Particle size effect on surface/interfacial tension and Tolman length of nanomaterials: A simple experimental method combining with theoretical.

Surface tension and interfacial tension are crucial to the study of nanomaterials. Herein, we report a solubility method using magnesium oxide nanoparticles of different radii (1.8-105.0 nm, MgO NPs) dissolved in pure water as a targeted model; the surface tension and interfacial tension (and their temperature coefficients) were determined by measuring electrical conductivity and combined with the principle of the electrochemical equilibrium method, and the problem of particle size dependence is discussed. Encouragingly, this method can also be used to determine the ionic (atomic or molecular) radius and Tolman length of nanomaterials. This research results disclose that surface/interfacial tension and their temperature coefficients have a significant relationship with particle size. Surface/interfacial tension decreases rapidly with a radius <10 nm (while the temperature coefficients are opposite), while for a radius >10 nm, the effect is minimal. Especially, it is proven that the value of Tolman length is positive, the effect of particle size on Tolman length is consistent with the surface/interfacial tension, and the Tolman length of the bulk does not change much in the temperature range. This work initiates a new era for reliable determination of surface/interfacial tension, their temperature coefficients, ionic radius, and Tolman length of nanomaterials and provides an important theoretical basis for the development and application of various nanomaterials.

Rational design of Bi2Sn2O7/Bi5O7I S-scheme heterojunction for visible photocatalytic oxidation of emerging pollutants.

The construction of an S-scheme heterostructure is considered as a promising strategy for enhancing photocatalytic performance. Herein, a three-dimensional Bi5O7I (BOI) microsphere decorated with Bi2Sn2O7 (BSO) nanoparticles was prepared for the first time via a simple ultrasonic-assisted electrostatic self-assembly strategy and used for the degradation of 2,4-dinitrophenylhydrazine. 3 wt% Bi2Sn2O7/Bi5O7I has the highest degradation activity (93.7 %), with an apparent rate constant of 0.0848 min-1, which is 2.55 times that of the original Bi5O7I (0.0333 min-1). Moreover, the optimal binary heterojunction photocatalyst has good reusability and universal applicability. The results of cyclic voltammetry tests clarify that the optimal photocatalyst can provide more surface reactive sites. The results of radical trapping experiments and electron spin resonance indicate that holes (h+) and superoxide radicals are the main active radicals in the degradation process of 2,4-dinitrophenylhydrazine. Photoelectrochemical and photoluminescence confirm that 3 wt% Bi2Sn2O7/Bi5O7I composites exhibit the highest separation rate of photogenerated carriers. Finally, based on the results of experimental studies and theoretical calculations, the S-scheme charge transfer path on Bi2Sn2O7/Bi5O7I composite is determined. This work provides a new perspective on how to design high-performance S-scheme bismuth oxyhalide-based heterojunction photocatalysts for solar energy conversion.

Combustion process of a promising catalyst [Cu(Salen)] for HMX-CMDB propellants.

Metal organic complexes are regarded as a series of promising combustion catalysts for solid rocket propellants. Their effects on the combustion performance of propellants are closely related to the reaction mechanism. Here, the metal-organic complex Cu(Salen) was investigated as a candidate material for the combustion catalyst of the HMX-added composite modified double-base propellant (HMX-CMDB). The combustion performance of the propellant was found to be evidently enhanced in the presence of Cu(Salen) compared with the propellant samples containing Benzoic-Cu or without catalyst. The addition of Cu(Salen) can improve the burning rate and combustion efficiency of the propellant - and greatly reduce the burning rate pressure index. Analysis shows that the addition of Cu(Salen) can increase the combustion area, flame brightness and combustion surface uniformity of the propellant to a higher degree. The sample can spray more beams of bright filaments on the flat combustion section, and the amount of gas generated by decomposition also greatly increases. In addition, Cu(Salen) shows amazing advantages in improving the surface of the propellant and the temperature gradient of the combustion flame.

Efficient activation of peroxydisulfate by g-C3N4/Bi2MoO6 nanocomposite for enhanced organic pollutants degradation through non-radical dominated oxidation processes.

Persulfate-assisted photocatalysis technology is considered to be a promising method for the rapid and efficient degradation of organic pollutants in water environment remediation. In this study, a novel g-C3N4/Bi2MoO6/PDS (CN/BMO/PDS) system is constructed and applied in 2,4-dinitrophenylhydrazine (2,4-DPH) degradation under visible light irradiation. Compared with the CN/BMO system, the degradation rate of 2,4-DPH is significantly improved from 59.7% to 90.2% within 60 min in the combined CN/BMO/PDS system. The enhanced performance can be attributed to the superior synergetic effects of CN/BMO, PDS and visible light irradiation. More importantly, singlet oxygen (1O2) is determined as the main reactive species based on the radical scavenging experiments and electron paramagnetic resonance (EPR), which indicates that the combined system can achieve non-radical oxidative degradation of pollutants, instead of the traditional radical oxidation process. In addition, the active sites of the reaction during the non-radical 1O2 oxidation are calculated by density functional theory (DFT), and the stability and reusability of catalyst are also investigated. In brief, the CN/BMO/PDS system has great application potential for removing organic pollutants from wastewater.

Effect of Bi2WO6/g-C3N4 composite on the combustion and catalytic decomposition of energetic materials: An efficient catalyst with g-C3N4 carrier.

An effective strategy involving a suitable carrier is needed to improve the dispersion, combustion and catalytic performances of catalyst nanoparticles. Herein, a Bi2WO6/g-C3N4 composite employing g-C3N4 as the catalyst carrier was prepared by a one-step in situ hydrothermal method, which was used as the combustion catalyst of solid propellants. The catalyst's structure, morphology and its catalytic decomposition on several energetic materials were characterized by a series of analyses. The optimal ratio of g-C3N4 and Bi2WO6 was systematically determined. The results demonstrate that Bi2WO6/g-C3N4 (4:6) composite can diminish the decomposition temperatures of ammonium perchlorate (AP), cyclotrimethylenetrinitramine (RDX), dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50) and cyclotrimethylenetrinitramine + nitrocellulose (RDX + NC) by 25.0, 5.2, 24.0 and 1.2 (4.9) ° C, and reduce their apparent activation energy by 59.5, 116.7, 11.6 kJ mol-1, respectively. Moreover, the laser ignition tests indicate that Bi2WO6/g-C3N4 can effectively promote the ignition performance of RDX and RDX + NC. A possible mechanism of Bi2WO6/g-C3N4 on AP was proposed. The g-C3N4 catalyst carrier is superior to GO carrier due to its low cost, simple synthesis process, improved combustion and catalytic performances, as well as high N content. These make it have broad engineering application prospects in solid propulsion and other energetic materials.

Construction of S-scheme Bi2WO6/g-C3N4 heterostructure nanosheets with enhanced visible-light photocatalytic degradation for ammonium dinitramide.

Photocatalysis technology is considered as a promising environmental remediation strategy. Herein, photocatalytic degradation of ammonium dinitramide (ADN, main component of propellant) was investigated over Bi2WO6/g-C3N4 (BWO/CN) heterostructure nanosheets prepared by a one-step in-situ hydrothermal method. The operating conditions including ADN initial concentration, catalyst dosage, initial pH, temperature and green oxidizer (hydrogen peroxide) were optimized systematically. Under optimal conditions, the photocatalytic degradation rate of ADN over BWO/CN can reach 98.93% after 80 min visible-light irradiation. Besides, the composite has excellent stability for ADN treatment and nitrate ions are the major degradation products. Furthermore, S-scheme heterojunction mechanism was proposed to explain the extremely high REDOX performance of BWO/CN composite.

Unusual Cu-Co/GO Composite with Special High Organic Content Synthesized by an in Situ Self-Assembly Approach: Pyrolysis and Catalytic Decomposition on Energetic Materials.

An interesting Cu-Co/GO composite with special high organic content was accidentally fabricated for the first time via a one-pot solvothermal method in the mixed solvent of isopropanol and glycerol. The Cu-Co/GO composite was calcined separately in three different atmospheres (air, nitrogen, and argon) and further investigated by a series of characterization techniques. The results indicate that the spinel phase nano-CuCo2O4 composite, nanometal oxides (CuO and CoO), and nanometal mixture of Cu and Co were unexpectedly formed after calcination in air, N2, and Ar atmospheres, respectively, and the possible reaction mechanism was discussed. The specific mass losses of the Cu-Co/GO composite calcined in air, N2, and Ar atmospheres were 28.14 %, 21.68 %, and 23.76 %, respectively. The catalytic decomposition performances of the as-prepared samples for cyclotrimethylenetrinitramine (RDX) and the mixture of nitrocellulose (NC) and RDX (NC + RDX) were investigated and compared via DSC method, and the results demonstrate that Cu-Co/GO composites obviously decrease the thermal decomposition temperature of RDX from 242.3 to 236.5 (before calcination), 238.6 (air), 235.8 (N2), and 228.6 °C (Ar), respectively. Cu-Co/GO(Ar) composite exhibits the best catalytic decomposition performance among all samples, which makes the decomposition temperature of RDX and NC + RDX decrease by 13.7 and 4.9 °C and the apparent activation energy of decomposition for RDX decrease by 110.1 kJ/mol. The enhanced catalytic performance of Cu-Co/GO(Ar) composite could be attributed to the smaller particle size, better crystallinity, and specific well-dispersed metal atoms, whereas the Cu-Co/GO(air) composite after air calcination presents a bad catalytic performance due to the removal of GO.

High-substitute nitrochitosan used as energetic materials: Preparation and detonation properties.

In order to develop new high-energy materials utilizing natural products, a high-substitute nitrochitosan was prepared with different methods. Prepared processes and detonation properties of the nitrochitosan samples were systematically studied. The nitration substitute degree, nitrogen content, exothermic decomposition enthalpy, heat of combustion, impact sensitivity, detonation velocity and detonation pressure of the prepared high-substitute nitrochitosan were 2.01, 16.67 %, -2226 J g-1, -7831.6 ±â€¯116.3 J g-1, >14.2 J, 7.81 km s-1, and 24.03 GPa, respectively. Compared with nitrocellulose (NC), the nitrogen content, impact sensitivity and detonation properties of the prepared nitrochitosan were significantly improved. Nitrochitosan and RDX can form a uniform composite in acetone. With the increase of RDX content, the impact sensitivity of composite increased, but the composite was more stable and not easy to decompose. High-substitute nitrochitosan presents a potential application in solid propellants.

Effects of metal-organic complex Ni(Salen) on thermal decomposition of 1,1-diamino-2,2-dinitroethylene (FOX-7).

The development of novel combustion catalysts is critical for improving combustion performance of high-energy solid propellants. In this work, a nickel-based Schiff base complex, N,N'-bis(salicylidene)ethylenediamino nickel [Ni(Salen)], as a candidate for the combustion catalyst of solid propellants, was synthesized with high purity. The effects of Ni(Salen) on the thermal decomposition reaction of FOX-7, which is closely related to its combustion properties in propellants, were systematically investigated and the corresponding mechanisms were also evaluated through comparison and analysis. Under the action of Ni(Salen), peak temperatures of the two decomposition processes of FOX-7 were reduced from 235.7 and 296.3 °C to 233.7 and 268.7 °C, respectively. The investigations into the mechanisms revealed the interactions between the Schiff base skeleton in Ni(Salen) and FOX-7, which promotes the decomposition of the remaining FOX-7. In addition, it was found that NiO, which was a decomposition product of Ni(Salen), also played an important role in promoting the thermal decomposition of FOX-7.

Novel Energetic Coordination Polymers Based on 1,5-Di(nitramino)tetrazole With High Oxygen Content and Outstanding Properties: Syntheses, Crystal Structures, and Detonation Properties.

In this study, a series of novel 1,5-di(nitramino)tetrazole (DNAT)-based bimetallic energetic coordination polymers, MK2(DNAT)2·4H2O [M = Fe, Cu, Ni, Co, and Zn], were designed and synthesized in a simple and convenient self-assembly synthetic process. The obtained compounds were fully characterized by IR spectroscopy, multinuclear NMR spectroscopy, elemental analysis, and differential scanning calorimetry (DSC). Additionally, the structures of target compounds were confirmed by single-crystal X-ray diffraction. Based on the room-temperature X-ray densities (2.095-2.138 g cm-3) and the calculated (CBS-QB3) heats of formation (-41.3 to 170.5 kJ mol-1), the detonation properties such as detonation velocities (8,147.0-8,478.4 m s-1) and detonation pressures (29.7-32.8 GPa) were computed using the EXPLO5 v6.04 program. Their excellent energetic properties indicated that they could serve as promising "green" primary explosives for replacement of lead azide (LA).

A Review on the Reactivity of 1-Amino-2-Nitroguanidine (ANQ).

1-Amino-2-nitroguanidine (ANQ) is a high-energy nitrogen-rich compound with good detonation properties and low sensitivities. ANQ has only a central carbon atom with three small groups around it, including an amino, a hydrazine and a nitroxyl group. Though the molecular structure of ANQ is very simple, its reactivity is surprisingly abundant. ANQ can undergo various reactions, including reduction reaction, acylation reaction, salification reaction, coordination reaction, aldimine condensation reaction, cyclization reaction and azide reaction. Many new energetic compounds were purposely obtained through these reactions. These reactions were systematically summarized in this review, and detonation properties of some energetic compounds were compared. In the field of energetic materials, ANQ and some derivatives exhibit good application prospects.

Aromatic Nucleophilic Substitution of FOX-7: Synthesis and Properties of 1-Amino-1-Picrylamino-2,2-Dinitroethylene (APDE) and Its Potassium Salt [K(APDE)].

Two energetic compounds, 1-amino-1-picrylamino-2,2-dinitroethylene (APDE) and its potassium salt [K(APDE)] were synthesized through an aromatic nucleophilic substitution reaction between FOX-7 and picryl chloride. APDE and K(APDE) were characterized by elemental analysis, IR, NMR spectroscopy, and X-ray diffraction. APDE has a 3D wavy layered stacking structure similar to FOX-7. K(APDE) (peak temperature (Tip )=185.6 °C and impact sensitivity (IS)=19.6 J) presents better stability than APDE (tap =133.3 °C and IS=15.7 J). The reasons why the stability of APDE is lower than that of FOX-7 and picryl chloride are analyzed. The detonation velocity (D) and detonation pressure (P) of APDE (8.36 km s-1 and 31.3 Gpa) are close to those of FOX-7 and RDX. The thermal decomposition of K(APDE) is very violent, and its detonation performance (D=9.14 km s-1 and P=38.6 Gpa) is comparable to that of HMX, indicating that K(APDE) has good potential to be a high explosive.

Theoretical study of a series of 4,4'-azo-1H-1,2,4-triazol-5-one based nitrogen-rich salts as potential energetic compounds.

Density function theory has been employed to systemically study 4,4'-azo-1H-1,2,4-triazol-5-one (ZTO) and its six nitrogen-rich salts at two different calculated levels (B3LYP/6-31G(d,p) and B3PW91/6-31G(d,p)). Their optimized geometries, electronic structures and molecular electrostatic potentials were further studied. Based on the two computed methods, the results of the optimized geometries show that the calculated structure of each compound adopted at the two different levels are rather similar except salt 7 with some differences. The values of the energy gaps indicate that compound 3 has the highest reactivity among salts 2-7. The crystal densities were corrected using the Politzer approach based on these two optimized levels. The density values with slight deviation indicate that the two calculated levels are applicable and the results are convincible. Based on the isodesmic reactions and Born-Haber energy cycle, the solid-phase heats of formation (HOFs) were predicted. Detonation parameters were evaluated using the Kamlet-Jacobs equations on the foundations of the calculated densities and HOFs. The results manifest that salt 2 exhibits the best detonation performance due to its highest density (1.819 g cm-3), followed by salt 6. Moreover, impact sensitivities of compounds 1-7 were assessed using the calculated Q values to correlate with h 50. Combining the detonation performance with safety, 1-7 exhibit good comprehensive properties and might be screened as a composition of modern nitrogen-rich energetic compounds.

Thermolysis, nonisothermal decomposition kinetics, specific heat capacity and adiabatic time-to-explosion of [Cu(NH3)4](DNANT)2 (DNANT= dinitroacetonitrile).

A new energetic copper complex of dinitroacetonitrile (DNANT), [Cu(NH3)4](DNANT)2, was first synthesized through an unexpected reaction. The thermal decomposition of [Cu(NH3)4](DNANT)2 was studied with DSC and TG/DTG methods. The gas products were analyzed through a TG-FTIR-MS method. The nonisothermal kinetic equation of the exothermic process is dα/dT = 10(10.92)/ß4(1 - α)[-ln(1 - α)](3/4) exp(-1.298 × 10(5)/RT). The self-accelerating decomposition temperature and critical temperature of thermal explosion are 217.9 and 221.0 °C. The specific heat capacity of [Cu(NH3)4](DNANT)2 was determined with a micro-DSC method, and the molar heat capacity is 512.6 J mol(-1) K(-1) at 25 °C. Adiabatic time-to-explosion of Cu(NH3)4(DNANT)2 was also calculated to be about 137 s.

4,9,12,15-Tetra-oxa-3,5,8,10,14,16-hexa-aza-tetra-cyclo-[11.3.0.0.0]hexa-deca-1(16),2,5,7,10,13-hexaen-3-ium-3-olate monohydrate.

The organic mol-ecule in the title monohydrate, C(6)N(6)O(5)·H(2)O, presents an almost planar configuration, the greatest deviation from the least-squares plane through the atoms being 0.061 (1) Šfor the O atom within the seven-membered ring. Each water H atom is bifurcated, one forming two O-H⋯N hydrogen bonds and the other forming O-H⋯N,O hydrogen bonds. The result of the hydrogen bonding is the formation of supra-molecular layers with a zigzag topology that stack along [001].

Non-isothermal decomposition kinetics, heat capacity and thermal safety of 37.2/44/16/2.2/0.2/0.4-GAP/CL-20/Al/N-100/PCA/auxiliaries mixture.

The specific heat capacity (C(p)) of 37.2/44/16/2.2/0.2/0.4-GAP/CL-20/Al/N-100/PCA/auxiliaries mixture was determined with the continuous C(p) mode of microcalorimeter. The equation of C(p) with temperature was obtained. The standard molar heat capacity of GAP/CL-20/Al/N-100/PCA/auxiliaries mixture was 1.225 J mol(-1)K(-1) at 298.15K. With the help of the peak temperature (T(p)) from the non-isothermal DTG curves of the mixture at different heating rates (ß), the apparent activation energy (E(k) and E(o)) and pre-exponential constant (A(K)) of thermal decomposition reaction obtained by Kissinger's method and Ozawa's method. Using density (ρ) and thermal conductivity (λ), the decomposition heat (Q(d), taking half-explosion heat), Zhang-Hu-Xie-Li's formula, the values (T(e0) and T(p0)) of T(e) and T(p) corresponding to ß â†’ 0, thermal explosion temperature (T(be) and T(bp)), adiabatic time-to-explosion (t(TIad)), 50% drop height (H(50)) of impact sensitivity, and critical temperature of hot-spot initiation (T(cr,hot spot)) of thermal explosion of the mixture were calculated. The following results of evaluating the thermal safety of the mixture were obtained: T(be) = 441.64K, T(bp) = 461.66 K, t(Tlad) = 78.0 s (n = 2), t(Tlad) = 74.87 s (n = 1), t(Tlad) = 71.85 s (n = 0), H(50) = 21.33 cm.

Thermal behaviors, nonisothermal decomposition reaction kinetics, thermal safety and burning rates of BTATz-CMDB propellant.

The composite modified double base (CMDB) propellants (nos. RB0601 and RB0602) containing 3,6-bis (1H-1,2,3,4-tetrazol-5-yl-amino)-1,2,4,5-tetrazine (BTATz) without and with the ballistic modifier were prepared and their thermal behaviors, nonisothermal decomposition reaction kinetics, thermal safety and burning rates were investigated. The results show that there are three mass-loss stages in TG curve and two exothermic peaks in DSC curve for the BTATz-CMDB propellant. The first two mass-loss stages occur in succession and the temperature ranges are near apart, and the decomposition peaks of the two stages overlap each other, inducing only one visible exothermic peak appear in DSC curve during 350-550 K. The reaction mechanisms of the main exothermal decomposition processes of RB0601 and RB0602 are all classified as chemical reaction, the mechanism functions are f(alpha)=(1-alpha)(2), and the kinetic equations are dalpha/dt = 10(19.24)(1-alpha)(2)e(-2.32x10(4)/T) and dalpha/dt = 10(20.32)(1-alpha)(2)e(-2.32x10(4)/T). The thermal safety evaluation on the BTATz-CMDB propellants was obtained. With the substitution of 26% RDX by BTATz and with the help of the ballistic modifier in the CMDB propellant formulation, the burning rate can be improved by 89.0% at 8 MPa and 47.1% at 22 MPa, the pressure exponent can be reduced to 0.353 at 14-20 MPa.

Preparation, non-isothermal decomposition kinetics, heat capacity and adiabatic time-to-explosion of NTOxDNAZ.

NTOxDNAZ was prepared by mixing 3,3-dinitroazetidine (DNAZ) and 3-nitro-1,2,4-triazol-5-one (NTO) in ethanol solution. The thermal behavior of the title compound was studied under a non-isothermal condition by DSC and TG/DTG methods. The kinetic parameters were obtained from analysis of the DSC and TG/DTG curves by Kissinger method, Ozawa method, the differential method and the integral method. The main exothermic decomposition reaction mechanism of NTOxDNAZ is classified as chemical reaction, and the kinetic parameters of the reaction are E(a)=149.68 kJ mol(-1) and A=10(15.81)s(-1). The specific heat capacity of the title compound was determined with continuous C(p) mode of microcalorimeter. The standard mole specific heat capacity of NTOxDNAZ was 352.56 J mol(-1)K(-1) in 298.15K. Using the relationship between C(p) and T and the thermal decomposition parameters, the time of the thermal decomposition from initialization to thermal explosion (adiabatic time-to-explosion) was obtained.

Thermal behavior, specific heat capacity and adiabatic time-to-explosion of G(FOX-7).

[H(2)N=C(NH(2))(2)](+)(FOX-7)(-)-G(FOX-7) was prepared by mixing FOX-7 and guanidinium chloride solution in potassium hydroxide solution. Its thermal decomposition was studied under the non-isothermal conditions with DSC and TG/DTG methods. The apparent activation energy (E) and pre-exponential constant (A) of the two exothermic decomposition stages were obtained by Kissinger's method and Ozawa's method, respectively. The critical temperature of thermal explosion (T(b)) was obtained as 201.72 degrees C. The specific heat capacity of G(FOX-7) was determined with Micro-DSC method and theoretical calculation method and the standard molar specific heat capacity is 282.025 J mol(-1) K(-1) at 298.15 K. Adiabatic time-to-explosion of G(FOX-7) was also calculated to be a certain value between 13.95 and 15.66 s.

[Application of fingerprint chromatogram in quality assessment of apple cider].

Fingerprints of 14 apple cider samples from different manufacturers were studied using high performance liquid chromatography (HPLC) with an electrochemical detector (ECD). The analysis was carried out on a Zorbax SB-C18 column at 30 degrees C with 2% (v/v) methanol aqueous solution-4% (v/v) acetic acid aqueous solution as mobile phase at a flow rate of 0.8 mL/min. The electrochemical detector was set at 0.7 V. By calculating the relative retention times of certain peaks with chlorogenic acid as the reference standard, 8 common peaks in the samples were analyzed. Relative retention times for the common peaks of various samples were calculated, and the similarities of all the samples were figured out through each peak area with the vectorial angle cosine method and correlative coefficient method. The results indicated that apple cider products of the same manufacturer have good similarity, with the similarities greater than 92.7%. According to this experiment, effectual microcosmic information for apple cider analysis was gained through HPLC and ECD. Moreover, this test method will help the analysis and the control of product quality, the development of new products and the establishment of trade standard.