Preparation of body armour material of Kevlar fabric treated with colloidal silica nanocomposite

Abstract

To safeguard bodies of soldiers better, including their necks and joints, a novel armour material was exploited using nanocomposite. Compared with traditional armour materials, this new material possessed superior barrier property and more comfortable characteristics. The new armour material was made of Kevlar cloth and shear thickening fluid (STF). Colloidal silica particles were first synthesised via the Stöber synthesis method and then they were used to prepare a suspension with solvent of polyethylene glycol 200. At last, Kevlar cloth was treated with the suspension and the resultant was named as STF–Kevlar nanocomposite. In this process, the particle sizes were characterised with scanning electron microscopy. The rheological properties were measured with a Physica MCR301 stress controlled rheometer. The results showed that the silica particles could be determined to be monodispersed spherical particles. The suspension, named the shear thickening fluid, had shear thickening characteristic. The property of multilayer STF–Kevlar nanocomposite targets was compared to that of the neat Kevlar cloth and the results indicated that the STF–Kevlar nanocomposite had an improvement in barrier property and was more flexible and comfortable. The mechanism that could improve the barrier property of STF–Kevlar was briefly explained.     

Preparation and characterization of imidazolyl ionic liquid-based shear thickening dispersion system

Shear thickening liquid (STF) is a new nonNewtonian fluid widely used in industrial production. In this paper, a novel shear thickening and dispersing system, namely poly methyl methacrylate (PMMA)/1-butyl-3-methylimidazole hexa-fluorophosphate ([BMIM]PF₆), was prepared using ultrasonic with PMMA as the dispersing phase and [BMIM]PF₆ as the dispersing medium. The stability, thixotropic, reversibility, rheology, and viscoelasticity of the dispersion system was studied, respectively. The dispersed system has good stability. The dispersed system shows high response sensitivity to shear rate, as well as good reversibility to shear thickening. Compared with traditional silicon dioxide/polyethylene glycol dispersion system, PMMA/[BMIM]PF₆ dispersion system displays a significantly enhanced shear thickening effect. Nonionic surfactant triton X-100 of 4 wt% can greatly improve PMMA/[BMIM]PF₆ dispersion system's shear thickening behavior. This paper provides a new idea for the further development of protective materials by using STF.     

Application of shear thickening fluid in ultra high molecular weight polyethylene fabric

An advanced stab‐resistant material composed of shear thickening fluid (STF) and ultra high molecular weight polyethylene (UHMWPE) fabric was investigated. STF was prepared by dispersing nanosilica (SiO₂) into ethylene glycol. The shear thickening behavior of STF with the increase of the shear rate was observed by PhysicaMCR301. STF/UHMWPE composite fabric was synthesized by impregnating UHMWPE fabric in STF dilution. Stab resistant experiment was conducted on a self‐made stab test machine with knife and spike as stab tool. The results demonstrate that the stab resistant property of the UHMWPE fabric is greatly improved by impregnating STF. The stab resistant property is greatly increased with the increase of mass fraction of silica in STF. Especially, when the mass fraction of SiO₂ in STF is 38%, the stab resistance force and energy absorption of STF/UHMWPE are optimal for knife and spike threats. With the same stab resistant properties, the flexibility of UHMWPE fabric impregnated with STF is higher than that of the neat fabric. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of silica morphology on the shear-thickening behavior of shear thickening fluids and stabbing resistance of fabric composites

Shear-thickening fluid (STF) refers to a system where nonaggregating solid particles are suspended in a specific fluid. Due to its unique viscosity variation, STFs have attracted a lot of attention as soft body armor materials for impact protection. In this work, two kinds of STFs were designed using polyethylene glycol (PEG) and spherical or irregularly shaped silica particles. Rheological results showed that shear thickening can even occur at lower shear rates in the irregularly shaped silica-based STF; however, the thickening range of the spherical silica-based STF was broader. Meanwhile, the composites prepared with STFs and aramid fabrics exhibited better antistab properties than neat fabrics. Compared to composite prepared with irregularly shaped silica-based STF, spherical silica-based STF/aramid composite had better stabbing resistance. In addition to the binding effect of silica particles to the fiber bundle, it was considered that when the fabric composite was subjected to impact, spherical particles were easier to slide so that the STF was more likely to be thickened to achieve a greater viscosity, resulting in the better stabbing resistance performance. Our studies will provide guidance for the design of the high-performance soft body armor equipment. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48809.     

Rheological behavior of concentrated silica suspension and its application to soft armor

The objective of this study is to develop an advanced stab and/or ballistic proof material composed of shear thickening fluid (STF) and Kevlar composite fabric. In this study, we prepared STF using sphere silica and fumed silica as silica particles and ethylene glycol and polyethylene glycol (PEG 200) as medium fluid, respectively. And the rheological properties of the STF were investigated under different conditions. Also, we impregnated Kevlar fabrics with the STF, and investigated the stab and ballistic resistances of the targets layered by the STF impregnated Kevlar fabrics. From the results, we observed that the STF significantly showed the reversible liquid–solid transition at a certain shear rate, and the STF treatment significantly improved the stab and ballistic resistance of Kevlar fabric. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Shear thickening fluids in protective applications: A review

A thorough and critical review on Shear Thickening Fluids (STFs) is presented based on a literature survey. The rheological properties of STFs are discussed considering many factors affecting shear thickening behavior and the use of STFs in protective systems is reviewed. The main focus of this review is multi-phase STFs, relatively new to the literature (in the last five years). Multi-phase STFs include a second phase in suspensions and the influences of this additional phase on rheological behavior and protective applications are discussed extensively. Based on this extended review, STF do benefit protective applications, but the major contribution is not driven by the shear thickening behavior. Rather, STFs are responsible for the increase in friction along fabrics and enhanced fiber/yarn coupling in fabric based protective systems. As a result, of these effects, the load transfer is spread over a wider area and penetration depth is lowered in an impacted structure.     

不同体系剪切增稠液体的流变行为研究

剪切增稠液体是指其表观粘度随剪切速率增加而变大的一类流体。工业生产中,剪切增稠的出现会阻碍输送管道,破坏生产设备。针对这种情况,人们对如何降低流体粘度造成的不利影响进行了大量研究。另一方面,剪切增稠液体是“液体防弹材料”的关键组成部分,并且在减震、控制方面也具有可观的应用潜力。该文采用原生粒径为50 nm 的SiO2和80～100 nm 的 CaCO3分别作为分散相,聚乙二醇（PEG）200为分散介质,采用超声分散法制备得到不同固含量的剪切增稠液。并通过纳米粒度仪和扫描电镜对分散相粒子团聚情况进行分析;通过应力控制流变仪分别对 SiO2/PEG200和 CaCO3/PEG200悬浮分散体系的稳态流变性能进行分析。结果表明,两种体系试样在测试中均出现剪切增稠现象,并且分散相质量分数越高,剪切增稠效果越明显;而高质量分数的 SiO2/PEG200体系的粘度变化范围更大,增稠现象更为明显。     

Influence of carrier fluid on the electrokinetic and rheological properties of shear thickening fluids

This paper presents a study on the influence of hydroxyl groups and oxygen atoms together with chain length and branching of carrier fluid on the rheological and electrokinetic properties of shear thickening fluid (STF). An STF is non-Newtonian fluid behaviour in which the increase of viscosity increases with the applied shear rate. Ethylene glycol, triethylene glycol, 1,3-propanediol, glycerin, poly(propylene glycol) of different molecular weight and poly(propylene glycol) triol were used as the carrier fluids (dispersants). Silica powder with an average particle size of 100 nm was used as the solid phase. Zeta potential, particle size distribution (by DLS technique), steady-state and dynamic rheological measurements were conducted. Experimental results indicate that a different amount of hydroxyl groups and oxygen atoms together with chain length and branching of carrier fluids have a significant influence on the intermolecular interactions thereby and on the rheological properties of suspensions. Depending on the composition, it is possible to control rheological properties. The use of a suitable carrier fluid allows the required pattern flow to be obtained, from Newtonian through shear thinning to shear thickening, given specific shear conditions.     

剪切增稠液体的性能及其在柔性防刺材料中的应用

介绍了剪切增稠液体的特点、增稠机制及其流变性能的主要影响因素。在此基础上,又从机织物、针织物、非织造布角度列举并介绍了剪切增稠液体在柔性防刺材料中的研究现状,并对其在柔性防刺材料中的研究以及未来的发展做出了展望。     

Enhanced ethanol sensing and mechanism of Cr-doped ZnO nanorods: Experimental and computational study

The pristine and Cr-doped ZnO nanorods were successfully synthesized via a facile hydrothermal route. We found that the ethanol gas response of ZnO was improved significantly by Cr doping. In particular, the enhanced gas-sensing mechanism was investigated by first-principles calculations upon proposed surface adsorption models. The calculated results revealed that the Cr-doped ZnO (0 0 0 1) surface enabled transfer larger electrons and adsorb more oxygen molecules than that of undoped one, thus holding the potential for further enhancement in gas response of ZnO-based sensors.     

静电纺丝法制备Y掺杂ZnO纳米材料及其光催化性能

通过调节前驱液组分,使用电纺丝法和焙烧工艺,制备Y掺杂ZnO纳米颗粒,采用透射电子显微镜、X射线衍射、光致发光光谱、N_2吸附-脱附和XPS等进行表征。结果表明,Y掺杂ZnO材料具有明显的球形结构,与纯ZnO相比,纳米粒径更小,结构更疏松,具有较大的比表面积,晶体材料的禁带宽度相应变窄。光催化污染物降解实验表明,Y掺杂ZnO能够提高ZnO材料的光催化性能,Y掺杂物质的量分数为0.25%时,光催化降解性能最好,表明Y掺杂是一种有效提高ZnO材料光催化性能的改性手段。     

剪切增稠液体材料的研究现状及其在人体防护装备上的应用

总结了国内外剪切增稠液体材料的研究现状,从其流变特性、增稠机理及其应用于人体防护装备的发展等方面进行了综述。阐述了影响剪切增稠液体材料流变性能的一些因素的研究现状,包括分散相粒子的性质、分散介质的性质、亲水长链高分子的添加量和温度等。     

Friction and Shear Strength at the Nanowire–Substrate Interfaces

The friction and shear strength of nanowire (NW)–substrate interfaces critically influences the electrical/mechanical performance and life time of NW-based nanodevices. Yet, very few reports on this subject are available in the literature because of the experimental challenges involved and, more specifically no studies have been reported to investigate the configuration of individual NW tip in contact with a substrate. In this letter, using a new experimental method, we report the friction measurement between a NW tip and a substrate for the first time. The measurement was based on NW buckling in situ inside a scanning electron microscope. The coefficients of friction between silver NW and gold substrate and between ZnO NW and gold substrate were found to be 0.09–0.12 and 0.10–0.15, respectively. The adhesion between a NW and the substrate modified the true contact area, which affected the interfacial shear strength. Continuum mechanics calculation found that interfacial shear strengths between silver NW and gold substrate and between ZnO NW and gold substrate were 134–139 MPa and 78.9–95.3 MPa, respectively. This method can be applied to measure friction parameters of other NW–substrate systems. Our results on interfacial friction and shear strength could have implication on the AFM three-point bending tests used for nanomechanical characterisation.     

表面活性剂湍流减阻研究进展

表面活性剂较高分子聚合物在流体管道输运中具有可逆机械降解特性的优点,更适用于存在高剪切的场合以及封闭的循环回路进行减阻,但存在对其复杂流变特性及减阻机理认识不完善的问题,使得其在减阻领域的应用受到了限制。本文回顾了作者近年来在表面活性剂溶液微观结构、复杂流变学特性、湍流结构以及其与减阻和传热性能之间的内在联系方面的研究进展;介绍了表面活性剂减阻和壁面微沟槽协同作用减阻的研究成果;指出通过拉伸流的方式能够在压损较小的情况下更有效地提高表面活性剂溶液的传热性能。针对表面活性剂现有研究的不足,本文提出4条建议作为表面活性剂的未来研究方向,分别为开发环境友好型高效表面活性减阻剂、强化换热装置的优化设计及优化布置、表面活性剂与其他减阻方式耦合特性的深入研究以及表面活性剂在尺度放大、防腐和减阻持久性方面的实际工业应用研究。     

涡发生器与螺旋片强化不同曲率的壳侧传热

为考察涡发生器与螺旋片对不同曲率的套管式换热器壳侧的传热强化效果,在不同中径的壳侧安装了相同密度的螺旋片和三角翼型涡发生器。以空气为介质,在Re=680～16000范围内,采用实验和数值模拟方法研究了壳侧的传热和阻力特性,考察了不同曲率下复合强化的壳侧的综合性能,分析了传热强化机理。结果表明,曲率越大,壳侧传热系数越高,摩擦因数越大。对曲率分别为0.131、0.321和0.440的3种换热器壳侧,涡发生器将其传热系数平均提高了31.52%、20.83%和18.33%。小曲率和复合强化的壳侧综合性能更好。涡发生器改变了换热器壳侧的流场结构,提高了速度场和温度场之间的协同性,从而提高了换热器壳侧的传热效果。     

Mechanical,acoustic, and thermal performances of shear thickening fluid–filled rigid polyurethane foam composites: Effects of content of shear thickening fluid and particle size of silica

Shear thickening fluid (STF) features a rheological property, and rigid polyurethane (PU) foams feature low thermal conductivity and excellent acoustic insulation. In this study, an STF/PU rigid foam composite sandwich structure was designed using different contents (0, 0.5, 1, or 1.5 wt %) of STF that contained 14 nm, 40 nm, or 75 nm silicon dioxide (SiO₂). The effects of STF content and silica size on the cell structure, mechanical performance, acoustic absorption, and thermal performance of the STF/PU foam were explored. The test results show that STF/PU foam exhibited three characteristic acoustic absorption peaks, and the maximum acoustic absorption coefficient reached 0.841. STF addition increased compression, bending strength, and maximum acoustic coefficient, as well as initial mass loss temperature. STF-filled PU foam composites containing 14 nm and 40 nm SiO₂ had a mild rise in thermal insulation. The rigid STF/PU foam composites with a cell structure had the maximum thermal conductivity of 0.22 W m⁻¹ K⁻¹ and sound absorption coefficient of 0.841, which confirm that they are a good candidate for sound-absorbing energy conservation materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47359.     

纳米、微米ZnO对PPESUK复合材料性能的影响

用热压成型法制备了纳米、微米ZnO填充联苯型聚醚砜酮(PPESUK)复合材料;考察了复合材料的显微硬度和弯曲强度;并研究了干摩擦条件下纳米、微米ZnO对复合材料摩擦磨损性能的影响。利用扫描电子显微镜观察分析PPESUK／ZnO复合材料磨损表面形貌及磨损机理。结果表明,在干摩擦条件下纳米ZnO填充PPESUK的转移膜不完整,致使对偶钢环对复合材料表面产生严重的犁削;而微米ZnO填充PPESUK的主要磨损机理是严重的磨粒磨损。     

ZnS/ZnO异质结光催化剂的应用研究进展

硫化锌（ZnS）和氧化锌（ZnO）具有无毒、环境友好和制备简单等优点,并且常温下拥有优异的物理化学特性和催化活性,所以一直都是光催化领域研究的热点材料。然而,单一ZnS和ZnO光催化剂表现出低的太阳能利用率、量子效率和光稳定性,极大地限制了它们的实际应用。将ZnS与ZnO复合形成异质结不仅可以拓宽光吸收波长范围,而且能促进载流子的转移和空间分离,增强光催化活性和稳定性。归纳了半导体异质结（Ⅱ型异质结、Z型异质结和S型异质结）中载流子的转移路径及光催化机理,综述了ZnS/ZnO异质结在能源和环境催化领域中的应用研究进展及其光催化性能的影响因素和提升策略,最后对其目前存在的问题和未来的发展方向进行了总结与展望。     

Superlow friction and diffusion behaviors of a steel-related system in the presence of nano lubricant additive in PFPE oil

The lubrication performances of diamond like carbon (DLC) films were investigated by a ball-on-disc tribometer under perfluoropolyether (PFPE) oil lubrications. The influence of nano lubricant additives in PFPE oil on the tribological properties of DLC films was evaluated. The experimental results show that the solid-liquid synergy lubrication is beneficial to improve the tribological properties of the steel-related friction system and the tribological properties of the friction pair are significantly influenced by lubrication modes and the types and contents of nano lubricant additives under PFPE oil lubrication. The friction system exhibits super low friction behaviors under PFPE oil with nano MoS₂ lubricant additive lubrication due to the excellent compatibility of nano MoS₂ additives with PFPE oil. Coefficient of friction (CoF) of the friction system is as super low as 0.02 under PFPE oil with 0.2?wt.% nano MoS₂ additive lubrication. Superlow friction mechanism is attributed to the pointlike contact of nano MoS₂ additive as soft phase and the excellent diffusion behaviors of nano MoS₂ additives in PFPE oil. The potential usefulness of nano MoS₂ particles as the lubricant additives in PFPE oil for the steel/DLC films has been demonstrated.     

Electrical characterization of ZnO-based thin film nanodiodes fabricated through atomic layer deposition: Effect of electron beam irradiation on interfacial property

ZnO thin films were deposited onto p-type (P-Si) Si wafers using atomic layer deposition. The rectifying performance of the deposited ZnO thin films was confirmed by current–voltage characteristics. P-Si/ZnO-based nanodiodes were subjected to electron irradiation. Depending on the irradiation conditions, the diode performance changed significantly. At 0.8 MeV, the diode was degraded in terms of both forward and reverse currents. At 2.5 MeV, the reverse current in the nanodiode decreased and the forward current increased, leading to significant enhancement in the current ratio. The electrical response was monitored using impedance spectroscopy. Impedance analysis indicated that depletion regions are significantly affected by electron irradiation.