Morphology, dynamic mechanical and thermal studies
纳米技术
Ferroelectric selfassembled PbTiO3 perovskite nanostructures onto (100) SrTiO3 substrates from a novel microemulsion aided sol–gel preparation method M L Calzada et al 2007 Nanotechnology 18 375603
Morphology and oxide shell structure of iron nanoparticles grown by sputtergas aggregation C M Wang et al 2007 Nanotechnology 18 255603
Laser-induced assembly of gold nanoparticles into colloidal crystals N Harris et al 2007 Nanotechnology 18 365301
Nanotechnology
Advanced Manufacturing Technology
Definition
Systems for transforming matter, energy, and information, based on nanometer-scale components with preciselnanotechnology has also been used more broadly to refer to techniques that produce or measure features less than 100 nanometers in size.
Polymer Science and Engineering
Polymer Science and Engineering Polymer science and engineering is a fascinating and rapidly evolving fieldthat plays a crucial role in various industries, including healthcare, electronics, automotive, and packaging. The study of polymers involves understanding the chemical and physical properties of macromolecules and their applications in different materials and products. As a polymer scientist or engineer, one must possess a deep understanding of polymer synthesis, characterization, processing, and performance to develop innovative and sustainable solutions to real-world challenges. One of the key aspects of polymer science and engineering is polymer synthesis, which involves the creation of macromolecules with specific chemical compositions and structures. This process can be achieved through various methods, including addition polymerization, condensation polymerization, and ring-opening polymerization. Each method offers unique advantages and limitations, and the choice of synthesis route depends on the desired properties and applications ofthe polymer. Furthermore, advancements in polymer synthesis techniques, such as controlled/living polymerization and click chemistry, have enabled the design and production of complex polymer architectures with precise control over their molecular structure and properties. In addition to synthesis, thecharacterization of polymers is essential for understanding their structure-property relationships and ensuring consistency in their quality and performance. Polymer scientists and engineers utilize a wide range of analytical techniques, including spectroscopy, chromatography, microscopy, and rheology, to analyze the chemical composition, molecular weight, morphology, thermal stability, and mechanical properties of polymers. These analyses provide valuable insights into the structure and behavior of polymers, guiding the development of new materials with tailored properties and improved performance. Once synthesized and characterized, polymers undergo processing to shape them into useful products.This stage involves various techniques such as extrusion, injection molding, blow molding, and 3D printing, each suited for different types of polymers and applications. The processing conditions significantly influence the final properties and performance of the polymer products, making it crucial for polymer engineers to optimize processing parameters to achieve the desired outcomes.Moreover, advancements in processing technologies, such as microfluidics and nanocomposite processing, have opened up new possibilities for creating advanced polymer-based materials with enhanced functionality and performance. Furthermore, the field of polymer science and engineering is increasingly focused on developing sustainable and environmentally friendly polymers to address global concerns about plastic pollution and resource depletion. This has led to the emergence of biodegradable polymers, bio-based polymers, and recycling technologies that aim to reduce the environmental impact of polymer materials. As a result, polymer scientists and engineers are actively involved in research and development efforts to create eco-friendly alternatives to conventional polymers without compromising on performance and functionality. In conclusion, polymer science and engineering is a dynamic and multidisciplinary field that continues to drive innovation across various industries. The ability to design and manipulate macromolecular structures at the molecular level offers endless opportunities for creating advanced materials with tailored properties and performance. As the demand for sustainable and high-performance polymers continues to grow, the role of polymer scientists and engineers becomes increasingly vital in shaping a more sustainable and technologically advanced future.。
自粘型聚硼硅氧烷复合材料性能
自粘型聚硼硅氧烷复合材料性能商旭静*, 薛志博, 沈尔明, 王 刚, 滕佰秋, 朱崇伟（沈阳发动机研究所 制造工程技术研究室，沈阳 110015）摘要：聚硼硅氧烷属于超分子材料，材料本身具备物理交联网络结构，具有耐高低温、耐候、电绝缘、自修复等特性，但现有方法制备的聚硼硅氧烷材料力学性能差，限制了其在一些领域的应用。
本工作采用高分子量聚甲基乙烯基硅氧烷（VMQ）与硼酸（BA）在高温环境下反应，制备一种含乙烯基的聚硼硅氧烷，通过引入乙烯基结构和气相法白炭黑，经热硫化处理，得到具有表面自粘性的聚硼硅氧烷复合材料。
测定聚硼硅氧烷复合材料的结构、动态力学性能、热稳定性、力学性能以及自粘性能，通过红外反射光谱确认B—O—Si结构。
结果表明：聚硼硅氧烷复合材料的内部形成了B∶O动态键，材料表面具有一定的自粘性能，自粘形成的剥离强度能达到4 N/cm，拉伸强度可达4.154 MPa，5%热失重温度为394.8 ℃，具有良好的力学性能和热稳定性。
关键词：聚硼硅氧烷复合材料；损耗因子；力学性能；自粘性doi：10.11868/j.issn.1005-5053.2023.000046中图分类号：TQ333 文献标识码：A 文章编号：1005-5053(2023)04-0122-07Properties of self-adhesive polyborosiloxane compositeSHANG Xujing*, XUE Zhibo, SHEN Erming, WANG Gang, TENG Baiqiu, ZHU Chongwei（Manufacturing Engineering Technology Department , Shenyang Engine Design Institute, Shenyang 110015, China）Abstract: Polyborosiloxane（PBS） is a supramolecular material， the material itself has a physical cross-linked network structure, and has the characteristics of high and low temperature resistance, weather resistance, electrical insulation and self-healing. However, the mechanical properties of polyborosiloxane material prepared by existing methods are poor, which limits its application in some fields. In order to improve the mechanical properties of polyborosiloxane and broaden the application field of the material, in this paper, a vinyl-containing polyborosiloxane was prepared by reacting high-molecular-weight polymethylvinylsiloxane（VMQ）with boric acid（BA）at high temperature. The polyborosiloxane composite material with surface self-adhesiveness was obtained by introducing vinyl structure and fumed white carbon black and undergoing thermal vulcanization treatment. The structure, dynamic mechanical properties, thermal stability, mechanical properties and self-adhesive properties of polyborosiloxane composite were measured, and the formation of B—O—Si structure was confirmed by infrared reflection spectroscopy. The results show that the B∶O dynamic bond is formed inside the polyborosiloxane composite material, and the surface of the material has certain self-adhesive properties. The peel strength formed by self-adhesion can reach 4 N/cm, the tensile strength is 4.154 MPa, and 5 % thermal mass loss temperature is 394.8 °C, which means that the sample has good mechanical properties and thermal stability.Key words: polyborosiloxane；loss factor；mechanical properties；self-adhesion随着航空装备的高速发展，对硅橡胶复合材料的功能性提出更高的要求，如耐高温特性、自修复性、粘接性、电磁屏蔽性和阻尼性，传统的硅橡胶材料难以满足材料的使用需求，在硅橡胶分子主链上引入特定的杂原子能赋予材料更多的功能性。
改性石墨烯改性氧化铝协同提高硅脂的导热性能研究
河南科技Henan Science and Technology 能源与化学总772期第二期2022年1月改性石墨烯/改性氧化铝协同提高硅脂的导热性能研究史浩龙王蓉唐秀之（中南大学航空航天学院，湖南长沙410000）摘要：随着集成电路的发展，对热管理材料的性能提出了日益严苛的要求。
借助接枝在氧化石墨烯(GO)上的烯丙基胺的碳碳双键与硅氢键的反应，将硅油分子接枝在GO表面，同时对Al2O3采用十六烷基三甲氧基硅烷进行表面修饰。
采用扫描电子显微镜(SEM)、傅里叶转换红外光谱(FTIR)、X射线光电子能谱(XPS)和热失重分析(TGA)等手段对材料的形貌、组成、热稳定性等进行了表征分析。
研究发现，填充了改性后的Al2O3和GO后导热硅脂的导热性能明显提高。
因此，对填料表面的适当修饰是一种有效提高硅脂导热性能的策略。
关键词：表面改性；石墨烯；氧化铝；导热硅脂中图分类号：TB332文献标志码：A文章编号：1003-5168（2022）2-0088-05 DOI:10.19968/ki.hnkj.1003-5168.2022.02.021Synergistic Improvement of Thermal Conductivity of Sili⁃cone Grease by Modified Graphene/Modified AluminaSHI Haolong WANG Rong TANG Xiuzhi(School of Aeronautics and Astronautics,Central South University,Changsha410000,China)Abstract:With the development of integrated circuits,more and more stringent requirements are put for⁃ward for the performance of thermal management materials.Silicone oil molecules were grafted on the surface of graphene oxide(GO)by the reaction of carbon carbon double bond and silicon hydrogen bondof allylamine grafted on graphene oxide(GO).At the same time,Al2O3was modified by cetyltrimethoxysi⁃lane.The morphology,composition and thermal stability of the materials were characterized by scanning electron microscopy(SEM),fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectros⁃copy(XPS)and thermogravimetric analysis(TGA).It is found that the thermal conductivity of thermal conductive silicone grease filled with modified Al2O3and GO is significantly improved.Therefore,the ap⁃propriate modification of the filler surface is an effective strategy to improve the thermal conductivity of silicone grease.Keywords:surface modification;Graphene;Alumina;thermal conductive silicone grease收稿日期：2021-11-04基金项目：湖南省自然科学基金面上项目“多孔（还原）氧化石墨烯增韧聚合物基复合材料”（2020JJ4726）。
advanced materials reasearch分区 -回复
advanced materials reasearch分区-回复Advanced materials research is a crucial area in scientific studies that aims to develop innovative materials with enhanced properties and functionalities. In this article, we will delve deeper into this field, exploring its significance, research methodologies, and potential applications.To begin with, let us define what advanced materials are. These materials are engineered to possess superior properties when compared to traditional ones, enabling numerous desirable characteristics such as improved strength, flexibility, electrical conductivity, thermal resistance, and more. These materials are often created by manipulating their structures at the atomic or molecular level, allowing for better control over their properties and performance.The significance of advanced materials research cannot be overstated. These materials offer a wide range of possibilities and have the potential to revolutionize various industries such as electronics, aerospace, automotive, energy, healthcare, and many others. By developing materials with enhanced properties, scientists and engineers can create more efficient devices, strongerand lighter structures, and sustainable energy solutions, among other advancements.Now let's move on to the research methodologies employed in advanced materials research. Scientists utilize various techniques and approaches to develop and study these materials. One common method is synthesis, which involves creating new advanced materials through chemical reactions or physical processes. This process may include techniques such as vapor deposition, sol-gel synthesis, electrochemical methods, and more.Characterization techniques also play a crucial role in advanced materials research. These methods allow researchers to analyze the properties and structure of materials at various scales. Techniques like electron microscopy, X-ray diffraction, spectroscopy, and thermal analysis provide valuable information about the composition, crystal structure, surface morphology, and thermal behavior of advanced materials.Moreover, computational modeling and simulations are extensively used in advanced materials research. These tools enable scientists to predict and understand the behavior of new materials beforeactual synthesis and testing. By utilizing computer simulations, researchers can optimize material properties and identify potential limitations or challenges.Now that we have an understanding of the research methodologies, let's explore the potential applications of advanced materials. One prominent area where these materials have made significant advancements is in electronics. Advanced materials like graphene, carbon nanotubes, and semiconducting polymers have transformed the field, enabling advancements in flexible displays, wearable electronics, and high-performance transistors.In the field of energy, advanced materials are crucial for developing efficient and sustainable solutions. Materials such as perovskite solar cells, advanced battery materials, and catalysts for energy conversion have the potential to revolutionize the renewable energy sector. These materials offer higher energy conversion efficiencies, longer battery life, and improved performance.In the healthcare industry, advanced materials are being developed for applications such as drug delivery, tissue engineering, and medical implants. Biomaterials with tailored properties canpromote tissue regeneration, enhance drug delivery efficiency, and reduce implant rejection rates. Advanced materials offer the potential to significantly improve patient outcomes and advance medical treatments.In conclusion, advanced materials research is a multidisciplinary field with immense potential for technological advancements. By employing synthesis, characterization, and computational modeling techniques, scientists can develop materials with enhanced properties. These materials find applications in various industries, ranging from electronics to energy and healthcare. As the field continues to progress, we can anticipate remarkable advancements that will shape the future of technology and innovation.。
Poly(butylene sucinate-co-adipate)montmorillonite
1. Introduction
Poly(butylene succinate-co-adipate) (PBSA) is an environmental benign biodegradable polymer made of butylene succinate adipate random copolymer [1,2]. It is synthesized by polycondensation of 1,4-butanediol with succinic and adipic acids [3,4]. A schematic view of the chemical structure of the pure PBSA is illustrated in Fig. 1. PBSA is thermoplastic polyester with many interesting properties, including biodegradability; melt processability and chemical resistance. Because of the ‘green’ feature, it has been proposed as a degradable plastic for uses in serviceware, grocery, waste-composting bags, mulch films, etc [5]. However, its poor properties such as softness, gas-barrier, and thermal stability limit its end-use applications.
g-C3N4增强木塑的制备和表征
Preparation and characterization of wood–plastic composite reinforced by graphitic carbonnitrideBingrong Lei a ,Yaru Zhang a ,Yanjin He a ,Yongfeng Xie a ,Baiping Xu b ,Zhidan Lin d ,Langhuan Huang a ,Shaozao Tan a ,⇑,Meigui Wang b ,⇑,Xiang Cai c ,⇑aDepartment of Chemistry,Jinan University,Guangzhou 510632,ChinabDepartment of Light Chemical Engineering,Guangdong Industry Technical College,Guangzhou 510300,China cDepartment of Light Chemical Engineering,Guangdong Polytechnic,Foshan 528041,China dDepartment of Materials Science and Engineering,Jinan University,Guangzhou 510632,Chinaa r t i c l e i n f o Article history:Received 9June 2014Accepted 16October 2014Available online 24October 2014Keywords:Wood plastic composite Graphitic carbon nitride Mechanical properties Thermal properties Outward colora b s t r a c tThe aim of this study was to evaluate and characterize various properties of experimental composition prepared from graphitic carbon nitride (g-C 3N 4),wood flour (WF)and polypropylene (PP).g-C 3N 4with different concentrations (1wt.%,3wt.%,5wt.%and 10wt.%)were used as reinforcing filler for wood plas-tic compositions (WPCs).Maleic anhydride grafted polypropylene (PP-g-MA)was added as a coupling agent to increase the interaction between the components.Water absorption,morphology,physical,mechanical and thermal properties of the as-prepared composites were evaluated.The results showed that the tensile modulus of the composite was increased by 142.9%with increasing of g-C 3N 4contents to 5wt.%,reaching approximately 498MPa compared to WPC.Moreover,the flexural and tensile strengths reached their maximum values when the concentrations of g-C 3N 4were 1wt.%and 3wt.%,respectively.When maintaining the g-C 3N 4at a low concentration,it was well dispersed in the WPC with thin plate shape.However,when more g-C 3N 4(3–10wt.%)was introduced,the enhancing effect began to diminish because of the agglomeration of g-C 3N 4which caused poor interfacial adhesion.The water absorption results showed a lower value with the addition of 1wt.%g-C 3N 4,and the thermal tests showed that the degradation temperature shifted to higher value clearly after the addition of g-C 3N 4.Besides,with the addition of g-C 3N 4improved the outward color compared to the control sample.Crown Copyright Ó2014Published by Elsevier Ltd.All rights reserved.1.IntroductionWood flour (WF)is gaining more and more acceptance as a kind of filler for polymers due to its low density,easy availability,bio-degradation,high stiffness,renewability and relatively low cost.In addition,the renewable and biodegradable characteristics of wood fibers facilitate their ultimate disposal by composting or incineration.According to the advantages of wood fiber,the production of wood plastic composites (WPCs)and its application in many areas has attracted much attention in the past ten years [1].They were used in interior decoration and construction indus-tries such as decking,railing,fencing,docks,landscaping timbers,and in a number of automobile industries [2].However,when com-bining thermoplastics with wood fibers by conventional methods,the highly hydrophilic characters of the lignocelluloses materials make them incompatible with the thermoplastics which are highly hydrophobic.The incompatibility leads to poorer interfacial adhesion between thermoplastics and wood filler,and worse of the composite properties.In addition,the hydroxyl groups between wood fibers can form hydrogen bonds which can lead to agglomeration the fibers into bundles and unevenly distribution throughout the non-polar polymer matrix during the compound-ing processing [3,4].However,the WF is mainly made of cellulose,hemicelluloses,lignin and pectins,which leads to water absorption of the WPC resulting in debonding fibers and degradation of the fiber–matrix interface.In addition,the high moisture absorption of natural fibers may cause dimensional change of the resulting composite and weakened the interfacial adhesion [5,6].WPC in the extrusion process are mainly affected by the barrel tempera-ture and the die temperature.Due to the high temperate leads to the carbonization of WF,the appearance color of the products is affected.Many studies were devoted to enhancing the physical and mechanical properties of these composite materials,such as the/10.1016/j.matdes.2014.10.0410261-3069/Crown Copyright Ó2014Published by Elsevier Ltd.All rights reserved.⇑Corresponding authors.E-mail addresses:tanshaozao@ (S.Tan),1987103016@ (M.Wang),cecaixiang@ (X.Cai).tensile and flexural strengths [7].Usually there areto accomplish this through the use of different the filler can be treated with coupling agent or terms of the particle size,such as processing WF [8],silane treatment [9],heat treatment [10],or sodium hydroxide [11].On the other hand,using such as nanoclay or carbon nanotubes is one of to reinforce the mechanical properties of the nano-materials have positive results including increased tensile and flexural strength,high low water absorption [12,13].Many researchers the nanoclay as nanofiller to improve physical properties of WPC [12,14].In the recent years,nitride (g-C 3N 4)has been widely used in many catalytic areas,especially for oxygen reduction reaction since Wang et al.have founded its photocatalytic ability to produce hydrogen from a methanol aqueous solution under visible-light irradiation [15].However,to the best of our knowledge,g-C 3N 4has not been used as reinforcement for WPC.In this study,pure melamine was used to prepared the g-C 3N 4by directly heating [16].The main objective of this work was to study the effect of g-C 3N 4as a reinforcing agent on the physico-mechanical properties of WPC.2.Experimental details 2.1.MaterialsMelamine was purchased from Tianjin Municipality kemi’ou Chemical Reagent Co.,Ltd.;PP (T30S)was purchased from China Petroleum Chemical Co.,Ltd.(Maoming,China);the satiric acid (lubricant)and coupling agent (PP-g-MA,grafting degree was 0.8%)were supplied by Ma Ji Sen composite materials Co.,Ltd.;wood flour (WF,<150l m)was supplied by Wei Hua spice Co.,Ltd.(Guangdong,China).2.2.Preparation of g-C 3N 4The g-C 3N 4was prepared by simple calcination of melamine powder under air atmosphere.First,an certain amount of the mel-amine power were put into a semi-closed alumina crucible with a cover.Second,the crucible was heated to 550°C for 2h,at a heat-ing rate of 2°C min À1.After cooling to room temperature,the obtained yellow sample was grinded into powder and dried at 85°C.2.3.Preparations of samplesThe g-C 3N 4,WF,PP,stearic acid and PP-g-MA were weighed according to formulations given in Table 1.All of the pure fillers were dried at 85°C in the convection oven for 48h prior to use.Process for preparing WPC based on PP was schematically shown in Fig.1.The mixtures were prepared by using a twin screw extru-der (SHJ-20with average screw diameter of 20mm and average L /D ratio of 40),with a temperature profile of 175/180/185/190/195/195/190°C and a rotating speed of 150rpm,and then theextruded strands were passed through a trough before palletized.Totally 6sets of blends and composite samples were fabricated.The pellets were injected into ISO standard specimens by using an injection molding machine (HMT OENKEY)at 190°C.The actual samples were shown in the Fig.2.2.4.CharacterizationX-ray diffraction (XRD)patterns were recorded on a diffractom-eter (D /max-1200)using graphite monochromatic Cu K a radiation (k =0.1541nm)at a generator voltage of 40kV and a current of 40mA.Measurements were conducted within a 2h range of 2.0–70.0°at a scanning rate of 2°/min.Fourier transform infrared spectrometer (FTIR)spectra between 500and 4000cm À1were obtained on a Nicolet 6700spectrometer (USA).Scanning elec-tronic microscope (SEM)was performed on JSM-6330F scanning electron microscope with an accelerating voltage of 20.0kV.The fracture surfaces of samples were coated with a thin layer of gold before SEM observation.2.5.Water absorption propertiesThe water absorption test was conducted as per ASTM:D570-98.Before testing,five specimens were dried in an oven for 48h at 100±3°C.The weight of dried specimens was measured at an accuracy of 0.001g.The dimensions of samples for water absorption test were 80mm Â10mm Â4mm.The conditioned specimens were placed in a container filled with deionized water,supported on their edges,and entirely immersed and kept at 23±1°C for 16days.At the end of 24±1h,48±1h,96±1h,192±1h,384±1h,the specimens were removed from the water one at a time,all surface water wiped off with a dry cloth and weighed immediately.Five replications were tested and their average values were reported.The value of the water absorption in percentage was calculated by using the following Eq.(1):WA t ð%Þ¼W t ÀW 0W 0Â100ð1Þwhere WA t is the water absorption (%)at time t ,W 0is the oven dried weight and W t is the weight of specimen at a given immersion time.Table 1The blend design of compounding materials for respective composite.Sample PP (wt.%)WF (wt.%)PP-g-MA (wt.%)g-C 3N 4(wt.%)Stearic acid (wt.%)PP 950302WPC5540302WPC/CN 15440312WPC/CN 35240332WPC/CN 55040352WPC/CN 1045403102Fig.1.Scheme of the process for preparing WPC based on PP.104 B.2.6.Mechanical propertiesThe tensile andflexural tests were carried out by using a Universal Testing Machine(LLOYD LR100K)according to the ISO standards527-1[17]and178[18],respectively.The notched Izod impact strengths were conducted following ISO standards179-1 [19]with impact type test machine(ZBC-50).Five replications were tested and their average values were reported.2.7.Thermal propertiesThermal behaviors of WPC and WPC/CN were examined by using a thermo gravimetric analyzer(TGA)to determine the weight loss as a function of temperature.Each composite was heated from30to800°C at a rate of10°C/min under nitrogen atmosphere.3.Results and discussion3.1.XRD analysisFig.3illustrates the X-ray diffraction pattern of the prepared g-size of one tris-s-triazine unit(0.713nm),which could be attrib-uted to the presence of a tilt angularity in the structure[15,16]. The above result indicated that the as-prepared g-C3N4possesseda tri-s-triazine-based structure and the g-C3N4phase was formed.3.2.FTIR spectraFTIR spectra of g-C3N4were shown in Fig.4,which exhibited three characteristic absorption regions located around 3412cmÀ1,1200–1650cmÀ1and799cmÀ1.The adsorption band centered at3412cmÀ1could be ascribed to the stretching mode of OH bond.The broad absorption band at3231cmÀ1could be attributed to the stretching vibration of NH2or N–H groups,sug-gesting the small amount of contamination of hydrogen[21,22]. It was suggested that a small amount of amino groups remained in the samples prepared by direct heating of the melamine.Zhao et al.[23]reported that residual hydrogen atoms bound to the edges of the graphic-like C–N sheet in the form of C–NH2and 2C–NH bonds.Peaks appeared at the range from1241to 1638cmÀ1were attributed to the stretching vibration of graphitic C–N single and double bond characters[24],which again con-firmed the existence of poly(tri-s-triazine)-based p-conjugated systems in g-C3N4heterojunctions.The sharp peak at799cmÀ1 was ascribed to the typical breathing vibration of the triazine units [16,25].The FTIR spectra which obtained confirming that the prod-ucts were the same to the literature treated at550°C under the air atmosphere.3.3.Water absorption propertiesThe water absorption behavior was important to investigation of the durability of the WPC exposing to the environmental condi-tions.The water uptake results of PP,WPC and WPC/CN after immersion in distilled water for sixteen days were shown in Fig.5.As seen,pure PP barely absorbed moisture due to its hydro-phobic nature.However,the amount of water uptake was suddenly increased with the incorporation of WF into PP.So the absorptionFig.2.Images of samples made with different content of g-C3N4.Fig.3.XRD patterns for the synthesized g-C3N4.Fig.4.FTIR spectrum for the synthesized g-C3N4.Design66(2015)103–109105which was even lower than the WPC sample.The reason might be that well dispersity was achieved for1wt.%of g-C3N4which gave better interfacial adhesion of the g-C3N4to the matrix and better water barrier performance[26].According to Das et al.[27],water saturated the cell wall offiber,and then water occupied void spaces.However,when the g-C3N4filler was added from1wt.%to10wt.%,the water uptake of composite was increased,and it was attributed to the agglomerate of g-C3N4that increased voids and crack fractions during the compounding process.This hypoth-esis was also confirmed by SEM images(Fig.7d–f).From which it can be seen that more crack were created when the composite con-tained10wt.%g-C3N4.So the composite would absorb more water in our experimental ranges offillers(more than1wt.%).3.4.SEM analysisFractured surfaces of the composites were obtained by impact fracture at room temperature.Fig.7showed the SEM photographs of the fracture surfaces of the ually some of the stacked plate-shaped g-C3N4would delaminate under plastic shearing process(Fig.6).Thus,the delaminated g-C3N4had higher surface area to be in contact with polymer matrix which it would partly increase the mechanical strength of the composites[28]. Through SEM study,the distribution and compatibility between thefillers and the matrix can be found.Fig.7a showed that the sur-face of the as-prepared g-C3N4was quite smooth and it was in stacked plate shapes.In Fig.7b,the crack could be clearly found between the matrix and the woodfibers.This was attributed to the hydrophilic nature of thefibers and their poor homogeneity in the plastic matrix.Thus,it could be implied that the interfacial interaction between the WF and the PP matrix in the composites was weak,which means thefibers can leave the matrix easily and cavities can also be easily created when stress was applied. Finally,the generated cavities and cracks in WPC would accelerate to water absorption and reduce the mechanical properties.The surface of WPC containing1wt.%g-C3N4analyzed by SEM was depicted in Fig.7c.The stacked plate-shaped g-C3N4was delami-nated under plastic shearing process,and the g-C3N4was well dis-persed in the PP matrix.Thus the1wt.%content of g-C3N4filler showed the maximumflexural strength value which was larger than the other samples,and the decrease in water absorption.This could be further supported by Fig.5.However,Fig.7d showed that the interfacial interaction between g-C3N4and PP matrix was weak,this might due to the hydrophilic nature of the nanofiller, it would easily cause agglomerate when high content of g-C3N4 was rge agglomeration of g-C3N4can be found in Fig.7e and f.Due to the agglomeration,the g-C3N4existed in the form of stack plate but not the delaminated plates.In addition,the agglomeration caused bad interfacial adhesion and more cracks and cavities in the interfacial area.The weak interfacial adhesion hindered stress transferring from the matrix to thefibers which was harmful to the mechanical properties and water absorption of the composite compared with the compositefilled with lower content of g-C3N4.This were further supported by the mechanical tests and water absorption tests.3.5.Mechanical propertiesWhen the woodfiber was added into PP,theflexural and tensile modulus of the composites were increased compared to PP as shown in Table2.This might be attributed to the better stiffness of woodfibers compared with PP.Theflexural and tensile strengths of WPC/CN had the maximum values when the contents of g-C3N4are1wt.%and3wt.%respectively.However,they were decreased when more g-C3N4was added compared with the con-trol sample.As observed from Table2,the composites exhibited a negative elongation at break effect with the addition of g-C3N4. When PPfilled with woodflour show brittle behavior,thus the elongation at break of WPC and WPC/CN decreased markedly com-pared to PP.Fig.8illustrated the effect of g-C3N4content on theflexural properties of WPC/CN.Theflexural strength of the compositesFig.5.Water absorption curves of PP,WPC and WPC/CN.The schematic illustrations of changes of g-C3N4during compoundingprocess.Fig.7.SEM images:(a)g-C3N4,(b)WPC,(c)the fracture surface of WPC/CN1,(d)thefracture surface of WPC/CN3,(e)the fracture surface of WPC/CN5and(f)the fracturesurface of WPC/CN10.Design66(2015)103–109was increased slightly at the1wt.%content of g-C3N4compared to the WPC sample and it began to decrease as more g-C3N4was added.Theflexural strength of the composite mainly depended on the interfacial interaction and the properties of constituents [29,30].The result suggested that the low content of g-C3N4 (1wt.%)had better homogeneous dispersion and better interfacial interactions in the WPC,which enabled effective stress transferring from matrix tofibers and then leading to highflexural strength. But with higher content,the g-C3N4began to agglomerate which resulted in poor dispersion in WPC and then theflexural strength began to decrease,so the composite with10wt.%g-C3N4showed the minimumflexural strength,decreased by7.6%compared the WPC sample.Fig.8showed that theflexural modulus increased with increasing g-C3N4content in the composite,the reason might be that theflexural modulus of g-C3N4was higher than WF.Since theflexural modulus in composite mainly depended on the modu-lus of individual component[33].In addition,plate-shapedfillers had high aspect ratios,and this property increased the wettability of thefillers by the matrix,therefore it was helpful to transfer stress from polymer to the plate-shapedfillers.Fig.9illustrated the effect of g-C3N4content on the tensile properties of WPC/CN.When woodfiber was added,the tensile strength of WPC was decreased compared to pure PP(Table When WF was added in thermoplastics,the tensile strength would be decreased[31].Similar to theflexural strength,the tensile strength of WPC/CN was increased atfirst,tensile strength(3wt.%g-C3N4)among theThen,it was decreased as the g-C3N4wasthat3wt.%g-C3N4had positive effect on tensileg-C3N4reinforced polymer composite.Thisbridge’s function of g-C3N4,which led to betterefficiency from the matrix to thefiller andstrengths.Similar observations of otherPP composites were reported[32].Fig.9alsothat more addition(more than3wt.%)of g-C3N4improve tensile strength.This could be explained again by agglomeration of the g-C3N4.The aggregation of g-C3N4was harm-ful to mechanical properties of the resultant nanocomposites.The tensile modulus of WPC/CN was increased with increasing g-C3N4 content in the composite.But when10wt.%g-C3N4was added into WPC,the tensile modulus was decreased slightly.As it could be seen from Fig.9,with increasing of g-C3N4contents to5wt.%, the tensile modulus value was increased by142.9%,reaching approximately498MPa compared to WPC.This enhancement in tensile modulus might be attributed to the decrease in mobility the polymer chains which might that because the stack state 3N4had restrained the mobility of polymer chains.Fig.10illustrated the Izod impact strengths of the composites made with different content of g-C3N4.The test results showed impact strengths of composite were reduced with increasing content of g-C3N4in WPC.But the impact strengths of the compos-with1wt.%and3wt.%g-C3N4content were almost the same.Table2The mechanical properties of PP,WPC and WPC/CN.Fig.8.Effect of g-C3N4content on theflexural properties of WPC/CN.Fig.9.Effect of g-C3N4content on the tensile properties of WPC/CN.Effect of g-C3N4content on the notched Izod impact strength of WPC/CN.B.Lei et al./Materials and Design66(2015)103–109107The most important reason for the decrease might be that g-C 3N 4platelet restricted the motion of polymer chains and made the composites ually,increasing g-C 3N 4content would constrain ductile deformation of the PP matrix and an increasing proportion of the fracture energy,thus the Izod impact strengths decreased with increasing content of g-C 3N 4in WPC.3.6.Thermal propertiesThe TGA curves were very important to study the thermal prop-erties and degradation behaviors of the composite applied in high temperature.Manufacture of the WPC containing high content of wood fiber at high temperature would degrade the cellulosic mate-rials that led to undesirable effects on the properties of the composite.Fig.11showed the mass loss curves of PP,WPC and WPC/CN.The TGA curve of pure PP showed single-mass loss step from 333°C to 466°C.However,the maximum degradation rate shitted to a higher temperature when PP was mixed with wood fiber,indi-cating that the WF improved the thermal stability of the polymer compared with the pure PP.This could be attributed to the high thermal stability of lignin in WF [33].The cure for WPC mainlyhad two decomposition stages.The first decomposition peak (248–375°C)was mainly due to the thermal decomposition of WF [34],and the second one (406–490°C)was mainly due to ther-mal decomposition of PP (See Table 3).Another important feature was that the addition of g-C 3N 4to the polymer blend clearly increased the degradation temperature of the composite.Obviously,the WPC/CN mainly showed two decompositions stages.The temperature of degradation of the polymer blend with varying amounts of g-C 3N 4increased from 422to 440°C in comparison to WPC sample.Table 4shows the decomposition temperature at different weight loss (T D %)and residual weight (RW%)for WPC and WPC/CN.It was observed that the decomposition temperature values were increased due to the addition of g-C 3N 4into the polymer blend.The 20%weight loss temperature of composite was increased by about 30.5°C when the addition of g-C 3N 4was up to 10wt.%.It was obvious that the decomposition temperatures of 40%,60%and 80%weight loss were all increased when the g-C 3N 4content was increased.But the 40%and 60%weight loss temperatures of composites made scarcely influence between 3wt.%and 5wt.%addition of g-C 3N 4.This might be due to the poor dispersion and agglomeration of g-C 3N 4.The maximum improvement in thermal stability was observed by the inclusion of 10wt.%g-C 3N 4.The RW%value at 600°C for composites was increased with increasing content of g-C 3N 4.This might be attributed to the presence of g-C 3N 4plate which acted as a barrier and delayed the decomposition of volatile products [35].4.ConclusionsThe effects of g-C 3N 4on the physical,mechanical and morpho-logical properties of the WF/PP composites were investigated.The physical and mechanical test results indicated that the properties of the WPC were significantly influenced by the content of g-C 3N 4.The large surface area of g-C 3N 4enhances flexural and tensile modulus of the composites.A suitable content of g-C 3N 4could also improve flexural and tensile strength of the composites.The sample with 1wt.%g-C 3N 4showed lower water absorption.However,the overloaded g-C 3N 4caused the aggregation and then affected the physical and mechanical properties.The addition of g-C 3N 4obviously improved the degradation temperature and the outward color of the WPC.In this study,the addition of g-C 3N 4from 1wt.%to 3wt.%was found to be the optimal condition to prepare WF/PP composite.AcknowledgementsThis work was financially supported by the National Natural Sci-ence Foundation of China (21271087,51172099,11272093and 21006038),the Foundation of Science and Technology Projects of Guangdong Province (2011B010700080),and the 2013Jinan Uni-versity Challenge Cup for Student Extracurricular Academic Science and Technology Work Competition (201312B07and201312B49).Fig.11.TGA curves for PP,WPC and WPC/CN.Table 3The notched Izod impact strengths of PP,WPC and WPC/CN.Samples Impact strengths (kJ/m 2)PP 3.556±0.055WPC3.481±0.227WPC/CN 1 3.295±0.206WPC/CN 3 3.287±0.197WPC/CN 5 3.091±0.163WPC/CN 102.394±0.048Table 4Thermal analysis of WPC and WPC/CN composites.SamplesTemperature of decomposition (T D )in °C at different weight loss (%)RW%at 600°C20%40%60%80%WPC382.36454.36467.46482.1815.01WPC/CN 1383.45457.10470.73488.7316.96WPC/CN 3386.18460.10475.09599.4520.20WPC/CN 5402.55460.9475.63645.8221.50WPC/CN 10412.91465.23480.00670.3625.21Design 66(2015)103–109References[1]Ashori A.Wood–plastic composites as promising green-composites forautomotive industries.Bioresour Technol2008;99:4661–7.[2]Ashori A.Effects of nanoparticles on the mechanical properties of rice straw/polypropylene composites.J Compos Mater2013;47:149–54.[3]Raj RG,Kokta pounding of cellulosefibers with polypropylene:effectoffiber treatment on dispersion in the polymer matrix.J Appl Polym Sci 1989;38:1987–96.[4]Kazayawoko M,Balatinecz JJ,Matuana LM.Surface modification and adhesionmechanisms in woodfiber–polypropylene composites.J Mater Sci 1999;34:6189–99.[5]Bisanda ETN,Ansell MP.The effect of silane treatment on the mechanical andphysical properties of 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PPEEP体系的形态、固化行为和耐热性研究(1)
高校化学工程学报２００６年ｌＯ月２实验部分２．１原料ＰＰＥ，美国１ＧＥ公司生产，数均分子量％＝１２５００ｇ．ｍｏｌ～；环氧树脂为ｓｈｅｌｌ公司的Ｅｐｏｎ８２８；固化剂ＤＤＳ（二氨基二苯砜），化学纯，上海医药化学试剂公司生产：ＴｍＣ（三烯丙基异氰酸酯），湖南浏阳有机化工有限公司提供；三氯乙烯，分析纯，广州化学试剂厂生产。
２．２试样的制备把ＰＰＥ和环氧树脂放入三颈瓶中，通过机械搅拌，在油浴锅中慢慢加热到１８０℃，保温２ｈ左右，形成均匀的溶液；然后，冷却到１００℃，把固化剂ＤＤＳ加入到溶液中，在真空下搅拌３０ｍｉｎ；如有需要，此时可连同Ｔ越Ｃ一起加入，在搅拌均匀后，把混合物倒入预热的钢模中进行固化２ｈ。
２．３仪器测试等温ＤＳＣ测试和耐热性分析均采用德国ＮＥＴｚＳＣＨ公司的ＳＴＡ４４９Ｃ型综合热分析仪，Ｎ２气氛：ＦＴ．ＩＲ用美国Ｎｉｃｏｌｅｔ３６０型红外光谱仪；固化样品的相态利用ＪＸＡ一８４０型扫瞄电镜（ＳＥＭ）观察其断裂面。
３结果与讨论３．１形态图ｌ的（ａ）和（ｂ）分别为２０％ＰＰＥ／ＥＰ三氯乙烯蚀刻前后的形态，在溶剂蚀刻后对应于ＰＰＥ相有一些残留的孔存在。
这表明ＰＰＥ的耐化学药品性没有得到改善，暗示ＰＰＥ和ＥＰ之间缺乏明显的交联。
（ｃ）和（ｄ）为２０％ＰＰＥ／ＥＰ体系加入一定量的ＴＡＩＣ（总重的２０％）在三氯乙烯蚀刻前后的形态。
从（ｃ）和（ｄ）可以看出，含有ＴｍＣ的ＰＰＥ／ＥＰ体系在三氯乙烯蚀刻前后没有明显的变化，表明在加入ＴｍＣ后ＰＰＥ的耐溶剂性得到了很大的提高。
这是由于ＴｍＣ一方面溶于环氧树脂，另一方面ＰＰＥ芳环上的甲基受到Ｔ刖Ｃ自由基的攻击而和Ｔ舢Ｃ形成枝接的共聚物【６１，受制于ＴｍＣ网络中，使ＰＰＥ很难被芳香烃和卤代烃溶解。
图２的（ａ）和（ｂ）是４０％ＰＰＥ／ＥＰ体系分别在１６０℃和２２０℃固化２ｈ的ｓＥＭ图，从（ａ）和（ｂ）对比可看出分散相环氧树脂的颗粒尺寸由于固化温度的降低而减小。
在低温固化时，由于体系的粘度较高，阻碍（ｄ）图１２０％ＰＰＥ脚体系在１８０℃固化２ｈ的ＳＥＭＦｉｇ．１ＳＥＭｉｍａｇｅ０ｆ２０％ＰＰＢ７ＥＰｓｙＳｔｅｍｓｃｕｒｃｄａｔ１８０℃ｆｏｒ２ｈ．（ａ）Ｏ％ＴＡＩｃ（ｂ）Ｏ％ＴＡＪＣ（ｅｔｃｈｃｄ）（ｃ）ｗｉｍ２０％ＴＡＩｃ（ｄ）ｗｉｔｈ２０％ＴＡＩＣ（ｅｔｃｈｅｄ）（ａ）（”图２４０％ＰＰＥ／ＥＰ体系的ｓＥＭＦｉｇ．２ＳＥＭｉｍａｇｅＯｆ４０％ＰＰＥ厄Ｐｓｙｓｔｅｍｓ（ａ）ｃｕｒｅｄａｔｌ６０℃ｆｏｒ２ｈ（ｂ）ｃｕｒｅｄａｔ２２０℃ｆｏｒ２ｈ分散相环氧树脂小液滴的合并。
CoFeC纳米材料替代稀土永磁(APL)
Experimental evidence for the formation of CoFe2C phase with colossal magnetocrystalline-anisotropyAhmed A. El-Gendy, Massimo Bertino, Dustin Clifford, Meichun Qian, Shiv N. Khanna, and Everett E. CarpenterCitation: Applied Physics Letters 106, 213109 (2015); doi: 10.1063/1.4921789View online: /10.1063/1.4921789View Table of Contents: /content/aip/journal/apl/106/21?ver=pdfcovPublished by the AIP PublishingArticles you may be interested inEnhanced magnetic behavior, exchange bias effect, and dielectric property of BiFeO3 incorporated in(BiFeO3)0.50 (Co0.4Zn0.4Cu0.2 Fe2O4)0.5 nanocompositeAIP Advances 4, 037112 (2014); 10.1063/1.4869077Facile synthesis of single-phase spherical α″-Fe16N2/Al2O3 core-shell nanoparticles via a gas-phase method J. Appl. Phys. 113, 164301 (2013); 10.1063/1.4798959High temperature phase transformation studies in magnetite nanoparticles doped with Co2+ ionJ. Appl. 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Lett. 88, 033105 (2006); 10.1063/1.2165276Experimental evidence for the formation of CoFe 2C phase with colossal magnetocrystalline-anisotropyAhmed A.El-Gendy,1,2,a)Massimo Bertino,3Dustin Clifford,1Meichun Qian,3Shiv N.Khanna,3,a)and Everett E.Carpenter 1,a)1Department of Chemistry,Virginia Commonwealth University (VCU),1001West Main,Richmond,Virginia 23284,USA 2Nanotechnology and Nanometrology Lab.,National institute for standards (NIS),136Tersa,Haram,Giza 12211,Egypt 3Department of Physics,Virginia Commonwealth University (VCU),701West Grace,Richmond,Virginia 23284,USA(Received 6April 2015;accepted 17May 2015;published online 28May 2015)Attainment of magnetic order in nanoparticles at room temperature is an issue of critical importance for many different technologies.For ordinary ferromagnetic materials,a reduction in size leads to decreased magnetic anisotropy and results in superparamagnetic relaxations.If,instead,anisotropy could be enhanced at reduced particle sizes,then it would be possible to attain stable magnetic order at room temperature.Herein,we provide experimental evidence substantiating the synthesis of a cobalt iron carbide phase (CoFe 2C)of nanoparticles.Structural characterization of the CoFe 2C carbide phase was performed by transmission electron microscopy,electron diffraction and energy electron spectroscopy.X-ray diffraction was also performed as a complimentary analysis.Magnetic characterization of the carbide phase revealed a blocking temperature,T B ,of 790K for particles with a domain size as small as 561nm.The particles have magnetocrystalline anisotropy of 4.662Â106J/m 3,which is ten times larger than that of Co nanoparticles.Such colossal anisotropy leads to thermally stable long range magnetic order.Moreover,the thermal stability constant is much larger than that of the commonly used FePt nanoparticles.With thermal stability and colossal anisotropy,the CoFe 2C nanoparticles have hugepotential for enhanced magnetic data storage devices.VC 2015AIP Publishing LLC .[/10.1063/1.4921789]Due,in part,to the enhanced thermal properties associ-ated with anisotropy,1–7nanomagnets with unusually high—or,colossal—magnetic anisotropy are critical for the advancement of major technologies such as spintronics,bio-medical applications,and permanent magnetic application.To achieve colossal anisotropy,the size,composition,and atomic arrangement of the nanoparticles must be controlled.If,in addition,the collective properties of the assembled nanoparticles were controlled,the resulting material would offer energy efficient correlated switching of the spins with no standby power dissipation,making it ideal for spintronic applications.8–10We recently demonstrated 1that assembled cobalt car-bide (Co 3C)(1062nm)nanoparticles synthesized via pol-yol process have high thermal properties.We determined that the atomic arrangement within the Co 3C nanoparticles consisted of alternating cobalt and carbon layers.Magnetic measurements indicated that the material had a coercivity of 360.1kOe which is comparable to that of some permanent rare earth magnets.This is a seemingly paradoxical result as bulk cobalt is a soft magnetic material and carbon has been known to quench magnetic moment.Subsequent theoretical studies indicated that the high coercivity resulted from the controlled mixing between the cobalt d-states and the carbonp-states which reduced the separation between the filled and unfilled d-states and enhanced the magnetic anisotropy.1,2This unusually high anisotropy yielded blocking tempera-tures exceeding 570K,which were higher than any previ-ously reported values for particles of this size and were in good agreement with theoretical determinations.1,2Extensive work on bulk alloys has shown that the Fe-Co alloys offer high magnetic moments and coercivity.In fact,the Slater-Pauling limit is reached at around 35%cobalt.This raises the question of whether similarly enhanced magnetic properties could be achieved by making Fe-Co nanoparticles.In a recent work,we conducted theoretical studies to examine whether magnetocrystalline anisotropy even greater than that of Co 3C can be achieved by producing another type of carbide called the CoFe 2C phase.2Preliminary studies predicted that a combination of Fe and Co atoms in the phase would produce higher magnetic moments and that separation of the Co layers via C atoms would yield a higher anisotropy.The combination of increased magnetic moment and anisotropy would thus lead to much higher blocking temperature,T B ,than the Co 3C nanoparticles.While this CoFe 2C carbide phase has been postulated by first principles theory,previous experimental efforts could only produce a mixture of two phases of Co x C and Fe x C.2Herein,we report the synthesis of a phase of transition metal carbides using supercritical ethanol.The synthesis was optimized to produce single crystals (several having rod-likea)Authors to whom correspondence should be addressed.Electronic addresses:aelgendy@;ecarpenter2@;and snkhanna@.0003-6951/2015/106(21)/213109/5/$30.00VC 2015AIP Publishing LLC 106,213109-1APPLIED PHYSICS LETTERS 106,213109(2015)morphology)containing mixed carbide phases of Fe and Co (Fe 5C 2,Co 2C,and Co 3C)and a carbide phase of Fe and Co that we refer to as CoFe 2C.In the CoFe 2C phase,the transi-tion metal layers are separated by intervening layers of carbon atoms in a manner that allows for partial mixing of C p-states with Fe and Co d-states.The CoFe 2C phase has not been previously produced;hence,no x-ray diffraction (XRD)standard data currently exist.The CoFe 2C material possesses a 1:2Co:Fe ratio determined using inductively coupled plasma-mass spectrometry (ICP).Furthermore,the material’s long range ferromagnetic order is far greater than that of single phase Co 2C,Co 3C,or Fe 5C 2nanoparticles allowing unusually large magnetocrystalline anisotropies.The CoFe 2C phase was synthesized under supercritical ethanolic conditions using cobalt acetate,iron acetate,and fumaric acid as precursors.Transmission electron micros-copy (TEM)was used to characterize the morphology of a CoFeC sample.Energy filtered TEM image maps were acquired for different areas of the sample to examine the diffusion of the Co and Fe elements (below Figs.1and 2).The sample had few larger rods embedded in the rest of the sample that consisted of smaller spherical particles.The presence of Fe within Co rich regions indicated that phase CoFe 2C was formed.Across sample regions,the CoFe 2C nanoparticles were spherical in shape (Figs.S1(a)and S1(b))and possessed an average size of 20.2nm 64.6nm (Fig.S1(c)),measured horizontally at the widest diameter.The TEM images indi-cated the presence of Co within all Fe rich areas of the sample (Fig.S2).XRD studies were performed to further characterize the phase structure of the synthesized samples.In particular,the diffraction data of the formed particles were compared with the characteristic peaks of the known Co x C and Fe x C y phases.For the CoFe 2C sample,the Bragg reflections matchwith a slightly higher 2h shift for Co 2C and Fe 5C 2as shown in Fig.3(a).High temperature annealing at 773K and X-ray diffraction with a high-temperature camera (HTK-XRD)at 893K were conducted (Fig.3(b))to test the thermal stability of the particles.The XRD pattern of the as-synthesized and annealed samples at 773K (Figs.3(a)and 3(b))revealed no change in the phase or crystallite size.As multiple mixed carbide phases would normally decompose to Co and Fe 3O 4at that temperature,it was concluded that a single and thermally stable CoFe 2C phase was present (Fig.3(b)).Once the tem-perature was raised to 893K,the XRD displayed different phase structure of Fe 3C (Fig.3(c)).To further characterize the as-synthesized particles,mul-tiple electron diffractograms were acquired to confirm the presence of the CoFe 2C phase presence (Fig.4).The red arrows in the selected diffraction area (Fig.4(a))indicate a long range order that was confirmed by dark field as shown in Fig.4(b).Fig.4(b)shows dark-field image with BF inset showing long range order Bragg reflection(d ¼5.0060.25A˚),which will be related later to the long range magnetic order of the carbide phase.Fig.4(c)displays the electron diffraction pattern with approx.inverse d-spacings that match with the XRD data confirming the formation of CoFe 2C phase.In comparison,the annealed sample of CoFe 2C at 893K showed an absence of the rod structures and growth of the observed nanoparticles into larger sizes (see Fig.S3).XRDFIG.1.BF-TEM image of CoFe 2C rods (left).Energy filtered images of the CoFe 2C rods showing the C,Co,O,and Fe elemental maps (right).Fe and Co regions of the rods are indicated by redarrows.FIG.2.Electron diffraction pattern of CoFe 2C rods (Figure 1)and approxi-mated d-spacings shown (left).Line plot of rotational averaging shown (right)with peaks representing inverse d-spacings observed from Bragg reflections indiffractogram.FIG.3.XRD for spherical particles:(a)as prepared,(b)annealed at 773K,and (c)HTK-XRD at 893K.analysis of the annealed sample at 893K showed no long range order (see Fig.S4).This result is consistent with the XRD pattern of the annealed sample at 893K,shown previously in Fig.3(c).The magnetic properties of the synthesized sample were examined using vibrating sample magnetometer (VSM)measurement of the magnetization dependence on the exter-nal magnetic field at temperatures ranging from 50–900K.The obtained hysteresis curves shown in Fig.5(a)are due to the collective response of the assembly of particles.We would like to add that the magnetic particles are separated by interlayers that are largely carbon.The sample indicates an average interparticle distances of 24–30nm between the particle centers.This would lead dipolar interactions in the range of a few Kelvin which can be neglected in our analysis that involves temperature range (50–900K).The observed loops show ferromagnetic behavior for the CoFe 2C sample at all temperature ranges and no knee was observed behind the remanence magnetization M r .This once again demonstrates the formation of the pure CoFe 2C phase,which is consistent with TEM and XRD results.The CoFe 2C shows lower coercivity (H C )of 520Oe and higher saturation magnetization (M S )of 81emu/g at 300K in comparison to the published data of Co 3C phase.According to the rema-nence to saturation ratio (M r /M S )of approximately 0.5and the coercive field of the remanent H Cr to coercive field H C ratio (H Cr /H C )of 2,our sample has single magnetic domain structure.The magnetic properties for the sample did not change after annealing at 773K;however,an observable change occurred after annealing at 893K,resulting in M S of 173emu/g and H C of 150Oe (Fig.5(b)).Such data confirmed the change in atomic structure and decomposition into phases as was previously observed in the XRD peaks.As the temperature dependent coercivity can be used to determine the blocking temperature,the observed coercivitywasFIG.4.Additional electron diffraction patterns of as-prepared CoFe 2C:(a)long range order highlighted by red circles,(b)dark-field with BF inset showing long range order Bragg reflec-tion (d ¼5.0060.25A˚)and (c)electron diffraction pattern with approx.inversed-spacings.FIG.5.(a)Magnetization dependence as a function of the magnetic field at different temperatures.(b)Comparison of the magnetization curves before and after annealing at 773and 893K.(c)Variation of coercivity with temperature.plotted as a function of T1/2in Fig.5(c).The data revealed blocking temperature,T B,at H C0to be790K and the coer-civity at0K to be1.3kOe.From those results,the effective magnetocrystalline anisotropy K eff and the magnetic domain size was determined using the Neel Brown equation11and the initial slopes of the M versus H curves12,13to be 4.662Â106J/m3and561nm,respectively.We also ana-lyse the experimental data of the coercivity dependence on the temperature using Sharrock’s formula.14Wefind a K eff of3.8Â106J/m3,which is in good agreement with the value obtained using Neel Brown equation.In addition,the thermal stability of the sample up to773K confirmed the long range magnetic order up to T B at790K.In comparison to our origi-nal Co3C nanoparticles,the CoFe2C shows higher K eff and smaller H C than Co3C.To probe the origin of the observed collective behaviors and to provide guidance to the composition of the carbide phase,first principles electronic structure calculations of the magnetic moment and anisotropy in possible CoFe2C phase were conducted.6Since the mixed phase decomposes into a mixture of Co2C and Fe3C at high temperatures,one could assume a cobalt iron carbide phase obtained by replacing one of the Co sites in Co2C by Fe,or Co2FeC and CoFe2C compositions obtained by replacing one or two Co sites in Co3C by Fe atoms.All structures were based on the XRD of Co2C and Co3C phase and were further optimized until the force acting on each atom was less than1meV/A˚,where selected Co sites were replaced by Fe atoms.The anisotropy in nanoparticles is largely magnetocrystalline anisotropy energy(MAE)due to spin orbit coupling.To calculate the MAE,we calculated the change in energy due to spin orbit coupling by constraining the moments along different direc-tions.The difference between the maximum and the mini-mum energy is the MAE.Comparing the calculated magnetic moments at the Co and Fe sites in various compositions,the Co sites in Co2C have a magnetic moment of1.0l B per atom while the Fe sites in an assumed Fe3C have a moment of2.77l B per atom.The average moment per atom in all the mixed phases is higher than those in pure Co2C,which is consistent with the experimental observations of higher saturation magnet-ization.In fact,the Fe sites in Co2FeC and CoFe2C have magnetic moments of3.09and3.06l B per atom,respec-tively,which are much higher than in pure Fe3C.The moment at the Co sites is also slightly higher than in Co3C.Regarding magnetic anisotropy,the calculated magnetic anisotropic energies in the pure phases of Co2C and Co3C have similar value,while that in Fe3C is slightly higher than in cobalt.As mentioned earlier,the key issue is whether the magnetic moment and the anisotropy could be substantially enhanced my mixing Fe and Co.For the alloy phases,our cal-culated magnetic anisotropy energies per formula unit in the Co2FeC and CoFe2C were found to be higher than in pure phases of Co2C and Co3C.Through an analysis of the change in energy along various directions,the studies indicated that the phase is marked by uniaxial anisotropy with a MAE of 0.373meV/formula unit that is almost80%higher than in the pure cobalt bined with the fact that it also has a higher magnetic moment per atom,we believe that the forma-tion of this phase is the source of higher magnetization and anisotropy observed in the experiment.The primary source of the enhanced anisotropy is the controlled mixing between the Fe or Co d-states and the C p-states.15From all the obtained results,CoFe2C nanomagnets have the superior magnetic properties and can be a good candidate for data storage applications.16Moreover,the estimated thermal stability constant(TSc;ratio between magnetic anisotropy and thermal energy,depending on the magnetic size and the phase transition temperature of5nm and790K,respectively)was73,which is higher than that of the FePt materials(TSc¼60)16currently used for data stor-age devices.The abovefindings on the effect of the temperature and the particle size on the direction and thefluctuation time of the magnetic moment could be condensed into a single simple3Dfigure that represents the effect of temperature on the rotation of the magnetic moment.This is shown in Fig.6. The color indicates the change in the temperature range start-ing from the lower temperatures(blue regions)up to the very high temperatures(black regions).The effect of the thermal energy on change of the magnetic moment direction has been implied from0 to25 ,resulting in a magnetic moment rotation image of the particle around its easy axis(Fig.6). Such small effect of the thermal energy on the angle con-firms the presence of the long magnetic range order obtained from the experimental measurements.To conclude,the present studies indicate that unusually large MAE can be accomplished in CoFe2C nanoparticles consisting of cobalt and iron layers separated by carbon atoms.The long range order of the nanospherical CoFe2C up to790K exhibits better thermal stability than the Co3C nano-rods,which lose their order at570K.1The hysteresis loops show no knee beside M r,indicating the formation of single phase of CoFe2C nanoparticles.From all the abovefindings, the mixed phases of Co x C and Fe x C can be combined to form a phase of CoFe2C nanoparticles of high T B,smaller domain size of5nm,and colossal K eff.These nanoparticles could be used for the next generation of thermal stable data storage devices.Towards this end,it will be interesting to examine if other transition metal carbides could also exhibit similar enhancements.The sample has been synthesized using the supercritical condition of ethanol as the following:Co acetate in ethanolþFe acetate(1:1)has been added to fumaric acid with(3:1)metal to carbon ratio and150ml of absolute ethanol.The reaction temperature andpressure FIG.6.The temperature dependence on the rotation of the magnetic moment around the easy axis which appears in a part of the circle whose radius is the average angular radius(rotation distance)of the CoFe2C particles.was278C at69bar,respectively,for2.30h.The reaction has been done under mixture atmosphere of Argon and ethyl-ene gases.The elemental chemical analysis for the sample reveals Co:Fe ratio of1:2.First Principles studies were carried out within a density functional framework using the Vienna Ab initio Simulation Package(VASP).17–19All authors would like to acknowledge the help of the Virginia Commonwealth Nanomaterials Core Characterization Facility.They acknowledge thefinancial support from ARPA-e REACT Project1574-1674.S.N.K. acknowledges support from Department of Energy(DOE) under Award No.DE-SC0006420.A.A.E.has done the synthesis,the characterization,and the magnetic studies and wrote the experimental part of the paper.M.B.and D.M.C.have done the TEM images.M.Q. has done the theoretical part.S.N.K.has written the theoretical part and discussed the experimental part with A.A.E.E.E.C.has discussed all the data and revised the whole paper with A.A.E.and S.N.K.1A.A.El-Gendy,M.Qian,Z.J.Huba,S.N.Khanna,and E.E.Carpenter, Appl.Phys.Lett.104,023111(2014).2M.Qian and S.N.Khanna,J.Appl.Phys.114,243909(2013).3H.Kuramochi,H.Akinaga,Y.Semba,M.Kijima,T.Uzumaki,M. Yasutake,A.Tanaka,and H.Yokoyama,Jpn.J.Appl.Phys.44,2077 (2005).4A.A.El-Gendy,E.M.M.Ibrahim,V.O.Khavrus,Y.Krupskaya,S. Hampel,A.Leonhardt,B.B€u chner,and R.Klingeler,Carbon47,2821 (2009).5H.Wang,S.P.Wong,W.Y.Cheung,N.Ke,M.F.Chiah,H.Liu,and X. X.Zhang,J.Appl.Phys.88,2063(2000).6J.J.Delaunay,T.Hayashi,M.Tomita,S.Hirono,and S.Umemura,Appl. Phys.Lett.71,3427(1997).7A.A.El-Gendy,T.Almuigateeb,and E.E.Carpenter,J.Magn.Magn. Mater.348,136(2013).8P.P.Cowburn and M.E.Welland,Science287,1466(2000).9G.Csaba, A.Imre,G.H.Bernstein,and W.Porod,IEEE Trans. Nanotechnol.1,209(2002).10S.Salahuddin and S.Datta,Appl.Phys.Lett.90,093503(2007).11E.C.Stoner and E.P.Wolfarth,Philos.Trans.R.Soc.London,Ser.A 240,599(1948).12A.A.El-Gendy,V.O.Khavrus,S.Hampel,A.Leonhardt,B.Beuchner, and R.Klingeler,J.Phys.Chem.C114,10745(2010).13D.Clifford,A.A.El-Gendy,A.Lu,D.Pestov,and E.Carpenter,J.Flow Chem.4(3),148(2014).14M.P.Sharrock,J.Appl.Phys.76,6413(1994).15H.Coufal,L.Dhar,and C.D.Mee,MRS Bull.31,374(2006).16S.N.Piramanayagam,Platinum Met.Rev.65,262(2012).17G.Kresse and J.Furthmuller,Phys.Rev.B54,11169(1996).18G.Kresse and J.Hafner,J.Phys.Condens.Matter6,8245(1994).19See supplementary material at /10.1063/1.4921789for more TEM images and size distribution.。
circulation期刊-1950年-circulation期刊-1950年-10.full (232)
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Morphology,dynamicmechanicalandthermalstudiesonpoly(styrene-co-acrylonitrile)modifiedepoxyresin/glassfibrecomposites
NisharHameeda,P.A.Sreekumarb,BejoyFrancisa,WeiminYangc,*,SabuThomasa,*
aSchoolofChemicalSciences,MahatmaGandhiUniversity,PriyadarshiniHillsP.O.,Kottayam,Kerala686560,India
bNationalInstituteofTechnologyCalicut,NITCP.O.,Calicut,Kerala673601,India
cCollegeofMechanicalandElectricalengineering,BeijingUniversityofChemicalTechnology,Beijing100029,China
Received25January2007;receivedinrevisedform23July2007;accepted9August2007
AbstractPoly(styrene-co-acrylonitrile)(SAN)wasusedtomodifydiglycidyletherofbisphenol-A(DGEBA)typeepoxyresincuredwithdia-minodiphenylsulfone(DDS)andthemodifiedepoxyresinwasusedasthematrixforfibrereinforcedcomposites(FRPs)inordertogetimprovedmechanicalandthermalproperties.E-glassfibrewasusedasthefibrereinforcement.Themorphology,dynamicmechanicalandthermalcharacteristicsofthesystemswereanalyzed.Morphologicalanalysisrevealedheterogeneousdispersedmorphology.Therewasgoodadhesionbetweenthematrixpolymerandtheglassfibre.Thedynamicmoduli,mechanicallossanddampingbehaviourasafunctionoftemperatureofthesystemswerestudiedusingdynamicmechanicalanalysis(DMA).DMAstudiesshowedthatDDScuredepoxyresin/SAN/glassfibrecompositesystemshavetwoTgscorrespondingtoepoxyrichandSANrichphases.Theeffectofthermo-
plasticmodificationandfibreloadingonthedynamicmechanicalpropertiesofthecompositeswerealsoanalyzed.Thermogravimetricanalysis(TGA)revealedthesuperiorthermalstabilityofcompositesystem.Ó2007ElsevierLtd.Allrightsreserved.
Keywords:A.Glassfibre;A.Polymermatrixcomposites;B.Thermalproperties;E.Thermosettingresin;SAN
1.IntroductionOverthepastdecades,considerableprogresshasbeenmadetounderstandthemorphologicalstructuresandresultingpropertiesofmulticomponentthermosettingblends[1–4],andtheircomposites[5–7].Majorityofthethermosettingblendsarepreparedstartingfromahomoge-neoussolutionofthermoplastic(orelastomer)polymersinthermosetprecursors.Amongthethermosettingpolymers,epoxyresinsarethemostwidelyusedforhigh-performanceapplicationssuchas,matricesforfibrereinforcedcompos-
ites,coatings,structuraladhesivesandotherengineeringapplications[8–10].Epoxyresinsarecharacterizedbyexcellentmechanicalandthermalproperties,highchemicalandcorrosionresistance,lowshrinkageoncuringandtheabilitytobeprocessedunderavarietyofconditions[11].Oncefullycured,epoxiesformhighlycrosslinked,three-dimensionalnetworks.Thedenselycrosslinkednatureofthematerialenablesmanyofitssuperiorproperties.How-ever,thehighlevelcrosslinkinginepoxynetworksleadstoinherentbrittlematerialsandthatconstraintsmanyofitsapplications.Severalstudieshavebeenmadetoimprovethetoughnessandcrackresistanceofepoxyresin.Onesuc-cessfulmodificationmethodistheincorporationofsecond-aryrubberyphasethatseparatesfromthematrixduringcuring,leadingtodifferentmorphologies[12–15].Theadvantageofrubbertougheninginthermosetsisthat,
1359-835X/$-seefrontmatterÓ2007ElsevierLtd.Allrightsreserved.doi:10.1016/j.compositesa.2007.08.009
*Correspondingauthors.Tel.:+914812730003/1036;fax:+91481
2731002.E-mailaddresses:yangwm@mail.buct.edu.cn(W.Yang),sabut@sancharnet.in,sabut552001@yahoo.com(S.Thomas).
www.elsevier.com/locate/compositesaAvailable online at www.sciencedirect.comComposites:PartA38(2007)2422–2432fracturetoughnesscanbeimproveddramatically.How-ever,elastomermodificationwillleadtosignificantreduc-tioninthemodulusandthermalstabilityofthematerial.Inrecentyears,high-performancethermoplasticshavebeenextensivelyusedtotoughenthermosettingresins[16–18],becauseoftheirhighmodulusandglasstransitiontemperatures.Theincorporationofthermoplastic,initiallymiscible,whichphaseseparatesduringtheepoxy-hardenercuringreaction,leadstotoughnessimprovedepoxynet-works.Anewmaterialisgeneratedwithdistinctpropertieswithrespecttothatofthecomponentpolymers.Thephaseseparationuponcrosslinkingisduetotheincreaseinmolecularweightofepoxyresin.Inthermoplasticmodifiedepoxyresin,usuallythermoplasticdispersedphaseoraco-continuousphasestructureyieldsgreaterfracturetough-ness.Thefinalstructureofthesystemisusuallyinfluencedbythemolarmass,thermoplasticweightfraction,reactionrateandviscosityduringphaseseparation.Differenttypesofthermoplasticshavebeenusedtomodifyepoxyresinsuchas,PES,PEI,PEEK,ABS,etc.[19–23].Thermosetshavehistoricallybeentheprincipalmatrixmaterialforcompositesalthoughthermoplasticsareusedinmanyapplications[24–26].Thepropertiesofthecom-positesandthefactorsinfluencingtheirpropertieswereextensivelystudied[27–29].Theuseofepoxyresinasthematrixforfibre-reinforcedcompositesinstructuralappli-cationshasbeenincreasedsignificantly[30–32].Highspe-cificstiffness,strength,dimensionalstability,selectiveelectricalproperties,lightweightandexcellentcorrosionresistancemakethemvaluableforautomobileandaero-spaceindustries[33–35].Mostofthefibre-reinforcedcom-positesofferacombinationofstrengthandmodulusthatareeithercomparableorbetterthanmanyoftheconven-tionalandtraditionalmetallicmaterials.Theextentofadhesionofpolymerblendmatrixtothereinforcingele-ments,especiallyfibres,isveryimportant.Itiswellknownthatstresspassesfromthefibrestothematrixthroughtheinterface.Therefore,theadhesiveforceaffectsthestrengthandrigidityofthereinforcedplasticsandtheirfracturebehaviour[36].Glassfibreisoneamongthehighstrengthandhighmodulusmaterialusedforthepreparationoflargevarietiesofcomposites[37,38].Glassfibreshavefoundveryextensiveuseinplastics,mostcommonly,in