Southampton scientist develop silica nanofibers 15 times stronger than steel by weight

Research by (Optoelectronics Research Centre) ORC Principal Research Fellow Dr Gilberto Brambilla and ORC Director Professor Sir David Payne has resulted in the creation of the strongest, lightest weight silica nanofibres – ‘nanowires’ that are 15 times stronger than steel and can be manufactured in lengths potentially of 1000’s of kilometres.

Their findings are already generating extensive interest from many companies around the world and could be set to transform the aviation, marine and safety industries. Tests are currently being carried out globally into the potential future applications for the nanowires.

Their findings are already generating extensive interest from many companies around the world and could be set to transform the aviation, marine and safety industries. Tests are currently being carried out globally into the potential future applications for the nanowires.

Guesstimating the tensile strength from the ambiguous statement

In 2009, these same two researchers described the ultimate strength of silica nanowires at 10 GPa. (Nanoletters – The Ultimate Strength of Glass Silica Nanowires). The theoretical σf of silica nanowires is above 30 GPa.

In the past decade nanowires have attracted an increase interest because of their extraordinary mechanical strength. In fact, material properties in the nanoregime are extremely different from those found in macroscopic samples: few crystalline materials have shown a tensile strength in excess of 10 GPa in the form of nanowires. Still the length of defect-free crystalline nanowires is limited to a few millimeters and the strength of long nanowires is compromised by defects. The strength of glass nanowires is less affected by single defects. In this paper we present the ultimate strength of glass silica nanowires manufactured by a top-down fabrication technique; this is the highest value reported for glass materials. The measured ultimate strength is in excess of 10 GPa and increases for decreasing nanowire diameters. Scanning electron micrographs of the broken fragments showed a fragile rupture.

Regular fiberglass (has a tensile strength of 100 MPa, Polyester and Chopped Strand Mat Laminate 30% E-glass, density 1.4 grams per cubic centimeter)

Structural steel ASTM A36 steel has a tensile strength of 400 MPa. The density is 7.8 grams per cubic centimeter.

Silica nanofibers have a density of about 2.0 to 2.3 grams per cc (4 times less dense than steel). So I think a strength 15 times steel by weight would be about tensile strength of 1.6 GPa (which is not too impressive).

They do say high strength steel.

Steel, high strength alloy ASTM A514 has 760 MPa and there are other types of steel with up to 2600-5300 MPa of tensile strength (same density).
Really good fiber glass Polyester and Continuous Rovings Laminate 70% E-glass has 800 MPa tensile strength and 1.9 density.

About 8 GPa is less than the ultimate strength and would be impressive.
Kevlar is 2.757 GPA and density of 1.44.

So I think the material might be twice as strong as Kevlar but is still 10 to 50 times weaker than the ultimate strength of carbon nanotubes or graphene.

“With synthetic fibres it is important to have high strength, achieved by production of fibre with extremely low defect rates, and low weight,” says Dr Brambilla.

“Usually if you increase the strength of a fibre you have to increase its diameter and thus its weight, but our research has shown that as you decrease the size of silica nanofibres their strength increases, yet they still remain very lightweight. We are the only people who currently have optimised the strength of these fibres.

“Our discovery could change the future of composites and high strength materials across the world and have a huge impact on the marine, aviation and security industries. We want to investigate their potential use in composites and we envisage that this material could be used extensively in the manufacture of products such as aircraft, speedboats and helicopters,” he adds.

Professor Payne explains: “Weight for weight, silica nanowires are 15 times stronger than high strength steel and 10 times stronger than conventional GRP (Glass Reinforced Plastic). We can decrease the amount of material used thereby reducing the weight of the object.

“Silica and oxygen, required to produce nanowires, are the two most common elements on the earth’s crust, making it sustainable and cheap to exploit. Furthermore, we can produce silica nanofibres by the tonne, just as we currently do for the optical fibres that power the internet.”

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