Design and evaluation of bio-based composites for printed circuit board application

We adopted a new approach focusing on the development of greener materials for the printed circuit boards (PCBs) in this study. The bio-based composites from soybean oil resins, chicken feathers, and E-glass fibers could potentially replace the traditional E-glass fiber reinforced epoxy composites used in PCBs. The flame retardancy of the PCB was achieved by halogen-free melamine polyphosphate and diethylphosphinic salt. The essential properties of the bio-composites/bio-PCB were evaluated, including mechanical properties, electrical properties, thermal properties, flammability, and peel strength. The properties were found promising for PCB application.     

Electrospun composite nanofibers for tissue regeneration

Nanotechnology assists in the development of biocomposite nanofibrous scaffolds that can react positively to changes in the immediate cellular environment and stimulate specific regenerative events at molecular level to generate healthy tissues. Recently, electrospinning has gained huge momentum with greater accessibility of fabrication of composite, controlled and oriented nanofibers with sufficient porosity required for effective tissue regeneration. Current developments include the fabrication of nanofibrous scaffolds which can provide chemical, mechanical and biological signals to respond to the environmental stimuli. These nanofibers are fabricated by simple coating, blending of polymers/bioactive molecules or by surface modification methods. For obtaining optimized surface functionality, with specially designed architectures for the nanofibers (multi-layered, core-shell, aligned), electrospinning process has been modified and simultaneous 'electrospin-electrospraying' process is one of the most lately introduced technique in this perspective. Properties such as porosity, biodegradation and mechanical properties of composite electrospun nanofibers along with their utilization for nerve, cardiac, bone, skin, vascular and cartilage tissue engineering are discussed in this review. In order to locally deliver electrical stimulus and provide a physical template for cell proliferations, and to gain an external control on the level and duration of stimulation, electrically conducting polymeric nanofibers are also fabricated by electrospinning. Electrospun polypyrrole (PPy) and polyaniline (PAN) based scaffolds are the most extensively studied composite substrates for nerve and cardiac tissue engineering with or without electrical stimulations, and are discussed here. However, the major focus of ongoing and future research in regenerative medicine is to effectively exploit the pluripotent potential of Mesenchymal Stem Cell (MSC) differentiation on composite nanofibrous scaffolds for repair of organs.     

Manufacture of a hydrophobic CaO/polylactic acid composite

In this study, the surface of calcium oxide (CaO) was modified with n-octadecyltrichlorosilane [CH₃(CH₂)₁₆CH₂SiCl₃] to obtain modified calcium oxide (CaO-M). CaO and CaO-M were melt-blended with polylactic acid (PLA) to prepare PLA/CaO and PLA/CaO-M, respectively. Moisture absorption measurement showed that the surface of modified CaO was changed from hydrophilic to hydrophobic. CaO and PLA had a tendency to agglomerate after blending, whereas the blend of CaO-M and PLA showed no signs of agglomeration, and the distribution of CaO-M in PLA was homogeneous. In addition, CaO-M had a heterogeneous nucleation effect on PLA, which effectively inhibited cold crystallization and promoted crystallization of PLA. In conclusion, CaO-M can be used as a nucleating agent of PLA.     

无机填料的改性及其在复合材料中的应用

阐述了填料表面改性技术即偶联剂处理技术、表面活性剂处理技术、等离子体处理技术的最新研究进展 ,介绍了几种典型无机填料在复合材料中的应用现状以及填料粒径、形状和含量对填充效果的影响     

复合材料装甲技术的发展及应用

介绍了复合材料装甲的优点、防护机理及其在武器装备中的重要性。详细论述了国内外复合材料装甲的技术发展现状及其在作战中的应用 ,并指出未来先进复合材料装甲的研究发展趋势     

Electrospun nanofiber composites with micro-/nano-particles for thermal insulation

Polyacrylonitrile (PAN) nanofiber and silica aerogel (SAG) laminated composites were prepared via electrospinning for thermal insulation. Conventional single nozzle and co-axial electrospinning were used to increase the fraction of aerogel particles in the composite sheets while maintaining the mechanical strength of the sheet. When the core-shell electrospinning technique with co-axial nozzle was applied, the proportion of aerogel particles increased two fold without a deterioration of the mechanical properties. The average thermal conductivity of the laminated composite sheet was reduced by approximately 12.5% as compared to the nanofiber composite prepared using the single-nozzle electrospinning technique. For additional reduction in thermal conductivity, hollow glass microspheres (HGM) was inserted between the interlayer spacing of the electrospun sheets to increase the interlayer spacing. When HGM particles were inserted, it was observed that the thermal conductivity decreased by approximately 20% compared to that of the specimen without particles.     

Degradable bio-based epoxy vitrimers based on imine chemistry and their application in recyclable carbon fiber composites

Traditional epoxy resin materials are widely used in coatings, composite materials, electronic packaging materials, etc. They are usually made of unsustainable fossil resources and cannot be recycled under mild conditions. Degradable thermosetting resins with dynamic covalent structure provide a potential solution to this conflict. In this paper, using biomass energy vanillin, m-xylylenediamine and 1, 6-hexanediamine as raw materials, two dynamic imine bond curing agents were synthesized, and then cured with DGEBA to prepare two bio-based imine epoxy vitrimers. The thermal and mechanical properties of two imine epoxy vitrimers were studied and compared in detail. Results showed that the two types of polymers exhibit excellent thermal stability and solvent resistance. At the same time, the tensile strength, modulus and elongation at break were comparable to or even better than those of conventional bisphenol A epoxy resin. In addition, due to the hydrolysis of the dynamic imine bonds, vitrimers had degradable characteristic, and its degradation also exhibited temperature, solvent and acidity dependence. More importantly, the recyclable carbon fiber reinforced polymer composites made of these two vitrimers could be completely degraded under weak acid conditions, and the nondestructive recycling of carbon fiber composites could be realized. We envision that this vitrimers with simple process, excellent comprehensive properties and degradability will make it a potential candidate for applications in sustainable structural materials.

     

A production engineers view of advanced composite materials: Part 2 The manufacture of advanced composites,components and structures

The conversion of the raw materials of fibre composites, usually prepreg, into components is discussed in the second of this series of articles. The subject is a large and growing one. It has therefore only been feasible to cover some of the more important processes and aspects of them.     

软溶液工艺(SSP)在先进无机材料领域的应用及进展

软溶液工艺（soft solution processing简记为SSP）是近年国际上发展起来的先进材料制备的重要工艺技术，也是具有环境协调性的工艺技术，本文概枋了软溶液工艺技术的基本原理，特点及其在先进无机材料制备中的应用和发展，重点介绍软溶液工艺的几种技术（包括水热技术，电化学技术）及其在先进无机材料制备中的应用原理，范围和特点，指出水热电化学技术是很有发展前景的软溶液工艺，最后对软溶液工艺技术的发展前景和条件进行了展望和评述。     

Electrospun single-walled carbon nanotube/polyvinyl alcohol composite nanofibers: structure-property relationships

Polyvinyl alcohol (PVA) nanofibers and single-walled carbon nanotube (SWNT)/PVA composite nanofibers have been produced by electrospinning. An apparent increase in the PVA crystallinity with a concomitant change in its main crystalline phase and a reduction in the crystalline domain size were observed in the SWNT/PVA composite nanofibers, indicating the occurrence of a SWNT-induced nucleation crystallization of the PVA phase. Both the pure PVA and SWNT/PVA composite nanofibers were subjected to the following post-electrospinning treatments: (i) soaking in methanol to increase the PVA crystallinity, and (ii) cross-linking with glutaric dialdehyde to control the PVA morphology. Effects of the PVA morphology on the tensile properties of the resultant electrospun nanofibers were examined. Dynamic mechanical thermal analyses of both pure PVA and SWNT/PVA composite electrospun nanofibers indicated that SWNT-polymer interaction facilitated the formation of crystalline domains, which can be further enhanced by soaking the nanofiber in methanol and/or cross-linking the polymer with glutaric dialdehyde.     

Electrospun carbon-tin oxide composite nanofibers for use as lithium ion battery anodes

Composite carbon-tin oxide (C-SnO(2)) nanofibers are prepared by two methods and evaluated as anodes in lithium-ion battery half cells. Such an approach complements the long cycle life of carbon with the high lithium storage capacity of tin oxide. In addition, the high surface-to-volume ratio of the nanofibers improves the accessibility for lithium intercalation as compared to graphite-based anodes, while eliminating the need for binders or conductive additives. The composite nanofibrous anodes have first discharge capacities of 788 mAh g(-1) at 50 mA g(-1) current density, which are greater than pure carbon nanofiber anodes, as well as the theoretical capacity of graphite (372 mAh g(-1)), the traditional anode material. In the first protocol to fabricate the C-SnO(2) composites, tin sulfate is directly incorporated within polyacrylonitrile (PAN) nanofibers by electrospinning. During a thermal treatment the tin salt is converted to tin oxide and the polymer is carbonized, yielding carbon-SnO(2) nanofibers. In the second approach, we soak the nanofiber mats in tin sulfate solutions prior to the final thermal treatment, thereby loading the outer surfaces with SnO(2) nanoparticles and raising the tin content from 1.9 to 8.6 wt %. Energy-dispersive spectroscopy and X-ray diffraction analyses confirm the formation of conversion of tin sulfate to tin oxide. Furthermore, analysis with Raman spectroscopy reveals that the additional salt soak treatment from the second fabrication approach increases in the disorder of the carbon structure, as compared to the first approach. We also discuss the performance of our C-SnO(2) compared with its theoretical capacity and other nanofiber electrode composites previously reported in the literature.     

Electrospun composites of PHBV,silk fibroin and nano-hydroxyapatite for bone tissue engineering

Electrospinning of fibrous scaffolds containing nano-hydroxyapatite (nHAp) embedded in a matrix of functional biomacromolecules offers an attractive route to mimicking the natural bone tissue architecture. Functional fibrous substrates will support cell attachment, proliferation and differentiation, while the role of HAp is to induce cells to secrete extracellular matrix (ECM) for mineralization to form bone. Electrospinning of biomaterials composed of polyhydroxybutyrate-co-(3-hydroxyvalerate) with 2% valerate fraction (PHBV), nano-hydroxyapatite (nHAp), and Bombyx mori silk fibroin essence (SF), Mw = 90KDa, has been achieved for nHAp and SF solution concentrations of 2 (w/vol) % each and 5 (w/vol) % each. The structure and properties of the nanocomposite fibrous membranes were investigated by means of Scanning Electron Microscopy in combination with Energy Dispersive X-Ray Analysis (SEM/EDX), Fourier Transformed Infrared Spectroscopy (FT-IR), uniaxial tensile and compressive mechanical testing, degradation tests and in vitro bioactivity tests. SEM images showed smooth, uniform and continuous fibre deposition with no bead formation, and fibre diameters of between 10 and 15 μm. EDX and FT-IR confirmed the presence of nHAp and SF. After one month in deionised water, tests showed less than 2% weight loss with the samples retaining their fibrous morphology, confirming that this material biodegrades slowly. After 28 days of immersion in Simulated Body Fluid (SBF) an apatite layer was visible on the surface of the fibres, proving their bioactivity. Preliminary in vitro biological assessment showed that after 1 and 3 days in culture, cells were attached to the fibres, retaining their morphology while presenting a flattened appearance and elongated shape on the surface of fibres. Young's modulus was found to increase from 0.7 kPa (± 0.33 kPa) for electrospun samples of PHBV only to 1.4 kPa (± 0.54 kPa) for samples with 2 (w/vol) % each of nHAp and SF. Samples prepared with 5 (w/vol) % each of nHAp and SF did not show a similar improvement.     

新型矿物基功能复合材料的制备技术及应用

通过功能体与硅酸盐矿物之间的复合来解决功能材料在合成、结构及性能等方面的问题,有望获得功能优异的新型复合材料。重点介绍了功能体与硅酸盐矿物复合的主要思路及方法,包括表面负载、孔道层间的组装、插层复合等关键制备技术的实施效果。同时系统综述了生态环境、催化、储能、光、电、磁性、屏蔽吸波等高附加值矿物基功能复合材料的研究现状及进展。     

Electrospun nano composites of poly(vinyl pyrrolidone)/ nano-silver for antibacterial materials

Poly(vinyl pyrrolidone) (PVP) and nanosilver are promising candidates for biomedical applications because of their biocompatibility and antibacterial efficacy, respectively. In this research, three kinds of nanosilver particles (NSPs) were prepared using the seed mediate growth method and added to electrospinning solutions. PVP/NSPs composites were prepared by electrospinning of 10 wt% PVP solutions that contained NSPs in ethanol. The electrospinability of PVP/NSPs nanowebs in ethanol was investigated according to three different concentrations of NSPs. The Electrospun PVP/NSPs nanocomposites were photocross-linked to improve their water stability. The antibacterial efficacy of the PVP/NSPs nanocomposites was assessed against three types of bacteria; Staphylococcus aureus, Klebsiella pneumoniae and Escherichia coli. The photocross-linked PVP/NSPs nanocomposites had high water stability and significant antibacterial efficacy against all three types of bacteria. Therefore, these composites could be applied as antimicrobial materials.     

Mechanical,thermal and morphological properties of a bio-based composite derived from banana plant source

This paper focuses on the synthesis and testing of a novel bio-based composite structure in which banana fibres was infused with resin made from banana sap. The mechanical, thermal, morphological and biodegradation properties of the bio-composite were characterized and it was found that the material was suitable for general non-functional components. Mechanical tests indicated 15% increase in tensile strength, 12% improvement in tensile modulus and a 25% improvement in flexural modulus when compared to structures produced without banana sap. At elevated temperatures a decrease in the moduli was observed. The thermal stability of the biocomposite composite improved and this corresponded with an increase in the glass transition temperature. Morphological studies using scanning electron microscopy revealed improved compatibility between the fibre and banana sap matrix. This resulted in improved dynamic modulus values and low damping values. Finally, degradation tests revealed increased microbial activity on the banana sap composite. This was indicative of improved biodegradation rates.     

A fibre coating process for advanced metal-matrix composites

A fibre coating process has been used to produce continuously reinforced advanced metal-matrix composites with up to 8% volume fraction of SiC fibre. Matrix materials were an / titanium alloy (Ti-Al-V), a dispersion-strengthened titanium alloy (Ti-Al-V-Y), a rapid solidification processed aluminium alloy (Al-4.3Cr-0.3Fe), and intermetallic compounds Ti₃Al and TiAl. Thick metal coatings are shown to adhere well to the fibres, no evidence is found for chemical reaction between the coating and the fibre during the coating process, and the coated fibres can be handled and bent without damage. Tensile test data for Ti-Al-V alloy reinforced with 21% SiC fibre show a modulus near to a theoretical prediction, but tensile strength significantly below prediction. Loss of strength is attributed to the formation of a brittle reaction product during hot consolidation. The advantages and potential of the coated-fibre route for MMC production are discussed.     

Simplified compression bending test method for advanced composites

In the past, one of the authors has proposed a new bending test method, namely a compression bending test. The test was based on buckling and is suitable for advanced composites because the undesirable stress concentration from the loading nose is removed. The original paper dealt with the measurement of the bending strength and successive papers with the methodology used to measure the bending modulus. In the present paper, a new device has been designed by which the total system is drastically simplified. In addition, systematic comparison of all methods has been carried out. During a series of experiments, the superiority of the present compression bending test method was demonstrated.