Co:MgAl₂O₄ nanopowders were synthesized via reverse-strike co-precipitation, and highly transparent Co:MgAl₂O₄ ceramics were fabricated via vacuum sintering and HIP post-treatment. The influence of the amount of ammonium carbonate addition on the properties of the as-synthesized precursor, nanopowders and ceramics were investigated. The result shows that the volume of ammonium carbonate has an impact on the dispersity of Co:MgAl₂O₄ nanopowders and the optical quality of ceramics. The agglomeration of Co:MgAl₂O₄ nanopowders is affected due to the final pH value, and the nanopowders obtained at 0.5 L ammonium carbonate appear less agglomeration. The optimum optical quality of final Co:MgAl₂O₄ transparent ceramics with 0.5 L ammonium carbonate can be obtained, having a high in-line transmittance of 84.4% at 400 nm and 86.9% at 1 100 nm, as well as the average grain size of 21.3 μm.

Si₃N₄-SiC_w composites were prepared via a sinter-hot isostatic pressing (sinter-HIP) process with Yb₂O₃-Al₂O₃ as sintering additives. The effect of titania (TiO₂) addition on the densification and mechanical properties of Si₃N₄-SiC_w composites was investigated. The results show that the addition of titania enhances the densification of Si₃N₄-SiC_w composites. The flexural strength, fracture toughness and Vickers hardness of Si₃N₄-8%SiC_w composites firstly increase and then decrease with increasing titania content. Si₃N₄-8%SiC_w composites containing 3% TiO₂ have a near-theoretical density and optimal mechanical properties (i.e., the relative density of (99.5±0.1)%, the flexural strength of (1 301±87) MPa, the fracture toughness of (7.8±0.1) MPa·m^1/2, and the Vickers hardness of (16.2±0.1) GPa). The formation of SiO₂ and TiN based on the in-situ reaction between TiO₂ with Si₃N₄ contributes to the improvement of the interfacial strength of bonding between SiC whisker and Si₃N₄ matrix as well as the mechanical behaviors of the composites.

Effect of friction-induced surface damage on the dissolution behavior of borosilicate glass was investigated by optical microscopy, reciprocating ball-on-flat tribometry, and optical profilometry. The results show that the corrosion behaviors of borosilicate glass are sensitive to the type of friction-induced subsurface damage. An enhanced dissolution rate at the wear track appears when forming the subsurface densification of glass and disappears as thermally annealing the wear track at (0.9×T_g) K for 2 h. In contrast, an enhanced dissolution volume at the wear track still occurs when forming the subsurface cracking of glass under given tribological conditions and does not disappear after thermally annealing the wear track at (0.9×T_g) K for 2 h, but disappears only when thermally annealing at a higher temperature for a longer duration.

Ultra-thin electronic glass becomes popular due to the rapid development of electronic information technology, and electronic glass tends to be large, thin and flexible. The development of comprehensive energy supply and energy regulation method for the large tonnage electronic glass furnace to ensure the melting quality of electronic glass is a premise of realizing the large-scale and stable production of high-quality electronic glass. In this paper, the operating state of electronic glass furnace with different electric power ratios was analyzed via numerical simulation. The influence of electric energy ratio on the glass melting quality, heat transfer efficiency and working environment of electrode was investigated. The results show that energy transferred from combustion space is obviously reduced at an electric energy ratio of 67.7%, and it is more difficult to gain the high-temperature glass at the surface of glass tank. Moreover, the maximum electric current density of electrodes is the serviceability limit of electrode materials in a total electric power range of 1 300-1 400 kW, greatly accelerating the electrode erosion. The better glass melting quality is obtained when an electric energy supply ratio is 57.89%. Moreover, the efficient and stable operation of electronic glass furnace during service period was obtained.

To improve the application efficiency of steel fibres and the properties of ultra-high performance concrete (UHPC) composites, the formation and optimization of fibres content and its 3D network in UHPC matrix were investigated. A basic UHPC mixture was designed using a modified Andreasen & Andersen (MAA) particle packing model. The formation of fibres network and the effect of steel fibres on the UHPC properties were analyzed. The experimental results reveal that casting at one side of the mould benefits the orientation of steel fibres, and a higher steel fibres content results in more disordered orientation of steel fibres and increases the possibility of fibres connection, which is not conductive to the development of particle packing structure and workability of UHPC. The addition of steel fibres contributes to the development of UHPC mechanical properties, but the excessive addition of steel fibres will cause the reduction of the fibre application efficiency. The use of steel fibres has both positive and negative effects on the UHPC properties, thus there is a need for the optimization of steel fibre 3D network to improve the fibre application efficiency and obtain expected UHPC products.

Ultra-high performance concrete (UHPC) with excellent performance was prepared with two kinds of ultra-fine copper-plated steel fibers with different shapes. The multiple high-speed impact compression experiments of UHPC were carried out by a split Hopkinson pressure bar. The effects of strain rate, impact times, steel fiber types and hybrid fibers on the impact resistance of UHPC were investigated. The dynamic damage evolution of UHPC under multiple impact was characterized by X-ray computed tomography and the damage degree of UHPC was quantitatively analyzed. The results show that the reinforcing effect of end hook steel fibers on UHPC is a slightly better than that of straight steel fibers, and the material with 1% straight steel fibers and 2% end hook steel fibers has the optimum static and dynamic mechanical properties. An improved dynamic increase factor model was proposed. It is indicated that the simulated data by this model are in reasonable agreement with the experimental results.

Compressive mechanical behavior of the steel-polypropylene hybrid fiber reinforced ultra-high performance concrete (SP-UHPC) with respect to the impacts of fiber types, fiber aspect ratio and volume fraction was investigated. The monotonic and cyclic compression tests were both conducted. Besides, the fiber reinforcing mechanism was analyzed by scanning electron microscopy. The results demonstrate that the inclusion of steel-polypropylene hybrid fiber can enhance the compressive mechanical properties of UHPC. Compared to the UHPC without fiber addition, the SP-UHPC shows a ductile failure mode with improved peak stress, peak strain, toughness and alleviated stiffness degradation process. Based on the experimental data, a constitutive model was proposed for SP-UHPC subjected to cyclic compression, which could be used to predict the mechanical response of the SP-UHPC at various fiber parameters.

Strain-hardening and cracking behavior of UHPC incorporating hydrophobic polyethylene (PE) fibers modified at different concentrations of silane coupling agent (SCA) solution were investigated. The results indicate that for UHPC with a low water binder ratio (0.18), the fiber modified with 3% SCA solution has a better strain-hardening behavior and a more significant multi-cracking behavior. The mechanism for the effect of the surface modification of PE fibers on the strain-hardening of UHPC is due to an effective chemical bonding between the functional groups of SCA attached on the surface of PE fibers and matrix, in which the free hydroxyl group condenses with C-S-H, and the hydroxyl group forms a complexation bond with Ca²⁺ in Ca(OH)₂.

Limestone calcined clay cement (LC³) was used to prepare three kinds of ultra-high performance concrete (UHPC) with different calcined clay contents, and the effects of calcined clay contents on the static and dynamic mechanical properties of UHPC were evaluated by dynamic mechanical analysis, scanning electron microscopy-energy disperse spectroscopy and mercury intrusion porosimetry. The results show that compared to the reference group, the maximum enhancements of loss factor, loss modulus and storage modulus of UHPC incorporated with LC³ of 46.7%, 50.0% and 102.0%, respectively. The slump flow of UHPC is decreased by 20.5%, 26.9%, and 29.2% when calcined clay content is increased from 0 to 35%, 40% and 45%, respectively. Also, compared to the reference group, the compressive and flexural strengths of UHPC incorporated with 35% calcined clay are increased by 13.78% and 27.11%, respectively. In addition, UHPC incorporated with 30%-40% calcined clay has better static and dynamic mechanical properties, environmental friendliness, as well as economic efficiency.

Textile reinforced ultra-high performance concrete (TR-UHPC) with carbon textile and steel fiber was prepared. The tension stiffening behavior of TR-UHPC and synergistic effects of textile and short fibers were investigated by means of experimental and numerical studies on the mechanical characteristics of textile, UHPC, interfacial bonding and TR-UHPC composites. The prepared TR-UHPC exhibits a pronounced strain-hardening behavior with multiple cracking. The tensile strength, post-crack stiffness and ductility are apparently improved. The tensile behavior of TR-UHPC is mainly affected by the bridging mechanism of steel fibers as the volume fraction of steel fiber is increased from 0.5% to 1.5%. The bonding characteristics between textile and UHPC governs as the fiber volume fraction further increases to 2.0%. The numerical model incorporates the primary mechanisms including tensile properties of textile, stress-crack width relationship of UHPC and interfacial bonding between textile and UHPC. It is indicated that the simulated data by the model are in reasonable agreement with the experimental results.