TY - BOOK

T1 - Designability and Versatility of Thermoplastic Forming for Bulk Metallic Glasses

AU - Cai, Fei-Fan

N1 - no embargo

PY - 2024

Y1 - 2024

N2 - Bulk metallic glasses (BMGs) are a novel class of metallic alloys possessing amorphous structures that set them apart from traditional crystalline alloys. The amorphous structure of BMGs lacks crystalline defects, such as grain boundaries, twins, and dislocations, resulting in their desirable properties, including high elasticity, hardness, toughness, good wear resistance, and good corrosion resistance. However, the requirement of BMGs in rapid cooling restricts the fabrication of complex shapes through casting, limiting their practical applications. Luckily, BMGs can be shaped and patterned through thermoplastic forming (TPF) by viscous flow deformation when heated to the supercool liquid region (SCLR). Therefore, the present thesis aims to enhance the practicality and functionality of BMGs through TPF approaches.The first focus targets ‘‘designability’’. It was believed that ‘‘BMGs can not be deformed and patterned once the materials are crystallized.’’ The concerns about the crystallization during TPF are the loss of deformability and mechanical properties of BMGs. This work uses Ti40Zr10Cu34Pd14Sn2 BMG to demonstrate that ‘‘if the initial crystallization event is the formation of nanocrystals, the BMGs can still be shaped and patterned via TPF, even with the nanocrystallization.’’ A TPF strategy of allowing nanocrystallization during the process is implemented to create surface patterns from macro- to nano-scales and hierarchical structures integrating micro- and nano-patterns on the same surface. Moreover, the study suggests that Ti40Zr10Cu34Pd14Sn2 BMG possesses crystallization tolerance to TPF, and slight crystallization is allowed before losing its mechanical properties.The second focus demonstrates the ‘‘versatility’’ for biomedical applications. In-vitro assays using Saos-2 cell lines were tested on four different surface topographies of Ti40Zr10Cu34Pd14Sn2 BMG, including: (a) Flat (mirror-polished), (b) Micro-pattern (2.5 μm square protuberances), (c) Nano-pattern (400 nm protrusions), (d) Hierarchical-pattern (400 nm protrusions on 2.5 μm square protuberances). Based on the findings of in-vitro studies, two potential biomedical applications of TPF patterned Ti40Zr10Cu34Pd14Sn2 BMG are then suggested: (i) Dental or orthopedic tissue implants and (ii) a toolbox for studying cell response on rigid and ordered surfaces.The final focus combines the ‘‘designability’’ and ‘‘versatility’’ for catalytic applications. The hydrogen evolution reaction (HER) performance of Pt57.5Cu14.7Ni5.3P22.5 BMG with flat, micro-patterned, and nano-patterned surfaces is explored. The nano-patterned Pt-BMG exhibits long-term stability and self-improving behavior after 1000 linear sweep voltammetry (LSV) cycles. Surface characterizations indicate that a layer of CuxO foam was formed on top of the nano-patterned surface after 1000 LSV cycles. The formation of CuxO foam is explained by a three-step process involving Cu dissolution of Pt-BMG and dynamic hydrogen bubble templating (DHBT) electrodeposition without using copper salt.The present thesis reveals the prospect of utilizing the TPF process for a wide range of mediocre glass forming systems and semi-crystalline composites into surface-enhanced functional materials without sacrificing mechanical properties. Beyond implant applications, biocompatible BMGs provide a toolbox for studying cell response on rigid and ordered surfaces in biomedical research. TPF-patterned BMGs combining dynamic bubble templating electrodeposition could be a feasible strategy to synthesize metal or metal-oxide foams for catalytic applications.

AB - Bulk metallic glasses (BMGs) are a novel class of metallic alloys possessing amorphous structures that set them apart from traditional crystalline alloys. The amorphous structure of BMGs lacks crystalline defects, such as grain boundaries, twins, and dislocations, resulting in their desirable properties, including high elasticity, hardness, toughness, good wear resistance, and good corrosion resistance. However, the requirement of BMGs in rapid cooling restricts the fabrication of complex shapes through casting, limiting their practical applications. Luckily, BMGs can be shaped and patterned through thermoplastic forming (TPF) by viscous flow deformation when heated to the supercool liquid region (SCLR). Therefore, the present thesis aims to enhance the practicality and functionality of BMGs through TPF approaches.The first focus targets ‘‘designability’’. It was believed that ‘‘BMGs can not be deformed and patterned once the materials are crystallized.’’ The concerns about the crystallization during TPF are the loss of deformability and mechanical properties of BMGs. This work uses Ti40Zr10Cu34Pd14Sn2 BMG to demonstrate that ‘‘if the initial crystallization event is the formation of nanocrystals, the BMGs can still be shaped and patterned via TPF, even with the nanocrystallization.’’ A TPF strategy of allowing nanocrystallization during the process is implemented to create surface patterns from macro- to nano-scales and hierarchical structures integrating micro- and nano-patterns on the same surface. Moreover, the study suggests that Ti40Zr10Cu34Pd14Sn2 BMG possesses crystallization tolerance to TPF, and slight crystallization is allowed before losing its mechanical properties.The second focus demonstrates the ‘‘versatility’’ for biomedical applications. In-vitro assays using Saos-2 cell lines were tested on four different surface topographies of Ti40Zr10Cu34Pd14Sn2 BMG, including: (a) Flat (mirror-polished), (b) Micro-pattern (2.5 μm square protuberances), (c) Nano-pattern (400 nm protrusions), (d) Hierarchical-pattern (400 nm protrusions on 2.5 μm square protuberances). Based on the findings of in-vitro studies, two potential biomedical applications of TPF patterned Ti40Zr10Cu34Pd14Sn2 BMG are then suggested: (i) Dental or orthopedic tissue implants and (ii) a toolbox for studying cell response on rigid and ordered surfaces.The final focus combines the ‘‘designability’’ and ‘‘versatility’’ for catalytic applications. The hydrogen evolution reaction (HER) performance of Pt57.5Cu14.7Ni5.3P22.5 BMG with flat, micro-patterned, and nano-patterned surfaces is explored. The nano-patterned Pt-BMG exhibits long-term stability and self-improving behavior after 1000 linear sweep voltammetry (LSV) cycles. Surface characterizations indicate that a layer of CuxO foam was formed on top of the nano-patterned surface after 1000 LSV cycles. The formation of CuxO foam is explained by a three-step process involving Cu dissolution of Pt-BMG and dynamic hydrogen bubble templating (DHBT) electrodeposition without using copper salt.The present thesis reveals the prospect of utilizing the TPF process for a wide range of mediocre glass forming systems and semi-crystalline composites into surface-enhanced functional materials without sacrificing mechanical properties. Beyond implant applications, biocompatible BMGs provide a toolbox for studying cell response on rigid and ordered surfaces in biomedical research. TPF-patterned BMGs combining dynamic bubble templating electrodeposition could be a feasible strategy to synthesize metal or metal-oxide foams for catalytic applications.

KW - Bulk metallic glass

KW - thermoplastic forming

KW - surface modification

KW - patterning

KW - hierarchical structure

KW - titanium alloy

KW - implant

KW - biomedical application

KW - biocompatibility

KW - antibacterial property

KW - platinum alloy

KW - electrocatalyst

KW - hydrogen evolution reaction

KW - Massive Metallische Gläser

KW - thermoplastische Umformung

KW - Oberflächenmodifikation

KW - Strukturierung

KW - hierarchische Struktur

KW - Titanlegierung

KW - Implantat

KW - biomedizinische Anwendung

KW - Biokompatibilität

KW - antibakterielle Eigenschaften

KW - Platinlegierung

KW - Elektrokatalysator

KW - Wasserstoffentwicklungsreaktion

U2 - 10.34901/mul.pub.2024.228

DO - 10.34901/mul.pub.2024.228

M3 - Doctoral Thesis

ER -