To eliminate the Bi segregation and interfacial embrittlement of the SnBi/Cu joints, we deliberately added some Ag or Zn elements into the Cu substrate. Then, the reliability of the SnBi/Cu–X (X = Ag or Zn) solder joints was evaluated by investigating their interfacial reactions, tensile property, and fatigue life compared with those of the SnBi/Cu and SnAg/Cu joints. The experimental results demonstrate that even after aging for a long time, the addition of the Ag or Zn elements into the Cu substrate can effectively eliminate the interfacial Bi embrittlement of the SnBi/Cu–X joints under tensile or fatigue loadings. Compared with the conventional SnAg/Cu joints, the SnBi/Cu–X joints exhibit higher adhesive strength and comparable fatigue resistance. Finally, the fatigue and fracture mechanisms of the SnBi/Cu–X solder joints were discussed qualitatively. The current findings may pave the new way for the Sn–Bi solder widely used in the electronic interconnection in the future.

3D spatially-resolved polychromatic microdiffraction was used to nondestructively obtain depth-dependent elastic strain gradients and dislocation densities in the constituent phases of a directionally solidified NiAl–Mo eutectic composite consisting of ∼500–800 nm Mo fibers in a NiAl matrix. Measurements were made before and after the composite was compressed by 5% and 11%. The Mo fibers were analyzed both in their embedded state and after the matrix was etched to expose them as pillars. In the as-grown composite, due to differential thermal contraction during cooldown, the Mo phase is under compression and the NiAl phase is in tension. After the prestrains, the situation is reversed with the Mo phase in tension and NiAl matrix in compression. This result can be explained by taking into account the mismatch in yield strains of the constituent phases and the elastic constraints during unloading. The dislocation density in both the Mo and NiAl phases is found to increase after prestraining. Within experimental uncertainty there is little discernible difference in the total dislocation densities in the Mo phase of the 5% and 11% prestrained specimens. However, the density of the geometrically necessary dislocations and the deviatoric strain gradients increase with increasing prestrain in both the Mo and NiAl phases.

This article reports on low (below 800 °C) melting temperature characteristics of a Zr-Ti-Ni-Cu alloy system, designed by adding a small amount of Cu to a Zr-Ti-Ni eutectic alloy system in the Zr-rich corner of the Zr-Ti-Ni system. A series of Zr-Ti-Ni-Cu-based alloy buttons of varying Cu content was fabricated by an arc melting machine. The melting temperature ranges of the quaternary alloys were systematically examined by differential thermal analysis (DTA). As a result, a quaternary eutectic alloy of composition Zr54Ti22Ni16Cu8 with a low melting temperature range from 774 °C to 783 °C was found. In addition, structural and chemical analysis results for the slowly solidified, quaternary eutectic alloy sample revealed equivalent quaternary eutectic structure and phases to those of the ternary eutectic Zr50Ti26Ni24 alloy, except for a small amount of Cu dissolved in individual constituent phases. The wetting angle tested at 800 °C for 60 s on the commercially pure titanium was about 25°.

In this study, we report low temperature x-ray diffraction studies combined with electrical resistance measurements on single crystals of iron-based layered superconductor FeSe to a temperature of 10 K and a pressure of 44 GPa. The low temperature high pressure x-ray diffraction studies were performed using a synchrotron source and superconductivity at high pressure was studied using designer diamond anvils. At ambient temperature, the FeSe sample shows a phase transformation from a PbO-type tetragonal phase to a NiAs-type hexagonal phase at 10 ± 2 GPa. On cooling, a structural distortion from a PbO-type tetragonal phase to an orthorhombic Cmma phase is observed below 100 K. At a low temperature of 10 K, compression of the orthorhombic Cmma phase results in a gradual transformation to an amorphous phase above 15 GPa. The transformation to the amorphous phase is completed by 40 GPa at 10 K. A loss of superconductivity is observed in the amorphous phase and a dramatic change in the temperature behavior of electrical resistance indicates formation of a semiconducting state at high pressures and low temperatures. The formation of the amorphous phase is attributed to a kinetic hindrance to the growth of a hexagonal NiAs phase under high pressures and low temperatures.

A dual-phase (DP) Ni–66.7%Co alloy with an average grain size of 16 nm was fabricated by electrodeposition. It exhibited an ultimate tensile strength of 1800–2080 MPa, together with an elongation to failure of 10–15% at room temperature. The remarkable ductility of this DP alloy with critical scale grains was attributed to its sustained high rate of strain hardening. Its fracture surface showed an unexpected deeply dimpled structure similar to that of coarse-grained ductile materials, which also witnesses the improved ductility.

In the sophisticated architectures of various biominerals, a multilevel hierarchy of lengths from nanometers to millimeters is commonly observed. In this article, superstructures composed of inorganic crystals associated with organic molecules from carbonate-based biominerals were identified and categorized as mesocrystals, which are composed of crystallographically oriented crystals. For the production of hierarchically structured mesocrystals, two strategies using self-organized growth with organic agents in aqueous solution systems were proposed. Arranged structures of micrometric and nanometric units were induced with an insoluble gel matrix and soluble adsorbable organic molecules, respectively. Consequently, bioinspired hierarchical crystals were successfully achieved by combining the matrix and soluble species.

This study examined the degradation of the device performance of InGaZnO4 (IGZO)-based thin-film transistors after annealing at high temperatures in air ambient. Using various characterization methods including scanning electron microscopy, x-ray diffraction, and transmission electron microscopy, we were able to disclose the details of a two-stage phase transformation that led to the device performance degradation. The Mo electrodes first succumbed to oxidation at moderate temperatures (400∼500 °C) and then the Mo oxide further reacted with IGZO to produce an In–Mo–O compound with some Ga at higher temperatures (600∼700 °C). We analyzed our results based on the thermodynamics and kinetics data available in the literature and confirmed that our findings are in agreement with the experimental results.

Despite many investigations on the corrosion behavior of NiTi shape memory alloys (SMAs) in various simulated physiological solutions by electrochemical measurements, few have reported detailed information on the corrosion products. In the present study, the structure and composition of the corrosion products on NiTi SMAs immersed in a 0.9% NaCl physiological solution are systematically investigated by scanning electron microscopy (SEM), x-ray energy dispersion spectroscopy (EDS), and x-ray photoelectron spectroscopy (XPS). It is found that attack by Cl− results in nickel being released into the solution and decrease in the local nickel concentration at the pitting sites. The remaining Ti reacts with dissolved oxygen from the solution to form titanium oxides. After long-term immersion, the corrosion product layer expands over the entire surface and XPS reveals that the layer is composed of TiO2, Ti2O3, and TiO with relatively depleted Ni. The growth rate of the corrosion product layer decreases with immersion time, and the corrosion product layer is believed to impede further corrosion and improve the biocompatibility of NiTi alloy in a physiological environment. It is found that the release rate of nickel is related to the surface structure of the corrosion product layer and immersion time. A corrosion mechanism is proposed to explain the observed results.

We report on an approach for laser surface nitriding of Ti6Al4V alloy coupled with an applied stress field. A surprising finding was that, with increasing the applied stress levels, the decreased residual stress, the nitrogen concentration near the surface, and the surface microhardness of the nitrided layer were associated with the increased friction coefficient. Across the depth of the nitrided layer, the hardness, the elastic modulus, and the wear resistance (H/E) measured by nanoindentation decreased gradually and were ascribed to the gradient of nitrogen concentration in the melt zone.

Minor Fe additions are necessary to enhance the corrosion resistance of commercial Cu-Ni alloys. The present paper aims at optimizing the Fe content in three alloy series Cu90(Ni,Fe)10, Cu80(Ni,Fe)20, and Cu70(Ni,Fe)30 (at.%) from the viewpoint of their corrosion performance in a 3.5% NaCl solution. An Fe/Ni = 1/12 solid solubility limit line was revealed in the Cu-Ni-Fe phase diagram. Three Fe/Ni = 1/12 alloys, Cu90Ni9.23Fe0.77 (at.%) = Cu-8.6Ni-0.7Fe (wt.%), Cu80Ni18.46Fe1.54 = Cu-17.3Ni-1.4Fe, and Cu70Ni27.7Fe2.3 = Cu-26.2Ni-2.1Fe, show the best corrosion performances in their respective alloy series. The Fe/Ni = 1/12 solubility limit is explained by assuming isolated Fe-centered FeNi12 cuboctahedral clusters embedded in a Cu matrix. The three Fe/Ni = 1/12 alloys can be respectively described by cluster formulas [Fe1Ni12]Cu117, [Fe1Ni12]Cu52, and [Fe1Ni12]Cu30.3. The Fe/Ni = 1/12 rule may serve an important guideline in the industrial Cu-Ni alloy selection because above this limit, easy precipitation would negate the corrosion properties of the Cu-Ni-based alloys.

In biology, organic-inorganic hybrid materials are used for several purposes, in particular, for protection and mechanical support. These materials are generally optimized for their function through precise control over the structure, size, shape, and assembly of the component parts and can be superior to many synthetic materials. The shapes and forms of minerals encountered in nature strongly contrast with those that are generally formed in a synthetic environment. According to current understanding, this is achieved through different modes of control: their shape can be controlled by restricting their growth to a confined space or by influencing their preferred direction of growth; in addition, for crystalline materials, polymorph selection and oriented nucleation are achieved through specific interactions between a template or additive and the developing nucleus. Also, controlled arrangement of nanoparticles into superstructures can lead to a complex structure. The understanding and, ultimately, the mimicking of these processes will provide new synthetic routes to specialized organic-inorganic hybrid materials. On the other hand, transformation of existing complex hierarchical natural structures such as wood or diatom frustules into other materials using shape-preserving chemistry is another approach toward minerals with complex biomimetic structure. The theme topic in this issue will focus on recent biomimetic and bioinspired approaches used to achieve control over the shape and organization of mineral and organic-inorganic hybrid materials. The different contributions will also highlight the advantages of these methods for advanced materials synthesis, and possible applications will be discussed.

Strontium titanate (SrTiO3) is widely used in electronic devices, and it is a model material for understanding the structural and dielectric properties of grain boundaries (GBs). In such materials, the GBs often play a dominant role in sintering and microstructural behavior. Abnormal grain growth (AGG) is a commonly observed phenomenon. Most studies explained that GBs contain continuous liquid films, and this liquid assists interface diffusion resulting in fast growth. However, few studies investigate the AGG behavior without any liquid. In this study, GB morphology and chemistry have been characterized by high-resolution transmission electron microscopy and x-ray energy-dispersive spectrometry, respectively. Different distributions of GB morphology have been observed in abnormal grains and matrix grains, and GB chemistry varies with different morphological type GBs. By correlating GB morphology and chemistry, a possible mechanism for AGG is proposed.

The Ce-doped yttrium ortho- and pyrosilicate powders were prepared in a powder form by the formamide-modified sol-gel method. Crystal structure was checked by x-ray diffraction and sample morphology by transmission electron microscopy measurements. Both ortho- and pyrosilicate pure phases were obtained by the previously mentioned preparation procedure and proper annealing temperature was determined to obtain the maximum scintillation efficiency. Luminescence spectra and decays were measured to better evaluate the source of efficiency losses in the scintillator mechanism of samples heat-treated at lower temperatures. The potential of this preparation method for manufacturing the nanocomposite scintillators was discussed.

Congruent Er:Mg:LiNbO3 crystals were grown by the Czochralski method from the melts containing fixed 0.5 mol% Er2O3 while varied MgO content ranged from 0.0 to 8.0 mol%. The Mg and Er contents in the crystals were determined by neutron activation analysis. In the presence of Er codopant, the Mg threshold concentration with respect to optical damage is determined from the measured OH absorption spectra. The results show that the Er codopant has less effect on both the Mg threshold concentration and Mg segregation coefficient, which is within 1.13–1.23 as the Mg concentration is below the threshold while within 0.88–0.98 when above the threshold, consistent with the only MgO doping case. On the other hand, the practical Er concentration in the crystal is closely related to the Mg content and shows definite Mg threshold effect. Below the threshold, the Er concentration decreases linearly with the increased Mg concentration in the crystal; above the threshold, the decrease is more remarkable and follows another linear function. The Mg concentration effect on the Er segregation coefficient is discussed from the viewpoint of the Mg doping effect on the solubility of Er ions in the crystal.

The kinetics of intermetallic compound (IMC) layer and Cu dissolution at Sn1.5Cu/Cu interface under high magnetic field was experimentally examined. It is found that the IMC layer growth is controlled by flux-driven ripening process. The high magnetic field promotes the growth of IMC layer, retards the dissolution of Cu substrate, and decreases the content of Cu solute at the liquid–IMC interface front. Based on the experimental results, it is considered that the magnetization induced by magnetic field promotes the ripening process for IMC layer growth. The Lorentz force dampening the convection and magnetization decreasing the Cu solubility limit can retard the Cu dissolution and change the solute distribution at the liquid–IMC interface front.