ABSTRACT
The emergence of three-dimensional (3D) printing promises a disruption in the design and on-demand fabrication of smart structures in applications ranging from functional devices to human organs. However, the scale at which 3D printing excels is within macro- and microlevels and principally lacks the spatial ordering of building blocks at nanolevels, which is vital for most multifunctional devices. Herein, we employ liquid crystal (LC) inks to bridge the gap between the nano- and microscales in a single-step 3D printing. The LC ink is prepared from mixtures of LCs of nanocellulose whiskers and large sheets of graphene oxide, which offers a highly ordered laminar organization not inherently present in the source materials. LC-mediated 3D printing imparts the fine-tuning required for the design freedom of architecturally layered systems at the nanoscale with intricate patterns within the 3D-printed constructs. This approach empowered the development of a high-performance humidity sensor composed of self-assembled lamellar organization of NC whiskers. We observed that the NC whiskers that are flat and parallel to each other in the laminar organization allow facile mass transport through the structure, demonstrating a significant improvement in the sensor performance. This work exemplifies how LC ink, implemented in a 3D printing process, can unlock the potential of individual constituents to allow macroscopic printing architectures with nanoscopic arrangements.
ABSTRACT
The abundant application of metallized paper and the quick growth of their wastes lead to the removal of a huge amount of valuable resources from economic cycle. In this work, for the first-time, the thermal micronizing technique has been used to directly transform the metallized paper wastes to Al-Si nano-rod and Al nano-particles for use as the input in different manufacturing sectors such as additive manufacturing or composite fabrication. Structure of metallized paper has been investigated using FT-IR analysis and first-principle plane-wave calculation. Then, based on the structure of metallized paper, thermal micronizing technique has been modified to directly transform this waste into nano materials. Structure of nano-particles and nano-rods has been investigated using SEM, TEM, and XPS analysis. Results showed two main Al-Si nano-rod and Al nano-particle morphologies created as a result of the different surface tensions, which facilitate their separation by Eddy current separation technique. These quick transformation and facile separation together make this technique a unique process to deal with this complex waste and producing value-added products which can re-capture these high value materials from waste and make the reforming economically viable.
ABSTRACT
A large piezoelectric coefficient of 76 pm/V along the diameter direction, approaching that of lead-based piezoelectrics, is observed in hydrothermally synthesized Pb-free Bi0.5(Na0.8K0.2)0.5TiO3 nanotubes. The 30-50 nm diameter nanotubes are formed through a scrolling and wrapping mechanism without the need of a surfactant or template. A molar ratio of KOH/NaOH = 0.5 for the mineralizers yields the Na/K ratio of â¼0.8:0.2, corresponding to an orthorhombic-tetragonal (O-T) phase boundary composition. X-ray diffraction patterns along with transmission electron microscopy analysis ascertain the coexistence of orthorhombic and tetragonal phases with (110) and (001) orientations along the nanotube length direction, respectively. 23Na NMR spectroscopy confirms the higher degree of disorder in Bi0.5(Na1- xK x)0.5TiO3 nanotubes with O-T phase coexistence. These findings present a significant advance toward the application of Pb-free piezoelectric materials.
ABSTRACT
A new approach to the synthesis of hierarchical micro- and mesoporous MOFs from microporous MOFs involves a simple hydrolytic post-synthetic procedure. As a proof of concept, a new microporous MOF, POST-66(Y), was synthesized and its transformation into a hierarchical micro- and mesoporous MOF by water treatment was studied. This method produced mesopores in the range of 3 to 20â nm in the MOF while maintaining the original microporous structure, at least in part. The degree of micro- and mesoporosity can be controlled by adjusting the time and temperature of hydrolysis. The resulting hierarchical porous MOF, POST-66(Y)-wt, can be utilized to encapsulate nanometer-sized guests such as proteins, and the enhanced stability and recyclability of an encapsulated enzyme is demonstrated.
