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You searched for subject:(Nanoporous foam). Showing records 1 – 3 of 3 total matches.

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NSYSU

1. Wu, Tzu-Yang. Microstructure and properties of nanoporous silver fabricated by chemical dealloying of Ag-Al alloys.

Degree: Master, Materials and Optoelectronic Science, 2014, NSYSU

The pure Ag nanoporous foams are prepared by simple chemical dealloying of the melt spun Ag30Al70, Ag35Al65, and Ag40Al60 (in at%) ribbons, measuring ~8 mm in width and ~100 ï­m in thickness. Ag30Al70 is located with the Al content greater than the eutectic composition, and the other two are less than the eutectic point. The composition difference would affect the microstructure and grain structure before dealloying and the porous morphology after dealloying. The melt-spun ribbons contain only the face-centered cubic (FCC) ï¡-Ag phase and the hexagonal ïº-Ag2Al intermediate phase. Through proper chemical dealloying in HCl, the ïº-Ag2Al phase would be etched away, leaving the pure Ag ligaments. The resulting open-cell foams are characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM) in terms of secondary and backscattered electron image (SEI and BEI) and energy dispersive spectrometry (EDS), as well as Brunauer Emmet and Teller (BET), Vickers microhardness, nanoindentation, mini-tension, and other means for their functional properties. In this report, the mechanical response is presented. The three pure Ag open-cellporous foams dealloyed from Ag30Al70, Ag35Al65, and Ag40Al60 possess the average pore size and of 500, 300 and 100 nm, respectively. Pore porosity is 69%, 66%, 58%, respectively. The specific surface area, measured by BET, is 4.1, 3.9 and 2.3 m2/g, respectively. The surface area decreases with decreasing pore porosity. The average micro-hardness readings for these three foams are 2.4, 2.9 and 4.5 Hv. Based on nanoindentation measurements. The elastic modulus data of these three foams are 521, 620, 916 MPa and the hardness data of these three foams are 26, 32, 43 MPa, respectively. The modulus and hardness both decrease with increasing pore porosity. Ag nano-porous foams were characterized by four point probe, and the resistivity increases exponentially with increasing pore porosity. In antimicrobial testing, Ag thin film and Ag ribbon (both without nano-pores) have better antimicrobial ability than Ag nano-porous foams. The current pore size in the Ag nano-porous foams appears too small for bacteria to penetrate, reducing the antimicrobial capability. Keywords: Nanoporous foam, Ag, mechanical response, hardness, resistivity, Antimicrobial test Advisors/Committee Members: J. C. Huang (chair), Jui-Hung Hsu (committee member), T. G. Nieh (chair), Luke Hsiung (chair), Jason Shian-Ching Jang (chair).

Subjects/Keywords: mechanical response; hardness; resistivity; Antimicrobial test; Ag; Nanoporous foam

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APA (6th Edition):

Wu, T. (2014). Microstructure and properties of nanoporous silver fabricated by chemical dealloying of Ag-Al alloys. (Thesis). NSYSU. Retrieved from http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0728114-124346

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Wu, Tzu-Yang. “Microstructure and properties of nanoporous silver fabricated by chemical dealloying of Ag-Al alloys.” 2014. Thesis, NSYSU. Accessed April 22, 2019. http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0728114-124346.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Wu, Tzu-Yang. “Microstructure and properties of nanoporous silver fabricated by chemical dealloying of Ag-Al alloys.” 2014. Web. 22 Apr 2019.

Vancouver:

Wu T. Microstructure and properties of nanoporous silver fabricated by chemical dealloying of Ag-Al alloys. [Internet] [Thesis]. NSYSU; 2014. [cited 2019 Apr 22]. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0728114-124346.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Wu T. Microstructure and properties of nanoporous silver fabricated by chemical dealloying of Ag-Al alloys. [Thesis]. NSYSU; 2014. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0728114-124346

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


North Carolina State University

2. Siripurapu, Srinivas. Blend- and Surface-Assisted Foaming of Polymers with Supercritical Carbon Dioxide.

Degree: PhD, Chemical Engineering, 2003, North Carolina State University

This thesis involves development of novel micro- and nanocellular foamed polymers using judicious polymer processing strategies with supercritical carbon dioxide (scCO₂). Apart from serving as a processing aid in the form of a transient plasticizer, scCO₂ is a powerful blowing agent to manufacture foamed plastics. It is also a viable replacement for the harmful chemical blowing agents such as chlorofluorocarbons, hydrofluorochlorocarbons and perfluorocarbons that are still prevalent in the foaming industry. This thesis focuses on improving our fundamental understanding of polymer foaming with scCO₂ to create novel materials that cannot be synthesized otherwise using traditional foaming technologies. In particular, we aim at creating new polymer foaming paradigms via either judicious polymer blending or introduction of surfaces to the polymer matrix. Novel experimental apparatus, utilizing both a continuous extrusion process and a batch process, have been designed and constructed to study various foaming applications with scCO₂. We show that microcellular foams (foams with pores on the order of 10 μm) containing semicrystalline polymers can be generated continuously by blending with a compatible amorphous polymer. Blends of miscible poly(vinylidene fluoride) (PVDF) – poly(methyl methacrylate) (PMMA) blends yield vastly improved microcellular morphologies compared to PVDF alone. We find that blend miscibility, viscosity reduction facilitated by scCO₂ and reduction or elimination of crystalline melting point of the polymer blend are key factors in producing these materials. The latter part of this dissertation investigates the feasibility of a scCO₂-based foaming procedure to generate micro and nanoporous thin polymer films. Our experimental findings reveal that controlling scCO₂ diffusion from film surfaces is the critical factor towards realizing uniform porosity in polymer films. We use a combination of physical constrains on film surfaces and introduction of interfaces via addition of a nanoscale filler or a tailored non-ionic surfactant to generate controlled foamed structures. Foaming experiments are conducted on 100 μm thick PMMA films with a variety of additives including colloidal silica (particle diameter of 10-12 nm), Zonyl fluorosurfactants, block and graft copolymer of PMMA with a CO₂-philic group such as a fluoropolymer (1,1-dihydroperfluorooctyl methacrylate) and a siloxane (poly (dimethyl siloxane)) in the presence of CO₂. The addition of a low molecular weight block copolymer (PMMA-b-PFOMA) with a CO₂-soluble block (PFOMA) and a polymer-miscible block (PMMA) are found to provide the highest increase in cell nucleation densities and smallest cell sizes. Advisors/Committee Members: Dr. Richard J. Spontak, Committee Co-Chair (advisor), Dr. Saad A. Khan, Committee Co-Chair (advisor), Dr. Joseph M. DeSimone, Committee Member (advisor), Dr. John H. van Zanten, Committee Member (advisor).

Subjects/Keywords: polymer surfactants; polymer blends; high pressure rheology; controlled foam nucleation; carbon dioxide; nanoporous polymers; microcellular foam; supercritical fluids

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APA (6th Edition):

Siripurapu, S. (2003). Blend- and Surface-Assisted Foaming of Polymers with Supercritical Carbon Dioxide. (Doctoral Dissertation). North Carolina State University. Retrieved from http://www.lib.ncsu.edu/resolver/1840.16/5218

Chicago Manual of Style (16th Edition):

Siripurapu, Srinivas. “Blend- and Surface-Assisted Foaming of Polymers with Supercritical Carbon Dioxide.” 2003. Doctoral Dissertation, North Carolina State University. Accessed April 22, 2019. http://www.lib.ncsu.edu/resolver/1840.16/5218.

MLA Handbook (7th Edition):

Siripurapu, Srinivas. “Blend- and Surface-Assisted Foaming of Polymers with Supercritical Carbon Dioxide.” 2003. Web. 22 Apr 2019.

Vancouver:

Siripurapu S. Blend- and Surface-Assisted Foaming of Polymers with Supercritical Carbon Dioxide. [Internet] [Doctoral dissertation]. North Carolina State University; 2003. [cited 2019 Apr 22]. Available from: http://www.lib.ncsu.edu/resolver/1840.16/5218.

Council of Science Editors:

Siripurapu S. Blend- and Surface-Assisted Foaming of Polymers with Supercritical Carbon Dioxide. [Doctoral Dissertation]. North Carolina State University; 2003. Available from: http://www.lib.ncsu.edu/resolver/1840.16/5218

3. Li, Yuan. Synthesis and mechanical characterization of transversely isotropic nanoporous platinum.

Degree: MS, Mechanical Engineering, 2011, Georgia Tech

Nanoporous (NP) metal foams combine desirable characteristics of metals with unique nanoarchitectural features to yield weight normalized properties far superior than either dense metals or bulk metal foams. Due to their high surface to volume ratios these structures show great promise as components of fuel cells, as sensors and have been suggested for use in biological applications, for example as antimicrobial scaffolds or as platforms on which to explore biological material behavior. While most NP metal foams are isotropic, structures with anisotropic features spanning different length scales can further extend applications. This work examines the parameters controlling the synthesis of transversely isotropic NP Platinum foam by dealloying an amorphous Pt-Si alloy. The structure that is examined in this work is hierarchical with Voronoi polyhedra that form on the free surface and under each polyhedral hyper-structure, nanocrystalline NP Pt foam forms with radial struts of length ~60 nm and grain size of 5 nm. The size of the polyhedra can be tailored by changing the dealloying potential. In turn, the mechanical properties of these structures as assessed by nanoindentation can range from 1 to 3GPa depending on the geometric arrangement of the struts. Finally, the initiation location of these structures and the relationship between electrochemical parameters and dealloying front evolution is examined. Advisors/Committee Members: Antoniou, Antonia (Committee Chair), Pierron, Olivier (Committee Member), Zhu, Ting (Committee Member).

Subjects/Keywords: Foam; Corrosion; Amorphous; Nanoporous; Metal; Platinum; Porous materials; Nanostructured materials; Metal foams

nanoporous platinum foam with 0.7V dealloying voltage and 200s dealloying period, (c)… …qualitative inspection on nanoporous materials behavior. 1.3.2.2 Size Effect A variety of NP foam… …parameters on transversely isotropic nanoporous (NP) platinum foam synthesized from… …the rate of diffusion of Si in the electrolyte. Keywords: nanoporous, metal, foam… …nanoporous platinum foam with 0.7V dealloying voltage and 200s dealloying period, (c)… 

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Li, Y. (2011). Synthesis and mechanical characterization of transversely isotropic nanoporous platinum. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/42927

Chicago Manual of Style (16th Edition):

Li, Yuan. “Synthesis and mechanical characterization of transversely isotropic nanoporous platinum.” 2011. Masters Thesis, Georgia Tech. Accessed April 22, 2019. http://hdl.handle.net/1853/42927.

MLA Handbook (7th Edition):

Li, Yuan. “Synthesis and mechanical characterization of transversely isotropic nanoporous platinum.” 2011. Web. 22 Apr 2019.

Vancouver:

Li Y. Synthesis and mechanical characterization of transversely isotropic nanoporous platinum. [Internet] [Masters thesis]. Georgia Tech; 2011. [cited 2019 Apr 22]. Available from: http://hdl.handle.net/1853/42927.

Council of Science Editors:

Li Y. Synthesis and mechanical characterization of transversely isotropic nanoporous platinum. [Masters Thesis]. Georgia Tech; 2011. Available from: http://hdl.handle.net/1853/42927

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