Gerilme Tabanlı Kendiliğinden Birleşme:Mikro Nano Entegrasyonunda Kırılma Mekaniği Uygulamaları

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2008Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2008Katmanlı yapılarda gözlemlenen kırılma, yapı üzerinde etkili olan mekanik gerilimlerin doğasına bağlı olarak çeşitli çatlak şekillerine yol açmaktadır. Çatlakların gerek açıklıkları gerek yönleri, tamamen katmanlı yapı özellikleri ve gerilimlerin uygulanış biçimine bağlı olarak numuneden numuneye tekrar edilebilir şekilde gözlemlenebilir. Bunun sonucunda gerilimleri kontrol ederek çatlak yönlerini tayin etme fırsatı ortaya çıkmaktadır. Yön tayini, ilk önce tek kristal yapıya sahip Si alttaş üzerindeki ince SiO2 kaplamalarında gösterilmiştir. Alttaşın derin reaktif iyon aşındırması gibi tekniklerle mikro boyutta şekillendirilmesi ile tayin edilen gerilim dağılımı, aynı anda binlerce çatlağın deterministik bir şekilde oluşmasını sağlamaktadır. Ayrıca çatlak açıklıklarının nano mertebesinde olması ve çatlağın SiO2 ve Si arayüzünde durması sayesinde, çatlakların ikinci bir malzeme ile doldurulmaları, nanotel imalatını mümkün kılmaktadır. Böylece çatlak ağı, bir nanotel ağına dönüştürülür. Yonga üzerinde her çatlağın başlangıç noktasının koordinatı ve yönü bilindiği için üst yapıların litografi kullanılarak bu nanotel ağına göre hizalanması mümkün olmaktadır. Bu tür bir sistem entegrasyonu, mikro bir tahrik mekanizmasının iki nanotele göre hizalanarak imaline dayalı bir cımbız cihazının bünyesinde gerçekleştirilmiştir. Çalışma, nanoteknolojinin büyük ihtiyaçlarından biri olan, nano yapıların kontrollü imalatına yönelik olup, uygulamalı mekaniğin bu alanda üstlenebileceği role işaret etmektedir.Various crack patterns are observed in multilayers depending on the nature of applied stresses. Crack opening and propagation paths can be obtained in a repeatable fashion if multilayer material properties and the stress state are precisely controlled. This leads to the possibility of dictating crack paths by controlling the stress state, which was first demonstrated on SiO2-coated Si samples. By patterning the Si substrate through deep reactive ion etching one can determine the distribution of stresses and dictate the simultaneous formation of thousands of cracks. Furthermore, since crack openings are at nanoscale and they arrest at the substrate/thin film interface, one can fill the cracks with a second material and obtain nanowires. Hence, a network of cracks is transformed into a network of nanowires. Since one knows the coordinates of the initiation point of cracks and their orientation, one can easily align subsequent lithography steps with respect to the existing nanowires. This aspect of system integration is demonstrated in the case of a gripper device with two nanoscale endeffectors attached at the tip of a microscale actuator. The study addresses the issue of controlled fabrication of nanostructures, one of the main issues faced by nanotechnology, and the role that applied mechanics can play in this field

Synthesis, Characterization and Antibacterial Activity of Imidazole Derivatives of 1,10-Phenanthroline and their Cu(II), Co(II) and Ni(II) Complexes

Six new CuL1 (L1 = 4-bromo-2-(1H-imidazo[4,5-f][1,10]phenanthroline-2-yl)phenol), CoL1, NiL1, CuL2 (L2 = 2-(1H-imidazo[4,5-f] [1,10]phenanthroline-2-yl)-5-methoxyphenol), CoL2 and NiL2 complexes were synthesized. L1 and L2 ligands were prepared by the condensation of 1,10-phenanthroline-5,6-dione with 5-bromosalicylaldehyde and 2-hydroxy-4-methoxybenzaldehyde, respectively. The structures of the compounds were determined by elemental analyses, IR,UV-visible, 1H-NMR, TGA, magnetic susceptibilities and molar conductance measurements. It is observed that the synthesized complexes have tetragonal and distorted square pyramidal geometrical structures. Antibacterial activity of the ligands and their metal complexes were tested against selected bacteria by disc diffusion method.KEY WORDS 1,10-Phenanthroline, imidazole, complex, antibacterial activity

Monte Carlo simulation for statistical mechanics model of ion channel cooperativity in cell membranes

Voltage-gated ion channels are key molecules for the generation and propagation of electrical signals in excitable cell membranes. The voltage-dependent switching of these channels between conducting and nonconducting states is a major factor in controlling the transmembrane voltage. In this study, a statistical mechanics model of these molecules has been discussed on the basis of a two-dimensional spin model. A new Hamiltonian and a new Monte Carlo simulation algorithm are introduced to simulate such a model. It was shown that the results well match the experimental data obtained from batrachotoxin-modified sodium channels in the squid giant axon using the cut-open axon technique.Comment: Paper has been revise

Low/Zero-Carbon Buildings for a Sustainable Future

Fossil fuel-based energy consumption is still dominant in the world today, and there is a consensus on the limited reserves of these energy resources. Therefore, there is a strong stimulation into clean energy technologies to narrow the gap between fossil fuels and renewables. In this respect, several commitments and codes are proposed and adopted for a low energy-consuming world and for desirable environmental conditions. Sectoral energy consumption analyses clearly indicate that buildings are of vital importance in terms of energy consumption figures. From this point of view, buildings have a great potential for decisive and urgent reduction of energy consumption levels and thus greenhouse gas (GHG) emissions. Among the available retrofit solutions, greenery systems (GSs) stand for a reliable, cost-effective and eco-friendly method for remarkablemitigation of energy consumed in buildings. Through the works comparing the thermal regulation performance of uninsulated and green roofs, it is observed that the GS provides 20°C lower surface temperature in operation. Similar to green roofs, vertical greenery systems (VGSs) also reduce energy demand to approximately 25% as a consequence of wind blockage effects in winter. Therefore, within the scope of this chapter, GSs are evaluated for a reliable and effective retrofit solution toward low/zero carbon buildings (L/ZCBs)

Mechanical Properties of Silicon Nanowires with Native Oxide Surface State

Silicon nanowires have attracted considerable interest due to their wide-ranging applications in nanoelectromechanical systems and nanoelectronics. Molecular dynamics simulations are powerful tools for studying the mechanical properties of nanowires. However, these simulations encounter challenges in interpreting the mechanical behavior and brittle to ductile transition of silicon nanowires, primarily due to surface effects such as the assumption of an unreconstructed surface state. This study specifically focuses on the tensile deformation of silicon nanowires with a native oxide layer, considering critical parameters such as cross-sectional shape, length-to-critical dimension ratio, temperature, the presence of nano-voids, and strain rate. By incorporating the native oxide layer, the article aims to provide a more realistic representation of the mechanical behavior for different critical dimensions and crystallographic orientations of silicon nanowires. The findings contribute to the advancement of knowledge regarding size-dependent elastic properties and strength of silicon nanowires.Comment: 11 pages, 10 figure

Recent passive technologies of greenhouse systems: a review

There are 130 countries produces greenhouse vegetables commercially with more than 1.1 million acres in 2016. Most of the greenhouses deal with high operating costs due to the great energy needs. The high heat loss because of the greenhouse envelope material is responsible for the high energy demand in greenhouses. Nevertheless, each area having a specific need which affects to the energy level and conventional greenhouse technologies tend to have poor U-values. It causes energy for heating is very dominant up to 85% of the total greenhouse energy demand in cold climates countries. While, for the hot climate countries the energy for cooling is more prevalent. Therefore, this paper presents the latest technological developments used in greenhouses in various countries used to control the microclimate in the greenhouse focusing on passive techniques. It is found that PCM recently used to provide heating and cooling for Mediterranean climate. Moreover, closed greenhouse concept based system for Northern climatic improves the reduction energy demands by 80% with a potential payback of 6 years. Additionally, for most countries double glazing envelopes to be the most frequently powerful to increase the greenhouse performance

Stacking in Colloidal Nanoplatelets: Tuning Excitonic Properties

Cataloged from PDF version of article.Colloidal semiconductor quantum wells, also commonly known as nanoplatelets (NPLs), have arisen among the most promising materials for light generation and harvesting applications. Recently, NPLs have been found to assemble in stacks. However, their emerging characteristics essential to these applications have not been previously controlled or understood. In this report, we systematically investigate and present excitonic properties of controlled column-like NPL assemblies. Here, by a controlled gradual process, we show that stacking in colloidal quantum wells substantially increases exciton transfer and trapping. As NPLs form into stacks, surprisingly we find an order of magnitude decrease in their photoluminescence quantum yield, while the transient fluorescence decay is considerably accelerated. These observations are corroborated by ultraefficient Forster resonance energy transfer (FRET) in the stacked NPLs, in which exciton migration is estimated to be in the ultralong range (>100 nm). Homo-FRET (i.e., FRET among the same emitters) is found to be ultraefficient, reaching levels as high as 99.9% at room temperature owing to the close-packed collinear orientation of the NPLs along with their large extinction coefficient and small Stokes shift, resulting in a large Forster radius of similar to 13.5 nm. Consequently, the strong and long-range homo-FRET boosts exciton trapping in nonemissive NPLs, acting as exciton sink centers, quenching photoluminescence from the stacked NPLs due to rapid nonradiative recombination of the trapped excitons. The rate-equation-based model, which considers the exciton transfer and the radiative and nonradiative recombination within the stacks, shows an excellent match with the experimental data. These results show the critical significance of stacking control in NPL solids, which exhibit completely different signatures of homo-FRET as compared to that in colloidal nanocrystals due to the absence of inhomogeneous broadening

Вплив попиту на процес ціноутворення

The creep behavior of nanocellulose films and aerogels are studied in a dynamic moisture environment, which is crucial to their performance in packaging applications. For these materials, the creep rate under cyclic humidity conditions exceeds any constant humidity creep rate within the cycling range, a phenomenon known as mechanosorptive creep. By varying the sample thickness and relative humidity ramp rate, it is shown that mechanosorptive creep is not significantly affected by the through-thickness moisture gradient. It is also shown that cellulose nanofibril aerogels with high porosity display the same accelerated creep as films. Microstructures larger than the fibril diameter thus appear to be of secondary importance to mechanosorptive creep in nanocellulose materials, suggesting that the governing mechanism is found between molecular scales and the length-scales of the fibril diameter.funding agencies|BiMaC Innovation|

Determination of mechanical properties of different sized silicon and silica nanowires tested in SEM

To push miniaturization in electronics forward, integration of silicon or silica nanowires into microelectromechanical based sensors (MEMS) becomes essential, because they were found to enhance the overall sensitivity and noise immunity. With respect to mechanical stress may develop in nanowires in operation of the MEMS system, their stability need to be checked to ensure long-term reliability. The monolithic fabrication includes a controlled two-step chip-on-wafer etching technique resulting in double-anchored wires with the minimum width of 35 nm, the maximum width of 74 nm and a height of 168 nm with clamped wire endings for silicon [1,2]. Based on this idea clamped silica wires with widths between 150 to 200 nm and heights of 50 nm and 372 nm were created due to prior coating of a silicon bulk with a silsesquioxane precursor in addition to subsequent e-beam irradiation [3]. Dimensions and shape of the wire cross-sections were exemplary investigated using transmission electron microscopy, while the determination of the respective wire´s length between the clamped endings of 2 to 12µm and the in-situ three-point-bending tests were carried out within a scanning electron microscope. A micromanipulator equipped with a piezo-resistive force sensor, shaped like a cantilever conventionally used for atomic force microscopes was loaded and unloaded at the wires mid-span and forces were detected. Simultaneously the systematic tests were recorded in scanning electron micrographs taken each second to extract force-displacement (f-d) curves of the different sized nano-objects. As expected for brittle material, silicon nanowires showed well-known f-d behavior. Considering a modulus of elasticity of 169 GPa for bulk [100] silicon and the influence of the native oxide finite element simulation (FEM) exactly fit to the experimental data leading to the conclusion that no size dependence for elastic properties was identified [4]. Same observations were made with silica wires until a stress level of about 0.1 to 0.4 GPa is reached and a superplastic deformation without fracture of the wires takes place. The validation of the f-d results from the systematic study of the fracture behavior of silicon wire is in progress. Due to the special wire geometry (small width in relation to height) buckling occurs during loading, implemented within a finite-element simulation, which needs still further refinement. Finally, this study will help to predict mechanical behavior (or vice versa the dimensions) of MEMS integrated silicon nanowires. The project leading to this application has received funding from the EMPIR programme Strength-ABLE co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation programme. [1] Z. Tasdemir, N. Wollschläger, W. Österle, Y. Leblebici and B. E. Alaca: A deep etching mechanism for trench-bridging silicon nanowires, Nanotechnology 27 (2016) 095303. [2] M. Yilmaz, Y. Kilinc, G. Nadar, Z. Tasdemir, N. Wollschläger, W. Österle, Y. Leblebici and B. E. Alaca: Top-down technique for scaling to nano in silicon MEMS, J. Vac. Sci. Technol. B 35 (2017) 022001-1 [3] M. Yilmaz, N. Wollschläger, M. Nasr Esfahani, Österle, Y. Leblebici and B. E. Alaca: Superplastic behavior of silica nanowires obtained by direct patterning of silsesquioxane-based precursors, Nanotechnology 28 (2017) 115302. [4] N. Wollschläger, Z. Tasdemir, I. Häusler, Y. Leblebici, W. Österle and B. E. Alaca: Determination of the Elastic Behavior of Silicon Nanowires within a Scanning Electron Microscope, J. Nanomat. (2016) 4905838-