Materials Thermodynamics

Chang, Y. Austin; Oates, W. Alan

doi:10.1002/9780470549940

Cited by 21 publications

(22 citation statements)

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“…This is attributable to the presence of the continuous Ag network along GBs, which inhibits preferential oxidation of GBs and then enhances overall oxidation resistance of powder without sacrificing electrical conductivity. The enhanced oxidation resistance can be ascribed to high dissociation pressure of Ag 2 O compared to Cu 2 O and CuO2728. This means that the preferential oxidation of GB could be inhibited by coverage of Ag phase.…”

Section: Discussionmentioning

confidence: 99%

Ultrahigh Oxidation Resistance and High Electrical Conductivity in Copper-Silver Powder

Wang

et al. 2016

Sci Rep

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The electrical conductivity of pure Cu powder is typically deteriorated at elevated temperatures due to the oxidation by forming non-conducting oxides on surface, while enhancing oxidation resistance via alloying is often accompanied by a drastic decline of electrical conductivity. Obtaining Cu powder with both a high electrical conductivity and a high oxidation resistance represents one of the key challenges in developing next-generation electrical transferring powder. Here, we fabricate a Cu-Ag powder with a continuous Ag network along grain boundaries of Cu particles and demonstrate that this new structure can inhibit the preferential oxidation in grain boundaries at elevated temperatures. As a result, the Cu-Ag powder displays considerably high electrical conductivity and high oxidation resistance up to approximately 300 °C, which are markedly higher than that of pure Cu powder. This study paves a new pathway for developing novel Cu powders with much enhanced electrical conductivity and oxidation resistance in service.

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Section: Discussionmentioning

confidence: 99%

Ultrahigh Oxidation Resistance and High Electrical Conductivity in Copper-Silver Powder

Wang

et al. 2016

Sci Rep

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“…The chemical interaction term is attractive (0.123 eVatom À1 ), [23] but the volume mismatch contribution [24] overcompensates for the former, resulting in phase separation. The cohesive energy of the bulk alloy is the sum of the chemical and strain contributions, the latter originating from the atomic volume mismatch.…”

Section: Growth Mechanism Of Au-ni Alloys and Nanoscale Alloyingmentioning

confidence: 99%

Nanoscale Structuring in Au–Ni Films Grown by Electrochemical Underpotential Co‐deposition

et al. 2014

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Nanoscale phase separation is a simple but powerful method for the self‐assembly of nanostructures, which enables properties to be tuned by tailoring the phase composition, size, and topology of the structures. We demonstrate, contrary to thermodynamic predictions, the spontaneous nanoscale phase separation of Au–Ni alloy films, grown by electrochemical underpotential deposition of Ni onto a surface constantly renewed by the ongoing reduction of Au at overpotential. Strain‐energy relaxation during film growth, in combination with the net attractive interaction between Au and Ni atoms, results in the dynamic formation of a nanoscale alloy structure, consisting of Au‐rich grains of about 5 nm in size surrounded by relatively thick (2–3 nm) Ni‐rich grain boundaries. The estimated cohesive energy of such alloy configurations is stronger than that of the phase‐separated mixture, suggesting the formation of an unexpected local equilibrium configuration for the Au–Ni binary system, stabilized by the grain nanosize and the high density of grain boundaries.

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“…Interface chemical reactions [31,32] between the metal electrodes and the Ti oxide can be a major source of these interface states. The Ellingham diagram [33] is a useful tool, if used properly, to predict the possibility that reactions may occur. For example, one may expect that Cr cannot reduce TiO 2 based on the fact that the free energy of formation of Cr 2 O 3 is above that of TiO 2 in the Ellingham diagram, as shown in Fig.…”

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confidence: 99%

Metal/TiO2 interfaces for memristive switches

et al. 2011

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The interfaces between metal electrodes and the oxide in TiO 2 -based memristive switches play a key role in the switching as well as in the I -V characteristics of the devices in different resistance states. We demonstrate here that the work function of the metal electrode has a surprisingly minor effect in determining the electronic barrier at the interface. In contrast, Ti oxides can be readily reduced by most electrode metals. The amount of oxygen vacancies created by these chemical reactions essentially determines the electronic barrier at the device interfaces.The memristor, the fourth fundamental passive circuit element [1][2][3], has a wide variety of potential applications based on its promising device properties [1][2][3][4][5][6][7], including non-volatility, fast switching (<10 ns), low energy (∼1 pJ/operation), multiple-state operation, scalability and stackability. As suggested by the name, memristors can be used for information storage [8][9][10][11][12][13][14]. Moreover, memristors can function as stateful Boolean logic gates via the material implication operation [15]. In addition, memristors can also be used for neuromorphic computing [16,17] because of their analog switching, and some hybrid circuits due to their ease of stacking [18,19].Among all the kinds of switching materials that have been reported, oxides are the most extensively studied [4]. The interfaces between the metal electrodes and the oxide play a crucial role, especially for bipolar switches [5,6,20]. Under an applied electric field, oxygen vacancies can drift into the interface region, reducing the electronic barrier and resulting in a low-resistance state. Under an electric field with the opposite polarity, the oxygen vacancies are repelled away from the interface region, recovering the electronic barrier to regain the high resistance state [6,21,22]. A family of nanodevices with different switching and currentvoltage (I -V ) characteristics has been demonstrated by manipulating the elemental composition at the two interfaces of a simple metal/oxide/metal device stack [23]. For a crossbar array of memristors in a storage/memory circuit, sneak path currents [24] can be minimized by using memristors with a rectifying I -V characteristic, especially when they are in the low-resistance state. Therefore, interface engineering is critical to obtain the desired switching behavior and electrical properties for memristive devices.From a semiconductor physics point of view, the work function of the electrode metal might be an important factor in determining the electronic barrier at the metal/oxide interface [25]. This barrier in our thin film devices is not a traditional Schottky barrier because the oxide film is amorphous with a large concentration of defects and likely thinner than the depletion region of the semiconducting oxide. We prepared a set of 5 µm × 5 µm cross-point devices with six different top electrode metals (Au, Pt, Ag, Ni, W and Ti) to examine the effect of these contacts on the I -V characteristics, as show...

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Materials Thermodynamics

Cited by 21 publications

References 0 publications

Ultrahigh Oxidation Resistance and High Electrical Conductivity in Copper-Silver Powder

Ultrahigh Oxidation Resistance and High Electrical Conductivity in Copper-Silver Powder

Nanoscale Structuring in Au–Ni Films Grown by Electrochemical Underpotential Co‐deposition

Metal/TiO2 interfaces for memristive switches

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