The fracture toughness of 617 Ni-based weld metal (WM) under different elevated temperatures was tested with a novel method and its fracture mechanism was investigated in this paper. It was found that the fracture toughness of WM was lower than that of base metal (BM) at the same temperature, which was mainly due to the coarse columnar structure, differences in misorientation, and precipitated phases. For both BM and WM, the fracture toughness was lower at elevated temperature due to decreased strength. Much more micro-voids caused by Ti(C, N) and M23C6 inside grains of BM could be observed adjacent to the crack path, which accounted for the dramatically decreased fracture toughness of BM at elevated temperature. In comparison, fewer micro-voids could be observed in WM due to the lack of those second particles. As a result, the J0.2 value and propagation path morphology both showed that the WM had more stable microstructure even though possessing lower toughness.

Theoretical calculations and experimental observations show MoTe2 is a type II Weyl semimetal, along with many members of transition metal dichalcogenides family. We have grown highly crystalline large-area MoTe2 thin films on Si/SiO2 substrates by chemical vapor deposition. Very uniform, continuous, and smooth films were obtained as confirmed by scanning electron microscopy and atomic force microscopy analyses. Measurements of the temperature dependence of longitudinal resistivity and current–voltage characteristics at different temperature are discussed. Unsaturated, positive quadratic magnetoresistance of the as-grown thin films has been observed from 10 to 200 K. Hall resistivity measurements confirm the majority charge carriers are hole.

Magnetic field-assisted freeze-casting of porous alumina structures is reported. Different freeze-casting parameters were investigated and include the composition of the original slurry (Fe3O4 and PVA content) and the control of temperature during the free casting process. The optimum content of the additives in the slurry were 3 and 6 wt% for PVA and Fe3O4, respectively. These conditions provided the most unidirectional porous structures throughout the length of the sample. The sintering temperature was maintained at 1500 °C for 3 h. The application of a vertical magnetic field (parallel to ice growth direction) with using a cooling rate mode technique was found to enhance the homogeneity of the porous structure across the sample. The current study suggests that magnetic field-assisted freeze-casting is a viable method to create highly anisotropic porous ceramic structures.

Microencapsulation of functioning cells for transplantation therapies is particularly promising, but the cells must retain their proper physiology and viability after being encapsulated. K-562 cells are multipotential and exhibit erythroid, megakaryocytic, or granulocytic properties that can be exploited by using an array of physiologically differentiating factors. The potential for cell differentiation makes it attractive the use of K-562 cells as functional model to the assessment of the effects of encapsulation on cell viability and physiology. Thus, alginate and hybrid alginate matrices were produced by extrusion technique for K-562 cell encapsulation. The produced systems were composed of bare alginate (1–3 wt%) and alginate in combination with chitosan or silica. The resulting materials were characterized by dynamic laser scattering, zeta potential measurements, small-angle X-ray scattering, and Fourier transform infrared spectroscopy. To assess viability, the encapsulated cells were subjected to the Trypan blue exclusion technique and NAD(P)H-dependent oxidoreductase (MTT) assays; hemin-induced erythroid differentiation capacity was also evaluated. The encapsulated alginate-based systems were shown to be monomodal and bimodal, depending on the nature of the capsule, with mean sizes in the range between 414 and 4.129 nm. Encapsulated cells exhibited viability ratios compatible with their use for prolonged cell cultures. Erythroid differentiation occurred in the range between 39 and 44%. The present results allow the consideration of the viability of therapeutic cells encapsulated in both bare alginate and in hybrid matrices.

Hydrogen lithography has been used to template phosphine-based surface chemistry to fabricate atomic-scale devices, a process we abbreviate as atomic precision advanced manufacturing (APAM). Here, we use mid-infrared variable angle spectroscopic ellipsometry (IR-VASE) to characterize single-nanometer thickness phosphorus dopant layers (δ-layers) in silicon made using APAM compatible processes. A large Drude response is directly attributable to the δ-layer and can be used for nondestructive monitoring of the condition of the APAM layer when integrating additional processing steps. The carrier density and mobility extracted from our room temperature IR-VASE measurements are consistent with cryogenic magneto-transport measurements, showing that APAM δ-layers function at room temperature. Finally, the permittivity extracted from these measurements shows that the doping in the APAM δ-layers is so large that their low-frequency in-plane response is reminiscent of a silicide. However, there is no indication of a plasma resonance, likely due to reduced dimensionality and/or low scattering lifetime.

A scalable preparation of in situ N-doped disordered carbon nanosheets from reduced melamine formaldehyde resin is demonstrated. For the first time, nanosheets prepared by such a process have been tested as anodes for lithium ion and sodium ion batteries. Li-ion battery half-cell delivers a reversible capacity of about 500 mA h/g at a specific current of 100 mA/g, and also a capacity of 250 mA h/g at a specific current of 500 mA/g is retained after 600 cycles. For Na-ion batteries, a reasonable capacity of about 150 mA h/g is recorded at a specific current of 50 mA/g, and a capacity of 120 mA h/g at a specific current of 250 mA/g is retained after 350 cycles. The sloppy low-voltage profile obtained for both the lithium ion and sodium ion cells corresponds to the nanosheet anodes, being soft carbon-like, thereby demonstrating superior cycling stability and safety by avoiding metal plating and dendrite formation.

The stress and hence strain fields in a cantilever deforming as per power-law creep vary across the length and thickness of the sample, which allow obtaining multiple stress–strain pairs from a single test. Here, a high-throughput method is described to quantify the primary-cum-steady-state creep response of materials by testing a single cantilever sample in bending and mapping strain fields using digital image correlation. The method is based on the existence of stress invariant points in a cantilever, where the value of stress does not change during creep. It is demonstrated that strain evolution throughout primary and steady-state stages at these points is identical to the creep response obtained under uniaxial tests. Furthermore, the gained insights were exploited to obtain various parameters of a power-law type primary-cum-steady-state creep equation by testing only one cantilever sample. The developed method allows obtaining uniaxial creep curves at multiple stresses by testing a single cantilever, thereby reducing the time and number of samples required to understand the creep behavior of a material. The method has been validated by performing bending tests on Al and comparing the results with those of corresponding uniaxial tests.

The adoption of selective laser melting (SLM) for fabrication of porous titanium has resulted in many new investigations into the complex design parameters associated with porous architecture of high spatial resolution. The development of meta-materials has included research into the effects of unit cell architecture (strut versus sheet), porosity, pore size, and other factors on the performance of metallic scaffolds. The current study examined the interactive effects of varying the gyroid sheet unit cell size and overall specimen size on the compressive behavior of Ti–6Al–4V ELI porous scaffolds manufactured via SLM. The increasing unit cell size relative to specimen geometry was found to decrease the compressive strength and stiffness of the overall structure and shift the material fracture mode. The understanding of the relationship between unit cell size and specimen geometry can be used to optimize mechanical properties of implants with constrained volumes and pore/wall size requirements to optimize properties of porous titanium implants for strength and osseointegration.

We here design and fabricate a new kind of copper matrix composites, where titanium carbide nanoparticles are in situ incorporated into and embedded within the copper matrix, by virtue of laser powder-bed-fusion (L-PBF) process. We made a multiscale examination on the microstructures of the additively manufactured samples, unraveling that there are many unusual microstructural features, including grain refinement, the existence of high-density dislocations, and supersaturation of titanium solute atoms in the as-printed metal matrix composites. These unique microstructural features are mainly interpreted by the intense thermal history and the rapid solidification nature of the L-PBF process. The resultant composites then integrate the most important four strengthening mechanisms in metals: grain boundary strengthening, dislocation strengthening, solid solution strengthening, and second-phase strengthening, rendering this new kind of copper matrix composites a remarkably high yield strength (~490 MPa) and large uniform elongation (~12%), surpassing many high-performance copper matrix composites and copper alloys.

Titanium and its alloys are probably the most suitable materials for selective laser melting (SLM) additive manufacturing to process. However, the high cost of raw powder materials limits the industrial application of as-printed Ti products. In this study, we have formulated a cost-affordable Ti–TiB composite powder for SLM, to simultaneously achieve excellent mechanical performance and cost effectiveness. The optimization of the processing parameters will be shown to lead to high relative density (99.3%) for the as-printed Ti–TiB composites containing (0.5, 1, and 2 wt%) TiB2. Furthermore, by incorporating TiB2, the as-printed composites exhibit much improved fracture strength (up to 1813 MPa) and microhardness (up to 412 HV), among which the Ti–0.5 wt% TiB2 has demonstrated a great combination of strength (1007 and 1646 MPa as yield and fracture strengths, respectively) and tensile ductility (~8%). The solidification pathway for the Ti–TiB composite during SLM has been investigated, and the underlying mechanism for achieving high yield strength is discussed based on existing models for shear-lag strengthening, grain refinement, and dispersion strengthening.

Nanostructures are considered to have great potential and are widely used in energy storage and sensing devices, and atomic layer deposition (ALD) is of great help for better nanostructure fabrications. ALD can help to preserve the original properties of materials, and, meanwhile, the excellent film quality, nanoscale precise thickness control, and high conformality also play important role in fabrication process. To enhance the performance of energy storage and sensor devices, ALD has been used in directly fabricating active nanostructures, depositing protective passivation layers, etc. ALD is a convenient technique which has been widely engaged in energy-related fields including electrochemical conversion and storage, as well as in sensor and biosensors. The related research interest is increasing significantly. In this review, we summarize some of the latest works on ALD for batteries, supercapacitors, and sensors, and demonstrate the benefits of ALD comprehensively. In these devices, different materials are deposited by ALD under different conditions to achieve better battery performance, higher supercapacitor capacitance, and higher sensitivity. This review fully presents the strengths of ALD and its application in energy storage and sensing devices and proposes the future prospects for this rapidly developing technology.

A detailed electron backscatter diffraction (EBSD) characterization was utilized to investigate abnormal grain growth behavior of nanocrystalline (NC) Au films constrained by a flexible substrate under cyclic loading. Abnormally grown grains (AGGs) in front of about 15 fatigue cracks were picked out to investigate the grain reorientation behavior during abnormal grain growth in the fatigue crack tip in the cyclically deformed thin films. It shows that the AGGs exhibited 〈001〉 orientation along the loading direction, whereas grains grown far away from fatigue cracks had no significant texture change. The cyclic cumulative shear strain was found to play a key role in grain reorientation. A lattice rotation model was proposed to elucidate the grain reorientation mechanism during abnormal grain growth. Such grain reorientation behavior of NC metals was found to provide an intrinsic resistance of the NC metals to fatigue damage.

This study investigates the effect of C on the deformation mechanisms in Fe–C alloys by molecular dynamics simulations. In uniaxial tensile simulations, the face-centered-cubic (fcc) structures of Fe–C alloys undergo the following deformation processes: (i) fcc→body-centered-cubic (bcc) martensitic transformation, (ii) deformation of bcc phase, and (iii) bcc→hcp martensitic transformation, which are significantly influenced by the C concentration. For the low C concentrations (0–0.8 wt%) fcc phase, the fcc→bcc phase transformation accords a two-stage shear transformation mechanism based on the Bain model, the deformation mechanism of the bcc phase is the first migration of twinning structures and then elastic deformation, and the bcc→hcp phase transformation follows Burgers relations resulting from the shear of the bcc close-packed layers. However, for the fcc phase with high C concentrations (1.0–2.0 wt%), the fcc→bcc phase transformation follows a localized Bain transformation mechanism impeded by the C atoms, the bcc phase only experiences elastic deformation, and the bcc→hcp phase transformation also conforms to Burgers relations but become localized due to the addition of more C atoms. Because of the different phase transformation mechanisms between the high C and low C supercells, the dislocation generation mechanism is also different.

Porous metals represent a class of materials where the interplay of ligament length, width, node structure, and local geometry/curvature offers a rich parameter space for the study of critical length scales on mechanical behavior. Colloidal crystal templating of three-dimensionally ordered macroporous (3DOM, i.e., inverse opal) tungsten provides a unique structure to investigate the mechanical behavior at small length scales across the brittle–ductile transition. Micropillar compression tests show failure at 50 MPa contact pressure at 30 °C, implying a ligament yield strength of approximately 6.1 GPa for a structure with 5% relative density. In situ SEM frustum indentation tests with in-plane strain maps perpendicular to loading indicate local compressive strains of approximately 2% at failure at 30 °C. Increased sustained contact pressure is observed at 225 °C, although large (20%) nonlocal strains appear at 125 °C. The elevated-temperature mechanical performance is limited by cracks that initiate on planes of greatest shear under the indenter.

Localized deformation, including that by the deformation-induced shearing martensitic phase transformation, is responsible for hardening and embrittlement in irradiated face-centered cubic alloys. These localized deformation processes can have profound consequences on the mechanical integrity of common structural metals used in extreme radiation environments such as nuclear reactors. This article aims to review and understand exactly how irradiation affects the martensitic phase transformation in face-centered cubic alloys, with an emphasis on austenitic stainless steel, given its ubiquity in the archival literature. The influence of irradiation on stacking fault energy and subsequent implications on the phase transformation are discussed. Mechanisms by which irradiation-induced microstructures enhance the phase transformation are also described, including the surface energy contribution of irradiation-induced cavities (i.e., voids and bubbles) toward the critical martensite nucleation energy, and partial dislocation–cavity interactions. A deformation mechanism map illustrates how irradiation-induced cavities can modulate the martensitic transformation pathway.

In recent years, intracranial thrombectomy stent has been an important method to treat ischemic stroke caused by acute thrombosis. In this paper, a new intracranial thrombectomy stent with a fish scale-like structure was designed and its mechanical properties were studied by a finite element method. The porosity of all stents was more than 80%. The space occupation ratio (SOR) of the stents increased linearly with the increase of strut thickness, while the strut width had little effect on SOR. The maximum equivalent stress and strain, the directional deformation and overall radial load of the stent decreased with the increase of strut thickness, however, the strut width has little impact on these parameters. The stents with 0.2 mm strut width and the thickness of 0.15 and 0.20 mm had better radial load performance, and the stent with 0.2 mm strut width and 0.15 mm strut thickness had better contact performance with the vessel wall and displayed better flexibility. Therefore, the present study provides a theoretical basis for the design of new intracranial thrombectomy stent.

Grain refinement has been applied to enhance the materials strength for miniaturization and lightweight design of nuclear equipment. It is critically important to investigate the low-cycle fatigue (LCF) properties of grain refined 316LN austenitic stainless steels for structural design and safety assessment. In the present work, a series of fine-grained (FG) 316LN steels were produced by thermo-mechanical processes. The LCF properties were studied under a fully reversed strain-controlled mode at room temperature. Results show that FG 316LN steels demonstrate good balance of high strength and high ductility. However, a slight loss of ductility in FG 316LN steel induces a significant deterioration of LCF life. The rapid energy dissipation in FG 316LN steels leads to the reduction of their LCF life. Dislocations develop rapidly in the first stage of cycles, which induces the initial cyclic hardening. The dislocations rearrange to form dislocations cell structure resulting in cyclic softening in the subsequent cyclic deformation. Strain-induced martensite transformation appears in FG 316LN stainless steels at high strain amplitude (Δε/2 = 0.8%), which leads to the secondary cyclic hardening. Moreover, a modified LCF life prediction model for grain refined metals predicts the LCF life of FG 316LN steels well.

This study revealed that the mass ratio of large anisometric particles (platelets) to ultrafine, equiaxed particles strongly influences dynamic and quasistatic compressive response and the process of damage evolution in ice-templated alumina materials. The improved sinterability between particles of significantly dissimilar size and morphology enabled the utilization of a high mass ratio of the particles in harnessing a markedly enhanced level of strength in highly porous ice-templated ceramics. The high volume fraction of platelets increased lamellar bridge density and resulted in dendritic morphology as opposed to lamellar morphology without platelets. All the materials showed strain rate-sensitivity, where strength increased with strain rate. Materials with highly dendritic morphology exhibited the best performance in terms of maximum strength and energy absorption capacity, and the performance improved from quasistatic to dynamic regime. Direct observation of the process of damage evolution revealed the effects of both strain rate and ratio of platelets to ultrafine particles.

Fullerene dimers have attracted extensive attention due to their unique structures and fascinating properties. Here, fullerene dimer derivatives with four to six carbon atoms in the esters are designed and synthesized. The property differences that caused by the carbon number in the esters of the fullerene dimers are investigated by performing their electrochemical, optical, and photoelectric measurements. As the carbon atom numbers in the esters increase from four to five and six, the absorption intensities increase to 1.6- and 4.4-folds. The intensities of the fluorescence spectra increase to 1.8- and 5.2-folds. Their photocurrent increases to 2- and 7-folds under the irradiation of a 405-nm laser. The LUMO energy levels move downward slightly from −3.89 to −3.90 and −3.92 eV, respectively. Our results indicate that as the carbon number increases, the carbon chain lengths in the ester structures increase, very slight effects produced on the energy levels of the fullerene dimers, but strongly contribute to their chemical activities and thus the photoelectronic efficiencies.

The addition amount and dispersion of inorganic particles into poly(lactic acid) (PLA) still remain a great difficulty, and in the present study, epoxidized soybean oil was used to improve the compatibility between hydroxyapatite (HA) and PLA via the melt blending method. Scanning electron microscopy shows that HA particles can be well dispersed in the PLA matrix when the addition amount is less than 20% in mass, whereas the agglomeration of HA particles and a discrete phase of PLA could be observed when the amount increases to 30%. Therefore, the maximum amount of HA particles can be achieved for the composite with 20% HA which can be also maintaining the bending strength of 71.6 MPa. The osteoblast cells were used to characterize the biocompatibility of the HA/PLA composite, and the results indicate that the number of cells in per unit volume cultured on the HA/PLA composite is 10% higher than that of the PLA. Based on the improved cell biocompatibility and mechanical strength compared to PLA, the composite of HA/PLA prepared in the present study can be served as a potential candidate for the bone fracture repair.