- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Role of polysiloxanes in the synthesis of aligned porous silicon oxycarbide ceramics
摘要： The present work focuses on establishing the role of polysiloxane precursors in the synthesis of aligned porous polymer derived silicon oxycarbide ceramics. The precursors used for the synthesis are, polymethylhydrosiloxane, vinyl terminated polydimethylsiloxane and cyclic tetramethyl-tetravinlycyclotetrasiloxane. Hydrotalcite is used for attaining aligned macroporosity during the crosslinking stage itself. Subsequently, pyrolysis of the sample has been carried out to synthesize the ceramics. The evolution of pore structure in these PDCs during the crosslinking and pyrolysis is co-related to the thermal decomposition behaviour. The pore morphology, structure and the size were analyzed using SEM, X-ray computed tomography and BET. Our studies confirm the presence of bimodal porosity in these PDCs. These PDCs have a specific surface area ranging from 77 - 160 m2/g and a total pore volume ranging from 0.18 - 0.29 cm3/g. These results could be significant for achieving a controlled synthesis process of porous materials suitable for various applications like adsorption, filtering and electrochemical storage.
关键词： Mesoporous,X-Ray computed tomography,Pyrolysis,Polymer derived ceramics,Specific surface area
更新于2025-09-23 15:22:29
-
Optical and magneto-optical properties of Nd0.1La0.1Y1.8O3 transparent ceramics
摘要： Transparent ceramics in the form of yttrium oxide (Y2O3) doped with La and Nd and pure yttrium as a reference material were successfully prepared via modified sol-gel processes and hot isostatic pressure sintering. Their structure and microstructure were examined by means of scanning electron microscopy and X-ray diffraction, which revealed the high density and single-phase character of these materials. Their optical and magneto-optical properties were also analyzed. Emission spectra of Nd0.1La0.1Y1.8O3 after excitation performed with a continuous 808 nm laser beam showed strong and sharp emission lines. The luminescence lifetime was also investigated. The doped material exhibited a high Verdet constant of over 1000 deg/T?m. The figure of merit was calculated in the VIS spectrum. The investigated transparent oxide ceramics can be considered a promising material for application in lasers and magneto-optical devices.
关键词： Y2O3,Verdet constant,Optical properties,Luminescence,Microstructure,Transparent ceramics
更新于2025-09-23 15:22:29
-
Efficacy of phototherapy with different conventional surface treatments on adhesive quality of lithium disilicate ceramics
摘要： Aim: The aim of the present study was to evaluate shear bond strength (SBS) of LDC and resin composite in combination with phototherapy and different ceramic surface treatments. Materials and Method: Forty Lithium Disilicate Glass Ceramic (LDC) disks measuring (4x4x9mm) were fabricated. The specimens were randomly divided into four groups (n=10 each) according to the surface treatment. Group 1 HF+ Silane (Control); Group 2 HF+ Ultrasonic bath + Silane; Group 3 SECP (Self etch ceramic primer) and Group 4 phototherapy (Er, Cr: YSGG) + Silane. On each ceramic disk a resin build-up was done. For SBS the specimens were subjected to increasing load with a transversal velocity of 1ml/min on a universal testing machine on a ceramic resin interface. Failure mode was evaluated using digital microscope. The failure modes were divided into adhesive, cohesive and admixed interface. Data through bond strength testing was tabulated using statistical program for social science (SPSS). Means and standard deviations were compared using analysis of variance and Tukey's post hoc test (p<0.05) Results: The maximum and minimum bond strength was observed in group 2 [19.58(1.011)] and group 1 [17.14(1.122)] respectively. The bond strength among experimental group 1 [17.14 (1.122)] and group 4 [17.48(1.145)] were found to be comparable. Specimens in Group 2 displayed significantly higher bond strength among all experimental groups. Commonly adhesive failure mode was observed in the present study, with an incidence of 60%, 100% and 70% in groups 1,2 and 3 correspondingly Conclusion: Phototherapy using laser at frequency 30Hz and 4.5 W can be used as a surface conditioner for LDC alternate to HF acid. Conditioning of LDC using Self-etch ceramic primer showed better SBS outcomes as compared to phototherapy (Er, Cr: YSGG laser).
关键词： bond strength,microleakage,Phototherapy,lithium disilicate ceramics
更新于2025-09-23 15:22:29
-
Enhanced luminescent properties of Tb3+-doped transparent oxyfluoride glass-ceramics containing YF3 nanocrystals
摘要： Tb3+-doped transparent oxyfluoride glass-ceramics (GC) containing YF3 nanocrystals have been fabricated via a traditional melt-quenching route with appropriate thermal-treatment. The microstructural, luminescent and optical properties of the synthesized material were investigated systematically. The precipitated particles in the glass phase of GC540 are YF3 nanocrystals with a mean size of around 20 nm, which has been confirmed and estimated by XRD and TEM. Compared with the precursor glass (PG), the emission intensity at 545 nm (5D4→7F5) of YF3: Tb3+-doped GC is significantly enhanced (under ultraviolet and X-rays excitation) and the lifetime of GC is longer. It can be confirmed that the preferential enrichment of Tb3+ in the precipitated low-phonon-energy YF3 nanocrystals can effectively reduce non-radiative transitions. The obtained results confirm that such Tb3+-doped YF3 GC might be useful as a novel X-ray scintillating material for slow event detection.
关键词： X-ray excited luminescence spectra,luminescent properties,YF3,Glass-ceramics
更新于2025-09-23 15:22:29
-
Effects of sintering temperature on the microstructure and luminescence of LuAG:Pr ceramics
摘要： The effects of the sintering temperature on the microstructure and luminescence of Lu3Al5O12:Pr (LuAG:Pr) ceramics was investigated by density, X-ray diffraction (XRD), scanning electron microscopy (SEM), grain size, attenuated total reflection Fourier transform infrared spectroscopy (ATR FTIR), photoluminescence (PL), radioluminescence (RL), and thermoluminescence (TL) measurements. A Czochralski-grown single crystal was used as reference. The increase of the sintering temperature promoted progressive structural modifications toward the characteristics of the single crystal. The presence of an amorphous phase was strongly detrimental to the luminescence of LuAG:Pr, with its elimination leading to enhanced RL and reduced TL emission. Evidence of synergism between the F-related defects and the Pr3+ 4f - 4f and 4f - 5d transitions was also found with the presence of these defects being detrimental to the 4f - 5d scintillation.
关键词： ceramics,sintering temperature,luminescence,microstructure,thermoluminescence,Lu3Al5O12:Pr
更新于2025-09-23 15:22:29
-
[IEEE 2018 IEEE International Ultrasonics Symposium (IUS) - Kobe, Japan (2018.10.22-2018.10.25)] 2018 IEEE International Ultrasonics Symposium (IUS) - Lead-Free Sodium Potassium Niobate Based Piezoelectric Thick Film Bimorph Structure for Energy Harvesting
摘要： A novel piezoelectric ceramic-based bimorph energy harvester (PEH) is proposed in this paper for scavenging energy from low-frequency vibrations in many types of applications, such as in the human body or in industry. The PEH is based on a lead-free piezoelectric ceramic material (NKN-based) and is designed to operate efficiently at frequencies below 100 Hz. Experimental results show that the device can generate a power density of up to 22 μW/cm3 under an acceleration of 1 g at 20 Hz, which is highly competitive with existing energy harvesters. This work demonstrates the potential of using lead-free materials for sustainable energy harvesting technologies.
关键词： piezoelectric energy harvesting,NKN-based materials,low-frequency vibrations,lead-free ceramics,bimorph structure
更新于2025-09-23 15:22:29
-
A novel Nd <sup>3+</sup> -doped MgO-Al <sub/>2</sub> O <sub/>3</sub> -SiO <sub/>2</sub> -based transparent glass-ceramics: towards excellent fluorescence properties
摘要： Generally, glass-ceramics have superior properties compared to their parent glasses. Here, we prepared a novel Nd3+-doped MgO-Al2O3-SiO2-based transparent glass-ceramics with excellent fluorescence properties. The effects of Nd2O3 content on the structure and properties of glass-ceramics were studied, aiming to provide a key guidance for preparing this transparent glass-ceramics. The results revealed that the glass stability increased originally and then decreased with increasing Nd2O3 content, so did the variation of wavenumbers in infrared spectra. And these glass-ceramics are mainly composed of cordierite with residual glassy phase. The three phenomenological intensity parameters (Ω2,4,6) and radiative properties were estimated by Judd-Ofelt theory, and the values of Ω2 first decreased and then increased with increasing Nd2O3 content. Three main emission peaks ascribed to the transitions from 4F3/2 to 4I9/2, 4I11/2, 4I13/2 at 898, 1057, 1330 nm were observed, respectively. The branching ratios for 4F3/2→4I11/2 transition increased as the Nd2O3 content raised, and the fluorescence lifetimes of the 4F3/2 level were found to increase first and then decrease with Nd2O3 content (from 181 to 726 μs). The excellent fluorescence properties indicate that this novel glass-ceramics can be used as a potential solid-state optical functional material for 1.06 μm laser emission.
关键词： MgO-Al2O3-SiO2,Judd-Ofelt theory,Nd3+-doped,Transparent glass-ceramics,Solid-state optical functional materials
更新于2025-09-23 15:22:29
-
Joining of AlN and Al with Compositional Graded Layer by Centrifugal Mixed-Powder Method
摘要： In this study, joining of AlN and Al with compositional graded layer is made by centrifugal mixed-powder method (CMPM). The mixed-powder of AlN particles and Al particles is inserted into a spinning mold with bulk-shaped AlN, and then molten Al is poured into the spinning mold with the mixed-powder and bulk-shaped AlN. As a result, the molten Al penetrates into the space between the mixed-powder by the centrifugal force, and at the same time, the Al particles can be melted by heat from the molten Al. Then AlN and Al can be joined with compositional graded layer after solidification. Micromechanics-based analysis is also employed to understand the thermal stress relaxation by the compositional graded layer.
关键词： Joining,Ceramics/metal joining,Thermal stress relaxation,Functionally graded materials (FGMs),Micro-mechanics,Centrifugal mixed-powder method (CMPM)
更新于2025-09-23 15:22:29
-
High piezoelectricity of BiScO3-PbTiO3 ceramics prepared by two step sintering
摘要： (1-x)BiScO3-xPbTiO3 (BSPT) ferroelectric ceramics were prepared by two-step sintering. Dielectric measurements in combination with diffraction contrast transmission electron microscopy (TEM) were used to confirm the phase diagram of BSPT system. From these results, the low temperature phase diagram for BSPT was achieved. In present study, high piezoelectric properties with piezoelectric coefficients (d33≈545pC/N, d33*≈920pm/V) and planar electromechanical coupling factor (kp ≈57%) are achieved in the ceramcs at the composition x=0.64, indicating a future high-temperature piezoelectric application.
关键词： Dielectrics,Phase diagram,Two step sintering,Ceramics
更新于2025-09-23 15:22:29
-
Effect of Zn substitution in Cr3+ doped MgAl2O4 mixed spinel nanoparticles on red/NIR emission properties
摘要： Red/Near-infrared (NIR) emitting Mg1-xZnxAl1.98Cr0.02O4 nanoparticles were synthesized by co-precipitation followed by firing(1200°C). Gradual shift of XRD peaks with Zn-content confirmed complete solid-solution formation. HRTEM revealed hexagonal sheet-like structures and lattice fringes revealed their single-crystallinity. Owing to refractory nature of MgAl2O4, particles were smaller(~38nm) in Mg-rich samples and gradually increased(~58nm) with Zn-substitution. Due to trigonal distortion, the fine splitting of the 4T1g level of Cr3+ manifests as asymmetric band(400nm) in the excitation spectrum. Cr3+ emission was clearly observed, comprising of R-line and multi-phonon side-bands on either side, with maximum R-line intensity for x=0.5. With increasing x, side-bands were more pronounced probably due to the band-gap difference of end members. High Dq/B(3.5-3.9), suggested Cr3+ in a strong crystal-field. Racah-parameter(B) variations suggest increased electron delocalization over molecular orbitals for higher Mg2+ substitutions. Longer lifetimes(23-34ms) are well-suited for bioimaging and optoelectronic applications. Such a simple synthesis can be easily extended to other important phosphors.
关键词： MgAl2O4,Luminescence,Nanoparticles,Phosphors,ZnAl2O4,Oxide ceramics
更新于2025-09-23 15:21:21