CaMgAl-layered double hydroxides (CaMgAl-LDHs) were synthesized by a co-precipitation method to prepare sodium oleate-modified, borate-intercalated CaMgAl-LDHs (O-CaMgAl-LDHs) using in-situ intercalation and modification, and the LDHs samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), and thermal gravimetric analysis (TGA). The FESEM observations showed that the as-prepared CaMgAl-LDHs had a lamellar structure with a particle size of 200~500 nm, while the O-CaMgAl-LDHs had a plate-like structure with a particle size of about 100 nm. TGA showed that O-CaMgAl-LDHs resulted in higher thermal stability at high temperature compared to CaMgAl-LDHs. O-CaMgAl-LDHs/ABS composites were prepared by adding O-CaMgAl-LDHs to acrylonitrile-butadiene-styrene resin (ABS) to test the resulting flame retardancy and mechanical properties, and the results showed that the limiting oxygen index (LOI) could increase from 18% to 26%, while the mechanical properties decreased significantly when the added fraction was 40% (relative to ABS). O-CaMgAl-LDHs, ammonium polyphosphate (APP) and expandable graphite (EG) were added into the ABS to prepare ABS composites, and the effects of different compositions on the flame retardancy and mechanical properties of the ABS composites were investigated. The results showed that, when adding 5 g of O-CaMgAl-LDHs, 1 g of APP, and 14 g of EG into 40 g of ABS, the LOI of the ABS composite reached 28.8%, and the composite prepared could meet the V-0 grade requirements of the UL-94 combustion test, while the flexural strength decreased only 21.9% compared to pure ABS, the smallest decrease compared to all of the other composites.

In this work, monodisperse spherical vaterite calcium carbonate (CaCO3) was synthesized at room temperature and atmospheric pressure through a simple and efficient "phase transfer-precipitation" route using phosphogypsum (PG) as raw material, sodium gluconate(SG) as phase transfer agent and CO2 as precipitator. CaCO3 samples were characterized by Field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and Dynamic light scattering (DLS). The composition of the as-obtained sample was almost monodisperse spherical vaterite CaCO3 by adjusting the concentration of SG and other operational conditions. The effects of SG and STP on the formation of CaCO3 microspheres were investigated. The results indicated that the existence of SG inhibited the nucleation and growth of calcite but promoted the formation of vaterite. The effects between SG and Ca2+ played a key role in the formation process of monodisperse spherical vaterite CaCO3. The existence of STP can effectively control the further growth and enhance the uniformity of the particle size of CaCO3 microspheres. These studies are promising for the industrial preparation and further commercial applications of monodisperse spherical vaterite CaCO3.

Calcium carbonate (CaCO₃) whiskers are promising materials for the high-value utilization of calcium-based resources. Here, aragonite whiskers were synthesized at a carbonation temperature of 90 °C using carbide slag ammonium leachate as the calcium source and CO₂ as the precipitant. The effects of control agents, carbonation temperature, Ca²⁺ solution feeding rate, CO₂ flow rate, and stirring speed on whisker morphology and aspect ratio were systematically investigated. Characterization via SEM and XRD revealed that the optimal conditions—carbonation temperature of 90 °C, Ca²⁺ feeding rate of 1.2 mL∙min⁻¹, ethanol addition of 2 mL, CO₂ flow rate of 150 mL∙min⁻¹, and stirring speed of 300 rpm—yielded uniform CaCO₃ whiskers with an average length of ~10 μm, an aspect ratio of ~24, and an aragonite purity of 99.42%. TEM confirmed that the whiskers are single crystals growing preferentially along the [001] direction. Hydroxyl groups were found to suppress lateral growth on the (200) facet, favoring elongation along the c-axis and enabling high-aspect-ratio whisker formation. These findings provide useful guidance for the scalable synthesis and industrial application of aragonite whiskers.

The difficult-to-remove CaSO₄ scale layer attached to an evaporator wall is a major problem in related industries.

Ultrafine nano-silica, with its smaller particle size compared to conventional nano-silica, is typically synthesized via gas-phase methods that require complex raw materials and processes. Here, we report optimized conditions for preparing ultrafine nano-silica via a precipitation reaction between fluosilicic acid waste and aluminum hydroxide. The optimal conditions determined were as follows: reverse feeding, surfactant addition at 3.0%, aluminum-to-silicon ratio of 2.00, reaction time of 30 min, reaction temperature of 90 °C, and stirring rate of 250 rpm. Under these conditions, ultrafine nano-silica with a uniform particle size of approximately 11 nm was successfully synthesized. Characterization of samples prepared by different feeding methods showed that the reverse feeding method yielded ultrafine nano-silica with superior performance indicators compared to the forward feeding method. Analysis of system changes during synthesis indicated that the feeding method influenced the acidic or alkaline environment of the substrate, affecting SiF ₄ hydrolysis and the subsequent dehydration and condensation of Si-(OH) ₄ monomers, leading to variations in silica particle agglomeration. Further, an analysis of the effects of alkyl chains in surfactants on the surfaces of silica particles, including -OH substitution or Si-O-Si bond cleavage, provided insights into the action mechanism of surface groups on ultrafine nano-silica particles.