Gelation of Hole Transport Layer to Improve the Stability of Perovskite Solar Cells

To achieve high power conversion efficiency(PCE) and long-term stability of perovskite solar cells(PSCs), a hole transport layer(HTL) with persistently high conductivity, good moisture/oxygen barrier ability, and adequate passivation capability is important. To achieve enough conductivity and effective hole extraction, spiro-OMe TAD, one of the most frequently used HTL in optoelectronic devices, often needs chemical doping with a lithium compound(LiTFSI). However, the lithium salt dopant induces crystallization and has a negative impact on the performance and lifetime of the device due to its hygroscopic nature. Here, we provide an easy method for creating a gel by mixing a natural small molecule additive(thioctic acid, TA) with spiro-OMe TAD. We discover that gelation effectively improves the compactness of resultant HTL and prevents moisture and oxygen infiltration. Moreover, the gelation of HTL improves not only the conductivity of spiro-OMe TAD, but also the operational robustness of the devices in the atmospheric environment. In addition, TA passivates the perovskite defects and facilitates the charge transfer from the perovskite layer to HTL. As a consequence, the optimized PSCs based on the gelated HTL exhibit an improved PCE(22.52%) with excellent device stability.

Rheo-optic in situ synchronous study on the gelation behaviour and mechanism of waxy crude oil emulsions

An improved rheo-optic in situ synchronous measurement system was employed to investigate the gelation behaviour and mechanism of waxy crude oil emulsions. By combining transmitted natural light and reflected polarized light microscopy, a multiangle composite light source was built to achieve the simultaneous observation of wax crystals and emulsified water droplets, as well as their dynamic aggregation process. Main outcomes on the microscopic mechanism were obtained by developed microscopic image processing method. It was found that the microstructure of W/O waxy crude oil emulsion has the evolution of “individual structure--homogeneous aggregate structure--heterogeneous coaggregate structure--floc structure” during the static cooling, which results in the four stages during gelation process. Different from previous studies, the aggregation of emulsified water droplets was found to be more significant and contributes to the formation and development of the wax crystals-emulsified water droplets coaggregate, which plays a decisive role in the further evolution of the gelled microstructure. Time series microscopic images show the dynamic aggregation of emulsified water droplets and wax crystals. Two different aggregation behaviours between wax crystals and water droplets were observed. That wax crystals can not only embed in gaps between adjacent water droplets and enhance the structure, but also surround the outside of the water droplets and continue to grow resulting in the interconnection of different coaggregates to form a larger floc structure. In addition, correlation between viscoelasticity and microstructure evolution of waxy crude oil emulsions of different water contents was discussed. With increasing water contents, the microstructure is changed from wax crystal flocculation structure as the main skeleton and the emulsified water droplets embedded in it, into the aggregation of emulsified water droplets occupying the main position. When the number of wax crystals and water droplets reaches a certain ratio, did wax crystals form coaggregates with emulsified water droplets, and the remaining wax crystals formed an overall flocculation structure, the viscoelasticity of the waxy crude oil emulsion is the highest.

Versatile MXene Gels Assisted by Brief and Low‑Strength Centrifugation

Due to the mutual repulsion between their hydrophilic surface terminations and the high surface energy facilitating their ran-dom restacking,2D MXene nanosheets usually cannot self-assemble into 3D macroscopic gels with various applications in the absence of proper linking agents.In this work,a rapid spontaneous gelation of Ti3C2Tx MXene with a very low dispersion concentration of 0.5 mg mL^(-1) into multifunctional architectures under moderate centrifugation is illustrated.The as-prepared MXene gels exhibit reconfigurable internal structures and tunable rheological,tribological,electrochemical,infrared-emissive and photothermal-conversion properties based on the pH-induced changes in the surface chemistry of Ti_(3)C_(2)T_(x) nanosheets.By adopting a gel with optimized pH value,high lubrication,exceptional specific capacitances(~635 and~408 F g^(-1) at 5 and 100 mV s^(-1),respectively),long-term capacitance retention(~96.7%after 10,000 cycles)and high-precision screen-or extrusion-printing into different high-resolution anticounterfeiting patterns can be achieved,thus displaying extensive potential applications in the fields of semi-solid lubrication,control-lable devices,supercapacitors,information encryption and infrared camouflaging.

Highly Porous Yet Transparent Mechanically Flexible Aerogels Realizing Solar-Thermal Regulatory Cooling

The demand for highly porous yet transparent aerogels with mechanical flexibility and solar-thermal dual-regulation for energy-saving windows is significant but challenging.Herein,a delaminated aerogel film(DAF)is fabricated through filtration-induced delaminated gelation and ambient drying.The delaminated gelation process involves the assembly of fluorinated cellulose nanofiber(FCNF)at the solid-liquid interface between the filter and the filtrate during filtration,resulting in the formation of lamellar FCNF hydrogels with strong intra-plane and weak interlayer hydrogen bonding.By exchanging the solvents from water to hexane,the hydrogen bonding in the FCNF hydrogel is further enhanced,enabling the formation of the DAF with intra-layer mesopores upon ambient drying.The resulting aerogel film is lightweight and ultra-flexible,which pos-sesses desirable properties of high visible-light transmittance(91.0%),low thermal conductivity(33 mW m^(-1) K^(-1)),and high atmospheric-window emissivity(90.1%).Furthermore,the DAF exhibits reduced surface energy and exceptional hydrophobicity due to the presence of fluorine-containing groups,enhancing its durability and UV resistance.Consequently,the DAF has demonstrated its potential as solar-thermal regulatory cooling window materials capable of simultaneously providing indoor lighting,thermal insulation,and daytime radiative cooling under direct sunlight.Significantly,the enclosed space protected by the DAF exhibits a temperature reduction of 2.6℃ compared to that shielded by conventional architectural glass.

Investigation of the effect of hydrocarbons and monoesters in the gelators’composition on the properties of edible oleogel

Natural wax gelators have different compositions of compounds(hydrocarbons,wax esters,free fatty alcohols,and free fatty acids),which results in oleogels with varying properties.To maintain a consistent composition,the individual components can be added to the original wax gelator.The content of hydrocarbons and wax esters greatly affects the structuring process of liquid edible oils with waxes.The aim of this study was to evaluate the possibility of modifying the properties of beeswax as a gelling agent by adding hydrocarbons or monoesters to obtain oleogels with specific properties.Various tests were conducted to assess the changes in the oleogel properties,such as color,microstructure,oil-binding capacity,thermal and textural properties.The research results have shown that the addition of the studied fractions has led to a significant change in all properties of oleogels.The initial size of oleogel crystals(7.29±1.80μm)changed after adding fractions,varying from 5.28μm to 12.58μm with hydrocarbons and from 9.95μm to 30.41μm with wax esters.The addition of 30%–50% hydrocarbons decreased the ability of the oleogels to bind oil and made them less firm compared to samples with 10%-20% hydrocarbons.Adding 10%-20% monoesters increased the firmness of the oleogels,but this indicator decreased when their content was increased to 50%.The obtained data indicate that hydrocarbons and wax esters can be used for targeted correction of the gelling properties of beeswax.

Preparation and Properties of Spray Polyurea Elastomer for Aquaculture Foam Floating Balls

[Objectives] This study was conducted to develop a polyurea elastomer which can be sprayed on the surface of expanded polystyrene (EPS) floating balls, so as to improve the surface strength and service life of the floating balls. [Methods] The effects of the types and amounts of isocyanate, chain extenders and polyether polyols on the gelation rate, adhesion and wear resistance of polyurea elastomer were investigated, and it was finally determined the preparation process of polyurea elastomer using liquid isophorone diisocyanate (IPDI) and amino-terminated polyether (D2000) as the main raw materials, dimethylthiotoluene diamine (E300) as the chain extender and silica as the wear resistance modifier through two-step solution polymerization of prepolymerization and chain extension. [Results] The physical properties and chemical resistance tests of spray polyurea elastomer showed that it had good physical properties and acid and alkali resistance, and could meet the requirements of spraying and protection of EPS floating ball surface in marine environment. [Conclusions] Polyurea elastomer coating can improve the aging resistance, wear resistance and acid and alkali resistance of EPS floating balls, and prevent them from being fragile and floating randomly to form marine floating garbage which results in "white pollution".

Effect of Cationic Surfactant on the Gelation of HPAM by Cr(III)

The effect of cationic surfactant cetyltrimethylammonium bromide (CTAB) on the gelation of partially hydrolyzed polyacrylamide (HPAM) by Cr (III) was investigated by using rheological measurements. The results indicated that the CTAB concentration has a pronounced effect on the viscoelastic properties of the gelling system.

Ultralight Magnetic and Dielectric Aerogels Achieved by Metal-Organic Framework Initiated Gelation of Graphene Oxide for Enhanced Microwave Absorption

The development of a convenient methodology for synthesizing the hierarchically porous aerogels comprising metal–organic frameworks(MOFs)and graphene oxide(GO)building blocks that exhibit an ultralow density and uniformly distributed MOFs on GO sheets is important for various applications.Herein,we report a facile route for synthesizing MOF/reduced GO(rGO)aerogels based on the gelation of GO,which is directly initiated using MOF crystals.Free metal ions exposed on the surface of MIL-88A nanorods act as linkers that bind GO nanosheets to a three-dimensional porous network via metal–oxygen covalent or electrostatic interactions.The MOF/rGOderived magnetic and dielectric aerogels Fe_(3)O_(4)@C/rGO and Ni-doped Fe_(3)O_(4)@C/rGO show notable microwave absorption(MA)performance,simultaneously achieving strong absorption and broad bandwidth at low thickness of 2.5(-58.1 dB and 6.48 GHz)and 2.8 mm(-46.2 dB and 7.92 GHz)with ultralow filling contents of 0.7 and 0.6 wt%,respectively.The microwave attenuation ability of the prepared aerogels is further confirmed via a radar cross-sectional simulation,which is attributed to the synergistic effects of their hierarchically porous structures and heterointerface engineering.This work provides an effective pathway for fabricating hierarchically porous MOF/rGO hybrid aerogels and offers magnetic and dielectric aerogels for ultralight MA.

The Fabrication of Microstructure Surface of Superhydrophobic Coating by Surface Gelation Technology

The microstructured surface of materials were fabricated by a two-step acid-base catalyzed sol-gel process. In fluorinated polymer with PTFE doping, the well-proportioned composite sols were prepared using sol-gel processing under the hydrochloric acid and deficiency of water conditions. After the substrate was coated by composite sols, and the gelation treatment on the surface of composite coating, the micrometer-scale and nanometer-scale hierarchical structures were formed in surface layer of material. XPS and TEM technologies were employed to identify that the gelation occurs just on the surface of composite coating. The morphology of coating surface was observed by SEM and AFM technologies. The microstructured surface of material can be fabricated using this inexpensive and easily controlled method on low surface energy resin materials, the super-hydrophobic coatings materials can be prepared.

Chitosan-Pectin Synergistic Interaction and Gelation

Mixed gels of chitosan-pectin were prepared by varying the ratio of constituents in the presence of NaCl. Mixed gel at 3%of total polysaccharide concentration with addtion of 12%NaCl showed a synergistic maximum when the ratio of chitosan to pectin was 60: 40. The effect of the polysaccharide concentration, the preparation temperature (T p), the time of incubation, balk salt concentration, the molecular weight and the degree of deacetylation of chitosan on gelation have been studied. Interaction mechanism between molecules of both polysaccharides was investigated by FT-IR spectrometry.

Synergistic Interaction and Gelation in Cationic Guar Gum-Sodium Alginate System

The synergistic interaction between the cationic guar gum (the ammonium hydroxy-propyl-trimethyl chloride of guar gum) and sodium alginate has been studied. The effects of the mass ratio of them, mixed temperature, balk salt ion concentration, incubation time and pH value on gelation were investigated. It has been observed that there was a gel strength maximum when the mass ratio was 0.6, the mixed temperature was 70°C, the balk salt ion concentration was 1.0 mol·L?1, the incubation time was 30 min and the pH value was 8. Interaction between molecules of these two polysaccharides was investigated by FT-IR spectrometry. Key words cationic guar gum - sodium alginate - gelation - synergism CLC number O 629.12 Foundation item: Supported by the National Natural Science Foundation of China(29574173)Biography: He Dong-bao (1945-), male, Associate professor, research direction: modifying and gelating of natural polysaccharides.

Gelation Mechanism of Erythromycin Ethylsuccinate During Crystallization

In this paper, the gelation mechanism of erythromycin ethylsuccinate(EES) during crystallization is investigated for the first time. The generated semisolid gel-like phase exhibited a 3D fibrillar network morphology and the typical rheological properties of gels. The fibers inside the gel-like phase were confirmed to be new types of EES solvates using powder X-ray diffraction, thermogravimetric analysis/differential scanning calorimetry, and gas chromatography. The gelation and crystallization regions in EES-1-propanol solid–liquid phase diagram were determined. Analyses of solvent parameters showed that moderate solvent polarity may promote EES gelation. Fourier transform infrared spectra, nuclear magnetic resonance spectra, and scanning electron microscopy analyses indicated that through intermolecular hydrogen bonds, EES and solvent molecules assembled into fibers via crystallographic mismatch branching growth. The fibers intertwined into a 3D network microstructure and formed a gel-like phase, completely immobilizing the solution.

Diffusion of Acetic Acid Across Oil/Water Interface in Emulsification-Internal Gelation Process for Preparation of Alginate Gel Beads

Alginate has been widely used in cell microencapsulation and drug delivery systems in the form of gel beads or microcapsules.Although an alternative novel emulsification-internal gelation technology has been established and both the properties and the potential applications of the beads in drug delivery systems have been studied,the mechanism has not been well understood compared with the traditional droplet method（external gelation technology）.On the basis of our previous knowledge that the novel technology is composed of complicatedly consecutive processes with multistep diffusion and reaction,and the diffusion of acetic acid across oil/water interface being the prerequisite that determines the occurrence and rate for the reactions and the structures and properties of final produced gel beads,a special emphasis was placed on the diffusion process.With the aid of diffusion modeling and simple experimental design,the diffusion rate constant and diffusion coefficient of acetic acid across oil/water interface were determined to be in the orders of magnitude of 10-6 and 10-16,respectively.This knowledge will be of particular importance in understanding and interpreting the formation,structure of the gel beads and the relationship between the structure and properties and guiding the preparation and quality control of the gel beads.

Gelation Phenomenon During Crystallization of Cefpiramide Sodium

Unlike the adverse eff ect caused by the gelation during crystallization process, gelation of cefpiramide sodium was found to provide ideal product properties, such as a larger and more regular crystal shape. The causes of the gelation phenomenon and the mechanism of gel-crystal transition during the crystallization of cefpiramide sodium were both investigated in this work. The gel was formed due to the strapping of the solvents by the networks of cefpiramide sodium molecules. The whole gel-crystal transition process was divided into the following three stages:(1) when the temperature decreased, the system reached a metastable-state gelation;(2) the initial microcrystal in the gel grew slowly because of the low supersaturation;and (3) the gel fi nally disappeared, and a larger and more regular crystal was formed. The Hansen solubility parameters were used to analyze the eff ects of the solvents on this gelation;the analysis results can serve as guidance for solvent screening in the actual production process.

Impact of Ultra-Sonication on Gelation Process in Dairy Products Incorporated with Polysaccharides

Conventional or traditional methods for the use of food processing have been outperformed by novel approaches recently. One such promising technology is ultra-sonication and recent studies have shown better effects in physical characteristics of food which are induced by ultrasound. The previous researches further emphasize that the introduction of ultra-sonication on dairy proteins has resulted in the improvement of their structural, physical and chemical properties while it is widely used in hydrocolloid systems to accelerate the gelation process. Therefore this theory could be useful for the gelation of milk proteins in the presence of a polysaccharide. After discussing briefly on hydrocolloids and the theory of ultrasound, the possibility and the impact of ultrasound on gelation of milk protein mixtures with Carrageenan is highlighted in this study. The inherent characteristics of both milk proteins and carrageenan and properties of the ultrasound treatment have cumulatively effect on gelation. Therefore, there is a necessity to develop specific variables depending on the type of dairy product.

Characterising the Progress of Gelation in Tofu Making with Ohmic Heating

In tofu making by heat treatment, the addition of coagulant ionizes the proteins as a result of heat dissolution and the ionized proteins aggregate with the coagulant to form protein clusters. The electrical conductivity (EC) of the soya milk emulsion varies in response to the progress of gelation. By ohmic heating, the applied current and voltage directly indicate the electrical conductivity of the soya milk emulsion and then indirectly the progress of tofu gelation. In this paper, ultrasonic measurement is adopted to explore the feasibility of using EC as an indicator of tofu gelation. Experiments showed a strong correlation between EC and ultrasonic measurement in characterisation of tofu gelation.

A study of function mechanism of hemxamethyl tetra-amine in gelation process of uranium

The UO2 ceramic microspheres are the most important materials in the spherical fuel elements for high temperature reactor (HTR). A process for preparation of UO2 kernels known as total gelation process of uranium (TGU) was developed as the production process of 10 mW HTR at Tsinghua University. The TGU process is based on the traditional sol-gel process, external gelation process and internal gelation process of uranium (EGU and IGU), which implies that the gelation action is initiated both by ammonia out of the gel particles and hemxamethyl tetra-amine (HMTA) inside the gel particles. The gelation behavior and the properties of uranium microspheres were investigated of the solution with and without HMTA. It is observed that good spherical particles can be obtained without HMTA in the sol, which indicates a more controllable and industrialized route will be set up. Contrasts between this route and the traditional EGU were also listed.

Rheological behavior during thermotropic gelation of polyacrylonitrile concentrated solutions

Dynamic viscoelastic properties of polyacrylonitrile(PAN)/DMSO/H2O solutions with different H2O contents were studied as a function of temperature.These PAN solutions gradually became gel with decreasing temperature.The sol-gel transition took place at a critical gel temperature,at which the scaling law of G'(ω)～G″(ω)∝ωn held,allowing an accurate determination of the critical gel temperature by means of the frequency independence of the loss tangent.The gel point of PAN solutions increases with increasing H2O content.The scaling exponent n(=0.86) at the gel point is confirmed to be universal for PAN gels,which is independent of temperature,suggesting the similarity of the fractal structure in the critical PAN gels.

Pregelation Behaviour of Coagulation Processes with the Constant-Reaction-Number Kernel

We propose an irreversible binary coagulation model with a constant-reaction-number kernel, in which, among all the possible binary coagulation reactions, only p reactions are permitted to take place at every time. By means of the generalized rate equation we investigate the kinetic behaviour of the system with the reaction rate kernel K（i;j） = （ij）^w （0 ≤w〈1/2）, at which an i-mer and a j-mer coagulate together to form a large one. It is found that for such a system there always exists a gelation transition at a finte time to, which is in contrast to the ordinary binary coagulation with the same rate kernel. Moreover, the pre-gelation behaviour of the cluster size distribution near the gelation point falls in a scaling regime and the typical cluster size grows as （to - t）-1/（1-2w）. On the other hand, our model can also provide some predictions for the evolution of the cluster distribution in multicomponent complex networks.

A NOVEL EOR POLYMER (Ⅰ)—STUDY ON GELATION OF RESORCINOL-FORMALDEHYDE SYSTEMS

Factors affecting the gelation of resorcinol-formaldehyde systems have been examined overvariable ranges applicable to oilfield use. Gelation of resorcinol-formaldehyde (RF) system wassensitive to pH,salinity and hardness. Generally,this gel system could be used in fresh water orlow salinity brine at pH higher than about 9. The application would require careful monitoring ofinjection fluids to avoid premature gelation or prolonged shut-in times,especially under conditionsof low salinity and high pH. Salinity and hardness compatibilities of the system were improved bysulfomethylation of resorcinol. Aqueous sulfomethylated resorcinol formaldehyde (SMRF)system could be used in brine with higher salinity and hardness and at a wider pH range of 5--10.