Narrow Results

This work studies the effect of the substrate temperature on the microstructure and properties of CoCrFeNiNb_x high entropy alloy (HEA) coatings fabricated by magnetron sputtering. The results indicate that all three CoCrFeNiNb_x HEA coatings were composed of a simple FCC solid solution with a columnar structure. As the substrate temperature increased, Nb content in the FCC matrix increased while the grain size first decreased and then increased. Accordingly, CoCrFeNiNb_x HEA coatings exhibited an increasing micro-hardness and a decreasing fracture toughness with the increasing substrate temperature. Moreover, CoCrFeNiNb_x HEA coating deposited at 200^∘ had better corrosion performance, which was due to its better surface quality and denser columnar structure compared to the other two coatings.

We say a family of strings over an alphabet is an UMFF if every string has a unique maximal factorization over . Foundational work by Chen, Fox and Lyndon established properties of the Lyndon circ-UMFF, which is based on lexicographic ordering. Commencing with the circ-UMFF related to V-order, we then proved analogous factorization families for a further 32 Block-like binary orders. Here we distinguish between UMFFs and circ-UMFFs, and then study the structural properties of circ-UMFFs. These properties give rise to the complete construction of any circ-UMFF. We prove that any circ-UMFF is a totally ordered set and a factorization over it must be monotonic. We define atom words and initiate a study of u, v-atoms. Applications of circ-UMFFs arise in string algorithmics.

The branch of coding theory that is based on formal languages has produced several methods for defining code properties, including word relations, dependence systems, implicational conditions, trajectories, and language inequations. Of those, the latter three can be viewed as formal methods in the sense that a certain formal expression can be used to denote a code property. Here we present a formal method which is based on transducers. Each transducer of a certain type defines/describes a desired code property. The method provides simple and uniform decision procedures for the basic questions of property satisfaction and maximality for regular languages. Our work includes statements about the hardness of deciding some of the problems involved. It turns out that maximality can be hard to decide even for "classical" code properties of finite languages. We also present an initial implementation of a LAnguage SERver capable of deciding the satisfaction problem for a given transducer code property and regular language.

Recent measurements in the top quark sector at the Fermilab Tevatron collider are discussed. Measurements at the Tevatron use up to 9.7 fb^-1 of data corresponding to the full data sets recorded by each of the experiments, CDF and DØ. This review discusses the most recent measurements of inclusive and differential top quark cross-sections in strong and electroweak production of top quarks and related measurements, as well as measurements of angular distributions related to asymmetries in top quark production. Furthermore, the current status of precision measurements of the mass of the top quark is discussed. Where available, combinations of CDF and DØ results are presented.

Local events are characterized by “where”, “when” and “what”. Just as (bosonic) spacetime forms the backdrop for location and time, (fermionic) property space can serve as the backdrop for the attributes of a system. With such a scenario I shall describe a scheme that is capable of unifying gravitation and the other forces of nature. The generalized metric contains the curvature of spacetime and property separately, with the gauge fields linking the bosonic and fermionic arenas. The super-Ricci scalar can then automatically yield the spacetime Lagrangian of gravitation and the Standard Model (plus a cosmological constant) upon integration over property coordinates.

A novel Al-7.5Zn-1.6Mg-1.4Cu-0.12Zr alloy was subjected to the retrogression and re-ageing (RRA) treatments at a lower range of retrogression temperatures from 170 to 200°C. The effect of RRA on the mechanical properties, electrical conductivity and the microstructure of the alloy has been investigated. The results indicate that an increase in the yield strength of the alloy can be achieved after RRA treatment. With increase of the retrogression temperature, the retrogression time for keeping the strength levels similar to T6 temper decreases rapidly. When submitted to RRA at 170°C for 90-120 min, the alloy can obtain a good performance on both SCC and mechanical strength; the electrical conductivity was above 40%IACS, reaching values typical for T76 condition and the tensile yield strength values were 552-570 MPa which is higher than that of the T6 temper. The microstructure is a very fine distribution of GP zones and η′ precipitates inside grains, similar to T6 condition and η precipitates on grain boundaries distributed similarly to T7 temper.

Compared with the conventional In718 alloy, the addition of Al at the level of 1.24% and 1.50% greatly increases the precipitation of γ′ phase and the compact form of γ″/γ′/γ″ structure, which has been demonstrated in previous studies. The δ phase precipitation at the grain boundaries is noticeably suppressed. Large amount of Laves phase ((Fe, Ni, Cr)₂(Nb, Mo)), small amount of M₇C₃ carbide and σ phase ((Fe, Ni)(Cr, Mo, Nb)) are precipitated at the grain boundaries. After aging at 680°C, the grain boundary precipitates are increased significantly. Large amount needle-like σ phase is precipitated at the grain boundary in the alloy with 1.50% Al. After aging at 680°C for 1000h, the grain boundary precipitates are worsened further, but the coarsening of the compact form γ″/γ′/γ″ is lighter than the γ″ phase in the normal In718 alloy.

The tensile strength at room temperature and 680°C are increased due to Al increasing. While the tensile ductility and impact toughness of the alloy decrease significantly, and a sharp decrease has been found during the long term aging at 680°C.

The mechanism by which Al influencing the microstructure and mechanical properties of In718 alloy is to be discussed.

Copper matrix composites reinforced with graphene nanoplatelets (GNPs) were prepared by vacuum hot pressing of ball milled mixtures of powders. Two grades of GNPs were used; one with average thickness of 2 nm and average lateral size of 6 $\mu$m and another with much larger lateral size of 80 $\mu$m. Microstructure and properties of as-prepared composites containing 10 vol.% GNPs were studied. The GNPs sheets are uniformly distributed and well aligned in the Cu matrix. The microstructure observation shows that the GNPs-2–6 exhibits a better dispersion in the Cu matrix than GNPs-2–80. The addition of fine GNPs-2–6 lead to $\sim$31% higher tensile strength and approximately same electrical conductivity of the Cu matrix, while the GNPs-2–80/Cu composite only shows a $\sim$15% increase of tensile strength and a lower electrical conductivity than the Cu matrix.

In this paper, diamond single crystals doped with LiH and boron additives were synthesized in ${\mathrm{\text{Fe}}}_{64}{\mathrm{\text{Ni}}}_{36}$–$\mathrm{\text{C}}$ system under high pressure and high temperature. Under the fixed pressure condition, we found that the synthesis temperature increased slightly after the addition of LiH in the synthesis system. The {100}-orientated surface morphology was investigated by scanning electron microscopy (SEM). The nitrogen concentration in the obtained diamond was analyzed and evaluated using Fourier transmission infrared spectroscopy (FTIR). Furthermore, the electrical properties of Ib-type and boron-doped diamond before and after hydrogenation using Hall effect measurement, which suggested that the conductivity of diamond co-doped with hydrogen and boron was obviously enhanced than that of boron-doped diamond.

Two novel aluminum nitride (which is bct-AlN at ambient pressure, and h-AlN at higher pressure) were predicted using first-principles calculations. The mechanical and phonon dispersion results indicate that bct-AlN is mechanically and dynamically stable at zero pressure, h-AlN phase can be stabilized by increasing pressure and it is mechanically and dynamically stable at 10 GPa. bct-AlN is more favorable than rs-AlN in thermodynamics at ambient pressure. Our calculated band gap of bct-AlN is 5.85 eV. It can be used as semiconductor device and optoelectronic device due to its inherent wide direct band gap. For bct-AlN, the shortest Al–N bond length is 1.8476 Å and its bond order index is 1.28, which shows that strong covalent bonds are formed between Al atoms and N atoms. Moreover, the anisotropy of Young’s modulus and optical properties can be noticed obviously for bct-AlN.

This paper presents the results of a study on the production of nanofiber anisotropic nanoporous materials based on silk fibroin and cotton cellulose by electrospinning using a rotating screen-receiver of nanofibers in the form of a thin material. The difference in the anisotropic properties of the nanofiber material is shown by the method of birefringence, sorption of water vapor and filtration of a liquid-phase mixture. The possibility of using nanofiber nanoporous fibroin and cotton cellulose materials as a nanofilter of gaseous and liquid-phase mixtures has been shown.

The generalized Skyrme potential is used to calculate the properties of neutron matter in the form of the Thomas–Fermi model. The binding energy per particle, spin symmetry energy, free energy, pressure, entropy, sound velocity and magnetic susceptibility are calculated as a function of density ρ. The results are comparable with those obtained by Friedman and Pandharipande, who used the Urbana v₁₄ potential plus an effective repulsive three-body force.

In recent years, the application of fractal theory in construction materials has drawn tremendous attention worldwide. This special issue section containing seven papers publishes the recent advances in the investigation and application of fractal-based approaches implemented in construction materials. The topics covered in this introduction mainly include: (1) the fractal characterization of construction materials from nano- to micro-scales; (2) combining fractals methods with other theoretical, numerical and/or experimental methods to evaluate or predict the macroscopic behavior of construction materials; (3) the relationship of fractal dimension with the macro-properties (i.e. mechanical property, shrinkage behavior, permeability, frost resistance, abrasion resistance, etc.) of construction materials.

In a manufacturing industry, often the quality characteristic under study is found to have only one of the two specification limits viz., upper specification limit (USL) or lower specification limit (LSL). In such cases the process capability indices (PCI) designed for bilateral specifications become inappropriate. However, in the literature only a few indices are available to address this problem. In the present paper, we have made an extensive study of the PCI's for unilateral specifications with a brief discussion of their possible fields of applications and drawbacks, if any. We have also proposed a logical formulation of a parameter of one of these indices which reduces the subjectivity of the index and hence makes it more suitable for practical application. An example, with the computed values of the various PCI's, is discussed to make a comparative study of the performance and inter-relationship between these PCI's. We have concluded the paper with a discussion on the future scope of study in this field.

TiAlSiN coating was deposited on high-speed steel (HSS) samples and cemented carbide tool inserts, respectively, by a new coating preparation procedure, and its properties and cutting performance were characterized. The coating thickness, chemical composition, microstructure morphology and mechanical properties were investigated by X-ray fluorescence measurement system, energy dispersive spectrometer (EDS), scanning electron microscope (SEM), nanoindentation, Rockwell hardness tester and ball-on-disc tribometer. A 3D orthogonal cutting experiment model was established by DEFORM-3D to study the influences of different coating thicknesses on cutting force and temperature, and the field cutting experiment was carried out. The results show that the thickness of TiAlSiN coating is 3.14$\mu$m prepared by the 3$\mu$m preparation procedure, microhardness is 36.727GPa with the Si content of about 5.22at.% as well as good fracture toughness and adhesion strength. The TC4 and AISI 1045 cutting tool inserts with 4$\mu$m coating thickness have the minimum cutting forces of about 734.7N and 450.7N, respectively. Besides, tool inserts with a thickness of 3$\mu$m have the minimum cutting temperatures of about 510.2${}^{\circ }$C and 230.6${}^{\circ }$C, respectively.

This work presents the influence of changing Ar:N₂ gas ratio on the growth and properties of InAlN films. InAlN films were deposited on $p$-type Si(111) substrates by using magnetron co-sputtering method in 6:12, 10:10, 12:8 and 12:6 Ar:N₂ mixtures at 300${}^{\circ }$C. The surface, structural, electrical and optical properties of the deposited films were evaluated at different Ar:N₂ ratios. The grain size and film thickness were increased by increasing the Ar flow with respect to N₂. Structural characterization by X-ray diffraction (XRD) revealed an improvement in the crystalline quality of the $c$-axis-oriented InAlN film by adjusting the Ar:N₂ ratio to 12:8, however no diffraction peak corresponding to InAlN was detected at 6:12 Ar:N₂ mixture. The surface roughness of InAlN film exhibited an increasing trend whereas the electrical resistivity of the film was decreased by increasing the Ar:N₂ ratio. The bandgap of InAlN film was calculated from the optical reflectance spectra and it was found to change by changing the Ar:N₂ gas ratio. The analysis of results from this work shows that the InAlN film with improved physical properties can be obtained through reactive magnetron co-sputtering method by adjusting the Ar:N₂mixture to 12:8.

High-entropy alloys (HEAs) have recently received significant attention in the materials science community. Some of these alloys can display a good combination of mechanical properties. The perfect dense and smooth coatings of AlFeCrNiMo HEA have been deposited by direct current magnetron sputtering method. The coatings possess single BCC crystal structure. The thickness of the coatings increases with increasing deposited time and plasma power. The coatings display excellent high hardness and Young’s modulus. The corrosion resistance of all coatings in acidic and salt media is better than that of 201 stainless steel. It is expected that the HEA coatings have very broad application prospects.

Molybdenum oxide (MoO₃) films were deposited on glass, Al, Mo and Si substrates at room temperature in Ar-O₂ plasma by RF magnetron sputtering system. The as-deposited films were annealed in air at 400^∘C and 500^∘C. X-ray diffraction (XRD) results revealed that films annealed at 400^∘C on all the substrates exhibited diffraction peaks of orthorhombic (α) and monoclinic (β) phases of MoO₃. By increasing the annealing temperature to 500^∘C, the $\alpha$-MoO₃ phase on glass became more significant when compared with the $\beta$-MoO₃ phase. In contrast, the $\beta$-MoO₃ phase was more prominent in the case of film grown on the Mo substrate. The Fourier transform infrared spectroscopy (FTIR) analysis indicated stretching vibrational modes of Mo$=$O and transverse optical modes of Mo-O-Mo on all the substrates. The surface morphology of MoO₃ films on glass shows a flat surface at 400^∘C that was changed into a layered-like structure at 500^∘C. In the case of MoO₃ films on Al and Si, arbitrary-shaped particles were transformed into needle and rod shapes, respectively, with increase of annealing temperature from 400^∘C to 500^∘C. The film annealed on Mo substrate at 400^∘C revealed corrugated particles that were changed into coarse and elongated particles at 500^∘C. The morphological changes in MoO₃ film with increase of annealing temperature were associated with tensile strain developed inside MoO₃ due to lattice and thermal mismatch between the film and the substrate.

Titanium alloys are widely used in aerospace and other fields due to their advantages of low density, high specific strength and good corrosion resistance. Laser oscillating welding is an innovative process in the realm of welding technology. In this study, two laser oscillating welding methods (circular and linear) were employed to analyze the influence of different oscillation parameters on the formation of titanium alloy. The results indicate that the oscillation frequency has a significant impact on weld formation. The laser scanning trajectory also affects weld formation, with circular and linear scanning trajectories resulting in better weld quality. Finally, the effects of oscillation modes on the microstructure and properties of laser oscillating welding titanium alloy were investigated based on optimized process parameters. Among them, circular laser oscillating welding of titanium alloy exhibits higher tensile strength, with a maximum tensile strength of up to 1188.3MPa.

Advanced forming technologies have been evolving at a rapid pace with the products applicability in the industrial fields of aerospace and automobile especially for the materials like aluminum and titanium alloys (light weight) and ultra-high strength steels. Innovative forming methods like hydroforming (tube and sheet) have been proposed for industries throughout the world. The ever-increasing needs of the automotive industry have made hydroforming technology an impetus one for the development and innovations. In this paper, the review on various developments towards lightweight materials for different applications is presented. The influencing process parameters considering the different characteristics of the tube and sheet hydroforming process have also been presented. General ideas and mechanical improvements in sheet and tube hydroforming are given late innovative work exercises. This review will help researchers and industrialists about the history, state of the art in hydroforming technologies of the lightweight materials.