Graphite oxide has become an important precursor for graphene oxide, reduced graphene oxide, and a wide range of other graphene-based materials or composites. In numerous Hummers’ methods for the preparation of graphite oxide, water is added to promote the oxidization reaction but causes problems of tedious purification and liquid waste, which raises concerns of environment processing cost in the large-scale production of graphite oxide. Herein, we propose a highly efficient oxidization of chemical expandable graphite (CEG) for one-step preparation of graphite oxide while water is not added during the oxidization. This method features a direct separation of the solid reactant from the liquid oxidant, allowing the reuse of waste acid and quick centrifugal washing of products close to neutral pH. This strategy also benefits the highly efficient utilization of the oxidant potassium permanganate (KMnO4), indicated by the high monolayer/bilayer yield (∼90%) of graphene oxide for a KMnO4/CEG mass ratio as low as 2.5. Without the hydration reaction, which generally leads to etching of graphitic sheets, the graphene oxide platelets made from this strategy readily maintain a large size of 30∼110 μm for the CEG of 80 mesh grids (∼175 μm), making the current method suitable for the preparation of thermally and electrically conductive graphene films. This work provides a more efficient and environmentally friendly preparation technique for the industrial production of graphite oxide and relevant materials.

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Abstract:The effect of wall roughness with different lubricant film thicknesses on the characteristics of adhered fuel films of diesel-n-butanol blending fuels after spray impingement has been investigated. Four steel plates with different types of roughness (root mean square height-Sq) that were coated with different lubricant film thicknesses (h l ) were used as impinged walls. The experimental conditions included dry walls (h l = 0), semi-wetted walls (SWW) with different thin oil films (0 < h l /Sq < 1), and fully wetted walls (FWW) with a thick lubricant film (h l > Sq). The results indicate that the adhered fuel mass ratio (ε) of blended fuel with 25% n-butanol (B25) was higher than that of blended fuel with 15% n-butanol (B15) under the same conditions. ε increased with an increase in Sq on the dry walls, but, under SWW conditions, it decreased with an increase in oil film thickness. The fuel film morphology was almost unaffected by the change in Sq, but the results implied that the roughness parameter-Skewness (Ssk) exerted a greater impact. The mean thickness h a and accumulated diameter D l of the adhered fuel film increased with an increase in h l , but, under FWW conditions, the effect of the roughness on the adhered film's features was insignificant.

Traditional cooling methods for electronic chips cannot fully meet the increasing cooling requirement of chips with high heat flux at present, so finding high-efficiency and low-cost cooling functional materials, and cooling methods with high efficiency has been a hot spot to explore. In this article, using Fluent 6, we construct a grooved channel physical model and analyze cooling effects of ethylene glycol/water ice slurry as a functional material on the chips under conditions that baffle lengths are 60mm, 80mm and 90mm, the mass flow rates are 0.4kg/s, 0.3kg/s and 0.2kg/s, and the ice fractions are 15%, 20%, 25% respectively. The results show that the chip cooling rate is increasing effectively and the temperature uniformity is better as well as the utilization rate of the latent heat is increasing as the length of baffles, the mass flow rate and the ice fraction are increasing, but the pressure loss resulted from the local effects of the inlet and corners cannot be ignored. Considering the cooling effect and the uniformity of temperature field, the length of baffles should be 83%-93% of length of flow path. In practical projects, the temperature difference between inlet and outlet should be reduced and the diameter of pipes should be decreased in order to take full advantage of the huge latent heat of the ice slurry while the ice is completely melted. Therefore, ice slurry as a functional material has a great potential to cool high integrated electronic chips.

Ice crystal growth problem have attracted special attention due to in heat transfer deterioration and pump power consumption increasing, by adding very small amount of suitable additives can control the ice crystal growth. This paper investigates ice crystal growth in isothermal condition when adding four different additives, and then calculate the energy between surfactants and ice crystal to explain the effect of different additives. The results indicate that the interaction is Coulomb interaction and Van der Waals interaction for anionic and nonionic surfactant respectively. This method provides a method to explore the mechanism of controlling ice crystal growth with surfactant.