Preparation of bioactive glass ceramic nanoparticles by combination of sol-gel and coprecipitation method

SiO2-CaO-P2O5 ternary bioactive glass ceramic nanoparticles were prepared via the combination of sol-gel and coprecipitation processes. Precursors of silicon and calcium were hydrolyzed in acidic solution and gelated in alkaline condition together with ammonium dibasic phosphate. Gel particles were separated by centrifugation, followed by freeze drying, and calcination procedure to obtain the bioactive glass ceramic nanoparticles. The investigation of the influence of synthesis temperature on the nanopartilce's properties showed that the reaction temperature played an important role in the crystallinity of nanoparticle. The glass ceramic particles synthesized at 55 degrees C included about 15% crystalline phase, while at 25 degrees C and 40 degrees C the entire amorphous nanopowder could be obtained.

Characterization and optimization of AuNPs labeled by Raman reporters on glass based on silver enhancement

In this report, gold nanoparticles (AuNPs) labeled by Raman reporters (AuNPs-R6G) were assembled on glass and used as the seeds to in situ grow silver-coated nanostructures based on silver enhancer solution, forming the nanostructures of AuNPs-R6G@Ag, which were characterized by scanning electron microscopy (SEM) and UV-visible spectroscopy. More importantly, the obtained silver-coated nanostructures can be used as a surface enhancement Raman scattering (SERS) substrate. The different SERS activities can be controlled by the silver deposition time and assembly time of AuNPs-R6G on glass. The results indicate that the maximum SERS activity could be obtained on AuNPs-R6G when these nanostructures were assembled on glass for 2 h with silver deposition for 2 min.

Solid-state dye-sensitized solar cells using TiO2 nanotube arrays on FTO glass

Highly ordered, vertically oriented TiO2 nanotube arrays were prepared by potentiostatic anodization of titanium on FTO-coated glass substrate and for the first time successfully applied in the fabrication of solid-state dye sensitized solar cells (SSDSCs), giving a power conversion efficiency of 1.67% measured under an irradiation of air mass 1.5 global (AM 1.5 G) full sunlight. Furthermore, 3.8% efficiency was reached with a 2.8 mu m thin TiO2 nanotube array film based on a metal free organic dye using ionic liquid electrolyte.

The mechanical and thermal behaviors of glass bead filled polypropylene

Notch Izod impact strength of poly(propylene) (PP)/glass bead blends was studied as a function of temperature. The results indicated that the toughness for various blends could undergo a brittle-ductile transition (BDT) with increasing temperature. The BDT temperature (T-BD) decreased with increasing glass bead content. Introducing the interparticle distance (ID) concept into the study, it was found that the critical interparticle distance (IDc) reduced with increasing test temperature correspondingly. The static tensile tests showed that the Young's modulus of the blends decreased slightly first and thereafter increased with increasing glass bead content. However, the yield stress decreased considerably with the increase in glass bead content. Dynamic mechanical analysis (DMA) measurements revealed that the heat-deflection temperature of the PP could be much improved by the incorporation of glass beads. Moreover, the glass transition temperature (T-g) increased obviously with increasing glass beads content. Differential scanning calorimetry (DSC) results implied that the addition of glass beads could change the crystallinity as well as the melting temperature of the PP slightly.

Mechanical and thermal properties of glass bead-filled nylon-6

The mechanical and thermal properties of glass bead-filled nylon-6 were studied by dynamic mechanical analysis (DMA), tensile testing, Izod impact, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) tests. DMA results showed that the incorporation of glass beads could lead to a substantial increase of the glass-transition temperature (T-g) of the blend, indicating that there existed strong interaction between glass beads and the nylon-6 matrix. Results of further calculation revealed that the average interaction between glass beads and the nylon-6 matrix deceased with increasing glass bead content as a result of the coalescence of glass beads. This conclusion was supported by SEM observations. Impact testing revealed that the notch Izod impact strength of nylon-6/glass bead blends substantially decreased with increasing glass bead content. Moreover, static tensile measurements implied that the Young's modulus of the nylon-6/glass bead blends increased considerably, whereas the tensile strength clearly decreased with increasing glass bead content.

Investigation on preparation and fluorescence properties of oxy-fluoride glass co-doped with Er3+ and Yb3+

The glass sample based on the composition of 45PbF(2)-45GeO(2)-10WO(3) co-doped with Yb3+/Er3+ was prepared by the fusion method in two steps: melted at 950 degreesC for 20 similar to 25 min then annealed at 380 degreesC for 4 h. Through the V-prism it is found that the refractive index of host glass and the sample are 1.517 and 1.65 respectively. The transmittance was observed by using the ultraviolet-visible-infrared spectrometer in the wavelength range from 0.35 to 2.5mum. The transmittaitce of the host glass is beyond 73%. That of the sample is beyond 50% and there are characteristic absorption peaks of rare-earth ions. The emission spectrum was measured by using the Hitachi F-4500 fluorescent spectrometer pumped by 980 nm semiconductor laser. There are a strong emission peak at 530 nm and a weak peak at 650 nm.

Surface enhanced Raman scattering of p-aminothiophenol self-assembled monolayers in sandwich structure fabricated on glass

A sandwich structure consisting of Ag nanoparticles (NPs), p-aminothiophenol (p-ATP) self-assembled monolayers (SAMs), and Ag NPs was fabricated on glass and characterized by surface enhanced Raman scattering (SERS). The SERS spectrum of a p-ATP SAM in such sandwich structure shows that the electromagnetic enhancement is greater than that on Ag NPs assembled on glass. The obtained enhancement factors (EF) on solely one sandwich structure were as large as 6.0 +/- 0.62x10(4) and 1.2 +/- 0.62x10(7) for the 7a and 3b(b(2)) vibration modes, respectively. The large enhancement effect of p-ATP SAMs is likely a result of plasmon coupling between the two layers of Ag NP (localized surface plasmon) resonance, creating a large localized electromagnetic field at their interface, where p-ATP resides. Moreover, the fact that large EF values (similar to 1.9 +/- 0.7x10(4) and 9.4 +/- 0.7x10(6) for the 7a- and b(2)-type vibration modes, respectively) were also obtained on a single sandwich structure of Au NPs/p-ATP SAMs/Ag NPs in the visible demonstrates that the electromagnetic coupling does not exist only between Ag NPs but also between Au and Ag NPs.

Up-conversion spectrum properties of the oxy-fluoride glass co-doped with Er3+ and Yb3+

Up-conversion of 45PbF(2)-45GeO(2)-10WO(3) oxy-fluoride glasses co-doped with Yb3+ and Er3+ ions were prepared by fusion method through melting at 1223 K and then annealing at 653 K for 4 h. Transmittance of the undoped host glass was beyond 73% in a range of 0.6-2.5 mu m and the co-doped glasses still provided good transmittance beyond 50%. Refractive indices of the host and co-doped glasses were 1.517 and 1.650, respectively. Blue, green and red fluorescence spectra were observed in a range of 400-700 nm under 980 nm diode laser excitation. Up-conversion spectra at about 410, 518, 530and 650 nm were assigned to the 4f electron transitions of H-2(9/2) -> I-4(15)/(2), H-2(15/2) -> I-4(15/2) S-4(3/2) -> I-4(15/2) and F-4(9/2) -> I-4(15/2) of Er3+ ion, respectively. The mechanism of energy transfer between Yb3+ and Er3+ ions in the glass was analyzed. Raman shift shows the non-radiative relaxation of the glass sample is low.

A new blue phosphorescent glass-ceramic: Rare-earth-doped calcium aluminoborate

A new blue phosphorescent glass-ceramic, Eu2+ and Nd3+, co-doped CaO-Al2O3-B2O3, was synthesized. After the irradiation with ultraviolet (UV) light, the glass-ceramic emitted blue long-lasting phosphorescence (LLP) with a spectrum peaking at about 464 nm ascribed to the characteristic 4f(6)5d(1) -> 8S(7/2) transition of Eu2+. This phosphorescence can be seen in the dark 1 h after the irradiation. However, the transparent Eu2+ and Nd3+ co-doped CaO-Al2O3-B2O3 glass did not show the phosphorescence. By the X-ray diffraction diffusion (XRD) data, alpha-CaAl2B2O7 was demonstrated to be the crystallites in the glass-ceramic. We think that alpha-CaAl2B2O7:Eu2+ Nd3+ crystallites produced during the heat treatment of the glass contribute to the LLP of the glass-ceramic.

Effects of reinforcement filler and temperature on the stability of beta-crystal in glass bead filled polypropylene

The effects of crystallization temperature (T,), glass bead content and its size on the, formation of beta-crystal and structural stability of originally formed beta-crystal in glass bead filled polypropylene (PP) were examined. The differential scanning calorimetry (DSC) measurements indicated that the amount of beta-phase in PP crystals was a function of the crystallization temperature and glass bead content. For a constant crystallization temperature, it was observed that the amount of beta-crystal initially increased with increase in glass bead content up to 30 wt.%, and then decreased slightly with further increase in the filler content. From the DSC data, a disorder parameter (S) was derived to define the structural stability of originally formed beta-crystals. The structural stability of originally formed beta-crystals was enhanced with increase in either the crystallization temperature or the glass bead content. Also, the influence of glass bead size (4-66 mu m) on the formation and stability of beta-crystals in PP/glass bead blends was studied. Large glass bead particles suppressed the formation and decreased the stability of beta-crystals.

Nonisothermal crystallization behavior of glass-bead-filled polypropylene

The effects of the glass-bead content and size on the nonisothermal crystallization behavior of polypropylene (PP)/glass-bead blends were studied with differential scanning calorimetry. The degree of crystallinity decreased with the addition of glass bead, and the crystallization temperature of the blends was marginally higher than that of pure PP at various cooling rates. Furthermore, the half-time for crystallization decreased with an increase in the glass-bead content or particle size, implying the nucleating role of the glass beads. The nonisothermal crystallization data were analyzed with the methods of Avrami, Ozawa, and Mo. The validity of various kinetic models for the nonisothermal crystallization process of PP/glass-bead blends was examined. The approach developed by Mo successfully described the nonisothermal crystallization behavior of PP and PP/glass-bead blends. Finally, the activation energy for the nonisothermal crystallization of pure PP and PP/glass-bead blends based on the Kissinger method was evaluated.

Mechanical and thermal properties of high-density polyethylene toughened with glass beads

Glass beads were used to improve the mechanical and thermal properties of high-density polyethylene (HDPE). HDPE/glass-bead blends were prepared in a Brabender-like apparatus, and this was followed by press molding. Static tensile measurements showed that the modulus of the HDPE/glass-bead blends increased considerably with increasing glass-bead content, whereas the yield stress remained roughly unchanged at first and then decreased slowly with increasing glass-bead content. Izod impact tests at room temperature revealed that the impact strength changed very slowly with increasing glass-bead content up to a critical value; thereafter, it increased sharply with increasing glass-bead content. That is, the lzod impact strength of the blends underwent a sharp transition with increasing glass-bead content. It was calculated that the critical interparticle distance for the HDPE/glass-bead blends at room temperature (25degreesC) was 2.5 mum. Scanning electron microscopy observations indicated that the high impact strength of the HDPE/glass-bead blends resulted from the deformation of the HDPE matrix. Dynamic mechanical analyses and thermogravimetric measurements implied that the heat resistance and heat stability of the blends tended to increase considerably with increasing glass-bead content.

Pressure-dependent glass-transition temperatures of poly(methyl methacrylate)/poly(styrene-co-acrylonitrile) blends

The pressure-dependent glass-transition temperatures (T-g's) of poly(methyl methacrylate) (PMMA)/poly(styrene-co-acrylonitrile) (SAN) blends were determined by pressure-volume-temperature (PVT) dilatometry via an isobaric cooling procedure. The Gordon-Taylor and Fox equations were used to evaluate the relationships between the T-g's and compositions of the PMMA/SAN system at different pressures. The relationships were well fitted by the Gordon-Taylor equation, and the experimental data for T-g positively deviated from the values calculated with the Fox equation. Also, the influence of the cooling rate (during the PVT measurements) on T-g was examined.