FIELD OF THE INVENTION

The present invention generally relates to powdered materials, objects containing such powdered materials, and methods of making and using the same.

BACKGROUND OF THE INVENTION

Powder processing of metals includes capacitive discharge sintering, direct metal laser melting, electron beam melting, and other techniques. These processes have been used to create near net shape parts, and occasionally to control microstructure. This microstructure control is limited to grain size and grain orientation control. This control is all dependent on heat input. What is desired is to control nucleation and growth kinetics within the structure independent of, or in conjunction with, thermal input.

Prior art exists in which nanoparticles are used in melts to help seed crystallization. This is usually accomplished by adding nanoparticles into a molten alloy, physically distributing them, and then casting the resulting material. These nanoparticles are generally ceramic because they must be added and mixed in the melt. Metal particles and certain desirable ceramic particles would likely be dissolved and therefore cannot be used in this prior-art process. The microstructures which develop during such processing can be easily attributed to the casting process. The microstructures have nanoparticles segregated to the interdendritic regions. See, for example, Chen et al., “Rapid Control of Phase Growth by Nanoparticles,”Nature Communications,5:3879, May 2014; and Xu et al., “Theoretical Study and Pathways for Nanoparticle Capture during Solidification of Metal Melt,”Journal of Physics: Condensed Matter,24 (2012) 255304.

There are no known methods to develop three-dimensional nanoparticle architectures within metal microstructures. These architectures could significantly improve material properties by impeding, blocking, or redirecting dislocation motion in specific directions. This could be used to control failure mechanisms well beyond anything available in isotropic or anisotropic materials today.

Generally, improved methods of controlling solidification in powder materials, and compositions suitable for such methods, are needed. Preferably, the control of solidification does not require active, dynamic adjustment of reaction parameters during the solidification process.

SUMMARY OF THE INVENTION

The present invention addresses the aforementioned needs in the art, as will now be summarized and then further described in detail below.

Some variations provide a powdered material comprising a plurality of particles, wherein the particles are fabricated from a first material, and wherein each of the particles has a particle surface area that is surface-functionalized with a second material containing nanoparticles and/or microparticles selected to control solidification of the powdered material from a liquid state to a solid state. The surface functionalization may be continuous or intermittent (i.e. discontinuous across the surface).

In some embodiments, the powdered material is characterized in that on average at least 1% or at least 10% of the particle surface area is surface-functionalized with the nanoparticles and/or the microparticles.

The particles may be present as a loose powder, a paste, a suspension, a green body, or a combination thereof. The particles may have an average particle size from about 1 micron to about 1 centimeter. In some embodiments, the first material is selected from the group consisting of ceramic, metal, polymer, glass, and combinations thereof.

The nanoparticles and/or microparticles have an average maximum particle dimension from about 1 nanometer to about 100 microns. In some embodiments, the average maximum particle dimension is less than 100 nanometers. In these or other embodiments, the nanoparticles and/or microparticles have an average minimum particle dimension from about 1 nanometer to about 1 micron, such as less than 100 nanometers.

The nanoparticles and/or microparticles may be fabricated from a second material selected from the group consisting of metal, ceramic, polymer, carbon, and combinations thereof. The first material and the second material may compositionally be the same or different.

Other variations provide a method of controlling solidification of a powdered material, the method comprising:

providing a powdered material comprising a plurality of particles, wherein the particles are fabricated from a first material, and wherein each of the particles has a particle surface area that is surface-functionalized with a second material containing nanoparticles and/or microparticles;

melting at least a portion of the powdered material to a liquid state; and

semi-passively controlling solidification of the powdered material from the liquid state to a solid state.

The particles, prior to the melting, may be present as a loose powder, a paste, a suspension, a green body, or a combination thereof, for example. In some embodiments, at least 2 vol % or at least 10 vol % of the powdered material is melted to form the liquid state.

The particles of first material may have an average particle size from about 1 micron to about 1 centimeter. The first material may be selected from the group consisting of ceramic, metal, polymer, glass, and combinations thereof. The second material (nanoparticles and/or microparticles) may be fabricated from a selected from the group consisting of metal, ceramic, polymer, carbon, and combinations thereof.

There are various types of semi-passive control of solidification. In some embodiments, semi-passively controlling solidification includes nucleation control. In these or other embodiments, semi-passively controlling solidification includes thermodynamic control. In these or other embodiments, semi-passively controlling solidification includes thermal conductivity control. In certain embodiments, semi-passively controlling solidification includes eutectic or peritectic reaction control. In any of these or other embodiments, semi-passively controlling solidification includes rejection of contaminants reacted with the nanoparticles and/or microparticles.

In some embodiments, the solid state is a three-dimensional microstructure containing the nanoparticles and/or microparticles as inclusions distributed throughout the solid state.

In some embodiments, the solid state is a layered microstructure containing one or more layers comprising the nanoparticles and/or microparticles.

The method may further include creating a structure through one or more techniques selected from the group consisting of additive manufacturing, injection molding, pressing and sintering, capacitive discharge sintering, and spark plasma sintering. The present invention provides a solid object or article comprising a structure produced by a process comprising such a method.

Some variations provide a solid object or article comprising at least one solid phase (i) containing a powdered material as described, or (ii) derived from a liquid form of a powdered material as described. The solid phase may form from 0.25 wt % to 100 wt % of the solid object or article, for example.

Other variations of the invention provide a solid object or article comprising a continuous solid phase and a three-dimensional network of nanoparticle and/or microparticle inclusions distributed throughout the continuous solid phase, wherein the three-dimensional network blocks, impedes, or redirects dislocation motion within the solid object or article.

In some embodiments, the nanoparticle and/or microparticle inclusions are distributed uniformly throughout the continuous solid phase. The nanoparticle and/or microparticle inclusions may be present at a concentration from about 0.1 wt % to about 50 wt % of the solid object or article.

The nanoparticles and/or microparticles may have an average maximum particle dimension less than 100 nanometers, an average minimum particle dimension less than 100 nanometers, or both of these.

The solid phase may be fabricated from a first material selected from the group consisting of ceramic, metal, polymer, glass, and combinations thereof. The nanoparticles and/or microparticles may be fabricated from a second material selected from the group consisting of metal, ceramic, polymer, carbon, and combinations thereof. The second material may be the same as or different than the composition of the solid phase.

