This study describes results from mechanical tests conducted on magnesium single crystals in comparison with polycrystalline magnesium. It was found by impact testing that the magnesium single crystal is highly ductile due to energy absorption by twinning and slip, while the polycrystalline samples fracture easily upon impact. Compressive testing along two orthogonal directions at low plastic strains was also performed. The microstructure studies by electron backscatter diffraction and XRD pole figure analysis revealed profuse ( $10\overline12$ ) twinning when compression is done along the growth plane (72 16 $\overline {88}$ 62). The twinning and interaction between different twin modes resulted in incipient recrystallization at strains as low as 8% at room temperature. Compression along the nearly orthogonal plane (2 2 $\bar{4}$ 15) was marked by a much lower degree of both twinning and recrystallization. The variation in microstructural response with the orientation of loading allows for a wide range for tailoring mechanical properties of pure magnesium single crystals without any need of alloying.

Al–Zn–Mg–Cu–Zr alloys are very important aeronautical materials because of their low density, high strength, and high ductility. Corrosion failure is a significant factor causing aviation accidents, which should be investigated to develop an aeronautical material but has not been done yet. In this work, the effects of aging mechanisms on the exfoliation corrosion behavior of a spray deposited Al–Zn–Mg–Cu–Zr alloy were investigated. Natural aging (NA), single-stage aging (SA), and retrogression and re-aging (RRA) were treated on specimens before exfoliation corrosion testing. Corrosion attacks were evaluated using the optical microscope (OM) and scanning electron microscope (SEM). Corrosion mechanisms were deduced on the basis of polarization curve results and an equivalent circuit. The RRA sample exhibited the smallest corrosion attack among the three samples, while the NA sample showed the largest corrosion attack. Intergranular corrosion on grain boundaries was discussed to understand the exfoliation corrosion process in the RRA sample. The amount and size of precipitates in grain interior and grain boundary of RRA samples are larger than those in SA and NA samples, leading to the low corrosion susceptibility of the RRA sample.

Microstructural and crystallographic aspects of high-velocity forming or “rapid” forming of rolled sheets of pure copper have been investigated in this work. Significant changes in crystallographic orientation and microstructure were observed when thin (0.5 mm) metal sheets of annealed copper were subjected to high strain rate deformation in a conventional shock tube at a very low impulse magnitude (∼0.2 N s), which is inconceivable in conventional metal forming. Shock-loaded samples show characteristic texture evolution with a high brass {110}〈112〉 component. A significant change in grain orientation spread was observed with increasing amount of effective strain without any drastic change in grain size. The texture after deformation was found to be strain-dependent. The path of texture evolution is dependent on the initial texture. Misorientation was limited to less than 5°. Deformation bands and deformation twins were observed. There was a decrease in twin [Σ3 coincidence site lattice (CSL)] boundary number fraction with increasing strain due to the change in twin boundary character to high-angle random boundary (HARB) as a result of dislocation pile up. The study shows the probability of a high-velocity shock wave forming pure Cu.

Hot deformation behavior and microstructure evolution of as-cast Mn18Cr18N austenitic stainless steel were investigated by isothermal compression experiments. The results indicate that the microstructure evolution of the as-cast Mn18Cr18N steel is sensitive to strain rates. Discontinuous dynamic recrystallization, characterized by nucleation and growth controlled by grain boundary migration, occurs at lower strain rates. However, higher strain rates result in higher adiabatic temperature rise, which could be contributed to dynamic recrystallization (DRX) nucleation and growth by acceleration boundary migration. In addition, at higher strain rates, a large number of deformation microbands in the interior of coarse columnar grains were observed, which would provide potential nucleation sites for DRX. Meanwhile, a great number of Σ3 twins were observed, which reveals that twinning accelerates the separation of subgrains from bulging grain boundaries, and the iterative processing among Σ3 twins and its variants promotes the transformation from specific CSL grain boundaries to random high-angle boundaries.

Diketopyrrolopyrrole (DPP) is a critically important building block that has gained importance in the organic electronics community because of its wide applicability in various devices. In this work, the thiophene flanked DPP moiety attached to alkyl chains of various lengths (this includes straight octyl and branched ethyl hexyl units) has been used as the monomer for electropolymerization. This paper focuses on the study of optical, thermal, solid state ordering and electrochemical properties of these electron deficient monomers using various characterization techniques such as UV–Vis spectrometry (UV), photo-luminescence spectroscopy (PL), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), cyclic voltammetry (CV), as well as ab initio modeling. These monomers exhibit broad absorption spectra from the ultraviolet (280–400 nm) to visible (400–600 nm) regions and emission spectra between 560 and 610 nm. The band gaps of these monomers were calculated to be in the range of 2.00–2.20 eV. These monomers were electropolymerized by scanning the potential between −0.5 and 2.0 V versus ferrocene for up to 50 cycles on a glassy carbon electrode.

A superelastic Ti–40Nb alloy enhanced with Cu element (0, 2.5, 5, 7.5, and 10 wt%) was synthesized by a spark plasma sintering method to obtain biomaterials with an antimicrobial effect. The microstructure results showed that β phase was the main phase in (Ti–40Nb)–Cu alloys while Ti2Cu was synthesized with the Cu addition above 5 wt%. (Ti–40Nb)–Cu alloys exhibited high compressive strength over 1693.08 MPa, high yield strength of 1140.26–1619.14 MPa, low elastic modulus in the range of 43.91–58.01 GPa, low elastic energy (14.81–24.73 MJ/m3), and together with large plastic strain over 18.5%. High concentration of Cu ion released steadily from alloys in early 7 days, then the released concentration of Cu ion showed long-lasting and moderate. Comparing with the Ti–40Nb alloy, high antimicrobial activity was pronounced on (Ti–40Nb)–Cu alloys, and (Ti–40Nb)–Cu alloys showed more inhibitory activity against bacteria (E. coli and S. aureus) than fungi (C. albicans). Cu contents in alloys influenced the Cu ion release, which in turn affected the antimicrobial activity. As a good combination of low elastic modulus, high mechanical properties, good elastic energy, and excellent antimicrobial performance, (Ti–40Nb)–Cu alloys offer potential advantages to prevent stress shielding and exhibit an excellent antimicrobial property for hard tissue replacements.

The plastic deformation mechanisms and the microstructure development during creep deformation of L12-hardened Co-base superalloys show a number of unique features. The preferred orientation of rafting is determined by their positive lattice mismatch. In addition, the regular interfacial dislocation networks often found in rafted specimens of other types of superalloys do not form. While the ordered γ′-L12 precipitates are supposed to harden the material, they are actually found to be frequently cut by partial dislocations generating stacking faults. In this work, specimens from creep tests interrupted at different strains were investigated using transmission and scanning electron microscopy. By this, it is possible to find out which of these processes take place in which stage of creep deformation. For a better understanding of creep deformation, the balance between γ′ cutting and dislocation activity within the matrix channels is of special interest.

Sintered zirconium carbide (C/Zr ≈ 0.95) was studied by pulsed electrical heating method with microsecond duration. Thermophysical properties such as Joule energy, heat of melting, the specific heat, and electrical resistance were measured in the temperature range of 2500–5000 K by this method for the first time. The steep increase of the specific heat just before melting may be associated with the formation of nonequilibrium pairs point Frenkel defects at high temperatures under fast heating. It was established that the melting of the carbide occurs in the temperature range: solidus—3450 K and liquidus—3850 K, that is close to the values presented in some equilibrium phase diagrams of the system Zr–C. This means that there is no shift of the phase transition points at the heating rates up to 108 K/s, and makes it possible to use this method for the study of high temperature behavior of the complex substances. The comparison of the data of measured properties with the literature data is provided.

The rheological behavior of composites made with high-density polyethylene (HDPE) and chitosan was studied. Composites were prepared by melt processing in a laboratory internal mixer. Maleic anhydride grafted HDPE (PE-g-MA) was used as compatibilizer to enhance the dispersion of chitosan in the HDPE matrix. Different percentages of chitosan and compatibilizer (up to a maximum of 25 phr) were added into HDPE to prepare composites. Characterization of the composites with parallel plate rheometer and laboratory internal mixer revealed that the presence of chitosan increases the complex viscosity, loss modulus, storage modulus and the torque (i.e., melt viscosity), and the combination chitosan/compatibilizer has a similar, if slighter, effect. At higher filler levels it is clear that the PE-g-MA affected the microstructure of the compounds, possibly increasing matrix–filler interactions and acting as an effective compatibilizer.

As an atomic-thick layer material, graphene has a large specific surface area, high electron mobility, and high sensitivity to electronic perturbations from the binding of molecules, all of which are attractive properties for developing electronic sensing devices. This article focuses on graphene-based electronic sensors [field effect transistor (FET) sensors] for detecting biomolecules, including DNA, protein, and bacteria, among others. This article will cover three morphologies of graphene materials in biosensing applications: graphene nanosheet, graphene nanoribbon, and vertically-aligned graphene. The unique structure and electronic properties of graphene enable the FET sensor for the low concentration and rapid detection of biomolecules, thereby addressing the limitations of conventional optical sensing technologies such as ELISA, Western Blot, and electrochemical method. The advantages of graphene-based sensing technology are highlighted and recent progress on graphene-based electronic sensors for detecting biomolecules is reviewed and discussed.

A new lithium ion hybrid supercapacitor is reported, in which the negative electrode was made from ZnO nano-crystals coated with a nitrogen doped carbon, and a positive electrode composed of activated carbon. The ZnO nano-crystals were highly dispersed in a nitrogen doped carbon matrix through a bio-inspired route. Dopamine, used as the nitrogen and carbon source, self-polymerized and deposited onto the surface of ZnO nano-crystal. After pyrolysis, a nitrogen doped amorphous carbon coated ZnO nano-crystal materials were obtained. The characteristics of the synthesized carbon coated ZnO nano-crystal electrode as well as the electrochemical performance of the hybrid device were investigated. The ZnO nano-crystal structure was preserved in the course of the carbon coating. The lithium ion supercapacitor demonstrated a high capacity and good cycling stability. Such good performance can be attributed to improved conductivity, the prevention of ZnO nano particles from pulverization and the high degree of crystallinity of the ZnO material.

A new waterborne acrylic (WAC) hybrid adhesive was evaluated for an untreated polypropylene lamination. The WAC hybrid adhesive was formulated with a new class of porous clay heterostructure (PCH), which was modified with 3-(trimethoxysilyl)propyl methacrylate (as a coupling agent) to promote chemical bonding with the acrylic matrix to form a methacrylate-functionalized PCH (MPCH). The WAC hybrid adhesive was based on copolymers (2-ethylhexyl acrylate, ethylene glycol methyl ether acrylate, 2-(hydroxyethyl) methacrylate, styrene and acrylic acid) with varying amounts of MPCH. The scanning electron microscopy micrographs revealed the presence of a well dispersed MPCH distributed throughout the matrix. The optimal adhesive performance, in terms of the 180° peel strength of bonded joints, of 140.2 N/m was achieved using 1.5 wt% of MPCH, while the thermal stability of the adhesives was improved with increasing MPCH loading levels.

Ball milling induced the formation of nanocrystalline and amorphization phase in Fe–25.68% Dy2O3 powder mixtures (mass fraction, %). The microstructure was investigated by using X-ray diffraction and transmission electron microscopy. The transformation of Dy2O3 from cubic to monoclinic crystal structure and then to the amorphization was observed during ball milling. A few Dy atoms were dissolved into Fe crystal structure, which was discussed using mechanical kinetics. After 48 h of ball milling, the homogenous mixtures of supersaturated nanocrystalline solid solution of Fe (Dy, O) and Dy2O3 amorphization were formed and the elements of Fe, Dy, and O were distributed uniformly in the ball-milled particles. During the whole ball mining process, a rapid decrease in Fe grain size was observed over the initial time period, while a constant value was presented in later stage, resulting in a final size of about 20 nm. The mechanism of the microstructural evolution of powder mixtures was analyzed and discussed.

Morphology can play a critical role in determining function in organic photovoltaic (OPV) systems. Recently molecular acceptors have showed promise to replace fullerene derivatives as acceptor materials in bulk heterojunction solar cells and have achieved >10% efficiencies in single junction devices. The nearly identical mass/electron densities between the donor (polymer) and acceptor (molecule) materials results in poor material contrast compared to fullerene-based OPVs and therefore morphology characterization using techniques that rely on mass/electron density variations poses a challenge. This inhibits a fundamental understanding of the structure–property relationships for non-fullerene acceptor materials. We demonstrate that low angle annular dark field scanning transmission electron microscopy and resonant soft X-ray scattering form a set of complementary tools that can provide quantitative characterization of fullerene as well as non-fullerene based organic photovoltaic systems.

The near-threshold behavior of long cracks is studied in this paper using precracked flat dogbone specimens of a commercial aluminum alloy in peak-aged and overaged conditions. After introducing the initial crack in compression precracking, the crack was propagated approximately with the constant range of the stress intensity factor at values just above or below the corresponding threshold values. It was found that there were two major mechanisms which kept the crack from continuous extension. First, the crack front was pinned by primary precipitates. This effect was rather pronounced and lead to significant kinking in the crack front and ductile ridges on the fracture surface. The second mechanism was shear-controlled crack extension of very long cracks with plastic zones ahead of the crack tip, very similar to stage-I small cracks. Interaction with primary precipitates deflected the shear-controlled cracks but did not change the crack extension mode.

Hot isotherm compression tests were performed in temperature range of 350–500 °C and at strain rates of 0.0005 to 0.5 s−1 for Al6061 alloy reinforced with alumina nanoparticles. Effect of deformation parameters and optimal conditions for hot working this nanocomposite were comprehended thoroughly via hot working data analyses, electron microscopy images, and X-ray diffractograms. The results indicated the severity of hot deformation process and an increase in the activation energy to 320 kJ/mol due to the addition of nanoparticles. Dynamic recovery (DRV) was considered as the individual determinative softening mechanism during hot deformation of this nanocomposite, and no sign of dynamic recrystallization (DRX) phenomenon observed in the same domain. The unstable region occurred at high strain rates and temperature range of 350–500 °C accompanied with happening drastic defects such as shear bands and cracks. Furthermore, the value of both critical strain and critical stress increased with increasing the strain rate and alumina addition. On the other hand, increasing the temperature decreased the value of critical strain and facilitated the initiation of softening mechanisms.

The Ph.D. work of Jan H. van der Merwe in 1949 established a new paradigm for the understanding of dislocation dynamics in restricted volumes. This led to a comprehensive understanding of plasticity, or strain relaxation, in the context of strained-layer semiconductor structures. However, this understanding was largely overlooked in the context of traditional metallurgy and micromechanics. We identify four reasons for this, the apparent need for an unstrained substrate in van der Merwe’s theory, the supposed inapplicability to strain gradients, the supposed inapplicability to the Hall–Petch effect (dependence of strength on the inverse square root of grain size), and an emphasis on understanding strain hardening rather than the yield point. Addressing these four points in particular, here it is shown how the insights of van der Merwe and of the earlier work by Lawrence Bragg lead to a coherent and unified view of the size-effect phenomena ranging from the Hall–Petch effect to the strain-gradient plasticity theory.

Stretchability of polyimide-supported nanocrystalline Au films with a thickness ranging from 930 to 20 nm was evaluated by uniaxial tensile testing. The results show that the fracture strain gradually decreased with decreasing the film thickness. Such degraded stretchability depends on plastic deformation mechanisms associated with the length scales. As the film thickness is larger than 90 nm, local thinning in the grown grains contributed to the high stretchability. Full dislocation behaviors including dislocation pileup in the 930 nm-thick film, the activation of Frank–Read dislocation source in the 170 nm-thick film and the grain boundary dislocation source in the 90 nm-thick film were dominated plastic deformation. As the film thickness is less than 40 nm, low stretchability of thin films resulted from intergranular fracture, and partial dislocation behaviors became prevailed. Evident grain growth happened in the films studied except for the 20 nm-thick film, which is expected to be involved in the stretchability of the nanocrystalline metal films on flexible substrates.

The effect of mold temperature on microstructure and mechanical properties of a rheo-squeeze casting (RSC) Mg–3Nd–0.2Zn–0.4Zr (NZ30K) alloy were investigated. The results indicated that the rise of mold temperature contributed to the increase of particle size and alloy density and the decrease of dislocation density. The rapid coarsening and then the normal growth of the particles during solution treatment were observed, and the long-rod-like Zn2Zr3 phase occurred. After age treatment, rod-like β′ precipitate was found in the conventional squeeze casting (CSC) alloy, while two types of precipitates including β′ phase and small plate-like β″ phase were observed in the RSC alloy. The amount of Zn2Zr3 phase was increased with rising mold temperature. Compared with the T6-treated CSC sample, the T6-treated RSC sample presented higher mechanical properties due to the larger precipitation strengthening contribution, and the yield strength, ultimate tensile strength, and elongation were up to 160 MPa, 296 MPa, and 7.7%.

We report results of the studies relating to the fabrication of nanostructured zirconia (nZrO2) based immunosensor for cardiac troponin I biomarker (acute myocardial infarction) detection. One step, low temperature hydrothermal process was used for the synthesis of nZrO2 (∼5 nm). This nZrO2 was functionalized with 3-aminopropyl triethoxy silane (APTES) and thereafter it was electrophoretically deposited on to indium tin oxide (ITO) coated glass electrode. EDC/NHS surface chemistry was used for covalent immobilization of monoclonal anti-troponin-I (anti-cTnI) antibodies onto APTES/nZrO2/ITO electrode. The structural, morphological and functional characterization of the synthesized nanoparticles and the fabricated immunoelectrode were conducted via X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and electrochemical techniques. The results of electrochemical response studies of BSA/anti-cTnI/APTES/nZrO2/ITO immunoelectrode reveal that, this platform can be used for efficient detection of cardiac troponin I (cTnI) biomarker with a wide linear detection range (0.1–100 ng/mL) and sensitivity [3.9 µA mL/(ng cm2)].