Hexagonal Matrix Research Articles

Multiscale study of different types of interface of a buffer material in powder-based directed energy deposition: Example of Ti6Al4V/Ti6Al4V - Mo/Mo - Inconel 718

When it is difficult to deposit a material A on a material B, it is possible to create a Functionally Graded Material (FGM) using a buffer material between them to avoid the appearance of defects. The literature shows that it is very difficult, nay impossible, to have an efficient metallurgical bond between Ti6Al4V and Inconel-Mo alloys without cracks, porosities or delamination. A buffer material is therefore needed (here 25% Ti6Al4V – 75% Mo) and the fine analysis of the two interfaces thus created makes it possible to define the relevance of the choice of the buffer. Moreover, the understanding of the phenomena taking place at the interface allows the preservation of the structural integrity of a FGM made by additive manufacturing. CLAD® powder-based directed energy deposition allows the building of parts containing FGM and/or buffer materials directly during the process. The study of the interfaces at both sides of the buffer material is essential. In this paper, the first interface 100 Ti6Al4V / 25 Ti6Al4V – 75 Mo (in wt%) is smooth, suggesting that there has been diffusion between both alloys. The second one, 25 Ti6Al4V – 75 Mo / 30 Inconel 718 – 70 Mo, contains numerous exotic structures between both alloys. For such a sharp interface, we show in this paper that a microscopic study is not sufficient, but a finer scale is necessary to have a good metallurgical insight. Thus, EDS, TKD and X-ray crystallography were performed right on this interface and revealed three main structures: a hexagonal matrix, a cubic structure and an ordered hexagonal one. The hexagonal matrix appears to consist of Ni3Ti and the ordered hexagonal one of NiMo.

An enhanced, near-term HCPB design as driver blanket for the EU DEMO

The Helium Cooled Pebble Bed (HCPB) breeding blanket is a candidate as driver blanket for the EU DEMO. The reference design of the HCPB is based on a cooling plate “sandwich” arrangement built in Multi-Module Segments. This architecture significantly improved the tritium breeding performance (TBR = 1.15) and the plant circulating power (≈130 MW) compared to the former ITER-like “beer-box”-like design (TBR<1.10, plant circulating power>200 MW). However, several issues remain with this design, in which (1) the still large power required per He circulator (beyond the state-of-the-art for these components) and (2) the large tritium inventory foreseen in Be have been identified as the most critical. After a basic research for a concept that mitigates these key issues, a fission-like configuration based on a hexagonal matrix of radial fuel-breeder pin assemblies has been found to solve many of the outstanding issues present in the reference design. This design has been developed for the latest EU-DEMO 2017 baseline. It features Be12Ti neutron multiplier, which largely reduces the tritium retention, swelling and reactivity issues compared to pure Be. The substitution of the relatively complex CPs by simpler fuel-breeder pins improves the heat transfer capability of the breeder zone (BZ), allowing 20°C higher blanket outlet temperature and drastically reducing an order of magnitude the pressure drop in the BZ. The paper reports the successful set of nuclear, thermo-hydraulic and thermo-mechanical performances, together with some notes about the manufacturing and assembly strategy, the improved RAMI features and emphasizes the reduction of the plant circulating power to a remarkably low figure (˜90 MW), enabling the use state-of-the-art He turbomachinery. Due to some inherent issues connected to the use of Be as neutron multiplier which cannot be simply solved by design, a parallel long research has identified molten lead as a cost-effective, low risk substitute for Be. Taking as basis the HCPB fuel-breeder pin concept, an alternative helium cooled Molten Lead Ceramic Breeder has been derived and some key performance figures are reported. The paper concludes with a discussion on the results and their implications on future development steps.

A systematic analysis of perturbations for hexagonal mixing matrix

We present a systematic analysis of perturbative Hexagonal (HG) mixing for describing recent global fit neutrino mixing data with normal and inverted hierarchy. The corrections to unperturbed mixing are parametrized in terms of small orthogonal rotations [Formula: see text] with modified PMNS matrix of the forms [Formula: see text]. Here, [Formula: see text] is rotation in [Formula: see text] sector and [Formula: see text] is unperturbed Hexagonal mixing matrix. The detailed numerical investigation of all possible cases is performed with scanning of parameter space using [Formula: see text] approach. We found that the perturbative schemes governed by single rotation are unable to fit the mixing angle data even at [Formula: see text] level. The mixing schemes which involve two rotation matrices only [Formula: see text] are successful in fitting all neutrino mixing angles within [Formula: see text] range for normal hierarchy (NH). However for inverted hierarchy (IH), only [Formula: see text] is most preferable as it can fit all mixing angles at [Formula: see text] level. The remaining perturbative cases are either excluded at [Formula: see text] level or successful in producing mixing angles only at [Formula: see text] level. To study the impact of phase parameter, we also looked into CP violating effects for single rotation case. The predicted value of [Formula: see text] lies in the range [Formula: see text] for [Formula: see text] and [Formula: see text] case with normal (inverted) hierarchy.

The Integrative Dimensions of the Hexagonal Diffraction Matrix With Balanced Technology Perspectives to Maximize Performance in the Light of the Market Economy, a Proposed Strategic Vision

The Integrative Dimensions of the Hexagonal Diffraction Matrix With Balanced Technology Perspectives to Maximize Performance in the Light of the Market Economy, a Proposed Strategic Vision

High Thermoelectric Figure of Merit Achieved in Cu2S1- xTe x Alloys Synthesized by Mechanical Alloying and Spark Plasma Sintering.

Chalcogenides have been considered as promising thermoelectric materials because of their low cost, nontoxicity, and environmental benignity. In this work, we synthesized a series of Cu2S1- xTe x (0 ≤ x ≤ 1) alloys by a facile, rapid method of mechanical alloying combined with spark plasma sintering process. The Cu2S1- xTe x system provides an excellent vision of the competition between pure phase and phase transformation, entropy-driven solid solution, and enthalpy-driven phase separation. When the Te concentration increases, the Cu2S1- xTe x system changed from the pure monoclinic Cu2S at x = 0 to monoclinic Cu2S1- xTe x solid solution at 0.02 ≤ x ≤ 0.06 and then transforms to hexagonal Cu2S1- xTe x solid solution at 0.08 ≤ x ≤ 0.1. The phase separation of hexagonal Cu2Te in the hexagonal Cu2S matrix occurs at 0.3 ≤ x ≤ 0.7 and finally forms the hexagonal Cu2Te at x = 1. Owing to the changed band structure and the coexisted Cu2S and Cu2Te phases, greatly enhanced power factor was achieved in all Cu2S1- xTe x (0 < x < 1) alloys. Meanwhile, the point defect introduced by the substitution of Te/S atoms strengthened the phonon scattering, resulting in a lowered lattice thermal conductivity in most of these solid solutions. As a consequence, Cu2S0.94Te0.06 exhibits a maximum ZT value of 1.18 at 723 K, which is about 3.7 and 14.8 times as compared to the values of pristine Cu2S (0.32) and Cu2Te (0.08), respectively.

Decision Making Problem for Medical Diagnosis Using Hexagonal Fuzzy Number Matrix

Fuzzy set theory plays a vital role in medical fields. There are varieties of models involving fuzzy matrices to deal with different complicated aspects of medical diagnosis. Fuzzy set theory is highly suitable and applicable for developing knowledge based system in medicine for the tasks of medical findings. The field of medicine and decision making are the most fruitful andinteresting area of applications of fuzzy set theory. In this paper, we have applied the notion of Hexagonal fuzzy membership matrix in a medical diagnostic model. The advantage of this model is, if the patient-matrices are known, then it is possible to find which patient is suffering from what kind of disease. Most probably the fuzzy decision model in which overall ranking or ordering of different fuzzy sets are determined by using comparison matrix.

The Performance of the Athena X-ray Integral Field Unit at Very High Count Rates

The Athena X-ray Integral Field Unit (X-IFU) will operate at 90 mK a hexagonal matrix of 3840 Transition Edge Sensor pixels providing spatially resolved high-resolution spectroscopy (2.5 eV FWHM up to 7 keV) between 0.2 and 12 keV. During the observation of very bright X-ray sources, the X-IFU detectors will receive high photon rates going up to several tens of counts per second per pixel and hundreds per readout channel, well above the normal operating mode of the instrument. In this paper, we investigate through detailed end-to-end simulations the performance achieved by the X-IFU at the highest count rates. Special care is notably taken to model and characterize pulse processing limitations, readout-chain saturation effects, as well as the non-Gaussian degradation of the energy redistribution from crosstalk at the focal plane level (both thermal and electrical). Overall, we show that the instrument performance should safely exceed the scientific requirements, and in particular that more than 50 % throughput at 1 Crab in the 5–8 keV band can be achieved with better than 10 eV average resolution with the use of a Beryllium filter, enabling breakthrough science in the field of bright sources.

Complementary multi-mode low-frequency vibration energy harvesting with chiral piezoelectric structure

This letter proposes a complementary multi-mode low-frequency vibration piezoelectric energy harvester (PEH) which is mainly composed of three chiral folded beams in a light hexagonal matrix. The chiral structure can be constrained in two typical boundary conditions, each of which results in two different natural modes according to different effective stiffnesses. Numerical simulation and experimental results verified this property and found that the frequency responses are complementary for two PEH units with different boundary conditions. By connecting these two units electrically, the frequency bandwidth can be broadened by producing total four resonant peaks. Furthermore, external magnetic force was introduced to enable tuning of the frequency response. The proposed PEH with tunable multi-mode properties has potential applications in practical low-frequency vibration environments.

Re-entrant inclusions in cellular solids: From defects to reinforcements

A contrast in Poisson ratio is a possible strategy to enhance the stiffness of composite structures. In solid materials Poisson ratio is hardly tailorable unless cellular architectures are considered. Here, we first investigated the effect of a single re-entrant inclusion acting as a defect into a regular (non-re-entrant) honeycomb lattice. Building on this, we generated regular patterns of re-entrant inclusions into a regular hexagonal cellular matrix and we characterized the apparent stiffness and Poisson ratio of the obtained structures. We also explored the role of the intrinsic material properties of the inclusion as well as of its closest environment on the interplay between the deformations of different phases in the lattice. Our main finding is that a small fraction of re-entrant inclusions (around 12%) is sufficient to generate a substantial augmentation in stiffness (300%) at constant overall relative density and without inducing strong anisotropy. Eventually, we fabricated by 3D polyjet printing bi-material composite architectures to demonstrate the superior mechanical behavior obtained exploiting the Poisson effect.

A Critical Review of Mg–Zn–Y Series Alloys Containing I, W, and LPSO Phases

Magnesium and its alloys are playing an increasingly important role in the transportation industry due to the pressing demand of lightweight structures to improve fuel efficiency and reduce CO2 emissions. But the shortcomings of poor room temperature (RT) formability and high temperature strength, tension–compression asymmetry, and anisotropy are among the major issues which are currently limiting their widespread applications. Recently, research and development activities of Mg–Zn–Y series alloys have significantly increased because of their superior mechanical properties arising from the formation of different ternary phases known as I (Mg3YZn6), W (Mg3Y2Zn3), and LPSO (Mg12YZn). In this review article, the crystal structure of these phases and their orientation relationships with hexagonal magnesium matrix are discussed. Recent advances about I, W, and LPSO phase containing Mg alloys are presented, along with the effects of these phases on the microstructural evolution and mechanical properties including tensile, compressive, fatigue, and creep resistance. Important aspects involving thermal stability, phase transformation, and influence of heat treatment are also described. Based on the current status, some existing issues are pointed out and further studies are suggested so as to warrant safe and reliable lightweight structural applications of Mg–Zn–Y alloys in the automotive industry.

Achieving Continuous Anion Transport Domains Using Block Copolymers Containing Phosphonium Cations

Triblock and diblock copolymers based on isoprene (Ip) and chloromethylstyrene (CMS) were synthesized by sequential polymerization using reversible addition–fragmentation chain transfer radical polymerization (RAFT). The block copolymers were quaternized with tris(2,4,6-trimethoxyphenyl)phosphine (Ar3P) to prepare soluble ionomers. The ionomers were cast from chloroform to form anion exchange membranes (AEMs) with highly ordered morphologies. At low volume fractions of ionic blocks, the ionomers formed lamellar morphologies, while at moderate volume fractions (≥30% for triblock and ≥22% for diblock copolymers) hexagonal phases with an ionic matrix were observed. Ion conductivities were higher through the hexagonal phase matrix than in the lamellar phases. Promising chloride conductivities (20 mS/cm) were achieved at elevated temperatures and humidified conditions.

Review on the properties of hexagonal boron nitride matrix composite ceramics

Novel hexagonal boron nitride (h-BN) matrix composite ceramics exhibit versatile and greatly improved properties compared with the traditional h-BN ceramics, such as excellent mechanical properties, high-temperature resistance, thermal shock resistance, ablation resistance, and molten metal erosion resistance. They have potential important applications in the field of aerospace, electronics, metallurgy, machinery, nuclear energy, etc. As such, much attention are paid by both academia and industry on materials science and technology. In this paper, the special crystal structure and unique characteristics of h-BN are firstly briefly introduced. Then, the state-of-the-art development on mechanical properties, thermal shock resistance, ablation resistance, ion erosion resistances, molten metal erosion resistance and the damage mechanisms of novel h-BN matrix composite ceramics under harsh serving environments are reviewed, including textured h-BN matrix composite ceramics with anisotropic properties targeted for heat management applications. Moreover, the possible future research focus on h-BN and h-BN matrix composite ceramics are also forecasted.

Antiplane analysis for an elliptical inclusion in 1D hexagonal piezoelectric quasicrystal composites

An elliptical inclusion embedded in an infinite 1D hexagonal piezoelectric quasicrystal matrix is analysed in the framework of linear piezoelasticity of quasicrystals. Using the technique of conformal mapping, the closed-form solutions of the complex potentials, all the field quantities in the matrix and the inclusion are obtained under far-field antiplane mechanical loads of the phonon and phason fields and an inplane electrical load. Several special cases, such as a homogeneous material, a soft and permeable inclusion, an impermeable inclusion, a line inclusion, a rigid inclusion and a crack are reduced by the present results. Some numerical examples are provided to shows the variations of the stresses of the phonon and phason fields and the electric field with the shape of hole/inclusion, the dielectric permittivity and the distance from the hole/inclusion.

An innovative SiPM-based camera for gamma-ray astronomy with the small size telescopes of the Cherenkov Telescope Array

A prototype camera for one of the Cherenkov Telescope Array (CTA) projects for the small size telescopes, the single mirror Small Size Telescope (SST-1M), has been designed and is under construction. The camera is a hexagonal matrix of 1296 large area (95 mm2) hexagonal silicon photomultipliers. The sensors are grouped into 108 modules of 12 pixels each, hosting a preamplifier board and a slow-control board. Among its various functions, this latter implements a compensation logic that adjusts the bias voltage of each sensor as a function of temperature. The fully digital readout and trigger system, DigiCam, is based on the latest generation of FPGAs, featuring a high number of high speed I/O interfaces, allowing high data transfer rates in an extremely compact design.

Microstructure and mechanical properties of the novel Hf25Sc25Ti25Zr25 equiatomic alloy with hexagonal solid solutions

The novel Hf25Sc25Ti25Zr25 (at.%) equiatomic alloy comprised of hexagonal solid solutions was designed and cast by arc melting of high purity elemental precursors. The predominant volume of the as-cast state exhibited a hexagonal structure and near-equal atomic concentrations of elements. Traces of the second hexagonal phase with a content not exceeding 6vol.% were located in regions between coarse laths of the acicular matrix. The as-cast alloy subjected to room temperature compression developed very strong hardening effect resulting in high strength of 1802MPa and yield stress of 698MPa. After deformation, frequent slip bands within the solid solution matrix along with high density of dislocations were present. The new alloy showed high thermal stability. Annealing at 1000°C for 5h led to dissolution of Ti enriched solid solution and to precipitation of the Sc plate-like phase with cubic structure embedded in the hexagonal matrix. As a result, only a slight reduction in compressive properties, as compared to the as-cast state, was experienced. An assessment of the quantum mechanical approach to the alloy developed was conducted by calculations of structural and elastic properties based on the atomistic-level model of the alloy in the framework of the density functional theory.

Growth mechanism of cubic BN using Li3BN2 solvent under high pressure

The pressure and temperature region of the cubic BN precipitation was studied using Li3BN2 as synthetic solvent over the pressure and temperature range from 3.5 to 6GPa and 1100 to 1800°C for a duration of 0.3–11h. The pressure and temperature region of cubic BN formation in the BN-Li3BN2 was bounded by lowest temperature line and highest temperature line of cubic BN formation at constant pressure value. We determined these lines as P(GPa)=[T(°C)/30]−37 for the lowest temperature line and P(GPa)=[T(°C)/465]+0.79 for the highest temperature boundary between cubic and hexagonal BN. The recovered samples reacted at pressure lower than about 5GPa were mixture of re-crystallized hexagonal BN and cubic BN crystals. Meta-stable hexagonal BN grew rapidly in the cubic BN stable pressure and temperature region and cubic BN was grown slowly in the meta-stable hexagonal BN matrix.

Study of the structural and magnetic properties of Fe‐doped ZnO

AbstractIn this work we study the ZnO powder nanoparticles mechanically alloyed doped with iron to investigate the structural, microstructural and magnetic properties using X‐ray diffraction (XRD) and Vibrating Sample Magnetometer (VSM). The ZnO starting pure powder exhibited a hexagonal crystal structure with space group P63mc of ZnO, however, with the introduction of 1% Fe in the ZnO milled powder, the hexagonal ZnO phase remained unchanged, whereas the microstructural parameters were subject to significant variations due to the introduction of Fe atoms into the ZnO hexagonal matrix to replace oxygen ones. (© 2015 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Viability of MCM-41 Inorganic Membrane Separator in Secondary Nickel-Zinc Cell

The viability of MCM-41 inorganic membrane as a separator material in secondary nickel-zinc cell is investigated. MCM-41 mesoporous material consists of arrays of hexagonal nano-channels. The membrane is synthesized by dip-coating procedures from parent solution comprising of quarternary ammonium surfactant, cethyltrimethylammonium bromide C16H33(CH3)3NBr (CTAB), hydrochloric acid (HCl), deionized water (H2O), ethanol (C2H5OH), and tetraethylortosilicate (TEOS). Both the anodic zinc foil and cathodic nickel hydroxide electrodeposited film are coated with MCM-41 membrane. The Ni/MCM-41/Zn alkaline cell is then subjected to 100-cycle durability test. The charge-discharge plot showed typical secondary zinc anode profile – rapid capacity fading. X-ray diffraction analysis on the dismantled cell indicated the transformation of MCM-41 hexagonal matrix structure into MCM-50 lamellar gel form which prevent the mesoporous cell separator from diminished in the caustic alkaline surround.

Facile Preparation of Ammonium Molybdophosphate/Al‐MCM‐41 Composite Material from Natural Clay and Its Use in Cesium Ion Adsorption

AbstractOrdered hexagonal mesoporous aluminosilicate matrix (Al‐MCM‐41) with incorporated ammonium molybdophosphate (AMP) was successfully synthesized by a one‐pot synthesis method with natural clay from low‐grade potash ores of Qinghai salt lake as the silica and aluminum source. We introduced a modified “liquid‐phase transport” step, which allowed the use of impure natural clay as a starting material to directly produce pure product without sedimentation pretreatment. The resultant product was characterized by X‐ray fluorescence (XRF) spectroscopy, FTIR spectroscopy, XRD, TEM, 27Al and 31P magic‐angle spinning (MAS) NMR spectroscopy, and N2 adsorption/desorption, which indicated that the AMP was immobilized in the mesoporous structure of Al‐MCM‐41. The adsorption capacity of the final product for the removal of cesium ions in solution was also investigated. The results suggested that salt lake clay is a promising low‐cost precursor for the production of mesoporous aluminosilicate supports through one‐pot syntheses, and the final composite material is effective for the adsorption of cesium ions from solutions containing other alkali metal ions.

Upconversion effective enhancement by producing various coordination surroundings of rare-Earth ions.

In this manuscript, we present a simple route to enhance upconversion (UC) emission by producing two different coordination sites of trivalent cations in a matrix material and adjusting crystal field asymmetry by Hf(4+) co-doping. A cubic phase, Y3.2Al0.32Yb0.4Er0.08F12, with these structural characteristics was synthesized successfully by introducing a small ion (Al(3+)) into YF3. X-ray diffraction (XRD), nuclear magnetic resonance (NMR), transmission electron microscopy (TEM), X-ray spectroscopy (XPS), and fluorescence spectrophotometry (FS) were employed for its crystalline structure and luminescent property analysis. As a result, the coordination environments of the rare-earth ions were varied more obviously than a hexagonal NaYF4 matrix with the same Hf(4+) co-doping concentration, with vertical comparison, UC luminescent intensities of cubic Y3.2Al0.32Yb0.4Er0.08F12 were largely enhanced (∼32-80 times greater than that of different band emissions), while the maximum enhancement of hexagonal NaYF4 was by a factor of ∼12. According to our experimental results, the mechanism has been demonstrated involving the crystalline structure, crystal field asymmetry, luminescence lifetime, hypersensitive transition, and so on. The study may be helpful for the design and fabrication of high-performance UC materials.