A method of forming a component having an internal passage defined therein, said method comprising: forming a precursor core having a shape corresponding to a shape of the internal passage ; forming a hollow structure around an outer wall of the precursor core ; wherein the hollow structure is formed from a first material ; removing the precursor core from within the hollow structure ; characterized in that said method further comprises: disposing an inner core within the hollow structure such that the hollow structure and the inner core form a jacketed core ; wherein the inner core is formed from an inner core material ; wherein disposing the inner core within the hollow structure comprises complementarily shaping the inner core by an interior portion of the hollow structure , such that the inner core has a shape corresponding to the shape of internal passage ; positioning the jacketed core with respect to a mold ; introducing a component material in a molten state into a cavity of the mold , wherein the component material is an alloy and the first material is at least one constituent material of the alloy, such that the component material in the molten state at least partially absorbs the hollow structure from a portion of the jacketed core within the cavity ; and cooling the component material in the cavity to form the component , wherein the inner core defines the internal passage within the component . forming a precursor core having a shape corresponding to a shape of the internal passage ; forming a hollow structure around an outer wall of the precursor core ; wherein the hollow structure is formed from a first material ; removing the precursor core from within the hollow structure ; characterized in that said method further comprises: disposing an inner core within the hollow structure such that the hollow structure and the inner core form a jacketed core ; wherein the inner core is formed from an inner core material ; wherein disposing the inner core within the hollow structure comprises complementarily shaping the inner core by an interior portion of the hollow structure , such that the inner core has a shape corresponding to the shape of internal passage ; positioning the jacketed core with respect to a mold ; introducing a component material in a molten state into a cavity of the mold , wherein the component material is an alloy and the first material is at least one constituent material of the alloy, such that the component material in the molten state at least partially absorbs the hollow structure from a portion of the jacketed core within the cavity ; and cooling the component material in the cavity to form the component , wherein the inner core defines the internal passage within the component . disposing an inner core within the hollow structure such that the hollow structure and the inner core form a jacketed core ; wherein the inner core is formed from an inner core material ; wherein disposing the inner core within the hollow structure comprises complementarily shaping the inner core by an interior portion of the hollow structure , such that the inner core has a shape corresponding to the shape of internal passage ; positioning the jacketed core with respect to a mold ; introducing a component material in a molten state into a cavity of the mold , wherein the component material is an alloy and the first material is at least one constituent material of the alloy, such that the component material in the molten state at least partially absorbs the hollow structure from a portion of the jacketed core within the cavity ; and cooling the component material in the cavity to form the component , wherein the inner core defines the internal passage within the component . <EOS>