Combined Effect Of Pressure Research Articles

Combined Effect of Pressure and Temperature on Nitrogen Reduction Reaction in Water

The synthesis of ammonia starting from nitrogen and using electrochemical processes is considered an interesting strategy to produce ammonia in a sustainable way. However, it requires not only the development of efficient catalysts for nitrogen reduction but also the optimization of the operating conditions of the employed electrochemical devices. In this work, we optimize the kinetics and the thermodynamics of the electrocatalytic nitrogen reduction reaction in water by developing a pressurized H-cell that may operate at temperatures up to 80 °C. Ni foam with low Au loading (0.08 mg cm−2) has been adopted as a catalyst at the cathode. Ammonia has been produced during chronoamperometry experiments in a saturated N2 atmosphere and measured by the indophenol blue method. The effect of voltage, temperature, and pressure has been studied. The nitrogen reduction experiments have been repeated under saturated Ar. To remove contributions due to environmental contamination, we determined the net value as the difference between the produced ammonia in N2 and in Ar. The ammonia yield increases by increasing the temperature and the pressure. The best results have been obtained by using the combined effects of temperature and pressure. Operating at 5 bar of saturated N2 and 75 °C, a production rate of 6.73 μg h−1·cm−2 has been obtained, a value corresponding to a 5-fold enhancement, compared to that obtained under ambient conditions and room temperature.

Exploring the influence of additives on the ignition, combustion and quenching of electrically controlled solid propellants

AbstractThe influence of additives on the decomposition and combustion characteristics of electrically controlled solid propellants was investigated through small scale experiments. Carbon black and aluminum additives were explored in a polyethylene oxide, lithium perchlorate propellant. Additives were used to improve the voltage response and their impact on ignition and combustion was characterized. The data showed that conductive additives can mitigate the loss of solid phase conductivity through solvent evaporation and that ignition delay decreases with higher voltage and solid phase conductivity. Steady‐state combustion experiments showed that electrical decomposition of the propellants proceeded more rapidly than a purely thermal stimulus illustrating the importance of electrochemistry in ECSP combustion. The combined effects of pressure and voltage on combustion rates were summarized in Saint‐Robert's burn relations. The regression rates increased with both applied voltage and pressure. The pressure deflagration limit of propellants with the carbon black additive was significantly reduced compared to a neat PEO/LP propellant, whereas the addition of 10 % aluminum did not affect the pressure deflagration limit.

Screening of conditions for the acetic acid production from H2 and CO2 by Thermoanaerobacter kivui in a pressurized stirred tank bioreactor

Growing concerns regarding climate change have heightened interest in utilizing carbon dioxide as a valuable carbon source for chemical production. The acetogen Thermoanaerobacter kivui is a thermophilic bacterium that converts CO2 and H2 streams into acetic acid. Nevertheless, the limited solubility of the gaseous substrates in the liquid medium has often led to low productivity by the biocatalyst employed. This study aims to enhance the cell-specific acetic acid productivity of T. kivui by combining pressure, the composition of the inlet gas mix, and in-flow gas rate. Firstly, the combined effect of pressure and gas composition was assessed through a Design of Experiments approach. Tests were performed in a pressurized bioreactor and indicated that acetic acid cell-specific productivity was achieved at 10 bar, providing a 3:1 H2:CO2 blend. Subsequently, supplying this blend at high pressure into the vessel of the reactor, an in-flow gas rate screening was performed to identify completely the parameters that allowed the maximum acetic acid productivity. The optimal flow rate was 60 mL.min−1, and the acetic acid cell-specific productivity reached 2.90 g.g−1.h−1. Additionally to the experiments in the bioreactor, tests in serum bottles were performed to investigate the influence of the osmotic condition due to different salts and acetic acid inhibition on T. kivui. Results indicated that salts and acetic acid concentration impaired bacteria growth and affected the production of further acetic acid. Nevertheless, a metabolic shift toward the production of formic acid was observed specifically by adding the HCO3– ion.

An exact solution for the entropy base flow of electroosmotic magneto-nanofluid through microparallel channel

An exact solution of steady state, electroosmotic, transient magnetohydrodynamic (MHD) flow, and heat transfer of a viscous and incompressible electrically conducting nanofluid consists of water and Cu metal, through a microparallel channel under the combined effect of pressure and vertically acting magnetic field is found. An exact solution is calculated through Laplace transform using the software of Mathematica to find the steady velocity and temperature field depending on many dimensionless parameters. The electromagnetic couple effect, the volumetric generation of heat caused by the Joule heating effect, and viscous dissipation are considered to analyze the thermally fully formed heat flow problem based on the steady part of the velocity field. The exact result of the temperature field is obtained by taking the uniform boundary heat flux. The significant parameter of heat flow known as the Nusselt number, depending on the height of the microtube, is defined. At last, the entropy generation of MHD temperature flow is analyzed. The interpretation of variations that occurred in internal and external entropy generations is given and consequences are explained.

Influence of TMAO and Pressure on the Folding Equilibrium of TrpCage.

Trimethylamine-N-oxide (TMAO) is an osmolyte known for its ability to counteract the pressure denaturation of proteins. Computational studies addressing the molecular mechanisms of TMAO's osmolyte action have however focused exclusively on its protein-stabilizing properties at ambient pressure, neglecting the changes that may occur under high-pressure conditions where TMAO's hydration structure changes to that of increased water binding. Here, we present the first study on the combined effect of pressure and TMAO on a mini-protein, TrpCage. The results showed that at high pressures, nonpolar residues packed less tightly and the salt bridge of TrpCage was destabilized. This effect was mitigated by TMAO which was found to be strongly depleted from the protein/water interface at 1 kbar than at 1 bar ambient pressure, thus counterbalancing the thermodynamically unfavorable effect of elevated pressure in the free energy of folding. TMAO was depleted from charged groups, like the salt bridge-forming ones, and accumulated around hydrophobic groups. Still, it stabilized both kinds of interactions. Furthermore, enthalpically favorable TrpCage-water hydrogen bonds were reduced in the presence of TMAO, causing a stronger destabilization of the unfolded state than the folded state. This shifted the protein-folding equilibrium toward the folded state. Therefore, TMAO showed stabilizing effects on different kinds of groups, which were partially enhanced at high pressures.

Pre‐storage hypobaric treatment reduces microbial spoilage and maintains eating quality of strawberry fruits during low temperature conditions

Strawberry fruits are highly perishable and susceptible to microbial decay. In this study, influence of atmospheric pressure, postharvest delay in hypobaric treatment, and combined effect of pressure and exposure duration on storage quality of strawberries were evaluated. Treatment at 40 kPa for 4 h without postharvest delay inhibited fungal decay and retained visual quality which contributed to 13% increase in marketable life of strawberries compared with control. Further study revealed that microbial control and storage quality of strawberries treated either at 20 kPa for 2 h or 40 kPa for 4 h were statistically comparable. After 12 days, strawberries treated at 20 kPa for 2 h had 14.3% higher radical scavenging activity, 13.9% higher phenolic contents and 17.7% higher ascorbic acid than control fruits. Thus, pre-storage treatment at 20 kPa for 2 h without postharvest delay effectively retained fruit quality and extended storage life of strawberries for 6 more days compared with control. Novelty impact statement Hypobaric treatment is a potential non-chemical technique used to disinfect and extend storage life of strawberries. Results showed that hypobaric treatment at 20 kPa for 2 h without any postharvest delay can be adopted to disinfect strawberries from microbial infection and to extend marketable life. These findings may help in developing commercial hypobaric technology for perishable and decay-susceptible fruits and vegetables.

Physico-mechanical performance of fly ash based geopolymer brick: Influence of pressure − temperature − time

Trillions of masonry fired-clay bricks are being produced globally every year, however, their manufacturing process is far from eco-friendly. This work was designed to develop fly ash (FA)-based geopolymer brick, a sustainable alternative to fired-clay brick. For the optimum manufacturing technique, physico-mechanical performance was assessed by molding pressure (0, 20, and 40 MPa), curing temperature (ambient, hot), and curing time (7 and28 days) as well as combined effect of these parameters. It was observed that the molding pressure densifies the mixture and results in decrease in porosity and water absorption. As a result, the strength was increased significantly (more than 180 %). For the curing temperature, the hot curing state was well collaborated with the higher molding pressure of 40 MPa to develop the compressive strength compared with the ambient-curing condition due to the high rate of geopolymerization. The curing time was found to be not significant for the strength development. The strength was enhanced more than 600 % when the combined effect of pressure − temperature − time was applied. Although, 40 MPa molding pressure showed higher strength, however, the 20 MPa molding pressure could sufficiently satisfy the ASTM strength criteria. The correlation matrix was developed, and it was observed that pressure − temperature has 0.91 correlation with the strength and recommended as the optimum technique. The pilot-scale test confirmed that the physico-mechanical properties satisfied the standards. Furthermore, mechanical strength was found to be in good correspondence with the physical properties under all strength enhancing techniques, which was reconfirmed with the microstructural analysis using scanning electron microscope.

Exploring the relationship between urbanization and water environment based on coupling analysis in Nanjing, East China.

The degradation of water environment (WE) has constrained the sustainable development of cities, while the rapid urbanization also exacerbates water environment change. However, the complicated relationship between urbanization and WE is far from clearly understood. In this study, a comprehensive index system for urbanization and WE was applied along with the System Index Evaluation Model (SIEM) and a Coupling Coordination Degree Model (CCDM) to analyze the coupling between urbanization and WE in Nanjing, East China, from 1990 to 2018. The comprehensive index of urbanization increased from 0.0392 in 1990 to 0.9890 in 2018, showing a clear increasing trend. Demographic and spatial urbanization made the largest contribution to urbanization development from 1990 to 2010, while economic urbanization became the largest contributor to urbanization development between 2011 and 2018. Under the combined effects of pressure, state, and response subsystems, the comprehensive WE index showed an upward trend with some fluctuations from 1990 to 2018. The degree of coupling coordination between urbanization and WE displayed an overall upward tendency, growing from 0.18 in 1990 to 0.95 in 2018. The coupling coordination state transitioned from a serious imbalance during the low coupling period (1990–1992) into the superior coordination of the highly coupled period (2011–2018). With the continuous urbanization in the future, in addition to ensuring the optimal management of surface water, protection of groundwater should be reinforced. The results advance our understanding of the dynamic relationship between urbanization and WE and provide important implications for urban planning and water resource protection.

An effective route for tuning microstructure and properties of sintered Nd-Fe-B magnets: Low pressure sintering technology

In this study, a novel low pressure sintering method for mass industrial preparing Nd-Fe-B magnets with high performance was proposed. The results indicated that the properties of magnets can be greatly enhanced via low-pressure sintering method by tuning the grain size and rich-RE phase distribution. Under the combined effects of pressure and temperature, the flowability of rich-RE liquid phase was enhanced and which made it easy to achieve liquid phase sintering process, resulting in the close theoretical density and high performance of the sintered magnets. The optimum properties (Br = 14.10kGs, Hcj = 14.11kOe and (BH)max = 46.47MGOe) were obtained at the sintering temperature of 980 °C under 2.0 MPa gas pressure field, which is far below the conventional manufacturing temperature for commercial Nd-Fe-B magnets (1060 °C). This work could offer a valuable method to obtain sintered Nd-Fe-B magnets with superior microstructure and excellent properties.

The Combined Effect of Pressure and Temperature on Kefir Production-A Case Study of Food Fermentation in Unconventional Conditions.

Food fermentation under pressure has been studied in recent years as a way to produce foods with novel properties. The purpose of this work was to study kefir production under pressure (7–50 MPa) at different temperatures (17–32 °C), as a case study of unconventional food fermentation. The fermentation time to produce kefir was similar at all temperatures (17, 25, and 32 °C) up to 15 MPa, compared to atmospheric pressure. At 50 MPa, the fermentation rate was slower, but the difference was reduced as temperature increased. During fermentation, lactic and acetic acid concentration increased while citric acid decreased. The positive activation volumes (Va) obtained indicate that pressure decreased the fermentation rate, while the temperature rise led to the attenuation of the pressure effect (lower Va). On the other hand, higher activation energies (Ea) were observed with pressure increase, indicating that fermentation became more sensitive to temperature. The condition that resulted in a faster fermentation, higher titratable acidity, and higher concentration of lactic acid was 15 MPa/32 °C. As the authors are aware, this is the second work in the literature to study the combined effect of pressure and temperature on a fermentative process.

Combined effects of temperature field and ultrasonic vibration on bubble motion in laser joining of plastic to metal

A previous study has found that applying ultrasonic vibration in laser joining of Polyethylene terephthalate (PET) plastic to Ti metal can greatly reduce bubbles formed in the joint. In this study, the theoretical basis on the combined effects of pressure and temperature fields on the trajectory of bubbles was analyzed using finite element simulation. A non-uniform temperature field influences the evaporation momentum pressure acting on a bubble, causing it to travel from a low to a high temperature region. A properly designed ultrasonic transducer tool, however, can create an unbalanced pressure field around a bubble. Under the combined effects of these elements, bubbles in the molten pool can be made to escape from the joint. The predicted results and obtained experimental outcomes matched well, which were also supported by the evidence of captured high-speed camera images.

Effects of finite ion size on transport of neutral solute across porous wall of a nanotube

Effect of finite ion size on the transport of a neutral solute across the porous wall of a nanotube is presented in this study. Modified Poisson–Boltzmann equation without the Debye–Huckel approximation is used to determine the potential distribution within the tube. Power law fluid is selected for the study, as its rheology resembles closely to the real-life physiological fluids. The flow within the tube is actuated by the combined effects of pressure and electroosmotic forces. Steady-state solute balance equation is solved by the similarity technique in order to track the solute transport across the tube. The effects of ionic radius, ionic concentration, and flow behavioral index on the length-averaged Sherwood number, permeate flux, and permeate concentration are analyzed. This study will be extremely helpful in predicting the transport characteristics of a neutral solute in real physiological systems and also to fine-tune the performance of microfluidic devices having porous wall.

Numerical optimization of warm hydromechanical deep drawing process parameters and its experimental verification

Abstract Warm Hydromechanical Deep Drawing (WHDD) is considered as an effective sheet metal forming process to overcome low formability problems of lightweight materials, such as aluminum and magnesium alloys, at room temperature. WHDD process combines the advantages of Hydromechanical Deep Drawing (HDD) and Warm Deep Drawing (WDD) processes. In this study, interactive and combined effects of Pressure (P) and Blank Holder Force (BHF) variation on the formability of the AA 5754 aluminum alloy sheets in the WHDD process were investigated experimentally and numerically. Different from available studies, the optimal fluid pressure (P) and blank holder force (BHF) profiles, which were determined numerically using adaptive FEA integrated with fuzzy logic control algorithm (aFEA-FLCA), were validated experimentally for the first time in literature. Consequently, limiting drawing ratios (LDR) of AA5754 material were recorded as 2.5, 2.625, and 3.125 for HDD, WDD, and WHDD processes, respectively. Thus, it was demonstrated that the formability of lightweight materials, such as AA5754, could be increased significantly using the WHDD process through the proposed optimization method. This method was also implemented into the WHDD of an industrial part with complex geometry, successfully forming sharp features with minimal thinning at reduced levels of force, pressure, and time. Consequently, it is reasonably to state that the method developed in this study can be adopted for the manufacturing of any other part using the WHDD process.

Extraction of chitosan from squid pen waste by high hydrostatic pressure: Effects on physicochemical properties and antioxidant activities of chitosan

Squid pen sample was treated by high hydrostatic pressure (HHP) prior to the extraction of chitosan. The physicochemical and antioxidant activities of the chitosan obtained with HHP (HHP-CS) were compared with chitosan of untreated squid pen sample (UT-CS). The chitosan extraction yield was optimized using response surface methodology, and the optimum condition was achieved at pressure of 500 MPa, extraction time of 10 min, and 1% (w/w) acetate concentration. The maximum yield of chitosan sample from the chitin of squid pens treated by HHP reached 81.9%. Among the process variables, the combined effects of pressure and acetate concentration significantly enhanced the extraction of chitosan from squid pens. The HHP-CS was found to be significantly effective in enhancing the fat binding capacity, water binding capacity, and water solubility index. SEM image analysis suggested that the HHP-CS had a rough surface with high porosity, while UT-CS exhibited a smooth surface. In vitro antioxidant assay suggested that HHP-CS had significantly higher DPPH radical scavenging activity, greater reducing power, and a stronger ferrous ion chelating effect than did UT-CS. Therefore, HHP can be an excellent alternative method for improving the physicochemical properties and antioxidant activities of chitosan from squid pens.

Exploring the Limits of Transition‐Metal Fluorination at High Pressures

AbstractFluorination is a proven method for challenging the limits of chemistry, both structurally and electronically. Here we explore computationally how pressures below 300 GPa affect the fluorination of several transition metals. A plethora of new structural phases are predicted along with the possibility for synthesizing four unobserved compounds: TcF7, CdF3, OsF8, and IrF8. The Ir and Os octaflourides are both predicted to be stable as quasi‐molecular phases with an unusual cubic ligand coordination, and both compounds formally correspond to a high oxidation state of +8. Electronic‐structure analysis reveals that otherwise unoccupied 6p levels are brought down in energy by the combined effects of pressure and a strong ligand field. The valence expansion of Os and Ir enables ligand‐to‐metal F 2p→M 6p charge transfer that strengthens M−F bonds and decreases the overall bond polarity. The lower stability of IrF8, and the instability of PtF8 and several other compounds below 300 GPa, is explained by the occupation of M−F antibonding orbitals in octafluorides with a metal‐valence‐electron count exceeding 8.

Exploring the Limits of Transition-Metal Fluorination at High Pressures.

Fluorination is a proven method for challenging the limits of chemistry, both structurally and electronically. Here we explore computationally how pressures below 300 GPa affect the fluorination of several transition metals. A plethora of new structural phases are predicted along with the possibility for synthesizing four unobserved compounds: TcF7 , CdF3 , OsF8 , and IrF8 . The Ir and Os octaflourides are both predicted to be stable as quasi-molecular phases with an unusual cubic ligand coordination, and both compounds formally correspond to a high oxidation state of +8. Electronic-structure analysis reveals that otherwise unoccupied 6p levels are brought down in energy by the combined effects of pressure and a strong ligand field. The valence expansion of Os and Ir enables ligand-to-metal F 2p→M 6p charge transfer that strengthens M-F bonds and decreases the overall bond polarity. The lower stability of IrF8 , and the instability of PtF8 and several other compounds below 300 GPa, is explained by the occupation of M-F antibonding orbitals in octafluorides with a metal-valence-electron count exceeding 8.

Near-equal compressibility of liver oil and seawater minimises buoyancy changes in deep-sea sharks and chimaeras.

Whereas upper ocean pelagic sharks are negatively buoyant and must swim continuously to generate lift from their fins, deep-sea sharks float or swim slowly buoyed up by large volumes of low-density oils in their livers. Investigation of the pressure, volume, temperature (PVT) relationships for liver oils of 10 species of deep-sea Chondrichthyes shows that the density difference between oil and seawater, Δρ, remains almost constant with pressure down to full ocean depth (11 km, 1100 bar), theoretically providing buoyancy far beyond the maximum depth of occurrence (3700 m) of sharks. However, Δρ does change significantly with temperature and we show that the combined effects of pressure and temperature can decrease buoyancy of oil by up to 10% between the surface and 3500 m depth across interfaces between warm southern and cold polar waters in the Rockall Trough in the NE Atlantic. This increases drag more than 10-fold compared with neutral buoyancy during horizontal slow swimming (0.1 m s-1), but the effect becomes negligible at high speeds. Chondrichthyes generally experience positive buoyancy change during ascent and negative buoyancy change during descent, but contrary effects can occur at interfaces between waters of different densities. During normal vertical migrations buoyancy changes are small, increasing slow-speed drag no more than 2- to 3-fold. Equations and tables of density, pressure and temperature are provided for squalene and liver oils of Chimaeriformes (Harriotta raleighana, Chimaera monstrosa, Hydrolagus affinis), Squaliformes (Centrophorus squamosus, Deania calcea, Centroscymnus coelolepis, Centroscyllium fabricii, Etmopterus spinax) and Carcharhiniformes (Apristurus laurussonii, Galeus murinus).

Olive Pomace-Derived Carbon Materials-Effect of Carbonization Pressure under CO2 Atmosphere.

The valorization of waste and by-products from various industrial activities is a must in our world of depleting natural resources and increasing volume of environmentally negative waste materials. The economic utilization of solid biowaste involves predominantly its use as a carbon-neutral energy resource or a precursor of porous carbon materials, with a potential application range including sorption processes, energy storage, and electric engineering. With the considerable number of lignocellulosic residues tested and applied as the most suitable porous material precursors, such as woods, shells, stones, peels, husks, and stalks of various crop plants, there is still space and need for further developments in the valorization of high amounts of other types of biowaste. Here, the olive pomace was considered because of both the vast volume and the environmentally undesired (when stored) phytotoxic effect of its components. While the literature on chemical (acidic and alkali treatment) and physical activation (temperature, carbon dioxide, and/or steam) of various biowaste precursors is considerable, the effects of pressure in the carbonization step are reported rarely, although the results observed are promising. The same applies to reports on the application of olive pomace for porous materials production, which indicate that olive pomace currently seems to be underestimated as a carbon materials precursor. In the study presented, the combined effects of pressure (0.1–3 MPa), temperature (800 °C), and carbon dioxide atmosphere in the carbonization of olive pomace were assessed on the basis of qualitative and quantitative data on micro- and mesoporosity of the carbon materials produced. The results showed the positive effect of increasing the process pressure on the development of a porous structure, and particularly, on the development of supermicropores and ultramicropores under the carbonization conditions applied. Carbon material with the most developed porous structure and the highest share of micropores was obtained under the maximum pressure tested.

Pressure induced martensitic transition, magnetocaloric and magneto-transport properties in Mn-Ni-Sn Heusler alloy

Abstract In this work, we report the effect of hydrostatic pressure (P) on the martensitic transition in Mn50Ni40Sn10 Heusler alloy using the magnetization and electrical resistivity measurements. Martensitic transition temperature (TM) is found to shift significantly to higher temperatures with the application of pressure, which reflects the stabilization of the martensite phase. On the other hand, TM shifts to lower temperatures with magnetic field, which implies the stabilization of the austenite phase. The estimated rate of change of martensitic transition temperature with pressure (dTM/dP) for the present alloy is ∼4.6 K/kbar. The alloy shows a maximum negative magnetoresistance (MR) of 9.6% for P = 4 kbar at the martensitic transition. A large isothermal magnetic entropy change (ΔSM) of 16.6 J/kg.K and a refrigerant capacity (RC) of ∼146 J/kg are observed at TM under ambient pressure. Both quantities are found to decrease with the increase of pressure. The values of ΔSM and adiabatic temperature change (ΔTad), calculated from heat capacity measurements are ∼11.3 J/kg.K and −3.4 K respectively for 50 kOe field change. The observed pressure and field dependence results have been explained using the Clausius-Clapeyron equation. The combined effect of pressure and field on the martensitic transition is also discussed.

Combined Effect of Pressure and Carbon Dioxide Activation on Porous Structure of Lignite Chars.

Lignite is an important natural resource with the application potential covering present and future energy systems, including conventional power plants and gasification systems. Lignite is also a valuable precursor for the production of porous materials of tailored properties for various environmental applications, including the removal of contaminants from gaseous or liquid media. Although the lignite-based activated carbons are commercially available, various approaches to produce carbon materials of desired properties are still being reported, covering temperature, partial oxidation and chemical activation effects on surface and structural properties of these materials. Limited data is, however, available on the effects of pressure as the activation parameter in shaping the porous structure of carbonaceous materials, in particularly lignite-derived. In the study presented the combined effect of carbon dioxide activation and pressure in the range of 1–3 MPa at the temperature of 800 °C on the development of porous structure of lignite chars was reported. The study was also focused on poor-quality resources valorization by using a relatively low calorific value, low volatiles and high ash content lignite as a carbon material precursor. The results showed that the application of pressure in carbon dioxide-activation process at 800 °C results in generation of chars of comparable or higher specific surface area than the carbon materials previously received with demineralization and carbon dioxide activation of lignite. They also proved that the combined pressure and carbon dioxide activation may be effectively applied in conversion of low quality lignite into valuable porous materials.