Advanced Materials Research Vols. 146-147

Abstract: This study aims to investigate the morphologies and the existing phases of calcium sulfate crystal by the reaction of H2SO4 with Ca(NO3)2·4H2O in acid medium using microscopic method and XRD powder diffraction. A series of experiments were designed for studying the crystal morphology and the hydrated form under coexisitence of phosphoric acid and nitric acid at 338K. The micrograph results show that in the H3PO4-HNO3-H2O system, the crystal shapes are changed from thick-long rod to thin-short rod, then needle-like even tiny needle gradually with the increase of acid content in solution. The solubility of calcium sulfate increases gradually with the increase of phosphoric acid or nitric acid concentration in solution. The XRD results show that with the increasing of acid concentration, the form of calcium sulfate is transferred from dihydrate to hemihydrate, that is, at higher acid concentration condition calcium sulfate hemihydrate is more stable in solution with the particles to be tiny and needle-like; while at lower acid concentration condition the crystals are mainly calcium sulfate dihydrate with larger rod particles which indicate a good filtration properties.

Abstract: Silver electrochemical migration results in the degradation of surface insulation resistance, and has been attributed to the dendritic bridge between adjacent conductors. In this paper, the electrochemical migration behavior of both Ag-plated Cu powder and pure silver powder in conductive thick film (CTF) are investigated. By Electrochemical migration test (water drop+ DC bias method), and the SEM and XRD examinations, it was found that the silver electrochemical migration in CTF was minimized when the Ag-plated Cu powder substitute silver powder in CTF. This is ascribed to the galvanic coupling effect that plays an important role in the migration inhibition. As sacrifice anode copper restrains the cathodic silver from dissolving in solution so as to decreases the probability of dendritic growth.

Abstract: There are continuous high concerns on formation protection technology in international petroleum engineering field. The reservoir drill-in fluid (RDF) is the first non-native fluid to contact formation, and which influences directly the ultimate capacity of oil and gas well. The paper discusses the smart RDF design method based on conventional drilling fluid. The designed RDF system is characterized as good formation damage control, as well as the performance easily adjusted for field application. The technology combines ideal packing technology with active calcium carbonate to obtain low permeability filter cake, high return permeability and low initial flowing pressure. The sized calcium carbonates contribute to develop sealing zone for preventing filtrate and solids from invading into formation, and the organophilic passageway in filter cake (the active calcium carbonate) is favorable to open automatically passageway for oil and gas during production. Different modifiers used to ground calciumcarbonate surface modification are evaluated in laboratory. And the laboratory results show modified calcium carbonates are comfortable with conventional drilling fluids additives such as XC(Xanthan ), potassium polyacrylate(K-PAM), sodium carboxymethyl cellulose(Na-CMC).

Abstract: In this paper microstructures and mechanical properties of the Mg-xGd-Er (x=5, 7, 9 and 11wt.%) alloys were characterized and discussed. The results show that the alloys with different Gd were mainly composed of α-Mg solid solution, semi-continuous network-like secondary phases of Mg5Gd and cuboid-shaped compound of Mg(GdEr). The ensile strength and yield strength increase as the content of Gd increase. This improved mechanical properties are mainly ascribed to the formation of network-like secondary phases of Mg5Gd.

Abstract: This paper provides a new method to repair the steel pipe with fatigue cracks by using carbon fiber reinforced polymer (CFRP). Cracks may arise in Pressure pipeline in service because of low cycle fatigue. Crack defect is the biggest problem, because crack will gradually propagate and seriously threaten the safe operation of pipeline. This paper provides a repair and calculation method for pressure pipeline with fatigue cracks, and some specific engineering cases are given based on this method.

Abstract: The purpose of this work was to investigate the effects of pre-load static load and dynamic load on the visco-elastic in polycarbonate. In the paper, static-dynamic sweep experiment of polycarbonate was performed on EPLEXOR 500N, which was manufactured by GABO of Germany. The variation laws of storage modulus, loss modulus and loss tangent as changing dynamic load in a large range were systematically analyzed and the spectral characteristics of dynamic-viscoelastic under static-dynamic loads were obtained. The experiment results on dynamic visco-elastic under the high load shows that the load effects on dynamic visco-elasticity of polycarbonate performing on the changing of the dynamic visco-elastic parameters, storage modulus become lager with the increasing of static load and decreasing with the increasing of dynamic load, while loss tangent decreases with the increasing of dynamic load and varies in a more complicated pattern as the increasing of static load.

Abstract: A numerical model is developed to describe the kinetics of the microstructure evolution in an atomized droplet of Mg-9wt%Al alloy. The model is coupled with the heat transfer controlling equations to simulate the solidification process of the atomized droplets. The numerical results show that the microstructure development is a result of the common action of the nucleation and growth of grains. The nucleation events take place at a critical supercooling for a given droplet. As the droplet size decreases, the critical supercooling increases significantly. The volume fractions of the phases formed during the period of the recalescence, the segregated solidification and the eutectic reaction are sensitive to the droplet size. It is demonstrated that the developed model describes the microstructure evolution process well.

Abstract: Some attempts for getting Grüneisen parameter are discussed. After comparing, the Grüneisen parameter got from Grüneisen EOS and Vinet EOS is consistent with the experimental data. However, we are not sure which method can describe the behavior of the Grüneisen parameter good under high pressures, because of the lack of directly measured data for Grüneisen parameter under high pressures. So, the technology for directly measuring Grüneisen parameter should be developed for clarifying this problem by experiments.

Abstract: Porosity occurred in the 5182 aluminum alloy strip cast by a vertical type high speed twin roll caster. The porosity was caused by high-roll-speed and low-roll-load. Improvement of the porosity was tried by a scraper. The scraper was mounted on the roll, and the scraper was moveable depend on the thickness of the solidified layer on the roll. The scraper scribed the semisolid layer to improve the porosity. The scraper was useful to decrease the porosity of roll cast 5182 aluminum alloy strip.

Abstract: For Fe-Al powder compacts, using high-energy laser beam combustion synthesis preparation for Fe-Al alloy. The microstructure and properties were analysised by X-ray diffractometer, optical microscopy and abrasive wear testing machine.The result indicated that synthetic products deviate from the equilibrium state of the intermediate phase and Al-rich phase produced; With the increase of aluminum content, the content of Al-rich phase increase, raising the level of the sample density; With the increase of aluminum content,morphology from fine acicular,strip noticeable,flake lath to massive growth; Synthesis of Fe-70at% sample of its uniform and a high densification, it has excellent wear and corrosion resistance.