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When we hear the term "abrasive substances"We jump in the air imagining some liquid that can harm us. This is not always the case, in this category there are many different types of substances and it is necessary to make distinctions. For example, abrasives can also be very useful in certain industrial sectors and in some domestic work. So let's take the time to understand what the abrasive substances and how they behave. They are usually used in the form of powder; applied to sheets of paper or canvas; or sintered to form abrasive wheels or stones.
Abrasive substances: characteristics
They are substances used in mechanical processing because they are particularly hard. They can be natural but also artificial and are not a recent discovery, they were also extracted and used in the times of Ancient Greece. In particular, there is evidence of the extraction of emery, a Naxos, and of pumice, in Aeolian Islands.
Let's see better how they behave. In addition to being very hard, they have a crystalline nature and a minimal level of brittleness. There hardness it certainly remains the feature that makes them special and it is therefore also the one we are most interested in measuring to understand how abrasive a substance is and to what extent we can exploit it for its properties.
There Mohs scale it is the oldest and simplest method. 10 mineral species of increasing hardness are taken and evaluated gradually when our substance manages not to be scratched by them. There Knoop scale it is a bit more precise and measures the hardness in kg / mm2, durometers are used that apply pressure with a diamond point on the material to be evaluated.
The chemical nature of these substances is also an important element to know, to also understand how they behave when they come into contact with others, and then there is what is called toughness. It is not a typing error, it is called the mechanical resistance of an abrasive which becomes important when performing grinding operations. In some cases we also look at the grain, the diameter of its grains, the smaller it is the larger the grain, the less roughness there are and the operating speed increases.
Abrasive substances: what they are for
Those who work in the sector know how useful the abrasive substances, and they can be used very differently. For sharpening and cutting, for example, but also to create abrasive soaps or abrasive pastes. And it is only part of the possible uses.
Abrasive substances: what they are
Let's start by dividing these substances into two broad categories, which are rather easy to identify: natural and artificial ones. Among the first we find many known stones such as quartz, silica, pumice, sandstone, diamond, emery and garnet. Among the artificial there are aluminum and iron oxides, boron azide, silicon carbide, glass, boron carbide.
Let's take a closer look at some of them starting from diamond, one of the hardest substances in the world. Beyond the jewels, in the industrial field we find it often used, in its less valuable varieties such as Ballas and carbonado but above all the Bort, gray or black in color and with a highly continuous microcrystalline structure. This special diamond is used both to work ornamental diamonds and to treat metals and to cut silicon for semiconductors. We can also find it inserted in ceramic or metal agglomerates or incorporated in resins, to be used on grinding wheels, saws and probes for drilling.
The other material natural abrasive on which we focus is the quartz, crystalline and colorless stone used for the production of flexible abrasives or as a powder, to be added to some detergents. On an industrial level it can be used in the sandblasting operations of metallic materials and in the cleaning of glass and metals. And the pumice stone? In appearance it seems brittle but instead it is abrasive, used mainly in powder form in the packaging of household detergents and for cleaning metals.
They are increasingly used instead of natural ones, have a synthetic origin and can be "studied at the table" so that we have the most stable characteristics possible. Let's see some examples even if the names won't tell us much if we don't work in a technical field. The synthetic diamond it replicates the natural one but manages to be harder and at the same time more convenient in terms of costs. The first to produce it was General Electric in 1955. Boron carbide is obtained from a chemical reaction carried out inside the electric oven in which boric anhydride is reacted with excess coal. The substance obtained, as a powder, is used for the processing of semi-precious stones and optical glasses.
The Cubic Boron Nitride it is the second hardest substance after diamond, it is artificial and is inserted into the blades for cutting meteorites also because it resists much higher temperatures than diamond-based abrasives.