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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
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Characterisation of AlN nano thin films prepared by PLD
摘要： Aluminium nitride (AlN) nano thin films have been prepared by pulsed laser deposition (PLD) in this paper. The microstructure and grain size of the nano thin films were characterised by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that the PLD conditions such as laser fluence, ambient pressure and substrate temperature influence the thickness, morphology and grain size of the nano thin films obviously, i.e. the surface of the nano thin films becomes rough while the grain size increases with increasing the laser fluence, ambient pressure and substrate temperature. In addition, there exists a preferred orientation growth in the thin films.
关键词： microstructure,pulsed laser deposition (PLD),aluminium nitride,grain size,Nano thin films
更新于2025-09-23 15:22:29
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Microstructural interpretation of charge transport dynamics of chemically derived ZnCo2O4 under mechanical milling
摘要： In this work, milling effect on chemically synthesized nanocrystalline Zinc Cobaltite (ZnCo2O4) has been investigated and we report how the structural and electrical properties vary with the milling span. Phase pure ZnCo2O4 has been successfully synthesized via simple and cost-effective co-precipitation method and then it has been milled for one, four and eight hours respectively. XRD confirms formation of single phase cubic structure for both milled and unmilled nano-powders. Different microstructural parameters has been estimated from Rietveld analysis, which shows particle size reduction from ~29.64 nm for unmilled sample to ~18.13 nm for eight hour milled sample. TGA-DSC curve of as prepared sample shows good temperature stability that helps to estimate the appropriate sintering temperature for the samples. TEM analysis also gives values of grain size in agreement with Reitveld analysis. Frequency dependent ac conductivity curve obeys universal Jonscher power law and temperature dependence of frequency exponent is explained by small polaron transaction. Comparable activation energies from hopping mechanism and relaxation process indicates similar transport mechanism. Superimposed scaling spectra obeys TTSP principle. AC conductivity increases with frequency as a result of hopping of the charge carriers. Smaller particles with reduced strain gives enhanced conductivity as well as enhanced value of hopping frequency. This further suggests creation of excess charge carriers in milled samples. Cole-Cole plot shows non-Debye type behavior of the samples. The dielectric loss factor increases with lowering of particle size since smaller grains contributes to faster charge conduction.
关键词： TGA-DSC,Mechanical milling,Electrical characterisation,dielectric loss factor,Microstructure
更新于2025-09-23 15:22:29
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Label-free nanoparticle sensors based on a triple-layer-coated microsphere structure
摘要： We present a design for a sensitive, label-free nanoparticle sensor based on triple-layer-coated microsphere resonators. The surfaces of the microsphere structure are coated with three layers that have high, low, and high refractive indexes from inside to outside, respectively. We theoretically and numerically investigate two cladding modes, we call the inner mode and outer mode. The resonance wavelengths of the two modes are used to detect the resonance wavelength shift caused by a single-nanoparticle. Numerical calculation suggests that if we change the thickness of the middle layer, the device offers another degree of freedom to obtain higher detection sensitivity. We build a model to accurately describe a nanoparticle close to the microsphere. The method for the sensors may promote the design of biosensing applications.
关键词： Optical materials and properties,Sensors,Simulation and modelling,Microstructure
更新于2025-09-23 15:22:29
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Comparison of basis functions and q-space sampling schemes for robust compressed sensing reconstruction accelerating diffusion spectrum imaging
摘要： Time constraints placed on magnetic resonance imaging often restrict the application of advanced diffusion MRI (dMRI) protocols in clinical practice and in high throughput research studies. Therefore, acquisition strategies for accelerated dMRI have been investigated to allow for the collection of versatile and high quality imaging data, even if stringent scan time limits are imposed. Diffusion spectrum imaging (DSI), an advanced acquisition strategy that allows for a high resolution of intra-voxel microstructure, can be sufficiently accelerated by means of compressed sensing (CS) theory. CS theory describes a framework for the efficient collection of fewer samples of a data set than conventionally required followed by robust reconstruction to recover the full data set from sparse measurements. For an accurate recovery of DSI data, a suitable acquisition scheme for sparse q-space sampling and the sensing and sparsifying bases for CS reconstruction need to be selected. In this work we explore three different types of q-space undersampling schemes and two frameworks for CS reconstruction based on either Fourier or SHORE basis functions. After CS recovery, diffusion and microstructural parameters and orientational information are estimated from the reconstructed data by means of state-of-the-art processing techniques for dMRI analysis. By means of simulation, diffusion phantom and in vivo DSI data, an isotropic distribution of q-space samples was found to be optimal for sparse DSI. The CS reconstruction results indicate superior performance of Fourier-based CS-DSI compared to the SHORE-based approach. Based on these findings we outline an experimental design for accelerated DSI and robust CS reconstruction of the sparse measurements that is suitable for the application within time-limited studies.
关键词： diffusion MRI,sparse acquisition,q-space undersampling,microstructure,compressed sensing,basis functions,diffusion spectrum imaging
更新于2025-09-23 15:22:29
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Phase field modeling of grain boundary migration and preferential grain growth driven by electric current stressing
摘要： A phase field model incorporating the electrostatic free energy and the grain orientation effect is developed and employed to study the grain boundary migration and preferential grain growth in widely used beta-tin (β-Sn) under electric current stressing. The directional migration of grain boundaries and the preferential growth of the grain with its orientation having low electrical resistivity along the electric current direction are theoretically clarified. In a bicrystal system containing a circular grain, the shrinkage velocity and morphology changes of grains are dominated by the competition effect between the grain boundary energy and the electrostatic free energy; in particular, the high-density electric current can induce the instability of grain morphology evolution. Moreover, grain morphology evolution leads to the change of the voltage across the β-Sn system; it is found that the voltage decreases over time in a tricrystal system, while the variation of the voltage across the bicrystal system is related to the above-mentioned competition effect. The proposed model and results provide insights into the orientation-related microstructure evolution under electric current stressing.
关键词： preferential grain growth,electric current stressing,microstructure evolution,grain boundary migration,beta-tin,phase field model
更新于2025-09-23 15:21:21
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Effect of Nb addition on microstructure and properties of laser cladding NiCrBSi coatings
摘要： NiCrBSi coatings with different Nb additions have been prepared by laser cladding. The microstructure, phase composition, hardness, and wear resistance of the coatings were studied by scanning electron microscopy (SEM), electron probe microanalyser (EPMA), X-ray diffraction (XRD), microhardness tester and M-200 wear tester. The results show that the phases in the NiCrBSi coating without Nb addition include γ-Ni, Cr23C6, Cr7C3, Ni3B, Ni3Si2 and CrB. The NbC phase appears in coatings after the addition of Nb element. When the addition of Nb is 2 wt-%, the NbC particles with a size of about 1.2 μm were found in the coating, and the amount of NbC is about 1.8 vol.-%. With the increase of Nb addition, the size and amount of NbC in the coatings also increased. When the addition of Nb is 6 wt-%, the size of NbC is about 2.3–6.1 μm and the morphology of NbC changed from particle to quadrangular and petaloid shaped. In addition, when the addition of Nb is 2 wt-%, the hardness and wear resistance of the coating are the best, and the wear resistance of the coating is 104% higher than that without Nb addition.
关键词： Nb addition,wear resistance,microstructure,hardness,Laser cladding,NiCrBSi coatings
更新于2025-09-23 15:21:21
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Thermal stability investigation of the SS/MO/Al <sub/>2</sub> O <sub/>3</sub> spectrally selective solar absorber coatings
摘要： A novel Mo/Al2O3 spectrally selective solar absorber coating is deposited onto stainless steel (SS) substrates using magnetron sputtering method, which exhibits a high absorptance (α) of 0.90 and a low emittance (ε) of 0.08. In order to investigate the thermal stability, the SS/Mo/Al2O3 coatings are annealed in air and vacuum at di?erent temperatures. The surface morphology, microstructure, composition distribution, di?usion and optical properties before and after high-temperature annealing are characterised by scanning electronic microscopy (SEM), atom force microscopy (AFM), X-ray di?raction (XRD), micro-Raman spectroscopy, UV–vis spectrophotometer and emissometer. Experimental results indicate that the coatings are stable in air at 350°C. The values of solar absorptance and emittance below 350°C are 0.87–0.90 and 0.06–0.08, respectively. The coatings remain stable after annealed at 600°C in vacuum for 2 h with a good spectral selectivity (α/ε) of 0.89/0.06.
关键词： microstructure,Spectrally selective coating,annealing,thermal stability
更新于2025-09-23 15:21:21
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Mechanically tuned molybdenum dichalcogenides (MoS2 and MoSe2) dispersed supramolecular hydrogel scaffolds
摘要： An intriguing way of tuning the mechanical efficiency of a supramolecular hydrogel network (SHGel) has been achieved by dispersing MoS2 and MoSe2. Depending upon the nature of chalcogens, the rheological properties of molybdenum dichalcogenides dispersed supramolecular hydrogel are varied. According to the variation of rheological properties, the morphologies of diverse molybdenum dichalcogenides dispersed hydrogel networks are changed. MoS2 enhances the mechanical performances of a supramolecular hydrogel. The incorporation of MoSe2 nano-fillers in the MoS2 dispersed supramolecular hydrogel lowers the mechanical properties gradually compared to the dispersion of pure MoS2. The dispersion of pure MoSe2 exclusively lowers the mechanical efficiency of the supramolecular hydrogel resulting in a drastic alteration of the morphological pattern of MoSe2 nano-fillers dispersed hydrogel under ambient condition.
关键词： MoSe2,Mechanical tuning,MoS2,Hydrogel,Microstructure
更新于2025-09-23 15:21:21
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Systematic microstructural development with thermal diffusivity behaviour from nanometric to micronic grains of strontium titanate
摘要： Strontium titanate is a promising candidate for applications in thermoelectric, thermal management applications, and modern electronic devices because of its desirable thermal stability, chemical stability, and semiconducting behaviour. However, the absence of its important systematic development, having grain size from several nanometric up to micronic size with evolving thermal diffusivity behaviour, triggers the need for filling up the vacuum. Two different heat treatments have been carried out onto the samples which were with presintering and without presintering. Nanometer-sized compacted powder samples were sintered from 500 to 1400 °C using 100 °C increments. The parallel characterizations of structural, microstructural and thermal diffusivity properties were systematically carried out. Interestingly, three significant value-differentiated groups: weak, moderate, and strong thermal diffusivity were observed, resulting from the influence of different phonon-scattering mechanisms through a systematic development of microstructural properties for both heat treatments.
关键词： Strontium titanate,Thermal conductivity,Thermal diffusivity,Microstructure
更新于2025-09-23 15:21:21