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Nanocrystalline CeO2 films with thickness of approximate 250 nm were grown on Si substrates using a sol-gel process with spin-coating method. The films were then irradiated with 1.5 MeV Au ions to the doses of 2.5, 15.0 and 35.0 dpa at room temperature. Electron microscope results show that the surface of the as-grown CeO2 film is very smooth, and no any cracks are detected. The as-grown CeO2 film is cubic fluorite structure with an average grain-size of 6.4 nm. The nanocrystalline CeO2 films remain cubic structure under all irradiation conditions. The crystallinity and average grain-size of the CeO2 film decrease with the increase of irradiation dose, which is due to the competing effects of electronic and nuclear energy loss. As the irradiation dose is up to 35.0 dpa, the crystal quality is obviously deteriorated as well as the surface microstructure. Raman spectra also confine that the grain-size of the nanocrystalline CeO2 films decreases with the irradiation dose increase. X-ray photoelectron spectroscopy (XPS) results reveal that parts of Ce4+ in the nanocrystalline CeO2 films change to Ce3+, and oxygen vacancy concentration also increases after irradiation. All these samples exhibit two emission bands in the photoluminescence (PL) spectra, and the relative emission intensity of the defect peak centered at 500 nm is enhanced by ion irradiation, which also indicates that irradiation introduces oxygen vacancies into the nanocrystalline CeO2 films. This work provides a useful way to control the grain-size and oxygen vacancy of the nanocrystalline CeO2 films through ion implantation technique.

The present paper reports the irradiation behavior of nanostructured NiCoCr medium entropy alloy enhanced by Y-Hf-O nanooxides and fine grains produced by powder metallurgy. Ion beam irradiation to a peak dose of 130 dpa at 580°C produced neither detectable void swelling nor irradiation-induced hardening, in contrast to significant void swelling and property degradation of single phase NiCoCr concentrated solid-solution alloy under the similar irradiation condition. The dispersed nanooxides and high density of grain boundaries act as defect sinks that effectively annihilate irradiation-induced interstitials and vacancies. Furthermore, high-density nanooxides maintain their crystalline structures and stabilize the grain boundaries during irradiation.

Flexible strain sensors have been garnering substantial attention since being proven to be an effective means to acquire critical biomarkers for monitoring the states of the movement of organisms. This work introduces a flexible metal thin film strain sensor with micro/nano structure which has large measurement range and high sensitivity strain measurement. The large measurement range can be realized by the bugles that avoiding expanding of cracks and the high sensitivity is attributed to the disconnection-reconnection process by nanoscale cracks. In experiments, a flexible strain sensor with 30 nm Au nano-film was researched, and the results show that the maximum strain measurement range of the Au nano-film flexible sensor with micro/nano bulge structure can reach to 80%, and the gauge factor (GF) can reach to 20. In addition, the good repeatability and stability were proved by more than 1000 times cycles. Finally, this flexible sensor was attached to human’s fingers for real-time monitoring of the state of human joints and was demonstrated to have good comprehensive performance and usability. These features create opportunities for applying in many fields like wearable medical devices, e-skin, flexible robots and so on.

As one of the most concerned sensitive materials, carbon nanotubes (CNTs) are widely used in flexible sensors for wearable electronic devices. Here, we present an electromechanical sorting method that applies to micropyramid single-walled CNT (SWNT)-film flexible force sensor to further enhance its sensitivity. The principles of the method are as follows. When the micropyramid structure is under pressure, stress concentration will occur at its tip, and the resistivity of the SWNT film coated on the surface of the micropyramid structure will change remarkably, which leads to changes in the resistance of the SWNTs. The resistance of quasimetallic SWNTs increases greatly under pressure, whereas that of metallic SWNTs increases minimally (band theory). Therefore, when the threshold voltage was applied to SWNTs, the metallic SWNTs exposed in the air were oxidized and failed when the current induced defects in the graphite layer, whereas the quasimetallic SWNTs with a high gauge factor remained functional. The experimental results showed that the sensitivity of the sorted SWNTs flexible force sensor was 3.4891 kPa−1, which denotes an improvement of 56.86% compared with the initial unsorted devices. In addition, the flexible force sensor exhibited low power consumption, which is less than a microwatt, and good repeatability and stability. Finally, the sensor was successfully used in the knuckles of a person's fingers to monitor finger motions.

CoCrNi -medium-entropy alloy (MEA) has been widely investigated due to its superior mechanical properties that overcome strength-ductility tradeoff. Here we show further property enhancement of CoCrNi MEA by introducing nano-scale features. Both CoCrNi and oxide dispersion strengthened (ODS) CoCrNi are fabricated by mechanical alloying and spark plasma sintering. Microstructural characterization and mechanical testing of these nanostructured MEAs revealed that the nano-scale features significantly improves the strength of the alloys. In ODS-CoCrNi MEA, Y2Ti2O7 oxides with an average diameter of 7.3 ± 3.2 nm are incoherent with the matrix, and a specific orientation relationship exists between Y2Ti2O7 and the matrix, which is [011]Y2Ti2O7//[011]Matrix, (400)Y2Ti2O7//(200)Matrix and (22 2 ‾ )Y2Ti2O7//(11 1 ‾ )Matrix. The recrystallization and grain growth processes are effectively suppressed by the introduction of Y2Ti2O7 nanoparticles. Strengthening mechanism analyses indicate that the strength improvement of ODS-CoCrNi is mainly ascribed to the precipitation strengthening of Y2Ti2O7

Cu-0.75Cr-0.1Zr-0.3Ti-0.1V (wt.%) alloys were fabricated by vacuum induction melting, and the effects of joint Ti and V addition on the recrystallization behavior, mechanical property and corrosion resistance of the alloys were investigated. Compared with International Thermonuclear Energy Reactor (ITER) grade CuCrZr (IG-CuCrZr) alloys, the recrystallization resistance of the CuCrZrTiV alloys is highly improved by the addition of Ti and V. The outstanding recrystallization resistance of the CuCrZrTiV alloys is attributed to the reduced stacking-fault energy and the presence of high-density coherent precipitates. The corrosion resistance of the CuCrZrTiV alloys is much higher than the IG-CuCrZr alloys. Two-step thermomechanical treatments are applied to further improve the performance of the CuCrZrTiV alloys, and the tensile strength and ductility of the alloys are improved simultaneously. Enhancement of the strength is ascribed to high-density precipitates, dislocations and subgrains in the CuCrZrTiV alloys after two-step thermomechanical treatments. The texture changes from {112} α texture to {110} brass texture after two-step thermomechanical treatments, and deformation twins form during the development of the brass texture, which improves the ductility of the alloys. This work provides an effective way to improve the performance of the CuCrZrTiV alloys by increasing recrystallization resistance and two-step thermomechanical treatments.

The microstructure and nano-hardness of the pure copper and oxide dispersion-strengthened (ODS) copper alloy subjected to 1.4 MeV Au ions irradiation at room temperature were investigated. After irradiation, dislocation-loops form in both materials, while voids can only be generated in the pure copper. Compared with the irradiated pure copper, larger average diameter and lower number density of irradiation-induced dislocation-loops were detected in the ODS copper alloy, revealing that high-density dislocation and large volume of Al2O3 particles existing in the ODS copper alloy can act as effective sinks for the irradiation-induced defects. It was also detected that irradiation hardening in the ODS copper alloy is lower than that in the pure copper. The microstructure and nano-hardness results reveal that the ODS copper alloy has a better irradiation tolerance than the pure copper. In addition, the average diameter of the Al2O3 particles in the ODS copper alloy decreases after irradiation, because the Al–O chemical bonds are decomposed and the atoms are redistributed in the matrix during the irradiation process. This work reveals that the irradiation tolerance of the copper can be effectively enhanced by adding nano-sized Al2O3 particles into the matrix.

1.2 Hf and 1.5 Y2O3 (wt.%) were added into CoCrFeNi (CCFN) high-entropy alloy (HEA) to fabricate oxide dispersion strengthened CoCrFeNi (ODS-CCFN) composite by mechanical alloying and spark plasma sintering. Microstructures, including XRD, SEM, EBSD, and TEM of CCFN and ODS-CCFN HEAs were investigated to identify the effects of introducing nano-sized oxides into CCFN HEA. These HEAs compose of FCC matrix and a small amount of Cr7C3 and Cr2O3, and a few of MnCr2O4 is only detected in CCFN HEA. High-density Y2Hf2O7 with the average diameter of 6.9 ± 4.2 nm uniformly distribute in the matrix and Cr7C3 of ODS-CCFN. Lattice misfit calculations indicate that Y2Hf2O7 particles exhibit a coherent interface with the matrix, and a semi-coherent interface with Cr7C3. The average sizes of all phases, including grain, Cr7C3 and Cr2O3, are highly refined in ODS-CCFN. The effects of microstructure changes on properties of CCFN HEA were also detected. Compared with CCFN, the tensile yield strength of ODS-CCFN increases from 978 MPa to 1.25 GPa with a reasonable elongation decreases from 2.6% to 1.9%. The increase in yield strength for ODS-CCFN is mainly ascribed to the precipitation strengthening of Y2Hf2O7 and highly refined grains, Cr7C3 and Cr2O3. The electrical resistivity of ODS-CCFN is lower than that of CCFN, the reason may be that the existence of Y2Hf2O7 particles reduce the lattice distortion of the matrix, and make the electrical resistivity decrease. The corrosion resistance of ODS-CCFN HEA is highly improved in both sulfuric acid solution and sodium chloride solution because its passive current density is largely reduced by the addition of Hf and Y2O3.

Cu–Cr–Zr alloy has been widely considered to be used as heat sink materials in the fusion reactor due to its superior properties. However, Cu–Cr–Zr alloy suffers significant creep deformation and softening as the temperatures is above 300–400 °C. Advanced Cu alloys with high strength, high conductivity and high thermal stability need to be developed to meet the requirements in the future fusion reactor. In this work, a novel Cu–Cr–Zr–Fe–Ti–Y alloy was designed and prepared by vacuum induction melting, followed by homogenization treatment, hot-rolled, solid solution, cold-rolled and aging treatments. Tensile properties, hardness and electrical conductivity of the alloys aging at different temperatures were tested. The alloy aged at 500 °C exhibits excellent tensile strength up to 541 MPa and high electrical conductivity of 82% IACS. The alloy maintains high tensile strength even annealing at 500 °C for 72 h. The microstructures of the alloy were characterized by optical, scanning and transmission electron microscopy, and it is found that the high thermal stability of the novel alloy is mainly contributed to two reasons. One is the high friction of low-ΣCSL grain boundaries (mainly Σ3) with low energy detected in the matrix, which are difficult to slid and have higher thermal stability than general high-angle grain boundaries. Another one is the two kinds of high-density precipitates detected in the matrix. The larger Cr1·4Fe particles are semi-coherent with the matrix, and the orientation relationship is [011]Cu//[011]Cr1·4Fe, (100)Cu//(01 1 ‾ )Cr1·4Fe and (11 1 ‾ )Cu//( 2 ‾ 1 1 ‾ )Cr1·4Fe. The smaller Cr particles are coherent with the matrix, and the orientation relationship is [011]Cu//[ 1 ‾ 11]Cr, (100)Cu//(01 1 ‾ )Cr and (0 1 ‾ 1)Cu//(211)Cr. The strengthening mechanism of the alloy was analyzed in details, and the calculation yield strength (480 MPa) is well coincident with the experimental value (473 MPa).

Microstructure and mechanical properties of two kinds of oxide dispersion strengthened concentrated solid solution alloys (CSAs), FeCoNi-1.5Y2O3 (FCNY) and FeCoNi-1.2Ti-1.5Y2O3 (FCNTY), are studied through a comparing investigation with FeCoNi (FCN) CSAs. All these alloys are fabricated by mechanical alloying, spark plasma sintering, hot rolling and annealing treatment. For three kinds of alloys, both the as-milled powders and bulk materials are of single face-centered cubic structure. Electron backscattered diffraction results reveal that the texture transformation is suppressed during the hot rolling process because the movement of grain boundaries is hindered by the oxide particles. Compared with FCN CSAs, grains are refined by 43% and 47% for FCNY and FCNTY CSAs, respectively. Nano-sized Y2O3 (monoclinic structure) and Y2Ti2O7 (pyrochlore structure) particles are uniformly distributed in FCNY and FCNTY CSAs, respectively. Both Y2O3 and Y2Ti2O7 particles show a semi-coherent relationship with the matrix. Yield strength of FCN, FCNY and FCNTY CSAs is 559, 981 and 1050 MPa, respectively. Theoretical calculations illustrate that high strength of FCNY and FCNTY CSAs comes from refined grains and high-density nano-sized oxide particles.

FeCoNi concentrated solid-solution alloys (CSAs) and its modified version strengthened by in-situ formed nano-sized particles are successfully manufactured through mechanical alloying and spark plasma sintering method. Both the as-milled powders and the bulk materials are of single face-centered cubic structure. After sintering and heat treatment, grains are refined by 68% with the addition of oxides. In oxide dispersion strengthened (ODS) FeCoNi CSAs, the majority of nano-sized particles with diameter ranging from a few to ~ 40 nm are uniformly distributed in the matrix, and most of them are identified as Y2Ti2O7. Electron backscattered diffraction results reveal that the recrystallization process is suppressed due to the existence of the nano-sized particles. The size and distribution of oxide particles in the matrix can be controlled by adjusting experiment parameters of the mechanical alloying process and annealing treatment. Refined grains and high-density nano-sized particles result in enhanced compressive yield strength for ODS-FeCoNi CSAs at room temperature and 700 °C, which is 1295 MPa and 127 MPa, respectively.

Nanocrystalline CeO 2 films with around 250 nm thickness were deposited on Si (0 0 1) substrates by a facile sol–gel process with spin coating method. The films are of cubic fluorite structure, and some lattice distortions exist in the film. The phase stability and small change in lattice parameter at different annealing temperatures indicate the good thermal stability of the nanocrystalline CeO 2 films. The average grain-size and surface roughness of the films increase with the increase of annealing temperature. The content of Ce 3+ and oxygen vacancy is very high in the nanocrystalline CeO 2 films, while, the films still remain cubic phase regardless of its high level non-stoichiometric composition. All the annealed samples show two emission bands, and the defect peak centered at ∼500 nm shows a red-shift. The intensity of the green-emission band increases with the increasing annealing temperature, which might result from the increasing concentration of oxygen vacancies caused by the valence transition from Ce 4+ to Ce 3+ , and it has also been confirmed by the X-ray photoelectron spectroscopy results. This work demonstrates that oxygen vacancy plays an important role on the properties of the nanocrystalline CeO 2 film, and it also provides a possible way to control the concentration of oxygen vacancies.

This work presents an early look at irradiation effects on China low activation martensitic (CLAM) steel with nanocrystalline grains (NC-CLAM steels) under 500 keV Xe-ion bombardment at room temperature to doses up to 5.3 displacements per atom (dpa). The microstructure in the topmost region of the steel is composed of nanocrystalline grains with an average diameter of 13 nm. As the samples were implanted at low dose, the nanocrystalline grains had martensite lath structure, and many dislocations and high density bubbles were introduced into the NC-CLAM steels. As the irradiation dose up to 5.3 dpa, a tangled dislocation network exists in the lath region, and the size of the bubbles increases. X-ray diffraction results show that the crystal quality decreases after irradiation, although the nanocrystals obviously coarsen. Grain growth under irradiation may be ascribed to the direct impact of the thermal spike on grain boundaries in the NC-CLAM steels. In irradiated samples, a compressive stress exists in the surface layer because of grain growth and irradiation-introduced defects, while the irradiation introduced grain-size coarsening and defects gradients from the surface to matrix result in a tensile stress in the irradiated NC-CLAM steels. Nanoindentation was used to estimate changes in mechanical properties during irradiation, and the results show that the hardness of the NC-CLAM steels increases with increasing irradiation dose, which was ascribed to the competition between the grain boundaries and the irradiation-introduced defects.

Nanocrystalline zirconia (ZrO2) powders were prepared by a sol–gel process followed by annealing treatments from 500 to 1200 °C. Phase transformation, microstructural features and photoluminescence properties were characterized by X-ray diffraction, transmission election microscopy and photoluminescence spectra, respectively. The results show that both monoclinic phase and tetragonal phase exist in the nanocrystalline ZrO2 powders at annealing temperature in the range of 500–900 °C, and the concentration of monoclinic phase increases with increasing the annealing temperature. Tetragonal phase is totally transformed to monoclinic phase when annealing temperature is up to 900 °C. The average grain size of the powders also increases when annealing temperature increases. Two emission peaks centered at 390 nm (named as I390) and 470 nm (named as I470) exist in the photoluminescence spectra, and the intensity ratio of I390 to I470 decreases with increasing annealing temperature. The grain size is proposed to be responsible for the phase transformation in the nanocrystalline ZrO2 powders.

Nanocrystalline yttria stabilized zirconia (YSZ) film (with 8 mol% Y2O3) was synthesized via a sol–gel method. Phase stability, grain-growth and defects of the YSZ film were investigated under 500 keV Xe6+ ions irradiation to doses up to an average value of 22.2 displacements per atom (dpa). Atomic force microscope results show that the surface of the as-grown YSZ film is quite smooth and free of cracks. Transmission electron microscope results reveal that the average grain-size of the as-grown samples is around 12.6 nm. With increasing irradiation does up to 22.2 dpa, the average grain size increases, no phase transformation or amorphization is observed, which indicates that the phase structure of the nanocrystalline cubic YSZ film is quite stable. Two strong and broad emission peaks were detected in the YSZ film, and the emission intensity decreases obviously after irradiation. The possible mechanism of the grain growth was also discussed.

In recent years, nanocrystalline materials with grain size below 100 nm have attracted much interest due to their excellent chemical, physical, and optical properties. This review focuses on the irradiation effects of nanocrystalline materials. It has been generally believed that nanocrystalline materials have a great potential to increase irradiation resistance in the future reactor because of a large fraction of grain boundaries or interfaces that could absorb and annihilate mobile defects which produced during irradiation. Some calculation results and experiment results revealed that nanocrystalline materials can enhance irradiation resistance, while some reports showed that nanocrystalline materials exhibit worse irradiation resistance, or even amorphous at a lower irradiation dose compared with their bulk materials. During the irradiation process, the grain growth dominated by irradiation dose, thermal effect or defects was also disputed. Irradiation is also an important tool to tailor the grain size, phase structure and physical properties of the materials.

Self-assembly growth of ZnO-based axial and radial junctions via a kind of two-step method was reported. It was first prepared by a chemical vapor deposition (CVD) method, and then followed by an aqueous solution method to obtain ZnO-based junctions. The formation of the axial or radial junction depends on the sample prepared by the first step. If the microrods grown by the CVD method are pure ZnO, axial junction forms when the sample is put into the solution for further growth, otherwise, radial junction forms if the microrods grown by the first step are doped ZnO. It is attributed to the fastest growth direction in the formation of axial junction and radial junction is quite different. The photoluminescence spectra of the samples reveal that the junctions are quite different from the microrod films prepared by the first step. This work provides a useful way to fabricate ZnO-based junctions, which is important for designing nanodevices.

The influence of cobalt on the microstructural, magnetic and magnetocaloric properties of LaFe11.5-xCoxSi1.5C0.2 (x=0.50-0.85) compounds was investigated. The ingots were prepared by using a vacuum induction melting furnace. Before annealing, a large amount of 1:13 phase was distinctly observed. Nearly single 1:13 phase was obtained after annealing at 1353 K for only 3 days. The easy formation of 1:13 phase in the annealing process could be attributed to carbon doping. The Curie temperature (T-C) increases linearly with increasing the cobalt content. Although the maximum magnetic entropy changes of the compounds decrease rapidly when T-C rises from 275 to 298 K, and it decreases mildly when T-C continues to rise. Two composite refrigerants based on the compounds are proposed. Their entropy changes remains approximately constant over the temperature range from 266 to 292 K and 289 to 309 K. (C) 2012 Elsevier BY. All rights reserved.

Nanocrystalline zirconia (ZrO2) film with thickness of 305 nm deposited on a silicon substrate was irradiated with 2 MeV Au ions to different fluences at different temperatures. The implanted ion profiles were measured by time-of-flight secondary ion mass spectrometry (ToF-SIMS) and simulated using the stopping and range of ions in matter (SRIM) code, respectively. The experimental results show that a large fraction of the incident Au ions penetrates through the ZrO2 film and are deposited into the Si substrate. At the interface of ZrO2 and Si, a sudden decrease of Au concentration is observed due to the much larger scattering cross section of Au in ZrO2 than in Si. The depth profile of the Au ions is measured in both the ZrO2 films and the Si substrates, and the results show that the Au distribution profiles do not exhibit a dependence on irradiation temperature. The local Au concentration increases proportionally with the irradiation fluence, suggesting that no thermal or irradiation-induced redistribution of the implanted Au ions. However, the Au concentration in the ZrO2 films, as determined by SIMS, is considerably lower than that predicted by the SRIM results, and the penetration depth from the SIMS measurements is much deeper than that from the SRIM predictions. These observations can be explained by an overestimation of the electronic stopping power, used in the SRIM program, for heavy incident ions in light targets. Overestimation of the heavy-ion electronic stopping power may lead to errors in local dose calculation and underestimation of the projected range of slow heavy ions in targets that contain light elements. A quick estimate based on a reduced target density may be used to compensate the overestimation of the electronic stopping power in the SRIM program to provide better ion profile prediction.

Nanostructured pure ZnO (PZO) and Sn doped ZnO (SZO) were deposited on glass templates by chemical deposition method. Before the deposition, electrically conductive silver paste was pasted at the two ends of the glass templates as electrodes. The gas sensing properties of the nanostructured PZO and SZO were systematically investigated by our home-made system, and the results show that Sn doping decreases the response to tested gases. However, it remarkably shortens the response time and recovery time of the sensor. Both PZO and SZO show higher response to acetone than to ethanol, while the response time and recovery time of PZO and SZO to ethanol are shorter than those to acetone, which indicates that the selectivity of ZnO nanostructures to ethanol and acetone are different.

The corrosion behavior of magnetic refrigeration material La(Fe 0.94 Co 0.06 ) 11.7 Si 1.3 in distilled water has been studied using X-ray diffraction analysis, weight loss method, scanning electron microscopy and X-ray photoelectron spectroscopy. Results show that La(Fe 0.94 Co 0.06 ) 11.7 Si 1.3 compound suffers electrochemical preferential corrosion in distilled water. La(Fe 0.94 Co 0.06 ) 11.7 Si 1.3 compound contains three phases which are matrix phase, a small amount of α-Fe phase and La-rich phase. The matrix phase with NaZn 13 structure works as anode to be corroded. The final corrosion products on sample surface are La 2 O 3 , γ-Fe(OOH), Co(OH) 2 and H 2 SiO 3 , respectively. Corrosion has decreased the maximum magnetic entropy change of the compound.

(Mn,Fe) codoped ZnO nanowires were synthesized on silicon substrates in situ using a chemical vapor deposition method. The structure and property of the products were investigated by X-ray, electron microscopy, Raman, photoluminescence, and superconducting quantum interference device magnetometer. The doped nanowires are of pure wurtzite phase with single crystalline, and the elements distribute homogeneously in the doped nanowires. Photoluminescence spectrum of the doped nanowires is dominated by a deep-level emission with a negligible near-band-edge emission. The magnetic hysteresis curve with a coercive field of 35 Oe is clearly observed at 300 K, resulting from room-temperature ferromagnetic ordering in the (Mn,Fe) codoped ZnO nanowires, which has great potential applications for spintronics devices.

Strain sensors used in electronic skins, wearable devices for health monitoring, and implanted devices should have high sensitivity, flexibility, simplicity, and low cost. The fabrication of highly sensitive and flexible nanomaterial-based strain sensors generally requires self-assembly, transfer, and other complex processes. Thus, this study proposed a simple and efficient method for the production of a flexible strain sensor based on Au thin film, which was prepared only through common microfabrication technologies and could realize the mass production of highly sensitive and flexible strain sensors. A transitional Cr layer was fabricated for the improvement of the adhesion force between the Au and polyimide films. Additionally, the gauge factor of the sensor reached 220, and the sensor exhibited good repeatability during the multiple cycle tests. Moreover, the response time of sensor was approximately 300?ms. The high sensitivity was attributed to the combined action of microcrack formation and the size effect of the ultra-thin films, which were characterized through atomic force microscopy and scanning electron microscopy. Because of these excellent properties, this ultrasensitive and flexible strain sensor based on Au thin films has potential applications in electronic skins and wearable devices.

The magnetic properties and magnetocaloric effects (MCEs) in La 0.8 R 0.2 (Fe 0.919 Co 0.081 ) 11.7 Al 1.3 (R=Pr, Nd) compounds have been investigated. When Pr and Nd substitute for La, the Curie temperature of compounds decreases. The values of the MCEs are enhanced significantly by a partial substitution of Nd for La. Under the field change of 2 and 5 T, the maximum magnetic entropy changes for La 0.8 Nd 0.2 (Fe 0.919 Co 0.081 ) 11.7 Al 1.3 compound are −4.56 and −9.46 J/Kg K, respectively. It can be exploited for room temperature magnetic refrigeration material.

Vertically aligned carbon nanotube (CNT) arrays were synthesized on a silicon substrate via vaporization of ethylene (C2H4) using a hot-filament chemical vapor deposition (HF-CVD) method. The as-grown arrays were etched using a dual ion mill and the field emission properties of the CNTs before and after etching were studied. It was found that the structure of the emitter tips and the morphology of the CNT arrays influenced the field amplification factor ( β ) which is an important parameter for the field emission properties. SEM and TEM analyses indicated that the changes in the macroscopic morphology of the CNT array and structure of the CNT tips were responsible for the improvement in emission after 10 min etching.

The effects of different annealing conditions on the phase formation with NaZn13 structure were investigated in La(Fe1–xCox)11.9Si1.1 (x=0.068) compounds. It was found that the 1:13 phase was not formed directly from the melt upon cooling but via a peritectic reaction between the pro-peritectic γ-Fe and the La-rich phase. Annealing temperature was very important for the formation of 1:13 phase. Ice water was confirmed to be a preferable quenching medium. La(Fe1–xCox)11.9Si1.1 (x=0.068) compounds with almost single 1:13 phase were obtained at 1473 K after 15 d.

The effect of niobium on glass-formation ability and soft magnetic properties were studied in Fe-Gd-B glassy alloys. The glassy alloys exhibited high glass-formation ability when the element of Nb was added. Bulk glassy rod (Fe0.87Co0.13)68.5Gd3.5Nb3B25 with a diameter up to 3 mm was produced by copper mold casting. The size of the atom might play an important role in increasing glass-formation ability. The coercive force of glassy (Fe0.87Co0.13)71.5-xGd3.5NbxB25 (x=1.2, 1.5, 2, 2.5, 3, 4) alloys decreased after the addition of niobium element and was in the range of 1.5–2.9 A/m. The permeability spectrum of (Fe0.87Co0.13)70.3Gd3.5Nb1.5B25 glassy ribbon showed that the relaxation frequency (fo) was 6.1 MHz.

High-temperature AC magnetic properties for (Fe 0.5 Co 0.5 ) 73.5 Cu 1 Nb 3 Si 13.5 B 9 alloy annealed at various temperatures have been investigated using an impedance analyzer. Annealing temperature T a has obvious effects on high-temperature AC magnetic properties of the alloy. The Hopkinson peak appears only in the amorphous alloy when T a ≤ 703K. As T a increases above 733K, the real part of the complex initial permeability β i ' descends gradually, β i ' decreases more slowly with temperature in the high temperature range. The high-temperature (about 750K) AC initial permeability for the alloy annealed at T a =763K has been found to maintain a stable high value of 950 up to a frequency of ∼ 1 × 10 5 Hz. Partial substitution of Co for Fe in the Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 alloy leads to an increase of around 110K of the Curie temperature of the amorphous phase, much higher than Ge-containing Finemet alloy.

Magnetic entropy changes of Ni53.6Mn23.2Ga23.2 and M54.7Mn20.2Ga25.1 alloys on the heating and cooling processes were studied in this article. The magnetic entropy change (Delta S-H) is negative on the heating process. While the magnetic entropy change (Delta S-C) is positive on the cooling process. For Ni53.6Mn23.2Ga23.2, the difference between the peak values of Delta S-H and Delta S-C is small under the field change of 2 T. But for Ni54.7Mn20.2Ga25.1, the difference between the peak values of Delta S-H and Delta S-C is large under the field change of 2 T. (C) 2006 Elsevier B.V. All rights reserved.

This report focuses on ac magnetic properties of (Fe 0.5 Co 0.5 ) 73.5 Cu 1 Nb 3 Si 13.5 B 9 alloy in the high temperature. The effects of replacing 50% Fe by Co in Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 alloy on the static magnetic properties have also been studied. Addition of Co leads to an increase around 110 K of the Curie temperature of the amorphous phase, much higher than Ge-containing Finemet alloy. The material has much better ac magnetic properties than Hitperm alloy. An excellent stability of initial permeability in high temperature (up to 650 K) and high frequency (up to 5 × 10 5 Hz) can be observed with respect to the Co-free alloy.

Large-area ZnS nanowires were synthesized through a vapor phase deposition method. X-ray diffraction and electron microscopy results show that the products are composed of single crystalline ZnS nanowires with a cubic structure. The nanowires have sharp tips and are distributed uniformly on silicon substrates. The diameter of the bases is in the range of 320–530 nm and that of the tips is around 20–30 nm. The strong ultraviolet emission in the photoluminescence spectra also demonstrates that the ZnS nanowires are of high crystalline perfection. Field emission measurements reveal that the ZnS nanowires have a fairly low threshold field, which may be ascribed to their very sharp tips, rough surfaces and high crystal quality. The perfect field emission ability of the ZnS nanowires makes them a promising candidate for the fabrication of flexible cold cathodes.

This paper presents an important improvement for precise AC magnetic measurement under sinusoidal magnetic flux by using the digital feedback of harmonic compensation. Core loss-testing can be simply carried out with the sinusoidal magnetic flux even at a magnetic induction up to 1.87 T. The principle, circuit diagram, experimental results and its analysis are reported. Also it is found that the hysteresis loss per cycle P is smaller after correcting the magnetic flux waveform than before.

The effect of hydrogenation on the structures and magnetic properties of magnetic regenerators HoCu 2 (CeCu 2 -type), ErNi 2 (MgCu 2 -type) and ErNi (FeB-type) has been investigated. All these compounds can form crystalline hydrides which remain in the structure of the original compound. In the case of ErNi 2 , hydrogenation induces volume expansion up to 13% compared with the parent compound. The magnetic moment and the Curie temperature of the crystalline hydrides decreases as the hydrogen content increases. In the case of ErNi and HoCu 2 , there is a little change in the lattice parameters and magnetic properties of the crystalline hydrides compared with original compounds. Amorphous hydrides are also observed after the hydrogenation of ErNi 2 and HoCu 2 compounds.

The effects of temperature span of the first-order phase transition on the entropy change are investigated experimentally in NiMnGa alloys. The correlation between the transition temperature span from the ferromagnetic martensite to paramagnetic austenite and the magnetic entropy change is found. A wider transition temperature span leads to “table”-like Δ S peak and a narrow one leads to “λ”-like Δ S peak in NiMnGa alloys with the magnetic phase transition in the vicinity of the structural phase transition. The structure phase transition process also affects the relative cooling power.

The phase transition process and magnetic entropy change Δ S of Ni 54.5 FeMn 20 Ga 24.5 alloy were studied. Substitution of Fe for Ni increases the Curie temperature and decreases the temperature of martensitic phase transition. The transition from ferromagnetic martensitic to ferrormagnetic austenitic state leads to an abrupt increase of magnetization below 0.5 T and an abrupt decrease of magnetization above 0.5 T. The sign of Δ S changes from positive to negative with increasing the applied field from 0.5 to 2 T. The maximal value of the positive magnetic entropy change Δ S is about 3.1 J/kg K for the applied field from 0 to 0.5 T. The increase of applied field from 1.5 T results in a negative Δ S . The peak of negative Δ S is - 2.1 J / kg K for a field change of 2 T.

Microstructural and hardening changes of Fe-0.2wt.%V alloy and pure Fe irradiated with 100 keV hydrogen ions at room temperature were investigated. It was found that dislocation density varies dramatically after irradiation, ranging from dislocation free to dense areas with tangled and complex dislocation configuration. As the irradiated Fe-0.2wt.%V samples were annealed at 773 K, the irradiation-induced dislocation loops disappear, while many small precipitates with enriched C distribute in the matrix. Some large precipitates with enriched V were also observed. The hardness of Fe-0.2wt.%V alloy and pure Fe increases after irradiation, which ascribes to the formation of dislocation loops in the irradiated specimens. Compared with pure Fe, the size of the irradiation-introduced dislocation loops in Fe-0.2wt.%V alloy decreases and the density increases, the change of the hardness also decreases., {"references":["C. Dethloff, E. Gaganidze, V.V. Svetukhin, J. Aktaa, \"Modeling of\nhelium bubble nucleation and growth in neutron irradiated boron doped\nRAFM steels,\" J. Nucl. Mater., vol. 426, pp. 287-297, July 2012.","W.B. Liu, C. Zhang, Z.G. Yang, Z.X. Xia, G.H. Gao, Y.Q. Weng, \"Effect\nof surface nanocrystallization on microstructure and thermal stability of\nreduced activation steel,\" Acta Metallurgica Sinica, vol. 49, pp. 707-716,\nJun. 2013.","Z. Jiao, N. Ham, G.S. Was, \"Microstructure of helium-implanted and\nproton-irradiated T91 ferritic/martensitic steel,\" J. Nucl. Mater. vol. 367,\npp. 440-445, Aug. 2007.","I.I. Chernov, S.Y. Binyukov, B.A. Kalin, M. Win,T.Swe, S.V. Chubarov,\nA.N. Kalashnikov, A.G. Ioltukhovskiy, M.V. Leontyeva-Smirnova,\n\"Behavior of helium in steel 16Cr12W2VTaB under various implantation\ntemperatures,\" J. Nucl. Mater., vol. 367, pp. 468-472, Aug. 2007.","H. Ogiwara, A. Kohyama, H. Tanigawa, H. Sakasegawa, \"Helium effects\non mechanical properties and microstructure of high fluence\nion-irradiated RAFM steel,\" J. Nucl. Mater., vol. 367, pp. 428-433, Aug.\n2007.","C. Liu, H. Klein, P. Jung, \"Embrittlement of RAFM EUROFER97 by\nimplanted hydrogen,\" J. Nucl. Mater., vol. 335, pp. 77-82, Oct. 2004.","T. Hino, Y. Katada, Y. Yamauchi, M. Akiba, S. Suzuki, T. Ezato,\n\"Deuterium retention of ferritic steel irradiated by energetic hydrogen\nions,\" J. Nucl. Mater., vol. 386-388, pp. 736-739, Apr. 2009.","Y.N. Huang, F.R. Wan, X. Xiao, S. Shi, Y. Long, S. Ohnuki, N.\nHashimoto, \"The effect of isotope on the interaction between hydrogen\nand irradiation defect in pure iron,\" Fusion Eng. Des., Vol. 85, pp.\n2203-2206, Sept. 2010.","F. Zhao, F.R. Wan, \"Microstructure change of reduced activation\nFerritic/Martensitic steels after ion irradiation,\" J. Nanjing University, vol.\n45, pp. 258-263, Apr. 2009.\n[10] M. PapaRao, V.S. Sarma, S. Sankaran, \"Development of high strength\nand ductile ultra-fine grained dual phase steel with nano sized carbide\nprecipitates in a V-Nb microalloyed steel,\" Mater. Sci. Eng. A, vol. 568,\npp. 171-175, Jan. 2013.\n[11] M. Ando, H. Tanigawa, S. Jitsukawa, T. Sawai, Y. Katoh, A. Kohyama,\nK. Nakamura, H. Takeuchi, \"Evaluation of hardening behaviour of ion\nirradiated reduced activation ferritic/martensitic steels by an\nultra-micro-indentation technique,\" J. Nucl. Mater., Vol. 307-311, pp.\n260-265, Dec. 2002."]}

Under various amplitude of AC magnetic fields domain wall motion is the main mechanism in the magnetization process. This includes domain wall bulging and domain wall displacing. In this paper complex permeability-frequency spectra of (Fe 1− x Co x ) 73.5 Cu 1 Nb 3 Si 13.5 B 9 ( x = 0 , 0.5 ) nanocrystalline alloys were measured as a function of the AC magnetic field, ranging from 0.001 to 0.04 Oe. Obvious changes have been found in complex permeability spectra for alloy x = 0 with the change of the amplitude of AC magnetic field, but variation of AC magnetic field has little effect on complex permeability spectra for alloy x = 0.5 . This is attributed to the increased pinning field after substitution of Fe with Co in Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 nanaocrystalline alloy.

Single-crystalline nanostructured Zn1−xMnxS, a diluted magnetic semiconductor, was achieved via a simple vapour phase deposition on silicon substrates. Morphology, structure, and composition of the nanostructured Zn1−xMnxS were studied by using x-ray diffraction, transmission electron microscopy, and energy-dispersive spectroscopy. The nanostructured Zn1−xMnxS is composed of nanowires and nanobelts, which are quite flexible and free of defects. Both of them have smooth and straight surfaces with lengths over 10 µm. They possess cubic structure with a principal axis along their axes. The nanostructured Zn1−xMnxS exhibits paramagnetic behaviour. Photoluminescence study shows a blue band and a yellow band, which are due to the surface states and the transitions of Mn2+ (4T1(G)–6A1(S)), respectively. The growth of the nanostructured Zn1−xMnxS could be explained by a self-catalyst growth mechanism.

An oxide diluted magnetic semiconductor, windmill Zn 1− x Co x O ( x = 0.0 5 ) was successfully synthesized by using a vapor phase deposition method. X-ray diffraction and electron microscopy studies demonstrate that the windmill Zn 1− x Co x O structures are of single crystal exhibiting a wurtzite phase. The structures show ferromagnetic behavior below a Curie temperature of ∼50 K. Photoluminescence spectra of the structures show near-band-edge emission of ZnO is not obviously affected by the doping of cobalt. Their absorption spectra indicate the transparence of the Zn 1− x Co x O structures in the visible region. These results suggest that the Zn 1− x Co x O structures have great potential applications in transparent spintronics and magnetic-optical devices.

Single crystals of diluted magnetic semiconductor Cd1−xMnxIn2Te4 with x = 0.1 , 0.22 and 0.4 were grown by the Bridgman method. Several regions composed of α + β 1 , α + β + β 1 , β and In2Te3+Te phases were found to crystallize in orders due to the solute partition at the growth interface. The magnetic susceptibility and Kerr effect of β -phase crystals with different compositions cut from the ingot were measured. The results revealed the anti-ferromagnetic interactions between Mn2+ ions in the crystal. Meanwhile, the negative rotation angles for x = 0.1 and 0.22 and positive with small values for x = 0.4 were detected.