纤维增强复合材料装甲防护性能影响因素分析研究

本文从树脂基体、增强材料以及成型工艺等多方面采用正交试验设计开展了舰船防护用纤维增强复合材料研究工作,分析了各因素对复合材料装甲材料防护12.7 mm穿燃弹性能的影响,找出了较优的树脂配方、增强纤维以及成型工艺参数。     

基于表面理论的温拌SBS改性沥青-集料体系的粘附性

采用躺滴法检测了掺加1.5%、3%的Sasobit和0.5%、1%的Evotherm 3G制备得到的温拌SBS改性沥青与蒸馏水、甘油和甲酰胺3种液体的接触角;基于表面自由能理论,对比了温拌SBS改性沥青在无水条件下的表面自由能和粘聚功以及在有水条件下的剥落功;同时,考察了温拌SBS改性沥青和石灰岩质集料的粘附功和配伍率。结果表明:采用躺滴法可以准确检测温拌SBS改性沥青与常用检测液体的接触角;以粘聚功、粘附功、剥落功、配伍率作为评价指标可用于表征温拌SBS改性沥青-集料体系的粘附性;温拌SBS改性沥青的表面自由能及其分量、粘聚功、配伍率随着Sasobit掺量的增大而减小,但随着Evotherm温拌剂掺量的增加而增大;水的参与降低了温拌剂对SBS改性沥青-集料体系粘附性影响的差异;Evotherm温拌剂有助于改善温拌SBS改性沥青的水敏感性,Sasobit温拌剂增加了温拌SBS改性沥青的水敏感性。     

电加工8418钢的能量分配与表面粗糙度模型

针对电火花加工8418钢构建一种采用不同电极材料加工时的表面粗度模型。采用实验与有限元仿真分析相结合的手段,首先通过实验分别得到紫铜电极、CuW70电极加工8418钢的表面粗糙度Ra,然后采用ANSYS软件仿真分析单脉冲放电加工8418钢的电蚀凹坑半径与深度,结合表面粗糙度模型计算出仿真Ra,通过对比实验得到的表面粗糙度Ra,分析得出紫铜电极、CuW70电极加工8418钢时工件上的能量分配系数η分别为33%和24%。最后对能量分配系数和表面粗度模型进行了实验验证,通过误差分析,不同电极加工的表面粗糙度最大误差为9.59%,证明了能量分配系数和表面粗度模型是准确的。通过对比实验和分析结果,得出不同电极材料对能量分配系数的影响,同时随着脉冲放电能量的增加,η对凹坑半径与深度的影响增大,采用紫铜电极与CuW70电极加工8418钢时Ra差异增大。     

Performance of porous asphalt mixture with various additives

The objective of this study is to evaluate the approaches to improve the durability and strength of the porous asphalt through laboratory testing. Porous asphalt specimens were prepared using three types of binders: high-viscosity binder (HVB), PG76-22 and PG70-22. Various additives: fibre, hydrated lime and DBS polymer, were utilised in the porous asphalt. Comprehensive laboratory tests, including strength test, binder draindown test, Cantabro abrasion test, moisture susceptibility test, rutting test, thermal stress restrained sample test, and permeability test, were conducted. It is found that HVB significantly improved the overall performance of the porous asphalt; DBS additive improved its high-temperature performance, but lowered the cracking resistance at low temperature as well as the durability; fibre enhanced its durability and anti-cracking performance at low temperature; hydrated lime improved its moisture stability while weakening its durability. It is concluded that HVB and polyester fibre should be used in all porous asphalt; DBS additive is good for porous asphalt in high-temperature areas, and hydrated lime can be added to porous asphalt in rainy areas.     

The interlaminar shear failure characteristics of asphalt pavement coupled heating cables

Nowadays, heating cables are used as heat sources for heating pavements in practical engineering. However, there is a contradiction between the snow melting function and the interlaminar stability of heating pavement. In order to solve the contradiction, the interlaminar failure behavior of asphalt mixture coupled heating cables specimen (AMCS) was researched, through experiments and the finite element method. Under the different conditions of heating cables and rolling times, a series of direct shear tests was performed at the interface of AMCS, to compare the interlaminar stability of three different AMCS. Meanwhile, based on the bilinear cohesive zone model and coulomb friction model a 2D finite element model was established, to simulate this shear failure processes and make up for the limitations of the experiment. According to above test and simulation results, the failure mechanism and the weakest interface in AMCS were found, and the influence of the heating cable’s diameter and embedded spacing on the interlaminar shear strength were found. Then, a modified coulomb theorem model was proposed to predict the shear strength of the AMCS. This research enriches the design theory of the heating pavement and it has great significance for its structural design of heating asphalt pavement.     

Mechanical and Reaction Properties of Al/TiH2/PTFE under Quasi‐Static Compression

TiH₂ is introduced into Al/PTFE reaction system for the first time. In order to study the mechanical and reaction properties of Al/TiH₂/PTFE composites, five kinds of mixtures with different TiH₂ contents and the contrasting TiH₂/PTFE mixture are prepared. The true stress–strain curves and reaction phenomena are recorded during the quasi‐static compression experiments; The reaction residues are analyzed with XRD to understand the reaction mechanism. The results show that the introduction of TiH₂ can significantly influence the strength of the composites; With the increasing of TiH₂ content, the mechanical strength is firstly increase and then decrease; When the content is the same, the reinforcing effect of TiH₂ particles on PTFE matrix is greater than that of Al. Violent reaction are observed in the four Al/TiH₂/PTFE composites with the content of TiH₂ below 20%, but not in TiH₂/PTFE. Furthermore, compared with Al/PTFE material, special flames are found during the reaction of composites with TiH₂, which become even more obvious with the increasing of TiH₂ content. The material reaction mechanism denotes that the high temperature of the crack tip result in the reaction of Al and PTFE, which activates TiH₂ to release hydrogen and generate TiC, resulting TiH₂ to fully release its energy.

     

New Insight into Procedure of Interface Electron Transfer through Cascade System with Enhanced Photocatalytic Activity

Recombination of photogenerated electron–hole pairs is extremely limited in the practical application of photocatalysis toward solving the energy crisis and environmental pollution. A rational design of the cascade system (i.e., rGO/Bi₂WO₆/Au, and ternary composites) with highly efficient charge carrier separation is successfully constructed. As expected, the integrated system (rGO/Bi₂WO₆/Au) shows enhanced photocatalytic activity compared to bare Bi₂WO₆ and other binary composites, and it is proved in multiple electron transfer (MET) behavior, namely a cooperative electron transfer (ET) cascade effect. Simultaneously, UV–vis/scanning electrochemical microscopy is used to directly identify MET kinetic information through an in situ probe scanning technique, where the “fast” and “slow” heterogeneous ET rate constants (K_eff) of corresponding photocatalysts on the different interfaces are found, which further reveals that the MET behavior is the prime source for enhanced photocatalytic activity. This work not only offers a new insight to study catalytic performance during photocatalysis and electrocatalysis systems, but also opens up a new avenue to design highly efficient catalysts in photocatalytic CO₂ conversion to useful chemicals and photovoltaic devices.     

Crystal structure of Cr4AlB4: A new MAB phase compound discovered in Cr-Al-B system

In this communication, the crystal structure of Cr_4AlB_4, a new MAB phase compound(where M is a transition metal, A is Al or Si, B is boron) discovered in Cr-Al-B system is reported. This new MAB phase was synthesized from a mixture of CrB and Al powders at 1000?C and its crystal structure was determined by a combination of X-ray diffraction, first-principles calculations and energy dispersive X-ray spectroscopy(EDS). Cr_4AlB_4 crystallizes in an orthorhombic structure with Immm space group. The lattice constants are a = 2.9343(6) ?, b = 18.8911(0) ?, c = 2.9733(7) ?, and the atomic positions are Cr1 at 4 g(0, 0.2936(5),0), Cr2 at 4 h(0.5, 0.5859(7), 0), Al at 2 b(0, 0.5, 0.5), B1 at 4 h(0, 0.3839(8), 0.5) and B2 at 4 g(0.5, 0.6646(2),0.5).     

Facile growth of homogeneous Ni(OH)<Subscript>2</Subscript> coating on carbon nanosheets for high-performance asymmetric supercapacitor applications

The growth of a Ni(OH)₂ coating on conductive carbon substrates is an efficient way to address issues related to their poor conductivity in electrochemical capacitor applications. However, the direct growth of nickel hydroxide coatings on a carbon substrate is challenging, because the surfaces of these systems are not compatible and a preoxidation treatment of the conductive carbon substrate is usually required. Herein, we present a facile preoxidation-free approach to fabricate a uniform Ni(OH)₂ coating on carbon nanosheets (CNs) by an ion-exchange reaction to achieve the in situ transformation of a MgO/C composite to a Ni(OH)₂/C one. The obtained Ni(OH)₂/CNs hybrids possess nanosheet morphology, a large surface area (278 m²/g), and homogeneous elemental distributions. When employed as supercapacitors in a three-electrode configuration, the Ni(OH)₂/CNs hybrid achieves a large capacitance of 2,218 F/g at a current density of 1.0 A/g. Moreover, asymmetric supercapacitors fabricated with the Ni(OH)₂/CNs hybrid exhibit superior supercapacitive performances, with a large capacity of 198 F/g, and high energy density of 56.7 Wh/kg at a power density of 4.0 kW/kg. They show excellent cycling stability with 93% capacity retention after 10,000 cycles, making the Ni(OH)₂/CNs hybrid a promising candidate for practical applications in supercapacitor devices.

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