Preparation and Performance of a Fluorine-Free and Alkali-Free Liquid Accelerator for Shotcrete

Based on aluminum sulfate,a fluorine-free and alkali-free liquid accelerator(FF-AF-A)was prepared in this study.The setting time and compressive strength of three cement types with different FF-AF-A dosages were fully investigated.The compatibility of the FF-AF-A with the superplasticizers were also investigated,and the early hydration behavior and morphology of the hydration products of reference cement paste with the FF-AF-A were explored by hydration heat,X-ray diffractometry(XRD),and scanning electron microscopy(SEM).Test results indicated that adding the FF-AF-A at 8 wt%of the cement weight resulted in 2 min 35 s initial setting time and 6 min 30 s final setting time.The 1-day compressive strength of the cement mortar with 8 wt%of FF-AF-A reached 13.5 MPa,which represents an increase of 35%as compared to the strength of cement mortar without the FF-AF-A,and the 28-day compressive strength ratio was 119%.In addition,the FF-AF-A also showed good compatibility with different superplasticizer dosages.The results show that,when the FF-AF-A was added to the cement paste,it promoted the formation of ettringite crystals due to the aluminum ions(Al^(3+))and sulfate ions(SO_(4)^(2-))reacted with gypsum in the cement,as well as promoted the hydration of tricalcium aluminate(C_(3)A)and tricalcium silicate(C3S)leading to the overall structure becomes more compact.As a consequence,the hydration heat rate of the cement sharply increased,the cement paste setting time is shortened,and the compressive strength of cement mortar is improved.

Preparation of Fluorine-free MXene Ti_(3)C_(2)T_(x) and Its Electrical Properties

The fluorine-free MXene was prepared by Lewis acid salt etching of ternary layered ceramic MAX phase material.The structure of fluorine-free MXene was characterized by scanning electron microscopy(SEM)and X-ray diffractometry(XRD).The study finds that the layer spacing of fluorine-free MXene is approximately twice that of MXene etched by the liquid-phase method,compared to the conventional liquidphase method.It also has greater capacitive properties.Therefore,the MXene prepared by this method shows a great potential for application in the field of capacitors.

Seaweed Fiber Fabricated with Agar Alkali-Free Extracted from Gracilaria lemaneiformis

The sulfate groups in agar structure played a good role in the formation of fiber.However,commercially available agar is usually extracted from red algae by alkali treatment to decrease the content of sulfate group for the purpose of high gel strength.In this paper,an alkali-free method of agar extraction from Gracilaria lemaneiformis was proposed for the wet-spinning purpose.This method is environmentally friendly,reduces the extraction steps,saves energy,and reduces the production cost of agar fiber.The improved agar preparation process not only has higher agar yield,but also has higher molecular weight and sulfate group content,which is beneficial to the preparation and forming of fiber and makes the fiber have higher mechanical strength and elongation.Therefore,this extraction technology has broad application prospect in the textile field.

Dissolution of TiO_(2) and TiN inclusions in CaO–SiO_(2)–B_(2)O_(3)-based fluorine-free mold flux

Mold flux serves the crucial metallurgical function of absorbing inclusions, directly impacting the smoothness of the casting process as well as the cast slab quality. In this study, the dissolution behavior and mechanism of Ti O_(2)and Ti N inclusions in molten Ca O–Si O_(2)–B_(2)O_(3)-based fluorine-free mold flux were explored by in situ single hot thermocouple technology combined with X-ray photoelectron spectroscopy.The results showed that Ti O_(2) inclusions are effectively dissolved by the molten slag within 76 s, during which the original octahedral [Ti O_(6)]^(8-)structures are destroyed and convert to the networker tetrahedral [Ti O_(4)]^(4-)structures. However, the dissolution rate is much lower for Ti N inclusions than for Ti O_(2)inclusions. This can be attributed to the fact that the Ti N particles need to be oxidized and then dissolved in the molten slag to form tetrahedral [Ti O4]4-and octahedral [Ti O_(6)]^(8-)structures during the Ti N inclusion dissolution process, which is accompanied by the generation of a large amount of N_(2)gas. Moreover, Ca Ti O_(3)crystals tend to nucleate and grow on bubble surfaces with sufficient octahedral [Ti O_(6)]^(8-)structures and Ca^(2+)ions, eventually resulting in the molten slag being in a solid–liquid mixed state.

A dilute fluorine-free electrolyte design for high-voltage hybrid aqueous batteries

Fluorinated salts and/or high salt concentrations are usually necessary to produce protective films on the electrodes for high-voltage aqueous batteries,yet these approaches increase the cost,toxicity and reaction resistances of battery.Herein,we report a dilute fluorine-free electrolyte design to overcome this dilemma.By using the LiClO_(4) salt and polyethylene glycol dimethyl ether(PED)solvent and optimizing the LiClO_(4)/PED/H_(2)O molar ratio,we formulate a 1 mol kg^(-1)3 V-class hybrid aqueous electrolyte that enables reversible charge/discharge of 2.5 V LiMn_(2)O_(4)|Li_(4)Ti_(5)O_(12) full cell at both low(0.5C,92.4%capacity retention in 300 cycles)and high(5C,80.4%capacity retention in 2000 cycles)rates.This excellent performance is reached even without the generation of protective film on either anode or cathode as identified by in/ex situ characterizations.The selection of appropriate ingredients that have both high stability and strong interactions with water is critical to widen the potential window of electrolyte while suppressing parasitic reactions on the electrodes.This work suggests that expensive and toxic fluorinate salts are no longer necessary for 3 V-class aqueous electrolytes,boosting the development of low-cost,environmentally-friendly,high-power and high-energy-density aqueous batteries.

Understanding fluorine-free electrolytes via small-angle X-ray scattering

Fluorine-free electrolytes have attracted great attention because of its low-cost and environmental friendliness. However, so far, little is known about the solution structures of these electrolytes. Here,we compare the solvation phenomenon of sodium tetraphenylborate(NaBPh_(4)) salt dissolved in organic solvents of propylene carbonate(PC), 1,2-dimethoxyethane(DME), acetonitrile(ACN) and tetrahydrofuran(THF). Small-angle X-ray scattering(SAXS) reveals a unique two-peak structural feature in this saltconcentrated PC electrolyte, while solutions using other solvents only have one scattering peak.Molecular dynamics(MD) simulations further reveal that there are anion-based clusters in addition to the short-range charge ordering in the concentrated NaBPh4/PC electrolyte. Raman spectroscopy confirms the existence of considerable contact ion pairs(CIPs). This work emphasizes the importance of global and local structural analysis, which will provide valuable clues for understanding the structureperformance relationship of electrolytes.

Development and application of fluorine-free mold powder for low carbon steel

Fluorine in mold powder is known as harmful to human health and the environment. Being the advocate of green production, Baosteel developed an environmentally friendly mold powder without fluorine. The main problem of fluorine-free flux film is small heat resistance and thus the heat transfer intensity of the mold is too large, which to some extent hinders the increase of the casting speed. With the heat flow simulation equipment, controlling precipitation of crystal in flux and solidification temperature properly, fluorine-free mold powder for low carbon steel,which substitutes F with B203 ,was successfully developed and applied in industrial production. The production results show that, by using boronic fluorine-free mold powder,the boron increment in molten steel is less than 1.3ppm for conventional aluminium killed low carbon steel.

Effect of AI_(2)O_(3)and MgO on crystallization and structure of Ca0-Si0_(2)-B_(2)0_(3)-based fluorine-free mold flux

The crytallization behavior and melt structure of the CaO-Si0^(2-)B20_(3)-based fluorine-free mold fux were investigated.The results show that the crytallization of the mold fux was first inhibited and then promoted with the increase in Al_(2)0_(3) content from 4 to 12 wt.%.However,it was enhanced by MgO in the range of 2-10 wt.%.The results of Fourier transform infrared spectroscopy and Raman spectroscopy showed that Al_(2)0_(3) worked as a network former in the mold flux melt when its content was in the range of 4-8 wt.%,whereas it worked as the network breaker to provide 0^(2-)when its content was in the range of 8-12 wt.%.In addition,the combined efects from the charge compensation by Mg^(2+)and the network broken by 0^(2-)led to the increase in some typicalT-O-T(AI-O-A1,B-O-B,etc.,)and simpler structural units(Q^(2)(Si),B_^(O-)in the[B0_(2)0^(-)],.etc.)when the MgO content was in the range of 2-6 wt.%.The continuous increase in 0^(2-)provided by the addition of MgO from 6 to 10 wt.%further depolymerized the network of the melt and fnally caused fast crystallizationo.

A Facile and Green Construction of Biomimetic, Fluorine-free and Superhydrophobic Melamine Sponge with Magnetic-driven Function for Efficient Oil–water Separation and Oil Absorption

Inspired by nature,a superhydrophobic and magnetic melamine sponge(BFSM-MF)was fabricated by a one-step dip-coating method.Aiming at replacing nano-Fe_(3)O_(4) particles with a complex preparation process and high cost,the commercial and cheap Fe_(3)O_(4) originated from magnetite was employed as a magnetic substance.To acquire superhydrophobicity,the hierarchical mirco/nano-sized structure with low surface energy was mainly contributed by bonding hydrophobic Fe_(3)O_(4) and graphene with silicone resin onto the surface of the melamine sponge.The results demonstrated that the water and oil static contact angle values of BFSM-MF were 160°and 0°,revealing that BFSM-MF was superhydrophobic and super-oleophilic.Moreover,the self-cleaning ability,magnetic-driven oil absorption ability and continuous oil–water separation performance of BFSM-MF have also been evaluated.As expected,BFSM-MF possessed magnetic-driven oil absorption ability and the oil–water separation efficiency for light oil reaches 98%±1%.In addition,the adsorption capacity and recycling performance of diff erent organic solvents were systematically investigated.Therefore,the development of biomimetic,fluorine-free and superhydrophobic foam with magnetic-driven eff ect has potential application value in marine oil spill treatment and separation of domestic oil pollution.

Study on Glass Fiber Dispersion Technology in SiO_2 Aerogel-glass Fiber Composite Insulation Materials

In order to improve the mechanical properties of SiO_2 aerogel-glass fiber composites, effects of different solvents(cyclohexane, n-hexane, ethanol, acetone) and different dispersing modes(planetary ball milling, ultrasonic dispersion and mechanical stirring) and dispersing duration(10-40 min) on the dispersion of chopped alkali-free glass fiber bundles were studied to determine the best dispersion process. On this basis, the materials were batched according to the mass fraction of SiO_2 aerogel powder to chopped alkali free glass fiber bundles of 90:10, and a certain amount of zinc oxide light-screening agent and phenolic resin binder were added. SiO_2 aerogel glass fiber composite specimens were prepared by direct adding chopped alkali free glass fiber bundles and pre-dispersed chopped alkali free glass fiber bundles, respectively. The cold crushing strength and the thermal conductivity at different surface temperatures(300, 400, 500 and 600 ℃, respectively)of the specimens were measured. The results show that:(1) the optimum dispersion process of chopped alkali-free glass fiber bundles is using ethanol as solvent and mechanical stirring for 30 min;(2) pre-dispersion of chopped alkali-free glass fiber bundles has little effect on the thermal conductivity of SiO_2 aerogel-glass fiber composites but can improve the cold crushing strength.

Multifunctional fluorine-free superhydrophobic coating with flame-retardant,anti-icing,anti-corrosion,and oil-water separation properties

A fluorine-free and multifunctional superhydrophobic coating(r-MSC)was prepared by the one-step spraying method.The coating had superhydrophobic and low-adhesion properties with the water contact angle of 161.5°�1°and the sliding angle of 3.2°�0.5°.It could be prepared by spraying while maintaining superhydrophobic surface characteristics on any substrates.The coating owed outstanding mechanical durability and chemical stability.Moreover,the coating also possessed the ability of self-cleaning,anti-fouling,anti-icing,and flame retardant ability.Importantly,the presence of multifunc-tional coating endowed the substrate with both water-resistant and fireproof properties.Besides,it also showed excellent oil-water separation ability,which presented the oil-water separation efficiency of over 90%for different types of oils after 10 separation cycles.Furthermore,the coating could improve corrosion inhibition performance and the corrosion current density was reduced by two orders of magnitude from the polarization curve.The r-MSC had the advantages of simple preparation,fluorine-free,environ-mentally friendly and appropriate for large-area fabrication,which could be applied to various fields.

A comparison study on interfacial properties of fluorine-bearing and fluorine-free mold flux for casting advanced high-strength steels

A comparison study on interfacial properties of a traditional fluorine-bearing(F-bearing)mold flux and a newly designed fluorine-free(F-free)mold flux to produce advanced high-strength steels(AHSSs)by compact strip production technology was conducted.The results showed that these two kinds of mold fluxes gradually spread out on the typical AHSS substrate when slags began to melt with the increase in heating temperature,and they had a good interfacial ability between the two mold fluxes and the AHSS substrate,and there was no other interfacial reaction except the oxidization of steel substrate by the mold fluxes.In comparison,the wettability of the designed F-free mold flux with the AHSS substrate was better than that of the F-bearing mold flux.The reason could be explained as the addition of B_(2)O_(3) would increase the complexity and polymerization degree of the melt structure and weaken the attractive force between the ions and ionic groups,then leading to a better wettability.Besides,B_(2)O_(3) is an effective flux,which can reduce the melting temperature obviously,and the surface tension of the liquid F-free mold flux would get reduced with the addition of B_(2)O_(3).