Papers by Keyword: Supercritical Carbon Dioxide

Abstract: This research explores the feasibility of utilising supercritical carbon dioxide (scCO₂) as a coolant coupled with minimum quantity lubrication (MQL) as a lubricant, to replace conventional coolant and lubricating fluids (CLF’s) in small diameter deep hole drilling (DHD) of austenitic stainless steel (AISI 304L). The study investigates the impact of scCO₂+MQL on hole quality, surface roughness, and tool wear parameters in comparison to high-pressure soluble oil cutting fluid (HPC). The motivation stems from the need to supply sustainable and environmentally conscious CLF alternatives within the machining industry, specifically addressing the reduction of dependence on traditional HPC’s.ScCO₂+MQL offers significant advantages under specific conditions, particularly with mid-range feed rates and higher cutting speeds. On average, drilling under scCO₂+MQL conditions achieved a success rate 71% as effective as when drilling with HPC, however the difference can be attributed to the set of cutting conditions optimised primarily for HPC, not for scCO2. The results indicate the viability of scCO₂+MQL and its ability to produce results comparable to HPC. It also emphasises the complexities of transitioning from traditional CLFs to sustainable alternatives like scCO₂+MQL in DHD processes. The outcomes present an encouraging case for the environmental and cost benefits associated with scCO₂+MQL. However, it also highlights the need for further investigation and optimisation, particularly in tool design, to enhance performance and address the existing challenges.

Abstract: In this article, the supercritical carbon dioxide (Sc-CO₂) was used as a medium for hot-drawing of F-III fibers. The conditions of hot-drawing were selected to be the temperature of 250 °C, pressure of 14 MPa, time of 60 min, and different tensions, which were 0, 3, 4.5, 6, and 7.5 g·d^-1, respectively. All samples including the untreated and treated F-III fibers were characterized by a mechanical tester and X-ray diffraction (XRD). Results showed that the Sc-CO₂ and applied tension could both promote the crystallinity and degree of orientation of F-III fibers at a temperature below the Tg of F-III fibers in Sc-CO₂. Moreover, compared with the untreated, the tensile strength and modulus of treated F-III fibers tended to increase with the increase of tension in the range of 0 ~ 6 g·d^-1. In summary, this provided a new treatment mode for the hot-drawing of fibers.

Abstract: In view of the increasing demand for lithium and the unequal distribution of lithium deposits worldwide, local deposits such as the zinnwaldite deposit at Zinnwald/Cínovec are increasingly coming into focus. It could be shown that especially the direct carbonation process with supercritical CO₂ represents a promising approach for a technical implementation due to the low chemical consumption as well as the high selectivity for lithium. Moreover, besides primary ore (zinnwaldite), the method is also suitable for recovering lithium carbonate from black mass, the lithium-containing fraction from lithium ion battery recycling.

Abstract: A facile surface modification method for PPTA-pulp was developed to improve the adhesion to rubber matrix. Tensile strength tests and SEM were used to evaluate the adhesion of PPTA-pulp with rubber matrix, and the results indicated that surface treatment of PPTA pulp in supercritical carbon dioxide fluid was an efficient method to increase interfacial adhesion between PPTA-pulp and rubber matrix. Attenuated Toyal reflectance Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to investigate the surface structure and composition of untreated and treated PPTA-pulp in supercritical carbon dioxide fluid. The results indicated that the interaction of macromolecules, the crystal structure and the surface composition of PPTA-pulp changed during supercritical carbon dioxide fluid, particularly for the surface morphology and composition.

Abstract: In recent years, supercritical carbon dioxide, as a green chemical solvent, is widely used. The surfactants for polymerization in supercritical fluids have become one of the important issues. This paper mainly discusses the mechanism and influence of the surfactants in supercritical carbon dioxide system. The choice and design principle of surfactants and the recent development of surfactants were introduced in detail.

Abstract: In recent years, tamarind seeds extracts are used widely in food, pharmaceutical and textile industry due to unique functions as cooking oil, antibacterial and thickening agent. In this study, a simple static technique is used to obtain the solubility of tamarind seed in supercritical carbon dioxide because there is no study on that yet. The solubility measured is performed at temperatures and pressures ranging from 40^oC, 60^oC, 80^oC and 3000psi, 5000psi and 7000psi respectively; resulting in mass fractions in the 6.00 x 10^-8 to 5.84 x 10^-7 range. The Chrastil model is used to correlate the experimental data. The oil yield extract in range of 0.0375 to 0.365g.

Abstract: Polyester fabric was pretreated with 3-aminopropyltrimethoxysilane (APTMS) through supercritical carbon dioxide (scCO₂) process before electroless copper plating. APTMS pretreated polyester fibers were characterized by contact angle. Deposit weight, surface morphology and electromagnetic interference (EMI) shielding effectiveness (SE) of electroless copper plated polyester fabrics were investigated. The results show that polyester fibers are covered with APTMS after APTMS modification in scCO₂ medium. Copper coatings on the polyester fibers are uniform after copper plating. Electromagnetic interference shielding effectiveness of the copper plated polyester fabric arrives at 60-80dB at frequencies ranging from 2 to 18 GHz.

Abstract: Using supercritical CO₂ as the foaming agent, rigid polyvinyl chloride (R-PVC) foam sheets were prepared in a continuous extrusion foaming system. The effects of dioctyl phthalate (DOP) on the rheological properties of PVC were investigated using a Brabender torque rheometer while other basic formula remained unchanged. The influences of DOP content on microstructure, mechanical properties and density of PVC micro foamed sheet were investigated with scanning electron microscopy (SEM). The results showed that the addition of DOP resulted in increased flexibility and the elongation at break of the foamed PVC sheet, while the mechanical properties of foamed PVC sheet decreased with the increase of DOP content, implying that excessive addition of DOP will cause gas escape and bubble coalescence in the foaming process. Low density PVC foam sheets with fine cell morphology were obtained when 2 phr DOP was added in PVCformula.

Abstract: Kenaf fibers were dyed with capsanthin using supercritical carbon dioxide. Response surface methodology, based on a three level and three variable small central composite design, was employed to obtain the best possible combination of dyeing time, temperature and pressure for maximum K/S value.The optimum conditions were as follows: dyeing time of 60 min, temperature of 119.99 °C and pressure of 30 MPa. Under these conditions, the K/S value was 17.54, which was similar to the value predicted by the model.

Abstract: A cleaning process for dyeing apparatus was investigated by employed a self-developed supercritical equipment. The solubility of C.I. Disperse Red 167 was evaluated with acetone, ethanol and carbinol in supercritical carbon dioxide at temperatures of 60, 80,100 and 120 °C and pressures ranging from 12 to 28 MPa. As revealed from the experimental results, the optimal cleaning conditions were as follows: cleaning temperature 100 °C, cleaning pressure 18 MPa, and cleaning time 40 min. Acetone was the most suitable cosolvent and the best cleaning effect was obtained when its concentration was 1%.