US 7,416,328 B2 · System and method for a thermogravimetric analyzer having improved dynamic weight baseline

Abstract

Systems and methods for minimizing extraneous forces and calculating corrected weights of samples based on buoyancy factors for a thermogravimetric analyzer (TGA). The TGA includes a balance chamber and a furnace configured to heat a sample. A null balance is provided in the balance chamber and is used to measure the sample weight change during heating. The furnace includes a cylinder open at the top to receive a sample. The bottom of the cylinder is closed except for a small hole that allows a thermocouple to pass through. An infrared heat source may be provided to heat the cylinder. The balance chamber can be thermally isolated from the furnace using an actively cooled plate and a system of heat shields disposed between the furnace and balance chamber. A thermocouple disk is further provided to limit gas flow in the furnace and increase reliability of sample weight measurements.

Claims38

Dependent claims

A thermogravimetric analyzer comprising:

(a) a balance chamber;
(b) a furnace containing an infrared heat source configured to heat a cylinder contained therein, the cylinder adapted to transfer heat to a sample;
and
(c) an actively cooled plate positioned between the balance chamber and the furnace, wherein the actively cooled plate is a water-cooled plate, the thermogravimetric analyzer further comprising a null balance located in the balance chamber, a filament connected to the null balance, a sample pan supported by the filament in the furnace, a thin metallic tube enclosing the filament, and a plurality of heat shields supported by the thin metallic tube and disposed between the balance chamber and the furnace.

1 more element

A method for calculating a weight of a sample in a thermogravimetric analyzer comprising a balance chamber for housing a balance, a furnace arranged beneath the balance chamber to heat the sample, a pan for supporting a sample in the furnace, a filament connecting the pan to the balance, and a thin tube surrounding the filament and having attached heat shields, the method comprising:

(a) measuring a weight ms of the sample at a predetermined temperature;
(b) calculating a buoyancy factor for the pan and filament (ba) based on the predetermined temperature and calculating a buoyancy factor for the sample (bs) based on the predetermined temperature according to:
b
a
=
V
a
⁢
ρ
t
⁡
(
1
-
T
t
T
)
or a mathematical equivalent, and
b
s
=
V
i
⁢
m
s
m
i
⁢
ρ
i
⁡
(
1
-
T
i
T
)
or a mathematical equivalent;
and
(c) calculating a corrected weight (m) according to:
m=ms−bs−ba or a mathematical equivalent, wherein Va is apparatus volume, that of the pan and a portion of a pan suspension filament, ρt is gas density when a pan weight is tared, and Tt is absolute gas temperature when the pan weight is tared, wherein mi is an initial weight of the sample, ρi is gas density when the initial weight of the sample is measured, Ti is absolute temperature of the gas when the initial weight of the sample is measured, Vi is volume of the sample when the initial weight of the sample is measured, and T is absolute temperature of the gas during the experiment.

41 more elements

Dependencies are inferred from the claim text.

System and method for a thermogravimetric analyzer having improved dynamic weight baseline

Life of this patent

System and method for a thermogravimetric analyzer having improved dynamic weight baseline

Life of this patent

Abstract

Claims38