Study of ZrSiB Coatings Obtained by Magnetron Sputtering of ZrB2-20%Si and ZrB2-50%ZrSi2 Cathodes

Physics of Atomic Nuclei - A comparative study of ZrSiB coatings obtained by magnetron sputtering with the use of cathodes of different phase composition is carried out. The optimal compositions...     

Structure and Properties of ZrC/C Heteromodulus High-Temperature Composites

Russian Physics Journal - The influence of free carbon on densification and mechanical properties of ZrC/C heteromodulus composites is studied. It is shown that free carbon in the amount of up to 3...     

Effects of Annealing on Microstructure and Optical Properties of TiO2 Sculptured Thin Films

The evolution of microstructure and optical properties of TiO2 sculptured thin films under thermal annealing is reported. XRD, field emission SEM, UV-Vis-NIR spectra are employed to characterize the microstructural and optical properties. It is found that the optimum annealing temperature for linear birefringence is 500℃. The maximum of transmission difference for linear birefringence is up to 18%, which is more than twice of that in as-deposited thin films. In addition, the sample annealed at 500℃ has a minimum of column angle about 12℃. The competitive process between the microstructural and optical properties is discussed in detail. Post-annealing is a useful method to improve the linear birefringence in sculptured thin films for practical applications.     

电泳法(EPD)制备YBCO超导涂层的微结构及其性质

采用顶部籽晶技术和熔融织构工艺改善晶界弱连接 ,并研究不同尺寸的籽晶对超导涂层微结构和超导性质的影响 ;用与基片同样尺寸的籽晶制备 YBCO超导涂层 ,再经过高压氧处理过程 ,YBCO超导涂层的临界电流密度有很大提高     

Effects of Explosive Particle Microstructure Parameters on NQR Parameters in RDX

The effects of the particle size, density and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) content on 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) nuclear quadrupole resonance (NQR) line have been studied at 5, 10, 15 and 20?°C. The RDX line at 3.41?MHz has been measured in 17 different quality lots. The RDX line was not modified in this temperature range but was strongly altered in some lots. No significant correlation was found between line characteristics and particle sizes or particle bulk densities. Correlation coefficients were computed between the HMX content measured using high-performance liquid chromatography and the NQR line intensity and NQR line width. Significant correlations were found. They were based on the study of 11 RDX lots which exhibited 4 different HMX contents from 0 to about 9 percent in weight. Further studies are needed to precise the HMX effect in relation with the HMX location. HMX can be located inside or outside the RDX crystal. Further studies are also needed to determine the line broadening mechanism.     

Effects of Rapid Thermal Processing on Microstructure and Optical Properties of As-Deposited Ag2O Films by Direct-Current Reactive Magnetron Sputtering

（111） preferentially oriented Ag2O film deposited by direct current reactive magnetron sputtering is annealed by rapid thermal processing at different annealing temperatures for 5 min. The film microstructure and optical properties are then characterized by x-ray diffractometry, scanning electron microscopy, and spectrophotometry, respectively. The results indicate that no clear Ag diffraction peak is discernable in the Ag2O film annealed below 200°C. In comparison, the Ag2O film annealed at 200°C begins to exhibit characteristic Ag diffraction peaks, and in particular the Ag2O film annealed at 250°C can demonstrate enhanced Ag diffraction peaks. This implies that the threshold of the thermal decomposition reaction to produce Ag particles is approximately 200°C for the Ag2O film. In addition, an evolution of the film surface morphology from compact and pyramid-like to a rough and porous structure clearly occurred with increasing annealing temperature. The porous structure might be attributable to the escape of the oxygen produced during annealing, while the rough surface might originate from the reconstruction of the surface. The dispersion of interference peak intensity in the reflectance and transmission spectra could be attributed to the Ag particles produced. The lowered crystallinity and Ag particles produced induce a lattice defect, which results in an enhanced transmissivity in the violet region and a weakened transmissivity in the infrared region.     

CaO-SiO2绿光玻璃陶瓷荧光体的沉积组织结构对发光性质的影响

采用半熔化-淬冷的一步法制备了一种新型的硅酸钙绿光玻璃陶瓷,通过变化在1 550℃的保温时间,研究了玻璃陶瓷中沉积的微观结构对发光性质的影响.延长保温时间,玻璃陶瓷中沉积的发光晶体β-Ca SiO4:Eu2+和发光玻璃相的比例趋于减少,导致样品发射光谱红移,透明度增加.本论文同时分析了SiO2晶粒在玻璃基体中的沉积现象...     

Effect of Process Parameters on Laser Damage Threshold of TiO2 Coatings

We investigate the laser damage behaviour of an electron-beam-deposited TiO2 monolayer at different process parameters. The optical properties, chemical composition, surface defects, absorption and laser-induced damage threshold （LIDT） of films are measured. It is found that TiO2 films with the minimum absorption and the highest LIDT can be fabricated using a TiO2 starting material after annealing. LIDT is mainly related to absorption and is influenced by the non-stoichiometric defects for TiO2 films. Surface defects show no evident effects on LIDT in this experiment.     

Characteristics of ZrC/ZrN and ZrC/TiN multilayers grown by pulsed laser deposition

ZrC/ZrN and ZrC/TiN multilayers were grown on (1 0 0) Si substrates at 300 °C by the pulsed laser deposition (PLD) technique using a KrF excimer laser. X-ray diffraction investigations showed that films were crystalline, the strain and grain size depending on the nature and pressure of the gas used during deposition. The elemental composition, analyzed by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS), showed that films contained a low level of oxygen contamination. Simulations of the X-ray reflectivity (XRR) curves acquired from films indicated a smooth surface morphology, with roughness below 1 nm (rms) and densities very close to bulk values.Nanoindentation results showed that the ZrC/ZrN and ZrC/TiN multilayer samples exhibited hardness values between 30 and 33 GPa, slightly higher than the values of 28-30 GPa measured for pure ZrC, TiN and ZrN films.     

Energy Parameters of an Electron Beam and Structure and Mechanical Properties of Composite Coatings

Russian Physics Journal - An important parameter of non-vacuum electron-beam cladding is the surface density of the input energy that depends on the beam current and the specimen travel speed. The...     

The Morphology and Electronic Properties of Si Nanoscale Structures on a CaF2 Surface

Technical Physics - The surface morphology, crystal structures, and band-energy parameters have been studied for nanofilms and regularly arranged nanoscale Si phases with a thickness of 1–2...     

Microstructure and Properties of Polypropylene/Clay Nanocomposites

Nanocomposites of polypropylene (PP) containing various contents of Cloisite 15A nanoclay particles were prepared by one-step melt compounding in a twin screw extruder. Tensile and impact properties of the nanocomposite systems were investigated and correlated with their microstructures. The tensile modulus increased with an increase in Cloisite 15A content but the tensile strength, elongation at break, and impact strength were decreased. WAXS and TEM studies showed almost exfoliated structures. There was a decrease in permeability values with an increase in nanoclay content up to 5 wt. %. Exceeding this content of nanoclay had no significant effect on permeation due to the aggregation phenomenon at high concentrations of the nanoparticles. Most of the examined micromechanical models for prediction of the tensile modulus of the nanocomposite were successful despite being based on fiber-shaped fillers. An exfoliated structure of clay within the nanocomposite was assumed for the modeling using a molecular dynamics simulations approach, employing Dreiding, Forcite, and COMPASS force fields, in order to investigate the best one for a successful estimation of elastic modulus. Relative to the experimental modulus values of the nanocomposites, which were around 1100–1200 MPa, the COMPASS force field had the best correlation with the values with a slight departure of about 10%.     

Control over the Magnetic Properties of Co/Pt-based Multilayered Periodical Structures

Technical Physics - The possibility of controlling the magnetic properties of multilayered periodical structures with perpendicular magnetic anisotropy, which are based on cobalt and platinum...     

Wear resistance of ZrC/TiN and ZrC/ZrN thin multilayers grown by pulsed laser deposition

ZrC/TiN and ZrC/ZrN multilayers thinner than 350 nm were grown on (100) Si substrates at a temperature of 300 °C by the pulsed laser deposition (PLD) technique using a KrF excimer laser (λ=248 nm, pulse duration τ=25 ns, 8.0 J/cm² fluence and 40 Hz repetition rate). Cross-sectional transmission electron microscopy, Auger electron spectroscopy depth profiling and simulations of X-ray reflectivity curves indicated that there was intermixing between the deposited layers at the interfaces as well as between the first layer and the substrate. Nanoindentation investigations found hardness values between 35 and 38 GPa for the deposited multilayers. Linear unidirectional sliding wear tests were conducted using a ball-on-plate tribometer under 1 N normal force. Wear tracks were produced in a Hysitron nanoindenter with 1 μm radius diamond tip under a 500 μN load. High-resolution cross-sectional transmission electron microscopy studies of the wear tracks showed that the multilayers withstood these tests without significant damage. The results could be explained by the use of a high laser fluence during deposition that resulted in very dense and strongly adherent nanocrystalline layers.     

Effects of Bi2O3 Addition in Micro- and Nanoscale on the Structural and Electrical Properties of Zn1-xBixO varistors

Two similar sets of Zn_1-xBi_xO ceramic varistors with various x values (0.00?≤x≤?0.20) have been prepared by using Bi₂O₃ additions with two different sizes. In the first set, Bi₂O₃ nanoparticles (≈200 nm) were used, while Bi₂O₃ microparticles (≈5 μm) were used in the second set. It was found that addition of Bi up to 5 % for both sets did not affect the wurtzite-type hexagonal structure of ZnO, but with increasing Bi above 5 %, some unknown lines were clearly observed in XRD spectra. The grain sizes are increased in both sets with increasing Bi content up to 2.5 %, followed by a decrease with further increase of Bi up to 20 %, and their values for microparticle additions were larger than that of the sets containing nanoparticle additions. Two nonlinear regions were formed in the I–V curves of ZnO due to Bi₂O₃ nanoparticle additions above 5 %. However, this behavior was completely absent in the samples containing Bi₂O₃ microparticles. Moreover, the breakdown field and nonlinear coefficient decreased with Bi₂O₃ addition up to 5 % for both sets, followed by an increase with further increase of Bi up to 20 %, and their values were higher for nanoparticle additions than that of microparticles. A reverse behavior was recorded for the electrical conductivity. The results have been discussed in terms of Bi₂O₃ nanosize grains which may be localized at the grain boundaries of ZnO ceramics.     

Comparative study of the core level photoemission of the ZrB2 and ZrB12

X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) were used to investigate the binding energies and valence band for ZrB₂ and ZrB₁₂. The Zr 3d and B 1s core levels were identified. The Zr 3d core level shows a spin–orbit split 3d_5/2 and 3d_3/2 while that for B 1s core level exhibited a single symmetric peak, these being typical of zirconium and boride signals. Comparing the Zr 3d and B 1s core levels with metallic Zr, B₂O₃ and ZrO₂ reference materials only a negative chemical shift for Zr 3d associated to ZrB₂ was observed, which suggests that the charge transfer model based on the concept of electronegativity was not applicable to explain the superconductivity in the ZrB₁₂ sample. The measured valence band using UPS is consistent with the band-structure calculations indicating a higher density of states (DOS) at E_F for ZrB₁₂ respect to ZrB₂. Finally, we found that the weak mixed B-p and Zr-d states for ZrB₁₂ is crucial for the superconductivity due to the state population increased the DOS at the E_F.     

Effects of Processing Parameters on Flow-Induced Crystallization of iPP in Microinjection Molding

Flow-induced crystallization has long been an important subject in polymer processing. Varying processing conditions can produce different morphologies, which lead to different properties. Recent studies have indicated that the final morphology is, in fact, dictated by the formation of crystallization structures under flow. This study deals with the influence of processing parameters on the polymorphism and crystallization orientation of isotactic polypropylene (iPP) in microinjection molding. Crystallinity and polymorphism were investigated by means of differential scanning calorimeter (DSC) and one-dimensional wide-angle X-ray diffraction (1D-WAXD). Crystalline orientation was characterized by two-dimensional wide-angle X-ray diffraction (2D-WAXD). Herman's orientation functions determined from the flat-plate wide-angle X-ray diffraction patterns were used to evaluate the orientation level of microparts. It was found that the effect of processing parameters on the crystallinity was not obvious, but these processing parameters had a great influence on the β-modification content of microparts. When the mold temperature was 150°C, β-modification still formed in microparts because the thermal stability of the β-modification was enhanced with increasing the mold temperature; The β-modification content of microparts decreased obviously when the injection time was 1 s compared to the longer injection time. However, the β-modification content of microparts increased with increasing the injection pressure. In addition, the γ-modification existed in the microparts at the mold temperatures of 150 and 160°C. From Herman's orientation functions, we know that the influence of processing parameters on α-crystalline orientation in microparts was small. But the processing parameters can affect the degree of the β-modification orientation. A shish-kebab structure was observed in some regions throughout the longitudinal sections of all the microparts by the SEM analysis.     

Influence of bilayer periods on structural and mechanical properties of ZrC/ZrB2 superlattice coatings

ZrC/ZrB₂ multilayered coatings with bilayer periods ranging from 4.4 to 35.5 nm were synthesized by r.f. magnetron sputtering. X-ray diffraction, scanning electron microscopy and nanoindention were employed to investigate the microstructure and mechanical properties of the nanoscale multilayers. The results indicated that all coatings had the clear multilayered structure with mixed ZrB₂(0 0 1), ZrB₂(0 0 2) and ZrC(1 1 1) preferred orientations. The maximum hardness (41.7 GPa) was observed in the multilayer with 27.5-nm thick period, which is about 25% higher than the rule-of-mixture value of the monolithic ZrC and ZrB₂ coatings. It also exhibited the best adhesion. Its critical load was over 70 mN. While through insert ZrB₂ into ZrC layer periodically, higher residual stress built in ZrC layer can be released.     

The Effects of Different Processing Methods on the Morphology and Properties of PP/EPDM/Nano-CaCO3 Ternary Blend

The effects of different processing methods (direct extrusion, two-step extrusion or lateral injection extrusion) on the morphology of polypropylene (PP)/ethylene-propylene-diene terpolymer (EPDM)/calcium carbonate nanoparticles (nano-CaCO₃) ternary blend were investigated, including the morphology of the EPDM phase and the distribution of nano-CaCO₃ particles, by means of scanning electron microscopy (SEM). The results showed that the processing methods had a significant influence on the morphology of the EPDM phase and the distribution of nano-CaCO₃ particles. In the lateral injection extruded blends, it was amazingly observed that the EPDM particles encapsulated the PP phase tightly, and the dimension of EPDM particles was remarkably decreased. It was also found that the content of nano-CaCO₃ particles in the matrix of the lateral injection extruded blends was less than that of the two-step extruded blend, and that of the direct extruded blend was most. The properties of the ternary blend, including dynamic mechanical properties, rheological properties, and crystallization, were characterized in order to confirm the variety of morphologies caused by the different processing methods. The differences in the crystallization temperature, elastic modulus, and glass transition temperature of the blends prepared by different methods well agreed with the variation of their morphology.