Summary: Flexible heaters were prepared by extruding platinum‐catalyzed silicone rubber compound with electroconductive carbon black (CB) and SnO2/Sb coated titanium dioxide (TiO2). Two types of acicular‐shaped TiO2 with average particle sizes of 1.7 and 5.2 µm, and two types of spherical‐shaped TiO2 with average particle sizes of 0.3 and 2.5 µm were selected. Thermoelectric switching phenomena were investigated for the silicone rubber/CB/TiO2 system. Positive temperature coefficient (PTC) was significant when the acicular filler was added rather than spherical ones. Resistivity change and thermal reproducibility of the extruded heaters were also investigated by applying periodically AC voltage of 220 V. The heaters containing acicular‐shaped TiO2 exhibited excellent electrical reproducibility.
Scanning electron micrograph of the fractured surface of the extruded composites. 相似文献
This work investigates the relationships between the components of powders, namely, the powder surface morphology, the flow characteristics and the compressibility of low-energy (microcomposite) and high-energy (nanocomposite) ball milled powders of Al 6061 alloy reinforced with TiO2 particles. The morphology of the above powder as the function of reinforcement and the milling time was studied by using the scanning electron microscope (SEM). The changes in powder characteristics such as the apparent density, tap density, true density and flow rate were examined by the percentage of reinforcement and milling time. The cohesive nature of the powder was also investigated in terms of Hausner ratio and Kawakita plot. Further, the particle/agglomerate size of low-energy and high-energy ball milled powders was explained by the laser particle size analyzer. X-ray peak broadening analysis was used to determine structural properties of mechanically alloyed powders. The compressibility behavior was examined by the compaction equation proposed by Panelli and Ambrosio Filho to investigate the deformation capacity of the powder. The compressibility behavior, namely, the densification parameter (A) of the microcomposite powder (irregular morphology) was decreased significantly with increasing TiO2 content due to the disintegration of TiO2 particles and the cluster formation followed by its agglomeration. The compressibility behavior, namely, the densification parameter (A) of the nanocomposite powder (equiaxed and almost spherical) was decreased slowly with increasing TiO2 content due to work hardening on the matrix powder. With increased milling time, the compressibility behavior of AA 6061-10 wt.% TiO2 composite powders increased up to 30 h of milling due to embedding of TiO2 particles with matrix and changes in powder morphology and finally decreased after 40 h due to work hardening effect. 相似文献
The development of Hydroxyapatite (HAP)/Titania (TiO2) composite coatings on metallic implants have received a great deal of attention during the recent years owing to their superior advantages in biomedical applications. The present study has focused on the in situ formation of HAP/TiO2 composite powders through aqueous precipitation technique. Five different HAP/TiO2 composite powders of varied HAP to TiO2 ratios has been synthesized in the present study and the results were compared with the stoichiometric HAP, Rutile TiO2 and Anatase TiO2 which also have been synthesized by adapting a similar synthetic procedure. All the synthesized powders have been analyzed using X-ray diffraction (XRD) and X-ray fluorescence (XRF) techniques. Rietveld Refinement technique has been employed to generate quantitative information about the structural characteristics and phase content in all the powder samples. Further, the electrophoretic deposition (EPD) method has been employed to fabricate HAP/TiO2 composite coatings on 316 L SS and the resultant coatings were analyzed for its quantitative structural characteristics. The results from the present investigation has confirmed that concentration of TiO2 in the HAP/TiO2 composites and heat treatment temperatures have played a major role in the degradation of HAP to β-Tricalcium phosphate and also in the conversion of Anatase to Rutile TiO2 phase. 相似文献
In this paper, we prepared ECAs (electrical conductive adhesives) with high electrical conductivity by using Ag-coated copper powder and M − II (Ti3C2Tx/Ag powder) as conductive filler. M-Ⅰ (Ti3C2Tx) and M-Ⅱ were prepared by acid etching and hydrothermal methods, respectively, and the electrochemical properties of M-Ⅱ and the effects of different contents of M-Ⅱ on the conductivity of ECAs were investigated. M − II has a unique reticular structure which helps to create conductive pathways, and its high specific surface area provides a large number of active sites for charge storage, resulting in increased electrical conductivity. The experimental results show that the best conductivity is achieved when the M-Ⅱ powder content is 1.2%, with a volume resistivity of 4.84 × 10−6 Ω m, at which time the Ag-coated Cu powder content is 69.8%. It has been shown in many studies that only when Ag-coated copper powder content is 70%–80%, the resistivity reaches about 10−6 Ω m. This work showed that adding a small amount of M − II and reducing the amount of Ag-coated copper powder could maintain the high electrical conductivity of ECAs. 相似文献
The preparation of rubber sheet impregnated with titanium dioxide particles is presented. This method is simple and low cost based on the use of commercial TiO2 powder directly mixing with rubber latex (60% HA) and distilled water. The morphology and roughness of the sheet surface increased with increasing amount of distilled water. Sheet impregnated with anatase (Imp-An) showed uniform, small grains with dense structure and well surface coverage more than one with P25 (Imp-P25). Their photocatalytic activities were evaluated using methylene blue (MB) as a model organic dye compound. These impregnated sheets could degrade MB solution under UV-light irradiation. Comparing with the commercial TiO2 samples in powder form (anatase from Carlo Erba and Degussa P25) the efficiencies of photocatalytic degradation of MB fall in the decreasing order as: P25 (powder) > anatase (Carlo Erba) (powder) > Imp-An sheet > Imp-P25 sheet. However, the impregnated sheet has an advantage over the loose powder that the catalyst sheet can be recovered after used and can be reused. 相似文献
Recent improvements in the performance of photocatalysts made it possible to tackle pollution through environment friendly methods. This study investigates the modification of the photocatalytic activity of TiO2 by employing WO3 and conductive polymers, namely, polyaniline (Pani) and polypyrrole (Ppy). Basing on our previous improvement of TiO2 using a conductive polymer and activated carbon (AC), this study determines the activated carbon forms of TiO2. The prepared composites are characterized using X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared, thermogravimetric analysis, Brunauer–Emmet–Teller, and UV–Vis spectroscopy. The specific surface area of the mesoporous composites is as follows: WO3/TiO2·AC (Pani) > WO3/TiO2·AC (Ppy) > WO3/TiO2·Pani > WO3/TiO2·Ppy (127 > 98 > 68 > 44 m2 g?1), which exhibited a similar trend to the photocatalytic performances (100 > 95 > 91 > 72 % conversion rate). This result could be attributed to higher porosity, surge of charge separation, and photo-responding range extension induced by the synergistic effect of WO3, conducting polymers, and TiO2 in the samples. 相似文献
AbstractA correlation between the online during mixing measured conductance of carbon black (CB) filled silicone rubber and macrodispersion of CB determined by optical microscopy and microdispersion analysed by AFM has been established. The online conductance is a suitable tool to characterise the effect of technological parameters (e.g. rotor type, speed, mixing temperature) and material parameters (matrix viscosity, CB type and content) on the macro- and microdispersion directly during the mixing process. Thus, a modified method of the online conductance measurement can be used as the in-process method for monitoring the production process of electrical conductive polymer materials with low viscosity, e.g. liquid silicone rubbers. 相似文献
Summary: Various output heaters were extruded with CB‐filled HDPE composites. The effects of crystallinity on the PTC and thermal reproducibility of the quenched, annealed, and E‐beam crosslinked heaters were examined during heating and cooling cycles at an applied voltage of 220 V. Conductor resisitivity and PTC effect of the heaters increased as crystallinity of composites increased. During the thermal cycling test, significant changes in heater‐output and resistivity for annealed and quenched heaters were observed. However, for quenched/E‐beam radiated and annealed/E‐beam radiated heaters no significant difference was found. These results indicate that the annealing process did not affect the thermal and electrical reproducibility of HDPE/CB heaters significantly.
Acetylene black aggregates in polyethylene matrix. 相似文献