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Proceedings Papers
Proc. ASME. IMECE2020, Volume 13: Micro- and Nano-Systems Engineering and Packaging, V013T13A006, November 16–19, 2020
Paper No: IMECE2020-24052
Abstract
Magnetic assembly of micro/nano materials are of great interest due to their unique properties. These nano-scale materials can be ensemble with other matrixes to prepare for new functional micro/nano composites with enhanced specific properties such as, thermal conductivity. In this study, we demonstrated the distribution and magnetic alignment of nickel (Ni) nanoparticle/nanowires inside of a non-magnetic matrix, (e.g., water or a molten wax), experimentally and computationally. A two-dimensional Monte Carlo simulation model is employed to investigate the aggregate structures of Ni nanoparticle/nanowires subjected to a one-directional static magnetic field. It is anticipated that the applied magnetic strength will influence the attractive forces between nanoparticle/nanowires that will produce chain-like cluster structures parallel to magnetic direction where the aligned chains will be separated by a range of distances that are also function of magnetic field strength.
Proceedings Papers
Proc. ASME. IMECE2020, Volume 12: Mechanics of Solids, Structures, and Fluids, V012T12A052, November 16–19, 2020
Paper No: IMECE2020-23515
Abstract
The attractive mechanical properties of nickel-based superalloys primarily arise from an assembly of γ′ precipitates with desirable size, volume fraction, morphology and spatial distribution. In addition, the solutioning cooling rate after super solvus heat treatment is critical for controlling the features of γ′ precipitates. However, the correlation between these multidimensional parameters and mechanical hardness has not been well established to date. Scanning electron microscope (SEM) images with different γ′ precipitates were investigated in this study, and artificial neural network (ANN) method was used to build a microstructure-mechanical property model. The critical step in this work is to extract different microstructural features from hundreds of SEM images. In order to improve the accuracy of prediction, the cooling rate was also considered as the input. In this work, the methodology was proved to be capable of bridging microstructural features and mechanical properties under the inspiration of material genome spirit.
Proceedings Papers
Che-Fu Su, Xinrui Xiang, Hamed Esmaeilzadeh, Jirui Wang, Edward Fratto, Majid Charmchi, Zhiyong Gu, Hongwei Sun
Proc. ASME. IMECE2019, Volume 6: Energy, V006T06A100, November 11–14, 2019
Paper No: IMECE2019-10457
Abstract
Enhancing the thermal conductivity of phase change materials (PCMs) is attracting attention for renewable energy applications such as solar, geothermal and wind energy. The use of energy storage can significantly improve the efficiency of renewable energy systems due to their intermittent nature. Latent heat thermal energy storage is a particularly attractive technique due to its high capacity can store energy at near constant temperature corresponding to the phase transition temperature of the PCMs. The present work aims to overcome this undesirable property of low thermal conductivity by manipulating metal fillers including nickel (Ni) nanoparticles/nanowires within the paraffin wax to improve its thermal property. In present work, a finite element method (FEM) was developed to obtain a fundamental understanding of the behavior of the Ni particles/wires under a uniform magnetic field by predefined magnetic pads. In the model, the Navier-Stokes equations were introduced as governing equations for the fluid field and the magnetic field was simulated by Maxwell’s equations. Then the motion of single Ni wire was modeled and the translation and rotational movements of the wire was studied in this paper.
Proceedings Papers
Proc. ASME. IMECE2019, Volume 2A: Advanced Manufacturing, V02AT02A026, November 11–14, 2019
Paper No: IMECE2019-10349
Abstract
The superalloy products formed by multi-pass conventional spinning are widely used in rotary forming parts with complex shapes. As the connection of each forming pass, the attaching-mandrel process has an important influence on forming quality and production efficiency. The hot spinning process is usually adopted in superalloy forming because its poor plasticity in normal temperature, meanwhile, it brings the poor surface quality of the parts and huge energy consumption. For this reason, the cold spinning and the attaching-mandrel process of nickel-base superalloy GH3030 are studied. The combination method of experiment and simulation is used to study the attaching-mandrel process based on one-forward-pass spinning process. The effects of pass pitch and the attaching-mandrel velocity on the tool forces, parts stress field, strain field and wall thickness distribution are analyzed. The microstructure of the part is divided into three layers: outer, middle and inner layer. The grain size of each layer is compared. Then the effect of different pass pitch on the grain structure is clarified. The results show that the reasonable pass pitch and the attaching-mandrel velocity can improve the forming quality and production efficiency. The multi-pass cold spinning process on superalloy GH3030 is feasible. The excessive pass pitch can cause seriously grain elongation, the grain boundaries are blurred, and even cracking.
Proceedings Papers
Proc. ASME. IMECE2019, Volume 2B: Advanced Manufacturing, V02BT02A035, November 11–14, 2019
Paper No: IMECE2019-12122
Abstract
Directed energy deposition (DED) is a major additive manufacturing (AM) process, which employs high energy beams as the heat source to melt and deposit metal powder in a layer-by-layer fashion such that complex components can be manufactured. In this study, a magnetic-field-assisted DED method is applied to control the microstructure and element distribution in the deposited materials. For this purpose, to control the microstructure of DED-built 316L stainless steel, a horizontal magnetic field is introduced during the DED process at different levels of magnetic field intensities (i.e., 0T, 1.0T and 1.8T). Scanning electron microscopy (SEM) and energy dispersive X-Ray spectroscopy (EDS) are used to characterize the microstructure of components obtained with different magnetic field strengths. The results show that the microstructure of deposited materials is significantly affected by the external magnetic field. Also, the result of interdendritic microsegregation pattern presents a transformation from continuous morphology to discrete morphology because of the applied magnetic field. Along with the increasing horizontal magnetic field intensity, nickel and chromium content are changed significantly in austenite and ferrite.
Proceedings Papers
Proc. ASME. IMECE2019, Volume 9: Mechanics of Solids, Structures, and Fluids, V009T11A056, November 11–14, 2019
Paper No: IMECE2019-11186
Abstract
Since the operating condition of thermal power plants has become harsher for minimizing the emission of CO 2 , Ni-based superalloys, such as Alloy 617 and 625, have been used in the plants to replace the conventional ferritic materials. Unfortunately, the increase of coefficient of thermal expansion compared with conventional steels is a concern. In addition, Ni-based superalloys have to suffer creep-fatigue random loading because thermal power plants have to compensate the random output of various renewable energies. It was found that the lifetime of Ni-based superalloys under creep-fatigue loading was much shorter than that under simple fatigue or creep loading. Thus, it has become very important to clarify the crack mechanism and establish the quantitative theory for estimating their lifetime under various loading conditions at elevated temperatures. Thus, the elucidation of the initial damage mechanism of Alloy 625 under various loading is indispensable. Hence, the initial cracking mechanism of Alloy 625 at grain boundaries under creep loading was investigated experimentally. The creep test was applied to small specimens in Argon atmosphere. The change of the micro texture during the creep test was observed by using SEM. It was confirmed that all the initial cracks appeared at certain grain boundaries. The change of the crystallinity was observed by EBSD (Electron Back-Scatter Diffraction) analysis quantitatively. It was found that the local accumulation of dislocations at the cracked grain boundaries caused the initial cracks at those grain boundaries. The initiation of cracks appeared clearly between two grains which had difference of KAM (Kernel Average Misorientation) values larger than 0.2. Therefore, dislocations were accumulated at one side of the grain boundary. By measuring the KAM values near grain boundaries, the appearance of initial cracks can be predicted approximately.
Proceedings Papers
Proc. ASME. IMECE2019, Volume 12: Advanced Materials: Design, Processing, Characterization, and Applications, V012T10A027, November 11–14, 2019
Paper No: IMECE2019-11411
Abstract
Multi-layered carbon nanostructures are the next leap for many advanced consumer and industrial applications that require both high strength and uniquely high electrical and thermal properties. Applications of three-dimensional (3D) carbon nanostructures have already been theorized to include wearable technology, processor chip heat transfer material, and flexible electronics. 3D carbon nanostructures appear in the form of carbon nanotubes (CNTs) and layered graphene tiers, however, many structures previously examined have been limited to one or two graphene layers or non-repeatable structured patterns. Many of the electrical and thermal properties of CNTs are still being investigated, but the initial studies demonstrate promising results such as the thermal conductivity ranging in the thousands W/m-K. Developing new ways to fabricate these structures at a reasonable cost has become a primary focus for graphene-based research. In this study, 3D carbon nanostructure samples are 3D printed using laser lithography, then a series of high temperature furnace burns and Nickel Chemical Vapor Deposition (CVD) is utilized to leave a previously multi-species structure as a solely carbon-species structure with mostly carbon sp-2 bonds. CVD has proven to be a leading method for forming graphene due to the ability to control graphene nucleation across larger surfaces and structures. Nanoscale 3D printing of carbon structures also allows for a great degree of freedom towards the creation of repeatable patterns or structures that are currently trying to be achieved in other studies. This study employs the use of controlled cleanroom environments with cutting edge technology and machines to fabricate the 3D carbon nanostructures.
Proceedings Papers
Proc. ASME. IMECE2018, Volume 9: Mechanics of Solids, Structures, and Fluids, V009T12A001, November 9–15, 2018
Paper No: IMECE2018-88197
Abstract
We investigate the relationship between the average profile height and the average plastic strain of a grain in a polycrystalline material under plastic tensile strain using Crystal Plasticity Finite Element Method (CPFEM). The simulation consists of using an anisotropic grain embedded in an isotropic sample undergoing tensile plastic deformation. 150 different lattice orientations for the embedded anisotropic grain are used to represent all possible grain orientations. We found that plastic strain in the loading direction is not related to the surface profile height. However, the plastic strains in the direction normal to the surface and the transverse direction are linearly proportional to the average profile heights, irrespective of the grain orientation. The magnitude of the plastic strain in the direction normal to the surface decreases with increasing surface profile height. It is vice versa for plastic strains in the transverse direction. These results establish a possibility of determining a grain’s plastic strains from the profile height.
Proceedings Papers
Proc. ASME. IMECE2018, Volume 8A: Heat Transfer and Thermal Engineering, V08AT10A034, November 9–15, 2018
Paper No: IMECE2018-86947
Abstract
A multiscale modeling that integrates electronic scale ab initio quantum mechanical calculation, atomic scale molecular dynamics simulation, and continuum scale two-temperature model description of the femtosecond laser processing of nickel film at different thicknesses is carried out in this paper. The electron thermophysical parameters (heat capacity, thermal conductivity, and electron-phonon coupling factor) are calculated from first principles modeling, which are further substituted into molecular dynamics and two-temperature model coupled energy equations of electrons and phonons. The melting thresholds for nickel films of different thicknesses are determined from multiscale simulation. Excellent agreement between results from simulation and experiment is achieved, which demonstrates the validity of modeled multiscale framework and its promising potential to predict more complicate cases of femtosecond laser material processing. When it comes to process nickel film via femtosecond laser, the quantitatively calculated maximum thermal diffusion length provides helpful information on choosing the film thickness.
Proceedings Papers
Proc. ASME. IMECE2018, Volume 1: Advances in Aerospace Technology, V001T03A011, November 9–15, 2018
Paper No: IMECE2018-86576
Abstract
Thermal Barrier Coatings have been widely used in modern turbine engines to protect the nickel based metal substrate from the high temperature service conditions, 1600–1800 K. In this study, some of the failure mechanisms of typical Air Plasma Sprayed Thermal Barrier Coatings (TBC) used in after-burner structures composed of three major layers: Inconel 718 substrate, NiCrAlY based metallic bond coat (BC) and Yttria Stabilized Zirconia (YSZ) based ceramic top coat (TC) are investigated. Investigation of the cracking mechanism of TBC in terms of design and performance is very important because the behavior of TBCs on ductile metallic substrates is brittle. To this end, four-point bending experiments conducted in Kütükoğlu (2015) is analyzed by using the Extended Finite Element Method (XFEM). All the analyses are conducted with the commercial finite element software ABAQUS. Three different models with varying TC and BC thicknesses are studied under four-point bending. It is observed that multiple vertical cracks are initiated in the TC. Cracks initiate at the top of YSZ and propagate through the whole TC. It is observed that the average crack spacing increases with the increasing thickness of the TC. Numerical results are found to be consistent with the experimental results. In other words, the average crack spacing for three different models are similar with the experimental results.
Proceedings Papers
Proc. ASME. IMECE2018, Volume 3: Biomedical and Biotechnology Engineering, V003T04A036, November 9–15, 2018
Paper No: IMECE2018-87552
Abstract
Soil is a vital natural resource that regulates our environment sustainability and provide essential resources to humans and nature. Nowadays, with an increasingly populated and urbanized world, pollution is widely recognized as a significant challenge to soil and groundwater resources management. The most common chemicals found in soils and water plumb in a dissolved state and considered as potential pollutants are heavy metals, dyes, phenols, detergents, pesticides, polychlorinated biphenyls (PCBs), and others organic substances, such as organic matter. Unlike organic contaminants, heavy metals are not biodegradable and tend to accumulate in living organisms and many heavy metal ions are known to be toxic or carcinogenic. Toxic heavy metals of particular concern zinc, copper, nickel, mercury, cadmium, lead and chromium. Electrokinetic remediation deserves particular attention in soil treatment due to its peculiar advantages, including the capability of treating fine and low permeability materials, and achieving consolidation, dewatering and removal of salts and inorganic contaminants like heavy metals in a single stage. In this study, the remediation of artificially chromium contaminated soil by electrokinetic process, coupled with Eggshell Inorganic Fraction Powder (EGGIF) permeable reactive barrier (PRB), was investigated. An electric field of 2 V cm −1 was applied and was used an EGGIF/soil ratio of 30 g kg −1 of contaminated soil for the preparation of the permeable reactive barrier (PRB) in each test. Results proved that the study of chromium mobility revealed the predominance in its transportation through the soil towards the anode, due essentially to the existence of chromium in the form of oxyanions (chromate and dichromate), which confers a negative charge to the molecule. Chromium removal by electrokinetic remediation was faster in low levels of concentration and the utilization of citric acid as buffer and complexing agent allowed to maintain pH of soil below the precipitation limit for this element. It was obtained high removal rates of chromium in both experiments, especially near the anode. In the normalized distance to cathode of 0.8 it was achieved a maximum removal rate of chromium of 55, 59 and 60% in initial chromium concentration of 500 mg kg −1 , 250 mg kg −1 and 100 mg kg −1 , respectively. The viability of the new coupling technology developed (electrokinetic with EGGIF permeable reactive barrier) to treat low-permeability polluted soils was demonstrated. Based on the proved efficiency, this remediation technique has to be optimized and applied to real soils in order to validate it as a large-scale solution.
Proceedings Papers
Proc. ASME. IMECE2017, Volume 14: Emerging Technologies; Materials: Genetics to Structures; Safety Engineering and Risk Analysis, V014T11A018, November 3–9, 2017
Paper No: IMECE2017-71370
Abstract
Galvanic sludge is a solid waste produced by the surface treatment industry, classified as hazardous because of their high concentration of heavy metals, which in its final destination is disposed in waste disposal facilities, with economic costs to the holders. Through hydrometallurgical processing, it is possible to extract valuable metals, with low costs involved, while the hazardous level of the residue is reduced. In the present work, the heap leaching method was studied as a solution to the treatment of these residues, which in order to consist in a valuable option, processing and operation costs must be kept as low as possible. For the experimental testing, a closed loop lixiviation column for hydrometallurgical treatment of galvanic sludge with possibility of continuous flow of the leachate (and static process as well) was constructed, simulating the heap leaching process. The galvanic waste in study, delivered by a local surface treatment company, was both chemically and physically characterized, proving to be rich in valuable metals like Nickel, Chromium and Copper. The waste material was characterized both for physical parameters (grain size) and chemical composition. The lixiviation trials, with a maximum duration of 1 week, were conducted. The influence upon the extraction rate of metals such as Nickel, Chromium and Copper, of parameters such as the concentration of the leaching agent (sulfuric acid) and time were tested. In order to quantify the leachate circulation effect, a static trial was conducted as well. Extraction rates of 35.5 % of Nickel, 14% of Copper and 13.6 % of Chromium were obtained after 6 hours in a dynamic trial, with 100 g/L sulfuric acid solution concentration. The acid consumption rate was correlated with the metal extraction. Finally, the results were compared with others obtained in previous galvanic sludge agitation lixiviation and laterites heap leaching works.
Proceedings Papers
Che-Fu Su, Junwei Su, Hamed Esmaeilzadeh, Jirui Wang, Edward Fratto, Majid Charmchi, Zhiyong Gu, Hongwei Sun
Proc. ASME. IMECE2017, Volume 8: Heat Transfer and Thermal Engineering, V008T10A053, November 3–9, 2017
Paper No: IMECE2017-72202
Abstract
The high conductive nickel (Ni) nanoparticles mixed with paraffin wax at two different volume ratios were prepared to investigate thermal conductivity enhancement of Phase Change Material (PCM) under random and aligned particle distribution. For each particle concentration, two samples were prepared. After mixing of the particles into the melted paraffin through sonication, one sample was placed in a static magnetic field to align the nanoparticles while the PCM was allowed to solidify; whereas, the second sample was solidified immediately after sonication to obtain a randomly distributed nanoparticles in the solid PCM. The thermal conductivity of both nanoPCM samples along with a pure paraffin sample were measured experimentally. The conductivity of both nanoPCM samples were substantially higher than the pure wax and the sample with magnetically aligned nanoparticle exhibited significantly higher thermal conductivity in comparison to the randomly distributed nanoPCM sample. It was anticipated that the configuration of the metallic fillers that are parallelly aligned with the applied heat flux direction does enhance the heat dissipation through the particle chains. However, the magnitude of thermal enhancement and sample fabrication in larger scales require further research efforts.
Proceedings Papers
Proc. ASME. IMECE2017, Volume 9: Mechanics of Solids, Structures and Fluids; NDE, Structural Health Monitoring and Prognosis, V009T12A011, November 3–9, 2017
Paper No: IMECE2017-72139
Abstract
In this study, interrupted creep and creep-fatigue tests of Alloy 617, which is a candidate alloy for boiler tubes and pipes of A-USC (advanced ultra-supercritical) power plants of the 700°C-class, were conducted to investigate damage evolution process. Also, the change of the micro texture of the alloy was continuously observed at a fixed area to elucidate the mechanism of damage evolution under creep and creep-fatigue loading from the viewpoint of the change of the order of atom arrangement using EBSD (Electron Back-Scatter Diffraction) analysis. The conditions of the creep test were a temperature of 800°C and the stress of 150 MPa in inert gas (99.9999% Ar). The stress-controlled creep-fatigue tests were carried out at 800°C in Ar using stress ratio R = −1 and hold time of 10 minutes at peak tension. IQ (Image Quality) values, which are the average sharpness of the obtained diffraction pattern, were used for evaluating the change of the micro texture during the tests. In both creep and creep-fatigue test, intergranular cracks appeared. The IQ value decreased monotonically in the vicinity of grain boundaries with the decrease of fracture life, indicating that the crystallinity of grain boundaries degraded faster than that of grains. This localized damage around grain boundaries was attributed to the intergranular crack propagation in the creep and creep-fatigue test. In addition, all the grain boundaries with IQ value lower than 85% of IQ value in as-received specimen were found to be cracked during both creep and creep-fatigue test. Therefore, there was the critical IQ value around grain boundaries at which intergranular cracks occurred under creep or creep-fatigue loading condition.
Proceedings Papers
Daniel S. Park, J. Upadhyay, K. Sharmin, J. F. Robbins, I. Schoegl, K. E. Thompson, D. E. Nikitopoulos
Proc. ASME. IMECE2017, Volume 10: Micro- and Nano-Systems Engineering and Packaging, V010T13A025, November 3–9, 2017
Paper No: IMECE2017-71639
Abstract
A ceramic-based micromodel was fabricated with batching of green alumina ceramics mixed with polymer binders, extrusion of the green alumina tapes, and hot embossing of the green tapes with a metal mold. The metal mold fabricated using optical lithography of SU8 and electroforming of nickel contained 2.5D pore network geometry in 13 layers of a rock, Boise sandstone. The hot embossing process enabled the generation of the pore network geometries with a minimum feature size of 25 μm and for distinct formation of the 13 layers of the 2.5D pore geometry of the rock. The green ceramic micromodels were processed with solvent extraction, thermal debinding, and sintering. The sintered micromodels showed significant shrinkages at all directions of the micromodels, which were 17.6% in x, 17.5% in y, and 14.6% in z. The sintered, 2.5D rock-based ceramic micromodel was capped with a thin glass cover slide and used for flow visualization with a fluorescent dye and fluorescent nano-particles. The dye-filled micromodel showed good flow connectivity and fluorescence signal intensity dependence on depth. It was observed that the peak particle concentration close to the observation window and gradual decrease in particle concentration along the depth. The higher velocities were measured in the low flow resistance region with velocity variations along the depth. The microfabricated 2.5D ceramic micromodels will allow resistance to harsh experimental conditions such as high temperature and pressure, and opportunity for investigation of the complex flow patterns in 3D.
Proceedings Papers
Proc. ASME. IMECE2016, Volume 14: Emerging Technologies; Materials: Genetics to Structures; Safety Engineering and Risk Analysis, V014T11A034, November 11–17, 2016
Paper No: IMECE2016-67071
Abstract
Computational design for property management of composite materials offers a cost sensitive alternate approach in order to understand the mechanisms involved in the thermal and structural behavior of material under various combinations of inclusions and matrix material. The present study is concerned with analyzing the elasto-plastic and thermal behavior of Al 2 O 3 -Ni droplet composites using a mean field homogenization and effective medium approximation (EMA) using an in-house code. Our material design approach relies on a method for predicting potential optimum thermal and structural properties for Al 2 O 3 -Ni composites by considering the effect of inclusion orientation, volume, size, thermal interface resistance, percolation and porosity. The primary goal for designing such alumina-based composites is to have enhanced thermal conductivity for effective heat dissipation and spreading capabilities. At the same time, other functional properties like thermal expansion coefficient, elastic modulus, and electrical resistivity have to be maintained or enhanced. The optimum volume fraction was found to occur between 15 and 20 vol. %Ni while the average nickel particle size of 5 μm was found a minimum size that will enhance the thermal conductivity. The Young’s modulus was found decreasing as the volume fraction of nickel increases, which would result in enhanced fracture toughness. Electrical conductivity was found to be greatly affected by the percolation phenomenon in the designed range of volume fraction minimum particle size. As a validation, Al 2 O 3 composites with 10% and 15% volume fraction Ni and droplet size of 18 μm are developed using spark Plasma Sintering process. Thermal conductivity and thermal expansion coefficient of the samples are measured to complement the computational design. Microstructural analysis of the sintered samples was also studied using optical microscope to study the morphology of the developed samples. It was found that the present computational design tool was accurate enough in predicting the desired properties of Al 2 O 3 -Ni composites.
Proceedings Papers
Proc. ASME. IMECE2016, Volume 14: Emerging Technologies; Materials: Genetics to Structures; Safety Engineering and Risk Analysis, V014T11A010, November 11–17, 2016
Paper No: IMECE2016-65514
Abstract
The properties of carbon nanotubes are dependent, in part, on the size of the catalyst metal nanoparticles from which the carbon nanotubes are grown. Annealing is a common technique for forming the catalyst nanoparticles from deposited films. While there is ample work connecting catalyst film properties or catalyst nanoparticle properties to carbon nanotube growth outcomes, the control of catalyst nanoparticle size by means other than the variation of initial film thickness is less explored. This work develops an empirical correlation for the control of nickel nanoparticle equivalent diameter by modification of anneal plateau temperature and anneal plateau time, thereby providing an additional avenue of control for catalyst properties. It has been hypothesized that the size of catalyst nanoparticles can be predetermined by appropriate selection of the initial catalyst film thickness, plateau temperature, and plateau time of the annealing process. To this end, buffer layers of 50 nm titanium, followed by 20 nm aluminum, were deposited onto silicon substrates via electron beam evaporation. Nickel catalyst layers were then deposited with thicknesses of either 5, 10, or 20 nm. Samples of each of the three nickel layer thicknesses were annealed in an ambient air environment at different combinations of 500, 600, 700, 800, and 900 °C plateau temperature and 5, 10, and 15 minute plateau time. Representative time-temperature curves corresponding to each plateau temperature were also acquired. The end result was a set of 45 samples, each with a unique combination of initial nickel film thickness, anneal plateau temperature, and anneal plateau time. Resulting nanoparticles were characterized by atomic force microscopy, and distributions of nanoparticle equivalent diameter were collected via a watershed algorithm implemented by the Gwyddion software package. Comparison of the 45 parameter combinations revealed a wide range of nanoparticle sizes. In most cases, comparable equivalent diameters were obtained from a variety of parameter combinations. Thus, results provide multiple options for achieving the same nanoparticle diameter, for use in cases where additional restraints are present. To facilitate such decisions, a correlation was developed that connected catalyst nanoparticle diameter to the three process parameters of initial catalyst film thickness, anneal plateau temperature, and anneal plateau time. For example, a given initial Ni film thickness can be annealed to a specified nanoparticle size by selecting anneal plateau temperature and plateau time per the correlation, provided that comparable buffer layers were chosen. This correlation provides a more robust array of options for specification of catalyst nanoparticle size and final carbon nanotube properties for a specific application.
Proceedings Papers
Proc. ASME. IMECE2015, Volume 10: Micro- and Nano-Systems Engineering and Packaging, V010T13A014, November 13–19, 2015
Paper No: IMECE2015-50657
Abstract
Fabrication of 2.5D rock-based micromodels with high resolution features is presented using SU-8 multi-layer lithography and nickel electroforming for nickel molds. Processes associated with SU-8 were carefully optimized by the use of the vacuum contact, the use of UV filter, and controls of UV exposure doses and baking times. The use of SU-8 MicroSpray enabled the easy fabrication of multi-layers of SU-8, while exhibiting some total thickness variations. The thirteen layered SU-8 samples showed reliable patterning results for features at 10 and 25 μm resolutions, and minor pattern distortions of features at the 5 μm resolution. Flycutting method employed in multi-layer lithography of SU-8 yielded accurate total thickness control within ±1.5 μm and excellent pattern formation for all of 5, 10, and 25 μm features. Electroforming of nickel was optimized with electroplating bath composition and electroplating parameters such as current density to realize the high resolution nickel mold. The fabricated nickel molds from flycutting based SU-8 samples revealed the feasibility of manufacturing the minimum features down to 5 μm for thirteen layers without any pattern distortions. The replication-based micromolding method will allow for fabrication of micromodels in a variety of materials such as polymers and ceramics. The high resolution, 2.5D micromodels will be used for investigation of pore-scale fluid transport, which will aid in understanding the complicated fluidic phenomena occurring in the 3D reservoir rock.
Proceedings Papers
Proc. ASME. IMECE2015, Volume 6B: Energy, V06BT07A009, November 13–19, 2015
Paper No: IMECE2015-52624
Abstract
The traditional refrigerants used in the vapor compression cycles have significant environmental impacts due to their high global warming potential. To address this challenge, solid-sate cooling technologies without using any aforementioned fluids have been developed rapidly during the past decades. Thermoelastic cooling, a.k.a. elastocaloric cooling, is a new concept, and thus no systematic studies of it have been conducted to date. Heat recovery plays an important role in the performance of the cooling systems, affected by the parasitic internal latent heat loss inside the cycle. A novel heat recovery (HR) scheme was been proposed in our previous study to minimize such parasitic internal latent heat loss. The objective of this study is to further investigate the performance improvement potential of the proposed heat recovery method by introducing the optimization study using the previously validated heat recovery model. The dynamic model details are revisited. The assumptions behind the model are re-examined by using the real thermoelastic cooling prototype geometries and materials properties of nickel-titanium tubes. A multi-objective optimization problem was formulated for the model and solved by MatLab. The heat recovery efficiency and the heat recovery duration were used as optimization objectives. A well-spread Pareto solutions were obtained, and a final solution was chosen with a 6.7% penalty in HR efficiency but six times faster cycle.
Proceedings Papers
Proc. ASME. IMECE2015, Volume 15: Advances in Multidisciplinary Engineering, V015T19A028, November 13–19, 2015
Paper No: IMECE2015-52012
Abstract
Large recycled high-density polyethylene (HDPE) structural members, difficult to manufacture by extrusion processes, have been created by the hot plate welding of simple plastic lumber sections. Hot plate welding generates better joint strength than any other welding method currently employed in plastic manufacturing. However, to achieve the desired temperature of the thick plate to melt the polymer uniformly, the process needs a high amount of heat energy requiring furnace (or resistance) heating of a considerable mass. A new method which could combine the heating element and a thin plate into one source could be more efficient in terms of heat loss and thus energy used. The premise of this investigation is to replace the hot plate with a very thin piece of high resistance nickel-chromium alloy ribbon to localize the application of heat within a plastic weld joint in order to reduce energy loss and its associated costs. This resistance ribbon method uses electrical current to reach an adequate temperature to allow for the welding of the HDPE plastic. The ribbon is only slightly larger than the welding surface and very thin to reduce the loss of excess heat through unused surface area and thick sides. The purpose of this project was to weld recycled high-density polyethylene (HDPE) using resistance welding and to match the tensile strength results considered acceptable in industry for hot plate welding, that is, equal to or greater than 80% of the base material strength. Information obtained through literature review and previous investigations in our laboratories established welding (heating) temperature and time as testing factors. Designed experimentation considered these factors in optimizing the process to maximize the weld tensile strength. A wide-ranging full-factorial experimental design using many levels was created for the initial testing plan. Tensile strengths obtained after welding under the various condition combinations of weld temperature and time revealed a region of higher strength values in the response surface. After the wide-range initial testing, the two control parameters, heating temperature and heating time, were ultimately set up in a focused Face Centered Cubic (FCC) Response Surface Method (RSM) testing design and the tensile strength response was then analyzed using statistical software. The results obtained indicated a strong correlation between heating time and heating temperature with strength. All welded samples in the final testing set exhibited tensile strength of over 90% base material, meeting the goal requirements. A full quadratic equation relationship for tensile strength as a function of welding time and temperature was developed and the maximum tensile strength was achieved when using 280°C for 60 seconds.