Nanoscale Substructure Research Articles

Phonons reveal coupled cholesterol-lipid dynamics in ternary membranes

Experimental studies of collective dynamics in lipid bilayers have been challenging due to the energy resolution required to observe these low-energy phonon-like modes. However, inelastic x-ray scattering (IXS) measurements—a technique for probing vibrations in soft and biological materials—are now possible with sub-meV resolution, permitting direct observation of low-energy, phonon-like modes in lipid membranes. Here, IXS measurements with sub-meV energy resolution reveal a low-energy optic-like phonon mode at roughly 3 meV in the liquid-ordered (Lo) and liquid-disordered phases of a ternary lipid mixture. This mode is only observed experimentally at momentum transfers greater than 5 nm−1 in the Lo system. A similar gapped mode is also observed in all-atom molecular dynamics (MD) simulations of the same mixture, indicating that the simulations accurately represent the fast, collective dynamics in the Lo phase. Its optical nature and the Q range of the gap together suggest that the observed mode is due to the coupled motion of cholesterol-lipid pairs, separated by several hydrocarbon chains within the membrane plane. Analysis of the simulations provides molecular insight into the origin of the mode in transient, nanoscale substructures of hexagonally packed hydrocarbon chains. This nanoscale hexagonal packing was previously reported based on MD simulations and, later, by NMR measurements. Here, however, the integration of IXS and MD simulations identifies a new signature of the Lo substructure in the collective lipid dynamics, thanks to the recent confluence of IXS sensitivity and MD simulation capabilities.

Improving strength-conductivity synergy of Al-Cu-(Sn/Er) alloy with nanoscale substructure

As a conductive material for power transmission, Al-Cu alloy is widely used in power engineering, microelectronics and other fields. In view of the contradiction between the conductivity and strength of aluminum alloy, Sn and Er elements were selected to micro-alloy Al-Cu alloy. Al-Cu, Al-Cu-Sn and Al-Cu-Sn-Er alloys were prepared by near-liquidus casting. After solution treatment, it was subjected to three-stage alternating process of rolling and aging. The effects of micro-alloying and alternating process on the microstructure and properties of Al-Cu alloy were studied. The results show that the precipitated phase Al2Cu of Al-1.12 Cu alloy is rod-shaped after the first-stage process, and the average size is about 278±87 nm. The precipitated phases in the Al-Cu-Sn alloy are Al2Cu (average size of about 206±79 nm) and nano-sized β-Sn particles. The fine β-Sn nanoparticles in the Al-Cu-Sn-Er alloy heterogeneously nucleated on Al8Cu4Er (average size of about 167±45 nm), making Al8Cu4Er grow into particles. After secondary processing, stacking faults (SFs) appeared in the substructures of the three alloys, and the precipitated phases were further refined. The size of most precipitated phases in Al-1.13Cu-0.12Sn and Al-1.01Cu-0.15Sn-0.22Er alloys is reduced to nanometer level. After the three-stage process, some of the Al2Cu precipitates in the Al-Cu alloy are also refined to the nanometer level, and the precipitates in the other two alloys are all refined to the nanometer level. Nanotwins also appear in Al-1.01Cu-0.15Sn-0.22Er alloy. The tensile strength of Al-1.13Cu-0.12Sn and Al-1.01Cu-0.15Sn-0.22Er alloys after three-stage alternating process is 303 MPa and 327 MPa, respectively. The elongations are 21.6 % and 23.3 %, respectively. The relative conductivity was 61.7 %IACS and 59.8 %IACS, respectively. The synergistic effect of microalloying of Sn and Er elements and three-stage alternating processing technology not only reduces the size of precipitates and twins in the alloy to the nanometer level, but also adjusts the distribution of dislocation tangles and stacking faults (SFs), improves the substructure configuration, and improves the mechanical and electrical properties of conductive aluminum alloys.

Ultrahigh strength CuCr/diamond composites fabricated by powder metallurgy

CuCr/Diamond (Dia) composites were fabricated by high-energy ball milling and rapid hot-press sintering. The studied CuCr/Dia composites exhibited excellent mechanical properties, reaching a hardness of 187 HV, an ultimate tensile strength of 1010 MPa. In-situ transition layers of Cr3C2 and Cr23C6, ranging between 10 and 30 nm, were generated at the Cu/diamond interface. This transition layers significantly enhanced the bonding strength between the diamond and the Cu matrix. The load could be effectively transfer to the diamond particle due to the strong bonding. Additionally, nanoscale sub-structures in the matrix can enhance the composite's strength. The studied composite displayed superior strength compared to other copper matrix composites. These findings could extend the applications of the copper-based composites with ultrahigh strength.

Nanoscale imaging of tumor cell exosomes by expansion single molecule localization microscopy (ExSMLM)

Tumor cell exosomes play a very important role in the process of tumor cell proliferation and metastasis. However, due to the nanoscale size and high heterogeneity of exosomes, in-depth understanding of their appearance and biological characteristics is still lacking. Expansion microscopy (ExM) is a method that embeds biological samples in a swellable gel to physically magnify the samples to improve the imaging resolution. Before the emergence of ExM, scientists had invented several super-resolution imaging techniques that could break the diffraction limit. Among them, single molecule localization microscopy (SMLM) usually has the best spatial resolution (20–50 nm). However, considering the small size of exosomes (30–150 nm), the resolution of SMLM is still not high enough for detailed imaging of exosomes. Hence, we propose a tumor cell exosomes imaging method that combines ExM and SMLM (i.e. Expansion SMLM, denoted as ExSMLM), which can realize the expansion and super-resolution imaging of tumor cell exosomes. In this technique, immunofluorescence was first performed to fluorescently label the protein markers on the exosomes, then the exosomes were polymerized into a swellable polyelectrolyte gel. The electrolytic nature of the gel made the fluorescently labeled exosomes undergo isotropic linear physical expansion. The expansion factor obtained in the experiment was about 4.6. Finally, SMLM imaging of the expanded exosomes was performed. Owing to the improved resolution of ExSMLM, nanoscale substructures of closely packed proteins were observed on single exosomes, which has never been achieved before. With such a high resolution, ExSMLM would have a great potential in detailed investigation of exosomes and exosome-related biological processes.

Microstructure and Mechanical Properties of Gradient Nanostructured Q345 Steel Prepared by Ultrasonic Severe Surface Rolling

In this work, ultrasonic severe surface rolling (USSR), a new surface nanocrystallization technique, is used to prepare gradient nanostructure (GNS) on the commercial Q345 structural steel. The microstructure of the GNS surface layer is characterized by employing EBSD and TEM, and the result indicates that a nanoscale substructure is formed at the topmost surface layer. The substructures are composed of subgrains and dislocation cells and have an average size of 309.4 nm. The GNS surface layer after USSR processing for one pass has a thickness of approximately 300 μm. The uniaxial tensile measurement indicates that the yield strength of the USSR sample improves by 25.1% compared to the as-received sample with slightly decreased ductility. The nanoscale substructure, refined grains, high density of dislocations, and hetero-deformation-induced strengthening are identified as responsible for the enhanced strength. This study provides a feasible approach to improving the mechanical properties of structural steel for wide applications.

Structural features of a composite material produced by electric pulsed pressing from iron‑based multi‑component powder mixtures

The study is dedicated to the electric pulse pressing use for the composite materials production from diffusion‑alloyed iron powders. It is shown that the addition of a low–melting metal component, tin, has a positive effect on the compaction of the composite iron powder during electric pulse pressing. The density of samples from Dystaloy AB iron powder with the addition of 10 % tin reaches 7.3–7.5 g/cm3. It is impossible to obtain such a density in the conventional cold pressing process at a pressure of 100– 120 MPa. It is established that due to the short duration of thermal exposure during electric pulse pressing, diffusion processes do not have time to pass and the distribution of alloying elements in the iron base is uneven. A short thermal exposure causes oxidation of the surface of the powder particles, which also negatively affects the diffusion processes. Therefore, when obtaining alloyed powder materials by electric pulse pressing, the process must be carried out in a protective atmosphere. The revealed presence of a nanoscale substructure formed due to the effects of intense plastic deformation and temperature indicates the hardening of the powder composite material during electric pulse pressing. These features can be useful in the development of technologies alternative to the warm pressing of plasticized powders.

Additively manufactured AlSi10Mg ultrathin walls: Microstructure and nano-mechanical properties under different energy densities and interlayer cooling times

For additive manufacturing (AM) applications of lightweight aluminum alloy parts such as radiators, it is necessary to understand the relationship between internal microstructure and local mechanical properties. The microstructure characteristics and its formation mechanism of AlSi10Mg ultrathin walls fabricated by selective laser melting (SLM) under different energy densities and interlayer cooling times were investigated, and its evolution regularity with energy density was also analyzed. The nano-mechanical properties of different regions on the ultrathin-walled cross-section and their responses with energy density were also explored. The main results show that non-banding regions and banding regions distributed alternately like sandwiches are formed in ultrathin walls, which have fine solidified cellular structure and columnar dendrite network, accompanied by nano-scale substructure formed in grains. Although the microstructure characteristics and nano-mechanical properties of ultrathin walls are insensitive to interlayer cooling time, the single-track energy density significantly affects the coarsening of solidification structure and its substructure evolution. With the increase of single-track energy density, the interaction between various strengthening mechanisms related to the evolution of microstructure comprehensively affects the nano-hardness of different macro-areas in ultrathin walls, which follows the trend of increasing first and then decreasing, and higher nano-hardness can be obtained when the dimensionless single-track energy density is between 10 and 20. The findings of this work are beneficial to optimize the SLM process of AlSi10Mg alloy to manufacture ultrathin-walled parts with ideal microstructure and mechanical properties for potential applications in aerospace, automotive and other fields.

Chemically characterizing the cortical cell nano-structure of human hair using atomic force microscopy integrated with infrared spectroscopy (AFM-IR).

The use of conventional microscopy and vibrational spectroscopy in the optical region to investigate the chemical nature of hair fibres on a nanometre scale is frustrated by the diffraction limit of light, prohibiting the spectral elucidation of nanoscale sub-structures that contribute to the bulk properties of hair. The aim of this work was to overcome this limitation and gain unprecedented chemical resolution of cortical cell nano-structure of hair. The hybrid technique of AFM-IR, combining atomic force microscopy with an IR laser, circumvents the diffraction limit of light and achieves nanoscale chemical resolution down to the AFM tip radius. In this work, AFM-IR was employed on ultra-thin microtomed cross-sections of human hair fibres to spectrally distinguish and characterize the specific protein structures and environments within the nanoscale components of cortical cells. At first, a topographical and chemical distinction between the macrofibrils and the surrounding intermacrofibillar matrix was achieved based on 2.5×2.5μm maps of cortical cell cross-sections. It was found that the intermacrofibrillar matrix has a large protein content and specific cysteine-related residues, whereas the macrofibrils showed bigger contributions from aliphatic amino acid residues and acidic-/ester-containing species (e.g. lipids). Localized spectra recorded at a spatial resolution of the order of the AFM tip radius enabled the chemical composition of each region to be determined following deconvolution of the Amide-I and Amide-II bands. This provided specific evidence for a greater proportion of α-helices in the macrofibrils and correspondingly larger contributions of β-sheet secondary structures in the intermacrofibrillar matrix, as inferred in earlier studies. Analysis of the parallel and antiparallel β-sheet structures, and of selected dominant amino acid residues, yielded further novel composition and conformation results for both regions. In this work, we overcome the diffraction limit of light using atomic force microscopy integrated with IR laser spectroscopy (AFM-IR) to characterize sub-micron features of the hair cortex at ultra-high spatial resolution. The resulting spectral analysis shows clear distinctions in the Amide bands in the macrofibrils and surrounding intermacrofibrillar matrix, yielding novel insight into the molecular structure and intermolecular stabilization interactions of the constituent proteins within each cortical component.

Hairy and iridescent chaetae of the sea mouse Aphrodita (Annelida, Errantia)

AbstractThe bright iridescent chaetae of Aphrodita species have fascinated scientists for decades. The particular nanoscale substructure of these chitinous bristles resembles photonic crystals and manipulates the incident light in a way that results in spectacular structural coloration. Even though Aphrodita's chaetae have garnered great attention from the field of biomimetics, the few previous ultrastructural studies primarily focused on acicular chaetae that are much less iridescent than the thin capillary notochaetae. In this paper, we present new ultrastructural data on the chaetae of two species of Aphrodita and illustrate their formation process. Our results allow us to specify the prerequisite for iridescent chaetae. Aphrodita species are dorsally covered with a matted felt of intertwined chaetae, and we further discuss the evolution of feltage chaetae in Aphroditiformia. In addition to iridescent feltage chaetae, we also provide new insights into the chaeotogenesis of pilose chaetae. For the first time, our study shows that the hairy tips and ornamentation of the chaetae is formed by follicle cells alone and thus attribute a further role to this type of cells.

Rapid sonochemical synthesis of copper doped ZnO grafted on graphene as a multi-component hierarchically structured visible-light-driven photocatalyst

Three-dimensional (3D) hierarchical structures (HSs) have demonstrated excellent properties for various applications that are attributable to their distinctive micro-sized architecture with nanoscale substructures. Recently, the ultrarapid sonochemical approach was found to be an effective strategy for synthesizing single component HSs with uniform morphologies in comparison to the direct precipitation technique. We here report the fabrication of copper doped zinc oxide grafted on graphene layers (ZnO-Cux-GOy) for exploring the capability of this ultrarapid approach for synthesizing multi-component HSs. Interestingly, the morphology of ZnO-Cux-GOy HSs studied through electron microscopy revealed the growth of ZnO HSs decorated with Cu nanoparticles and interconnected by graphene layers. ZnO-Cux-GOy HSs demonstrated three-fold higher efficiency in the photodegradation of ibuprofen (IBU) under visible light irradiation in comparison to pristine ZnO HSs, which is attributable to the combined influence of the doped Cu2+ ions and graphene, enabling improved visible light absorption and inhibiting the recombination of photogenerated charges. Thus, the novel ultrarapid sonochemical synthesis strategy demonstrated here is anticipated to open up a new horizon for the time-saving and scalable design of multi-component HSs of various materials for a myriad of applications.

The Role of Lattice Curvature in Structural Degradation of the Metal Surface Layer of a Rail under Long-term Operation

The evolution/degradation of the structure and phase composition of rail head material of 100-meter differentially quenched rails after extremely long-term operation is analyzed. It is shown that similar conditions of loading result in different structural transformations on the rail head surface. The formation of lattice curvature in crystal interstitial sites and initiation of highly mobile interstitial structural states there cause a dissolution of pearlite. It occurs at a depth of ≈10 mm. It is superimposed by the formation of a nanoscale substructure in the tread surface in a layer ≈2 mm thick. The nanoparticles of the carbide phase precipitate on the boundaries of the substructure. The failure of the rail metal will proceed, in the first place, in the surface layer where a critical level of the crystal lattice curvature is formed and the concentration of interstitial vacancies is maximum.

Modeling of Localized Inelastic Deformation at the Mesoscale with Account for the Local Lattice Curvature in the Framework of the Asymmetric Cosserat Theory

In the paper, inelastic strain localization in homogeneous specimens and mesovolumes of a polycrystalline material is modeled based on the asymmetric theory of an elastoplastic Cosserat continuum in a two-dimensional formulation for plane strain. It is assumed that rotational deformation in loaded materials occurs due to the development of localized plastic deformation as well as bending and torsion of the material lattice at the micro- and nanoscale levels. For this reason, the parameters of the micropolar model are considered as functions of inelastic strain for each local mesovolume of the continuum. It is shown that the observed parabolic hardening can be attributed to a large extent to the development of rotational deformation modes, bending and torsion, and appearance of couple stresses in the loaded material. The modeling results indicate that if rotational deformation is stopped in the loaded material, its accommodation capacity decreases, the local and macroscopic inelastic strains sharply increase, leading to a much more rapid formation of fracture structures. Conversely, the formation of meso- and nanoscale substructures with high lattice curvature in materials promotes the activation of rotational deformation modes, reduction of localized strains, and relaxation of stress concentrators.

Формування нанорозмірної полігонізаційної субструктури та її вплив на фізико-механічні властивості металів, стопів і напорошених покриттів

Формування нанорозмірної полігонізаційної субструктури та її вплив на фізико-механічні властивості металів, стопів і напорошених покриттів

Multiple nanostructures in high performance Cu2S0.5Te0.5 thermoelectric materials

Cu2(S,Te) solid solution material has shown excellent thermoelectric performance with a maximum zT value up to 2.1. Previous work has observed specific mosaic nanocrystals in this solid solution which is considered to be responsible for its ultra-low thermal conductivity. In the present study, we performed in-depth microstructural examinations by transmission electron microscopy and revealed additional multiform nanostructures in Cu2S0.5Te0.5 solid solution. Apart from widely existed mosaic nanocrystals, nano-domains of ordered structure, nanoscale periodic antiphase domains, stacking faults and polytype have been observed. Formation of such abundant nanoscale substructures could be related to the large mismatch in atomic size between S and Te solute elements. These nanostructures are all coherently embedded in the matrix lattice. Thereafter, continuous carrier transportation is still guaranteed while in the meantime phonon scattering is enhanced by such high density of structural imperfection. Thus, solid solution strategy in Cu2S0.5Te0.5 matches well with the phonon-glass electron-crystal concept for high performance thermoelectric materials.

Nanostructured Strengthening of Springs and Spring Steels

The paper considers the problem of nanostructured strengthening of spring steels and springs, the idea of steel nanostructured strengthening determined not only by grain sizes but also by subgrain sizes is justified. Design schemes of thermal strain nanoscale substructure patterning in spring material produced by hot and cold coiling were implemented. Patterning of nanoscale substructure was experimentally proved. Strength analyses of spring steels and springs showed the dominant effect of nanoscale substructure on spring limited life increasing not less than 10 times at cyclic fatigue tests. Spring compression at cyclic loading decreases 10 times.

Structure of A-C Type Intervariant Interface in Nonmodulated Martensite in a Ni-Mn-Ga Alloy.

The structure of A-C type intervariant interface in nonmodulated martensite in the Ni54Mn25Ga21 alloy was studied using high resolution transmission electron microscopy. The A-C interface is between the martensitic variants A and C, each of which has a nanoscale substructure of twin-related lamellae. According to their different thicknesses, the nanoscale lamellae in each variant can be classified into major and minor lamellae. It is the boundaries between these lamellae in different variants that constitute the A-C interface, which is thus composed of major-major, minor-minor, and major-minor lamellar boundaries. The volume fraction of the minor lamellae, λ, plays an important role in the structure of A-C interfaces. For major-major and minor-minor lamellar boundaries, they are symmetrical or asymmetrical tilt boundaries; for major-minor boundary, as λ increases, it changes from a symmetrical tilt boundary to two asymmetrical microfacets. Moreover, both lattice and misfit dislocations were observed in the A-C interfaces. On the basis of experimental observations and dislocation theory, we explain how different morphologies of the A-C interface are formed and describe the formation process of the A-C interfaces from λ ≈ 0 to λ ≈ 0.5 in terms of dislocation-boundary interaction, and we infer that low density of interfacial dislocations would lead to high mobility of the A-C interface.

Nanoscale technology for engineering products

The implementation of nanoscale technology for engineering products is a complex and relevant task. One innovative solution for this task is the development of thermal strain processing (TSP) directed to form a nanoscale substructure in structural steels. Principles and methods of submicrocrystalline structures forming in steels during wire-production stages of sized mill rolls according to the proposed technology are discussed in this paper. The proposed principle of nanoscale structure formation is based on a combination of fast induction heating, plastic flow of a complex direction, and cooling within the range of scientifically based thermal and speed modes.

Influence of spray coating mode options for getting a nanoscale substructure with increased stability

Influence of spray coating mode options for getting a nanoscale substructure with increased stability

Solid state transformation of the crystalline monohydrate (CH3NH3)PbI3(H2O) to the (CH3NH3)PbI3 perovskite.

Colorless crystals of (CH3NH3·H2O)PbI3 spontaneously lose water at 298 K which triggers a transformation to the black (CH3NH3)PbI3 perovskite in the solid state as a porous microcrystalline solid with nanoscale substructure, but the dihydrate (CH3NH3)4PbI6·2H2O) requires much more forcing conditions to produce (CH3NH3)PbI3.

Consolidation of High Performance AA6061 and AA6061-SiC<sub>p</sub> Composite Processed by High Pressure Torsion

Discs of monolithic AA6061 and AA6061 reinforced with SiCp were processed via combination of hot compaction of the mixed powders followed by high pressure torsion (HPT). HPT processing was investigated using incremental revolutions up to four, under pressures of 1 and 3 GPa. Structural evolution of the powders before and after HPT processing was investigated using scanning electron microscope (SEM). HPT processing of AA6061 discs produced a trimodel structure with micron-scale grains, subgrains and nanoscale substructure of 29, 1.9 μm, and 250 nm, respectively. Reinforcement with SiCp resulted in a refined structure with micron-scale grains, subgrains and nanoscale substructure of 25, 1.9 μm, and 184 nm respectively. The presence of SiCp at the triple junctions and along the grain boundaries enhanced the rate of strain hardening of the Al-matrices and significantly refined the grain size. More pronounced refinements of the grains, subgrains, and substructures were observed with increasing the HPT pressure up to 3 GPa.