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排序方式: 共有647条查询结果,搜索用时 15 毫秒
91.
Ida Sadeghi Kevin Ye Michael Xu Yifei Li James M. LeBeau Rafael Jaramillo 《Advanced functional materials》2021,31(45):2105563
The making of BaZrS3 thin films by molecular beam epitaxy (MBE) is demonstrated. BaZrS3 forms in the orthorhombic distorted-perovskite structure with corner-sharing ZrS6 octahedra. The single-step MBE process results in films smooth on the atomic scale, with near-perfect BaZrS3 stoichiometry and an atomically sharp interface with the LaAlO3 substrate. The films grow epitaxially via two competing growth modes: buffered epitaxy, with a self-assembled interface layer that relieves the epitaxial strain, and direct epitaxy, with rotated-cube-on-cube growth that accommodates the large lattice constant mismatch between the oxide and the sulfide perovskites. This work sets the stage for developing chalcogenide perovskites as a family of semiconductor alloys with properties that can be tuned with strain and composition in high-quality epitaxial thin films, as has been long-established for other systems including Si-Ge, III-Vs, and II-VIs. The methods demonstrated here also represent a revival of gas-source chalcogenide MBE. 相似文献
92.
Aditya T. Kasarekar Nathan W. Bolander Farshid Sadeghi Spyros Tseregounis 《International Journal of Mechanical Sciences》2007,49(6):690-703
This paper presents a numerical model that maps the evolution of contact pressure and surface profile of Hertzian rough contacting bodies in fretting wear under partial slip conditions. The model was used to determine the sliding distance of the contacting surface asperities for one cycle of tangential load. The contact pressure and sliding distance were used with Archard's wear law to determine local wear at each surface asperity. Subsequently, the contact surface profile was updated due to wear. The approach developed in this study allows for implementation of simulated and/or measured real rough surfaces and study the effects of various statistical surface properties on fretting wear. The results from this investigation indicate that an elastic–perfectly plastic material model is superior to a completely elastic material model. Surface roughness of even small magnitudes is a major factor in wear calculations and cannot be neglected. 相似文献
93.
Morphology enhancement of TiO2/PVP composite nanofibers based on solution viscosity and processing parameters of electrospinning method
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Soraya Mirmohammad Sadeghi Mohammadreza Vaezi Asghar Kazemzadeh Roghayeh Jamjah 《应用聚合物科学杂志》2018,135(23)
In this work, different sol solutions with various titanium tetraisopropoxide (TIP)/glacial acetic acid ratios in 2‐propanol with 5 wt % poly(vinyl pyrrolidone) (PVP) (Mw = 360,000 g/mol) were prepared and electrospun. Composition of the prepared sols and as‐spun TiO2/PVP nanofibers were determined by Fourier transform infrared and Raman spectroscopy methods. Morphology of the electrospun TiO2/PVP nanofibers was studied by scanning electron microscopy and transmission electron microscopy (TEM) techniques. Rheometry measurements of the sol solutions showed decrease of viscosity upon the addition of TIP to the polymer solutions with constant polymer and acid concentrations. The sol solution having the lowest viscosity (at shear rate 10 s?1) but the highest TIP/glacial acetic acid ratio showed beaded nanofibers morphology when electrospun under 10 and 12 kV applied voltage while injection rate, needle tip to collector distance, and needle gauge were kept constant. However, smooth electrospun TiO2/PVP composite nanofibers with the average nanofibers diameters (148 ± 79 nm) were achieved under the same condition when applied voltage increased to 15 kV. TEM micrographs of the electrospun TiO2/PVP nanofiber showed that the TiO2 particles with continuous structure are formed at the middle of the nanofiber and distributed along its axis. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46337. 相似文献
94.
Effect of polyethylenimine addition and washing on stability and electrophoretic deposition of Co3O4 nanoparticles
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Ali Asghar Sadeghi Ghazvini Ehsan Taheri‐Nassaj Babak Raissi Reza Riahifar Maziar Sahba Yaghmaee 《Journal of the American Ceramic Society》2018,101(2):553-561
In this work, the parameters of cobalt oxide suspension such as conductivity, zeta potential, particle size, stability, and finally the electrophoretic behavior of particles in the absence and presence of polyethylenimine (PEI) in acetone medium were investigated. Also, the effects of washing on the stability and electrophoretic deposition of Co3O4 were studied. Characterization of the obtained layer by optical microscopy revealed that there was no deposition in the suspension without PEI, while a uniform layer was formed in the presence of PEI additive. Scanning electron microscopy (SEM) results confirmed the uniformity of layer obtained in acetone using PEI additive. Moreover, SEM results demonstrated that more porous microstructures were obtained at longer deposition durations. The difference in the porosity of the layers, as indicated by the SEM micrographs, is attributed to increase in the deposition time. 相似文献
95.
NEt3 was found to be a simple, mild, and efficient catalyst for the synthesis of 2-aminothiazole derivatives from the reaction of different ketones, thiourea, and iodine in EtOH media under mild conditions for the first time. Present methodology offers several advantages, such as simple procedure, shorter reaction times, and milder conditions, and takes place at reflux temperature, with operational simplicity and with excellent yields. 相似文献
96.
Reservoir oil and gas content tends to rise up to the surface as long as their potential energy levels are sufficient. In order to amplify this energy, either during the time when oil is uprising on its inherent energy or since after, so as to facilitate the traveling of oil to the surface, enhanced oil recovery (EOR) methods come into play. Furthermore, the increasing demand for oil from one hand, and the shrinkage of producible reserves on the other hand, have made it unavoidable to undertake EOR techniques. Built in this research was a 10-element model of reservoir fluid to simulate its behavior. Furthermore, slim tube simulation was undertaken to determine minimum miscibility pressure for various gases. Then, different scenarios of natural depletion, CO2 injection, methane injection, and water injection were simulated by ECLIPSE 300 software package with the results of different scenarios compared. The results indicated water injection to be associated with higher recovery factor. 相似文献
97.
98.
M. H. Sadeghi M. J. Haddad T. Tawakoli M. Emami 《The International Journal of Advanced Manufacturing Technology》2009,44(5-6):487-500
Titanium and its alloys are attractive materials due to their unique high strength–weight ratio that is maintained at elevated temperatures and their exceptional corrosion resistance. The major application of titanium has been in the aerospace industry. On the other hand, titanium and its alloys are notorious for their poor thermal properties and are classified as difficult-to-machine materials. The problems that arise during grinding of titanium alloys are attributed to the high specific energy and high grinding zone temperature. Significant progress has been made in dry and semidry machining recently, and minimal quantity lubrication (MQL) machining in particular has been accepted as a successful semidry application because of its environmentally friendly characteristics. A number of studies have shown that MQL machining can show satisfactory performance in practical machining operations. However, there has been few investigation of MQL grinding of special alloys like titanium alloys and the cutting fluids to be used in MQL grinding of these alloys. In this study, vegetable and synthetic esters oil are compared on the basis of the surface quality properties that would be suitable for MQL applications. The cutting performance of fluids is also evaluated using conventional wet (fluid) grinding of Ti–6Al–4V. As a result, synthetic ester oil is found to be optimal cutting fluids for MQL grinding of Ti–6Al–4V. 相似文献
99.
Sadeghi S Ding H Shah GJ Chen S Keng PY Kim CJ van Dam RM 《Analytical chemistry》2012,84(4):1915-1923
We demonstrate a new approach to impedance measurement on digital microfluidics chips for the purpose of simple, sensitive, and accurate volume and liquid composition measurement. Adding only a single series resistor to existing AC droplet actuation circuits, the platform is simple to implement and has negligible effect on actuation voltage. To accurately measure the complex voltage across the resistor (and hence current through the device and droplet), the designed system is based on software-implemented lock-in amplification detection of the voltage drop across the resistor which filters out noise, enabling high-resolution and low-limit signal recovery. We observe picoliter sensitivity with linear correlation of voltage to volume extending to the microliter volumes that can be handled by digital microfluidic devices. Due to the minimal hardware, the system is robust and measurements are highly repeatable. The detection technique provides both phase and magnitude information of the real-time current flowing through the droplet for a full impedance measurement. The sensitivity and resolution of this platform enables it to distinguish between various liquids which, as demonstrated in this paper, could potentially be extended to quantify solute concentrations, liquid mixtures, and presence of analytes. 相似文献
100.
D. Shahriari A. Amiri M. H. Sadeghi 《Journal of Materials Engineering and Performance》2010,19(5):633-642
In hot forging of Nimonic 115, it is desirable to determine friction coefficients. Changing magnitudes of temperature and
type of lubricant at the surface of the workpiece and dies influence friction coefficient. This paper describes an experimental
investigation of friction under hot forging conditions using the ring compression test. The 3D FEM simulations were used to
derive the friction calibration curves and to evaluate material deformation, geometric changes, and load-displacement results.
A series of ring compression tests were carried out to obtain friction coefficients for a number of lubricants including mica
plate, glass powder, graphite powder, and dry condition. The experiments show how the variations in temperature at the interface
affected frictional behavior. On the basis of these results, mica is recommended for hot forging of Nimonic 115 and its friction
coefficient is approximately 0.3. 相似文献