Observation of a Broadened Magnetocaloric Effect in Partially Crystallized Gd60Co40 Amorphous Alloy

To investigate the effect of crystallization treatment on the structure and magnetocaloric effect of Gd60Co40 amorphous alloy, the melt-spun ribbons were annealed at 513 K isothermally for 20, 40 and 60 min. The results indicate that, with increasing annealing time, the Gd4Co3 (space group P63/m) and Gd12Co7 (space group P21/c) phases precipitated from the amorphous precursor in sequence. In particular, in the samples annealed for 40 and 60 min, three successive magnetic transitions corresponding to the phases of Gd4Co3, Gd12Co7 and remaining amorphous matrix were detected, which induced an overlapped broadened profile of magnetic entropy change (|ΔSM|) versus temperature. Under magnetic field changing from 0 to 5 T, |ΔSM| values of 6.65 ± 0.1 kg−1·K−1 and 6.44 ± 0.1 J kg−1·K−1 in the temperature spans of 180–196 K and 177–196 K were obtained in ribbons annealed for 40 and 60 min, respectively. Compared with the fully amorphous alloy, the enhanced relative cooling power and flattened magnetocaloric effect of partially crystallized composites making them more suitable for the Ericsson thermodynamic cycle.

Long-term Stabilized Amorphous Calcium Carbonate – an Ink for Bio-inspired 3D Printing

Amorphous Calcium Carbonate (ACC) is a highly unstable amorphous precursor many organisms utilize for the formation of crystals with intricate morphology and improved mechanical properties. Herein, we report for the first-time high-yield long-term stabilization of ACC, achieved via its co-precipitation in the presence of high amounts of Mg and an acetone-based storage protocol. A novel use of the formed high-Mg ACC paste as an ink for 3D printing techniques allows the formation of bio-inspired intricately shaped calcium carbonate geometries. The obtained ink can dry, though retains its amorphous nature, at a variety of temperatures ranging from 25 to 150˚C enabling various applications such as cultural heritage reconstruction and artificial reefs formation. We also show the on-demand low-temperature crystallization of the 3D printed ACC models, similar to what is achieved by organisms in nature. Using this bio-inspired crystallization route via transient amorphous precursor also enables the presence of high Mg levels within the calcite crystalline lattice, far beyond the thermodynamically stable solubility level. High levels of Mg incorporation, in turns, encompasses a great promise for the enhancement in the mechanical properties of the crystallized calcite 3D objects akin naturally found crystalline CaCO₃.

Long-term Stabilized Amorphous Calcium Carbonate – an Ink for Bio-inspired 3D Printing

Amorphous Calcium Carbonate (ACC) is a highly unstable amorphous precursor many organisms utilize for the formation of crystals with intricate morphology and improved mechanical properties. Herein, we report for the first-time high-yield long-term stabilization of ACC, achieved via its co-precipitation in the presence of high amounts of Mg and an acetone-based storage protocol. A novel use of the formed high-Mg ACC paste as an ink for 3D printing techniques allows the formation of bio-inspired intricately shaped calcium carbonate geometries. The obtained ink can dry, though retains its amorphous nature, at a variety of temperatures ranging from 25 to 150˚C enabling various applications such as cultural heritage reconstruction and artificial reefs formation. We also show the on-demand low-temperature crystallization of the 3D printed ACC models, similar to what is achieved by organisms in nature. Using this bio-inspired crystallization route via transient amorphous precursor also enables the presence of high Mg levels within the calcite crystalline lattice, far beyond the thermodynamically stable solubility level. High levels of Mg incorporation, in turns, encompasses a great promise for the enhancement in the mechanical properties of the crystallized calcite 3D objects akin naturally found crystalline CaCO₃.

Heterostructural transformation of mesoporous silica–titania hybrids

Mesoporous silica (SBA-15 with the BJH pore size of 8 nm) containing anatase nanoparticles in the pore with two different titania contents (28 and 65 mass%), which were prepared by the infiltration of the amorphous precursor derived from tetraisopropyl orthotitanate into the pore, were heat treated in air to investigate the structural changes (both mesostructure of the SBA-15 and the phase and size of the anatase in the pore). The mesostructure of the mesoporous silica and the particle size of anatase unchanged by the heat treatment up to 800 °C. The heat treatment at the temperature higher than 1000 °C resulted in the collapse of the mesostructure and the growth of anatase nanoparticles as well as the transformation to rutile, while the transformation of anatase to rutile was suppressed especially for the sample with the lower titania content (28 mass%). The resulting mesoporous silica-anatase hybrids exhibited higher benzene adsorption capacity (adsorption from water) over those heated at lower temperature, probably due to the dehydroxylation of the silanol group on the pore surface. The photocatalytic decomposition of benzene in water by the present hybrid heated at 1100 °C was efficient as that by P25, a benchmark photocatalyst.