Enhancing the detonation performance of azobistriazole energetic derivatives via inducing N-oxide groups.

The N-oxide strategy plays a crucial role in regulating the performance and safety of energetic materials. This study mainly addresses the question of how the N-oxide group affects the properties of azobistriazole and its derivatives. Our findings indicate that the N-oxide group can increase the density of the system, and its effect on the enthalpy of formation depends on the specific situation. The N-oxide groups can effectively improve the density and energetic properties. Some of the energetic derivatives containing N-oxide groups have a density as high as 2.097 g cm-3 (D3-NO(2)) and a detonation velocity as high as 10 275 m s-1 (C6-NO(2)). The effect of N-oxide groups on the enthalpy of formation depends on the specific circumstances. The effect of N-oxide groups on the stability of azobistriazole energetic derivatives is relatively complex. Among them, the N-oxide group on the triazole ring has an opposite effect on the bond dissociation enthalpy of functional groups. When the N-oxide group is on the 1,2,3-triazole ring, it can improve C-R (R is equal to C(NO2)3, NF2, NHNO2, NO2, and ONO2 respectively) bond dissociation enthalpy, and when it is on the 1,2,4-triazole ring, it will reduce the C-R bond dissociation enthalpy. When the N-oxide group is located on the azo bond, the bond dissociation enthalpy of the azo bond will be significantly reduced. This article systematically explores the effect of N-oxide groups on the properties of azobistriazole energetic derivatives, which will help people better utilize N-oxide groups to design and synthesize new energetic materials.

CTD Sensors for Ocean Investigation Including State of Art and Commercially Available.

Over 70% of the earth's surface is covered by oceans; globally, oceans provides a huge source of wealth to humans. In the literature, several sensors have been developed to investigate oceans. Electrical conductivity temperature depth (CTD) sensors were used frequently and extensively. Long-term accurate CTD data is important for the study and utilization of oceans, e.g., for weather forecasting, ecological evolution, fishery, and shipping. Several kinds of CTD sensors based on electrics, optical, acoustic wave and radio waves have been developed. CTD sensors are often utilized by measuring electrical signals. The latest progress of CTD sensors will be presented in order of performance. The principles, structure, materials and properties of many CTD sensors were discussed in detail. The commercially available CTD sensors were involved and their respective performances were compared. Some possible development directions of CTD sensors for ocean investigation are proposed.

Thermal Insulation and Flame Retardancy of the Hydroxyapatite Nanorods/Sodium Alginate Composite Aerogel with a Double-Crosslinked Structure.

As advanced thermal management materials, aerogels have great research value in the fields of engineering insulation, pipeline transportation, and packaging insulation. The composite interaction of the two-phase interface and the construction of a porous structure have an important impact on the thermal properties. Herein, a novel HANRs/SAB composite aerogel was prepared using sodium alginate (SA) with hydroxyapatite nanorods (HANRs), combined with boric acid crosslinking and freeze drying. In the prepared sample, the calcium ions in HANRs and SA formed the first layer of binding force and the chemical crosslinking of sodium alginate with boric acid formed the second layer of strong binding force, which effectively supported the skeleton of the aerogel and enhanced the overall mechanical properties. The modulus and maximum compressive strength of the obtained HANRs/SAB aerogel were 2.39 and 0.75 MPa, respectively, while the bulk density was 0.038-0.068 g·cm-3. Based on the prominent physical structure, the as-prepared HANRs/SAB aerogel exhibited good thermal insulation (∼35.15 mW·m-1·K-1) and outstanding flame retardant performance. Flame-retardant boric acid and high-thermal stability HANRs could effectively prevent heat transfer and organic combustion, thus resulting in an extremely low smoke gas release (11.3 m2 m-2). Therefore, the low-cost biopolymer composite aerogel based on a crosslinking strategy has broad application prospects in the field of thermal insulation and flame retardancy.

Cogel Strategy for the Preparation of a "Thorn"-Like Porous Halloysite/Gelatin Composite Aerogel with Excellent Mechanical Properties and Thermal Insulation.

This work presents the preparation and property characterization of a biomass gelatin (GA)-based aerogel. Halloysite nanotubes (HNTs) were used to improve the mechanical strength, pore size distribution, and thermal stability of the aerogel. Polyethyleneimine (PEI) and (3-glycidyloxypropyl)trimethoxysilane (GPTMS) were utilized to increase the interfacial interaction between HNTs and GA through chemical cross-linking. Green, sustainable, and low-cost composite aerogels were prepared by "cogel" and freeze-drying techniques. The experimental results show that the HNTs/GA composite aerogel has a low density (31.98-57.48 mg/cm3), a high porosity (>95%), a low thermal conductivity (31.85-40.16 mW m-1 K-1), and superior moldability. In addition, the mechanical strength and thermal insulation properties of the HNTs/GA composite aerogels with a "thorn"-like lamellar porous network structure are different in the axial direction versus the radial direction. The maximum compressive strength, maximum compressive modulus, and corresponding specific modulus in the axial direction were 1.81 MPa, 5.45 MPa, and 94.8 kN m kg-1, respectively. Therefore, the biomass/clay composite aerogel will be a sustainable and renewable functional material with high mechanical strength and thermal insulation properties, which is expected to further promote biomass and clay for high value utilization.

Ultralight, hydrophobic, monolithic konjac glucomannan-silica composite aerogel with thermal insulation and mechanical properties.

Konjac glucomannan (KGM) aerogel was prepared by a facile freeze-drying process, which was used as green sustainable biopolymer matrix to synthesis three-dimensional (3D) network interpenetrated KGM-SiO2 aerogel with thermal insulation performance and high mechanical properties. Herein, we explored that the potential structure-performance relationship of KGM aerogel between the physical parameters, morphology and thermal insulation. Besides, the preparation conditions of KGM aerogel including concentration of KGM, Na2CO3-to-KGM mass ratio were investigated. Meanwhile, the KGM aerogel and KGM-SiO2 aerogel were characterized using scanning electron microscopy, Fourier transform infrared spectrometer, Brunauer-Emmett-Teller method, thermogravimetric analysis and contact angle test. Results showed that the as-prepared KGM aerogel exhibited excellent thermal insulation performance (λ = 0.021 W m-1 K-1) and low bulk density (ρ = 0.030 g cm-3) when concentration of KGM was 2 wt% and Na2CO3-to-KGM mass ratio of 0.12. In order to improve the mechanical properties and high hydrophobicity of biopolymer aerogel, a novel of KGM-SiO2 aerogel was successful fabricated by incorporating methylsilsesquioxane (MTES) derived SiO2 into the KGM matrix via the freeze-drying method. The obtained aerogel exhibited remarkable compressive strength (δmax = 1.65 MPa at 80% strain), high specific surface area of 416.1 m2 g-1, high hydrophobicity (θ = 146° for water) and low thermal conductivity of 0.032-0.039 W m-1 K-1. Thus, the high-performance KGM-SiO2 aerogel would be further expand the thermal insulation application in sustainable development and energy-saving building.

A pseudo three-zone simulated moving bed with solvent gradient for quaternary separations.

In a SMB with solvent gradient, as the eluotropic strength of the liquid in zone II (between the extract-port and feed-port) is higher than that in zone III (between the feed-port and the raffinate-port), the solute can move forward in zone II but backward in zone III to be trapped in the two zones consequently. On this basis, a pseudo-SMB was proposed to separate two medium retained solutes (B1 and B2) from a quaternary mixture by selectively trapping the two solutes. Once the columns in zones II and III are saturated with the target solutes, the solvent dissolving the feed is introduced at the feed-port to remove the least retained solute (A) from the raffinate-port and the most retained solute (C) from the extract-port. The two target components trapped in zones II and III are purified accordingly. At the same time, solute B1 would distribute in the columns of zone III whereas solute B2 spread in the columns of zone II if solute B2 had a stronger retention than solute B1. Thereby, the two medium retained solutes B1 and B2 could be recovered separately from the columns in zones II and III. This scheme was validated by the successful separation of capsaicin (B1) and dihydrocapsaicin (B2) from a crude capsaicinoids.

Study on retention factor and resolution of tocopherols by supercritical fluid chromatography.

To develop a process for separation of natural alpha-tocopherol from gamma- and delta-tocopherols by supercritical fluid chromatography, the effects of pressure, temperature and the ethanol concentration in the mobile phase on the retention factor and resolution of tocopherols were studied comprehensively. The ranges of the studied pressure, temperature and ethanol concentration were 12 to 20 MPa, 30 to 90 degrees C and 0 to 6.54 wt% respectively. It was found that the retention factors of the tocopherols decrease as the ethanol concentration in the mobile phase increases. The resolution of tocopherols increases as the temperature increases and as the pressure decreases, and there is a maximum of the ethanol concentration curve at a definite temperature and pressure. A simplified model of the retention factor ln k' = A + B/T + C rho - D(rho/T) + E(rho2/T) based on the unified molecular theory was proposed. The experimental data were correlated by the model with the AARD% less than 14.70%.