Vacuum-helium-leak-detection method based on carbon-nanotube-based field-emission sensor

Patent metadata

Field	Value
Publication number	US-12276576-B2
Application number	US-202318093823-A
Country	US
Kind code	B2
Filing date	Jan 6, 2023
Priority date	Jan 6, 2022
Publication date	Apr 15, 2025
Grant date	Apr 15, 2025

Abstract

A vacuum-helium-leak-detection method based on a carbon-nanotube-based field-emission sensor that includes a carbon-nanotube-based cathode having a Raman amorphous peak ID/graphite peak IG ratio greater than 1.0. The method involves: setting a field-emission current at an initial, small emission current, recording an average of values of the field-emission current in a time period t, forming a sensing characteristic curve of the sensor, and performing fitting on the sensing characteristic curve so as to obtain an index curve; converting pressure values of helium gas into vacuum leak rates; and packaging the cathode into a vacuum chamber in a system to be detected, performing testing when a helium stream in the system to be detected reaches balance, obtaining an average of current variations in the time period t during the testing, and comparing the average with the index curve so as to determine a vacuum leak rate of the system to be detected.

First claim

What is claimed is:

1. A vacuum-helium-leak-detection method based on a carbon-nanotube-based field-emission sensor, which includes a carbon-nanotube-based cathode having a Raman amorphous peak I D /graphite peak I G ratio greater than 1.0 and an electrically conductive anode, the method including steps of:
(1) performing a Joule-heat degassing process on the carbon-nanotube-based cathode for a time period to with a large field-emission current having a density J 0 so that Joule heat makes carbon nanotubes of the cathode release gas that was absorbed on their surfaces previously thus enters the carbon nanotubes into an intrinsic emission state;
(2) upon completion of the degassing process, setting the field-emission current to an initial, small emission current thereof rapidly, recording an average of values of the field-emission current in a time period t, testing the carbon-nanotube-based cathode for field-emission sensing effect with helium gas at different pressure levels so as to form a sensing characteristic curve of the carbon-nanotube-based field-emission sensor, performing fitting on the sensing characteristic curve so as to obtain an index curve, and converting the different pressure levels of the helium gas into corresponding vacuum leak rates; and
(3) packaging the carbon-nanotube-based cathode into a vacuum chamber in a system to be detected, performing testing when a helium stream reaches balance, obtaining an average of current variations in the time period t from the testing, comparing the average of the current variations with the index curve obtained in Step (2) so as to determine a vacuum leak rate of the system to be detected.

2. The vacuum-helium-leak-detection method of claim 1 , wherein the carbon-nanotube-based cathode is prepared using a CVD method, which involves: preparing a film used to form the carbon-nanotube-based cathode at a high temperature by using a Hastelloy alloy as a substrate, using argon as a protective gas, and using acetylene as a carbon-source gas required by growth of the carbon nanotubes.

Assignees

• Univ Wenzhou

Inventors

• Dong Changkun
• Liu Ruizi
• Wang Jie

Classifications

• G01M3/3272 Primary

  for verifying the internal pressure of closed containers · CPC title

• G01N27/416

  Systems (G01N27/27 takes precedence) · CPC title

• G01N27/308

  at least partially made of carbon · CPC title

• G01N27/304

  Gas permeable electrodes · CPC title

• G01M3/34 Primary

  by testing the possibility of maintaining the vacuum in containers, e.g. in can-testing machines · CPC title