Hysteresis loops of MgB2 + Co composite tapes

The (MgB₂)_1?x Co _x composite tapes fabricated by the ex situ PIT method were investigated. The structural and magnetic properties were characterized. Only MgB₂ and Co phases were observed in the composites while x ≤ 0.2. A superconducting transition temperature was stable for these samples. Enhancement of the critical current density is found for x = 0.1.     

Hydration mechanism of a novel PCCP + DCPA cement system

A novel partially crystallized calcium phosphate (PCCP) + dicalcium phosphate anhydrous (DCPA) system bone cement was introduced and the mechanism of the hydration was studied by means of solubility product constant (K _sp), XRD, pH value, and BET. Results showed that DCPA was more soluble than PCCP and HA was the most insoluble compound, and DCPA disappeared fast during hydration of the cement. Therefore, the mechanism of the hydration in the PCCP + DCPA system cement was the dissolution and hydrolysis of DCPA and PCCP. And their by-products H₃PO₄ and Ca(OH)₂ reacted through a acid-base neutralization reaction, thus the DCPA and PCCP dissolution and hydrolysis process happened until DCPA and/or PCCP was exhausted. As the conserving time prolonged, fine nano-scale pores were formed due to the hydroxyapatite precipitated into the pores, which were occupied by water before.     

Temperature Dependence of Densities and Excess Molar Volumes of the Ternary Mixture (1-Butanol + Chloroform + Benzene) and its Binary Constituents (1-Butanol + Chloroform and 1-Butanol + Benzene)

Densities ρ of the 1-butanol + chloroform + benzene ternary mixture and the 1-butanol + chloroform and 1-butanol + benzene binaries have been measured at six temperatures (288.15, 293.15, 298.15, 303.15, 308.15, and 313.15) K and atmospheric pressure, using an oscillating U-tube densimeter. From these densities, excess molar volumes (V ^E) were calculated and fitted to the Redlich–Kister equation for all binary mixtures and to the Nagata and Tamura equation for the ternary system. The Radojković et al. equation has been used to predict excess molar volumes of the ternary mixtures. Also, V ^E data of the binary systems were correlated by the van der Waals (vdW1) and Twu–Coon–Bluck–Tilton (TCBT) mixing rules coupled with the Peng–Robinson–Stryjek–Vera (PRSV) equation of state. The prediction and correlation of V ^E data for the ternary system were performed by the same models.     

Solid-state amorphization of Cu + Zr multi-stacks by ARB and HPT techniques

A series of CuZr binary alloys with wide composition range were fabricated through ARB and HPT techniques using pure Cu and Zr metals as the starting materials. Bulk alloy sheets with thickness of about 0.8 mm after ARB process and alloy disks with 0.30 mm in thickness and 10 mm in diameter after HPT process can be obtained, respectively. The structures of all the alloys were found to be gradually refined with the increase of ARB cycles or HPT rotations. As a result, nanoscale multiple-layered structure was formed for the 10 cycled ARBed specimens, which could partially transform into amorphous phase during subsequent low temperature annealing. While for the as-HPTed sample, the alloy was completely amorphized after 20 rotations without any heat treatment. The thermal stabilities of the amorphous alloys were studied. The deformation behavior and the amorphization mechanism during the ARB and HPT process were put forward and discussed.     

Reactive sintering mechanism of Ti + Mo<Subscript>2</Subscript>C and Ti + VC powder compacts

TiC reinforced Ti-matrix composites have been synthesized successfully by reactive sintering of Ti-1.5%Fe-2.25%Mo (wt%) powder compacts with addition of Mo₂C and VC particles. The reactions for the formation of TiC particles start at 600 °C, but the distribution of TiC particles and the densification behavior in the two compacts are significantly influenced by the metal carbides (Mo₂C or VC). The compact with addition of Mo₂C has a relative density of 98% after sintering at 1300 °C for 1.5 h, but TiC particles are agglomerated in the Ti matrix. The compact with addition of VC has a relative density of about 91% after sintering at 1300 °C for 1.5 h, but TiC particles distribute more homogenously in the Ti matrix. Different TiC particle distribution and densification behaviors are attributed to the reaction rates between Ti and metal carbides and the subsequent diffusion process.     

Measurement of Vapor–Liquid Equilibrium for the DME + Diisopropyl Ether Binary System and Correlation for the DME + CO<Subscript>2</Subscript> + Diisopropyl Ether Ternary System

Vapor–liquid equilibrium (VLE) data have been measured with a static-type VLE apparatus for the dimethyl ether (DME)–diisopropyl ether (DIPE) binary system at five temperatures within the range from 293.04 K to 352.70 K. An isothermal correlation for the experimental data has been carried out based on the Peng-Robinson equation of state. The regressed binary interaction parameters were used to estimate VLE for the DME–CO₂–DIPE ternary system at 298.15 K. From the study, it is demonstrated that DIPE is an excellent absorbent for separation in the DME synthesis process from syngas.     

The activation of 〈c + a〉 non-basal slip in Magnesium alloys

The activation of 〈c + a〉 non-basal slip system can help to improving the mechanical properties of Magnesium alloys. The activation conditions of 〈c + a〉 non-basal slip system in Mg alloys are reviewed, such as the addition of lithium elements, increasing temperatures, and regions of stress concentration, and so on. Moreover, the article summarizes our results from the work on Mg alloys using equal channel angle pressing with back pressure, and points out that 〈c + a〉 non-basal slip systems also become active much easier under hydrostatic pressure, which will help to open new window to explore the basic physics of the activation of non-basal slip.     

Thermal and mechanical properties of EPDM/PP + thermal shock-resistant ceramic composites

Dynamic vulcanizate blends of polypropylene (PP) and ethylene–propylene-diene rubber (EPDM) were filled with 5 wt% of micro-scale ceramic powder. To overcome the difficulty of particles dispersion and adhesion, the filler was modified through grafting using three kinds of organic molecules. A combination of Raman data with thermogravimetric analysis (TGA) results prove that grafting of organic macromolecules onto ceramic surfaces takes place. Dynamic mechanical analysis (DMA) has been performed from −100 to +50 °C; addition of the ceramic increases the storage modulus E′, more so for modified filler. Compared to PP and thermoplastic vulcanizate (TPV), a higher thermal expansion is seen after addition of the ceramic filler, a result of creation of more free volume. The tensile modulus of the composites is about 1.2 times that of pure TPV, an increase in the rigidity clearly caused by the ceramic. Fracture surfaces show weak bonding of filler particles to the matrix. In the sample containing modified filler the tensile deformation is going through the polymer matrix. The brittleness, B, decreases upon surface modification of the ceramic. The highest value of B is seen for the PP + unmodified ceramic while lower B values are obtained for TPV and its composites.     

The effect of metastability on room temperature deformation behavior of β and α + β titanium alloys

The deformation behavior of single-phase metastable β-titanium alloys and two-phase α+metastable-β alloys strongly depends on the degree of stability of the β-phase. Recently, it has been shown that the tensile deformation behavior, as well as the creep deformation behavior at low temperatures (<0.25T _m), is strongly influenced by the degree of metastability. For example, the titanium β-alloy Ti–13.0wt%Mn, which has higher stability than the titanium β-alloy Ti–14.8wt%V, deforms by slip only; whereas the latter deforms by slip and twinning. In addition to the mechanical properties, the deformation mechanisms also depend on the degree of metastability. Further, the deformation mechanisms of a given metastable β-alloy depend on whether the β-phase is present by itself as a single-phase alloy, or in the presence of α-phase in the form of a two-phase alloy. For example, it was found that a metastable Ti–V alloy deforms by slip and twinning when it is in the form of a single-phase alloy, but deforms by slip and martensitic transformation when the same metastable β-phase is present in a two-phase α + β alloy. The mechanical properties of the metastable β alloys in turn depend on these deformation mechanisms. These recent developments are reviewed in this article.     

Modeling of effects of thermomechanical processing on elevated-temperature mechanical properties of in situ (TiB + TiC)/Ti-1100 composite

An in situ (TiB + TiC)/Ti-1100 composite was prepared by reacting B₄C and Ti. The effect of the amount of deformation during thermomechanical processing (TMP) on the microstructure, orientation of TiB whiskers, and the mechanical properties of the composite were investigated. Improvements in the composite tensile strength from TMP are discussed in terms of grain refinement and TiB whisker rotation. A model is suggested to predict the TiB whisker orientation factor for the composite after TMP with various amounts of deformation. Based on the effect of grain refinement and rotation of the TiB whiskers, the yield strengths of the composite after TMP with various amounts of deformation were modeled. The modeled values agreed well with the test results.     

Interfacial properties of (Ag + CuO) brazes used as sealing materials in SOFC stacks

Ceramic insulation layers in combination with air braze filler metals were investigated as material compositions suitable for joining the metallic components in planar solid oxide fuel cell stacks. This paper reports on a series of wetting experiments for determination of the interfacial properties of pure Ag and Ag + CuO brazes in contact with the oxides MgO, MgAl₂O₄, Al₂O₃ and the mixture MgO + MgAl₂O₄, as well as with ferritic steel at 1273 K. The long-term stability of the ceramic/Ag + CuO/steel joints after exposure for longer periods of time (1000 h) at 1073 K is also assessed. The influence on joining of CuO additions in the noble metal was investigated following two different routes. The first one involved melting of Ag + 4 wt% CuO brazes on the surface of solid substrates (ceramic, steel), and the second one involved melting of pure Ag on the substrates coated with a thin CuO_x layer. No differences in the values of the measured contact angles were observed. Furthermore, it was found that the reactions taking place at the interface braze/steel at the initial stage of brazing is extended in the case of Ag + 4 wt% CuO during the long-term exposure at envisaged operating temperature limiting the stability of the joint.     

‘Seed + expand’: a general methodology for detecting publication oeuvres of individual researchers

The study of science at the individual scholar level requires the disambiguation of author names. The creation of author’s publication oeuvres involves matching the list of unique author names to names used in publication databases. Despite recent progress in the development of unique author identifiers, e.g., ORCID, VIVO, or DAI, author disambiguation remains a key problem when it comes to large-scale bibliometric analysis using data from multiple databases. This study introduces and tests a new methodology called seed + expand for semi-automatic bibliographic data collection for a given set of individual authors. Specifically, we identify the oeuvre of a set of Dutch full professors during the period 1980–2011. In particular, we combine author records from a Dutch National Research Information System (NARCIS) with publication records from the Web of Science. Starting with an initial list of 8,378 names, we identify ‘seed publications’ for each author using five different approaches. Subsequently, we ‘expand’ the set of publications in three different approaches. The different approaches are compared and resulting oeuvres are evaluated on precision and recall using a ‘gold standard’ dataset of authors for which verified publications in the period 2001–2010 are available.     

Molecular Heteroconjugation Equilibria in (n-Butylamine + Acetic Acid) Systems in Binary (Dimethyl Sulfoxide + 1,4-Dioxane) Solvent Mixtures

The acidity constants of molecular acid, K _a (HA), cationic acid, K _a (BH⁺), as well as the equilibrium constants of anionic homoconjugation, , cationic homoconjugation, , and molecular heteroconjugation, K_AHB, have been determined in (n-butylamine + acetic acid) systems without proton transfer in binary [dimethyl sulfoxide (DMSO) + 1,4-dioxane (D)] solvent mixtures. The constants were determined by using the potentiometric titration method at a fixed ionic strength. It is concluded that the molecular heteroconjugation constants in the mixed solvent systems studied are linearly related to the 1,4-dioxane content. Furthermore, in the (acid + base) systems without proton transfer, the direction of titration (direct B + HA or reverse HA + B) has been found to affect the precision of determination of reliable values of molecular heteroconjugation constants. Moreover, it has been found that the relative dielectric constants of the solvent mixtures studied change linearly as a function of solvent composition, as well as solvent components do not show interactions of solvent–solvent type.     

Investigating the wear characteristics of engineered surfaces: low-temperature plasma nitriding and TiN + MoS x hard-solid lubricant coating

Significant progress has been made in the past decade in plasma nitriding with a majority of the research work focusing on improving hardness and wear resistance of the nitrided surface through the reduction of nitriding temperature, pressure or time. Hard-solid lubricating coatings have also been extensively studied for lowering the wear rate and coefficient of friction of traditional hard coatings such as TiN by the combined effect of hardness and solid lubrication. In this study, the wear characteristics of low-temperature plasma-nitrided steel substrate performed using a Saddle-field fast atom beam source and TiN + MoS _x hard-solid lubricant coating deposited by a closed-field magnetron-sputtering technique have been investigated. The thin hard layer in plasma-nitrided substrates exhibited much higher hardness and lower wear compared to the untreated substrate in pin-on-disc wear testing. In addition, the study of the wear track morphology of the nitrided samples evidenced significant reduction of deeper ploughing and plastic deformation due to higher hardness and load supporting of the nitrided layer. On the other hand, due to the incorporation of MoS₂ in TiN coating, the wear resistance and coefficient of friction were greatly improved in TiN + MoS _x coating compared to pure TiN coating. In contrast to TiN coating, a relatively smoother wear track with less abrasive wear also supported the beneficial effects of adding MoS₂ in TiN coating.     

Production and characterization of AA6082-(Si3N4 + Gr) stir cast hybrid composites

The present research work emphasizes the development of hybrid aluminum (AA6082) matrix composites (HAMCs) reinforced with different weight percentages (wt.%) of ball-milled (silicon nitride (Si₃N₄) + graphite (Gr)) ceramic particulates by conventional stir casting process. Si₃N₄ and Gr are ball milled to obtain a definite density of combined powder. The weight percentage of ball-milled ceramic powder is varied from 0 to 12 wt.% in a stage of 3%. The microstructures as well as mechanical properties of the fabricated hybrid composites are analyzed. The scanning electron micrograph reveals the uniform distribution of ball-milled (Si₃N₄ + Gr) ceramic particulates in the aluminum matrix. The distribution of ball-milled (Si₃N₄ + Gr) ceramic particulates has also been analyzed with x-ray diffraction (XRD) technique. Both the hardness and ultimate tensile strength have enhanced with a reduction in percentage elongation with increase in weight percentage of ball-milled (Si₃N₄ + Gr) ceramic particulates in the aluminum matrix.     

Dual structure O + B2 for enhancement of hardness in furnace-cooled Ti2AlNb-based alloys by powder metallurgy

Powder metallurgic Ti₂AlNb alloys were sintered at 900 °C, 990 °C, 1060 °C, and 1100 °C (i.e. in the O + B2, α₂ + B2 + O, α₂ + B2, and B2 phase region, respectively) for 12 h, followed by water quenching and furnace cooling. Quenching was employed to reserve the high-temperature phase and microstructure, and furnace cooling aimed to regulate the room-temperature microstructure for the enhancement of hardness. Widmanstatten B2 + O structure, which contributes to the properties, was induced from B2 crystals by sintering, unless the alloy was treated in the α₂ + B2 phase region. With the elevation of the sintering temperature, the content of α₂ phase became lower in the furnace-cooled alloys, and the hardness was improved accordingly. The highest hardness performance, 389 ± 23 HV, was obtained in the alloy solution treated in the single B2 region, and the alloy was comprised of complete O + B2 Widmanstatten structure.     

Evolution of microstructure,texture and grain boundary character in a severely cold rolled Ti + Nb IF steel

Severe cold rolling (up to 99.5% reduction) of a Ti + Nb IF steel has been found to produce nano-sized to ultrafine grains. The γ fibre intensity increases with the level of cold deformation. The fraction of high angle grain boundaries increases with increasing rolling reduction and then levels off at the highest deformation level. The coincidence site lattice boundary fraction increases continuously with increase in the amount of cold rolling.     

Vibrational measurements of Na/Ni(111) and (Na + CO)/Ni(111)

The vibrational properties of Na atoms and of Na coadsorbed with CO on Ni(111) have been studied by high-resolution electron energy loss spectroscopy. Loss measurements showed a significant weakening of the alkali–substrate bond as a function of the alkali coverage. Moreover, we found that coadsorbed CO molecules dramatically influence the vibrational properties of Na adatoms. The Na–Ni stretching frequency (22 meV) measured on the Na/Ni(111) system shifted down to 13 meV for the (Na + CO)/Ni(111) surface. This unexpected result was ascribed to a charge transfer from Na to CO. Present findings give new insights on the nature of the alkali–substrate and alkali–CO bond.     

Influence of (Zn + F) double doping on the structural,morphological, photoluminescence,optoelectrical properties and antibacterial activity of CdS thin films

The effects of (Zn + F) double doping on the structural, morphological, optical and electrical properties of CdS thin films is reported in this paper. Polycrystalline nature is observed for all the films. Zn-doped and (Zn + F) doubly doped CdS films exhibit a strong (0 0 2) preferential orientation similar to that of the undoped film. The (0 0 2) plane of the Zn-doped and (Zn + F) doubly doped films shift towards higher Bragg angles favoring a contraction in their lattice parameter values. Increased transparency and blue shift in optical band gap is observed for the doubly doped films. The electrical resistivity values of the undoped, Zn-doped, (Zn + F) doubly doped CdS thin films are found to be in the order of 10^?1 Ω-cm. From the obtained results it is found that the physical properties of Zn-doped CdS films got enhanced when co-doped with fluorine, and the (Zn + F) doubly doped CdS thin films seem to be a potential candidate for future optoelectronic device applications. Antibacterial activity of the as deposited films were carried against E. coli gram negative bacteria and from the zone of inhibition it is confirmed that the (Zn + F) doubly doped CdS thin films can be used as a good antimicrobial agent against pathogenic microorganisms.