The disclosed technology relates generally to material systems which include a plurality of particles and methods of making the same. The particles have a core and a shell which encapsulates the core and has at least one atomic element not included in the core. The cores of the particles have a median maximum dimension that is less than 10 microns and a median of at least one axial dimension that is between 10 nm and 500 nm. The shells of the particles have a median thickness that is less than 100 nm, a silicon concentration that is between 10% and 50% on the basis of the weight of the shells, and an aluminum concentration that is between 0.01% and 5% on the basis of the weight of the shells.
