US 6,981,426 B2Granted

Method and apparatus to measure gas amounts adsorbed on a powder sample

AssigneeTsinghua University

InventorsDezheng Wang, Fei Wei, Jinfu Wang

Life of this patent

Estimating the term…

Loading patent…

Abstract

A method and apparatus for measuring the gas amounts adsorbed on a powder which directly measures pressure changes in a gas supply chamber with the use of differential pressure sensors between the gas supply chamber and a reference chamber which gas amount is maintained constant. Calculations of the gas amounts adsorbed are based on the pressure changes in a sample cell and the pressure changes in the gas supply chamber or a gas reference chamber. The method and apparatus of this invention measures the adsorption or desorption isotherm or gas uptake at constant pressure curve of a powder with, as compared with presently available measurement techniques, increased accuracy and resolution. The experimental data can be analyzed to obtain information on the surface area, pore size distribution, pore volume, pore structure and diffusion coefficient of the powder.

Claims16

Dependent claims

A method for measuring gas amounts adsorbed by a powder sample in a system comprising a supply chamber of predetermined volume, a reference chamber, a temperature and temperature difference measuring means for said supply chamber and reference chamber, a pressure difference measuring means between said supply chamber and reference chamber, a sample cell of predetermined free space and containing a powder sample, a pressure measuring means for said sample cell, and an evacuating means, the method comprising the steps of:

(a) evacuating said supply chamber said reference chamber, and said sample cell;
(b) providing said powder sample a surrounding of a substantially constant known temperature;
(c) isolating said sample cell, said supply chamber, and said reference chamber from said evacuating means and isolating said sample cell from said supply chamber and said reference chamber;
(d) using a gas supply to supply gas to said supply chamber and said reference chamber, then isolating said supply chamber and said reference chamber from said gas supply by valving means;
(e) isolating said supply chamber from said reference chamber by valving means, waiting for the pressure to stabilize in both chambers, then measuring the pressure difference and temperature difference between them and the temperatures thereof;
(f) supplying gas from said supply chamber to said sample cell using a gas flow control means;
(g) measuring the pressure difference and temperature difference between said reference chamber and said supply chamber and the temperatures thereof, and using said pressure difference, temperature difference, and temperatures, and the volume of said supply chamber, calculating the amount of gas that flowed out from said supply chamber;
(h) measuring the pressure in said sample cell and using said pressure and the free space and temperature of said sample cell, calculating the amount of gas added to the free space in said sample cell;
(i) calculating by the arithmetic difference of the gas amounts in steps (g) and (h) the gas amount adsorbed by said powder sample to get the data point of adsorbed amount at this pressure in said sample cell;
and
(j) repeating steps (f) to (i) until the pressure in said sample cell has increased to the required pressure, whereby obtaining data points of adsorbed amount at the increasing pressures in said sample cell.

8 more elements

A method for measuring gas amounts adsorbed by a powder sample in a system comprising a supply chamber of predetermined volume, a reference chamber, a temperature measuring means for said supply chamber and reference chamber, a pressure difference measuring means between said supply chamber and reference chamber, a sample cell of predetermined free space and containing a powder sample, a pressure measuring means for said sample cell, and an evacuating means, the method comprising the steps of:

(a) evacuating said supply chamber, said reference chamber, and said sample cell;
(b) providing said powder sample a surrounding of a substantially constant known temperature;
(c) isolating said sample cell, said supply chamber, and said reference chamber from said evacuating means and isolating said sample cell from said supply chamber and said reference chamber;
(d) using a gas supply to supply gas to said supply chamber and said reference chamber, then isolating said supply chamber and said reference chamber from said gas supply by valving means;
(e) isolating said supply chamber from said reference chamber by valving means, waiting for the pressure to stabilize in both chambers, then measuring the pressure difference between them and the temperatures thereof;
(f) supplying gas from said supply chamber to said sample cell using a gas flow control means;
(g) measuring the pressure difference between said reference chamber and said supply chamber and the temperatures thereof, and using said pressure difference and temperatures, and the volume of said supply chamber, calculating the amount of gas that flowed out from said supply chamber;
(h) measuring the pressure in said sample cell and using said pressure and the free space and temperature of said sample cell, calculating the amount of gas added to the free space in said sample cell;
(i) calculating by the arithmetic difference of the gas amounts in steps (g) and (h) the gas amount adsorbed by said powder sample to get the data point of adsorbed amount at this pressure in said sample cell;
(j) repeating steps (f) to (i) until the pressure in said sample cell has increased to the required pressure, whereby obtaining data points of adsorbed amount at the increasing pressures in said sample cell;
(k) providing for said reference chamber a predetermined volume;
(l) following step (j), isolating said sample cell from said supply chamber and said reference chamber, and evacuating to vacuum said supply chamber and said reference chamber;
(m) isolating said reference chamber from said supply chamber and said evacuating means, and continue evacuating said supply chamber;
(n) supplying gas from said sample cell to said reference chamber using said gas flow control means;
(o) measuring the pressure and temperature of said reference chamber, and using the pressure, temperature, and volume of said reference chamber, calculating the amount of gas added to said reference chamber;
(p) measuring the pressure in said sample cell, calculating the change in pressure in said sample cell, and using this pressure change, free space, and temperature of said sample cell, calculating the amount of gas removed from the free space in said sample cell;
(q) calculating the arithmetic difference of the gas amounts of steps (o) and (p) to calculate the gas amount desorbed by said powder sample, and subtracting this desorbed amount from the amount adsorbed at the highest pressure in step (j) to get a data point of adsorbed amount at this pressure in said sample cell;
and
(r) repeating steps (n) to (q) until the pressure in said sample cell has fallen to a specified pressure, whereby obtaining said data points of adsorbed amount at the decreasing pressures in said sample cell.

16 more elements

Dependencies are inferred from the claim text.

Facts

Application: 10/736,829Filed 15 Dec 2003
Priority: CN 310028510 Jan 2003
Published: US 2004/0134258 A115 Jul 2004
Granted: 3 Jan 2006
Term ends: Not estimatedThe source records don’t support an estimate.

Classification4 codes

G01N 7/04
By absorption, adsorption, or combustion of components and measurement of the change in pressure or volume of the remainder: by absorption or…
G01N 15/0893
Investigating volume, surface area, size or distribution of pores; Porosimetry: by measuring weight or volume of sorbed fluid, e.g. B.E.T. method
G01N 2015/0866
Investigating permeability, pore-volume, or surface area of porous materials: sorption
G01N
Investigating or analysing materials by determining their chemical or physical properties