Advanced Materials Research Vols. 631-632

Abstract: The mechanical properties and morphologies of fume precipitate and rice husk silica filled EP composites have been compared. The density, specific area of the silica decreases in the order of fume silica, precipitate silica and rice husk silica, while the silica size increases with the order above. It is shown that the fume silica/EP exhibits the highest flexural strength and modulus, followed by the precipitate silica/EP and the rice husk silica/EP. The rice husk silica/EP exhibits the highest in impact strength as silica is 1 phr. Over 5 phr of silica, fume silica/EP has the highest in impact strength, while the rice silica/EP is better than precipitate silica/EP. Scanning electron microscopy (SEM) results show that the fume silica has best dispersion and least filler agglomerates in matrix. The better dispersion will be responsible for the higher reinforcing and processing viscosity of the fume silica.

Abstract: In order to precisely predict the sensitivity of Ф18 mm transmission-mode GaAs photocathode, a concept of integral diffraction intensity is proposed based on X-ray diffraction principle after analyzing the predecessors′ limitations of testing the micro-area of such photocathode and GaAs photocathode of image intensifier tube is plane electron source in this paper. The integral diffraction intensity on the entire photocathode surface was obtained by multi-points detection in the effective area of the photocathode with integral method. The crystal quality of entire photocathode surface will be taken with the integral diffraction intensity. According to the principle, X-ray diffraction testing for 4 samples of GaAs photocathode modules was executed with high-resolution four-wafer X-ray Diffractometer whose test spot size is 4 mm×5 mm. The diffraction curves were obtained and the integral diffraction intensity was calculated. Subsequently the 4 photocathode modules was activation processed with Cs-O in ultra-high vacuum system simultaneity the photocurrent of photocathode modules was measured. Comparing the variation of diffraction curve with integral diffraction vs photocathode photocurrent curve, they show that the greater the integral diffraction intensity of is, the more photocurrent is in the photocathode module. The variation relation curve between X-ray integral diffraction intensity and photocurrent in the photocathode was fitted with least square method. The curve, which accords with logarithm curve and whose fitting degree is 0.878, was achieved. Since photocathode sensitivity is direct proportion to photocathode photocurrent. The above results prove that A Practicality Φ18mm photocathode of image intensifier tube is plane electron source, GaAs photocathode sensitivity and other photoelectric performance lies on entire photocathode surface crystal quality, the photocathode module integrality reflected by the integral diffraction intensity plays crucial role of GaAs photocathode sensitivity. So integral sensitivity of Ф18 mm transmission-mode GaAs photocathode can be precisely predicted with X-ray integral diffraction intensity, some feasible ideas for further research of GaAs photocathode was obtained in this paper.

Abstract: Silicon sensors, widely used in high energy and nuclear physics experiments, suffer severe radiation damage that leads to degradations in sensor performance. These degradations include significant increases in leakage current, bulk resistivity, space charge concentration, and free carrier trapping. For LHC (Large Hadron Collider) applications, where the total fluence is in the order of 1x10¹⁵ neq/cm² for 10 years, the increase in space charge concentration has been the main problem since it can significantly increase the sensor full depletion voltage, causing either breakdown if operated at high biases or charge collection loss if operated at lower biases than full depletion. For LHC Upgrade, or the sLHC, however, with an increased total fluence up to 1x10¹⁶ neq/cm², the main limiting factor for Si detector operation is the severe trapping of free carriers by radiation-induced defect levels.

Abstract: Since the 1990s the novel materials named HEAs concepts come into being, it was concerned by researchers because of its superior performance. This paper describes the concept and formation criteria of the HEAs, at the same time, summaries detail the methods of preparation and new achievements.

Abstract: A novel type of photonic crystal fiber for high birefringence and zero-walkoff is proposed based on polymer, the fiber is composed of a solid polymer core and a cladding with square lattice elliptical air-holes along the fiber length. The optical birefringence and polarization-dependent leakage loss are studied numerically based on the full-vector finite element method(FEM). Numerical results show that the proposed fiber has heightened modal birefringence of the order of 10^-2; and the leakage loss is reduced to 0.08dB/m at wavelength of 0.65μm when it has 10 rings of elliptical air-holes. So the proposed PCFs may be useful in the field of high birefringence polarization-maintaining optical communication.

Abstract: A type of phenolic resin (PF) was prepared by using TiO₂ nanoparticles modified with KH-550 as composite filler and modifier, and then the composite modified PF were used as adhesive to prepare semi-metallic friction materials samples. TG analysis of the prepared nano-TiO₂ /PF composites was conducted on SETARAM-TG2DSC92216 thermal analyzer that was made in France, and the friction and wear property comparison tests of the samples were carried out on XD-MSM fixed speed friction-wear machine. The results show that the heat resistance of phenolic resin after being compositely modified by TiO₂ nanoparticles can be improved, carbon residue rate increases10% at 600°C；the friction coefficient of the corresponding sample slightly increases；the wear rate clearly decreases at high temperature, and wear rate decreases 10% at 350°C.

Abstract: In this paper, the development in the degradation of microcystic toxins and algae removal by TiO₂ photocatalysts is reviewed, analyzing the prospect and pinpointing the key factor of the technology. TiO₂, which is insoluble, nontoxic, inexpensive and catalyst-efficient, shows good chemical inertness. For the degradation of microcystic toxins and algae removal, TiO2 photocatalysts is superior to the traditional processing technology and method, contributing a lot to environmental protection.

Abstract: The diffusion bonding of 316L stainless steel with Ni interlayer in the temperature range of 850-1050°C, under a uniaxial pressure 10 MPa for 60 min is investigated. The diffusion bonds have been evaluated light microscopy, SEM, X-ray diffraction and tensile test. The main result is that the introduction of the interlayer may reduce the room temperature strength but increase the high temperature strength. This is attributed to the transformation of Fe_0.64Ni_0.36 formed in bonding process into FeNi₃ at high temperature. Kirkendall voids are formed in the Ni interlayer near the interface where the specimen fractured. Fractographic study indicates that the fracture mode of the joints is strongly affected by the bonding and testing temperature. The fracture is a mixed mode of brittle and ductile fracture in high temperature tensile test, while it is brittle fracture at room temperature.

Abstract: The modified guar gum was synthesized with guar gum as material and bromododecane as etherifying agent by suspension polymerization method. The solution and gel of the modified guar gum were also prepared. The structure and the property of the modified guar gum were analysized by Fourier transform infrared spectrum (FT-IR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The heat resistance and the viscoelasticity modulus of the gel were also researched by rheometer. The results of FT-IR and XRD show that the hydrophobic long chain has been introduced into the guar gum successfully. TGA indicates that the modified guar gum has higher thermal stability. The rheology tests reflect that with different temperature conditions, the shear viscosity, the viscoelasticity modulus of the gel and the heat resistance of the modified guar gum are both better than that of the unmodified guar gum. The modified guar gum can be used as thickener of fracturing fluid, and it can reduce its amount.

Abstract: This paper presents a spherical percolation model for dual-porosity media reservoir, where the quadratic-gradient term, wellbore storage and three types of outer boundary conditions: constant pressure boundary, closed boundary and infinity boundary were considered. Then a new method: Similar Constructive Method was put forward for solving this type of percolation model. And solutions of the dimensionless reservoir pressure and the dimensionless bottomhole pressure in Laplace space were obtained. It was proved that these solutions had a similar structure. The Similar Constructive Method is an elementary and algebraic method, simple and practical. And the similar structure of solutions can simplify the well test analysis software programming and analyze the reservoir parameter’s affection on pressure conveniently. The present research has a great academic significance and application value in oil-gas field development.