In cavitation experiments with deuterated acetone, tritium decay activity above background levels was detected. In addition, evidence for neutron emission near 2.5 million electron volts was also observed, as would be expected for deuterium-deuterium fusion. Control experiments with normal acetone did not result in tritium activity or neutron emissions. Hydrodynamic shock code simulations supported the observed data and indicated highly compressed, hot (10 ⁶ to 10 ⁷ kelvin) bubble implosion conditions, as required for nuclear fusion reactions.

Spray-drying and the nanoscale Kirkendall diffusion process are used to prepare nickel sulfide hollow nanospheres/reduced graphene oxide (rGO) composite powders with excellent Na-ion storage properties. Metallic Ni nanopowder-decorated rGO powders, formed as intermediate products, are transformed into composite powders of nickel sulfide hollow nanospheres/rGO with mixed crystal structures of Ni₃S₂ and Ni₉S₈ phases by the sulfidation process under H₂S gas. Nickel sulfide/rGO composite powders with the main crystal structure of Ni₃S₂ are also prepared as comparison samples by the direct sulfidation of nickel acetate–graphene oxide (GO) composite powders obtained by spray-drying. In electrochemical properties, the discharge capacities at the 150^th cycle of the nickel sulfide/rGO composite powders prepared by sulfidation of the Ni/rGO composite and nickel acetate/GO composite powders at a current density of 0.3 A g⁻¹ are 449 and 363 mA h g⁻¹, respectively; their capacity retentions, calculated from the tenth cycle, are 100 and 87%. The nickel sulfide hollow nanospheres/rGO composite powders possess structural stability over repeated Na-ion insertion and extraction processes, and also show excellent rate performance for Na-ion storage.

Porous FeS nanofibers with numerous nanovoids for use as anode materials for sodium-ion batteries were prepared by electrospinning and subsequent sulfidation. The post-treatment of the as-spun Fe(acac)₃-polyacrylonitrile composite nanofibers in an air atmosphere yielded hollow Fe₂O₃ nanofibers due to Ostwald ripening. The ultrafine Fe₂O₃ nanocrystals formed at the center of the fiber diffused toward the outside of the fiber via Ostwald ripening. On sulfidation, the Fe₂O₃ hollow nanofibers were transformed into porous FeS nanofibers, which contained numerous nanovoids. The formation of porosity in the FeS nanofibers was driven by nanoscale Kirkendall diffusion. The porous FeS nanofibers were very structurally stable and had superior sodium-ion storage properties compared with the hollow Fe₂O₃ nanofibers. The discharge capacities of the porous FeS nanofibers for the 1^st and 150^th cycles at a current density of 500 mA·g^–1 were 561 and 592 mA·h·g^–1, respectively. The FeS nanofibers had final discharge capacities of 456, 437, 413, 394, 380, and 353 mA·h·g^–1 at current densities of 0.2, 0.5, 1.0, 2.0, 3.0, and 5.0 A·g^–1, respectively.

The first-ever study of nickel selenide materials as efficient anode materials for Na-ion rechargeable batteries is conducted using the electrospinning process. NiSe₂-reduced graphene oxide (rGO)-C composite nanofibers are successfully prepared via electrospinning and a subsequent selenization process. The electrospun nanofibers giving rise to these porous-structured composite nanofibers with optimum amount of amorphous C are obtained from the polystyrene to polyacrylonitrile ratio of 1/4. These composite nanofibers also consist of uniformly distributed single-crystalline NiSe₂ nanocrystals that have a mean size of 27 nm. In contrast, the densely structured bare NiSe₂ nanofibers formed via selenization of the pure NiO nanofibers consist of large crystallites. The initial discharge capacities of the NiSe₂-rGO-C composite and bare NiSe₂ nanofibers at a current density of 200 mA g⁻¹ are 717 and 755 mA h g⁻¹, respectively. However, the respective 100^th-cycle discharge capacities of the former and latter are 468 and 35 mA h g⁻¹. Electrochemical impedance spectroscopy measurements reveal the structural stability of the composite nanofibers during repeated Na-ion insertion and extraction processes. The excellent Na-ion storage properties of these nanofibers are attributed to this structural stability.