A crushing mill with a single roller inside a driven cylindrical shell inner surface, both with horizontal and parallel but offset axes is disclosed. In some embodiments, the roller has protrusions such that as the roller and shell rotate rock or other material may be crushed between the shell and the roller, respectively. In some embodiments, the shell and the roller each have surface protrusions such that rock or other materials may be crushed between the shell and the roller as they rotate. In some embodiments the shell and the roller operate at differential speeds with respect to each other to induce shear forces on the material to be crushed.

A process for producing metastable nanocrystalline alpha-alumina (-Al.sub.2O.sub.3) having particle sizes smaller than 12 nm. Starting crystallites of -Al.sub.2O.sub.3 having a particle size larger than 12 nm, typically on the order of about 50 nm, are ball-milled at low temperatures to produce a nanocrystalline -Al.sub.2O.sub.3 powder having a particle size of less than 12 nm, i.e., below the theoretical room temperature thermodynamic size limit at which -Al.sub.2O.sub.3 changes phase to -Al.sub.2O.sub.3, wherein the powder remains in the -Al.sub.2O.sub.3 phase at all times.

A process for producing metastable nanocrystalline alpha-alumina (-Al.sub.2O.sub.3) having particle sizes smaller than 12 nm. Starting crystallites of -Al.sub.2O.sub.3 having a particle size larger than 12 nm, typically on the order of about 50 nm, are ball-milled at low temperatures to produce a nanocrystalline -Al.sub.2O.sub.3 powder having a particle size of less than 12 nm, i.e., below the theoretical room temperature thermodynamic size limit at which -Al.sub.2O.sub.3 changes phase to -Al.sub.2O.sub.3, wherein the powder remains in the -Al.sub.2O.sub.3 phase at all times.

A method for producing fatty acid alkyl esters and glycerol implementing a set of transesterification reactions between at least one vegetable or animal oil and at least one aliphatic monoalcohol includes: introducing, into a three-dimensional microball mill at least one vegetable and/or animal oil, at least one aliphatic monoalcohol and at least one heterogenous and/or homogenous catalyst in order to form an initial mixture; grinding the initial mixture at a temperature50 C., in a three-dimensional microball mill, for a residence time5 minutes; recovering, at the outlet of the three-dimensional mill, a final mixture including at least fatty acid alkyl esters, glycerol, the catalyst and the aliphatic monoalcohol that has not reacted; and separating this final mixture of a first phase including the fatty acid alkyl esters and of a second phase including the glycerol, the aliphatic monoalcohol that has not reacted and the catalyst.

A method for producing fatty acid alkyl esters and glycerol implementing a set of transesterification reactions between at least one vegetable or animal oil and at least one aliphatic monoalcohol includes: introducing, into a three-dimensional microball mill at least one vegetable and/or animal oil, at least one aliphatic monoalcohol and at least one heterogenous and/or homogenous catalyst in order to form an initial mixture; grinding the initial mixture at a temperature50 C., in a three-dimensional microball mill, for a residence time5 minutes; recovering, at the outlet of the three-dimensional mill, a final mixture including at least fatty acid alkyl esters, glycerol, the catalyst and the aliphatic monoalcohol that has not reacted; and separating this final mixture of a first phase including the fatty acid alkyl esters and of a second phase including the glycerol, the aliphatic monoalcohol that has not reacted and the catalyst.

A method for the cryogenic grinding of at least one powder comprising the following steps: (a) introducing a cryogenic fluid into an attrition mill comprising attrition means, (b) introducing the powder or powders into the attrition mill, and (c) setting the attrition mill in rotational motion, and whereinthe ratio V.sub.MA/(V.sub.MA+V.sub.FC) of the volume of the attrition means V.sub.MA to the sum of the volume of the attrition means V.sub.MA and the volume of the cryogenic fluid VFC is comprised between 0.2 and 0.8, and the rotational speed of the attrition mill during step (c) is between 100 rpm and 20,000 rpm. Further, particles of metal or metal alloy, to the use thereof, to a coating method employing them and to the use of such a coated material.

A method for the cryogenic grinding of at least one powder comprising the following steps: (a) introducing a cryogenic fluid into an attrition mill comprising attrition means, (b) introducing the powder or powders into the attrition mill, and (c) setting the attrition mill in rotational motion, and whereinthe ratio V.sub.MA/(V.sub.MA+V.sub.FC) of the volume of the attrition means V.sub.MA to the sum of the volume of the attrition means V.sub.MA and the volume of the cryogenic fluid VFC is comprised between 0.2 and 0.8, and the rotational speed of the attrition mill during step (c) is between 100 rpm and 20,000 rpm. Further, particles of metal or metal alloy, to the use thereof, to a coating method employing them and to the use of such a coated material.

A sleeve insert for covering one or more selected surfaces of one or more pulp lifters of a discharge end assembly including a discharge end wall of a mill shell partially defined by an outer perimeter wall thereof, the pulp lifters being mounted on the discharge end wall. The sleeve insert is formed to cover the selected surfaces to mitigate wear to which the selected surfaces are subjected when the sleeve insert is located in a predetermined position relative to the selected surfaces.

A method for producing fatty acid alkyl esters and glycerol implementing a set of transesterification reactions between at least one vegetable or animal oil and at least one aliphatic monoalcohol includes: introducing, into a three-dimensional microball mill at least one vegetable and/or animal oil, at least one aliphatic monoalcohol and at least one heterogenous and/or homogenous catalyst in order to form an initial mixture; grinding the initial mixture at a temperature50 C., in a three-dimensional microball mill, for a residence time5 minutes; recovering, at the outlet of the three-dimensional mill, a final mixture including at least fatty acid alkyl esters, glycerol, the catalyst and the aliphatic monoalcohol that has not reacted; and separating this final mixture of a first phase including the fatty acid alkyl esters and of a second phase including the glycerol, the aliphatic monoalcohol that has not reacted and the catalyst.

A method for producing fatty acid alkyl esters and glycerol implementing a set of transesterification reactions between at least one vegetable or animal oil and at least one aliphatic monoalcohol includes: introducing, into a three-dimensional microball mill at least one vegetable and/or animal oil, at least one aliphatic monoalcohol and at least one heterogenous and/or homogenous catalyst in order to form an initial mixture; grinding the initial mixture at a temperature50 C., in a three-dimensional microball mill, for a residence time5 minutes; recovering, at the outlet of the three-dimensional mill, a final mixture including at least fatty acid alkyl esters, glycerol, the catalyst and the aliphatic monoalcohol that has not reacted; and separating this final mixture of a first phase including the fatty acid alkyl esters and of a second phase including the glycerol, the aliphatic monoalcohol that has not reacted and the catalyst.