Study of an Energetic-oxidant Co-crystal: Preparation, Characterisation, and Crystallisation Mechanism

An energetic co-crystal consisting of the most promising military explosive 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) and the most well-known oxidant applied in propellants ammonium perchlorate has been prepared with a simple solvent evaporation method. Scanning electron microscopy revealed that the morphology of co-crystal differs greatly from each component. The X-ray diffraction spectrum, FTIR, Raman spectra, and differential scanning calorimetry characterisation further prove the formation of the co-crystal. The result of determination of hygroscopic rate indicated the hygroscopicity was effectively reduced. At last, the crystallisation mechanism has been discussed

Localization model description of the interfacial dynamics of crystalline Cu and

Many of the special properties of nanoparticles (NPs) and nanomaterials broadly derive from the significant fraction of particles (atoms, molecules or segments of polymeric molecules) in the NP interfacial region in which the interparticle interactions are characteristically highly anharmonic in comparison to the bulk material. This leads to relatively large mean square particle displacements relative to the material interior, often resulting in a strong increase interfacial mobility and reactivity in both crystalline and glass NPs. The ‘Debye–Waller factor’, or the mean square particle displacement $$ on a ps ‘caging’ timescale relative to the square of the average interparticle distance \upsigma ^{2}$$, provides an often experimentally accessible measure of the strength of this anharmonic interaction. The Localization Model (LM) of the dynamics of condensed materials relates this thermodynamic property to the structural relaxation time$$\tau _{\alpha }$$, determined from the intermediate scattering function, without any free parameters. Moreover, the LM allows for the prediction of the diffusion coefficient D when combined with the ‘decoupling’ or Fractional Stokes-Einstein relation linking$$\tau _{\alpha }$$to D. In the current study, we employed classical molecular dynamics simulation to investigate the structural relaxation and diffusion of model$$\hbox {Cu}_{\mathrm {64}}\hbox {Zr}_{\mathrm {36}}$$metallic glass and Cu crystalline NPs with different sizes. As with previous studies validating the LM on model bulk and crystalline materials, and for the interfacial dynamics of thin crystalline and metallic glass films, we find the LM model also describes the interfacial dynamics of model crystalline metal (Cu) and metallic glass ($$\hbox {Cu}_{\mathrm {64}}\hbox {Zr}_{\mathrm {36}})$$ NPs to a good approximation, further confirming the generality of the model

Defect chemistry in 2D atomic layers for energy photocatalysis

Conspectus Photocatalysis is a promising technology to simultaneously relieve the worldwide energy crisis and environmental pollution issues, providing an effective avenue for carbon neutrality. Numerous efforts have been dedicated to the reasonable design of photocatalytic materials to improve the photocatalytic efficiency. Among these, building two-dimensional (2D) atomic layers with suitable energy band structure offers an alternative configuration to optimize bulk charge separation and surface reactions at the same time. The limited thickness of the 2D atomic layer favors the rapid bulk charge migration to the surface, reducing the recombination of electron-hole pairs and boosting the bulk charge separation efficiency. Moreover, the 2D atomic layer configuration makes the surface atomic structure easily regulated, for example, engineering defects. In 2D atomic layers, even infinitesimal amounts of defects can unlock the great potential that exists for tailoring the carrier concentration, electronic states, spin nature, and so on. The specific defects can introduce defect energy levels into the band gap and extend the light absorption. The carrier dynamic can be regulated by the defects and optimize the charge separation efficiency. Moreover, these defect configurations provide specific reactive sites to bind with different molecules, tuning the intermediate formation and facilitating reaction progression. In this Account, we present the group’s recent research progress in search of defective 2D atomic layers for energy photocatalysis. We start with the classification of defects in the 2D atomic layers, such as anion vacancies, cation vacancies, vacancy associates, single atom doping, pits, amorphization, grain boundaries, and single-metal-atom chains. Then, different defect controlling formation strategies are introduced to engineer various defects in 2D atomic layers with an emphasis on formation principle, such as thickness controlling, curve controlling strategy, template directed strategy, etching strategy, and matrix induction. Additionally, the critical roles of defects for enhanced photocatalytic performance from different aspects are highlighted, including electronic structure tailoring, charge trapping, interface interaction strengthening, reactant adsorption and activation, molecular intermediate interaction force tuning, and reaction energy barriers and paths, to acquire the fundamental insight of the photocatalytic mechanism and elucidate the relationship between the defective local allocation and photocatalytic behavior. Finally, diversified energy-related photocatalytic applications over defective 2D atomic layers are discussed, such as water splitting, N2 reduction, and CO2 reduction. We hope that this Account can facilitate the development of defect chemistry in 2D atomic layers and realize high-efficiency photocatalysis.Ministry of Education (MOE)This work was supported by National Natural Science Foundation of China (No. 22205108), Jiangsu Specially Appointed Professorship, Fundamental Research Funds for the Central Universities (No. 30922010302), Start-Up Grant from Nanjing University of Science and Technology (No. AE89991/397), Singapore Ministry of Education AcRF Tier 2 (MOE2019-T2-2-105 and MOE-MOET2EP10121-0006), AcRF Tier 1 (RG7/21)

Defective materials for CO₂ photoreduction: from C₁ to C₂₊ products

Photocatalytic CO2 conversion to carbon-based products has been proven as a versatile method to manage carbon balance. Engineering defects into photocatalysts is an effective strategy to maneuver their performance for CO2 reduction. This critical review summarizes the advantages, state-of-the-art progress, remaining challenges, and perspectives regarding defective materials for CO2 photoreduction, especially based on two-dimensional materials. Different types of defects are employed to tailor the electronic structure, atomic coordination configuration, carrier concentration or electrical conductivity for CO2 photoreduction, namely anion vacancies, cation vacancies, vacancy pairs, planar defects and volume defects. The strategies for defect construction, defect identification are summarized. The key roles of various defects for CO2 photoreduction from various aspects are presented, such as light absorption and electronic structure, charge separation and transfer, reactant adsorption and activation, reaction energy barriers, reaction pathways. Especially, the C[sbnd]C coupling via defect engineering is highlighted, certainly shows greater potentiality for future CO2 photoreduction. Finally, major challenges and opportunities regarding the future exploration of defective materials for CO2 photoreduction are presented.Ministry of Education (MOE)This work was supported by National Natural Science Foundation of China (22205108), Jiangsu Specially Appointed Professorship, Singapore Ministry of Education AcRF Tier 2 (MOE2019-T2-2-105), AcRF Tier 1 RG4/17, RG161/19, Fundamental Research Funds for the Central Universities (No. 30922010302) and Start-Up Grant from Nanjing University of Science and Technology (No. AE89991/397)

Effect of Material Properties on the Foaming Behaviors of PP-Based Wood Polymer Composites Prepared with the Application of Spherical Cavity Mixer

For the low weight and high strength, the microcellular extrusion foaming technology was applied in the preparation of polypropylene (PP)-based wood polymer composites, and the spherical cavity mixer was used to construct an experimental platform for the uniform dispersion of wood flour (WF). The effects of PP molecular configuration on the composite properties and cell morphology of samples were also investigated. The experimental results indicated that the application of a spherical cavity mixer with a cavity radius of 5 mm could effectively improve the mixing quality and avoid the agglomeration of WF. In addition, compared with the branched molecule, the linear molecule not only increased the melting temperature by about 10 °C, but also endowed composites with a higher complex viscosity at a shear rate lower than 100 s−1, which contributed to the cell morphology of more microporous samples

Fabrication of Magnetic Porous Silica Submicroparticles for Oil Removal from Water

With the development of world oil production and the increase of transportation, oil spillage accidents showed a rising trend, which was not only harmful to the ecological environment but also a huge threat to people’s health. Herein, we reported a novel kind of linear-coated magnetic silica submicrometer materials with controlled porosity for oil spill cleanup. The results showed that the submicrometer composite materials with superhydrophobicity, superoleophilicity and good magnetic response, which had a significant effect on oil absorption and was used to absorb different oils up to 11.51 times of its own weight. More importantly, the oil-absorbed material could be recycled in the auxiliary magnetic field and still exhibited an excellent performance after the 20th cycle. With a combination of simple synthesis process, magnetic responsivity, and excellent hydrophobicity, the modified magnetic porous silica submicroparticles have broad application prospects as a promising absorbent

Fabrication of Magnetic Porous Silica Submicroparticles for Oil Removal from Water

With the development of world oil production and the increase of transportation, oil spillage accidents showed a rising trend, which was not only harmful to the ecological environment but also a huge threat to people’s health. Herein, we reported a novel kind of linear-coated magnetic silica submicrometer materials with controlled porosity for oil spill cleanup. The results showed that the submicrometer composite materials with superhydrophobicity, superoleophilicity and good magnetic response, which had a significant effect on oil absorption and was used to absorb different oils up to 11.51 times of its own weight. More importantly, the oil-absorbed material could be recycled in the auxiliary magnetic field and still exhibited an excellent performance after the 20th cycle. With a combination of simple synthesis process, magnetic responsivity, and excellent hydrophobicity, the modified magnetic porous silica submicroparticles have broad application prospects as a promising absorbent

Massive preparation and characteristics of submicron dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50)

In order to make the shape of raw dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) particles more regular and suitable for coating, modification, charging and other applications, submicron TKX-50 was prepared with average particle size of 120 nm through a low-temperature ball milling technique by 1 kg per batch in this study. The morphology and structure of prepared submicron TKX-50 were characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD) and fourier transform infrared spectroscopy (FT-IR). The thermal decomposition properties were analyzed by thermogravimetric analysis (TG) and differential scanning calorimetric (DSC) techniques, and the thermal decomposition process of submicron TKX-50 was investigated using TG-FTIR technology, by which the gas products would be detected. Moreover, the mechanical sensitivities were also evaluated. The results showed that the prepared submicron TKX-50 was spherical in shape and the structures of crystal and molecule had no change compared to raw TKX-50. The thermal decomposition temperature of submicron TKX-50 was shifted about 14-18 ºC towards lower temperature, while its activation energy value was increased according to the Kissinger method and the Kissinger-Akahira-Sunose (KAS) method. The most-abundant decomposition products of submicron TKX-50 were HCN, CO2, N2O, NH3 and a small amount of H2O. In addition, submicron TKX-50 showed excellent safety, which guaranteed its predictable applications on ammunitions with high energy and low sensitivity