The fatigue properties of CrMoW rotor steel were investigated by a high temperature ultrasonic fatigue system. Fatigue tests of CrMoW rotor steel up to 1×10¹⁰ cycles had been conducted at room temperature and 600℃ respectively. Results reveal that the type of S-N curves present continuously descending at room temperature and 600℃. Fatigue fracture occured over 109 cycles. Fractograph of specimens show that Crack initiate mainly from the surface for the specimens that fatigue life is less than 1×10⁷ cycles, but crack initiate mostly from inclusions for those that fatigue life is greater than 1×10⁷ cycles at room temperature. It is found that crack can also initiate at inclusions, but the modes of crack initiation do not play a decisive role for the fatigue life at high temperature. Threshold values of fatigue crack growth obtained by measuring the size of fisheye are 3.4 MPam^1/2 and 1.0 MPam^1/2 at room temperature and 600℃ respectively.

The friction and wear behavior of the natural tooth enamel and dentin in sliding against a highly polished glass ceramic, polymer ceramic, zirconia and pure titanium respectively were investigated through a fretting friction and wear testing in an artificial saliva test environment by UMT-2 friction and wear testing machine. While the worn surface morphology was observed by scanning electron microscopy (SEM), the roughness was measured by roughness instrument and the abrasion loss was weighed by an electronic balance. The results show that after friction and wear testing, the abrasion loss of the enamel and dentin against the four kind of materials all showed a statistically difference within P < 0. 05, which possessed significant positive correlation with the hardness of the four kinds restoration materials, the enamel and the dentin. The mass loss of the dentin against poly ceramic and the enamel against glass ceramic was the closest ones to that of the control group of the dentin.

Low cycle fatigue tests for different strain ranges were conducted for 316L stainless steel at 600℃ under uniaxial loading. The results show that the dynamic strain aging (DSA) can be observed for three strain ranges. The concept of stress drop has been introduced to characterize the degree of serrated yielding for different strain ranges. The difference in the serrated yielding amount for different strain ranges can be attributed to the different interactions between solute atoms and dislocations. The maximum stress drop is related to the cyclic hardening or cyclic softening. DSA is related to the number of cycles. The material presents the obvious DSA for a few cycles and then followed by weak serrated yielding, even disappearing. However, the serrated yielding can be observed again before fatigue failure. The difference of serrated yielding can be attributed to the types of atom atmospheres at different cycles. A-type serrated wave was observed for smaller strain range, however, types of A, B, A+B, C, and B+C serrated wave can be found for different cycles and different phases in one cycle for larger strain range. Finally, the crack source region and crack propagation region of the fatigue fracture were observed by SEM.

The magnitude and distribution of the interfacial stresses along the radial-, axial- and circumferential directions at fiber side of fiber reinforced composites SiC_f / Ti-6Al-4V with the change of thermal expansion coefficient and elasticity modulus of the matrix are analysed by three-dimensional model established by using finite element method. The results show that the change of interfacial residual stress is proportional to that of thermal expansion coefficient of matrix, and the no-uniformity of distribution of the residual stress along the circumferential direction of fiber decreases with the decrease of thermal expansion coefficient. In addition, interfacial residual stress usually increases with the increase of elasticity modulus of matrix, but the increase of which reduces gradually.

The characteristics for the evolution of grain orientation and texture of ring shaped blanks of sand- and centrifugal-casting Q235B respectively were investigated by electron backscatter diffraction (EBSD) technique, while the blanks have been subjected to hot compression with a strain rate of 0.1 s^-1 at different temperatures. The results show that the grain size of the blanks after hot compression at 1000℃ becomes smaller in the deformed microstructure, but a few grains maintains as in cast state. The mechanisms of the microstructure evolution may be ascribed to dynamic recovery and large strain geometric dynamic recrystallization. For centrifugal cast ones, the percentage of high-angle boundary in 20°-50° is 22%, but after hot compression at 1100℃ it shows a homogenous microstructure with equiaxed grains because of sufficient recrystallization, while the mis-orientation distribution of grain boundaries still presents a typical characteristic of double-peaks and the proportion of the high-angle boundaries reaches to 60%-75%. The textures of sand casting Q235B are a small amount cube texture {001}<100> and {001}<110> along <001>//ND at 1000℃, while the main textures are Goss texture {110}<001> and r-cube texture {110}<001> at 1100℃. For centrifugal casting ones at 1000℃, {110}<110> and Cu texture {112}<111> distributes along ε orientation; at 1100℃ the types of texture including {001}<110> and {111}<110> transformed from {111}<112> along γ orientation. The orientation density is higher due to the high extent of recrystallization.

Welding thermal cycle process of test steels containing different Nb was investigated under different heat inputs with a Gleeble-3800 thermo-mechanical simulator. The microstructural characteristics of the coarse-grained heat-affected zone (CGHAZ) were observed by using optical microscope (OM), scanning electron microscope (SEM) and electron backscatter diffraction (EBSD), while their impact toughness was tested. The results indicate that with the increasing heat input, lath bainite transformed gradually into granular bainite, and the size and proportion of M/A islands increased, while the average grain size also increased. Under the same heat input, austenite in high Nb steel was refined obviously, with more dispersive and refined M/A islands distributed in the microstructure of high Nb steel, and the proportion of high angle boundaries was high. With the increasing heat input, the impact toughness of steels decreased sharply. The critical heat input value for a sharp decrease in impact toughness were approximately 35 kJ/cm for high Nb steel and 25 kJ/cm for low Nb steel. However, the impact toughness of the high Nb steel was significantly higher than that of the lower Nb steel in the range of experimental parameters.

The diatomite based flame-retardant materials for external thermal insulation board of exterior wall were preparedby sol-gels method with NaOH (2 molL^-1) and Na₂SiO₃ (1 molL^-1) simultaneously as the chemical activator, and then characterized by means of various methods. Results showed that aftera thin-plastering of the prepared flame-retardant diatomitewas applied on expandable polystyrene board, the limiting oxygen indexthe complex EPSboard can reached 36.8%, and itscombustion performance can meetthe requirement of UL-94 V1. SEM results demonstrated that the NaOH and Na₂SiO₃ were benefit for the diatomite to form dense amorphous silica layer, XRD and FT-IR results showed that "depolymerization-reconstruction" of the diatomite structure occurred in the alkaline media, and which would further be reconstructed during firing.

Microstructure of hot rolled and annealed Mg-3Zn-2Gd alloy was characterized by optical microscopy and scanning electron microscopy. Meanwhile, their tensile mechanical properties at ambient temperature were tested. The results show that the microstructure of the alloy sheet is refined after rolling by the strain range from 23% to 67% and the average grain size decreases from 10 μm to 4 μm by the rolling strain of 67%. Lots of twins and shear bands in the initial microstructure decrease gradually. When the rolling strain increases to 67%, the shear bands disappear, and meanwhile the dynamic recrystallization grains and few twins exist, while the tensile mechanical properties of the alloy are enhanced significantly. Tensile strength σ_b and yield strength σ_0.2 increase from 255 MPa and 215 MPa for the non-rolled alloy to 305 MPa and 300 MPa for the rolled alloy by strain 67% respectively, while the elongation δ first increases, and then decreases. After annealed at 573 K for 1 h, the rolled alloy experienced static recrystallization, in the meanwhile, the non-uniform deformation areas disappeared and finally showed a microstructure of fine and uniform equiaxed grains, and the relevant σ _b and σ _0.2 decreased to 265 MPa and 235 MPa, respectively, while δ slightly increases to 19.0%. The tensile fracture consists of a large number of dimples presenting the typical characteristic of ductile fracture.

Whisker-like carbon nanotubes (WCNTs) were produced by chemical vapor deposition (CVD) and then purified by graphitization at high temperature. The WCNTs were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectra and thermogravimetric analysis (TGA). Water suspension consisted of WCNTs as functional material and cellulose fibers as matrix was prepared by speed-cutting procedure, and then WCNTs containing composite papers were prepared with the above suspension by vacuum filtration. The conductivity of the composite papers increased from 14.1 S/m to 325.1 S/m after incorporation of the graphitized WCNTs. A supercapacitor cell with two-electrodes was constructed with 1 mol/L LiPF₆ as electrolyte. The electrochemical performance of supercapacitor was examined by cyclic voltammetry and galvanostatic charge/discharge. The results indicated that the supercapacitor has a maximum capacitance of 90 F/g by a scan rate of 1 mV / s. The specific energy and specific power reached 21.3 Wh/kg and 2.1 kW/kg respectively by a current density of 800 mA/g. These showed an excellent application prospect of the modified carbon nanotubes for supercapacitors.

Composite phase change materials were synthesized with expanded graphite (EG) as carrier and paraffin as phase change component. The microstructure and properties of the composite phase change materials were characterized by means of scanning electron microscopy, differential scanning calorimetry, RC-4 temperature recorder, Fourier infrared spectrometer and X- ray diffraction analyzer.Results confirm that the composite phase change material is a combination of EG and paraffin.With the increase of EG content, the latent heat and phase change temperature of composite phase change materials decreased, however their dispersibility, stability and thermal conductivity increased, whilst they showed enhanced efficiency with shorten heat storage time; The temperature of the heat storage process has obvious effect on the transformation time of the composite phase change materials; Therefore, in order to ensure the composite phase change materials with appropriate microstructure and good performance, the fraction of EG should be controlled around 10%.

A series of polyester ureidemultiblock copolymers (PBSu-co-PBAu) composed of the pre-prepared poly(butylene-succinate-urea) (PBSu) and poly(adipate-succinate-uera) (PBAu) were successfully synthesizedby melt polymerization processes with toluene-2, 4-diisocyanate(TDI) as a chain extender. Then the structure, thermal properties, mechanical properties and biodegradable properties of the copolymers were characterized by means of¹H-NMR, DSC, TG, XRD, universal tensile machine and hydrolytictest respectively. The results indicated that the toughness of multiblock copolymers was enhanced by the incorporation of PBAu. The multiblock copolymers possessed excellent thermal stability and biodegradable properties, as well as tensile properties superiorto the homopolymers PBSu and PBAu, the unmodified-PBS and -PBA. Besides, the thermal properties, biodegradability and mechanical properties of the multiblock copolymers can be adjusted by varying the dose of PBSu and PBAu.