Nanostructured materials

Production of nanostructured materials, similar to the complex structure of nano-calcite of hard tissues, egg shell, teeth and bone, are an attractive field of research. Calcium phosphates with clinical applications, such as hydroxyapatite (HA) (Ca 10 (PO4) 6 (OH) 2) have been widely used in regeneration of bone and fabrication of medical implants, mainly due to the chemical composition and structure similarity between HA and the mineral part of bones and teeth, and also as gene and drug delivery is used. High surface area of HA make it useful for drug release. Moreover, it has antibacterial property and potential applications in rapid microbial detection, treatment of heavy metals from aqueous solutions. Biological synthesis has been attracted more attention for compatibility to human safety.

Most of the challenges experienced by many engineering materials originate from the surface which later leads to total failure, hence affecting the resultant mechanical properties and service life. However, these challenges have been addressed thanks to the invention of a novel surface mechanical attrition treatment (SMAT) method which protects the material surface by generating a gradient-structured layer with improved strength and hardness without jeopardizing the ductility. The present work provides a comprehensive literature review on the mechanical properties of materials after SMAT including the hardness, tensile strength and elongation, and residual stress. Firstly, a brief introduction on the different forms of surface nanocrystallization is given to get a better understanding of the SMAT process and its advantages over other forms of surface treatments, and then the grain refinement mechanisms of materials by SMAT from the matrix region (base material) to the nanocrystallized layer are explained. The effects of fatigue, fracture, and wear of materials by the enhanced mechanical properties after SMAT are also discussed in detail. In addition, the various applications of SMAT ranging from automotive, photoelectric conversion, biomedical, diffusion, and 3D-printing of materials are extensively discussed. The prospects and recent research trends in terms of mechanical properties of materials affected by SMAT are then summarized.

TiO 2 has already established itself as one of the most attractive nanomaterials for the functionalisation of textiles due to its unique structural, physicochemical, optical and electrical properties, nontoxicity and low cost. This review paper provides a comprehensive overview of recent advances in the chemical and physical modification of textile fibres with TiO 2 nanoparticles and nano-/microstructures and summarises the most important findings on the application processes and performance of TiO 2-modified textile substrates. Photocatalytic self-cleaning, antimicrobial activity, UV protection, hydrophobicity, thermal stability, flame retardancy and electrical conductivity are highlighted as central discussion topics in the review. Insights into the mechanisms for providing functional properties are presented; the influence of various factors on functionality is shown; and the latest strategies for TiO 2 surface modification to enhance visible light photocatalytic activity, including multiphase heterojunctions, ion doping, metal doping/loading, coupling with other semiconductors and surface sensitization, are discussed. This paper presents some new ideas for producing TiO 2-functionalized textile surfaces and suggests future research perspectives and directions in this research area.

This review on perovskite (ABO3) materials focuses primarily on ferroelectric films used in devices for charge storage such as Pb(Zr, Ti)O3 (PZT) for non-volatile ferroelectric random access memory (FeRAM) and high dielectric constant materials containing (Ba, Sr)TiO3 (BST), but it also emphasizes general principles on the integration of electroceramics in devices and microelectro mechanical systems (MEMS). The number of papers reported in the literature on ferroelectrics has expanded greatly in the past 20 years, but classical reliability problems in ferroelectric devices remain. Greater emphasis is needed on understanding key mechanisms which result in degradation of ferroelectric materials’ electrical characteristics in devices over time and with usage particularly between the ferroelectric film and electrode interface. In addition, better quantification of numerical measures of thin films are needed in order to more closely relate the process conditions to the materials characteristics and the resultant electrical properties. Furthermore, materials reliability and analysis of complex systems is a topic that needs further consideration when researching/working with ferroelectric devices. Finally, problems with materials reliability in ferroelectric devices are in need of further detailed investigation by researching and understanding the mechanisms which are the root causes of ferroelectric polarization losses in actual devices.

Developing strong, damage-tolerant, and functional steels shapes the backbone for industrial innovations in manufacturing, energy, transportation, and safety. Examples are Fe-Cr steels for emission-reduced turbines; weight reduced and ultra-high strength Fe-Mn steels for light-weight and safe mobility; magnetic Fe-Si steels for low-loss electrical motors and generators; or stainless steels for power plants. These examples document the necessity of developing improved high strength and yet ductile steels. Most traditional hardening mechanisms, however, such as enabled by solutes, dislocations, or precipitates, albeit leading to high strength, often reduce ductility rendering the material brittle and susceptible for failure. This phenomenon is sometimes referred to as the inverse strength-ductility problem.
The reduction of the grain size offers a pathway for increasing both, strength and toughness of steels. Here we develop this concept further in that we combine this strategy with the manipulation of individual interfaces by grain boundary segregation and local phase transformation. More specific, we enable grain boundaries in steels not only as barriers against dislocation motion but also as regions where segregation and nanoscale phase transformation occur. Such locally transformed regions can act as compliance layers impeding for instance crack penetration among lath martensite lamellae.

Lipid based drug delivery systems have been widely studied and reported over the past decade and offer a useful alternative to other colloidal drug delivery systems. Skin is a popular route of drug delivery for locally and systemically acting drugs and nanoparticles are reported as a potential formulation strategy for dermal delivery. Although the skin acts as a natural physical barrier against penetration of foreign materials, including particulates, opportunities exist for the delivery of therapeutic nanoparticles, especially in diseased and damaged skin and via appendageal routes such as the openings of hair follicles. The extent and ability of nanoparticles to penetrate into the underlying viable tissue is still the subject of debate although recent studies have identified the follicular route as the most likely route of entry; this influences the potential applications of these dosage forms as a drug delivery strategy. This paper reviews present state of art of lipid-based nanocarriers focussing on solid lipid nanoparticles, nanostructured lipid carriers and nanoemulsions, their production methods, potential advantages and applications in dermal drug delivery.

Steels containing reverted nanoscale austenite (cRN) islands or films dispersed in a martensitic matrix show excellent strength, ductility
and toughness. The underlying microstructural mechanisms responsible for these improvements are not yet understood, but are observed to be strongly connected to the cRN island or film size. Two main micromechanical effects are conceivable in this context, namely: (i) interaction of cRN with microcracks from the matrix (crack blunting or arresting); and (ii) deformation-induced phase  transformation of cRN to martensite (TRIP effect). The focus here is on the latter phenomenon. To investigate size effects on cRN transformation independent of other factors that can influence austenite stability (composition, crystallographic orientation, defect density, surrounding phase, etc.), a model (TRIP-maraging steel) microstructure is designed with support from diffusion simulations (using DICTRA software) to have the same, homogeneous chemical composition in all cRN grains. Characterization is conducted by in-situ tension and bending experiments in conjunction with high-resolution electron backscatter diffraction mapping and scanning electron microscopy imaging, as well as post-mortem transmission electron microscopy and synchrotron X-ray diffraction analysis. Results reveal an unexpected “smaller is less stable” effect due to the size-dependent competition between mechanical twinning and deformation-induced phase transformation.

Vanadium pentoxide (V2O5) thin films were deposited on glass substrates using spray pyrolysis technique. Aqueous solution of ammonium vanadate with 0.1 M concentration was used to deposit V2O5 thin films at different substrate temperatures. The structural, morphological, electrical, optical and vapour sensing properties of the films were investigated. XRD patterns confirmed the polycrystalline nature of the films with orthorhombic structure. Crystallite size was increased with an increase in the substrate temperature. SEM images showed the formation of films with flower like morphology. From the optical absorbance spectra, the optical band gap was determined and varied between 3.34 to 3.24 eV. The charge carrier concentration was found to be increased with substrate temperature. Room temperature xylene sensing characteristics of the films were investigated. The influence of substrate temperature on the vapour sensing characteristics of V2O5 is reported.

Metals have been mankind's most essential materials for thousands of years; however, their use is affected by ecological and economical concerns. Alloys with higher strength and ductility could alleviate some of these concerns by reducing weight and improving energy efficiency. However, most metallurgical mechanisms for increasing strength lead to ductility loss, an effect referred to as the strength– ductility trade-off 1,2. Here we present a metastability-engineering strategy in which we design nanostructured, bulk high-entropy alloys with multiple compositionally equivalent high-entropy phases. High-entropy alloys were originally proposed to benefit from phase stabilization through entropy maximization 3–6. Yet here, motivated by recent work that relaxes the strict restrictions on high-entropy alloy compositions by demonstrating the weakness of this connection 7–11 , the concept is overturned. We decrease phase stability to achieve two key benefits: interface hardening due to a dual-phase microstructure (resulting from reduced thermal stability of the high-temperature phase 12); and transformation-induced hardening (resulting from the reduced mechanical stability of the room-temperature phase 13). This combines the best of two worlds: extensive hardening due to the decreased phase stability known from advanced steels 14,15 and massive solid-solution strengthening of high-entropy alloys 3. In our transformation-induced plasticity-assisted, dual-phase high-entropy alloy (TRIP-DP-HEA), these two contributions lead respectively to enhanced trans-grain and inter-grain slip resistance, and hence, increased strength. Moreover, the increased strain hardening capacity that is enabled by dislocation hardening of the stable phase and transformation-induced hardening of the metastable phase produces increased ductility. This combined increase in strength and ductility distinguishes the TRIP-DP-HEA alloy from other recently developed structural materials 16,17. This metastability-engineering strategy should thus usefully guide design in the near-infinite compositional space of high-entropy alloys. To realize the TRIP-DP-HEA concept, we switch from the equi-atomic Fe 20 Mn 20 Ni 20 Co 20 Cr 20 (atomic per cent, at%) 6 system to the non-equiatomic Fe 80 − x Mn x Co 10 Cr 10 (at%) system, which exhibits partial martensitic transformation of the face-centred cubic (f.c.c.) to the hexagonal close-packed (h.c.p.) phase upon cooling from the high-temperature single-phase region. This change enables development of a dual-phase microstructure in which both phases obtain the maximum benefit of the solid-solution strengthening effect and one phase, owing to the decreased stacking fault energy 18 , undergoes deformation-induced displacive transformation. The partial martensitic transformation during quenching is the only possible approach that can lead to the formation of a DP-HEA with phases of identical chemical composition (that is, high-entropy phases). The alloys were synthesized with varying Mn contents in a vacuum induction furnace using pure metals, hot-rolled to 50% thickness at 900 °C, homogenized at 1,200 °C for 2 h in an Ar atmosphere, and water-quenched. Further grain refinement was achieved by cold-rolling (to 60% thickness) and 3-min annealing at 900 °C in an Ar atmosphere. The chemical composition of the HEAs measured by wet-chemical analysis is given in Extended Data Table 1. Microstructure characterization down to 30-nm resolution reveals that the Fe 80 − x Mn x Co 10 Cr 10 (at%) system indeed demonstrates the targeted change in phase stability (see the X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) data in Fig. 1). A single f.c.c. phase structure was obtained when the Mn content was 45 at% and 40 at% (Fe 35 Mn 45 Co 10 Cr 10 and Fe 40 Mn 40 Co 10 Cr 10 , respectively). Figure 1 | XRD patterns and EBSD phase maps of Fe 80 − x Mn x Co 10 Cr 10 (x = 45 at%, 40 at%, 35 at% and 30 at%) HEAs. θ is the Bragg angle. The Mn content plays an important part in phase constitution, tuning phase stability for the activation of specific displacing transformation mechanisms, for example, enabling TWIP or TRIP effects. We note that the 35 at% Mn alloy has only trace amounts of the h.c.p. phase, and hence is not referred to as a DP-HEA.

https://www.nature.com/articles/s41586-020-2409-3

Laser additive manufacturing is attractive for the production of complex, three-dimensional parts from metallic powder using a computer-aided design model1,2,3. The approach enables the digital control of the processing parameters and thus the resulting alloy’s microstructure, for example, by using high cooling rates and cyclic re-heating4,5,6,7,8,9,10. We recently showed that this cyclic re-heating, the so-called intrinsic heat treatment, can trigger nickel-aluminium precipitation in an iron–nickel–aluminium alloy in situ during laser additive manufacturing9. Here we report a Fe19Ni5Ti (weight per cent) steel tailor-designed for laser additive manufacturing. This steel is hardened in situ by nickel-titanium nanoprecipitation, and martensite is also formed in situ, starting at a readily accessible temperature of 200 degrees Celsius. Local control of both the nanoprecipitation and the martensitic transformation during the fabrication leads to complex microstructure hierarchies across multiple length scales, from approximately 100-micrometre-thick layers down to nanoscale precipitates. Inspired by ancient Damascus steels11,12,13,14—which have hard and soft layers, originally introduced via the folding and forging techniques of skilled blacksmiths—we produced a material consisting of alternating soft and hard layers. Our material has a tensile strength of 1,300 megapascals and 10 per cent elongation, showing superior mechanical properties to those of ancient Damascus steel12. The principles of in situ precipitation strengthening and local microstructure control used here can be applied to a wide range of precipitation-hardened alloys and different additive manufacturing processes.

Main
Parts built by laser additive manufacturing (LAM) experience a specific thermal history. First comes a rapid quenching from the liquid state, followed by an intrinsic heat treatment (IHT), that is, cyclic re-heating that consists of a multitude of short temperature spikes6,9,15. In directed energy deposition (DED), parts are built layer-wise by laser melting of powder fed by a carrier gas through a nozzle1,3. In DED, the IHT is pronounced and hence provides opportunities to locally adjust the microstructures7,8,9,15,16. Yet new materials must be tailor-designed to best exploit these specific conditions, as conventional alloy compositions cannot be expected to perform efficiently as they have been optimized for other processing routes, for example, casting or forging.

We recently showed that the IHT can trigger nickel-aluminium (NiAl) precipitation in an iron–nickel–aluminium (Fe–Ni–Al) alloy9. This so-called maraging steel draws properties from two important phase transformations. Initially, a soft nickel-rich martensitic microstructure forms upon quenching through an austenite-to-martensite transformation. This martensite is later hardened by a second phase transformation to form intermetallic nanoprecipitates. Therefore, conventionally produced as well as LAM-produced commercial maraging steels (for example, 18Ni-300) need to undergo a costly ageing treatment to form property-enhancing intermetallic precipitates17,18,19,20,21,22. Iron–nickel–titanium (Fe–Ni–Ti) alloy systems show extremely fast kinetics for Ni3Ti precipitation17,18,19,21,22,23, making them ideally suited for in situ precipitation hardening by exploiting the short temperature peaks during IHT.

Here the digital control of the DED process parameters allowed us to locally exploit these two phase transformations and adjust the microstructure to create a new material inspired by Damascus steel. The layered structure of Damascus steel originally resulted from repeatedly folding and forging macrocomposites consisting of a hard steel and a soft steel and lends excellent strength and ductility to the composite11,12,13,14. We utilize this concept here and produce a Damascus-like maraging steel, not by folding and forging but by fabricating layered microstructures by exploiting rapid quenching, sequential in situ heating and local phase transformation. We specifically designed an Fe19Ni5Ti (wt%) alloy to exploit the rapid quenching and IHT of the DED (see Methods section Supplementary discussion of the alloy design concept’ for more details). We adjusted the DED process parameters to regulate the time–temperature profile during the fabrication process, which enabled precise, local control of the martensite formation as well as the precipitation, and hence of the mechanical behaviour. Our approach avoids a time-consuming and costly post-process ageing heat treatment, and also provides the possibility to locally tune the microstructure, which would not be possible with conventional heat treatments.

"This textbook provides conceptual, procedural, and factual knowledge on solid state and nanostructure physics. It is designed to acquaint readers with key concepts and their connections, to stimulate intuition and curiosity, and to enable the acquisition of competences in general strategies and specific procedures for problem solving and their use in specific applications. To these ends, a multidisciplinary approach is adopted, integrating physics, chemistry, and engineering and reflecting how these disciplines are converging towards common tools and languages in the field.

Each chapter discusses essential ideas before the introduction of formalisms and the stepwise addition of complications. Questions on everyday manifestations of the concepts are included, with reasoned linking of ideas from different chapters and sections and further detail in the appendices. The final section of each chapter describes experimental methods and strategies that can be used to probe the phenomena under discussion.

Solid state and nanostructure physics is constantly growing as a field of study where the fascinating quantum world emerges and otherwise imaginary things can become real, engineered with increasing creativity and control: from tinier and faster technologies realizing quantum information concepts, to understanding of the fundamental laws of the Universe, unifying the tiniest lengths below those of nuclear constituents with the giant cosmic distances. Elements of Solid State Physics and of Crystalline Nanostructures will offer the reader an enjoyable insight into the complex concepts of solid state physics."

By using a combinatorial approach we study the strain hardening of two austenitic high-Mn low density steels, namely, Fe–30.5Mn–2.1Al–1.2C and Fe–30.5Mn–8.0Al–1.2C (wt.%), containing different precipitation states. The strain hardening of the alloy with low Al content is attributed to dislocation and twin substructures. The precipitation of intergranular M3C-type carbides strongly influences the fracture mode. We associate the strain hardening behavior of the alloy with high Al content to the precipitation of shearable nanosized kappa-carbides and their role in the development of planar dislocation substructures.

Austenite formation, which originated from a fined-grained ferrite plus carbide microstructure, was observed during tensile testing at
973 K (60 K below Ae1, the equilibrium austenite–pearlite transformation temperature). Scanning electron microscopy, electron
backscatter diffraction and atom probe tomography results reveal the mechanism of austenitic transformation below Ae1. The initial
fine-grained microstructure, in combination with the warm deformation process, determines the occurrence of strain-induced austenite formation below Ae1. The initial fine-grained microstructure essentially contains a higher dislocation density to facilitate the formation of Cottrell atmospheres and a larger area fraction of ferrite/carbide interfaces which serve as austenite nucleation sites. The warm deformation promotes the Ostwald ripening process and the increase in dislocation density, and hence promotes the accumulation of local high carbon concentrations in the form of Cottrell atmospheres to reach a sufficiently high thermodynamic driving force for austenite nucleation. The critical carbon concentration required for the nucleation of austenite was calculated using classical nucleation theory, which correlated well with the experimental observations.

Knowledge extraction by just Reading books is a distinctive property. Although text can be a medium of communication but speech signal is more effective means of communication than text. In this paper work Optical Character recognition (OCR) Based Speech Synthesis System has been discussed using myRIO under LabVIEW platform as front end .Although lot of work has been done in the field of OCR and Speech Synthesis individually, but it is first OCR based Speech Synthesis System using FPGA implementation in myrio. Each page of the book to be read are been turned using automatic page turner and the text is been captured using a camera, and electronic translation of the captured image is been done by myRio using OCR technique and the recognized text is been converted to speech using ACTIVEX speech synthesizer.

Due to the layer-by-layer build-up of additively manufactured parts, the deposited material experiences a cyclic reheating in the form of a sequence of temperature pulses. In the current work, this " intrinsic heat treatment (IHT) " was exploited to induce the precipitation of NiAl nanoparticles in an Fe-19Ni-xAl (at%) model maraging steel, a system known for rapid clustering. We used Laser Metal Deposition (LMD) to synthesize compositionally graded specimens. This allowed for the efficient screening of effects associated with varying Al contents ranging from 0 to 25 at% and for identifying promising concentrations for further studies. Based on the existence of the desired martensitic matrix, an upper bound for the Al concentration of 15 at% was defined. Owing to the presence of NiAl precipitates as observed by Atom Probe Tomography (APT), a lower bound of 3e5 at% Al was established. Within this concentration window, increasing the Al concentration gave rise to an increase in hardness by 225 HV due to an exceptionally high number density of 10 25 NiAl precipitates per m 3 , as measured by APT. This work demonstrates the possibility of exploiting the IHT of the LMD process for the production of samples that are precipitation strengthened during the additive manufacturing process without need for any further heat treatment.

The population of all non-equilibrium lattice defects in materials is referred to as microstructure. Examples are point defects such as substitutional and interstitial atoms, and vacancies; line defects such as dislocations; planar defects such as interfaces and stacking faults; or mesoscopic defects such as second-phase precipitates. These types of lattice imperfections are usually described in terms of their structural features, breaking the periodicity of the otherwise regular crystalline structure. Recent analytical probing at the nanoscale has revealed that their chemical features are likewise important and characteristic. The structure of the defects as well as their individual chemical composition, that is their chemical decoration state, which results from elemental partitioning with the adjacent matrix, can significantly influence the electrical and thermal transport properties of thermoelectric materials. The emergence of atom probe tomography (APT) has now made routinely accessible the mapping of three-dimensional chemical composition with sub-nanometer spatial accuracy and elemental sensitivity in the range of tens of ppm. Here, we review APT-based investigations and results related to the local chemical decoration states of various types of lattice defects in thermoelectric materials. APT allows to better understand the interplay between thermoelectric properties and microstructural features, extending the concept of defect engineering to the field of segregation engineering so as to guide the rational design of high-performance thermoelectric materials.

A B S T R A C T In the present work, ultrafine-grained Al-Zn-Mg alloy produced by high energy ball milling and Spark Plasma Sintering was synthesized. The Hall-Petch strengthening due to grain refinement (about 150 nm) is preserved and the Orowan's effect attributed to the presence of the hardening phase η' is obtained in a single-step during the sintering. Maximum compression stresses as high as 736 MPa and 830 MPa were reached in quasistatic and dynamic conditions respectively. Hardness was increased from 124 HV5 for a consolidated coarse grained material to 196 HV for a consolidated ultrafine-grained (UFG) material. The mechanical properties obtained in this study were all superior to the ones of the reference AA7020-T651.

We report on the investigation of the off-stoichiometry and site-occupancy of kappa-carbide precipitates within an austenitic (g), Fe-29.8Mn-7.7Al-1.3C (wt.%) alloy using a combination of atom probe tomography and density functional theory. The chemical composition of the k-carbides as measured by atom probe tomography indicates depletion of both interstitial C and substitutional Al, in comparison to the ideal stoichiometric L012 bulk perovskite. In this work we demonstrate that both these effects are coupled. The off-stoichiometric concentration of Al can, to a certain extent, be explained by strain caused by the k/g mismatch, which facilitates occupation of Al sites in k-carbide by Mn atoms (Mn-Al anti-site defects). The large anti-site concentrations observed by our experiments, however, can only be stabilized if there are C vacancies in the vicinity of the anti-site.

Materials produced by selective laser melting (SLM) experience a thermal history that is markedly different from that encountered by conventionally produced materials. In particular, a very high cooling rate from the melt is combined with cyclical reheating upon deposition of subsequent layers. Using atom-probe tomography (APT), we investigated how this nonconventional thermal history influences the phase-transformation behavior of maraging steels (Fe–18Ni–9Co–3.4Mo–1.2Ti) produced by SLM. We found that despite the “intrinsic heat treatment” and the known propensity of maraging steels for rapid clustering and precipitation, the material does not show any sign of phase transformation in the as-produced state. Upon aging, three different types of precipitates, namely (Fe,Ni,Co)3(Ti,Mo), (Fe,Ni,Co)3(Mo,Ti), and (Fe,Ni,Co)7Mo6 (l phase), were observed as well as martensite-to-austenite reversion around regions of the retained austenite. The concentration of the newly formed phases as quantified by APT closely matches thermodynamic equilibrium calculations,

A high density of grain boundaries can potentially increase structural materials' strength, but at the expense of losing the materials' strain hardening ability at high flow stress levels. However, endowing materials with grain size gradients and a high density of internal interfaces can simultaneously increase the strength and strain hardening ability. This applies particularly for through-thickness gradients of nanoscale interface structures. Here we apply a machining method that produces metals with nanoscale interface gradients. Conventional bulk plastic deformation such as rolling, a process applied annually to about 2 billion tons of material, aims to reduce the metal thickness. We have modified this process by introducing severe strain path changes, realized by leading the sheet through a U-turn while preserving its shape, an approach known as 'hard turning'. We applied this process at both room temperature and 77 K to a NiCrCo medium entropy alloy. Micropillar compression was conducted to evaluate the mechanical response. After hard turning at room temperature, the surface microstructure obtained a ~50% increase in yield stress (0.9 GPa) over the original state with homogeneous grain size (0.4 GPa), but the initial strain hardening rate did not show significant improvement. However, after hard turning at 77 k, the gradient nanolaminate structure tripled in yield stress and more than doubled its initial strain hardening rate. The improvements were achieved by introducing a specific microstructure that consists of gradient nano-laminates in the form of nanospaced twins and martensite in the face center cubic (fcc) phase. This microstructure was formed only at cryogenic temperature. It was found after turning at room temperature that only nanospaced twins were present in the fcc phase inside nanolaminates that had formed at the surface. The origin of the enhanced strain hardening mechanism was studied. Joint density functional theory (DFT) and axial next nearest neighbor Ising (ANNNI) models were used to explain the temperature-dependent phase formation of the NiCrCo nanolaminate at the surface of the hard-turned material.

We have used neutron powder diffraction to make a comprehensive study of the crystal structure in Pr2Fe17 nanocrystalline compounds. These nanostructured materials have been obtained by high-energy ball milling from an arc-melted bulk polycrystalline alloy. The Th2Zn17-type rhombohedral crystal structure of the starting bulk alloy is maintained after milling for 10 and 20 hours. The studied alloys are ferromagnetic below TC = 286±1 K (bulk) and TC approx 300±20 K (milled). These materials exhibit strong magneto-volume anomalies below TC, such as a negative coefficient of thermal expansion (αV approx -30 × 10-6 K-1).

The highly ordered mesoporous silica media, SBA-15, was synthesized and incorporated with iron, aluminum, and zinc oxides using an incipient wetness impregnation technique. Adsorption capacities and kinetics of metal-impregnated SBA-15 were compared with activated alumina which is widely used for arsenic removal. Media impregnated with 10% of aluminum by weight (designated to Al 10SBA-15) had 1.9-2.7 times greater arsenate adsorption capacities in a wide range of initial arsenate concentrations and a 15 times greater initial sorption rate at ph 7.2 than activated alumina. By employing one- and two-site models, surface complexation modeling was conducted to investigate the relationship between the aluminum oxidation states in different media and adsorption behaviors shown by adsorption isotherms and kinetics since the oxidation phase of aluminum incorporated onto the surface of SBA-15 was Al-O, which has a lower oxidation state than activated alumina (Al2O 3). Surface complexation modeling results for arsenate adsorption edges conducted with different pH indicated that the monodentate complex (SAsO42-) was dominant in Al10SBA-15, while bidentate complexes (XHAsO4 and XAsO4-) were dominant in activated alumina at pH 7.2, respectively. In kinetic studies at pH 7.2 ± 0.02, Al10SBA-15 had only a fast-rate step of initial adsorption, while activated alumina had fast- and slow-rate steps of arsenate adsorption. Therefore, it can be inferred that the monodentate arsenate complex, predominant in Al10SBA-15, leads to faster adsorption rates than bidentate arsenate complexes favored with activated alumina. An arsenate adsorption behavior and arsenate surface complexation were thought to be well explained by aluminum oxidation states and surface structural properties of media.

http://www.ncbi.nlm.nih.gov/pubmed/14620839 
http://pubs.acs.org/doi/abs/10.1021/es0343712

ZnO-based materials have been synthesized by means of hydrothermal method from aqueous solutions of ZnOH42- in the presence of sodium-dodecyl sulphate (SDS). By means of a variety of analyses (SEM, AFM, IR, UV-vis and XRD) it is shown that this synthesis method allows to obtain ZnO microcrystals with well defined morphology and active toward hydrogen adsorption. The adsorption of hydrogen on these zinc oxide platelets has been investigated by FTIR spectroscopy and the results are compared with those obtained on ZnO, synthesized by combustion of zinc metal.

This is a progress report on elucidating the behaviour of liquids,
in particular water, in confined geometry on the nano- to mesoscale, and at interfaces. There are important measurements still to make, conclusions still to be drawn, and above all leaps of understanding still to be made. However, a number of important
features in the behaviour of these systems have recently become
clearer.
Nano-structuring of liquids and their crystals changes their Gibbs free energy, and hence their dynamics. This may most readily be probed by monitoring the alteration of phase changes as a function of temperature, together with changes in other parameters, particularly the confinement diameter. Such studies may be performed by monitoring the change in the pressure (at constant temperature) of the liquid in its own vapour (Kelvin equation), or by monitoring the change in the freezing/melting temperature (at constant pressure) of a crystal in its own liquid (Gibbs–Thomson equation).
In the latter case the melting and freezing temperatures of liquids
are modified by the changes in the volumetric Gibbs free energy
due to nanostructuring; this is related to the surface energy of
the curved interface between the crystal and its own liquid. This is thus dependent on the geometry of the interface between the crystal and its liquid. There is still discussion on this point as to the exact geometric constants and functional forms that are applicable for different confining geometries. Experimental evidence is presented for the cases of cylindrical pores (SBA-15), and for pores that on average are spherical (sol–gel). However, reconciling this comparative data with melting/freezing temperatures in each of these systems still pose a number of questions.
It is well known that bulk brittle ice has a hexagonal structure,
while brittle ice that forms in pores may be cubic in structure [1,2], Figs. 10 and 11. Adjacent surfaces appear to further alter the dynamics and structure of confined liquids and their crystals, leading in the case of a water/ice system to a state of enhanced rotational motion (plastic ice) just below the confined freezing/
melting transitions. This plastic ice layer appears to form at both
the ice–silica interface and the ice–vapour surface, and reversibly
transforms to brittle ice at lower temperatures. There is good evidence to suggest that the plastic ice at a silica interface transforms to cubic ice, while the plastic ice at vapour surfaces transforms to hexagonal ice. That this plastic ice may correspond to a layer at the crystal surface is suggested by the presence of only amorphous ice in confined systems with small dimensions (<3 nm diameter), whereas systems with larger dimensions (10 nm) contain brittle cubic ice and also some hexagonal ice (if a vapour interface is present); even larger systems (>30 nm) contain predominately hexagonal ice. It is conjectured that this layer of plastic ice at vapour surfaces may be present at the myriad of such interfaces in macroscopic systems, such as snow-packs, glaciers and icebergs, and may be an explanation for the need for plastic terms in the macroscopic dynamical models of these systems [3].
These results also point the way forward for a wide-range of
cryoporometric metrology studies of systems that are ‘difficult’
for NMR, such as high iron content clays and rocks, as well as age concrete. Results are presented for cryoporometric measurements on meteorite samples with a significant metallic content, exhibiting T2 relaxation times down to 2.5 us.

 The object of investigation were the magnetic interactions in nanostructured Fe3O4 assemblies of two kinds (powder and film) where particles of similar size present nearly uniform domains in a close to planar arrangement with spacings sufficient for magnetic interactions. We discuss the use of the soft-chemistry method, i.e. the modified ‘ferrite plating’ (MFP) technique, for the synthesis of polycrystalline films of magnetite with nanosized crystallites.

This article focuses on four topics that demonstrate the importance of atom probe tomography for obtaining nanostructural information that provides deep insights into the structures of metallic alloys, leading to a better understanding of their properties. First, we discuss the microstructure–coercivity relationship of Nd-Fe-B permanent magnets, essential for developing a higher coercivity magnet. Second, we address equilibrium segregation at grain boundaries with the aim of manipulating their interfacial structure, energies, compositions, and properties, thereby enabling benefi cial material behavior. Third, recent progress in the search to extend the performance and practicality of the next generation of advanced high-strength steels is discussed. Finally, a study of the temporal evolution of a Ni-Al-Cr alloy through the stages of nucleation, growth, and coarsening (Ostwald ripening) and its relationship with the predictions of a model for quasi-stationary coarsening is described. This information is critical for understanding high-temperature mechanical properties of the
material.

The microstructure of explosive cladding joints formed among parallel Ti and steel plates was examined by electron microscopy. The bonding interface and the bulk materials around it form pronounced hierarchical microstructures. This hierarchy is characterized by the following features: at the mesoscopic scale of the hierarchy a wavy course of the interface characterizes the interface zone. This microstructure level is formed by heavy plastic shear waves (wavelength≈0.5mm)which expand within the two metal plates during the explosion parallel to the bonding interface. At the micro-scale range, intermetallic inclusions (size≈100–200m) are formed just behind the wave crests on the steel side as a result of partial melting. Electron diffraction revealed FeTi and metastable Fe9.64Ti0.36. Most of the observed phases do not appear in the equilibrium Fe–Ti phase diagram. These intermetallic inclusions are often accompanied by micro-cracks of similar dimension. At the smallest hierarchy level we observe a reaction layer of about 100–300nm thickness consisting of nano-sized grains formed along the entire bonding interface. Within that complex hierarchical micro- and nanostructure, the mesoscopic regime, more precisely the type and brittleness of the intermetallic zones, seems to play the dominant role for the mechanical behavior of the entire compound.

The environmental and economical merits of converting solar energy into electricity via photovoltaic cells have caused an ever increasing interest among developed and developing countries to allocate more budget on photovoltaic systems in order to boost up their efficiency in recent years. Besides the material and design parameters, there are several omnipresent factors such as dust, humidity and air velocity that can influence the PV cell's performance. There have been a handful of studies conducted on the effect of various influential parameters on the efficiency and performance of photovoltaic cells; however none has taken all these three parameters into account simultaneously. In this study the impact of dust accumulation, humidity level and the air velocity will be elaborated separately and finally the impact of each on the other will be clarified. It is shown that each of these three factors affect the other two and it is concluded that in order to have a profound insight of solar cell design, the effect of these factors should be taken into consideration in parallel.

http://www.sciencedirect.com/science/article/pii/S1364032112001050