Mechanisms and Process Model of Ultra-Refining of Metals by Crystallization via a rotating cooled cylinder

The pro­ject aims to explo­re an alter­na­ti­ve method for the syn­the­sis of pure metals. The core ele­ment is frac­tion­al crystal­liza­ti­on, which is to be con­duc­ted through an intern­al­ly coo­led rota­ting crystal­li­zer (in short named “coo­led fin­ger”), on which the ultra-pure metal from a con­ta­mi­na­ted melt grows. This method has in the case of suc­cess the poten­ti­al to replace the cur­rent zone mel­ting pro­cess. Howe­ver, the under­stan­ding of an effec­ti­ve appli­ca­ti­on of this method, par­ti­cu­lar­ly the pro­cess con­trol­ling para­me­ters as well as a descrip­ti­on of the mecha­nisms in the pro­cess, is curr­ent­ly lacking.

By inter­play of ther­mo­phy­si­cal com­pu­ta­ti­ons and soli­di­fi­ca­ti­on simu­la­ti­on on a macro­sco­pic pro­cess and micro­sco­pic micros­truc­tu­re sca­le, the demi­xing pro­ces­ses at the pro­gres­si­ve pha­se boun­da­ry are to be quan­ti­ta­tively descri­bed and cor­re­la­ted with pro­cess para­me­ters. Exten­si­ve DoE-sup­port­ed expe­ri­men­tal inves­ti­ga­ti­ons to veri­fy and vali­da­te nume­ri­cal pre­dic­tions are per­for­med on alu­mi­num. Alu­mi­num has been cho­sen here as the model metal due to the exis­tance of the requi­red ther­mo­dy­na­mic and phy­si­cal data for the simu­la­ti­on that allo­wing a quan­ti­ta­ti­ve stu­dy of the fun­da­men­tal prin­ci­ples and domi­nant pro­cess para­me­ters for the cold fin­ger method. Alu­mi­num is cost-effec­ti­ve in various puri­ties, which means a signi­fi­cant reduc­tion in rese­arch costs.

The pro­ject results are aimed at pro­cess win­dows for effi­ci­ent clea­ning and the asso­cia­ted para­me­ters and pro­cess models for con­trol­ling the soli­di­fi­ca­ti­on front dyna­mics. The coope­ra­ti­on of three working groups with dif­fe­rent rese­arch inte­rests aims to pro­vi­de a quan­ti­ta­ti­ve under­stan­ding of the poten­ti­al of this — so far — unex­plo­red crystal­liza­ti­on pro­cess. The phy­si­cal­ly-based simu­la­ti­on model will faci­li­ta­te sim­pli­fied trans­fer to other alloy­ing systems.

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The pro­ject is fun­ded by the Deut­sche For­schungs­ge­mein­schaft (DFG) under the refe­rence num­ber PF 394/28–1.