Preformed Particles Research Articles

Experimental evaluation of temporary plugging performance and mechanism analysis of degradable preformed particle gel based on NMR technology

Utilizing chemical temporary plugging systems to further increase the stimulated reservoir volume (SRV) and improve oil recovery (IOR) has become a hot topic in the current petroleum industry. Pre-formed gel particles (PPG) possess excellent swelling properties and can form high-strength plugging in high-permeability channels. In addition, degradable pre-formed gel particles (DPPG) further exhibit self-degradation characteristics and excellent temporary plugging and fluid diverting performance. In our previous studies, we examined the temporary plugging mechanisms of DPPG prepared with different molecular weight (MW) of crosslinking agents (PEGDA) through bottle tests and core displacement experiments. However, the microscopic swelling mechanism and temporary plugging mechanism in pore throats of reservoir cores are still unclear. In this paper, comprehensive research was conducted on the microscopic temporary plugging mechanism of DPPG prepared with different MW crosslinking agents using both and method. Results showed that DPPG with different compositions had different micro-swelling performance. NMR-T2 analysis for bottle test showed that DPPG-M1 (with the smallest MW of crosslinking agent) gradually decreased in nuclear signal during the water absorption and swelling process, and had the largest swelling volume and swelling rate. On the other hand, DPPG-M5 (with the largest MW of crosslinking agent) exhibited a slow diffusion process of surface water towards the nucleus, resulting in the smallest swelling volume and swelling rate. However, its complete degradation time was longer. Moreover, the NMR T2 (i.e., spin-spin relaxation time) results of the cores in the dynamic temporary plugging experiment showed that the decrease of the MW of the crosslinking agent enhanced the plugging performance, but with less damage to the formation. The MRI images confirmed that DPPG-M5 had better injection capability in the core and caused greater damage to the core. The research results of this study showed that NMR technology can reveal the temporary plugging mechanism of DPPG from a micro-level perspective.

Persistent free radicals in natural organic matter activated by iron particles enhanced disinfection byproduct formation

The widespread presence of iron (Fe) particles and natural organic matter (NOM) in drinking water distribution systems (DWDS) can significantly affect tap water quality, contributing to aesthetic issues and potentially generating harmful disinfection byproducts (DBPs). This study revealed that Fe particles, when combined with humic acid (HA), substantially increased DBP formation during chlorination. Fe particles (particularly preformed Fe particles) significantly increased haloacetic acid (HAA) formation by activating the persistent free radicals (PFRs) in the HA. Compared with the control system without Fe particles, greater than 2 times of HAA increase were observed for the system with Fe pariticles. PFRs accumulated on Fe particle surface could generate hydroxyl radicals, facilitating the decomposition of HA into smaller molecules, which were more reactive with chlorine disinfectants, thus elevated the DBP formation including both known and unknown N-DBPs and Cl-DBPs. The DBP promotion effect of in-situ formed Fe particles was much less than that of preformed Fe particles although both in-situ formed and preformed Fe particles could accumulate PFRs from HA. In-situ formed particles primarily accumulated carbon-centered PFRs, while preformed particles accumulated oxygen-centered PFRs. To mitigate the Fe particle induced water quality risks, it is crucial to control iron pipe corrosion and iron release in DWDS. In addtion, the optimization of treatment processes such as coagulation and filtration to more completely remove NOM and Fe particles could help minimize the DBP formation.

One-pot approach for acoustic directed assembly of metallic and composite microstructures by metal ion reduction

Acoustic-directed assembly is a modular and flexible bottom-up technique with the potential to pattern a wide range of materials. Standing acoustic waves have been previously employed for patterning preformed metal particles, however, direct patterning of metallic structures from precursors remains unexplored. Here, we investigate utilization of standing waves to exert control over chemical reaction products, while also exploring their potential in the formation of multi-layered and composite micro-structures. Concentric micro-structures of gold and silver were obtained by introducing a metal precursor salt and a reducing agent into a cylindrical piezoelectric resonator that also served as a reservoir. In addition, we introduce an innovative approach to directly fabricate metallic multi-layer and composite structures by reducing different metal ions or adding nanoparticles during the reduction step. We showcased our method through the fabrication of layered structures, incorporating a combination of gold and silver, as well as structures composed of silver and hematite nanoparticles. The produced structures were characterized through both surface and cross-sectional analyses, revealing the influence of the acoustic field on the mesostructure as well. This innovative approach is promising for production of complex microstructures with enhanced functionality and controlled properties.

Rapid and sustainable production of nano and micro medicine crystals via freeze-dissolving technology

Modern pharmaceutical manufacturing emphasizes the need for sustainable technologies. Fine particles, including nano and micro-sized crystals, are increasingly important, particularly in the production of inhalation medicines. A novel application of freeze-dissolving technology has been demonstrated in the production of metronidazole, a model drug. This process involves creating frozen spherical particles by introducing a tert-butanol solution containing dissolved metronidazole into liquid nitrogen. Various antisolvents, such as n-hexane, n-heptane, ethanol, n-propanol, n-butanol, or n-pentanol, were employed to dissolve these frozen templates at temperatures ranging from 248.15 to 278.15 K. During this process, pre-formed metronidazole fine particles within the frozen template were released into the antisolvent solution. An alternative method involved placing these frozen particles into a vacuumed freeze dryer to extract the fine particles. The new freeze-dissolving technology can save 99% both energy and time compared to the traditional freeze-drying method, demonstrating a significantly more efficient and sustainable pharmaceutical manufacturing approach.

The Interaction and Rheological Behavior of Preformed Gel Particles with Surfactants

Heterogeneous combination flooding systems are composed of surfactant and viscoelastic preformed gel particles (PGP) that can migrate in the pores. The interactions between PGP and surfactants have an important impact on the system. In our research described here heterogeneous aqueous suspensions of PGP and an anionic surfactant (sodium dodecyl benzene sulfonate, SDBS) or a nonionic surfactant coconut oil alkanolamide, (CDEA) were prepared. The effects of SDBS and CDEA on the swelling and rheological properties of the PGP was investigated. In addition, the influence of SDBS and CDEA on the thermal effects of PGP was studied. The results showed that the swelling ratio, apparent viscosity and storage modulus of the PGP decreased with the increase of SDBS concentration. On the contrary, the CDEA increased the swelling ratio and the rheological properties of PGP. The specific heat capacity ( C p ) of PGP increased with the SDBS concentration and decreased with the CDEA concentration. Similar to the rheological behavior, the influence of interactions on the PGP molecular thermal motion was related to the concentration of the surfactants. Therefore, studying the variation of C p with concentration can provide reference for the reasonable dosage of surfactants in heterogeneous oil displacement systems and a new perspective for investigating the interaction between surfactant and PGP or other polymers.

Application of efficient and sustainable freeze-dissolving technology in manufacturing of KHCO3 ultrafine particles

The development of ultrafine particles provided a new way to solve problems in the fields of energy, environment, and medicine, and had become one of the most promising technologies. Therefore, the application of ultrafine particles required the development of cleaner, greener, and more efficient preparation methods. The new freeze-dissolving technology has been applied in manufacturing of KHCO3 ultrafine particles, with an aqueous solution of 0.02–0.1 g KHCO3/g water. Frozen ice particles were formed after dripping the solution into liquid nitrogen. The antisolvent ethanol was used to dissolve the ice spherical template at a temperature below 273.15 K, and the pre-formed KHCO3 ultrafine particles inside the ice template remained in the ethanol aqueous solution. The ice particles were put into the freeze dryer to isolate the ultrafine KHCO3 particles. Compared with the particles produced with traditional freeze-drying technology, the ultrafine powder/particles produced by the freeze-dissolving technology were smaller with narrower size distribution. The freeze-dissolving technology has demonstrated a much more sustainable and efficient manufacturing process than the traditional freeze-drying process. In addition, the influence of the concentrations of KHCO3 and the sizes of ice particles were investigated with the discussions of mechanisms.

Antibiotic photocatalysis and antimicrobial activity of low-cost multifunctional Fe3O4@HAp nanocomposites.

Water contamination by multiple pollutants is a serious environmental issue originating from the many diverse sources of pollution. It has worsened with the appearance of new contaminants, named emerging micropollutants, such as drug residues which are considered a potential threat to human health and/or ecosystems. These require prior treatment before release into the environment. Simultaneous adsorption and photocatalysis as well as solid-liquid separation are promising technologies for water treatment. In order to obtain low cost photoactive nanocomposites, porous and magnetic Fe3O4-hydroxyapatite (wFeHAp) nanocomposites were prepared by soft chemistry from the dissociation of natural phosphate into Ca2+ and H3PO4 precursors, further neutralized by ammonia in the presence of preformed Fe3O4 particles. The magnetic nanocomposites were characterized and examined as effective antibacterial agents. Fe3O4 association with apatite modifies the surface properties of the wFeHAp nanocomposite materials, yielding efficient antimicrobial activity for S. aureus, B. subtilis, E. coli and K. pneumoniae strains. The photocatalytic removal of ciprofloxacin (CPF) and oxytetracyclin (OXT) antibiotics in water was also evaluated. The wFeHAp nanocomposites adsorbed and degraded the selected antibiotics successfully. Toxicity evaluation of the treated water after photodegradation using the four strains demonstrates the absence of toxic by-products at the end of the reaction. Therefore, Fe3O4@HAp nanoparticles are valuable for antimicrobial and photocatalysis applications.

Acrylamide preformed particle gels with movable-crosslinking for conformance control

In order to improve the deformation ability of the preformed gel particles (PPGs), the movable-crosslinking structure was introduced into the gel network. Herein, polyrotaxane cross-linkers were synthesized by a three-step method, and acrylamide and polyrotaxane cross-linkers form gel. The structure of polyrotaxane cross-linkers was characterized by IR, HNMR, and X-ray diffraction. The findings demonstrate the successful insertion of vinyl into cyclodextrin, resulting in the formation of crosslinking points. The gel with movable-crosslinking has better deformation ability, and the breaking elongation of gel is 937%, showing excellent deformation ability Through temperature resistance and salt resistance, it shows that the expansion ratio of gel is higher than that of ordinary gel. The injectability of the gel was investigated and the sand pack plugging test was conducted. The injectivity experiment shows that the gel with movable-crosslinking has positive injectivity, can migrate to the depth of the formation, and has excellent water-plugging effect.

Dilute Gd hydroxycarbonate particles for localized spin qubit integration.

Molecular spins are considered as the quantum hardware to build hybrid quantum processors in which coupling to superconducting devices would provide the means to implement the necessary coherent manipulations. As an alternative to large magnetically-dilute crystals or concentrated nano-scale deposits of paramagnetic molecules that have been studied so far, the use of pre-formed sub-micronic spherical particles of a doped Gd@Y hydroxycarbonate is evaluated here. Particles with an adjustable number of spin carriers are prepared through the control of both particle size and doping. Bulk magnetic properties and continuous wave and time-domain-EPR spectroscopy show that the Gd spins in these particles are potential qubits with robust quantum coherence. Monolayers of densely-packed particles are then formed interfacially and transferred successfully to the surface of Nb superconducting resonators. Alternatively, these particles are disposed at controlled localizations as isolated groups of a few particles through Dip-Pen Nanolithography using colloidal organic dispersions as ink. Altogether, this study offers new material and methodologies relevant to the development of viable hybrid quantum processors.

Interface hydrogen bonding dominated perfluorooctanoic acid (PFOA) accumulation by iron particles in drinking water pipes

Iron particle is one of the key factors inducing discoloration in drinking water distribution system (DWDS), but the mechanism of iron particles on the accumulation of trace organic pollutants in DWDS is not clear. Here, iron-based pipes from real DWDS were used to investigate the perfluorooctanoic acid (PFOA) accumulation mechanisms in DWDS. Results showed that old unlined pipes had a much higher accumulation capacity for PFOA than new pipes. Among the corrosion products in old pipes, Fe2O3 and Fe3O4 did not have obvious accumulation for PFOA, while FeOOH exhibited a strong accumulation effect for PFOA. Furthermore, the in-situ formed iron particles contributed more to PFOA accumulation than pre-formed iron particles. Interestingly, PFOA caused an increase in turbidity and particle size of in-situ formed iron particles. Mulliken charge of F-bonded Fe increased from +1.28 e to +1.30 e, which indicated that the oxidation state of Fe-center was strengthened by PFOA. When dissolved oxygen existed, a PFOA-FeOOH-O2 linkage could form through COO–Fe coordination and O2 interface adsorption, which enhanced cytotoxicity due to the generation of •OH radicals. These findings implied that interface hydrogen bonding dominated PFOA accumulation by iron particles in DWDS, which would increase the risks of discoloration.

Facile Fabrication of Starch-Based Microrods by Shear-Assisted Antisolvent-Induced Nanoprecipitation and Solidification.

Rod-like particles have attracted increasing attention because of their unique shape-dependent properties, which enable their superior performance compared to their isotropic counterparts. Thus, rod-like particles have potential applications in many fields, especially in biomedicine. However, the fabrication of uniform rod-like particles is challenging because of the principle of interfacial energy minimization. Herein, we present a facile, rapid, and cost-effective strategy for preparing starch-based microrods with tunable aspect ratios via shear-assisted antisolvent-induced nanoprecipitation and solidification. The preformed spherical particles swollen by the mixed solvent were elongated by the shear force and solidified in rod-like shape by antisolvent induction. The resulting starch-based microrods can encapsulate hydrophobic active substances and be modified with functional groups, indicating their potential applications as drug carriers and biologically active materials. The formation mechanism of the starch-based microrods discovered in this study provides a new perspective on the fabrication of rod-like polymer particles.

Human Serum Albumin Mitigates Formation of Fatty Acid Particles in Polysorbate-Containing Solutions

Over seventy percent of marketed monoclonal antibody therapeutics contain between 0.001% and 0.1% (w/v) polysorbate, as it has a generally beneficial stabilizing effect that increases drug product shelf life. However, polysorbate has also been shown to contribute to particle formation due to auto-oxidation and hydrolysis,1 which results in free fatty acids and subsequent fatty acid particle formation. Although the impact of fatty acid particles on the safety and efficacy of drug products has not been fully evaluated, it is advantageous to mitigate particle formation due to degradation of polysorbate, improving the consistency of a product's quality attributes (in this case particulate levels) throughout its lifecycle. In this report, we describe a simple experimental assay to rapidly generate fatty acid particles. Further, we show that the presence of human serum albumin (HSA) is sufficient to prevent the formation of fatty acid particles. Separately, we demonstrate that HSA can also rapidly and completely solubilize pre-formed particles. These results point to a highly plausible mechanistic explanation of previous observations and diminishes concern regarding low levels of particles in the final drug product.

Regioselective Seeded Polymerization in Block Copolymer Nanoparticles: Post-Assembly Control of Colloidal Features.

Post‐assembly modifications are efficient tools to adjust colloidal features of block copolymer (BCP) particles. However, existing methods often address particle shape, morphology, and chemical functionality individually. For simultaneous control, we transferred the concept of seeded polymerization to phase separated BCP particles. Key to our approach is the regioselective polymerization of (functional) monomers inside specific BCP domains. This was demonstrated in striped PS‐b‐P2VP ellipsoids. Here, polymerization of styrene preferably occurs in PS domains and increases PS lamellar thickness up to 5‐fold. The resulting asymmetric lamellar morphology also changes the particle shape, i.e., increases the aspect ratio. Using 4‐vinylbenzyl azide as co‐monomer, azides as chemical functionalities can be added selectively to the PS domains. Overall, our simple and versatile method gives access to various multifunctional BCP colloids from a single batch of pre‐formed particles.

Biocompatible Nanoparticles Based on Amphiphilic Random Polypeptides and Glycopolymers as Drug Delivery Systems.

In this research, the development and investigation of novel nanoobjects based on biodegradable random polypeptides and synthetic non-degradable glycopolymer poly(2-deoxy-2-methacrylamido-d-glucose) were proposed as drug delivery systems. Two different approaches have been applied for preparation of such nanomaterials. The first one includes the synthesis of block-random copolymers consisting of polypeptide and glycopolymer and capable of self-assembly into polymer particles. The synthesis of copolymers was performed using sequential reversible addition-fragmentation chain transfer (RAFT) and ring-opening polymerization (ROP) techniques. Amphiphilic poly(2-deoxy-2-methacrylamido-d-glucose)-b-poly(l-lysine-co-l-phenylalanine) (PMAG-b-P(Lys-co-Phe)) copolymers were then used for preparation of self-assembled nanoparticles. Another approach for the formation of polypeptide-glycopolymer particles was based on the post-modification of preformed polypeptide particles with an oxidized glycopolymer. The conjugation of the polysaccharide on the surface of the particles was achieved by the interaction of the aldehyde groups of the oxidized glycopolymer with the amino groups of the polymer on particle surface, followed by the reduction of the formed Schiff base with sodium borohydride. A comparative study of polymer nanoparticles developed with its cationic analogues based on random P(Lys-co-d-Phe), as well as an anionic one—P(Lys-co-d-Phe) covered with heparin––was carried out. In vitro antitumor activity of novel paclitaxel-loaded PMAG-b-P(Lys-co-Phe)-based particles towards A549 (human lung carcinoma) and MCF-7 (human breast adenocarcinoma) cells was comparable to the commercially available Paclitaxel-LANS.

Synthetic Strategies for Polymer Particles with Surface Concavities.

Over the past decade or so, there has been increasing interest in the synthesis of polymer particles with surface concavities, which mainly include golf ball-like, dimpled and surface-wrinkled polymer particles. Such syntheses generally can be classified into direct polymerization and post-treatment on preformed polymer particles. This review aims to provide an overview of the synthetic strategies of such particles. Some selected examples are given to present the formation mechanisms of the surface concavities. The applications and future development of these concave polymer particles are also briefly discussed.

Hierarchical Microphase Behaviors of Chiral Block Copolymers under Kinetic and Thermodynamic Control

Hierarchical Microphase Behaviors of Chiral Block Copolymers under Kinetic and Thermodynamic Control

Mixed RuxIr1−xO2 Supported on Rutile TiO2: Catalytic Methane Combustion, a Model Study

AbstractWith a modified Pechini synthesis, mixed RuxIr1−xO2 is grown on rutile‐TiO2 with full control of the composition x, where the preformed TiO2 particles serve as nucleation sites for the active component. Catalytic and kinetic data of the methane combustion over RuxIr1−xO2@TiO2 and unsupported RuxIr1−xO2 catalysts reveal that the least active catalyst is RuO2@TiO2 (onset temperature: 270 °C), while the most active catalyst is Ru0.25Ir0.75O2 with an onset temperature below 220 °C. Surprisingly, even Ru0.75Ir0.25O2@TiO2 is remarkably active in methane combustion (onset temperature: 230 °C), indicating that little iridium in the mixed RuxIr1−xO2 oxide component already improves the activity of the methane combustion considerably. We conclude that iridium in the mixed RuxIr1−xO2 oxide enables efficient methane activation, while ruthenium promotes the subsequent oxidation steps of the methyl group to produce CO2. Kinetic data provide a reaction order in O2 of zero, while that of methane is close to one, indicating that the methane activation is rate limiting. The apparent activation energy varies among RuxIr1−xO2 from 110 (x=0) to 80 kJ ⋅ mol−1 (x=1). This variation in the apparent activation energy may be explained by the variation in adsorption energy of oxygen. Under the given reaction conditions the catalyst's surface is saturated with adsorbed oxygen and only if oxygen desorbs, methane can be activated and the methyl group can be accommodated at the liberated surface metal sites.

Free silver nanoparticles doped by potassium: Work-function change in experiment and theory.

The composition-dependent change in the work-function (WF) of binary silver-potassium nanoparticles has been studied experimentally by synchrotron-based x-ray photoelectron spectroscopy (PES) and theoretically using a microscopic jellium model of metals. The Ag-K particles with different K fractions were produced by letting a beam of preformed Ag particles pass through a volume with K vapor. The PES on a beam of individual non-supported Ag-K nanoparticles created in this way allowed a direct absolute measurement of their WF, avoiding several usual shortcomings of the method. Experimentally, the WF has been found to be very sensitive to K concentration: Already at low exposure, it decreased down to ≈2 eV-below the value of pure K. In the jellium modeling, considered for Ag-K nanoparticles, two principally different adsorption patterns were tested: without and with K diffusion. The experimental and calculation results together suggest that only efficient surface alloying of two metals, whose immiscibility was long-term textbook knowledge, could lead to the observed WF values.

Novel preformed gel particles with controllable density and its implications for EOR in fractured-vuggy carbonated reservoirs

The pre-crosslinked gel particles has been perceived as an important alternative to improve oil recovery from fractured-vuggy carbonate reservoirs. However, it remains a great challenge for the applications in high temperature and high salinity reservoirs. In this context, we firstly developed novel preformed gel particles with controllable density (PGPCD) which can be used at high temperature (140 °C) and high salinity (250 g/L) fractured-vuggy carbonate reservoirs for in-depth profile control and displacement. Then, the swelling property, toughness, injectivity, EOR potential and EOR mechanisms of PGPCD were investigated. Experimental results show that PGPCD has favorable swelling ability, toughness, and controllable density due to the introduction of sodium montmorillonite and modified foamed acrylate rubber (ACM) powders. Moreover, PGPCD has favorable injectivity, and can mitigate water channeling in the form of “filling accumulation”, “bifurcation accumulation”, and “necked accumulation”. After the treatment, PGPCD achieves incremental oil recovery in a range of 16%–26% of original oil in place. Taken together, our findings suggest the role of PGPCD in promoting the incremental oil recovery at high temperature and high salinity reservoirs, especially in fractured-vuggy carbonate bottom water reservoirs.

The effects of the toughening mechanism and the molecular weights between cross-links on the fatigue resistance of epoxy polymer blends

The fatigue resistance of epoxy polymer blends incorporating different types of preformed polymer particles was evaluated in terms of fatigue threshold and fatigue crack propagation (FCP). The fatigue thresholds of epoxies modified with polyamide-12 (PA12) particles were associated with higher stress intensity factor ranges (ΔK) than those of pure epoxies, irrespective of the molecular weights between cross-links (Mc). In contrast, the fatigue thresholds of epoxy blends with core-shell rubber (CSR) particles were affected by Mc. The FCP curve for a highly crosslinked CSR-toughened epoxy with Mc of 1110 g/mol was located at higher ΔK values compared with data for the corresponding pure epoxy. In contrast, the fatigue threshold of a moderately cross-linked CSR-modified epoxy with Mc of 2360 g/mol appeared in the lower ΔK range relative to the pure epoxy. Both cavitation of the CSR particles and plastic deformation of the latter epoxy were localized in a narrow area.