Academic literature on the topic 'Hexagonal bipyramid structure'

Take into account additive manufacturing while design lattice implant can improve load-bearing properties and decrease construction weight. The usage of lattice structure and biomaterials makes it possible to solve the main problem of arthroplasty – preservation of the implant after surgery in the patient's body. Unfortunately, nowadays biomaterials do not have the necessary strength capacity. In spite of this, a lot of researches are directed towards to develop new design methods or improve the existing ones. There are number of articles focused on in-situ testing and quality control of lattice structures. The study is devoted to investigate the buckling of lattice structures under uniaxial compression with synchronous X-ray computed tomography scanning. In the article an experimental study of lattice structures of two kinds has been carried out. Edges of hexagonal bipyramid were a basic cell of the samples. The distribution of basic cells in the first type of construction was uniform, and was non-uniform in the second type. The studied samples were manufactured by laser stereolithography method. The lattice structures were loaded step-by-step with a longitudinal compressive load. The loading of the specimens was carried out in cooperation with their scanning by X-ray computed tomography. As a result, the displacement fields of structures at each step of loading were obtained. The general and local buckling of lattice structures was revealed. The general buckling occurred at the second loading step for each type of structure. Local buckling was observed at the third loading step. The influence of the architecture of the lattice structures on the buckling process was revealed. The effect of interruption of the buckling process was observed in the specimen with non-uniform distribution of basic cells. And because of that the structure continued to work in compression. In other words, the lattice architecture "dampened " the bending components of the displacement vector.

In this work, ZnO nanocrystals (NCs) have been effectively synthesized by a simple, efficient and cost-effective method using coconut husk extract as a novel fuel. The synthesized NCs are characterized by UV-Vis, XRD, FT-IR, SEM, EDX, Raman and PL studies. The obtained ZnO were found to be UV-active with a bandgap of 2.93 eV. The X-ray diffraction pattern confirms the crystallinity of the ZnO with hexagonally structured ZnO with a crystallite size of 48 nm, while the SEM analysis reveals the hexagonal bipyramid morphology. Photocatalytic activities of the synthesized ZnO NCs are used to degrade methylene blue and metanil yellow dyes.

Secondary phases that form during the corrosion of nuclear waste forms may influence both the rate of waste form dissolution and the release of radionuclides [1]. The identification of these phases is critical in developing models for the corrosion behavior of nuclear waste forms. In particular, the secondary uranyl (VI) minerals that form during waste form alteration may control uranium solubility and release of radionuclides incorporated into these phases [2].The U6+ cation in uranyl minerals is almost always present as a linear (UO2)2+ ion [3]. This uranyl (Ur) ion is coordinated by four, five, or six anions (ϕ) in the equatorial plane resulting in the formation of square (Urϕ4), pentagonal (Urϕ5), and hexagonal (Urϕ6) bipyramids, respectively [3]. These bipyramid polyhedra may polymerize to form complex infinite sheet structures. The linking of Urϕ5 is observed in a number of uranyl minerals formed during waste glass and spent fuel corrosion [2,4], such as weeksite [Na,K(UO2)2(Si205)3*4H2O] and β-uranophane [Ca[(UO2)(SiO3OH)]2*5H2O].

We have designed possible structures of isomers of fullerenes from C₅₈ to C₆₀. The fullerenes studied refer to four-, five- and six-fold symmetry, they being divided into two classes, perfect (basic) having ordinary symmetry and intermediate having topological symmetry. We have used three the most natural mechanisms of their formation, namely, fusion of carbon cupolas having the same symmetry; fusion of fullerenes having compatible symmetry and embedding carbon dimers into the hexagons with a specific surrounding of initial fullerenes. The energies of the fullerenes calculated through the use of molecular mechanics are presented together with their graphs. We have separated fragments of curvature and put into accordance with their centers the centers of principal stresses. The arrangement of both centers for the five observed experimentally isomers of fullerene C₆₀ corresponds to five geometric figures: icosahedron, pentagonal, hexagonal, deformed hexagonal bipyramids and cube. As a result the binding energy of isomers can be considered not only as a global quantity, but as a surface distribution.