Synthesis and characterization of a new organic-inorganic hybrid polyphosphazene polymer

A new organic-inorganic hybrid polyphosphazene polymer was synthesized via sequential nucleophilic substitution using allylamine and phenol. The polymer was characterized by FTIR, 1H-NMR, and 31P-NMR spectra. The thermal properties were studied by DSC and TGA. It was found that the polymer has good thermal stability. Char yields of the polymer reaches to 48.6% at 800 ℃. The high char yield makes it possible in theory for the polymer to be used as flame retardant. By cross linking, the thermal stability of the polymer could be improved further.     

Theoretical Investigations on the Structure,Density, Thermodynamic and Performance Properties of Bis（2,2-dinitropropyl） formal

Density functional method was used to investigate the IR spectrum,heat of formation and thermal stability of a new energetic material bis(2,2-dinitropropyl) formal(BDNPF).The detonation velocity and pressure were evaluated by using the Kamlet-Jacobs equations based on the theoretical density and heat of formation.The bond dissociation energies for the weakest bonds were analyzed to investigate the thermal stability of the title compound.The results show that the C(1)-N(1) bond is predicted to be the trigger bond during pyrolysis.The crystal structure obtained by molecular mechanics belongs to the P21 space group,with the lattice parameters to be Z = 2,a = 11.5254,b = 6.2168,c = 9.5000  and ρ= 1.66 g/cm3.     

A novel terbium complex using oxadiazole derivative as a neutral ligand： Synthesis and properties

A novel terbium complex using 1,3,4-oxadiazole derivative as a neutral ligand was synthesized and characterized. Its thermal stability and photoluminescent properties were studied. The strong emission peaked at 546 nm with a full width at half maximum of 5 nm was observed in the pure terbium complex film under excitation of 328 nm light, which is attributed to the characteristic emission of terbium ion. The good thermal stability and intense sharp emission of this terbium complex display its potential application in electroluminescence devices.     

Synthesis and Photoelectrical Properties of D-A Type Carbazole-quinoline

The key issues concerning the design and synthesis of high fluorescent efficiency, good thermal stability of organic blue materials should be solved urgently in organic light emitting diodes. In this article, three D-A type blue emitters based on carbazole and phenylquinoline with flexible chains were prepared through Friedlander condensation reaction in relatively high yield. The photoelectric properties of all compounds were studied by UV-vis absorption, emission spectra and cyclic voltammograms. Density functional theory calculations(DFT) were performed to obtain a better understanding of the electronic structures. Interestingly, compound a3 with the highest fluorescence quantum yield of 0.53 can be applied into blue light emission materials on account of good thermal performance. Furthermore, a1～a3 with narrow band gap make them become potential candidates in the fields of OLED, solar cells and OFET.     

FUNDAMENTAL PROBLEMS IN FINITE ELEMENT SIMULATION OF WAVE MOTION

The transmitting boundary condition is written in a compact form, which can be direct-ly incorporated into finite elements. Basic characteristics of discretization are analyzed throughstudies on wave motion in a one-dimensional discrete model and their differences from those in thecorresponding continuum. Tbe analysis leads to identifying a frequency band within which thesimulation is possible, and to a suggestion of using the lumped-mass finite element model forthe simulation. Mechanism of the oscillation instability is then illuminated in the frequencydomain by amplification at the artificial boundary and multi-reflection of wave motion in afinite discrete model. Based on understanding of the mechanism, a modified transmittingboundary condition is devised for eliminating the instability. The special stability criterion forthe modified boundary is finally presented for the one-dimensional model.     

A Novel Carbon Nanotube-Supported NiP Amorphous Alloy Catalyst and Its Hydrogenation Activity

A carbon nanotube-supported NiP amorphous catalyst (NiP/CNT) was prepared by induced reduction. Benzene hydrogenation was used as a probe reaction for the study of catalytic activity. The effects of the support on the activity and thermal stability of the supported catalyst were discussed based on various characterizations, including XRD, TEM, ICP, XPS, H2-TPD, and DTA. In comparison with the NiP amorphous alloy, the benzene conversion on NiP/CNT catalyst was lower, but the specific activity of NiP/CNT was higher, which is attributed to the dispersion produced by the support, an electron-donating effect, and the hydrogen-storage ability of CNT. The NiP/CNT thermal stability was improved because of the dispersion and electronic effects and the good heat-conduction ability of the CNT support.     

Temperature Controlled Lateral Pattern Formation in Confined Polymer Thin Films

The thermal induced topography change in a model system consisting of a polymer film on a Si substrate capped by a thin metal layer has been studied by using AFM. Regular lateral patterns over large areas were observed on the surface when the system was heated to a sufficiently high temperature. 2D-FFT analysis to the AFM images indicates that the patterns are isotropic and have well defined periodicities. The periodicities of the characteristic patterns are found to depend strongly on the annealing temperature. The study of the ki-netics of the formation reveals that such a topography forms almost instantaneously once the critical tempera-ture is reached. It is suggested that this wave-like surface morphology is driven by the thermal expansion co-efficient mismatch of the different layers. This method for generating regular wave-like patterns could be used as a general method for patterning various organic materials into micro/nanostructures.     

Effects of preparation conditions of Au/FeOx/Al203 catalysts prepared by a modified two-step method on the stability for CO oxidation

Composite oxide FeO x /Al 2 O 3 -supported gold catalysts were prepared by a modified two-step method. The effects of preparation conditions on the initial catalytic activity and long-time stability were studied for CO oxidation. XRD, XPS and in situ FTIR were employed to investigate the state of FeO x and the species on the catalyst surface. The results showed that Au/FeO x /Al 2 O 3 catalysts prepared by this method exhibited high activity and high stability in a wide pH value range. Calcination pretreatment was proved to be beneficial to improving the activity and stability. The beneficial effects of FeO x acting as a structural promoter could be ascribed to the ability to supply active oxygen species. As the precursor of FeO x , Fe(NO 3 ) 3 is superior to FeCl 3 for obtaining higher stability.     

MISCIBILITY, THERMAL STABILITY AND RETENTION OF PVP FOR CROSSLINKED PVA/PVP BLENDS

The thermal behavior, miscibility, crystallite conformation and thermal stability ofcrosslinked(CL-) PVA/PVP blends were studied by DSC and TG methods, respectively. DSCresults showed that in the blend, the crystallinity,T_m and T_c of PVA were obviously lower thanthose of pure PVA; the crystal growth changed from three dimensional to two dimensional andonly a single T_g was detected. These facts demonstrated that this crystalline and amorphousblend have good miscibility. TG curves showed that providing the quantity of K_2S_2O_8 added ismore than 3 wt%,in the blends PVA will form a stable CL-network, whose thermal degradationtemperature was near to that of PVP. But crosslinking reaction will not take place for PVP. Theprocesses of thermal degradation of CL-blends are based on combining both the thermaldegradation of PVP and that of PVA crosslinked with corresponding quantity of K_2S_2O_8 CL-agent, respectively. The UV measurements showed that 75 wt% of PVP may be remained in CL-blend hydrogelscrosslinked by adding (3--5 wt% )K_2S_2O_8. This is mainly due to the stable CL-network formed and the good compatibility and properentanglement between the composites in the CL-blends.     

Second-order Nonlinear Optical Properties of a Series of Benzothiazole Derivatives

The second-order nonlinear optical (NLO) properties of a series of benzothiazole derivatives were studied by use of the ZINDO-SOS method.These chromophores are formed by a donor- π- bridge-acceptor system,based on a nitro group connected with benzothiazole as the acceptor and a hydroxyl-functional amino group as the donor.For the purpose of comparison,we also designed molecules in which nitrobenzene is an acceptor,The calculation results indicate that benzothiazole derivatives exhibit larger second-odrder polarizabilities than nitrobenzene derivatives.In order to clarify the origin of the NLO response of these chromophores,their electron properties were investigated as well.The benzothiazole derivatives are good candidates for application in electro-optical device due to their high optical nonlinearities,good thermal and photonic stability.     

JOB-9003炸药热老化寿命评估及其结构表征

采用经典的布氏压力计对JOB-9003炸药在60~90℃低温点及110~140℃高温点进行了热分解实验,并对其热老化寿命进行了评估,利用SPME-GC-MS、XPS对低温段分解释出的气体种类和分解后的凝聚相分别进行了定性分析和表面结构分析。结果表明:JOB-9003炸药在60~90℃下具有较好的热安定性能,不易发生热分解反应,其表面结构没有发生变化;当分解深度达0.1%时,JOB-9003炸药在60℃下可贮存34.4年。     

Amine and nitramine functionalization of imidazole-triazine and triazole-triazine skeletons: Exploring for potential multipurpose energetic materials

A series of five and six-membered C-C bonded energetic materials ( 2 – 7 ) based on a combination of imidazole-triazine and triazole-triazine backbones were designed, synthesized, and characterized using NMR, IR, Mass spectrometry, and TGA-DSC studies. Further, the structure of compound 4 was supported by single-crystal X-ray analysis. All the newly synthesized energetic compounds exhibit good density, excellent thermal stability, good detonation performance, and low mechanical sensitivity toward impact and friction. Among all, the nitrate salt 4 exhibits balanced properties, including high density (1.80 g cm⁻³), excellent thermal stability (254°C), good detonation velocity (8178 m s⁻¹), and low sensitivity towards impact and friction. The facile synthetic feasibility, thermal stability, energetic performance, and insensitivity of all the molecules suggest they can be used as an insensitive secondary explosive in various defense and civilian applications.     

Correlations Between Laser Induced Breakdown Spectroscopy (LIBS) and Dynamical Mechanical Analysis (DMA) for Assessment of Aging Effect on Plastic Bonded Explosives (PBX)

Plastic Bonded Explosives (PBXs) are explosive materials, in which sensitive explosive powders with high detonation performance are bound together in a matrix using small quantities of a synthetic polymer. They provide good thermal stability and improve cook‐off properties with negligible shrinkage. Laser‐induced breakdown spectroscopy (LIBS) has been introduced as a novel method for assessment of thermal aging in PBXs. Thermal aging of fifteen samples of PBXs with the same composition has been studied in two temperatures 60 and 70 °C for 5 period times during 29 d. Dynamical mechanical analysis (DMA) has also been done on different aged samples in order to validate the LIBS results. Among different molecular bands, LIBS data showed that the changes in line intensity in CN and AlO molecular radiations could be used to assess aging effects. Principle component analysis (PCA) chemometric method was also implemented in order to obtain more accurate discrimination between different samples. Since there is a good agreement for the outputs of LIBS data and DMA results, LIBS technique can be introduced a reliable method for assessment of thermal aging of PBXs.     

Thermal decomposition of the high-performance oxidizer ammonium dinitramide under pressure

Ammonium dinitramide (ADN) is a promising new oxidizer for solid propellants because it possesses both high oxygen balance and high energy content, and does not contain halogen atoms. A necessary characteristic of solid propellants is chemical stability under various conditions. This study focused on the thermal decomposition mechanism of ADN under pressurized conditions. The pressure was adjusted from 0.1 to 6 MPa, while ADN was heated at a constant rate. The exothermal behavior and the decomposition products in the condensed phase during heating were measured simultaneously using pressure differential scanning calorimetry (PDSC) and Raman spectrometry. PDSC analyses showed the multiple stages of exotherms after melting. The exothermal behavior at low temperatures varied with pressure. Analysis of the decomposition products indicated that ammonium nitrate (AN) was generated during decomposition of ADN at all pressures. At normal pressure, AN was produced at the same time as start of exotherm. However, the temperature at which the ratio of ADN in chemical species in the condensed phase began to decrease under high pressure was higher than that at atmospheric pressure despite the existence of significant exotherm. At initial stage, thermal decomposition of ADN that does not generate AN was thought to be promoted by increased pressure.     

Effect of polymer addition amount and type on thermal decomposition behavior of spray-dried particles comprising ammonium nitrate,potassium nitrate,and polymer

Certain properties of ammonium nitrate (AN), such as high hygroscopicity and the thermal transformation of the crystal structure accompanied by volume changes, pose problems for industrial applications of AN. To solve these problems, we previously prepared AN-based particles by spray-drying. The particles contained potassium nitrate (PN) as a phase stabilizer and a polymer (e.g., PVA, CMCs, and Latex) to produce a moisture-resistant material. Herein, we investigate the thermal decomposition of spray-dried AN/PN/polymer particles by differential scanning calorimetry and Thermogravimetry–Differential thermal analysis. Comparison of the thermal decomposition of AN/PN/polymer materials with different amounts and types of polymers suggested that thermal decomposition at lower temperatures resulted from the reaction of AN with the molten polymer or decomposition products derived from the polymer. Therefore, it can be concluded that the thermal stability of the AN/PN/polymer was exclusively determined by the thermal properties of the polymer components.     

Thermolysis of ammonium nitrate/potential donor of active chlorine compositions

The thermal stability of the ammonium nitrate (AN)/sodium salt of 1,3-dichlor-2,4,6-trioxo-1,3,5-triazacyclohexane (DC) composition has been studied. The factors of influence on the rates of reactions in the composition, namely, a water content, composition wetting methods, a dispersion of composition components, sample mass values, have been examined. The water presence in the composition reduces its thermal stability. The mechanism includes the partial dissociation of AN to HNO₃ and NH₃ and the hydrolysis of DC with the formation of some unstable Cl-containing compounds (chloramines, nitrogen chloride). The reaction of ammonium cation with active chlorine has been found to give rise to the explosion of the AN/DC composition. Such a situation is typical for other ammonium salt/DC compositions.     

Influence of lime-containing additives on the thermal behaviour of ammonium nitrate

Ammonium nitrate (AN) is one of the main nitrogen fertilizers used in fertilization programs. However, AN has some serious disadvantages — being well soluble in water hardly 50% of the N-species contained are assimilated by plants. The second disadvantage of AN is associated with its explosive properties. The aim of this paper was to clarify the influence of different lime-containing substances — mainly Estonian limestone and dolomite — as internal additives on thermal behaviour of AN. Commercial fertilizer grade AN was under investigation. The amount of additives used was 5, 10 or 20 mass%, or calculated on the mole ratio of AN/(CaO, MgO)=2:1 in the blends. Experiments were carried out under dynamic heating condition up to 900°C (10°C min⁻¹) in a stream of dry air or N₂ by using Setaram Labsys 2000 equipment coupled to Fourier transform infrared spectrometer (FTIR). The results of analyses of the gaseous compounds evolved at thermal treatment of neat AN indicated some differences in the decomposition of AN in air or in N₂. At the thermal treatment of AN’s blends with CaCO₃, MgCO₃, limestone and dolomite samples the decomposition of AN proceeds through a completely different mechanism — depending on the origin and the content of additives, partially or completely, through the formation of Mg(NO₃)₂ and Ca(NO₃)₂.     

Thermal characteristics of ammonium nitrate, carbon, and copper(II) oxide mixtures

Ammonium nitrate (AN) has been extensively used as an oxidizer in energetic compositions, and is a promising compound as a propellant and gas generator. It is well-known that metal oxides help to address some of the disadvantages of AN, such as low stability and a low burning rate in these applications. In order to investigate the effects of copper(II) oxide (CuO) on the thermal decompostion of AN mixtures, the thermal characteristics of AN, carbon, and CuO mixtures were measured using simultaneous differential scanning calorimetry and thermogravimetry–differential thermal analysis connected with infrared spectroscopy and mass spectrometry. As a combustible material, activated carbon (AC), and carbon black (CB) were used in this study. In the TG–DTA results for AN/AC/CuO and AN/CB/CuO mixtures in an open cell, an exotherm was observed at approximately 210 and 230 °C, respectively. In addition, the IR and mass spectra of the gases produced from the AN/AC/CuO and AN/CB/CuO mixtures indicated the presence of CO₂. Notably, the effect of CuO addition on the oxidation of the AN/AC/CuO mixture was different from that on the AN/CB/CuO mixture; the oxidation of AC shifted to a lower temperature, while the oxidation of CB shifted to a higher temperature. These results suggest that the effect of CuO on the oxidation of different types of carbon depends on the chemical reactivity of the carbon, which is derived from its physical properties.     

Thermogravimetric study of some crosslinked copolymers based on poly(acrylonitrile-co-divinylbenzene)

Copolymer networks based on acrylonitrile (AN)/divinylbenzene (DVB) have been investigated by thermogravimetric analysis (TG) to evaluate their thermal stability in nitrogen atmosphere. Thermal stability was determined from TG-DTG curves to investigate the influence of AN and DVB in the synthesis of copolymers on the copolymer thermal properties. The TG and DTG curves of copolymers clearly show two thermodegradation stages. The solid residues produced after thermodegradation stages were analyzed by FTIR and elemental analysis (CHN). The decomposition temperatures were dependent on amount of AN and DVB used as the crosslinking agent. The degradation temperatures of copolymers were influenced by the diluent system during their synthesis. FTIR analyses indicate that the cyclization of the polymer proceeds before any mass loss.     

Storage modulus’ variation in aging and its application in assessing the stability of emulsion explosive matrix

An investigation was performed into the stability of bulk emulsion explosive matrix (BEEM) via studying on the variation of storage modulus in aging. The experimental results show that there is a tight relationship between storage modulus (G′) and the stability of BEEM. The increase of the amount of ammonium nitrate (AN) crystals in aging leads to the increase of G′. When the amount of AN crystals reaches a certain extent, the vastly destroyed microstructure results in the disappear of viscoelastic property of BEEM. The results demonstrated that the less growth ratio of G′ causes a better stability of BEEM. The G′ was used to investigate the effect of the nature of emulsifier and continuous phase on the stability of BEEM. It is found that the chemical structure of head group, the length of hydrophobic chain and the content of emulsifier affect the stability of BEEM. Besides that, the viscosity and polarity of continuous phase also have important effect on the stability of BEEM.