Y₂O₃:xBi³⁺ (x=0.05-1.0% (mole fraction)) phosphors were synthesized by a solid-phase reaction route. Effect of Bi³⁺ concentration on the phase composition, microstructure and photoluminescence (PL) performance was investigated. The results show that the lattice parameter and cell volume of Y₂O₃ host increase with the increase of Bi³⁺ concentration. In addition, the phosphors are equiaxed grains, and the grain size increases gradually from 250 to 600 nm with the Bi³⁺ concentration increasing. The emission spectra of Y₂O₃:Bi³⁺ phosphors excited by ultraviolet light (λ_EX=335 nm) are composed of three broadband emission spectra centered at 370 nm, 410 nm and 483 nm. The ultraviolet-emission at 370 nm and blue-light emission at 410 nm appear due to ³A_u→¹A_g and ³E_u→¹A_g electron transitions of S₆ sites of Bi³⁺, respectively. The blue-green emission at 483 nm occurs due to ³B→¹A electron transition of C₂ sites of Bi³⁺. The Y₂O₃:0.25%Bi³⁺ phosphor shows the optimal PL performance. The concentration quenching occurs when Bi³⁺ concentration is higher than 0.25% due to the dipole-dipole interaction between Bi³⁺ ions. The color coordinate of Y₂O₃:0.25%Bi³⁺ is (0.159 2, 0.218 1), and the color rendering index Ra is 69.27, indicating that the as-synthesized blue-green phosphors have a broad application prospect in the field of white light-emitting diode.

(Ba_0.97Eu_0.03)(Mg_(1-x)/3Nb_2(1-x)/3Zr_x)O₃ phosphors were prepared via a solid-state route. The crystal structure and luminescent properties were investigated. A phase structure transformation from hexagonal to cubic occurs as Zr⁴⁺ content (x) increases to 0.05, thus weakening the luminescence properties. When x>0.05, the crystal structure is cubic. The introduction of Zr⁴+into the phosphor increases the tilting of BO₆ octahedron, which makes the energy level split and broadens the bonding energy range of B—O bond, thus enhancing the absorption of near ultraviolet (NUV) light and increasing the intensity of charge transfer band (CTB). The CTB intensity increases the sensitization effect of the host on Eu³⁺ and improves the luminescent properties in NUV and blue light regions. The chromaticity coordinate of the phosphor shifts from (0.658, 0.342) to (0.642, 0.358) due to Zr⁴⁺ substitution, indicating its potential application in the excitation of NUV (395 nm) LED chips.

Fe³⁺ doped α-Al₂O₃ particles with average sizes of 12 nm, 82 nm, and 229 nm and the same Fe content were prepared by a chemical precipitation method. The lattice parameters, microstructure, energy gap, and the luminescence performance were investigated. The results show that Fe³⁺ doped α-Al₂O₃ particles with different sizes are pure α-Al₂O₃ phases. The energy gap decreases and the lattice parameters first decrease and then increase with increasing the particle size. The lattice parameters of the sample with an average particle size of 12 nm are a=b=0.478 3 nm, c=1.304 7 nm, the energy gap is 4.06 eV, and the sample exhibits a good luminescence performance under 305 nm excitation. Moreover, Fe³⁺ doped α-Al₂O₃ nanoparticles with an average particle size of 12 nm disperse well and have a narrow size distribution (5-55 nm), and can form a stable colloid suspension in ultrapure water.

Ti-Al₂O₃ composite samples were prepared using sintered alumina and metallic titanium as the raw materials and phenolic resin as the binder. The samples were placed in a graphite crucible and sintered in a carbon tube furnace at 1 600 ℃ in flowing nitrogen. The phase evolution of the sintered samples was analyzed. The results showed that titanium firstly reacted with nitrogen to form titanium nitride. When the content of titanium reached 12%, it can also be fully nitrided. The titanium nitride formed was mostly a flaky structure, and the rest was whisker-like. A small amount of carbon monoxide in nitrogen atmosphere can diffuse into the sample, and form a stable titanium carbonitride solid solution. For samples with 3% titanium, the strength of the sample with 3% graphite decreased by 50%. Similar titanium carbonitride solid solution was formed in Ti-Al₂O₃ samples with and without graphite. Al₅O₆N was found in the corundum sample, but not in Samples with titanium. Alumina can exist stably in the Ti-Al₂O₃ samples with metal titanium added. The phase evolution mechanism model of Ti-Al₂O₃ samples was established.

In order to solve the problem of high porosity of refractory castables due to the poor water wettability, graphite flakes (GF) were coated by TiC using titanium powders (Ti) via self-propagating high-temperature synthesis (SHS). The phase composition and microstructure of the products were investigated by X-ray diffraction, scanning electron microscopy and energy dispersive spectrometry. The water wettability of TiC-coated GF (CT) was evaluated by Zeta potential measurement, sedimentation test and water contact angle measurement, respectively. The results show that TiC coating with a continuous and uniform thickness of 763 nm is formed on the GF surface. Compared to uncoated GF and the sample with n(GF):n(TiC)=1:1 (GT) prepared by mechanical mixing, the sample CT has the maximum Zeta potential value, no delamination occurs when the sample CT disperses in water, and the contact angles with water is 26°. In addition, the physical properties, oxidation resistance and slag corrosion resistance of Al₂O₃-MgO refractory castables with GF, GT, and CT as well as castables without graphite (labled as CGF, CGT, CCT, and C0, respectively) were also determined. The apparent porosity of CCT castable is 13.4%, which is 39.37% and 11.26% lower than that of CGF and CGT castables, respectively. The decarbonized depth of CCT castable is 8.0 mm, which is 14.89% and 8.05% lower than that of CGF and CGT castables, respectively. The slag corrosion area of CCT castable is 29% , which is 19.44%、6.45% and 3.33% lower than that of C0, CGF and CGT castables, respectively.

Industrial silica bricks were obtained in tunnel kiln by sintering at 1450 ℃ with crystalline silica as a raw material, and lime milk and iron scale as binders. The creep in compression tests was carried out on 7 fired bricks with different residual quartz contents according to the standard GB/T 5073—2005. The results show that the test can be divided into three stages from room temperature to the end of creep according to the change of deformation rate. The distinct expansion stage occurs from room temperature to 900 ℃, and the expansion is positively correlated to the residual quartz content. The distinct shrinkage stage appears from 900 to 1 450 ℃, and the shrinkage is negatively correlated to the residual quartz content. The creep tends to be steady at 1 450 ℃, and the samples with a low residual quartz content show a better stability. The creep curve of silica brick obtained based on GB/T 5073 is not consistent with the expansion or contraction during the whole heating process. At the creep temperature (i.e., ≤1 470 ℃), cristobalite will translate to tridymite, and the samples with a low residual quartz content tend to be negative (i.e., shrinkage), while those with a high residual quartz content are positive (i.e., expansion). The residual quartz content has an influence on the creep process. It could be questionable to evaluate creep high-temperature performance of silica brick just according to GB/T 5073—2005 creep test method.

There are two inherent drawbacks in designing ultra-high performance concrete (UHPC) by the modified Andreasen-Andersen (MAA) model, i.e., unproven reliability under wet conditions and ignorance of disturbing effect of steel fiber on particle packing skeleton. In this work, the D-optimal mixture design model and the equivalent spherical diameter of steel fires were adopted to verify and optimize the MAA model, and the properties of the optimized UHPC were utilized to verify the feasibility of the new proposed method. The results reveal that the MAA model is also suitable to be utilized under wet conditions. Moreover, the equivalent spherical diameter of steel fibers (L=13 mm, d=0.2 mm) is 5.65 mm, which is determined by evaluating the effect of screening particles and steel fibers on wet packing density. In addition, the employed steel fibers that are treated as spheroidal particles can be implanted into the MAA model for the optimized design of new UHPC, which has a densely packing structure and an admirable compressive strength.

A nano-, micron-, and millimeter-sized multi-scale fiber composite reinforced ultra-high performance concrete (UHPC) was proposed. The mechanical properties of UHPC can be improved by suppressing the defects of different sizes with different fibers. Carbon nanotubes, micron-sized calcium carbonate whiskers, and millimeter-sized steel fibers were used to design 7 groups of UHPC specimens. The axial tensile and compressive stress-strain curves of UHPC were measured. The results show that the initial crack strength and strain of UHPC are determined by the millimeter-sized steel fiber in a macro-scale. However, micron- and nano-sized fibers have little effect on the initial crack strength and strain. The addition of calcium carbonate whiskers and carbon nanotubes changes the tensile behavior of UHPC specimens after cracking, thus enhancing the strain hardening capability. The tensile and compressive properties of UHPC with different sizes of fibers are similar. The addition of calcium carbonate whisker has a positive effect rather than that of carbon nanotube when mixing with steel fiber. The effect becomes optimum when adding calcium carbonate whiskers and carbon nanotubes.

Direct tensile tests were carried out on three types of ultra-high performance concrete (UHPC) specimens with different thicknesses of arc-shaped dog bone shape, and the relationship among axial tensile stress, strain, and crack of UHPC was analyzed. The results show that the tensile strength of UHPC increases slightly, the ability to limit crack development increases, the strain capacity decreases significantly, and the strain softening rate increases as the specimen thickness decreases from 100 mm to 30 mm. When the crack width is less than 0.2 mm, the post-crack stress of UHPC increases slightly. After the main crack forms, the crack development rate and the post-crack stress decline rate increase correspondingly. The tensile strain value is fitted from the main crack width, and it is indicated that the main crack development process of UHPC specimen be in reasonable agreement with the strain softening stage.

Ultra-high performance concrete (UHPC) was designed with different replacement percentages of manufactured sand, i.e., 0%, 25% 50%, 75%, and 100% (in mass fraction). The properties of the UHPC, including the quasi static and dynamic mechanical properties, were examined. The results show that the compressive strength of UHPCs with manufactured sand as fine aggregates is similar to that of the reference mixture with only river sand. The UHPC with manufactured sand has superior dynamic mechanical properties. The UHPC with manufactured sand has an effect on its strain rate, and the dynamic increase factor has a logarithmic function relation with the strain rate. In addition, the finite element method was also employed to simulate the impact process of the UHPC with manufactured sand.