Liquid phase sintering (LPS) is a process for forming high performance, multiple-phase components from powders. It involves sintering under conditions where solid grains coexist with a wetting liquid. Many variants of LPS are applied to a wide range of engineering materials. Example applications for this technology are found in automobile engine connecting rods and high-speed metal cutting inserts. Scientific advances in understanding LPS began in the 1950s. The resulting quantitative process models are now embedded in computer simulations to enable predictions of the sintered component dimensions, microstructure, and properties. However, there are remaining areas in need of research attention. This LPS review, based on over 2,500 publications, outlines what happens when mixed powders are heated to the LPS temperature, with a focus on the densification and microstructure evolution events.

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Review: liquid phase sintering

The synthesis of stable, monodisperse, shaped copper nanoparticles has been difficult, partially because of copper's propensity for oxidation. This article reports the findings of an investigation of a synthetic route for the synthesis of size-controllable and potentially shape-controllable molecularly capped copper nanoparticles. The approach involved the manipulation of reaction temperature for the synthesis of copper nanoparticles in organic solvents in the presence of amine and acid capping agents. By manipulating the reaction temperature, this route has been demonstrated for the production of copper nanoparticles ranging from 5 to 25 nm. The size dependence of the melting temperature of copper nanoparticles, especially for surface melting, is believed to play an important role in interparticle coalescence, leading to size growth as the reaction temperature is increased. Control of the reaction temperature and capping molecules has also been demonstrated to produce copper nanoparticles with different ...

Synthesis of size-controlled and shaped copper nanoparticles.

An intense pulsed light (IPL) from a xenon flash lamp was used to sinter copper nanoink printed on low-temperature polymer substrates at room temperature in ambient condition. The IPL can sinter the copper nanoink without damaging the polymer substrates in extremely short time (2 ms). The microstructure of the sintered copper film was investigated using X-ray powder diffraction (XRD), optical microscopy, scanning electron microscopy (SEM), X-ray micro tomography, and atomic force microscopy (AFM). The sintered copper film has a grainy structure with neck-like junctions. The resulting resistivity was 5 μΩ cm of electrical resistivity which is only 3 times as high as that of bulk copper. The IPL sintering technique allows copper nanoparticles to be used in inkjet printing on low-temperature substrates such as polymers in ambient conditions.

/pdf/intense-pulsed-light-sintering-of-copper-nanoink-for-printed-19b23bldz2.pdf

Intense pulsed light sintering of copper nanoink for printed electronics

Review of non-reactive and reactive wetting of liquids on surfaces.

Thermo-mechanical behavior of low-dimensional systems: The local bond average approach

The wetting behaviors of α-Al2O3 single crystals with three different faces—R(01[Onemacr]2), A(01[Twomacr]0), and C(0001)—and polycrystals (PC) by molten aluminum were studied over a wide temperature range using both a conventional and an improved sessile-drop method. The critical factors affecting the wettability, such as temperature, atmosphere, substrate surface roughness, and crystallographic orientation, and the influence from the experimental technique, were thoroughly investigated. The results show that the aluminum surface oxidation and the thickness of the oxide film have a pronounced effect on the wettability, especially at low temperatures. To eliminate this effect, the experimental temperature must be over a critical value. Vacuum favors lowering this value compared with atmosphere, and the improved sessile-drop method, particularly using an impingement-dropping mode (I-mode), helps to weaken this effect by mechanical disruption and removal of the oxide film. However, the dropping distance and the dropping force must be controlled to prevent a receding contact angle. The effects of the substrate surface roughness and temperature are not significant in the case of a clean and a fine-prepared aluminum surface. On the other hand, the effect of the aluminum crystallographic orientation is noticeable and the wettability is in the order of R > A > PC > C. The intrinsic contact angles of the Al/α-Al2O3 system in the temperature range 1000°–1500°C were estimated to be 76°–85° for the R and A faces, 88°–100° for the C face, and 77°–90° for the polycrystal, depending on the temperature.

Critical Factors Affecting the Wettability of α‐Alumina by Molten Aluminum

The surface tension of molten copper was measured by the oscillating drop method using a falling droplet. The surface oscillation of the droplet was quite simplified during the falling, and consequently, the surface tension was calculated using Rayleigh's equation. The measurements were carried out in a wide temperature range including the undercooling state. The obtained surface tension of copper is expressed as follows:

https://iopscience.iop.org/article/10.1088/0957-0233/16/2/014/pdf

Measurement of surface tension of molten copper using the free-fall oscillating drop method

http://www.jwri.osaka-u.ac.jp/~dpt9/Scripta(2003)Al2O3First.pdf

Wetting of (0001) α-Al2O3 single crystals by molten Al

http://www.jwri.osaka-u.ac.jp/~dpt9/Acta(2003)Al2O3Al.pdf

The influence of surface structure on wetting of α-Al2O3 by aluminum in a reduced atmosphere

http://www.jwri.osaka-u.ac.jp/~dpt9/Acta(2006)TwoMethods.pdf

Taihei Matsumoto

Papers

Critical Factors Affecting the Wettability of α‐Alumina by Molten Aluminum

Measurement of surface tension of molten copper using the free-fall oscillating drop method

Wetting of (0001) α-Al2O3 single crystals by molten Al

The influence of surface structure on wetting of α-Al2O3 by aluminum in a reduced atmosphere

Surface tension of molten silicon measured by microgravity oscillating drop method and improved sessile drop method