Stress Assisted Controlled Fabrication of Nano Channels and Their Flow Characteristics

2004 ◽  
Author(s):  
Sathyanarayanan Mani ◽  
Taher M. Saif
Keyword(s):  
Thin Film ◽  
Experimental Data ◽  
Silicon Dioxide ◽  
Silicon Substrate ◽  
Flow Characteristics ◽  
Square Root ◽  
Proportionality Constant ◽  
Flow Through ◽  
Oxide Stress ◽  
Stress Raisers

A method to fabricate nano channels narrower than 50nm without the need for any nano lithography is presented. The nano channels are formed by cracking a thin film of silicon dioxide on a silicon substrate by residual stress alone. However, for controlled initiation of cracks on oxide, stress raisers are planted on a silicon substrate by deep RIE. These channels are used to study capillary driven fluid flow through nanochannels. Experimental analysis suggests that the flow rate is inversely proportional to the square root of time, which is in agreement with the theoretical model. From the theoretical plot that fits the experimental data the value of the proportionality constant is determined. From this value it is possible to back calculate the meniscus contact angle if we know the surface energy of the fluid or vice versa.

Indentation Fracture Studies of a BaTiO3 Thin Film on a Silicon Substrate

1995 ◽  
Vol 403 ◽  
Author(s):  
Wai-Ming Ho ◽  
Ran Fu ◽  
Kai-Tak Wan ◽  
Ji Chou ◽  
Tong-Yi Zhang
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Residual Stresses ◽  
Silicon Substrate ◽  
Square Root ◽  
Indentation Fracture ◽  
Batio3 Thin Film

AbstractIt has been experimentally and theoretically found that the critical applied stress intensity factor for indentation cracking also depends linearly on the reciprocal of the square root of crack length when the indentation fracture technique is used to measure residual stresses in thin films.

Flow characteristics and a permeability model in nanoporous media with solid-liquid interfacial effects

2017 ◽  
Vol 5 (1) ◽  
pp. SB1-SB8 ◽  
Author(s):  
Jiulong Wang ◽  
Hongqing Song ◽  
Weiyao Zhu ◽  
Yuhe Wang ◽  
John Killough
Keyword(s):  
Thin Film ◽  
Solid Wall ◽  
Flow Characteristics ◽  
Average Pore ◽  
Flow Rates ◽  
Interfacial Effects ◽  
Nanoporous Media ◽  
Flow Through ◽  
Repulsive Forces ◽  
Solid Liquid

Molecular dynamics simulations of water flow through nanotubes have demonstrated higher flow rates than the flow rates predicted using classical models and a significant change in flow patterns due to the thin film that forms on the solid wall of the tubes. We have developed a two-region analytical model that described the flow characteristics and permeability of fluid flow through nanoporous media and considered the solid-liquid interfacial effects. Our model considers the influence of various interfacial effects, including long-range van der Waals forces, double-layer repulsive forces, and short-range structure repulsive forces, and it establishes relationships between the permeability and the average pore diameter, porosity, surface diffusion, and contact angle by numerical calculations. Our results indicate that the permeability calculated using the present model (with interfacial effects) is more than 30 times the results that were calculated using the Kozeny-Carman equation (without interfacial effects). The thickness of the thin film significantly affects the flow characteristics. We have gained new insight and guidance regarding the development of nanoscale pore reservoirs, such as shale gas and shale oil.

scholarly journals Review and a Theoretical Approach on Pressure Drop Correlations of Flow through Open-Cell Metal Foam

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3153
Author(s):  
Huizhu Yang ◽  
Yongyao Li ◽  
Binjian Ma ◽  
Yonggang Zhu
Keyword(s):  
Experimental Data ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Metal Foam ◽  
Flow Characteristics ◽  
Metal Foams ◽  
High Porosity ◽  
Open Cell ◽  
Wide Range ◽  
Flow Through

Due to their high porosity, high stiffness, light weight, large surface area-to-volume ratio, and excellent thermal properties, open-cell metal foams have been applied in a wide range of sectors and industries, including the energy, transportation, aviation, biomedical, and defense industries. Understanding the flow characteristics and pressure drop of the fluid flow in open-cell metal foams is critical for applying such materials in these scenarios. However, the state-of-the-art pressure drop correlations for open-cell foams show large deviations from experimental data. In this paper, the fundamental governing equations of fluid flow through open-cell metal foams and the determination of different foam geometry structures are first presented. A variety of published models for predicting the pressure drop through open-cell metal foams are then summarized and validated against experimental data. Finally, two empirical correlations of permeability are developed and recommended based on the model of Calmidi. Moreover, Calmidi’s model is proposed to calculate the Forchheimer coefficient. These three equations together allow calculating the pressure drop through open-cell metal foam as a function of porosity and pore diameter (or strut diameter) in a wide range of porosities ε = 85.7–97.8% and pore densities of 10–100 PPI. The findings of this study greatly advance our understanding of the flow characteristics through open-cell metal foam and provide important guidance for the design of open-cell metal foam materials for different engineering applications.

Comparison of Aerobic and Anoxic-Aerobic Digestion of Waste Activated Sludge

1985 ◽  
Vol 17 (8) ◽  
pp. 1475-1478 ◽  
Author(s):  
A P. C. Warner ◽  
G. A. Ekama ◽  
G v. R. Marais
Keyword(s):  
Experimental Data ◽  
Activated Sludge ◽  
Waste Activated Sludge ◽  
Activated Sludge Process ◽  
Cycle Times ◽  
Waste Sludge ◽  
Volatile Solids ◽  
In Series ◽  
Flow Through ◽  
Theoretical Simulations

The laboratory scale experimental investigation comprised a 6 day sludge age activated sludge process, the waste sludge of which was fed to a number of digesters operated as follows: single reactor flow through digesters at 4 or 6 days sludge age, under aerobic and anoxic-aerobic conditions (with 1,5 and 4 h cycle times) and 3-in-series flow through aerobic digesters each at 4 days sludge age; all digesters were fed draw-and-fill wise once per day. The general kinetic model for the aerobic activated sludge process set out by Dold et al., (1980) and extended to the anoxic-aerobic process by van Haandel et al., (1981) simulated accurately all the experimental data (Figs 1 to 4) without the need for adjusting the kinetic constants. Both theoretical simulations and experimental data indicate that (i) the rate of volatile solids destruction is not affected by the incorporation of anoxic cycles and (ii) the specific denitrification rate is independent of sludge age and is K4T = 0,046(l,029)(T-20) mgNO3-N/(mg active VSS. d) i.e. about 2/3 of that in the secondary anoxic of the single sludge activated sludge stystem. An important consequence of (i) and (ii) above is that denitrification can be integrated easily in the steady state digester model of Marais and Ekama (1976) and used for design (Warner et al., 1983).

Residual Stress Measurement in Silicon Substrate After Local Thermal Oxidation Using Microscopic Raman Spectroscopy

1991 ◽  
Vol 226 ◽  
Author(s):  
Hideo Miura ◽  
Hiroshi Sakata ◽  
Shinji Sakata Merl
Keyword(s):  
Residual Stress ◽  
Raman Spectroscopy ◽  
Tensile Stress ◽  
Oxide Film ◽  
Film Thickness ◽  
Silicon Dioxide ◽  
Thermal Oxidation ◽  
Silicon Substrate ◽  
Nitride Film ◽  
Oxide Film Thickness

AbstractThe residual stress in silicon substrates after local thermal oxidation is discussed experimentally using microscopic Raman spectroscopy. The stress distribution in the silicon substrate is determined by three main factors: volume expansion of newly grown silicon–dioxide, deflection of the silicon–nitride film used as an oxidation barrier, and mismatch in thermal expansion coefficients between silicon and silicon dioxide.Tensile stress increases with the increase of oxide film thickness near the surface of the silicon substrate under the oxide film without nitride film on it. The tensile stress is sometimes more than 100 MPa. On the other hand, a complicated stress change is observed near the surface of the silicon substrate under the nitride film. The tensile stress increases initially, as it does in the area without nitride film on it. However, it decreases with the increase of oxide film thickness, then the compressive stress increases in the area up to 170 MPa. This stress change is explained by considering the drastic structural change of the oxide film under the nitride film edge during oxidation.

ON AN ORIENTATION TRANSITION IN NEMATIC LIQUID CRYSTALS INDUCED BY THE THICKNESS OF THE SAMPLE

1993 ◽  
Vol 07 (18) ◽  
pp. 1215-1222
Author(s):  
A. L. ALEXE-IONESCU
Keyword(s):  
Experimental Data ◽  
Phase Transitions ◽  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Tilt Angle ◽  
Critical Thickness ◽  
Large Range ◽  
Square Root ◽  
Chiral Molecules ◽  
Homeotropic Orientation

An orientation transition observed in nematic liquid crystal samples, induced by the thickness, is interpreted in a new way. By supposing that the nematic liquid crystal contains chiral impurities, it is shown that the homeotropic orientation is stable only for thicknesses smaller than a critical one, and is dependent on the concentration of the chiral molecules. At the critical thickness, the transition from the homeotropic orientation to the distorted one is characterized by a tilt angle proportional to the square root of the actual thickness minus the critical one. This trend is typical of second order phase transitions. The agreement between the theory and the experimental data is fairly good over a large range of thickness of the sample.

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