Ignition processes and characteristics of charring conductive polymers with a cavity geometry in precombustion chamber for applications in micro/nano satellite hybrid rocket motors

The arc ignition system based on charring polymers has advantages of simple structure,low ignition power consumption and multiple ignitions,which bringing it broadly application prospect in hybrid propulsion system of micro/nano satellite.However,charring polymers alone need a relatively high input voltage to achieve pyrolysis and ignition,which increases the burden and cost of the power system of micro/nano satellite in practical application.Adding conductive substance into charring polymers can effectively decrease the conducting voltage which can realize low voltage and low power consumption repeated ignition of arc ignition system.In this paper,a charring conductive polymer ignition grain with a cavity geometry in precombustion chamber,which is composed of PLA and multiwall carbon nanotubes(MWCNT)was proposed.The detailed ignition processes were analyzed and two different ignition mechanisms in the cavity of charring conductive polymers were revealed.The ignition characteristics of charring conductive polymers were also investigated at different input voltages,ignition grain structures,ignition locations and injection schemes in a visual ignition combustor.The results demonstrated that the ignition delay and external energy required for ignition were inversely correlated with the voltages applied to ignition grain.Moreover,the incremental depth of cavity shortened the ignition delay and external energy required for ignition while accelerated the propagation of flame.As the depth of cavity increased from 2 to 6 mm(at 50 V),the time of flame propagating out of ignition grain changed from 235.6 to 108 ms,and values of mean ignition delay time and mean external energy required for ignition decreased from 462.8 to 320 ms and 16.2 to 10.75 J,respectively.The rear side of the cavity was the ideal ignition position which had a shorter ignition delay and a faster flame propagation speed in comparison to other ignition positions.Compared to direct injection scheme,swirling injection provided a more favorable flow field environment in the cavity,which was beneficial to ignition and initial flame propagation,but the ignition position needed to be away from the outlet of swirling injector.At last,the repeated ignition characteristic of charring conductive polymers was also investigated.The ignition delay time and external energy required for ignition decreased with repeated ignition times but the variation was decreasing gradually.

Regulatable Orthotropic 3D Hybrid Continuous Carbon Networks for Efficient Bi-Directional Thermal Conduction

Vertically oriented carbon structures constructed from low-dimen-sional carbon materials are ideal frameworks for high-performance thermal inter-face materials(TIMs).However,improving the interfacial heat-transfer efficiency of vertically oriented carbon structures is a challenging task.Herein,an orthotropic three-dimensional(3D)hybrid carbon network(VSCG)is fabricated by depositing vertically aligned carbon nanotubes(VACNTs)on the surface of a horizontally oriented graphene film(HOGF).The interfacial interaction between the VACNTs and HOGF is then optimized through an annealing strategy.After regulating the orientation structure of the VACNTs and filling the VSCG with polydimethylsi-loxane(PDMS),VSCG/PDMS composites with excellent 3D thermal conductive properties are obtained.The highest in-plane and through-plane thermal conduc-tivities of the composites are 113.61 and 24.37 W m^(-1)K^(-1),respectively.The high contact area of HOGF and good compressibility of VACNTs imbue the VSCG/PDMS composite with low thermal resistance.In addition,the interfacial heat-transfer efficiency of VSCG/PDMS composite in the TIM performance was improved by 71.3%compared to that of a state-of-the-art thermal pad.This new structural design can potentially realize high-performance TIMs that meet the need for high thermal conductivity and low contact thermal resistance in interfacial heat-transfer processes.

Fatigue behavior of basalt-aramid and basalt-carbon hybrid fiber reinforced polymer sheets

In order to study the fatigue failure mode and fatigue life laws of basalt-aramid and basalt-carbon hybrid fiber reinforced polymer （ FRP ） sheets, fatigue experiments are carried out, considering two hybrid ratios of 1 ： 1 and 2：1 under different stress levels from 0.6 to 0.95. The results show that fractures occur first in carbon fibers or aramid fibers for the specimens with hybrid ratio of 1： 1, namely B1A1 and B1C1, while a fracture occurs first in basalt fibers for the specimens with a hybrid ratio of 2： 1, namely B2A1 and B2C1. The fatigue lives of the hybrid FRP sheets increase with the improvement of the content of carbon fibers or aramid fibers, and the influence of the carbon fibers content improvement to fatigue life is more significant. The fatigue performance of B2A1 is relatively worse, while the fatigue performance of B1C1 and B2C1 is relatively better. Finally, a new fatigue stiffness degradation model with dual variables and double inflection points is presented, which is applicable to both hybrid and normal FRP sheets.

Preparation of Organic/Inorganic Hybrid Polymer Emulsions with High Silicon Content and Sol-gel-derived Thin Films

A novel polymer/SiO2 hybrid emulsion(PAES)was prepared by directly mixing colloidal silica with polyacrylate emulsion(PAE)modified by a saline coupling agent.The sol-gel-derived thin films were obtained by addition of co-solvents into the PAES.The effects ofγ-methacryloxypropyltrimethoxysilane(KH-570)content and co-solvent on the properties of PAES films were investigated.Dynamic laser scattering(DLS)data indicate that the average diameter of PAES(96 nm)is slightly larger than that of PAE(89 nm).Transmission electron microscopy (TEM)photo discloses that colloidal silica particles are dispersed uniformly around polyacrylate particles and some of the colloidal silica particles are adsorbed on the surface of PAE particles.The crosslinking degree data and Fourier transform infrared(FT-IR)spectra confirm that the chemical structure of the PAES is changed to form Si-O-Si-polymer crosslinking networks during the film formation.Atomic force microscope(AFM)photos show the solvent induced sol-gel process of colloidal silica and the Si-based polymer distribution on the film surface of the dried PAES.Thermogravimetric analysis(TGA)curves demonstrate that the PAES films display much better thermal stability than PAE.

Hybrid polymer electrolyte for Li–O_2 batteries

Li–O_2 batteries have attracted much attention because of their high specific energy. However, safety problem generated mainly from the flammable organic liquid electrolytes have hindered the commercial use of Li–O_2 batteries. One of the competitive alternatives is polymer electrolytes due to their flexibility and non-flammable property. Moreover, the hybrid polymer electrolyte with enhanced electrochemical properties would be achieved by incorporating inorganic filler, liquid plasticizer and redox mediator into the polymer. While most researches of the hybrid polymer electrolyte focused on Li-ion batteries, few of them took account into its application in Li–O_2 batteries. In this review, we mainly discuss hybrid polymer electrolytes for Li–O_2 batteries with different composition. The critical issues including conductivity and stability of electrolytes are also discussed in detail. Our review provides some insights of hybrid polymer electrolytes for Li–O_2 batteries and offers necessary guidelines for designing the suitable hybrid polymer electrolyte for Li–O_2 batteries as well.

Dynamic and buckling analysis of polymer hybrid composite beam with variable thickness

This work deals with a study of the dynamic and buckling analysis of polymer hybrid composite(PHC) beam. The beam has variable thickness and is reinforced by carbon nanotubes(CNTs) and nanoclay(NC) simultaneously. The governing equations are derived based on the first shear deformation theory(FSDT). A three-phase HalpinTsai approach is used to predict the mechanical properties of the PHC. We focus our attention on the effect of the simultaneous addition of NC and CNT on the vibration and buckling analysis of the PHC beam with variable thickness. Also a comparison study is done on the sensation of three impressive parameters including CNT, NC weight fractions, and the shape factor of fillers on the mechanical properties of PHC beams,as well as fundamental frequencies of free vibrations and critical buckling load. The results show that the increase of shape factor value, NC, and CNT weight fractions leads to considerable reinforcement in mechanical properties as well as increase of the dimensionless fundamental frequency and buckling load. The variation of CNT weight fraction on elastic modulus is more sensitive rather than shear modulus but the effect of NC weight fraction on elastic and shear moduli is fairly the same. The shape factor values more than the medium level do not affect the mechanical properties.

Analysis on the Durability of Hybrid Polymer Composites for Power FGD System

The corrosion condition of flue gas desulfurization (FGD) equipment for the coal-fired power plant was defined as the strong corrosion grade. The lining system of hybrid polymer composite was used in internal cylinder of steel chimney, and a corrosion-resistant and heat-resistant protective layer was formed on the metal surface. The corrosion-resistant and ageing-resistant properties of hybrid polymer composite prepared at low temperature after four years of practical use were investigated by differential scanning calorimeter (DSC), scanning electron microscopy (SEM) and measurement of gravimetric variation, contact angle, abrasion resistance, bonding strength and tensile strength. The properties of hybrid polymer composites prepared at 25℃ and –15℃ were comparatively analyzed in the paper.

SYNTHESIS AND BIOTECHNOLOGICAL APPLICATIONS OF VINYL POLYMERINORGANIC HYBRID AND MESOPOROUS MATERIALS

We describe the sol-gel synthesis of a new family of organic-inorganic hybrid materials, in which various vinyl polymers are covalently bonded to and uniformly distributed in inorganic oxide matrices. The materials can be tailored to have both good toughness and hardness while maintaining excellent optical transparency. Doping the sol-gel metal oxides with optically active compounds such as D-glucose results in new optical rotatory composite materials. Removal of the dopant compounds from the composites affords mesoporous oxide materials; which represents a new, nonsurfactant-templated route to mesoporous molecular sieves. We have successfully immobilized a series of enzymes and other bioactive agents in mesoporous materials. Catalytical activities of the enzyme encapsulated in mesoporous materials were found to be much higher than those encapsulated in microporous materials.

Preparation and properties of a POSS-containing organic-inorganic hybrid crosslinked polymer

A novel POSS-containing organic-inorganic hybrid crosslinked polymer was prepared by hydrosilylation reaction of octahydridosilsesquioxane （TsHs） with 4,4＇-bis（4-altyloxybenzoyloxy）phenyl （diene A）. Its structure and property was characterized by FFIR, 29Si NMR, TGA and ellipsometer, respectively. The results show that the hybrid polymer possesses high thermal stability and low dielectric constant of 1.97 at optical frequencies.

Elastic modulus prediction for hybrid polymer composites

To improve on the mechanical properties of polymers in general, the concept of hybrid composites was developed by using two or more different reinforcements in the same matrix, or by using two or more different sizes of the same reinforcement (auto-hybrid composites). In this case, most of the literature results showed that the resulting elastic modulus can be well approximated by the simple rule of mixture (linear additive law) from the tensile modulus of each reinforcement used alone. But is some cases, a positive deviation from this linear approximation was reported up to a point where an optimum composition can give a modulus above the value of both reinforcements used separately. In this work, a simple model is presented to show that positive deviations are possible and the optimum reinforcement ratio is around 25/75 in terms of the lowest/highest reinforcing particle. The model is also compared with literature data where good qualitative agreements are obtained as a first approximation.

SYNTHESIS AND CHARACTERIZATION OF STRUCTURALLY WELL-DEFINED POLYMER-INORGANIC HYBRID NANOPARTICLES VIA ATRP

Atom transfer radical polymerization (ATRP) using cuprous chloride/2,2'-bipyridine (bipy) was applied to graft polymerization of styrene on the surface of silica nanoparticles to synthesize polymer-inorganic hybrid nanoparticles, 2-(4Chloromethylphenyl) ethyltriethoxysilane (CTES) was immobilized on the surface of silica nanoparticles through condensation reaction of the silanol groups on silica with triethoxysilane group of CTES. Then ATRP of St was initiated by this surface-modified silica nanoparticles bearing benzyl chloride groups, and formed PSt graft chains on the surface of silica nanoparticles. The thickness of the graft chains increased with reaction time. End group analysis confirmed the occurrence of ATRP. Thermal analysis indicated that thermal stabilization of these resulting hybrid nanoparticles also increases with polymerization conversion. The results above show that this 'grafting from' reaction could be used for the preparation of polymer-inorganic hybrid nanoparticles with controlled structure of the polymer's end groups.

PAC-P(AM-BA)杂化高分子絮凝剂制备及絮凝效能评价

针对油田化学驱污水难处理问题,采用水溶液自由基胶束聚合法,以聚合氯化铝(PAC)为无机组分,丙烯酰胺(AM)、丙烯酸丁酯(BA)为有机单体,合成一种新型无机-有机杂化高分子絮凝剂(PAC-P(AM-BA))。利用傅里叶变换红外光谱仪(FT-IR)、热重分析仪(TGA)、扫描电子显微镜(SEM)和比表面积分析仪(BET)对絮凝剂进行表征。结果表明,BA以化学键连接在聚丙烯酰胺(PAM)长链中,无机组分与有机组分之间以离子键连接。PAC-P(AM-BA)热分解温度为233.93℃,比表面积为30.351m^(2)·g^(-1)。絮凝实验结果表明,PAC-P(AM-BA)最佳投加量为20 mg·L^(-1),沉降时间为10 h,其絮体分形维数为1.733。在絮凝效能对比实验中,PAC-P(AM-BA)的平均除油率为90.3%,较阳离子聚丙烯酰胺(CPAM)和复配型絮凝剂(PAC+PAM)分别高出16.4%和29.0%。

基于MOOC的“高分子化学”线上线下混合式教学模式改革与研究

“高分子化学”是材料类专业的重要课程,理论体系严谨,知识点众多。传统教学方式难以引起学生兴趣,学习自主性较弱。通过构建基于MOOC的线上线下混合式教学,以问题为驱动,强化过程考核,学生参与度和自主学习效率得到了提高。由近年来本校高分子材料与工程专业学生的课程目标达成度评价数据发现,线上线下混合式教学和考核模式的改革产生了显著成效。

聚乙烯醇基凝胶聚合物电解质的制备及在锌离子混合电容器中的应用

锌离子混合电容器(ZIHC)兼有电池高能量密度和电容器高功率密度的特点,是下一代能源存储设备的有力竞争者,但电池型阴极-电容型阳极ZIHC的研究中使用的多为电解质溶液,容易泄漏而导致安全风险。针对这一问题,文中以纤维素、羟乙基纤维素和聚乙烯醇为原料,通过冷冻-解冻和电解液吸收的方法,快速制备了具有蜂巢状的三维网络形貌的凝胶聚合物电解质(GPE)。优化的GPE不仅具有良好力学性能(拉伸强度0.24 MPa、断裂伸长率289%),而且表现出较高的离子电导率(58.5 mS/cm)。使用GPE、二氧化锰阴极和活性炭阳极组成的ZIHC,其比电容和能量密度分别为31.5 F/g和15.0 Wh/kg,2 A/g充放电循环1.5×104次后比电容保持率约80%,展示出GPE在ZIHC领域中潜在的应用价值。原料环保和方便快捷的制备方法为能量存储和柔性可穿戴电子领域应用的GPE研究提供了新的思路。

Investigation on ignition characteristics of charring conductive polymers stimulated by electric energy

The arc ignition based on charring conductive polymers has advantages of simple structure,low ignition power consumption and restart capacity,which bringing it broadly application prospect in hybrid propulsion system of micro/nano satellite.In order to optimize the performance of arc ignition system,it is essential to have a deeper understanding of the ignition processes and ignition characteristics of charring conductive polymers.In this paper,the thermal decomposition,electrical conductivity and thermal conductivity characteristics of charring conductive polymers with different conductive additives and matrix materials were comprehensively evaluated.An experimental investigation was conducted to determine the ignition behaviors and characteristics of different charring conductive polymers in a visual ignition combustor.The experiment result showed that the ignition delay and external energy required for ignition are negatively correlated with voltage and initial temperature of the ignition grain,but positively correlated with oxidizer flow velocity.Compared with charring conductive polymers containing multi-walled carbon nanotube,the ignition delay of charring conductive polymers with carbon black is significantly higher and the pyrolysis time is relatively longer.However,the ignition and initial flame propagation of charring conductive polymers with carbon black is more violent and more inclined to carbon particle ignition.Finally,the restart characteristic of different charring conductive polymers was studied.The ignition delay and external energy required for ignition of different charring conductive polymers all reduced with the increasing of the number of ignitions.However,the ignition characteristics would not change a lot after repeated ignition.

“高分子化学”线上线下课堂教学设计——以“逐步聚合”为例

利用线上线下混合式教学方法探讨了逐步聚合反应在“高分子化学”课程中的教学效果。线上线下混合教学模式以互联网为依托,打破传统线下课堂上时间与空间的限制,既以学生为中心,又能增加课程的趣味性,强化学生的自学能力,实现“教”和“学”的双向互动。以逐步聚合反应作为教学设计案例,采用线上线下双程教学模式,系统化应用混合式教学模式,从课前、课堂、课后及评价四个方面入手,提升培养人才的质量,促进“高分子化学”课程教学的创新发展。

竹纤维高分子菌肥对杂交柑橘产量及品质的影响

为揭示基于新型竹纤维高分子材料的竹纤维高分子菌肥对杂交柑橘产量与品质的影响,以井研县五年生杂交柑橘爱媛38号为试材,沟施竹纤维高分子菌肥0 g/株+生物有机肥6 kg/株(CK)、竹纤维高分子菌肥100 g/株+生物有机肥6 kg/株(T_(1))、竹纤维高分子菌肥200 g/株+生物有机肥6 kg/株(T_(2))及竹纤维高分子菌肥300 g/株+生物有机肥6 kg/株(T_(3)),探究不同处理杂交柑橘产量与品质变化。结果表明,与CK相比,竹纤维高分子菌肥处理柑橘果实单果重增加,结果数、单株产量和总产量均显著增加(P<0.05),其中处理T_(2)单果重、单株产量和总产量均最高,而处理T_(1)结果数最多。竹纤维高分子菌肥处理柑橘果实维生素C、可溶性固形物、可溶性糖、还原性糖、糖酸比与固酸比均高于CK,其中处理T_(1)柑橘果实可溶性固形物、可溶性糖、糖酸比均最高,较CK分别提高了20.98%、29.45%、20.12%;处理T_(2)柑橘果实维生素C、还原性糖含量均最高,较CK分别提高了21.40%、23.61%;处理T_(3)柑橘果实固酸比最高,较CK提高33.78%。综合分析可知,竹纤维高分子菌肥100 g/株+生物有机肥6 kg/株对井研地区杂交柑橘土壤养分与树体营养有显著促进作用,并有助于杂交柑橘果实提质增产,在实际生产中具有重要的指导与应用价值。竹纤维高分子菌肥能显著提升土壤养分,并促进柑橘植株汲取养分,使其树体维持较适宜的营养水平,从而促进杂交柑橘果实生长,提高其产量与品质。

A New Type of Hybrid Fish-like Microrobot

In order to develop a new type of fish-like microrobot with swimming, walking, and floating motions, in our past research, we developed a hybrid microrobot actuated by ionic conducting polymer film （ICPF） actuators. But the microrobot had some problems in walking and floating motions. In this paper, we propose a concept of hybrid microrobot （see Fig. 1）. The microrobot is actuated by a pair of caudal fins, a base with legs and an array of artificial swim bladders. We have developed a prototype of the base with legs and one artificial swim bladder, respectively, and carried out experiments for evaluating their characteristics. Experimental results show the base with legs can realize walking speed of 6 mm/s and rotating speed of 7.1 degrees/s respectively, and the prototype of the artificial swim bladder has a maximum floatage of 2.6 mN. The experimental results also indicate that the microrobot has some advantages, such as walking motion with 2 degrees of freedom, the walking ability on rough surface （sand paper）, the controllable floatage, etc. This kind of fish-like microrobot is expected for industrial and medical applications.

Recent Progress on Metal–Organic Framework and Its Derivatives as Novel Fire Retardants to Polymeric Materials

High flammability of polymers has become a major issue which has restricted its applications.Recently,highly crystalline materials and metal–organic frameworks(MOFs),which consisted of metal ions and organic linkers,have been intensively employed as novel fire retardants(FRs)for a variety of polymers(MOF/polymer).The MOFs possessed abundant transition metal species,fire-retardant elements and potential carbon source accompanied with the facile tuning of the structure and property,making MOF,its derivatives and MOF hybrids promising for fire retardancy research.The recent progress and strategies to prepare MOF-based FRs are emphasized and summarized.The fire retardancy mechanisms of MOF/polymer composites are explained,which may guide the future design for efficient MOF-based FRs.Finally,the challenges and prospects related to different MOFbased FRs are also discussed and aim to provide a fast and holistic overview,which is beneficial for researchers to quickly get up to speed with the latest development in this field.

Hybrid supercapacitor based on polyaniline doped with lithium salt and activated carbon electrodes

Polyaniline（PANI） nanofiber was synthesized by interfacial polymerization utilizing the interface between HC1 and CCl4. The hybrid type supercapacitors （PLi/C） based on Li-doping polyaniline and activated carbon electrode were fabricated and compared with the redox type capacitors （PLi/PLi） based on two uniformly Li-doping polyaniline electrodes. The electrochemical performances of the two types of supercapacitors were characterized in non-aqueous electrolyte. PLi/C supercapacitors have a wider effective energy storage potential range and a higher upper potential. At the same time, the PLi/C supercapacitor exhibits a specific capacity of 120.93 F/g at initial discharge and retains 80% after 500 cycles. The ohmic internal resistance （REs） of PLi/C supercapacitor is 5.0 Ω, which is smaller than that of PLi/PLi capacitor （5.5 Ω）. Moreover, it can be seen that EtgNBF4 organic solution is more suitable for using as organic electrolyte of PLi/C capacitor compared with organic solution containing LiPFr.