Nonaxisymmetric high-aspect-ratio ellipsoids under shear: Lowest-order correction for finite aspect ratios

This publication presents the results of complex parametrical strength investigations of typical wings for regional aircrafts obtained by means of the new version of the four-level algorithm (FLA) with the modified module responsible for the analysis of aerodynamic loading. This version of FLA, as well as a base one, is focused on significant decreasing time and labor input of a complex strength analysis of airframes by using simultaneously different principles of decomposition. The base version includes four-level decomposition of airframe and decomposition of strength tasks. The new one realizes additional decomposition of alternative variants of load cases during the process of determination of critical load cases. Such an algorithm is very suitable for strength analysis and designing airframes of regional aircrafts having a wide range of aerodynamic concepts. Results of validation of the new version of FLA for a high-aspect-ratio wing obtained in this work confirmed high performance of the algorithm in decreasing time and labor input of strength analysis of airframes at the preliminary stages of designing. During parametrical design investigation, some interesting results for strut-braced wings having high aspect ratios were obtained.

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A novel fabrication technique for high-aspect-ratio nanopillar arrays for SERS application

RSC Advances ◽

10.1039/d0ra09145f ◽

2020 ◽

Vol 10 (73) ◽

pp. 45037-45041

Author(s):

Tianli Duan ◽

Chenjie Gu ◽

Diing Shenp Ang ◽

Kang Xu ◽

Zhihong Liu

Keyword(s):

Aspect Ratio ◽

High Aspect Ratio ◽

Fabrication Technique ◽

Novel Technique ◽

Aspect Ratios ◽

Nanopillar Arrays

A novel technique is demonstrated for the fabrication of silicon nanopillar arrays with high aspect ratios.

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Saturation Profile Based Conformality Analysis for Atomic Layer Deposition: Aluminum Oxide in Lateral High-Aspect-Ratio Channels

10.26434/chemrxiv.12366623.v2 ◽

2020 ◽

Author(s):

Jihong Yim ◽

Oili Ylivaara ◽

Markku Ylilammi ◽

Virpi Korpelainen ◽

Eero Haimi ◽

...

Keyword(s):

Aspect Ratio ◽

Atomic Layer Deposition ◽

High Aspect Ratio ◽

Atomic Layer ◽

Profile Measurement ◽

Aspect Ratios ◽

New Information ◽

Layer Deposition ◽

Rectangular Channels ◽

Saturation Profile

<p>ABSTRACT: Atomic layer deposition (ALD) raises global interest through its unparalleled conformality. This work describes new microscopic lateral high-aspect-ratio (LHAR) test structures for conformality analysis of ALD. The LHAR structures are made of silicon and consist of rectangular channels supported by pillars. Extreme aspect ratios even beyond 10 000:1 enable investigations where the adsorption front does not penetrate to the end of the channel, thus exposing the saturation profile for detailed analysis. We use the archetypical trimethylaluminum (TMA)-water ALD process to grow alumina as a test vehicle to demonstrate the applicability, repeatability and reproducibility of the saturation profile measurement and to provide a benchmark for future saturation profile studies. Through varying the TMA reaction and purge times, we obtained new information on the surface chemistry characteristics and the chemisorption kinetics of this widely studied ALD process. We propose new saturation profile related classifications and terminology. </p>

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Focused Ion Beam: Advanced Technique for Device Modification

MRS Proceedings ◽

10.1557/proc-337-741 ◽

1994 ◽

Vol 337 ◽

Cited By ~ 2

Author(s):

Marsha Abramo ◽

Loren Hahn

Keyword(s):

Aspect Ratio ◽

High Aspect Ratio ◽

Focused Ion Beam ◽

Ion Beam ◽

Semiconductor Materials ◽

Advanced Technique ◽

Aspect Ratios ◽

Chip Technology ◽

Design Changes ◽

Critical Feedback

ABSTRACTFocused ion beam (FIB) technology is used to modify circuits for early-product design debug; it also has the capability to create probe points to underlying metallurgy, allowing device characterization while maintaining full functionality. These techniques provide critical feedback to designers for rapid verification of proposed design changes.Current FIB technology has its limitations because of redeposition of sputtered material; this phenomena may induce vertical electrical shorts and limit the achievable aspect ratio of a milled via to 6:1. Therefore, innovative enhancements are required to provide modification capability on planar chip technology which may utilize up to five levels of metallurgy. The ability to achieve high-aspect-ratio milling is required to access underlying circuitry. Vias with aspect ratios of 10:1 are necessary in some cases.This paper reviews a gas-assisted etching (GAE) process that enhances FIB milling by volatilizing the sputtered material, examines the results obtained from utilizing the GAE process for high-aspect-ratio milling, and discusses selectivity of semiconductor materials (silicon, aluminum, tungsten and silicon dioxide).

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High-Aspect-Ratio Electroplated Structures With 2μm Beamwidth

10.1115/imece1999-0241 ◽

1999 ◽

Author(s):

Xiaobin Li ◽

Siddharth Kiyawat ◽

Hector J. De Los Santos ◽

Chang-Jin “CJ” Kim

Keyword(s):

Aspect Ratio ◽

High Aspect Ratio ◽

Stress Gradient ◽

Optimization Method ◽

Nickel Layer ◽

Driving Voltage ◽

Aspect Ratios ◽

Nickel Electroplating ◽

Electroplating Process ◽

Micro Structures

Abstract Narrow beamwidth is highly desirable for many micromechanical elements moving parallel to the substrate. A good example is the electrostatically driven flexure structure, whose driving voltage is determined by the width of the beam. This paper presents the process flow and the result of a high-aspect-ratio electroplating process using photoresist (PR) molds. Following a systematic optimization method, PR molds with aspect ratios up to 4.0 were fabricated with a beamwidth of only 2.1μm. Higher aspect ratios, up to 6.8, were achieved using PR double coating technique, with a beamwidth of 2.6μm. Using a Cr/Cu seed layer, nickel electroplating was successfully carried out to translate the PR molds into nickel micro-structures. We observed bend-down of the fully released nickel cantilevers that are over 8μm thick. Further investigation suggested a combined effect of residual stress gradient in the electroplated nickel layer and in-use stiction of the cantilever beams.

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Fabrication of Ultra-High Aspect Ratio (>420:1) Al2O3 Nanotube Arraysby Sidewall TransferMetal Assistant Chemical Etching

Micromachines ◽

10.3390/mi11040378 ◽

2020 ◽

Vol 11 (4) ◽

pp. 378 ◽

Cited By ~ 2

Author(s):

Hailiang Li ◽

Changqing Xie

Keyword(s):

Aspect Ratio ◽

High Aspect Ratio ◽

Chemical Etching ◽

Atomic Layer ◽

Nanotube Arrays ◽

Al2o3 Layer ◽

Practical Applications ◽

Aspect Ratios ◽

Layer Deposition

We report a robust, sidewall transfer metal assistant chemical etching scheme for fabricating Al2O3 nanotube arrays with an ultra-high aspect ratio. Electron beam lithography followed by low-temperature Au metal assisted chemical etching (MacEtch) is used to pattern high resolution, high aspect ratio, and vertical silicon nanostructures, used as a template. This template is subsequently transferred by an atomic layer deposition of the Al2O3 layer, followed by an annealing process, anisotropic dry etching of the Al2O3 layer, and a sacrificial silicon template. The process and characterization of the Al2O3 nanotube arrays are discussed in detail. Vertical Al2O3 nanotube arrays with line widths as small as 50 nm, heights of up to 21 μm, and aspect ratios up to 420:1 are fabricated on top of a silicon substrate. More importantly, such a sidewall transfer MacEtch approach is compatible with well-established silicon planar processes, and has the benefits of having a fully controllable linewidth and height, high reproducibility, and flexible design, making it attractive for a broad range of practical applications.

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Numerical Investigation into Flutter and Flutter-Buffet Phenomena for a Swept Wing and a Curved Planform Wing

International Journal of Aerospace Engineering ◽

10.1155/2019/8210235 ◽

2019 ◽

Vol 2019 ◽

pp. 1-19 ◽

Cited By ~ 1

Author(s):

Mario Rosario Chiarelli ◽

Salvatore Bonomo

Keyword(s):

Aspect Ratio ◽

High Aspect Ratio ◽

High Speed ◽

Sensitivity Study ◽

Fuel Saving ◽

Swept Wing ◽

Instability Condition ◽

Aspect Ratios ◽

Numerical Studies ◽

Classical Flutter

The results of numerical studies carried out on high-aspect-ratio wings with different planforms are discussed: the transonic regime is analysed for a swept wing and a curved planform wing. The wings have similar aspect ratios and similar aerodynamic profiles. The analyses were carried out by CFD and FE techniques, and the reliability of the numerical aerodynamic results was proven by a sensitivity study. Analysing the performances of the two wings demonstrated that in transonic flight conditions, a noticeable drag reduction can be obtained by adopting a curved planform wing. In addition, for such a wing, the aeroelastic instability condition, consisting in a classical flutter, is postponed compared to a conventional swept wing, for which a flutter-buffet instability occurs. In a preliminary manner, the study shows that, for a curved planform wing, the high speed buffet is not an issue and at the same time notable fuel saving can be achieved.

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Aerosol Jet Printing of Silver Lines with A High Aspect Ratio on A Heated Silicon Substrate

Materials ◽

10.3390/ma13030730 ◽

2020 ◽

Vol 13 (3) ◽

pp. 730 ◽

Cited By ~ 5

Author(s):

Alexey Efimov ◽

Pavel Arsenov ◽

Denis Kornyushin ◽

Anna Lizunova ◽

Ivan Volkov ◽

...

Keyword(s):

Electrical Resistivity ◽

Aspect Ratio ◽

Substrate Temperature ◽

High Aspect Ratio ◽

Silicon Substrate ◽

Silver Films ◽

Aspect Ratios ◽

Jet Printing ◽

Rate Of Evaporation ◽

Aerosol Jet Printing

In this work, we studied the formation of conductive silver lines with high aspect ratios (AR = thickness/width) > 0.1 using the modernized method of aerosol jet printing on a heated silicon substrate. The geometric (AR) and electrical (resistivity) parameters of the formed lines were investigated depending on the number of printing layers (1–10 layers) and the temperature of the substrate (25–300 °C). The AR of the lines increased as the number of printing layers and the temperature of the substrate increased. An increase in the AR of the lines with increasing substrate temperature was associated with a decrease in the ink spreading as a result of an increase in the rate of evaporation of nano-ink. Moreover, with an increase in the substrate temperature of more than 200 °C, a significant increase in the porosity of the formed lines was observed, and as a result, the electrical resistivity of the lines increased significantly. Taking into account the revealed regularities, it was demonstrated that the formation of silver lines with a high AR > 0.1 and a low electrical resistivity of 2–3 μΩ∙cm is advisable to be carried out at a substrate temperature of about 100 °C. The adhesion strength of silver films formed on a heated silicon substrate is 2.8 ± 0.9 N/mm2, which further confirms the suitability of the investigated method of aerosol jet printing for electronic applications.

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Solidification Processing Routes to High Aspect Ratio Reinforcements in γ-TiAl

MRS Proceedings ◽

10.1557/proc-194-89 ◽

1990 ◽

Vol 194 ◽

Cited By ~ 3

Author(s):

J. J. Valencia ◽

J. P. A. Löfvander ◽

J. Rösler ◽

C. G. Levi ◽

R. Mehrabian

Keyword(s):

Solid Solution ◽

Aspect Ratio ◽

Creep Strength ◽

High Aspect Ratio ◽

Anisotropic Growth ◽

Solidification Processing ◽

Aspect Ratios ◽

The Matrix ◽

Solute Strengthening

AbstractAdditions of ∼5%B1 and ∼9%Ta to binary γ-TiAl result in the formation of a monoboride isomorphous with TiB but containing Ta in solid solution. This boride exhibits strongly anisotropic growth from the melt, producing rod-like primary phases which are of potential interest for creep strengthening of the γ matrix. Fibrous borides with aspect ratios larger than ∼20 and volume fractions of ∼0.12 have been produced in arc-melted Ti-48AI-9Ta-4.3B alloys. Creep testing at 1255 K indicates that these “in-situ” composites have much higher creep strength than γ-TiAl, but the contribution of the reinforcements is relatively small compared with the solute-strengthening of the matrix.

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Two-step synthesis of high aspect ratio gold nanorods

Open Chemistry ◽

10.1007/s11532-005-0012-y ◽

2006 ◽

Vol 4 (1) ◽

pp. 160-165 ◽

Cited By ~ 2

Author(s):

Tom Mortier ◽

André Persoons ◽

Thierry Verbiest

Keyword(s):

Aspect Ratio ◽

Gold Nanorods ◽

High Aspect Ratio ◽

Cetyltrimethylammonium Bromide ◽

Surfactant Concentration ◽

Synthetic Method ◽

Aspect Ratios ◽

Seed Mediated

AbstractWe describe a very simple, two-step synthetic method to prepare gold nanorods with extremely high aspect ratios (> 20) and average lengths of more than 1000 nm. The method is based on a seed-mediated growth in presence of the surfactant cetyltrimethylammonium bromide. The length and aspect ratios of the nanorods can be manipulated by varying the surfactant concentration.

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