Magnetotactic bacteria mineralize nanometer-size crystals of magnetite (Fe3O4) through a series of protein-mediated reactions that occur inside of organelles called magnetosomes. Mms6 is a transmembrane protein thought to play a key role in magnetite mineralization. We used both electron and fluorescent microscopy to examine the subcellular location of Mms6 protein within single cells of Magnetospirillum magneticum AMB-1 using Mms6-specific antibodies. We also purified magnetosomes from M. magneticum to determine if Mms6 was physically attached to magnetite crystals. Our results show that Mms6 proteins are present during crystal growth, and Mms6 is found in direct contact with the magnetite crystals or within the lipid/protein membrane surrounding the magnetite crystals. Mms6 was not detected at other subcellular locations within the bacteria or isolated fractions. Because Mms6 was found to completely surround the magnetosomes rather than being localized to one specific area of the magnetosome, it appears that this protein could act on the entire magnetite crystal during the biomineralization process. This supports a model in which Mms6 functions to regulate Fe3O4 crystal morphology. This knowledge is important for future in vitro experiments utilizing Mms6 to synthesize tailored nanomagnets with specific physical or magnetic properties.

The structural organization of the palliostracum—the dominant part of the shell which is formed by the mantle cells—of Glycymeris glycymeris (Linné 1758) is comprised of five hierarchical levels with pronounced structural commonalities and deviations from other crossed-lamellar shells. The hierarchical level known as second order lamellae, present within other crossed-lamellar shells, is absent highlighting a short-coming of the currently used nomenclature. On the mesoscale, secondary microtubules penetrate the palliostracum and serve as crack arrestors. Moreover, the growth lamellae follow bent trajectories possibly impacting crack propagation, crack deflection, and energy dissipation mechanisms whilst circumventing delamination. Finally, at least two structural elements are related to external circatidal and circaanular stimuli. This emphasizes that endogeneous rhythms may contribute and (co-)control the self-organization of a complex mineralized tissue and that it is insufficient to rely fully on a reductionistic approach when studying biomineralization.

Understanding magnetosome magnetite biomineralization is of fundamental interest to devising the strategies for bioinspired synthesis of magnetic materials at the nanoscale. Thus, we investigated the early stages of magnetosome formation in this work and correlated the size and emergent crystallinity of magnetosome nanoparticles with the changes in chemical environment of iron and oxygen by utilizing advanced analytical electron microscopy techniques. We observed that magnetosomes in the early stages of biomineralization with the sizes of 5–10 nm were amorphous, with a majority of iron present as Fe3+, indicative of ferric hydroxide. The magnetosomes with intermediate sizes showed partially crystalline structure with a majority of iron present as Fe3+ and trace amounts of Fe2+. The fully maturated magnetosomes were indexed to magnetite. Our approach provides spatially resolved structural and chemical information of individual magnetosomes with different particle sizes, attributed to magnetosomes at different stages of biomineralization.

We have recently reported the repair of carious enamel using a full-length amelogenin–chitosan hydrogel through guided stabilization and growth of mineral clusters. The objective of this study was to further evaluate the enamel repair potential of smaller amelogenin peptides like LRAP (leucine-rich amelogenin peptide) and compare their efficiency with their full-length counterpart. The demineralized tooth slices treated with a single application of LRAP–chitosan hydrogel for 3 days showed a dense mineralized layer consisting of highly organized enamel-like apatite crystals. Focus-ion beam technique showed a seamless growth at the interface between the repaired layer and native enamel. There was a marked improvement in the surface hardness after treatment of the demineralized sample with almost 87% recovery of the hardness value to that of sound enamel sections. This current approach can inspire the design of smaller peptide analogues based on naturally occurring amelogenin as a competent, low-cost, and safe strategy for enamel biomimetics to curb the high prevalence of incipient dental caries.

Although there are numerous reports on the synthesis of spherical materials, the development of new approaches remains important for theory construction to realize tailor-made synthesis of spherical materials. Herein, we report the synthesis of polydispersed spherical particles of H2Ti2O5 intercalated with a polyethyleneamine, such as an ethylenediamine, on the basis of a solvothermal treatment using concentrated polyethyleneamine aqueous solutions. The diameter of the micrometer-sized spheres enlarged with increasing amine concentration in the reaction solution. It was speculated that high ionic strength caused the self-assembly of polyethyleneamine-intercalated H2Ti2O5, resulting in the formation of spherical agglomerates. The spheres had a specific a surface area of 200 m2 g−1 and approximately 5 nm pores, and these values were controlled by amine concentration and treatment time. Conversion to single phase anatase and rutile without changes in spherical morphology was achieved by heat treatment. The present approach may assist with the design morphology of agglomerates.

Conventional retrogression and re-aging (RRA) treatment could not be put to good use for combination property of Al–Zn–Mg–Cu alloys. The new RRA treatment fitted for spray formed Al–Zn–Mg–Cu alloy was investigated by transmission electron microscope, tensile, and conductivity tests. The results show that the pre-aging treatment with under aging of 120 °C for 16 h is beneficial for the redissolution of matrix precipitates during retrogression treatment. With the retrogression of 200 °C for 8 min, grain boundary precipitates are discrete and the corrosion resistance of the alloy is drastically increased. After re-aging (120 °C for 24 h) the strength of the alloy is increased again. According to the above-mentioned new RRA treatment, the ultimate tensile strength, yield strength, elongation, and conductivity of the alloy are 791 MPa, 736 MPa, 8.5%, and 39.5% IACS respectively, which is higher than that after conventional RRA treatment.

Evidences show that the composition of β″ formed in age hardening of Al alloys should be the prototype Mg5Si6 with Al and/or Cu addition. In the present work, molecular dynamics simulations are carried out to investigate the influence of the addition of Al and/or Cu to the mechanical properties of the prototype Mg5Si6. Our simulations imply that Mg5Si6 with both Al and Cu addition has relatively poor mechanical performance when compared with other three models. The snapshots of atomic configurations during uniaxial tension test illustrate that only if both Al and Cu dissolve in β″, clusters can form through Al atoms segregating around Cu atoms, thus applying different stress fields on the Al matrix, resulting different mechanical properties in comparison with other three β″ models.

Dissimilar materials of S235JR steel and AZ31B Mg alloy were welded by metal inert-gas arc welding. Interface characteristics and mechanical behavior of intermetallic compound layer at the Mg/steel interface in the welded joint were investigated. The intermetallic compound layer was mainly made up of FeAl phase, which exhibited unequal thickness at different positions in the interface. The growth coefficient of FeAl intermetallic compound layer could be expressed as K = K0 exp(−Q/RT) with Q of 195 kJ/mol. The kinetics of growth of the intermetallic compound layer indicated that its formation and growth were mainly driven by elements diffusion, and hence the thickness of the layer was dependent on peak temperature and reaction time which were determined by welding parameters. The FeAl intermetallic compound layer with high hardness was the weak zone where cracks inclined to derive and propagate during tensile testing. The fracture surfaces displayed both brittle and ductile features.

Herein, Cu and Cu–Ge alloys with different stacking fault energies (SFEs) are prepared via rolling at room temperature (RTR) and via a combination of high-pressure torsion (HPT) and RTR (HPT + RTR). The x-ray diffraction measurements reveal that the grain size, dislocation density, and twin density vary with the strain and SFEs. The tensile tests indicate that the strength of materials with medium SFEs increases initially and then slightly declines, while the ductility is enhanced by increasing the strain via HPT. In contrast, for low-SFE materials, enhanced strength and improved ductility may be achieved simultaneously through increasing the strain to a high level. The variation of strength with respect to strain is primarily dependent on the solute concentration and SFE. The underlying mechanisms governing the effect of strain and SFE on the microstructures and mechanical properties of the metals are also discussed.

Synchrotron radiation real-time imaging technology was performed to in situ study the Cu–Ni cross-interaction in Cu/Sn/Ni solder joints under temperature gradient during soldering. The direction of temperature gradient significantly influenced the Cu–Ni cross-interaction. When Ni was the hot end, both Cu and Ni atoms could diffuse to the opposite interfaces, resulting in the occurrence of the Cu–Ni cross-interaction at both interfaces. The consumption of the Cu cold end was abnormally large, whereas that of the Ni hot end was limited. When Cu was the hot end, only Cu atoms could diffuse to the opposite interface, resulting in the occurrence of the Cu–Ni cross-interaction only at the cold end. The Cu hot end was seriously consumed, whereas the Ni cold end was still intact. The interfacial intermetallic compounds were always thicker at the cold end than at the hot end, especially at the Ni/Sn cold end. Cu imposed more damaging effect than Ni under temperature gradient. Based on the atomic fluxes, a model was proposed to discuss the effect of temperature gradient on the Cu–Ni cross-interaction and the interfacial reactions in the Cu/Sn/Ni solder joints.

Ti–47Al–1.0W–0.5Si (at.%) alloy was directionally solidified in the range of growth rate (V) (V = 3–100 μm/s) at a constant temperature gradient (G = 18 K/mm). It was found that α phase was the primary phase of the alloy. Both primary dendritic arm spacing (λ) and interlamellar spacing (λs) decreased with increase of the growth rate (V) according to the relationship of λ ∝ V −0.356 and λs ∝ V −0.49, respectively. The Solidification segregation occurred since the enrichment of the solute element W in primary α phase during solidification. The degree of the segregation increased with the increase of the growth rate (V). The results also revealed that the lamellar orientation was not always perpendicular to the growth direction (GD) because the GD of primary α dendritic deviated from the preferred $\left\langle {0001} \right\rangle$ direction. The microhardness increased with increasing growth rate (V) according to H V ∝ 289.5V 0.12 because of the microstructure refinement.

The effect of strain range on dynamic strain aging (DSA) is discussed based on the low cycle fatigue tests for different strain ranges conducted for 316L stainless steel at strain rate of 1 × 10−3 s−1. The variations of stress drop and hardening ratio are both compared for different strain ranges. The variations of stress drop are attributed to the dependence of vacancy concentration on strain range. The hardening ratio is higher at 600 °C than those at 20 °C and secondary hardening behavior occurs for larger strain range. The dependence of DSA on the number of cycles and the wave type for different stages are analyzed. Obvious DSA is observed in first few cycles, followed by weakening serrated yielding. However, the serrated yielding occurs again before fatigue failure. The difference of serrated yielding can be explained by the types of atom atmospheres at different cycles. A serrated wave is observed for smaller strain ranges, however, A, B, A + B, C, and B + C serrated waves can be found at different cycles for larger strain range. Finally, the crack nucleation and propagation on fracture surfaces are characterized by scanning electron microscope (SEM).

The aim of the present work was to study the effect of the finishing rolling temperature on interpass recrystallization promotion of an Nb-stabilized AISI 430 steel, via torsion tests simulation of a Steckel mill. The occurrence of interpass recrystallization was investigated by interrupting the tests before predetermined passes and analyzing the samples via electron backscatter diffraction (EBSD). The results revealed that interpass recrystallization can be promoted by decreasing the initial hot rolling temperature; which results in increased strain hardening during the passes and therefore, increased stored energy for recrystallization. The torsion test results concurred with those obtained by EBSD measurements. Furthermore, an optimum temperature range of 900–840 °C was found to promote interpass recrystallization during hot rolling.

The microstructure, room temperature compressive property, and elevated temperature tensile property of directionally solidified NiAl–Cr(Mo)–(Hf,Dy) hypereutectic alloy were investigated. The directional solidifications of liquid metal cooling technique (LMC) and zone melted liquid metal cooling technique (ZMLMC) were adopted. In the LMC alloy, the well-aligned and fully eutectic lamellar structure parallel to the growth direction is obtained. The interlamellar spacing gradually decreases with increasing the withdrawal rate, and the compressive yield strength gradually increases. In the ZMLMC alloy, the eutectic lamellar structure is disordered and not parallel to the growth direction, and the quantities of Cr(Mo) primary phases are observed. Compared to the ZMLMC alloy, the LMC alloy has a better combination property because of the well-aligned lamellar structure. The observations of crack propagation and fracture surface are performed to better understand the fracture behavior.

Bulk cementite samples with chromium (Cr) concentrations of 0, 3.01, 6.03, 8.22, and 9.76 wt% were prepared by mechanical alloying and spark plasma sintering. The elastic modulus, elastic recovery, and hardness increased with increasing chromium content. The maximum microhardness was 1070.74 HV (Vickers hardness) and the maximum elastic modulus was 199.32 GPa using a nanoindentation device. The effect of different concentrations of Cr on the wear behavior of the cementite plowing depth, roughness, debris from the worn surfaces, and weight loss due to wear were measured using pin-on-disk tribometric equipment. It was found that both the morphology and the abrasion resistance of a surface worn by microcutting and microplowing increased markedly with increasing Cr content.

To find the optimal Quenching and Partitioning (Q&P) process parameters of low-alloy wear resistant steel, various Q&P processes including quenching temperature, partitioning temperature and partitioning time were designed and tested by using orthogonal experiment method. Through analysis of orthogonal experiment, quenching temperature was the most important influential factor on the impact toughness and hardness, and partitioning time played a critical role on tensile strength. The optimal Q&P heat treatment parameters of low alloy wear resistant steel were partitioning at 350 °C for 10 min immediately after quenching at 100 °C. The microstructure of samples was composed of martensite laths and retained austenite. The relative volume fraction of retained austenite increased with the increase of quenching temperature and decreased gradually with the lengthening of partitioning time. Combining the results of Energy dispersive spectrometer, the reason for decrease of retained austenite was the existence of carbide precipitation and the carbide was (Fe, Cr)3C7. Compared to the traditional heat treatment of quenching and low temperature tempering, the samples under Q&P treatment displayed higher toughness and maintained relatively high tensile strength and wear resistance.