Quasi Two-Dimensional Evaporation and Boiling Under Reduced Pressure

2017 ◽  
Vol 25 (01) ◽  
pp. 1750003 ◽  
Author(s):  
Keita Ogawa ◽  
Yuichi Yasumoto ◽  
Mitsuhiro Matsumoto ◽  
Hidenobu Wakabayashi
Keyword(s):  
Organic Liquid ◽  
Incident Light ◽  
Thin Liquid Film ◽  
Glass Plate ◽  
Float Glass ◽  
Laminated Plates ◽  
Two Dimensional ◽  
Test Liquid ◽  
Reduced Pressure ◽  
Solvent Vapor

To study the washing mechanism of laminated plates with solvent vapor, we have experimentally investigated evaporation dynamics of liquid confined between solid plates under reduced pressure. As the test liquid, we use deionized water and several organic compounds. To visualize the fluid motion in the thin gaps, we adopt glass plates. When a test liquid is sandwiched between a normal (float) glass plate and a ground (sand-blasted) one, vertically incident light passes through the plates without much scattering; once the liquid starts to evaporate, dried rough surface of the ground glass scatters the light and we can monitor the flow pattern. Based on the transmitted light intensity, the whole plate area is categorized into three regions; completely wet, completely dry, and semi-dry one; the last one is supposed to be the state that thin liquid film spreads on the plate. In the case of water, many tiny spots of semi-dry region appear and expand at the initial stage, which is probably cavitation of dissolved gas. In organic liquid cases, evaporation seems to start from the edges of the plates. At a later stage, the semi-dry region expands with complicated branching patterns. In all cases, occasional rapid motions of liquid were observed, which correspond to two-dimensional flash boiling. We also investigated the influence of the control pressure, the surface roughness, and the plate deformation.

scholarly journals Rational Design and Simulation of Two-Dimensional Perovskite Photonic Crystal Absorption Layers Enabling Improved Light Absorption Efficiency for Solar Cells

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2460
Author(s):  
Jian Zou ◽  
Mengnan Liu ◽  
Shuyu Tan ◽  
Zhijie Bi ◽  
Yong Wan ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Solar Cells ◽  
Photonic Crystal ◽  
Incident Light ◽  
Absorption Efficiency ◽  
Utilization Efficiency ◽  
Photonic Crystal Structure ◽  
Two Dimensional ◽  
Photoelectric Conversion ◽  
Absorption Layer

A two-dimensional perovskite photonic crystal structure of Methylamine lead iodide (CH3NH3PbI3, MAPbI3) is rationally designed as the absorption layer for solar cells. The photonic crystal (PC) structure possesses the distinct “slow light” and band gap effect, leading to the increased absorption efficiency of the absorption layer, and thus the increased photoelectric conversion efficiency of the battery. Simulation results indicate that the best absorption efficiency can be achieved when the scattering element of indium arsenide (InAs) cylinder is arranged in the absorption layer in the form of tetragonal lattice with the height of 0.6 μm, the diameter of 0.24 μm, and the lattice constant of 0.4 μm. In the wide wavelength range of 400–1200 nm, the absorption efficiency can be reached up to 82.5%, which is 70.1% higher than that of the absorption layer without the photonic crystal structure. In addition, the absorption layer with photonic crystal structure has good adaptability to the incident light angle, presenting the stable absorption efficiency of 80% in the wide incident range of 0–80°. The results demonstrate that the absorption layer with photonic crystal structure can realize the wide spectrum, wide angle, and high absorption of incident light, resulting in the increased utilization efficiency of solar energy.

scholarly journals Investigation of the Heteroepitaxial Process Optimization of Ge Layers on Si (001) by RPCVD

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 928
Author(s):  
Yong Du ◽  
Zhenzhen Kong ◽  
Muhammet Toprak ◽  
Guilei Wang ◽  
Yuanhao Miao ◽  
...  
Keyword(s):  
High Temperature ◽  
Buffer Layer ◽  
Layer Thickness ◽  
Growth Temperature ◽  
Crystalline Quality ◽  
Initial Growth ◽  
Two Dimensional ◽  
High Quality ◽  
Reduced Pressure

This work presents the growth of high-quality Ge epilayers on Si (001) substrates using a reduced pressure chemical vapor deposition (RPCVD) chamber. Based on the initial nucleation, a low temperature high temperature (LT-HT) two-step approach, we systematically investigate the nucleation time and surface topography, influence of a LT-Ge buffer layer thickness, a HT-Ge growth temperature, layer thickness, and high temperature thermal treatment on the morphological and crystalline quality of the Ge epilayers. It is also a unique study in the initial growth of Ge epitaxy; the start point of the experiments includes Stranski–Krastanov mode in which the Ge wet layer is initially formed and later the growth is developed to form nuclides. Afterwards, a two-dimensional Ge layer is formed from the coalescing of the nuclides. The evolution of the strain from the beginning stage of the growth up to the full Ge layer has been investigated. Material characterization results show that Ge epilayer with 400 nm LT-Ge buffer layer features at least the root mean square (RMS) value and it’s threading dislocation density (TDD) decreases by a factor of 2. In view of the 400 nm LT-Ge buffer layer, the 1000 nm Ge epilayer with HT-Ge growth temperature of 650 °C showed the best material quality, which is conducive to the merging of the crystals into a connected structure eventually forming a continuous and two-dimensional film. After increasing the thickness of Ge layer from 900 nm to 2000 nm, Ge surface roughness decreased first and then increased slowly (the RMS value for 1400 nm Ge layer was 0.81 nm). Finally, a high-temperature annealing process was carried out and high-quality Ge layer was obtained (TDD=2.78 × 107 cm−2). In addition, room temperature strong photoluminescence (PL) peak intensity and narrow full width at half maximum (11 meV) spectra further confirm the high crystalline quality of the Ge layer manufactured by this optimized process. This work highlights the inducing, increasing, and relaxing of the strain in the Ge buffer and the signature of the defect formation.

scholarly journals Novel Two-Dimensional Layered MoSi2Z4 (Z = P, As): New Promising Optoelectronic Materials

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 559
Author(s):  
Hui Yao ◽  
Chao Zhang ◽  
Qiang Wang ◽  
Jianwei Li ◽  
Yunjin Yu ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Incident Light ◽  
Optoelectronic Devices ◽  
Large Family ◽  
Middle Layer ◽  
Optoelectronic Device ◽  
First Principles Calculation ◽  
Polarization Angle ◽  
Two Dimensional ◽  
Conducting Materials

Very recently, two new two-dimensional (2D) layered semi-conducting materials MoSi2N4 and WSi2N4 were successfully synthesized in experiments, and a large family of these two 2D materials, namely MA2Z4, was also predicted theoretically (Science, 369, 670 (2020)). Motivated by this exciting family, in this work, we systematically investigate the mechanical, electronic and optical properties of monolayer and bilayer MoSi2P4 and MoSi2As4 by using the first-principles calculation method. Numerical results indicate that both monolayer and bilayer MoSi2Z4 (Z = P, As) present good structural stability, isotropic mechanical parameters, moderate bandgap, favorable carrier mobilities, remarkable optical absorption, superior photon responsivity and external quantum efficiency. Especially, due to the wave-functions of band edges dominated by d orbital of the middle-layer Mo atoms are screened effectively, the bandgap and optical absorption hardly depend on the number of layers, providing an added convenience in the experimental fabrication of few-layer MoSi2Z4-based electronic and optoelectronic devices. We also build a monolayer MoSi2Z4-based 2D optoelectronic device, and quantitatively evaluate the photocurrent as a function of energy and polarization angle of the incident light. Our investigation verifies the excellent performance of a few-layer MoSi2Z4 and expands their potential application in nanoscale electronic and optoelectronic devices.

Absorption and Emission of Light in Quantum Structures

2020 ◽  
pp. 343-418
Author(s):  
Vurgaftman Igor
Keyword(s):  
Quantum Wells ◽  
Radiative Recombination ◽  
Quantum Wires ◽  
Incident Light ◽  
Optical Gain ◽  
Two Dimensional ◽  
Intersubband Transitions ◽  
Recombination Rates ◽  
Zinc Blende ◽  
Two Dimensional Materials

This chapter shows how to calculate the absorption coefficient, optical gain, and radiative recombination rates in quantum wells and superlattices. A detailed treatment of both interband and intersubband transitions is presented, and their differences and similarities are considered in detail. The optical properties of wurtzite quantum wells and zinc-blende quantum wires and dots are also discussed. Finally, the interaction of excitonic transitions with incident light in quantum wells is considered as a model for other two-dimensional materials.

Accessing Highly Oriented Two-Dimensional Perovskite Films via Solvent-Vapor Annealing for Efficient and Stable Solar Cells

Nano Letters ◽  
2020 ◽  
Vol 20 (12) ◽  
pp. 8880-8889
Author(s):  
Xiaoming Zhao ◽  
Tianran Liu ◽  
Alan B. Kaplan ◽  
Chao Yao ◽  
Yueh-Lin Loo
Keyword(s):  
Solar Cells ◽  
Two Dimensional ◽  
Solvent Vapor ◽  
Vapor Annealing ◽  
Solvent Vapor Annealing

Numerical Investigation of EHD Conduction Pumping of Liquid Film With Phase-Change

2007 ◽  
Author(s):  
Miad Yazdani ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Heat Transfer ◽  
Liquid Film ◽  
Phase Change ◽  
Flow System ◽  
Thin Liquid Film ◽  
Finite Thickness ◽  
Constant Heat Flux ◽  
Two Dimensional ◽  
Enhanced Heat Transfer ◽  
Constant Heat

Electrohydrodynamic (EHD) conduction pumping is associated with the heterocharge layers of finite thickness in the vicinity of the electrodes, generated by the process of dissociation of the neutral electrolytic species and recombination of the generated ions. This paper numerically investigates the EHD conduction pumping of a thin liquid film in the presence of phase change. The flow system comprises a liquid film flowing over a two-dimensional flat plate while the vapor phase extended far beyond the interface to result in almost motionless vapor. The channel is separated into four different sections: the entrance, electrode, evaporation, and downstream sections. The entrance, electrode and downstream regions are adiabatic while a constant heat flux is applied in the evaporation side. The concept of EHD conduction pumping of liquid film in the presence of phase change is demonstrated in this paper. The enhanced heat transfer due to conduction pumping is evaluated.

Three-Dimensional Shear Driven Thin Liquid Film in a Duct

2006 ◽  
Author(s):  
H. Lan ◽  
M. Friedrich ◽  
B. F. Armaly ◽  
J. A. Drallmeier
Keyword(s):  
Film Thickness ◽  
Liquid Film ◽  
Flow Rate ◽  
High Speed ◽  
Volume Flow Rate ◽  
Incident Light ◽  
Thin Liquid Film ◽  
Air Flow ◽  
Three Dimensional ◽  
Vof Model

Measurements and predictions of three-dimensional shear driven thin liquid films by turbulent air flow in a duct are reported. FLUENT - CFD code is used to perform the numerical simulations and the Reynolds Averaged Navier-Stokes and continuity equations along with the Volume of Fluid (VOF) model and the realizable k-ε turbulence model are implemented for this task. Film thickness and width are reported as a function of air flow rate, liquid film volume flow rate and surface tension, and a comparison with preliminary measured results is made. The thickness of the shear driven liquid film is measured using an interferometric technique that makes use of the phase shift between the reflection of incident light from the top and bottom surfaces of the thin liquid film. The spatial resolution is determined based on the spot size of the incident light, which for the current configuration of the transmitting optics is approximately 10 microns. The resulting fringe pattern is imaged using a high-speed imaging camera operating at 2000 frames per second. The technique has proved successful in measuring thickness between 100 and 900 microns in these shear driven films. Simulation results reveal that higher gas flow velocity decreases the film thickness but increases its width, while higher liquid film flow rate increases the film thickness and increases its width. Reasonable comparison appears to exist between preliminary measured and simulated results.

Method of Grouping and Cutting Pattern of Cutting Problem of Two-Dimensional Plate

2012 ◽  
Vol 462 ◽  
pp. 194-198
Author(s):  
Xue Shao Qiu ◽  
Yin He Zhang ◽  
Jie Yun Wu ◽  
Xue Man Ma
Keyword(s):  
Integer Programming ◽  
Programming Model ◽  
Glass Plate ◽  
Time Algorithm ◽  
Raw Material ◽  
Two Dimensional ◽  
Material Usage ◽  
Cutting Pattern ◽  
Specific Implementation ◽  
Pattern Problem

Through a case of glass plate cutting, two-dimensional cutting pattern problem of rectangular blanks is discussed. The raw material is cut and layout by applying the method of grouping and two-stage cutting pattern types. Here first all the blanks are divided into different groups based on certain requirement, and then two-dimensional cutting pattern problem is transformed into two one-dimensional cutting problems. Through constructing an integer programming model, the cutting program of the raw material can be obtained step by step by calculating in LINGO. Because here the precise algorithm of integer programming is applied, which is not the time algorithm of polynomial, in the specific implementation, there shouldn’t be more variables, so all the data should be divided into different groups to calculate. In each group, there should be no more than 6 blanks, which are grouped according to their size. This algorithm is simple and easy to operate with a high material usage.

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