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Atomically dispersed supported catalysts hold considerable promise as catalytic materials. The ability to employ and stabilize them against aggregation in complex process environments remains a key challenge to the elusive goal of 100% atom utilization in catalysis. Herein, using a Gd-doped ceria support for atomically dispersed surface Pt atoms, we establish how the combined effects of aliovalent doping and oxygen vacancy generation provide dynamic mechanisms that serve to enhance the stability of supported single-atom configurations. Using correlated, in situ X-ray absorption, photoelectron, and vibrational spectroscopy methods for the analysis of samples on the two types of support (with and without Gd doping), we establish that the Pt atoms are located proximal to Gd dopants, forming a speciation that serves to enhance the thermal stability of Pt atoms against aggregation.

The laryngeal tissue is sensitive to the operating force of the surgical instrument in the tissue resection. A large operating force may cause rupture of the vocal cords and surrounding tissues, which affect the patients’ normal voice. However, a small operating force cannot achieve tissue resection. Based on experience, surgeons can estimate the operating force in the process of using a surgical robot. The estimated operating force is usually inaccurate, which may increase the failure rate of surgery. Therefore, a fiber Bragg gratings (FBGs)-based 3-D force sensing sensor for the surgical robot, which consists of two flexible hinges in series is designed. And the force sensing model is constructed through mechanical modeling and temperature decoupling algorithm. The experimental results show that the designed sensor has a resolution of 14.3, 9.7, and 13.8 mN for external forces ${F_{x}},{F_{y}}$ , and ${F_{z}}$ , respectively. The proposed mechanism has good axial and lateral force sensing capability. In the experiment of simulating diseased tissue with the silicone-steel ball, the designed sensor can accurately determine the position of the steel ball, which verifies the effectiveness and feasibility of the designed FBG sensor in force perception.

In this study, nanoindentation technology is utilized to investigate the in situ mechanical behavior of small-sized packaging materials. Rather than the ideal cases with unprestressed materials which have been intensively studies, this paper focuses on the effect of surface stress by prestressing the materials to be indented by a Berkovich indenter. The loading process until the maximum penetration depth is simulated by finite element (FE) models. With elastoplastic materials as described by a power-law model, extensive FE predictions are performed with the wide ranges of Young’s modulus, yield strength and hardening exponent with and without pre-strain. FE results show that with different prestress values, the applied load-penetration depth responses vary in a highly consistent manner. The residual indentation profiles are found to be closely related with the stress state due to the pre-strain values. On the basis of FE simulations, a dimensionless function is therefore derived and a reverse algorithm is proposed to estimate the constitutive parameters and also the surface stress of elastoplastic materials. With one of the most commercialized lead-free solder materials in electronic packaging structures, the proposed reverse algorithm is utilized to estimate the residual stress based on the nanoindentation response of solder samples with different annealing conditions.

High-energy shot peening treatment was applied to improve the Al/steel tungsten inert gas welding–brazing lap joint. The mechanical properties and microstructure evolution of the joint were investigated. Results showed that the mechanical properties of weld were evidently reinforced due to microstructure transformation of joint surface layer. The grain structure in the joint surface layer was distorted and refined. Large compressive residual stress was introduced into the joint surface, and its hardness obviously increased due to strain hardening. When the peening pressure was 0.15 MPa, the tensile shear strength of the joint reached the maximum value (199.6 MPa), which was 16.5% higher than that of the as-welded joint.

Ultrasonic vibration (USV) can optimize the microstructure of the seam and enhance the mechanical properties of the joint; thus, it has been employed to profitably assist Al/steel welding–brazing. The effects of USV on Al/steel welding–brazing joining were investigated. Without the USV treatment, coarse aluminum dendrites, the second phases of Al–Si eutectic and Al3FeSi with large sizes were formed in the joint. Under the USV treatment, the refinement of the aluminum matrix, spheroidization of the Al–Si eutectic, and fragmentation of Al3FeSi were produced, which resulted from the effects of cavitation and acoustic streaming induced by the USV treatment. The maximum value of the tensile shear strength of the ultrasonic–treated joint could be achieved at an optimum ultrasonic vibration power of 0.8 kW, which had ∼30% increment compared with the raw joint, owing to the fine–grained strengthening and dispersing strengthening of Al–Si eutectic and Al3FeSi. The ductile fracture was located in aluminum base metal.

Triple sheets of DP 600/A5052 aluminum alloy/DP 600 steel were joined by means of resistance spot welding in this study. The experimental results showed that the microstructure of fusion zone was lath martensite for DP 600 and column crystals for A5052. Their grains coarsened with increasing distance away from the base metals. The interface zone between DP 600 and A5052 was composed of continuous Fe2Al5 intermetallic compound (IMC) layer and needle-like Fe4Al13 IMC. When welding time prolonged from 8 cycles to 17 cycles, the average length of Fe4Al13 phase adjacent to A5052 shortened from 2.3 μm to 0.89 μm, whereas the thickness of Fe2Al5 IMC layer near DP 600 widened from 1.59 μm to 2.59 μm. The tensile-shear load of DP 600/A5052/DP 600 joints reached a maximum value of 10.796 kN with 14 cycles welding time. Failure during tensile-shear testing occurred along DP 600/A5052 interfaces because Fe2Al5 and Fe4Al13 were brittle phases, but an amount of tearing area was found on the fracture surface.

Severe plastic deformation led to surface grain refinement when treated using high energy shot-peening (HESP); the average grain size was ∼20–30 μm in the top, which was ∼10% of the unpeened ones. The broken Si (Al–Si) particles refined by HESP were important in dislocation multiplication and movement to facilitate the surface modifications. After HESP, residual compressive stress along the hardened layer was induced in the surface of the seam. The highest residual stress along the surface reached ∼200 MPa and the maximum along thickness occurred in sub-surface region. Microhardness values decreased as the distance increased through thickness. At peening pressures of 0.3 and 0.4 MPa, the average tensile shear strength of the joint remained at 195 MPa, which was equivalent to ∼90% that of the base Al alloy. The cracks and pores in the surface were eliminated and a fracture was located in the base Al alloy.

Under tungsten inert gas heating, a sound Ti6Al4V/Al5052 lap joint was obtained with the addition of zinc, which enhanced the spreadability of Al-based filler on Ti6Al4V substrate. Under high heat input, a serrated TiAl3 layer, which was replaced by a TiZn16 + TiAl3 dual sublayer under low heat input, was observed at the brazing interface. TiAl3, Si, and Al–Si eutectic compounds were found in the fusion zone. The microhardness of the fusion zone was higher than those of the heat-affected zone and the Al5052 substrate given the presence of intermetallic compounds. At the optimal welding current of 80 A, the tensile-shear strength of the joint reached 180 MPa, which was equivalent to 80% the tensile-shear strength of the base Al5052 alloy. Failure occurred at the welded seam. The fracture surface was characterized by quasi-cleavage patterns. The effect of zinc on the spreadability of liquid filler metal and the formation of the Ti6Al4V/Al5052 lap joint were discussed.

Nanopore-based DNA sequencing is considered to be a low-cost, high resolution and superfast method. Solid state nanopores, especially MoS2 nanopores, have been considered to be a promising choice for DNA sequencing. However, researchers still have a very limited understanding of the effects of multiple factors on MoS2-based DNA sequencing. In this study, the effects of the applied voltage and the diameter of the MoS2 nanopore on the resolution of DNA sequencing were investigated. Our results demonstrate that the translocation time of DNA can increase with a decrease in the applied voltage. DNA can be stretched significantly to translocate a 2 nm nanopore under a high applied voltage (>400 mV nm-1). To achieve a 1 base per μs translocation speed (1 GHz bandwidth), we suggest that three methods could be applied, including a decrease in the applied voltage, a decrease in the diameter of the MoS2 nanopore or modification of the MoS2 nanopore. In addition, the size of the nanopore can severely affect the possibility of DNA entering the nanopore, and the translocation time of DNA could be significantly increased with a smaller MoS2 nanopore. These findings may help to design MoS2 nanopores with higher resolution for use in DNA sequencing.

In this paper, a femtosecond laser line-scanning irradiation was used to induce the periodic surface microstructure on HgCdTe crystal. Low spatial frequency laser induced periodic surface structures of 650–770 nm and high spatial frequency laser induced periodic surface structures of 152–246 nm were respectively found with different scanning speeds. The evolution process from low spatial frequency laser induced periodic surface structures to high spatial frequency laser induced periodic surface structures is characterized by scanning electron microscope. Their spatial periods deduced by using a two-dimensional Fourier transformation partly agree with the predictions of the Sipe-Drude theory. Confocal micro-Raman spectral show that the atomic arrangement of induced low spatial frequency laser-induced structures are basically consistent with the crystal in the central area of laser-scanning line, however a new peak at 164 cm −1 for the CdTe-like mode becomes evident due to the Hg vaporization when strong laser ablation happens. The obtained surface periodic ripples may have applications in fabricating advanced infrared detector.

Resistance spot welded joints in different configurations of DP600 and DC54D were investigated to elucidate the nugget formation process and mechanical properties of the resultant joints. Results show that, when the welding time was less than 4 cycles, the fusion zone (FZ) was not formed, but the heat-affected zone (HAZ) occurred with a “butterfly” shape. In 4 cycles, the FZ in dissimilar sheets occurred with an “abnormal butterfly” shape because of nugget shift. When the welding time increased to 14 cycles, the FZ exhibited a “bread loaf” shape and the weld shifted to “dog bones.” The nugget can be divided into three regions, namely, FZ, HAZ1, and HAZ2, and the FZ consisted of lath martensite. The micro hardness of DP600 FZ was lower than that of HAZ because of the dilution of DC54D. The failure mode of B changed from interfacial failure to plug failure during the nugget formation process. The tensile-shear load of sound weld is 6.375, 6.016, and 19.131 kN.

The effects of high energy shot peening (HESP) on the microstructures and mechanical properties of tungsten inert gas (TIG) welded-brazed Mg/Ti joints were investigated, in terms of surface characteristics, residual stress variation, grain size, dislocation density and tensile strength of the resulting joints. The results show that HESP under an optimized Almen intensity of 0.16 mm N resulted in the surface defects elimination, high compressive residual stress, fine-grain strengthening and strain strengthening of Mg/Ti joint. All these factors contributed to the significant improvement in mechanical properties of the joints, leading to a notable enhancement (24.5%) in tensile strength of the Mg/Ti joint to 241 MPa over the joints without HESP treatment (193.5 MPa). However, further increment in Almen intensity to 0.24 mm N resulted in severe internal cracks within the joint, which deteriorated the mechanical properties of Mg/Ti joints.

The drying process is a significant step in the manufacturing process of enteric hard capsules, which affects the physical and chemical properties of the capsules. Thus, the drying characteristics of plant-based enteric hard capsules were investigated at a constant air velocity of 2 m/s in a bench scale hot-air dryer under a temperature range of 25 to 45 °C and relative humidity of 40 to 80%. Results indicate that the drying process of the capsules mainly occur in a falling-rate period, implying that moisture transfer in the capsules is governed by internal moisture diffusion rate. High temperature and low relative humidity reduce drying time but increase the drying rate of the capsules. Investigation results of the mechanical properties and storage stability of the capsules, however, reveal that a fast drying rate leads to plant-based enteric hard capsules of low quality. Scanning electron microscopy further demonstrates that more layered cracks appear in capsules produced under a faster drying rate. The Page model yielded the best fit for describing thin-layer drying of the capsules based on the coefficient of determination and reduced chi-square. Moreover, it was established that the effective moisture diffusivity of the capsules increases with an increase in drying temperature or reduction in relative humidity.

Resistance spot welding of 22MnB5/HSLA350 and its weldability are investigated. From base material to the nugget, the microstructure of 22MnB5 side can be expressed as M/tempered M+ granular carbides/F+M/fine M/lath M, and on HSLA350 side, F+M/F+flocculent P+tempered M/F+flocculent P+M/F+M/lath M are observed. The heat-affected zone (HAZ) of 22MnB5 exhibits obvious softening region and strengthening region caused by the tempered M and quite fine M, respectively. The peak load of welded joints undergoes two stages of a dramatic increase and a subsequent decrease with increases in the welding current. The maximum value (13.82 kN) of peak load is achieved at a welding current of 8 kA. The failure modes involving interfacial failure (IF), pullout failure from the galvanized steel (PFG), pullout failure from boron steel and tearing of the galvanized steel (PFB-TG) and pullout failure from the boron steel (PFB) are discussed in detail.

A broadband MoS2-based absorber composed of Ag rod/MoS2/dielectric/Ag is proposed in the visible band. The relative bandwidth is 65% for the absorption above 80%. The absorber also has the properties of polarization-independence and wide-angle absorption. Impedance matching theory is used to analyze the physical mechanism of the broadband absorption. By investigating the absorption property of each part of the absorber, it is found that the absorption is enhanced by introducing the two-dimensional material MoS2. The broadband absorber can be changed to be multiband absorber by changing the thickness of dielectric substrate. This structure provides a new perspective to enhance absorption in the visible band and has promising applications in solar cells.

Recently magnesium and its alloys have been proposed as a promising next generation orthopedic implant material, whereas the poor corrosion behavior, potential cytotoxicity, and the lack of efficient drug delivery system have limited its further clinical application, especially for the local treatment of infections or musculoskeletal disorders and diseases. In this study, we designed and developed a multifunctional bilayer composite coating of poly(lactic acid)/brushite with high interfacial bonding strength on a Mg-Nd-Zn-Zr alloy, aiming to improve the biocorrosion resistance and biocompatibility of the magnesium-based substrate, as well as to further incorporate the biofunctionality of localized drug delivery. The composite coating consisted of an inner layer of poly(lactic acid) serving as a drug carrier and an outer layer composed of brushite generated through chemical solution deposition, where a facile pretreatment of UV irradiation was applied to the poly(lactic acid) coating to facilitate the heterogeneous nucleation of brushite. The in vitro degradation results of electrochemical measurements and immersion tests indicated a considerable reduction of magnesium degradation provided the composite coating. A systematic investigation of cellular response with cell viability, adhesion, and ALP assays confirmed the coated Mg alloy induced no toxicity to MC3T3-E1 osteoblastic cells but rather fostered cell attachment and proliferation and promoted osteogenic differentiation, revealing excellent biosafety and biocompatibility and enhanced osteoinductive potential. An in vitro drug release profile of paclitaxel from the composite coating was monitored with UV-vis spectroscopy, showing an alleviated initial burst release and a sustained and controlled release feature of the drug-loaded composite coating. These findings suggested that the bilayer poly(lactic acid)/brushite coating provided effective protection for Mg alloy, greatly enhanced cytocompatibility and bioactivity, and, moreover, possessed local drug delivery capability; hence magnesium alloy with poly(lactic acid)/brushite coating presents great potential in orthopedic clinical applications, especially for localized bone therapy.

In situ chemical oxidation polymerization of pyrrole on the surface of sulfur particles was carried out to synthesize a sulfur/polypyrrole (S/PPy) nanocomposite with core-shell structure. The composite was characterized by elemental analysis, X-ray diffraction, scanning/transmission electron microscopy, and electrochemical measurements. XRD and FTIR results showed that sulfur well dispersed in the core-shell structure and PPy structure was successfully obtained via in situ oxidative polymerization of pyrrole on the surface of sulfur particles. TEM observation revealed that PPy was formed and fixed to the surface of sulfur nanoparticle after polymerization, developing a well-defined core-shell structure and the thickness of PPy coating layer was in the range of 20–30 nm. In the composite, PPy worked as a conducting matrix as well as a coating agent, which confined the active materials within the electrode. Consequently, the as prepared S/PPy composite cathode exhibited good cycling and rate performances for rechargeable lithium/sulfur batteries. The resulting cell containing S/PPy composite cathode yields a discharge capacity of 1039 mAh·g−1 at the initial cycle and retains 59% of this value over 50 cycles at 0.1 C rate. At 1 C rate, the S/PPy composite showed good cycle stability, and the discharge capacity was 475 mAh·g−1 after 50 cycles.

Ultrasonic assisted tungsten inert gas welding–brazing technology was developed to refine coarsening columnar α-Mg grains of Mg/Ti joints. In this study, ultrasonic vibration was introduced into molten pool of Mg/Ti joints with frequency of 20 kHz and maximum power of 1·6 kW. The results showed that, with ultrasonic power of 1·2 kW, the morphology of columnar α-Mg grains was refined to approximately equiaxed grains and the average grain size of columnar grains decreased from 200 to ∼50 μm. Moreover, the maximum joint strength of joints increased ∼18·1% to 228 N mm−1 over the joints welded without ultrasonic vibration (193 N mm−1). Furthermore, the optimised Mg/Ti joint fractured at base metal zone rather than fusion zone upon tensile–shear loading, indicating that efficient grain refinement was attained. However, welding voids occurred with the ultrasonic power further increased to 1·6 kW, which resulted in the decrease in mechanical properties.

A versatile route applied to the synthesis of thermoresponsive magnetite nanoparticles involved the formation of nanoparticles by coprecipitation of Fe2+/Fe3+ in the presence of an alkaline solution, followed by attachment of the reversible addition-fragmentation transfer (RAFT) agents onto the surface of the Fe3O4 nanoparticles via the electrostatic interactions, subsequent grafting from polymerization of N-isopropylacrylamide (NIPAM) through surface-initiated RAFT polymerization. The surface-initiated RAFT polymerization can be conducted in a well-controlled manner, as revealed by the linear kinetic plot, linear evolution of number-average molecular weights (M n ) versus monomer conversions, and the relatively narrow molecular weight distributions (M w /M n < 1.5) of the grafted PNIPAM chains. The as-synthesized hybrid nanoparticles showed thermoresponsive behavior and were characterized by FTIR, XPS, TGA, VSM, DLS, and TEM, etc.

A fascinating nanoobject, hydrophobic polymer brushes with a hard core of silica nanoparticles and a relatively soft shell of polystyrene-block-poly(ϵ -caprolactone) (PS-b-PCL), was easily constructed by surface-initiated atom transfer radical polymerization (ATRP) of styrene, ring-opening polymerization (ROP) of ϵ-caprolactone and click reaction. The structure and morphology of the as-prepared hybrid nanomaterials were characterized and confirmed by FTIR, 1H-NMR, TGA and TEM. We believe that the breakthrough associated with formation of such a complex nanoobject would open a door for the fabrication of novel functional nanomaterials or nanodevices with designable structure and tailor-made properties.

A 1 kHz femtosecond double-pulse sequence irradiation is used to study the temporal evolution of nanograting in fused silica by controlling the delay times and polarization combinations of two independent beams from a Mach–Zehnder interferometer. A lateral laser-scan experiment with speed at 5 µm s−1 and each pulse energy of 1 µJ is firstly performed with the delay time from sub-picosecond to 10 ps, and then the written nanostructures are systematically studied under a cross-polarized microscope because the intensity of birefringence signal nearly corresponds to optical retardance and development level of the induced nanograting. The trend shows that the induced nanogratings can continue developing with a decrease of delay time in the case of the linear polarization pulse arriving before. In another vertical laser-scan experiment at the same speed and pulse energy, the morphologies of nanogratings embedded in the lines are characterized by scanning electron microscope after mechanical polishing and chemical etching. The self-organized patterns have a commonly spatial period of 200–300 nm and the orientation is always perpendicular to the polarization of the first laser pulse, and the second pulse in each sequence seems to promote the as-formed nanograting developing further even if the polarized direction is different from the previous pulse. These new findings verify again that a localized memory effect can make positive feedback to reinforce the patterned nanostripes. In that process, the impact ionization from the seed electrons left by the first pulse excitation and the photoionization of self-trapped excitons with lower ionization threshold results in an increase of the re-excited carriers during the second pulse irradiation and the subsequent development of the as-formed nanograting. Our result provides further proofs for understanding the physical mechanism of nanograting strongly connection with the interplay on multiple ionization channels.

A versatile method was developed for the chain-end functionalization of the grafted polymer chains for surface modification of nanoparticles with functionalized groups through a combination of surface-initiated atom-transfer radical polymerization (ATRP) and Huisgen [3 + 2] cycloaddition. First, the surface of SiO 2 nanoparticles was modified with poly(methyl methacrylate) (PMMA) brushes via the “grafting from” approach. The terminal bromides of PMMA-grafted SiO 2 nanoparticles were then transformed into an azide function by nucleophilic substitution. These azido-terminated PMMA brushes on the nanoparticle surface were reacted with alkyne-terminated functional end group via Huisgen [3 + 2] cycloaddition. FTIR and 1 H NMR spectra indicated quantitative transformation of the chain ends of PMMA brushes onto SiO 2 nanoparticles into the desired functional group. And, the dispersibility of the end-functional polymer-grafted SiO 2 nanoparticles was investigated with a transmission electron microscope (TEM).