Dissolution Mechanism Research Articles

Fabrication of multi-layered polymer-based polypill using single-nozzle Fused Deposition Modeling and its dissolution mechanism

The meteoric rise of additive manufacturing has enabled it to create remarkable feats in the field of pharmaceutics and drug delivery applications. The main objective of this study was to print a polypill, having two drugs of common ailments in different layers, using a single nozzle Fused Deposition Modeling (FDM), instead of using a complex and cost-intensive dual extrusion printer. This was accomplished through a thermally fused filament. Myo-inositol (MI) and methylcobalamin (MCB) were the two drugs used for the present study. Initially, polyvinyl alcohol (PVA) filaments have been loaded with these drugs using Hot Melt Extrusion (HME) method and then, fused using heat and this blended filament has been fed into the FDM printing apparatus. These filaments have been used to finally obtain a polypill containing drugs in an alternate layer fashion. Various tests related to the filaments and tablets have been carried out to analyse the chemical, physical and thermal feasibility of this research attempt. The thermal analysis like Differential Scanning Calorimetry (DSC), Thermogravimetric (TGA) analysis tests confirmed filaments to be stable at printing temperature and FTIR results affirmed non-existence of any adverse degradation reaction in the drugs or other constituents. In-vitro dissolution studies were also conducted on the polypill and it was revealed that the dissolution rate for MI has been significantly higher than that of MCB drug. MI drug released completely in 5 h while MCB part was complete by 6.5 h. Finally, the drug dissolution behaviour was examined based on the dissolution data.

Enhancing plasticity in laser additive manufactured high-entropy alloys: The combined effect of thermal cycle induced dissolution and twinning

Breaking the trade-off between strength and ductility and pursuing stronger and more ductile metal materials has been a long-standing dream for scientists. Interestingly, even for the same material, different manufacturing methods can lead to significantly different performance. In this study, we utilized different laser additive manufacturing techniques (laser direct energy deposition (LDED), and laser powder bed fusion (LPBF)) to fabricate FeCoCrNiMo0.5 high-entropy alloy (HEA). Through microstructural analysis, we discovered a novel thermal cycling-induced dissolution (TCID) mechanism. By controlling the cooling rate post thermal cycling, we achieved the dissolution of precipitate phases and increased the Mo content within the matrix. Based on this phenomenon and supported by theoretical calculations, we revealed a reduction in stacking fault energy (SFE), which gave rise to a twinning-induced plasticity (TWIP) mechanism. This led to a dramatical increase in plasticity (LDED: 1.6 %, LPBF: 17.7 %) in the LPBF alloy, while maintaining similar strength (LDED: 784.9 MPa, LPBF: 840.89 MPa). This study provides guidance for designing metals structures with balanced strength and plasticity.

Synergistical improvement in toughness and strength of multi-doped W-Hf-Y2O3 alloy via formation of complex oxide particles

As the primary candidate material for plasma facing components (PFCs) in fusion reactor, the serious brittleness of tungsten has become an urgent issue to be solved. In this work, a multi-doped W-Hf-Y2O3 alloy was prepared by high-energy ball milling and spark plasma sintering, aiming at improving its toughness through formation of complex oxide particles. Complex Y2Hf2O7 with pyrochlore structure were developed in the multi-doped WHY alloy due to dissolution and precipitation mechanism, which was confirmed by the combined characterization results of X-ray diffraction (XRD), electron probe microanalysis (EPMA) and transmission electron microscope (TEM). Complex oxide particles of Y2Hf2O7 with average size of 38.8 nm were densely distributed in the alloy. The formation of complex Y2Hf2O7 particles with nano-scale size not only consumed the impurity of oxygen, but also played a critical role in grain refinement because of Zener pinning effect. Improvement in mechanical properties of the multi-doped WHY alloy was then achieved, and the fracture toughness and compressive strength reached 19.7 MPa·m1/2 and 2223.4 MPa, respectively.

How to achieve nanometer flat surfaces: Pulsed electrochemical machining of bulk metallic glass

The Bulk Metallic Glass (BMG) Vitreloy 105 (Zr52.5Ti5Ni14.6Cu17.9Al10) as well as two crystalline reference materials of the same composition were machined with Pulsed Electrochemical Machining (PECM). One reference material was nano crystalline with an average grain size of 11 nm and the second one was a fine grain crystalline sample with an average grainsize of 110 nm. The goal was to achieve maximum surface quality in terms of roughness by utilizing a readily available industrial process. Samples were characterized by tactile profilometer, atomic force microscopy and electron microscopy methods. The results show superior surface quality of the amorphous samples over the reference materials with an average roughness depth as low as 1 nm. The observed dissolution mechanism of the BMG differs from the reference materials -as in contrast to the crystalline alloys that show a passive layer formation - no such surface layer other than the native oxide could be observed. The PECM procedure is found to be a promising post-processing step for BMGs with a resulting surface that can face even the most challenging surface quality requirements.

Pore-Scale Numerical Simulation of Acid-Rock Reaction Processes in Carbonate Reservoirs.

In the process of acidizing carbonate reservoirs, dissolution is employed for reservoir modification to enhance recovery rates. This study establishes a numerical model at the pore scale for acid-rock reaction flow based on a microscopic continuum medium model, integrating phase-field theory and component transport models. Subsequently, the results of the Darcy-Brinkman-Stokes model are compared to those of the arbitrary Lagrange-Euler method to validate the accuracy of the model. Finally, the flow behavior of the acid solution at the pore scale and the complex dissolution mechanisms in carbonate reservoirs are analyzed. The research indicates that the microscopic pore-scale dissolution in carbonate reservoirs mainly manifests as five dissolution modes: uniform dissolution, compact dissolution, conical wormholes, dominant wormhole, and ramified wormholes. Different distributions of microfractures will alter the flow state of the acid solution and the rock-acid reaction process within the pores. Once the wormhole breakthrough occurs, there is an increased probability of acid flow through the wormhole to the outlet, leading to a decrease in the effectiveness of the acidizing carbonate reservoirs. A proper understanding of pore-scale acid-rock reaction laws is of great significance for the development of carbonate oil and gas reservoirs.

Dynamics of oil–CO2–water three-phase under the nanopore confinement effect: Implications for CO2 enhanced shale oil recovery and carbon storage

The widespread nanopores, diverse minerals, and varying water saturation in shale reservoirs complicate the mechanism analysis and performance prediction of CO2 enhanced oil recovery (CO2-EOR) and CO2 storage (CS) in hydrated nanopores. Therefore, molecular dynamics methods were used to simulate the process of CO2 replacing shale oil in hydrated nanopores of inorganic, organic and composite minerals. Importantly, the effects of mineral type, temperature, pressure and water content on CO2-EOR and CS performances in hydrated nanopores were analyzed, and the CO2-EOR mechanisms of dissolution, extraction, viscosity reduction, miscibility and competitive adsorption were revealed. The results show that water in illite, kerogen, and composite nanopores are distributed in the forms of water films, water clusters (films), and water columns, respectively. The replacement efficiency of shale oil in three types of nanopores is improved with increased water content but reduced in kerogen nanopores under high water content. Water is not conducive to the diffusion and viscosity reduction of oil in nanopores, but the miscibility and competitive adsorption of CO2 and oil are improved. The replacement efficiency is positively correlated with temperature and pressure. The increasing temperature promotes diffusion and viscosity reduction of oil and competitive adsorption between CO2 and oil in hydrated nanopores, and increasing pressure promotes miscibility and competitive adsorption. Water columns in kerogen and composite nanopores reduce the CS performance, while thin water films in illite nanopores improve it. Moreover, an excellent CS rate can be achieved at high temperatures and pressures, but the high temperature is not conducive to CS stability. This study provides a theoretical basis for CO2 injection to improve oil production and carbon storage performance in hydrated shale reservoirs and contributes to the optimization of CO2 injection schemes.

Purification mechanism of microcrystalline graphite and dissolution of non-carbon impurity during alkali autoclave-acid leaching

Purification mechanism of microcrystalline graphite and dissolution of non-carbon impurity during alkali autoclave-acid leaching

Enhanced Triethylamine Detection at Room Temperature Using a Layered MoS2 Nanosheet-Coated PPy Nanorod: A Comprehensive Study.

The rapid and reliable detection of triethylamine (TEA), a toxic, explosive, volatile organic compound at room temperature, is highly significant for food safety, environmental, and human health monitoring. This manuscript reports a layered molybdenum disulfide (MoS2) nanosheet-coated polypyrrole (PPy) nanorod-based heterostructure sensor (MsPy) which offers superior sensing properties toward TEA at room temperature (25 °C). Herein, different MsPy nanocomposites were synthesized, followed by a controlled sulfidation reaction through dissolution, diffusion, and regrowth mechanisms. Optimizing the ratio of the precursor of molybdenum trioxide (MoO3/PPy) is crucial for achieving effective deposition of a layered MoS2 nanosheet on the PPy surface. The as-prepared MoS2 nanosheet-coated PPy sensor (MsPy_40) enables one to selectively detect trace TEA vapor at 25 °C with a detection lower limit of 0.5 ppm. The MsPy_40 sensor exhibits 17 times higher response than the pristine MoS2 nanosheet to 50 ppm TEA, with rapid response (∼3.9 s) and recovery (∼19.6 s), along with better stability, good selectivity, and remarkable repeatability. The significantly enhanced sensing performance is attributed to the unique surface morphology of the layered MoS2 nanosheet-coated PPy nanorod and the formation of a p-n heterojunction between PPy and MoS2.

Pulsed Magnetic Field Treatment Effects on Undissolved Carbides in Continuous Casting Billets of GCr15 Bearing Steel

The study investigates the effect of pulsed magnetic fields on undissolved carbides in high-carbon chromium bearing steel GCr15 billets. The billets were subjected to heat treatment at 950 °C, with a pulsed magnetic field of varying durations applied during the process. The influence of the pulsed magnetic field on the distribution of undissolved carbides within the billets was investigated, and the thermodynamic and kinetic mechanisms of undissolved carbides dissolution were explored. The results indicate that the area percentage of undissolved carbides in the microstructure decreases from 1.68% to 0.06% after applying a pulsed magnetic field for 10 min, and the size of undissolved carbides decreases from 17.5 μm to 4.9 μm. When a pulsed magnetic field is applied for 30 min, all undissolved carbides dissolve. The statistics demonstrate that the average size of undissolved carbides is reduced from 14.19 μm to 0.63 μm, with a reduction percentage reaching 96%. Over the same duration, the number density of the undissolved carbides decreases from (0.19~0.55)/mm2 to (0.03~0.1)/mm2, and the percentage area of the undissolved carbides decreases from (1.26~1.68)% to (0~0.02)%. Thermodynamically, applying a pulsed magnetic field lowers the dissolution energy barrier of undissolved carbides and modifies their transformation temperature. Kinetically, the rate of alloy element diffusion is enhanced by increasing the frequency of atomic jumps. This research aims to provide new insights into enhancing the contact fatigue life of bearing steel, increasing the proportion of special steel, and optimizing the steel deep-processing process.

Modeling hydrogeological conditions of noble gases in water and aqueous electrolyte solutions

Dissolved noble gases in water hold significant potential as tracers and precursors in various hydrogeological and geological applications, particularly in understanding surface water-groundwater interactions. These applications necessitate precise solubility predictions. Employing the fugacity-fugacity approach, our study models the solubilities of Neon, Argon, Krypton, Xenon, and Radon in both pure water and electrolyte solutions. Leveraging the Cubic-Plus-Association Equation of State, we achieve remarkable accuracy, with average deviations below 2.5 % for vapor pressure, liquid, and vapor-phase densities. Additionally, in water–gas binary systems, deviations in gas solubilities within pure water remain under 5.0 %. Extending our analysis to water–gas-salt ternary systems, our model demonstrates deviations smaller than 5.6 %. Alongside discussing the gas dissolution mechanism, this work emphasizes the adaptability of the model, informed by robust experimental and modeling data. The interpretations derived from modeling hydrogeological conditions are poised to enhance our understanding of hydrological processes, thereby assisting planners and water managers in achieving sustainable development and management of water resources.

Efficient cellulose dissolution and derivatization enabled by oxalic/sulfuric acid for high-performance cellulose films as food packaging

The performance of cellulose-based materials is highly dependent on the choice of solvent systems. Exceptionally, cellulose dissolution and derivatization by efficient solvent have been considered as a key factor for large-scale industrial applications of cellulose. However, cellulose dissolution and derivatization often requires harsh reaction conditions, high energy consumption, and complex solubilizing, resulting in environmental impacts and low practical value. Here we address these limitations by using a low-temperature oxalic acid/sulfuric acid solvent to enable cellulose dissolution and derivatization for high-performance cellulose films. The dissolution and derivatization mechanism of the mixed acid is studied, demonstrating that cellulose is firstly socked by oxalic acid, then more hydrogen bonds ionized by sulfuric acid break cellulose chain, and finally the esterification reaction between oxalic acid and cellulose is catalyzed by sulfuric acid. Solutions containing 8 %–10 % cellulose are obtained and can be stored for a long time at −18 °C without significant degradation. Moreover, the cellulose film exhibits a higher tensile strength of up to 66.1 MPa, thermal stability, and degree of polymerization compared to that fabricated by sulfuric acid. These unique advantages provide new paths to utilize renewable resources for alternative food packaging materials at an industrial scale.

Improving intergranular cracking and stress corrosion cracking resistance of highly sensitized AA5083 Al-Mg alloy via reversion heat treatment

This study systematically examines the impact of reversion heat treatments (220–280 ℃ for 1 h) on the microstructure evolution, electrochemical corrosion, intergranular cracking (IGC) and stress corrosion cracking (SCC) of a severely sensitized (175 ℃/100 h) AA5083 alloy. Increasing the reversion temperature gradually enhances the corrosion resistance by dissolving the β′-Al3Mg2 phase, with the optimal treatment identified as 280 ℃/1 h. The βˊ phase maintains its planar film shape and continuously covers the grain boundaries after reversion treatment below 240 °C, but spheroidizes at the triple junctions at 260 °C. The morphology of the βˊ phase is dictated by grain boundary diffusion and interface diffusion. Reversion treatments improve SCC resistance by dissolving the β′ phase and reducing yield strength, attributed to anodic dissolution and hydrogen embrittlement mechanisms. This research offers valuable insights into the practical benefits of reversion treatments for Al-Mg alloy marine applications, addressing safety concerns related to sensitization.

Study on the Microstructure Evolution and Strength Deterioration of Powder Crystal Dolomite under Dissolution

To study the influence of water–rock interactions on the deterioration of rock, particularly the problems of the complex dissolution mechanism of dolomite and the difficulty in establishing chemical damage, dolomite obtained from a tunnel in Yuxi City was utilized. The macroscopic and microscopic dissolution characteristics of dolomite were analyzed using an indoor dissolution test combined with the hydrochemical characteristics of the study area, which were found to be favorable for dissolution. The dissolution of dolomite indicates the chemical decomposition of dolomite crystals, and the crystal failure mode is divided into intergranular dissolved pores and intracrystalline micropore development. Under various pH conditions, as H + is immersed in the rock sample, the failure mode of the rock sample develops from longitudinal cracks to transverse and longitudinal staggered cracks. Based on the aforementioned conclusions, in addition to the principle of chemical kinetics and the generalized Lemaitre strain equivalence principle, a damage model suitable for dolomite chemical erosion was defined. The fitting degree between the calculated value of uniaxial compressive strength and the experimental value reaches 98%, which is of excellent prediction accuracy and reliability. The model for dolomite chemical damage proposed herein provides a theoretical basis for dolomite dissolution damage; the theory of rock chemical damage is thereby enhanced.

Corrosion of F/M steels and austenitic steels in Pb-Mg at different temperatures

Pb83Mg17 is expected to be a potential coolant for lead cooled fast reactors because of its less toxic radioactive products and possible acceptable corrosion rate without additional oxygen control in comparison with LBE. In order to evaluate the compatibility of structural steels and Pb-Mg, two F/M steels (SIMP, T91) and two austenitic steels (316L, 15-15Ti) were tested in Pb-Mg at 350, 450 and 550 °C with exposure time ranging from 100 h to 2000 h in this work. Compared with the slight corrosion or no obvious corrosion of F/M steels, austenitic steels have suffered very serious dissolution corrosion which is significantly influenced by temperature and exposure time. The corrosion rate of austenitic steels is controlled by dissolution or diffusion mechanism at different temperatures.

Characterization and Dissolution Mechanism of Low-Molecular-Weight Organic Acids or Inorganic Mesoporous Particle-Based Piperine Amorphous Solid Dispersions.

The objective of the current study is to prepare amorphous solid dispersions (ASDs) containing piperine (PIP) by utilizing organic acid glycyrrhizic acid (GA) and inorganic disordered mesoporous silica 244FP (MSN/244FP) as carriers and to investigate their dissolution mechanism. The physicochemical properties of ASDs were characterized with scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), and differential scanning calorimetry (DSC). Fourier transform infrared spectroscopy (FTIR) and one-dimensional proton nuclear magnetic resonance (1H NMR) studies collectively proved that strong hydrogen-bonding interactions formed between PIP and the carriers in ASDs. Additionally, molecular dynamic (MD) simulation was conducted to simulate and predict the physical stability and dissolution mechanisms of the ASDs. Interestingly, it revealed a significant increase in the dissolution of amorphous PIP in ASDs in in vitro dissolution studies. Rapid dissolution of GA in pH 6.8 medium resulted in the immediate release of PIP drugs into a supersaturated state, acting as a dissolution-control mechanism. This exhibited a high degree of fitting with the pseudo-second-order dynamic model, with an R2 value of 0.9996. Conversely, the silanol groups on the outer surface of the MSN and its porous nanostructures enabled PIP to display a unique two-step drug release curve, indicating a diffusion-controlled mechanism. This curve conformed to the Ritger-Peppas model, with an R2 > 0.9. The results obtained provide a clear evidence of the proposed transition of dissolution mechanism within the same ASD system, induced by changes in the properties of carriers in a solution medium of varying pH levels.

A critical meta-analysis of CO2-water-rock interaction in basalt for CO2 storage: A review based on global and Indian perspective

Global warming and energy security lead to the hunt for alternative energy sources and CO2 emission mitigation technologies like carbon capture and storage (CCS). CCS is a prominent technique and its success depends on the sites of storage and agents influencing the storage efficiency. Geological formations are much safer as compared to oceanic injection for CO2 storage and include formations like sedimentary and igneous formations. Igneous formations like peridotite, komatiites, and basalt have huge potential to store CO2 and take the least time to convert the injected gas into solid carbonates along with the advantage of negligible leakage (as injected gas converts to carbonates through carbon mineralization). Carbon mineralization is a complex process involving the interaction of water–CO2–rock to form solid carbonates. In this review, we have highlighted the carbon mineralization in basalt by discussing the dissolution and precipitation mechanism. The discussion includes the uncertainty in the role of aluminum ions and siderite precipitation during CO2 storage in basalt. The review article also presents the first insight for the qualitative assessment of the CO2 storage potential of Deccan volcanic provinces (DVP) in India concerning the rock composition, injection depth, and type of injection. The mineralogy, and structure of the Basaltic province of DVP support CO2 storage. The principal minerals including calcic plagioclase and pyroxene, support mineral carbonation. Out of the total available area of DVP, 95% consists of tholeiitic basalt, exhibiting a simple flow structure. Additionally, the area is seismically safe for CO2 storage. The challenges and future research gap areas highlighted in this review article include suitable depth for injection, lateral continuity, the role of geothermal gradient, water availability, and public acceptance. Thus, the article provides a critical insights into the exploration and development of CCS technologies in India, emphasizing the importance of the Deccan Volcanic Provinces in achieving net-zero goals.

Detecting phase transitions in lattice gauge theories: Production and dissolution of topological defects in 4D compact electrodynamics

We present the application of microcanonical inflection point analysis (MIPA)—a novel and powerful method for the systematic identification and classification of phase transitions (PTs)—to the microcanonical formulation of lattice gauge theories. Specifically, we explore how this approach sheds light on collective phenomena such as the emergence of topological order in quantum field theories. As a case study, we show how to systematically characterize PTs in 4D U(1) lattice electrodynamics. Beyond identifying the well-established deconfinement PT (DPT) associated with pair dissolution, classified as a first-order PT, we uncover two higher-order PTs not observed before. Thanks to the application of the MIPA, we identify an independent third-order PT in the confined phase and indications of a dependent third-order PT in the deconfined (Coulomb) phase. To gain physical insights into these PTs, we numerically compute the average number density of monopolar and pair defects as a function of energy. Notably, our findings reveal that the pair dissolution mechanism extends beyond a singular transitional phenomenon coinciding with the DPT. Instead, it encompasses a spectrum of transitional phenomena, as indicated by the rates of acceleration and deceleration in the dissolution of pairs as a function of energy. Finally, we briefly discuss how such a method can be extended to more complex quantum field theories on a lattice. Published by the American Physical Society 2024

Study on Chalcopyrite Dissolution Mechanism and Bioleaching Community Behavior Based on Pulp Concentration Gradient at 6 °C

Low-temperature bioleaching is relevant to the recovery of metals in alpine mines, but its development has been constrained by low bioleaching rates at high pulp concentrations. To this end, the bioleaching effect of the microbial community after the domestication of pulp concentration at 6 °C was studied. Domestication improved the bioleaching rate of copper. Environmental scanning electron microscopy (ESEM), X-ray diffraction (XRD), and electrochemical measurements revealed that the domestication process aggravated the corrosion of the chalcopyrite surface by accelerating its dissolution reaction. High-throughput sequencing technology indicated that Acidithiobacillus spp., Leptospirillum spp., and Acidiphilium spp. were the major lineages of the domesticated microbial community. The analysis of the microbial community revealed that domestication changed the microbial structure, enhancing the adaptability of the microbial community to pulp concentrations and acidic conditions. This study uncovered the mechanism by which domestication enhanced the bioleaching efficiency of the microbial community at low temperatures.

Enhancing the solubility of carbamazepine using ionic liquids: An experiment and theoretical calculation

This work investigates the solubility and dissolution mechanism of the insoluble drug, carbamazepine (CBZ), classified as class II drug in the Biopharmaceutical Classification System, in environmentally friendly solvent ionic liquids (ILs). The COSMO-RS model is used to identify suitable ILs for solubilizing CBZ. Experimental data of six ILs confirms the accuracy of the model, validating its usefulness for IL selection. The solubility of CBZ is influenced by both the anionic structure and temperature. Cytotoxicity tests on HUVEC and GES-1 cells show that all ILs are safe for CBZ dissolution. Based on solubility and toxicity data, [EMIM][Ac] is determined to be the optimal IL.The dissolution mechanism of CBZ in ILs is explored using the σ-profile calculated from the COSMO-RS model and quantum chemical (QC) analysis. ILs with anions that have effective hydrogen bond (HB) acceptability ([Ac]-) are found to be the most efficient solvents for CBZ solvation. ILs with longer alkyl chains in the imidazole cations exhibit reduced polarity, increasing their affinity with CBZ. Therefore, [EMIM][Ac] is the superior IL choice due to its moderate polarity in [EMIM]+ and ideal cationic characteristics with long alkyl chains, along with the strong HB acceptability of [Ac]- anions. The findings have significant implications for choosing appropriate solvents, namely ionic liquids, for CBZ, as well as for selecting solvents with comparable structures for other medicines.

Dissolution dynamics of partially protected poly(4-hydroxystyrene) in organic developers investigated by a quartz crystal microbalance (QCM) method

Poly(4-hydroxystyrene) (PHS) molecules in solid films are connected to each other through polar and nonpolar molecular interaction and hydrogen bonds. Although the dissociation of phenolic hydroxyl groups plays a major role in the dissolution of PHS films in tetramethylammonium hydroxide (TMAH) aqueous developer, it is important to clarify the effects of other interactions. In this study, we investigated the dissolution dynamics of partially protected PHS in organic developer by a quartz crystal microbalance method to deepen the fundamental understanding of the dissolution dynamics of chemically amplified resists. The dissolution dynamics in the solvents, in which the phenolic hydroxyl groups are hardly dissociated, was measured. In a 50 vol% methanol aqueous developer, a large swelling was observed. By decreasing the polarity of the developer, the dissolution dynamics was significantly changed. In the hexyl acetate, the dissolution kinetics of PHS films became similar to that in TMAH aqueous developer although the dissolution mechanism is different.