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1.
ACS Omega ; 9(3): 4013-4018, 2024 Jan 23.
Artículo en Inglés | MEDLINE | ID: mdl-38284042

RESUMEN

Molecular dynamics (MD) simulations were performed on the energetic molecular perovskite (C6H14N2)[NH4(ClO4)3], with excellent detonation properties, thermal stability, and high specific impulse, which is a potential replacement for AP as the next generation propellants. The cohesive energy density, binding energy, pair correlation function, maximum bond length (Lmax) of the N-H trigger bond, and mechanical properties of the (C6H14N2)[NH4(ClO4)3] were reported. The calculated cohesive energy density and binding energy decrease with increasing temperature, indicating a gradual decrease in the thermal stability with temperature. In addition, H···O hydrogen bonding interactions have been found based on the results of pairwise correlation functions. The maximum length (Lmax) of the N-H trigger bond was calculated and used as a criterion to theoretically judge the impact sensitivity. The maximum bond length of the N-H trigger bond grows gradually with temperature; however, it does very slightly yet gradually above 373 K. This suggests that an increase in temperature leads to a higher impact sensitivity and lower thermal stability. However, this effect becomes less pronounced when the temperature surpasses 373 K. Moreover, the calculated mechanical data indicate that as the temperature rises, the material's stiffness, hardness, yield strength, and fracture strength all decrease. The material's ductility shows an upward trend with increasing temperature, reaching its peak at 373 K and subsequently declining as the temperature continues to rise.

2.
Int J Mol Sci ; 24(15)2023 Jul 27.
Artículo en Inglés | MEDLINE | ID: mdl-37569443

RESUMEN

Binders mixed with explosives to form polymer-bonded explosives (PBXs) can reduce the sensitivity of the base explosive by improving interfacial interactions. The interface formed between the binder and matrix explosive also affects the thermal conductivity. Low thermal conductivity may result in localized heat concentration inside the PBXs, causing the detonation of the explosive. To investigate the binder-explosive interfacial interactions and thermal conductivity, PBXs with polyurethane as the binder and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/2,4,6-trinitrotoluene (CL-20/TNT) co-crystal as the matrix explosive were investigated through molecular dynamics (MD) simulations and reverse non-equilibrium molecular dynamics (rNEMD) simulation. The analysis of the pair correlation function revealed that there are hydrogen bonding interactions between Estane5703 and CL-20/TNT. The length of the trigger bonds was adopted as a theoretical criterion of sensitivity, and the effect of polymer binders on the sensibility of PBXs was correlated by analyzing the interfacial trigger bonds and internal trigger bonds of PBXs for the first time. The results indicated that the decrease in sensitivity of CL-20/TNT mainly comes from the CL-20/TNT contact with Estane5703. Therefore, the sensitivity of CL-20/TNT-based PBXs can be further reduced by increasing the contact area between CL-20/TNT and Estane5703. The thermal conductivity of PBXs composed of Estane5703 and CL-20/TNT (0 0 1), (0 1 0) and (1 0 0) crystal planes, respectively, were calculated through rNEMD simulations, and the results showed that only the addition of Estane5703 to the (1 0 0) crystal plane can improve the thermal conductivity of PBX100.


Asunto(s)
Sustancias Explosivas , Trinitrotolueno , Sustancias Explosivas/química , Simulación de Dinámica Molecular , Polímeros/química , Conductividad Térmica , Trinitrotolueno/análisis , Trinitrotolueno/química
3.
ACS Omega ; 8(23): 20272-20282, 2023 Jun 13.
Artículo en Inglés | MEDLINE | ID: mdl-37332777

RESUMEN

The existing in situ preparation methods of solid polymer electrolytes (SPEs) often require the use of a solvent, which would lead to a complicated process and potential safety hazards. Therefore, it is urgent to develop a solvent-free in situ method to produce SPEs with good processability and excellent compatibility. Herein, a series of polyaspartate polyurea-based SPEs (PAEPU-based SPEs) with abundant (PO)x(EO)y(PO)z segments and cross-linked structures were developed by systematically regulating the molar ratios of isophorone diisocyanate (IPDI) and isophorone diisocyanate trimer (tri-IPDI) in the polymer backbone and LiTFSI concentrations via an in situ polymerization method, which gave rise to good interfacial compatibility. Furthermore, the in situ-prepared PAEPU-SPE@D15 based on the IPDI/tri-IPDI molar ratio of 2:1 and 15 wt % LiTFSI exhibits an improved ionic conductivity of 6.80 × 10-5 S/cm at 30 °C and could reach 10-4 orders of magnitude when the temperature was above 40 °C. The Li|LiFePO4 battery based on PAEPU-SPE@D15 had a wide electrochemical stability window of 5.18 V, demonstrating a superior interface compatibility toward LiFePO4 and the lithium metal anode, exhibited a high discharge capacity of 145.7 mAh g-1 at the 100th cycle and a capacity retention of 96.8%, and retained a coulombic efficiency of above 98.0%. These results showed that the PAEPU-SPE@D15 system displayed a stable cycle performance, excellent rate performance, and high safety compared with PEO systems, indicating that the PAEPU-based SPE system may play a crucial role in the future.

4.
ChemistryOpen ; 12(4): e202200246, 2023 04.
Artículo en Inglés | MEDLINE | ID: mdl-37009889

RESUMEN

As vaccine adjuvants, polyacrylate materials can induce a specific immune response in the body and have been widely studied in recent years due to their advantages, such as their safety, effectiveness, and low required dosage. In this study, a series of polyacrylates with hydrophobic physical crosslinking and chemical crosslinking were prepared using precipitation polymerization, and their structures were characterized by nuclear magnetic resonance spectroscopy and Fourier-transform infrared spectroscopy. The optimal reaction conditions were determined according to the effect of reaction time, azodiisobutyronitrile, Span 60, allyl pentaerythritol, and octadecyl methacrylate (OMA) contents on the viscosity of the polyacrylate microgel, combined with the effects of allyl pentaerythritol and OMA contents on the subcutaneous immune safety of the polyacrylate microgel in BALB/c mice. The polyacrylate microgels with different OMA contents showed good biological safety. In addition, in vivo immunity experiments were carried out in mice to analyze the adjuvant properties of ovalbumin as a model antigen. Based on the titer results of the IgG1 and IgG2a antibodies, with 1 wt % OMA content, the polyacrylate microgel vaccine could optimally induce the body to produce an immune response type dominated by Th2-type humoral immune response and supplemented by Th1-type cellular immune response.


Asunto(s)
Microgeles , Animales , Ratones , Ovalbúmina/farmacología , Células TH1 , Células Th2 , Adyuvantes Inmunológicos/química , Adyuvantes Inmunológicos/farmacología , Antígenos/farmacología , Adyuvantes Farmacéuticos/farmacología
5.
Small ; 19(33): e2301310, 2023 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-37080949

RESUMEN

Methods allow the enhancement of nanofibers via self-assembly are potentially important for new disciplines with many advantages, including multi-anchor interaction, intrinsic mechanical properties and versatility. Herein, a microfluidic-assisted self-assembly process to construct hydroxyl functionalized boron nitride nanosheets (OH-BNNS)/graphene oxide (GO)/thermoplastic polyurethane (TPU) composite nanofiber film, in which stable and precisely controlled self-assembly is fulfilled by the confined ultra-small-volume chip is demonstrated. Multiple fine structural analyses alongside with the density-functional theory (DFT) calculations are implemented to confirm the synergistic effect of noncovalent interactions (hydrogen bonding interaction, π - π stacking interaction, and van der Waals attraction) plays a critical role in the robust micro-structure and a massive 700% enhancement of mechanical strength via adding only 0.3 wt% OH-BNNS and GO. Importantly, profiled from broadband optical absorption ability, robust mechanical properties and outstanding flexibility, the self-assembled 3D OH-BNNS/GO/TPU nanofiber film reveals an adorable evaporation rate of 4.04 kg m-2  h-1 under one sun illumination with stable energy transfer efficiency (93.2%) by accompanying hydrogen bonding interaction. This microfluidic-assisted self-assembly strategy will provide a constructive entry point for the rational design of nanofibers and beyond.

6.
RSC Adv ; 12(38): 24647-24653, 2022 Aug 30.
Artículo en Inglés | MEDLINE | ID: mdl-36128377

RESUMEN

Density functional theory (DFT) simulations were conducted to study the crystal structures, and mechanical and electronic properties of a series of new energetic molecular perovskites, including (C6H14N2)[Na(ClO4)3], (C6H14N2)[K(ClO4)3], (C4H12N2)[Na(ClO4)3] and (C6H14N2O)[K(ClO4)3], abbreviated as DAP-1, DAP-2, PAP-1, and DAP-O2, respectively. By calculating the elastic constants, moduli (Young's modulus E, bulk modulus B, and shear modulus G), Poisson ratio ν and Pugh's ratio B/G, we found that the four energetic molecular perovskites not only possessed good mechanical stability but excellent mechanical flexibility and ductility. In addition, DFT calculations were used to investigate the electronic properties of all of the perovskite compounds. The band gaps of DAP-1 and DAP-2 were comparable, and the band gap of PAP-1 was the smallest and that of DAP-O2 was the largest. A comprehensive analysis of the density of states and the M-O bonding characteristics provided a good explanation for the band gap characteristics. Besides, we found that the modulus properties of these molecular perovskite energetic compounds are also tightly bound to the strength of M-O bonding.

7.
ACS Omega ; 7(20): 17185-17191, 2022 May 24.
Artículo en Inglés | MEDLINE | ID: mdl-35647461

RESUMEN

Density functional theory simulations were carried out to investigate energetic molecular perovskite (C6H14N2)(NH2NH3)(ClO4)3 which was a new type energetic material promising for future application. The electronic properties, surface energy, and hydrogen bonding of (100), (010), (011), (101), (111) surfaces were studied, and the anisotropic impact sensitivity of these surfaces were reported. By comparing the values of the band gaps for different surface structures, we found that the (100) surface has the lowest sensitivity, while the (101) surface was considered to be much more sensitive than the others. The results for the total density of states further validated the previous conclusion obtained from the band gap. Additionally, the calculated surface energy indicated that surface energy was positively correlated with impact sensitivity. Hydrogen bond content of the surface structures showed distinct variability according to the two-dimensional fingerprint plots. In particular, the hydrogen bond content of (100) surface was higher than that of other surfaces, indicating that the impact sensitivity of (100) surface is the lowest.

8.
ACS Omega ; 7(11): 9333-9342, 2022 Mar 22.
Artículo en Inglés | MEDLINE | ID: mdl-35356691

RESUMEN

We used all-atom molecular dynamics simulations to study the ion transport in the 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide/poly(vinylidene fluoride) (EMITFSI/PVDF) system with 40.05 wt % EMITFSI at different temperatures. The glass-transition temperature (T g = 204 K) of this system shows a good agreement with the experimental value (200 K). With the increase of temperature, the peaks of the pair correlation function show an increasing trend. Interestingly, the coordination numbers of ion pairs and the degree of independent ion motion are mainly affected by the binding energy between ion pairs as the temperature increases. In addition, the ion transport properties with increasing temperature can be studied by the ion-pair relaxation times, ion-pair lifetimes, and diffusion coefficients. The simulation results illustrate that the ion transport is intensified. Especially, the cations can always diffuse faster than the anions. The power law shows that mobilities of anions and cations are seen to exhibit a "superionic" behavior. With the increase of temperature, transference numbers of anions decrease first and then increase and transference numbers of cations show the opposite changes; ionic conductivity increases gradually; and viscosity decreases gradually, indicating that the diffusion resistance of ions decreases. In general, after adding PVDF into the EMITFSI system, the glass-transition temperature and viscosity increase, the ionic conductivity and degree of independent ion motion decrease, and diffusion coefficients of cations decrease faster than those of the anions.

9.
Nanotechnology ; 33(10)2021 Dec 13.
Artículo en Inglés | MEDLINE | ID: mdl-34823235

RESUMEN

Graphene materials are widely used as a physical barrier when applying anticorrosion polymer coatings due to their large surface area and layered structure. However, the electrical conductivity of intrinsic graphene can accelerate galvanic corrosion and shorten the protection period. In this work, fluorine and nitrogen co-doped graphene oxide (FNGO) was synthesized by a hydrothermal process and acted as an anticorrosion filler in waterborne styrene acrylic coatings. Styrene acrylic coatings with 0.4 wt% FNGO showed a corrosion current density that was two orders of magnitude lower than the other samples in the potential polarization test and the largest impedance modulus in the electrochemical impedance spectroscopy results. The outstanding corrosion protection was attributed to the graphene acting as a physical barrier and the synergistic effect of the doped fluorine and nitrogen. In addition to the 'labyrinth effect' of the graphene matrix, the nitrogen atoms inserted in the graphene plane and fluorine atoms grafted on the graphene simultaneously adjusted the electrical properties of graphene, prohibiting electron transport between it and the styrene acrylic resin matrix. This result indicates that doped graphene oxide has great potential to increase the corrosion resistance of waterborne coatings.

10.
Colloids Surf B Biointerfaces ; 207: 112015, 2021 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-34364252

RESUMEN

A series of polyacrylate/nanoemulsion composites were prepared to form a new kind of nanoemulsion, their particle sizes and polydispersity indices were measured. The particle sizes of the polyacrylate/nanoemulsion composites are consistent with nanoemulsions used in the system. In addition, an ELISA-specific antigen-antibody binding method was used for physical adsorption experiments on ovalbumin. Results showed that the adsorption performance of the polyacrylate/nanoemulsion system is best when the particle size was 55 nm, and the nanoemulsion content was 20 wt%, 30 wt%, or 40 wt%. Meanwhile, in order to select the optimum experimental conditions, in vivo immunity experiments in mice were carried out to analyze the adjuvant properties of ovalbumin as a model antigen. Analysis of ovalbumin-specific IgG, IgG1, and IgG2a antibody titers showed the best results when the particle size of the polyacrylate/nanoemulsion composites is 55 nm, the polyacrylate content is 0.5 wt%, and the nanoemulsion contents is 20 wt%. Meanwhile, titer analysis also showed that the polyacrylate obviously enhanced the IgG2a titer in mice. Our polyacrylate/nanoemulsion composites can both stimulate humoral and cellular immunity and have an enhanced adjuvant effect on water-soluble protein antigens.


Asunto(s)
Adyuvantes Inmunológicos , Antígenos , Adyuvantes Inmunológicos/farmacología , Animales , Inmunidad Celular , Ratones , Ovalbúmina , Tamaño de la Partícula
11.
Molecules ; 26(16)2021 Aug 12.
Artículo en Inglés | MEDLINE | ID: mdl-34443464

RESUMEN

In order to better understand the role of binder content, molecular dynamics (MD) simulations were performed to study the interfacial interactions, sensitivity and mechanical properties of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/2,4,6-trinitrotoluene (CL-20/TNT) based polymer-bonded explosives (PBXs) with fluorine rubber F2311. The binding energy between CL-20/TNT co-crystal (1 0 0) surface and F2311, pair correlation function, the maximum bond length of the N-NO2 trigger bond, and the mechanical properties of the PBXs were reported. From the calculated binding energy, it was found that binding energy increases with increasing F2311 content. Additionally, according to the results of pair correlation function, it turns out that H-O hydrogen bonds and H-F hydrogen bonds exist between F2311 molecules and the molecules in CL-20/TNT. The length of trigger bond in CL-20/TNT were adopted as theoretical criterion of sensitivity. The maximum bond length of the N-NO2 trigger bond decreased very significantly when the F2311 content increased from 0 to 9.2%. This indicated increasing F2311 content can reduce sensitivity and improve thermal stability. However, the maximum bond length of the N-NO2 trigger bond remained essentially unchanged when the F2311 content was further increased. Additionally, the calculated mechanical data indicated that with the increase in F2311 content, the rigidity of CL-20/TNT based PBXs was decrease, the toughness was improved.

12.
RSC Adv ; 11(46): 29042-29051, 2021 Aug 23.
Artículo en Inglés | MEDLINE | ID: mdl-35478560

RESUMEN

Smart polymeric vesicles with both tertiary amine and epoxy functional groups were fabricated for the first time via a reversible addition-fragmentation chain transfer dispersion polymerization approach, using (2-(diisopropylamino)ethyl methacrylate (DIPEMA) and glycidyl methacrylate (GlyMA) in an ethanol-water mixture. Monitoring of the in situ polymerization revealed the low molecular weight distributions and the intermediate structures of spheres and worms, indicating an evolution in particle morphology. A phase diagram was constructed for reproducible fabrication of the vesicles, and copolymer composition was found to be more related to particle morphology. The vesicles exhibited superior structural stability for the cross-linking of the core through epoxydiamine chemistry, and intelligent pH responsibility due to the presence of the tertiary amine groups. The cross-linked vesicles showed good stability and reversibility during the swelling and shrinking cycles by switching the pH values, which endowed them with potential cell-like transmission functions. This research thus provides a method for producing structurally stable pH-responsive polymeric vesicles, and the reported vesicles are based on commercially available starting materials for possible industrial scale-up.

13.
Adv Mater ; 33(3): e2006093, 2021 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-33274802

RESUMEN

Fabrication of soft piezoelectric nanomaterials is essential for the development of wearable and implantable biomedical devices. However, a big challenge in this soft functional material development is to achieve a high piezoelectric property with long-term stability in a biological environment. Here, a one-step strategy for fabricating core/shell poly(vinylidene difluoride) (PVDF)/dopamine (DA) nanofibers (NFs) with a very high ß-phase content and self-aligned polarization is reported. The self-assembled core/shell structure is believed essential for the formation and alignment of ß-phase PVDF, where strong intermolecular interaction between the NH2 groups on DA and the CF2 groups on PVDF is responsible for aligning the PVDF chains and promoting ß-phase nucleation. The as-received PVDF/DA NFs exhibit significantly enhanced piezoelectric performance and excellent stability and biocompatibility. An all-fiber-based soft sensor is fabricated and tested on human skin and in vivo in mice. The devices show a high sensitivity and accuracy for detecting weak physiological mechanical stimulation from diaphragm motions and blood pulsation. This sensing capability offers great diagnostic potential for the early assessment and prevention of cardiovascular diseases and respiratory disorders.


Asunto(s)
Técnicas Biosensibles/métodos , Dopamina/química , Electricidad , Nanofibras/química , Polivinilos/química
14.
BMC Plant Biol ; 19(1): 41, 2019 Jan 25.
Artículo en Inglés | MEDLINE | ID: mdl-30683049

RESUMEN

BACKGROUND: Schima superba (Theaceae) is a popular woody tree in China. The obscure chromosomal characters of this species are a limitation in the development of high-density genetic linkage maps, which are valuable resources for molecular breeding and functional genomics. RESULTS: We determined the chromosome number and the karyotype of S. superba as 2n = 36 = 36 m, which is consistent with the tribe Schimeae (n = 18). A high-density genetic map was constructed using genotyping by sequencing (GBS). A F1 full-sib with 116 individuals and their parents (LC31 × JO32) were sequenced on the Illumina HiSeq™ platform. Overall, 343.3 Gb of raw data containing 1,191,933,474 paired-end reads were generated. Based on this, 99,966 polymorphic SNP markers were developed from the parents, and 2209 markers were mapped onto the integrated genetic linkage map after data filtering and SNP genotyping. The map spanned 2076.24 cM and was distributed among 18 linkage groups. The average marker interval was 0.94 cM. A total of 168 quantitative trait loci (QTLs) for 14 growth traits were identified. CONCLUSIONS: The chromosome number and karyotype of S. superba was 2n = 36 = 36 m and a linkage map with 2209 SNP markers was constructed to identify QTLs for growth traits. Our study provides a basis for molecular-assisted breeding and genomic studies, which will contribute towards the future research and genetic improvement of S. superba.


Asunto(s)
Cromosomas de las Plantas/genética , Theaceae/genética , Mapeo Cromosómico , Marcadores Genéticos/genética , Técnicas de Genotipaje , Cariotipificación , Polimorfismo de Nucleótido Simple/genética , Sitios de Carácter Cuantitativo/genética , Análisis de Secuencia de ADN
15.
J Hazard Mater ; 175(1-3): 423-8, 2010 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-19954888

RESUMEN

Molecular dynamical (MD) simulations with the COMPASS force field were employed to investigate the influences of temperature (T), the concentration of F(2314) binder (W%), and crystal defects on the mechanical properties, binding energy (E(bind)), and detonation properties of epsilon-CL-20(001)/F(2314) PBX (polymer bonded explosives). T was found to have some influences on the mechanical properties, and the PBX at 298 K was considered with better mechanical properties. By radial distribution function g(r) analysis the three types of hydrogen bonds, H...O, H...F, and H...Cl were predicted as the main interaction formats between F(2314) and epsilon-CL-20, and the strength of these interactions changed with temperature changing. The isotropic properties of the PBX increased with W% increasing, but each modulus and E(bind) did not monotonously vary with W% increasing. The detonation properties of the PBX decreased with the increasing W%, and the PBX with 4.69% F(2314) was regarded with good detonation properties. The existence of crystal defects (vacancy or adulteration) might increase the elasticity but destabilize the system to some extent, and the mechanical properties of PBX were chiefly determined by the main body explosive. The above information was thought guidable for practical formulation design of PBX.


Asunto(s)
Sustancias Explosivas/química , Algoritmos , Simulación por Computador , Cristalización , Elasticidad , Sustancias Peligrosas , Enlace de Hidrógeno , Polímeros/química , Probabilidad , Estrés Mecánico , Temperatura
16.
J Hazard Mater ; 167(1-3): 810-6, 2009 Aug 15.
Artículo en Inglés | MEDLINE | ID: mdl-19231074

RESUMEN

An all-atom force field for ammonium perchlorate (AP) is developed with the framework of pcff force field. The structural parameters of AP obtained with the modified force field are in good agreement with experimental values. Molecular dynamics (MD) simulations have been performed to investigate AP/HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane) composite at different temperatures. The binding energies, thermal expansion coefficient, and the trigger bond lengths of HMX in the AP/HMX composite have been obtained. The binding energies of the system increase slightly with temperature increasing, peak at 245K, and then gradually decrease. The volume thermal expansion coefficient of the AP/HMX composite has been derived from the volume variation with temperature. As the temperature rises, the maximal lengths of the trigger bond N-NO(2) of HMX increase gradually. The simulated results indicate that the maximal length of trigger bond can be used as a criterion for judging the sensitivity of energetic composite.


Asunto(s)
Simulación por Computador , Percloratos/química , Compuestos de Amonio Cuaternario/química , Termodinámica , Modelos Moleculares , Movimiento (Física)
17.
J Hazard Mater ; 164(2-3): 1082-8, 2009 May 30.
Artículo en Inglés | MEDLINE | ID: mdl-18938030

RESUMEN

Molecular dynamics simulations have been performed to investigate well-known energetic material cyclotrimethylene trinitramine (RDX) crystal and RDX-based plastic-bonded explosives (PBXs) with four typical fluorine-polymers, polyvinylidenedifluoride (PVDF), polychlorotri-fluoroethylene (PCTFE), fluorine rubber (F(2311)), and fluorine resin (F(2314)). The elastic coefficients, mechanical properties, binding energies, and detonation performances are obtained for the RDX crystal and RDX-based PBXs. The results indicate that the mechanical properties of RDX can be effectively improved by blending with a small amount of fluorine polymers and the overall effect of fluorine polymers on the mechanical properties of the PBXs along three crystalline surfaces is (001)>(010) approximately (100) and PVDF is regarded to best improve the mechanical properties of the PBXs on three surfaces. The order of the improvement in the ductibility made by the fluorine polymers on different surfaces is (001) approximately (010)>(100). The average binding energies between different RDX crystalline surfaces and different polymer binders are obtained, and the sequence of the binding energies of the PBXs with the four fluorine polymers on the three different surfaces is varied. Among the polymer binders, PVDF is considered as best one for RDX-based PBXs. The detonation performances of the PBXs decrease in comparison with the pure crystal but are superior to those of TNT.


Asunto(s)
Simulación por Computador , Sustancias Explosivas , Triazinas , Cristalización , Flúor , Plásticos , Polímeros
18.
J Phys Chem B ; 112(13): 3882-93, 2008 Apr 03.
Artículo en Inglés | MEDLINE | ID: mdl-18331016

RESUMEN

On the basis of density functional theory (DFT) and molecular dynamics (MD), the structural, electronic, and mechanical properties of the energetic material bicyclo-HMX have been studied. The crystal structure optimized by the LDA/CA-PZ method compares well with the experimental data. Band structure and density of states calculations indicate that bicyclo-HMX is an insulator with the band gap of ca. 3.4 eV and the N-NO(2) bond is the reaction center. The pressure effect on the bulk structure and properties has been investigated in the range of 0-400 GPa. The crystal structure and electronic character change slightly as the pressure increases from 0 to 10 GPa; when the pressure is over 10 GPa, further increment of the pressure determines significant changes of the structures and large broadening of the electronic bands together with the band gap decreasing sharply. There is a larger compression along the c-axis than along the a- and b-axes. To investigate the influence of temperature on the bulk structure and properties, isothermal-isobaric MD simulations are performed on bicyclo-HMX in the temperature range of 5-400 K. It is found that the increase of temperature does not significantly change the crystal structure. The thermal expansion coefficients calculated for the model indicate anisotropic behavior with slightly larger expansion along the a- and c-axes than along the b-axis.


Asunto(s)
Compuestos Bicíclicos Heterocíclicos con Puentes/química , Compuestos Bicíclicos con Puentes/química , Simulación por Computador , Sustancias Explosivas/química , Modelos Químicos , Temperatura , Presión Hidrostática , Conformación Molecular
19.
J Hazard Mater ; 156(1-3): 201-7, 2008 Aug 15.
Artículo en Inglés | MEDLINE | ID: mdl-18243539

RESUMEN

To investigate the structure and performance of simple and double bases propellants, the nitrocellulose (NC), nitroglycerin (NG), and double mixed system (NC+NG) have been simulated by using the molecular dynamics (MD) method with the COMPASS force field. The interactions between NC and NG have been analyzed by means of pair correlation functions. The mechanical properties of the three model systems, i.e. elastic coefficients, modulus, Cauchy pressure, and Poisson's ratio, etc., have been obtained. It is found that the rigidity, ductibility, and tenacity of the double bases propellants (NC+NG) are stronger than those of simple base propellants (NC), which attributes to the effect of NG and the strong interactions between NC and NG. The detonation properties of the three systems have also been calculated and the results show that compared with the simple base propellant (NC), the detonation heat and detonation velocity of the double base propellants (NC+NG) are increased.


Asunto(s)
Sustancias Explosivas/química , Modelos Moleculares , Estructura Molecular
20.
J Phys Chem B ; 111(7): 1559-66, 2007 Feb 22.
Artículo en Inglés | MEDLINE | ID: mdl-17266354

RESUMEN

Molecular dynamics has been applied to investigate the low-sensitivity explosive TNAD (trans-1,4,5,8-tetranitro-1,4,5,8-tetraazadecalin)-based polymer-bonded explosives (PBXs) with four typical fluorine polymers, PVDF (polyvinylidenedifluoride), PCTFE (polychlorotrifluoroethylene), F(2311) (fluorine rubber), and F(2314) (fluorine resin). The elastic constants, mechanical properties (tensile modulus, bulk modulus, shear modulus, and Poission ratio), binding energies, and detonation performances are first reported for the TNAD-based PBXs. The results show that the mechanical properties of TNAD can be effectively improved by the addition of small amounts of fluorine polymers, and the overall effect of fluorine polymers on the mechanical properties of the PBXs along three crystalline surfaces is (001) > (010) > (100). On each crystal surface, improvement in the ductibility made by the fluorine polymers changes approximately in the sequence of PVDF > F(2311) > F(2314) > PCTFE. The binding energies between different TNAD crystalline surfaces and different polymer binders with the same chain segment or mass fraction both decrease in the order of (010) > (100) > (001). The binding properties of the polymers with the same chain segment on each crystal surface of TNAD increase as PVDF < F(2311) < F(2314) < PCTFE, while those of different polymers in the same content decrease in the sequence of PVDF > F(2311) > F(2314) > PCTFE. The detonation performances of the PBXs decrease in comparison with the pure crystal, but they are superior to those of TNT.

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