Mass Production and Assembly of Ultra-High Temperature Ceramic (UHTC) Nanowires - TiC
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2025-07-11 |
| Journal | ECS Meeting Abstracts |
| Authors | Sreeram Vaddiraju, Jitendra Choudhary, Ryan Loden |
Abstract
Section titled āAbstractāUltra-high temperature ceramics (UHTCs), typically the non-stoichiometric carbides and nitrides of metal such as Ta, Zr and Ti, have melting temperatures higher than 3000 o C.(1) They also have excellent mechanical properties, such as hardness and wear resistance. The Vickers hardness of ZrC 1-x and TaC 1-x, ranging respectively between 16-29 and 13-25 GPa,(1) are comparable to the Vickers harness of diamond of 79.7 GPa.(2) Metal-like electrical conductivities of these carbides could be gauged from the room-temperature electrical resistivity of TaC 1-x of 0.4 Ī¼Wm,(1) which is only slightly higher than that of copper of 0.1 Ī¼Wm.(3) Room-temperature thermal conductivities of ZrC 1-x and TaC 1-x of 35 and 25 Wm -1 K -1 , respectively, are also comparable to that of graphite of 100-200 Wm -1 K -1 .(1). Therefore, in many ways, UHTCs are similar to carbon nanotubes (CNTs). However, a few differences also exist between UHTC materials and CNTs. While CNTs exhibit mechanical flexibility, the current UHTC materials are mechanically brittle in nature. Contextually, a fundamental question that needs to be addressed is whether it is possible to selectivity engineer the mechanical properties and thermal conductivities of UHTCs. In other words, reducing the thermal conductivities of UHTCs and increasing their thermal shock resistance will be desirable for their use as thermal barriers for high-temperature electronics. The current techniques employed for synthesizing and assembling UHTCs include (i) reactions of the respective metal hydrides with carbon, (ii) direct reaction of elements, (iii) the carbothermal reduction of their respective metal oxides, and (iv) hot pressing and spark plasma sintering. A drawback with UHTCs currently is that sintering for assembling these materials is difficult and requires temperatures on the order of 2300 o C.(4) These high temperatures lead to grain coarsening,(4) as grains grow to micron sizes upon densification.(5) Techniques such as spark plasma sintering and alloying with other metals help in circumventing some of these problems to some extent, and aid in high density consolidation of grains of sizes on the order of 1.5-2 mm.(4) However the resulting UHTCs still exhibit lower thermal shock resistances (TSRs) and fracture toughnesses.(6) The current UHTC materials also possess very high densities, imposing significant weight concerns when used in vehicles that are weight sensitive.(6) One of the nanostructured morphologies useful to engineer both the thermal conductivities and the TSRs of UHTCs is nanowires. In single-crystal nanowires, the nanoscale nanowire diameters could be tuned independent of the microscale nanowire lengths.(7) The microscale lengths aid in retaining properties, such as electrical conduction.(8-10) At the same time, the nanoscale nanowire diameters could be used to tune properties, such as thermal conductivities and mechanical flexibilities.(10, 11) However, as individual nanowires are not used in applications involving UHTCs, it is imperative to assemble nanowires of UHTCs in any desired fashion. In this context, this presentation will discuss methods for the mass production of UHTC nanowires, and their assembly via welding into nanowire networks with controlled packing densities. More specifically, the synthesis and assembly of TiC nanowires will be discussed in detail in this manuscript. Strategies for the mass production of TiC nanowires will also be addressed in detail in this presentation. References: Shabalin IL. 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