# US 12,183,570 B2 · Methods of forming a field emission cathode

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- Number: US 12,183,570 B2
- Document ID: US12183570B2
- Status: Granted
- Kind: B2
- Application number: 18/247,263
- Filed: 2021-09-29
- Published: 2023-12-21
- Granted: 2024-12-31
- Earliest claimed: 2020-09-30
- Assignees: NCX Corporation
- Applicants: NCX Corporation
- Inventors: Cheng Qian
- Web page: https://patentgrep.com/patent/US12183570B2

## CPC

- H01J 9/025: {of field emission cathodes}
- C01B 32/17: Purification
- H01J 1/3048: {Distributed particle emitters}
- H01J 2201/30469: Carbon nanotubes (CNTs)
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}

## Abstract

A method for fabricating a field emission cathode, the field emission cathode including a substrate having a field emission layer engaged therewith, where the field emission layer includes a plurality of purified carbon nanotubes. The carbon nanotubes are purified via a graphitization or annealing process.

## Claims

### Claim 1

A method of forming a field emission cathode, comprising:
depositing a field emission material on to a substrate, the field emission material comprising a plurality of purified carbon nanotubes, wherein the purified carbon nanotubes are obtained via a graphitization process, the graphitization process comprising exposing a plurality of carbon nanotubes to a temperature of at least 1500° C. under a vacuum for a predetermined length of time ranging from about 12 hours to about 72 hours to purify the plurality of carbon nanotubes.

### Claim 2 (depends on 1)

The method of claim 1, wherein exposing the plurality of carbon nanotubes comprises exposing the plurality of carbon nanotubes to a temperature of between 1500° C. and 3000° C.

### Claim 3 (depends on 1)

The method of claim 1, wherein exposing a plurality of carbon nanotubes comprises exposing the plurality of carbon nanotubes to a vacuum of about 1×10−3 torr to about 1×10−8 torr during exposure of the plurality of carbon nanotubes to the temperature.

### Claim 4 (depends on 1)

The method of claim 1, comprising forming the plurality of carbon nanotubes by a chemical vapor deposition process, a laser ablation process, or an arc discharge process.

### Claim 5 (depends on 1)

The method of claim 1, wherein depositing the field emission material comprises depositing the field emission material on to the substrate comprising a metal, an alloy, a glass, or a ceramic.

### Claim 6 (depends on 1)

The method of claim 1, wherein depositing the field emission material comprising the plurality of purified carbon nanotubes comprises depositing the field emission material on to the substrate via spray coating, ink jet printing, screen printing, dip coating, electrophoresis or combinations thereof.

### Claim 7 (depends on 1)

The method of claim 1, further comprising exposing the cathode to a post-deposition process.

### Claim 8 (depends on 1)

The method of claim 1, further comprising exposing the cathode to a post-deposition process.

### Claim 9

A method of forming a field emission cathode, comprising:
purifying a plurality of carbon nanotubes via a graphitization process, the graphitization process comprising exposing a plurality of carbon nanotubes to a temperature of at least 1500° C. under a vacuum for a predetermined length of time ranging from about 12 hours to about 72 hours to purify the plurality of carbon nanotubes, to obtain a plurality of purified carbon nanotubes; and
depositing a field emission material comprising the plurality of purified carbon nanotubes on to a substrate to form the cathode.

### Claim 10 (depends on 9)

The method of claim 9, comprising forming the plurality of carbon nanotubes by a chemical vapor deposition process, a laser ablation process, or an arc discharge process.

### Claim 11 (depends on 9)

The method of claim 9, wherein the graphitization process comprises exposing the plurality of carbon nanotubes to a temperature of about 1500° C. to about 3000° C. under a vacuum of about 1×10−3 torr to about 1×10−8 torr for a length of time of about 12 hours to about 72 hours.

### Claim 12 (depends on 9)

The method of claim 9, wherein depositing the field emission material comprises depositing the field emission material on to the substrate comprising a metal, an alloy, a glass, or a ceramic.

### Claim 13 (depends on 9)

The method of claim 9, wherein depositing the field emission material comprises depositing the field emission material comprising the plurality of purified carbon nanotubes on to the substrate via spray coating, ink jet printing, screen printing, dip coating, electrophoresis, or combinations thereof.

### Claim 14 (depends on 9)

The method of claim 9, further comprising exposing the cathode to a post-deposition process.

### Claim 15

A method of forming a field emission cathode, comprising:
depositing a field emission material comprising a plurality of carbon nanotubes on to a substrate to form the cathode; and
exposing the cathode to a graphitization process, the graphitization process comprising exposing a plurality of carbon nanotubes to a temperature of at least 1500° C. under a vacuum for a predetermined length of time ranging from about 12 hours to about 72 hours, to purify the plurality of carbon nanotubes.

### Claim 16

A method of forming a field emission cathode, comprising:
depositing a field emission material on to a substrate, the field emission material comprising a plurality of purified carbon nanotubes, wherein the purified carbon nanotubes are obtained via a graphitization process, the graphitization process comprising exposing the plurality of carbon nanotubes to a temperature of about 1500° C. to about 3000° C. under a vacuum of about 1×10−3 torr to about 1×10−8 torr for a length of time of about 12 hours to about 72 hours.

### Claim 17 (depends on 16)

The method of claim 16, comprising forming the plurality of carbon nanotubes by a chemical vapor deposition process, a laser ablation process, or an arc discharge process.

### Claim 18 (depends on 16)

The method of claim 16, wherein depositing the field emission material comprises depositing the field emission material on to the substrate comprising a metal, an alloy, a glass, or a ceramic.

### Claim 19 (depends on 16)

The method of claim 16, wherein depositing the field emission material comprising the plurality of purified carbon nanotubes comprises depositing the field emission material on to the substrate via spray coating, ink jet printing, screen printing, dip coating, electrophoresis or combinations thereof.

### Claim 20

A method of forming a field emission cathode, comprising:
purifying a plurality of carbon nanotubes via a graphitization process, the graphitization process comprising exposing the plurality of carbon nanotubes to a temperature of about 1500° C. to about 3000° C. under a vacuum of about 1×10−3 torr to about 1×10−8 torr for a length of time of about 12 hours to about 72 hours, to obtain a plurality of purified carbon nanotubes; and
depositing a field emission material comprising the plurality of purified carbon nanotubes on to a substrate to form the cathode.

### Claim 21 (depends on 20)

The method of claim 20, comprising forming the plurality of carbon nanotubes by a chemical vapor deposition process, a laser ablation process, or an arc discharge process.

### Claim 22 (depends on 20)

The method of claim 20, wherein depositing the field emission material comprises depositing the field emission material on to the substrate comprising a metal, an alloy, a glass, or a ceramic.

### Claim 23 (depends on 20)

The method of claim 20, wherein depositing the field emission material comprises depositing the field emission material comprising the plurality of purified carbon nanotubes on to the substrate via spray coating, ink jet printing, screen printing, dip coating, electrophoresis, or combinations thereof.

### Claim 24 (depends on 20)

The method of claim 20, further comprising exposing the cathode to a post-deposition process.

### Claim 25

A method of forming a field emission cathode, comprising:
depositing a field emission material comprising a plurality of carbon nanotubes on to a substrate to form the cathode; and
exposing the cathode to a graphitization process, the graphitization process comprising exposing the plurality of carbon nanotubes to a temperature of about 1500° C. to about 3000°° C. under a vacuum of about 1×10−3 torr to about 1×10−8 torr for a length of time of about 12 hours to about 72 hours, to purify the plurality of carbon nanotubes.