Platinum Fabric Made from Platinum Fibre

A length of multi-core wire combining platinum and copper was cut into pieces 1 mm in length. The copper was then removed to produce short platinum fibres having a diameter of 0.1 μm. These fibres were then dispersed in water and filtered to form a non-woven “fabric”. The non-woven platinum “fabric”, made from the 0.1 μm fibre, was then heat-treated at 650°C to strengthen it – platinum begins to melt at 700°C. Figures 2 and 3 show heat-treated platinum fibres. Despite the classification of the filter components as heat-resistant materials, the micrographs suggest that the maximum working temperature for the filter is 600°C.

The separation characteristics of a non-woven fabric filter composed of platinum fibres 0.1 μm in diameter was assessed at the Matsumoto Laboratory, Division of Materials Science and Chemical Engineering, Faculty of Engineering, Yokohama National University. Test samples had specifications: basis weight (weight per unit area of filter) of 210 to 830 g m⁻²; thickness of 0.09 to 0.34 mm; and porosity of 88 to 90%. The Table gives specifications of the fibre in detail.

The following results were found:

These results were compared with those of other material filters. The porosity of materials that have a mean fine pore diameter of less than 1 μm and which are widely used, was 30% or less, while the porosity of the 0.1 μm diameter platinum fibre filters reached 90%, as described above. Such high porosity for the platinum fibre filter may be due to a combination of factors: low filtration pressure loss, less-pronounced pressure increase, and superior filter characteristics. In addition, despite a maximum working temperature of 600°C, the filter is significantly resistant to heat and exhibits the corrosion resistance that is expected of platinum materials. However, due to high cost, this filter is currently used only in special analyses, and in minute quantities.

The potential application as electrically conductive fillers for porcelain enamel was suggested by a porcelain enamel manufacturer (2). In this application, platinum fibre is described as being used in glass-lining materials, which are utilised as insulating material for glass-lined devices used by the chemical, pharmaceutical and food industries.

These materials have volume resistivity of 1 × 10¹³ to 1 × 10¹⁴ Ω cm. Thus, agitation in nonaqueous solutions containing organic substances results in a significant buildup of excess electric charge over leak charge. This can result in static charges of several tens of thousand or hundreds of thousand volts that could lead eventually to damage or explosion of the glass-lining materials, even if the glass-lined devices are electrically earthed. It is standard practice to embed or wind platinum or tantalum wires in or around the glass lining materials, but such treatment primarily has a local effect and is inadequate.

An example in (2) describes how the addition of 0.5 wt.% of platinum fibre of diameter 0.5 μm and length 2 mm to porcelain enamel reduced the volume resistivity to 1.3 × 10³ Ω cm. This can effectively prevent electrostatic buildup. If, however, platinum powder is used, 20 wt.% of platinum powder must be added to achieve a volume resistivity of 4.7 × 10³ Ω cm.

A container that had to be glass-lined every three months to repair damage caused by static discharge was replaced with a container made of electrically conductive enamel, using the said method. After five years, the container remains serviceable and exhibits no problems.