Magnesium chloride and magnesium hydroxide.

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Magnesium chloride and magnesium hydroxide.

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Magnesium chloride and magnesium hydroxide.

Messaggioda Aldebaran » 13/04/2010, 8:59

"Binding materials based upon magnesium compounds. Dry magnesium hydroxide
and magnesium chloride are mixed in powder form, the weight ratio of the
magnesium oxide contained in the magnesium hydroxide to magnesium chloride
lying between about 0.8 and 2.0. Magnesium chloride may be used in the form of
its hexahydrate, and, additionally, in the form of dihydrates. The dry product
may be stored for months, in plastic sacks or bags, without coking. Thereafter,
mixing the dry product with water yields magnesium oxide mortar. "


Magnesium chloride
and 'abundantly present in seawater or in salt (not washed) or in the dolomite rock consists of widespread double carbonate of calcium and magnesium.
It 'also in dolomite, magnesite, brucite, carnallite, and olivine (there are exhaustive treatises on wikipedia).
These minerals are good for sharpening, among other things in general have Mohs hardness of quartz and derivatives and / or dell'Ortoclasio (6-7) as well as having the same refractive index (n = 1.54). The magnesium chloride hexahydrate in its form, and under normal conditions (used to grind, that 'its crystal habit has sfaccettaure with which you can remove sufficient quantity' of metal) has refractive index, incidentally, 1.56.
We now magnesium hydroxide.
This is fine as a binder, binders are placed first in the dough from the other strands and then also with respect to abrasive, it can 'get by mixing magnesium oxide with water and mix the solution will tutto.La' basic, such as the binders in mineral quartz type Arkansas.
The solid binder improves its effectiveness if it is mixed with wax fine. The same effect you get if you mixed magnetic powder or solid metal magnetized in the binder.
The binder and abrasive stones for sharpening any should be so 'broken:
First, suitable abrasives may be selected from, zeolites, calcite (calcium carbonate), Dolomites, feldspar, silicas, silicates, carbonates, alumina, bicarbonates, borates, sulphates and polymeric materials such as polyethylene, mixtures of calcium carbonate and magnesium ( as dolomite), sodium carbonate, potassium sulphate, alumina, hydrated alumina, aluminum oxide, semi-aluminum oxide, cubic boron nitride. Calcite, feldspar and dolomite and mixtures thereof are particularly preferred because of their low cost, suitable hardness and color.

Preferred abrasives for use in general purpose compositions have a Moh hardness of 2-6, although higher hardness abrasives can be used for specialized applications.
The best size of such abrasive particles fall within the scope of 0,5-400 microns, 10-200 microns, but it would be better.
The percentage of abrasive should be between 15-45% ,0,1-0, 5% of wax or magnetic powder, the remaining binder.
The aluminum oxide as an abrasive and 'better for metal than abrasive diamond or silicon carbide, worse than these two nell'abrasione of non-metals.
The bond matrix in which abrasive grains are fixed and may include a variety of organic materials such as rubber, shellac, or resin, inorganic materials such as clay. Inorganic glass-based binders can be used to sharpen cutting tools commonly used when mixed with emery, while the resin binders are used for removing coarse foundry operations.
A variety of products are used as additives to create proper porosity and spacing. In the past they were used, sawdust, ground nut shells, and coke, but now prefer to use wax balls. Sulfur and chlorine compounds inhibit welding pieces of metal on stone during the rubbing, these compounds also improve overall heat loss during sharpening, creating, in fact, adequate porosity '.
The pressure that must be submitted so the stone 'obtained is 100-5000 pounds per square inch for about 10-30 seconds.
The cooking time varies with binder :149-200 degrees with regard to bond with resin stones and 927-1260 degrees for glass constraints.
Commercially available phenolic resins suitable for this purpose are:
Resol phenolic resins, phenol with multi formaldeide.In this case the molar ratio of formaldehyde and phenol or be or 0,6:1 1.5:1.
Other organic elements and not to be used as binders are different resins with phenol and formaldehyde, aminoplast, fenoloplasti, unsaturated polyester resins, vinyl resins, alkyd resins,
allyl resins, furan resins, epoxy-epoxy, polyurethanes, polimmidi.
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Aldebaran
 
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