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The vacancies are found generally more stable than the interstitials. Some point defects may deteriorate the ability to resist external compression and reduce the phonon thermal conductivity.

Se dopants improved the Li+ ionic conductivity of Li6PS5−xSexCl and Li5.5PS4.5−xSexCl1.5 significantly, and Se-doped SSEs showed better interfacial stability with LiCoO2 than sulfides-type SSEs.

The structural, mechanical, thermal, and electronic properties of a series of Gd-site and Zr-site substituted Gd2Zr2O7 pyrochlores have been investigated by first-principles calculations. Substitution of Gd3+ with smaller and heavier Yb3+ introduces strong phonon scattering effects and results in Gd1.5Yb0.5Zr2O7 exhibiting the lowest thermal conductivity. Substitution of Gd3+ with larger and lighter La3+ does not give as much reduction in the thermal conductivity as in Yb3+-doped Gd2Zr2O7. As for Ti4+, Hf4+ and Ce4+ substitution for Zr4+-site in Gd2Zr2O7, slight changes in thermo-physical properties are observed for Gd2Zr2-yTiyO7 and Gd2Zr2-yHfyO7 pyrochlores, while the substitution of Ce4+ for Zr4+ site results in significantly smaller Young's modulus, better ductility, smaller Debye temperature, and lower thermal conductivity. With the increasing Ce content, the Young's modulus subsequently decreases by 22.2–59.9 GPa. The thermal conductivity of Gd2Zr2O7 is significantly reduced by 21% with complete Ce doping at the Zr-site based on the Clarke's model. This is mainly caused by the fact that larger guest ions incorporation weakens the bonds and enhances the phonon scattering in the host oxides and thus effectively lowers the thermal conductivity. Considering the improved thermo-physical properties, the Gd2Zr2-yCeyO7 may be a more promising candidate of the next-generation topcoat materials for thermal barrier coatings than the pure Gd2Zr2O7. This study provides a theoretical perspective to design and select good thermally insulating materials at high temperatures.

The effects of stacking periodicity on the electronic and optical properties of GaAs/AlAs superlattice have been explored by density functional theory calculations. Among the (GaAs)m/(AlAs)m, (GaAs)1/(AlAs)m and (GaAs)m/(AlAs)1 (m = 1 to 5) superlattices, the band gaps of (GaAs)m/(AlAs)1 superlattices decrease significantly as the layer of GaAs increases, and the cut-off wavelengths are found to locate in the near infrared region. For (GaAs)m/(AlAs)1 SLs, the conduction bands shift toward Fermi level, resulting in the smaller band gap, while conduction bands of (GaAs)1/(AlAs)n SLs slightly shift to higher energy, which lead to comparable band gaps. The layer number of GaAs shows negligible effects on the reflectivity spectra of superlattice structures, while the absorption coefficient shows a red-shift with the increasing layer of GaAs, which is beneficial for the application of GaAs/AlAs superlattice in the field of near infrared detector. These results demonstrate that controlling the number of GaAs layers is a good method to engineer the optoelectronic properties of GaAs/AlAs superlattice.

Oxygen ions (O+) were implanted into fused silica at a fixed fluence of 1 × 1017 ions/cm2 with different ion energies ranging from 10 keV to 60 keV. The surface roughness, optical properties, mechanical properties and laser damage performance of fused silica were investigated to understand the effect of oxygen ion implantation on laser damage resistance of fused silica. The ion implantation accompanied with sputtering effect can passivate the sub-/surface defects to reduce the surface roughness and improve the surface quality slightly. The implanted oxygen ions can combine with the structural defects (ODCs and E′ centers) to reduce the defect densities and compensate the loss of oxygen in fused silica surface under laser irradiation. Furthermore, oxygen ion implantation can reduce the Si–O–Si bond angle and densify the surface structure, thus introducing compressive stress in the surface to strengthen the surface of fused silica. Therefore, the laser induced damage threshold of fused silica increases and the damage growth coefficient decreases when ion energy up to 30 keV. However, at higher ion energy, the sputtering effect is weakened and implantation becomes dominant, which leads to the surface roughness increase slightly. In addition, excessive energy aggravates the breaking of Si–O bonds. At the same time, the density of structural defects increases and the compressive stress decreases. These will degrade the laser laser-damage resistance of fused silica. The results indicate that oxygen ion implantation with appropriate ion energy is helpful to improve the damage resistance capability of fused silica components.

When the GaAs/AlGaAs superlattice-based devices are used under irradiation environments, point defects may be created and ultimately deteriorate their electronic and transport properties. Thus, understanding the properties of point defects like vacancies and interstitials is essential for the successful application of semiconductor materials. In the present study, first-principles calculations are carried out to explore the stability of point defects in GaAs/Al0.5Ga0.5As superlattice and their effects on electronic properties. The results show that the interstitial defects and Frenkel pair defects are relatively difficult to form, while the antisite defects are favorably created generally. Besides, the existence of point defects generally modifies the electronic structure of GaAs/Al0.5Ga0.5As superlattice significantly, and most of the defective SL structures possess metallic characteristics. Considering the stability of point defects and carrier mobility of defective states, we propose an effective strategy that AlAs, GaAs, and AlGa antisite defects are introduced to improve the hole or electron mobility of GaAs/Al0.5Ga0.5As superlattice. The obtained results will contribute to the understanding of the radiation damage effects of the GaAs/AlGaAs superlattice, and provide a guidance for designing highly stable and durable semiconductor superlattice-based electronics and optoelectronics for extreme environment applications.

Doping of cations in A2B2O7-type pyrochlores, either on A or B site, can modify the physical properties of compounds significantly. In this work, the structural, thermo-mechanical and electronic properties of Nd-doped Gd2Zr2O7 pyrochlores (Gd2−yNdyZr2O7 and Gd2Zr2−yNdyO7) have been investigated by density functional theory calculations. It is found that the Nd incorporation into Gd-site leads to the formation of Gd2Zr2O7-Nd2Zr2O7 solid solutions, which remain the pyrochlore-type structures, whereas the introduction of Nd into Zr-site induces a pyrochlore-to-defect fluorite structural transition. Further calculations show that Nd substitution for Gd-site has a minor effect on the thermal–mechanical and electronic properties of Gd2Zr2O7. However, incorporation of Nd into Zr-site results in smaller Young’s modulus, better ductility, stronger elastic anisotropy and lower Debye temperature than pure Gd2Zr2O7. In addition, the incorporation of Nd into Zr-site results in an increasing number of electrons locating at the Fermi level with the increasing concentration of substitutional Nd atoms, which eventually leads to an insulating-to-metallic transition. This study suggests that incorporation of Nd into Zr-site can be an alternative way to tune the mechanical, electronic, and thermal properties of Gd2Zr2O7.

MXenes is a new group of two-dimensional materials via etching of the ‘A’ element from MAX phases. Depending on the functional group, MXenes can be semiconductors or metals. In this paper, first-principles calculations have been performed to investigate the effects of single vacancy defects on a semiconducting MXene, Sc2CF2 monolayer. The theoretical results show that V-Sc can induce magnetism in the host monolayer, while V-C and V-F result in n-type conductivity. For V-Sc doped Sc2CF2, tensile strains enhance the total magnetic moment which remains constant with applied compressive strains. As a result, by manipulating the fabrication parameters, the magnetic and conductive properties of Sc2CF2 can be tuned without the need of chemical doping.

As a promising visible-light-driven photocatalyst for hydrogen generation, InNbO4 of high efficiency dictates the requirements on the high specific surface area and tailored band structure that arouse increasing efforts but remain challenge. Herein, we report fabrication of nanosized InNbO4 embedded with nano-voids via apolyacrylamide sol-gel route. It exhibits excellent photocatalytic H2 evolution rates up to ∼68.1 μmol·h−1·g−1, much better than as-reported counterparts (∼1 μmol·h−1·g−1) obtained via solid-state reaction or doping treatments. The particle sizes, density of nano-voids, as well as the bandgap energy are modulated by using different chelating agents, including tartaric acid (TA), citric acid (CA), acetic acid (AA). Based on high resolution high angle annular dark-field (HAADF) characterizations, it interesting to discover that the photocatalytic performance shows obvious dependence on the voids size. Nano-voids (2–8 nm) can maximize the specific surface and thus enhance the photocatalytic performance, while lattice-scale voids (

GaAs has been demonstrated to be a promising material for manufacturing semiconductor light-emitting devices and integrated circuits. It has been widely used in the field of aerospace, due to its high electron mobility and wide band gap. In this study, the structural and photoelectric characteristics of Si-doped GaAs under different gamma irradiation doses (0, 0.1, 1 and 10 KGy) are investigated. Surface morphology studies show roughen of the surface with irradiation. Appearance of transverse-optical (TO) phonon mode and blueshift of TO peak reflect the presence of internal strain with irradiation. The average strain has been measured to be 0.009 by Raman spectroscopy, indicating that the irradiated zone still has a good crystallinity even at a dose of 10 KGy. Photoluminescence intensity is increased by about 60% under 10 KGy gamma irradiation due to the strain suppression of nonradiative recombination centers. Furthermore, the current of Si-doped GaAs is reduced at 3V bias with the increasing gamma dose. This study demonstrates that the Si-doped GaAs has good radiation resistance under gamma irradiation, and appropriate level of gamma irradiation can be used to enhance the luminescence property of Si-doped GaAs.

Cadmium selenide (CdSe) nanocrystals are important photoelectric materials. Doping heterovalent impurities such as silver (Ag) in CdSe nanocrystal quantum dots (QDs) can provide additional charge carriers, which can significantly enhance the performance of CdSe QDs for their potential applications in high-efficiency photovoltaic devices. Using density functional theory (DFT) based calculations with the Heyd-Scuseria-Ernzerhof (HSE06) screened hybrid functional, we demonstrate that Ag doping can affect the structural, electronic and optical properties of CdSe QDs significantly. The location and number of Ag dopant atoms are critical factors for modifying the electronic structure, in particular the change of energy position and shape of the valence and conduction band edges. It is found that doping of Ag atoms into the core region of a CdSe nanoparticle induces metallic-like electronic characteristics with a dense number of electrons emerging at the Fermi level. However, incorporation of Ag dopant into the surface of a CdSe quantum dot introduces some mid-gap states that mainly consist of Se 4p states, and results in a new sub-bandgap electronic transition from mid-gap states to the conduction band. The calculated absorption spectra indicate that doping of just one or two Ag atoms greatly strengthens the absorption in the ultraviolet-visible regime and extends the absorption edges of CdSe QDs into the infrared regime. In particular, the spectra show a high-intensity absorption band between 424 and 600 nm with just 1 Ag atom incorporated into the CdSe QDs. Based on the improved absorption spectra, the present results provide a science-based strategy for designing Ag-doped CdSe QDs with enhanced visible light absorption for their application in high-efficiency photovoltaic devices.

A systematic density functional theory study is performed to investigate the mechanical stability, elastic moduli, Debye temperature, thermal conductivity and electronic structures of Gd 2- y Th y Zr 2 O 7 and Gd 2 Zr 2- y Th y O 7 . All the Th-doped Gd 2 Zr 2 O 7 compositions are found to be structurally and mechanically stable. As compared with the pure Gd 2 Zr 2 O 7 , Th incorporation into both Gd-site and Zr-site results in generally better ductility, lower Debye temperature, and reduced thermal conductivity. The reduction in thermal conductivity can be as high as 25–32%, depending on the content of the Th substituent. Our calculations suggest that Th-doped Gd 2 Zr 2 O 7 , especially Gd 2 Zr 2- y Th y O 7 , exhibits better mechanical and thermal properties that are beneficial to its application as thermal barrier coating material at high temperatures than the pure state.

(Mg, Ca, Ba)-ferrite magnetic nanoparticles were successfully synthesized through modifying the atomic ratio of polysaccharide and chelating agent at an optimal sintering temperature. In the process, the polysaccharide plays an important role in drastically shrinking the precursor during the gel drying process. In the metal-complex structure, M 2+ ion active sites were coordinated by −OH of the water molecules except for EDTA anions. The MFe 2 O 4 magnetic nanoparticles exhibited enhanced magnetic properties when compared with nano-MFe 2 O 4 of similar particle size synthesized by other synthesis route reported in the literature. In particular, the sintering temperature improves the crystallinity and increases the hysteresis loop squareness ratio of (Mg, Ca, Ba)-ferrite nanoparticles significantly.

Highly dispersed ferrite magnetic nanoparticles (MFe2O4, where M=Mg, Ca, Ba) were synthesized through a modified polyacrylamide gel route based on the use of carbon particles. By manipulating the sintering temperature and carbon concentration, the formation of (Mg, Ca, Ba)-ferrite phase can be suppressed to produce the intermediate phases of MCO3 (M=Mg, Ca, Ba) and Fe2O3. The novel MFe2O4 magnetic nanoparticles exhibited high crystallinity and hysteresis loop squareness ratio. Furthermore, the MFe2O4 magnetic nanoparticles exhibited improved surface morphology when compared with nano-MFe2O4 of similar particle size synthesized by the polyacrylamide gel route reported in the literature. Morphology and magnetic properties of MFe2O4 magnetic nanoparticles change also appears to be strongly dependent on the divalent metal M. These results bring up new ideas for the design of highly dispersed ferrite magnetic nanoparticles with tuned magnetic properties through a versatile polyacrylamide gel route.

3Ag2 and AuAg). The results show that the migration mechanisms of He atoms mainly depend on the crystal structures of alloys, and their migration energy barriers are aected by the migration paths in Au‐Ag alloys. He interstitials preferentially occupied the most stable sites, but it is dicult for He interstitials to migrate to nearest most stable sites via second stable positions at room temperature. When He atom is at the tetrahedral position which has higher formation energy, it possibly migrates to nearest tetrahedral positions directly for AuAg alloy. In addition, comparing the migration of He defects in the two alloys, we found that the properties of migration energy and relative stability of He atoms probably slightly depend on the mass‐density of Au‐Ag alloys.

In this study, an ab initio molecular dynamics method is employed to compare the responses of SiC, TiC and ZrC to low energy irradiation. It reveals that C displacements are dominant in the cascade events of the three carbides. The associated defects in SiC are mainly Frenkel pairs and antisite defects, whereas damage end states in TiC and ZrC generally consist of Frenkel pairs and very few antisite defects are created. It is proposed that the susceptibility to antisite formation in SiC contributes to its crystalline-to-amorphous transformation under irradiation that is observed experimentally. The stronger radiation tolerance of TiC and ZrC than SiC can be originated from their different electronic structures, i.e., the and bonds are a mixture of covalent, metallic, and ionic character, whereas the bond is mainly covalent. The presented results provide underlying mechanisms for defect generation in SiC, TiC and ZrC, and advance the fundamental understanding of the radiation resistances of carbide materials.

In this paper we report a simple method to fabricate a novel subwavelength structure surface on fused silica substrate using one-step reactive ion etching with two-dimensional polystyrene colloidal crystals as masks. The etching process and the morphologies of the obtained structure are controlled. We show that the period of the obtained fused silica pillar-like arrays were determined by the initial polystyrene nanoparticle size. The height of pillar arrays can be adjusted by controlling the etching duration, which is proved to be of importance in tailoring the antireflection properties of subwavelength structures surface. The novel subwavelength structures surface exhibit excellent broadband antireflection properties, but the size of the pillar affects the antireflective properties in short wavelength region. We anticipate this method would offer a convenient and scalable way for inexpensive and high-efficiency high power laser field designs.

The nucleation and growth of helium (He) clusters in bcc iron (Fe) are simulated using molecular dynamics method. The self-interstitial atoms (SIAs) can be emitted from the He clusters, and the evolution of these SIAs depends on the spatial distribution of He clusters. A 1/2 interstitial loop is presented from the emitted SIAs for the two He clusters separated far away from each other, but a interstitial loop is formed at special conditions. A new mechanism for the formation and growth of a interstitial loop in bcc Fe due to He clustering is proposed.

The hydrogenation and dehydrogenation behaviors of a zirconium alloy were in-situ studied by scanning electron microscopy and transmission electron microscopy. The zirconium alloy can absorb hydrogen to form Zr hydride which is enhanced by the relaxation of inner stress in the alloy. The hydrogen is generated from an ion/electron beam stimulated decomposition of an organometallic precursor, trimethyl (methylcyclopentadienyl) platinum (IV), in a scanning electron microscope and focused ion beam system. The formed δ -type zirconium hydride that has a face centered cubic structure was observed to grow as preferentially oriented platelets in the zirconium alloy matrix. The platelets have a common crystallographic relationship of [010] α //[1-10] δ , (001) α //(111) δ . The dehydrogenation of the zirconium hydride was in-situ investigated in a transmission electron microscope by heating the materials. It was found that the δ -ZrH 1.5–1.66 hydride transformed into ζ -ZrH 0.25 at 450 °C even at a longer heating time. The experiment demonstrates a new way for in-situ study of hydrogenation behaviors of other hydrogen storage alloys.

The solubility of Pu in Gd2Zr2O7 has been investigated by the density functional theory plus Hubbard U correction. It is found that the formation of PuGdZr2O7, Gd2PuZrO7 and Gd2Pu1.5Zr0.5O7 are exothermic, whereas Pu0.5Gd1.5Zr2O7, Pu1.5Gd0.5Zr2O7 and Gd2Pu0.5Zr1.5O7 are energetically less stable than their respective separated states. The calculations show that both the Gd and Zr lattice sites can be substituted by the Pu, which is consistent with the immobilization behavior of uranium in Gd2Zr2O7 observed experimentally. The site preference of Pu in Gd2Zr2O7 is found to be dependent on the chemical environment, i.e., Pu prefers to substitute for Gd-site under Gd-rich and O2-rich conditions and for Zr-site under Zr-rich and O2-rich conditions.

The electronic and magnetic properties of C-doped α-Al2O3 have been investigated using density functional theory calculations. It is found that magnetism can be induced by doping C at Al and O sites, in which the spin densities are mainly located on the C dopant. Doping C at the Al-site leads to band gap narrowing and greatly modifies the upper valance band, while doping C at the O-site affects the band edges of α-Al2O3 slightly. Based on the dipole selection rules, we have also assigned the sub-band electron transitions in both α-Al2O3:CAl and α-Al2O3:CO.

Density functional theory calculations have been carried out to study Pu accommodation in La 2 Zr 2 O 7 . Our calculations show that Pu can be incorporated into both the La and Zr lattice sites in La 2 Zr 2 O 7 , which agrees well with the recent experimental observations. As Pu substitutes for the Zr-site, the interaction is stronger than that in La 2- y Pu y Zr 2 O 7 and the mechanical properties are influenced significantly. Also, it is found that order-disorder transition occurs more easily in Pu-containing La 2 Zr 2 O 7 than the pure zirconate, suggesting that the radiation tolerance of La 2 Zr 2 O 7 can be enhanced by Pu incorporation.

In this study, an ab initio molecular dynamics method is employed to study low energy recoil events in zirconate pyrochlores (A 2 Zr 2 O 7 , A = La, Nd and Sm). It shows that both cations and anions in Nd 2 Zr 2 O 7 and Sm 2 Zr 2 O 7 are generally more likely to be displaced than those in La 2 Zr 2 O 7 . The damage end states mainly consist of Frenkel pair defects, and the Frenkel pair formation energies in Nd 2 Zr 2 O 7 and Sm 2 Zr 2 O 7 are lower than those in La 2 Zr 2 O 7 . These results suggest that the order–disorder structural transition more easily occurs in Nd 2 Zr 2 O 7 and Sm 2 Zr 2 O 7 resulting in a defect-fluorite structure, which agrees well with experimental observations. Our calculations indicate that oxygen migration from 48f and 8b to 8a sites is dominant under low energy irradiation. A number of new defects, including four types of cation Frenkel pairs and six types of anion Frenkel pairs, are revealed by ab initio molecular dynamics simulations. The present results may help to advance the fundamental understanding of the irradiation response behavior of zirconate pyrochlores.

In this study, the low energy radiation responses of AlAs, GaAs and GaAs/AlAs superlattice are simulated and the radiation damage effects on their electronic structures are investigated. It is found that the threshold displacement energies for AlAs are generally larger than those for GaAs, i.e., the atoms in AlAs are more difficult to be displaced than those in GaAs under radiation environment. As for GaAs/AlAs superlattice, the Ga and Al atoms are more susceptible to the radiation than those in the bulk AlAs and GaAs, whereas the As atoms need comparable or much larger energies to be displaced than those in the bulk states. The created defects are generally Frenkel pairs, and a few antisite defects are also created in the superlattice structure. The created defects are found to have profound effects on the electronic properties of GaAs/AlAs superlattice, in which charge transfer, redistribution and even accumulation take place, and band gap narrowing and even metallicity are induced in some cases. This study shows that it is necessary to enhance the radiation tolerance of GaAs/AlAs superlattice to improve their performance under irradiation.

ZrC and TiC have been proposed to be alternatives to SiC as fuel-cladding and structural materials in nuclear reactors due to their strong radiation tolerance and high thermal conductivity at high temperatures. To unravel how the presence of defects affects the thermo-physical properties under irradiation, first-principles calculations based on density function theory were carried out to investigate the mechanical and thermal properties of defective ZrC, TiC and SiC. As compared with the defective SiC, the ZrC and TiC always exhibit larger bulk modulus, smaller changes in the Young’s and shear moduli, as well as better ductility. The total thermal conductivity of ZrC and TiC are much larger than that of SiC, implying that under radiation environment the ZrC and TiC will exhibit superior heat conduction ability than the SiC. One disadvantage for ZrC and TiC is that their Debye temperatures are generally lower than that of SiC. These results suggest that further improving the Debye temperature of ZrC and TiC will be more beneficial for their applications as fuel-cladding and structural materials in nuclear reactors.

In this study, a density functional theory method is employed to investigate the effects of isovalent and aliovalent substitution of Sm3+ on the phase stability, thermo-physical properties and electronic structure of Gd2Zr2O7. It is shown that the isovalent substitution of Sm3+ for Gd3+ results in the formation of Gd2Zr2O7-Sm2Zr2O7 solid solution, which retains the pyrochlore structure and has slight effects on the elastic moduli, ductility, Debye temperature and band gap of Gd2Zr2O7. As for the aliovalent substitution of Sm3+ for Zr4+ site, a pyrochlore-to-defect fluorite structural transition is induced, and the mechanical, thermal properties and electronic structures are influenced significantly. As compared with the Gd2Zr2O7, the resulted Gd2SmyZr2-yO7 compositions have much smaller elastic moduli, better ductility and smaller Debye temperature. Especially, an amount of electrons distribute on the fermi level and they are expected to have larger thermal conductivity than Gd2Zr2O7. This study suggests an alternative way to engineer the thermo-physical properties of Gd2Zr2O7 and will be beneficial for its applications under stress and high temperature.

In this study, an ab initio molecular dynamics method is employed to investigate the response behavior of α-Al2O3 to low energy irradiation. Different from the previous experiments, our calculations reveal that the displacements of oxygen dominate under electron irradiation and the created defects are mainly oxygen vacancy and interstitial. The experimental observation of the absorption peaks appearing at 203, 233 and 256 nm for α-Al2O3 under electron irradiations should be contributed by the oxygen defects and these defects will reduce the transmittance of α-Al2O3, which agrees well with the very recent experiment. This study demonstrates the necessity to reinvestigate the threshold displacement energies of α-Al2O3, and to introduce recombination center for oxygen defects to improve its optical properties and performance under radiation environment.

The behavior of the Zr(Fe,Cr,Nb)2 precipitate in a China-brand Zr–Sn–Nb–Fe–Cr alloy under a 500 keV Ne ion beam irradiation and post heating were studied by in-situ transmission electron microscopy (TEM). It is found that the Zr(Fe,Cr,Nb)2 precipitate with the hexagonal close packed (hcp) structure is the major secondary phase particle (SPP) in this zirconium alloy. At the temperature of 310 °C, the precipitate starts to be amorphized after having been irradiated to 0.5 displacement per atom (dpa). The critical irradiation dose for the precipitate to be completely amorphized is 1.0 dpa. The amorphized Zr(Fe,Cr,Nb)2 precipitate starts to be recrystallized when it was heated up to 600 °C. The temperature for the recrystallization of the amorphized Zr(Fe,Cr,Nb)2 precipitate is determined to be between 450 °C and 600 °C. Instead of forming large single grain crystals, some nanocrystals that have the same crystal structure to that of the precipitate before being amorphized were formed during the recrystallization.

Efficient nebulization of liquid sessile droplets (water and water/glycerol mixtures) was investigated using standing waves generated using ZnO/Si surface acoustic wave (SAW) devices under different RF powers, frequencies and liquid viscosity (varied glycol concentrations in water). At such high RF powers, there are strong competitions between vertical jetting and nebulization. At lower SAW frequencies of 12.3 and 23.37 MHz, significant capillary waves and large satellite droplets were generated before nebulization could be observed. At frequencies between 23.37 and 37.2 MHz, spreading, displacement or occasionally jetting of the parent sessile droplet was frequently observed before a significant nebulization occurred. When the SAW frequencies were increased from 44.44 to 63.3 MHz, the minimum RF power to initiate droplet nebulization was found to increase significantly, and jetting of the parent droplet before nebulization became significant, although the average size of the nebulized particles and ejected satellite droplets appeared to decrease with an increase in frequency. With the increase of glycerol concentration in the test sessile droplets (or increase in liquid viscosity), nebulization became difficult due to the increased SAW damping rate inside the liquid. Acoustic heating effects were characterized to be insignificant and did not show apparent contributions to the nebulization process due to silicon substrate’s natural effect as an effective heat sink and the employment of a metallic holder beneath the ZnO/Si SAW device substrates.

We investigate the geometry and electronic structures of α-Al2O3:VO + AlX systems based on first-principles calculations where VO represents one oxygen vacancy and AlX stands for IIIA atoms (B, Ga, In, and Tl) substituting of one Al atom. It is found that all the aluminates maintain the hexagonal symmetry as the pure α-Al2O3 structure and the lattice parameters a, b, and c are expanded with the increase of the IIIA atoms radius. The electronic property analysis indicates that the band gaps are considerably reduced and the reductions are also related to the radius of doping atoms. But unlike the situation of transition metal doped α-Al2O3 the decreases of the band gap are not due to the spreading of d states, but are mainly owing to the ns states at the bottom of the conduction band.

In this paper, LaMnO3/α-Al2O3magnetic nanocomposites were synthesized through using a soft-chemistry route. The synthesis strategy in this work is based on a soft-chemistry process using a polyacrylamide gel route in which citric acid is employed as the chelating agent. The composites were characterized by thermogravimetric and differential scanning calorimetry analyses, X-ray diffraction, scanning electron microscope, energy dispersive x-ray spectroscopy and vibrating sample magnetometer. Scanning electron microscope observation reveals that the content of α-alumina decreases with the increase of number of sample surface particle in the composites. Magnetic hysteresis loop measurement shows that the LaMnO3sample exhibit paramagnetism at room temperature. Interestingly, the weak ferromagnetism at room temperature was observed for a composition of 0.7 α-Al2O3/ 0.3 LaMnO3. The forming mechanisms and magnetic properties of α-Al2O3/ LaMnO3composites have been discussed based on the experimental results.

The γ-Al2O3 and C-doped γ-Al2O3 powders have been synthesized by a modified polyacrylamide gel method. XRD, SEM and luminescence characterization have been used to study the prepared samples. The results indicate that the particle size and morphology of the samples depend on the choice of chelating agent. In comparison with pure γ-Al2O3 sample, the intensity of emission peak at 420 nm of C-doped γ-Al2O3 powders has been obviously enhanced, which is expected to widen the potential applications of C-doped γ-Al2O3 composite powders. The photoluminescence spectrum detected at λex= 386 nm shows a new peak located at 440 nm due to oxygen vancancies distributed on the surface of the composite. Interestingly, the intensity of the emission peak located at 440 nm (C-doped γ-Al2O3) increases with the decrease of crystallite size.