Papers by Keyword: Oxidation Resistance

Abstract: The silicon-boron(Si-B) pitch was successfully synthesized by solution-thermal treatment method using coal pitch, polycarbosilane and borane pyridine as starting materials. The B-Si pitch carbonization product was attained by carbonization in the temperature 900°C under flowing argon. The Si-B pitch prepared and its carbonization product were characterized by SEM, FT-IR, TG-DSC and XRD. The results show that the carbonization product has C-Si and C-B bonds and the silicon and boron components of the product is still amorphous when it is treated at 900°C. The weight loss of the Si-B pitch carbonization product at 900°C for 12h in air atmosphere is only 3.76wt%. The weight loss of the product is less than 4 wt% when the oxidation temperature reaches 1180°C. The prepared B-Si pitch carbonization product possesses good anti-oxidation property at high temperature in air atmosphere.

Abstract: Cu-based alloys have been regarded as one of the most promising phase change materials (PCMs) in industrial waste heat recovery and solar thermal electric generation. In this paper, the oxidation behavior and the containment of liquid Cu were investigated. It was found that with the small addition of aluminum, the oxidation resistance of Cu-based PCMs was greatly enhanced. Notably, its latent heat density remained high. The containment of PCMs was achieved by depositing a Ni-base exterior coating on Cu spheres through barrel plating, rack plating and electroless plating processes. The deposition rates, surface topography, and the crystallography of the coatings depended largely on the plating process. The cyclic thermal was tested at last.

Abstract: In order to improve the anti-oxidation of C/C composites, a C/SiC functionally graded coating for C/C composites was prepared by low pressure chemical vapor deposition (LPCVD) using methyltrichlorosilane (MTS, CH3SiCl3) and H2 as precursors. The relative amount of C and SiC in coatings was varied by controlling the input ratio of H2 to MTS. The phase composition and morphology were examined by scanning electron microscope (SEM) and X-ray diffraction (XRD), and the content distribution of C and SiC phases were investigated by energy dispersive spectroscopy (EDS). The isothermal oxidation test was evaluated at 900 °C and 1500 °C respectively. The results showed that the as-obtained coatings were possessed of a dense and uniform structure, and the SiC content in coatings increased with an increment of the molar ratio of H2 to MTS. The C/SiC coating had a good oxidation resistance.

Abstract: In the paper, N,N′-bis(4-hydroxybenzyidene)azine (BHBYA) has been synthesized by p-hydroxybenzaldehyde and hydrazine as raw materials. The structure was determined by X-ray diffraction. The Schiff base crystallizes is in the monoclinic P21/c space group. The results of antimicrobial activity showed that it has a good inhibition on Cucumber Damping-Off and Rice Blast. The findings of oxidation resistance experiment indicated that it has an excellent inhibitory effect on peroxidation of olein.

Abstract: The microstructural evolution related to the thickness of thermal barrier coating (TBC) and their thermal stabilities have been investigated with a specific attention to defect species as well as to its morphology with the thermal exposure time. The TBCs with different thicknesses of 600 and 2,000 µm were prepared by air plasma spray (APS) process and the thermal exposure tests were performed at 950^C in a furnace with a dwell time of 100 hrs till 500 hrs. The thickness of thermally grown oxide (TGO) layer in the TBC with 2,000 µm is thinner than that with 600 µm. Also, the TBC with 2,000 µm is more efficient in improving the oxidation resistance of bond coat than that with 600 µm. Vickers indentation methods are used to evaluate the interfacial stabilities. Indentation impression and crack formation of the TBC of 600 µm is easily occurred in comparison with that of 2,000 µm, showing relatively longer cracks, independent of thermal exposure. However, the crack formation and propagation through the interface does not observed in the TBC with 2,000 µm, showing crack propagation through the top coat near the interface. These results imply that the interfacial stability of TBC can be also improved with increasing the coating thickness.

Abstract: Based mainly on SiC aggregate and fine powder, silicon powder, flake graphite (300 μm, 45 μm), α-Al₂O₃ micro-powder and AlN powder, Graphite-SiAlON bonded SiC composite were prepared. The influence of graphite addition, which varied from 0 to 9.7%, and its grain size on the oxidation resistance was investigated at 1 150 °C under air atmosphere. The results show that: 1) mass change rate reduces with the increase of graphite addition, the mass change rate of sample with 45 μm graphite is higher than that of sample with 300 μm graphite; 2) the cold modulus of rupture of sample with 45 μm graphite after oxidation is higher than that of sample with 300 μm graphite; 3)the oxidation resistance declines along with the increase of graphite addition, additionally, the oxidation resistance of sample with 45 μm graphite is superior to that of sample with 300 μm graphite; 4) 7.5% graphite is recommended as the proper addition.

Abstract: A primary study on the resistance to high-temperature-oxidation of 430 ferrite stainless steel and its oxidation process before and after the addition of RE elements was reported. Results show that the oxidation resistance of 430 ferrite stainless steel after adding RE is indeed great. The value of oxidation rate of Sample 1 (without adding RE) is 2.87 times higher than Sample 2, respectively at 1423K after oxidizeing for totally 144h. And the dense and adherent Cr2O3 scale and FeCr2O4 scale are formed and played the protection role to the 430 ferrite stainless steel. In the internal oxidation layer, the pinning effect of silicon dioxide is strengthened by RE.

Abstract: Microstructures, morphologies and energy spectrums of oxidized films and their cross sections of plasma sprayed alloy coating Co-02 with Co-base, Co-04 whose matrix is nickel partially instead of cobalt and NDCo-02 with Ni-base substituting for Co-base were investigated. The result indicates that the coatings of these three kinds of alloys are white austenite base and Cr₇C₃ and Cr₇(C, B)₃ eutectic; Co-02 produces Cr2O3 oxidation protection film, and there were distinct areas with shortage of chromium in Co-04 and NDCo-02 coatings where CoCr₂O₄ and NiCr₂O₄ oxidation protection films were produced with spinel structure, these efficiently improved oxidation resistance; these three kinds of alloys have super oxidation resistance which increases according to NDCo-02,Co-04 and Co-02 orderly. The level of oxidation resistance was assessed.

Abstract: The oxidation resistance of Ni-Si-Ti-C, Ni-Si-C-Nb in-situ reinforcement clad layers has been investigated by cyclic oxidation tests at the temperature 1100°C. The oxidation performance were characterized by Thermo-gravimetric (TG),scanning electron microscopy (SEM) and X-ray diffractometer (XRD),the TG date indicates good oxidation resistant was reached for the clad layers. The kinetic constant Kp and the micrograph of oxidized samples shown that NbC reinforce clad layers which oxide products including NiO, SiO2 and Nb2O5 has better oxidation resistant than TiC reinforce clad layers which oxide products including NiO, some SiO2 and TiO2.

Abstract: The oxidation resistance and high temperature mechanical properties of FeCrNi heat-resisting steel are analyzed and studied. The results show that the oxidation resistance of the heat-resisting steel is improved remarkably after adding RE. The value of oxidation rate of Sample 1 (without adding RE) is 1.71 times higher than Sample 2, respectively at 1423K. And the value of oxidation rate of Sample 1 is 1.4 times higher than Sample 2, respectively at 1473K. The fracture mode of heat-resisting stainless steel is typical cleavage fracture, but dimple fracture after adding RE into the steel. The high temperature mechanical properties of heat-resisting steel is improved obviously by RE. In comparison with heat-resisting stainless steel without RE, the reduction of area of heat-resisting stainless steel with RE is increased 26.27% at 1123K.