High gradient directional solidification furnace

A directional solidification furnace for impressing a steep thermal gradient across a sample material comprising:

• an elongated tube adapted to receive and have translated therethrough a material-containing ampule;
• temperature-influencing means disposed outside said tube and along its length and defining in said tube a hot end region adjacent one end, a heated, but cooler region adjacent the other end and an intermediate region having a steep thermal gradient;
• said temperature-influencing means including a passive insulating element disposed around said intermediate region of said tube, a cooling element disposed between said passive insulating element and said cooler region, a booster heater element disposed between said passive insulating element and said hot region, and a plurality of heating elements disposed around said hot region and said cooler region;
• insulation means enclosing selected ones of said heating elements so as to provide a flat temperature profile in said end regions;
• and
• an external housing enclosing and supporting the said elements and insulation.

A directional solidification furnace adapted to provide along its length two relatively uniform elevated temperature regions with a region of steep thermal gradient therebetween comprising:

• an elongated tube adapted to receive and have translated therethrough a material-containing ampule;
• a plurality of annular elements disposed side-by-side along the length of and in heat-transfer relation with said tube, said elements comprising:
• a first relatively narrow, high-power heating element disposed around the tube adjacent its hotter end and adapted to be operated in such a manner as to compensate for heat loss out the said tube end;
• a first relatively wide heating element disposed adjacent said first high-power heating element over a major portion of the hotter end region of said tube;
• a first passive insulating element disposed over said tube adjacent said first wide heating element;
• a narrow, high-power booster heating element disposed over said tube adjacent to said first passive heating element;
• a second passive insulating element disposed over said tube adjacent said booster and enclosing the circumference of said steep thermal gradient region;
• a cooling element disposed over said tube and adjacent said second passive insulating element;
• a second relatively wide heating element disposed over said tube adjacent to said cooling element;
• and
• a second relatively narrow, high-power heating element disposed over said tube adjacent to said second relatively wide heating element and adjacent to the cooler end of said tube;
• insulation means disposed around all of said elements except said second relatively wide heating element;
• and said coo1ing element;
• and
• housing means.