Recrystallized Silicon Carbide Tubular Ceramic Membranes

Recrystallized silicon carbide (R-SiC) tubular ceramic membranes are high-performance inorganic separation membranes manufactured from high-purity SiC (≥99%) via a recrystallization sintering process. They feature an asymmetric multilayer structure consisting of a support layer, an intermediate layer, and a separation layer. The support material exhibits excellent mechanical and thermal properties, while the separation layer provides precise filtration accuracy and ultra-high flux. The membranes combine outstanding chemical stability, high temperature resistance, and superior mechanical strength, making them widely used in solid-liquid separation, material concentration, and advanced wastewater treatment.

The key to R-SiC membranes lies in the recrystallization sintering process - at temperatures above 2400°C in a vacuum environment, silicon carbide particles undergo a phase transition from solid to gas and back to solid, forming neck connections via an evaporation-condensation mechanism. This creates a highly interconnected porous structure in the separation layer. The entire membrane layer is made of pure SiC without any sintering aids. The separation layer thickness is approximately 120 μm, with a narrow pore size distribution covering both microfiltration (MF) and ultrafiltration (UF) ranges (0.04 μm - 1.0 μm), enabling precise solid-liquid separation. The support layer has a relatively high density (porosity ≤ 17%), ensuring the structural integrity of the overall element.

R-SiC membranes resist strong acids, strong alkalis, and aggressive oxidising agents (ozone, sodium hypochlorite, hydroxyl radicals, etc.) across the full pH range of 0-14. This tolerance allows for a broad choice of cleaning chemicals and enables frequent, high-intensity chemical cleaning without degrading the membrane layer.

The naturally hydrophilic surface (contact angle only 0.3°) delivers a pure water flux 3-5 times higher than that of conventional alumina or zirconia membranes, significantly reducing membrane area requirements and system footprint. Additionally, the surface carries a negative charge at pH > 3, which repels negatively charged contaminants such as bacteria, oil droplets, and proteins, effectively slowing down fouling.

The support material exhibits a flexural strength of 90-100 MPa at room temperature, which increases to 100-110 MPa at 1200°C - demonstrating exceptional load-bearing capacity under elevated temperatures. With a crushing strength of 300 MPa, hardness of 1800-2000 kg/mm², and fracture toughness of 1.8-2.0 MPa*m¹/², the membrane element ensures long-term reliable operation under harsh conditions.

The material offers high thermal conductivity (35-36 W/(m*K) at 1200°C) and a low coefficient of thermal expansion (4.6 × 10⁻⁶ /°C), resulting in excellent thermal shock resistance that withstands rapid temperature fluctuations. The maximum operating temperature reaches 1650°C (oxidising atmosphere), far exceeding that of conventional ceramic membranes, making it suitable for high-temperature filtration and reaction environments.

Under normal maintenance, the design service life reaches 3-5 years. Low operating pressures (0.1-0.3 MPa) reduce energy consumption by 30%-50%, while efficient backwashing and CIP (clean-in-place) procedures keep maintenance simple and cost-effective.

• Operating pressure: Typically 0.1-0.3 MPa, low transmembrane pressure ensures energy efficiency
• Backwashing: Periodic backwashing with permeate or clean water restores over 90% of the initial flux
• CIP cleaning: Compatible with NaOH, HNO₃, NaClO, and other agents; can withstand aggressive and frequent cleaning cycles without shortening membrane life
• End-of-life disposal: The membrane can be fully incinerated or recycled, producing no secondary pollution - environmentally friendly

Recrystallized silicon carbide tubular ceramic membranes offer a compelling combination of full-pH tolerance, ultra-high flux, superior high-temperature strength (increasing at 1200°C), a low coefficient of thermal expansion, and a maximum operating temperature of 1650°C. These attributes establish R-SiC membranes as an indispensable technology in the advanced membrane separation sector. They are particularly suitable for challenging applications involving highly corrosive fluids, high temperatures, oily streams, or particle-laden media. By reducing both capital investment and operational expenses while improving permeate quality and system reliability, R-SiC membranes are poised to play an increasingly significant role in emerging strategic fields such as new energy, fine chemicals, and environmental remediation. As manufacturing technologies continue to mature, their adoption is expected to expand further across diverse industrial sectors.