초록

An abrasive element consisting substantially of a glass material that is at least partially devitrified.

대표청구항 ▼

1. An abrasive solid cast member for use in a grinding or polishing wheel, the cast member comprising a plurality of pieces of crushed silica glass cullett heat treated to form a unitary body of at least partially devitrified glass. 2. A cast member as claimed in claim 1, having a portion comprising

1. An abrasive solid cast member for use in a grinding or polishing wheel, the cast member comprising a plurality of pieces of crushed silica glass cullett heat treated to form a unitary body of at least partially devitrified glass. 2. A cast member as claimed in claim 1, having a portion comprising a substantially amorphous material. 3. A cast member as claimed in claim 1, comprising or incorporating a plurality of voids formed for example by gas bubbles, preferably air bubbles. 4. A cast member as claimed in claim 3, wherein the voids are substantially uniformly dispersed within the element. 5. A cast member as claimed in claim 3, wherein the voids are provided in at least a surface layer of the element. 6. A cast member as claimed in claim 5, wherein voids are exposed in the surface layer thereby to present sharp edges at the surface. 7. A cast member as claimed in claim 3, wherein the voids have a nominal diameter in the range of from around 50 nm to around 5 mm, preferably from around 1 micron to around 1 mm, more preferably around 10 microns to around 500 microns, still more preferably around 100 microns to around 500 microns. 8. A cast member as claimed in claim 1, wherein the volume of the element in the form of devitrified material is in the range from around 20% to around 80%, optionally around 50%. 9. A cast member as claimed in claim 1, comprising a plurality of regions of a crystallised glass material at a free surface of the element. 10. A cast member as claimed in claim 1, consisting essentially of an amorphous glass material and a crystallised glass material. 11. A cast member as claimed in claim 1, wherein the devitrified material comprises at least a portion having a needle morphology. 12. A cast member as claimed in claim 1, having a hardness value of around 5.5 on the Moh scale. 13. A cast member as claimed in claim 1, in the shape of a disc suitable for use as a grinding or polishing wheel. 14. A cast member as claimed in claim 13, comprising at least one support member arranged to prevent shatter of the disc. 15. A cast member as claimed in claim 14, wherein the support member has at least a portion embedded within the disc. 16. A grinding or polishing wheel comprising a cast member as claimed in claim 1. 17. A wheel as claimed in claim 16, comprising a plurality of elements each in the shape of a segment of a disc structure, the segments being coupled together thereby to form the wheel. 18. A wheel as claimed in claim 17, wherein the segments are coupled together by means of a hub member. 19. A grinding or polishing wheel as claimed in claim 16, wherein the cast member is in the form of a disc. 20. A building element in the form of a solid cast member consisting essentially of a plurality of pieces of crushed silica glass cullett heat treated to form a unitary body of at least partially devitrified glass. 21. A cast member as claimed in claim 20, in the shape of at least one selected from amongst a cuboid, an ellipsoid, a prism, a cone, a tetrahedron, a pyramid, a polyhedral solid, a sphere, a triangle, a disc structure and a segment of a disc structure. 22. A building element as claimed in claim 20, in the form of a building brick. 23. A method of forming an abrasive element for use in a grinding or polishing wheel, the method comprising the steps of: providing a plurality of pieces of a crushed silica glass cullett; andsubjecting the pieces of cullett to a heat treatment thereby to form a solid cast member from the cullett, the heat treatment resulting in at least partial devitrification of the crushed silica glass cullett. 24. A method as claimed in claim 23, wherein the step of providing a plurality of pieces of the crushed silica glass cullett further comprises providing a plurality of pieces of a filler material arranged to undergo thermal decomposition during said heat treatment thereby to provide a plurality of voids. 25. A method as claimed in claim 24, where the filler material comprises at least one selected from amongst husks of a plant material, crushed egg shell and a polymer material. 26. A method as claimed in claim 24, wherein the pieces of filler material have a size in the range of up to around 500 um, optionally up to around 250 um. 27. A method as claimed in claim 23, wherein the plurality of pieces of crushed silica glass cullett have an average size in a range selected from amongst up to around 4 mm, around 4 mm to around 2 mm, from around 3 mm to around 1 mm, from around 1.5 mm to around 0.75 mm, from around 1.5 mm to around 500 microns and up to around 100 microns. 28. A method as claimed in claim 23, wherein the abrasive element is formed to have a disc or disc-like shape, the element comprising a support member having at least a portion embedded within the element. 29. A method as claimed in claim 23, whereby the heat treatment comprises the step of heating to a temperature in the range from about 700° C. to about 1100° C., optionally around 750° C. to around 950° C. 30. A method as claimed in claim 23, whereby the heat treatment comprises the step of heating to a temperature in the range from about 800° C. to about 1000° C., optionally around 975° C. 31. A method as claimed in claim 23, whereby the heat treatment comprises the step of heating to a temperature in the range from about 850° C. to about 950° C., preferably from about 900° C. to about 920°, more preferably about 900°. 32. A method as claimed in claim 23, whereby the heat treatment comprises the step of heating to a temperature in the range from about 700° C. to about 1100° C. for a period of from around 1 hour to around 3 hours, preferably from about 700° to about 950° C., more preferably from around 900° C. to around 920°, still more preferably around 900°. 33. A method as claimed in claim 23, whereby the heat treatment comprises the step of heating to a temperature in the range from about 700° C. to about 1100° C. for a period of around 2 hours, preferably from about 700° to about 950° C., more preferably from around 900° C. to around 920°, still more preferably around 900°. 34. A method as claimed in claim 23, wherein the heat treatment comprises the step of heat treating the crushed silica glass cullett thereby to melt at least a portion of said crushed silica glass cullett; subsequently cooling to form a solid cast member having at least a portion comprising a devitrified material. 35. A method of forming a building element, the method comprising the steps of: providing a plurality of pieces of a crushed silica glass cullett; andsubjecting the pieces of cullett to a heat treatment thereby to form a solid cast member from the cullett, the heat treatment resulting in at least partial devitrification of the crushed silica glass cullett.