沥青树脂和炭纤维的复合性能

流化床催化裂化(Fluid catalytic ciracking,FCC)油浆富芳馏份(Fluid catalytic ciracking rich aromatic,FCCRF)与交联剂对苯二甲醇(1,4-benzenedimethanol,PXG)在催化剂对甲基苯磺酸(Para-toluene sulphonic acid,PTS)的作用下,加热至120℃以上,制得的沥青树脂是一种新型的热固性树脂。沥青树脂在一定条件下与炭纤维或炭纤维纸热压成型。成型料在空气中250℃-10h和300℃-2h热处理后,其热力学性能无明显变化;在强酸、强碱中处理1h~70h,质量几乎无变化;说明沥青树脂与炭纤维或炭纤维纸的复合材料热稳定性和化学稳定性尚好。沥青树脂与炭纤维或炭纤维纸的复合材料在高纯氮保护下,经950℃~1000℃热处理后制得炭/炭复合材料,由SEM观察可见炭/炭复合材料无空洞、劈裂,力学性能尚可,断口炭纤维拉出小于10μm,说明沥青树脂与炭有较强的亲和力,与炭纤维黏合很好。FCC油浆富芳馏份制备的沥青树脂,作为炭/炭复合材料的基质是可行的。     

Zone-melted unidirectional solidification of particulate dispersed composites

In order to solve the problem of particles settling and agglomeration in front of solidifying interface in unidirectional solidification (UDS) experiments, a zone-melted process has been utilized in this study. The experimental results show that, the melting zone could be kept in 30–40 mm width and the zone melted UDS experiments are realized with Al₂O₃ particle reinforced aluminum-matrix composites. But particle settling still occurs in the liquid, and becomes severe as the particle volume fraction decreases. However, when the volume fraction of the particles is more than 20–22 vol.%, no further settling occurs under a solidification rate of 8–16 mm/h. Investigation on the interaction of particles and solid/liquid interface reveals that the Al₂O₃ particles are rejected into liquid and pushed by the growing solid phase in Al₂O_3(P)/Al and Al₂O_3(P)/Al-0.23wt.%Ce composites. Some particles are mechanically entrapped between cells, and distributed along the crystal grain boundaries.     

Preparation of Pt dispersed porous carbon particles from polyimide particles

We investigated the preparation of Pt and Pt/Ru bimetallic fine particles dispersed in polyimide particles by precipitation from various polyamic acid solutions containing Pt and Ru complexes, followed by the carbonization of the resulting polyimide particles. As Pt complexes, platinum(II) acetylacetonate [Pt(acac)₂], trimethylplatinum iodide [PtIMe₃], and (trimethyl) methylcyclopentadienylplatinum [Pt(MeCp)Me₃] were used. As Ru complexes, ruthenium(III) acetylacetonate [Ru(acac)₃], acenaphthylene heptacarbonyl triruthenium [(C₁₂H₈)Ru₃(CO)₇], and tetracarbonylbis(-cyclopentadienyl)diruthenium [Ru₂(CO)₄Cp₂] were used. Bow tie-like polyimide particles containing Pt or Pt/Ru bimetallic particles could be obtained from pyromellitic dianhydride /m-phenylenediamine (PMDA/MPD) polyamic acid containing Pt and Ru complexes. Sheaf-like polyimide particles were obtained by using 4,4-oxydianiline(ODA) as diamine. The morphologies of polyimide particles strongly depend on the kind and the concentration of Pt and Ru complexes. We could obtain Pt or Pt/Ru bimetallic fine particles dispersed in porous carbon particles, which morphologies are the same as the polyimide particles used as carbon precursors, by heat-treatment of the obtained polyimide particles. Pt and Pt/Ru fine particles in the range of 310 nm were contained in bow tie-like or sheaf-like carbon particles. The addition of Ru complexes to polyamic acid solutions decreased the sizes of Pt particles in carbon particles.     

HRTEM observations on composites of tin and tin dioxide nanoparticles dispersed on carbon nanotubes by single-atoms-to-clusters method

Nano-composites of tin and tin dioxide particles were synthesized on carbon nanotubes by the single-atoms-to-clusters (SAC) method, and their structures were investigated by high-resolution transmission electron microscopy. By changing the heat-treatment temperature during the SAC process, two different types of samples were obtained. The samples prepared around 450 K were aggregates of 2-4 nm-sized tin dioxide nanoparticles, and their size distributions on carbon nanotubes are in the range 20-40 nm. The other samples formed above 600 K had a core-shell structure of diameter 20-40 nm. The core and shell were made of tin single crystal and disordered oxidized tin, respectively. The thickness of the oxidized layers was ca. 4 nm.     

High-sensitivity bolometers from self-oriented single-walled carbon nanotube composites

In this work, films of horizontally aligned single-walled carbon nanotubes were thermally and electrically characterized in order to determine the bolometric performance. An average thermal time constant of τ = 420 μs along with a temperature coefficient of resistance of TCR = -2.94% K(-1) were obtained. The maximum voltage responsivity and detectivity obtained were R(V) =230 V/W and D* = 1.22 × 10(8) cm Hz(1/2)/W, respectively. These values are higher than the maximum voltage responsivity (150 V/W) and maximum temperature coefficient of resistance (1.0% K(-1)) previously reported for carbon nanotube films at room temperature. The maximum detectivity was obtained at a frequency of operation of 1.25 kHz.     

An amperometric detector formed of highly dispersed Ni nanoparticles embedded in a graphite-like carbon film electrode for sugar determination

We achieved improved detection limits for sugars by developing a novel thin film containing 0.8% highly dispersed Ni nanoparticles in disordered graphite-like carbon (Ni-NDC) as a detection electrode for high-performance liquid chromatography. The Ni-NDC film was prepared in one step by a simple radio frequency (rf) sputtering method at a temperature below 200 degrees C. We characterized the film by XPS, TEM, and AFM analysis and found that the average Ni nanoparticle size was 3 nm and that the film consisted of a mixture of Ni, NiO, Ni2O3, and Ni(OH)2. We studied the electrochemical detection of sugars using the 0.8% Ni-NDC film electrode. The film electrode had excellent electrocatalytic ability and good stability compared with a Ni-bulk electrode with regard to the electrooxidation of sugars. We employed the Ni-NDC film as an HPLC detection electrode. We achieved a good separation of four sugars (glucose, fructose, sucrose, lactose) at a relatively low constant detection potential (0.40 V vs Ag/AgCl) and a linearity of over 3 orders of magnitude. We obtained improved detection limits for the investigated sugars, namely, 20, 25, 50, and 37 nM for glucose, fructose, sucrose, and lactose, respectively. This is at least 1 order of magnitude lower than the detection limits obtained with a Ni-bulk electrode with the same measurement condition. The Ni-NDC film electrode also showed good reproducibility with a relative standard deviation of 1.75% for 40 consecutive injections of glucose in a flow system.     

Crack deflection by the transformable particles dispersed in composites

The crack deflection in transformable particle-reinforced composites is studied in the present paper.The contribution of phase transformation on the crack tip J_k-integral (k = 1, 2) is explicitly determined bythe material configurational theory. For the crack deflection angle from its original crack path induced by thephase transformation it can be shown that the crack initiates in the direction along which the potential energyrelease rate in terms of the crack tip J_k-integral possesses a stationary (maximum) value. The influence of oneindividual particle near the crack tip on the crack deflection is studied by accounting for both dilatant and sheartransformation components. Furthermore, an FEM method is developed to model the stress-induced phasetransformation on the basis of a macroscopic phenomenological constitutive model where multiple particlesare taken to be non-uniformly distributed in a matrix.Numerical simulations are performed to observe the crackdeflection by a cluster of particles. The results show a significant non-symmetric stress distribution locally atthe crack tip, causing the crack to deflect. It is found that regions in the material with a higher volume fractionof transformable particles tend to deflect the crack growth more.     

Structural capacitor materials made from carbon fibre epoxy composites

In this paper, an approach towards realising novel multifunctional polymer composites is presented. A series of structural capacitor materials made from carbon fibre reinforced polymers have been developed, manufactured and tested. The structural capacitor materials were made from carbon fibre epoxy pre-preg woven laminae separated by a paper or polymer film dielectric separator. The structural capacitor multifunctional performance was characterised measuring capacitance, dielectric strength and interlaminar shear strength. The developed structural CFRP capacitor designs employing polymer film dielectrics (PA, PC and PET) offer remarkable multifunctional potential.     

Ultrafine magnetic metal dispersed carbons prepared from anisotropic pitch and metal acetylacetonate complexes

Transition metal (Fe, Co or Ni) dispersed carbon composites were prepared using the mixtures of metal acetylacetonate complex as a source of metal particles and an anisotropic coal-tar pitch as a carbon matrix precursor by heat treatment at the temperatures up to 1000°C. Mixing of the metal complexes and the pitch by dissolving in quinoline permitted the notable fine dispersion of the complex in the pitch. Then the resulting mixtures were easily converted to the metal dispersed carbons by pyrolysis under an inert atmosphere. The appeared particles were Fe₃O₄/-Fe/Fe₃C, -Co or Ni when using the corresponding metal complex. Besides, their particle diameters were much less than 30 nm and distributed evenly throughout the carbon matrix. The magnetic properties of the metal dispersed carbons were evaluated with a vibrating sample magnetometer, and it was found that saturation magnetization and coercive force ranged from 1.03 × 10^–5 to 5.65 × 10^–5 Wb · m/kg and from 0.21 × 10⁴ to 3.06 × 10⁴ A/m, respectively.     

The properties of carbon fiber reinforced aluminum composites formed by the ion-plating process and vacuum hot pressing

An ion-plating technique was applied to deposit aluminum on carbon fibers. The coated fibers were used to manufacture a carbon fiber reinforced metal composite by vacuum hot pressing.The composite thus produced has comparatively high strength, high modulus and excellent performance at high temperature. The effects of the vacuum hot-pressing conditions and the fiber fraction on the composite properties are discussed.     

软硬混编预制体增强沥青基4D-C/C材料的拉伸破坏行为

以X-Y平面依次铺设炭纤维束、Z向穿插炭棒的4D软硬混编为预制体,采用沥青液相常压、高压浸渍/炭化-石墨化循环致密工艺制备4D-C/C复合材料。通过该材料Z向(炭棒方向)的拉伸实验,测定其拉伸性能和力学行为,并采用SEM分析试样表面及断口形貌。结果表明:宏观上拉伸试样以炭棒整体拔出的形式破坏;细观尺度上,试样表面形成了与载荷方向垂直的贯穿性裂纹,裂纹以2 mm左右的距离呈等间距分布;材料进一步的破坏过程中,基体裂纹在X-Y向纤维束中呈线性扩展,快速分割了基体材料,使4D-C/C复合材料的拉伸破坏演变为1D-C/C复合材料的破坏模式,由于炭棒与基体炭界面结合弱,炭棒以拔出方式失效和破坏。     

Graphitization behaviour of carbon fibre-glassy carbon composites

Carbon fibre-carbon composites were fabricated by aligning PAN-based carbon fibre unidirectionally in furfuryl alcohol resin char. The graphitization behaviour was investigated by an X-ray diffraction technique and by the measurement of magnetoresistance. The time-temperature superimposition study for interlayer spacing resulted in an activation energy of 242±35 kcal mol⁻¹. The kinetic study on magnetoresistance agreed with the result of X-ray measurement. The activation energy is that for the graphitization of the layer structure formed in the glassy carbon matrix of the composites. The graphitization mechanism of the layer structure is the same as that of soft carbons.     

Proton conducting composites of heteropolyacid hydrates dispersed with salt hydrates

Proton conduction in the composites of heteropolyacid hydrates (Phosphotungstic acid : PTA·nH₂O and Phosphomolybdic acid : PMA·nH₂O) with salt hydrates like Aluminium sulphate and Ammonium paratungstate (APT) as dispersoids has been studied and compared with the composites PTA : Al₂O₃ and PMA : Al₂O₃. Thermal analysis, XRD and IR studies on acid and salt hydrates dispersed phase systems reveal the formation of composites. A significant increase in the ionic conductivity has been observed in the composites. It has been found that the conductivity of 0.5PTA + 0.5Al₂(SO₄)₃·16H₂O is 1.1 × 10^–2 S·cm^–1 and that of 0.55PMA + 0.45APT is 1.3 × 10^–3 S·cm^–1 at 65% R.H. The temperature and humidity dependence of bulk electrical conductivity of the composites is also reported.     

Synthetic and biological composites formed byin situ precipitation

Filler particles are frequently put into polymers to improve the stiffness or strength. There are a number of other applications such as magnetic coatings and piezoelectric transducers where second phase particles are introduced to give the composite special properties. Many biological materials, including bone, are also composite with particles reinforcing a polymer matrix. In the preparation of the synthetic materials the filler is normally blended into the polymer. In the biological materials the particles are grownin situ within the polymeric matrix, and under the control of the matrix. Here we review the growth of particles when constrained by a polymeric matrix, both in natural and synthetic materials. We discuss the principles governing such processes and the potential for the production of highly structured composite materials by this route.     

Double layer microwave absorber based on Cu dispersed SiC composites

The present work has been focused on designing an efficient and cost-effective double layer microwave absorber in 8.2–12.4?GHz frequency range. For the same, Cu particles were dispersed in SiC to achieve enhanced microwave absorption by combining the excellent dielectric characteristics of SiC with highly conductive Cu. Cu dispersed SiC composites were prepared by dispersing various weight fractions of Cu particles in the SiC matrix using planetary ball mill. The Cu dispersion in SiC yielded excellent relative complex permittivity values translating into a decrease in the reflection loss (RL) values of dispersed composites as compared to the pristine counterpart. The minimum RL of ?17.18?dB has been observed for 2?wt% Cu dispersed SiC composite at 11.81?GHz with a thickness of 1.3?mm and bandwidth corresponding to ?10?dB is 1.77?GHz. Genetic algorithm approach has been implemented to design double layer microwave absorber to further enhance the microwave absorption of the prepared composites for realizing a cost-effective solution. The optimum double layer results show the RL of ?32.16?dB at 11.05?GHz with 1.67?mm total thickness and bandwidth corresponding to ?10?dB is 2.35?GHz.