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Due to their lower pressure drop, impinging cold-plates are preferred over parallel flow cold-plates when there is no strict space limitation (i.e. when flow can enter perpendicular to the electronic board). Splitting the flow into two branches cuts the flow rate and path in half, which leads to lower pressure drop through the channels. A groove is used to direct the flow exiting the diffuser into the channels. The number of the geometric design parameters of the cold-plate will vary depending on the shape of the groove. In this research, the response surface method (RSM) was used to optimization the fin geometry of an impinging cold-plate with a trapezoidal cross section groove. The cold plate is used for warm water cooling of electronics. Three fin parameters (thickness, height, and gap) and three groove parameters were optimized to reach minimum values for hydraulic and thermal resistances at fixed values of coolant inlet temperature, coolant flow rate, and electronic chip power.
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Pressure-dependent topographic evolutions of cold-sintered zinc oxide surfaces
By applying atomic force microscope to the flat in-plane polycrystalline microstructure, pressure-dependent topographic evolutions can be studied with respect to surface dihedral angle and groove geometry. Using a cold-sintered zinc oxide densified at 200 °C as a model system, this study demonstrates an experimental methodology for the quantification of relative grain boundary energetics in cold-sintered material systems and an associated geometric model for connecting the morphological change and underlying mechanochemical phenomenon at various uniaxial pressures ranging from 70 to 475 MPa. Depending on the applied pressure, the anisotropic grain growth, normal grain growth, and coarsening of particles are distinctively observed according to the changes in the groove geometry, suggesting that the growth kinetics can be considered as a function of pressure.
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- Award ID(s):
- 1728634
- PAR ID:
- 10341874
- Date Published:
- Journal Name:
- Journal of Materials Chemistry C
- Volume:
- 9
- Issue:
- 48
- ISSN:
- 2050-7526
- Page Range / eLocation ID:
- 17313 to 17318
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Due to their lower pressure drop, impinging cold-plates are preferred over parallel flow cold-plates when there is no strict space limitation (i.e. when flow can enter perpendicular to the electronic board). Splitting the flow into two branches cuts the flow rate and path in half, which leads to lower pressure drop through the channels. A groove is used to direct the flow exiting the diffuser into the channels. The number of the geometric design parameters of the cold-plate will vary depending on the shape of the groove. In this research, the response surface method (RSM) was used to optimization the fin geometry of an impinging cold-plate with a trapezoidal cross section groove. The cold plate is used for warm water cooling of electronics. Three fin parameters (thickness, height, and gap) and three groove parameters were optimized to reach minimum values for hydraulic and thermal resistances at fixed values of coolant inlet temperature, coolant flow rate, and electronic chip power.more » « less
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Abstract Ceramics such as lead zirconate titanate (PZT) tend to dissolve incongruently, and thus pose a challenge in the cold sintering process. Moist lead nitrate has previously been shown to enable a cold sinter‐assisted densification of PZT by a viscous phase sintering mechanism. In this paper, lead acetate trihydrate is demonstrated to lower the required temperature of the cold sintering step to 200°C. This densification process was described as a two‐step process: cold sintering of PZT with lead acetate trihydrate and post‐annealing the as‐cold sintered PZT ceramics. Unlike in the case of lead nitrate, PZT densification with lead acetate trihydrate occurs by a liquid phase assisted sintering mechanism, leading to an as‐cold sintered relative density of 84% at 200°C. After performing a post‐anneal step at 900°C, >97% relative densities were achieved in samples that were cold sintered with lead acetate trihydrate. This step not only densified PZT but also refined the grain boundaries. In the post‐annealed samples, the room‐temperature relative permittivity at 100 Hz was ~1600, slightly higher than that reported in samples that used lead nitrate as a sintering aid; the loss tangent was about 3.8%. For measurements at 10 Hz, the remanent polarization in both cases was ~28 µC/cm2. Both Rayleigh analysis and aging studies showed that a higher irreversible contribution to the permittivity exists in samples that used lead nitrate as a cold sintering aid.more » « less
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Study examines binder deposition methods (bulk vs. selective printing) and sintering atmospheres (vacuum vs. H2) on binder jetted 316 L stainless steel components. The density of the H2-sintered specimens was found to be lower (up to 5%) compared to the vacuum-sintered parts with the final density of 99.7%. Grain size analysis indicated smaller grains in the H2-sintered parts (∼26 μm) compared to vacuum-sintered condition (∼33 μm) in the bound area which could be attributed to the presence of residual pores that impeded grain growth. The H2-sintered specimens exhibited an elongation of 25% and an ultimate tensile strength (UTS) of 460 MPa, whereas the vacuum-sintered parts displayed an elongation of 70% and a UTS of 550 MPa. Fractography analysis using microscopy and micro-computed tomography revealed ductile fracture in the vacuum-sintered samples, while the H2-sintered parts exhibited a combination of brittle and ductile fracture due to remnant pores in the microstructure.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d1tc04651a
