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- 2018
- tumor imaging
- conductivity
- MRI
- EPT
- Electrical properties tomography
- Optoelectronic Information Science and Engineering
- Ghent University
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Mono and co-substitution of Sr2+ and Ca2+ on the structural, electrical and optical properties of barium titanate ceramics
摘要： In this work, Ba0.9Sr0.1TiO3, Ba0.7Sr0.3TiO3, Ba0.5Sr0.5TiO3, Ba0.5Ca0.25Sr0.25TiO3 and Ba0.5Ca0.5TiO3 have been synthesized to evaluate the influence of mono and co-substitution of A-site dopants (Sr2+ and Ca2+) on the structural, electrical and optical properties of BaTiO3 ceramics. Sr2+ added samples showed a tetragonal structure which became slightly distorted with increasing Sr2+ concentration and finally achieved a cubic structure for x = 0.50. Ba0.5Ca0.5TiO3 also retained their tetragonality with limited solubility. Presence of second phase, CaTiO3 demonstrated the fact of restricted solubility. The concurrent effect of Sr2+ and Ca2+ didn't alter the tetragonal structure. Sr2+ substitution enhanced the apparent density as well as grain size which stimulated the domain wall motion and improved dielectric properties. However, the ferroelectric nature of Ba1-xSrxTiO3 was poor due to the redistribution of point defect at grain boundary. The optical band gap was found to be reduced from 3.48 eV to 3.28 eV with increasing Sr2+ content. Co-substitution of cations improved the electrical property significantly. The highest value of dielectric constant was found to be ～547 for Ba0.5Ca0.25Sr0.25TiO3 ceramics. Both Ba0.5Ca0.25Sr0.25TiO3 and Ba0.5Ca0.5TiO3 had developed P-E loop having lower coercive field and moderate optical band gap energy. Co-doping with Sr2+ and Ca2+ was a good approach enhancing materials electrical as well as optical property.
关键词： Dielectric properties,Grain size,X-ray diffraction,Optical properties,Sintering
更新于2025-11-21 11:18:25
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Laser additive manufacturing of Zn-2Al part for bone repair: Formability, microstructure and properties
摘要： Zinc (Zn) alloys are promising bone repair materials due to their inherent degradability, favorable mechanical property and biocompatibility. In this investigation, laser powder bed fusion (LPBF) known as a representative additive manufacturing technique was applied to fabricate Zn-2Al (wt.%) part for bone repair application. A low energy density (Ev) led to the formation of pores and resultant insufficient densification rate due to the high liquid viscosity within the molten pool. In contrast, a high Ev caused the evaporation of Zn powder and resultant failure of LPBF. With Ev increasing, the obtained grains and the precipitated lamellar eutectic structure contained η-Zn and α-Al phase became coarsened, which could be attributed to the enhanced heat accumulation and consequently decreased cooling rate. At optimized Ev of 114.28 J/mm3, fully dense Zn-2Al part with a densification rate of 98.3±1.4% was achieved, which exhibited an optimal hardness of 64.5±1.8 Hv, tensile strength of 192.2±5.4 MPa and a moderate corrosion rate of 0.14 mm/year. In addition, in vitro cell tests confirmed its good biocompability. This study indicated that LPBF processed Zn-2Al part was a potential material for bone repair.
关键词： Zn alloys,laser additive manufacturing,mechanical properties,degradation rate,biocompability
更新于2025-11-21 11:18:25
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Unraveling the electrical properties of solution-processed copper iodide thin films for CuI/n-Si solar cells
摘要： The effects of temperature and liquid-phase iodination on the electrical property of spin coated CuI thin films have been investigated in details. The XRD study indicates that CuI thin films are polycrystalline in nature and I-doping enhances the crystal quality and size of the films. The SEM images show that the surface uniformity of the CuI thin films increases due to I-doping. The doping of iodine increases the conductivity as well as carrier concentration and mobility of the films as confirmed by Hall study. The temperature dependent resistivity of CuI film shows a sharp fall of resistivity at ~80 °C for un-doped films whereas this behavior disappears for I-doped films. The optical transmittance and band gap of the I-doped films also increases indicating high degeneracy of the films. These findings imply that I-doped spin coated CuI thin films are potential candidate for the solution-processed CuI/n-Si solar cells.
关键词： liquid-phase I-doped,spin coat,CuI thin films,switching-behavior,electrical properties
更新于2025-11-21 11:18:25
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Laser Welding of Dissimilar Metal Joint of 6061 Al Alloy and Al Matrix Composite
摘要： In this paper, dissimilar metal joints of 6061 aluminum alloy and aluminum matrix composite material are investigated by laser welding. TiB2 particles were added into the lap joint. The welding process, microstructure, and the corrosion properties of welding joints are examined. The results demonstrate that the selected optimization process parameters are laser power 6 kW, welding speed 0.6 mm/s, pulse width 11.5 ms, and laser frequency 4.5 Hz. There are a few obvious pores in the molten pool. Al2Ti, Fe2Si, and Al0.5Fe3Si0.5 are present in the microstructure. During the welding process, some TiB2 particles are decomposed and reacted with molten Al. Other TiB2 particles are nucleated and solidi?ed, and the excess TiB2 particles are pushed to the grain boundaries by molten Al. TiB2 particles are wetted well by molten matrix metal. The corrosion resistance of alloys in di?erent conditions decreased in the following order: the weld beam >6061 Al > AMC.
关键词： aluminum matrix composite,laser welding,TiB2 particles,microstructure,6061 aluminum alloy,dissimilar metal joints,corrosion properties
更新于2025-11-21 11:18:25
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Development of a high strength Al–Zn–Si–Mg–Cu alloy for selective laser melting
摘要： Despite additive manufacturing processes are already widely used in several industrial applications, there are few materials that are specifically designed and optimized for these technologies. Currently, only few Al alloys are available on the market and employed for 3D printing of structural parts. In particular, SieMg bearing alloys are the most common Al alloys for additive manufacturing, featuring high processability but moderate mechanical properties. By this work, we studied the effect of Si addition on the hot cracking susceptibility of a high strength AleZneMgeCu alloy. A preliminary activity has been carried out by blending AleZneMgeCu and AleSieMg powders and analysing their microstructure and properties achieved after selective laser melting. Eventually a new AleZneSieMgeCu alloy has been designed, produced as powder alloy by gas atomization and tested. The microstructure and phase transformations of the new alloy has been investigated by synchrotron X-ray diffraction, differential scanning calorimetry and microscope analysis. The AleZneSieMgeCu alloy processed by selective laser melting featured a relative density of 99.8%, no hot cracks were noticed within the investigated microstructures. The ability of the new alloy to respond to aging starting from both as built and solution annealed conditions has been also evaluated. A good response to direct aging (directly from as built condition) was demonstrated, featuring yield strength and ultimate tensile strength of 402 and 449 MPa, respectively, and hardness of 174 HV after optimized aging at 165 (cid:1)C for 2 h.
关键词： Differential scanning calorimetry,Metal additive manufacturing,Mechanical properties,Synchrotron X-ray diffraction,High strength Al alloy
更新于2025-11-21 11:18:25
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Effect of rare earth Pr doping on core characteristics of electrodeposited nanocrystalline Cu2O films: a film for optoelectronic technology
摘要： Undoped and Pr doped Cu2O nanocrystalline ?lms were fabricated by the electrodeposition method. These ?lms were studied to investigate the formation, morphology, optical, and photoresponse properties on Pr doping concentrations (i.e., 0, 1, 3, and 5 wt%). Structural studies of the deposited Cu2O:Pr ?lms exposed the cubic crystal structure with polycrystalline nature. The crystallite size is decreased from 54 to 29 nm by increasing the Pr doping concentrations. The Raman peaks at 110, 147, 215, 413, and 633 con?rm the Cu2O phase and well matched with the XRD results. The morphological study shows that the pyramid-shaped particles are homogeneously arranged on the ?lm surfaces. The absorption is high for the ?lm deposited with the 5% Pr doping is due to the maximum thickness than the other ?lms. The calculated band gap values of Cu2O:Pr ?lms were reduced from 2.06 to 1.90 eV with raising the Pr doping level. PL spectra showed high intense emission peak at 617 nm which con?rms the NBE emission of Cu2O lattice. Index of refraction (n) and coef?cient of extinction (k) values were increased on increasing the doping concentration from 0 to 5%. From photosensitivity analysis, there is an increase of photoresponse behavior with respect to illuminated current.
关键词： Electrodeposition,Structural,Optical and electrical properties,Morphological
更新于2025-11-21 11:18:25
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White light emitting thermally stable bismuth phosphate phosphor Ca <sub/>3</sub> Bi( <scp>PO</scp><sub/>4</sub> ) <sub/>3</sub> :Dy <sup>3+</sup> for solid state lighting applications
摘要： White light emitting dysprosium doped Ca3Bi(PO4)3 phosphor was successfully synthesized via co-precipitation method for the first time and the structural, vibrational, morphological and luminescent properties have been investigated for solid state lighting applications. The X-ray diffraction (XRD) and structural refinement studies reveal that the synthesized phosphors consist of single phase with cubic structure. The field emission scanning electron microscopy (FE-SEM) images reveal that the as-synthesized phosphor has micron size with an irregular shape. Under near ultraviolet (n-UV) and blue excitation, the phosphor exhibits white light emission via a combination of blue (~451 nm) and yellow (~575 nm) emission bands. The optimized concentration of Dy3+ ions is 6.0 mol % after which the concertation quenching takes place. The process of energy transfer between Dy3+ ions is due to dipole-dipole interaction, which was confirmed by applying Dexter and Reisfeld’s Energy Transfer (ET) formula. The CIE chromaticity coordinates for the optimized phosphor were (0.329, 0.377), which lie in the white light region. The emission intensity remains to 83.41% at 373 K to that of at room temperature, which indicates good thermal stability. The above mentioned results demonstrate that Ca3Bi(PO4)3 is a potential phosphor for solid state lighting applications.
关键词： White LEDs,Structural and luminescent properties,White light emission,Phosphor,Thermally stable
更新于2025-11-21 11:18:25
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Dielectric properties of porous SiC/Si3N4 ceramics by polysilazane immersion-pyrolysis
摘要： The SiC nanotubes were synthesized on porous Si3N4 matrix by polysilazane immersion-pyrolysis. The β-SiC and free C contents increased with the increasing dipping times, which cause some clear vibration and loss peaks of the dielectric constant patterns emerged at around 12.9 GHz and 14.7 GHz in the samples of 20 wt% and 30 wt% benzoic acid, respectively. The re?ectivity of the obtained ceramics were ?7dB ～ ?10dB from the frequency of 8 GHz–18 GHz, which means that the amount of 80%–90% electromagnetic wave could be attenuated. The ceramics containing 40 wt% benzoic acid showed the high loss, low re?ectivity and a wide absorbing band, indicating the high absorbing e?ciency and good dielectric properties.
关键词： Dielectric properties,Si3N4,Dipping,SiC
更新于2025-11-21 11:18:25
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The effect of build orientation on the microstructure and properties of selective laser melting Ti-6Al-4V for removable partial denture clasps
摘要： Statement of problem. Selective laser melting (SLM) Ti-6Al-4V has been used for removable partial dentures, but the impact of SLM Ti-6Al-4V build orientation is not evident. Purpose. The purpose of this in vitro study was to investigate the microstructure and properties of SLM Ti-6Al-4V clasps with different build orientations compared with cast Ti-6Al-4V clasps. Material and methods. Forty-eight clasps were made from Ti-6Al-4V alloys by SLM with 3 different build orientations (SLM0, SLM45, and SLM90) and cast (CAST) as a control. The microstructure was investigated by using a metallographic microscope and a confocal laser scanning microscope. The fit and surface roughness of the clasps were measured, and the physical properties were evaluated. In addition, the von Mises stresses in the clasps were calculated by finite element analysis. All specimens were then subjected to insertion and removal tests in artificial saliva to model 5 years of clinical use. After these tests, 3-point bend tests were used to analyze the fracture surface of the clasp arms, which were observed by using a scanning electron microscope. All data were statistically analyzed (a=.05). Results. The microstructure of the Ti-6Al-4V specimens was a comixture of a+b phases. In addition, growth directions of b grains were approximately parallel to the build orientation, with acicular a grains present between b grains. SLM0 and SLM45 had significantly higher roughness than SLM90. Even though the fit was inferior to that of SLM90, SLM0 and SLM45 still performed better than cast specimens (P<.05). The finite element analysis showed that the maximum von Mises stress was located on the middle part of the retainer arms and that the values of the 0.50-mm undercut clasps were much lower than the elastic limit. In addition, the decrease of retentive force in SLM90 clasps was less than that of the CAST group (P<.05). CAST clasps showed brittle fracture, whereas all SLM clasps showed ductile fracture. Conclusions. The microstructure of SLM Ti-6Al-4V affected the properties of clasps by changing the anisotropy of specimens. Among the tested groups, SLM90 clasps had the best fit, the lowest surface roughness, and the best fatigue resistance. Furthermore, SLM Ti-6Al-4V clasps could be engaged into 0.50-mm undercuts.
关键词： Selective laser melting,Ti-6Al-4V,build orientation,removable partial denture clasps,properties,microstructure
更新于2025-11-21 11:08:12
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Effects of TiO <sub/>2</sub> doping on microstructure and properties of directed laser deposition alumina/aluminum titanate composites
摘要： Al2O3-based composite ceramics have excellent high temperature performance and are ideal materials for preparing hot end components. However, poor fracture toughness and thermal shock resistance limit its applications. Based on the excellent low thermal expansion characteristics and thermal shock resistance of Al2TiO5 ceramic, different composition ratios of Al2O3/Al2TiO5 composite ceramics were prepared by directed laser deposition (DLD) technology. Effects of TiO2 doping amount on microstructure and properties of the composite ceramics were investigated. Results show that α-Al2O3 phase is discretely distributed in the continuous aluminum titanate matrix when TiO2 doping amount between 2 and 30 mol%. With the increase of TiO2 doping amount, content of Al2O3 gradually decreases and its morphology changes from cellular to dendritic. When TiO2 doping amount reaches 43.9 mol%, the microstructure transforms into fine Al2TiO5/Al6Ti2O13 eutectic structure. Property test results show that Al2O3/Al2TiO5 composite ceramics have good comprehensive mechanical properties when TiO2 doping amount between 2 and 6 mol%.
关键词： Al2O3/Al2TiO5,microstructure,Additive manufacturing,properties,composite ceramics
更新于2025-11-21 11:03:13