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To investigate the effect of supercritical CO2 saturation on acoustic emission (AE) signal properties in hot dry rock failure process, AE tests were conducted on granite under uniaxial compression. The results revealed that the strength of granite was obviously decreased after supercritical CO2 saturation, and new frequency bands appeared in the high-frequency region of AE and dominant frequency dispersion was enhanced. Dominant frequency mode was evolved from single mode dominated by high frequency to complex mode distributed in multiple frequencies indicating the failure modes diversified. Furthermore, supercritical CO2 saturation resulted in more uniform distribution of energy events and wider distribution of magnitude during granite failure. The decrease of b value as the prediction basis for failure might not be applicable. In addition, the degradation of the cementation degree of granite mineral particles and particle size were considered to be the fundamental reasons for the variation of AE properties.

Using supercritical CO2 as a fracturing or heat exchange medium can not only improve the thermal recovery efficiency of geothermal energy but can also store CO2 and reduce CO2 emissions. The pore s...

The present work demonstrates a simple method to prepare nanostructured Ni films with different morphologies with the assistance of porous anodic aluminum oxide (AAO) membranes. A great distinction is observed as the Ni films deposited onto the top and bottom sides of AAO membranes. The wetting properties of as-prepared membranes are investigated by measuring the contact angles of water on the surfaces. Results show that the static water contact angle changes dramatically from 124°±1° to 45°±1° on different Ni films, implying a change of the wettability from hydrophobicity to hydrophilicity affected by the surface patterns. This versatile approach can be conducted on various materials with potential applications in a broad range of fields.

High undercoolings up to 305 K have been successfully achieved in the bulk Fe 81 Ga 19 magnetostrictive alloy melts by means of glass fluxing combined with superheating cycling method. Microstructural evolution of Fe 81 Ga 19 alloy is investigated systematically with respect to different undercoolings. The results of grain refinement are interpreted in terms of dendrite remelting and recrystallization mechanism, respectively.

Using electromagnetic levitation melting combining with fluxing method, the Fe 83 Ga 17 alloys were undercooled up to 173 K through superheating–cooling cycles. The results showed that the microstructure was closely related to the undercooling. When the undercooling was lower than 53 K, the structures consisted of coarse dendrites and some dark particles in interdendrite. With the increase of undercooling, the solidified microstructures tended to be integrated, and the grain had preferred orientation. The texture of [1 0 0] orientation were developed by the undercooling process. The cooling rate of heat treatment significantly affects the microstructure of Fe 83 Ga 17 alloys. The water-quenched process could restrain the precipitation of DO 3 phase, and the low cooling rate in the process of furnace cooling could lead to form the metastable DO 3 phase.

The microstructure and microhardness of a cast Al-10wt%Mg (henceforth Al-10Mg) alloy with 0.2wt% addition of Al-5Ti-0.25C master alloy were compared with those of a refiner-free alloy of similar chemical composition. It was found that this level of the master alloy addition not only caused an effective grain refinement, but also caused a significant increase in the microhardness of the Al-10Mg alloy. Microchemical analysis revealed that TiC particles existed in the grain center. The relationship between the holding time and grain size was also studied. It shows that the grain refining efficiency is faded observably with the holding time. This is explained in terms of the instability of TiC particles.

Adopting glass fluxing combined with superheating cycling method, the undercooling and its stability of Fe 83 Ga 17 alloy melts were investigated using different kinds of denucleating glass: B 2 O 3 , 90% NaSiCa + 10% B 2 O 3 (simplified as Na–Si–Ca–Al–B) and 70% Na–Si–Ca–Al–B + 30% Na 2 B 7 O 4 . The results showed that different glass has different denucleating mechanism. The purification of B 2 O 3 glass is only a physical process, by which the stable bulk undercooling cannot be obtained during superheating–cooling cycles. While taking Na–Si–Ca–Al–B glass as purifying agent, its denucleating mechanism is a comprehensively physicochemical process. But the stability of undercooling is still undesirable because of the separation between melt and glass during cooling process in superheating cycling. A stable bulk undercooling can be obtained by physicochemical denucleating process in the case of 70% Na–Si–Ca–Al–B + 30% Na 2 B 7 O 4 molten glass owing to its suitable viscosity.