The effect of interfacial modification on flexural strength of epoxy composites filled with modified ZrB₂-Al₂O₃ composite fillers was investigated in order to explore the stress distribution of modified composites under external load. The mechanical performance of epoxy composites filled with 0 vol%, 1 vol%, 3 vol% and 5 vol% unmodified and modified ZrB₂-Al₂O₃ fillers was characterized by three point bending (TPB) tests. The fracture surfaces of epoxy composites were observed by scanning electronic microscope (SEM). The results showed that the epoxy composite reinforced by 1 vol% modified fillers exhibited the optimal mechanical performance. According to the Von Mises stress contours simulated by finite element models (FEM) and the SEM images, it was shown that the modified ZrB₂-Al₂O₃ multiphase fillers could homogenize the stress in the epoxy composites due to the transition effect resulted from the interfacial modification layers on the surfaces of multiphase fillers. It contributed to the improvement of mechanical performance of epoxy composites further.

Slow positron beam was applied to study the depth profile structure of the virgin and the aged high-temperature vulcanized silicone rubber (HTV). Scanning electron microscope (SEM) images show that the surface of virgin sample is smooth, while the outdoor aged samples are all rough. According to the S(E) curves obtained by slow positron beam, in a depth of more than 1 μm, the S parameter of the sample aged at low-potential side keeps the same value with the virgin one; while the S values of the highpotential side aged sample remain rather low in a depth of about 5 μm. Thermo gravimetric analysis (TGA) results show that the sample in high potential side contains more inorganic constituents than that of other samples. The results are attributed to the strong electric field induced corona aging at high potential side of the composite insulator.

Nanoparticles and microparticles reinforced Al matrix composites were fabricated by spark plasma sintering, and the microstructure and tribological properties were investigated systemically. The nano-Al₂O₃ particle and micro-Al₂O₃ particle uniformly dispersed in Al matrix composites. The introduction of nanoparticles is beneficial to the decrease of friction coefficient and wear rate, while microparticles are responsible to the high friction coefficient, resulting in the abrasive wear. With the introduction of both nanoparticles and microparticles, their synergic effect will lead to the variation of tribological behavior.

The modification of graphitic carbon nitride can significantly improve the photocatalytic performance of graphitic carbon nitride (g-C₃N₄). Fe₂O₃/nitrogen-deficient g-C₃N_4-x composite catalysts were prepared with dicyandiamide as the precursor and Fe³⁺ doped in this study. The composite catalysts were characterized by XRD, SEM, FT-IR, XPS and photocurrent measurements. Close interaction occurred between Fe₂O₃ and nitrogen deficient g-C₃N_4-x, more photogenerated electrons were created and effectively separated from the holes, resulting in a decrease of photocarrier recombination, and thus enhancing the photocurrent. Photocatalytic performance experiments showed that Fe₂O₃ / nitrogen deficient g-C₃N_4-x could utilize lowenergy visible light more efficiently than pure g-C₃N₄, and the removal rate was 92% in 60 minutes.

The aluminum matrix composites (AlB₂+α-Al₂O₃)/Al were fabricated by in situ reaction synthesis from an Al-B₂O₃ system. The reaction pathways, apparent activation energies and tensile properties were analyzed by using differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and equipped energy dispersive spectroscopy (EDS). The results showed that there are two-step reactions in the Al-B₂O₃ system. The first-step is 15Al+7B₂O₃→7α-Al₂O₃+AlB₁₂+2B and the second-step is 2B+AlB₁₂+6Al→7AlB₂. Their corresponding apparent activation energies are 352 and 444 kJ/mol, respectively. The tensile strength and elongation rate of the composites are 190.5 MPa and 6.6%, respectively.Compared with ordinary aluminum base material, the performance is superior. There are many dimple and cracked α-Al₂O₃ reinforcements in tensile fracture surface layer.

A Fe modified Na₂WO₄ compound was synthesized by a solution impregnation method and was ball-milled with MgH₂ to constitute a novel MgH₂-Fe₂O₃/Na₂WO₄ composite. The effects of the Fe₂O₃/Na₂WO₄ additive on the hydrogen storage properties of MgH₂ together with the corresponding mechanism were investigated. At 423 K, within the first 200 seconds, the hydrogen absorption amount of MgH₂+20 wt% Fe₂O₃/Na₂WO₄ was almost 5 times that of pure MgH₂. And at 573 K, its total hydrogen desorption amount was 7 times that for pure MgH₂. Meanwhile, its onset dehydrogenation temperature was 110 K lower than that of pure MgH₂. It was worth noting that the MgH₂+20 wt% Fe/Na₂WO₄ presented the lower dehydrogenation reaction activation energy (E _a) of 35.9 kJ·mol^-1 compared to that of pure MgH₂. The active MgWO₄, Mg₂FeH₆ and MgO formed during the milling process were responsible for the improvement of the hydrogen storage properties for MgH₂.

The Z-type ferrites of nominal composition Ba₃Co₂Fe₂₄O₄₁+x wt% Bi₂O₃, where x=0.25, 0.5, 1.0, 1.5, 2.0, were prepared by conventional ceramic processes. The influence of Bi₂O₃ content on the bulk densities, microstructures, magnetic and dielectric properties of Z-type ferrite samples were systematically examined so as to obtain materials with low magnetic and dielectric loss tangent over a frequency ranging from 600 to 800 MHz. The experimental results showed that addition of Bi₂O₃ lowered the sintering temperature (1 020 ℃) and then reduced the average grain size (<2 μm) and enhanced the resistivity (>2.68×10⁸ Ω•cm) dramatically, which consequently decreased the magnetic and dielectric loss. Additionally, the low loss factors were observed at the Bi₂O₃ content x = 1.0, i e, tan δ _μ/μ’ = 0.013 and tan δ _ε/ε’ = 0.001 at 800 MHz, and such materials could be used for antennas miniaturization from 600 to 800 MHz.

We studied the local structure and properties of six-fold coordinated silicon (Si^[6]) in BaO-SiO₂-P₂O₅ glasses. Nuclear magnetic resonance (NMR) and Raman spectroscopy revealed the existence of six-fold coordinated silicon species and network former units (NFUs) in the BaO-SiO₂-P₂O₅ glasses. The glass transition temperature (T _g), which was measured by differential scanning calorimetry, increased rapidly along with the increase of SiO₂ from 0 to 10 mol%, then declined and finally increased again, which showed a “Z” trend along with the increase of SiO₂ while the density of the glasses showed the opposite trend. When the addition of SiO₂ is 16 mol%, T _g decreased to an extremely low value (807.9 K). Besides, the Vickers indentation hardness (H _v) had been significantly enhanced from 4.66 to 6.63 GPa by adding 16 mol% SiO₂. Furthermore, the liquid fragility index (m) of the glasses declined slowly firstly and then increased rapidly when the amount of SiO₂ is greater than 13 mol%.

Different failure modes and morphologies were found in the chemical vapor infiltration (CVI) 2D C/SiC torque tubes with different thickness. To characterize the density and porosity of the ceramic matrix composite (CMC) torque tube, a CT test was conducted. The archimedes drainage method was used to measure the density and porosity, and by adopting FEM software, the stress distribution and failure strength of the ceramic matrix composite torque tubes were calculated. A universal material test machine was used to implement torsional tests. Different torsional behaviors of CMC torque tubes with two different thicknesses were showed in the stress-strain curves. To analyze the predominant failure factors, SEM was used to observe the failure morphologies and cracks. 5 mm thickness CMC torque tube has reasonable fracture morphologies and a higher maximum shear strength and modulus.

Si/Cu₃Si@C composites encapsulated in CNTs network (SCC-CNTs) were synthesized via the combination of ball-milling and CVD methods. SCC-CNTs consist of conductive Cu₃Si, amorphous carbon layer, cross-linked CNTs, and the etched pores, which can play the synergistic effects on the improvement of electronic conductivity and Li⁺ diffusion. The volume expansion of Si anode is also suppressed during the electrochemical process. The SCC-CNTs composites demonstrate a remarkably improved electrochemical performance compared with pure Si, which can deliver a discharge capacity of 2 171 mAh·g⁻¹ at 0.4 A·g⁻¹ with ICE of 85.2%, and retain 1 197 mAh· g⁻¹ after 150 cycles. This work provides a facile approach to massively produce the high-performance Si-based anode materials for next-generation LIBs.

We developed cordierite-mullite composite ceramic materials to package and encapsulate PCM, and presented a preparation process from raw materials of kaolin, talc and alumina. The properties and microstructre of cordierite-mullite composite ceramic were studied. Due to the strengthening effects of mullite, the sample C2 (80 wt% of cordierite and 20 wt % of mullite) sintered at 1 420 °C possessed excellent physical properties. Determined by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) analysis, cuboid-shaped cordierite crystals and needle-like or long quadrilateral-prism mullite crystals with staggered patterns were found, which endowed the composites preferable mechanical strength. After 30 cycles of thermal shock (room temperature to about 1 100 °C, air-cooled), the sample presented superior thermal shock resistance, which is suitable to be applied as solar thermal storage materials.

A serial of ordered meso-macroporous phosphotungstic acid (HPW) supported on SiO₂ nanocomposites were successfully prepared by a homogeneous precipitation method, using monodispersed polystyrene (PS) microspheres and cationic surfactant as structure directing agent. These nanocomposites were used as catalysts for oxidative desulfurization (ODS) of model fuel. The materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ adsorption-desorption isothrem, X-ray diffraction (XRD), and Fourier transform infrared spectra (FTIR). The characterization results suggested that the as-prepared material possessed ordered meso-macroporous architectures with Keggin type phosphotungstic acid dispersed homogeneously in SiO₂ matrix. Under the selected reaction conditions, dibenzothiophene (DBT) in model fuel can be removed within 2 h at room temperature (30 °C). In addition, only 1.2% of efficiency lose than the fresh catalyst even after 5 cycles.

Ti(C,N)-TiB₂ cermets were fabricated from Ti(C,N), TiB₂, Co and WC powder mixtures via a vacuum hot pressing process. The influence of TiB₂ content on their microstructures and mechanical properties was investigated. As a result of the elevated TiB₂ contents, two types of core-rim microstructures were present in the Ti(C,N)-TiB₂ cermets, and remarkably improved mechanical properties were achieved. With the increase of TiB₂ content, the flexural strength, fracture toughness and hardness of the Ti(C,N)-TiB₂ cermets first increased, and then decreased, while their relative density consistently decreased. Attributed to an integration of the intergranular and intrangranular fracture behaviors, the Ti(C,N)-TiB₂ cermets with 20 wt% TiB₂ content exhibited the best overall properties with the relative density, hardness, fracture toughness and flexural strength at 99.3%, 1 995 H V, 7.92 MPa·m^1/2 and 1 114 MPa, respectively. The underlying mechanism for their enhanced properties was studied in detail.

High-quality LDH-SO₄-CO₃ whiskers were synthesized via liquid precipitation method using MgSO₄·7H₂O and Al₂(SO₄)₃·18H₂O as precursors and Na₂CO₃-NaHCO₃ buffer solution as precipitant. The influence of buffer solution concentration on the characteristics of the samples was investigated. The as-grown whiskers were characterized by X-ray diffraction, transmission electron microscopy, and Brunauer-Emmett-Teller N₂ specific surface area measurements. The results show that the buffer solution concentration has significant impact on whiskers with intercalated structure. The LDH-SO₄-CO₃ whiskers with well-defined geometry, distinct intercalated structure, decent quality, and excellent dispersing capability can be obtained under the following conditions: buffer solution volume ratio of 45%, reaction temperature of 83°C, and reaction time of 182 h. The obtained whiskers are well-crystallized and exhibit homogeneous morphology consisting of fber bars.

The CaCu₃Ti₄O₁₂ (CCTO) ceramic was prepared through conventional solid-state method. The effects of synthesis process (synthesis temperature and synthesis time) of powder on ceramic microstructures, CuO segregation and electrical properties were investigated. The phase composition was determined by X-ray diffraction and the microstructure was examined by SEM. The dielectric constant, dielectric loss, and resistance of the ceramic were also determined by a precision impedance tester. The results show that, as the synthesis temperature increases, the CCTO ceramic grain size decreases and the stoichiometric ratio of Cu/Ca at the grain boundary increases, the dielectric constant increases and the dielectric loss decreases (40 < f < 10 kHz). In addition, when the synthesis time is shorter than 12 h, the Cu/Ca ratio of CCTO decreases and the dielectric constant increases with time increase. However, when the synthesis time exceeds 12 h, this trend is just the opposite. It is further proved that Cu at the grain boundary is not conducive to the dielectric constant of CCTO.

A LiFePO₄/C composite was synthesized by a simple solid-state reaction method using glucose as reductive agent and carbon source and FePO₄ as precursor, which was prepared by introduction of Na₃PO₄ as phosphorus source and pH regulator in order to pursue lower cost and environmental protection. The structure and morphology of FePO₄ and LiFePO₄/C were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Furthermore, electrochemical performance of LiFePO₄/C was investigated by galvanostatic charge–discharge tests and cyclicvoltammogram (CV). The results indicate that FePO₄ obtained has a small particle size and uniform particle distribution, which is demonstrated to be applicable as the iron source to synthesize LiFePO₄/C. Prepared LiFePO₄/C shows an excellent rate capability and cycle performance. At rates of 0.1 C, 0.2 C, 1 C and 2 C, the initial discharge capacities of 161, 158, 145 and 120 mAh/g were achieved, respectively and the discharge capacity is 154, 153, 140 and 116 mAh/g after 400 cycles. The employed method of preparing FePO₄ by introduction of Na₃PO₄ has advantages such as low cost, safe raw material, environmental benign and recyclable products, which is suitable for industrial production.

The effects of surface adsorption of bovine serum albumin (BSA) and human gamma-globulin (HGG) on the tribological performance of a DLC film were investigated using a quartz crystal microbalance with dissipation (QCM-D), a ball-on-disk reciprocating tribometer, and a three-electrode electrochemical cell. The results showed that the wear depth in the BSA solution was higher than that in the HGG solution. In the HGG solution, the HGG-adsorbed layer could act as a lubricating layer and protect the DLC film from wear. The wear volume of DLC film in BSA and HGG mixture solution was higher than that in single HGG solution. This may be because the BSA molecules inhibit the formation of HGG adsorbed layer during sliding.

In order to investigate the synergistic effect of re-dispersible powder-ethylene-vinyl acetate copolymer (EVA) and polypropylene fiber on the crack resistance of concrete under thermal fatigue loading, the compressive strength, ultimate tensile strength, ultimate tensile strain and tensile modulus of elasticity were tested. In addition, ultrasonic method and scanning electron microscope analysis were used to explain the microstructure mechanism. The results show that polypropylene fiber-reinforced concrete presents a better performance on crack resistance than ordinary concrete, and the synergism of EVA and polypropylene fiber can improve the anti-cracking ability of concrete further.

In order to study the effect of electromagnetic compound treatment on the mechanical property, cutting performance and microstructure of cemented carbide, the samples were treated by a self-made electromagnetic compound treatment device with different magnetic field strength (H=1, 1.25 and 1.5 T). The electromagnetic compound treatment method was proposed to couple pulsed magnetic field and pulsed current. The results show that after the pulsed magnetic field treatment, the values of the transverse rupture strength of the samples were respectively reduced by 21%, 20.6% and 20.1%; the cutting performance was decreased by about 4.5%, which means the tool life was decreased. After the electromagnetic compound treatment, the values of the transverse rupture strength of the rectangular samples were respectively increased by 8%, 8.6% and 9.5%, and the tool life was increased by 4.2%, 7% and 10.3%. After the electromagnetic compound treatment, the pulse current provided the driving force for dislocation motion. A strong pulse current driving force is more likely to make the dislocation multiply and slip. A high density dislocation cell is formed within the material, so the mechanical properties were significantly increased.

An electro-deposition method has been recently proposed to repair cracked reinforced concrete. To evaluate the corrosion resistance of the reinforcing steel in cracked concrete, three different parameters including type of auxiliary electrode, electrode distance, and current density were studied. Tafel polarization curve was used to evaluate the corrosion resistance of the steel. Self-corrosion potential and corrosion current of the steel were tested. The results indicate that the corrosion resistance improvement of the reinforcing steel is optimal as prism titanium mesh is applied as auxiliary electrode, followed by the flaky titanium mesh and the column titanium bar. When the electrode distance is 60 mm, the corrosion resistance improvement of the reinforcing steel is optimal, and with 80 mm electrode distance, the corrosion resistance improvement is the poorest. The property falls in between them when 40 mm electrode distance is used. Moreover, the corrosion resistance improvement of the reinforcing steel increases as the current density goes up.

The internal curing effect of superabsorbent polymer (SAP) on the properties of high performance concrete (HPC) under marine wetting and drying cycles (WD cycles) was investigated. Compressive strength, hydration and chloride migration were experimentally investigated and the results were evaluated by compasison with those under fresh water curing (FW). Water absorption and porosity were also evaluated only under WD cycles. The results showed the important influence of wetting and drying cycles on the properties of SAP modified HPC properties. Carefully designed, SAP minimized the long-term compressive strength of HPC under marine WD cycles. The hydration rate was faster in the initial curing, but became lower as compared with that cured in FW. In addition, SAP improved the long-term water absorption resistance and chloride migration resistance of HPC under marine WD cycles. The examination of the porosity showed a lower increase of the volume of capillary pores in SAP modified HPC under long term WD cycles compared with that without SAP. Therefore, internal curing by SAP could improve the durability properties of HPC under marine WD cycles.

The scope of the present paper is to understand the effects of crystalline admixture on the self-healing capacity of the cementitious composites. Previous studies were examined and a conclusion was drawn to the effect that different additives to crystalline admixture tend to improve self-healing of concrete for larger cracks. It is recommended that initial treatment with chemical admixture can stimulate and heal further cracks and it has the better repeatability trend in mixing with the concretes and mechanical recovery is possible even under repetitive preloading. Effective self- healing with chemical admixtures even under open-air exposure, leads to study the importance of a service ability design parameter including the maximum allowable crack width by repeatability analysis as a function of the exposure with the concept of sealable crack width.

The viscoplasticity and compressive strength of cement with high erosion performance were studied. The influences of curing temperature and content of ground granulated blast furnace slag (GGBFS) on these performances of the medium heat cement (including high iron and low calcium phase) were also investigated. The results indicate that the medium heat cement with high iron phase can maintain better fluidity and low temperature sensitivity than that of ordinary Portland cement at high temperature. GGBFS can play an important role in improving the fluidity and stability of the slurry, and avoid the cement setting and hardening prematurely at high temperatures. The microstructure analysis shows that a large amount of CH with layer shape appear in the slurry. The amount of this gel layer in the slurry increased as the curing temperature elevated. The layer can make the cement stone structure more denser, so that the compressive strength of samples are enhanced in the later stage. When the medium heat cement contains 40% GGBFS, the system has the best flow performance and stability under high temperature environment, and can be applied to mass concrete with excessive internal temperature.

The adsorption behaviors and dispersing properties of polycarboxylate superplasticizer (PCE) with different functional groups were systematically analyzed to reveal the theory and methods of modifying PCE molecular structures and regulating PCE performances. By substituting carboxylic groups with sulfonic groups, ester groups or acylamino groups, respectively, modified PCEs with different functional groups were synthesized. Results show that introducing low amount of ester groups or sulfonic groups into the PCE molecules has no negative effects on the fluidity of cement paste, while introducing acylamino groups into PCE molecules significantly weakens the fluidity of cement paste. At low amount (when the molar ratio of sodium methallyl sulfonate to TPEG is lower than 0.4), the rapid adsorption of sulfonic groups onto the cement particles contributes to the high dispersing performance of the sulfonic group modified PCEs. When the substitution ratio of acrylic acid by sulfonic acid is higher than 0.4, the viscosity and the yield stress of cement paste increases sharply. Redundant sulfonic groups lead to the excessive charge density of the PCE, which contributes to the inhomogeneous adsorption on the cement grains and hence results in the decline of the dispersing performance. Substitution of carboxylic group by acylamino group or ester group slightly changes the viscosity as well as the yield stress of cement paste. Introducing sulfonic group into PCE molecule improves the adsorption behavior of PCEs, while introducing ester group or acylamino group into PCE depresses the adsorption properties.

Calcium sulfate whisker (CaSO₄ whiskers), a new type of microfiber material, was used in cement matrix to increase the strength of the cement based composites. Effect of CaSO₄ whiskers on the mechanical properties of the resulting cement mortar was also studied. The results showed that the flexural strength and compressive strength of the mortar specimen was improved as high as 28.3% and 8.5% by incorporating 5 wt% CaSO₄ whiskers. Also, the chemical composition and structural transformation of the hardened cement matrix with CaSO₄ whiskers were identified by X-ray diffraction (XRD) and scanning electron microscope (SEM). Conclusion can be drawn that CaSO₄ whiskers can effectively retard the formation and restrict the coalescence of micro-crack expansion. The interaction mechanism of CaSO₄ whisker on the reinforcement is mainly on three aspects: whisker pullout, crack deflection, and crack bridging. Mercury intrusion porosimetry (MIP) tests have confirmed that for 28 d cement mortar, the harmless pores increased from 9.33% to 10.62%, and the harmful pores decreased from 2.08% to 1.90%. Therefore, the whisker can optimize the pore size distribution of the resulting cement mortar.

Three different kinds of coatings were coated on the concrete surface, and the changes in appearance, surface roughness, microstructure and components of coatings in artificial sewage were investigated. In addition, the strength, micrograph, mineral compositions and pore structure of concrete specimens after removing coatings were also studied. The results show that epoxy coal tar pitch coating (ECTPC) has the best effect of protecting concrete from the sewage corrosion. After being immersed in sewage for 90 days, the compressive strength of concrete coated with ECTPC is still as high as that of specimen immersed in water, and the cement paste has a high CH content and dense structure with low porosity, which mainly accounts for its excellent barrier property and certain antibacterial function. Cement-based bactericidal coating (CBC) also has good effectiveness to sewage corrosion of concrete. The strength and microstructure of concrete coated with CBC in sewage are still significantly superior to those of uncoated concrete. Although cement-based capillary crystalline waterproofing coating (CCCWC) is a good waterproof material, it is not suitable for the corrosion resistance of concrete in sewage. After 2 months corrosion, almost all of the CH crystals in coating reacted with the metabolic acid substance by microbes. Therefore, the strength and pore structure of concrete coated with CCCWC are only slightly superior to those of uncoated concrete. Overall, the protective effect of cement-based inorganic coatings is relatively poor.

A novel thermal-protective coating has been successfully prepared by CPED process on a cast Al-12%Si alloy with the addition of ZrO₂ nano-particles in the electrolyte. The microstructures and phase composition of the coatings were analyzed by SEM and XRD, and the heat insulation performance and the thermal shock resistance of the coatings were investigated. With ZrO₂ nanoparticles addition, the cathode plasma discharge on the coating surface is more obvious than that without ZrO₂ nanoparticles addition, the coating is more uniform and compact, and the thickness of the coating increases. Furthermore, the content of Zr and Y elements increases and the degree of crystallization of the coating is more complete. The formation of the solid solution of yttrium stabilized zirconia is promoted by cathode plasma discharge. In addition, the thermal insulation temperature increases as ZrO₂ nano-particles are added to the electrolyte. After 1 000 cycles of thermal shock, there was no cracking in the coating surface layer, which indicated that the CPED coating with ZrO₂ nanoparticles addition possessed a good thermal shock resistance.

The as-cast pure magnesium (Mg), with a purity of 99.99%, was hot-extruded at 300 °C to prepare a Mg bar with a diameter of 8 mm. The microstructure and mechanical properties of the sample before and after extrusion were investigated. The results show that the as-extruded microstructure is obviously refined with a large number of subgrains rather than equiaxed grains. A great number of (102) tensile twins can be observed significantly in the microstructure at the temperature. Mechanical properties including yield strength (YS) and ultimate tensile strength (UTS) increase greatly but uniform elongation (UE) decreases slightly as a result of work hardening.

Dense Fe-Al-Cr coatings with approximately 50 μm in thickness are successfully prepared on the 1045 carbon steel substrates via a laser cladding process. Proper Cr content (5 at% Cr) will lead to decrease in the melting point, and improves the viscosity of the liquid and the nucleation rate of the molten pool, leading to refining grains of the solidification structure. As a result, the Fe-29Al-5Cr laser cladding layer exhibits the best hardness, plasticity properties, and wear resistance at 400 °C. Excessive Cr for the Fe-29Al-7.5Cr coating leads to the formation of Cr2Al in the grain boundaries and thermal vacancies during the solidification process, resulting in inferior mechanical properties and poor tribological behavior.

A novel semisolid micro fused-casting (MFC) for preparing A356 alloy strips is proposed, and the effects of process parameters of pouring temperature on the microstructure and properties of A356 alloy strips are investigated. MFC means that the semisolid metal slurry was pressed out from the outlet of bottom of crucible to the movable plate, and directly solidified and formed layer by layer. The microstructure and properties of A356 semisolid alloy slurry were influenced by the cooling conditions. Results show that the aluminu alloy A356 strip samples fabricated by micro fused-casting had good performances and uniform structures with the pouring temperature at 595 °C and the substrate movement speed at 18 mm/s. The fine grains of the primary α-Al phase with average grain size of 53 μm and shape factor up to 0.72 was obtained, the ultimate tensile strength of the aluminum alloy A356 strip reaches 243.79±3.91 MPa, while the average vickers hardness is 82.65±1.86 HV.

The effects of aging time and temperature on the formation and growth behavior of interfacial intermetallic compound (IMC) of Sn-16Sb/Cu(wt%) solder joints prepared by using dip soldering were investigated. The results show that the major IMCs between Sn-16Sb solder and Cu substrate after thermal aging are Cu₃Sn and Cu₆Sn₅. The thickness of the interfacial IMC in Sn-16Sb/Cu is linearly against the square root of aging time, which indicates that the growth of IMC is mainly controlled by diffusion between Cu and Sn atoms. By using linear regression method, the growth rate constants of interfacial IMC layers are 1.254×10^-18, 8.821×10^-18 and 1.22×10^-17 m²s^-1 for Sn-16Sb/Cu joints aged at 120, 150 and 170 °C, respectively. Besides, the activation energy of the interfacial IMC growth was also calculated to be 68.27 kJ/mol. The IMC grain diameters after aging treatment increase with the increasing aging time, with i e, d = 0.492t ^0.106, d = 0.543t ^0.143 and d = 0.290t ^0.263 for aging temperatures of 120, 150 and 170 °C, respectively. Besides, by using nanoindentation, the softening of Sn-16Sb solder was found during aging treatment. Moreover, the U-shape evolution of the values in hardness and Young's moduli was found in this work.

Two novel non-fullerene small molecule acceptors were prepared with the conjugated backbone of 5H-fluoreno[3, 2- b:6, 7- b’] dithiophene carrying the electron deficient unit of dicyanomethylene indanone (DICTFDT) and rhodanine (TFDTBR), respectively. The two acceptors exhibited excellent thermal stability and strong absorption in the visible region. The LUMO level is estimated to be at -3.89 eV for DICTFDT and -3.77 eV for TFDTBR. When utilized as the acceptor in bulk heterojunction polymer solar cells with the polymer donor of PBT7-Th, the optimized maximum power conversion efficiency of 5.12% and 3.95% was obtained for the device with DICTFDT and TFDTBR, respectively. The research demonstrates that 5H-fluoreno[3, 2- b:6, 7- b’] dithiophene can be an appealing candidate for constructing small molecular electron acceptor towards efficient polymer:non-fullerene bulk heterojunction solar cells.

To decrease the modulus and increase the mechanical properties of recycled PET by introducing the flexible segments, the recycled polyethylene-terephthalate (PET) was modified by the chain extender produced with 2, 4, 6, 8-tetramethyl-2, 4, 6, 8-tetra (2, 3-epoxypropoxy) propylcyclotetrasiloxane by the hydrosilylation reaction. Different percentages of chain extender were used in order to investigate the effect of chain extender content on the modulus of PET. The dynamic mechanical analysis was performed on PET samples, which showed that T _g of PET was firstly raised by the addition of chain extender and then decreased. Small amplitude shearing test performed on PET samples confirmed that the addition of the flexible segments could remarkably decrease the modulus of PET, which would be helpful for the extrusion process. The entanglements from branches were also influenced by the addition of extender.

In order to investigate how to enhance the teeth fracture resistance after the post and core treatment, an in vitro study was conducted to measure the fracture resistance of endodontically treated teeth restored with cast post and core with two kinds of surface treatment technology and acid etching preparation on the dentinal surface. Sixty-four recently extracted human single-rooted first premolars were endodontically treated and sectioned approximately 1.5 mm above the cementoenamel junction to remove the coronal portion. Each specimen received a cast post, core build-up and a metal alloy crown restoration. All teeth were randomly divided into the smooth surface post, core repair group, the sand blasting surface post, and core repair group, each group was divided into 10 s, 30 s, 60 s acid corrosion treatment group and control group. In acid test groups, an acid etching solution was applied for 10, 30 and 60 seconds, respectively, to the root canal wall surface. Each specimen was embedded in acrylic resin block and tested in an electronic universal testing machine. Fracture loads results showed that canal acid etching could increase teeth fracture resistance strength both in smooth groups and sandblasting group, and achieved the best effect when acid etching for 30 s. Sand spray treatment on the surface of the cast metal post can improve the flexural strength of the teeth after postcrown restoration. Acid etching on the root canal wall surfaces and sand spray treatment on the surface of the cast metal post can improve the flexural strength of the root after post-crown restoration. Therefore, these two methods could be used to strengthen the tooth fracture resistance, and maintain the long-term therapeutic effect of cast post and core restoration.