A mechanistic model is developed for the force-depth relationship of ion-irradiated materials, which is conducted by spherical nano-indentation. With irradiation effect, the pop-in phenomenon almost disappears that is ascribed to the irradiation-induced defects serving as dislocation nucleation sites that facilitate the generation of new dislocations. After materials yielding, the evolution of statistically stored dislocations, geometrically necessary dislocations and irradiation-induced defects mutually contributes to the force-depth relationships with irradiation effect. Thereinto, the increase of loading force originates from the impediment of slipping dislocations by irradiation-induced defects. By comparing with the experimental data of Fe–12Cr alloy, a reasonable agreement is achieved.

Irradiation damage and its evolution in noble gas ion-irradiated tungsten have not been investigated in detail other than in the case of helium ion irradiation. In this study, irradiation-induced vacancy-type defects in helium ion- and neon ion-irradiated tungsten were investigated by using a slow positron beam, and their annealing behavior in the temperature range of 20∘C-900∘C was compared by characterizing the Doppler broadening of positron annihilation radiation spectra. In helium ion-irradiated tungsten, slight aggregation of irradiation-induced vacancy-type defects was observed upon annealing, but eventually, a large portion of the vacancy clusters was eliminated after annealing at 900∘C. In contrast, in neon ion-irradiated tungsten, irradiation-induced vacancy-type defects were observed to aggregate significantly at 300∘C and 600∘C. In addition, the large vacancy clusters formed by the aggregation survived even after annealing at 900∘C.

The thermal evolution of vacancies and vacancy clusters in tungsten (W) has been studied. W (100) single crystals were irradiated with 200 keV hydrogen (H) ions to a low damage level (5.8×10−3 dpa) at 290 K and then annealed at temperatures in the range of 500–1800 K. The resulting defects were characterized by positron annihilation lifetime spectroscopy (PALS) and positron annihilation Doppler broadening spectroscopy (DBS). Annealing at 700 K resulted in the formation of clusters containing 10–15 vacancies, while at 800 K and higher temperatures clusters containing about 20 vacancies or more were formed. Reduction of the defect concentration likely accompanied by further coarsening of the clusters started at 1300 K and ended at 1800 K with the complete defect recovery. The determined cluster sizes at 700 K and 800 K were larger than the estimated minimum cluster sizes that are thermally stable at these temperatures, indicating that the migration and ensuing coalescence of small clusters plays an important role in cluster growth.

Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode particles were coated with anatase TiO2 layer to improve its cycle stability. The TiO2 coating was synthesized by the hydrolyzation method and subsequent annealing treatment ranging from 500 ℃ to 600 ℃. The well-ordered layered α-NaFeO2-type structure survives in the TiO2 coating process. The nanothick anatase TiO2 layer coveres on the surface of NCM811. The annealing temperature of coating was controlled to improve the electrochemical performances. The TiO2-coated NCM811 cathode annealed at 600 ℃ demonstrates the optimal capacity retention of 104.9% after 100 cycles at the current rate of 0.1 C, in contrast to 64.1% of pristine NCM811 and 96.7% of the coated sample annealed at 500 ℃.

This work studies the cationic surfactant effects (CTAB) on the morphology and particle size of the hydroxyapatite (HAp), using the microwave method keeping the pH, time and temperature constant. The obtained products were characterized using transmission electron microscopy, X-ray diffraction, FT-IR and EDS spectroscopy. TEM results showed that surfactant had great impact on size of hydroxyapatite. The smallest nanorods structures with mean size of 43.17 nm in diameter and 136.52 nm in length were obtained by using 0.45w% [in proportion of Ca and P precursors] of surfactant. XRD analysis confirmed the presence of hexagonal hydroxyapatite and showed the crystallite size dimensions by Rietveld analysis. FT-IR technique corroborated the HAp presence by characteristic vibrational modes and EDS spectroscopy displayed the Ca/P ratio in all the samples. This work could be taken into account as a base for composite biomaterials development for gas sensing and biomaterial applications.

Here, we report on an economical, viable, one-step method for fabrication of Higher Manganese Silicide MnSi1.75 (HMS). Fabrication of the HMS was followed by spark plasma sintering (SPS) at different temperatures (850, 900, 950 and 1000 °C), after which the thermoelectric and mechanical properties were investigated. It was found that the electrical conductivity significantly increased with increasing SPS temperature. This was attributed to the simultaneous increase of carrier concentration and mobility, while a reduction in the Seebeck coefficient was attributed to the formation of secondary phase in the HMS samples. A low thermal conductivity of 1.86 W/mK at 723 K was obtained for the sample sintered at 850 °C, which was attributed to increased scattering of heat-carrying phonons due to pores or voids, and grain boundaries. In addition, a maximum ZT of 0.27 was obtained at 723 K for the HMS-1000 sample, which is comparable with other previously reported data for undoped HMS material. Nevertheless, the HMS-1000 sample exhibited compressive strength of 1208 MPa and fracture toughness of 1.99 MPa m1/2, which is significantly higher than other state-of-the-art thermoelectric materials. The proposed fabrication method could be adopted for mass market applications requiring superior mechanical and thermoelectric properties.

The γ-C2S that constitutes stainless-steel argon oxygen decarburization (AOD) slag is known to generate calcite and silicate gel through reaction with CO2. In this study, the mechanical performance and microstructure characteristics of cementitious materials that contained AOD slag were investigated with respect to carbonation. AOD slag that contained 38.1% γ-C2S was used. It was crushed into two different finenesses; and paste specimens were prepared, in which up to 60% of ordinary Portland cement (OPC) was replaced by AOD slag. The specimens were cured in environments with CO2 concentrations of 0%, 5%, 10%, and 15%, to analyze the influence of the CO2 concentration. The compressive strengths were measured for the evaluation of the mechanical performances; and the pore size distributions were measured using a mercury intrusion penetrometer, to examine microstructural changes. Thermogravimetry/derivative thermogravimetry (TG-DTG) analyses were employed for the measurement of the CO2 uptake, and the influences of the CO2 uptake on the compressive strength and microstructure were analyzed. In the non-CO2 curing environment, the compressive strength decreased and the number of pores increased as the substitution rate of the AOD slag increased. However, when the CO2 concentration increased, the specimen with AOD slag exhibited a decrease in the porosity and increase in strength. The influence of the fineness of the AOD slag was significantly different when the substitution rate was 30%, and non-significant when it was 60%.

This work investigates the fabrication and improvement of the polyurethane (PU)-based polymer concrete (PC) for rapid cementitious runway repair. To overcome the low strength and moduli typically exhibited by the PU binders, the ground glass fiber (GGF) particles were employed to enhance the final mechanical parameters of the PU-based PC. A series of laboratory characterization and mechanical tests were conducted to analyze the structure and properties of the PU/GGF composites and the PU-based PC. The experimental results ascertain the enhancing mechanism of GGF particles, and a suitable GGF content is obtained. The present work reveals that the GGF particles can be a reinforcing filler for the PU-based PC.

Particle packing methods are very useful for reducing the cement consumption of concrete mixtures and consequently the CO2 emissions associated with them. They usually also increase the solids concentration of the mixes, which fosters particle interlock. This work evaluates the influence of the packing of aggregates on the static modulus of elasticity of concretes with compressive strengths of 25 and 40 MPa. The granular skeleton was arranged using experimental particle packing methods, maintaining a constant compressive strength throughout the process. The packing density had a relative increase of 8% and 10% for the 25 and 40 MPa concretes, respectively, and produced an average increase in the concrete static modulus of elasticity of 21% at 7 days and 8% at 28 days.

Even presenting several drawbacks, especially regarding environmental impact, concrete is the most consumed human-made material worldwide. In this sense, incorporating steel fibres and recycled aggregates, and applying the functionally graded material concept may help in the sustainability of concrete. In this paper, relationships between mechanical properties, embodied CO2, cost, among other parameters of functionally graded concretes (FGC) incorporating steel fibres and recycled aggregates were studied. The test results show that the FGC mechanical performance is inferior to fibre reinforced concrete but superior to fibre reinforced recycled aggregate concrete. Therefore, the FGC studied could be used in lower loading capacity applications, such as car parks and cycling lanes. In terms of embodied CO2 and cost, the FGC studied are more affected by the content of fibre than the content of recycled aggregates. Also, equations correlating design and sustainability parameters with reinforced thickness and content of fibre were proposed.

Sulfonated asphalt and natural rock asphalt were used to toughen oil well cement paste (OWCP). The difference of micro-morphology, surface functional groups and heat resistance of two kinds of asphalt was studied. Rock asphalt was treated by low-temperature plasma, and the mechanism of improving hydrophilicity was further analyzed and explained. The toughness of cement-based composites with asphalt was analyzed from triaxial stress-strain curves. Interface characteristics between sulfonated asphalt or rock asphalt and cement paste were gained. The crack propagation in cement paste was discussed systematically by using SEM microscopic observation. The results show that the thermal stability of the rock asphalt is higher than that of the sulfonated asphalt. XPS analysis results show that oxygen-containing functional groups, such as C–OH, CO, and C–O appear on the surface of rock asphalt treated by oxygen plasma. The surface free energy of plasma-treated rock asphalt was increased from 27.05 mJ·m−2 to 53.29 mJ·m−2, which indicates the improvement of hydrophilicity of the surface of rock asphalt. Triaxial stress-strain curve analysis results show that 3% content of sulfonated asphalt and treated rock asphalt can improve the toughness of oil well cement paste. A good interfacial transition zone with few micropores is found between the cement hydration products and sulfonated asphalt or treated rock asphalt by using SEM microscopic observation. SEM observation of crack propagation behavior in cement-based composites with asphalt indicated that sulfonated asphalt and plasma-treated rock asphalt improved the toughness of oil well cement by deflecting, bending and bridging the cracks.

A bituminous pavement is composed of several layers. The bonding of the interfaces between these layers is essential to ensure the durability of the pavement structure. Un-bonded interfaces can cause early deterioration of the surface courses due to the poor distribution of mechanical loads induce by the traffic onto the base-layers. The bonding between asphalt layers depends on several parameters such as the laying temperature, the use or not of bitumen emulsions to bond the interfaces. Bonding is usually characterized by shear, tensile or torsion tests. This paper focuses on the effects of loading rate, test temperature, specimens’ size and emulsion content on the shear strength evaluated through the shear and tensile tests. In part 1, the shear bond test (SBT) and tensile adhesive test (TAT) were firstly performed on two-layered specimens bonded or not with emulsion. Their diameters were 100 or 150 mm. The tests were carried out at 50 mm.min-1 and 20 °C to evaluate the laying conditions (laying temperature, use or not of emulsion). These results were then compared to those of one-layer specimens without interface. The results of part 1 investigations showed that: i) the shear strengths of small samples are 1.3 times higher than that of big specimens, ii) the shear strength resulting from different laying conditions can be classified, from the highest to the lowest, as follows: hot on hot (H/H) bonding, hot on cold (H/C) bonding with emulsion C69B2 and hot on cold (H/C) bonding without emulsion, iii) the failure strengths of TAT are 2.2 times lower than those of SBT. In part 2, the SBT was performed on two-layered specimens of 100 mm in diameter at three loading rates (0.5, 5, 50 mm.min-1) and test temperatures (−10 °C, 5 °C, 20 °C). In this second test series, 250 and 500 g.m-2 of bitumen emulsion C69B2 and styrene-butadiene rubber (SBR) polymer emulsion were used to bond the interfaces. Based on these results the master curves of shear strength were built based on the frequency-temperature superposition principle (FTSP). Furthermore, an explanation of the interfaces bonding mechanism based on the bitumens’ macromolecules chains mobility across the interface is proposed. This interpretation required the introduction of some interface bonding parameters: the degree of intimate Dic contact, the degree of healing Dh and the degree of bonding Db. Finally, the master curves of the degree of healing and degree of bonding were also built based on the frequency-temperature superposition principle (FTSP).

Since the ratification of the Kyoto protocol by the EU in 2002, Members States have committed themselves both to reducing their greenhouse gas emissions and to environmental sustainability, inter allia by using cements with alternative additions that incorporate industrial waste. In this paper, ionic mobility through a pozzolanic cement is studied. The cement contains substitutions of 10% and 20% rejected ballast waste and is prepared for railway infrastructure (slab or ballast less track) that is exposed to extreme climatic conditions (high thermal amplitudes and saline environments). Studied with CT-Scanning, ionic mobility can be observed along the cement pores. The cement with 10% substitutions of ballast waste was considered ideal to minimize ionic penetration and cement deterioration.

In recent years, polymer cement mortars using polymer dispersions have been widely used as finishing and repairing materials in the construction industry, because of their excellent properties compared with plain cement mortar. In particular, polymer cement mortar’s superior adhesion to that with plain cement mortar and concrete has attracted a great deal of attention from researchers, who have developed a number of unique applications for improving adhesion. The adhesion behavior between polymer cement mortar and substrate at the interface is known to be important for the improvement of adhesion of polymer cement mortar as a repair and reinforcement materials. This research was experimented on the mix designs and curing methods that affect the behavior of these interfaces. I want to present not only optimum mix design but also optimum curing condition of polymer cement so that construction workers will be able to use it properly as special material related to RC structure on site. The purpose of this study is to evaluate the effect of curing conditions on the adhesion in tension of polymer cement mortar to cement concrete substrate compared, with plain cement mortar. Polymer cement mortars using three polymer dispersions with various polymer-cement ratios are prepared and tested for the adhesion in tension of specimens subjected to four curing conditions: standard, dry, water, and under high temperature. The test results show that the adhesion in tension of polymer cement mortars increases with increasing polymer-cement ratio, irrespective of the polymer type and curing conditions, and it is the highest under standard curing. The polymer cement mortars have high adhesion in tension in the order ethylene–vinyl acetate (EVA) > styrene-butadiene rubber (SBR) > styrene-vinyl acrylic ester (SAE). The failure modes of specimens under conditions I and II and at high P/C of 15–20%, which showed high adhesion in tension, revealed relatively high S ratios, indicating cohesion failure of the base concrete. It is apparent from this study that the adhesion in tension of polymer cement mortars is considerably influenced by the curing condition, polymer-cement ratio, and type of polymer.

Objective To evaluate and compare the viscoelastic properties of dentine and resin-based dental materials by bulk compressive test and the Burgers model. Materials and methods Sound dentine, three resin composites as well as a resin-based cement were prepared into cylindrical specimens (n = 8). A bulk compressive creep test was applied with a constant load of 300 N (23.9 MPa) for 2 h, followed by another 2 h recovery. The maximum strain, creep stain, percentage of recovery and permanent set was measured using a linear variable displacement transducer. The viscoelastic properties were characterized via the Burgers model, and the instantaneous elastic, viscous as well as elastic delayed deformation were separated from the total strain. Data were analysed via ANOVA (or Welch's Test) and Tukey (or Games–Howell Test) with a significance level of 0.05. Results Sound dentine presented the lowest maximum strain, creep strain, permanent set and the highest percentage of recovery, followed by 3 resin composites with comparable parameters, while the cement showed a significantly higher maximum strain, permanent set and lower percentage of recovery (p < 0.001). The Burgers model presented acceptable fits for characterization viscoelastic processes of both dentine and resin-based dental materials. Viscous and elastic delayed strain of dentine was significantly lower than those for tested materials (p < 0.001) with the highest instantaneous elastic strain percentage. Similar viscous and delayed strain was found among the 4 resin-based materials (p > 0.05). Significance Sound dentine exhibited superior creep stability compared to resin-based dental materials. The viscous deformation in sound dentine could be ignored when loading parallel to dentine tubules.

Abstract The synthesis and characterization of Dy-doped \(\hbox {Lu}_{{1}}\hbox {Gd}_{{2}}\hbox {Ga}_{{2}}\hbox {Al}_{{3}}\hbox {O}_{{12}}\) are reported in this article. Solid-state reaction method is used to synthesize the material. X-ray diffraction and scanning electron microscopy characterization techniques are used to study the phase and structure of the synthesized material. Luminescence, which is the main property of the phosphor material, is characterized by UV- and X-ray-induced luminescence spectroscopy. \(\hbox {Lu}_{{1}}\hbox {Gd}_{{2}}\hbox {Ga}_{{2}}\hbox {Al}_{{3}}\hbox {O}_{{12}}{:}\hbox {Dy}^{3+}\) phosphor shows its highest emission spectra in blue and yellow regions. A combination of yellow and blue gives us white light, displayed by chromaticity diagram for this phosphor. Hence, this phosphor may be used in white-light-emitting diodes. The absorption spectra of our material match well with spectral curve of LEDs. Therefore, it may be used in LEDs applications.

Abstract Nanoparticle (NP)-loaded filter paper (FP)-based surface-enhanced Raman scattering (SERS) substrates have been prepared using differently shaped gold (Au) NPs. The shape of Au NPs plays a significant role in the amplification of SERS signal. Here, two differently shaped Au NPs were synthesized using two different techniques: (a) femtosecond (fs) laser ablation in liquid and (b) chemical method. Spherical shaped Au NPs were obtained using fs ablation of a bulk Au target in distilled water and Au nanostars (NSs) were achieved through chemical process utilizing N-vinyl-2-pyrrolidone as a reducing/capping agent. The size and shapes of these synthesized NPs and NSs were investigated meticulously using different characterization techniques such as transmission electron microscopy, field emission scanning electron microscopy and X-ray diffraction. Both the NPs and NSs were subsequently loaded onto commercially available FP by simple drop casting method. To achieve higher number of hot spots, the aggregated spherical NPs were obtained by addition of NaCl. The non-aggregated spherical, aggregated spherical, and star Au NPs loaded on FP were used for the detection of a dye (Nile blue) and an explosive molecule (Picric acid).

Abstract Theoretical calculations are performed on lattice thermal conductivity (LTC) and related parameters for the zinc blende and wurtzite structure of InAs nanowires (NWs) with diameters of 50, 63, 66, 100 and 148 nm through the Morelli–Callaway model. For the model to be efficiently applicable, the longitudinal and transverse modes are considered. The melting point of the various-sized NWs is considered to estimate the Debye and phonon group velocities. The impacts of Grüneisen parameter, dislocations and surface roughness are also successfully utilized to address the calculated and measured LTC of the semiconductor under investigation. Results show that the Grüneisen parameter increases with decreasing NW diameter and that phonon confinement leads to an observable deviation of the calculated LTC curve from that of the experimental one in the case of bulk InAs. We assume that NW boundaries, dislocations and imperfections are responsible for the scattering of phonons along with electrons and other phonons because of normal and Umklapp processes. Therefore, at a specified temperature, LTC depends on the size and crystal structure of the semiconductor. As such, the thermal and mechanical parameters of InAs can be greatly modified by decreasing the size and dimension of the semiconductor as a result of the quantum-confinement effect.

Abstract High-strength bainitic steels are considered potential candidates for the 3rd generation of advanced high-strength steels (AHSS). The main characteristic of silicon-alloyed steels is the presence of carbide-free bainite, obtained by low-temperature austempering. Salt bath boriding is an effective method for increasing wear resistance and provides high corrosion resistance. The combination of these two treatments is called boro-austempering and is a promising alternative to increase the wear resistance of AHSS. In the present work, samples were borided at 900 °C for 2 h, direct-cooled from that temperature and isothermally held in a salt bath at 360 °C for 1 and 3 h. The substrate and the layers produced were characterized by optical microscopy (OM), scanning electron microscopy (SEM), x-ray diffraction (XRD), Vickers microhardness (HRV) and microadhesive wear tests. The tribological characteristics of the layers were compared with those of the substrate. The microscopic analysis showed the effectiveness of boro-austempering treatment in the production of carbide-free bainite microstructure and the surface borided layers. As a result, there were increases in surface wear resistance up to 115% when compared to the substrate.

Abstract Multilayered Al/Ni energetic structural materials integrating exothermic properties and mechanical properties were prepared by the method of electrodeposition and hot pressing in this research. Then, the uniaxial quasi-static compression and split Hopkinson pressure bar experiments were conducted at strain rates from 10−4 to 6.5 × 103 s−1 at room temperature. The effects of compression strain rate on the microstructure evolution and the compressive properties of multilayered Al/Ni energetic structural materials were systematically investigated. With increasing quasi-static compression strain rate, the compression strength increased slightly for two kinds of Al/Ni multilayers prepared under different hot pressing time. With the hot pressing process extending to 4 h, the dynamic compression strength of multilayered Al/Ni composites monotonically increased from 494.7 to 564.2 MPa with increasing strain rate. It was shown that Al/Ni energetic structural materials exhibited evident strain hardening and strain rate strengthening. However, when the compression strain rate reached 6500 s−1, the Al/Ni composite prepared with the hot pressing time of 1 h showed prominent thermal softening. Notwithstanding, it was found that the compression strength of Al/Ni composite prepared at 4 h was evidently higher than that at 1 h, since the second phase reinforcement counteracted the thermal softening. In addition, the critical failure strain presented obviously increasing tendency with the increased compression strain rates.

Abstract In order to study the transformation-induced plasticity (TRIP) effect in a NiTi shape-memory alloy composite, an in situ NbTi-NiTi composite was prepared by vacuum arc melting, hot forging and wire drawing. An unusual ductile–brittle variation phenomenon was observed by means of a series of tensile tests. The composite was brittle in the absence of transformation at 200 °C, and the fracture strain was about 2%. With lowering the tensile temperature, the composite became ductile when stress-induced martensitic transformation occurred, and the elongation increased to about 18% (a ninefold increase) during tensile test at room temperature. This ductile–brittle variation phenomenon indicates that the stress-induced martensitic transformation of NiTi alloy helps to improve the ductility of the composite, which is just the exhibition of TRIP effect in the NbTi-NiTi composite. Different from conventional TRIP steels, the TRIP behavior in NiTi induces only an increase in the elongation, but not any increase in fracture strength.

Abstract Forming processes of continuous fiber reinforced thermoplastic materials are oftentimes limited to high volume production due to the high costs for tooling and processing machines. This study suggests the combined use of a cold and simple tool and high forming speeds to reduce tooling and processing costs and enable the usage of common stamping machines. Half sphere samples are produced from single and two-layer polypropylene and glass fiber organo-sheets in a custom built drop tower and analyzed for their geometry, degree of re-consolidation, surface quality and potential fiber damage using a variety of microscopy techniques. While only mediocre degrees of re-consolidation and limited surface qualities can be achieved with the combination of a cold tooling and state-of-the-art forming speeds of 0–0.5 ms−1, the usage of a higher forming speed of 3 ms−1, vastly improves surface qualities and the degree of re-consolidation without any detectable fiber damage. This effect is more pronounced in the dual layer material. Extensive knowledge on the forming behavior of continuous fiber reinforced thermoplastics at high cooling rates and high speeds of deformation is required for sufficient process control and future studies need to further elaborate and quantify the influencing factors and limits of high-speed forming of continuous fiber reinforced thermoplastics.

Abstract Silicide-based thermoelectric (TE) materials are promising candidates for automotive TE generators, which can collect wasted heat and convert it into electricity. Adequate strategies should be used to manufacture highly efficient silicide-based TE devices. This review summarizes novel strategies for obtaining materials that feature excellent TE properties and mechanical reliability. Controlling the carrier concentration and band structure could increase their electronic transport properties, while nanostructure engineering could effectively reduce their lattice thermal conductivity. Moreover, well designed microstructures are required to obtain mechanically reliable TE materials, which indicates that precisely controlling their nanostructure is essential for the improved trade-off relationship between TE and mechanical properties. While many challenges should still be overcome, the development of highly efficient TE materials and devices could represent new solutions for the global energy crisis. Graphic Abstract

Abstract The texture evolution of copper tube manufactured by floating plug drawing process was investigated by Electron Backscatter Diffraction techniques and Visco-Plastic Self-consistent (VPSC) modelling method. The results obtained from experimentation indicate that the initial textures of copper tube transformed sharply after the first pass of the drawing process, and the final textures in the tube consist of Goss {110} <001> and P {110} <111> components. The VPSC model was established in order to study the texture transformation and the activity of slip systems of the tube during the drawing process. Two types of transformation paths were proposed to explain the mechanism of the texture evolution, which has a good agreement with the VPSC simulation results.

Abstract Invar foils. Graphic Abstract

Abstract The Sn–Mg eutectic alloy is a potential replacement for the traditional Sn-38.1 wt%Pb solder alloy, since lead has been banned because of its risk to human health and the environment. However, studies in the literature related to the Sn-2.1 wt%Mg alloy are restricted to mechanical, electrical and thermal properties. Therefore, this study aims to evaluate the corrosion behavior of this alloy, as a function of the microstructural arrangement obtained from directional solidification performed in a transient heat extraction regime. The thermal solidification parameters (solidification growth rate and cooling rate) were determined along the length of the casting for correlations with microstructural features. The resulting microstructure was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. Subsequently, the electrochemical impedance spectroscopy, linear polarization, equivalent circuit and evolution of hydrogen release analyzes were performed to evaluate the corrosion behavior of the samples in a 0.5 M NaCl solution at 25 °C. Interphase spacing and Mg2Sn fraction were found to influence the corrosion behavior, showing higher corrosion resistance for a more refined microstructure. Graphic Abstract

Abstract Gas sensors are widely used in many industrial and home applications. There is therefore continued need to develop novel gas sensor substrates which provide good mechanical and electrical stability, and good flexibility in comparison with the conventional alumina and silicon-based materials. In this paper, we present the experimental results on flexible gas sensors based on the Kapton foil and alumina substrate covered by copper oxide as a gas-sensitive layer. These sensors exhibited good mechanical stability and gas-sensing characteristics. The Kapton-based CuO gas sensors were tested under exposure to acetone in the 0.05–1.25 ppm range (150 °C, 50%RH). The results confirmed that sensors deposited on the flexible substrate such as Kapton can be used in the exhaled breath analyzers dedicated to diabetes biomarker detection or other applications for which the elastic substrate is needed. Graphic Abstract

Abstract The solid solution of relaxor and lead titanate single crystals have been an excellent choice for electromechanical applications such as energy harvesters, SONARs, transducers, and biomedical equipment. The mechanical quality factor (Qm) plays a crucial role in such applications using high power resonance condition. In this work, 32 mode (011) oriented along thickness direction, Generation-III piezoelectric single crystals based on PMN-PZT [71Pb(Mg1/3Nb2/3)O3–29PbZrTiO3] have been grown by solid state single crystal growth method. The Mn doping concentration in the crystals were systematically controlled within the range of 0 to 1.0 mol.%. The piezoelectric properties noticeably varied with the Mn doping concentration when the content is over 0.1 mol.%. In order to obtain significant enhancement in Qm in PMN-PZT single crystals, especially, the Mn doping concentration should be higher than 0.7 mol.% (which offers highest figure of merit) for high power resonance applications. Graphic Abstract

Abstract The trap states at ultraviolet/ozone (UV/O3)-treated Al2O3/GaN interfaces of p-type metal-oxide-semiconductor capacitors (pMOSCAPs) are analyzed through a frequency-dispersion capacitance–voltage (C–V) measurements. X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy are applied to confirm a formation of ultrathin oxide layer (Ga2Ox) on GaN surface by the UV/O3 treatment. The trapped charge density and interface trap density improved from 7.30 × 1011 to 2.79 × 1011 cm−2 eV−1 averaged over the bandgap of GaN and from 1.28 × 1013 to 4.08 × 1012 cm−2 eV−1 near the conduction band edge of GaN, respectively, owing to the passivation of Ga2Ox layer at the Al2O3/GaN interfaces. Mechanism for the improved trap states in pMOSCAPs is identified based on the reduced defect states at both Al2O3/Ga2Ox and Ga2Ox/GaN interfaces. Graphic Abstract

Abstract In this paper, the microwave characteristics of typical photosensitive material InP under different light irradiation are studied. The measurement sensor is a reflection-type hemispherical quasi-optical resonator with an operating frequency range from 20 to 40 GHz, an operating mode of TEM00q, and a quality factor of 18,000 or more. For the short-time irradiation experiment, the variation of InP microwave characteristics with the irradiation power of 20 mW, 60 mW, 100 mW, and 200 mW, is studied by frequency-domain and time-domain scanning methods, respectively. The measurement results indicate that the microwave characteristics of InP change significantly even under weak light irradiation. Taking 100 mW and 200 mW irradiation power as examples, the long-time irradiation experiment performed on InP lasting 1.5 min is carried out. The measurement result curves clearly show the influence of the thermal and non-thermal effects on the InP microwave characteristics at the instant of the monochrome light source opening and closing and during irradiation. Furthermore, the temperature distribution of InP during 200 mW irradiation is real-time imaged by a thermal infrared imager to verify the existence of thermal effect during irradiation. The measurement results are in good agreement with the theoretical analysis. Graphic Abstract The microwave properties of InP under short-time and long-time irradiation are analyzed by frequency-domain and time-domain scanning methods, especially the effects of thermal and non-thermal on microwave properties during long-term irradiation.

Abstract The possibility of preparing highly (002) oriented Ti films on the Si (100) substrate was studied using RF sputtering. The deposition behavior was compared between floating and grounded substrates at room temperature. Highly (002) oriented Ti films could be successfully prepared on the floating Si (100) substrate, which was revealed by X-ray diffraction and high resolution transmission electron microscope. To understand the different deposition behavior between floating and grounded substrates, the incident energy of ions during RF sputtering was estimated from the substrate temperature measured by the K-type thermocouple. The incident energy on the floating substrate was lower by 20% than that on the grounded substrate. It was suggested that the lower incident energy on the floating substrate would be responsible for the deposition of highly (002) oriented Ti films at room temperature. Graphic Abstract

Abstract The columnar NaNbO3-based particles with a perovskite structure were successfully synthesized through topochemical microcrystal conversion. First, the precursor was fabricated by facile MSS in the Nb2O5–KCl system. A good dispersion and high aspect ratio were satisfied simultaneously with a small amount of SrCO3 and KSr2Nb5O15 (KSN) seed. Then, columnar NaNbO3-based particles, 10 μm in length and 1 μm in diameter, were obtained via the simple molten salt reaction from the precursor. The results of NaNbO3-based ceramics suggested that the as-synthesized NaNbO3-based particles had the good mechanical properties and homogeneous chemical composition. Graphic Abstract

Abstract In a metal/n-Ge structure, Fermi level pinning tends to occur. The insertion of an oxide layer at the interface between electrodes and n-Ge can effectively reduce the Schottky barrier height. However, the attachment of metal and oxide can cause diffusion of oxygen to the metal due to Gibbs free energy, which degrades the contact characteristics. In this study, we investigated the effects of a laminated electrode on the current density at a metal/GeO2/n-Ge structure. Ni, Pt, Al, or Ti layers with thicknesses of 0.5–20 nm were formed, followed by a deposition of 200-nm-thick Al. The J–V curves of these samples showed that the current density of the Al/Ti/GeO2/n-Ge structure was the largest among them and was about 126 times larger than that of the Al/GeO2/n-Ge structure. We also found that the current density depended on the film thickness of Ti and was the highest at the film thickness of about 2.5 nm or less. To investigate the effect of the Ti interlayer on the current density, we obtained the depth profiles of X-ray photoelectron spectroscope spectra of the Al/Ti/GeO2/n-Ge and Al/GeO2/n-Ge structures. Analysis showed that the diffusion of the oxygen to Al was limited by the 20-nm-thick Ti, and the oxygen was diffused to Al when the film thickness of Ti was about 1 nm. These results demonstrate that laminated oxide structures such as AlOx/TiOx and TiOx/GeO2 can form on the sample with 1-nm-thick Ti, which increases the current density. Graphic Abstract

Abstract In two-dimensional materials, black phosphorus has shown excellent performance as electrode materials for lithium- and sodium-ion batteries, due to its thermodynamic stability, layered anisotropic structure, and electrical conductivity. Recently, high capacity anodes based on black phosphorus as an active component for potassium-ion batteries (PIBs) have also been reported. However, in-depth studies are required to clarify the adsorption and diffusion of K ions on black phosphorus and the K–P reaction mechanism. In this work, the surface adsorption, bulk diffusion, and K–P binary phase formation were firstly investigated in detail using first-principle calculations. We found that compared with Li and Na, K has the lowest diffusion energy barrier in the bulk phase (0.182 eV for zigzag type and 2.013 eV for armchair type). Black phosphorus structure irreversibly collapses when the K ion concentration is up to 0.625, and no K3P phase is formed through the electrochemical profiles obtained by calculation of the binary phase alloy structures. Furthermore, the maximum capacitance of black phosphorous for PIBs is calculated to be 864.8 mAh.g−1. This work will help in understanding the mechanism and further improving the performance of K-ion batteries. Graphic Abstract

Abstract The origin of efficiency-lifetime trade-off in triplet–triplet fusion (TTF) type blue fluorescent organic light-emitting diodes (OLEDs) was investigated and the device structure to resolve the issue was developed. The efficiency and lifetime were simultaneously improved in the blue OLEDs by developing a multilayer hole transport stack which can adjust carrier densities and recombination zone in the emitting layer (EML). It was found that electron leakage from EML and high spatial density of excitons in the vicinity of the electron blocking layer for high TTF rates by narrow recombination zone are the detrimental factors for efficiency-lifetime trade-off. A multilayer hole transport stack employing a deep highest occupied molecular orbital hole transport layer and an electron blocking layer combined with an appropriate hole blocking layer simultaneously improved the power efficiency by 16% at 500 cd/m2 and lifetime by almost 100% (from 73 h up to 145 h). In addition, the low efficiency in the low luminance region was also completely controlled, resulting in negligible efficiency variation in the entire luminance range. Graphic Abstract

Abstract Controlling ferromagnetic thickness (t) and properties such as saturation magnetization (Ms) and effective magnetic anisotropy constant (Keff) has been regarded as critical for the performance of magnetic tunnel junctions (MTJs) with interfacial perpendicular magnetic anisotropy. Here, we report the effects of hybridizing a CoFeB layer with a FeNiSiB layer as part of a magnetic free layer structure. We deposited thin film stacks by magnetron sputtering on Si wafers with thermal oxides and carried out post-deposition heat treatment at 300 °C for 1 h in a vacuum under a magnetic field. We found that Ms and Keff could be tuned by adding a layer of amorphous FeNiSiB. While the Ms and Keff values were modified, the tunneling magnetoresistance (TMR) ratios of the MTJs were maintained, even though the CoFeB thickness was decreased by half. Moreover, an asymmetric bias voltage dependence of TMR was suppressed in the MTJs with FeNiSiB/CoFeB hybrid free layers due to improvements in the interface quality between the CoFeB/MgO interfaces. Graphic Abstract

Abstract With the recent development of wearable/portable electronic devices, the power sources need to be flexible and miniaturized. As the power supply, a dielectric capacitor is used for systems requiring high power in a short time, which in turn necessitates dielectric materials with high energy density and fast discharging time for device miniaturization. In this study, we attempt to improve the energy density of organic materials by blending normal ferroelectric P(VDF-HFP), which offers high dielectric breakdown strength, and relaxor ferroelectric P(VDF-TrFE-CFE), which provides a high dielectric constant. The role of P(VDF-HFP) as a defect in the P(VDF-TrFE-CFE) crystallite improved the properties of the relaxor-ferroelectrics. Increasing the terpolymer content in the blended films reduced the normal ferroelectric β-phase, which revealed that non-polar phase was induced. The copolymer and terpolymer were blended in various weight ratios (10:0, 7:3, 5:5, 3:7, 1:9 and 0:10) and cast into films. The blends with a copolymer/terpolymer ratio of 1:9 showed reduced hysteresis and remnant polarization, compared to those of the pure terpolymer, and a higher maximum polarization (Pmax) value at an electric field of 250 MV/m, indicating a less saturated polarization at high electric field. To conclude, the PVDF-based copolymer/terpolymer (1:9 ratio) blends showed the highest energy density (6.58 J/cm3). Graphic Abstract

Abstract We investigate the effects of the low-temperature (LT) GeSn buffer layers on Sn surface segregation during the growth of the additional GeSn layers. Sn surface segregation was observed in the GeSn layers formed on Si substrates at the growth temperature of 300 °C. However, there was no Sn surface segregation in the GeSn layers grown at 300 °C on the LT GeSn buffer layers formed at 225 °C. The Sn surface segregation was limited by the effects of the LT buffer layers. Crystallinity of the GeSn layers grown at 300 °C on the LT GeSn buffer layers was investigated by Raman spectroscopy. The full width at half maximum of the Ge–Ge Raman spectrum obtained from the GeSn layers was about 3.1 cm−1, which means that the formed GeSn layers have excellent crystallinity. We have successfully demonstrated that the LT GeSn buffer layers can limit the Sn surface segregation, which increases the growth temperature and improves crystallinity of the GeSn layers. Graphic Abstract

Abstract Recently, layered structures composed of nanofibers have gained attention as a novel material to mimic skin tissue in wound healing applications. The aim of this study is to develop a novel hybrid bilayer material composed of zein based composite film and nanofiber layers as a wound dressing material. The upper layer was composed of H. perforatum oil incorporated zein film including MMT and the bottom layer was comprised of 3D electrospun zein/MMT nanofibers to induce wound healing with the controlled release of H. perforatum oil. The bilayer composites were characterized in terms of mechanical test, WVP, water uptake and surface wettability. Antimicrobial activity of the wound dressings against microorganisms were investigated by disc diffusion method. In vitro cytotoxicity of monolayer film and bilayer structure was performed using WST-1 assay on HS2 keratinocyte and 3T3 cell lines. Results indicated that the prepared monolayer films showed appropriate mechanical and gas barrier properties and surface wettability for wound healing. Controlled release of H. perforatum oil was obtained from fabricated membranes up to 48 h. Bilayer membranes showed antimicrobial activity against E. coli, S. aureus, and C. albicans and did not show any toxic effect on NIH3T3 mouse fibroblast and HS2 keratinocyte cell lines. In vitro scratch assay results indicated that H. perforatum oil had a wound healing effect by inducing fibroblast migration. The proliferation study supported these results by increasing fibroblast proliferation on H. perforatum oil loaded bilayer membranes.

Abstract Objective To improve sensitivity and uniformity of MR images obtained using a phased array RF coil, an inductively coupled secondary resonator with RF detuning circuits at 300 MHz was designed. Materials and methods A secondary resonator having detuning circuits to turn off the resonator during the transmit mode was constructed. The secondary resonator was located at the opposite side of the four-channel phased array to improve sensitivity and uniformity of the acquired MR images. Numerical simulations along with phantom and in vivo experiments were conducted to evaluate the designed secondary resonator. Results The numerical simulation results of |B1+| in a transmit mode showed that magnetic field uniformity would be decreased with a secondary resonator having no detuning circuits because of unwanted interferences between the transmit birdcage coil and the secondary resonator. The standard deviation (SD) of |B1+| was decreased 57% with a secondary resonator containing detuning circuits. The sensitivity and uniformity of |B1−| in the receive mode using a four-channel phased array were improved with the secondary resonator. Phantom experiments using a uniform saline phantom had 20% improvement of the mean signal intensity and 50% decrease in the SD with the secondary resonator. Mice with excess adipose tissue were imaged to demonstrate the utility of the secondary resonator. Conclusion The designed secondary resonator having detuning circuits improved sensitivity and uniformity of mouse MR images acquired using the four-channel phased array.

Abstract Objectives Chemical Shift Encoded Magnetic Resonance Imaging (CSE-MRI)-based quantification of low-level (< 5% of proton density fat fraction—PDFF) fat infiltration requires highly accurate data reconstruction for the assessment of hepatic or pancreatic fat accumulation in diagnostics and biomedical research. Materials and methods We compare three software tools available for water/fat image reconstruction and PDFF quantification with MRS as the reference method. Based on the algorithm exploited in the tested software, the accuracy of fat fraction quantification varies. We evaluate them in phantom and in vivo MRS and MRI measurements. Results The signal model of Intralipid 20% emulsion used for phantoms was established for 3 T and 9.4 T fields. In all cases, we noticed a high coefficient of determination (R-squared) between MRS and MRI–PDFF measurements: in phantoms <0.9924–0.9990>; and in vivo <0.8069–0.9552>. Bland–Altman analysis was applied to phantom and in vivo measurements. Discussion Multi-echo MRI in combination with an advanced algorithm including multi-peak spectrum modeling appears as a valuable and accurate method for low-level PDFF quantification over large FOV in high resolution, and is much faster than MRS methods. The graph-cut algorithm (GC) showed the fewest water/fat swaps in the PDFF maps, and hence stands out as the most robust method of those tested.

Abstract High dielectric loss is one of the current obstacles to the application of dielectric materials. In this paper, we synthesized a new dielectric material, i.e., (Yb + Ta)-co-doped TiO2 dielectric material. The (Yb0.5Ta0.5)xTi1−xO2 ceramics were synthesized by the solid-state reaction method. It has been found that (Yb0.5Ta0.5)xTi1−xO2 ceramics had a dense ceramic microstructure, and (Yb0.5Ta0.5)xTi1−xO2 ceramics exhibited the rutile TiO2 structure. All (Yb0.5Ta0.5)xTi1−xO2 ceramics exhibited low dielectric loss (< 0.1) and large dielectric constant (> 105). The optimal dielectric properties are obtained at a doping level of x = 0.05 with dielectric constant of 5.1 × 105 and dielectric loss of 0.037. Further study of the thermal stability of the dielectric properties was performed in the temperature range from − 50 to 250 ℃, which indicates that the ceramic sample with x = 0.05 co-dopant concentration maintains good dielectric properties in the temperature range from − 50 to 100 ℃. XPS shows that high dielectric properties can be explained by the electron-pinned defect-dipole mechanism.

Abstract Semi-organic lithium hydrogen phthalate dihydrate crystal has been grown using a slow evaporation solution growth technique. It belongs to the orthorhombic crystal system. The nucleation cure is calculated for different temperatures. The various intermolecular interactions were found out using Hirshfeld surfaces. The vibrational analysis was affirmed using FTIR and FT-Raman spectra. The lithium hydrogen phthalate dihydrate has good transmittance in the UV–Vis–NIR region. The decomposition happens in various stages. The etch pit was determined using the water solvent. The surface damage happens due to the decomposition of the crystal.

Abstract To maximize the photocatalytic performance of practical energy devices, F-doped TiO2 particles are anchored on g-C3N4 nanosheets through the liquid phase deposition (LPD) and calcination process. The photocatalytic activity of F-doped TiO2/g-C3N4 (T-CN) composite is evaluated by the degradation of Rhodamine B (RhB) solution under visible-light illumination. The T-CN-300 sample (contain 300 mg g-C3N4) degrades 97% RhB after its illumination for 20 min. The quantum yield of the T-CN-300 sample is about three times higher than that of the pristine F-TiO2 and g-C3N4 samples. Moreover, the trapping experiments of the T-CN-300 sample indicate that the superoxide radical (·O2−) is the main active species upon the photocatalytic process. The spin-trapping experiments confirm that the T-CN-300 sample can produce more·O2− species than the other samples. The reduced interfacial charge transfer resistance of the T-CN-300 sample significantly enhances the photocurrent. The results reveal that the unique heterojunction of F-TiO2 and g-C3N4 can effectively separate the photogenerated electron–hole pairs, accelerate the photocatalytic reaction, and increase the ·O2− species in the photodegradation system.

Abstract In this study, the graphene oxide (GO)-TiO2 nanocomposite film prepared by the sol–gel method was used to optimize the photoelectric performance of the perovskite solar cells (PSCs), which structure is based on the carbon electrode and no hole transport layer. Through a series of scientific experiments, it has been proved that the GO–TiO2 nanocomposite film has excellent electrical properties. The electron transport layer which containing 1 wt% of GO makes the PSCs have the most excellent performance. Compared with the controlling PSCs, the photoelectric conversion efficiency of PSCs, which containing 1 wt% GO, increased by 9.3%, from 12.44 to 13.60%. Short-circuit current density (Jsc) increased by 5.99%, from 21.55 to 22.84 mA/cm2, and open circuit voltage remained basically unchanged. It can be seen from the measurement results that the trend of incident photon-to-electron conversion efficiency spectrum is consistent with J–V characteristics, indicating that the PSCs device containing 1 wt% GO has the best electron extraction and transfer performance. However, when too much GO is used, the increased surface charge trap state will lead to the acceleration of carrier recombination and the decrease of electron transport path, and the photovoltaic parameters show a downward trend.

Abstract Hybrid carbon dots/titanium dioxide (CDs/TiO2) photoelectrodes for use in high-performance dye-sensitized photovoltaic solar cells were obtained by a facile one-step hydrothermal approach. The structural, morphological, and optical properties of the as-obtained samples were analyzed by powder X-ray diffraction analysis, transmission electron microscopy, Raman spectroscopy, ultraviolet–visible (UV–Vis) diffuse reflectance spectroscopy, and photoluminescence spectroscopy, revealing anatase crystal structure with individual spherical molded nanoparticles for both TiO2 and the composite samples. The size of the nanoparticles ranged from 30 to 40 nm, being consistently decorated on the carbon dots. The CDs/TiO2 samples exhibited enhanced surface area (112 m2/g) and pore size (30–35 nm) compared with bare TiO2 (77 m2/g and 42–48 nm), which is invaluable for improving solar cell efficiency. The J–V characteristic illustrated that the CDs/TiO2 photoanode resulted in high photovoltaic conversion efficiency (PCE) of 15.5% compared with 7.8% when using bare TiO2. These results suggest that incorporation of carbon dots enhanced the PCE of the cells using bare TiO2. A mechanism for this improvement is also proposed in detail.

Abstract Few studies have investigated the electrical and gas sensing properties of reduced graphene oxide/titanium dioxide (rGO/TiO2) composite thin films by spray pyrolysis technique. In this work, we report the synthesis and systematic investigation of structural, morphological and gas sensing properties of rGO-loaded TiO2 nanocomposite thin films. The XRD and AFM results suggest that both pure and rGO/TiO2 nanocomposite showed crystalline with tetragonal anatase phase and individual spherical shaped nanoparticles with average diameter of around 20–30 nm was observed. rGO/TiO2 nanocomposite showed high surface area (112 m2/g) and larger pores (11.2 nm) than bare TiO2 (89 m2/g; 32.3 nm). This huge surface area can beneficial for enhancing the gas sensing performance. Resistive type gas sensor set up was constructed and studied the sensing responses towards H2S and CO2 gases. The results suggest that the rGO/TiO2 nanocomposite sensor showed high sensitivity (92%), stability (only loss 3.5%), fast response (30 s) and recovery time (25 s) towards CO2 gas. The improved gas sensing mechanism of the proposed sensor was discussed in detail.