Three-dimensional (3D) printing method

1. A three-dimensional (3D) printing method, comprising:

applying a build material onto a fabrication bed, the build material consisting of:

an inorganic particle; and

a polymer attached to the inorganic particle, the polymer being nano-beads having an average diameter ranging from about 3 nm to about 1500 nm;

heating the build material to a temperature ranging from about 5° C. to about 50° C. below a melting point of the polymer;

selectively applying a coalescent dispersion on a portion of the build material with an inkjet applicator, the coalescent dispersion including:

a carbon black pigment present in the coalescent dispersion in an amount ranging from about 3.0 wt % to about 6.0 wt % based on the total wt % of the coalescent dispersion; and

inorganic nanoparticles having an average diameter ranging from about 10 nm to about 500 nm, wherein the inorganic nanoparticles make up from about 10 wt % to about 40 wt % of the total wt % of the coalescent dispersion; and

exposing the applied build material and the applied coalescent dispersion to an electromagnetic radiation with a radiation source, whereby the coalescent dispersion absorbs the electromagnetic radiation and heats up the portion of the build material in contact with the coalescent dispersion to fuse the portion of the build material in contact with the coalescent dispersion and to form a layer of a three-dimensional (3D) object.

2. The 3D printing method as defined in claim 1 wherein the build material is applied on a contact surface of the fabrication bed, and the coalescent dispersion is selectively applied on the portion of the build material in a pattern of a cross-section of the layer of the 3D object to be formed, the cross-section being parallel to the contact surface.

3. The 3D printing method as defined in claim 1 , further comprising:

depositing an other layer of the build material on the layer of the 3D object;

selectively applying an other layer of the coalescent dispersion on at least a portion of the other layer of the build material; and

exposing the other layer of the build material and the other layer of the coalescent dispersion to electromagnetic radiation, whereby the coalescent dispersion absorbs the electromagnetic radiation and converts the absorbed electromagnetic radiation to thermal energy, whereby the coalescent dispersion absorbs the electromagnetic radiation and heats up the portion of the other layer of the build material in contact with the other layer of the coalescent dispersion to fuse the portion of the other layer of the build material in contact with the other layer of the coalescent dispersion and to form an other layer of the 3D object.

4. The 3D printing method as defined in claim 3 , further comprising repeating the depositing, the selectively applying, and exposing to create subsequent layers of the 3D object.

5. The 3D printing method as defined in claim 4 , further comprising:

exposing the 3D object to a cleaning process, thereby removing any non-fused build material from the 3D object, the cleaning process being selected from the group consisting of brushing, water-jet cleaning, sonic cleaning, blasting, and combinations thereof; and

exposing the 3D object to a heat treatment at a decomposition temperature of the polymer, thereby removing the polymer from the 3D object.

6. The 3D printing method as defined in claim 5 , further comprising annealing the 3D object at a melting temperature of the inorganic particle or at a temperature ranging from 1° C. to about 300° C. lower than the melting temperature of the inorganic particle.

7. The 3D printing method as defined in claim 1 wherein:

the build material includes the polymer in an amount ranging from about 0.1 wt % to about 10 wt % of a total weight percent of the inorganic particle in the build material; and

wherein the polymer has a glass transition temperature ranging from about 0° C. to about 200° C.

8. The 3D printing method as defined in claim 1 wherein a packing density of the applied build material and the applied coalescent dispersion ranges from about 0.35 g/cm 3 to about 0.9 g/cm 3 .

9. The 3D printing method as defined in claim 1 wherein the inorganic nanoparticles in the coalescent dispersion include:

a core particle selected from the group consisting of a metal, a metal alloy, a metal oxide, a ceramic, and combinations thereof; and

an other polymer attached to the core particle, the other polymer being i) a continuous coating having a thickness ranging from about 3 nm to about 1500 nm, or ii) nano-beads having an average diameter ranging from about 3 nm to about 1500 nm.

10. A three-dimensional (3D) printing system, comprising:

a fabrication bed;

a build material to be introduced into the fabrication bed, the build material consisting of:

an inorganic particle; and

a polymer attached to the inorganic particle, the polymer being nano-beads having an average diameter ranging from about 3 nm to about 1500 nm;

an inkjet applicator;

a coalescent dispersion to be selectively introduced by the inkjet applicator onto the build material in the fabrication bed, the coalescent dispersion including:

a carbon black pigment present in the coalescent dispersion in an amount ranging from about 3.0 wt % to about 6.0 wt % based on a total weight percent of the coalescent dispersion; and

inorganic nanoparticles having an average diameter ranging from about 10 nm to about 500 nm, wherein the inorganic nanoparticles make up from about 10 wt % to about 40 wt % of the total weight percent of the coalescent dispersion;

a radiation source to expose the coalescent dispersion and the build material in the fabrication bed to electromagnetic radiation.

11. The 3D printing system as defined in claim 10 , wherein the build material includes the polymer in an amount ranging from about 0.1 wt % to about 10 wt % of a total weight percent of the inorganic particle in the build material.

12. The 3D printing system as defined in claim 10 , wherein:

the inorganic particle of the build material is selected from the group consisting of a metal, a metal alloy, a metal oxide, a ceramic, and combinations thereof; and

the polymer of the build material has a glass transition temperature ranging from about 0° C. to about 200° C.

13. The 3D printing system as defined in claim 10 , wherein the inorganic particle of the build material is a metal, a metal alloy, a metal oxide, a ceramic, or a combination thereof having a particle density ranging from about 1 g/cm 3 to about 10 g/cm 3 and a particle size ranging from about 1 μm to about 100 μm.

14. The 3D printing system as defined in claim 10 , wherein:

the inorganic nanoparticles in the coalescent dispersion include:

a core particle selected from the group consisting of a metal, a metal alloy, a metal oxide, a ceramic, and combinations thereof; and

an other polymer attached to the core particle, the other polymer being i) a continuous coating having a thickness ranging from about 3 nm to about 1500 nm, or ii) nano-beads having an average diameter ranging from about 3 nm to about 1500 nm; and

the coalescent dispersion further includes a densification agent, a dispersant, a surfactant, a co-solvent, a biocide, or combinations thereof.

15. The 3D printing system as defined in claim 14 , wherein the other polymer is a polymer or a copolymer formed from a styrene monomer, an acrylic monomer, a derivative of an acrylic monomer, or a combination thereof, polyethylene, polypropylene, polyurethane, or a combination thereof.

16. The 3D printing system as defined in claim 10 , wherein the inkjet applicator is a thermal inkjet printhead or a piezoelectric inkjet printhead.