Ultramicro molybdenum nitride powder prepared using high-energy mechanochemical method

Using the specially designed mechanochemical ball-mill equipment, ultramicro molybdenum nitride powders were prepared from pure molybdenum powders in ammonia atmosphere at room temperature by high-energy ball milling. The structure and the particle size of the powders were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. The results show that the mass ratio of grinding media to powder was 8：1, after milling for 30 h the Mo2N of fcc structure was obtained, and the average particle size of the powders was around 100 nm. It is found that the chemisorption of ammonia onto the fresh molybdenum surfaces created by milling was the predominant process during solid-gas reaction, and the energy input due to introduction of highly dense grain boundaries and lattice defects offered the activation energy for the transition from Mo-N chemisorption to molybdenum nitride. In addition, the change of Mo electronic undersaturation induced by the grain refining accelerated the bonding between Mo and N. The mechanism model of whole nitriding reaction was given, During the high-energy ball milling processing, the rotational speed of milling played a critical role in determining the overall reaction speed.

Studies on Mechanochemical Method to Synthesize LDH Nanoparticles

Magnesium-ferrum layered double hydroxide （Mg-Fe-LDH） and zinic-aluminum layered double hydroxide （Zn-A1-LDH） compounds were prepared through a mechanochemical method. The influence of molar ratio of M2＋ to M3＋ （R value） on the property ofLDH nanoparticles has been studied and the results showed that R=3 ： 1 is the optimum value for the both samples. Besides pure water, the mixture of water and ethanol with the volume ratio of 3 ; 1 is also used to wash the precipitates and used as suspending agent during the peptization process and our results showed that the addition of ethanol can improve the monodispersity of LDH nanoparticles greatly.

Peroxymonosulfate assisted mechanochemical method for the degradation of phenanthrene in contaminated soils

In recent years,mechanochemical method has received attention in the field of degrading pollutants,especially for persistent organic pollutants.In this study,peroxymonosulfate(PMS)as a co-grinding reagent,coupled with contaminated soil were placed in a ball mill for mechanochemical reaction.Through investigating the influences of ball-milling parameters on the degradation efficiency,the reaction conditions were optimized.Under the optimal condition(mass ratio of soil to oxidant is 10:1,mass ratio of ball to material is 30:1,rotation speed of ball mill is 400 rpm),more than 98%phenanthrene(PHE)in contaminated soil could be degraded within 4 h.Meanwhile,the effects of soil organic matter content and soil type on the degradation efficiency were investigated.The results showed that the organic matter content was negatively correlated with the degradation efficiency.XPS analysis provided evidence for the breakage of the CeC bond and confirmed that Fe in soil was an important factor in activating PMS.XRD further verified the destruction of PHE structure.GC-MS analysis was performed to identify the intermediates and possible pathways were proposed.

Hydrodesulfurization activities of NiMo catalysts supported on mechanochemically prepared Al-Ce mixed oxides

Al2O3-CeO2 supports containing 1-10 wt%Ce were prepared mechanochemically by milling aluminum and/or cerium nitrates with NH4HCO3.Heteropolymolybdate,（NH4）4NiMo6O（24）,was used as the precursor of the Ni and Mo to prepare NiMo6/Al2O3-CeO2 components in catalysts by impregnation method.The physicochemical properties of the catalysts were determined using chemical analysis,X-ray diffraction,temperature-programmed H2 reduction,temperature-programmed NH3 desorption,X-ray photoelectron spectroscopy（XPS）,and the Brunauer-Emmett-Teller method.The catalyst acidity decreased with increasing Ce concentration in the support.XPS showed that the NiS/MoS ratio decreased two-fold for the Ce-modified alumina support.NiMo6/Al2O3,which had the highest acidity,showed the highest activity in hydrodesulfurization of 1-benzothiophene（normalized per weight of catalyst）.The concentration of surface MoOxSy species（which is equal to the concentration of Mo^（5＋）） gradually decreased to zero for catalysts with Ce concentrations 10 wt%.However,the activities of all the catalysts prepared mechanochemically from Al2O3 and Al2O3-CeO2supports significantly exceeded that of a reference NiMo6/Al2O3 catalyst prepared by impregnation method using the same precursor and with the same composition.

A novel method for AFRPs burrs removal:Principle of mechanochemo-induced fiber fracture

Burrs generated during the machining of Aramid-Fiber-Reinforced Composites(AFRPs)pose a challenge for the production efficiency of aircraft and helicopter housing parts.Existing studies have generally attempted to suppress burrs by referring to delamination suppression methods.In contrast to stratification,burrs are remediable machining defects.As such,a mechanochemical method with burrs trimming technological strategy are implemented to effectively combat burrs.Herein,we clarify the mechanism by which aramid fibers cannot be cut off using analytical and numerical models.In addition,the mechanism of fiber fracture with Modified Polyurethane Reactive Polymer(M-PUR),and development of anti-burr devices(thermostatic adhesive sealed generator)are discussed.Finally,the experimental results show that the reduction rate in burr length is 87%-91%through the mechanochemical method.The method not only opens a new avenue to solve the burr problem of aramid fibers but also builds an interdisciplinary bridge between polymer science and composite machining.