Experimental study of Al agglomeration on solid propellant burning surface and condensed combustion products

Aluminum(Al) particles are commonly added to energetic materials including propellants,explosives and pyrotechnics to increase the overall energy density of the composite,but aluminum agglomeration on the combustion surface may lower the combustion efficiency of propellants,resulting in a loss in twophase flow.Therefore,it is necessary to understand the agglomeration mechanism of aluminum particles on the combustion surface.In this paper,a high-pressure sealed combustion chamber is constructed,and high-speed camera is used to capture the whole process of aluminum accumulation,aggregation and agglomeration on the combustion surface,and the secondary agglomeration process near the combustion surface.The microscopic morphology and chemical composition of the condensed combustion products(CCPs) are then studied by using scanning electron microscopy coupled with energy dispersive(SEM-EDS) method.Results show that there are three main types of condensed combustion products:small smoke oxide particles oxidized by aluminum vapor,usually less than 1 μm;typical agglomerates formed by the combustion of aluminum agglomerates;carbonized agglomerates that are widely distributed,usually formed by irregular movements of aluminum agglomerates.The particle size of condensed combustion products is measured by laser particle size meter.As the pressure increases from 0.5 MPa to 1.0 MPa in nitrogen,the mass average particle size of aluminum agglomerates decreases by 49.7%.As the ambient gas is changed from 0.5 MPa nitrogen to 0.5 MPa air,the mass average particle size of aluminum agglomerates decreases by 67.3%.Results show that as the ambient pressure increases,the higher oxygen content can improve combustion efficiency and reduce the average agglomeration size of aluminum particles.

Morphology of Barium Hydrogen Phosphate Formation Induced by Phosphate-Mineralization Microbe

Phosphate-mineralization microbe was chosen to study the influences of bacterial mixture,filtrate,bacteria solution,bacterial body and bacterial secretion on barium hydrogen phosphate crystal formation.The chemical compositions and structures of samples were characterized with scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,and X-ray diffraction techniques（XRD）,revealing that the crystal morphology of barium hydrogen phosphate was dumbbell-shaped pattern,nanoparticles via aggregate clusters,irregular sphere with different sizes.The results indicated that bacterial body and bacterial secretion could induce the formation of irregular quadrilateral and spheres,respectively.But the effect of bacterial secretion was stronger than that of bacterial body when induced barium hydrogen phosphate crystal in bacteria solution.However,the crystals form could be affected only in bacterial mixture,but filtrate could induce the formation of nanoparticles.As a result,the bacteria and metabolites play an important role in the process of crystal nucleation,growth,and accumulation of barium hydrogen phosphate.

Structural optimization and performance trade-off strategies for semi-crystalline sulfonated poly(arylene ether ketone) membranes in high-concentration direct methanol fuel cells

Direct methanol fuel cells(DMFCs) have attracted extensive attention as promising next-generation energy conversion devices. However, commercialized proton exchange membranes(PEMs) hardly fulfill the demand of methanol tolerance for DMFCs employing high-concentration methanol solutions.Herein, we report a series of semi-crystalline poly(arylene ether ketone) PEMs with ultra-densely sulfonic-acid-functionalized pendants linked by flexible alkyl chains, namely, SL-SPEK-x(where x represents the molar ratio of the novel monomer containing multiple phenyl side chain to the bisfluoride monomers). The delicate structural design rendered SL-SPEK-x membranes with high crystallinity and well-defined nanoscale phase separation between hydrophilic and hydrophobic phases. The reinforcement from poly(ether ketone) crystals enabled membranes with inhibited dimensional variation and methanol penetration. Furthermore, microphase separation significantly enhanced proton conductivity. The SL-SPEK-12.5 membrane achieved the optimum trade-off between proton conductivity(0.182 S cm^(-1), 80 ℃), water swelling(13.6%, 80 ℃), and methanol permeability(1.6 × 10^(-7)cm~2 s^(-1)). The DMFC assembled by the SL-SPEK-12.5 membrane operated smoothly with a 10 M methanol solution, outputting a maximum power density of 158.3 mW cm^(-2), nearly twice that of Nafion 117(94.2 mW cm^(-2)). Overall, the novel structural optimization strategy provides the possibility of PEMs surviving in high-concentration methanol solutions, thus facilitating the miniaturization and portability of DMFC devices.

Petrophysical Texture Heterogeneity of Vesicles in Andesite Reservoir on Micro-Scales

It is of great significance to study the spatial distribution patterns and petrophysical complexity of volcanic vesicles which determine whether the reservoir spaces of the volcanic rocks can accumulate oil and gas and enrich high yields or not.In this paper,the digital images of three different textures of vesicular andesite samples,including spherical vesicular andesite,shear deformation vesicular andesite,and secondary filling vesicular andesite,are obtained by microscopic morphology X-CT imaging technology.The spatial micro-vesicle heterogeneity of vesicular andesite samples with different textures is quantitatively analyzed by fractal and multifractal methods such as box-counting dimension and the moment method.It is found that the shear stress weakens the spatial homogeneity since vesicles rupture are accelerated,elongated directionally,and connected with one another under the strain;the secondary filling breaks the vesicles,which significantly enhances the spatial heterogeneity.In addition,shear stress and secondary filling increase the complexity of vesicle microstructures characterized by different fractal and multifractal parameters.These conclusions will provide important theoretical and practical insights into understanding the degassing of volcanic rocks and prediction of high-quality volcanic reservoirs.

Refining performance of Al–3Ti–0.2C–5Sr on A356 alloy and electron microanalysis of ternary Al–Ti–Sr phases

The effect of Al-3Ti-0.2C-5Sr （wt%） grain refiner on the refining performance and modification of A356 alloy was investigated using optical microscope （OM）.The morphology and crystal structure of ternary Al-Ti-Sr phases in Al-3Ti-0.2C-5Sr refiner were analyzed by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）.The results show that the ternary Al-Ti-Sr phases in Al-3Ti-0.2C-5Sr refiner can promote the grain refining efficiency of A356 alloy.The ternary Al-Ti-Sr phases co-exist in two morphologies,i.e.,blocky-like phase and surround-like phase,besides,which both have the same chemical composition of Al34Ti3Sr.The crystal structure of Al34TiaSr is face-centered cubic,and the lattice parameter is determined to be about 1.52 nm.

Information integration research on cumulative effect of 'Siqi,Wuwei,and Guijing' in Traditional Chinese Medicine

OBJECTIVE:To study the morphological basis of the role of Siqi(cold as winter,cool as autumn,warm as spring,hot as summer),Wuwei(five flavors:sweet,pungent,salty,sour,and bitter),and Guijing(meridian tropism) through the use of information integration.METHODS:A14C-2-deoxy-glucose autoradiography method was adopted to determine the overall impact of treatment with 39 herbs on functions of various tissues and organs.Data was measured at 4hs after a single dose and following the last treatment of repeated doses for a week.Least-squares estimation was used and fitted for each herb regression effect of organs and tissues after singleand repeated treatment.The slope of the regression line represented the cumulative trend of the effect of the herbs(β),and the standard deviation of the slope(Sβ) was compared with those of the untreated animals(t 'test).All significantly cumulative effect trends were applied with an artificial neural network,which integrated the relationship among Siqi,Wuwei,and Guijing with tissues and organs.RESULTS:There is a certain relationship among the Siqi,Wuwei,Guijing and the anatomy of organs and tissues,but the different scores indicate that influence of Siqi,Wuwei,Guijing to anatomy of organs and tissues was a nonlinear state.CONCLUSION:Results demonstrated that the effects of Siqi,Wuwei,and Guijing have a morphological basis,and each concept was associated with multiple anatomical structures.