Solvent-nonsolvent Method Research Articles

Spherical core-shell CL-20@LLM-105 composites with excellent mechanical sensibility obtained by Pickering emulsion

The effect of crystallization conditions on the morphology, particle size and dispersibility of 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) was investigated by solvent-nonsolvent method, and nano-LLM-105 was successfully prepared and used as a surfactant after modification with stearic acid. A spherical core-shell composites of CL-20@LLM-105 was prepared by Pickering emulsion method. The morphology, crystal structure, and thermal decomposition properties were characterized by scanning electron microscopy (SEM), powder X-ray diffractometry (XRD), differential scanning calorimetry (DSC), fourier transform infrared (FT-IR) tested for impact and friction sensibility. The results showed that the prepared composites had a particle size of 50–100 μm, a spherical core-shell structure, and nano-LLM-105 was encapsulated on its surface. The peak thermal decomposition temperature of the composites was 252.7 ℃, which was 9.4 ℃ higher than that of the raw material CL-20. Compared with the CL-20/LLM-105 mixture with the same ratio, the characteristic drop height (H50) of the CL-20@LLM-spherical compoe-shell site was increased by 13 cm, and the explosion probability (P) was reduced by 43%. The spherical core-shell composites prepared by this method is characterized by high energy and excellent mechanical sensibility, which is expected to provide new ideas for the design of explosive formulations containing CL-20 and nanoenergy-containing materials in the direction of high safety and high energy.

Thermodynamics and energy properties of the lowest eutectic mixture of TNBA/MTNP

In light of the challenges posed by the low density, diminished energy levels, and shrinkage holes in the loading arise of the current cast-cured explosive liquid vehicle, TNT, the investigation of low-melting eutectic materials as potential substitutes for TNT has emerged as a focal point of research. By employing the solvent-nonsolvent method, the lowest eutectic mixture of TNBA(2,4,6-trinitro-3-bromoanisole)/MTNP(1-methyl-3,4,5-trinitropyrazole) was synthesized, distinguished by a moderate melting point and markedly elevated energy levels as compared to TNT. Comprehensive SEM, EDS, IR, XRD, and XPS analyses were conducted on the lowest eutectic mixture, substantiating the absence of any chemical interaction between TNBA and MTNP and affirming their exceptional compatibility. Moreover, an exploration into the thermal decomposition behavior and mechanism of the lowest eutectic mixture was undertaken, its mechanical sensitivity was tested, and its detonation performance was evaluated by EXPLO-5 software. The thermal decomposition parameters of the lowest eutectic mixture closely paralleled those of the precursor materials, with the thermal decomposition kinetics model function being identified as the Jander function. The impact sensitivity of the lowest eutectic was 48.1 cm and the friction sensitivity was 12%. Furthermore, the density of the lowest eutectic mixture surpassed 1.8 g/cm3, and its detonation velocity approached 8000 m/s, markedly surpassing the explosive performance of TNT.

Preparation and performances of DAP-4@FOX-7 energetic composites

The fluororubbers F2314, F2602, F2461, EVA and Estane were selected as the binders to modify the surface of molecular perovskite energetic material DAP-4. The DAP-4@FOX-7 energetic composites were prepared by coating with different contents of nano FOX-7 according to the solvent evaporation method and solvent-nonsolvent method in order to improve the safety performance of DAP-4. The morphologies, structures, and thermal properties of the DAP-4@FOX-7 energetic composites were characterized using Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and Differential Scanning Calorimetry (DSC), respectively. The sensitivities were tested and analyzed. The combustion performance was also tested. The results show that the modification on DAP-4 was affected by the type of binders. The coating effect of nano FOX-7 on DAP-4 is the best when the binder is EVA. The DAP-4 particles are completely and uniformly coated by nano FOX-7 particles with a 20% content, and the crystal structures of DAP-4 particles remain unchanged. As the content of nano FOX-7 increases from 5% to 25%, the sensitivities show a decreasing trend, and the combustion times gradually increase.

Preparation and study on combustion performance of AP@ZrH2 core-shell composite energetic materials with high volume energy density

The development of composite energetic material with high volume energy density could increase the range and loading capacity of solid propellants. In this study, a series of core-shell composite energetic materials AP@ZrH2 were fabricated by decorating ZrH2 on the ammonium perchlorate (AP) through a solvent-nonsolvent method. A substantial increase in combustion heat (13373.67 J/g) and maximum burning temperature (1415.33 °C) are detected in composites in contrast to physically mixed sample (10660.46 J/g and 837.22 °C). This is due to the enhancement of the decomposition performance of AP, which provides sufficient oxidation gas atmosphere for combustion of ZrH2. In addition, the delay time (524 ms) and burning time (114 ms) of composites are significantly decreased compared to the physical mixed sample (2145 and 256 ms). The remarkable combustion performance and burning rate could be attributed to reduced mass and heat transfer distances. Finally, the improvement of combustion efficiency in the composites makes the size of the residual particles smaller.

Bespoke Energetic Zeolite Imidazolate Frameworks-8 (ZIF-8)/Ammonium Perchlorate Nanocomposite: A Novel Reactive Catalyzed High Energy Dense Material with Superior Decomposition Kinetics

Aluminum is the universal fuel for solid propellants; however, its passive oxide layer could impede the full exploitation of its enthalpy. Meanwhile, common catalyst could not contribute to combustion enthalpy. This study shaded light on the multifunctional energetic metal-organic frameworks ZIF-8 with combustion enthalpy 21 KJ/g as high energy dense material as well as a novel catalyst for solid propellants. As-prepared ZIF-8 particles exhibited a highly crystalline structure with an average particle size of 40 nm. The performance of ZIF-8 as high-energy dense material was assessed to aluminum particles via integration into ammonium perchlorate (APC). ZIF-8/APC and Al/APC composites were prepared via the solvent–nonsolvent method; the decomposition enthalpy was investigated via DSC. ZIF-8 offered an increase in APC total decomposition enthalpy by 98.4%, to 39.11% for Al. ZIF-8 exhibited a superior catalytic behavior by lowering the APC high-temperature decomposition peak (HTD) by 81.48 °C compared to 70.3 °C for Al. The decomposition kinetics of ZIF-8/AP nanocomposite was investigated via Kissinger’s formula. The ZIF-8 offered a remarkable reduction in APC apparent activation energy at low-temperature decomposition peak and HTD peaks by peak by 16.5% and 30%, respectively. The superior catalytic performance of ZIF-8 was attributed to Zn+2 electron deficient centers with the exclusive formation of ZnO nanoparticles during combustion. ZIF-8 with gaseous decomposition products could boost specific impulses.

Study on Bonded Dispersant for Ultrafine CL-20

To improve the problem that ultrafine hexanitrohexaazaisowurtzite (CL-20) is prepared by the solvent nonsolvent method, which tends to coalesce and automatically affects its thermal properties, the bonding agent @CL-20 core-shell composite energetic materials (ammonium dodecylbenzene sulfonate@CL-20, trimethylsilyl monooleate@CL-20 and boron nitride@CL-20) were prepared by water suspension method. The coated ultrafine CL-20 was characterized by an optical microscope, scanning electron microscope (SEM), Fourier transforms infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC), and its sensitivity was tested according to GJB 772-1997. The results showed that the three bonded dispersants completely coated CL-20, and the crystal form of CL-20 was still ε-. Compared with the raw material CL-20, the characteristic drop increased by 27.5cm at most and the thermal decomposition temperature increased by 4 °C.

Study on the Preparation and Composition of Ultrafine CL-18/HNS

Using solvent-nonsolvent method, study on the preparation and composition of ultrafine CL-18/HNS. Scanning electron microscopy (SEM) was used to characterize the particle size and morphology. The FTIR spectra (IR), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) were utilized to determine whether the cocrystal explosive was prepared. Furthermore, the impact sensitivity and short pulse slapper sensitivity of cocrystal explosive was tested. Results show that the prepared samples are the mix of CL-18 and HNS but rather changed cocrystal appearance of ultrafine CL-18/HNS. The average particle size of cocrystal explosives are 0.98μ. The peak temperatures of exothermic decomposition are 205.36 °C, The impact probability of CL-18/HNS cocrystal explosives is 56 percent, and minimum initiation energy is 0.12J.

Influence of Nano-Reduced Graphene Oxide on the Thermal Characteristics of 1,3,5-Trinitro-1,3,5-Triazinane (RDX)

It is well known that the improvement in the energetic materials field needs to rally the efficiency by increasing the performance of the materials. Optimizing the sensitivity and the performance is considered a challenge that obstacle the developer to getting the required high-energy materials. Nanoparticles with reduced graphene oxide (RGO) rely on a new series of energy materials that can be produced chemically or thermally to reduce the oxygen content by exploiting the interlaying spacing and functionalization of the graphite basal planes. The RGO could easily disperse in an organic solvent due to its hydrophobic material and achieve a large surface area. In this paper, The production of RGO was discussed, and the solvent-nonsolvent method was applied to disperse the RGO on 1,3,5-trinitro-1,3,5-triazinane (RDX). Scanning electron microscopy (SEM) was used to check the morphology of the tested composition. The deflagration experiment was applied to determine the ignition temperature and delay. The thermal behavior was determined by TGA and DSC techniques. The results showed that the presence of RGO layers accumulated the heat release inside the crystals during the heating process and decreased the ignition temperature of the prepared composite RDX-RGO. The decomposition peak of RDX-RGO decreased dramatically compared with the individual RDX. The RGO acts as a catalyst and increases the reactivity of RDX.

Crystalline behaviors of HMX-Al composites in solvents: A molecular dynamics and experimental study

Abstract

Method for surface coating of octahdro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine with submicron 1,3,5‐triamino‐2,4,6‐trinitrobenzene

To improve the safety of octahdro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), a submicron energetic material, 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), was introduced to coat HMX by a novel method. This novel method contained the reaction crystallisation and the solvent–non-solvent method. X-ray diffraction, scanning electron microscope, and optical microscopy analyses showed that a homogeneous layer of TATB particles with submicron scale had been successfully coated on the surface of HMX particle. Differential scanning calorimetry and thermogravimetry indicated that the coated HMX only had an exothermic peak at 279.4 °C, and the phase transition temperature reached 213.5 °C and increased by 20.2 °C compared with the pure HMX. The content of the coating TATB was determined to be 6.2 wt.% through high-performance liquid chromatograph. Relative to the mechanically mixed HMX/TATB, the drop height (H 50) was increased from 23.0 to 74.1 cm, and the friction probability was reduced from 4 to 0% for the coated HMX.

Preparation of topographically modified poly(L-lactic acid)-b-Poly(ɛ-caprolactone)-b-poly(L-lactic acid) tri-block copolymer film surfaces and its blood compatibility

Hindering early platelet adhesion and enhancing human vascular endothelial cell proliferation on surfaces of the foreign materials play a key role in the prevention of coagulation. In order to develop topographically suitable surface for artificial grafts, topographically modified poly(L-lactic acid)-b-poly(ɛ-caprolactone)-b-poly(L-lactic acid) tri-block copolymer (PLLA-PCL-PLLA) film surfaces were cast using a simple solvent-nonsolvent method. PLLA-PCL-PLLA copolymer was synthesized, and was confirmed by 1H nuclear magnetic resonance (NMR) analysis. The molecular weight of the copolymer was measured using gel permeation chromatography (GPC). PLLAPCL-PLLA films were cast with various ratios of non-solvent in the solvent mixture. Tetrahydrofuran (THF) and ethyl alcohol (EtOH) were used as solvent and nonsolvent respectively. The hydrophobic characteristic of the surfaces was confirmed by the water contact angle (WCA). The prepared film surfaces were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD). Anti-platelet adhesion characteristic was evaluated using Lactate Dehydrogenase (LDH) assay and SEM images. Proliferation behavior of human vascular endothelial cell was investigated by water-soluble tatrazolium salt (WST) assay after 3 h, 1 day, 2 days and 4 days of cell culture on the film surface. Fabricated morphologically unique surface, which consists of submicron size width and nano size height rough structure, shows anti platelet adhesive ability and relatively higher human vascular endothelial cell proliferation behavior.

Surface Modification of Hydrophobic Resin with Tricaprylmethylammonium Chloride for the Removal of Trace Hexavalent Chromium

Chromium(VI) is one of the most toxic contaminants in the environment, even at low concentration. The conventional chemical precipitation process for Cr(VI) wastewater treatment becomes less effective at low Cr(VI) concentration. By a two-step solvent–nonsolvent method, tricaprylmethylammonium chloride (Aliquat 336) can be immobilized onto the surface of porous Amberlite XAD resin with good stability, giving Aliquat 336-modified resins (AMRs). Furthermore, the exposure of the cationic ammonium functional group facilitates the adsorption and stripping efficiency of Cr(VI). The amount of immobilized tricaprylmethylammonium chloride was 2.0 mmol/g of resin. A kinetic study showed that the adsorption of Cr(VI) was under film-diffusion control followed by intraparticle-diffusion control. The Cr(VI) adsorption capacity was as high as 1.37 mmol/g. More than 99% of the adsorbed Cr(VI) could be stripped during regeneration. For stability and reusability, the AMRs maintaine da high level of Cr(VI) adsorption even after four cycles of adsorption/stripping. The experimental results for actual wastewater demonstrated that the AMRs can be used effectively for the treatment of trace Cr(VI)-containing wastewater.

Preparation and Characterization of Insensitive HMX/Graphene Oxide Composites

AbstractTo improve the safety of HMX, a two‐dimensional (2D) graphene oxide (GO) was introduced to HMX by the solventnonsolvent method. The morphology, composition, thermal decomposition characteristic were characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), thermogravimetry (TG) and differential scanning calorimetry (DSC). Compared to the previous reports, GO sheets exhibited better desensitizing effect than [60]Fullerene and CNTs. When 2.0 wt‐% GO sheets were added, the impact sensitivity of raw HMX decreased from 100 to 10 %, and the friction sensitivity reduced from 100 to 32 %. The DSC results proved that GO sheets were compatible with HMX. In addition, by determining the thermal decomposition kinetic parameters of the samples, it was found that the activation energy (Ea) of HMX with 2.0 wt‐% GO increased by 23.5 kJ mol−1, suggesting that GO sheets could improve the thermal stability of HMX.

Cross-linked hyaluronic acid sub-micron particles: in vitro and in vivo biodistribution study in cancer xenograft model

This paper focused on the biodistribution of the cross-linked hyaluronic acid (HA-NPs) sub-micron particles in tumor-bearing mice. Solvent-non solvent method followed glutaraldehyde cross-linking utilized for the fabrication of HA-NPs. Size measurement and morphological analysis were performed by dynamic light scattering and electron microscopy, respectively and the size found to be in the range of 200-400nm. In vitro viability in LNCaP cell line was assessed by water soluble tetrazolium assay after 24h of exposure to sub-micron particles and no toxicity was found to higher concentration of 3mg/mL. Internalization of particles in prostate cancer cell LNCaP were studied by confocal microscopy with FITC labeled submicron particles and involvement of hyaluronan receptor mediated uptake/endocytosis was confirmed by competitive assay. Biodistribution studies were performed in xenograft prostate cancer mice model with fluorophore labeled particles and monitored in tumoral parenchyma with strong fluorescence, meanwhile very less signal in liver, kidney and spleen while no fluorescence found in lung after 24h of systemic administration; that shown ability of this HA based system to recognize cancer tissue. These result fetched that hyaluronic acid based system is selective for tumoral site and can be utilized to deliver bioactives in specific (targeting) and controlled (temporal) manner to cancerous tissue.

Thermal stable superhydrophobic polyphenylsilsesquioxane/nanosilica composite coatings

The superhydrophobic polyphenylsilsesquioxane (PPSQ)/nanosilica composite coatings were prepared by spray coating method with nano fumed silica (NFS) particles embedded in PPSQ matrix. The water contact angle (WCA) increased from 92.9° to 152.5° and the sliding angle (SA) decreased from more than 60° to 3.9° as the NFS content increased. The superhydrophobicity retained up to 500°C, sustained by the hierarchical micro–nano structures and excellent thermal stability of PPSQ. A superhydrophobic PPSQ coating with WCA of 152.6° and SA of 7.8° was obtained by solvent–nonsolvent method for comparison as well. However, it gradually lost superhydrophobicity at 200°C because of the elimination of nanostructures by the thermal softening of PPSQ.

Proliferation of Mesenchymal Stem Cell on Chitosan Films Associated with Convex Micro-topography

Topographical micro-structures of material surfaces are known to influence cell behavior. In this study, alignment and proliferation of mesenchymal stem cells (MSCs) on chitosan (CS) films with different microtopography was investigated. A modified solvent–non-solvent method was used to produce micro-well polystyrene films which were used as templates for preparation of micro-hilled CS films. The alignment and proliferation of MSCs on CS films were characterized by scanning electron microscopy and the MTT assay, respectively. Polystyrene films with different micro-well diameters were produced under different conditions. We successfully produced CS films with micro-hills of 10 μm (CS10) and 5–30 μm (CS5-30) by a molding approach. MSCs cultured on CS10 covered the tightly packed micro-hills and flattened polygonally. In contrast, MSCs on CS5-30 mostly adhered between loosely packed micro-hills and demonstrated elongated extensions. The proliferation rate of MSCs on CS5-30 was highest on day 4 (66% on CS5-30 versus 46% on CS10 and 24% on smooth CS) and day 8 (106% on CS5-30 versus 38% on CS10 and 72% on smooth CS). It is reasonable to suggest that spatially and dimensionally dispersed micro-hills on CS films facilitate the alignment and proliferation of MSCs. This may be used to physically modify CS for tissue-engineering applications.

Preparation of Thermosensitive Chitosan Formulations Containing 5-Fluorouracil/Poly-3-hydroxybutyrate Microparticles Used as Injectable Drug Delivery System

The auto-gelling and drug release properties of the thermosensitive chitosan-β-glycerophosphate formulation were investigated. According to rheological study, gelation lag time of chitosan/β-glycerophosphate (GP) solutions varied from 2 to 60min with different deacetylation degree of chitosan, pH, gelation temperature, and the particles in the sol. The gelation properties were also found to influence the release profiles of a hydrophilic drug, 5-fluorouracil (5-FU). Morphological examination by scanning electron microphotography demonstrated that large “pores” occurred during the gel-forming process, which created hydrophilic environment and led to the rapid initial release of the drug (85% in first 8h). Poly-3-hydroxybutyrate (PHB), a biodegradable material, was applied here as scaffold to capture 5-FU into microparticles with high encapsulation efficiency by solvent-nonsolvent method. Combination of these microparticles into the chitosan-β-GP formulation could drop the rapid initial release from 85% down to 29% in the optimized PHB content (75%, by mass). The release could sustain for about 10 months. This study provided an understanding of the potential of injectable implant using thermosensitive chitosan-β-GP formulation containing PHB based particles for the water soluble drugs that need the property of long-term delivery.