Review of emulsified asphalt modification mechanisms and performance influencing factors

In recent years,with the improvement of the requirements of road performance,modified emulsified asphalts with better performance has gradually replaced the emulsified asphalt and become the primary material for road maintenance.This paper introduces the modified emulsified asphalt materials commonly used in pavement maintenance projects,definitions and modified mechanisms of polymerized styrene butadiene rubber(SBR)modified emulsified asphalt,styrene butadiene styrene block polymer(SBS)modified emulsified asphalt and waterborne epoxy resin(WER)modified emulsified asphalt are summarized.The analysis focused on comparing the effects of modifiers,preparation process,auxiliary additives,and other factors on the performance of modified emulsified asphalt.In this paper,it is considered that the greatest impact on the performance of emulsified asphalt is the modifier,emulsifier mainly affects the speed of breaking the emulsion,stabilizers on the basic performance of emulsified asphalt evaporative residue is small;and when the modifier is distributed in the asphalt in a network,the dosage at this time is the recommended optimum dosage.Finally,this study recommends that in the future,the polymer-asphalt compatibility can be improved through composite modification,chemical grafting and other methods to continue to develop broader applicability and better performance of modified emulsified asphalt.

Modification Mechanism of Coconut Husk Activated Carbon Using FeSO4 and Fe(NO3)3

Modification conditions determine the surface topography and the active material phase composition of a catalyst.To study the influence of modification on a carbon-based sorbent,coconut husk activated carbon(AC)which was activated using HNO3 and modified by FeSO4 and Fe(NO3)3 was examined.The pore textures and surface chemical characteristics of the carbon materials were examined by scanning electron microscopy(SEM),Brunner-Emmet-Teller(BET),X-ray diffraction(XRD)and Fourier transform infrared(FTIR)spectroscopy.The surface topography,the pore structure,active materials,and functional groups of AC,AC modificated by HNO3(HNO3/AC for short),and AC modificated by FeSO4 and Fe(NO3)3(Fe/AC for short)were systematically studied.Subsequently,the mechanism of modifying the conditions for the carbon materials was determined.Results showed that the surface micro topography of HNO3/AC became unsystematic and disordered.After modification with FeSO4,the ferriferous oxide was mainly present as a near-spherical crystal.Ferriferous oxides from Fe(NO3)3 modification mainly exhibited a plate shape.HNO3 modification could enlarge the pores but decrease the specific surface area of AC.FeSO4 modification resulted in a new net post structure in the pore canal of AC.Fe(NO3)3 modification caused the pore space structure to develop in the interior,and a higher calcination temperature was useful for ablation.The ash content of the AC was substantially reduced upon HNO3 modification.Upon FeSO4 modification,α-FeOOH,α-Fe2O3 andγ-Fe2O3 coexisted under the condition of a lower concentration of FeSO4 and a lower calcination temperature,and a higher FeSO4 concentration and calcination temperature generated moreα-Fe2O3.The same Fe(NO3)3 modification and a higher calcination temperature were beneficial to the minor chipping formation ofγ-Fe2O3.A higher Fe(NO3)3 loading produced a lower graphitization degree.HNO3 modification formed various new oxygen-containing functional groups and few nitrogen-containing groups.Based on the cover,FeSO4 and Fe(NO3)3 modification could decrease the oxygen-containing and nitrogen-containing functional groups.These results could optimize the modification condition and improve physical and chemical properties of carbon-based sorbents.

Materials,preparation,performances and mechanism of polyurethane modified asphalt and its mixture:A systematic review

With the rapid development of asphalt pavement technology,it has attracted considerable attention to improving the durability of asphalt pavement.An effective action is to use modified asphalt with high performance and durability.Polyurethane(PU)has been used in asphalt pavement engineering to enhance the durability and service life of asphalt pavement because of its excellent high-temperature performance,toughness,wear resistance,aging resistance and oil resistance.However,PU modified asphalt technology is still in the exploratory stage.The preparation,modification mechanism and working performances of PU modified asphalt need to be further clarified.Therefore,this paper summarized the research progress of PU modified asphalt and its mixture.The composition of PU modified asphalt was introduced.The addition methods of PU materials and preparation process parameters of the PU modified asphalt were determined.The modification mechanism of PU on asphalt was discussed.The effects of polyurethane on asphalt were analyzed and the road performances of its mixture were evaluated.Finally,the development tendency towards PU modified asphalt and its mixture were forecasted.

Physical-mechanical properties of microbially induced calcite precipitation-treated loess and treatment mechanism

Loess disintegration can lead to geotechnical engineering problems,e.g.,slope erosion,wetting-induced landslide,and hydroconsolidation.Microbially induced calcite precipitation(MICP)technique is a potential loess reinforcing method.This study investigated the physical-mechanical properties of MICP-treated loess and then explored the mechanism of loess modification by MICP.Here,loess first underwent MICP treatment,i.e.,mixing loess with Sporosarcina pasteurii and cementation solution(CS).Then,the effects of the CS concentration(0.2,0.6,0.8,and 1 M)on the physical and mechanical properties of the MICP-treated loess were tested.Finally,the static contact angle test,scanning electron microscopy(SEM),and X-ray diffractometry(XRD)were conducted to study the mechanism of MICP treatment on loess.Results showed the following property changes of loess after MICP treatment:the liquid limit decreased by 1.7%,the average particle size increased from 6 to 47μm,the specific gravity decreased from 2.65 to 2.43,the unconfined compressive strength increased from 37 to 71 k Pa,and the disintegration time increased from 10 to 25 min.Besides,the shear strength also increased,and the shear strength parameters(cohesion c and internal friction angle?)varied with the CS concentration.The static contact angle tests indicated that the water absorption ability of loess was reduced after MICP treatment.SEM and XRD results verified that the CaCO_(3)from MICP was attributed to the above results.The above findings explained the mechanism of MICP treatment of loess:the CaCO_(3)coats and cements the particles,and fills the pores of loess,improving the strength and water stability of loess.

Manganese oxide and derivative-modified materials in advanced oxidation processes:A review of modification enhancement and activation mechanisms

Manganese oxides(MNO_(x)),as low-toxicity and high-abundance catalysts,have been demonstrated to hold great promise for application in advanced oxidation processes(AOPs).However,further application of this material is restricted due to its unsatisfactory oxidant activation efficiency.Fortunately,recently remarkable research on deep activation mechanisms and modification of MNO_(x)have been undertaken to improve its reactivity.Herein,modification enhancement mechanisms of MNO_(x)to efficiently degrade various organic contaminants were discussed and highlighted,including metal doping,coupling with other metal oxides,composite with carbonaceous material,and compounding with other support.The activation mechanisms of different MNO_(x)and derivative-modified material(such as doped MNO_(x),metal oxide-MNO_(x)hybrids,and MNO_(x)-carbonaceous material hybrids)were summarized in great details,which was specifically categorized into both radical and non-radical pathways.The effects of pH,inorganic ions,and natural organic matter on degradation reactions are also discussed.Finally,future research directions and perspectives are presented to provide a clear interpretation on the MNO_(x)initiated AOPs.

Effect of TiB2 and Al3Ti on the microstructure,mechanical properties and fracture behaviour of near eutectic Al−12.6Si alloy

A near eutectic Al−12.6Si alloy was developed with 0.0wt%,2.0wt%,4.0wt%,and 6.0wt%Al−5Ti−1B master alloy.The micro-structural morphology,hardness,tensile strength,elongation,and fracture behaviour of the alloys were studied.The unmodified Al−12.6Si al-loy has an irregular needle and plate-like eutectic silicon(ESi)and coarse polygonal primary silicon(PSi)particles in the matrix-likeα-Al phase.The P_(Si),E_(Si),andα-Al morphology and volume fraction were changed due to the addition of the Al−5Ti−1B master alloy.The hardness,UTS,and elongation improved due to the microstructural modification.Nano-sized in-situ Al3Ti particles and ex-situ TiB_(2)particles caused the mi-crostructural modification.The fracture images of the developed alloys exhibit a ductile and brittle mode of fracture at the same time.The Al−5Ti−1B modified alloys have a more ductile mode of fracture and more dimples compared to the unmodified alloy.

Progress of organic,inorganic redox flow battery and mechanism of electrode reaction

With the deployment of renewable energy and the increasing demand for power grid modernization,redox flow battery has attracted a lot of research interest in recent years.Among the available energy storage technologies,the redox flow battery is considered the most promising candidate battery due to its unlimited capacity,design flexibility,and safety.In this review,we summarize the latest progress and improvement strategies of common inorganic redox flow batteries,such as vanadium redox flow batteries,iron-chromium redox flow batteries,and zinc-based redox flow batteries,including electrolyte,membrane,electrode,structure design,etc.In addition,we introduce the latest progress in aqueous and non-aqueous organic redox flow batteries.We also focus on the modification mechanism,optimization design,improvement strategy,and modeling method of the redox flow battery reaction.Finally,this review presents a brief summary,challenges,and perspectives of the redox flow battery.

Three-dimensional composite Li metal anode by simple mechanical modification for high-energy batteries

Lithium(Li)metal is believed to be the“Holy Grail”among all anode materials for next-generation Li-based batteries due to its high theoretical specific capacity(3860 mAh/g)and lowest redox potential(−3.04 V).Disappointingly,uncontrolled dendrite formation and“hostless”deposition impede its further development.It is well accepted that the construction of three-dimensional(3D)composite Li metal anode could tackle the above problems to some extent by reducing local current density and maintaining electrode volume during cycling.However,most strategies to build 3D composite Li metal anode require either electrodeposition or melt-infusion process.In spite of their effectiveness,these procedures bring multiple complex processing steps,high temperature,and harsh experimental conditions which cannot meet the actual production demand in consideration of cost and safety.Under this condition,a novel method to construct 3D composite anode via simple mechanical modification has been recently proposed which does not involve harsh conditions,fussy procedures,or fancy equipment.In this mini review,a systematic and in-depth investigation of this mechanical deformation technique to build 3D composite Li metal anode is provided.First,by summarizing a number of recent studies,different mechanical modification approaches are classified clearly according to their specific procedures.Then,the effect of each individual mechanical modification approach and its working mechanisms is reviewed.Afterwards,the merits and limits of different approaches are compared.Finally,a general summary and perspective on construction strategies for next-generation 3D composite Li anode are presented.

Thermosetting resin modified asphalt:A comprehensive review

Thermosetting resins have advantages such as high strength,corrosion resistance,and aging resistance,and have excellent prospects for practical application as asphalt modifiers.In order to promote the research of thermosetting resin modified asphalt,to provide direction for its further research,this paper reviews the research progress of thermosetting resin modified asphalt in recent years.The material composition,modification mechanism,and curing behavior of epoxy asphalt,thermosetting polyurethane modified asphalt,unsaturated polyester modified asphalt,and other thermosetting resin modified asphalts are overviewed.Different types of thermosetting resin modified asphalt have different performances,the performance advantages of different thermosetting resin modified asphalts are summarized.At the same time,the existing problems in thermosetting resin modified asphalt and further research directions are provided.Encouraging researchers to produce thermosetting resin modified asphalts using waste or bio-based materials,and to study the recycling technologies and life cycle assessment of thermosetting resin modified asphalt.This paper provides a reference for the study of thermosetting resin modified asphalt.

Mechanistic understanding of Cu-based bimetallic catalysts

Copper has received extensive attention in the field of catalysis due to its rich natural reserves,low cost,and superior catalytic performance.Herein,we reviewed two modification mechanisms of co-catalyst on the coordination environment change of Cu-based catalysts:(1)change the electronic orbitals and geometric structure of Cu without any catalytic functions;(2)act as an additional active site with a certain catalytic function,as well as their catalytic mechanism in major reactions,including the hydrogenation to alcohols,dehydrogenation of alcohols,water gas shift reaction,reduction of nitrogenous compounds,electrocatalysis and others.The influencing mechanisms of different types of auxiliary metals on the structure-activity relationship of Cu-based catalysts in these reactions were especially summarized and discussed.The mechanistic understanding can provide significant guidance for the design and controllable synthesis of novel Cu-based catalysts used in many industrial reactions.

Physicochemical properties of coconut husk activated carbon modified by Fe(N0_(3))_(3)and Mn(N0_(3))_(2)

Fe-loaded activated carbon(AC)has high surface acidity and more active sites,while manganese-loaded AC has high oxygen content.Coconut husk AC modified by Fe-Mn was studied with the aim of revealing the modification mechanism.First,HNO_(3)AC was prepared using the nitric acid immersion method.Second,Fe-Mn/AC was prepared using the Fe(N0_(3))_(3)and Mn(N0_(3))_(2)sequential immersion.The effects of HNO_(3),Fe(N0_(3))_(3),and Mn(N0_(3))_(2)on the pore texture and surface chemical characteristics of carbon materials were examined by scanning electron microscopy,Brunauer-Emmett-Teller(BET)analysis,X-ray diffraction and Fourier-transform infrared spectroscopy.The surface topography,pore structure,active material,and functional groups of AC,HNO_(3)/AC,and Fe-Mn/AC were systematically studied.The following results were obtained.The surface of HNO_(3)AC has more ditches and air voids;the micropores of HNO_(3)AC are deformed and flattened compared to those of AC.The surface of Fe-Mn/AC exhibits an accumulation phenomenon.MnFe_(2)O_(4)and FeMn_(2)O_(4)formed more pore structures.AC and HNO_(3)AC have numerous micropores.The higher loading quantity of Fe-Mn results in bigger specific surface.The active components of Fe-Mn/AC-1,Fe-Mn/AC-2,Fe-Mn/AC-3,and Fe-Mn/AC-4 are MnFe_(2)O_(4),MnO_(0.43)Fe_(2.57)O_(4),Mn_(3)O_(4),and ot-Fe_(2)O_(3)>respectively.The surface functional groups of AC and HNO_(3)AC are oxygen-containing functional groups.The effect of Fe-Mn modifying conditions on functional group species is rare;however,Fe/AC has more oxygen-containing functional groups.These research findings can aid in the desulfurization and denitrification of the Fe-Mn/AC catalyst.