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As an innovative method that may change the manufacturing landscape in the near future, submerged arc additive manufacturing (SAAM) offers the benefits of flux protection and an inherent intrinsic heat treatment (IHT) for fabricating large-sized, high toughness parts in-situ. In this study, the influence of interlayer temperature on microstructure and mechanical properties of SAAM-processed low-carbon steel were elucidated with a particular focus on the toughening mechanism subjected to the in-situ IHT, which was first time comprehensively analyzed. Our SAAM-processed steel is found toughened in-situ by raising the critical fracture stress (reducing the effective grain size), and yield strength is also slightly lowered in-situ (softening the matrix), at a readily accessible interlayer temperature of ~200 °C for an optimal strength-toughness combination. This allows for the effective suppression of ductile-brittle transition (ductile-brittle transition temperature: ~ − 108 °C). The superior impact toughness (over 300 J at −60 °C) mainly origins from: (i) the pronounced amount of α-Fe (ferrite, BCC) that are intrinsically soft and facilitate plastic deformation, thereby impede the initiation and propagation of cracks; (ii) the fine-grained structure of multiple-recrystallized α-Fe phase and the increase of high-angle grain boundaries that make energy consumption more easily via tortuous crack propagating; (iii) the dispersedly distributed globular cementite structures formed by the decomposition of lamellar pearlite reduce the microcrack nucleation sites and release the strain concentration. The present SAAM method offers a solution for economically manufacturing large engineering components with uniform mechanical properties that exhibit an irreplaceable role in the low-temperature application with moderate strength requirements but extremely high in toughness.

Bi0.42Sb1.58Te3 + x wt % Cu1.8S (x = 0, 0.03, 0.05, and 0.1) bulk materials with enhanced thermoelectric and mechanical properties were fabricated by a solid-state reaction and spark plasma sintering. The thermoelectric properties, such as electrical transport properties and thermal conductivity, are highly dependent on the Cu1.8S content. The highest value of ZT obtained for Bi0.42Sb1.58Te3 with 0.05 wt % Cu1.8S is 1.23 at 373 K, and an optimistic average ZT of 1.2 is achieved at temperatures in the range of 323-448 K, which is 34% higher than that of the pristine sample. The highly enhanced ZT of the doped sample is attributed to the increased electrical conductivity and reduced lattice thermal conductivity caused by the effective element doping and the multiscale phonon scattering by quantities of point defects, twin boundaries, and nanopores. Further, the hardness obtained for this sample is 1.02 GPa, which is increased by 16% in comparison with that of the pristine sample. The conversion efficiency of the doped sample is also significantly higher than that of the pristine sample. Therefore, Cu1.8S is considered to be a promising dopant for enhancing the thermoelectric and mechanical properties of Bi-Sb-Te-based thermoelectric materials.

Piezoelectrics exhibit mechanical strain in response to electrical stimuli and vice versa. A high level of electric-field-induced strain with minimal hysteresis is desired for piezoelectric materials when used as actuators. The past two decades have seen extensive research into lead-free piezoelectrics to replace Pb(Zr,Ti)O3 and compositional engineering has been demonstrated to be an effective method to tailor their functional properties. Doped (K,Na)NbO3 (KNN) compositions with elaborate compositional tuning can exhibit enhanced electromechanical properties. However, a balance between enhanced properties and non-toxicity of the dopants should be considered. In this work, we propose to use microstructural engineering to enhance the properties. Based on phase-field simulations, we propose to take advantage of depolarization energies generated by polar-nonpolar interfaces, to increase the contribution of domain wall motion to electric-field-induced strain. Heterogeneous ferroelectric-paraelectric microstructures were introduced into a KNN ceramic via a two-step sintering process. Their presence was characterized by high-resolution transmission electron microscopy. Enhanced reversible domain wall motion was verified by in situ high-energy X-ray diffraction. Electric-field-induced strain is enhanced by 62% and 200% at 25 °C and 150 °C, respectively. Considering lead-free piezoelectrics also represent an emerging class of biomaterials for medical technology, the non-toxicity and biocompatibility of the investigated compositions are examined by in vitro cell viability assays. Our results demonstrate that microstructural engineering is a promising alternative approach to enhance the electric-field-induced strain of lead-free piezoelectrics while maintaining biocompatibility

A Bi2Te3/Bi2S3@Bi nanocomposite with a network microstructure was successfully synthesized via a hydrothermal method and spark plasma sintering. This composite was constructed from Bi2Te3 nanoparticles and Bi2S3@Bi nanowires, and its network structure is beneficial for obtaining excellent thermoelectric performance. A ZT peak of 1.2 at 450 K was realized for the nanocomposite sample.

The processes of heat treatment and subsequent hot rolling were carried on duplex-phase Mg-8Li-6Y-2Zn alloy to improve the electromagnetic interference (EMI) shielding effectiveness (SE) of the alloy. The microstructure and EMI SE of the alloy under different states were researched. The results show that, after heat treatment, a larger area fraction of second phase, LPSO phase, increases the multiple internal reflections of EM waves. The fine LPSO phases in the subsequent hot rolling can facilitate dynamically recrystallized grains refinement. Meanwhile, the hot rolling improves the electrical conductivity of the alloy. The increase of interfaces and electrical conductivity are both beneficial to improve the EMI SE of the alloy. The combination of heat treatment and hot rolling can provide an efficient strategy for improving the EMI SE of Mg-8Li-6Y-2Zn alloy.

MgB2 bulks with graphene doping were synthesized by high energy ball milling process. The effect of high energy ball milling and graphene doping on the microstructure and critical current density of MgB2 was studied systematically. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and physical property measurement system (PPMS), respectively. The densities of ball-milled graphene-doped samples were larger than those of pure samples. The superconducting properties of MgB2 could be increased by the high energy ball milling process, in comparison with the sample prepared by grinding process. Moreover, the significant improvement of superconducting properties for ball-milled MgB2 samples could be achieved with the addition of graphene. The combination of graphene doping and suitable ball milling could refine the grain and improve the inter-grain connectivity of MgB2. MgB2 with 3 at% graphene doping prepared by high energy ball milling with 2 h exhibited very high critical current density of 6.4 × 105 A/cm2 at 20 K and 0 T.

High electromagnetic shielding performance was achieved in the Mg–9Li–3Al–1Zn alloy processed by accumulative roll bonding (ARB). The microstructure, electromagnetic interference shielding effectiveness (SE) in the frequency of 30–1500 MHz and mechanical properties of the alloy were investigated. A model based on the shielding of the electromagnetic plane wave was used to theoretically discuss the EMI shielding mechanisms of ARB-processed alloy. Results indicate that the SE of the material increases gradually with the increase in the ARB pass. The enhanced SE can be attributed to the obvious microstructure orientation caused by ARB, and the alternative arrangement of alpha(Mg) phase and beta(Li) phase. In addition, with the increase in ARB pass, the number of interfaces between layers increases and the grain orientation of each layer tends to alignment along c-axis, which is beneficial to the reflection loss and multiple reflection loss of the incident electromagnetic wave.

Ferroelastic ABO4 type RETaO4 and RENbO4 ceramics (where RE stands for rare earth) are being investigated as promising thermal barrier coatings (TBCs), and the mechanical properties of RETaO4 have been found to be better than those of RENbO4. In this work, B-site substitution of tantalum (Ta) is used to optimize the thermal and mechanical properties of EuNbO4 fabricated through a solid-state reaction (SSR). The crystal structure is clarified by means of X-ray diffraction (XRD) and Raman spectroscopy; and the surface microstructure is surveyed via scanning electronic microscope (SEM). The Young’s modulus and the thermal expansion coefficient (TEC) of EuNbO4 are effectively increased; with respective maximum values of 169 GPa and 11.2 × 10−6 K−1 (at 1200 °C). The thermal conductivity is reduced to 1.52 W·K−1·m−1 (at 700 °C), and the thermal radiation resistance is improved. The relationship between the phonon thermal diffusivity and temperature was established in order to determine the intrinsic phonon thermal conductivity by eliminating the thermal radiation effects. The results indicate that the thermal and mechanical properties of EuNbO4 can be effectually optimized via the B-site substitution of Ta, and that this proposed material can be applied as a high-temperature structural ceramic in future. Keywords: Thermal barrier coatings, Rare earth niobates, Substitution, Thermal conductivity, Thermal expansion coefficients, Young’s modulus

SmTaO4 ceramics have excellent high-temperature phase stabilities and mechanical properties and show great potential for use as next-generation thermal barrier coating (TBC) materials. CeO2–SmTaO4 ceramics are prepared via high-temperature solid–state reaction. It retains a single monoclinic phase structure. Ce4+ was reduced to Ce3+ by high-temperature deoxidation, and the Ce3+ ions substitute for an equal number of Sm3+ ions. The CeO2–SmTaO4 ceramics had lower thermal conductivities [1.09–2.75 W/(m K)] than yttria-stabilized zirconia (YSZ) [2.1–2.7 W/(m K)] at 100–800 °C, which decreased dramatically with increasing temperature. SmTaO4 doped with 2% CeO2 had lower thermal conductivity [1.09 W/(m K), 800 °C] than SmTaO4 [1.42 W/(m K), 800 °C] and 2% ZrO2-doped SmTaO4 ceramics [1.22 W/(m K), 800 °C]. The low thermal conductivity is attributed to Ce3+ substitution for an equal number of Sm3+ ions, and because Ce3+ ions are the strongest phonon scattering centers, they can decrease the phonon mean free path effectively. The thermal expansion coefficient of 8% CeO2–SmTaO4 ceramics is approximately 10.3 × 10−6 K−1 at 1200 °C, which is slightly higher than that of both YSZ (10.0 × 10−6 K−1) and SmTaO4 (9.58 × 10−6 K−1). The outstanding thermophysical properties indicate that CeO2–SmTaO4 ceramics are potential TBC materials.

HfO2 alloying effect has been applied to optimize thermal insulation performance of HoTaO4 ceramics. X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy are employed to decide the crystal structure. Scanning electronic microscopy is utilized to detect the influence of HfO2 alloying effect on microstructure. Current paper indicates that the same numbers of Ta5+ and Ho3+ ions of HoTaO4 are substituted by Hf4+ cations, and it is defined as alloying effect. No crystal structural transition is introduced by HfO2 alloying effect, and circular pores are produced in HoTaO4. HfO2 alloying effect is efficient in decreasing thermal conductivity of HoTaO4 and it is contributed to the differences of ionic radius and atomic weight between Hf4+ ions and host cations (Ta5+ and Ho3+). The least experimental thermal conductivity is 0.8 W·K−1·m−1 at 900 °C, which is detected in 6 and 9 mol%-HfO2 HoTaO4 ceramics. The results imply that HfO2–HoTaO4 ceramics are promising thermal barrier coatings (TBCs) due to their extraordinary thermal insulation performance.

Zirconia alloying is one of the most effective approaches used to obtain optimal performance of YTaO4 ceramics as thermal barrier coatings (TBCs), making it an important method for investigation. In this work, (ZrO2)x-(YTaO4)1-x (x = 0, 0.1, 0.2, 0.3) ceramics are synthesized via solid-state reaction, after which an analysis of the phase composition and microstructures of the samples is conducted using X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) employed to characterize the variation of bond energy with composition reveals that Zr4+ ions simultaneously substitute Y3+ ions and Ta5+ ions in the structure of YTaO4 ceramics. Due to the zirconia alloying effect, the thermal conductivity of (ZrO2)x-(YTaO4)1-x ceramics significantly decreases, reaching a minimum of approximately 1.33 W m−1 K−1 at 900 °C, which is exceeding 40% lower than that of YSZ. The thermal expansion coefficients of (ZrO2)x-(YTaO4)1-x ceramics vary in some ranges (8.4–10.0 × 10−6 K−1, at 1200 °C), but are comparable to that of YSZ. In addition, this research systematically investigates the discipline of hardness and modulus changing with the composition. As is demonstrated by the excellent thermophysical properties it exhibits, (ZrO2)x-(YTaO4)1-x ceramic material is believed to be a prospective TBCs material.

A sequence of (La1-xHox)3NbO7 solid solutions were fabricated in this work, which were studied as candidate for thermal insulation materials. The lattices were identified via XRD, when SEM and EDS were used to characterize the microstructures and element distributions. The results showed that the highest modulus, hardness, and toughness of (La1-xHox)3NbO7 were 196 GPa, 9.2 GPa, and 1.6 MPa m1/2, respectively, and they accorded with the mechanical property requirements. Also, a low thermal conductivity (1.06 W m−1 K−1) and high thermal expansion coefficients (TECs: 11.3 × 10−6 K−1) were simultaneously realized in (La3/6Ho3/6)3NbO7, at high temperatures. No phase transition was detected up to 1,200°C, which proved their good high-temperature lattice stability. The intense anharmonic lattice vibrations might contribute to the outstanding thermal properties of (La1-xHox)3NbO7 ceramics. The suitable modulus, high hardness, low thermal conductivity, and high TECs of (La1-xHox)3NbO7 solid solutions proclaimed that they were exceptional thermal insulation ceramics.

Fluorite structural Yb3TaO7 and Yb3NbO7 with glass-like thermal conductivity are investigated as candidate thermal insulation materials in this work. The relationship between thermo-mechanical properties and crystal structure of Yb3TaO7 and Yb3NbO7 ceramics has been determined. The crystal structure is characterized via X-ray diffraction (XRD), Raman spectrum and X-ray photoelectron spectroscopy (XPS), and the microstructure is observed by scanning electron microscope (SEM). Yb3TaO7 and Yb3NbO7 exhibit the ultralow glass-like thermal conductivity (1.04 W m−1 K−1), which derives from the long-range disordered atomic arrangement. The weaker bonding strength leads to higher TECs, lower thermal conductivity and Young' modulus of Yb3NbO7, compared with Yb3TaO7. Besides, the outstanding high-temperature phase stability, high hardness and fracture toughness of Yb3TaO7 and Yb3NbO7 imply that they are promising high-temperature thermal insulation ceramics.

A systematic investigation concerned with Y1−xMgxTaO4−x/2 (x = 0, 0.08, 0.12, 0.16 and 0.20, respectively) ceramics was fabricated by a solid-state reaction method and characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and thermal analysis. XRD spectra display that all of the samples are excellently consistent with the standard XRD spectrum of monoclinic YTaO4 (PDF No. 24-1415; space group: I2 (5)). The Raman peaks of the samples doped with Mg2+ just widen slightly compared with those of pure YTaO4, which are in agreement with the results of XRD. The thermal conductivity of dense 7 wt%–8 wt% yttria-stabilized zirconia (7–8 YSZ) ceramic is about 2.5 W·m−1·K−1 at 900 °C, while the Y1−xMgxTaO4−x/2 (x = 0, 0.08, 0.12, 0.16 and 0.20) ceramics possess lower thermal conductivity in the range of 1.45–1.57 W·m−1·K−1 at 900 °C, which declines by 35% compared with that of 7–8 YSZ. The lower thermal conductivities of Y1−xMgxTaO4−x/2 (x = 0, 0.08, 0.12, 0.16 and 0.20) ceramics are originated from the enhanced phonon scattering caused by oxygen vacancy and Mg2+ ions defect complex. However, the thermal expansion coefficients are about 9.0 × 10−6–9.5 × 10−6 K−1 along with the different amounts of Mg2+ doping at 1200 °C. Compared to the pure sample, the thermal expansion coefficient decreases slightly when the Mg2+ doping amount is over 20%. The systematic investigations on the phase, microstructure, elastic and thermal properties of Y1−xMgxTaO4−x/2 (x = 0, 0.08, 0.12, 0.16 and 0.20) ceramics will provide guidance for its application at high temperature, especially as thermal barrier coatings.

Although the Cu1.8S compound consisting of cheap and earth-abundant elements has been reported to be a potential candidate of thermoelectric material, its thermoelectric performance is not very high. In this work, a fast doping strategy is offered to introduce both point defects and nanostructures into thermoelectric materials to improve the performance. Ball-milled Cu1.8S powders were mixed with different amounts of In2S3 powders and were then sintered into bulk samples by the spark plasma sintering (SPS) technique. During the SPS process, In2S3 was doped into the Cu1.8S matrix at 723 K for 10 min, and the fast doping process results in point defects and nanostructures of the Cu1.8S bulk sample including nanopores and those with an included second phase. On the one hand, In doping increased the effective mass of charge carriers in Cu1.8S and improved the Seebeck coefficient, whereas on the other hand, the nanostructures reduced thermal conductivity significantly. The phase structure and microstructure of Cu1.8S bulks are highly dependent on the In2S3 content. Density functional theory calculations revealed that Cu1.8S has an intrinsically low lattice thermal conductivity because of low-frequency localized vibrations from the Cu ionic migration and Cu vacancies. As a result, Cu1.8S+3 wt% In2S3 bulk sample achieved a ZT value of ∼1.4 at 773 K compared with that of 0.45 at 773 K for the pristine Cu1.8S sample; this value is the highest ZT value in sulfide thermoelectric materials at this temperature. The fast doping strategy demonstrated in this work can also be applied for reducing thermal conductivity and improving ZT values of other thermoelectric systems.

La-doped AgNbO3 lead-free ceramics were fabricated by conventional solid-state reaction, and the phase stability and energy storage properties were investigated. The temperature- and electric field-dependent dielectric constants show that the antiferroelectric (AFE) phase stability is enhanced via the La doping. Neutron diffraction was performed to obtain insights into the structural evolution with composition and temperature, where the local structural variation is found to involve subtle ion displacement as well as oxygen octahedral tilting, leading to the disruption of the long-range interactions, which is responsible for the enhanced AFE phase stability. As expected, the enhanced AFE phase stability, together with the improved breakdown strength, gives rise to a high energy density of 4.4 J cm−3 and an improved efficiency of 70%, which are achieved in 2 mol% La-doped AgNbO3 ceramics. Our research opens a new way to tailor the macroscopic properties by tuning the microstructure of AgNbO3-based materials.

Bi2S3 is an eco-friendly alternative compound for thermoelectric devices. However, the low electrical conductivity of the pristine Bi2S3 hinders the improvement of its ZT value, which further restricts its application in the field of thermoelectricity. In this work, we report the first attempt to optimize the thermoelectric properties of Bi2S3 by electroless nickel plating. A nickel plated Bi2S3 powder sample was synthesized by electroless nickel plating on the precursor Bi2S3 powder prepared by mechanical alloying. Then, the powder was sintered to a bulk material by spark plasma sintering. The relationships between the composition, microstructure and thermoelectric properties of the bulk samples were investigated. The XRD results showed a AgBi3S5 second phase which was formed by the reaction of Ag residues with the Bi2S3 substrate during the sintering process. The nickel element and AgBi3S5 second phase introduced in the nickel plating process directly affect the electronic conductivity and Seebeck coefficient of the nickel plating sample, resulting in the relatively high power factor of 244 μW m−1 K−2 at 628 K. What's more, the thermal conductivity of the sample was also reduced moderately, obtaining a low value of 0.40 μW m−1 K−1 at 628 K. Therefore, a maximum ZT value of 0.38 was obtained at 628 K for the nickel plated sample, which is three times higher than that (0.12 at 628 K) of pristine Bi2S3 materials.

A series of ceramics of (Y1-xDyx)TaO4 monoclinic phases (space group: I2 (5)) are prepared by the solid-state reaction method. The high-resolution transmission electron microscopy (HRTEM) suggest the (Y1-xDyx)TaO4 ceramics possess ferroelastic domain, which is derived from reversible second-order ferroelastic transformation between the high-temperature tetragonal (t) and low-temperature monoclinic (m) phase. Similar to metastable tetragonal YSZ ceramics, the ferroelastic toughening mechanism may exist in m-phase (Y1-xDyx)TaO4 ceramics through the shift or reorientation of ferroelastic domain under the stress field of a crack. The energy dispersive spectroscopy reveals that the elements of Y and Dy are inhomogeneous in the grain of (Y1-xDyx)TaO4 ceramics, which breaks down the relationship of concave parabola between thermal conductivity and composition parameter (x). Moreover, the thermal conductivities (1.7–2.0 W/m/k at 900 C) and thermal expansion coefficients (TECs) (10–11 × 10−6 K−1) of (Y1-xDyx)TaO4 ceramics are comparable to that of YSZ (yttria-stabilized zirconia). In view of the low thermal conductivity, high thermal expansion coefficients, good high-temperature phase stability and ferroelastic transformation, the (Y1-xDyx)TaO4 ceramics show great potentials in the application of high-temperature thermal insulator materials, particularly as thermal barrier coatings.

Rare earth tantalates (La1-XEuX)3TaO7 ceramics are synthesized via solid-state reaction in this work. The phase structure is characterized via X-ray diffraction and Raman spectrum, when the microstructure and element distribution are detected by scanning electron microscopy and energy dispersive spectroscopy. As for various properties, (La1-XEuX)3TaO7 ceramics own excellent absorption for the UV light and the band gap ranges from 4.0 to 4.7 eV. The highest thermal expansion coefficients reach 10.8 × 10−6 K−1 (1200 ℃) and the entire series of (La1-XEuX)3TaO7 ceramics exhibit excellent high-temperature phase stability. The minimum thermal conductivity reaches 1.04 W m−1 K−1 (500 ℃) ascribed to various phonon scattering mechanisms. The thermal radiation resistance relates to the crystal structure, which relies on the mean RE3+ ionic radius. The results reveal that (La1-XEuX)3TaO7 ceramics are candidate thermal insulation materials.

Cu2-xS compounds with low-cost and low-toxicity elements have been reported as good candidates for thermoelectric (TE) application. In this work, the Cu1.96S powders were synthesized by both hydrothermal synthesis (HS) and mechanical alloying (MA) methods. The HS synthesis process and mechanism was discussed in detail. The polycrystalline Cu1.96S bulk materials were obtained by condensing the powders (prepared by HS and MA) or the mixed HS and MA powers with the different ratio (1:0, 9:1, 1:9 and 0:1) using spark plasma sintering (SPS) technique. The phase structure, microstructure of the powders and bulk samples were checked. The results show that the Cu1.96S powders synthesized by HS are more stable than the powder prepared by MA method during the SPS process. And the thermoelectric properties of all bulk samples were investigated in detail at the temperature ranges from 323 to 773 K. The Cu1.96S bulk sample sintered by using mixed powders of 90 wt% HSed powders and 10 wt% MAed powders obtained the maximum ZT value of 1.01 at 773 K, which is currently the highest reported value for the Cu1.96S system at this temperature.

Ni–WC–La2O3 wear-resistant coatings are prepared by a plasma spray method on the pure iron. The microstructure and wear resistance of the coating are investigated. After La2O3 doping, the wear resistance of modified coating was enhanced significantly. The amount of coating wear was reduced by 61.9% and the friction coefficient was reduced by 35.7% because of the La2O3 content of 1.5 wt.% compared with the Ni–WC coating. La2O3 can suppress WC precipitation along the grain boundaries, and reduce the number of cracks in the substrate near the WC phase. Furthermore, the diffusion and segregation behavior of La atoms is studied by first-principle calculation. The simulation results show that La doping can increase the bonding energy between the WC particles and the Ni substrate, consequently improve the abrasion properties of the coating. The cohesive energy of the interface is the smallest when the La atoms occupies Ni atomic sites of the interface, as result a stable Ni–WC interface is formed on the interface. A Ni–La amorphous transition layer is formed on the Ni–WC interface. Its structure has rheological properties and relaxes the thermal stress of the interface, which reduces the Ni–WC interface cracking and improves the bonding strength.

A densification process has been conducted on isostatic graphite (IG-110, TOYO TANSO CO., Ltd., Japan) by impregnating phenolic resin to get the densified isostatic graphite (D-IG-110) with pore diameter of nearly 11 nm specifically for molten salt reactor application. The microstructure, mechanical, thermophysical and other properties of graphite were systematically investigated and compared before and after the densification process. The molten fluoride salt and Xe135 penetration in the graphite were evaluated in a high-pressure reactor and a vacuum device, respectively. Results indicated that D-IG-110 exhibited improved properties including infiltration resistance to molten fluoride salt and Xe135 as compared to IG-110 due to its low porosity of 2.8%, the average pore diameter of 11 nm and even smaller open pores on the surface of the graphite. The fluoride salt infiltration amount of IG-110 was 13.5 wt% under 1.5 atm and tended to be saturated under 3 atm with the fluoride salt occupation of 14.8 wt%. As to the D-IG-110, no salts could be detected even up to 10 atm attempted loading. The helium diffusion coefficient of D-IG-110 was 6.92 × 10−8 cm2/s, significantly less than 1.21 × 10−2 cm2/s of IG-110. If these as-produced properties for impregnated D-IG-110 could be retained during MSR operation, the material could prove effective at inhibiting molten fluoride salt and Xe135 inventories in the graphite.

Modification process has been conducted on commercial nuclear graphite IG-110 (Toyo Tanso Co., Ltd., Japan) by impregnation and pyrolysis of polycarbosilane (PCS) solution for getting the modified IG-110 (M-IG-110) coated by dense SiC coating for molten salt reactor. The microstructure and properties of graphite were systematically investigated and compared before and after the modification process. Results indicated that the M-IG-110 possessed of more excellent integrated properties including molten salt barrier property and oxidation resistance than bare IG-110 due to the filling effect of SiC particles in the pores of M-IG-110 and dense SiC coating adhering to the surface of M-IG-110. The fluoride salt infiltration amount of M-IG-110 under 5 atm was only 1.1 wt%, which was much less than 14.9 wt% for bare IG-110. The SiC coating derived from PCS exhibited remarkable compatibility with graphite substrate under high temperature and gave rise to excellent oxidation resistance of M-IG-110.

The effects of high hydrostatic pressure (HHP) treatments (200, 300, and 400 MPa for 1, 3, 5 and 10 min) on the shelling efficacy (the rate of shelling, the rate of integrity and yield of razor clam meat) and the physicochemical (drip loss, water-holding capacity, pH, conductivity, lipid oxidation, Ca2+ -ATPase activity, myofibrillar protein content), microbiological (total viable counts) and microstructural properties of fresh razor clam (Sinonovacula constricta) were investigated. HHP treatments significantly (P < 0.05) increased shelling efficiency, water-holding capacity, pH, conductivity, and lipid oxidation, and HHP-treated razor clam showed lower levels of microorganisms and drip loss than untreated razor clam. Levels of thiobarbituric acid reacting substances (TBA) in HHP-treated razor clam were greatly increased (up to 0.93 ± 0.09 mg MDA/kg at 400 MPa for 10 min) which was caused by the formation of hydroperoxides during HHP treatment. All HHP treatments were found to have adverse effects on the activity of Ca2+ -ATPase and the content of myofibrillar protein (MP), which might be due to the substantial damage to the tertiary structure of proteins at high pressure. Moreover, scanning electron microscopy (SEM) revealed the compaction of the muscle fibers and a decrease in the extracellular space with increasing pressure and holding time. This phenomenon was mainly correlated with the compaction of muscle fibers and denaturation, aggregation, and gelation of muscle protein triggered by high pressure. In general, HHP could be applied as a safe and effective nonthermal technology to produce high-quality shelled razor clam. PRACTICAL APPLICATION High hydrostatic pressure (HHP) is now well known as a nonthermal processing technology and becoming increasingly acknowledged. However, it has not been widely applied to shell seafood due to its uncertain influence on its quality and shelling property. This study could provide valuable information regarding the shelling efficacy, physicochemical properties, and microstructure of razor clam treated by HHP. And it demonstrated that HHP showed a positive impact on quality of razor clam treated by HHP.

In this study, the Mg-9Li-3Zn-0.5Gd/MWCNTs composite was prepared by the method of heat treatment+electrophoretic deposition (EPD)+accumulative roll bonding (ARB), and the microstructure, electrical conductivity, electromagnetic (EM) shielding properties in the X-band (8.2–12.4 GHz) and strength were evaluated. The microstructure characterization shows that, after five ARB cycles, MWCNTs are uniformly distributed in the Mg-Li matrix, and severe plastic deformation promotes the dynamic precipitation of the nano-scale secondary phase particles, which greatly weakens the lattice distortion of the Mg-Li matrix. Besides, MWCNTs induces a large amount of ultrafine nano-scale W-phase precipitation. The property evaluation indicates that the electrical conductivity, ultimate tensile strength and yield strength of C-ARB5 sheet are 7.60 MS/m, 280 MPa and 264 MPa, respectively, which are increased by 1.9%, 4.2% and 4.9% compared with ARB5 sheet. In the X-band frequency range, the electromagnetic interference (EMI) shielding effectiveness (SE) of ARB5 sheet is 77–96 dB, and that of C-ARB5 sheet is increased to 89–100 dB. The improvement of C-ARB sheets property is mainly attributed to the uniformly distributed MWCNTs inducing precipitation of ultrafine nano-scale W-phase.

The relationship between types of phases, microstructure and mechanical properties is always a critical challenge for the research and application of multiphase alloys. We report for the first time that NanoBlitz 3D method implemented in iNano is used to investigate the distribution of micro mechanical modulus and hardness for the entire complex multiphase alloy Fe-6.0W-5.0Mo-4.0Cr-2.0V-0.83C by constructing the two-dimensional mapping. In order to build the correlation between the microstructure and properties, the carbides in this tempering state steel are confirmed to be Fe3(W, Mo)3C, Cr15.58Fe7.42C6 and V8C7 by acid etching and XRD refinement. The phases mapping is obtained by electron probe micro-analysis. Exact element ratio is characterized for the nano-scale multielement carbides precipitates. The Young's modulus and hardness of the precipitated carbides are up to 330 GPa and 22 GPa, respectively. The distribution range of Young's modulus and hardness is during 150 to 250 GPa and 2.5 to 7.0 GPa for the matrix phases, respectively. The experimental Young's modulus and hardness results are verified by first-principles calculations combined with Voigt-Reuss-Hill approximation. In fact, this work provides a successful demonstration to three-dimensionally characterize the micro mechanical properties for all the ceramics and alloys.

Thermal barrier coatings (TBCs) are one of the most important materials in gas turbine to protect the high temperature components. RETa3O9 compounds have a defect-perovskite structure, indicating that they have low thermal conductivity, which is the critical property of TBCs. Herein, dense RETa3O9 bulk ceramics were fabricated via solid-state reaction. The crystal structure was characterized by X-ray diffraction (XRD) and Raman Spectroscope. Scanning electron microscope (SEM) was used to observe the microstructure. The thermal physics properties of RETa3O9 were studied systematically, including specific heat, thermal diffusivity, thermal conductivity, thermal expansion coefficients and high-temperature phase stability. The thermal conductivities of RETa3O9 are very low (1.33-2.37 W/m.K, 373-1073 K), which are much lower than YSZ and La2Zr2O7; and the thermal expansion coefficients range from 4.0×10-6 K−1 to 10.2×10-6 K−1 (1273 K), which is close to La2Zr2O7 and YSZ. According to the differential scanning calorimetry (DSC) curve there is not phase transition at the test temperature. Due to the high melting point and excellent high-temperature phase stability with these oxides, RETa3O9 ceramics were promising candidate materials for TBCs. This article is protected by copyright. All rights reserved.

Recently, researchers have been exploring the optimization of the thermoelectric properties of composite materials. Composite technology with many successful cases of enhancement in thermoelectric properties have been confirming effectively to optimize thermoelectric materials. In this study, Ru nano-micro composite particles were successfully introduced in commercial bismuth telluride (Bi2Te3) as second phase to simultaneously optimize the thermoelectric and mechanical properties. In a Bi2Te3 sample containing 1 wt% Ru (+1 wt% Ru), the ZT peak was measured to be 0.93 (at 150 °C) and the maximum Vickers hardness was measured to be 2.38 GPa. These values exceeded the values of a pure sample by 45.3% and 36%, respectively. The average ZT of the +1 wt% Ru sample at 50–200 °C was 0.86, which is comparable with the Bi2Te3-xSex system. By varying the Ru content, the components, microstructure, thermoelectric and mechanical properties of Bi2Te3 were manipulated and their interdependence demonstrated. The extent to which the thermoelectric and mechanical properties of Bi2Te3 can be optimized, via Ru compositing and nano-Bi2Te3 producing, is related by the complex nano-micro composite structure. The superior thermoelectric properties of composite materials hold great the commercial value and may reduce the input of raw materials.

The Cu–S compounds have been reported as promising thermoelectric materials with abundant element composition, low price, and low toxicity. In this work, SnxCu1.8−xS samples with different Sn contents (x = 0.005, 0.01, 0.03, and 0.05) were fabricated by mechanical alloying combined with spark plasma sintering. The phase structure and microstructure of all the bulk samples were checked by X-ray diffraction (XRD) and field emission scanning electron microscopy respectively. The thermoelectric transport properties, such as electrical conductivity, Seebeck coefficient, carrier concentration, carrier mobility, and thermal conductivity, were measured. The effect of second phase introduced by Sn addition on the thermoelectric properties of Cu–S system was investigated. The thermoelectric properties of samples were improved by the precipitations of two different second phases (Cu2SnS3 and Cu4SnS4). The second phase species depend on the Sn contents. Finally, the Sn0.01Cu1.79S bulk sample obtained the highest ZT value of 0.81 at 773 K, which is 1.6-fold higher than that of the pristine Cu1.8S sample due to the significantly reduced thermal conductivity by second phase and nanopores scattering.

In this paper, montmorillonite supported-nano TiO 2 photocatalytic composites are synthesized by an easily-operated solid diffusion process, in which montmorillonite is used as a support matrix. And the microstructures, morphologies and photocatalytic properties of the montmorillonite supported-nano TiO 2 composites are characterized and analyzed by scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, UV–vis spectroscopy, fluorescence spectroscopy and methylene blue degradation tests. The results show that montmorillonite matrix reduces agglomeration of nano-TiO 2 and enhances the absorption ability within the UV–vis range, consequently increases the photocatalytic activity of the composites. Meanwhile, the influence of TiO 2 /montmorillonite proportion on photocatalytic performances is explored, which indicates that 90 wt% TiO 2 /montmorillonite has optimal photocatalytic properties.

Strontium titanite (SrTiO3), which is an experimentally-friendly thermoelectric material, could be a promising candidate for thermoelectric power generation applications. The theorectical study indicates the co-doping of La and Nb could enhance the thermoelectric performance, however, the thermoelectric figure of merits (ZTs) of SrTiO3 are still low because the co-doping process at nano-scale is experimentally difficult to control. Here we report a high performance SrTiO3 with La-Nb co-doping, which are prepared by a combination of hydrothermal method and high-efficiency sintering. Nano-scale co-doping is successfully modulated by hydrothermal method, and nano-inclusions precipitate during sintering process, to form complex microstructures. In this case, the electrical and thermal transport properties are optimized simultaneously by doping concentration and dopants type, resulting in a record-high ZT >0.6 at 1000−1100 K in the 10 mol% La and 10 mol% Nb doped SrTiO3 bulk materials. The nano-scale modulation doping and microstructure controlling approach validated in the present study should be also applicable for other thermoelectric materials.

Thermoelectric materials are a relatively new functional material that can be used for the direct conversion of thermal energy to electrical energy through the transmission and interaction of carriers and phonons in the solid. Polycrystalline p-type Cu1.8S dispersed with x wt% SiC nanoparticle (x = 0.1, 0.5, 1.0, 3.0) thermoelectric materials were fabricated by mechanical alloying (MA) and spark plasma sintering (SPS). The effects of the SiC nanoparticles on the thermoelectric properties of the material were investigated. The phase structure and microstructure of all the bulk samples were checked by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. Compared to pristine Cu1.8S, Cu1.8S polycrystals dispersed with nano-SiC showed increased Seebeck coefficients, decreased electrical conductivities, and reduced thermal conductivities in the temperature range of 323–773 K. The maximum dimensionless figure of merit (ZT) was improved from 0.49 for pristine Cu1.8S samples to 0.87 for the 1.0 wt% SiC dispersed Cu1.8S sample at 773 K.

The tin dioxide ceramics were prepared by the traditional solid phase sintering method. Influence of different CeO2 doping amount on the microstructure, electrical resistivity and density of the tin dioxide ceramics by SEM and XRD and other analytical instrument. The relationship between composition, properties and structure were obtained. The results showed that when CeO2 doping quantity increased, the electrical resistivity of tin dioxide ceramics decreased firstly and then increased, the density of tin dioxide ceramics increased. When sintered temperature was 1430°C and the doping quantity of CeO2 was 0.7wt.%,the properties of tin dioxide ceramics was good, crystal growth was most complete,the electrical resistivity was 966.68mΩ·cm and the density was 5.72g/cm3.

The RETaO 4 ceramics with low-thermal conductivity were fabricated using a solid-state reaction. The phase composition and microstructures of high-temperature RETaO 4 (RE = Nd, Eu, Gd, Dy, Er, Yb, Lu) ceramics were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman spectroscopy. The RETaO 4 ceramics had lower thermal conductivity (1.38 to 1.94 W·m − 1 ·K -1 at 800 °C) than 7-8YSZ (2.37 and 2.47 W·m − 1 ·K − 1 at 800 °C, respectively). The porosity significantly affected the thermal conductivity of RETaO 4 ceramics. The RETaO 4 ceramics also had lower Vickers hardness than 8YSZ, which suggests that RETaO 4 has better fracture toughness and thermal tolerance.

Polycrystalline bulk Cu1.8S materials were fabricated using mechanical alloying (MA) and spark plasma sintering (SPS). The microstructure and thermoelectric transport properties were investigated in detail with emphasis on the effect of the mechanical alloying ball-milling process. Cu1.8S single-phase powders were directly synthesized from the elemental powders. High-density (>95%) p-type Cu1.8S bulk samples were fabricated using the subsequent SPS process at 773 K for 5 min. A Cu1.96S second phase was detected in the bulk samples when the ball-milling time was increased to 3 h, and the Cu1.96S content increased with increasing ball-milling time. The electrical properties and Seebeck coefficient of the Cu1.8S bulk samples were dependent on the milling time of the starting powders. The Cu1.8S bulk that was sintered by SPS using the powder treated with a 3 h ball-milling obtained a record-high power factor of 1552 μW m−1 K−2 at 773 K for the Cu–S system, which is 40% higher than that of pristine Cu1.8S. The ZT value of the Cu1.8S bulk sample that was sintered by SPS using the 12 h ball-milling treated powder reached 0.71, which is 67% higher than the ZT value of the sample that was sintered using the powder with a 1 h ball-milling time.

A pure Al coating and Al-Si coating were prepared on the surface of the DZ125 superalloy by hot-dipping. The Al-Si coating provides better thermal oxidation resistance than that of the pure Al coating due to the formation of a more compact Al 2 O 3 layer. The microstructure of the Al-Si coating shows a silicon-aluminium-based layer with Ta 5 Si 3 and AlHfSi phase forms after heat treatment in argon at 850 °C. This layer is a barrier to the diffusion of oxygen and other metal elements during cyclic oxidation, which has a significant effect on the formation of the compact Al 2 O 3 layer.

The electrical properties and microstructures of (1 − x ) Bi 1/2 Na 1/2 TiO 3 – x SrTiO 3 (BNT-ST100 x , 0.20 ≤ x ≤ 0.30) piezoceramics with different grain size distributions were investigated. The critical region separating the ferroelectric from ergodic relaxor is located around x = 0.26. Strains up to 0.2% could be achieved under a low driving fields ( E S max /E max >1000 pm/V. The electrostrain was largely depended on the grain size and an increment of strain up to ∼38% can be realized by increasing the grain size from 5 μm to 13 μm in the BNT-ST26 samples. The results indicate that the field-induced strain performance of BNT-based incipient piezoelectric ceramics can be tailored via microstructure modifications, an alternative strategy to enhance the electromechanical properties.

High temperature gas turbine sealing can increase the thermal efficiency of a gas turbine. In this paper, monoclinic phase YTaO 4 ceramics were fabricated via solid-state reaction. Phase composition and microstructures of the high-temperature-sintered YTaO 4 ceramics were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman Spectroscopy. Specific heat capacity rose gradually as temperature increased, due to volumetric expansion and phonon excitations. The thermal diffusivities and conductivities decreased significantly due to the effects of the porosity and phonon scattering. However, the thermal conductivities of the specimens were lower than that of 7–8 wt% yttria-stabilized zirconia (7-8YSZ), and YTaO 4 ceramics have better thermal stability than current (TBCs) material. The Vickers hardnesses of YTaO 4 ceramics as a function of sintering temperature were lower than that of 8YSZ, indicating YTaO 4 has better fracture toughness and thermal tolerance. The results demonstrate that YTaO 4 ceramics would be an excellent candidate for use as a thermal barrier coating material for high temperature gas turbines.

Thermoelectric materials, which directly convert heat into electricity based on the Seebeck effects, have long been investigated for use in semiconductor refrigeration or waste heat recovery. Among them, SnSe has attracted significant attention due to its promising performance in both p-type and n-type crystals; in particular, a higher out-of-plane ZT value could be achieved in n-type SnSe due to its 3D charge and 2D phonon transports. In this work, the thermoelectric transport properties of n-type polycrystalline SnSe were investigated with an emphasis on the out-of-plane transport through producing textural microstructure. The textures were fabricated using mechanical alloying and repeated spark plasma sintering (SPS), as a kind of hot pressing, aimed at producing strong anisotropic transports in n-type polycrystalline SnSe as that in crystalline SnSe. Results show that the lowest thermal conductivity of 0.36 Wm -1 K -1 was obtained at 783 K in perpendicular to texture direction. Interestingly, the electrical transport properties are less anisotropic and even nearly isotropic, and the power factors reach 681.3 μ Wm -1 K -2 at 783 K along both parallel and perpendicular directions. The combination of large isotropic power factor and low anisotropic thermal conductivity leads to a maximum ZT of 1.5 at 783 K. The high performance elucidates the outstanding electrical and thermal transport behaviors in n-type polycrystalline SnSe, and a higher thermoelectric performance can be expected with future optimizing texture in n-type polycrystalline SnSe.

Mg-Li matrix composite containing Ni0.4Zn0.4Co0.2Fe2O4 (NZCF) was fabricated by multi-layer composite rolling (MCR). Anti-electromagnetic interference composites with multi-scale microstructure were obtained, in which Mg-9Li alloy serves as the reflecting layer and NZCF particles serve as the absorbing layer. The microstructure, electrical conductivity, magnetic property, and electromagnetic interference (EMI) shielding property of the composites were investigated. The results show that, with the increase of NZCF content, the electrical conductivity of the composites decreases, the magnetic property increases, and its shielding capability increases. The electrical conductivity and magnetic property of the composites can be regulated and controlled by adding nano-scale Ni-Zn-Co ferrites, which provides an efficient strategy for producing metal matrix composites with high EMI property.

This work investigated the effect of MnO2 addition on the phase structure, microstructure, and electrical properties of AgSbO3-modified (Li,K,Na)(Nb,Ta)O3 (abbreviated as LKNNT-AS) lead-free piezoelectric ceramics with an optimized composition endowed with a state of two-phase coexistence. A small amount (0.1 wt%) of MnO2 can significantly further enhance the piezoelectric property of LKNNT-AS ceramics, whose piezoelectric constant d33 and converse piezoelectric coefficient d33* as well as planar electromechanical coupling factor kp reach 363 pC/N, 543 pm/V, and 0.49, respectively. The temperature stability of piezoelectricity in MnO2-modified LKNNT-AS samples also improved, which is associated with the more uniform and better thermally stable ferroelectric domains that were revealed by piezoresponse force microscopy.

In recent years, Fe–Mn–Al–C steel has been widely regarded as a promising lightweight material due to its excellent specific strength and good balance of strength and toughness. However, the performance of welded joints is crucial for the application of Fe–Mn–Al–C low-density steel. This paper aims to study the effect of different solution treatment times on the mechanical properties and microstructure of tungsten inert gas (TIG) welding of Fe-29Mn-9Al-0.9C low-density steel. After solution treatment, the phase types of the weld change and the granular ferrite transforms into austenite. Electron backscattered diffraction (EBSD) results show that with the increase of solution treatment time, dislocation density decreases, recrystallized grains grow, and the texture changes from uniform distribution to cubic texture again. It is concluded that in the early stage of recrystallization, dislocation walls are formed due to dislocation slip, which impedes dislocation movement in the process of stretching and thus improves the tensile strength. By controlling the time of solution treatment, the maximum tensile strength can be increased to 845.05[Formula: see text]MPa and the maximum elongation can be increased to 38.21%, which are all higher than for the welded joints without solution treatment.

The In2O3(ZnO)3+x mol%Ga2O3 (x = 0, 0.1, 0.3, 0.5, 1) ceramics were synthesized by a solid-state reaction process. The effect of Ga doping on the thermoelectric properties of the In2O3(ZnO)3 ceramics was studied. The phase structure and microstructure of all the bulk samples were checked by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. Additionally, the minimum thermal conductivity of 1.45 Wm−1K−1 at 973 K is obtained for 0.5% Ga-doped sample, which is 35% lower than that of the pristine sample. The significantly decreased thermal conductivity for Ga2O3-doped sample is due to the enhanced scattering of phonons, which is derives from the point defects caused by Ga-doping and the introduction of the second phase. As a result, the In2O3(ZnO)3+0.5 mol% Ga2O3 sample achieved the highest ZT value of 0.23 at 973 K.