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Influence of processing parameters on the microstructure and tensile property of 85 W-15Ni produced by laser direct deposition
摘要： The plate-like shape 85W-15Ni parts were produced by laser direct deposition technology with different processing parameters (laser power and scanning speed). The influence of processing parameters and their corresponding laser energy density on the microstructural characterization, phase composition and tensile property of 85W-15Ni samples was investigated. The results show that the relative density of samples increased with the laser energy density and the densification trend started to slow as the laser energy density reached 380-400 J/mm3, though the highest density value was obtained with laser energy of 425 J/mm3. With the increase of laser energy density, more disorder and fine W dendrites existed at the bonding region between deposition layers and more W-W grain boundaries formed at the central region of the layer. The 85W-15Ni samples produced with different processing parameters consisted of W and γ-Ni phase. To improve the tensile property, it is necessary to increase the laser energy density to obtain denser structure and reduce the residual pores or gaps. However, the excessive laser energy density resulted in the formation of more W-W grain boundaries that were detrimental to the tensile property. The best tensile properties were obtained at the laser energy density of 395 J/mm3.
关键词： 85W-15Ni,Laser direct deposition,Tensile property,Laser energy density,microstructural characterization
更新于2025-11-28 14:24:20
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Structural characterization of bulk and nanoparticle lead halide perovskite thin films by (S)TEM techniques
摘要： Lead halide (APbX3) perovskites, in polycrystalline thin films but also perovskite nanoparticles (NPs) have demonstrated excellent performances to implement a new generation of photovoltaic and photonic devices. The structural characterization of APbX3 thin films using (scanning) transmission electron microscopy ((S)TEM) techniques can provide valuable information that can be used to understand and model their optoelectronic performance and device properties. However, since APbX3 perovskites are soft materials, their characterization using (S)TEM is challenging. Here, we study and compare the structural properties of two different metal halide APbX3 perovskite thin films: bulk CH3NH3PbI3 prepared by spin-coating of the precursors in solution and CsPbBr3 colloidal NPs synthetized and deposited by doctor blading. Both specimen preparation methods and working conditions for analysis by (S)TEM are properly optimized. We show that CH3NH3PbI3 thin films grown by a one-step method results in the formation of tetragonal perovskite thin films with good adherence to an underlying TiO2 layer, which is characterized by a photoluminescence (PL) emission band centered at 775 nm. The perovskite thin films based on CsPbBr3 colloidal NPs, which are used as the building blocks of the film, they are preserved by the deposition process, even if small gaps are observed between adjacent NPs. The crystal structure of CsPbBr3 NPs is cubic, which is beneficial for optical properties due to its optimal band gap. The absorption and PL spectra measured in both the thin film and the colloidal solution of CsPbBr3 NPs are very similar, indicating a good homogeneity of the thin films and the absence of aggregation of NPs. However, a particular care was required to avoid long electron irradiation times during our structural studies, even at a low voltage of 80 kV, as the material was observed to decompose through Pb segregation.
关键词： structural characterization,TEM,thin films,optoelectronics,STEM,nanoparticles,perovskite
更新于2025-09-23 15:23:52
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Synthesis, Conductivity and Impedance Studies on across adjacent ring formed new metallo phthalocyanines
摘要： The synthesis and characterization of Co(II), Zn(II) and Ni(II) phthalocyanines (Pcs) 4, 5 and 6, respectively containing two Bis[2-(4-hydroxyphenyl)-2-propyl]benzene across adjacent ring formed at the peripheral positions are described. The Pcs were synthesized by cyclotetramerization of the previously prepared precursor 4,4’-bis[1,3-propylbenzene-2-p-phenoxy]phthalonitrile (3) with the presence of metal salt in boiling dry DMF under a dry nitrogen atmosphere. Elemental analysis, UV-Vis, FT-IR, MALDI-TOF mass and 1H-NMR spectrometry techniques were used for characterization of 4. DC and ac conductivity and impedance spectra (IS) measurements were performed on the films 5, and 6 between the temperatures 293 - 523 K and frequencies 40-100 kHz. The dc conductivity values were calculated as 2.11x10-10 S/cm, 3.48x10-10 S/cm, and 1.90x10-10 S/cm for the films of 4, 5, and 6 at room temperature. Activation energy values of the films were also calculated. ac conductivity results suggest that dominant charge transport mechanisms can be explained by hopping model depending on temperature and frequency range. From impedance spectra, Cole-Cole plots, the relaxation time in Debye dispersion relation is considered as a distribution of relaxation time values, rather than as a single relaxation time. To elucidate the structural, spectroscopic and bonding properties of the obtained compounds, DFT/TD-DFT calculations were performed.
关键词： Density functional theory,Conductivity,Electrical characterization,Impedance spectra,Metallophthalocyanine,Hopping
更新于2025-09-23 15:23:52
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Characterization of atypical polyaniline nano-structures prepared via advanced techniques
摘要： Conductive polymers had been the topic of a vast number of investigations during the last decades, so, the synthesis of conducting polymers and study of their physical properties has been of prime importance. One of these conductive polymers is polyaniline. The current work is to prepare polyaniline (PANI) nanostructured material via four different preparation techniques which were sol-gel, rapid mixing, sonochemical and supercritical carbon dioxide (SC-CO2) assisted polymerization. The morphology of the prepared PANI samples was determined using Transmission electron microscopy (TEM) and Scanning Electron Microscope (SEM). The molecular structure of prepared PANI samples was characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The electrical conductivity of the synthesized samples was assessed by using the four-probe method at room temperature. The surface area of the prepared samples was determined using Brunauer Emmett Teller (BET). The characterization results of the prepared PANI con?rm that the morphology, chemical composition, crystallinity, conductivity and surface area were altered signi?cantly as a consequence of its synthesis via atypical techniques.
关键词： Supercritical carbon dioxide assisted polymerization,Nanoparticles,Sonochemical,Polyaniline nano-structures,Nano?bers,Polyaniline characterization,Nanorods,Sol gel,Rapid mixing polymerization
更新于2025-09-23 15:23:52
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Structure, growth and characterization of a new naphthalene family crystal for fluorescence and third order nonlinear optical applications
摘要： In the present work we have investigated the fluorescence and nonlinear optical property of a new naphthalene family crystal, Decyl 6-(decyloxy)naphthalene-2-carboxylate (D6DN2C). This crystal was grown for the first time by slow evaporation solution technique (SEST). Single crystal X-ray diffraction analysis reveals that D6DN2C belongs to triclinic crystal system with centrosymmetric space group of Pī. The determined lattice parameters are a = 8.669(3) ?, b = 9.495(3) ?, c = 19.757(6) ?, α =82.697(1)°, β =77.726(1)°, γ = 65.465(1)°and volume = 1444.17(8)?3. Functional groups present in D6DN2C were identified by FT-IR studies. Transparency of the title crystal in UV–Visible region was analyzed and the optical band gap energy was found to be 3.51eV. Fluorescence spectra were recorded for the excitation wavelength of 300 nm. The negative third order nonlinear optical parameters like refractive index (n2), absorption coefficient (β) and susceptibility (χ(3)) were estimated by Z-scan studies.
关键词： Crystal structure,Characterization,Growth from solutions,Nonlinear optic materials,Organic compounds
更新于2025-09-23 15:23:52
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Radiative characteristics of Voronoi open-cell foams made from semitransparent media
摘要： The radiative characterization of open-cell foams made from semitransparent solids is more complex than that made from opaque media. This study aims to understand how the component radiative properties and structural parameters of such open-cell foams affect their radiative characteristics. A radiative transfer model was established in the limit of geometric optics for the radiative characterization of a family of numerically generated Voronoi foams with open cells. It considers the reflection and refraction at the solid surface and the transmission, absorption and scattering process inside the solid phase. It is found that when the solid phase is in reality partially transparent, the opaque solid assumption will lead to inaccurate outcomes. Strongly scattering solid phase may cause much radiative energy to be rejected via reflection behavior, which will weaken the absorptive capability of the foam sheets as radiation absorbers. In addition, the radiative transfer model established was applied in three popular ceramic foams (alumina, silicon carbide and zirconia). The model shows advances in the field of analyzing and explaining the spectral radiative characteristics of ceramic foams. The present work can provide useful guidance when open-cell foams made from semitransparent media become potential candidates for thermal applications.
关键词： Voronoi tessellation,Radiative characterization,Ceramic foam,Semitransparent
更新于2025-09-23 15:23:52
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Characterization of beam splitters in the calibration of a six-channel Stokes polarimeter
摘要： Polarization distortion in a beam splitter is a phenomenon where the polarization state of output light deviates from the theoretical expectation, which is inevitable and will result in significant errors in the optical systems. A theoretical analysis method based on Mueller matrix ellipsometry is proposed for characterizing the beam splitters and the application in the calibration of a six-channel Stokes polarimeter (SP) is shown. In this study, polarization distortions in the beam splitters including depolarization, linear birefringence, circular birefringence, linear dichroism, and circular dichroism have been considered. With the proposed method, the beam splitters are characterized by the polarization distortions and the effective optical parameters extracted. In our experiment, the Mueller matrices of two different commonly used beam splitters measured by a commercial Mueller matrix ellipsometer (MME) are consistently fitted by the proposed method and the residual errors have shown improvement compared to the conventional methods. A practical application of the proposed method is exhibited by calibrating a SP system containing two non-polarization beam splitters and three polarization beam splitters. With the proposed method introduced, the general error of the measured Stokes vector can be reduced from 3% to 1%, and the errors of the thickness measurement of standard SiO2 thin film samples are within 1 nm compared with the results reported by a commercial MME.
关键词： beam splitter,characterization,calibration,Stokes polarimeter,polarization distortion
更新于2025-09-23 15:23:52
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Contactless parametric characterization of bandgap engineering in p-type FinFETs using spectral photon emission
摘要： In the last decade it has become increasingly popular to use germanium enriched silicon in modern field effect transistors (FET) due to the higher intrinsic mobility of both holes and electrons in SiGe as compared to Si. Whether used in the source/drain region (S/D) as compressive stressor, which is an efficient mobility booster on Si channel devices, or as channel material, the SiGe increases channel carrier mobility and thus enhancing device performance. Because the germanium content modifies the effective bandgap energy EG, this material characteristic is an important technology performance parameter. The bandgap energy can be determined in an LED-like operation of electronic devices, requiring forward biased p-n junctions. P-n junctions in FETs are source or drain to body diodes, usually grounded or reversely biased. This investigation applies a bias to the body that can trigger parasitic forward operation of the source/drain to body p-n junction in any FET. Spectral photon emission (SPE) is used here as a non-destructive method to characterize engineered bandgaps in operative transistor devices, while the device remains fully functional. Before applying the presented technique to a p-type FinFET device, it is put to the proof by verifying the nominal silicon bandgap on an (unstrained) 120 nm technology FET. Subsequently the characterization capability for bandgap engineering is then successfully demonstrated on a SiGe:C heterojunction bipolar transistor (HBT). In a final step, the bandgap energy EG of a 14/16 nm p-type FinFET was determined to be 0.84 eV, which corresponds to a Si0.7Ge0.3 mixture. The presented characterization technique is a contactless fault isolation method that allows for quantitative local investigation of engineered bandgaps in p-type FinFETs.
关键词： p-n junction,Heterojunction bipolar transistor,Bandgap characterization,p-channel FinFET,SiGe, strained Si,Body diode, parasitic operation,Bandgap engineering,Body bias voltage,HBT,Contactless fault isolation,Spectral photon emission,MOSFET
更新于2025-09-23 15:23:52
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A CSRR-Based Sensor for Full Characterization of Magneto-Dielectric Materials
摘要： In this paper, a novel complementary split-ring resonator (CSRR)-based sensor for full characterization of magneto-dielectric materials is proposed. In general, the operation of microwave resonance-based sensor hinges on the shift in the resonance frequency and the change in the quality factor of the loaded structure. However, both the electric permittivity and the magnetic permeability of the material under test (MUT) have similar effect on the response of the sensor that makes the simultaneous determination of the permittivity and permeability challenging. To remove this difficulty, the main idea behind this paper is to localize the highest intensity of the electric and magnetic fields in two separate zones. By the analysis of the measured resonance frequency and quality factor, the real and imaginary parts of the electric permittivity and the magnetic permeability of the MUT can be determined. Although the characterization of the permittivity and permeability of materials using split-ring resonator and CSRR-based sensors has been widely used, to the best of our knowledge, the full characterization of magneto-dielectric materials using a single sensor has not yet been reported in this paper. As a proof of concept, the sensor was fabricated and used to measure the permittivity and permeability of several materials. Strong agreement between the extracted values and the reference data was achieved.
关键词： sensor,Complementary split ring resonator (CSRR),material characterization,split ring resonator (SRR),magneto-dielectric materials,permittivity and permeability
更新于2025-09-23 15:23:52
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Bonding of Large Substrates by Silver Sintering and Characterization of the Interface Thermal Resistance
摘要： Low-temperature silver sintering technology, which has been proven to be a promising die-attach solution, was extended to bonding large substrates. Strong bonding strengths for substrates greater than 25 mm × 50 mm were achieved by sintering a nanosilver paste at temperatures below 270oC with less than 5 MPa pressure. To characterize the thermal performance of the substrate-attach interface, we applied a transient thermal technique with cumulative structure function analysis. Using self-heating and temperature-sensitive threshold voltage of a power device, we measured the transient thermal responses of the device placed at various locations on the bonded structures. Each transient thermal response was used to determine cumulative structure function, which represents the relationship between cumulative thermal capacitance and cumulative thermal resistance from the device junction to the ambient environment. Two-dimensional maps corresponding to interface thermal resistance were obtained from structure function plots. We found that for well-bonded substrates, the average specific thermal resistance contributed by the sintered silver interface was between 5.20 mm2K/W and 5.78 mm2K/W with a variation of 4.7% to 6.0%.
关键词： silver sintering,Substrate-attach,two-dimensional map of interface thermal resistance,transient thermal characterization
更新于2025-09-23 15:23:52