Localized hyperthermia technique using magnetic particles, based on proposal brought forward by Gilchrist in 1957, continues to be an active area of research. It has been found that the viability of cancer cells is reduced and their sensitivity to chemotherapy and radiation increase when the human or animal malignant cells are heated to temperatures between 41–46°C [1
]. Magnetic hyperthermia provides the heat at the site of the tumor invasively by applying an external alternating magnetic field to the magnetic particles at the tumor site. The particles will heat up and conduct the heat to the tumor cells. The use of materials with Curie temperature in the range of 41–46°C is desired to provide a safeguard against overheating of normal cells, due to the decrease of magnetic coupling in the paramagnetic regime (above Tc). The binary alloy copper-nickel shows a promising magnetic phase transitions in the desired range of temperature for hyperthermia treatment of cancer.
The phase equilibria system for copper-nickel shows a linear progression for the Curie temperature, which starts at a composition of 67% nickel and 33% copper (by weight) for a temperature of 0°C [4
]. From the phase diagram of Cu-Ni alloy, the optimum amount of nickel in the alloy is determined to be 71–71.4% by weight to have a Curie temperature in the desired range of 41–46°C. A Cu-Ni alloy for hyperthermia applications has been produced first by Lilly et al [5
]. They fabricated self-regulating implants via physical melting. Bimetallic nanoparticles can be synthesized by a wide variety of physical methods, such as, sputtering [6
], mechanical alloying (ball milling) [7
], eletrodeposition [9
] or partial recrystallization of amorphous materials [10
]. Most of the methods yield two-phase nanocrystalline materials. For instance, Guo et al. [9
] have produced composite Cu-Ni nanostructures via an electrodeposition and template-based process. Natter et al. [11
] used a pulsed electrodeposition process, enabling the control of grain size and chemical composition of the deposited material. Control of the composition in the nanolevel is difficult [12
], since molecules and atoms in common techniques (e.g. chemical vapor deposition, plasma vapor deposition) do not necessarily arrange in the preferred composition, which was determined on bulk material on the macroscopic level.
In the present study we used a simple process that combines melting and ball milling of bulk materials. Koch [13
] has reviewed the facts of ball milling (mechanical alloying) and its impact on nanostructured materials, indicating that ball milling can produce average grain sizes below 100 nm. Even though Natter [11
] has shown that the chemical composition can be controlled via pulsed electrodeposition; and deposition on a porous substrate could possibly yield nanoparticles, it is nevertheless a complex process requiring expensive equipment, the control of several parameters and a lot experience. Additionally, this process is not feasible for industrial high-scale applications.