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Results for “Casting Optimization”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Process Research of Polycrystalline Silicon Material (PROPSM)

A passivation process (hydrogenation) that will improve the power generation of solar cells fabricated from presently produced, large grain, cast polycrystalline silicon (Semix), a potentially low cost material are developed. The first objective is to verify the operation of a DC plasma hydrogenation system and to investigate the effect of hydrogen on the electrical performance of a variety of polycrystalline silicon solar cells. The second objective is to parameterize and optimize a hydrogenation process for cast polycrystalline silicon, and will include a process sensitivity analysis. The sample preparation for the first phase is outlined. The hydrogenation system is described, and some early results that were obtained using the hydrogenation system without a plasma are summarized. Light beam induced current (LBIC) measurements of minicell samples, and their correlation to dark current voltage characteristics, are discussed.

Culik, J. S.↗
DOE OSTI2025

Optimization of edge bead removal (EBR) process to enhance defect reduction in optical lithography

Defect reduction remains a critical objective in the integrated circuit manufacturing process, particularly within the highly re-entrant lithography modules where minimizing defects is crucial. Defects at the wafer edge can contaminate lithography modules and downstream processing equipment, leading to redistribution onto the wafer surface and adversely affecting overall device yield. A persistent challenge in the resist coating process is the formation of resist edge beads, driven by the strong Van der Waals attraction of excess photoresist (PR) to itself and the underlying substrate. The edge bead removal (EBR) process is a standard cleaning step designed to eliminate these edge beads and prevent potential contamination. Here, in this study, we identify the sources of EBR induced defects and additional EBR process encroachment toward edge patterning during the EBR cleaning process. This study provides a comprehensive study aimed at optimizing the EBR cleaning process to effectively eliminate EBR-induced defects, thereby enhancing overall device yield. Specifically, we identify three primary defects induced by the EBR cleaning process: rainbow-type, finger-shaped, and teardrop-type defects. Our experimental study reveals that in addition to EBR rinse time, PR cast time is crucial parameters contributing to the formation of these defects. By properly optimizing the PR cast time and EBR rinse time, we were able to remove nearly 100 % of dense clusters of defects that were easily visible even at low magnification optical microscopy throughout the wafer edge. We observed that shorter PR casting times shows edge defects caused by inefficient EBR process because of insufficient time for PR to fully settle causing superfluous PR to continue flowing toward wafer edge during EBR clearing step, leading to partial removal of PR at the wafer edge and the formation of rainbow defects. Proper optimization of both PR casting time and EBR chemistries dispense time is essential to resolve these defects, ensuring efficient EBR cleaning process and improved overall device yield.

42 ENGINEERING↗
DOE OSTI2016

Synthesis of nanostructured/macroscopic low-density copper foams based on metal-coated polymer core–shell particles [Templated synthesis of nanowalled low-density copper foams]

A robust, millimeter-sized low-density Cu foam with ~90% (v/v) porosity, ~30 nm thick walls, and ~1 μm diameter spherical pores is prepared by the slip-casting of metal-coated polymer core–shell particles followed by a thermal removal of the polymer. In this paper, we report our key findings that enable the development of the low-density Cu foams. First, we need to synthesize polystyrene (PS) particles coated with a very thin Cu layer (in the range of tens of nanometers). A simple reduction in the amount of Cu deposited onto the PS was not sufficient to form such a low-density Cu foams due to issues related to foam collapse and densification upon the subsequent polymer removal step. Precise control over the morphology of the Cu coating on the particles is essential for the synthesis of a lower density of foams. Second, improving the dispersion of PS–Cu particles in a suspension used for the casting as well as careful optimization of a baking condition minimize the formation of irregular large voids, leading to Cu foams with a more uniform packing and a better connectivity of neighboring Cu hollow shells. Finally, we analyzed mechanical properties of the Cu foams with a depth-sensing indentation test. The uniform Cu foams show a significant improvement in mechanical properties (~1.5× modulus and ~3× hardness) compared to those of uncontrolled foam samples with a similar foam density but irregular large voids. As a result, higher surface areas and a good electric conductivity of the Cu foams present a great potential to future applications.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Advanced Anion Exchange Membranes with Tunable Water Transport for PGM-Free AEMFCs

This project advanced the synthesis, characterization, and testing of anion exchange membranes for use in fuel cells. Our goal was to improve the water transport in anion exchange membrane fuel cells to improve their performance and durability. Through the work in this project we: 1) developed new composite anion exchange membranes through polymer synthesis and membrane casting into mechanical supports; 2) optimized electrode architecture and cell conditions to achieve; 3) demonstrated an integrated approach to achieving over 1 W/cm 2 in an operating device. While we did not achieve 1000 hours of continuous operation, we demonstrated multiple runs of more than 300 hours of device performance at steady-state.

08 HYDROGEN↗
DOE OSTI2025

Jump-Start U.S. Manufacturing of High-Performance Permanent Magnets

Gas atomized feedstock powders for Nd-Fe-B based magnets are more robust and cost effective than the strip-cast sheet currently used as feedstock for milling by the magnet industry. However, gas atomized powder’s crystallinity and grain boundary phases are less ideal than the strip cast flake. We proposed to optimize the atomization process as well as the powder chemistry to address this issue and to eliminate heavy rare earth elements from these magnet alloys. Our goal is to help GKN-Hoeganaes, a US metal powder company, who used to make Nd-Fe-B magnets, to bring back US manufacturing of these high energy density permanent magnets.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Coreset Clustering on Small Quantum Computers

Many quantum algorithms for machine learning require access to classical data in superposition. However, for many natural data sets and algorithms, the overhead required to load the data set in superposition can erase any potential quantum speedup over classical algorithms. Recent work by Harrow introduces a new paradigm in hybrid quantum-classical computing to address this issue, relying on coresets to minimize the data loading overhead of quantum algorithms. We investigated using this paradigm to perform k-means clustering on near-term quantum computers, by casting it as a QAOA optimization instance over a small coreset. We used numerical simulations to compare the performance of this approach to classical k-means clustering. We were able to find data sets with which coresets work well relative to random sampling and where QAOA could potentially outperform standard k-means on a coreset. However, finding data sets where both coresets and QAOA work well—which is necessary for a quantum advantage over k-means on the entire data set—appears to be challenging.

42 ENGINEERING↗
NASA NTRS1978

Rheology of composite solid propellants during motor casting

In a study conducted to evaluate flow parameters of uncured solid composite propellants during motor casting, two motors (1.8M-lb grain wt) were cast with a PBAN propellant exhibiting good flow characteristics in a 260-in. dia solid rocket motor. Attention is given to the effects of propellant compositional and processing variables on apparent viscosity as they pertain to rheological behavior and grain defect formation during casting. It is noted that optimized flow behavior is impaired with solid propellant loading. Non-Newtonian pseudoplastic flow is observed, which is dependent upon applied shear stress and the age of the uncured propellant.

Rogers, C. J.↗
NASA NTRS1984

Changes in solidified microstructures

The properties and casting behavior of metals are significantly affected by their cast structure. This structure is optimized by producing columnar versus equiaxed grains and coarse versus fine grains by controlling solidification conditions. The transition from columnar to equiaxed grains is favored by: constitutional supercooling with effective nucleation of free dendrites; melting off and transport of dendrite tips and arms; mechanical vibration; falling down of free dendrites from a chilled top surface; and induced flow in the solidifying structure by oscillation of rotation.

Wallace, J. F.↗
NASA NTRS1990

An application of compound scaling to wind tunnel model design

An approach was developed for the stiffness design of aeroelastically scaled wind tunnel models. The object of designing such models is to make a structure whose stiffness matches a desired stiffness distribution. This design problem is cast as a formal constrained optimization problem and worked with two different optimization methods. A previous effort used the modified method of feasible directions (MFD) as implemented in a general purpose finite element based optimization code. In this effort, a special purpose finite element based optimization program was written and run using both MFD and compound scaling optimization methods. Results are presented comparing the final designs obtained using MFD and compound scaling.

French, Mark↗
NASA NTRS2017

LMI-Based Fuzzy Optimal Variance Control of Airfoil Model Subject to Input Constraints

This paper presents a study of fuzzy optimal variance control problem for dynamical systems subject to actuator amplitude and rate constraints. Using Takagi-Sugeno fuzzy modeling and dynamic Parallel Distributed Compensation technique, the stability and the constraints can be cast as a multi-objective optimization problem in the form of Linear Matrix Inequalities. By utilizing the formulations and solutions for the input and output variance constraint problems, we develop a fuzzy full-state feedback controller. The stability and performance of the proposed controller is demonstrated through its application to the airfoil flutter suppression.

optimal variance control↗
DOE OSTI2020

An error-in-constitutive equations strategy for topology optimization for frequency-domain dynamics

This paper presents a topology optimization formulation for frequency-domain dynamics to reduce solution dependence upon initial guess and considered loading conditions. Due to resonance phenomena in undamped steady-state dynamics, objectives measuring dynamic response possess many local minima that may represent poor solutions to a design problem, an issue exacerbated for design with respect to multiple frequencies. In this work, we propose an extension of the modified error-in-constitutive-equations (MECE) method, used previously in material identification inverse problems, as a new approach for frequency-domain dynamics topology optimization to mitigate these issues. The main idea of the proposed framework is to incorporate an additional penalty-like term in the objective function that measures the discrepancy in the constitutive relations between stresses and strains and between inertial forces and displacements. Then, the design problem is cast within a PDE-constrained optimization formulation in which we seek displacements, stresses, inertial forces, and a density-field solution that minimize our new objective subject to conservation of linear momentum plus some additional constraints. We show that this approach yields superior designs to conventional gradient-based optimization approaches that solely use a functional of displacements as the objective, while strictly enforcing the constitutive equations. The MECE strategy integrates into a density-based topology optimization scheme for void–solid or two-phase material structural design. We highlight the merits of our approach in a variety of scenarios for direct frequency response design, considering multiple frequency load cases and structural objectives.

42 ENGINEERING↗
DOE OSTI2019

The Effect of Membrane Structure Prepared from Carboxymethyl Cellulose and Cellulose Nanofibrils for Cationic Dye Removal

Water-stable and eco-friendly membranes were fabricated from carboxymethyl cellulose (CMC) acting as anionic adsorbent and cellulose nanofibrils (CNFs) as strengthening filler by solvent- and unidirectional freeze-casting processes, both supported with simultaneous citric acid (CA) mediated cross-linking. Spectroscopic, thermogravimetric and potentiometric titration techniques were applied to evaluate the efficacy of the cross-linking as well as to quantify the processing-dependant surface charge. In addition, the CMC/CNF assembling and membrane porosity were identified microscopically as the combinatorial effect of components ratio and the applied fabrication technique. Finally, the membrane’s cationic dyes adsorption capacity and kinetic were evaluated depending on the dyes ionization constants, solution pH, and the contact time using batch equilibrium experiment, and further evaluated for filtration performance at optimal pH. The resulting, freeze-casted membranes demonstrate anisotropic to isotropic and highly (> 90%) porous structures with gradient pore sizes (from few nm up to 200 µm range). This provides relatively high and stable flux rates (150–190 kL/m{sup 2} h MPa) with ~ 100% cationic dye adsorption, fast dynamic (8.536–5.446 kg/g min) and capacity (1828–1398 g/kg), which highlight their potential in dead-end filtration technologies without need for additional separation step. The similar dye adsorption capacity was assessed for denser and nano-porous (< 50 nm) solvent-casted membranes, however, with much lower and time-declining flux rates (100–10 L/m{sup 2} h MPa), demonstrating their potential usage in spiral wound-cross-flow modules. Both types of membranes anyhow showed high dye removal capacity (≥ 90%) even after 4th (solvent-casted) and 50th (freeze-casted) reusing cycle, present a high-value alternative to commercial activated carbons or other bio-nano-absorbents.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Roll-to-Roll SOFC Manufacturing for Low Cost Energy Generation

Oak Ridge National Laboratory (ORNL) and Redox Power Systems, LLC. collaborated on this project to develop an integrated, continuous roll-to-toll (R2R) manufacturing processes to produce solid oxide fuel cells (SOFCs). SOFCs are ceramic-based electrochemical devices that efficiently produce electricity from hydrogen-containing fuels, including natural gas. Standard processes for manufacturing SOFCs include tape casting of the anode and electrolyte, followed by stacking of the layers, and lamination using a uniaxial press or isostatic press. After high temperature firing, the cathode and electrical contact are screen printed and fired once again to complete the cell. This effort aimed to further develop R2R tape fabrication processes for green cell fabrication with the DOE Battery Manufacturing Facility (BMF) at ORNL as next generation improvements to current methods, focusing on R2R calendering and slot die coating for lower cost, high volume approaches for multilayer green cell fabrication. Two paths were investigated in parallel in this project. The first path was to optimize R2R processing using traditional tape cast materials from the Redox production chain on the BMF’s heated calender for compressing and laminating multilayer materials. The second path was to use BMF’s pilot-scale slot-die coater for R2R manufacturing as an alternative to tape casting of some or all of the layers in the green cell. Processes have been developed and and process conditions have been identified. Additionally, basic process economics were estimated for comparison to Redox current manufacturing approaches for the applicable process modules. The SBV program results will enable Redox to advance lower cost R2R manufacturing processes to produce millions of green cells per year on a single production line. As a result of this work, one invention disclosure has been submitted. In addition, one paper is under preparation for submission to a peer-reviewed journal.

30 DIRECT ENERGY CONVERSION↗
NASA NTRS1975

Preliminary study of oxide-dispersion-strengthened B-1900 prepared by mechanical alloys

An experimental oxide dispersion strengthened (ODS) alloy based on the B-1900 composition was produced by the mechanical alloying process. Without optimization of the processing for the alloy or the alloy for the processing, recrystallization of the extruded product to large elongated grains was achieved. Materials having grain length-width ratios of 3 and 5.5 were tested in tension and stress-rupture. The ODS B-1900 exhibited tensile strength similar to that of cast B-1900. Its stress-rupture life was lower than that of cast B-1900 at 760 C. At 1095 C the ODS B-1900 with the higher grain length-width ratio (5.5) had stress-rupture life superior to that of cast B-1900. It was concluded that, with optimization, oxide dispersion strengthening of B-1900 and other complex cast nickel-base alloys has potential for improving high temperature properties over those of the cast alloy counterparts.

Glasgow, T. K.↗
DOE OSTI2016

A modeling comparison of deep greenhouse gas emissions reduction scenarios by 2030 in California

California aims to reduce greenhouse gas (GHG) emissions to 40% below 1990 levels by 2030. We compare six energy models that have played various roles in informing the state policymakers in setting climate policy goals and targets. These models adopt a range of modeling structures, including stock-turnover back-casting models, a least-cost optimization model, macroeconomic/macro-econometric models, and an electricity dispatch model. Results from these models provide useful insights in terms of the transformations in the energy system required, including efficiency improvements in cars, trucks, and buildings, electrification of end-uses, low- or zero-carbon electricity and fuels, aggressive adoptions of zero-emission vehicles (ZEVs), demand reduction, and large reductions of non-energy GHG emissions. Some of these studies also suggest that the direct economic costs can be fairly modest or even generate net savings, while the indirect macroeconomic benefits are large, as shifts in employment and capital investments could have higher economic returns than conventional energy expenditures. These models, however, often assume perfect markets, perfect competition, and zero transaction costs. They also do not provide specific policy guidance on how these transformative changes can be achieved. Greater emphasis on modeling uncertainty, consumer behaviors, heterogeneity of impacts, and spatial modeling would further enhance policymakers' ability to design more effective and targeted policies. Here, this paper presents an example of how policymakers, energy system modelers and stakeholders interact and work together to develop and evaluate long-term state climate policy targets. Lastly, even though this paper focuses on California, the process of dialogue and interactions, modeling results, and lessons learned can be generally adopted across different regions and scales.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2024

Center For Actinide Science and Technology (CAST)

CAST encompassed 17 senior researchers in its first funding cycle and added two additional theorists briefly in the final two years. Approximately 37 graduate students and post-doctoral associates were supported by CAST. Within the 19 senior researchers there were changes in composition since the center was first funded. One researcher left associated with a move to another university. Two were phased out because they did not meet the expectations of CAST in terms of research performance. These decisions were always made in consultation with our External Advisory Committee (EAC) and DOE management. In fact, the phasing out of the two PI’s was suggested first by the EAC. Two new researchers were also brought in response to feedback at our midterm review where it was suggested that we needed increased theory support in CAST. No further changes were implemented since then, and CAST researchers thought that stability and optimal productivity was achieved.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1993

An investigation of squeeze-cast alloy 718

Alloy 718 billets produced by the squeeze-cast process have been evaluated for use as potential replacements for propulsion engine components which are normally produced from forgings. Alloy 718 billets were produced using various processing conditions. Structural characterizations were performed on 'as-cast' billets. As-cast billets were then homogenized and solution treated and aged according to conventional heat-treatment practices for this alloy. Mechanical property evaluations were performed on heat-treated billets. As-cast macrostructures and microstructures varied with squeeze-cast processing parameters. Mechanical properties varied with squeeze-cast processing parameters and heat treatments. One billet exhibited a defect free, refined microstructure, with mechanical properties approaching those of wrought alloy 718 bar, confirming the feasibility of squeeze-casting alloy 718. However, further process optimization is required, and further structural and mechanical property improvements are expected with process optimization.

Gamwell, W. R.↗