Metal–Organic Gel Leading to Customized Magnetic‑Coupling Engineering in Carbon Aerogels for Excellent Radar Stealth and Thermal Insulation Performances

Metal–organic gel(MOG)derived composites are promising multi-functional materials due to their alterable composition,identifiable chemical homogeneity,tunable shape,and porous structure.Herein,stable metal–organic hydrogels are prepared by regulating the complexation effect,solution polarity and curing speed.Meanwhile,collagen peptide is used to facilitate the fabrication of a porous aerogel with excellent physical properties as well as the homogeneous dispersion of magnetic particles during calcination.Subsequently,two kinds of heterometallic magnetic coupling systems are obtained through the application of Kirkendall effect.FeCo/nitrogen-doped carbon(NC)aerogel demonstrates an ultra-strong microwave absorption of−85 dB at an ultra-low loading of 5%.After reducing the time taken by atom shifting,a FeCo/Fe3O4/NC aerogel containing virus-shaped particles is obtained,which achieves an ultra-broad absorption of 7.44 GHz at an ultra-thin thickness of 1.59 mm due to the coupling effect offered by dual-soft-magnetic particles.Furthermore,both aerogels show excellent thermal insulation property,and their outstanding radar stealth performances in J-20 aircraft are confirmed by computer simulation technology.The formation mechanism of MOG is also discussed along with the thermal insulation and electromagnetic wave absorption mechanism of the aerogels,which will enable the development and application of novel and lightweight stealth coatings.

3D Collagen Gels:A Promising Platform for Dendritic Cell Culture in Biomaterials Research

The three-dimensional(3D)cell culture system has garnered significant attention in recent years as a means of studying cell behavior and tissue development,as opposed to traditional two-dimensional cultures.These systems can induce specific cell reactions,promote specific tissue functions,and serve as valuable tools for research in tissue engineering,regenerative medicine,and drug discovery.This paper discusses current developments in the field of three-dimensional cell culture and the potential applications of 3D type 1 collagen gels to enhance the growth and maturation of dendritic cells.

Compliant Iontronic Triboelectric Gels with Phase-Locked Structure Enabled by Competitive Hydrogen Bonding

Rapid advancements in flexible electronics technology propel soft tactile sensing devices toward high-level biointegration,even attaining tactile perception capabilities surpassing human skin.However,the inherent mechanical mismatch resulting from deficient biomimetic mechanical properties of sensing materials poses a challenge to the application of wearable tactile sensing devices in human-machine interaction.Inspired by the innate biphasic structure of human subcutaneous tissue,this study discloses a skin-compliant wearable iontronic triboelectric gel via phase separation induced by competitive hydrogen bonding.Solvent-nonsolvent interactions are used to construct competitive hydrogen bonding systems to trigger phase separation,and the resulting soft-hard alternating phase-locked structure confers the iontronic triboelectric gel with Young’s modulus(6.8-281.9 kPa)and high tensile properties(880%)compatible with human skin.The abundance of reactive hydroxyl groups gives the gel excellent tribopositive and self-adhesive properties(peel strength>70 N m^(−1)).The self-powered tactile sensing skin based on this gel maintains favorable interface and mechanical stability with the working object,which greatly ensures the high fidelity and reliability of soft tactile sensing signals.This strategy,enabling skin-compliant design and broad dynamic tunability of the mechanical properties of sensing materials,presents a universal platform for broad applications from soft robots to wearable electronics.

A Research Progress of CO_(2)-Responsive Plugging Channeling Gels

In the heterogeneous reservoirs,CO_(2) flooding easily leads to CO_(2) gas channeling,which can seriously affect sweeping efficiency and reduce oil recovery.After thoroughly investigating the advantages and shortcomings of various CO_(2) plugging technologies,this paper focuses on the feasibility of improving conventional water-alternating gas(WAG)through CO_(2)-responsive gel materials.Based on the different chemical reaction mechanisms between the unique chemical structure and CO_(2),changes in the material’s physical and chemical properties can respond to CO_(2).The feasibility of utilizing these property changes for CO_(2)-responsive plugging is explored.Various CO_(2)-responsive gels and gel nanoparticles have been extensively researched in different fields,such as energy,medicine,and biology.This paper surveys the molecular structures,chemical compositions,response mechanisms,and changes of these CO_(2)-responsive gels,aiming to draw insights into the carbon dioxide-enhanced oil recovery(CO_(2)-EOR)field.Finally,the key issues and future development direction of CO_(2)-responsive plugging gels were analyzed.

Effect of nano TiO_(2) and SiO_(2) on gelation performance of HPAM/PEI gels for high-temperature reservoir conformance improvement

Nanoparticles have been widely used in polymer gel systems in recent years to improve gelation performance under high-temperature reservoir conditions. However, different types of nanoparticles have different effects on their gelation performance, which has been little researched. In this study, the high-temperature gelation performance, chemical structure, and microstructure of polymer gels prepared from two nanomaterials (i.e., nano-SiO_(2) and nano-TiO_(2)) were measured. The conventional HPAM/PEI polymer gel system was employed as the control sample. Results showed that the addition of nano-TiO_(2) could significantly enhance the gel strength of HPAM/PEI gel at 80 ℃. The gel strength of the enhanced HPAM/PEI gel with 0.1 wt% nano-TiO_(2) could reach grade I. The system also had excellent high-temperature stability at 150 ℃. The enhanced HPAM/PEI gel with 0.02 wt% nano-TiO_(2) reached the maximum gel strength at 150 ℃ with a storage modulus (G′) of 15 Pa, which can meet the need for efficient plugging. However, the nano-SiO_(2) enhanced HPAM/PEI polymer gel system showed weaker gel strength than that with nano-TiO_(2) at both 80 and 150 ℃ with G′ lower than 5 Pa. Microstructures showed that the nano-TiO_(2) enhanced HPAM/PEI gel had denser three-dimensional (3D) mesh structures, which makes the nano-TiO_(2) enhanced HPAM/PEI gel more firmly bound to water. The FT-IR results also confirmed that the chemical structure of the nano-TiO_(2) enhanced HPAM/PEI gel was more thermally stable than nano-SiO_(2) since there was a large amount of –OH groups on the structure surface. Therefore, nano-TiO_(2) was more suitable as the reinforcing material for HPAM/PEI gels for high-temperature petroleum reservoir conformance improvement.

Dehydration Mechanism of Secondary Cross-linked Gels

In this paper, microscopic characteristics of preformed gels （PGs） and secondary cross-linked gels （SCG） with the same concentration were analyzed by atomic force microscopy （AFM）. Experimental results indicate that the microstructure of secondary cross-linked gels is a thick 3-D network, in which micro-holes and irregular macro-holes are embedded. The maximum width of the irregular macro-holes is 200 nm. In the SCG two different chemical bonds were formed, which leads to the structural inhomogeneity and the asymmetry of the crosslinking density. The structural inhomogeneity of SCG results in the formation of irregular macro-holes. The excessive cross-linking density is the primary reason for dehydration of SCG and the presence of irregular macro-holes in SCG can facilitate dehydration.

GELS技术在光交换以太网中的应用(本期优秀论文)

具有层次化分割思想的运营商骨干网传输(PBT)技术,实现了数据平台和控制平台的分离。为了解决PBT缺乏完善的控制、管理等相关功能的不足,探讨了将GMPLS Ethernet Label Switching (GELS)技术应用至光交换以太网的设想,提出了GELS在PBT中应用的初步方案。

Effect of AMPS(2-acrylamido-2-methylpropane sulfonic acid) content on the properties of polymer gels

The BST oilfield in the northwestern Taklamakan Desert is a fractured carbonate reservoir,but issues of water breakthrough are becoming increasingly severe with the development of water flooding.Unfortunately,the high-temperature and high-salt conditions(130°C,71695 mg/L)of the BST oilfield pose challenges for the development of plugging agents.In this study,the effects of 2-acrylamido-2-methylpropane sulfonic acid(AMPS)content on AM/AMPS copolymers and gels were studied through viscosity measurements,nuclear magnetic resonance(NMR),and cryo-scanning electron microscope(Cryo-SEM).Moreover,the AMPS stabilization mechanism of the polymers and gels was explained.Heatresistant and salt-tolerant gel systems were developed,and their gelation properties,thermal stability,injection capacity,and plugging ability were evaluated.Experimental results showed inconsistencies between the effects of AMPS content on the polymers and gels.For the polymers,the thermal stability increased with increased AMPS content in the polymer.However,excessive AMPS content resulted in poor gelation and low strength.The developed gel systems with S30 polymer(AMPS content is approximately 26%)exhibited excellent thermal stability,controllable gelation time,good injection capacity,and plugging ability.The field application results indicated that most production wells had a positive response,with reduced water-cut and increased daily oil production.

Activity and Enantioselectivity of Lipase Immobilized in CTAB Microemulsion-based Gels

Introduction The formation of gelatin-containing mieroemulsionbased gels（MBGs） was first described in 1986 and the physical/structural characterization was carried out by a number of groups with a variety of techniques including tracer diffusion, electrical conductivity, NMR, X-ray and small angle neutron scattering. The MBGs were proposed to comprise an extensive, rigid, interconnected network of gelatin/water rods stabilized by a monolayer of surfactant, in coexistence with a po- pulation of conventional W/O microemulsion droplets.

Crack buckling in soft gels under compression

Recent interest in designing soft gels with high fracture toughness has called for simple and robust methods to test fracture behavior. The conventional method of applying tension to a gel sample suffers from a difficulty of sample gripping. In this paper, we study a possible fracture mechanism of soft gels under uni-axial compression. We show that the surfaces of a pre-existing crack, oriented parallel to the loading axis, can buckle at a critical compressive stress. This buckling instability can open the crack surfaces and cre- ate highly concentrated stress fields near the crack tip, which can lead to crack growth. We show that the onset of crack buckling can be deduced by a dimensional argument com- bined with an analysis to determine the critical compression needed to induce surface instabilities of an elastic half space. The critical compression for buckling was verified for a neo- Hookean material model using finite element simulations.

A review of nuclear magnetic resonance(NMR) technology applied in the characterization of polymer gels for petroleum reservoir conformance control

Polymer gel systems have been widely applied to control excessive water and improve oil recovery(IOR)in petroleum reservoirs.They are usually divided into two main types,in-situ cross-linked polymer gels,and pre-formed polymer gels.In recent years,nuclear magnetic resonance(NMR) technology has been gradually applied to the research of polymer gel systems due to its unique analysis advantages.This paper is intent to review these works systematically.For in-situ cross-linked polymer gel systems,NMR can be used to characterize the chemical structure changes of the polymer,the cross-linker,and the auxiliary agent in the formulation of the polymer gel systems.Moreover,the gelation time and the gel strength of the in-situ cross-linked polymer gel systems can also be measured by NMR.For pre-formed polymer gels,NMR can be employed to detect the chemical structure of the designed products.Last,the NMR method can evaluate the plugging,water control,and oil improvement performance of the polymer gels in porous media without using dopants.This review can help readers build a more systematic understanding of the application of NMR technology in polymer gel systems for IOR and help re searchers to more deeply study the performance of polymer gel systems.

Examination of literature on colloidal dispersion gels for oil recovery

This paper examines literature that claims,suggests,or implies that floods with"colloidal dispersion gels"(CDGs)are superior to polymer floods for oil recovery.The motivation for this report is simple.If CDGs can propagate deep into the porous rock of a reservoir,and at the same time,provide resistance factors or residual resistance factors that are greater than those for the same polymer formulation without the crosslinker,then CDGs should be used in place of polymer solutions for most/all polymer,surfactant,and ASP floods.In contrast,if the claims are not valid,(1)money spent on crosslinker in the CDG formulations was wasted,(2)the mobility reduction/mobility control for CDG field projects was under-designed,and(3)reservoir performance could have been damaged by excessive loss of polymer,face-plugging by gels,and/or excessive fracture extension.From this review,the clear answer is that there is no credible evidence that colloidal dispersion gels can propagate deep into the porous rock of a reservoir,and at the same time,provide resistance factors or residual resistance factors that are greater than those for the same polymer formulation without the crosslinker.CDGs have been sold using a number of misleading and invalid arguments.Very commonly,Hall plots are claimed to demonstrate that CDGs provide higher resistance factors and/or residual resistance factors than normal polymer solutions.However,because Hall plots only monitor injection pressures at the wellbore,they reflect the composite of face plugging/formation damage,in-situ mobility changes,and fracture extension.Hall plots cannot distinguish between these effects-so they cannot quantify in situ resistance factors or residual resistance factors.Laboratory studiesdwhere CDG gelants were forced through short cores during 2-3 h-have incorrectly been cited as proof that CDGs will propagate deep(hundreds of feet)into the porous rock of a reservoir over the course of months.In contrast,most legitimate laboratory studies reveal that the gelation time for CDGs is a day or less and that CDGs will not propagate through porous rock after gelation.A few cases were noted where highly depleted Al and/or HPAM fluids passed through cores after one week of aging.Details about these particular formulations/experiments were sparse and questions remain about their reproducibility.No credible evidence indicates that the CDG can propagate deep into a reservoir(over the course of weeks or months)and still provide a greater effect than that from the polymer alone.With one exception,aluminum from the CDG was never reported to be produced in a field application.In the exception,Chang reported producing 1-20%of the injected aluminum concentration.The available evidence suggests that some free(unreacted)HPAM and aluminum that was associated with the original CDG can propagate through porous media.However,there is no evidence that this HPAM or aluminum provides mobility reduction greater than that for the polymer formulation without crosslinker.

Variation in Polymerization Degree of C-A-S-H Gels and Its Role in Strength Development of Alkali-activated Slag Binders

To investigate the variation in the degree of polymerization calcium aluminium silicate hydrate(C-A-S-H)gel and its role in the evolution of the strength of waterglass slag binders,the compressive strength,hydration products,degree of hydration of the slag,and the degree of polymerization of C-A-S-H gels of binders were examined.The experimental results indicate that the pH of the pore solution increased with an increase in the Na_(2)O concentration.However,mortar with an optimum compressive strength value of 81.0 MPa at 28 d was obtained when water glass modulus was 1.5.The main hydration product is a C-A-S-H gel for which the quantity and the degree of polymerization depend strongly on the Na_(2)O concentration;for a given range,both increase with increasing Na_(2)O concentration,thus yielding an enhanced strength.A further increase in the Na_(2)O concentration continuously increases the quantity of C-A-S-H gels while drastically reducing the degree of polymerization.The positive effect of the former is counteracted by the adverse effect of the latter,ultimately,leading to a decreased strength.Furthermore,we reveal that the degree of polymerization for C-A-S-H gels may be affected by pH,through a series of complex chemical reactions.

Facile Approach for Preparation of Xylan-based Double-network Hydrogels

In this study,xylan-based double-network(DN)hydrogels(xylanbased DN gels)with excellent mechanical properties were prepared using acrylic acid and acrylamide(AM)based on a DN approach.The first layer network was obtained by grafting and crosslinking polyacrylic acid(PAA)molecular chains onto xylan with ammonium persulfate(APS)as the initiator and N,N'-methylenebisacrylamide(MBA)as the crosslinking agent;this network was subsequently immersed into an aqueous AM monomer in the presence of APS and MBA for the preparation of the second layer network.The results showed that the double networks were crosslinked by covalent bonds and that the mechanical properties of the xylan-based DN gels were enhanced.Thus,the xylan-based DN gels exhibited a maximum compression stress of 24.9 MPa.The xylan-based DN gels could also recover 97%of their original height after 15 repeated compression cycles;this indicates that the xylan-based DN gels possessed high resistance to friction and wear.Therefore,the prepared xylan-based DN gels have considerable potential for tissue engineering applications.

In-Situ Synthesized Myoglobin Imprinted Poly(N-Isopropylacrylamide)/Silica Nanocomposite Gels by Using the Molecular Imprinting Method

Temperature sensitive imprinted poly(N-isopropylacrylamide) nanocomposite gels were syntheses via in-situ, free radical crosslinking polymerization of corresponding monomer in nano-sized silica and five different concentrations of myoglobin solution by using the molecular imprinting method. Mb adsorption from five different concentrations of Mb solutions was investigated by two types of nanocomposite gel systems prepared by non-imprinted and imprinted methods. Nanocomposite gels imprinted with Mb showed higher adsorption capacity and specificity for Mb than nanocomposite gels prepared by the usual procedure. The highest Mb adsorption was observed via the imprinted nanocomposite gels with 12.5% Mb. In addition, selectivity studies were also performed by using two reference molecules as fibrinogen and hemoglobin. The imprinted nanocomposite gels had higher adsorption capacity for Mb than the non-imprinted gels and also exhibited good selectivity for Mb and high adsorption rate depending on the number of Mb sized cavities.

Injectable self-healing nanocellulose hydrogels crosslinked by aluminum:Cellulose nanocrystals vs.cellulose nanofibrils

With excellent biocompatibility and unique physiochemical properties,nanocelluloses including cellulose nanocrystals(CNCs)and cellulose nanofibrils(CNFs)are promising candidates for preparing biomedical hydrogels.CNCs and CNFs are different in morphology and surface charges.Herein,CNCs and two CNFs(CNFs-C,Carboxylated CNFs;CNFs-P,Phosphorylated CNFs)were synthesized and applied to fabricate hydrogels through metal crosslinking.Aluminum crosslinking was found to be the best choice for enhancing the strength.This study systematically compared the morphologies,storage modulus,loss factor,continuous shear ramp,self-healing,swelling,in vitro degradation and injectable properties of the fabricated hydrogels,Further,a radar chart is summarized as guidelines to direct the rational selection to meet the specific requirements of further biomedical applications.At the same nanocellulose concentration and after Al^(3+)crosslinking,CNCs hydrogels had strong water holding capacity twice as much as that of CNFs hydrogels.While CNFs hydrogels showed higher hardness and stronger resistance to degradation than that of CNCs.These results provide detailed insights into nanocellulose hydrogels,making it possible to use these guidelines to select hydrogels for desired performance.

SYNTHESIS OF HIGH THERMOSTABLE SILICONE GELS CONSTRUCTED WITH LADDERLIKE POLYSILSESQUIOXANES

Heat-resistant silicone gels were synthesized by replacing the single main chain polymethylhydrosiloxane with reactive ladderlike polyhydrosilsesquioxane copolymers. Because of the interaction between polydimethylsiloxane chains and the ladderlike polysilsesquioxanes chains, the cyclization of the polydimethylsiloxane chains is hindered. The high thermal stability of the ladderlike polymers can improve the thermal stability of the silicone gels without sacrificing their good comprehensive properties.

Variational approximation methods for long-range force transmission in biopolymer gels

The variational principle of minimum free energy(MFEVP) has been widely used in research of soft matter statics.The MFEVP can be used not only to derive equilibrium equations(including both bulk equations and boundary conditions),but also to develop direct variational methods(such as Ritz method) to find approximate solutions to these equilibrium equations. We apply these variational methods to study long-range force transmission in nonlinear elastic biopolymer gels.It is shown that the slow decay of cell-induced displacements measured experimentally for fibroblast spheroids in threedimensional fibrin gels can be well explained by variational approximations based on the three-chain model of biopolymer gels.

STUDY ON ENRICHMENT AND SEPARATION OF TRACE ELEMENTS WITH SILICA GELS MODIFIED BY HETEROCYCLIC AZO DYES

Two types of modified silica gels were prepared by adsorption method and bonding method respectively. Enrichment and separation of trace metal ions have been done by using the column packed with modified silica gels.

SURFACE DYNAMIC FRICTION OF POLYMER GELS

The sliding friction of various kinds of hydrogels has been studied and it was found that the frictional behaviors ofthe hydrogels do not conform to Amonton's law F=μW which well describes the friction of solids. The frictional force andits dependence on the load are quite different depending on the chemical structures of the gels, surface properties of theopposing substrates, and the measurement condition. The gel friction is explained in terms of interracial interaction, eitherattractive or repulsive, between the polymer chain and the solid surface. According to this model, the friction is ascribed tothe viscous flow of solvent at the interface in the repulsive case. In the attractive case, the force to detach the adsorbing chainfrom the substrate appears as friction. The surface adhesion between glass particles and gels measured by AFM showed agood correlation with the friction, which supported the repulsion-adsorption model proposed by the authors.