MPa Pressure Research Articles

Development of polyvinyl chloride composites with enhanced mechanical properties using modified ceramic particles

Abstract The integration of ceramic particles into polyvinyl chloride (PVC) composites offers a promising approach and has garnered significant attention due to their potential for enhancing mechanical properties. This work investigated the development and characterization of PVC composites enhanced with modified ceramic particles. Ceramic particulates, clays, and other mineral rock materials (non-plastics) with activators were processed and incorporated into the PVC matrix at varying weight percentages (5–30 wt%) and particle sizes (40–80 µm). The ceramic–PVC mixtures were synthesized using hot compression molding under specific conditions of 75 MPa pressure and 160 °C temperature. Mechanical properties’ testing was conducted using ASTM D3039 standards, covering flexural, tensile, hardness, and impact tests for comprehensive characterization. Microstructural analysis was performed using scanning electron microscopy (SEM). Results indicated that ceramic reinforcement significantly enhanced the mechanical properties of PVC composites, with notable improvements in flexural strength, tensile strength, hardness, and impact resistance. Moreover, the impact of particle size was crucial, as microstructural analysis revealed improved interfacial bonding between ceramic particles and PVC matrix, particularly with finer particle sizes (40 µm), suggesting better stress transfer. The findings demonstrated that including modified ceramic particles can substantially improve the performance of PVC composites, making them suitable as high-strength construction tiles and impact-resistant flooring. Graphical abstract

Mechanistic insights and optimization of lignin depolymerization into aromatic monomers using vanadium-modified Dawson-type polyoxometalates.

Lignin, as the largest renewable aromatic resource, has significant opportunities for producing high-value products via catalytic depolymerization. However, its complex structure and stable chemical bonds present challenges to its transformation. This study explores the catalytic depolymerization of lignin to aromatic monomers by means of Dawson-type phosphomolybdovanadate polyoxometalates (POMs), understanding the underlying mechanisms. Furthermore, vanadium modification is employed to adjust the catalyst's oxidative and acidic properties, demonstrating that the vanadium content in Dawson-type POMs greatly influences monomer yield. The highest yield is achieved with H8P2Mo16V2O62 (V2). Optimal conditions include a reaction temperature of 150°C, 4h, an oxygen pressure of 1MPa, a methanol-to-water ratio of 8:2, and a mass ratio of the catalyst to the wood powder being 1:1, which leads to a total yield of aromatic monomers at 24%. POMs with high REDOX potential selectively oxidizes benzyl hydroxyl groups in lignin to benzyl carbonyl groups under the combined action of acidity and oxidation of polyacids. This weakens the βO4 bond and promotes CO bond cleavage. This approach, utilizing the tunable oxidative acidity of polyoxometalates to degrade lignin and produce various aromatic monomers, shows promising potential for lignin valorization and advancing a bio-economy based on lignocellulosic resources.

Improving the acidification kinetics, structural and sensory properties of low-fat yoghurt using high-pressure homogenization treatment

In this study, the impact of high pressure homogenization at 50, 100 and 150 MPa, on the physicochemical, rheological, textural, microstructural, and sensory properties as well as acidification kinetics of low-fat yoghurt was investigated. The results showed that a shorter fermentation time was obtained for yoghurt samples produced from high-pressure homogenized milk compared to the control sample. Homogenization of milk at high pressures resulted in an increase in the water holding capacity from 42.83 to 52.67 % and firmness from 1.01 to 1.45 N of yoghurt samples. The viscosity (Ƞ50) of yoghurt increased up to 0.446 Pa.s by milk homogenization and all yoghurt samples showed shear thinning behaviour. Microstructural analyses revealed that control sample had a typical open porous gel network of casein, while fewer porous and more dense protein network was observed in yoghurts from high pressure homogenized milk. The positive effect of the milk homogenization treatment on the sensory properties of yoghurts was observed as well. Principal component analysis visualized the effect of high pressure homogenization treatment and confirmed the close relationship between structural properties and overall acceptability. Among the tested low-fat yoghurts, high pressure milk homogenization at 150 MPa had the greatest potential for improving yoghurt structure, whereas 100 MPa pressure imparted the most acceptable sensorial properties.

Optimization of mechanical and physico-chemical properties of pseudo-oil palm trunk and coconut shell powder reinforced polyester composites for industrial applications

This study was to investigate the effect of pseudo-oil palm trunk (OPT) particles and coconut shell powder (CSP) on the mechanical and physico-chemical properties of a polyester composite. A factorial experimental design was employed to analyze the influence of particle size (315 and 630 µm) and OPT content (55–65%) with a fixed CSP content of 5%. The composite samples were produced using a cold molding technique under 1 MPa pressure, and their main properties were evaluated. The formulation with 315 µm particle sizes and 60% of OPT was the optimal for applications in building and automotive industries.

Performance study of oil-injection hermetic CO2 scroll compressor for automotive air conditioning system.

An oil-injection CO2 scroll compressor prototype and relative simulation model are developed for automotive Air Conditioning. The effects of oil to refrigerant mass ratio on the compressor performance are studied theoretically and experimentally. The results show that oil-injection is an effective way to improve the volumetric and indicated efficiencies, and reduce discharge temperature. The optimal oil-injection quantity varies at different conditions, and it decreases from 7.9% to 6.3% at fixed discharge pressure 10MPa when the suction pressure increases from 4.5MPa to 5MPa. Similar linear relationships are found and the different slopes of the line are exhibited at fixed suction and discharge pressure separately. Numerical results show that oil-injection has little influence on pressure in working chamber during suction and discharge process, but it can slow up the rising of pressure in compression process and reduce the salient of pressure at the end of compression process.

Effects of high-pressure and CaCl2 pretreatments on the salt taste-enhancing activity of hydrolysate derived from spent hen meat.

High-sodium intake has been proven to bring serious risks to public health. A potential sodium substitute of salt taste-enhancing hydrolysate (STEH) of protein has been focused on recently. The salt taste-enhancing activity (STEA) of STEH still needs to be improved. High-pressure and calcium chloride (CaCl2) pretreatments were reported to affect proteolysis and promote the release of bioactive peptides. Hence, we investigated effects of high-pressure and CaCl2 pretreatments on hydrolysis and STEA of STEH derived from spent hen. The pretreatments significantly influenced STEA of spent hen meat hydrolysate (SHH), especially 200 MPa pressure and 80 mmol L-1 CaCl2 pretreatments increased 27.1% salt taste intensity of SHH compared to that of blank (without pretreatments) according to sensory evaluation, the SHH umami also increased after pretreatments. In SHH, the proportion of peptides < 1000 Da increased up to 79.37% after the pretreatments compared to 73.68% of the blank. The degree of hydrolysis (DH) increased to 19.45% for moderate high-pressure (200 MPa) from 18.02% for blank, and the DH decreased after higher high-pressure and CaCl2 pretreatments, especially for CaCl2 in 80 mmol L-1. The change in particle size distribution of SHH has similar trends to DH. High-pressure and CaCl2 pretreatments increased STEA of SHH by affecting hydrolysis process. The STEA increase may be related to increased small-peptide proportion in SHH. Meanwhile, moderate high-pressure may promote protein unfolding and further increase DH according to particle size distribution of SHH. The combination of proteolysis and pretreatments of high-pressure and CaCl2 is a promising method to produce STEH. © 2024 Society of Chemical Industry.

High-Pressure Processing Influences Antibiotic Resistance Gene Transfer in Listeria monocytogenes Isolated from Food and Processing Environments.

The study aimed to assess the high-pressure processing (HPP) impact on antibiotic resistance gene transfer in L. monocytogenes from food and food processing environments, both in vitro (in microbiological medium) and in situ (in carrot juice), using the membrane filter method. Survival, recovery, and frequency of antibiotic resistance gene transfer analyses were performed by treating samples with HPP at different pressures (200 MPa and 400 MPa). The results showed that the higher pressure (400 MPa) had a significant effect on increasing the transfer frequency of genes such as fosX, encoding fosfomycin resistance, and tet_A1, tet_A3, tetC, responsible for tetracycline resistance, both in vitro and in situ. In contrast, the Lde gene (the gene encoding ciprofloxacin resistance) was not transferred under any conditions. In the food matrix (carrot juice), greater variability in results was observed, suggesting that food matrices may have a protective effect on bacteria and modify HPP efficacy. In general, an increase in MIC values for antibiotics was noted in transconjugants compared to donors. Genotypic analysis of transconjugants showed differences in genetic structure, especially after exposure to 400 MPa pressure, indicating genotypic changes induced by pressure stress. The study confirms the possibility of antibiotic resistance genes transfer in the food environment, even from strains showing initial susceptibility to antibiotics carrying so-called silent antibiotic resistance genes, highlighting the public health risk of the potential spread of antibiotic-resistant strains through the food chain. The findings suggest that high-pressure processing can increase and decrease the frequency of resistance gene transfer depending on the strain, antibiotic combination, and processing conditions.

Layered graphene oxide membrane for heavy metal separation via molecular dynamics simulation

Purification of water and industrial wastewater, especially those containing toxic metals, is a critical challenge for developing societies. Nano membranes, including two-dimensional graphene oxide nanomaterials, have recently gained prominence as an alternative to traditional polymer membranes. However, the efficacy of these membranes for the removal of heavy metals has not been extensively studied. In this work, molecular dynamics simulation is used to investigate the performance of graphene oxide membranes, with the oxidation ratio of 20 %, for the removal of mercury and arsenic ions at a concentration of 0.5 M, via reverse osmosis at 200 Mpa pressure. Results demonstrate that graphene oxide membranes are effective for separating heavy metal ions while maintaining good water flow. The mechanism of water molecule passage through the graphene oxide membrane is also investigated by analyzing the structural images of water molecules between the layers, water density diagrams in the nanochannel, and the number of hydrogen bonds at various channel inter-layer distances. In addition, raising the temperature of the aqueous solution from 300 to 340 K increases the water flux and decreases ion rejection. Increasing the concentration of mercury and arsenic ions from 0.5 to 1 M in the feed water leads to decrease in water flux with the least impact on ion rejection. Furthermore, the influence of membrane geometry on its performance is also investigated. By comparing the cross-flow and dead-end geometries, it is found that the cross-flow geometry performs better than the dead-end geometry both in water flux and the removal efficiency of mercury and arsenic ions. The potential of graphene oxide membranes in the treatment of wastewater containing heavy metals is highlighted by these findings, which provide insights into optimizing their design and operational parameters.

Improved CO2 capture capacity of waste sawmill dust derived activated carbon employing novel high-pressure CO2 activation

The porosity of activated carbon is significantly influenced by both the precursor biomass and the activation parameters. Waste sawmill wood (WSW) dust, an abundantly available precursor from the furniture manufacturing, construction, carpentry, and shipbuilding industries, was collected, dried, pulverized, carbonized, and activated using steam and a novel high-pressure CO2 activation approach. Activation was performed in a tubular furnace at 800 °C with a pure CO2 flow for 90 min at 1 MPa pressure (WSW-A800-CO2-90 min-1 MPa). Another activated carbon sample was synthesized from the same precursor at atmospheric pressure using steam flow at 700 °C for 20 min (WSW-A700-Steam-20 min). XRD and FTIR analyses were conducted to compare the structural information of both samples. Additionally, the thermal characteristics of the samples were determined by measuring their specific heat capacities. N2 and CO2 adsorption experiments were performed to investigate the porous properties and CO2 capture capacities of the synthesized samples. The activated carbon synthesized in a pressurized CO2 environment produced a BET surface area of 684 m2/g, while steam activation achieved a BET surface area of 947 m2/g. Interestingly, despite the lower surface area of the CO2-activated sample, it exhibited a higher CO2 adsorption capacity (106.29 mg/g at 5 °C and 110 kPa) compared to the steam-activated carbon due to its unique pore size distribution. The experimental CO2 adsorption data were also correlated with Langmuir, Freundlich, and modified Dubinin-Astakhov (D-A) models to elucidate the CO2 capture parameters, such as isosteric heat of adsorption, activation energy, and Gibbs free energy.

Exploring of laccase-like nanozyme and membrane filters for efficient removal of tetracycline hydrochloride

Laccase is utilized as green catalyst in the environmental catalysis. Nevertheless, the drawbacks such as poor stability and difficulty in recycling have seriously restricted its application. Here, we simulated the binding pocket and catalytic active site of nature laccase, and designed a laccase-mimicking nanozyme (named as GA-Cu and the average diameter was 600 nm) with high activity and stability by using Cu2+ as the active center, 2-aminoimidazole as well as glutathione (GSH) as the ligand. Compared with natural laccase, the GA-Cu nanozymes showed excellent stability and reusability under extreme conditions. Furthermore, to overcome the problems of difficult recycling and easy secondary contamination, we innovatively proposed to load GA-Cu nanozymes onto nylon membranes (GA-Cu@CS/GA-Cu/nylon membranes) by vacuum-assisted filtration using chitosan (CS) as a binder to degrade tetracycline hydrochloride (TC) by filtration. Encouragingly, 50 mg/L of TC was almost completely removed by filtration once at 0.15 MPa pressure. The results have showed that the GA-Cu@CS/GA-Cu/nylon membrane removed TC mainly through degradation, and more than 80 % of TC was degraded through desorption experiments. Finally, some degradation products were identified by LC-MS and three possible degradation pathways were proposed. These findings demonstrate the potential of GA-Cu@CS/GA-Cu/nylon membrane for environmental remediation, and will be a general and important strategy for the design of membrane filters based on the excellent performance of nanozyme.

Electrochemical Hydrogen Evolution Using Proton Transport through Graphene Monolayers

Pursuing sustainable hydrogen, electrochemical Hydrogen Evolution Reaction (HER) is crucial. However, challenges arise during HER, including the dissolution of catalytic materials and the formation of hydrogen bubbles on the electrode surface. Bubbles that evolve at an electrode may result in undesired blockage of the electrocatalytic surface, and ion conducting pathways in the electrolyte resulting energy losses1. Our study addresses this issue using monolayer graphene as a two-dimensional electrode with proton permeability.A graphene monolayer was synthesized using chemical vapor deposition (CVD) on a copper substrate. The fabrication process involved assembling the graphene monolayer on copper foil with nafion followed by hot pressing at 140°C for 2 minutes under 1.4 MPa pressure. Subsequently, this assembly was floated on Cu etchant (0.2 M (NH4)2S2O8 aqueous solution) facing Cu foil side overnight at 25°C and then rinsed Milli-Q water for several times. Platinum nanoparticles on graphene/nafion membrane was deposited using potential step method2. The electrochemical tests were carried out in 0.5 M H2SO4 vs RHE under argon (Ar) saturation using home-built electrochemical cell designed for proton permeable electrodes as illustrated Fig (a) and Cyclic voltammetry (CV) Fig (b) was performed Pt/Gr/N, Pt electrode at a scan rate of 50 mV/s.The hydrogen evolution performance of Pt/Gr/N measured in the proton permeable transport configuration in 0.5 M H2SO4 as evidenced by cyclic voltammetry revealing an observed lower overpotential of 17 mV at 10 mA/cm²(Pt-ECSA) suggests that proton transport occurs through the graphene layer, facilitating the hydrogen evolution reaction (HER) in gas phase without the generation of gas bubbles in electrolytes. This leads to minimal H2 reoxidation on Pt, which results in a positive shift in the observed onset potential and higher current density. On the other hand, Pt electrode in the conventional proton diffusion transport configuration exhibited a slightly higher overpotential of 28 mV at the same current density per Pt-ECSA, due to the HER in the solution phase. Indeed, hydrogen oxidation reaction (HOR) during the backward potential scan ofs the CV was observed only in the case of the conventional Pt electrode.1.Zhang C, Guo Z, Tian Y, et al. Nano Research Energy, 2: e9120063 (2023)2.Domínguez-Domínguez, et al. J Appl Electrochem 38:259–268 (2008) Figure 1

Properties of multiple rare earth oxides co-stabilized YDyGdSmNd-TZP ceramics

TZP starting powders containing 0.6 mol% each of yttria, dysprosia, gadolinia, samaria and neodymia stabilizer were fabricated by a wet chemical route by coating monoclinic zirconia with rare earth nitrates and subsequent calcination. The powders were consolidated by hot pressing in the temperature range between 1250 °C–1500 °C for 1 h at 60 MPa pressure. The materials were characterized with respect to microstructure, phase composition and mechanical properties. The materials combine high fracture toughness over the whole sintering temperature range with moderate hardness and attractive strength. XRD showed that a redistribution of stabilizers takes place during sintering, an initial highly tetragonal phase containing little or no stabilizer is successively eliminated and a stabilizer saturated tetragonal phase is progressively formed. The volume fraction of cubic increases with sintering temperature as the stabilizer content increases. Above 1500 °C, a plate-shaped aluminate phase is formed from the alumina sintering aid and rare earth oxide.

Vapor–liquid equilibria (VLE), density, and viscosity of the ternary mixtures of ethane, water, and bitumen at T = 190–210 °C and P = 2.5 MPa—Measurements and CPA-EoS modeling

In this paper, we study vapor-liquid equilibria (VLE) of a ternary system consisting of ethane, water and Mackay River bitumen. The experimental measurements were compared with the predictions of the Cubic Plus Association (CPA) Equation of State (EoS) model at temperatures ranging from 190 to 210 °C and at 2.5 MPa pressure. The feed mole fractions of ethane and water are varied while maintaining a constant bitumen mole fraction to study the VLE region and the associated thermophysical properties, such as the density and viscosity, of the liquid phase. The ternary phase diagrams are constructed at three different temperatures (190, 200, and 210 °C) and pressure at 2.5 MPa. Liquid (L), liquid–liquid (LL), vapor–liquid (VL), and vapor–liquid–liquid (VLL) phase boundaries are determined using phase stability analysis and flash calculations. The experimentally determined phase molar compositions are reported for ethane, water, and bitumen and compared with the model predictions. The AARDs for predicting the liquid phase composition for bitumen, water, and ethane are 1.71 %, 9.34 %, and 3.16 %, respectively. For the vapor phase composition, the AARDs for the water and ethane are 5.91 % and 4.75 %, respectively.

The Heating Under Micro Variable Pressure (HUMVP) Process to Decrease the Level of Saponin in Quinoa: Evidence of the Antioxidation and the Inhibitory Activity of α-Amylase and α-Glucosidase.

To reduce the level of saponin while preserving essential nutrients and antioxidative properties in quinoa (Chenopodium quinoa), this study delves into the optimization of the HUMVP process and thoroughly examines its effects on antioxidation as well as its inhibitory influence on α-amylase and α-glucosidase. The optimal HUMVP conditions involved wetting quinoa grains with 6% water (pH = 6.0) and subjecting them to a 4 min treatment under 0.35 MPa pressure. The values of •OH, DPPH, and ABTS•+ scavenging rate of the extracts from the quinoa sample (named Q2HUMVP) treated under the optimum HUMVP process were 70.02, 87.13, and 50.95%, respectively. Furthermore, the treatment preserved 95.20% of polyphenols and 73.06% of flavonoids, while the saponin content was reduced to 23.13% of that in raw quinoa. Notably, Q2HUMVP extracts demonstrated superior inhibitory activity against α-amylase and α-glucosidase compared to dehulled quinoa samples. The inhibition exhibited by the quinoa sample extracts on α-amylase and α-glucosidase was found to be reversible.

The Gasification and Pyrolysis of Biomass Using a Plasma System

This research paper analyzes the use of plasma technology to process biomass in the form of dried, mixed animal manure (dung containing 30% moisture). The irrational use of manure as well as huge quantities of it can negatively impact the environment. In comparison to biomass fermentation, the plasma processing of manure can greatly enhance the production of fuel gas, primarily synthesis gas (CO + H2). The organic part of dung, including the moisture, is represented by carbon, hydrogen, and oxygen with a total concentration of 95.21%, while the mineral part is only 4.79%. A numerical analysis of dung plasma gasification and pyrolysis was conducted using the thermodynamic code TERRA. For 300–3000 K and 0.1 MPa pressure, the dung gasification and pyrolysis were calculated with 100% dung + 25% air and 100% dung + 25% nitrogen, respectively. Calculations were performed to determine the specific energy consumption of the process, the composition of the products of gasification, and the extent of the carbon gasification. At 1500 K, the dung gasification and pyrolysis consumed 1.28 and 1.33 kWh/kg of specific energy, respectively. A direct-current plasma torch with a power rating of 70 kW and a plasma reactor with a dung processing capacity of 50 kg/h were used for the dung processing experiments. The plasma reactor consumed 1.5 and 1.4 kWh/kg when pyrolyzing and gasifying the dung. A maximum temperature of 1887 K was reached in the reactor. The plasma pyrolysis of dung and the plasma–air gasification of dung produced gases with specific heats of combustion of 10,500 and 10,340 kJ/kg, respectively. Calculations and experiments on dung plasma processing showed satisfactory agreement. In this research, exergy analysis was used to quantify the efficiency of the plasma gasification of biomass. One of the research tasks was to develop a methodology and establish standards for the further standardization of monitoring the toxic emissions of dioxins, furans, and Benzo[a]pyrene.

The influence mechanism of mechanical modification on fly ash carbonation to solidify heavy metals

Dry and wet milling, were selected to carry out modification experiments. The influence of mechanical modification pretreatment on fly ash carbonation to solidify heavy metals was explored, and its influence mechanism was revealed. Mechanical modification can improve the physical properties, and the continuous application of mechanical energy can activate the active sites which strengthen fly ash carbonation. The carbonation efficiency was obtained by 500–800 °C thermogravimetric analysis before and after carbonation. The average carbonation efficiency improved by dry milling is 2.28 %, and that improved by wet milling is 8.11 %. Carbonation has a good curing effect on Cr, Cd, Pb and As, especially when the CO2 is raised to supercritical. At 8 MPa pressure, the leaching concentrations of Cr, Cd, Pb and As decrease by 34.94 %, 7.00 %, 15.28 % and 35.85 %. The stabilization effect of fly ash carbonation on heavy metals is significantly improved after mechanical modification pretreatment. Comparison experiments on characterization of fly ash before and after mechanical modification shows that ball milling significantly increases the specific surface area. The crushing effect of wet milling is better, because the presence of water weakens the agglomeration of fine particles caused by van der Waal force. Mechanical modification can effectively improve the pore structure of fly ash and activate active sites which promote carbonation to form a larger physical wrapping area and strengthen stable carbonate formation. so mechanical modification effectively improves the solidification of heavy metals by carbonation.

Combined effect of compressing fresh concrete and curing regime on bonding performance of high strength repair mortar

High strength concrete (HSC) is highly appropriate for the retrofitting and rehabilitation of reinforced concrete structures due to its low permeability and high bonding strength. However, its low workability and sensitivity to curing conditions pose significant challenges for its implementation in such projects. This study introduces a novel technique to overcome the workability barrier of HSC while enhancing its bonding strength under various curing conditions. To achieve this, four different pressures (0, 0.87, 2.61, and 5.23 MPa) were applied to fresh high strength repair mortar (HSRM) and HSC for durations of 2, 4, and 8 h. Subsequently, different curing methods, including the wet sack method, steam curing method, and the use of curing compounds, were employed. The modulus of elasticity and compressive strength of HSC, in addition to bonding performance between substrate HSC and 28-day compressed HSRM, were evaluated using the “friction-transfer” and “twist-off” techniques, which are standard techniques for measuring the bonding strength of concrete both in the laboratory and in-situ. Also, to further assess the effect of curing regime and pressure on the microstructures of HSRM, SEM images of 28-day HSRM specimens were collected. The results indicated that increasing the pressure to 5.23 MPa and extending the duration to 8 h enhanced the ultimate torsional shear strength between HSRM and substrate HSC by an average of 174%. Additionally, the mechanical properties of HSC were considerably enhanced by applying 5.23 MPa pressure over 8 h. It is worth mentioning that the bonding strength between HSRM and substrate HSC without curing was highly affected by the duration of pressure application compared to the three investigated curing methods. The wet sack curing method was found to be the most effective for enhancing the degree of hydration and increasing the failure torsional shear stress of compressed HSRM specimens.

Simulation and Mechanistic Exploration of the Mid to Late-Stage Hydrothermal Carbonization Process in Biomass

Using C143H108O4 as the model for hydrochar, unsaturated small molecules necessary for polymerization reactions were added to extend the simulation of the hydrothermal carbonization (HTC) growth process. This enabled a comprehensive exploration of the pressure (density), small-molecule structure, water influence conditions, and related HTC reaction mechanisms in the middle to late stages of the process. The simulation results indicate that in a high-pressure system with a simulated pressure of 200MPa, there is a greater quantity of hydrochar formation when compared to systems at lower pressures. The addition of unsaturated small molecules, such as CH2O2, C4H5O, C4H6, C3H4, and C4H5 reduces the need for intermolecular dehydrogenation or hydrogen transfer reactions in the system, indirectly accelerating subsequent HTC reactions. In particular, the addition of H2O was detrimental to mid to late-stage HTC reactions, which are primarily dominated by both polymerization and aromatization reactions, as the addition was found to significantly increase the level of free H in the system. Consequently, compared with the absence of water, this results in the formation of a relatively hydrogen-rich environment in the molecular system, contrary to the requirements of mid to late-stage HTC reactions. Additionally, a recurring observation in mid to late-stage HTC reactions is the continuous occurrence and repetition of “polymerization-decomposition-polymerization” processes among large fragment molecules, representing a transition from unstable to relatively stable structures. Aromatization between fragments is crucial for transition to stable structures. Finally, in conjunction with wavefunction analysis of the polymer, it was observed that the aromatic polymer interactions gradually exerted a significant influence on the molecular structure as the temperature decreased to room temperature at 300K. This resulted in the gradual clustering of molecular structures, potentially contributing to the spherical and core-shell structures of the hydrochar microparticles.

Kinetics of CO2 hydrate formation in clayey sand sediments: Implications for CO2 sequestration

Hydrate-based CO2 sequestration beneath oceanic sediments is an emerging technique that involves the injection of CO2 into the hydrate stability zone (HSZ) beneath the seabed, forming hydrate cap that structurally traps the injected CO2 and reduces the risk of leaking CO2 from the storage sediment. Gas hydrates are adequately stable in sand sediments saturated with fresh water; however, the salinity of oceanic water impairs hydrate formation kinetics, stability, and CO2 storage capacity. In addition to sandstones, marine sediments are composed of many clay minerals that could affect hydrate formation. Therefore, this study experimentally simulates CO2 injection into sand and clayey sand sediments to assess the potential of CO2 hydrate formation. CO2 hydrates are formed inside a high-pressure reactor, which contains unconsolidated sediment bed/pack (silica sand; mixed sand with bentonite clay: 5 wt% and 10 wt%), saturated with de-ionized water or brine (3.3 wt% NaCl). Hydrate formation experiments were performed at 4 MPa pressure and 274.15 K temperature. Results show that CO2 hydrate formed within the sand sediment, with induction times of 6 and 8.5 h, for the de-ionized and brine systems, respectively. CO2 gas mole uptake in the de-ionized system was 71.54 mmol/mol however, in the brine system the gas uptake was 56.95 mmol/mol. Hence this 20.4% reduction in the gas uptake indicated the inhibition effect of salinity. In contrast, in the brine-saturated 5 wt% clay-sand sediment, the induction time was 6.5 h, indicating the promoting effect of the nano-sized clay particles. However, the gas uptake in this brine-saturated clay-sand sediment was reduced by 45.51% compared to the brine-saturated sand sediment. Increasing the clay content to 10 wt% prevented CO2 hydrate formation due to porosity reduction. Moreover, de-ionized water in clayey sand sediments prevented hydrate formation due to clay swelling. Finally, CO2 hydrate formation at the end of each experiment was visually confirmed.

Pressure-induced formability and degradability of block copolymers composed of poly(1,5-dioxepan-2-one) and poly(L-lactide)

An aliphatic polyether/carbonate block copolymer, comprising poly(1,5-dioxepan-2-one) (PDXO, glass transition temperature Tg: -38 °C) and poly(L-lactide) (PLLA, Tg: 55 °C), evinces remarkable formability under pressure at temperatures significantly below the melting point of PLLA. A quantitative and detailed evaluation of the low-temperature molding of the block copolymer was conducted using a capillary rheometer. The findings reveal that block copolymers with PDXO composition >55 wt% demonstrate a propensity to flow at room temperature under 50 MPa pressure. Consequently, the practice of low-temperature molding serves to mitigate the degradation of polymer chains during the molding process, thereby augmenting recyclability. Furthermore, the enzymatic degradability of the block copolymer was extensively investigated using lipase PS and proteinase K. An interplay between the structure of the block copolymer and the degradation kinetics was explored. The polymeric materials developed, possessing both pressure formability and degradability, hold promising potential as environmentally benign polymers with reduced environmental impact.