Neural network-based prediction of auto-ignition temperature of ternary mixed liquids.

Auto-ignition temperature (AIT) is one of the crucial exponents in the design of fire and explosion safety measures. Therefore, in this study, quantitative structure-property relationship approach was used to predict the AIT of ternary hybrid liquids based on molecular structure information. The optimal molecular descriptors were calculated and filtered using Mordred software. Twelve mixing rules were proposed for calculating molecular descriptors of mixtures. A prediction model for the AIT value of binary liquid mixtures was developed, validated and evaluated using a back propagation neural network (BPNN) and a one-dimensional convolutional neural network (1DCNN). The relative contribution and positive and negative correlations between individual molecular descriptors and AIT in the model were interpreted using the shapley additive explanations method. The results show that BPNN and 1DCNN models using mixing rule 1 have the best fitting ability, stability and prediction ability. The determination coefficient of the BPNN and 1DCNN models in the training set were 0.996 and 0.992, the root mean square errors were 3.613 °C and 5.284 °C, the mean absolute errors were 2.483 °C and 4.144 °C, the nash efficiency coefficient was 0.996 and 0.992, respectively, the willmott index was 0.999 and 0.998. and the values of the top three molecular descriptors of relative contribution, SssCH2, SsOH and SsCH3, were negatively correlated with the AIT values. The BPNN and 1DCNN models provide an accurate and reliable method for predicting ternary mixing liquid AIT.

Construction of composite chitosan-glucose hydrogel for adsorption of Co2+ ions.

Glucose and chitosan are compounded on a hydrogel (GC hydrogel) by an initiator and a crosslinking agent, and GC hydrogel are applied to treat Co2+ in wastewater. The samples were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). In the study of adsorption process, the influence of five factors on the adsorption process was studied. On this basis, the adsorption thermodynamics, kinetics and adsorption mechanism of isotherm were discussed. The results showed that the adsorption capacities of GC hydrogels for Co2+ 202mgg-1 at 20°C, pH=7 and adsorbent dosage is 0.01g. The study shows that the adsorption of heavy metal ions by GC hydrogel adsorbent is a single molecule chemisorption of the spontaneous process. In addition, GC hydrogel adsorbent has good cyclic stability.

Fabrication of Z-scheme Ag3PO4/TiO2 Heterostructures for Enhancing Visible Photocatalytic Activity.

In this paper, a synthetical study of the composite Ag3PO4/TiO2 photocatalyst, synthesized by simple two-step method, is carried out. Supplementary characterization tools such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and UV-vis diffuse reflectance spectroscopy were adopted in this research. The outcomes showed that highly crystalline and good morphology can be observed. In the experiment of photocatalytic performance, TiO2400/Ag3PO4 shows the best photocatalytic activity, and the photocatalytic degradation rate reached almost 100% after illuminating for 25 min. The reaction rate constant of TiO2400/Ag3PO4 is the largest, which is 0.02286 min-1, twice that of Ag3PO4 and 6.6 times that of the minimum value of TiO2400. The degradation effect of TiO2400/Ag3PO4 shows good stability after recycling the photocatalyst four times. Trapping experiments for the active catalytic species reveals that the main factors are holes (h+) and superoxide anions (O·- 2), while hydroxyl radical (·OH) plays partially degradation. On this basis, a Z-scheme reaction mechanism of Ag3PO4/TiO2 heterogeneous structure is put forward, and its degradation mechanism is expounded.

Anchoring Plasmonic Ag@AgCl Nanocrystals onto ZnCo2O4 Microspheres with Enhanced Visible Photocatalytic Activity.

In this work, a comprehensive investigation of the composite Ag@AgCl/ZnCo2O4 microspheres photocatalyst, prepared by a facile two-step method, is presented, and using complementary characterization tools such as X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X ray spectroscopy (EDX), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy (DRS), and Brunauer-Emmett-Teller (BET). Results show that the composite Ag@AgCl/ZnCo2O4 photocatalyst has good microspheres morphology and high crystalline and its absorption intensity in the whole spectrum range is higher than that of pure ZnCo2O4. It is observed that the specific surface area of the composite Ag@AgCl/ZnCo2O4 photocatalyst and the adsorption efficiency of rhodamine B (RhB) increase as a result of deposition of Ag@AgCl. In the Ag@AgCl/ZnCo2O4 degradation system of RhB, the photocatalytic degradation rate of 0.2Ag@AgCl/ZnCo2O4 becomes 99.4% within 120 min, and RhB is almost completely degraded. The reaction rate constant of composite 0.2Ag@AgCl/ZnCo2O4 photocatalyst is found to be 0.01063 min-1, which is 1.6 times that of Ag@AgCl and 10 times of the minimum value of ZnCo2O4. In addition, the radical capture experiment indicates that, in the reaction system of Ag@AgCl/ZnCo2O4, the main oxidative species of Ag@AgCl/ZnCo2O4 photocatalyst are superoxide anion (O·- 2- 2) and hole (h+) and not hydroxyl radical (·OH). Based on the results, a Z-scheme plasmon photocatalytic mechanism of Ag@AgCl/ZnCo2O4 composite system is proposed, to elucidate the RhB degradation.

Robust ultrafine ruthenium nanoparticles enabled by covalent organic gel precursor for selective reduction of nitrobenzene in water.

Metal nanoparticles (NPs) supported on nitrogen-doped porous carbon (NPC) are one type of promising heterogeneous catalysts. The tuning and understanding of metal-support interactions are crucial for the design and synthesis of highly durable and efficient heterogeneous catalytic systems. Here, we present an effective strategy to integrate ultrafine metal NPs into NPC via utilizing a covalent organic gel (COG) as the precursor for the first time. The ruthenium (Ru) NPs were uniformly dispersed in NPCs with the average size as low as 1.90 ± 0.4 nm. Irrespective of their ultrafine size, Ru NPs showed unprecedented stability and recyclability in Ru-catalyzed reduction of nitrobenzene and were greatly superior to commercial Ru/C and NPC-supported Ru NPs synthesized by the traditional post-loading method. This synthetic strategy can be extended to the synthesis of other metal or alloy NPs for a variety of advanced applications.

Optimized synthesis of novel hydrogel for the adsorption of copper and cobalt ions in wastewater.

Metal ions in wastewater endanger the environment and even human life. In this study, an optimized method was used to synthesize an excellent hydrogel to treat these metal ions. The samples were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA), and applied to treat the Cu(ii) and Co(ii) ions in wastewater. In the adsorption experiment, the influential factors such as pH, adsorption time, adsorbent dosage and concentration of heavy metal ions and regeneration efficiency were evaluated, and the adsorption kinetics, isotherms and thermodynamics were studied. The orthogonal optimization results show that the best condition for synthesis was when the degree of neutralization of acrylic acid (A) was 70%, the quantity of glucose (B) was 0.2 g, the quantity of chitosan (C) was 0.05 g, and the quantity of initiator (D) was 0.03 g. The influence of the four factors was in the order D > B > C > A. The adsorption performance was optimal under neutral conditions and the dosage of 0.02 g adsorbent was chosen as the best. Experiments show that the composite hydrogels exhibited excellent performance under optimal conditions: at 20 °C and pH = 7, the adsorption capacity of 100 mg L-1 of Cu(ii) by 0.01 g hydrogel was 286 mg g-1. The adsorption process of heavy metal ions by hydrogels conforms to pseudo-second-order kinetics and Langmuir isotherm model, which indicate a spontaneous endothermic reaction. Moreover, after five cycles, the removal rates of Cu(ii) and Co(ii) were 81% and 74.8%, respectively.

Anisotropic Compressive Behavior of Functionally Density Graded Aluminum Foam Prepared by Controlled Melt Foaming Process.

Aluminum foams with a functionally graded density have exhibited better impact resistance and a better energy absorbing performance than aluminum foams with a uniform density. Nevertheless, the anisotropic compression behavior caused by the graded density has scarcely been studied. In this paper, a density graded aluminum foam (FG) was prepared by a controlled foaming process. The effect of density anisotropy on the mechanical behavior of FGs was investigated under quasi-static compression and a low-velocity impact. Digital image correlation (DIC) and numerical simulation techniques were used to identify deformation mechanisms at both macro and cell levels. Results show that transverse compression on FGs lead to a higher collapse strength but also to a lower energy absorption, due to the significant decrease in densification strain and plateau stress. The deformation behavior of FGs under longitudinal compression was dominated by the progressive extension of the deformation bands. For FGs under transverse compression, the failure mode of specimens was characterized by multiple randomly distributed deformation bands. Moreover, the transverse compression caused more deformation on cells, through tearing and lateral stretching, because of the high lateral strain level in the specimens. It was concluded that the transverse compression of FGs lead to a lower plateau stress and a lower cell usage, thus resulting in a poorer energy absorption efficient; this constitutes a key factor which should be taken into consideration in structural design.

Fabrication and Characterization of Nanoenergetic Hollow Spherical Hexanitrostibene (HNS) Derivatives.

The spherization of nanoenergetic materials is the best way to improve the sensitivity and increase loading densities and detonation properties for weapons and ammunition, but the preparation of spherical nanoenergetic materials with high regularization, uniform size and monodispersity is still a challenge. In this paper, nanoenergetic hollow spherical hexanitrostibene (HNS) derivatives were fabricated via a one-pot copolymerization strategy, which is based on the reaction of HNS and piperazine in acetonitrile solution. Characterization results indicated the as-prepared reaction nanoenergetic products were HNS-derived oligomers, where a free radical copolymerization reaction process was inferred. The hollow sphere structure of the HNS derivatives was characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), and synchrotron radiation X-ray imaging technology. The properties of the nanoenergetic hollow spherical derivatives, including thermal decomposition and sensitivity are discussed in detail. Sensitivity studies showed that the nanoenergetic derivatives exhibited lower impact, friction and spark sensitivity than raw HNS. Thermogravimetric-differential scanning calorimeter (TG-DSC) results showed that continuous exothermic decomposition occurred in the whole temperature range, which indicated that nanoenergetic derivatives have a unique role in thermal applications. Therefore, nanoenergetic hollow spherical HNS derivatives could provide a new way to modify the properties of certain energetic compounds and fabricate spherical nanomaterials to improve the charge configuration.

Facile fabrication of Cu-based alloy nanoparticles encapsulated within hollow octahedral N-doped porous carbon for selective oxidation of hydrocarbons.

Hollow carbon materials with versatile chemical compositions and complicated shell architectures hold great promise in heterogeneous catalysis. However, it is a daunting challenge to synthesize metal alloy nanoparticles (NPs) supported by hollow nanostructures. Herein, we present a simple approach for facile fabrication of Pd-Cu alloy NPs embedded in hollow octahedral N-doped porous carbon (Pd-Cu@HO-NPC). The hollow material is derived from HKUST-1 coated by an imidazolium-based ionic polymer (ImIP). Water-sensitive HKUST-1 is simultaneously removed in the process of anion exchange between bromide in the ImIP shell and tetrachloropalladate in aqueous medium. The released Cu(ii) ions and exchanged Pd(ii) ions serve as Cu and Pd sources in the subsequent pyrolysis. The resultant Pd-Cu@HO-NPC exhibits high catalytic activity, selectivity, stability and recyclability in the aerobic oxidation of hydrocarbons. More attractively, the synthetic strategy is of excellent generality, and could be extended to the synthesis of Cu-based bimetallic and trimetallic alloy NPs, such as Pt-Cu@HO-NPC and Pd-Pt-Cu@HO-NPC. This work highlights the superiority of water-sensitive metal-organic frameworks in the ingenious design of hollow carbon materials incorporated with well-dispersed metal alloy NPs.

General Synthetic Route toward Highly Dispersed Ultrafine Pd-Au Alloy Nanoparticles Enabled by Imidazolium-Based Organic Polymers.

Bimetallic Pd-Au nanoparticles (NPs) usually show superior catalytic performances over their single-component counterparts, the general and facile synthesis of subnanometer-scaled Pd-Au NPs still remains a great challenge, especially for electronegative ultrafine bimetallic NPs. Here, we develop an anion-exchange strategy for the synthesis of ultrafine Pd-Au alloy NPs. Simple treatment of main-chain imidazolium-based organic polymer (IOP) with HAuCl4 and Na2PdCl4, followed by reduction with NaBH4 generated Pd-Au alloy NPs (Pd-Au/IOP). These NPs possess an unprecedented tiny size of 1.50 ± 0.20 nm and are uniformly dispersed over IOP. The electronic structure of the surface Pd and Au atoms is optimized via electron exchange during alloying, a net charge flowing resulting from counteranions is injected into Au and Pd to form a strong ensemble effect, which is responsible for a remarkably higher catalytic activity of Pd-Au/IOP in the hydrolytic dehydrogenation of ammonia borane than those of monometallic counterparts.

Theoretical insight into the solvent effect of H2O and formamide on the cooperativity effect in HMX complex.

The cooperativity effects of the H-bonding interactions in HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane)∙∙∙HMX∙∙∙FA (formamide), HMX∙∙∙HMX∙∙∙H2O and HMX∙∙∙HMX∙∙∙HMX complexes involving the chair and chair-chair HMX are investigated by using the ONIOM2 (CAM-B3LYP/6-31++G(d,p):PM3) and ONIOM2 (M06-2X/6-31++G(d,p):PM3) methods. The solvent effect of FA or H2O on the cooperativity effect in HMX∙∙∙HMX∙∙∙HMX are evaluated by the integral equation formalism polarized continuum model. The results show that the cooperativity and anti-cooperativity effects are not notable in all the systems. Although the effect of solvation on the binding energy of ternary system HMX∙∙∙HMX∙∙∙HMX is not large, that on the cooperativity of H-bonds is notable, which leads to the mutually strengthened H-bonding interaction in solution. This is perhaps the reason for the formation of different conformation of HMX in different solvent. Surface electrostatic potential and reduced density gradient are used to reveal the nature of the solvent effect on cooperativity effect in HMX∙∙∙HMX∙∙∙HMX. Graphical abstract RDG isosurface and electrostatic potential surface of HMX∙∙∙HMX∙∙∙HMX.

Concentration-dependence of the explosion characteristics of chlorine dioxide gas.

The explosion characteristics of chlorine dioxide gas have been studied for the first time in a cylindrical exploder with a shell capacity of 20 L. The experimental results have indicated that the lower concentration limit for the explosive decomposition of chlorine dioxide gas is 9.5% ([ClO(2)]/[air]), whereas there is no corresponding upper concentration limit. Under the experimental conditions, and within the explosion limits, the pressure of explosion increases with increasing concentration of chlorine dioxide gas; the maximum pressure of explosion relative to the initial pressure was measured as 0.024 MPa at 10% ClO(2) and 0.641 MPa at 90% ClO(2). The induction time (the time from the moment of sparking to explosion) has also been found to depend on the concentration of chlorine dioxide gas; thus, at 10% ClO(2) the induction time was 2195 ms, but at 90% ClO(2) the induction time was just 8 ms. The explosion reaction mechanism of ClO(2) is of a degenerate chain-branching type involving the formation of a stable intermediate (Cl(2)O(3)), from which the chain-branching occurs. Chain initiation takes place at the point of ignition and termination takes place at the inner walls of the exploder.

(R,R)-4,4'-Dibromo-2,2'-[cyclo-hexane-1,2-diylbis(nitrilo-methyl-idyne)]diphenol.

The mol-ecule of the title compound, C(20)H(20)Br(2)N(2)O(2), lies on a twofold axis. It contains two stereogenic C atoms with R chirality and thus it is the enatiomerically pure R,R-diastereomer. There is an intra-molecular O-H⋯N hydrogen bond.