Sintered magnesia refractories combined by in situ intergranular CaZrO 3 phases were synthesized using natural MgO-containing natural minerals with CaO and SiO 2 impurities and nano-sized ZrO 2 additive. A homogenous distribution of intergranular CaZrO 3 , independent from the intergranular CaO-MgO-SiO 2 phases, was formed in situ within the sintered magnesia aggregates by introducing 0.75 wt pct nano-sized ZrO 2 into the magnesite. The formation mechanism of the in situ intergranular CaZrO 3 phases was determined. The nano-sized ZrO 2 was introduced and uniformly distributed at grain boundaries of the magnesia due to the micron-nano-sized particles composite system and wetting grinding process. Then the CaO in impurities were prior to SiO 2 to react with the ZrO 2 for generating CaZrO 3 at the grain boundaries by increasing sintering temperature. Nevertheless, the nano-sized ZrO 2 particles were encapsulated in the MgO crystallites with similar particle size decomposed from brucite and prevented from reacting with CaO impurities in magnesite. The mixing homogeneity of magnesite particles and ZrO 2 particles and the direct contact between ZrO 2 and CaO impurities in magnesite has a crucial effect on the formation of intergranular CaZrO 3 phases. Furthermore, the intergranular CaZrO 3 phases could enhance the bonding of magnesia grains and have great potential for improving the service performance of magnesia.
Li Qiang,Wang Fuling,Wang Yanling,Forson Kobina,Cao Lili,Zhang Chenglin,Zhou Chang,Zhao Bo,Chen Jiashuo
Guar fracturing technology has been considered as a kind of popular EOR technology, but the weak static suspension capacity becomes a challenge due to the poor temperature resistance and stability of guar fracturing fluid. The main goal of this investigation is to explore the effect of different factors on the high-pressure static sand suspension of guar gum fracturing fluid by a synthetic efficient nano-ZrO 2 cross-linker. In particular, a mechanism of static suspended sand of nano-ZrO 2 cross-linker is analyzed by microscopic simulation. The adsorption performance of guar fracturing fluid on the shale surface is also studied for analyzing the environmental pollution and damage of guar gum fracturing fluid to shale reservoirs after cross-linking in this investigation. The results obtained that the inclusion of a small content of nano-ZrO 2 cross-linker (0.4%) leads to an apparent increase of fracturing fluid viscosity and decrease in the falling quality of gravel (104 mPa·s and 0.3 g) compared to the classical cross-linker (63 mPa·s and 3.5 g). The lower adsorption capacity of guar fracturing fluid containing nano-ZrO 2 cross-linker on the shale surface means that it has a weaker pollution ability to the shale reservoir than the commercially available cross-linker. Meanwhile, the grid structure density formed by nano-cross-linker and guar gum is considered to be the key factor to significantly change the suspended sand capacity. The investigation of nano-cross-linker cannot only provide necessary theoretical technology and data support for the stability of water-based fracturing fluid, efficient sand carrying, and the development of water-based fracturing technology, but also effectively protect the underground shale reservoir.
A series of cross-linked multiblock copoly(arylene ether sulfone) ionomer/nano-ZrO2 (CLQCPAES/nano-ZrO2) composite anion exchange membranes were prepared via block copolymerization, bromomethylation, ultrasonication blending, self-crosslinking, quaternization and alkalization. The structure, and the surface and cross section morphology of the CLQCPAES/nano-ZrO2 composite membranes were characterized by solubility tests, FT-IR, XRD and SEM analyses. The combination of the determined results revealed that the CLQCPAES/nano-ZrO2 composite membranes are a complex cross-linking networks of hydrophobic domains/hydrophilic domains/nano-ZrO2 with a clear zonal distribution of uniform nano-sized particles in the hydrophilic domains, when the nano-filler loading was below 7.5%. Basic performances of the CLQCPAES/nano-ZrO2 composite membranes were assessed to investigate their application in fuel cells in terms of the water uptake, swelling ratio, ion exchange capacity (IEC), hydroxide conductivity, thermal and mechanical properties, and alkaline stability. The modification of anion exchange membranes with multiblock ionomer structures, the use of a cross-linking technique and the introduction of nano-ZrO2 particles greatly enhanced the water uptake, hydroxide conductivity, mechanical properties and alkaline stability of the composite membranes. In particular, the CLQCPAES/7.5%ZrO2 membrane with an IEC value of 1.23 mmol g−1 exhibited the best comprehensive properties and constitutes a good potential candidate for an anion exchange membrane to be used in AEMFCs.
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