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The damage of corneal epithelium may lead to the formation of irreversible corneal opacities and even blindness. The migration rate of corneal epithelial cells directly affects corneal repair. Here, we explored ocu-microRNA 24-3p (miRNA 24-3p) that can promote rabbit corneal epithelial cells migration and cornea repair. Exosomes, an excellent transport carrier, were exacted from adipose derived mesenchymal stem cells for loading with miRNA 24-3p to prepare miRNA 24-3p-rich exosomes (Exos-miRNA 24-3p). It can accelerate corneal epithelial migration in vitro and in vivo. For application in cornea alkali burns, we further modified hyaluronic acid with di(ethylene glycol) monomethyl ether methacrylate (DEGMA) to obtain a thermosensitive hydrogel, also reported a thermosensitive DEGMA-modified hyaluronic acid hydrogel (THH) for the controlled release of Exos-miRNA 24-3p. It formed a highly uniform and clear thin layer on the ocular surface to resist clearance from blinking and extended the drug–ocular–epithelium contact time. The use of THH-3/Exos-miRNA 24-3p for 28 days after alkali burn injury accelerated corneal epithelial defect healing and epithelial maturation. It also reduced corneal stromal fibrosis and macrophage activation. MiRNA 24-3p-rich exosomes functionalized DEGMA-modified hyaluronic acid hydrogel as a multilevel delivery strategy has a potential use for cell-free therapy of corneal epithelial regeneration.

Microstructure and tensile properties ranged from ambient temperature to 700 ℃ of the 12Cr ODS steel were investigated by scanning electron microscopy, electron backscatter diffraction technique, and tensile tests. Results show that microstructure is composed of elongated grains with axis parallel to rolling direction. Ultimate tensile strength and 0.2% offset yield strength gradually decrease with increasing test temperature. Uniform elongation and total elongation reduce with the temperature rising up to 500 ℃, whereas increase at higher temperatures due to activation of slip systems. Moreover, ductility in rolling direction is better than that in transverse direction. Fracture surfaces suggest that a large number of small and uniform dimples, and predominant cleavage-like facets present in rolling direction, and transverse direction, respectively.

Recrystallization behavior of a two-way cold rolled 12Cr ODS steel during annealing in the range of 1273–1473 K was systemically investigated by means of scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy, and hardness testing. Results show that original grains with axis were rotated to axis parallel to normal direction after ∼60% reduction in thickness. Recovery stage was obvious at 1273 K annealing taking about 100 min, but at higher temperatures it was shortly followed by recrystallization. ∼84% recrystallization was observed after annealing at 1473 K for 60 min, indicating that the new cold rolling process decreases the recrystallization temperature in comparison with the as-fabricated specimen completing recrystallization at 1673 K. In addition, the microtexture evolution was characterized as recrystallization proceeded. The intensity of {111} and {111} components decreased, while intensive {110} component was obtained. Dependence of the stored energy on the orientation of deformed grains is presumed for the reduction of {111} and {111} components, and oriented growth is probably responsible for the enhancement of {110} texture after recrystallization.

The ODS steel, studied for more than thirty years, is an alloy characterized by very high performances, and depending on the purpose, its composition is changed in order to satisfy the requirements. In particular, the 12Cr ferritic ODS steel is widely regarded as a candidate structural material for fusion reactor and advanced next generation reactors. In this study, mechanical properties of the alloy will be tested at different temperatures: their dependency on the microstructure and on the temperature will be investigated, focusing the attention on the anisotropy of the alloy and how it affects its performances. Fracture surface analysis at room temperature will be also performed.

In this study, a technique that allows electron backscatter diffraction (EBSD) observation in the same point of interest under uniaxial tensile testing, i.e., a quasi in situ EBSD analysis technique, was developed and performed to investigate the interaction between slip and { 10 1 ¯ 2 } tensile twinning in a Zr alloy. Both the slip-independent and slip-assisted { 10 1 ¯ 2 } twins were investigated. The former twin is formed when the global stress surpassed the required critical stress, and the latter one is formed due to the local stress concentration near the grain boundary accumulated in the soft-oriented adjacent grain, although the global stress remains insufficient to activate the twinning. The formation of a slip-independent or slip-assisted { 10 1 ¯ 2 } twin seems to be closely linked to the crystal orientation relative to the loading direction. It is due to the bimodal basal texture exhibited in the present alloy that the slip-assisted twins can be observed. Furthermore, compared to slip-independent twins, the slip-assisted twinning is more likely to form at a higher strain, because substantial strain accumulation is essential to trigger its activation.

The anisotropy in creep properties and its microstructural origins in two oxide dispersion strengthened (ODS) steels (i.e., 12Cr-ODS-IMR and 12Cr-ODS-NIFS) were systematically investigated. Both ODS steels exhibited the anisotropic creep properties. The creep strength in longitudinal directions (LD) or extrusion directions (ED) specimens was better than that in transverse directions (TD) specimens. The microstructural characterizations revealed that both steels had elongated grains along the ED and relatively equiaxed grains in other orientations. Both steels had a streak-like distribution of precipitates along the ED that was composed of Ti-enriched precipitates and nano-scale oxide particles in local area. The fractography of the crept TD and LD specimens suggested that both steels fractured by the mixed ductile and brittle fracture modes. The propagation of cracks and intergranular decohesion along the boundaries of elongated grains were more severe in the TD specimens than in the LD specimens. The combined effects of elongated grain morphology with low grain shape aspect ratio and segregation of precipitates along the ED can explain the anisotropy in creep properties. The anisotropy in 12Cr-ODS-IMR steel was relatively higher than that in 12Cr-ODS-NIFS steel, and the additional cold rolling and lower final heat treatment temperature in 12Cr-ODS-IMR steel were responsible for it.

A combination of ion-accelerator irradiation, nanoindentation tests, and electron backscatter diffraction analysis was utilized to probe the crystal orientation dependence of irradiation-induced hardening in a Zr alloy. The nanohardness at the [0001] orientation exhibited the highest value, which gradually decreased when the orientation deviated from the [0001] axis to the [ 10 1 ¯ 0 ] and 2 1 ¯ 1 ¯ 0 axes, regardless of the irradiation dose. Crystal-orientation-dependent irradiation-induced hardening is further confirmed. The lowest hardening was observed at [0001] orientation, and the hardening effect intensified toward the [ 10 1 ¯ 0 ] and [ 2 1 ¯ 1 ¯ 0 ] orientations, reaching the maximum at a rotation angle of ~55° with respect to [0001].

The purpose of this study is to investigate the response of the precipitates against irradiation in F82H steels which are considered as main candidate structure material for the fusion DEMO reactor blanket. M23C6-type precipitates contained F82H-IEA steel, and MX- and M23C6-type precipitates contained F82H-BA12 steel were selected as experimental specimens. Iron irradiation at 673 K using ion accelerator was performed on both steels up to 50 dpa. After irradiation, the instability behavior of precipitates was characterized using transmission electron microscopy. It is found that in F82H-IEA specimens, the number density of radiation defects at 20 dpa was 3.26 × 1021 m−3, and the amorphization of M23C6 was undetected up to 50 dpa. Although Ostwald ripening occurred in M23C6 precipitates, the average size of M23C6 mildly decreased with irradiation dose within this study. For F82H-BA12 specimens, the shrinkage rate of MX- and M23C6-type precipitates was estimated respectively as 0.06 and 0.03 nm/dpa. Hence, the MX and M23C6-type precipitates in F82H steel exhibit an excellent irradiation resistance under the present irradiation condition. Moreover, the behaviors like amorphization and weakening in contrast were not observed in M23C6 precipitates in both specimens, which is different from electron irradiation, presumably due to the factors such as different damage rate. Keywords: F82H, Ion irradiation, Precipitates, Instability

The purpose of this study is to investigate the response of the precipitates against irradiation in F82H steels which are considered as main candidate structure material for the fusion DEMO reactor blanket. M23C6-type precipitates contained F82H-IEA steel, and MX- and M23C6-type precipitates contained F82H-BA12 steel were selected as experimental specimens. Iron irradiation at 673 K using ion accelerator was performed on both steels up to 50 dpa. After irradiation, the instability behavior of precipitates was characterized using transmission electron microscopy. It is found that in F82H-IEA specimens, the number density of radiation defects at 20 dpa was 3.26×1021 m−3, and the amorphization of M23C6 was undetected up to 50 dpa. Although Ostwald ripening occurred in M23C6 precipitates, the average size of M23C6 mildly decreased with irradiation dose within this study. For F82H-BA12 specimens, the shrinkage rate of MX- and M23C6-type precipitates was estimated respectively as 0.06 and 0.03 nm/dpa. Hence, the MX and M23C6-type precipitates in F82H steel exhibit an excellent irradiation resistance under the present irradiation condition. Moreover, the behaviors like amorphization and weakening in contrast were not observed in M23C6 precipitates in both specimens, which is different from electron irradiation, presumably due to the factors such as different damage rate.

In this study, the mechanical properties in a Zr-Nb alloy plate with bimodal basal texture microstructure have been evaluated by tensile, Vickers hardness and nano-indentation tests. Based on the results, the strength-hardness relationship is discussed with special attention paid to its textured microstructure. It is found that the correlation between strength and hardness varied greatly depending on whether the loading direction is parallel or perpendicular to the normal direction of the plate, demonstrating that the strength-hardness relationship is texture-dependent. In addition, the relation between strength and nano-hardness is obtained by subjecting specimens to cold rolling at various reduction rates. This allows for the evaluation of the strengthening effect using convenient and non-destructive nano-indentation tests instead of elaborate tensile tests, which may have particularly useful applications for nuclear engineering components when considering the irradiation strengthening occurred in these materials.

In order to clarify the instability of M23C6 in F82H steel under irradiation, both electron irradiation using a high voltage electron microscope (HVEM) and ion irradiation using an ion accelerator were performed. For the electron irradiation, in-situ observation under 2 MV electron irradiation and ex-situ high resolution electron microscopic (HREM) analysis were utilized to evaluate the response of M23C6 against irradiation. The temperature dependence of the irradiation induced instability of the carbide was first confirmed: 293 K < T < 573 K, by observation of lowering in contrast at the periphery of carbides, 698 K < T < 773 K, fragmentation at the interface between carbides and matrix, and at 773 K, formation and coarsening of new particles near the periphery of M23C6. HREM analysis showed the loss of the lattice fringe contrast at the pre-existing M23C6 precipitates at temperatures ranging from 473 to 773 K, indicating severe loss of crystallinity due to dissolution of the constituent atoms though irradiation- enhanced diffusion under the vacancy diffusion by the focused electron beam irradiation. For the ion irradiation, 10.5MeV-Fe3+ ion was applied to bombard the F82H steel at 673K to achieve the displacement damage of 20 dpa at the depth of 1.0 µm from surface. Cross-section TEM specimens were prepared by a focused ion beam technique. The shrinkage of carbide particles was observed especially near the irradiation surface. Besides, the lattice fringes at the periphery of carbide were observed in the irradiated M23C6 by the HREM analysis, which is different from that observed in the electron irradiation. It was clarified that the instability of M23C6 is dependent on the irradiation conditions, indicating that the flow rate of vacancy type defects might be the key factor to cause the dissolution of constituent atoms of carbide particles into matrix under irradiation.

Corrosion of pure Cr and pure W in molten FLiNaK at 773 K was investigated to deeply understand the effect of the alloying elements on the corrosion mechanisms of reduced activation ferritic/martensitic (RAFM) steels. The molten salt blanket environment was simulated by hydrogen fluoride gas bubbling. Electrochemical polarization and weight change measurements were conducted to estimate corrosion rates. The oxidation reaction rate of pure Cr was extremely high (instantly reached 2.9 × 104 mm/year). The corrosion rate of W was lower than that of the RAFM steel, JLF-1 steel, and pure Fe by one order of magnitude. W was nobler than Ni, which is known as a corrosion-resistant metal to the molten fluoride salts and hydrogen fluoride. The compatibility of W coating with the first wall structure of blankets was evaluated with the local tritium breeding ratio (TBR). When a Pb neutron multiplier was used, thin W coating almost did not affect the local TBR.

Tensile properties and microstructure of a Zr–1.8Nb alloy subjected to 140-MeV C 4+ ion irradiation at 573 K up to 5.3 dpa have been investigated by using 0.18 mm-thick tensile specimens. Irradiation damage was introduced into the tensile specimens homogeneously over entire thickness using a variable energy degrader. Irradiation-induced strengthening and embrittlement (loss of ductility) were successfully evaluated. The yield strength of irradiated specimens (3.1- and 5.3-dpa) was 137% and 145% of unirradiated specimen, whereas the total elongation of those irradiated specimens was less than a half of unirradiated specimen. It appears that the rate of embrittlement is fairly faster than the rate of strengthening. Transmission electron microscopy (TEM) observation on the 3.1-dpa specimen revealed that the bcc-Nb/Zr precipitates originally contained in the alloy were stable in terms of crystal structure and size. The size and number density of dislocation loops were 7.2 nm and 1.2 × 10 21 /m 3 for the -loops, 15.4 nm and 6.5 × 10 20 /m 3 for the -type loops, respectively. The increase of yield strength expected from these dislocation loops was ∼64% of the actual irradiation-induced strengthening, indicating that the dislocation loops are the main contributors for the irradiation-induced strengthening.

Zirconium-based (Zr-based) alloys have been widely used as materials for the key components in light water reactors (LWRs), such as fuel claddings which suffer from waterside corrosion, hydrogen uptakes and strength loss at elevated temperature, especially during accident scenarios like the lost-of-coolant accident (LOCA). For the purpose of providing a safer, nuclear leakage resistant and economically viable LWRs, three general approaches have been proposed so far to develop the accident tolerant fuel (ATF) claddings: optimization of metallurgical composition and processing of Zr-based alloys, coatings on existing Zr-based alloys and replacement of current Zr-based alloys. In this manuscript, an attempt has been made to systematically present the historic development of Zr-based cladding, including the impacts of alloying elements on the material properties. Subsequently, the research investigations on coating layer on the surface of Zr-based claddings, mainly referring coating materials and fabrication methods, have been broadly reviewed. The last section of this review provides the introduction to alternative materials (Non-Zr) to Zr-based alloys for LWRs, such as advanced steels, Mo-based, and SiC-based materials.

The crystal orientation of body centered cubic (bcc) precipitates embedded in hexagonal close packed (hcp) matrix is usually assumed to follow the so-called Burgers orientation relationship; however, this orientation relationship may not be maintained in the case where the precipitation occurs in parallel with the recrystallization of matrix. The Zr-2.5Nb alloy is a typical example of such a case. In the present study crystal orientations of bcc precipitates (Nb-rich β2 phase and Zr-rich β1 phase) in fully recrystallized hcp Zr matrix have been analyzed by means of electron backscatter diffraction (EBSD) and transmission Kikuchi diffraction (TKD). Based on the Euler angles determined by EBSD/TKD, the parallelism of atomic planes was examined one by one. The analysis was performed on 100 precipitates for each composition. The crystal orientations of the Nb-rich precipitates were practically random, whereas 28% of the Zr-rich precipitates followed the Burgers orientation relationship. Moreover, the fraction of the Nb-rich precipitates whose slip planes, either {110} or {112}, were parallel to those of the hcp Zr matrix, { 10 1 ¯ 0 }, was no greater than 5%. These results support a tentative conclusion of our previous study that the Nb precipitates are ideal Orowan type strong obstacles against gliding dislocations due to the crystal mismatch, even though they are softer than the matrix in terms of shear modulus.

In this work, the mechanical behavior of as-received and hydrogenated Zircaloy-4 fuel claddings was investigated by the newly developed advanced expansion due to compression (A-EDC) test and the conventional uniaxial tension (UT) test at room temperature, in order to, respectively, understand the hydride-induced embrittlement in tube longitudinal and hoop directions. The UT experimental results showed that the mechanical strength in the longitudinal direction slightly increased with hydrogen content, whereas the maximum strain decreased greatly with hydrogen increasing. In the case of A-EDC tests, the mechanical performance in the hoop direction seemed insensitive to the hydrogen content; no obvious decline in maximum strain was observed until 800 ppm H. The comparison between these two tests clearly reveals that the hydride-induced embrittlement is preferential to occur in the longitudinal direction, compared with the sluggish response in the hoop direction, which implied the enhanced ductility a...

The effect of elevated-temperature annealing in the range of 1473 K–1673 K on the coarsening kinetics of nanoparticles and microstructural evolution in an as-fabricated 12Cr-ODS steel was systematically investigated. Results show that the nanoparticles were extremely stable and continued precipitating during annealing at 1473 K, whereas, significant coarsening took place during exposure at 1673 K, increasing by 177% and 423% in diameter for 1 h and 24 h, respectively. Furthermore, heterogeneously distributed voids were developed, sizes of which increased distinctly at 1573 K and 1673 K for longer holding time. This is probably due to the growth and/or aggregation of Ar-entrapped and pre-existed voids in the as-fabricated condition. Additionally, no obvious changes were observed in microstructure and texture at 1473 K, nevertheless, full recrystallization were achieved at 1673 K for 24 h, and the major texture was not altered except reduction of the intensity. The apparent activation energy for recrystallization was experimentally calculated as 424 ± 22 kJ/mol, which was almost the same as that for nanoparticle coarsening, i.e., 412 ± 55 kJ/mol, suggesting that recrystallization proceeded accompanying with nanoparticle coarsening that would in turn stimulate the recrystallization process. It was deduced that recrystallization in the as-fabricated 12Cr-ODS steel was presumably not able to occur until the nanoparticles were dissolving and/or coarsening during annealing.

In PAA-g-lignin, phase separation, caused by the difference in expansion properties between lignin and polyacrylic acid, is used to build a porous hydrogel. In this study, PAA-g-APL was produced by grafting polyacrylic acid with acid-pretreated alkali lignin. Acid-pretreated alkali lignin acts as a hierarchical pore-forming agent that enhances the simultaneous adsorption capacities for Pb

Hardness behavior and deformation of the microstructure beneath the indentation in 12Cr-ODS steel after exposure to heavy ion irradiation at 573 K were investigated with combined applications of nano-indentation tests, EBSD analysis, and TEM observation. The inhomogeneous nano-indentation hardness behavior was firstly investigated in both non-irradiated and irradiated specimens and compared to those at room temperature (RT) irradiation. Subsequently, TEM observations were performed to understand the deformation behaviors beneath the indentation tested at typical low-indexed orientations. Obvious irradiation hardening was confirmed in both the normal direction (ND) and rolling direction (RD) specimens, and the hardening effect intensified with an increase in irradiation dose. Meanwhile, various anisotropic hardness behaviors were observed such as a lower hardness value and a weaker hardening effect in the RD specimen compared to the ND specimen, and a lower hardness value but a greater hardening effect in [001] orientation relative to [111] orientation. Furthermore, results from 573 K irradiation showed similar anisotropic hardness behaviors with those obtained from RT irradiation, despite the fact that irradiation at 573 K exhibited a weakened irradiation hardening effect in this steel. TEM observation of the deformation microstructure beneath the indentation reveals that (i) the depth of the deformation affected zone varied with orientation, ranging from ~6-9 times that of the indent depth, and (ii) distinct dislocation-grain boundary (GB) interactions beneath the indentations was confirmed to exhibit dependence on the geometric relation between GB and indenter impression direction. Correlation between the anisotropic hardness behavior and microstructural features is discussed based on Schmid factor analysis, comparison of geometric favorability between indenter and possible slip planes, and TEM observation of deformation microstructure. The results conclude that the anisotropic hardness behaviors in the present 12Cr-ODS steel are ascribed to the combined effect of crystal orientation and the non-uniform grain morphology with the existence of the elongated grains having low aspect ratio in the ND plane and nano-layered grains in the RD plane.

The microstructure of the 12Cr-ODS steel was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron backscatter diffraction (EBSD) techniques. The results showed that the microstructure consisted of fine and elongated grains, high density of dislocations, and large concentration of nm-scale oxide particles, which were identified as five types of crystal structures by high resolution TEM (HRTEM) imaging, such as monoclinic and cubic Y 2 O 3 , hexagonal and orthorhombic Y 2 TiO 5 , and cubic Y 2 Ti 2 O 7 . The dominant {001} component and weaker parallel to normal direction texture were observed. Besides, the yield stress was experimentally measured and quantitatively estimated. The findings indicated that theoretical calculation was in accordance with the experimental measurements, and strengthening contributions from solid-solution atoms and grain boundaries were linearly additive, whereas those from dislocations and oxide dispersoids were averaged by root mean square summation.

The effect of Mo addition on microstructures of β-quenched and subsequently annealed Zr-1.2Nb alloys is systematically investigated. Differential scanning calorimetry, electron backscatter diffraction, transmission electron microscopy, X-ray energy dispersive spectrometry techniques and microhardness tests are jointly utilized to characterize the microstructure and to evaluate the mechanical property. Martensitic microstructure, a mixture of lath martensites and lens martensites, is observed in the β-quenched specimens. Width of lath martensite reduces and fraction of lens martensite increases as the Mo content increases. This suggests that Mo addition retards slip deformation and enhances twinning deformation during the martensitic transformation, and that segregation of Mo atoms is also responsible for the lath width reduction. After annealing at 873 K, the martensitic structures are maintained, accompanying with the presence of numerous precipitates, which is attributed to the fact that the β-quenched microstructure is strain-relieved instead of being recrystallized. The distribution of the misorientation angle between the neighboring grains in both β-quenched and subsequently α-annealed specimens is predominantly around 60° regardless of the Mo content. Microhardness increases with increasing Mo content both in the β-quenched and the annealed specimens, and it drops greatly after annealing at a fixed composition. Keywords: Zr-Nb alloy, Zr-Nb-Mo, Martensite, Mo addition, Twinning, Precipitates

Two types of oxide dispersion strengthening (ODS) steels (i.e. 12Cr-ODS-NIFS and 12Cr-ODS-IMR) with similar chemical compositions were produced through different fabrication processing. A systematic comparison was performed to investigate the effects of different fabrication processing on microstructure and mechanical properties of ODS steels. Compared to 12Cr-ODS-NIFS, the 12Cr-ODS-IMR steel exhibited significantly enhanced mechanical properties, such as higher Vickers hardness, tensile strength and creep strength. To understand the microstructural reasons for the excellent mechanical properties of ODS steels, systematic microstructure characterizations were carried out through a combined study of X-ray diffraction, electron backscattered diffraction, and transmission electron microscopy. It was found that both steels had similar grain structures comprising fine and heavily deformed grains smaller than ~1 μm and elongated coarse grains larger than ~10 μm, both of which possessed similar precipitates including coarse TiC x O 1− x particles and homogenously distributed Y 2 TiO 5 nanoparticles with diameters of several nanometers. 12Cr-ODS-IMR had a finer grain size, larger aspect ratio of grain length to width, and higher density of dislocations, which should be derived from the additional cold rolling and responsible for its better mechanical properties compared with 12Cr-ODS-NIFS.

Dissimilar-metals bonding between V–4Cr–4Ti and Hastelloy X alloy was investigated by explosive welding, which is essential to connect coolant pipes of Flibe blanket and external components such as tritium extractor and heat exchanger in fusion reactor. The nano-indentation hardness and corresponding microstructure at the interface are evaluated. After the explosive welding, a characterization of the typical wavy interface indicates good weldability. Discontinuous vortex regions appear at the interface and reveal obvious hardening up to 806 HV. Microstructural analysis indicates that the interlayer consists of Ni37.1V21Cr20.5Fe15.4Mo4.4Ti1.0 Co0.6 with a fcc lattice structure and a high density of dislocations, and no intermetallic forms. Based on the compositions, the formation of solid solution was predicted by the entropy and enthalpy of the multi-component alloy system, despite the phase diagrams of binary alloys of the constituent elements indicating the formation of intermetallics. Study of hardening mechanism at the interlayer indicates that obvious hardening is mainly attributed to solid-solution hardening and dislocation hardening.

In PAA-g-lignin, phase separation, caused by the difference in expansion properties between lignin and polyacrylic acid, is used to build a porous hydrogel. In this study, PAA-g-APL was produced by grafting polyacrylic acid with acid-pretreated alkali lignin. Acid-pretreated alkali lignin acts as a hierarchical pore-forming agent that enhances the simultaneous adsorption capacities for Pb2+, Cu2+ and Cd2+ ions from wastewater. Notably, PAA-g-APL acted as a selective adsorbent for Pb2+ ions has an excellent selective removal coefficient α (20.22) in contaminated wastewater contained Cu2+ ions. Its molar partition coefficient for Pb2+ ions (68 %) is higher than that for either Cu2+ ions (28.6 %) or Cd2+ ions (3.4 %). At equilibrium, the total adsorption capacities of PAA-g-APL for Pb2+, Cu2+ and Cd2+ were 1.076 mmol g−1, 0.3233 mmol g−1 and 0.059 mmol g−1, respectively. The experimental kinetic data fitted well to a pseudo-second order model and to an intra-particle-diffusion model. The Freundlich isotherm model gave the best fit with the experimental equilibrium data. The ΔG° for PAA-g-APL is

Thermal aging experiments on a 9Cr-ODS steel were carried out at 700 °C with a period from 100 up to 10000 h, and the effects on mechanical properties and microstructural evolutions were investigated. It was found that hardness and tensile properties exhibited negligible degradation by thermal aging. The mixed ductile and brittle fracture modes in the tensile specimens remained almost no change. Although a slight recovery of grains/subgrain structures and dislocations took place, the homogeneously dispersed nano-size oxides with an ultrahigh density in matrix were not affected during the thermal aging. However, a significant coarsening of carbides around grain/subgrain boundaries appeared. Benefited from the extreme stability of nano-size oxides, the 9Cr-ODS steel possesses the excellent thermal stability of mechanical properties exposed to the elevated temperature of 700 °C up to 10000 h.

The anisotropic hardening response in a 12Cr-ODS ferritic steel was investigated before and after irradiation with 2.8 MeV Fe2+ at room temperature up to displacement damages of 0.5 and 15 dpa. For post irradiation examination, techniques of nano-indentation and orientation imaging microscopy were jointly applied to link crystal orientation with nano-hardness. Results showed that the averaged hardness of normal direction-transverse direction (TD-ND) specimen is less than that of rolling direction-transverse direction (RD-TD) specimen irrespective of the dose of irradiation damage. However, the amount of irradiation-induced hardening is observed to be weaker in TD-ND specimen relative to RD-TD specimen. These anisotropic phenomena are considered to be mainly attributed to the elongated grain structure with a very high grain aspect ratio of the present steel, in which smaller-sized grains are exhibited in TD-ND plane nevertheless fairly coarse grains are in RD-TD plane. In addition, the orientation dependent hardness and irradiation-induced hardening were confirmed. Specifically, the hardness of [001]-oriented grain is lower than that of [111]-oriented grain with and without irradiation. With the presence of irradiation, it was found that the extent of hardening is more obvious at [001]-oriented grain than [111]-oriented grain, which is attributed to a more activated primary {110} slip beneath the indenter when tested at [100]-oriented grain compared with [111]-oriented grain.

Mo-modified Zr–1.2Nb alloys were prepared and the effects of Mo addition on precipitation in Zr–Nb alloys were elucidated. It was found that an increase of Mo content decreased α→(α+β) phase transformation temperature in Zr–Nb alloys. A new kind of precipitate, β-(Nb, Mo, Zr), was identified in the Mo-containing alloys. These particles are formed because Mo atoms replace Nb atoms in the β-(Nb, Zr) phase. Further, it was found that Mo retarded the growth of the precipitates but increased their number density.

The alloying effects of Sn, Nb, Cr, and Mo on zirconium alloys were elucidated and compared. Electron backscatter diffraction, transmission electron microscopy, tensile test, and fractographic observation were jointly utilized to carry out detailed microstructural characterization and mechanical property evaluation. Results show that Mo is the most effective among these elements from the viewpoints of strengthening and reducing grain size. The strengthening mechanism for each element is also discussed. The order of solid-solution strengthening of these alloying elements is Cr > Nb > Sn, and the sequence is Cr ≈ Mo > Nb when precipitation strengthening is considered. Further, as far as the ability to impede dislocation motion is concerned, the sequence is Mo > Cr > Nb > Sn. The experimental results demonstrate that minor amount of Mo addition in zirconium alloys is greatly effective in strengthening the alloy and reducing the grain size.

The effect of aluminum on microstructure and properties of martensitic wear-resistant and heat-resistant steels was investigated. The results indicate that as-cast microstructure of the specimens is composed of ferrite, pearlite and carbides. After quenching at 1,000 °C and tempering at 600 °C, the microstructure of the specimens consists of tempered sorbite and Fe–Cr–Al intermetallic compounds which distribute directionally in the matrix and increase with increase in Al content. The additions of Al enhance the ambient tensile strength which reaches the peak at 1,230 MPa when the specimens contain 1.97 % Al. Oxidation notably decreases with the increase of Al and the average oxidation rates reduce to 0.0095 g m−2 h−1 at 650 °C and 0.0285 g m−2 h−1 at 800 °C, respectively. Wear resistance of the specimens containing Al obviously increased when compared to the Al-free specimens.

In this study, effect of tungsten on microstructure and properties of high chromium cast iron was investigated. The experimental results indicated that tungsten distributed uniformly in the matrix and carbides. W carbides are composed of WC1−x, W6C2.54 and CW3 and W2C. With the increase of tungsten content, bulk hardness and matrix microhardness both increased gradually and reached the peak at 62.62HRC and 913HV, respectively. All of the tungsten-containing alloys performed better than tungsten-free alloys in impact tests and alloys containing 1.03 wt% W showed the highest impact toughness at 8.23 J cm−2. Tungsten considerably improved the performance of high chromium cast iron on wear resistance and alloys containing 1.03 wt% W increased 205% compared to tungsten-free alloys. Therefore, tungsten can be used as an alloying element to increase the hardness and wear resistance without scarifying impact toughness in high chromium cast iron. Alloys containing 1.03 wt% tungsten showed the optimum properties.

The Fe-based coating was produced on the surface of the column substrate with a Al2O3 cylindrical sleeve by high frequency induction cladding, microstructure of the coating was investigated with scanning electron microscope (SEM), the crystal structure was characterized by X-ray diffractometer (XRD), the microhardness and wear resisitance of the coating were evaluated. The results show that a metallurgical bond between coating and substrate was obtained during the rapid solidification, the phases of the coating were composed of austenite and the eutectic of γ-Fe + (Cr, Fe)7(C, B)3. Compared with the substrate, the microhardness and wear resistance of the coating improved apparently, solid-solution strengthening and second-phase particle hardening led to these results.