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Correlation between laser spectroscopic studies and mechanical characterization of zirconia-based multiwall carbon nanotube ceramic composites
摘要： The hardness of zirconium oxide-based ceramic nanocomposites was correlated with the laser spectroscopic studies by analyzing the samples through nanosecond and femtosecond laser to see the viability of this technique as a fast and in situ for assessment of mechanical properties in nuclear industry. Zirconia incorporated with different vol% of multiwall carbon nanotubes were processed by the high frequency induction heated sintering. The composites were characterized by the nanosecond laser-induced breakdown spectroscopy (LIBS) with optimized delay time of 1, 2, and 3 μs and 200 and 300 mJ energies generated by laser Nd:YAG (λ = 1064 nm). The plasma temperature resulted by the ablation of different samples was estimated through intensity of selected zirconium lines using the Boltzmann plot method. The samples were mechanically characterized by the Vickers hardness test. The estimated plasma temperature and the ratio of Zr(II) with different intensities of Zr(I) emission lines show rather weak dependency and increase with surface hardness. The samples were scrutinized by the femtosecond laser micromachining through variation in depth and surface morphology of machined areas. It is found that deeper circular groove and enhanced erosion of disk shape by femtosecond laser machining are achieved for less hard materials and are in agreement with the LIBS analysis.
关键词： LIBS,Ceramics,Machining,Femtosecond,Nanocomposites
更新于2025-09-23 15:21:01
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Copper nanoparticles enhanced luminescence of Eu3+ doped lead tellurite glass ceramics
摘要： Structural, optical and magnetic properties of some lead tellurite glass ceramics doped with europium(III) ions and co-doped with fixed amounts of metallic copper nanoparticles (CuNPs) or copper(II) ions (via CuO) were investigated. Samples in the (Eu2O3)x·(TeO2)80·(PbO)(19.7-x)·(CuNPs)0.3 and (Eu2O3)x·(TeO2)80·(PbO)(19.7-x)·(CuO)0.3 systems with 0 ≤ x ≤ 10 mol% were obtained and investigated for the first time. Several techniques such as X-ray diffraction, UV-VIS, EPR and luminescence spectroscopies and density and magnetic susceptibility measurements were used in order to characterize the samples. XRD data show that the samples with low Eu2O3 contents (x ≤ 1 mol%) are amorphous while for higher europium oxide contents (x > 1 mol%) are glass ceramics. They also reveal that increasing the Eu2O3 content of samples the symmetry around the europium ions changes from face centered cubic to monoclinic. These symmetry changes are confirmed by the photoluminescence data. In addition, photoluminescence data show that the co-doping with metallic copper nanoparticles enhances the emission peaks of europium ions. UV-VIS absorption spectra show the presence of six coordinated copper (II) ions located at sites with a distorted octahedral symmetry. The EPR data confirm the presence of copper (II) ions in all the studied samples. Magnetic susceptibility measurements suggest the presence of europium ions in both their 3+ and 2+ valence states and evidence an important clustering tendency of europium ions even for low Eu2O3 contents.
关键词： EPR,UV-VIS,Photoluminescence,Magnetic susceptibility,Lead-tellurite glass ceramics,XRD
更新于2025-09-23 15:21:01
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Effect of Laser Beam Conditioning on Fabrication of Micro-Channels in Al <sub/>2</sub> O <sub/>3</sub> Bio-ceramics Using Nd:YAG Laser
摘要： In the present study, laser micro-milling tests were carried out to fabricate micro-channels on Alumina bio-ceramics (Al2O3), using a Q-Switched 30W Nd:YAG pulsed laser. A systematic approach based on a full factorial Design of Experiment (DoE) has been successfully applied with the aim to detect which and how the key input laser process parameters affect the channel dimensional accuracy. The examined process parameters were the laser beam scanning speed, the pulse frequency and the pulse intensity. Optical microscope was used to analyze the channel geometries responses (i.e. channel's top width, bottom width, depth, and taper wall angle). Moreover, mathematical models for predicting the micro-channel geometries are successfully proposed for controlled micro-milling of micro-channels in Al2O3. Results reveal that, the change of scanning speed and laser intensity significantly affected the ablated channel’s geometries. Further it is observed that the channel depth and width increase linearly with increasing of laser intensity and decreasing of scanning speed and not much affected by changing of pulse frequency. Finally, the experimental results bear a good agreement with the proposed prediction models.
关键词： micro-channels,Nd:YAG laser,Al2O3 bio-ceramics,Design of Experiment,Laser micro-milling
更新于2025-09-23 15:21:01
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Effect of Mn-doping on dielectric and energy storage properties of (Pb0.91La0.06)(Zr0.96Ti0.04)O3 antiferroelectric ceramics
摘要： Bulk ceramics with high recoverable energy density (Wre) and energy efficiency (h ) play a critical role in the development of pulsed power systems for miniaturization and lightweight. The orthorhombic phase (Pb,La)(Zr,Ti)O3-based antiferroelectric (AFE) ceramics have been regarded as one of the most promising candidates for pulsed power system applications due to their relatively high energy storage density and efficiency. However, the main drawback of orthorhombic phase (Pb,La)(Zr,Ti)O3-based AFE ceramics is relatively low dielectric breakdown strengthen (DBS), which has always restricted the improvement of energy storage density. In this study, an effectively method to increase DBS by the introduction of Mn has been proposed. The relative density of orthorhombic phase (Pb0.91La0.06)(Zr0.96Ti0.04)O3 (PLZT) ceramics was improved by Mn-doping. And the introduction of Mn can decrease the tolerance factor (t) of PLZT ceramics because the radius of Mn2+ is larger than that of B-site Zr4+/Ti4+, and thus enhancing antiferroelectricity. Meanwhile, the effects of Mn-doping on the phase structure, microstructure and dielectric properties of PLZT ceramics have been studied thoroughly in this study. It is found that the highest Wre of 7.65 J/cm3 is obtained at 1.0 mol% Mn-doped PLZT ceramic, which is obviously larger than that of undoped PLZT ceramic (5.71 J/cm3). These results suggest that the Mn-doped PLZT ceramics are potential energy storage materials in pulsed power systems.
关键词： Antiferroelectric ceramics,Energy storage performance,Mn-doping
更新于2025-09-23 15:21:01
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Thermal properties and remnant state variables of ferroelectric ceramics switched by both electric field and compressive stress at room temperature
摘要： A commercial poled ferroelectric cube specimen is subject to electric ?eld and compressive stress of various magnitudes at the reference temperature 20 °C. After reaching speci?c states of remnant polarization and remnant strains, temperature of the specimen increases under no external load, measuring changes in polarization and strains. Assuming constant values of thermal properties in the temperature range of interest, we estimated pyroelectric and thermal expansion coe?cients for all tested levels of electric and stress ?elds and plotted them versus remnant state variables at 20, 50, 80, and 110 °C. The distributions of thermal properties ?t well into quadratic curves independent of electric and stress ?elds at each of the four temperatures. One could predict successfully the quadratic ?tting curves at high temperatures by using the equations of quadratic ?tting curves at reference temperature. Remnant state variables also seem to have close correlation among themselves, independent of the levels of applied electric ?eld or stress. ? 2018 The Japan Society of Applied Physics
关键词： thermal properties,compressive stress,electric ?eld,ferroelectric ceramics,remnant state variables
更新于2025-09-23 15:21:01
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Improved upconversion photoluminescence properties of 0.965K0.4Na0.58Li0.02Nb0.96Sb0.04O3–0.035Bi0.5K0.5ZrO3:0.25%Er/xIn lead-free piezoelectric ceramics with balanced piezoelectric coefficient and Curie temperature
摘要： A series of erbium- and indium-doped 0.965K0.40Na0.58Li0.02Nb0.96Sb0.04O3–0.035Bi0.5K0.5ZrO3:0.25%Er/xIn lead-free piezoelectric ceramics with upconversion photoluminescence (UCPL) properties were prepared by the conventional solid state reaction. A systematical investigation into the effects of In3+ doping on the structural, dielectric, ferroelectric, piezoelectric, and UCPL properties of the ceramics was carried out. The distribution of Er3+-sites could be modified by In3+ doping according to the analysis of UV–Vis-NIR absorption cross-section, resulting in improved piezoelectric and photoluminescence properties of the ceramics. The optimized comprehensive properties are performed by the x = 0.25% samples of which the piezoelectric coefficient d33 ~ 257 pC/N, Curie temperature TC ~ 273 °C, remanent polarization Pr ~ 12.5 μC/cm2, dielectric constant εr ~ 1551, and d33 ~ 257 pC/N which is the supreme piezoelectric coefficient achieved in KNN-based UCPL ceramics as of now. The results demonstrate that erbium and indium co-doped KNN-based ceramics may have potential applications in electro-optical devices.
关键词： Upconversion photoluminescence,Erbium and indium co-doping,Piezoelectric coefficient,Lead-free piezoelectric ceramics,Curie temperature
更新于2025-09-23 15:21:01
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The effect of Yb3+ ion substitution on dielectric and microstructural properties of Y3Al5O12 ceramics
摘要： The electrical and dielectric properties of Y3Al5O12 (yttrium aluminum garnet, YAG) ceramics are investigated in detail. YAG:(Yb)x (0.01 ≤ x ≤ 0.09) was synthesized by a solid state reaction and characterized by X-ray powder diffraction, field emission scanning electron microscopy, and high-resolution transmission electron microscopy. The electrical and dielectric properties have been intensively studied under certain bias voltages up to a frequency of 10 MHz. These properties are dependent on the substitution rates, independent of the bias voltages. The experimental result shows that Yb3+ ion substitution into YAG ceramics significantly influences the conductivity, dielectric constant, and lossy mechanisms, which is probably owing to the 3d-Al ions and 4f-Yb ions incorporated at different positions of structural symmetries in Y3?xYbxAl5O12 (0.00 ≤ x ≤ 0.09) ceramics.
关键词： ceramics,Yb3+ ion substitution,Y3Al5O12,dielectric properties,microstructural properties
更新于2025-09-23 15:21:01
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Photonic and Electronic Properties of Fluoride Materials || Optical Properties of Fluoride Transparent Ceramics
摘要： A ceramic is a polycrystalline inorganic material excluding metals. The ceramic process was the first “arts of fire” to appear long before the metallurgy and glass making. The word ceramic comes from the ancient Greek and means “clay,” “potter’s clay.” The elaboration and use of ceramic evolved in the 20th century with the industrial development and the research on the chemistry of materials. A new class of ceramic appeared with the technical ceramics. For example, nitride and carbide are essential materials for a lot of industrial applications. Refractory ceramics, which are essential equipment for some sectors of industry as the glass industry or metallurgy, have evolved significantly since the beginning of the 20th century. It is the reason why nowadays the word “ceramic” refers to a polycrystalline material obtained by the thermal treatment of precursor batches in order to ensure a mechanical cohesion and a continuity of the properties of the manufactured product.
关键词： Fluoride,Optical Properties,Yb:CaF2,Transparent Ceramics,Laser Materials
更新于2025-09-23 15:21:01
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Orientation factor and piezoelectric property in textured (K,Na)NbO <sub/>3</sub> system ceramics with minimal templates
摘要： To lower the sintering temperature and decrease the weight ratio of templates required for fabricating textured (K,Na)NbO3 (KNN) system ceramics, the method of preparing platelike NaNbO3 (NN) single-crystal particles for the templates was improved. The NN crystal particles synthesized by the single-step molten salt method using a mixed salt were treated by ultrasonic vibration and subsequently screened. Using these improved templates, we developed the fabrication method for the textured KNN system ceramics by which the weight ratio of the templates required for the orientation control can be reduced to 1/10 of the conventional weight ratio. The effects of decreasing the weight ratio of templates on sintering temperature, orientation factor, and piezoelectric properties were investigated. In addition, the effects of adding Bi2O3 to KNN calcined powder were also studied to suppress abnormal grain growth, which appears in the textured samples fabricated using smaller amounts of the templates.
关键词： reactive template grain growth,molten salt synthesis,Bi2O3 addition,lead-free piezoelectric materials,ultrasonic treatment,textured ceramics
更新于2025-09-23 15:21:01
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Nonradiative energy transfer of electronic excitation between Tm3+ ions in Y2O3:Tm laser ceramics
摘要： The cross relaxation of Tm3t ions (3H4→3F4, 3H6→3F4) in Y2O3:Tm laser ceramics was studied. This process significantly affects the creation of an inverse population between the 3F4 and 3H6 levels of Tm3t ions in two-micron lasers when they are pumped to the 3H4 level by laser diodes with a wavelength of λexc~800 nm. The efficiency of the cross-relaxation process of Tm3t ions (3H4→3F4, 3H6→3F4) was equal to 97% for Y2O3:Tm ceramics with the thulium concentration of 3 at.%. It was revealed that the nonradiative transfer of electron excitation energy by Tm3t ions through cross-relaxation (3H4→3F4, 3H6→3F4) is due to the dipole-dipole mechanism. The interaction microparameter CDA was determined equal to 9.2?10?39 cm6/s.
关键词： Y2O3,Optical properties,Laser ceramics,Spectroscopy
更新于2025-09-23 15:19:57