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Nondestructive On Line PVC Measurement

IP.com Disclosure Number: IPCOM000050710D
Original Publication Date: 1982-Dec-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Ferrari, NL: AUTHOR [+3]

Abstract

A nondestructive method is proposed for determining the concentration of magnetic particles or pigment in a magnetic coating. Conventionally, the pigment volume concentration (PVC) of magnetic coatings is determined by measuring the amount of magnetic material (Delta-Fe(2)O(3)) by a vibrating sample magnetometer (VSM), by microprobe or by chemical analysis per given volume element, and then determining the thickness by plasma ashing a step or laser burning a step and measuring the step height. All these methods require destruction of the disk, are long and time consuming, and have major uncertainties. The article describes a method that has none of the above mentioned handicaps.

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Nondestructive On Line PVC Measurement

A nondestructive method is proposed for determining the concentration of magnetic particles or pigment in a magnetic coating.

Conventionally, the pigment volume concentration (PVC) of magnetic coatings is determined by measuring the amount of magnetic material (Delta-Fe(2)O(3)) by a vibrating sample magnetometer (VSM), by microprobe or by chemical analysis per given volume element, and then determining the thickness by plasma ashing a step or laser burning a step and measuring the step height. All these methods require destruction of the disk, are long and time consuming, and have major uncertainties. The article describes a method that has none of the above mentioned handicaps.

A disk substrate ready for coating is weighed similarly to the method employed to determine lube weights. The disk is then coated in the conventional way and processed to completion. During processing, the Fe(2)O(3) content is measured by X-ray fluorescence. This is a standard test for thickness determination during buffing.

The disks must be weighed before lubing. Thus, it would be best to use the same disks for lube weights and PVC. The difference in weight before lubing and before coating is then equal to the weight of the final coating. We designate the coating weight as W: W=Rho(Fe) V(Fe) +Rho(p)V(p) where the subscript Fe refers to the magnetic Fe(2)O(3) particles and p to the polymer. Rho and V are the density and volume, respectively. Since t...