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A new nanoindentation approach is developed in this study to determine both indentation size effect (ISE) and continuous apparent activation volume (V) during loading of nanocrystalline nickel (NC Ni) and nanocrystalline nickel-20 wt% iron alloy (NC Ni–Fe alloy). This approach involves conducting nanoindentation tests under loading modes controlled by both constant strain rate (CSR) and constant loading rate (CLR). Firstly, a new empirical expression for the parameter f in the modified Nix-Gao model is established to study the strain rate dependence of the ISEs created in the CSR and CLR tests. Then, continuous V data of each individual sample (indentation) during loading are obtained in the CLR test through the alternative use of continuous stiffness measurement technique. The stress dependence of V is analyzed based on Duhamel et al.’s model, which considers the role of vacancies generated during inhomogeneous dislocation nucleation. Finally, based on the above experimental and theoretical work as well as transmission electron microscopy observation, the influences of loading mode, loading rate, and material properties (stacking fault energy) on resulting intrinsic hardness of NC Ni and NC Ni–Fe alloy are analyzed. The nanoindentation approach developed in this study provides profound insights into the mechanical behaviors during loading and underlying mechanisms of materials.

A newly discovered peculiar microstructure at the rolling contact surface of bainitic rail steel has been investigated via positron annihilation technique and X-ray diffraction. The results show that the nanocrystalline layer is produced through low-temperature dynamic recrystallization. After hydrogen charged, low temperature dynamic recrystallization has been inhibited by hydrogen, and nanocrystalline layer at the surface decreases or disappears.

In this paper, nano-Ti-2Fe-0.1B alloys with different grain sizes were processed by high pressure torsion (HPT) deformation. The study examined the microstructural evolution of the Ti–2Fe-0.1B alloy during HPT and evaluated its mechanical properties through microhardness and tensile tests. The results of the microstructural observations revealed that the grain size of the Ti–2Fe-0.1B alloy progressively decreased from 3.14 μm in the as-annealed state to approximately 20 nm after 10 turns. In the initial state, the alloy consists of α-phase and β-phases, with a volume ratio of approximately 5:1. During the HPT process, transformations of α-phase and β-phase to ω-phase were observed. The primary reason for this is that the shear forces applied during the HPT process facilitated the phase transformation of the α-phase. Additionally, the presence of Fe element in the alloy altered the lattice compatibility between the grains of β-phase and ω-phase, thereby promoting the phase transformation of the β-phase, with the accumulated turns of HPT process, the fraction of ω-phase increased in the beginning gradually, then decreased, which reached to the maximum 80.8% in the 5 turns. This is higher than that of pure titanium and Ti–Fe alloys under the same conditions, because the proportion of the ω-phase increases with the increase in Fe content. Studies of mechanical properties demonstrated that HPT can substantially enhance the hardness of Ti–2Fe-0.1B alloys to as high as 483 HV, and the tensile strength of the Ti–2Fe-0.1B alloy was observed to increase from 725 MPa to 1568 MPa after 5 turns, which is much higher than Ti–6Al–4V subjected to the identical processing conditions. It can be ascribed to the exist of mass ω-phase as well as finer grain size in nanocrystalline Ti–2Fe-0.1B alloy.

Amorphous alloy is a popular choice for wastewater treatment because of its high active sites and high catalytic performance. It is different from the previous situation that the degradation performance of amorphous materials decreases first and then increases after crystallization. The degradation efficiency of Direct Yellow GR dye (DYGR) by Electro-Fenton (E-F) is gradually increases as the amorphous content of Fe41Co7Cr15Mo14C15B6Y2 amorphous alloy powder (MGs) is reduced in this work. The in-situ precipitation of (Fe, Cr)23(C, B)6 and Fe7C3 nanocrystals was discovered to decrease the electron work function (EWF) of the alloy powder, thus decreasing the amount of work needed to escape electrons and enhancing the electrocatalytic performance of the material. At the same time, the precipitation of (Fe, Cr)23(C, B)6 nanocrystals changed the chemical composition of the surface of MGs. After annealing, the Fe2+ concentration was higher than before regression, and the chemical potential energy between Fe2+ and Fe3+ was greater, thus facilitating the formation of ∙OH. This research offers novel perspectives on the utilization of nanocrystals in the management of amorphous alloy wastewater.

The development of biodegradable Zn alloys with comprehensive performance for biomedical applications is still challenging. Hence, the nanocrystalline Zn–Cu–Sr–Li alloys were prepared by alloying design and multi-pass high-speed hot rolling. The Zn–3Cu-0.2Sr-0.4Li alloy achieved nanoscale microstructures, resulting in high strength and an ideal corrosion rate that is more suitable for tissue repair cycles. Scanning Kelvin probe force microscopy analysis revealed the potential from high to low was ranked as: ε phase > SrZn13 phase > Zn grains > β phase. The nanoscale Zn grains and β particles formed numerous microcells, enhancing the microgalvanic corrosion effect. The Sr ions could be released more efficiently during the degradation in Li-containing alloys, which endowed the alloys with outstanding biocompatibility. Besides, the synergistic release of Zn ions and Cu ions during alloy degradation endowed the alloy with excellent antimicrobial ability against Staphylococcus aureus (inhibition zone diameter ≈ 7.5 mm). The antimicrobial ability of Zn–3Cu–0.2Sr–0.4Li alloy was superior among the reported biodegradable Zn alloys. These results demonstrated nanocrystalline Zn–Cu–Sr–Li alloys have comprehensive performance and broad application prospects in biodegradable bone implants, providing the experimental and theoretical basis for future research in the biomedical field.

In the present paper, two austenitic wear-resistant steels, namely 110Mn13 and 0Cr17Ni10Mn5Mo2 steels, were cold-rolled to a same hardness level of ∼270 HV. Mechanical properties and wear resistance under various applied loads were tested. The deformed microstructure, worn surface morphologies and wear debris were discussed to analyze the wear resistance. Results showed that a higher density of deformation twins and dislocations were generated in the 0Cr17Ni10Mn5Mo2 steel to reach a same hardness level with the 110Mn13 steel. Consequently, the 0Cr17Ni10Mn5Mo2 steel obtained higher yield strength (736 MPa) but lower ultimate strength (896 MPa), elongation (30.5%) and strain hardening rate than the 110Mn13 steel when the impact absorption energies were at a similar level of ∼170 J. The weight loss of the 0Cr17Ni10Mn5Mo2 steel reduced by over 40% compared to that of the 110Mn13 steel under the selected wear conditions. With the cold-rolled microstructure, the worn surface of both the test steels produced nanocrystalline layers. The nanocrystalline layer thickness of the 0Cr17Ni10Mn5Mo2 steel was over 5 μm, far larger than that of the 110Mn13 steel. Meanwhile, with the wear debris containing Cr-oxide adhering to the worn surface, which could facilitate the self-lubricating effect, the 0Cr17Ni10Mn5Mo2 steel presented better wear resistance than the 110Mn13 steel.

Although the catalytic properties of Au–Pt alloys have received widespread attention, there are a few of relevant studies on their microscopic deformation process. Considering that Au–Pt alloys are noble metals, and the costs of experiments are extremely high. Direct research experiments are extremely expensive. So the molecular dynamics method which can directly observe the evolution process of microstructure and analyze the mechanical behavior of each deformation stage of the material was adopted to explore the underlined relationship between the temperature and the compression deformation mechanism. The results show that during the process of compression deformation, lots of atoms in the crystal are converted into boundary atoms, the dislocation multiplication and the grain fragmentation occur. In different temperature intervals, along with the compression deformation, low temperature, medium temperature and high temperature recovery appear. Due to the influence of the dual mechanism of deformation and recovery, the deformation mechanism is different at different temperatures, at low temperature stage is mainly the dislocation multiplication and the grain fragmentation, at middle temperature stage is the combination of the opposite sign dislocation, and at high temperature stage is mainly the merger of the grain.

Relatively few studies have addressed the use of vacuum arc evaporation (VAE) in conjunction with high-power impulse magnetron sputtering (HiPIMS), due to differences in the respective pressure requirements. This paper describes the use of HiPIMS-enhanced VAE (HEVAE) technology for the deposition of TiN coatings on tungsten carbide and silicon wafers. We determined that HiPIMS could reduce the formation of macro-particle (MP) defects, while enhancing hardness and adhesion strength. Electron microscopy results revealed that both the quantity and size of MPs decreased inversely with HiPIMS power. Under the highest HiPMS power (4 kW), we observed a notable decrease in the size of columnar crystals and a significant increase in the number of nanocrystalline structures. The formation of nanocrystals enhanced hardness by reducing the probability of dislocations. Overall, HiPIMS power of 4 kW proved optimal in terms of MP formation, hardness (32.1 GPa), and adhesion strength (137 N).

Magnesium alloys, as the lightest structural alloys, provide the possibility of solving environmental problems by improving energy efficiency. Developing and maintaining nanocrystalline matrix is a huge challenge, and the key to achieving ultra-high strength. The nanocrystalline Ti/AZ61 composite prepared by hot pressing was annealed, and its microstructural evolution was characterized via SEM, XRD, and TEM, including the changes in magnesium matrix, Ti dispersions, and nano-scale precipitates. The density and mechanical properties of annealed composites were tested and analyzed. After annealing treatment at 623 K for 80 h, the average grain size of nanocrystalline Ti/AZ61 composites was 102 nm. 97% of Ti dispersions were submicron sized, and Ti3Al precipitates remained nanometer-sized. Ti dispersions and Ti3Al precipitates were uniformly distributed in the magnesium matrix. Compared with hot pressed composites, the crack that originated from the prior particle boundary (PPB) was restrained for annealed composites. The improved density and PPB bonding strength of annealed Ti/AZ61 composites had a positive impact on strength and plasticity. After annealing treatment for 40 h, the density increased from ∼2.041 g/cm3 to 2.066 g/cm3. The hardness, yield strength, and FFS were 146 HV, 493 MPa, and 5.6%, respectively, with corresponding increasing rates of 7%, 12%, and 65%, respectively.

The evolution of the microstructure and mechanical properties of a vacuum arc melted non-equiatomic Al0.4Co0.5V0.2FeNi high-entropy alloy (HEA) subjected to severe plastic deformation was investigated experimentally and by simulations. The present work explored duplex HEAs, comprising a face-centered cubic (FCC) matrix and a body-centered cubic (BCC) phase, towards outstanding their mechanical responses. The Al0.4Co0.5V0.2FeNi alloys had a duplex structure, i.e., with dispersed B2-phase islands (with sizes of dozens of microns) in several hundred micron-, even millimeter-sized FCC grains. The mechanical properties of this HEA were strongly deformation dependent, i.e., when deformation increased from 30 % up to 60 %, the yield strength and ultimate strength tensile increased from ∼0.9 GPa and 1.0 GPa to ∼1.2 GPa and 1.3 GPa, respectively. During tensile deformation, initial fractures occurred in the FCC phase located close to the interface between the FCC and BCC phases. With an increase of deformation, the fracture degree in the FCC phase got larger, and fractures also appeared in the BCC phase. Combined with the geometric dislocation density calculation results from an electron backscatter diffraction (EBSD) analysis, it can be seen that the dislocation density near the phase interface of FCC was higher, making it more likely to produce defects.

NiTi shape memory alloys have been widely explored because of their superelasticity. However, the application of conventional coarsed NiTi SMAs is limited by low superelastic stress and poor superelastic stability due to their low yield strength. In this study, nanocrystalline (NC) Ni47Ti50Fe3 alloy with average size is ∼15 nm was obtained by large deformation cold drawing and low temperature annealing. After ten cycles of loading (up to 6%)-unloading, the NC Ni47Ti50Fe3 alloy exhibited a high superelastic stress (1170 MPa)，low areduction rate of superelastic stress (12%) and small residual strain (0.66%). This overall performance is better than that of previous NiTi-based SMAs. We have suggested that this mainly stems from the synergistic reinforcement combines Fe element doping and high-density grain boundary.

In this paper, the microstructure evolution and thermal stability of nanocrystalline (NC) AZ31-2.5 wt%VP magnesium matrix composites were studied, while the hardness was analyzed. The results showed that the NC AZ31-2.5 wt%VP still kept NC scale after annealing at 300 °C and 350 °C. Even at 400 °C and 450 °C, the grain size of the annealed composite only grew to 113 nm and 132 nm, which was still in ultrafine grain scale, illustrating excellent thermal stability of NC AZ31-2.5 wt%VP. Furthermore, the V particles, which was uniformly distributed in the Mg matrix, had no obvious change in dimension after annealing, while it also had no new phase formed. The stabilization mechanism was expounded and found that the pinning effect of V particles effectively inhibited the grain growth of Mg matrix at high temperature. In addition, the grain growth kinetics equation (D6−D06=kt) was utilized to explain the grain growth behavior of NC AZ31-2.5 wt%VP, and the activation energy (Ea) of grain growth was calculated to be 130.9 kJ/mol, which was much higher than that of pure Mg (92 kJ/mol). Eventually, the hardness of NC AZ31-2.5 wt%VP was contrastive studied and the hardness evolution curves at different temperatures were obtained. After annealing treatment was performed at 450 °C for 180min, the hardness remained at 80 HV, which was higher than that of as-cast AZ31 (53 HV).

Nanocrystalline (NC) magnesium alloys and composites present potential for improving energy efficiency in transportation applications due to outstanding strength. Unfortunately, softening owing to grain growth at elevated temperature would induce fatal invalidity. The NC SiCp/AZ91 composite was isothermally annealed. A study on the thermal stability, including phase transformation, grain growth, softening, and strengthening mechanisms was carried out. After annealing treatment at 673 K for 240 min, the average grain size of AZ91-15vol.%SiCp composite increased from 29.0 nm to 53.1 nm. Coherent interface between nano-scale Mg17Al12 precipitates and Mg matrix was certified by HRTEM. Pinning effect due to the dispersing submicron SiC particles with size of 164 nm and nano-scale Mg17Al12 precipitates and dragging effect due to dissolving Al element were the reasons for excellent thermal stability. After annealing treatment, the hardness values of AZ91-xvol.%SiCp (x = 5, 10 and 15) composites were 1.61 GPa, 1.48 GPa and 1.78 GPa. Taking annealed AZ91-15vol.%SiCp composite as an example, there was no evident softening phenomenon and the decreasing ratio was ∼2% in comparison with milled composite with hardness of 1.82 GPa. Non-thermal sensitive SiC particles and high thermal stability Mg matrix played a key role in non-softening of composites.

Thermal stability and mechanical property of the multicomponent nanocrystalline Fe–ZrNbMoTa alloys were investigated. Single-phase nanocrystalline Fe–(ZrNbMoTa)x (x = 0.1, 0.2, 0.5 and 1 at. %) alloys were prepared by ball milling and followed by annealing in a set of predesigned condition. It was found that the Fe-based multicomponent alloys possess good thermal stability through 10 h annealing at 900 °C, which is attributed to the thermodynamics effect in the reduction of grain boundary energy caused by multicomponent co-segregation of Zr, Nb, Mo and Ta, and kinetics effect related to sluggish diffusion and Zener pinning of a small amount of second-phase precipitation. Additionally, nanocrystalline Fe–(ZrNbMoTa)x alloys show excellent mechanical properties. The hardness is 738.6 HV, and its yield strength and compressive strength reach up to 3100 MPa and 3600 MPa, respectively. These are attributed to the comprehensive effects of nanocrystalline, solid solution and second phase strengthening.

Ferrite nanoparticles are an emerging material for industrial and biomedical applications. Herein, a simple non-aqueous sol–gel method is used to synthesize CuxZn(1-x)Fe2O4 (x = 0.0, 0.25, 0.5, and 0.75) nanoparticles. X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–Vis spectroscopy, and a vibrating-sample magnetometer (VSM) were utilized to investigate the structural formation and magnetic merits of the prepared ferrite nanoparticles. The Rietveld refinement of the X-ray diffraction pattern confirmed the formation of single-phase cubic structures with Fd3¯m space groups for all samples. The increase in cu2+ concentration in zinc ferrite nanoparticles decreases the lattice parameters from 8.4418 to 8.4368. The energy gap of cu2+-doped zinc ferrite increases from 1.89 to 2.04 eV with a decrease in particle size. MH loop revealed an increase in Ms and Mr Parameters as Hc reduces with an increase in Cu2+ concentration in the zinc ferrite matrix. It was discovered that an increase in Cu2+ content improved the antibacterial activities of Cu2+-doped zinc ferrite against all bacterial species.

In this research, CoFeNi thick films were prepared through the electrodeposition process from a natural pH bath containing the complex agent of sodium citrate. By increasing applied current density, there is a transition from BCC (Fe) phase to BCC (Fe) + FCC (Co) phases and then to FCC (Co) phase. The XRD pattern showed a nanocrystalline structure for the CoFeNi thick films which was further confirmed by the TEM images. The magnetic properties of the synthesized magnetic films exhibit a noticeable decrease in the coercivity by decreasing the crystallite size which is consistent with the “D6” law. The resistivity of the CoFeNi thick films increased by decreasing the grain size which is due to the scattering of the charge carriers. The increase in the applied current density results in the gradual substitution of the iron atoms in CoFeNi films by nickel atoms leading to a reduction in saturation magnetization.

The isothermal oxidation behavior of multi-component high entropy alloys (HEAs), namely AlCuCrFeMn, AlCuCrFeMnW0.05, AlCuCrFeMnW0.1, and AlCuCrFeMnW0.5, was investigated and the behavior of the oxide layer was analyzed. All four HEAs were synthesized via mechanical alloying (MA) and consolidated by spark plasma sintering (SPS). The samples were oxidized in the air atmosphere at a temperature of 500 °C for 50 h. Based on the thermogravimetric result, the oxidation rate of the materials decreased with the increase of W content, and the values of parabolic constants were on a level similar to those observed in Ni–Al superalloys. However, higher content of W improves the continuity and internal position of the WO3 scale, which leads to increased oxidation resistance. Throughout the oxidation process, the composition of the phases of all materials changed significantly. The triple-thick oxide layer formed of Al2O3, Cr2O3, and WO3, developed in HEAs, has been carefully studied using the XPS technique.

In this article, we present a new Co2FeSi glass-coated microwire obtained by Taylor-Ulitovsky technique with nanocrystalline structure consisting of a mixture of bcc phase (lattice parameter, a = 5.640 Å, crystalline grain size, Dg = 17.8 nm) in as-prepared sample. The annealing temperature was fixed at 873 K, and the annealing time was 1 and 6 h. The annealing resulted in a significant increase of such nano-grains up to (31.6 nm). Perfect square hysteresis loops have been observed in all annealed samples at a wide temperature range (55–400 K) that are not seen in the as prepared sample. The thermal magnetic behavior for the annealed samples shows dramatic magnetic behavior at low temperature. Large irreversibility magnetic behavior with a blocking temperature (Tb = 150 K) has been observed for annealed sample for 1 h. Critical temperatures of 155 K and 105 K have been detected for annealed samples for 1 h and 6 h, respectively, where the behavior of M−H loops, coercivity and remanence changed. Below the critical point the M−H shows wasp-waisted, multistep magnetic behavior and complex magnetic reversal mechanism is supposed. The anomalous magnetic behavior is due to the coexistence of the ordered and disordered phases induced by annealing conditions below the room temperature. The difference in the magnetization behaviour, remanence, and coercivity values for Co2FeSi glass-coated microwires samples indicates the influence of internal stresses created by the presence of the glass coating. These finding opens the door to design spintronic devices based on the magnetization switching.

Nanoindentation creep behavior and underlying mechanisms of nanocrystalline (NC) Ni and NC Ni-20 wt% Fe (Ni-Fe) alloy were investigated at room temperature by a new testing method. The continuous creep strain rate versus creep stress data and hence the continuous apparent activation volume versus creep stress data in the entire holding stage on each single sample were achieved under a loading rate-controlled mode by a cooperative use of the continuous stiffness measurement (CSM) technique. Furthermore, the dependence of the apparent activation volume on the creep stress was interpreted by performing a theoretical analysis. Based on the above experimental and theoretical results and the high-resolution transmission electron microscope observation of the microstructures, the effects of the loading rate and stacking fault energy on the nanoindentation creep behavior of NC Ni and NC Ni-Fe alloy and the underlying mechanisms were analyzed. It was demonstrated that NC Ni-Fe alloy shows higher creep resistance in the transient regime, but lower creep resistance in the steady-state regime compared to NC Ni. The contact stiffness data obtained by the CSM technique in a strain rate-controlled mode can be used to determine the creep stress data from the creep displacement data obtained in a loading rate-controlled mode.

In order to investigate the effect of grain boundaries on the mechanical response in the micrometer and submicrometer levels, complementary experiments and molecular dynamics simulations were conducted on a model bcc metal, tantalum. Microscale pillar experiments (diameters of 1 and 2 μm) with a grain size of ~100–200 nm revealed a mechanical response characterized by a yield stress of ~1500 MPa. The hardening of the structure is reflected in the increase in the flow stress to 1700 MPa at a strain of ~0.35. Molecular dynamics simulations were conducted for nanocrystalline tantalum with grain sizes in the range of 20–50 nm and pillar diameters in the same range. The yield stress was approximately 6000 MPa for all specimens and the maximum of the stress–strain curves occurred at a strain of 0.07. Beyond that strain, the material softened because of its inability to store dislocations. The experimental results did not show a significant size dependence of yield stress on pillar diameter (equal to 1 and 2 um), which is attributed to the high ratio between pillar diameter and grain size (~10–20). This behavior is quite different from that in monocrystalline specimens where dislocation ‘starvation’ leads to a significant size dependence of strength. The ultrafine grains exhibit clear ‘pancaking’ upon being plastically deformed, with an increase in dislocation density. The plastic deformation is much more localized for the single crystals than for the nanocrystalline specimens, an observation made in both modeling and experiments. In the molecular dynamics simulations, the ratio of pillar diameter (20–50 nm) to grain size was in the range 0.2–2, and a much greater dependence of yield stress to pillar diameter was observed. A critical result from this work is the demonstration that the important parameter in establishing the overall deformation is the ratio between the grain size and pillar diameter; it governs the deformation mode, as well as surface sources and sinks, which are only important when the grain size is of the same order as the pillar diameter.

In this study, a preparation route of Co–Cu alloys with soft magnetic properties by high-pressure torsion deformation is introduced. Nanocrystalline, supersaturated single-phase microstructures are obtained after deformation of Co–Cu alloys, which are prepared from an initial powder mixture with Co-contents above 70 wt.%. Isochronal annealing treatments up to 400 °C further reveal a remarkable microstructural stability. Only at 600 °C, the supersaturated phase decomposes into two fcc-phases. The coercivity, measured by SQUID as a function of annealing temperature, remains significantly below the value for bulk-Co in all states investigated. In order to understand the measured magnetic properties in detail, a quantitative analysis of the magnetic microstructure is carried out by magnetic force microscopy and correlated to the observed changes in coercivity. Our results show that the rising coercivity can be explained by a magnetic hardening effect occurring in context with spinodal decomposition.

A novel titanium-based alloy with low density, high hardness, and corrosion resistance was manufactured and characterized in this paper. The Ti60Ni9Fe8Co8Si15 alloy was created from its elemental components and subjected to further manufacturing. To reach a homogeneous phase, the samples were broken into small pieces and were repeatedly re-melted with arc-melting. This base alloy was further processed to manufacture an amorphous/nanocrystalline material by ball milling followed by high-pressure torsion (HPT). For subsequent characterization, X-ray diffraction (XRD), pycnometer densitometry, scanning electron microscopy (SEM) with X-ray energy dispersive spectroscopy (EDS), and hardness measurements were performed. X-ray diffractometry confirmed the formation of a amorphous/nanocrystalline structure, as most of the characteristic peaks related to the crystalline phase disappeared or flattened after ball milling. In accordance, the hardness of the manufactured samples increased by nearly 50 HV compared to the base alloy. The density of the final alloy was measured to be 4.125 g/cm3, with a hardness of 762 ± 39 HV, which confirms that an exceptionally light and, at the same time, hard material was manufactured. In order to distinguish the effects of elemental composition and manufacturing on the measured properties of our alloy, a similar Ti-based alloy with a different elemental composition (Ti47Cu40Zr7.5Fe2.5Sn2Si1) was also prepared with the same proposed manufacturing process. This reference composition resulted in significantly lower hardness (489 ± 31 HV) at a significantly higher density (5.767 g/cm3).

W-Cu composites are commonly used as heat-sinks or high-performance switches in power electronics. To enhance their mechanical properties and mutually their usability, grain refinement of the initially coarse-grained microstructure was realized using high–pressure torsion. This leads to different microstructural conditions, exhibiting fine-, ultrafine-grained or nanocrystalline microstructures. Scanning as well as transmission electron microscopy was performed to analyze the respective grain size and microstructures. The hardness and Young’s modulus of the deformed specimens were quantified by nanoindentation testing. Furthermore, X–ray diffraction indicated a decreased grain size and changed lattice spacings upon increasing the deformation ratio. The deformed specimens were tested for their fracture behaviour by continuous stiffness measurements during in-situ microcantilever bending experiments. Here, mean J–integral values of 288 ± 38 J/m2 and 402 ± 89 J/m2 were determined for the 5 and 50 times turned specimens, respectively. The combination of different characterization methods applied on a W–Cu composite allows to identify both, beneficial and unfavourable microstructural components regarding the fracture properties.

In this study, the thermal stability of Ni–Nb–Ti metallic glasses was investigated under isothermal and non-isothermal conditions. The effectiveness of NiTi phases, one of the nanosized crystallized phases, as grain refiners for Al–Cu alloys was also investigated from a crystallographic point of view using the edge-to-edge matching (E2EM) model. Thermal analysis showed that NiTi phases promote solidification of α-Al, and these nanocrystalline phases also promote an Al–Cu eutectic reaction and inhibit the growth of eutectic phases. A significant refining effect of α-Al grains from 402.7 μm to 69.1 μm was achieved with 0.05 wt.% nanocrystalline phases. Simultaneously, values for yield strength, ultimate tensile strength and fracture strain of inoculated Al–Cu alloys were increased by 18%, 13% and 78% to 363.2 MPa, 534.3 MPa and 11.92%, respectively, when compared with those of uninoculated Al–Cu alloys. Strengthening mechanisms of Al–Cu alloys manipulated by the nanocrystalline phases are grain boundary strengthening and precipitation strengthening.

The existed synthesis methods for producing high microhardness nanostructured metal materials (NMMs) are usually at the cost of reducing the tensile strength and introducing heterogeneous elements, thus making forming ultrahigh strength ultrapure NMMs significantly challengeable. We unprecedentedly produced ultrapure (99.9997%) nickel deposits simultaneously with an ultrahigh strength and mirror-like surfaces as well as an appreciably high ductility by using our proposed ultrafine anode scanning electrodeposition (UAS-ECD). Distinctively, the UAS-ECD is a speed-dependent localized scanning electrodeposition rather than a commonly-used current-dependent electrodeposition. Therefore, the UAS-ECD can create NMMs at extremely high local current densities and with no additives. This makes it achievable to generate ultrahigh strength ultrapure NMMs with microhardness of 656 HV and tensile strength of 664 MPa (fracture elongation, 8.5%), which are respectively 29% and 30% higher than those reported in the literature. Further surprisingly, the samples’ tensile strength has only an approximately 1% reduction after being annealed. This is attributed to minimum impurities introduction and evenly distributed ultrafine grains formed. In addition, UAS-ECD is able to produce grain-varying deposits just by adjusting the anode’s scanning speed, conveniently achieving 65 wt%-95 wt% nano-& micro-sized grains composite NMMs. This work provides a novel strategy for synthesizing ultrahigh strength ultrapure NMMs.

A deep eutectic solvent (DES) is a eutectic system consisting of hydrogen bond donor and acceptor has been suggested as a promising formulation strategy for poorly soluble drugs. A DES consisting of choline chloride and levulinic acid in a 1:2 molar ratio was used to formulate a liquid solution of the model drug aprepitant. This formulation was tested in vitro (drug release and permeability) and in vivo (rat model) and compared with the performance of amorphous aprepitant and the commercial aprepitant nanocrystalline formulation. In this study a DES formulation is compared for the first time directly to other established enabling formulations. The in vitro drug release study demonstrated that the DES formulation and the amorphous form both were able to induce an apparent supersaturation followed by subsequent drug precipitation. To mitigate the risk of precipitation, HPMC was predissolved in the dissolution medium, which successfully reduced the degree of precipitation. In line with the results from the release study, an in vitro permeation study showed superior permeation of the drug from the DES formulation and from the amorphous form compared to the nanocrystalline formulation. However, the promising in vitro findings could not be directly translated into an increased in vivo performance in rats compared to the nanocrystalline formulation. Whilst the DES formulation (34 ± 4%) showed a higher oral bioavailability compared to amorphous aprepitant (20 ± 4%), it was on par with the oral bioavailability obtained from the nanocrystalline formulation (36 ± 2%).

Molecular dynamics (MD) simulations of creep generally face the problem that the creep most often evolves on time scales hard to capture with MD due to their typically short time step size. Consequently, MD studies of creep often use unrealistically high temperatures and stresses and simplified atomistic models to make creep-like processes happen on computationally accessible time scales. Apparently, this compromises the physical reliability of such studies. To alleviate this problem, we designed an MD model of titanium aluminide (TiAl) with a microstructure matching at least many of the key parameters of experimentally observed microstructures. We applied this MD model with stresses much lower than the ones used in most previous creep studies (well below yield stress) and in the temperature range 0.55TM-0.7TM, with melting temperature TM. Compared to typical previous MD studies, this much more realistic setup produces creep rates more than three orders of magnitude smaller and thus much closer to reality. We identified the driving mechanisms of primary creep on the nanosecond scale that agree very well with recent experimental observations, thus contributing towards the overarching goal of bridging the gap between atomistic creep simulations and continuum-scale creep simulations for engineering applications.

Polycrystalline magnesium aluminate spinel (MgAl2O4) is one of the most important structural ceramics with proven applications as a hard, temperature resistant material and as a high strength optical window. Here, we present a study of the reaction densification of nano-sized MgO (nMgO) and metastable γ-Al2O3 to form MgAl2O4 instead of the typical stable α-Al2O3 and micrometer-sized MgO (μMgO). We show that the reaction kinetics of γ-Al2O3 – nMgO are substantially faster and occur at significantly lower temperatures compared to previous kinetic studies of α-Al2O3 – μMgO, revealing that they are not controlled by the same mechanism. We propose that the enhanced reaction rates are caused by short diffusion distances, faster diffusion through defected γ-Al2O3 as well as similarities in crystal structure between products and reactants. Lastly, we show that understanding the reaction and densification kinetics of this reactant combination can be leveraged to produce a wide range of microstructures leading to nanoporous high temperature energy absorbing materials and highly dense optically transparent spinel.

Cryogenic mechanical alloying is a viable method to synthesize nanostructured alloys that exhibit improved mechanical properties without using highly contaminating, process control agents. However, cryogenically milled alloys still contain impurities introduced from the milling media and cryogenic fluid, and it is unclear how these milling parameters can be tailored to optimize alloy design. Here, milling media and cryogenic fluid were systematically varied and studied to quantify differences in impurity concentrations, microstructural evolution, and microhardness. Four derivatives of a Mo25Nb25Ta25W25 high entropy alloy were mechanically alloyed using tool steel or tungsten carbide milling media with either liquid N2 or Ar. Alloys were annealed for 100 h at 1000 °C or 1200 °C. Aberration-corrected scanning transmission electron microscopy (STEM) was primarily used to characterize as-milled and annealed specimens, and Vicker’s microindentation was used to compare hardness. Depending on the milling parameters, total impurity concentrations varied between 12 and 44 at.%, different impurity nitrides or carbides were identified in annealed specimens, and differences in hardness of up to 5 GPa were measured amongst the alloys. Overall, milling with LN2 led to the precipitation of ultrahard nitride phases that when combined with optimized heat treatments, improved the hardness beyond 17 GPa.

Sustainable recycling approaches are emerging topics for environmental safety of manufacturing technologies. Chips generated in high–speed machining (HSM) of as-quenched steels have a potential re-use for more sustainable and cost-efficient manufacturing routes, such as powder production from chip milling for additive manufacturing (AM). The objective of this study was to characterise tool-steel chips generated by HSM of an AISI-SAE H13 as-quenched workpiece and evaluate their potential use for powder production, as an alternative process to atomisation. Microhardness tests reveal that this type of waste has a suitable hardness for milling, which could be attributed to its microstructure. Chips were also analysed by X-ray diffraction, scanning and transmission electron microscopies, and transmission electron backscattering diffraction (t-EBSD) mapping. The microstructure of the areas adjacent to the adiabatic shear band (ASB), where intense material flow takes place, consists of thin martensite laths with high dislocation density and low angle grain boundaries (LAGB) or sub-grain regions. ASB consists of ultrafine and nanocrystalline grains. The results provide new insight on the grain-refining mechanism assisted by progressive martensite lath subdivision into small and near-equiaxed grains, as a direct result of intense strain accumulation and recrystallisation, endorsing HSM tool-steel chips as superior (nanocrystalline) and low-cost raw material for powder production.

FeCrAl alloys have been proposed as nuclear fuel cladding materials in hope of offering great potential in accident tolerance for light water reactors. However, only a limited amount of data has been published on their creep properties. This work aims to provide an atomic-scale insight into the creep behavior and deformation mechanism for nanocrystalline FeCrAl alloys, using molecular dynamics method. Both primary and steady state creeps are observed in all creep curves, and tertiary creep occurs at stresses above 2.5 GPa in the time period of the present simulation. As stress increases, the creep mechanism transits from Coble creep to grain boundary sliding, and then to the synergy of grain boundary sliding and dislocation creep. The turning points are about 0.8 GPa and 1.8 GPa, respectively. The dislocation motions are controlled by viscous gliding at low temperature, and then by climbing when temperature exceeds 1000 K. Moreover, the grain size and alloy composition have little impact on the transition of creep mechanism within the present research scope. The proposed creep mechanisms are further analyzed not only from the comparison between activation energies for diffusion and creep, but also from the representative atomic snapshots.

We present a novel application of a nanocrystalline boron-doped diamond electrode (B-NCDE) for the construction of an electrochemical DNA biosensor based on double-stranded DNA (dsDNA) for various bioanalytical applications. Surface characterization of the transducer surface (prior and after the fabrication of negatively charged O-terminated surface - O-B-NCDE) was performed by scanning electron microscopy (SEM), Raman spectroscopy, and linear sweep voltammetry (LSV) that was further used for the voltammetric determination, scan rate dependence investigation, and repeatability examination of dsDNA electrochemical oxidation at the O-B-NCDE. The fabrication of a dsDNA/O-B-NCDE biosensor via electrostatic adsorption of dsDNA involved a thorough optimization process of deposition potential (E dep ), deposition time (t dep ), and optimal saturation concentration (c g(satur) ) with optimal values of 0.3 V, 3 min, and 10 mg/mL. The bioanalytical applicability of the fabricated dsDNA/O-B-NCDE biosensor was verified by examining the nature of the interaction between dsDNA and five selected DNA intercalators - namely thioridazine hydrochloride (TR), trimipramine maleate (TRIM), levomepromazine maleate (LEV), imipramine hydrochloride (IMI), and prochlorperazine maleate (PER) - where intercalation was proven for all of the five tested compounds. Moreover, the proposed novel bioanalytical test offers the possibility to selectively distinguish between the phenothiazine representatives (TR, LEV, and PER) and representatives of tricyclic antidepressants group (TRIM and IMI)., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

High-entropy oxides (HEOs) stabilize multiple cations in a single solid solution phase, providing a new opportunity for property engineering in almost infinite compositional space. The structural stability and tunability of HEO are of great interest and importance but has not been well understood, especially under pressure. Here, we studied the structure evolution of a rock salt phase (Co0.2Cu0.2Mg0.2Ni0.2Zn0.2)O HEO using in situ synchrotron X-ray diffraction, pair distribution function, Raman spectroscopy up to ~43 GPa, and ex situ transmission electron microscopy, a pressure-induced reversible rock salt to highly distorted cubic phase transition was observed. These results suggest highly tunable lattice distortion in HEOs under pressure, which could promote the fundamental understanding and also guide applications of HEOs.

Nanocrystalline magnesium oxide was prepared by the sol–gel method from magnesium methoxide and characterized by Fourier transform infrared spectroscopy, thermal analysis, X-ray powder diffraction and transmission electron microscopy. Sol–gel derived nanocrystalline magnesium oxide along with a commercial nanocrystalline magnesium oxide was used as adsorbents to study the adsorption of two common, organophosphorous pesticides, diethoxy-[(2-isopropyl-6-methyl-4-pyrimidinyl)oxy]-thioxophosphorane (diazinon) and dimethoxy-(3-methyl-4-nitrophenoxy)-thioxophosphorane (fenitrothion). Adsorption of diazinon and fenitrothion on the sol–gel derived, and commercial nanocrystalline magnesium oxides was studied using UV–vis, FT-IR and 31P NMR spectroscopies. The effect of hydroxyl groups on edge/corner and flat panel of magnesium oxide in adsorption of diazinon and fenitrothion was investigated. The results showed that the adsorption of diazinon on the sol–gel derived nanocrystalline magnesium oxide is destructive whereas on commercial one is non-destructive. Commercial nanocrystalline magnesium oxide showed higher activity in the adsorption of fenitrothion than the sol–gel derived, and adsorptions on both nanocrystalline magnesium oxides are destructive.

In this study, nano crystalline vanadium carbide was synthesized by mechanical alloying method. V2O5, C and Mg powders were placed in a planetary ball mill and sampled after different milling times. XRD and FESEM were used for characterization of synthesized powder. Studies showed that crystalline V8C7 has been synthesized by 24 h milling and subsequently heat treatment at 800 °C. It was concluded that the V8C7 crystallites were nano sized and the lattice parameter deviated slightly from the standard size. Furthermore, milling led to increase in strain and decrease of vanadium carbide particle size.

The objective of the present work is to obtain ceramic materials of stabilized zirconia (Ca,Mg-PSZ) nanocrystalline by means of high-energy milling, starting from monoclinic zirconia and a raw material of high purity and low cost like the dolomite (CaMg(CO3)2). The high-energy milling of mixtures, especially in those that at least one of the components contains a carbonate or hidroxyl group or it is carried out in presence of water, it has become an alternative method to obtain nanocrystalline materials. In this work using high-energy ball-milling, nanopartícles of monoclinic zirconia and dolomite have been obtained with a average size of crystallite about 20 ± 5 nm. Starting from these, dense stabilized zirconia (Ca,Mg-PSZ) nanocrystalline materials have been obtained (98 % ρ/ρt) for sintering at 1200º-1300ºC during 18-48 minutes.El objetivo del presente trabajo es la obtención de materiales cerámicos de circona estabilizada (Ca,Mg-PSZ) nanocristalina mediante molienda de alta energía, a partir de circona monoclínica comercial y una materia prima de alta pureza y bajo coste como es la dolomita (CaMg(CO3)2). La molienda de alta energía de mezclas, especialmente en la que al menos uno de los componentes contenga un grupo carbonato, hidroxilo o se lleve a cabo en presencia de agua, se ha convertido en un método alternativo para obtener materiales nanocristalinos. En este trabajo, mediante un molino de bolas de alta energía se han obtenido nanopartículas de circona monoclínica y dolomita con un tamaño medio de cristalito de 20 ± 5 nm. A partir de estas se han preparado materiales cerámicos densos (98 % ρ/ρt) de circona (Ca, Mg-PSZ) nanocristalina por sinterización a 1200º y 1300ºC durante 18 y 48 minutos.