Phase constitutions of MoSiN anti-oxidation multi-layer coatings on CC composites by fused slurry

To improve the oxidation resistance of MoSi fused slurry coating fabricated in vacuum, MoSiN multi-layer coatings were synthesized on C/C composites in nitrogen atmosphere by fused slurry using same Mo and Si element powders. The phase compositions and microstructures were characterized by X-ray diffractometry (XRD), optical microscopy (OM), scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS). The results indicate that the MoSiN coating contains SiC inner layer and MoSi₂/Si main layer, which was similar with MoSi coating. Additionally, a thin outer layer with nano-filiform morphology has been found on the coating surface, which consists of SiC, Si₃N₄, AlN, Al₂O₃ and sialon phase. Oxidation experiments show that the MoSiN multi-layer coating exhibits excellent oxidation resistance at 1400 °C and anti-oxidizing potential ability at 1450 °C.     

Effect of water content in sol on optical properties of hybrid sol–gel derived TiO2/SiO2/ormosil film

Sol–gel derived TiO₂/SiO₂/ormosil hybrid planar waveguides have been deposited on soda-lime glass slides and silicon substrates, films were heat treated at 150 °C for 2 h or dried at room temperature. Different amounts of water were added to sols to study their impacts on microstructures and optical properties of films. The samples were characterized by m-line spectroscopy, Fourier transform infrared spectroscopy (FT-IR), UV/VIS/NIR spectrophotometer (UV–vis), atomic force microscopy (AFM), thermal analysis instrument and scattering-detection method. The refractive index was found to have the largest value at the molar ratio H₂O/OR = 1 in sol (OR means OCH₃, OC₂H₅ and OC₄H₉ in the sol), whereas the thickest film appears at H₂O/OR = 1/2. The rms surface roughness of all the films is lower than 1.1 nm, and increases with the increase of water content in sol. Higher water content leads to higher attenuation of film.     

Effects of He (90%)/H2 (10%) plasma treatment on electric properties of low dielectric constant SiCOH films

In microelectronics industry, integration of the low dielectric constant (low-k) material films is a continuing issue due to the decreasing device feature size. To improve electric properties, various post-deposition treatments of the low-k material films can be used. In this work, we used room temperature treatment of He/H₂ plasma and investigated the effects of plasma treatment on the electrical properties of low-k SiOCH films. Plasma treatment time changed from 300 to 1800 s. After treatment, the dielectric constant was decreased from 2.9 to 2.48, and the thickness of the low-k SiCOH films changed by only ～5%. The leakage current densities of the low-k SiCOH films were decreased to ～10^?11 A/cm², with treatment time ≥600 s. The breakdown occurred only around 2 V for films plasma-treated for 600 and 900 s. However, for 1800 s treatment time, the breakdown voltage was enhanced dramatically and breakdown occurred at applied voltage higher than 40 V. The surface composition change of the films after treatment was investigated by X-ray photoelectron spectroscopy (XPS). As the plasma treatment time was increased, the intensities of CC/CH and CSi peaks were decreased while the intensities of SiO and CO peaks were increased. It is thought that increase of oxygen content of the SiCOH film, after plasma treatment, contributed to leakage current reduction and breakdown voltage increase.     

Effect of annealing temperature on the microstructure and photoluminescence of low resistivity Si/SiN/TaN thin films using magnetron sputtering

A lot of studies have been devoted to the porous Si, erbium-doped Si and Si-embedded in dielectric matrix of SiO or SiN together with long-time conventional furnace annealing. Besides, it is noted that these Si nanostructured films were highly resistive and non-conducting. In this paper, we have investigated the effect of annealing temperature on the microstructure and photoluminescence of low-resistivity Si/SiN/TaN nanocomposite thin films which are deposited by magnetron sputtering and followed by rapid thermal annealing (RTA). All samples are of luminescence and staying low resistivity at about 1462–2162 μΩ cm which increases with increasing annealing temperatures. The asymmetric broad photoluminescence (PL) peak covered the wavelengths of 400–700 nm. The wide visible PL spectra can be deconvoluted into three bands of blue (~ 455 nm), green-yellow (~ 525 nm), and orange emissions (~ 665 nm), which correspond to the emission origins from unsatisfied states in imperfections of interface between the Si:O and SiN:O, located states related to the mixed SiO or SiN bonds in SiN:O layer and nc-Si embedded in SiN:O matrix. The detailed mechanism of broad visible PL was investigated in terms of microstructure and bonding configuration evolution. The relationship between the annealing temperature, microstructure and PL behavior of Si/SiN/TaN multilayer films is discussed and established.     

Surface aspects of discolouration in Bisphenol A Polycarbonate (BPA-PC), used as lens in LED-based products

The surface-related reactions during discolouration of Bisphenol A Polycarbonate (BPA-PC), used as LED lens plates, under thermal stress are studied. X-ray photoelectron spectroscopy (XPS) has been used to monitor the changes in the surface chemistry of BPA-PC plates over a temperature range of 100–140 °C for a period up to 3000 h. Increasing time under thermal stress is associated with the discolouration, and increase in the yellowing index (YI) of PC plastic lens. The XPS results show that discolouration is associated with oxidation at the surface, finding a significant increase in the signal ratio O_1s/C_1s in the XPS spectra of degraded specimens. During thermal ageing, the CH concentration decreases and new oxide features CO and OCO form, with the latter being a support for oxidation at the surface being a major reaction during discolouration. Results also show that irradiation with blue light during thermal ageing accelerates the kinetics of discolouration and the increased O_1s/C_1s ratio in XPS spectra.     

Fibroblast functionality on novel Ti30Ta nanotube array

In this study, the mechanical substrate and topographical surface properties of anodized Ti30Ta alloy were investigated using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and contact angle measurement. The anodization process was performed in an electrolyte solution containing HF (48%) and H₂SO₄ (98%) in the volumetric ratios 1:9 with the addition of 5% dimethyl sulfoxide (DMSO) at 15 V, 25 V and 35 V for 20 and 40 min, producing a nanotube architecture when anodized at 35 V for 40 min. Human dermal fibroblasts (HDF, neonatal) were utilized to evaluate the biocompatibility of Ti30Ta nanotubes and Ti30Ta alloy after 1 and 3 days of culture. Cellular adhesion, proliferation, viability, cytoskeletal organization and morphology were investigated using fluorescence microscope imaging, biochemical assay and SEM imaging respectively. The results presented identify altered material properties and improved cellular interaction on Ti30Ta nanotubes as compared to Ti30 Ta alloy.     

Nanoparticles of the giant dielectric material,calcium copper titanate from a sol–gel technique

The precursor of CaCu₃Ti₄O₁₂ (CCTO) nano particles have been successfully synthesized by sol–gel method at 90 °C. The dried precursor powder was milled and then calcined at 450 °C, 550 °C, 650 °C, 800 °C, 850 °C and 950 °C for 3 h. The phase formation of CCTO was analyzed by step by step using FTIR and XRD. Particle size and shape were evaluated by AFM. The XRD results of the powder calcined at 800 °C indicated the formation of CCTO phase. AFM studies showed that average particle size of the CCTO powder range 90–120 nm. The absorption bands corresponding to vibrations of CaO, CuO and TiOTi were observed at 606, 525 and 463 cm^? 1 using FTIR. The samples sintered at 1040 °C showed the densities as high as 96% of theoretical density. The grain sizes of sintered pellets were determined by FE-SEM. The dielectric properties of prepared samples were studied by LCR meter.     

Luminescence at 1.53 μm for a new Er3+-doped transparent oxyfluoride glass ceramic

Transparent 45SiO₂25Al₂O₃5CaO10NaF15CaF₂ glass ceramics doped with different levels of Er³⁺ were prepared. The spherical CaF₂ nanocrystals with 10–20 nm in size were verified to be homogeneously embedded among the glassy matrix. Room temperature absorption and emission spectra corresponding to ⁴I_13/2 ↔ ⁴I_15/2 transitions of Er³⁺ ions in precursor glasses and glass ceramics, respectively had been measured. For glass ceramics, with increasing of Er³⁺ content from 0.1 to 2.0 mol%, the FWHM values of the emission bands increased from 42 to 71 nm; meanwhile, the lifetime of ⁴I_13/2 level slightly reduced. However, both the values of FWHM and lifetime were larger than those of precursor glasses due to the change of ligand field of Er³⁺ ions.     

Metakaolin-based inorganic polymer composite: Effects of fine aggregate composition and structure on porosity evolution,microstructure and mechanical properties

This paper examines the phase transformation, pore evolution, microstructural and mechanical changes that occur in inorganic polymer cement (IPC) in the presence of three different grade of fine aggregates (ф < 100 μm) of ladle slag, nepheline syenite and quartz sand. Experimental results indicate that polycondensation was enhanced in nepheline syenite based specimens, compared to quartz sand, due to the increase in HMAS phases in relation to the dissolution and interaction of amorphous/disordered fraction of aggregates. HCS and HCAS with HMAS phases were identified in the ladle slag based specimens. The formation of these new phases reduced both the cumulative pore volume and pores size. The apparent increase in volume of capillary pores in ladle slag based specimens was explained by the residual bubbles from the carbonates included in raw slag. The flexural strength of the inorganic polymer cement increases from 4 MPa to 4.2, 4.8 and 6.8 MPa with the addition of 20 wt% of quartz sand, nepheline syenite and ladle slag respectively. These values increase significantly between 28 and 180 days of curing (9.1 MPa for ladle slag and 10.0 MPa for nepheline syenite). It was concluded that fines can be used to remove the HM and poorly bounded alumina oligomers in metakaolin based inorganic polymer matrices and improve the interfacial zone for the design of an optimum grade and high-performance composites.     

Investigation on the film-coating mechanism of alumina-coated rutile TiO2 and its dispersion stability

The alumina and alumina-coated rutile TiO₂ samples were synthesized by the chemical liquid deposition method under various pH values and aging temperature. The prepared samples were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), ζ-potential as well as X-ray photoelectron spectroscopy (XPS). The relationship between pH values, the dispersion stability, crystalline types and microstructure of alumina-coated rutile TiO₂ samples were studied. It is indicated that the coating film exhibited amorphous hydrous alumina (at pH 3–7), boehmite (at pH 7–9) and bayerite (pH > 11), respectively. And the higher aging temperature was in favor of the elevation of boehmite content of coating film. As the boehmite content increased, the dispersion stability was gradually enhanced and the prepared sample exhibited optimum dispersion stability at pH 9 and aging temperature 200 °C, respectively. The increase of steric hindrance and electrostatic repulsion led to the promotion of dispersion stability via coating hydrous alumina film on the surface of rutile TiO₂. The detection of AlO and the significantly enhancement of AlOTi intensity confirmed that the film coating process should be main attributed to both chemical bonding and physical adsorption.     

Synthesis,crystal structure,luminescent properties and photo degradation of mer-tris(8-Hydroxy-quinolinato-N,O)-indium(iii) hydrate 0.5 methanol solvate

Tris-(8-hydroxyquinioline) aluminium (Alq₃) is widely used in organic light emitting diodes as an emission and electron transport layer. In this study the effect of solvent molecules, in the solid state crystal lattice, on the photoluminescence properties of synthesized mer-tris(8-Hydroxy-quinolinato-N, O)-indium(iii) hydrate 0.5 methanol solvate (mer-[In(qn)₃]⋅H₂O⋅0.5 CH₃OH) was studied. Single crystals were obtained through a recrystallization process and single crystal X-ray diffraction was performed to obtain the unit cell structure. The main absorption peaks were assigned to ligand centered electronic transitions, while the solid state photoluminescence excitation peak at 440 nm was assigned to the 0–0 vibronic state of In(qn)₃. Broad emission at 510 nm was observed and was ascribed to the relaxation of an excited electron from the S₁–S₀ level. A powder sample was annealed at 130 °C for 2 h. A decrease in intensity was observed and could possibly be assigned to a loss of solvent species. To study the photon degradation, the sample was irradiated with an UV lamp for ∼15 h. The emission data was collected and the change in photoluminescence intensity with time was monitored. High resolution X-ray photoelectron spectroscopy (XPS) scans of the O-1s peak revealed that after annealing the binding energy shifted to lower energies indicating a possible loss of the H₂O and CH₃OH present in the crystal. The O-1s peak of the degraded sample indicated the possible formation of CO (∼532.5 eV), COH and OCOH (∼530.5 eV) on the phenoxide ring.     

Formaldehyde on TiO2 anatase (1 0 1): A DFT study

The adsorptions of formaldehyde molecule on the stoichiometric anatase TiO₂ (1 0 1) surface have been studied by first principles calculations. Four types of adsorption have been investigated at 0.25 ML coverage. Two of them are chemical adsorptions and the other two are physical adsorptions. For the chemical adsorptions, C, O atoms in the formaldehyde molecule form two bonds with the O_2c/O_3c and Ti_5c on the anatase (1 0 1) surface. The CO bond in the formaldehyde molecule is elongated and a dioxymethylene structure forms in the two chemical adsorptions. The OTi_5c interaction can be found in the two physical adsorptions and it is the only contacting point at the interface. No serious internal distortion in the formaldehyde molecule can be found in the physical adsorptions. The LDOS and the difference of the charge density are calculated to investigate the interface bonds of the adsorption. As the adsorption coverage increase, the molecules on the surface repel each other and weaken the adsorptions. For example, the chemical adsorption may become physical adsorption at high coverage.     

Synthesis of micron-sized porous CeO2SiO2 composite particles for ultraviolet absorption

Micron-sized porous composite particles composed of CeO₂ and SiO₂ nanoparticles were prepared for a UV absorption application by an aerosol spray-drying process from as-prepared CeO₂ nanoparticles, commercial SiO₂, and a polystyrene latex template. The morphology, structure crystallinity and pore size distribution of the as-prepared porous CeO₂SiO₂ composite particles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Barrett-Joyner-Halenda (BJH) method, respectively. The porous CeO₂SiO₂ composite particles, with diameters of approximately 10 μm, showed a spherical morphology. As the contents of CeO₂ in the precursor was increased from 0.25 wt% to 1.5 wt%, we observed a change in the morphology of the composite particles from compactly packed porous particles to loosely packed porous particles. The as-prepared CeO₂SiO₂ composite particles were composed of meso- and macropores in the range of 3–200 nm. The effect of the CeO₂ content on the porous composite particles in terms of the UV absorption properties was also investigated by UV-visible spectroscopy. When the content of CeO₂ exceeded 0.75 wt% in the precursor, the particles showed higher UV absorption values compared to those of commercial TiO₂ nanoparticles. The as-prepared porous CeO₂SiO₂ composite particles can therefore be promising materials given their high UV absorption value.     

Oversized hexagonal nanosheets of layered zinc hydroxysulfates via the hexamethylenetetramine-mediated solution route

Well-defined hexagonal nanosheets of layered zinc hydroxysulfate (Zn(OH)₂)₃(ZnSO₄)(H₂O)₅ with the side length of 1–20 μm and thickness of ∼50 nm has been synthesized by the thermal treatment of ZnSO₄–hexamethylenetetramine precursor in water–ethanol mixed solvent at 75 °C. The sheet-like morphology was found to closely depend upon the experimental conditions, such as the solvent and the precursor composition. In particular, the products can be easily converted to ZnO nanosheets upon exposing to the irradiation of electron beam.     

Preparation and characterization of sodium titanate nanowires from brookite nanocrystallites

Sodium titanate nanowires from brookite (or anatase) nanocrystallites were synthesized by a hydrothermal treating in 10 M NaOH aqueous solution at 180 °C. Their structures were characterized by XRD, TEM, HRTEM, XPS, and Raman spectra. The results indicated that though the structures of sodium titanate nanowires derived from brookite and antase were similar, there existed differences between them. The decrease of (2 0 0) plane spacing resulted from the increase of Na amount intercalated into TiO₂. The species of short TiO bonds in sodium titanate from brookite was more than that in sodium titanate from anatase. UV–vis absorption spectra showed a strong absorption not only in the ultraviolet range but also in the visible-light range.     

Dielectric properties of bismuth doped CaCu3Ti4O12 ceramics

Ca_1?3x/2Bi_xCu₃Ti₄O₁₂ (x = 0.0–0.3) ceramics were prepared by the conventional solid-state reaction method. X-ray powder diffraction analysis confirmed the formation of cubic CCTO phase except for subtle peaks of CuO. SEM micrographs suggested that the morphologies of doped CCTO ceramics had been sheet-like for high Bi-doping amount, and the dominant grain size decreasing could be seen for the small content of Bi-doping CCTO. Dielectric properties of pure and doped CCTO were investigated in a broad temperature range of 20–420 K. The results showed that bismuth doping could decrease the dielectric loss but suppress the dielectric temperature stability at the same time. Bi doped CCTO ceramics presented different relaxation properties. As to pure CCTO and BCCTO (x = 0.3) only one MW relaxation (Relaxation I) could be found, which moves to higher frequency with temperature increasing. However, two relaxation processes (Relaxation I and II) appear for BCCTO (x = 0.1–0.2). By means of complex impedance spectra analysis and Arrhenius fitting, we successfully separated the different conductive segments and explained the mechanisms of the two relaxation processes. Relaxation I appeared at low temperature could be attributed to the V_O doping energies inside CCTO grains which did not showed significant changing of activation energy after bismuth doping. For Relaxation II at higher temperature than Relaxation I, with activation energy obviously depending on the Bi-ion concentration, may be related with the V_O point defects at the grain boundaries.     

Synergistic effects of oxidized CNTs and reactive oligomer on the fracture toughness and mechanical properties of epoxy

The soft modifiers added to improve the fracture toughness of epoxies generally deteriorate their mechanical properties. Hence, oxidized multi-walled carbon nanotubes (O-CNTs) were added to the epoxy modified with reactive oligomer. The NCO terminated reactive oligomer acts as a cross-linker between the O-CNTs and the OH groups of the epoxies. The impact strengths of the 15 wt.% oligomer modified epoxy containing 0.5 wt.% of O-CNTs at room temperature (RT) and cryogenic temperature (CT) are enhanced by 23.6% and 69.5% compared to that of the unmodified epoxy. In addition to increasing fracture toughness, the tensile strength (TS) of the modified epoxy/O-CNTs at CT is found to be 91.7 MPa, which is comparable to that of the unmodified epoxy (92.1 MPa). Hence, the attachment of O-CNTs to the reactive oligomer modified epoxy can be an efficient approach to toughen epoxy resins without compromising their tensile properties.     

Poly (hydroxyethyl methacrylate-glycidyl methacrylate) films modified with different functional groups: In vitro interactions with platelets and rat stem cells

Copolymerization of 2-hydroxyethylmethacrylate (HEMA) with glycidylmethacrylate (GMA) in the presence of α-α′-azoisobisbutyronitrile (AIBN) resulted in the formation of hydrogel films carrying reactive epoxy groups. Thirteen kinds of different molecules with pendant NH₂ group were used for modifications of the p(HEMA-GMA) films. The NH₂ group served as anchor binding site for immobilization of functional groups on the hydrogel film via direct epoxy ring opening reaction. The modified hydrogel films were characterized by FTIR, and contact angle studies. In addition, mechanical properties of the hydrogel films were studied, and modified hydrogel films showed improved mechanical properties compared with the non-modified film, but they are less elastic than the non-modified film. The biological activities of these films such as platelet adhesion, red blood cells hemolysis, and swelling behavior were studied. The effect of modified hydrogel films, including NH₂, (using different aliphatic CH₂ chain lengths) CH₃, SO₃H, aromatic groups with substituted OH and COOH groups, and amino acids were also investigated on the adhesion, morphology and survival of rat mesenchymal stem cells (MSCs). The MTT colorimetric assay reveals that the p(HEMA-GMA)-GA-AB, p(HEMA-GMA)-GA-Phe, p(HEMA-GMA)-GA-Trp, p(HEMA-GMA)-GA-Glu formulations have an excellent biocompatibility to promote the cell adhesion and growth. We anticipate that the fabricated p(HEMA-GMA) based hydrogel films with controllable surface chemistry and good stable swelling ratio may find extensive applications in future development of tissue engineering scaffold materials, and in various biotechnological areas.     

Room temperature solid–solid reaction preparation of ironboron alloy nanoparticles and Mössbauer spectra

The amorphous ironboron alloy can be prepared very easily by a room temperature solid–solid reaction of the FeCl₃·6H₂O, CrCl₃·6H₂O and KBH₄ powders. The characterizations show that the product is mainly composed of amorphous ironboron alloy nanoparticles. ⁵⁷Fe Mossbauer spectra at 84 and 295 K show that there are three kinds of Fe-containing components in the sample. There are the superparamagnetic relaxation in Mössbauer spectra and the continuous distribution of internal magnetic field in the ironboron alloy.     

Surface modification on polyethylene terephthalate films with 2-methacryloyloxyethyl phosphorylcholine

In this study, the surface of polyethylene terephthalate (PET) was modified to improve the protein and cell adhesion behavior with low temperature ammonia plasma treatment followed by 2-methacryloyloxyethyl phosphorylcholine (MPC) grafting. The x-ray photoelectron spectroscopy (XPS) results showed that the COO^?, NCO and POH groups were successfully incorporated onto the sample surface after MPC grafting. Furthermore, formation of new bonds, N and NH on the sample surface grafted with MPC was recorded by Fourier transform infrared spectroscopy (FTIR). A large number of spherical particles at submicron to nanometer scale were also observed on the surface by atomic force microscopy (AFM). The cell adhesion experiments on PET film surfaces were evaluated and the highly hydrophilic surfaces could not promote cell adhesion and spreading. All results achieved in this study have clearly indicated that the method combining low temperature ammonia plasma treatment and MPC grafting is an effective way of producing a suitably hydrophilic PET surface with the capability of weakening the protein adsorption greatly.