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As a narrow band gap semiconductor, wurtzite β-CuGaO2 has drawn increasing attention in the area of solar energy. Although β-CuGaO2 has been theoretically predicted to possess ferroelectric polarization, its experimental ferroelectric characterization and practical applications have not yet been presented. Herein, firstly we experimentally confirmed its ferroelectric property via hysteresis loop measurement. The result showed a remanent polarization value of 10.20 μC·cm−2 with low coercive electric field of 6.45 kV·cm−1 at 20 Hz at room temperature, while the leakage current density (J) value was found to be 1.188 A·cm−2, which suggested the property of a larger remnant polarization with low coercive electric field than current value if the compactness was strengthened. Then, the synergistic effect of ferroelectric and semiconductor was comparatively highlighted by the experiment of pollutant degradation. Within 30 min, methyl orange degradation efficiency had reached 30.73% only in the case of spontaneous polarization (electricity), while it could reach 67.58% under the effect of pre-polarized β-CuGaO2 powder due to the modulating orientation of ferroelectric domains. Once irradiated (light), it was up to 92% within 30 min; in comparison, it merely took 16 min up to 92% degradation efficiency under both illumination and pre-polarization. If without illumination, it was 92.01% with 30 min in the condition of ordinary ultrasonic vibration (force) while under both illumination and ultrasonic vibration, only 11 min was spent to reach 92.79% degradation efficiency. All these results felicitously indicated that β-CuGaO2 had fascinating potential in energy harvesting (such as electricity, light, force) and transformation as wastewater environment remediation catalyst.

Highly textured, c-axis oriented thin films of undoped, Ba-doped, and Sr-doped La2CuO4 are successfully prepared on YSZ (100) substrates by using pulsed laser deposition. Intriguingly, the films undergo a structural transformation from T′(square-planar) to T (octahedral) crystal structure with partial substitution of Ba and Sr ions on La site. Meanwhile, the addition of both Ba and Sr dopants lead to reducing in polarization resistance and alternative kinetics of oxygen reduction reaction (ORR), hereinto La1·8Ba0·2CuO4 film presents superior electrochemical properties because it can accommodate much more oxygen vacancies than the other two films. First-principles calculations reveal that much lower O-defect formation energy originate fundamentally from the increase of Cu–O bond length along c-axis orientation after structural transformation from T′-phase to T-phase. These findings unveil the relationship between the structural transformation and ORR activity, and provide a novel approach to rational design film cathodes for higher electrochemical performance.

Hydrogen production by bio-oil steam reforming is an advanced production technology. It is a good method of coupling waste heat utilization with bio-oil steam reforming to produce hydrogen, which increases the cleaning ability of the bio-oil steam reforming system. A multi-zone steam generator using waste heat has been proposed, which can produce the heat source and steam source of the hydrogen system. The DEM model of the multi-zone steam generator was set up. The model has been used to investigate the effects of particle sizes (40 mm–80 mm). With increasing particle size, the flow index and the flow uniformity gradually decrease, the vertical velocity gradient increases in the area on both side with the zone steam generator, and the vertical velocity fluctuation amplitude gradually increases. So, the hydrogen production decreases from the particle size increasing.

A new high-pressure die-cast (HPDC) Mg–4Al–3La–1Ca–0.3Mn (ALaX431) alloy with high strength has successfully been fabricated. This HPDC alloy in peak-aged state exhibits tensile yield strength (TYS) of 220 MPa at room temperature and TYS of 145 MPa at 250 °C, higher than the corresponding strength of HPDC Mg alloys reported so far. These high strengths are mainly due to the formation of fine grained structure, semi-continuous reticular structure consisting of stable Al3La and (Mg,Al)2Ca particles along grain boundaries and numerous nanoscale Al2Ca precipitates within grains. Due to its higher strength than existing HPDC Mg alloys, the new developed alloy has great application potential.

The effect of strain rate on the β texture evolution during two-step hot forging of Ti-6246 alloy was investigated. The two-step forging consisted of 15% or 50% prior-β forging at 980°C and subsequent 60% or 25% forging at 870°C in the (α + β) dual-phase region. The total compression ratio was 75%, and the investigated strain rates were 0.01 and 1.0 s−1. The β forging texture showed typical {001} and {111} body-centered cubic textures. With increasing compression ratio in the (α + β) region and at a strain rate of 0.01 s−1, the amount of precipitated α phase increased. Dynamic recrystallization was rarely observed after forging in the (α + β) region at a strain rate of 0.01 s−1. Large amounts of α precipitates lowered the {001} β texture intensity through slip transmission between the α and β phases under the Burgers orientation relationship. However, in specimens forged at a strain rate of 1.0 s−1, as the compression ratio in the β single-phase region increased, the growth of dynamic-recrystallized β grains was promoted at the prior-β grain boundaries, where α-phase precipitation was not substantial. These effects resulted in a higher {001} texture intensity of the β phase in specimens forged at 1.0 s−1 compared with that of the β phase in specimens forged at 0.01 s−1.

Microstructures and mechanical properties of Mg–4.5Y–2.5Nd–1.0Gd–0.5Zr–xZn (x = 0, 0.5, 1.0, and 1.5; wt%) alloys under as-cast and peak-aged states were investigated in this work. The results indicate that the intermetallic phase components are closely dependent on Zn content. Under as-cast state, the dominant eutectic phase is Mg5RE in the alloys with 0 wt% and 0.5 wt% Zn additions while Mg5RE, 18R- and 14H-LPSO (long period stacking ordered) phases in the alloys with 1.0 wt% and 1.5 wt% Zn additions. After solution and peak-aging, the highest strength and hardness were obtained on the alloy with 0.5 wt% Zn addition. Transmission electron microscopy (TEM) characterizations revealed that there are denser and finer precipitates on basal (β′) and prismatic (γ″) planes, respectively. Therefore, the excellent mechanical performance of the alloy with 0.5 wt% Zn addition is mainly due to precipitation strengthening and grain boundary strengthening.

The discrete element geometric model of the horizontally buried-pipe steam generator was set up. The effects of particle size (20 mm–80 mm) on performances of the horizontally buried-pipe steam generator using waste heat in a bioethanol steam reforming hydrogen production system was studied. When the particle size increases, the particle layer flatness decreases, the particle layer flow ununiformity increases. The volatility of the particle residence time distribution increases with the particle size increases, and the standard deviation of the particle residence time increases. When the particle size increases, the voidage of the particle system increases. So the particle thermal resistance in the steam generator increases with the particle size increases, the steam production of the generator decreases, and the system hydrogen production of decreases.

This paper mainly describes the influence of changes in fin structure on the hydrogen production capacity of the methane-steam reforming system. The model of the triangular-fin-tube steam generator was set up. The effects of the fin height (34 mm–46 mm), fin root width (3 mm–6 mm) and the fin-type were studied. As the height of the fin increases (34 mm–46 mm), the CPC temperature at the outlet of the steam generator decreases (the maximum temperature decreases 23.6 K and the average temperature decreases 18.9 K). At the same time, the heat recovery efficiency increased from 96.3% to 98.4%, and so the system hydrogen production increases. As the fin root width increases (3 mm–6 mm), the CPC temperature at the outlet of the steam generator decreases (the maximum temperature decreases 3.7 K and the average temperature decreases 1.2 K). Meanwhile, the heat recovery efficiency increases from 97.5% to 98.1%, and so the system hydrogen production increases. When the fin type is changed from a straight fin to a triangular-fin, the average temperature of the solid particle decreases 30.5 K, the heat recovery efficiency increases by 7.9%, and the system hydrogen production increases.

Based on first-principles calculations, multiferroic properties of orthorhombic manganites (RMnO3, R = La-Lu) with E-type ground state have been achieved by lanthanide contraction (chemical pressure) and/or external strain. Our research demonstrates that a smaller R radius within the octahedral voids in RMnO3 results in the increase in the tilts of the octahedra but only a gentle change in the Jahn-Teller (JT) distortion. The reduction of the intraplane octahedral rotation angle and the narrowed eg states and lifting t2g band edge are mainly responsible for the intraplane magnetic transition from ferromagnetic (La-Gd) to zigzag-like spin arrangement (Ho-Lu). In turn, the center-broken E-type RMnO3 bulk characterizes the dominated electronic polarization behavior, benefiting from their distortion response to small R substitution, which gives rise to the strong magnetoelectricity. Subsequently, we have figured out the strain strategy for obtaining an E-type transition in light rare-earth manganites (La-Gd) by imposing a series of hypothetical strains, where the small intraplane rotation angle (Θ) and large JT distortion favor the small aspect ratios of a/b and c/b, respectively. The strained LaMnO3 and GdMnO3 achieve E-type transitions successfully by imposing a modest compressive strain along the a- and c-axes and remaining free along the b-direction. Simultaneously, their polarization behaviors were comparatively studied. It was found that the size of the A-site rare-earth ions has a great influence on the external strain response, in addition to its effect on the magnetic phase transition.

The development of high performance electrocatalysts to promote oxygen reduction reaction (ORR) and to prolong the durability of cathodes of solid oxide fuel cell is essential at intermediate or low temperatures. Here, we report a facile and efficient spray impregnation strategy in enhancing catalytic activity of La0.6Sr0.4Co0.8Fe0.2O3-δ (LSCF) due to the introduction of a multitude of homogeneous nanoparticles. With a highly active surface abundance in B-site cations, the modified LSCF cathode manifests an area-specific resistance (ASR) of ∼0.140 Ω cm2, only a fifth of that for a pristine LSCF cathode (∼0.764 Ω cm2) at 600 °C, and anode-supported fuel cells with the decorated LSCF cathode show markedly improved peak power densities (∼0.94 W cm−2 at 700 °C). Furthermore, the ORR kinetics of the modified LSCF cathode can be further enhanced by impregnating Ni(NO3)2·6H2O and Co(NO3)2·6H2O solution again. X-ray photoelectron spectroscopy analysis indicates that the homogeneous nanoparticles alter the distribution of Srsurface and Osurface. It is found that ‘Co’ decoration can effectively alleviate the surface aggregation of Sr and ‘Co’ and ‘Ni’ decoration play a pivotal role in the reactivation of electrode surface.

By first-principles calculations, lanthanide contraction is applied on a 1/1 (with symmetric center) and a 2/2 (with non-centrosymmetric polar structure) RTiO3 /RVO3 superlattices to realize quasi-continuous structural distortion modulation. The strong correlations of microscopic structural distortion, magnetic coupling and charge disproportionation accompanying metal-insulator transition (MIT) are clarified. It is found that the effect of lanthanide contraction on the 1/1 and 2/2 RTiO3 /RVO3 superlattices can induce ferromagnetic to antiferromagnetic transition within ab VO2 plane and the MIT occurs within these superlattices. And the MIT phenomenon is attributed to the charge disproportionation on V sites caused by the magnetic coupling transition. More structural distortion in the 2/2 RTiO3 /RVO3 superlattice is necessary than that of the 1/1 RTiO3 /RVO3 superlattice to induce the similar magnetic and MIT transition originating from the smaller interface/volume ratio. Based on these results, combining lanthanide contraction and epitaxial strain effects, multiferroic property is realized on 2/2 YTiO3 /YVO3 superlattice. Among all the structural parameters, aspect ratio c/a and Ti-O-V bond angles along the [001] direction are found to play the vital roles in the relevant transition process. Therefore, our calculations provide a microscopic guidance to design and synthesize new multiferroic materials.

Microstructures, mechanical properties and creep behavior of a gravity casting Mg−3Yb−0.6Zn−0.4Zr (wt%) alloy were investigated. The results indicate that the studied alloy has smaller grains compared with the conventional Mg−RE based casting alloys, and the dominant intermetallic phase is Mg2Yb although minor Mg41Yb5 was also found in grain interior. In addition, the studied alloy exhibits medium tensile strength but excellent ductility at room temperature. Simultaneously, a complicated serrated flow phenomenon was observed in its flow curves at 150–250 °C. Finally, we found that the studied alloy exhibits poor creep resistance compared with the conventional Mg−RE based alloys. This could be mainly attributed to both poor thermal stability Mg2Yb phase and discontinuous intermetallic phase skeleton. Also, based on the analyses of the stress exponent and activation energy as well as microstructural observation, dislocation climb was proposed as the dominated creep mechanisms of the studied alloy at 180–220 °C and 40–80 MPa.

In order to study the dehydrogenation reaction mechanism of ultra-low concentration methane in a thermal reverse-flow reactor, the effects of the cyclic period (120s–240s), the lean methane volume flow (90 Nm3/h to 180 Nm3/h), and the methane concentration (0.2 vol% to 0.8 vol%) on the dehydrogenation performance were studied systematically by using a thermal reverse-flow experimental system. When the methane concentration is 0.2 vol%, the reactor can achieve self-heat maintaining operation. With the increase in the methane concentration, the width of the high-temperature zone, the exhaust gas temperature, the methane conversion rate, and the maximum temperature of the heat-accumulator bed increase. With the increase in the lean methane volume flow, the width of the high-temperature zone, the distance between the center of the high-temperature zone and the center of the reactor, the maximum temperature, the exhaust gas temperature, and the methane conversion rate increase. With the increase in the cyclic period, the exhaust gas temperature and the deviation of the high-temperature zone increase, but the methane conversion rate and the maximum temperature decrease slightly.

The atomic-scale degree of B/B′ alternate cationic disorder is known to significantly influence the macroscopic properties of the quadruple perovskites AA3′B2B2′O12; however, the nature of this disorder has rarely been critically studied. Herein, the effect of B-site cationic arrangement on the electronic and magnetic properties of the quadruple perovskite CaCu3Fe2Nb2O12 was systemically investigated using the first-principles calculations. The results demonstrate that the B-site ordered CaCu3Fe2Nb2O12 is a ferrimagnetic insulator with antiferromagnetic coupling between the A′-site Cu and B-site Fe. The calculated total magnetic moment is 7.00 μB f.u.−1, which is apparently larger than the experimentally measured saturation magnetization because of different degrees of the B-site disorder. Furthermore, the electronic structures illustrate that the magnetic moments sharply decrease with an increase in the B-site antisite defects, i.e., the total magnetic moments obviously reduce with an increase in the B-site Fe/Nb disorder, and ultimately, no magnetism is observed. Interestingly, the B-site antisite defects not only introduce Fe–Fe antiferromagnetic coupling, but also induce the antiferromagnetic arrangement of Cu spins in the totally disordered structure. Cu–Fe and Fe–Fe magnetic coupling competition is coupled with antisite defects, and finally, Fe–Fe antiferromagnetic coupling turns into the dominating spin coupling in the disordered CaCu3Fe2Nb2O12. Moreover, the B-site antisite defects do not alter the insulator nature of the perovskite despite the significantly narrowed band gap. Our study opens up a novel avenue for the straightforward understanding of the effect of cationic ordering on the electronic and magnetic properties of quadruple perovskites and offers an additional opportunity for tailoring their characteristics.

Photothermal therapy (PTT) is a new treatment, and photoacoustic (PA) imaging-guided PTT has aroused extensive attention recently. Poly-2-phenyl-benzobisthiazole (PB) is a new type of conjugated polymer with good biocompatibility and excellent photothermal properties similar to single-walled CNT. However, the poor hydrophilicity of PB limits its application in biomaterials. In this work, chitosan-Cu(II) network structure was first constructed, and then the Cu(II) in-situ initiated the polymerization of aminobenzenedithiophenol and terephthalonitrile to obtain chitosan/PB composite. The excellent hydrophilicity of chitosan-based nanoparticle has successfully improved the water solubility of the obtained nanoprobe PB/CS. Additionally, PB/CS has an excellent PA signal. Thus, a simple and convenient nanosystem was fabricated and applied for PA imaging-guided PTT.

Although Zn–Zr intermetallic phases have been frequently reported in solution-treated Mg–RE–Zn–Zr systems (RE presents rare earth), the types, crystal structures and influence on precipitation remain to be systematically investigated. In this work, the intermetallic phases formed during solution treatment in a Mg–Sm–Zn–Zr alloy were studied using transmission electron microscopy. Four types, namely the plate phase, the spindle-like phase, the nano-scale granuliform phase and the rod-like phase were revealed. Except the first one, the other three ones are Zn–Zr phase. In addition, the granuliform phase presents quadrate-shaped or lath-shaped and was identified as Zn2Zr3. However, these two Zn2Zr3 phases with different shapes follow quite different orientation relationships with Mg matrix. Furthermore, three kinds of rod-like phases were observed: one across the grain boundary but only coherent with one grain, one covered by jagged Mg3Sm precipitates and one with no surficial phase. The former twos are Zn2Zr3 while the later one is Zn2Zr. Finally, this work indicates that only the plate MgZn2 phase and the rod-like Zn2Zr3 phase in the grain interior will act as heterogeneous nucleation sites for the Mg3Sm precipitates, thus influencing the precipitation.

Bringing oxygen atoms from infinite, passing equilibrium until short enough distances, we aim to reveal the 4f5d electron bonding property and its relevance to the peculiar physical properties within PrO2 based on both accounting for electron Coulomb repulsion and spin-orbit coupling effects in combination with Wannier function methods. The microscopic mechanism of static Janh-Teller distortions and the physical insight into the dynamic Jahn-Teller effects are clarified. Peculiarly, the magnetic coupling is suggested to be via 4f-5d-O2p-5d-4f pathway in PrO2, and the coupling between spin and orbital ordering of 4f electrons is for the first time disclosed. The 5d orbitals, hybridized with 4f electrons, are found to play important roles in these processes.

Layered perovskite oxide LaBa0.5Sr0.25Ca0.25Co2O5+δ (LBSCaCO) is studied as a potential cathode material for intermediate temperature solid oxide fuel cells (IT-SOCFs). Ca-free sample LaBa0.5Sr0.5Co2O5+δ (LBSCO) is also investigated for comparison. The thermal expansion coefficient (TEC) value is reduced from 26.2 × 10−6 K−1 to 20.0 × 10−6 K−1 by Ca doping. The electrical conductivity of LBSCaCO is above 500 S cm−1 from room temperature to 800 °C. Substitution of Sr by Ca can effectively enhance the electrochemical performance. The area specific resistance (ASR) values of LBSCaCO and LBSCO are 0.075 Ω cm2 and 0.084 Ω cm2 at 800 °C, respectively. Moreover, LBSCaCO cathode achieves an excellent outputting of 662 mW cm−2 at 800 °C. Based on these results, Ca doped layered perovskite LBSCaCO can be a cathode candidate material for IT-SOFC application.

P-type molecular sieve antimicrobial agents, which were grafted with potassium diformate using chitosan as an intermediat, were synthesized from hydrothermal process. The effects of hydrothermal process conditions (pH, reaction time, reaction temperature and mass ration of P-type molecular sieves: chitosan: potassium diformate) were investigated in detail. XRD, FTIR spectroscopy and SEM were applied to characterized the P-type molecular sieve antimicrobial agents. The antimicrobial performance of P-type molecular sieve antimicrobial agents were evaluated with the OD value and growth curve of Staphylococcus aureus. Atomic absorption spectrophotometer was introduced to measure the K+ concentration. Under the optimum synthesis condition of P-type molecular sieve antimicrobial agents (reaction temperature=50 °C, reaction time=3 h, and the mass ratio=3:1:2), the inhibitory rate of P-type molecular sieve antimicrobial agents was as high as 89%.

Theoretical and experimental endeavor were combined to investigate effects of Co-incorporating on crystal structure and oxygen vacancy formation energy and their influence on Sr2Co1 + xMo1 − xO6 − δ electrochemical performance systematically. From the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), it is found that introducing Co decreases the ordering of B-site cations. Most importantly, Co3 + content increases with the increasing Co, indicating more Co-O*-Co pairs are introduced within the compounds. Additionally note that the electrochemical performance of the materials is improved apparently when more Co is incorporated. Sr2Co1.5Mo0.5O6 − δ has an area-specific polarization resistance (ASR) as low as 0.030 Ω cm2 in a symmetrical cell at 800 °C. First-principles calculations found that the sequence of the oxygen vacancy formation energy was Co-O*-Co

Tensile creep resistance of a high-pressure die-cast Mg–4Al–4RE–0.3Mn (AE44) alloy was significantly deteriorated after substituting part RE with Ca. According to traditional power-law creep theories, the stress exponent and the activation energy were revealed as 6 and 217 kJ/mol, which indicate inconsistent mechanisms of dislocation climb and dislocation cross-slip, respectively. Then, transmission electron microscopy (TEM) observations illustrate that dislocation substructures developed during creep are variational with precipitate characters in α-Mg grains, creep stress levels and creep temperatures. Therefore, both stress exponent and activation energy obtained from traditional power-law creep theories are meaningless for the AE44 alloy with part RE substituted by Ca. Finally, the shrink of C36 phase lattice, the precipitation of Al 2 Ca precipitates and the denuded zones were observed in the crept samples, and all of them are responsible for the deterioration in creep resistance of the AEX422 alloy. Also, this paper provides insight into alloy design principles for further development of creep-resistance Mg–Al–RE based alloys.

We present a novel deep neural network (DNN) training scheme and resistive RAM (RRAM) in-memory computing (IMC) hardware evaluation towards achieving high accuracy against RRAM device/array variations and enhanced robustness against adversarial input attacks. We present improved IMC inference accuracy results evaluated on state-of-the-art DNNs including ResNet-18, AlexNet, and VGG with binary, 2-bit, and 4-bit activation/weight precision for the CIFAR-10 dataset. These DNNs are evaluated with measured noise data obtained from three different RRAM-based IMC prototype chips. Across these various DNNs and IMC chip measurements, we show that our proposed hardware noise-aware DNN training consistently improves DNN inference accuracy for actual IMC hardware, up to 8% accuracy improvement for the CIFAR-10 dataset. We also analyze the impact of our proposed noise injection scheme on the adversarial robustness of ResNet-18 DNNs with 1-bit, 2-bit, and 4-bit activation/weight precision. Our results show up to 6% improvement in the robustness to black-box adversarial input attacks.

The microstructure evolution and mechanical properties of as-extruded Mg-11.5Gd-4.5Y-0.3Zr (wt%) alloy with Zn and Nd additions were investigated. The addition of Zn inhibits the dynamic recrystallization (DRX) due to the presence of the long-period stacking ordered (LPSO) phase. The addition of Nd promotes the precipitation of the Mg5RE (RE: rare earth) phase. The existence of the densely distributed Mg5RE phase before hot extrusion promotes the DRX in subsequent hot extrusion process and leads to grain refinement. The increase in the number of Mg5RE phase particles degrades the mechanical properties of the resultant alloy. After hot extrusion, the studied alloys exhibit a bimodal microstructure consisting of fine dynamic recrystallized (DRXed) grains of several microns and strongly textured course un-DRXed grains. The as-extruded Mg-11.5Gd-4.5Y-1.5Zn-0.3Zr alloy exhibits an excellent balance of strength and ductility (tensile yield strength of 371 ± 3.0 MPa and elongation of 7.2 ± 0.8%). The alloy strengthening is attributed to the bimodal microstructure, the Mg5RE and LPSO phases, and the basal texture. The tensile yield strength of the as-extruded Mg-11.5Gd-4.5Y-1.5Zn-0.3Zr alloy can be further increased to 425 ± 2.5 MPa by precipitation hardening with the T5 treatment.

From the view point of compatibility of both crystalline and element with the prototypical perovskite-type electrolyte of La0.9Sr0.1Ga0.8Mg0.2O3-δ, a series of micro-Mg-doped La2NiO4+δ compounds with compositions of La2Ni1-xMgxO4+δ (x = 0.0, 0.02, 0.05 and 0.10) were successfully synthesized via a traditional sol-gel process and evaluated as cathode for intermediate-temperature solid oxide fuel cells (IT-SOFC). The effects of Mg-doping on crystal structures, bond properties and covalent states were analyzed by X-Ray Diffraction (XRD), Infrared spectra (IR) and X-ray photoelectron spectroscopy (XPS) techniques, respectively. It is found that Mg-doping is benefit for the migration of the interstitial oxygen by weakening the Ni(Mg) O bond. More importantly, we found that Mg doped at the subsurface under the Ni of (001) surface will promote both the O2 adsorption and decomposition process from the analysis of the oxygen migration dynamics. Considering the balance of electronic conductivity, it was indicated that La2Ni0.98Mg0.02O4+δ (LNM0.02) manifested the optimal electrochemical property with the lowest area specific resistance of 0.05 Ω cm2 at 800 °C, and along with a maximum power density of 528 mW cm−2 for an electrolyte supported single cell LNM0.02|LSGM|NiO-SDC at 800 °C with approximately 20% higher than that of the La2NiO4+δ (LN) (∼429 mW cm−2) cathode. The results indicate that introducing micro-dose of Mg into Ni-site in La2NiO4+δ compound is an efficient way to obtain an excellent cathode material for IT-SOFCs.

The microstructures and tensile properties of Mg–6.0Zn–0.6Zr (ZK60) and ZK60 + 1.8Gd (ZEK620 (RE = Gd)) alloys extruded at 290, 305, 320, 340 and 360 °C were investigated. The results indicate that Gd addition can refine the microstructures of ZK60 alloy and the extrusion parameters such as the extrusion temperature will influence the tensile properties of both as-extruded ZK60 and ZEK620 alloys, although it is much slighter for ZK60 alloy. And the sensitivity is closely related to the textures developed during extrusion. In addition, Gd addition will also clearly improve the tensile strength at room temperature (24 °C) and particularly at high temperatures (150 and 200 °C), due to the much finer grains and smaller intermetallic particles. The highest strength is achieved in the as-extruded ZEK620 alloy with extrusion temperature of 320 °C, with ultimate tensile strength (UTS) and tensile yield strength (TYS) of 405 and 375 MPa, respectively, which are improved by approximately 9% and 11% than those of the as-extruded ZK60 alloy which owns the highest strength at extrusion temperature of 290 °C.

The types and the detailed structures of the Mn-containing phases in the high-pressure die-casting Mg–4Al–4RE–0.3Mn alloy were thoroughly investigated using transmission electron microscopy (TEM). The results reveal five Mn-containing intermetallic phases with different morphologies, namely the regular blocky phase, the irregular blocky phase, the interlaced lath-shaped phase, the nano-scale phase on the surface of or embedded in the Al11RE3 particles, and the nano-scale precipitate in the α-Mg matrix. The former twos belong to Al10RE2Mn5 but the latter one contains numerous normal (11.1) twins and orientation twins. In addition, the third one simultaneously contains Al10RE2Mn5 and Al8REMn4, of which both are coherent with each other and contain normal twins. Finally, the last two nano-scale Mn-containing phases on the surface of or embedded in Al11RE3 and precipitated in α-Mg grains are Al10RE2Mn7 and Al8Mn5, respectively.

Microstructures and mechanical properties of a high-strength extruded Mg-3.5Sm-0.6Zn-0.5Zr alloy were thoroughly investigated. The results indicate that the dominant intermetallic phase in both as-cast and extruded samples is not the widely reported Mg 41 Sm 5 phase but Mg 3 Sm phase. After extrusion, the microstructures are composed of fine equiaxed dynamically recrystallized (DRXed) grains, coarse elongated unDRXed grains with ultrafine sub-grains, disintegrated intermetallic particles, and numerous small dynamically precipitated particles. Also, there are amounts of particularly dislocations in the Mg matrix after extrusion. Finally, numerous nano-scale plate β′ particles and lamellae β″ particles homogeneously precipitated in the matrix during artificial aging treatments. Therefore, the studied alloy exhibits very high ultimate tensile strength and yield strength, whose maximum values at room temperature are approximately 427 MPa and 416 MPa, respectively, much greater than most conventional Mg–RE based alloys with comparative or even much higher RE additions.

A high strength Mg-11.7Gd-4.9Y-0.3Zr (wt%) alloy with a weak tension-compression yield asymmetry has been successfully developed by pre-deformation annealing, hot extrusion and ageing. The effects of pre-deformation annealing on the microstructure evolution and mechanical properties are studied. The results reveal that pre-deformation annealing generates a large number of Mg5RE (RE: rare earth) phase particles and raises the fraction of dynamic recrystallization (DRX). The preformed Mg5RE particles not only enhance the DRX by particle simulated nucleation (PSN), but also facilitate the continuous DRX (C-DRX) by promoting the grain subdivision during hot extrusion. Without pre-deformation annealing, the as-extruded alloy exhibits a high tensile yield strength (TYS) of 376 ± 9.6 MPa but a low elongation to failure (EL) of 4.3 ± 0.1% due to the bimodal microstructure consisting of coarse un-DRXed grains with strong basal texture and fine DRXed grains with weak basal texture. After T5 treatment, the TYS further increases to 500 ± 5.5 MPa, whereas the EL reduces to 2.7 ± 0.4%. An excellent balance of strength and ductility (TYS of 343 ± 0.2 MPa and EL of 9.3 ± 0.9%) can be realized by pre-deformation annealing for 1 h due to the raised fraction of DRX and the weakened basal texture. T5 treatment further increases the TYS to 446 ± 3.8 MPa but reduces the EL to 3.0 ± 0.2%. The studied alloy exhibits good compressive performance, resulting in a weak tension-compression yield asymmetry. The grain refinement, Mg5RE and β ′ phases, and solute-segregated SFs contribute to the alloy strengthening.

This paper presents the results of lean methane oxidation in a two-chamber preheat catalytic reactor. A preheat catalytic reactor was built, and the effects of the space velocity (3800 h −1 to 8100 h −1 ), the inlet methane concentration (0.6 vol.% to 0.8 vol.%) and the inlet temperature of catalytic oxidation bed (420 °C–540 °C) were experimentally investigated. The results showed that when the space velocity is low, the methane conversion rate maintains a high value. But when the space velocity is higher than 7100 h −1 , the methane conversion rate decreases dramatically. With the increases of the inlet methane concentration and the inlet temperature, the overall temperature of the oxidation bed increases rapidly, the temperature increment of the first catalytic ceramic layer increases, the methane conversion rate increases.

The A-site ordered negative thermal expansion material LaCu3Fe4O12 (LaCFO) was comprehensively investigated by using first-principles calculations. A pressure-triggered crystal structural phase transition from space group Im3 (No. 204) to Pn3 (No. 201) and magnetic transformation from a G-type antiferromagnetic (G_AFM) ground state to ferrimagnetic (FerriM) coupling were observed in LaCFO via gradual compression of the equilibrium volume. Correspondingly, the Fe–Cu intersite charge transfer from Fe to Cu 3dxy orbital, expressed as 4Fe3+ + 3Cu3+ → 4Fe3.75+ + 3Cu2+, was simulated along with the magnetic phase transformation from the G_AFM configuration to the FerriM state. Intriguingly, the Fe charge disproportionation, formulated as 8Fe3.75+ → 5Fe3+ + 3Fe5+, appeared and was attributed to the strong hybridization between Fe 3d and O 2p orbitals in the FerriM state when the volumes were substantially compressed up to less than or equal to 80%V. Meanwhile, the external hydrostatic pressure also leads to a ...

Effects of minor Sr (x=0, 0.2, 0.6, 1.0 wt%) addition on microstructure, mechanical properties and creep behavior of high pressure die casting AZ91-0.5RE based alloys were thoroughly investigated. Experimental results show that the addition of Sr to HPDC AZ91-0.5RE based alloys can refine the microstructure including externally solidified crystal α-Mg and eutectic compound β-Mg17Al12. On the other hand, when the content of Sr reaches 1.0%, a small amount of plate-like Al4Sr phase can be formed. Moreover, minor of Sr addition can significantly decrease the volume fraction of β-Mg17Al12 precipitates of AZ91-0.5RE based alloys. In addition, the mechanical properties of AZ91-0.5RE based alloys can be improved remarkably with Sr addition, and the alloy containing 0.2% Sr exhibits the best mechanical properties at ambient temperature. Fractographic analyses demonstrate that the fracture modes of the alloy without and with Sr are quasi-cleavage fracture and ductile fracture, respectively. Furthermore, Creep properties of HPDC AZ91-0.5RE based alloys were obviously improved by adding Sr element. And creep mechanisms of the alloys with and without Sr at 150 °C/30–70 MPa and 50 MPa/140–160 °C are both considered to be dislocation climb controlled creep based on the analyses of the stress exponent and apparent activation energy. The AZ91-0.5RE-1.0Sr alloy presents the best creep resistance among the studied alloys, which is mainly attributed to the presence of thermally stable intermetallic compound of Al4Sr phase at the grain boundaries.

Structural and electronic properties of 3d transition metal Sc, Ti, Cr and Mn incorporated 2 H -WSe 2 have been systematically investigated by first-principles calculations based on density functional theory. The calculated formation energies reveal that all the doped systems are thermodynamically more favorable under Se-rich condition than W-rich condition. The geometry structures almost hold that of the pristine 2 H -WSe 2 albeit with slight lattice distortion. More importantly, the electronic properties have been significantly tuned by the dopants, i.e., metal and semimetal behavior has been found in Sc, Ti and Mn-doped 2 H -WSe 2 , respectively, semiconducting nature with narrowed band gap is expected in Cr-doped case, just as that of the pristine 2 H -WSe 2 . In particular, magnetic character is realized by incorporation of Mn impurity with a total magnetic moment of 0.96 μ B . Our results suggest chemical doping is an effective way to precisely tailor the electronic structure of layered transition metal dichalcogenide 2 H -WSe 2 for target technological applications.

Microstructural evolutions and mechanical properties of a Y-rich misch metal modified Mg–9Gd−3Y−0.6Zn−0.4Zr (wt.%) alloy were investigated. In the as-cast sample, the intermetallic phases are Mg5RE, Mg3RE and 14H-type long-period stacking ordered (LPSO) phase. After solution, all Mg3RE and most Mg5RE were dissolved while the 14H-LPSO plates were coarsened. The as-extruded alloy has a bimodal structure of ultra-fine dynamically recrystallized (DRXed) grains and coarse un-recrystallized grains, and is with a typical non-fiber texture. Disintegrated Mg5RE and 14H-LPSO particles aggregate in extrusion stringers while fine dynamically precipitated Mg5RE particles distribute at grain boundaries. After peak-aging, ultra-thin basal γ’’ and prismatic β’ precipitated in DRXed grain and un-recrystallized regions, respectively. The yield strength of the as-extruded and peak-aged alloys reaches to 385 MPa and 481 MPa, respectively, at room temperature, and to 320 MPa and 350 MPa, respectively, at 250 °C. Grain boundary strengthening from both grain boundaries and sub-grain boundaries in DRXed and un-recrystallized regions, respectively, and precipitation strengthening were revealed as the dominant strengthening mechanisms.

A high-strength Mg-4Sm-2Yb-0.6Zn-0.4Zr extruded alloy with bimodal microstructure was creep tested in compression at temperatures of 200 °C and 225 °C under applied stress in the range of 120–200 MPa. The creep curves of the alloy are dominated by a steady-state creep stage and a transient primary creep stage. An abnormal decrease of creep rate is observed in the later period of the steady-state creep stage, particularly the creep at high stress levels more significant, and the underlying reasons are proposed. Moreover, the alloy exhibits high stress exponents (n = 8.7 at 200 °C and n = 7.4 at 225 °C) and activation energies ranging from 225 kJ/mol to 310 kJ/mol. It is shown that the high stress exponents can be well rationalized by the commonly adopted threshold stress method in this work, which results in the modified stress exponents near 5, suggesting five power law, with some indicator of dislocation creep. Transmission electron microscopic observations revealed that cross-slip of dislocations is the dominant creep mechanism in recrystallized grains, while cross-slip of dislocations is operative in hot-worked grains. Besides, a fraction of γ" phase in hot-worked regions was transformed to γ′ phase during creep while not in recrystallized regions, thus coexistence of γ" and γ’ in hot-worked regions. Also, these γ-typed phases play an important role in creep of the studied alloy. Finally, the studied alloy owns better creep resistance than those of benchmark Mg alloys such as AE and AX series alloys.

The perovskite oxides, La1−xSrxNi0.5Mn0.5O3−δ (LSNM, x = 0.0, 0.05, 0.1, and 0.15), have been evaluated as promising cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The polycrystalline LSNM nanoparticles are synthesized by a glycine-nitrate combustion method. The Rietveld refinements to X-ray diffraction patterns indicate that LaNi0.5Mn0.5O3−δ (LS0.0NM) is within the mixed P b n m and R 3 ¯ c phases. However, the Sr-doping strategy initially makes the product only be R 3 ¯ c phase when x = 0.05, which is considered to be closely relevant to its high oxygen vacancy concentration. The R 3 ¯ c phase is also identified in x = 0.1 and 0.15 compounds. The electrochemical performance of LSNM has been performed by the electrochemical impedance spectra technique, and the La0.9Sr0.1Ni0.5Mn0.5O3−δ (LS0.1NM) demonstrates the optimal electrochemical property as evidenced by the lowest area specific resistance (ASR) of 0.12 Ω cm2 at 800 °C. Compared to the cobalt-containing cathode materials, the average thermal expansion coefficient (TEC) of LS0.1NM is about 11.33 × 10−6 K−1, matching well with the prototypical electrolyte La0.9Sr0.1Ga0.8Mg0.2O3−δ below 850 °C. The maximum power densities of the electrolyte-support single cell with the configuration of LS0.1NM|LSGM|NiO-SDC reach 440 and 331 mW cm−2 at 850 and 800 °C, respectively. Therefore, LS0.1NM could be considered as a novel potential cathode candidate for IT-SOFCs.

The structures of a petaloid phase, which acts as the dominant intermetallic phase in a high-pressure die-cast Mg–4Al–4Sm–0.3Mn alloy with outstanding ductility and strength, were thoroughly studied in this work. The results indicate that the petaloid phase is Al2Sm phase (face-centered cubic structure: a=0.7945 nm), not Al11Sm3, and composed of multiple (111) twins with the (111) plane serving as the twinning plane. However, most (111) twins are extraordinarily different from the conventional one, featuring a sandwiched structure with the filling being Al12Sm2Mn5 phase. Nevertheless, the appearance of Al12Sm2Mn5 bands is not always accompanied with twins. Finally, the underlying mechanisms for the peculiar Al2Sm structures were carefully discussed and revealed as a random heterogeneous nucleation of the Al2Sm phase on the pre-existed Al12Sm2Mn5 sites during solidification.

The effect of Nd addition and the influence of extrusion processes on the microstructure and mechanical properties of Mg–6Zn–0.5Zr (ZK60) and Mg–6Zn–1.5Nd–0.5Zr (ZKNd602) alloys were investigated. Nd element can obviously refine the microstructure of both as-cast and as-extruded Mg–Zn–Nd–Zr alloy. All of the extruded alloys exhibit a bimodal grain structure composed of equiaxed fine recrystallized (DRXed) grains and elongated coarse unDRXed grains. It is necessary to achieve high strength, particularly the yield strength, for ZKNd602 alloy, when it is extruded with a lower extrusion temperature, a suitable extrusion ratio and a relatively lower extrusion ram speed. In this study, the ultimate tensile strength (UTS), yield strength (YS) and elongation (El) of the extruded ZKNd602 alloy were 421 MPa, 402 MPa and 6.7 %, respectively, with extrusion temperature of 290 °C, extrusion ratio of 18:1 and a ram speed of approximate 0.4 mm·s−1. Meanwhile, the extrusion process has obvious effects on the room-temperature properties but weak effects on the high-temperature properties.

A series of Nd/Mg co-doped ceria electrolytes, Ce0.8Nd0.2−x MgxO2−δ (x = 0, 0.05, 0.10 and 0.15), were synthesised through a facile solgel method. The structure and electrical properties were characterised by X-ray diffraction, scanning electron microscopy and AC impedance spectroscopy. An appropriate elemental ratio of Nd/Mg in the co-doped experiment was found to be essential in improving the electrical performance of the ceria-based electrolytes. The optimum grain-boundary conductivity (2.28 × 10−2 S cm−1) and total conductivity (2.68 × 10−3 S cm−1) were obtained at the doping 10 at.% Nd and 10 at.% Mg.

Tensile yield strength of extruded Mg–5.3Zn–0.5Ca–0.5Ce/La (weight percent) alloy is remarkably increased to 316 MPa from 163 MPa, via the warm rolling process. The tension twinning can be activated after low-strain (5–21%) rolling, and the dynamic recrystallization occurs with increasing rolling reduction. The dislocations are gradually accumulated within the original grains during the rolling, and the number fraction of low angle grain boundary is increased. The coarse secondary phases are gradually broken into small pieces, due to the increased rolling deformation. The weak fiber texture with 10 1 0 parallel to extrusion direction in the extruded alloy is modified to the typical 0002 10 1 0 texture after rolling, and the yield strength is notably improved, because of the multiple strengthening effects (grain refinement, work hardening, dispersion and texture). A good balance between strength (> 310 MPa) and ductility (~ 9.5%), has been achieved through the warm rolling.

Microstructure and texture evolutions during tensile and compression deformation of an as-extruded Mg–11Gd–4.5Y–1Nd–1.5Zn–0.5Zr (wt%) alloy have been investigated using in-situ synchrotron radiation diffraction and subsequent microscopy. The alloy consists of 〈View the MathML source101¯0〉 fiber texture, {View the MathML source112¯0}[0001] and {View the MathML source112¯0}〈View the MathML source101¯0〉 texture components prior to deformation. The texture evolves from [0001] to 〈View the MathML source101¯0〉 in tension, but from 〈View the MathML source101¯0〉 to [0001] in compression. The evolution of texture is attributed to the activity of the tensile twinning and non-basal 〈a〉 type slip. The tendency of texture evolution depends on the favorable texture component for the activation of above deformation modes. The grain refinement, Mg5(Gd, Y, Nd) and LPSO phases, and the texture contribute to the improvement in strength. The authors thank Dr. Jan Bohlenand Dr. Sangbong Yi for their fruitful discussion. Prof. Florian Pyczak and Mr. Uwe Lorenzare acknowledged for the provision of access to the TEM facilities at Helmholtz-Zentrum Geesthacht. The access to the beam line PETRA III at DESY, Hamburg, Germany was provided under the proposal number I-20130153,andtheworkofN. Schellis greatly appreciated. This work is supported by the National Key Technologies R&D Program(2012BAE01B04,2012DFH50100,KGFZD-125-13-021,201001C0104669453). Zijian Yu would like to thank the Chinese Academy of Sciences and German Academic Exchange Service (CAS-DAAD)scholarship program (Grant Number: A/12/94735)for the financial support.