Stack Width Research Articles

KOH Activation with Microwave Irradiation and its Effect on the Physical Properties of Orange Peel Activated Carbon

Chemical activation with assisted microwave irradiation was used to produced activated carbon from orange peel waste. The activating agent was potassium hydroxide (KOH) with concentrations of 2 M, 3 M, and 4 M. The microwave irradiation was done for 15 minutes with a 630 Watt output power. KOH concentration affected the physical properties of OP-ACxM. With increasing KOH concentration, the interlayer spacing (d002 and d100 ) grew, stack height (Lc ) increased, and stack width (La) dropped. The number of pores on the surface of OP-ACxM increased after the chemical activation process. In OP-ACxM, FTIR analysis reveals the presence of O-H, C-H, C-C, C=O, C=C, and C-O.

Study on Analog/RF and Linearity Performance of Staggered Heterojunction Gate Stack Tunnel FET

Staggered heterostructure gate stack TFET is proposed. The analog, RF, and linearity performance of the device were studied in an ATLAS TCAD device simulator. The high K material HfO2 was used in gate stacking. The impact of the gate stack width on the analog, RF, and linearity performance was investigated. Analog/RF performance of the staggered heterostructure gate stack TFET were analyzed in terms of figure of merits (FOMs) like transconductance (gm), transconductance generation factor (TGF), voltage gain, electric field, cut off frequency (fT), maximum frequency of oscillation (fmax), and gain band width (GBW). Gate stacking architecture in heterostructure staggered TFET improves the Ion/Ioff ratio and reduces drain induced barrier lowering with respect to greater gate stack width (toxh), diminishing the short channel effects. Improvement in gm voltage gain, fT, fmax, and GBW) were observed as the gate stack width thickened. A fair comparison of FOMs such as VIP2, VIP3, IIP3, IMD3, and 1 dB–compression point (P1 dB) were carried out by varying the gate stack width to investigate the linearity performance. The simulation results reveal that staggered heterostructure gate stack TFET can be a reasonable competitor for low-power applications and in the design of RF circuits covering a wide range in frequencies of RF spectrum.

Optimization of annealing stack using design of experiment method in Batch Annealed HSLA Steel

Cold rolled HSLA steels are characterized by its high Yield to Tensile strength ratio. These steels are resistant to weld zone softening and grain coarsening, makes it suitable to fabricate to different automotive components. Key application includes automotive structural, reinforcement, suspension and chassis component etc. All these desirable properties are achieved by aiming the desirable chemistry and processing using the desired process parameters. High Strength Low-alloy steel sheets processed through Batch annealed route are prone to mechanical properties variations within batch annealing stack. Mechanical properties are function of actual strip temperature and time. In Batch Annealing, temperature of strip depends upon thickness, width, weight and stack position of the coil. Different coil parameters like weight, width, thickness, outer coil diameter along with process parameters like heating time, stack position were analyzed to work out the source of property variation. By using binary logistic regression it was found that width difference and weight difference are highly correlated with the property variation. Full factorial Design of experiments (DOE) was performed for stack width range and weight range in a stack. DOE response optimizer confirms that keeping width range of coils within the stack to minimum results in property variation of as low as 10MPa.

Proposal of stack Effect technology for predicted future years

Recently, stack effect is a general problem solver in providing vertical ventilation for urban environmental issues. However, study on resilient technology of stack effect for future years as predicted by climate trend should be conducted. Therefore, this research proposes a design of new technology on operable and adaptable vertical ventilation to the environmental change. The research method is conducted by comprehensive simulation of Ecotect Analysis, ANSYS Fluent and Matlab. Urban environment of Surabaya, as the research location, is the representative of tropical region. The results showed that the stack effect height and area could be modified instantly adjusting the environmental condition time by time in the future years. With 1.8 m of stack width, the proposed technology could capture 40 m3 of vertical air flow which is useful for physiological cooling and its dimension could be modified depending on the environmental condition. By providing resilient technology, predictable and sustainable ventilation method is offered to anticipate an unpredicted global warming and environmental change.

High sensitivity temperature sensor based on cascaded silicon photonic crystal nanobeam cavities.

We present the design, fabrication and characterization of a high sensitivity temperature sensor based on cascaded silicon photonic crystal (PhC) nanobeam cavities. Two PhC nanobeam cavities, one with stack width modulated structure and the other one with parabolic-beam structure are utilized to increase the sensitivity. Most of the light is designed to be confined in the cladding and the core for these two cavities, respectively. Due to the positive thermo-optic (TO) coefficient of silicon and the negative TO coefficient of SU-8 cladding, the wavelength responses red shift for parabolic-beam cavity and blue shift for stack width modulated cavity as the increase of the ambient temperature, respectively. Thus, the sensitivity for the temperature sensor can be improved greatly since the difference in resonant wavelength shifts is detected for the temperature sensing. The experimental results show that the sensitivity of the temperature sensor is about 162.9 pm/°C, which is almost twice as high as that of the conventional silicon based resonator sensors.

Activated carbon efficient atomistic model construction that depicts experimentally-determined characteristics

Construction of large-scale atomistic representations of activated carbon aids exploration of structure–property relationships. The construction approaches for existing structures are limited in the control over the distribution of structural features. Here, an initial atomistic representation of a lignite-based activated carbon was constructed using a construction strategy that allows control over the distributions of stacking, degree of orientation, and pore size. Fringe3D was used to produce a collection of 42 molecules within 25 stacks comprised of graphene sheets with control over their length, orientation, and stack height. Vol3D populated the specified 100×100×100Å cuboid volume with an assumed Gaussian distribution of stack width, without changing orientation and thus retaining regional organization. Eight of these were combined to create a large-scale structure. The pore size distribution was captured due to smaller microporosity caused by packing inefficiencies of the stacks and by inclusion of additional desired porosity. To demonstrate the control over the extent of curvature, three 200×200×200Å structures overall were constructed with varying extent of curvature. The construction protocols were efficient producing large-scale structures (∼330,000 atoms) constructed far more rapidly than traditional strategies using a personal computer.

Characterization of mesoporous carbon prepared from date stems by H3PO4 chemical activation

The present work was focused on the determination of texture, morphology, crystanillity and oxygenated surface groups characteristics of an activated carbon prepared from date stems. Chemical activation of this precursor at different temperatures (450, 550 and 650°C) was adopted using phosphoric acid as dehydrating agent at (2/1) impregnation ratio. Fourier transform infrared spectroscopy study was carried out to identify surface groups in date stems activated carbons. The microscopic structure was examined by nitrogen adsorption at 77K. The interlayer spacing (d200 and d100), stack height (Lc), stack width (La) and effective dimension L of the turbostratic crystallites (microcrystallite) in the date stems activated carbons were estimated from X-ray diffraction data (XRD). Results yielded a surface area, SBET, and total pore volume of 682, 1455, 1319m2/g and 0,343, 1,045 and 0.735cm3/g, for the carbon prepared at 450, 550 and 650°C, respectively. Scanning electron microscopy exhibits a highly developed porosity which is in good agreement with the porous texture derived from gas adsorption data and these results confirm that the activated carbon is dominated by network of slit-shaped mesopores morphology and in some cases by varied micropores morphologies.

Fine Structure Evaluation of the Pair Distribution Function with Molecular Models of the Argonne Premium Coals

The pair distribution function (PDF) is one means of evaluating the atomic spatial arrangements of coals. Analysis of PDF based on X-ray diffraction data provides structural information on turbostratic crystalline parameters that can be utilized to further characterize coal structure. With coalification, expectations are of limited growth in aromatic stacking and a slight growth in the aromatic cluster size over the lignite to medium-volatile bituminous range. The PDF can be also used to construct and validate atomistic representations for carbonaceous materials including coal. Here, the PDF was evaluated with molecular slice models of several Argonne Premium coals (Beulah-Zap, Illinois No. 6, Upper Freeport, Pocahontas No. 3), also a non-Argonne Hon Gai anthracite, and compared to experimental observations. Atomistic representations were generated directly from high-resolution transmission electron microscope (HRTEM) lattice fringe images. The Fringe3D approach populates aromatic moieties matching the distributions of fringe: length, layers per stack, interlayer spacing, and orientations to produce an aromatic slice model of limited depth. Perl scripts incorporated appropriate aliphatic and heteroatom components. This approach creates atomistic representations with greater ease, improved accuracy, and reduced computational expense than other construction approaches. The constructed coal models were partially geometry-optimized to achieve realistic bond lengths but without displacement of coal molecules enabling the distribution of fringe length, stacking, and orientations to be duplicated in 3D modeling space. The resulting coal slice models, devoid of cross-links, captured a distribution of turbostratic crystalline dimensions with an average cluster size of about 1 nm, an average interlayer spacing ranging between 0.37 and 0.39 nm, and an average stacking number of ∼2–3 in accordance with HRTEM and XRD data for Argonne coals. These structural models were used to predict PDFs and to evaluate the fine detail of the frequency spectra via examination of intermolecular and intramolecular contributions. There was good agreement between predicted and experimental observations. Analysis of the simulated intermolecular PDF contribution showed strong intensities with increasing coal rank in agreement with the growth in the stacking number and stack height observed from low- to high-rank coals. The simulated intramolecular PDF contribution showed shorter peak amplitudes for low-rank coals in comparison to high-rank coals in agreement with the increase in stack width as coal rank increases. To further examine these contributions, lattice models composed of pyrene molecules were also constructed via Fringe 3D and manipulated to directly investigate the effect of aromatic orientation distributions and stacking on the simulated PDF. Peak intensities of simulated intermolecular PDFs at the average interlayer spacing increased with the degree of alignment (ϕ) according to g(r)interd002 = 0.0014ϕ2 + 0.0107ϕ + 4.2784. This result was consistent with the slight increase in the stacking number observed from low- to high-rank coals with a more dramatic transition for anthracite.

Identification of Sun and Shade Leaves of Metasequoia occidentalis (Newberry) Chaney from the Middle Eocene of the Canadian High Arctic

Abstract Mummified leaves of Metasequoia occidentalis (Newberry) Chaney from the middle Eocene Buchanan Lake Formation at Napartulik, Axel Heiberg Island, were examined by transmission electron microscopy to determine whether sun- and shade-type leaves could be identified. Where discernable, features related to thylakoid geometry, such as the degree of grana stacking, the number of thylakoids per granum and grana stack width, were measured. The chloroplast characteristics of M. glyptostroboides Hu & Cheng leaves have a highly significant response to light intensity such that the leaves can be characterized as sun or shade leaves based on these features, indicating that adequately preserved chloroplasts in M. occidentalis leaves can also be characterized in this manner. Using data from the response of chloroplast ultrastructure to sun and shade environments in M. glyptostroboides leaves, four classification analyses, each using different combinations of chloroplast ultrastructural features, were performed ...

Model Predicted Effect of Process Variables on Kiln Drying of Pinus radiata Boards

The effects of kiln-drying process variables on drying time and final moisture content (MC) variability were assessed using a mathematical drying model (a kiln-wide model) developed earlier. Drying time was predicted to decrease by using higher air velocities and temperatures and, to a less extent, by increasing fan reversal frequencies. The drying time extended as board thickness or stack width increased. Increase in air velocity from 5 to 8 m/s tended to minimize the final MC variability. At least three reversals in the early stages of drying were required to reduce final moisture contents variation. The final MC variability increased with increasing stack width and with increasing temperature.

Expansion of mesocarbon microbeads

Expanded mesocarbon microbeads (EMCMB) were prepared from graphitized mesocarbon microbeads by a chemical method. The expanded volume of EMCMB was significantly influenced by the reaction time, temperature, weight ratio of sulfuric acid and nitric acid, the maximum value of which was 4.1 ml/g. The morphology and structure characters of MCMB after chemical reaction and expansion were also investigated by SEM, BET and XRD measurements. The results show that the spherical, layered structure of MCMB could be verified convincingly by SEM micrographs of EMCMB, and the values of crystallite parameters of intercalated MCMB and EMCMB such as Lc and La decreased significantly compared with that of pristine MCMB, indicating that the stack height and stack width of carbon layers in a crystallite decreased after intercalation reaction and expansion. Meanwhile, EMCMB with appropriate porosity using as anode material for lithium-ion batteries exhibited an excellent high-rate discharge capacity and good cycle stability at the large current density.

Simulation and Experiments of Stress Migration for Cu/low-k BEoL

Stress migration (SM) or stress-induced voiding experiments were conducted for two back-end-of-line (BEoL) technologies: Cu/FTEOS and Cu/low-k. Experiments have shown the mean time to failure (MTF) depends on inter-layer dielectric (ILD) materials properties, ILD stack and metal line width. Stress migration is worse in Cu/low-k, manifesting as significantly reduced MTF under accelerated testing. Line width also has a more profound effect on stress migration reliability in Cu/low-k than in Cu/FTEOS. Wider lines produce higher failure rates, due to larger stress magnitudes in Cu and larger active diffusion volumes. Stress modeling using finite element analysis (FEA) was performed to quantify the stress fields in the via-chain test structure used for SM reliability testing. In order to account for the effect of process steps on stress evolution, a process-oriented modeling approach was developed. Stress in the metal line is a function of ILD properties, ILD stack and metal line width. The concept of an SM risk index is proposed to assess BEoL stress migration reliability from both stress and energy perspectives. Comparison of the SM risk index for Cu/FTEOS and Cu/low-k shows that the latter is more prone to stress-induced voiding. Stress migration tests verify that MTF values decrease with increasing line width. Modeling results are consistent with experimental findings, while providing more insightful understanding of stress-driven mechanisms in stress migration.

Design optimization of multi-barrier tunneling devices using the transfer-matrix method

We present simulations of a recently published multi-barrier phase-state low electron device memory cell. For the proper consideration of tunneling through the insulating barriers we implemented a one-dimensional Schrödinger solver based on the transfer-matrix formalism into the device simulator MINIMOS-NT. We investigate the effect of barrier size and position on the I on/ I off ratio of the memory cell. We find that the position and thickness of the central shutter barrier can be used for device tuning. For high I on/ I off ratios the central shutter barrier (CSB) should be placed near the upper contact. Furthermore, a reduction in the stack width leads to increasing I on/ I off ratios. Although the use of the transfer-matrix method in a device simulator requires a number of assumptions, it turns out to be a viable tool for deepening the understanding of tunneling effects in devices where other tunneling models fail.

A study of the design for touch free linear eddy current brake

This paper describes the performances of eddy current brake according to the design parameters. The characteristics are analyzed by using 2-dimensional Finite Element Method (2-D FEM) in order to predict the effect of the design parameters. The magnet stack width is determined from equivalent stack width that is calculated by solution of the field with scalar potential. The validity of available calculation program with FEM is achieved by comparing with experimental value. From the results, the optimized magnet configuration of the eddy current braking system is designed to obtain not only the maximum braking force but also the minimum attraction force.

Interfacial studies of carbon-carbon composites

A detailed study of the microstructure of carbon-carbon composite was performed using transmission electron microscopy (TEM) techniques. Structural characterization is essential in order to fully understand the mechanical and physical properties of carbon-carbon composites. Thin samples of both transverse and longitudinal sections were prepared by using an ion-mill technique. An emphasis was placed on the interfaces between the fiber and the matrix in both longitudinal and transverse section. Bright field micrographs revealed different types of morphology existing within a complex 3D carbon-carbon composite. Dark field micrographs were used to analyze the crystallite size and orientation. Selected-area diffraction (SAD) and convergent-beam electron diffraction (CBED) were used to characterize the microstructure in terms of four parameters: preferred orientation parameter Z, stack height L c, stack width L a, and d 002 spacing. Interfacial analysis showed a very complex interphase between the matrix and the fibers with entirely distinctive microstructural properties.

Sound Radiation Patterns of Gas Turbine Exhaust Stacks

Radiation patterns for gas turbine exhaust stacks have been calculated for the case of wide-band noise, assuming negligibly low gas velocities and temperatures. Both shape of stack and band width of analyzing equipment are considered. Theoretical results are compared with data measured on models and on a prototype exhaust system.