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Amorphous Boron Suboxide
摘要： We study the atomic structure and the electronic and mechanical properties of amorphous boron suboxide (B6O) using an ab initio molecular dynamic technique. The amorphous network is attained from the rapid solidification of the melt and found to consist of boron and oxygen rich regions. In the boron rich regions, boron atoms form mostly perfect or imperfect pentagonal pyramid like configurations that normally yield the construction of ideal and incomplete B12 molecules in the model. In addition to the B12 molecules, we also observe the development of a pentagonal bipyramid (B7) molecule in the noncrystalline structure. In the oxygen rich regions, on the other hand, boron and oxygen atoms form threefold and twofold coordinated motifs, respectively. The boron rich and oxygen rich regions indeed represent structurally the characteristic of amorphous boron and boron trioxide (B2O3). The amorphous phase possess a small band gap energy with respect to the crystal. On the bases of the localization of the tail states, we suggest that the p-type doping might be more convenient than the n-type doping in amorphous B6O. Bulk modulus and Vickers hardness of the non-crystalline configuration is estimated to be 106 and 13-18 GPa, respectively, which are noticeably less than those of the crystalline structure. Such a noticeable decrease in the mechanical properties is attributed to the presence of open structured B2O3 glassy domains in the amorphous model.
关键词： hardness,amorphous,boron suboxide
更新于2025-09-19 17:15:36
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Luminescence and dielectric properties of Ni2+ ions added to calcio yttria borophosphate glasses for optoelectronic uses
摘要： Glass materials of composition CaO – Y2O3 – B2O3 – P2O5 added with different concentrations of NiO (Ni2+: CYBP) are synthesized by conventional rapid melt quenching method. Various physical properties of these glasses such as polaron radius (rp), molar volume (Vm), optical basicity (Λth) and refractive index (μ) are studied. As an elastic characterization Young’s modulus (Y), Poison ratio (σ) and micro hardness (H) of these glasses are studied. These grades suggest that the prepared materials are mechanically hard and exhibiting covalently interlinked structure. Further these samples are characterized by various techniques such as differential thermal analysis, thermoluminiscence, optical absorption, photoluminescence, Ionic conductivity and dielectric dispersion. The thermoluminiscence grades such as peak temperature maximum (Tm), shape symmetry factor (μsf) and activation energies ( Eτ, Eδ and Eω) are studied at various UV irradiation levels. These results strongly recommended that the both electron and hole trap centers were created at the deeper trap levels and contribute higher orders of thermoluminiscence emission with in these glasses subjected to higher orders of temperature and UV irradiation. The various optical absorption and photoluminescence factor's such as, optical band gap (Eo), nephelauxetic ratio (β), emission cross section (Ω), branching ratio (ζ) and radiative life times (τ) are studied. These grades found to be maximum for the material which has 0.5 mol% of NiO concentration may be most suggestible for optoelectronic application. The dc and ac conductivity (σdc & σac) of these glasses are estimated. The various dielectric parameter’s such as loss tangent (Tan (φ)), temperature region of relaxation (ΔT), density of states near Fermi level (N(Ef)), activation energies of both dipoles and conduction (Ed & Ec) are also calculated. These reports clearly disclose that the octahedrally located Ni2+ ions are increasing with increase NiO concentration with in present calcio yttria borophosphate glasses.
关键词： emission cross section,nephelauxetic ratio,micro hardness,trap depth parameters,Ni2+: CYBP glass materials,temperature region of relaxation
更新于2025-09-19 17:15:36
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Linear friction welding of Ti-6Al-4V parts produced by electron beam melting
摘要： The linear friction welding (LFW) of Ti-6Al-4V parts manufactured through electron beam melting (EBM) is investigated using different processing conditions of frequency (from 40 to 50 Hz) and pressure (from 55 to 75 MPa). The microstructure, hardness, and porosity of the different zones of the weld are analyzed in relation to the parent material. The experiments show that LFW is a viable technology for Ti-6Al-4V EBMed parts since it produces welds with hardness and microstructure comparable to those of the base material. Furthermore, the process is demonstrated to be quite robust in the range of specific power input going from ~0.7 to ~1.2 W/mm2. LFW of small EBMed parts to form larger components is of particular interest for the industrialization of titanium alloy aerospace components produced by means of additive manufacturing.
关键词： Titanium,microstructure,welding,hardness,Additive
更新于2025-09-19 17:15:36
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[IEEE 2018 NASA/ESA Conference on Adaptive Hardware and Systems (AHS) - Edinburgh (2018.8.6-2018.8.9)] 2018 NASA/ESA Conference on Adaptive Hardware and Systems (AHS) - A 400 Mrad radiation-hardened optoelectronic embedded system with a silver-halide holographic memory
摘要： The paper discusses the development and characterization of an optically reconfigurable gate array (ORGA) with a holographic memory system, focusing on its application in adaptive hardware systems. It presents experimental results on the performance and reliability of the ORGA under radiation conditions, comparing it with traditional FPGAs.
关键词： Adaptive Hardware,Radiation Hardness,FPGA,Optically Reconfigurable Gate Array,Holographic Memory
更新于2025-09-19 17:15:36
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[IEEE 2018 International Semiconductor Conference (CAS) - Sinaia (2018.10.10-2018.10.12)] 2018 International Semiconductor Conference (CAS) - Effect of the Deposition Conditions on Titanium Oxide Thin Films Properties
摘要： This paper presents the fabrication and characterization of titanium oxide thin films deposited by Pulsed Laser Deposition in different experimental conditions. The scope of this work is to investigate the effect of the oxygen pressure in the deposition chamber on the material properties. Thin films characterizations include the mechanical and tribological properties such as the modulus of elasticity, hardness and the adhesion force. The mechanical and tribological properties of the materials are experimentally determined by using the atomic force microscopy technique. The effect of the oxygen pressure on the film thickness is analyzed. As the pressure in the deposition process decreases, the thickness of the thin films increases, respectively. The surfaces roughness increases as the deposition pressure decreases that leads to a decrease of adhesion forces. Hardness and modulus of elasticity increases as the deposition pressure decreases. This study shows that the mechanical and tribological properties of the investigated thin films strongly depend on the grain size and the films density, which are influenced by the deposition conditions (the oxygen pressure in the deposition chamber).
关键词： pulsed laser deposition,thin films,adhesion force,hardness,modulus of elasticity
更新于2025-09-19 17:15:36
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Influence of Al2O3 addition on the hardness and in vitro corrosion behavior of laser synthesized Ti-Al2O3 coatings on Ti-6Al-4V
摘要： Titanium alloy (Ti-6Al-4V) has been mostly used for medical implants due to its good chemical and mechanical properties. However, this alloy has tendency to emanate toxic V and Al due to its low corrosion resistance in body conditions. In this work, an experimental study of laser cladding Ti-Al2O3 coatings with different Al2O3 fractions (5 wt.% Al2O3, 8 wt.% Al2O3, and 10 wt.% Al2O3) was carried out to establish a coating which could improve the hardness and corrosion resistance of Ti-6Al-4V alloy. Laser parameters of 900 W power, 0.6 m/min laser scan speed, and 2 l/min powder feed were used in this research. The microstructure, phase constituents, microhardness, and corrosion of the resultant coatings were characterized by scanning electron microscope (SEM), optical microscope (OPM), X-Ray Diffractometer (XRD), Vicker hardness tester, and potentiostat respectively. Results showed that a defect free coating was achieved at a coating with less Al2O3 content. Increase in Al2O3 addition resulted in increment of hardness with Ti-10 wt.% Al2O3 coating achieving an optimum hardness of about 2.2 times greater than that of the substrate. Moreover, considerable increment in corrosion resistance of Ti-6Al-4Valloy was achieved after laser deposition of various Ti-Al2O3 admixed coatings. An optimal corrosion rate reduction of about 81% and polarization resistance increment of 709% over the substrate were achieved at Ti-5 wt.% Al2O3 due to low porosity within the coating layer. It has been established that fabricating Ti-Al2O3 on Ti6Al4V through laser could be used in improving the surface hardness values and corrosion resistance.
关键词： Ti-Al2O3 coatings,Corrosion behavior,Laser cladding,Hardness properties,Ti-6Al-4Valloy
更新于2025-09-19 17:15:36
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Microstructure and properties of TiAlN/AlN multilayers with different modulation periods
摘要： The effects of thicknesses of AlN layer on microstructures and properties of TiAlN/AlN multilayers were studied. TiAlN/AlN multilayers had been deposited on 304 stainless steels by magnetron sputtering system. The microstructure and properties of the multilayers were characterized by X-ray diffraction, vicker hardness tester, atomic force microscopy, and friction abrasion tester. The results show that under “template effect” of TiAlN layer, AlN layer is changed into face-centered cubic and grow epitaxially with TiAlN layer. The superhardness effect could be generated in the region with sharp interface. With the thickness of AlN layer in TiAlN/AlN multilayers, the properties of multilayer are firstly increase and then decrease. When the AlN layer thickness is 3.2nm, the multilayer has excellent properties. The hardness of multilayer is 30.98GPa, the roughness of multilayer is 20.2nm, and the coefficient of friction of multilayer is 0.61.
关键词： Tribological property,Hardness,Modulation period,TiAlN/AlN
更新于2025-09-19 17:15:36
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Avalia??o do grau de convers?o de resinas compostas fotoativadas em diferentes tempos e potências
摘要： Introduction: Adequate polymerization is a crucial factor in obtaining optimal physical properties and clinical performance of composite resins. Objective: To evaluate the degree of conversion (DC) and hardness of composite resins photoactivated in different power densities and curing times. Materials and method: Eighty (n=80) composite resin specimens (FiltekTM Z350 XT color A2B) with 4 mm of diameter and 2 mm of thickness were produced, whereas forty (n=40) were meant for the evaluation of degree of conversion and forty (n=40) for hardness. Ten (n=10) specimens were produced for each group assessed, whereas five were meant for the evaluation of the degree of conversion and five for hardness (P10T2; P7T2; P4T2; P1T2; P10T4; P7T4; P4T4; P1T4). Resins of the degree of conversion and hardness were photoactivated by LED for 20 seconds at power intensities of 1000 mW/cm2, 700 mW/cm2, 400 mW/cm2, and 100 mW/cm2, for groups P10T2, P7T2, P4T2, and P1T2, respectively. Groups P10T4, P7T4, P4T4, and P1T4 were cured in the same power intensity, but for 40 seconds. Result: Regarding the degree of conversion, P1T2 resins had the lowest mean value of 22.67 %, and P10T4 resins had the highest mean value of 87.9%. As for hardness, P1T2 resins also had the lowest mean of 30.93 kgf/mm2, and P10T4 had the highest mean of 82.02 kgf/mm2. Conclusion: The higher the power of the curing unit, the higher the DC and hardness of composites resins. The results of this study suggest that a device with intensity of 100 mW/cm2 does not provide satisfactory degree of conversion and hardness, compromising the performance of the restorative material.
关键词： Composite resins,Hardness,Polymerization
更新于2025-09-19 17:15:36
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Surface microstructural characteristics and hardness of Cr-coated Zr702 sheet processed by pulsed laser
摘要： Microstructural characteristics and hardness of Cr-coated Zr702 sheet after the laser surface treatment (LST) were characterized and investigated by combined use of electron backscatter diffraction, electron channeling contrast imaging, energy dispersive spectrometry and hardness measurement. Results show that after the LST processing at 100 W, three zones with different microstructural characteristics are presented from the surface to the matrix: melted zone (MZ), solid-state phase transformation zone (SSPTZ) and matrix. Surface alloying with Cr occurs in the MZ, leading to the formation of a large number of discontinuous netlike ZrCr2 Laves phases. The SSPTZ is comprised of untransformed bulk α grains with internal substructures and fine martensitic plates. The appearance of such substructures can be attributed to dislocation movements induced by thermal stresses while the martensitic plates result from rapid β→α transformation induced by the pulsed laser. Hardness measurements show that the LST can remarkably increase surface hardness (by ~110%) of the Cr-coated Zr702 sheet, which can be ascribed to strengthening/hardening effects by solid solution of Cr, the formation of dense second phases and significant grain refinement.
关键词： Electron backscatter diffraction,Microstructure,Hardness,Laves phase,Zr702 sheet,Laser surface processing
更新于2025-09-19 17:13:59
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Laser Surface Hardening of Gun Metal Alloys
摘要： The effect of laser irradiation with different numbers of laser shots on the microstructure, the surface, and the hardness of gun metal alloy was studied by a KrF pulsed excimer laser system, X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and Vickers hardness test. The influence of 100–500 laser shots was irradiated on the surface hardness profile and on the microstructure of gunmetal alloy. XRD results showed the maximum 2θ shift, the maximum full width of half maximum FWHM, the maximum dislocation density, and the minimum crystallite size for the sample irradiated with 300 laser shots. The hardness was measured in three different regions at the laser irradiated spot, and it was found that maximum hardness was present at the heat affected zone for all samples. The hardness value of the un-irradiated sample of gun metal was 180, and the value increased up to 237 by raising the number of laser shots up to 300. The peak value of surface hardness of the laser treated sample was 32% higher than the un-irradiated sample. The Raman shift of the un-exposed sample was 605 cm?1 and shifted to a higher value of wave number at 635 cm?1 at 300 laser shots. The hardness value was decreased by further increasing the number of laser shots up to 500. The samples irradiated with 400 and 500 laser shots exhibited smaller hardness and dislocation defect density, which was assigned to possible annealing caused by irradiation.
关键词： hardness,heat affected zones,laser irradiation,gun metal
更新于2025-09-19 17:13:59