Effect of the addition of glasses as sintering aids on microstructure and properties of nanoalumina

ABSTRACT Alumina-Glass compositions were prepared to evaluate the effect of glass as sintering aids. The composites showed densification below 1100°C. The highest density values (~95%) were obtained for compositions based respectively on borosilicate (G2 and G3) and soda lime glasses (G4), all [A1] [A2] containing Na in the precursor powder. Samples G1 (K-based) and G5 (no K or Na in the precursor glass powder) presented irregular morphology with the presence of intergranular porosity. The composition G2, G3, and G4 presented uniform morphology corresponding to higher densification.

Spectroscopic Properties of Erbium-Doped Oxyfluoride Phospho-Tellurite Glass and Transparent Glass-Ceramic Containing BaF2 Nanocrystals

The ErF3-doped oxyfluoride phospho-tellurite glasses in the (40-x) TeO2-10P2O5-45 (BaF2-ZnF2) -5Na2O-xErF3 system (where x = 0.25, 0.50, 0.75, 1.00, and 1.25 mol%) have been prepared by the conventional melt-quenching method. The effect of erbium trifluoride addition on thermal, structure, and spectroscopic properties of oxyfluoride phospho-tellurite precursor glass was studied by differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR), and Raman spectroscopy as well as emission measurements, respectively. The DSC curves were used to investigate characteristic temperatures and thermal stability of the precursor glass doped with varying content of ErF3. FTIR and Raman spectra were introduced to characterize the evolution of structure and phonon energy of the glasses. It was found that the addition of ErF3 up to 1.25 mol% into the chemical composition of phospho-tellurite precursor glass enhanced 2.7 µm emission and upconversion. By controlled heat-treatment process of the host glass doped with the highest content of erbium trifluoride (1.25 mol%), transparent erbium-doped phospho-tellurite glass-ceramic (GC) was obtained. X-ray diffraction analysis confirmed the presence of BaF2 nanocrystals with the average 16 nm diameter in a glass matrix. Moreover, MIR, NIR, and UC emissions of the glass-ceramic were discussed in detail and compared to the spectroscopic properties of the glass doped with 1.25 mol% of ErF3 (the base glass).

Preparation and Characterization of Na2O-Y2O3-P2O5-SiO2 Transparent Glass Ceramics

Transparent glass ceramics containing Na3.6Y1.8(PO4)3 crystals were successfully synthesized using high temperature melting quenching and subsequent heat treatment of the precursor glass with a composition 15Na2CO3-3Y2O3-45SiO2-31H3BO3- 5.4P2O5-0.6Sb2O3 (mol%). The impact of heat treatment is investigated in detail. The glass sample was tested by differential scanning calorimetry analysis to determine the heat treatment system. The ideal heat-treated condition is at 650°C for 2 h. The structure and morphology properties were systematically analyzed by recording X-ray diffraction patterns and scanning electron microscopy images, which indicate that Na3.6Y1.8(PO4)3 crystal were precipitated homogeneously among the glass matrix. The microstructural of precursor glass and glass ceramic were compared by analyzing FTIR spectra, indicating the formation of phosphate groups in glass ceramic. The refractive index of glass ceramics samples were measured. In the visible region, the transmittance of glass ceramics is up to 85%. Moreover, the relationship between the refractive index of the sample and the transmittance is discussed.

Structural evolution of NASICON-type Li1+xAlxGe2−x(PO4)3 using in situ synchrotron X-ray powder diffraction

In situ synchrotron X-ray diffraction study of the synthesis of solid-electrolyte Li1+xAlxGe2−x(PO4)3 (LAGP) from the precursor glass reveals that an initially crystallized dopant poor phase transforms into the Al-doped LAGP at 800 °C.

Research on Processing Conditions of CBS Transparent Glass-Ceramics

On the basis of experimental verification, the optimum processing conditions of CaO-B2O3-SiO2(CBS) system transparent glass-ceramics were obtained. Composition of main raw powders (wt%) was:CaO 38%,SiO240%,B2O312%.The precursor glass was prepared by melting method and annealed at 560°C for 2h and cooled to room temperature at a speed of 5°C/min.The best nucleating agent is P2O5. The appropriate heat treatment regime to precursor glass was determined to be 2h at 600°C for nucleation and 3h at 780°C for crystallizition.Under this condition,the transmittion of glass-ceramics at the range of visable light is 72% in average and Sm3+keep good luminescence property doped in this host material.

Preparation and Characterization of Sm3+ Doped CBS Transparent Glass-Ceramics

Sm3+ doped transparent glass-ceramics of CaO-B2O3-SiO2 (CBS) system were prepared and characterized.The precursor glass was prepared by melting method and annealed at 450°C for 2h and cooled to room temperature at a speed of 5°C/min.The appropriate heat treatment schedule to precursor glass was determined to be 2h at 600°C for nucleation and 3h at 810°C for crystallizition.The transmittion of glass-ceramics at the range of visable light is 68% in average. Five main emission bands of Sm3+ are centered around 564nm,605nm,646nm,679nm and 789nm,which correspond to the 4G 5/2→6H 5/2,4G 5/2→6H 7/2,4G 5/2→6H 9/2,4G 5/2→6H 11/2 and 4G 5/2→6H 13/2 transitions.Very strong luminescence at around 599nm is observed in glass-ceramics,This indicates glass-ceramics to be a better host for Sm3+ than precursor glass and a hopeful laser material.

Investigations of lithium-chloro-borate glass-ceramic and its elastic properties

Elastic properties and microstructural studies of 0.3Li2O-0.2LiCl-0.5B2O3 glass-ceramics have been carried out for a precursor glass prepared using the rapid melt quenching technique. Quenched glasses were heat treated (by three step process) at 150 °C for 2, 4, 6, and 8 h. Scanning electron microscopy and X-ray diffraction studies clearly indicate gradual growth of different phases in the glass matrix with increasing time of heat-treatment. IR studies reveal the structural modification in the network as the precursor glass transformed into glass-ceramic. Elastic properties have been measured by performing ultrasonic wave velocity measurements at a frequency of 10 MHz. Longitudinal and shear moduli of the samples tend to increase with heat-treatment time. However, the bulk modulus is almost insensitive to heat treatment. The Debye temperature was found to increase, and the Poisson ratio lies in the range 0.2–0.3 (typical for covalently bonded networks) with an increase in heat-treatment time.

Growth of silver nanowires using mica structure as a template and ultrahigh dielectric permittivity of the nanocomposite

Fluorphlogopite mica crystallites of dimensions in the range 0.5 to 24 µm were grown within silicate glass of suitable compositions by heat treatment at 1168 K. After an ion exchange treatment (K+ ⇆ Ag+) the specimens were subjected to an electrodeposition reaction. With the optimum concentration of K+ ions in the precursor glass, electrodeposition brought about the growth of silver nanowires about 0.5 nm diameter within the nanochannels of the fluorphlogopite mica structure. By applying a voltage pulse of 20 volts of duration 3 s, break junctions could be induced in the nanowires. A high dielectric constant of around 1.0 × 107was found in the resultant specimen. This was shown to be quantum mechanical in origin and arose due to the presence of metal filaments about 1280 nm in length. An asymmetric voltage–current characteristic was recorded at 114 K in the case of the specimen containing silver nanowires grown within the mica structure. This is believed to arise due to formation of a nanojunction between the metal nanowire and silver nanoparticles with diameters of less than 3 nm. The latter were earlier shown to behave as insulators