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Petal-like MgAl2O4 spinel was successfully prepared using a novel inorganic salt-assisted nonhydrolytic sol-gel method without a template and was employed as absorbent in the removal of the Congo red (CR). The effects of the inorganic salt type, heat-treatment temperature, and dwelling time on the morphology and phase composition of the petal-like MgAl2O4 spinel were investigated systematically. Results indicated that when Na2MoO4 was employed as the salt and the heat-treatment temperature and dwelling time were 600 °C and 5 h, respectively, the as-obtained petal-like MgAl2O4 spinel exhibited a highly uniform morphology with a thickness of 19–23 nm and a length of 240–280 nm. The N2 adsorption-desorption results revealed that the petal-like MgAl2O4 exhibited a large BET specific surface area of 161 m2g-1 with a pore volume of 0.24 cm3g-1. The growth mechanism of the petal-like MgAl2O4 is believed to be the formation of a two-dimensional layered network structure by the coordination between the condensation product of the magnesium aluminium bimetallic alkoxides and the ions in the salt. The as-prepared MgAl2O4 petal exhibited an effective adsorption capacity toward anionic dyes CR. The maximum adsorption capacity of CR onto the mesoporous MgAl2O4 petal was found to be 572.01 mg/g, it is showed the petal-like MgAl2O4 exhibit huge potential of application in the field of environmental remediation.

Novel Ni-doped Al2TiO5 emerald green ceramic pigments were successfully synthesized for the first time. Several characterization techniques (XRD, XPS, SEM, TEM, UV–Vis, and automatic colorimeters) were used to determine the phase composition and stability of the pigments, as well as the valence state of the doped nickel ion. The results show that nickel ion replaces the Al3+ in the aluminum titanate lattice in the form of Ni2+, which reduces the distortion of the octahedral structure. Ni-doping of the aluminum titanate lattice produces an excellent coloring effect and significantly promotes the synthesis and stabilization of aluminum titanate. The novel pigments have excellent color stability while maintaining exceptional coloring performance and thermal stability in a base glaze synthesized at 1200 °C. These pigments show considerable potential for high-temperature applications.

Foam ceramics were fabricated by using sand shale, steel slag and magnesite as raw materials and SiC as foam agent. Influences of magnesite on crystalline phases, porosity, mechanical properties and pore structures were investigated via XRF, XRD, high-temperature microscope, Micro-CT and fractal dimension. Magnesite, benefits the formation of diopside and reduces fractal dimension. When 5% magnesite additions is added, the foam ceramics exhibit the optimized properties: bulk density of 1.12 g/cm3, total porosity of 56.79%, closed porosity of 50.71%, bending strength of 13.43 MPa and fractal dimension value of 1.11. Formation mechanism of diopside phase based on Gibbs free energy is also discussed in this paper.

Foam ceramics with high strength were successfully fabricated by using sand shale and steel slag as the major materials and SiC as foam agent. The influence of raw materials ratio and heat treatment temperatures on crystalline phases, porosity, mechanical properties and pore structures was investigated via XRF, XRD, SEM, DTA-TG, Micro-CT. The results indicate that the raw materials composed of 94 wt% sand shale and 6 wt% steel slag enable the fabrication of foam ceramics possessing strength of 29.98 MPa, bulk density of 0.821 g/cm3, total porosity of 67.22%, closed porosity of 55.27% and thermal conductivity of 0.08 W/(m·K). Micro-CT result shows that the pores with an average size of 267.05 μm are isolated. Pore wall thickness conforms to normal distribution, and it ranges from 18 to 42 μm. The superior property makes it promising high-strength and lightweight material in application fields, including thermal insulation materials and lightweight building materials.

The formation of α-cordierite glass-ceramics in the MgO–Al2O3–SiO2 system without and with addition of B2O3 was investigated. Moreover, the effects of different contents of B2O3 on the crystallization behavior, structure variation, thermal and physical properties of glass-ceramics were studied, and the action mechanism of B2O3 was systematically discussed by XRD, FT-IR and XPS. The results show that a proper amount of B2O3 shortens the crystallization route and reduces formation temperature of α-cordierite, which further promotes the direct precipitation of α-cordierite in MAS system. The glass-ceramics undergo the phase transitions from intermediate phases of MgO·Al2O3·SiO2 and Mg0·6Al1·2Si1·8O6 to pure α-cordierite without the addition of B2O3. However, the pure α-cordierite directly precipitates in the glass-ceramics adding 4 mol% B2O3 without intermediate phases. Low B2O3 content (4 mol%) promotes the crystallization of α-cordierite, while high B2O3 content (8–12 mol%) inhibits it, which is accompanied by the increase of thermal expansion coefficient from 1.70 × 10−6 °C−1 to 3.72 × 10−6 °C−1 and the decrease of Vickers hardness from 9.4 GPa to 6.9 GPa. B2O3 is confirmed to be very important in controlling the crystallization process of α-cordierite in this glass-ceramics system, and this study is helpful for providing the reference value for others to choose B2O3 and its content.

Stabilized aluminum titanate fibers were prepared via nonhydrolytic sol-gel (NHSG) method through linear self-assembly of precursors. The results show that NHSG method generates the heterogeneous condensation with the formation of Al–O–Ti, Mg–O–Ti, Fe–O–Ti, Mg–O–Al, Fe–O–Ti bonds, which ensures that magnesium ions and iron ions can enter aluminium titanate lattice and stabilize it at 750 °C. Bimolecular associated structure of chlorotitanium ethoxide titanium precursor promotes the self-linear-assemble of all precursors, which enables the excellent spinnability of sol. Stabilized aluminum titanate fibers have excellent corrosion resistance. The thermal expansion coefficient of stabilized aluminum titanate ceramic is −0.142 × 10−6°C−1.

The zircon-based encapsulation carbon black (C@ZrSiO4) inorganic pigments with controllable size were successfully prepared by non-aqueous sol-gel method with the assistance of soft mechano-chemistry (SMC) activation precursors. The XRD and FT-IR results showed that the SMC activation enhanced the reactivity of precursors and facilitated the formation of ZrSiO4 phase with the calcination temperature at 900–1050 °C, indicating the successfully synthesis of pure ZrSiO4 phase. The average size of C@ZrSiO4 inorganic pigments significantly declined from 45.20 to 4.50 μm with the increase of SMC activation time of precursors, however, the L* values of pigments increased from 24.11 to 46.35. It was mainly because of the decreased amounts of protected carbon in ZrSiO4 matrix and the enhanced light reflectance, which lead to the slight color change from deep black to gray black tone. The colored glaze samples presented a black hue after applied in the ceramic glaze at 1200 °C. Moreover, the black hue intensity of glazed samples was higher than that of the corresponding C@ZrSiO4 inorganic pigments, indicating the prepared pigments have excellent tinctorial strength and hiding power. These results ensure that the obtained C@ZrSiO4 inorganic pigments possess the outstanding chromatic performance, excellent high-temperature stability, high chemical stability and suitable particle size, and exhibit great potential in the application of the industrial ceramic decoration.

High quality zirconia whiskers have been successfully prepared by molten salt method, using zirconium oxychloride (ZrOCl2·8H2O) and sodium phosphate tribasic dodecahydrate (Na3PO4·12H2O) as precursor and molten salt, respectively. The effects of types of molten salt and heat treatment temperature on the formation of zirconia whiskers were characterized by XRD, Raman, DTA-TG, FE-SEM, TEM, SAED and HR-TEM. When Na3PO4·12H2O is utilized as molten salt and the heat treatment temperature is 900 °C, the as-prepared zirconia whiskers with length ranging from 4 µm to 8 µm show an average aspect ratio of 25. The obtained ZrO2 whiskers with monoclinic structure are elongated along [010] direction and exhibit a smooth surface with no distinct defects. The XRD and Raman results reveal that the phase transformation from tetragonal zirconia to monoclinic zirconia occurs with the increased crystal size and the water quenching treatment can significantly reduce the content of sodium zirconium phosphate [Na9–4×Zrx(PO4)3] in the final product. The growth mechanism of zirconia whiskers is supposed to be a dissolution-precipitation process. Since the sodium zirconium phosphate [Na9–4×Zrx(PO4)3] effectively promotes the dissolution of zirconia in liquid molten salt, zirconia can grow into zirconia whiskers according to its anisotropy.

Monodispersed alumina powders were prepared via nonaqueous precipitation process using aluminum powders as aluminum source, acetic acid as precipitant. Effect of oxygen donor and solvent alcohol such as methanol, ethanol, isopropanol on the preparation of ultrafine alumina powders and the precursor reaction mechanism have been investigated by XRD, FT-IR, TEM, FE-SEM and performance tests of sintered bodies. The intermolecular condensation of methanol with the catalysis of Lewis acid aluminum methoxide leads to hydrolysis of aluminum methoxide, forming amorphous precipitates, dehydration polycondensation of aluminum hydroxide and resulting in serious agglomeration of precipitates and alumina powders, the worst morphology and properties of sintered body. The pulling electron effect and steric hindrance of isopropyl group make the structure of aluminum isopropoxide overwhelmingly stable and relatively arduous to be replaced by precipitant acetic acid, which results in underdeveloped crystallinity and agglomeration of both precipitates and alumina powders, poor morphology and properties of sintered body. The optimized oxygen donor and solvent alcohol is ethanol. Monodispersed, high crystallinity C4H7AlO7 precipitates and alumina powders can be obtained when ethanol is used as oxygen donor and solvent, and the highest relative density, mechanical properties and the most homogeneous microstructure was obtained. The density, flexural strength, volume resistivity, breakdown voltage and thermal expansion coefficient are 99.1% of TD, 128.0 ± 2.2 MPa, 9.8 × 1016 Ω∙cm, 45.2 kV/mm and 7.6 × 10−6 °C−1, respectively. Precursor reaction mechanism is deduced that aluminum powders react with oxygen donor alcohol to form aluminum alkoxide with the catalyst iodine, and then react with acetic acid to form crystal C4H7AlO7 precipitates. Nonaqueous precipitation method is expected to become a promising candidate for mass production of alumina powders.

High strength, lightweight mullite whisker skeleton porous materials were prepared via novel facile nonaqueous precipitation method. The phase transition process of precipitate, microstructures and phase compositions of samples, and effects of aluminum fluoride amount on morphologies and properties of mullite whisker skeleton porous materials were investigated by DTA-TG, FE-SEM, XRD, the acid solubility and compressive strength tests. The growth direction of the whisker was determined. The growth mechanism of mullite whisker and formation mechanism of skeleton porous material were also investigated. The results show that the mullite phase forms at a low temperature of 900 °C via nonaqueous precipitation method, due to the formation of Al-O-Si bonds in the precipitate. The formation of mullite whiskers is controlled by gas-solid reaction and the whiskers grow along [001] direction. Well-developed mullite whiskers interlacedly grow into skeleton porous material at 1100 °C. The optimum mullite whisker skeleton porous material with the optimized aluminum fluoride amount of 1.3 of theoretical amount exhibits attractive properties of low density (1.21 g cm−3), high strength (158.6 MPa), low acid solubility (1.58 wt%), low thermal expansion coefficient (1.6 × 10−6 °C−1) and low thermal conductivity (0.28 W/(m K)). This material has the mean pore size of 542 nm and pore size distribution of 32–865 nm. It shows attractive application prospects in filtering and biomedical applications.

A zircon encapsulated carbon black (C@ZrSiO 4 ) pigment with high color rendering was synthesized via facile non-aqueous acetic acid (NAA) assisted sol-gel method using carbon-containing precursors (zirconium n -propoxide and tetraethoxysilane) as in-situ carbon sources. The effects of the NAA amount and heat treatment temperature on the structure and properties of the synthesized encapsulation pigments were characterized by XRD, FT-IR, FE-SEM, HR-TEM, EDS, XPS and CIELAB colorimeter, respectively. The results showed that the C@ZrSiO 4 encapsulated pigments heating at 1000 °C for 2 h in N 2 atmosphere presented a dense and stable encapsulation structure as well as deep dark hue when the mole ratio of NAA and Zr (NAA/Zr) was 3:1, and the chromaticity values were L* = 21.20, a* = 0.56, b* = −0.09 and C ab = 0.57, respectively, which were contributed to the high homogeneity at atomic level in ZrSiO 4 sol and the tight bonding between carbon black carbonized by carbon containing group and zircon matrix. In addition, the pigment exhibited excellent chemical stability, thermal stability and tinctorial strength when it was used in water, acid, alkali, organic solvents and ceramic glaze. Especially, these pigments improved the utilization of raw materials and avoided the use of heavy metals or transition metals as coloring agent, which was an environment-friendly black ceramic pigment.

A monodispersed Al2O3@YAG: Ce core-shell phosphor has been synthesized by coating Y2O3: Ce film on Al2O3 particle. The phosphor has particles size of 60–120 nm and shows high dispersity due to the high dispersed Al2O3 particles prepared by nonaqueous precipitation method. The core-shell structured phosphor consists of a corundum core and a YAG shell. The Al2O3@YAG: Ce core-shell yellow phosphor presents high yellow emission. The light-emitting diode (WLED) based on this yellow phosphor and InGaN blue chip displays high white purity. This Al2O3@YAG: Ce core–shell phosphor can be viewed as a promising candidate yellow phosphor for white LEDs.

Alumina powders were prepared via a novel nonaqueous precipitation method with aluminum powders as aluminum source and anhydrous acetic acid as precipitant. The thermal decomposition and phase transformation of crystal precipitate and the influence of precipitate aging were investigated via TG-DTA-MS, XRD, TEM, BET, FE-SEM and performance tests of sintered bodies. The results show crystal precipitate C 4 H 7 AlO 7 transforms to amorphous Al 2 O 3 at 300 °C, and then to γ -Al 2 O 3 at 950 °C, and finally to α -Al 2 O 3 at 1050 °C. The particle size of α -Al 2 O 3 prepared at 1100 °C is 50–100 nm with BET surface area of 25.98 m 2 ∙g −1 . FE-SEM morphology of sintered sample at 1400 °C shows excellent sinterability of the α -Al 2 O 3 powders. Aging eliminates aggregation, and leads to highly homogenized and densified particles. It also affects the densification behaviour during sintering and further influences density, thermal expansion coefficient, flexural strength, volume resistivity and electric breakdown strength of sintered bodies