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Composite ceramics are applied widely nowadays by combining superior properties of different ceramic materials. In this study, SiO 2 –Si 3 N 4 composite ceramics with higher mechanical properties and lower dielectric constant were successfully fabricated by nitriding diamond-wire saw silicon waste. The effect of gas atmospheres (N 2 , NH 3 , N 2 –H 2) and SiO 2 content (0%, 10%, 20%, 30%, 40%) on the microstructure and properties of composite ceramics were studied. It shows that the synthesis of SiO 2 –Si 3 N 4 composite ceramics can be obtained in the NH 3 atmosphere, and it is inevitable to form the Si 2 N 2 O phase in N 2 and N 2 –H 2 mixture atmospheres. Furthermore, the shrinkage rate and dielectric constant of the ceramics decreased as SiO 2 content increased from 0% to 40%. As for the porosity of the sintered ceramics, it first decreased and then increased, with a minimum of 1.73% at the SiO 2 content of 20%. However, the flexural strength of the sintered ceramics was the inverse of the porosity, with a maximum of 160.72 MPa at the SiO 2 content of 30%. For the sintered ceramic with 30% SiO 2 , the shrinkage rate, dielectric constant, porosity and flexural strength are 0.3%, 4.62, 1.97% and 160.72 MPa respectively. Thus, this study provides an environment-friendly and value-added approach to recycling photovoltaic waste and reducing the cost of the reactive sintering SiO 2 –Si 3 N 4 composite ceramics with excellent mechanical and dielectric properties. [ABSTRACT FROM AUTHOR]

This work focused on removed mode of titanium target material and deposition process of the TiN film in a novel dual pulse power magnetron sputtering (DPPMS), which could improve deposition rate and properties of the TiN film. The study was carried out using DPPMS with different target power ratios between the first and the second ionized periods (P w /P s). It was found that when P w /P s was changed from 0.9/1.6 to 0.3/2.2, the removed mode of target material changed from sputtering to sputtering and evaporation, and the deposition rate of TiN films increased from 26 to 61 nm/min. All TiN films showed face center cubic (fcc) crystal structure and typical columnar microstructure. The compactness and size of columnar structure were improved with P w /P s changed from 0.9/1.6 to 0.3/2.2. Additionally, the hardness of TiN film deposited at P w /P s of 0.3/2.2 reached up to 25.4 GPa. [ABSTRACT FROM AUTHOR]

The LiGd(MoO 4) 2 :Eu3+ phosphors were successfully synthesized using the hydrothermal method followed by calcination. The effects of different dosages of the cationic surfactant dodecyl trimethyl ammonium bromide (abbreviated as DTAB) on the luminescent properties were discussed in detail. It was found that the luminescence intensity of the sample at the optimum DTAB addition was 3.03 times higher than that without DTAB under the 465 nm excitation peak. The change of the morphology was observed by SEM and TEM, which indicated that there were many cracks on the surface of the sample at the optimal DTAB additive contents. Moreover, the average particle size of the sample at the optimum DTAB dosage is larger than that of the sample without DTAB. The lifetime of the sample with the optimum DTAB addition shorter than that without DTAB, and then the fluorescence scintillation could be reduced. Furthermore, the crystal field environment of Eu3+ ions were analyzed by Judd-Ofelt theory. [ABSTRACT FROM AUTHOR]

High-performance white light-emitting diodes (WLEDs) used for backlighting display applications require innovative and thermally stable narrow-band emission phosphors, particularly non-rare-earth Bi3+-activated phosphors. In this study, we demonstrate a defect-engineering strategy to create novel anti-thermal quenching phosphors Ca 3 Sc 2 Si 3 O 12 : x Bi3+ (CSSO: x Bi3+). Through structure refinement of CSSO: 0.06Bi3+ phosphor, we found that Bi occupies both Ca and Sc sites in the CSSO lattice. Direct visualization of atomic-resolution TEM and thermoluminescence spectra confirmed the formation of point defects due to the non-equivalent substitution of Ca2+ for Bi3+. Fluorescent-decay analysis revealed that two luminescence sites contribute to the blue-emitting of CSSO:Bi3+ phosphors. CSSO: 0.06Bi3+ phosphor exhibits outstanding thermal stability, with an integrated emission intensity of 103.6% at 423 K compared to that at 298 K. However, the addition of Li or Na as charge compensators reduced cationic defects, leading to a decrease in thermal stability. We believe that V C a ″ defects are primarily responsible for the anti-thermal quenching behavior of CSSO: x Bi3+ phosphors. An optimized CSSO: 0.06Bi3+ phosphor-based WLED displays a high color rendering index (CRI) of 90 and a wide color gamut (90% National Television System Committee (NTSC) standard), indicating its potential for use in industrial applications as a backlighting display. [ABSTRACT FROM AUTHOR]

Graphene was prepared by a simple chemical reduction of graphite oxide in the dimethylacetamide (DMAc)/H 2 O mixture solvent. The results from Fourier transform infrared spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy indicated that the reduction degree of graphene products increased with the increase in the volume ratio of DMAc and water (V DMAc /V H2O ), and kept constant when the V DMAc /V H2O ratio was equal or greater than 1. A reduction mechanism from graphite oxide to graphene was proposed. The epoxy groups and hydroxyl on the graphite oxide (GO) surface could be eliminated in the reduction process, whereas the carbonyl was converted to a hydroquinone structure. [ABSTRACT FROM AUTHOR]

Wettability control of laser textured SiC ceramic surfaces through the addition of pure elements was studied in this work. A correlation analysis between the elements C/O/Si/B/Al/Fe and the contact angle demonstrates that elements C/O/Si/B are all highly correlated with the wettability. The correlation of elements Fe/Al with the contact angle is relatively lower. Because elements C/Si are inherent elements in a SiC material, element O is derived from oxidation, and element B is added along with the additives during the sintering process. A more hydrophilic SiC surface was obtained by controlling the addition of element B. [ABSTRACT FROM AUTHOR]

Dy 2 O 3 –Sm 2 O 3 co-doped transparent glass ceramics (GCs) containing NaBi(WO 4) 2 crystalline phase were prepared by melt-curing-crystallization method. The optimal heat treatment condition is 580 °C/2 h. The optimum incorporation concentration of Dy 2 O 3 is 0.4%, exceeding which a quenching phenomenon dominated by quadrupole-quadrupole interactions emerges. Meanwhile, when the concentration of Dy 2 O 3 was fixed, the chromaticity coordinate of the sample moved the cool white light region to the warm white light region as the concentration of Sm 2 O 3 increased. The temperature-dependent emission spectra of the 0.4% Dy 2 O 3 -0.7% Sm 2 O 3 co-doped GC samples show that emission intensity at 575 nm at 185 °C still reaches 80% of the room temperature. The thermal quenching activation energy was 0.1537 eV and the activation energy after the addition of Mo6+ was 0.1957 eV. This study indicates that Dy 2 O 3 –Sm 2 O 3 co-doped GCs containing NaBi(WO 4) 2 crystalline phase can achieve light-color tunable emission, which is potentially valuable for solid-state color rendering and illumination applications. [ABSTRACT FROM AUTHOR]

Herein, we fabricated honeycomb ceramics with different porosities and pore shapes via the layer-by-layer deposition of cordierite (2MgO·2Al 2 O 3 ·5SiO 2) particle ink, obtaining proper rheological properties using a direct-writing technology. No collapses as well as minimal cracking and bending were observed in the internal structure of the samples after calcination. We measured and compared the internal porosity and specific surface area of honeycomb ceramics with the same pore shape but different pore dimensions, as well as the same pore dimension but different pore shapes. The samples were both loaded with an γ-Al 2 O 3 washcoat and Pd-based catalyst using the same method for the catalytic combustion of toluene. The different porosity and pore shape influenced the catalytic efficiency. This study may provide some useful guidelines for fabrication of honeycomb ceramics by direct writing technology, which could be used to remove volatile organic pollutants(VOCs). [ABSTRACT FROM AUTHOR]

A group of 1–3 type piezoelectric Pb (Mg 1/3 Nb 2/3)O 3 -PbTiO 3 /polyvinylidene fluoride (PMN-PT/PVDF) composite sheets are prepared using a complex two-step hot-pressing method. Then the molecular structure model of piezoelectric materials and an inverse piezoelectric simulation of the composites are performed to express the horizontal compression, indicating the clamping activity of ferroelectric PVDF on PMN-PT. As such, this composite sheet possesses a high dielectric permittivity (ε r) of 560 at 100 Hz for its compacted connecting of two phases. After polarization, a very large piezoelectric coefficient (d 33) of 1125 pC/N and a considerable electromechanical coupling factor (k t) of 0.43 is obtained in PMN-PT/PVDF sheet with a proper aspect ratio of 1.4 and a thickness of 2.1 mm, further indicating that promoting effect of PVDF matrix on the strain in Z-direction of PMN-PT. The result shows that ferroelectric PVDF serving as polymer matrix favors the electromechanical coupling effect, and may provide a prospect of the potential application of PMN-PT/PVDF composite in sensor or transistor for matrix ultrasonic probes. [ABSTRACT FROM AUTHOR]

In view of technical difficulties in preparing ceramics with complex shapes, gel casting combined with 3D printing was here adopted to prepare silicon carbide ceramic green body, and gaseous silicon infiltration sintering was used to prepare 3D lattice-structured ceramics. The preparation of the slurry, gel curing, and ceramic molding was investigated. Results demonstrate that the ratio of components affects the fluidity and stability of slurry. However, when volume fraction of the solid phase of the slurry reaches 56%, the viscosity of slurry is only 300 mPa s, and drying shrinkage rate of green body is 6.6%; these characteristics make slurry suitable for 3D complex model injection molding. Furthermore, both the temperature and the initiator affect gel curing speed. As the temperature and initiator content increase, the induction and gel time are rapidly shortened. When demolding at 300 °C and when gaseous silicon infiltration sintering is carried out at 1550 °C, a 3D lattice-structured ceramic with relative density of 87% and average compressive strength of 433 MPa can be obtained. [ABSTRACT FROM AUTHOR]

Charge transfer band (CTB) plays an important role for the phosphors in the improvement of luminescence intensities, as low light absorption coefficient of the luminescence centers of the rare earth ions. Here, Eu3+-activated La 2 Mo 2 O 9 phosphors were prepared by hydrothermal approach followed by calcination. Due to the special preparation process, the CTB of the phosphors could be effectively excited to get a very pure red emission. The structure of La 2 Mo 2 O 9 was characterized. The field environmental factors (h e) of La 2 Mo 2 O 9 :Eu3+ crystals were calculated based on complex chemical bond theory. The light absorption property of the MoO 7 8− group was studied. The results indicated that the luminescence of the CTB originated from the three parts like Eu3+-O2-, α -Mo6+-O2- and β -Mo6+-O2-. Moreover, the FE-SEM micrographs, the photoluminescence properties and the decay time of La 2 Mo 2 O 9 :Eu3+ phosphors with different doping concentration were analyzed, which will further be promoting the development of the Eu3+-activated La 2 Mo 2 O 9 phosphors. [ABSTRACT FROM AUTHOR]