increasing the calcination temperature. Finally, the synthesized Al₂O₃ ceramic nanofibers presented a catalytic conversion of methanol to DME of around 70% and a selectivity of 100% at 350 °C and 1 atm of pressure.     

Influence of pH on the morphology and photocatalytic activity of CuO obtained by the sonochemical method using different surfactants

In this work, copper oxide II (CuO) was obtained using different surfactants (PVP, PEG and EDA), as well as without surfactant (WS), varying synthesis pH (8, 11 and 13). The powders were characterized by X-ray diffraction (XRD), field scanning electron microscopy (SEM), Brunauer-Emmett-Teller method (BET), UV–Visible spectroscopy (UV–Vis), Fourier transform infrared spectroscopy (FTIR), photoluminescent properties and their photocatalytic properties were measured against the methylene blue dye under UV radiation. XRD patterns showed that a pH increase from 8 to 13 favors CuO single phase formation, whereas Cu₂(OH)₃(NO₃) secondary peaks appear at lower values. FTIR spectra confirmed the appearance of Cu₂(OH)₃(NO₃) through the vibrations related to the hydroxide nitrate. The SEM images showed the variations in morphology obtained through the different surfactants and the medium pH, in which, the morphology presents a leaf appearance with a lower value (pH =?8), while increasing the pH to 13, changed the morphology into agglomerate flower-like nanoparticles. The BET results showed that the samples obtained without surfactant and with PEG at pH =?8 had the highest and lowest surface area, being 18.935 and 4.531?m² g^?1, respectively. The photocatalytic activity shows that the CuO powders that have a small amount of Cu₂(OH)₃(NO₃) present better methylene blue dye degradability when illuminated by UV–Vis radiation.     

Characterization of europium doped yttrium nano-oxide prepared by plasma electrolysis in nitrate solution under air atmosphere at room temperature

Europium-doped yttrium oxide is widely used because its unique optical properties, excellent thermal stability, and chemical stability. This paper reports a process for preparing a Y₂O₃:Eu³⁺ red fluorescent material through plasma discharge electrolysis at room temperature in a normal atmosphere and a 0.38 M Y(NO₃)₃ - 0.02 M Eu(NO₃)₃ mixed rare earth nitrate solution. Several techniques, including emission spectroscopy, X-ray diffraction, TG-DSC thermal analysis, Fourier transform infrared spectroscopy and photoelectron spectroscopy, were performed to characterize the electrolysis process and the obtained products. The results show that the electrolytic products were mainly composed of Y(OH)₃, the electrolytic hydroxide products were not obviously granular, and Eu was uniformly distributed in the products. After heat treatment at 400–900 °C, cubic phase yttrium oxide was formed, and the products were irregular spherical, with particle sizes between 30 and 200 nm. After annealing at 800 °C, the products showed strong red emission at 612 nm, corresponding to ⁵D₀→⁷F₂ excitation. In addition, charge transfer band (CTB) absorption was observed in the excitation spectrum, and the emission spectra of fluorescent materials also showed some sharp emission bands generated by the ⁵D₀→⁷F_J (J = 0,1,3,4) transition. The colour coordinate of the Y₂O₃:Eu³⁺ powder produced by plasma electrolysis is close to the standard red coordinate, showing excellent colour properties.     

Fabrication and properties of Acid Yellow 49 dye-intercalated layered double hydroxides film on an alumina-coated aluminum substrate

The Acid Yellow 49(4-[2-(5-amino-3-methyl-1-phenyl-1H-pyrazol-4-yl)diazenyl]-2,5-dichloro benzenesulfonic acid) (denoted as PPDB) anion intercalated layered double hydroxides (LDH) film was fabricated through an ion-exchange method using a ZnAl-NO₃-LDH/alumina/aluminum film as precursor. The prepared film was investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), Thermogravimetric-differential thermal analysis (TG-DTA), UV-visible spectroscopy and the CIE 1976 L*a*b* color difference method. XRD patterns and FT-IR spectra confirm the successful incorporation of PPDB anions into the interlayer galleries of ZnAl-LDH with an expansion of d-spacing from 0.88 nm to 2.51 nm and the disappearance of characteristic absorption band of NO₃⁻ anions at 1384 cm⁻¹. The SEM morphologies show that the LDH films are mainly oriented with c axis of the platelet crystallites parallel to the substrate surface. Additionally, the obtained results suggest that the intercalation of PPDB into ZnAl-LDH host markedly improve the thermal stability and light fastness of PPDB.     

Ablation properties of aluminum silicate ceramic fibers and calcium carbonate filled silicone rubber composites

The ablative performance of aluminum silicate ceramic fiber (ASF) and calcium carbonate (CaCO₃) filled silicone rubber composites prepared through a two‐roll mill was examined. The properties of the composites were investigated by thermogravimetry, thermal conductivity measurements, and oxyacetylene torch testing. After the material was burnt, the structure and composition of the char were analyzed by Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy (SEM). The results of the ablation test showed that the ablation resistance improved greatly in an appropriate filler scope. Combined with SEM, it was proven that a firm, dense, and thermal insulation layer, which formed on the composites surface during the oxyacetylene torch test, was a critical factor in determining the ablation properties. Thermogravimetric analysis revealed that the thermal stability of the composites was enhanced by the incorporation of ASF and CaCO₃. The thermal conductivity measurements showed that the silicone rubber composites had a very low thermal conductivity ranging from 0.206 to 0.442 W m^?1 K^?1; this significantly prevented heat from transferring into the inner matrix at the beginning of the burning process. The proportion of 20/40 phr (ASF/CaCO₃) was optimum for improving the ablation resistance of the silicone rubber composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41619.     

Sol-gel synthesis and luminescence properties of Ba2SiO4:Sm3+ nanostructured phosphors

Ba₂SiO₄:Sm³⁺ nanostructure phosphors have been synthesized by a simple sol-gel method. Phase evaluation, structural characteristics and photoluminescence properties of the synthesized Ba₂SiO₄:Sm³⁺ powders were studied using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), Fourier transform infrared spectroscopy (FTIR), and photoluminescence spectroscopy (PL). X-ray diffraction results showed that all synthesized samples were single-phase barium silicate (Ba₂SiO₄) and samarium (Sm) ions were incorporated into the lattice of Ba₂SiO₄. Adding samarium to barium silicate changed the microstructure from vermicular to spherical structures. The Photoluminescence spectrum of Ba₂SiO₄:Sm³⁺ phosphors exhibited characteristic emission peaks at 562?nm which is due to the ⁴G_{5/2 →}⁶H_7/2 transition of samarium ions and corresponds to the orange region. The results showed that the barium silicate activated with 0.08?mol samarium exhibited the highest PL intensity.     

Mechanical properties and microstructure of HDPE/AL(OH)3/silicone oil composite

The effect of surface modification on the mechanical properties and microstructure of the composites of high‐density polyethylene (HDPE), silicone oil, and aluminum hydroxide [Al(OH)₃] was investigated. The dispersion of silicone oil in the HDPE composites was studied by scanning electric microscope (SEM) and differential scanning calorimetry (DSC). In the HDPE/Al(OH)₃/silicone oil composites, two types of dispersion structure of silicone oil were observed resulting from different surface modifications. In the composites surface modified with titanate NDZ‐130, calcium stearate, or oleic acid, silicone oil encapsulates around Al(OH)₃ particles, and both the notched impact strength and the elongation at break are very high. However, in the composites surface modified with silane KH‐550 or silane‐g‐HDPE, silicone oil and Al(OH)₃ particles separately disperse in HDPE, and both the notched impact strength and the elongation at break are very low. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1896–1903, 2002     

Synthesis of silicon-substituted hydroxyapatite by a hydrothermal method with two different phosphorous sources

Silicon-substituted hydroxyapatite (Si-HA) with up to 1.8 wt% Si content was prepared successfully by a hydrothermal method, using Ca(NO₃)₂, (NH₄)₃PO₄ or (NH₄)₂HPO₄ and Si(OCH₂CH₃)₄ (TEOS) as starting materials. Silicon has been incorporated in hydroxyapatite (HA) lattice by partially replacing phosphate (PO₄³⁻) groups with silicate (SiO₄⁴⁻) groups resulting in Si-HA described as Ca₁₀(PO₄)_6−x(SiO₄)_x(OH)_2−x. X-ray diffraction (XRD), Fourier transform IR spectroscopy (FTIR), inductively coupled plasma AES (ICP-AES) and scanning electron microscopy (SEM) techniques reveal that the substitution of phosphate groups by silicate groups causes some OH⁻ loss to maintain the charge balance and changes the lattice parameters of HA. The crystal shape of Si-HA has not altered compared to silicon-free reference hydroxyapatite but Si-incorporation reduces the size of Si-HA crystallites. Based on in vitro tests, soaking the specimens in simulated body fluid (SBF), and MTT assays by human osteoblast-like cells, Si-substituted hydroxyapatite is more bioactive than pure hydroxyapatite.     

Synthesis of YAG powders by the co-precipitation method

YAG (Y₃Al₅O₁₂) powders have been prepared by co-precipitation technique in which NH₄HCO₃ is used as a precipitant and Y₂O₃, A1((NO₃)₃·9H₂O—as raw materials. Two kinds of surfactant are added into the solution, i.e. Polyethylene glycol (PEG10000) as steric stabilizer and (NH₄)₂SO₄ as electrical stabilizer. The composition of YAG precursor, the phase formation process of YAG and the properties of the powders were investigated by means of differential scanning calorimetry and thermogravimetry analysis (DSC–TG), X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FT-IR) and Scanning electron microscopy (SEM). The results of XRD show that phase YAG crystallite can be obtained as precursors when heated at 900 °C for 2 h. The powders loosely dispersed with narrow size distribution and spherical shapes could be observed by SEM. It has been found that the presence of PEG and (NH₄)₂SO₄ is beneficial for the dispersion of the resulting YAG powder. In the presence of surfactants, the synthesized product consists of highly dispersed nano-sized particles.     

Novel synthesis and applications of yttrium silicates from a silicone resin containing oxide nano-particle fillers

In this paper, a novel method for the synthesis of yttrium silicates is presented. Such silicates are well known to be promising materials for protecting various substrates against high temperature oxidation, but they can typically be produced only after quite complicated processing. The use of preceramic polymers, in which a silicate article is obtained by direct thermal treatment in air of nano-composites consisting of silicone resins containing suitable oxide nano-particles, is a valid alternative, since the desired phases, i.e. Y-monosilicate (Y₂O₃·SiO₂) and Y-disilicate (Y₂O₃·2SiO₂) can be obtained by treatments at low temperature (1000–1400 °C). Y-disilicate could be employed for the manufacturing of dense and thick coatings on SiC foamed substrate, by simply dipping the substrates into silicone suspensions, before ceramic conversion. Y-monosilicate, that could be also useful for coatings, was found to exhibit promising characteristics, when doped with Eu₂O₃, making it of interest for application as red phosphor for LEDs.     

Studies on cermet behavior of Ni doped YSZ

A simple and cost effective combustion process is employed to prepare Ni/YSZ cermet from an aqueous solution containing ZrO(NO₃)₂·6H₂O, Y(NO₃)₃·6H₂O, Ni(NO₃)₂·6H₂O and urea followed by H₂ reduction. As prepared cermet was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy techniques. Processed powder of NiO-YSZ was found to be in crystalline form with homogeneous mixture of YSZ and NiO phases. On reduction, its mixed conductivity is suppressed partially. The impedance and dielectric properties of the cermet were studied over a frequency range 10?Hz to 2?MHz at different temperatures. M ? H behavior at different temperature (down to 5?K) including ZFC and FC at 500?Oe were studied. To understand and corroborate the conductivity behavior and mechanism involved with the magnetic Ni ion mediated YSZ cermet, we have also studied the electric field induced polarization behavior and predict that Ni magnetic ion has specific role towards the contribution of conductivity mechanism generally included in Ni/YSZ cermet used for SOFC applications.     

Biomimetic synthesis of spherical nano-hydroxyapatite in the presence of polyethylene glycol

Spherical nano-hydroxyapatite (nano-HA) was synthesized successfully by a biomimetic method using Ca(NO₃)₂·4H₂O and (NH₄)₃PO₄·3H₂O as reagents in the presence of polyethylene glycol (PEG). The crystalline phase, microstructure, chemical composition, and morphology of the obtained samples were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). The results show that spherical nano-HA with diameter of 30–50 nm can be synthesized in the presence of a certain concentration (2–6%) of PEG. The crystallinity of HA powder synthesized in the presence of PEG was higher than that synthesized in the absence of PEG, but the crystallinity of HA reduced with increasing the concentration of PEG. The electrical conductivity (EC) of the solution revealed that PEG reduced the transfer rate of Ca²⁺ in the process of HA crystallization, indicating the interaction between PEG and HA. The possible mechanism of formation spherical nano-HA was discussed.     

Structure formation in yttrium aluminum garnet (YAG) fibers

Polycrystalline yttrium aluminum garnet (YAG, Y₃Al₅O₁₂) fibers were prepared from aqueous solutions of aluminum chlorohydrate and yttrium chloride. Fiber processing was accomplished via dry spinning. Poly(vinylpyrrolidone) (PVP) was used as spinning aid. Polycrystalline YAG fibers were obtained by pyrolysis of the green fibers followed by sintering at defined temperatures in air. Ceramic fibers were 9–16 μm in diameter. Differential scanning calorimetry/thermogravimetric analysis coupled with mass spectrometry (DSC/TGA-MS) showed an exothermic peak at 920 °C assigned to the crystallization of YAG and an overall ceramic yield of 38% at 1400 °C. X-ray diffraction (XRD) analysis showed that phase-pure YAG can be obtained at 1600 °C after intermediate formation of Y₂O₃ and monoclinic yttrium aluminum oxide (YAM, Y₄Al₂O₉) phases.     

Study on char reinforcing of different inorganic fillers for expandable fire resistance silicone rubber

Sodium silicate monohydrate (NSH), glass frits (GF) and aluminum hydroxide (ATH) were incorporated into room temperature vulcanized (RTV) silicone rubber (SR) as char reinforcing materials to improve the fire resistance of intumescent flame retardant silicone rubber. SR composites containing only intumescent flame retardant such as phosphorus nitrogen composite flame retardant (NH₂-C) and expandable graphite (EG) were used as comparison samples. Limiting oxygen index (LOI) test, vertical burning test (UL-94), flame resistance test, scanning electron microscopy (SEM) and X-ray diffraction spectroscopy tests, as well as volume variation and compression strength of char residues were used to discuss the effects of the above-mentioned fillers on the fire resistance, char residue strength and char integrity of SR composites. The results showed that SR composite filled with only intumescent flame retardants EG and NH₂-C had excellent flame retardancy. After adding ATH, the char residue was relatively dense and had good compressive strength, but its thermal insulation performance was reduced. GF or NSH reduced the flame retardancy of SR composites, but it obviously played a role in binding combustion residues, forming new crystals and improving the stability of char residues.