Polyphenol content and antioxidant activity in mulberry powder treated at high temperature

The aim of this study was to investigate changes of polyphenols content and the antioxidant activity of mulberry fruit powder after heating at high temperature.The mulberry fruit powder was heated by baking method at different temperature and time.The DPPH scavenging ability,the OH^(•-) scavenging ability and the O_(2)^(•-) scavenging ability were used to evaluate the changes in the antioxidant activity of the mulberry fruit powder after the heat treatment.The results showed that 74.87%of the polyphenols in the mulberry powder were lost after heating at 150℃for 5 min,and almost all the polyphenols were lost with the increase of the heating time and temperature.The antioxidant experiment showed that the DPPH scavenging rate,OH^(•-) scavenging rate and O_(2)^(•-) scavenging rate of mulberry fruit powder were 68.90%,39.15%and 14.09%,respectively after treatment at 150℃ for 5 min.Mulberry fruit powder still has some potential to be added to baked goods as a functional ingredient.

INFLUENCE OF HEAT TREATMENT ON OXIDATION PROPERTIES OF C/C COMPOSITES FABRICATED BY HIGH PRESSURE IMPREGNATION CARBONIZATION

Felt base carbon/carbon composites fabricated by super-high pressure impregnation carbonization process (SPIC) were heat treated at high temperature 2773K. The oxidation properties of felt base carbon/carbon composites were investigated at different temperatures (773-1173K), and the microstructures of carbon/carbon composites were studied by SEM and X-ray diffraction. The experimental results showed that the inter-laminar distance of (002) plane (d002) deceased while the microcrystalline stack height (Lc) increased. The oxidation rate of felt base carbon/carbon composites was invari-able at certain temperatures. The oxidation mechanism of carbon/carbon composites changed remarkably at the oxidation temperature 973K. At the initial oxidation stage of carbon/carbon composites, carbon matrix was oxidized much more rapidly than carbon felt.

Low-temperature Rapid Synthesis of Ultrafine Hafnium Carbide Ceramic Powders

Nano hafnium carbide（HfC） powders were synthesized by sol-gel combining hightemperature rapid heat treatment process using citric acid and hafnium tetrachloride as the raw materials. The effects of ball milling treatment on the phase and morphology of pyrolysis products（HfO_2-C） and final HfC product were investigated and the influences of heat treatment temperature and holding time on the structure and properties of the synthesized hafnium carbide powders were also studied. The experimental results showed that the HfO_2-C powders with good uniformity and small particle size were prepared by controlling the milling time. Pure HfC powders with an average particle size of 500 nm were obtained at 1 700 ℃ with a holding time of 3 min, and the oxygen content was about 0.69 wt%, lower than that of the hafnium carbide powders prepared by SPS（0.97%）.

Synthesis of Iron-containing Carbon Microparticles from Deoiled Asphalt and Ferrocene

The deoiled asphalt as the carbon source and the ferrocene as the metal source and the catalyst precursor were chosen to synthesize iron-containing carbon microparticles through co-carbonization at the temperature of about 450℃ for 3 h. The resulting products were treated at 2 000 ℃ for 2 h. All samples were examined by high resolution transmission electron microscopy （HRTEM） and X-ray diffraction （XRD）. The results show that the iron particles in the heat-treated material are completely coated by carbon. In addition to the fully filled carbon microparticles as well as hollow carbon ones, also form carbon fibers with hollow centers. The formation mechanism of the as-prepared products was discussed briefly.

Effect of rhenium on the microstructure and mechanical behavior of Fe–2.25Cr–1.6W–0.25V-0.1C bainitic steels

A new ferritic creep resistant steel has been developed by eliminating Nb and adding 1.5 mass % Re to a ferritic steel grade T/P23 with the aim of enhancing its mechanical properties at high temperature.Cast ingots of both steels, new grade and ASTM T/P 23, were hot rolled at 900℃ and then submitted to a thermal treatment consisting of solubilization at 1050℃ and tempering at 700℃. Tempered bainitic microstructures obtained contain second phases reinforcing carbide particles, mainly M_6C and M_（23）C_6 at the boundaries of both, prior austenite grains and bainitic ferrite laths, as well as MC within the grains. Mechanical properties at temperatures ranging from 540 to 600℃ were studied by strain-ratechange tests in compression at strain rates between 10^（-7） and 10^（-4）s^（-1）. These tests showed high stress exponents（n ≥ 20） and activation energies（Q ≈ 400 k J/mol） for both alloys, which were associated with a dislocation movement mechanism with a strong interaction between dislocations and precipitates. On the other hand, a creep exponent of 5 was derived for the stress dependence of minimum creep rate from conventional-type creep tests at 600℃. Although this stress exponent is usually related to a dislocation climb controlled creep mechanism, remarkable microstructural degradation observed with increasing creep time makes difficult to elucidate the true deformation mechanism controlling creep.