Zewu Zhang

A new design strategy on cage insensitive high explosives: symmetrically replacing carbon atoms by nitrogen atoms followed by the introduction of N-oxides

In this work, using hexaprismane as a base skeleton, we designed a novel cage energetic compound 1,3,5,7,9,11-hexaazahexaprismane-1,3,5,7,9,11-hexaoxdies (HAHHO) by employing a new design strategy: symmetrically replacing six carbon atoms by nitrogen atoms in hexaprismane followed by the introduction of six N-oxides. Its detonation performance and sensitivity were estimated by using the density functional theory method. It was found that HAHHO possesses much higher energetic performance than 1,3,5,7-tetranitro-1,3,5,7-tetrazocane and lower sensitivity than 2,4,6-trinitrotoluene, suggesting that its overall performance are outstanding and may be considered as the potential candidate of insensitive high explosives. The special double cage structure of HAHHO may be an important reason why it has low sensitivity. The results show that our strategy used for designing HAHHO is practical and may be applied to design and develop other cage explosives with high energy and low sensitivity.

Selective deposition of Au-Pt alloy nanoparticles on ellipsoidal zirconium titanium oxides for reduction of 4-nitrophenol

Au-Pt alloy nanoparticles that are selectively anchored on TiO2 surface of the ellipsoidal zirconium titanium composite oxides were successfully prepared by a facile two-step method: prefabricated binary composite oxides on the ellipsoidal Fe2O3@SiO2 by a versatile cooperative template-directed coating method, and then in situ formation of Au-Pt alloy NPs with Sn2+ as the reduction agent. The alloy catalysts were characterized by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The result suggested that highly dispersive and ultrafine Au-Pt alloy nanoparticles were deposited onto TiO2 surface of the binary oxides solely. The particle size of nanoalloys was closely related to the ratio of Zr: Ti in the composite oxides shell. Increasing the content of Zr element led to a growth in the size of alloy nanoparticles. When used as catalysts for the reduction of 4-nitrophenol, the prepared supported alloyed catalysts exhibited high catalytic activity, and the sample could be easily recycled without a significant decrease of the catalytic activity.

The search for new powerful energetic transition metal complexes based on 3,3′-dinitro-5,5′-bis-1,2,4-triazole-1,1′-diolate anion: a DFT study

In this study, employing a new high oxygen balance energetic 3,3′-dinitro-5,5′-bis-1,2,4-triazole-1,1′-diolate anion (DNBTDO) as the bidentate ligand, NH3 and NH2NO2 as short energetic ligands, and Cu/Ni as the metal atoms, two series of novel energetic metal complexes were computationally designed. Their structures and properties were studied by density functional theory, electrostatic potential data, and molecular mechanics methods. The results showed that the designed metal complexes have high detonation performance and acceptable sensitivity: Cu/Ni(DNBTDO)(NH2NO2)2 (A3/B3) have better detonation properties and lower sensitivity than the most powerful CHNO explosive hexanitrohexaazaisowurtzitane, Cu/Ni(DNBTDO)(NH3)(NH2NO2) (A2/B2) have comparable energetic performance and sensitivity with 1,3,5,7-tetranitro-1,3,5,7-tetrazocane, Ni(DNBTDO)(NH3)2 (B1) has comparative energy level and sensitivity with 1,3,5-trinitro-1,3,5-triazinane. These five energetic metal complexes may be attractive to energetic materials researchers. Besides, both the energetic ligands and metal atoms could have a great influence on the structures, heats of formation, detonation properties, and stability of energetic metal complexes, and the effects are coupled with each other. This study may be helpful in the search for and development of new improved energetic materials.

Preparation of platinum nanoparticles immobilized on ordered mesoporous Co3O4–CeO2 composites and their enhanced catalytic activity

Using mesoporous silica KIT-6 as a template, ordered mesoporous Co3O4–CeO2 composites with different contents of cobalt were prepared via the hard template method. Uniform Pt nanoparticles stabilized by polyamidoamine (PAMAM) dendrimers were immobilized on different Co3O4–CeO2 composites, resulting in Pt-based supported catalysts. The prepared materials were characterized by several techniques such as transmission electron microscopy (TEM), nitrogen physical adsorption, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and energy dispersion X-ray analysis (EDX). The results showed that the Co3O4–CeO2 composites have a regular pore structure and high crystallinity. Moreover, the specific surface area of Co3O4–CeO2 reached 135.04 m2 g−1 for 10 mol% of cobalt (Co/(Co + Ce)). The introduction of cobalt could improve the structure of the supports and enhance the catalytic efficiency for the prepared Pt-based supported catalysts. The catalytic performances were evaluated by the reduction of 4-nitrophenol as monitored by UV-Vis spectra. In a comparison of the catalysts with different cobalt contents, it was found that Pt/meso-CeO2Co10 possessed the highest catalytic performance as well as good reusability.

Facile one-step synthesis of TiO 2 /Ag/SnO 2 ternary heterostructures with enhanced visible light photocatalytic activity

Novel TiO2/Ag/SnO2 composites were successfully prepared by a facile one-step reduction approach using stannous chloride as both SnO2 precursor and reducing agent. The Ag nanoparticles with sizes of 2.04–3.94 nm were located on TiO2 matrix and immobilized by the surrounded SnO2. The resulted TiO2/Ag/SnO2 nanocomposites were used as photocatalyst for photodegradation of methylene blue under visible light. The experimental results demonstrated that the visible light photocatalytic activity of the TiO2/Ag/SnO2 was significantly enhanced in comparison with the individual TiO2 or the binary composite (TiO2/Ag or TiO2/SnO2) and the degradation rate was up to about 9.5 times that of commercial TiO2. The photocatalytic activity of the TiO2/Ag/SnO2 composites could be well controlled by simply tuning the dosages of Ag precursor and the optimized activity of the composites was obtained when the dosage of Ag precursor was 2%. Moreover, the TiO2/Ag/SnO2 photocatalyst exhibited high stability for degradation of methylene blue even after four successive cycles.

Hierarchical Carbon Nanotube@SiO2-TiO2 Reinforced Polyurethane Composites: Thermal, Mechanical and Abrasion Resistance Properties

ABSTRACT In this study, novel polyurethane-based composites reinforced by hierarchical CNTs@SiO2-TiO2 were fabricated via in situ polymerization. Significant improvement of the composites in thermal stability was achieved by incorporating functionalized CNTs up to 2.0 wt%. Meanwhile, the tensile strength, strain-at-break, and Young’s modulus were greatly improved by increasing nanotube loading. The Abrasion losses could be significantly decreased to 30 mm3/1.61 km due to the addition of functionalized CNTs. Therefore, the introduction of nanosized hierarchical SiO2-TiO2 coated CNTs has a stimulative effect on the simultaneous mechanical reinforcement and abrasion resistance modification for polyurethane. GRAPHICAL ABSTRACT

Density Function Theory Study on Effects of Different Energetic Substituent Groups and Bridge Groups on Performance of Carbon-Linked Ditetrazole 2N-Oxides

Based on the parent tetrazole 2N -oxide, six series of novel carbon-linked ditetrazole 2N oxides with different energetic substituent groups (-NH2, -N3, -NO2, NF2, -NHNO2) and energetic bridge groups (-CH2-, -CH2−CH2-, -NH-, -N=N-, -NH−NH-) were designed. The overall performance and the effects of different energetic substituent groups and energetic bridge groups on the performance were investigated by density functional theory and electrostatic potential methods. The results showed that most of designed compounds have oxygen balance around zero, high heats of formation, high density, high energy, and acceptable sensitivity, indicating that tetrazole N -oxide is a useful parent energetic compound employed for obtaining high energy compounds, even only combined with some very common energetic substituent groups and bridge groups. Comprehensively considering the effects on energy and sensitivity, the -NO2, -NF2, -NHand -NH−NHare appropriate substituent groups for combining tetrozale N -oxide to design new energetic compounds, while -NH2, -N3, -CH2−CH2-, and -N=Nare inappropriate.