The effect of recrystallization fraction on quench sensitivity of Al-Zn-Mg-Cu alloys was investigated by means of thermal compression test, optical microscopy, and high-resolution transmission electron microscopy. Results show that the quench sensitivity, the size and area fraction of equilibrium phase for 7050 alloy increases with the increase of recrystallization fraction. The area fraction of recrystallization has a good linear correlation with the area fraction of equilibrium phase. When the recrystallization fraction increases from 10% to 58%, the relative hardness value increases from 7% to 17%, the length and thickness of the equilibrium phase increase from 265 nm and 35 nm to 422 nm and 82 nm, respectively, while the area fraction of the equilibrium phase also increases from 6.5% to 28.4%. The Al₃Zr particles in the sub-grained crystals have good coherency with the matrix, which are unfavorable to the equilibrium precipitation during the slow quenching process. However, the Al₃Zr particles in the recrystallized grains are beneficial to the equilibrium precipitation. The more recrystallization fractions, the more Al₃Zr particles that are incoherent with the matrix, so the more nucleation sites are precipitated by quenching, resulting in the increment of quench sensitivity.

Effect of quenching processes on the mechanical property and microstructure of a newly designed ultra-high strength marine engineering steel of low carbon (C<0.05) NiCrMo was investigated by means of thermo-Calc software, optical microscopy, scanning and transmission electron microscopy. Results show that secondary hardening occurred for the steel quenched from 910℃ and then aged at 525℃, resulting in a maximum peak hardness was 369 HV, while secondary martensite microstructures emerged for the steel quenched from 910℃ and then aged at 700℃ by air cooling, resulting in a peak hardness 361 HV. Thermo-Calc calculation result revealed that the mean particle radius of (Nb, Ti)C was obviously reduced with the decreasing quenching temperature within the range of 820~910℃, and the refined (Nb, Ti) C particles could effectively suppress the growth of austenite grains, thus improving grain boundary density of high or low angle in the matrix, which led to the increment of strength and toughness. Among others, the steel quenched from 820℃ presents the highest strength up to 1084 MPa, impact energy of 76 J for V-type impact test at -80℃, and the fracture fiber rate was up to 100%. Fractograph- and crack propagation-observation showed that the refinement of microstructure and second phase could hinder the expansion and fracture of dimples, while the refined martensite packet and block could significantly alter the crack propagation direction. Finally, the steel quenched from 820℃ presents the maximum unit length of 15 μm for the crack propagation path, implying a high toughness of the steel.

The geopolymer composites of coal gangue-slag were prepared with sodium hydroxide (NH) and sodium silicate (NS) as activator. The effect of slag content and NH modules on the fluidity of cement pastes and compressive strength of alkali-activated coal gangue-slag (AACGS) cementitious materials was investigated. The property of the prepared cementitious materials and the relevant cementation mechanism were investigated by means of mechanical test, XRD, FT-IR, MAS NMR and SEM-EDS. Results show that the slag content has significant effect on the pastes fluidity and compressive strength, while the NH module only has significant effect on the compressive strength of AACGS cementitious materials. Higher early strength may be produced for AACGS materials, for instance, when the slag content exceeds 20%, the 28 d strength is also higher than that of P. O42.5 pure cement. With the increase of slag content, the higher polymerization degree emerged for the silicate structure in the hydration products, which is consistent with the measured results of compressive strength. Since that Ca²⁺ has a stronger drive adsorption force than Na⁺, therewith the increase of slag content from 0 to 50% may result in denser matrix, of which the C-(A)-S-H in the microstructure has higher Ca/Si ratio but lower Al/Si ratio. The disordered network structure of AACGS, which consists of C-A-S-H gels and C-S-H gels and N-A-S-H gels, has good compatibility.

A fiber reinforced tailing cementitious composite (FRTCC) was prepared via engineered cementitious composite (ECC) technology. By replacing 50% natural send with tailing sand, the prepared composite presents distinct ductility and environmental friendly-features. The tensile, compressive, flexural and shear ductility of FRTCC as well as the toughening mechanism of polyvinyl alcohol (PVA) fiber were systematically investigated by means of cube compression-, direct tensile-, thin plate bending- and double shear-test. The influence of the content of PVA fiber and the ratio of water to binder on the ductility of FRTCC was examined. The definition of complete toughness ratio was proposed, and the toughness of FRTCC was characterized with a set of double characteristic parameters i.e. the toughness ratio and the toughness index. The results show that the content of PVA fiber and the ratio of water to binder exhibit remarkable synergistic effect on the ductility of FRTCC. The proper mix proportion can significantly improve the ductility and energy absorption capacity of FRTCC, thereby ensure that the FRTCC possesses characteristics such as cracking with multi-cracks, strain hardening and ductile fracture etc.

A series of controlled-release composites of polycapolactone (PCL)/aspirin(ASA) were fabricated via chemically induced phase separation technique with polycapolactone as carrier. The effect of different content of ASA on the morphology, biological activity, hydrophilic performance, porosity and controlled-release performance of the composites were investigated. Results show that the addition of the ASA played a crucial role for forming the unique nanofibrous structure of PCL/ASA composite. The nanofibrous structure of composite fades away with the increasing amount of ASA. The hydrophilic performance increases from 38.00% to 59.34% and the porosity decreases from 96.67% to 52.28% with the increasing ASA-content. Furthermore, both of the pure PCL and PCL/ASA composite all present good biological activity, in other word, both of the nanofibrous structure and ASA all exhibit effect on the biological activity of composite materials. The controlled release of the ASA relates to the structure of PCL/ASA composite, and the accumulated release amount of the PCL/ASA composite with micro- and nano-structure can reach to 25.23% over an equal period of time.

A self-lubricating composite coating of Ti-Ni+TiN+MoS₂/TiS with TiN, TiMo and Ti₂Ni as reinforcement phases, while MoS₂ and TiS as lubricant phases, was fabricated on Ti-6Al-4V alloy by laser cladding with composite alloy powder of NiCrBSi, TiN and Ni-coated MoS₂ as cladding materials. The phase compositions, microstructure, microhardness and tribological properties of the coating were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), microhardness tester and multi-purpose friction and wear testing machine,respectively. Results show that the mean microhardness of the composite coating (between 1060 and 1140HV_0.3) is about 3 times higher than that of the substrate (370HV_0.3). Due to the combined effect of hard reinforcing phases TiN, TiMo, and Ti-Ni, as well as lubricating phases MoS₂ and TiS, the friction coefficient (0.3199) and the wear mass loss (2.2 mg) of the composite coating are both lower than those of the substrate (0.3535 and 11.8 mg). Therefore, the prepared composite coating has good self-lubricating wear resistance.

Nitrogen-doped bagasse biochar BAC-EDA was prepared via a two-step process, namely, the bagasse biochar was prepared with bagasse as raw material and phosphoric acid as modifying agent and then on which nitrogen-containing functional groups were further coupled with ethylenediamine as dressing agent. The pore structure of BAC and BAC-EDA was characterized by means of BET, BJH and t-plot methods based on the experimental data of liquid nitrogen adsorption/desorption. Meanwhile acidic groups were characterized by FTIR method. Results show that pores of biochar BAC and BAC-EDA are mainly of mesopores with a small amount of micropores. There existed oxygen-containing acidic functional groups on the surface the nitrogen-doped bagasse biochar BAC-EDA, such as carboxyl groups, lactone groups and amino nitrogen-containing functional groups etc. The proportions of the micro-mesopores of the biomass carbon are constant before and after modification, which indicating that the introduction of the functional groups is realized simultaneously on the surface of both the micro- and meso-pores. Adsorption experiments show that the maximum adsorption amount of the modified BAC-EDA is 137 mg·g^-1, much higher than that of the plain BAC 73 mg·g^-1, indicating that the nitric acidoxidation and ethylenediamine modification effectively improve the adsorption capacity of biomass biochar. The Langmuir model can better describe the adsorption of Hg(Ⅱ) by BAC-EDA, further illustrating the homogeneity of the active sites of the modified carbon. Besides, the temperature is conducive to adsorption, showing that the process is a spontaneous endothermic process.

The segregation- and precipitation-behavior of superalloy K4169 with 0.03~0.65% Si (atomic fraction) in the temperature range of 1150℃~1360℃ via thermo-calc simulation and isothermal solidification experiment. Results show that not only the temperature of solidus-liquid will decrease but also the solid-liquid two-phase region will enlarge with the existence of Si. The liquidus temperature of the alloy decreases from 1354℃ to 1343℃ and the solidus temperature drops from 1241℃ to 1212℃ with the increasing of Si content from 0.03% to 0.64%. With the increasing of Si content, the enrichment of Nb and Mo are promoted in the residual liquid phase, resulting in the depletion of Cr and Fe, while the content of Laves phase increases along with the segregation. Different morphologies are delivered of Laves phase due to the different Si contents in the alloy. The reticular Laves phase was obtained with 0.03% and 0.23% Si, while large blocky laves phase was observed with 0.42% and 0.65% Si. Si has almost no effect on the morphology and precipitation temperature of MC carbide. Si not only affects the room temperature performance of the alloy, but also the elevated temperature performance of the alloy. When the Si content increased from 0.03% to 0.65%, both of the creep-rupture life and elongation are decreased obviously. Base on these research results, as an overall consideration, it is rational to control the Si content for K4169 alloy.

Nanocone arrays of ZnO were synthesized on Zn foil via a simple low temperature (60^OC) hydrothermal route. The morphology, structure and composition of the prepared nanocone arrays were characterized by means of scanning electron microscopy, X-ray diffractometer and energy disperse spectroscopy. Results show that the surface of Zn-substrate was fully covered by clustered ZnO-nanocones and standalone ZnO-nanocones, the nanocone arrays of ZnO are of high purity and high degree of crystallinity. The prepared nanocone arrays of ZnO exhibit good photocatalytic performance for aqueous solutions of methyl orange and methylene blue, indicating that the nanocone arrays of ZnO may be a general purpose photocatalyst for the degradation of different dyes. Furthermore, the possible growth and photocatalytic mechanisms of the nanocone arrays of ZnO were also analyzed.