Glasses with certain composition of different chemical compounds forms in a specific range only. Beyond the range it will be difficult to form the glass in normal melt quenching. is there any method to find the glass forming region through XRD data of a single glass sample?
Hi Hima,
glass forms when the cooling conditions are faster than crystallisation kinetics. WIth XRD (from what I know) you can constrain the existance of glass. With DSC (Differential Scanning Calorimetry) you can quantify the cooling speed across the glass transition area.
Best regards, Ulrich Küppers
In general DSC or DTA are the best tols, the easy and fast way will be measure the Delta Tx, distance between the glass transition Tg and the onset of crystallization Tx, or from the TTT diagram also based on DSC analysis.
I am not aware of any method to estimate glass forming ability for a broad composition range even within a limited set of given materials. In fact glass forming ability (or inversely crystallization kinetics) will often abruptly change by several orders of magnitude over very limited compositional range especially for materials that do not fit into the standard "glass former". It is necessary to know the purpose of the desired glass and probable method of forming etc..to determine "glass forming ability". i.e glass for fiber insulation formed from rapid cooling of the molten glass will have a different tolerable glass forming region than glass intended to be cast as bulk, machined and reheated for drawing optical fiber. Since they approach the crystallization region in different ways each has very different tolerance for glass forming and crystallization kinetics. Generally DSC, calculation of of Tx-Tg and the Hruby parameter, and calculation of critical cooling rates gives the best analysis of general stability. After nearly thirty years of making many different glass types from oxide, fluoride, heavy metal etc.. I still find thebest method to be good old experimentation making lots of glass samples especially if you know the general family of glass you want i.e. you are not trying to discover an entirely new class of glass former.
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