Papers by Keyword: Heat-Resistance

Abstract: Heat-resistance (scale resistance) is the steel corrosion fastness in dry gas at high temperatures. At the temperatures over 570 °С, the ferrous alloys oxidize, as ferric oxide (wustite) with simple cubic lattice appears on the metal surface. Such oxide lacks oxygen atoms (omission solid solution) and does not interfere with the diffusion between metal and oxygen. As a result of this process the brittle oxide-scale develops and the loss of metal increases. In order to increase the heat-resistance of steel, different alloying elements are included into its composition, forming oxides with the tight structure of crystal lattice. In this paper we’ve investigated the heat-resistance of some structural steels and analyzed their corrosion resistance in the high temperature aggressive environments of chemical productions.

Abstract: The preparation and characterizations of soluble copolymers poly (p-phenylene terephthamide-co-furandicarboxylic p-Phenylenediamine)(PPTA-co-PPF) by direct polycondensation was described. The chemical structure of polyamides was investigated by ¹H NMR and FT-IR. The good solubility of copolymers in organic solvents was certified at room temperature. Their thermal stability and mechanical properties were observed by TGA and tensile testing and then compared with that of traditional high performance aromatic polyamides (PPTA and PMIA, for example, with trademarks of Kevlar^® and Nomex^®). The furan ring incorporated polyamide was expected to form thermal reversible cross-linked polymer network through D-A reaction.

Abstract: In order to improve the toughness of epoxy resin, hydroxyl-terminated polyethersulfone (PES) with various amounts (0 wt.%, 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%) were added to bisphenol A epoxy resin (DER331)/ curing agent DETDA (E100) systems, and the influence of PES contents on curing process and heat-resistance was studied. Non-isothermal DSC was used to determine the curing process of uncured DER331/E100/PES systems at heating rate of 2°C/min, 5°C/min, 7°C/min, 10°C/min and 15°C/min separately, and the apparent activation energy was calculated based on Kissinger method. The morphology of the etched cured DER331/E100/PES systems with different PES contents was observed by SEM. The heat-resistance of these systems was investigated by DSC and TGA. The results showed that with the increasing of PES content the curing exothermic peak, the heat of curing reaction, the initial and final curing temperature all decreased at the first and then increased, indicating that when the PES content was low (5 wt.%, 10 wt.%), PES can facilitate the curing process, while, when PES content up to 15 wt.%, PES can prevent or weaken the curing reaction. SEM results indicated that the phase structure changed drastically depending on the PES content. The systems with 5 wt.% and 10 wt.% PES were epoxy-rich phase, with 15 wt.% PES was co-continuity phase, and with 20 wt.% PES showed complete phase inversion (PES rich phase). The glass transition temperature and thermo gravimetric analysis demonstrated that the addition of PES can increase the heat resistance of cured DER331/E100/PES systems.

Abstract: Up to now, many types of inorganic fibers have been developed. The main purpose is to develop composite materials with lightweight and high fracture toughness. Of these, carbon fiber has already established a very big market. By the way, representative oxide fibers (alumina/silica-based fibers) show heat-resistance’s limitation at around 1200°C. In order to improve the heat-resistance, some types of eutectic oxide-fibers have been studied. On the other hand, SiC fibers with both heat-resistance and oxidation-resistance were developed over 30 years ago. After that, lots of improvements have been performed, and finally several types of excellent heat-resistant SiC-polycrystalline fibers, which can be used up to about 1800°C, were developed from polycarbosilane. Using these fibers, lots of applications have been considered in the fields of aerospace, nuclear system, and so on. Furthermore, making the best use of the aforementioned production process, several types of functional ceramic fibers with gradient-like functional surface layers also have been developed. In this paper, of these inorganic fibers, heat-resistant SiC fibers will be addressed along with historical view point on ceramic fibers.

Abstract: Response surface analysis was applied to optimize the processing of preparing the heat-resistance of the cotton stalks bast fiber reinforced PLA composite. Effects of all factors were evaluated and three factors were selected, which were addition of TAIC, mass fraction of fibers and length of fibers. Subsequently, response surface analysis based on Box-Behnken experimental design was employed to evaluate the interactive effects of three factors. One mathematical model for the processing of composites as functions was established. The results showed that the optimal processing was that the addition of TAIC was 2.1%, the mass fraction of fibers was 26.7%, the length of fibers was 11.7mm, and the HDT of composite was 161.39°C. Under the optimal conditions, the true value was close to the predicted value.

Abstract: An OMMT (organic montmorillonite) was prepared by ion exchanging between Na-montmorillonite and cetyl trimethyl ammonium bromide (CTAB) and was applied to modify Dicyclopentadiene Dioxide Epoxy(R-122). FT-IR spectra showed that the organic molecules had intercalated into the layers of MMT successfully, X-ray diffraction illustrated that the spacing of layers of MMT increased from 1.43 nm to 3.85 nm. R-122 composite was prepared with this nano-organic montmorillonite. When the content of OMMT was 4.0% (wt%), the impact strenth of the composite reached to the highest(21.2 J/m), which is 92.7% higher than the pure R-122 . Morphology of the fracture checked by SEM, reveals a depth depended distribution which generated more new surface, thus can absorb more impact energy. Differential scanning calorimetry(DSC) showed that the thermal stability of the composite had improved compared with the pure resin. And what’s more, the improvement of toughness doesn’t hurt the resin’s heat resistance, it may provid a new way to prepare high performance R-122 composites.

Abstract: Roof is one of the main structures of a building, and it plays an important role in improving the degree of indoor thermal conformability so as to reduce the using of air-conditioner. Through a contrastive study on eco-roof and the common roof in a certain living district in Xiangtan City, the article comes to the conclusion: the water-storing green roof can enhance the urban eco-environment, modulate the indoor thermal property and decrease the using of air-conditioner.

Abstract: The heat-resistance of PLA is so poor that its application area was limited. It can be widely applied after improvement. In the process of making cotton stalk bast fibers reinforced PLA composites, adding TAIC a type of cross-linking agent in the experiment produces a kind of composites with good heat-resistance. Orthogonal experiment table including length and mass fraction of fibers, molding temperature and addition of TAIC was devised. Then the study focused on the heat-resistance of the composites and the analysis of range and variance were done. The optimal processing condition was obtained: length of fibers was 10mm, mass fraction of fibers was 30%, molding temperature was 175°C and addition of TAIC was 1%. In addition, fibers reinforced PLA composites without TAIC had better heat-resistance than the pure PLA material, the HDT raised 54°C, and the composites added TAIC obtained the best heat-resistance of all. This composite can be extensively used in many fields.

Abstract: The present work experimentally investigated the operating characteristics of a miniature loop heat pipe (LHP) under different power cycle. The miniature LHP with flat evaporator of 8mm thick is made of copper. The evaporator with sintered copper power wick is in series structure with compensation chamber. Water is working fluid. It is found that the LHP can start up at heat load of 15W with temperature oscillation and the maximum heat load is 160W with R_l=0.068°C/W. The LHP operates unstably under low heat load. The oscillating frequency of temperature rises with heat load increased. The operating performance of the LHP is affected by the power cycle.