Radiation effect on optical,morphological and magnetic properties of aluminum-substituted M phase barium hexaferrite

The effect of gamma irradiation on the features of aluminum-substituted barium hexagonal ferrite particles BaAl_xFe_12?xO₁₉ with 0?≤?x?≤?3.5 has been studied. Optical absorption measurements have been performed and the results reflected a great dependence of the fundamental absorption edge on the radiation dose. It is found that the calculated optical band gap (E_g) increases due to an increase in the homogeneity with an increase in the Al content. Increasing the radiation dose up to 1?MGy induces a direct transition and consequently decreases the energy gap. This behavior is associated with the generation of excess electronic localized states. Moreover, the characteristic features of the irradiated samples have been studied using a scanning electron microscope. Also, all samples were characterized using the X-ray diffraction technique, and the values of crystal size, microstrain and dislocation density were calculated. On the other hand, the magnetic behavior of the samples was studied using a vibrating sample magnetometer technique after each radiation dose. The saturation magnetization (M_s) and the magneton number (n_B) decrease with an increase in the Al³⁺ substitution and at the same time decrease with the radiation dose 250?kGy to 1?MGy.     

Modifications induced by gamma irradiation upon structural,optical and chemical properties of polyamide nylon-6,6 polymer

The effects of gamma rays were studied on the optical, structural and chemical properties of the PA-66 polymer samples. The polymer samples obtained from Goodfellow (Cambridge, UK) were irradiated with gamma rays at various doses ranging from 100 to 1250 kGy. The pristine and gamma rays irradiated samples were characterized by UV–visible (UV–VIS) spectroscopy, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. UV–VIS shows a shift in absorption toward the visible region for irradiated samples and a decrease in band gap energy (E_g). The XRD analyses show an increase in the crystalline nature of the polymer at higher doses as a result of significant decrease in the peak width of XRD patterns. The FTIR spectra show decrease in intensity and shift of various bands with increase in gamma dose.     

Influence of 60Co gamma irradiation on the structural and optical properties of 2-aminopyridinium 4-nitrophenolate 4-nitrophenol crystals

In this article, effect of gamma irradiation on the structural and optical properties of 2-aminopyridinium 4-nitrophenolate 4-nitrophenol (2AP4N) has been reported. The grown crystals of 2AP4N were exposed to ⁶⁰Co gamma rays with a dose of 50 kGy and 100 kGy. The radiation-induced effects were analyzed using X-ray diffraction, FT-IR, UV–visible, photoluminescence techniques. The refractive index was determined using a long arm spectrometer. The structural properties of the pristine and irradiated crystals were studied using powder XRD. The peak intensity decrease after irradiation may be attributed to the formation of point defects. The UV visible study reveals that the energy gap has decreased after irradiation and then has increased for the higher dose. The intensity variation in the PL spectra is due to colour center mechanism. The SHG efficiency of 2AP4N crystals was found to be unaffected by gamma irradiation.     

Effects of temperature-induced stress on the structural,electrical, and optical properties of ZnO:Ga thin films grown on Si substrates

Crystalline ZnO:Ga thin films with highly preferential c-axis oriented crystals were prepared on Si(001) substrates at different temperatures using the reactive magnetron sputtering technique. Effects of temperature-induced stress in ZnO:Ga films were investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), electrical transport, and spectroscopic ellipsometry measurements. XRD results showed that the films were highly c-axis (out-of-plane) oriented and crystallinity improved with growth temperature. The residual compressive stress in films grown at low temperature relaxes with substrate temperature and becomes tensile stress with further increases in growth temperature. Resistivity of the films decreases with increasing stress, while the carrier concentration and mobility increase as the stress increases. The mechanism of the stress-dependent bandgap of ZnO:Ga films grown at different temperatures is suggested in the present work.     

Overpotential deposition of Ag monolayer and bilayer on Au(1 1 1) mediated by Pb adlayer underpotential deposition/stripping cycles

Ultra-thin Ag films on the Au(1 1 1) surface were prepared via overpotential deposition (OPD) in the presence of Pb²⁺ ions. By carrying out repetitive Pb adlayer underpotential deposition (UPD) and stripping cycles during Ag bulk deposition, the two-dimensional growth of Ag films was significantly enhanced in high OPD. The Ag monolayer sample was made by comparing the voltammetry curves, in which the signatures for Pb adlayer UPD on Au(1 1 1) changed to that on Ag(1 1 1). As demonstrated by the X-ray specular reflectivity measurements, nearly complete monolayer and bilayer films can be made with optimized deposition procedures. On subatomic scale, however, we found that these films have significant higher root-mean-square displacement amplitudes than those underpotentially deposited Ag monolayer and bilayer on either Au(1 1 1) or Pt(1 1 1).     

Zn1—xMnx／ZnSe应变超晶格分子束外延生长及光学特性研究

用分子束外延方法在ＧａＡｓ（１００）衬底上成功生长了高质量的Ｚｎ１－ｘＭｎｘＳｅ／ＺｎＳｅ（ｘ＝０．１６），超晶格结构，用Ｘ射线衍射和低温光致发光（ＰＬ）对其结构，应变分布以及光学性能进行了研究，结果表明，２Ｋ温度下，Ｚｎ１－ｘＭｎｘＳｅ／ＺｎＳｅ超晶格的光致发光中主发光峰对应于ＺｎＳｅ阱中基态电子和基态轻空穴之间的自由激子跃迁，而且其峰位相对于ＺｎＳｅ薄膜材料的自由激子峰有明显移动。其中，当超晶     

The effect of Fe doping on structural and magnetic properties of nanocrystallite Co2Cr1-xFexAl Heusler alloys prepared by mechanical alloying

Mechanical alloying has been used to produce nanocrystallite Co2Cr1-xFexAl(x=0,0.4,0.6,1) Heusler alloys.The formation of the L21 phase of Co2Cr1-xFexAl by the mechanical alloying method was investigated.The effect of Fe doping on the structural and magnetic properties of the samples was also studied.The results were compared with the Slater Pauling prediction.A comparison between these samples and those prepared by the arc-melting method in the literature was made.An increase of the coercivity H c with the increasing Fe doping level was observed.This phenomenon was explained by the increases of lattice strain and magnetic anisotropy with the increasing Fe content.     

Surface alloys, overlayer and incommensurate structures of Bi on Cu(1 1 1)

Using surface X-ray diffraction, we have determined the structure of three different sub-monolayer phases of Bi on Cu(1 1 1). In contrast to an early report, we find that at a coverage of 1/3 monolayer a substitutional surface alloy is formed with a (√3 × √3)R30° unit cell. For increasing coverage, de-alloying occurs, leading to an overlayer structure at a coverage of 0.5 ML in which the Bi atoms form zigzag chains. The surface contains three domains of this phase. Finally, at a slightly higher coverage of 0.53 ML, the unit cell is compressed in one direction, leading to a uniaxial-incommensurate phase with three rotational domains.The structure determination includes relaxations in the topmost layers and therefore allows a detailed comparison of the most important bond distances. This shows that an increased charge density of the Cu(1 1 1) surface is the main driving force for the different phases.     

Temperature- and coverage-dependent evolution of the Au/Pd(1 1 0) surface structure

The morphology and the atomic scale structure of thin gold films (up to 2.5 ML) on Pd(1 1 0) were studied by means of scanning tunneling microscopy and surface X-ray diffraction. At room temperature the films exhibit a multilayer growth mode accompanied by the formation of highly anisotropic islands. Annealing above 500 K significantly increases the smoothness of the gold films, which are in registry with the substrate. Above a critical threshold of two monolayers a (1 × 2) missing-row reconstructed film is found. This reconstructed surface is well ordered after annealing at temperatures above 580 K. The specific gold film morphology is envisaged as a way to relax the strain caused by the mismatch between gold and palladium.     

Effects of high Fe substitution for Mn on phase transition and magnetic properties of YFexMn12−x compounds

YFe_xMn_12−x (x=7-10) compounds were synthesized; their structure and magnetic properties were investigated, the results reveal that a higher Fe concentration x makes the crystal phase change from ThMn₁₂-type to Th₂Zn₁₇-type, with the phase transition point x=9; the Curie temperature increases with increasing x, which becomes 290 K for x=8.8 and 150 K for x=7; and the magnetization also increases monotonically with increasing x until the phase transition point.     

Effects of proton irradiation on structure of NdFeB permanent magnets studied by X-ray diffraction and X-ray absorption fine structure

The effects of proton irradiation on the structure of NdFeB permanent magnet were investigated by X-ray diffraction and X-ray absorption fine structure (XAFS). The results reveal that proton irradiation has no effect on the long-range structure, but significantly affects the atomic local structure of the NdFeB magnet. The alignment degree of the magnet decreases and the internal stress of the lattice increases after proton irradiation. XAFS results show that the coordination number of Fe-Nd in the first neighboring coordination shell of the Fe atoms decreases and the disorder degree increases.     

Effect of Cd on the structural, magnetic and electrical properties of nanostructured Mn-Zn ferrite

Nanoparticles of Mn_0.5Zn_0.5−xCd_xFe₂O₄ (x=0.0, 0.1, 0.2 and 0.3) have been synthesized by a chemical co-precipitation method. The lattice constant increases with increasing Cd content. X-ray calculations indicate that there is deviation in the cation distribution in the nanostructured spinel ferrite. The dielectric constant and dielectric loss decrease for the samples with Cd content up to x=0.2. However the dielectric constant rises for x=0.3. This is due to an increase in the hopping process at the octahedral (B sites). The dielectric constant increases with increase in temperature, indicating a thermally activated hopping process. The DC resistivity increases with Cd content up to x=0.2 and decreases for Cd content x=0.3. The maximum magnetization of all the samples decreases with increase in Cd content.     

发光层的形态结构对电致发光器件性能影响的研究

详细研究了沉积在Poly(9-vinylcarbazole)(PVK)薄膜上的8－羟基喹啉铝（Alq3）薄膜的形态结构对电致发光器件ITO／PVK／Alq3/Mg-Ag性能的影响。研究结果表明：发光层（Alq3层）的表面形貌极大地影响发光层和金属阴极的接触面积,从而影响器件的电流－电压特性。发光层的表面越均匀连续,发光层和金属阴极的接触面积就越大,通过器件的电流就越大。在三种条件的器件中,基底温度为438K时制备的Alq3薄膜所对应的器件的量子效率最高,298K制备的器件的率效次之,77K制备的器件的效率最差。     

Effects of proton and electron irradiation on the structural and tribological properties of MoS2/polyimide

To study the structural and tribological properties of MoS₂/polyimide (MoS₂/PI) composite under the irradiation environment of proton and electron, the MoS₂/PI composites were investigated in a ground-based simulation facility, in which the energy of proton and electron was 25 keV and the flux was 2.5 × 10¹⁴ cm⁻² s⁻¹. The experimental results revealed that the simplex and combined irradiation of proton and electron induced bond break and cross-link, proton irradiation can break the PI bond easier than electron irradiation and then formed the graphite-like structure at surface area of the samples. Irradiation decreased the friction coefficient and wear rate remarkably of the composites comparing with the pristine one. The wear rate increased with the increasing of the proton and combined radiation time, and decreased with the electron radiation conditions.     

The structures of 1-bromoheptane and 1-bromononane monolayers adsorbed on the surface of graphite

X-ray diffraction and differential scanning calorimetry (DSC) have been used to confirm the formation of the solid monolayers of 1-bromoheptane (C7Br) and 1-bromononane (C9Br) on the surface of graphite. The X-ray diffraction patterns of these two species can be fitted by two possible monolayer structures with symmetries Pgb and P2. For one of these (C7Br) this ambiguity can be lifted using neutron diffraction and the Pgb plane group can be identified as the correct structural solution. Both of the unit cells contain two molecules forming an approximately 90^o zig-zag chain of bromine atoms with an inter-bromine distance of approximately 3.70?Å, which is similar to twice the Van der Waals radii of the bromine, suggesting rather little non-covalent interaction. The dipole moments in two adjacent chains are opposed leading to no net dipole for the layer as a whole.     

Effect of Ce and Cu co-doping on the structural,morphological, and optical properties of ZnO nanocrystals and first principle investigation of their stability and magnetic properties

Ce, Cu co-doped ZnO (Zn_1−2xCe_xCu_xO: x=0.00, 0.01, 0.02, 0.03, 0.04 and 0.05) nanocrystals were synthesized by a microwave combustion method. These nanocrystals were investigated by using X-ray diffraction (XRD), UV–visible diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). The stability and magnetic properties of Ce and Cu co-doped ZnO were probed by first principle calculations. XRD results revealed that all the compositions are single crystalline. hexagonal wurtzite structure. The optical band gap of pure ZnO was found to be 3.22 eV, and it decreased from 3.15 to 3.10 eV with an increase in the concentration of Cu and Ce content. The morphologies of Ce and Cu co-doped ZnO samples confirmed the formation of nanocrystals with an average grain size ranging from 70 to 150 nm. The magnetization measurement results affirmed the antiferro and ferromagnetic state for Ce and Cu co-doped ZnO samples and this is in agreement with the first principles theoretical calculations.     

激光辐照对热退火金属/掺氟二氧化锡透明导电薄膜光电性能的影响

采用532 nm纳秒脉冲激光对热退火的铝(Al)/掺氟二氧化锡(FTO)、铜(Cu)/FTO和银(Ag)/FTO三种双层复合薄膜表面分别进行处理, 结果显示薄膜样品的光电性能都得到提高.其中, 热退火Ag/FTO薄膜的平均透光率(400–800 nm)增幅最大, 从72.6%提高到80.5%, 主要是由于其表面产生了具有减反增透作用的光栅结构.激光辐照后热退火Ag/FTO薄膜的导电性也略有提高, 其方块电阻从5.6 Ω/sq下降到5.3 Ω/sq, 原因主要是激光辐照的热效应造成的退火作用使薄膜的晶粒尺寸增大, 减少了晶界散射而使载流子迁移率提高.计算结果显示, 激光辐照后热退火Ag/FTO薄膜的品质因子从0.73×10^-2Ω^-1增大为2.16×10^-2Ω^-1, 表明其综合光电性能得到显著提高.激光辐照可同步实现薄膜表面光栅结构的制备和附加退火作用, 这为金属层复合透明导电薄膜光电性能的综合优化提供了新的思路.     

Study of phase transitions in the system A1B11PO4 with A1 = Li,Rb and B11 = Mg,Ca, Sr,Ba, Zn,Cd, Pb

The series of the title compounds were prepared by solid-state reactions. The phase transitions between room temperature and 1450 °C were investigated by DTA and X-ray diffraction. All compounds undergo at least one reversible phase transition in the solid state. The Rb containing compounds, with the exception of those with Cd and Zn, show no liquid phase up to 1450 °C. The phases formed crystallize with various structures which can be described partly as distorted olivine, LiKSO₄, CsZnPO₄ or glaserite. RbCdPO₄ shows an incommensurate structure with a one-dimensional modulation.     

Ab initio vibrational spectra and structure of the ground state of HeScH2+

Potential energy and dipole moment surfaces of the ¹A′ ground state of HeScH²⁺ have been calculated using both the internally contracted single and double excitation multireference configuration interaction and the coupled-cluster singles and doubles augmented by a perturbative treatment of triple excitations levels of theory. Analytical functions have been fitted to the discrete surfaces employing a multidimensional least squares approach. These analytical functions have subsequently been embedded within a rectilinear normal-coordinate vibrational Hamiltonian in order to calculate vibrational states and transition intensities for low-lying states of HeScH²⁺.     

Influence of the Morphology of Lysozyme‐Shelled Microparticles on the Cellular Association,Uptake, and Degradation in Human Breast Adenocarcinoma Cells

The ultrasound‐assisted self‐assembly and cross‐linking of lysozyme at the water–air and water–perfluorohexane interfaces are shown to produce lysozyme‐shelled hollow microbubbles (LSMBs) and microcapsules (LSMC), respectively. The arrangement of lysozyme at the air–liquid or oil–liquid interfaces is accompanied by changes in the bioactivity and conformational state of the protein. The interaction of LSMB and LSMC with human breast adenocarcinoma cells (SKBR3) is studied. LSMB and LSMC are phagocyted by cells within 2 h without exerting a cytotoxic activity. The cellular internalization kinetics of LSMB and LSMC and the effects on cell cycle are evaluated using flow cytometry. Evidence for the internalization of microparticles and degradation within the cell are also monitored by confocal and scanning electron microscopic analyses. The integrity of cell membrane and cell cycle is not affected by LSMBs and LSMCs uptake. These studies show that the positively charged LSMB and LSMC are not cytotoxic and can be readily internalized and degraded by the SKBR3 cells. LSMBs and LSMCs show a different uptake kinetics and intracellular degradation pattern due to differences in the arrangement of the protein at the air–liquid or oil–liquid interfaces.