What are Nickel Sulphide Glass Inclusions?

Why would nickel sulphide cause glass to fracture without notice?

What are Nickel Sulphide Glass Inclusions?

Why does tempered glass break spontaneously and how can we help you get to the bottom of the root cause of glass failure.

Tempered glass can break for many reasons, some of them obvious, such as breakage due to high winds, damage to the surface or edge during installation, bad design of window frame being hit by a missile, to the somewhat less obvious reasons for example, inclusions in the glass of which nickel sulphide inclusion is just one.

Nickel Sulphide Inclusion, one of the most uncommon and invisible imperfections in glass but what are they and why can they lead to the unpredictable and spontaneous glass brakeage. Failure of a float glass panel due to nickel inclusion is a very rare event but it does happen and several times a year, our laboratory is asked to determine if a nickel sulphide was the root cause a sudden failure.

The raw materials used to manufacture glass contain many impurities with nickel being one such impurity. During processing the glass melt, this nickel reacts with sulphur to form minute nickel sulphide particles ranging in size between approx. 50 μm to 500 μm. When glass is being tempered, these nickel sulphide particles change from a low temperature structure to a high temperature structure which is crystalline in form. When the glass is cooled, the particle is unable to change back to its low temperature structure and over a period, it will slowly convert to its original low temperature form.

A nickel sulphide particle may end up in or close to the central tension zone in a glass panel, and on exposure to post installation temperatures (such as that from room heating or direct sunlight), the tiny particle may grow by upto 5%, cause the glass to instantaneously shatter.

The determination of the suspected root cause of a suspected nickel sulphide inclusion failure may be determined firstly by examining the intact glass in situ. The unique ‘butterfly pattern’, glass fracture being centred around a single point and the fractures radiating from that point.

We then move to optical analysis and by using digital microscopy, we can find the inclusion. If the inclusion is s spherical or slightly elliptical dark spot, there is a strong possibility that it is nickel sulphide.

Next, we use our bespoke analytical services including our Scanning Electron Microscope (SEM) which allows us to zoom in on the area of specific interest. While in the SEM, we can also carry out elemental analysis using energy dispersive X-ray spectroscopy (EDS) which identify the elements within the inclusion. The presence of high levels of Silica is expected, however when both nickel and sulphur are within the inclusion, a nickel sulphide inclusion will the cause of the failure.

The SEM-EDS allows us to perform targeted micro-analysis which can confirm or refute the contention that a nickel sulphide inclusion is the cause of a spontaneous glass failure. For premium advice, contact us here.

Our business is solving problems, so talk to us now.

Contact us