Engineering properties and microstructure of expansive soil treated with nanographite powder

To reduce geological disasters caused by expansive soil,it is crucial to use a new type of modified material to rapidly improve soil strength instead of traditional soil improvement materials such as lime and cement.Nanographite powder(NGP)has excellent properties,such as high adsorption,conductivity,and lubrication,since it has the characteristics of small size,large specific surface area,and high surface energy.However,previous studies on the improvement of expansive soil with NGP are not processed enough.To study the improvement effect of NGP on expansive soil,non-load swelling ratio tests,consolidation tests,unconfined compressive strength tests,mercury injection tests,and micro-CT tests on expansive soil mixed with different NGP contents were performed.The results show that the non-load swelling ratio,mechanical properties,and porosity of expansive soil show some increasement after adding NGP.The strength of expansive soil reaches the maximum when the NGP content is 1.450%.The cumulative mercury volume and compressive strain of expansive soil reach the maximum with the 2.0%NGP content.Finally,the modification mechanism of swelling,compressibility,microstructure,and compressive strength of expansive soil by NGP is revealed.

Characterization of Conductive Nanographite Melamine Composites

Composites based on melamine formaldehyde resins filled with exfoliated graphite or so called nanographite have been prepared to achieve electrical conductivity and improve mechanical strength and thermal stability. The nanographite was synthesized by thermal treatment of oxidized graphite and the incorporation into the melamine matrix was accomplished during the melamine formaldehyde reaction. A homogenous dispersion of the filler in the matrix and the forming of a connecting network based on graphite sheets were proved by SEM images. The graphite filler was able to increase the flexural strength of molded testing specimens compared to unfilled resins and electrical conductivity was achieved starting at 2 wt% nanographite.

Formation of Nanographite Using GaPO_4-LTA as Template

An attempt was made to prepare nanographite with uniform size by pyrolysis of 4-methyl pyridine (MPy), which is the structure-directing agent for the formation of GaPO4-LTA single crystals, in the GaPO4-LTA frame-work at 760 ℃. The as-prepared nanographite has been examined by Raman spectroscopy, transmission electron microscopy (TEM), electron spin resonance (ESR) and magnetization characterizations. The TEM image shows that the size of individual nanographite particles is about 7 nm, and it is proved that there are spins of sp2-type (π-type) radical electrons localized on the zigzag edge sites of the nanographite. The magnetic susceptibility of the nanographite shows crossover from a high-temperature diamagnetic to a low-temperature paramagnetic behavior, in good agreement with the theoretical expectation.

Preparation for Graphite Materials and Study on Electrochemical Degradation of Phenol by Graphite Cathodes

Nanographite flake through ultrasound dispersing expanded graphite which got by chemical oxidation and microwave puffing method have been prepared by natural flake graphite. The microstructures of natural flake graphite, expanded graphite and nanographite sheets were characterized by means of SEM, XRD, FTIR and Raman;the cathodes were made by NG, EG and nanographite, respectively;the electrolysis phenol was conducted by the diaphragm cell prepared cathode and the Ti/RuO2 anode. The results showed that the thickness of graphite flake was 18 nm, and the grain size and particle size decreased compared with the NG and EG;Nano-G showed the best electrochemical properties;in the diaphragm electrolysis system with the aeration conditions, the degradation rate of phenol reached 89.5% COD reached 81.3% under 120 min’s electrolysis, which was far above the degradation rate of phenol of EG cathode and NG cathode.

Assessment of water-based cutting fluids with green additives in broaching

In order to improve the cutting performance in broaching,the lubrication and cleaning effects offered by water-based cutting fluids with green additives need to be studied from the viewpoint of green manufacturing.Therefore,water-based solutions with castor oil,surfactant(linear alkylbenzene sulfonate,LAS),and nanographite were prepared by ultrasonic agitation and sprayed into the zone of broaching via atomization.The performances of the cutting fluids,in terms of the viscosity,specific heat,wetting angle,and droplet size,were evaluated to discuss their effects on the broaching load.Among the fluids,the addition of LAS into oil-in-water(WO-S),where its cutting fluid with 10 wt.%castor oil and 1.5 wt.%surfactant,exhibited the lowest broaching force.With regard to the lubricating and cleaning mechanisms,WO-S has good wettability and permeability,and hence,can lubricate the cutting edge of the tool to decrease the cutting load,cool the cutting edge to keep it sturdy,and clean the surface of the cutting edge to keep it sharp.The results reveal that the simultaneous addition of castor oil and LAS had remarkable effects on the lubrication and cleaning,and resulted in a broaching load reduction of more than 10%compared to commercial cutting fluids.However,the addition of nanographite could not improve the lubrication owing to its agglomeration.