THE STABILITY OF RADIALLY BOUNDED THIN FILMS

The linear stability of radially bounded thinning free films is examined for the case in which the surfaces of the film are initially plane and parallel. The two-dimensional time-dependent drainage flow computed by lubrication theory constitutes the base state. The linear stability of this flow with respect to axially symmetric varicose disturbance is treated in the quasistatic approximation. For thin films, disperse London-van der Waals attractive forces play a key role in determining the critical thickness at rupture, and the results are presented as predictions of critical film aspect ratio as a function of two dimensionless groups which are ratios of the important physical-chemical forces on the film. Predicted critical thicknesses are seen to agree well with the limited available experimental data.     

一个行业就有一种创新

你眼中的中国元素是什么?中国文化历史悠久,对于民族及生活文化更具有独特的气息。中国元素是被中国人认同的、凝结着中华民族传统文化精神,并体现民族的形象、符号或风俗习惯,保持中国文化象征性,均可被视为中国元素,包括少数民族、剪纸工艺、12生肖、舞龙舞狮等,我个人最爱的是剪纸。你印象最深的一件运用中国元素创作的作品是什么?在2009年,Qee制作了一只2.5英寸的剪     

Assessing the catalytic effect of coal ash constituents on the CO2 gasification rate of high ash, South African coal

The catalytic effect of inorganic species, within the ash, on the CO₂ gasification of three South African coals containing similar carbon-structural properties (elemental, structural and petrographical properties) was assessed. The reactivity of the coals with a particle size between 150 and 250 μm was determined in a thermo gravimetric analyser. The reactivity was measured at temperatures between 900 and 1000 °C, pressures between 1 and 10 bar, and fractions of CO₂ between 10 and 30%. For the selected coals, the reactivity decreased with ash content, and was found to be dependent on the composition of the ash. Specifically, the reactivity increased with calcium and magnesium content and alkali index.     

Shear-induced 1-D alignment of alumina nanoparticles in coatings

Atomic Force Microscopy and Scanning Electron Microscopy were used to study shear-induced alignment of alumina and silica nanoparticles in two-component polyurethane clear coatings. 1-D strings of nanoparticles, formed in an extended pearl-necklace fashion were observed near the surfaces of cured films at nanoparticle volume fractions less than 0.05. This alignment is affected by the shear conditions of the application method. When applied by spraying, linear particle strings as long as 5 cm were observed in the direction of shear. Nanoparticle strings were also found, to a lesser extent, when coatings were applied by a drawdown method. The phenomenon was not observed in coatings applied with minimal shear. These particle string formations, in addition to affecting the performance of coatings, may have broader implications in the field of nanomaterials. Our literature searches so far have not uncovered reports of stable, 1-D nanoparticle arrangements with same degree of linearity produced under simple shear with compositions having very low particle loadings. Presented at the 2006 FutureCoat! conference, sponsored by the Federation of Societies for Coatings Technology, in New Orleans, LA, on November 1–3, 2006.     

Hydrodeoxygenation of HMF over Pt/C in a continuous flow reactor

The three‐phase hydrodeoxygenation reaction of 5‐hydroxymethylfurfural (HMF) with H₂ was studied over a 10 wt % Pt/C catalyst using both batch and flow reactors, with ethanol, 1‐propanol, and toluene solvents. The reaction is shown to be sequential, with HMF reacting first to furfuryl ethers and other partially hydrogenated products. These intermediate products then form dimethyl furan (DMF), which in turn reacts further to undesired products. Furfuryl ethers were found to react to DMF much faster than HMF, explaining the higher reactivity of HMF when alcohol solvents were used. With the optimal residence time, it was possible to achieve yields approaching 70% in the flow reactor with the Pt/C catalyst. Much higher selectivities and yields were obtained in the flow reactor than in the batch reactor because side products are formed sequentially, rather than in parallel, demonstrating the importance of choosing the correct type of reactor in catalyst screening. © 2014 American Institute of Chemical Engineers AIChE J, 61: 590–597, 2015     

Examination of radio‐opacity enhancing additives in shape memory polyurethane foams

Three microparticle additives, tungsten (W), zirconium oxide (ZrO₂) , and barium sulfate (BaSO₄) were selected to enhance the radio‐opacity in shape memory polymer (SMP) foam biomaterials. The addition of filler causes no significant alterations of glass transition temperatures, density of the materials increases, pore diameter decreases, and total volume recovery decreases from approximately 70 times in unfilled foams to 20 times (4% W and 10% ZrO₂). The addition of W increases time to recovery; ZrO₂ causes little variation in time to shape recovery; BaSO₄ increases the time to recovery. On a 2.00 mean X‐ray density (mean X.D.) scale, a GDC coil standard has a mean X.D. of 0.62 ; 4% W enhances the mean X.D. to 1.89, 10% ZrO₂ to 1.39 and 4% BaSO₄ to 0.74. Radio‐opacity enhancing additives could be used to produce SMP foams with controlled shape memory kinetics, low density , and enhanced X ‐ray opacity for medical materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42054.     

Exfoliated production of single- and multi-layer graphenes and carbon nanofibres from the carbonisation of a co-polymer

Non-catalysed growth methodologies of carbon nanomaterial synthesis can represent lower costs and greener approaches and cause less damage to the nanomaterial. During the carbonisation of a polyacrylonitrile-based co-polymer, carbon nanofibres (CNFs) and single- and multi-layer graphenes (SLG and MLG) are generated. The accumulated fragmentation products of the co-polymer coalesce to form CNFs that radiate away from the monolith, whose dimensions are linked to their template growth along crests, which were formed from the out-gassing of volatile products of the polymer during the stabilisation step. The slight shrinkage of the carbonising monolith also leads to exfoliation of larger areas of the surface yielding single- and multi-layered graphenes. These results reveal a potentially useful process for the facile production of carbon nanomaterials.