Atomic Force Microscopy Tests Research Articles

Innovative xanthan gum-based nanocomposites for asphaltene precipitation prevention in shale and carbonate rocks

Asphaltene deposition in porous media creates many challenges in porous media. This study synthesizes ZnO/SiO2/xanthan nanocomposites (NCs) to adsorb asphaltene and reduce its effect on the shale and carbonate rocks. NCs structure is analyzed using SEM, EDX, BET, and FTIR tests. Also, the rocks' surface is analyzed by an atomic force microscopy (AFM) test after 48 and 96 h of contact with 20 ppm NCs and 20 mg asphaltene. Core flooding tests are performed on shale rocks using 20 ppm NCs at 5500, 4000, and 2500 psi at 48 h. Using AFM in calcite and dolomite formations and selecting core flooding tests based on that are new scenarios that followed in this paper. FTIR results confirm asphaltene adsorption on NCs's surface by changing 854 and 962 cm−1 peaks. AFM tests confirmed asphaltene adsorption on NCs surface, too. Average roughness, root mean square roughness, peak to valley roughness, and average size of the shale were higher than the carbonate sheets. At 20 ppm NCs in shale reservoirs, permeability reduction in porous media was increased up to 39.5 %, and asphaltene precipitation decreased from 8.95 and 20.06 wt% to 2.25 and 10.25 wt%, which shows our suggested scenarios were efficient.

Low-temperature performance and micro-structure of warm mix recycled composite aged asphalt

Given the cold winters in Inner Mongolia, the low-temperature performance of asphalt pavement is one of the key factors affecting the service life of roads. This study focuses on commonly used SBS modified asphalt and investigates the coupling effect of adverse factors such as solar radiation, high temperature, and precipitation on road surface asphalt. The objective is offer insights for improving the applicability and service life of warm mix recycled asphalt in cold regions. By using indoor simulation aging equipment, asphalt subjected to hot oxygen aging, composite water aging, and composite ultraviolet aging was prepared to investigate the low-temperature performance of warm mix recycled asphalt. Additionally, to explore the synergistic effect of new asphalt, regenerant, and warm mix agent on the regeneration of aged asphalt, this study analyzes the low-temperature performance and microstructure changes of recycled asphalt through bending beam rheometer (BBR) test, atomic force microscopy (AFM) test, and infrared spectroscopy (FTIR) test. The results show that as the degree of aging increases, the low-temperature crack resistance performance of asphalt deteriorates. Additionally, after the regeneration of aged asphalt, the damping ratio and dissipation energy ratio of warm mix recycled asphalt slightly enhances compared to hot mix recycled asphalt. Furthermore, the incorporation of a warm mix agent enhances the asphalt’s fluidity, viscosity, surface toughness, and further its low-temperature performance. The AFM test results show that the synergistic effect of warm mix agents and regeneration effectively restores the microstructure and surface roughness of asphalt. Moreover, the warm mix agent improves the dispersion uniformity of the SBS modifier in asphalt, helping prevent the agglomeration of asphalt slurry. Qualitative and quantitative analysis of asphalt through FTIR test demonstrates that the mechanisms of warm mix agents and regeneration on new and aged asphalt are a physical process. New asphalt and regeneration supplement the internal lightweight components of aged asphalt, enabling the restoration of most asphalt without affecting the structure of SBS modified asphalt. This project provides a theoretical basis for the engineering applicability of high content warm mix recycled asphalt (composed of 50 % aged asphalt) in large temperature range areas.

Investigation of adhesion of loess to shield’s cutting tools considering sand and clay additives

Soils, especially those containing a significant fraction of clay, adhering to shields’ cutting tools or clumping to each other could not only cause a low advance rate in tunnel construction but also difficulty in transporting tunnelling spoils for disposal. Although more than 80% silt is regarded as the major fraction, 10% clay also included in loess which is extensively spread over northwest China may aggravate the said issue. In addition to the mixing and fluidity tests, the atomic force microscopy (AFM) analysis was applied to explore the inherent mechanism that affected their adhesion properties when sand, kaolinite, and montmorillonite were introduced as additives. Results showed that the sand additive reduced not only the potential to trigger clay clogging but also the difficulty in transporting spoils for disposal. By contrast, the kaolinite additive increases the potential to trigger clay clogging and also aggravates the difficulty in transporting spoils for disposal. Despite that, the adhesion force was higher in the sand-loess mixture, most likely due to the non-swelling nature of kaolinite minerals. Therefore, the water rings cannot be developed impeding the formation of capillary phenomenon. The adhesion of the sand-loess mixture is controlled by the intermolecular force and rapidly disappears when submerged. Further, the montmorillonite additive increases further the potential to trigger clay clogging but causes great difficulty in transporting spoils for disposal. Results from the AFM test also indicated that the surface topography showed a small change, with the maximum adhesion force being 52.5 nN. The more the water rings developed, the more significant the capillary phenomenon, and the greater the adhesion force.

Utilizing phosphonyl carboxylic acid copolymer as an efficient depressant for flotation separation of chalcopyrite from galena: Experimental and DFT study

The research proposes an innovative galena depressant, known as Phosphonyl carboxylic acid copolymer (POCA), to enhance the efficiency of flotation separation between chalcopyrite and galena. Mineral flotation tests were conducted to investigate the flotation performance of chalcopyrite and galena. The inhibition mechanism of POCA on galena was studied using multiple characterization techniques including Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) testing, Zeta potential testing, X-ray photoelectron spectroscopy (XPS) analysis, atomic force microscopy (AFM) testing, contact angle testing, time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis, and density functional theory (DFT) calculations. In the flotation test, at a concentration of 10 mg/L sodium butyl xanthate (SBX) and pH 9, adding 50 mg/L POCA can reduce the flotation recovery of galena from 83.50 % to below 5 %, whereas the recovery of chalcopyrite was almost influenced. The testing conducted via ICP-OES revealed that POCA promotes the dissolution of Pb2+ from the galena surface. The adsorption of POCA on the galena surface was confirmed through zeta potential testing, XPS testing, contact angle, AFM testing, and ToF-SIMS analysis, it was noted that POCA exhibited high levels of adsorption on the galena surface. Density Functional Theory (DFT) calculations suggest that the chemical interaction between the sulfonic acid present in POCA and the Pb2+ active site of galena is regarded as the primary inhibition mechanism.

Structural and Morphological Characterization of MEH-PPV/Ag Composite

In this study, spin coating was used to prepare thin films of poly (2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylene vinylene) and silver (MEH-PPV/Ag) in this study. The physical characteristics of MEH-PPV/Ag thin films with various weight ratios (0.01, 0.02, 0.03, and 0.04%) were investigated by Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray diffraction analysis (XRD), and thermal testing. FTIR analysis showed that there were occurrences of the polymer's predicted chemical bonds. AFM tests show that when different amounts of silver are added to a polymer matrix, the film's surface roughness (root mean square) goes up from an average of 83.51 to 511.3 nm. FE-SEM analysis showed that a pure sample of the polymer formed evenly. However, when different amounts of Ag were added, clear balls or circles formed, showing the energy of mixing between the MEH-PPV and Ag. As silver addition transformed the polymer from amorphous to polycrystalline, XRD analysis revealed both phases. In tests comparing pure MEH-PPV to MEH-PPV/Ag, the polymer containing silver showed higher thermal conductivity.

Mesoscopic irreversible thermodynamics of aging kinetics of alpha polypeptides [DNA] under various constraints: Special reference to the simple spring mechanics

The mesoscopic irreversible thermodynamic treatment of α-polypeptides and the helical polynucleotides (DNA) furnishes two sets of analytical expressions, which allow us not only to analyze the reversible force–extension experiments performed by atomic force microscopy (AFM) but also to predict the irreversible “aging” kinetics of the single-stranded and double-stranded polynucleotides (ssDNA and dsDNA) helical conformations exposed to aqueous solutions and applied static stress systems under the various constraints. The present physicochemical cage model emphasizes the fact that the global Helmholtz free energy of the helical conformation acts not only under the stored “intrinsic” unusual torsional and bending elastic energies inherited by the unfolded helical structure of the amino-acid (peptides) or the nucleic-acid (nucleotide) backbone but also reveals the importance of the interfacial Helmholtz free energy density associated with the interaction of the side-wall branches within the surrounding aqueous solutions. The analytical expression obtained for the unfolding force vs extension (FE) shows a strong non-linear elasticity behavior under the twist angle constraint when the interfacial Helmholtz energy term is incorporating into the scenario. This behavior is in excellent quantitative agreement with the AFM test results obtained by Idiris et al. (2000) on the poly-L-glutamic acid [Glu(n)-Cys] exposed to aqueous solutions, which show that acidity increases the degrees of helicity.

Effect of 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) on Cu/Ta chemical mechanical planarization (CMP) in the barrier layer: A novel complexing agent and the dual role on Cu

Tantalum and its nitrides are used in barrier layers in copper interconnected ultra-large-scale integrated circuits. However, due to the different physical and chemical properties of copper (Cu) and tantalum (Ta), the difference in removal rates is a problem. This study developed an acidic barrier layer slurry with better Cu/Ta rate-selective properties. During the research and development process, it is found that the introduced novel complexing agent, 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA), has a bisexual effect on Cu while effectively enhancing the Ta removal rate. Therefore, the detailed analysis was carried out on the mechanism of PBTCA on Cu/Ta. In this study, the effects of the slurry fundamental composition, include pH value, oxidant H2O2 and complexing agent PBTCA, on Cu/Ta removal rate were firstly investigated by electrochemical and chemical mechanical planarization (CMP) experiments. Subsequently, XPS, SEM and AFM tests were utilized for in-depth analysis of the micro-activity mechanism of PBTCA. The concentration of PBTCA between 0.2 wt% and 0.3 wt% was found to have complexation effect on Cu, and the concentration between 0.3 wt% and 0.8 wt% was found to have corrosion inhibition effect on Cu, which verified that PBTCA has a dual effect on Cu. This phenomenon effectively reduces the difference of Cu/Ta removal rate and facilitates surface flattening. In addition, PBTCA is an environmentally friendly and biodegradable organophosphate condensate. Finally, the slurry stability experiments were carried out by average particle size and zeta potential tests. CMP experiments and atomic force microscopy (AFM) tests were employed to verify the performance of the slurry. It was concluded that the slurry was well stabilized with the oxidant addition, and the storage time had almost no effect on the removal rate and surface morphology of Cu and Ta. The results of the study provide a feasible method for barrier layer CMP.

Optimization and Mechanism of SiO2-Based Slurry Components for Atomically Smooth Gallium Nitride Surface Obtained Using Chemical Mechanical Polishing Technique

With the ongoing progress of mobile communication and new energy technologies, the market interest in high-frequency and high-power semiconductor devices has risen. Gallium nitride (GaN), a wide bandgap semiconductor material, has become a popular area of research in relevant fields. A sufficiently flat material surface can significantly enhance the device’s performance. Therefore, this paper explores the effect of oxidants on the quality of GaN surface during chemical mechanical polishing (CMP). Atomic force microscopy (AFM) was employed to examine the surface morphology of GaN after each CMP experiment. The aim was to evaluate the effect of specific slurry components on GaN surface quality. The results revealed that the introduction of oxidizers, particularly the potent oxidizer potassium persulfate (K2S2O8), was advantageous in reducing the surface roughness Sq and thus, enhancing the surface quality of GaN. The surface roughness (Sq) of GaN was reduced from 7.7 nm to 0.78 nm after the CMP process with the optimal components. AFM tests were conducted on different areas of the GaN surface within a range of 1 μm2, which revealed that clear images of the GaN atomic steps can be obtained, and the Sq can reach as low as 0.26 nm.

Topographical Analysis of Human Enamel after Phosphoric Acid Etching and Er,Cr:YSGG Laser Irradiation.

Introduction: Dental hard and soft tissues have been successfully removed by using the Er,Cr:YSGG laser, but there is a controversy about using lasers over conventional tooth surface preparation for bonding aesthetic restoration. Surface roughness and wettability in response to Er,Cr:YSGG laser irradiation are essential properties for restoration longevity. Methods: Fifty-one intact human premolars removed in orthodontic treatment were included in this study and divided into three groups (n=17). The first group (G1) was the control without surface treatment, (G2) was treated with 37% phosphoric acid for 15 seconds, and (G3) was treated with the Er,Cr:YSGG laser using the following parameters: 2 W or 3 W at 20 Hz, 10% air and water ratio using the MZ6 laser tip. The standardization of laser irradiation was accomplished by a computerized numerical control unit. The surface of the samples was evaluated by using a light microscope, profilometer, atomic force microscopy (AFM), SEM, and wettability tests. Results: The SEM examination revealed that the lased enamel surface was clean, irregular, and devoid of a smear layer, while the acid etch surface was relatively smooth and covered with a smear layer. The surface roughness of the lased enamel surface was significantly higher than that of other groups, according to the results of the profilometer as well as the AFM tests. The wettability test showed that the lased enamel surface recorded a significant reduction in the contact angle in comparison to the other groups. Conclusion: It can be concluded that the Er,Cr:YSGG laser can be used as an alternative and safe method to the acid-etching technique for surface treatment.

A new nanocomposite based on polylactic acid/butadiene rubber/clay: Morphology development and mechanical properties

AbstractIn this work, several samples based on poly(lactic) acid (PLA)/butadiene rubber (BR) blend with and without nanoclay (Cloisite 30B) were prepared using an internal mixer. Various methods were used to characterize the samples, including scanning electron microscopy (SEM), atomic force microscopy (AFM), x‐ray diffraction (XRD), rheometric mechanical spectrometer, stress–strain, and impact strength tests. The SEM results showed the droplet‐matrix morphology for all prepared samples. With the incorporation of nanoclay, the mean diameter of the BR droplets generated within the PLA matrix decreased. AFM test revealed the placement of nanoparticles in the PLA phase, which was consistent with the thermodynamic prediction of their location. The XRD test showed that the interlayer space of nanoclay expanded by 86% due to the diffusion of polymer chains between them. In the rheology test, this resulted in an increment in modulus and viscosity at low frequencies for the nanocomposites compared to the simple blend. The highest elongation at break was observed for the PLA/BR blend containing 10 wt% BR with approximately 40 times its value for the neat PLA, while the impact resistance increased up to three times.

Understanding the anisotropic wettability of spodumene from direct force measurement using AFM and density functional theory calculations

Wettability directly reflects the interaction between minerals, reagents, and water, and is a key factor determining the flotation separation of minerals. Wettability differences of the spodumene anisotropic crystal surfaces are investigated in this study using contact angle relaxation, atomic force microscopy (AFM), and density functional theory (DFT) calculations. The contact angle relaxation and AFM tests confirm the anisotropic wettability of spodumene surfaces from macro and micro perspectives, respectively, and the order of hydrophilicity is (010) > (100) > (110). The DFT calculations based on surface fracture key points and broken bond density explain the differences in the wettability of spodumene crystal surfaces, that is, the types of broken bonds and the number of broken bonds per unit area are the main influencing factors. The wettability of water molecules on different crystal surfaces is simulated based on the DFT calculations of the broken surface bonds and surface energy, which further verifies the experimental results.

Investigation on the influence of conditioning time on the performance of hot-recycled mixture under ambient temperature

Hot-recycled asphalt mixture (HRAM) has gained more attention due to its favorable performance and reuse of reclaimed asphalt pavement (RAP). However, involvement of the blending between virgin and aged asphalt may require more time to reach stability after the mixing process. It has been generally agreed that the change in degree of blending (DoB) between virgin and aged asphalt influences the performance of HRAM. Hence, it is of vital importance to reveal the development of the performances of HRAM in primary period and offer a reasonable conditioning time before conducting laboratory test to avoid over- or under-estimation. As many factors, including RAP content, aging degree of RAP and mixing procedure, may influence the conditioning time of HRAM, in this research, the HRAM with different RAP contents is taken into account. Specimens are stored at ambient environment (around 25 °C) for different days. Then, macroscopic performance tests evaluating high- and low-temperature performances as well as mechanical properties are conducted. Meanwhile, atomic force microscopy (AFM) is applied to quantify the change of nanoscale properties of HRAM under different conditioning time. The result shows that the macroscopic performances change significantly with conditioning time. But HRAM with different RAP contents exhibits distinct developing trend. Nevertheless, test results within 4 days varies significantly among all. AFM test reveals that DMT modulus increases with conditioning time, which is the reason for the performance change. Considering the time cost in laboratory testing, it is recommended for HRAM specimen to be conditioned at ambient temperature for at least 4 days before the tests. 7-day conditioning is better for HRAM with higher RAP content if time permits.

Improved sample preparation method on the morphology observation of hydrophilic polysaccharides for atomic force microscopy (AFM)

With the deepening of polysaccharide research, whether the real polysaccharide structure can be clearly observed directly affects researchers' understanding of polysaccharide structure and function. Therefore, the establishment of a suitable method to study polysaccharide structure is urgent. Konjac glucomannan (KGM), agar, and curdlan were selected in this paper to investigate the effects of drying temperature, plasticizer type and dosage on the molecular structure of polysaccharides in the preparation of polysaccharide samples for AFM testing. The experimental results showed that the molecular morphology changes of different polysaccharides varied at different drying temperatures. Adding a certain dose of plasticizer could relieve the shrinkage of the hydrophilic polysaccharide molecular chain during the drying process. Compared with Tween 20 and Tween 80, glycerol showed a superior effect on relieving molecular chain shrinkage with the same addition amount. Finally, a new polysaccharide sample preparation method for AFM was proposed, and the feasibility of the method was confirmed, which provided a new idea for better use of AFM to observe the morphology of polysaccharides.

Influence of Nitrogen Annealing Treatment on Optical, Microstructural, and Chemical Properties of Ga2O3 Film Grown by Plasma-Enhanced Atomic Layer Deposition

In this paper, high-quality β-Ga2O3 films were grown on silicon substrates by plasma-enhanced atomic layer deposition (PEALD). Effects of annealing temperature on β-Ga2O3 thin films were studied. Atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray reflection (XRR), and ultraviolet (UV) emission spectroscopy were used to systematically characterize Ga2O3 thin films. AFM test results showed that as annealing temperature increased from 500 to 900 °C, the roughness of film increased from 0.542 to 1.58 nm. XPS test results showed that the concentration of oxygen vacancies in annealed films was significantly reduced. After annealing, the energy band of the film increased from 4.73 to 5.01 eV, and the valence band maximum (VBM) increased from 2.58 to 2.67 eV, indicating that the annealing treatment under a nitrogen atmosphere can improve the quality of films. Results demonstrate that high-quality Ga2O3 films can be obtained by the annealing process after atomic layer deposition (ALD). The proposed method can realize an ideal stoichiometric ratio of the Ga2O3 thin film as well as precise control of its optical, electrical, and microstructural properties. This work lays the foundation for future application of Ga2O3 materials in photoelectric detection, power devices, transparent electronics, and other fields.

AFM Measurements and Testing Properties of HDPE and PBT Composites with Fillers in the Form of Montmorillonite and Aluminum Hydroxide.

This paper presents the effect of the addition of fillers such as aluminum hydroxide or montmorillonite on the structure and properties of polymers such as high-density polyethylene (HDPE) and polybutylene terephthalate (PBT). Both types of specimens were obtained by injection molding. X-ray diffraction examinations were performed on the materials obtained to determine the effect of the addition of the fillers used on the degree of crystallinity of the composites. The density and hardness of the composites were evaluated, and the static tensile test and the analysis of the structure parameters using atomic force microscopy (AFM) were also carried out. It was shown that the addition of powder fillers to polymers such as high-density polyethylene and polybutylene terephthalate affects the structure parameters such as surface roughness, mean grain size, anisotropy ratio, fractal dimension, the corner frequency of the composites, and mechanical properties such as Young's pseudo-modulus, average adhesion force, hardness, and tensile strength.

Exploration for Cohesion and Adhesion Characteristics of High Viscosity–Modified Asphalt: Impacts of Composition-Associated Factors and Thermal Aging

To analyze the impacts of composition-associated factors of high-viscosity asphalt mixtures and thermal aging on the cohesion and adhesion characteristics of high viscosity–modified asphalt (HVMA), neat asphalts (NAs), high-viscosity additives, and aggregates were selected, and several HVMAs were first prepared. Then, the prepared HVMAs were subject to contact angle testing, and their cohesion and adhesion behaviors and influencing factors were explored by multifactor orthogonal testing coupled with the surface free energy (SFE) concept. Further, the variations and influencing factors of cohesion and adhesion properties of relevant HVMAs under aging were analyzed in comparison with styrene-butadiene-styrene (SBS)-modified asphalts (SBSMAs) and NAs. Lastly, under aging, the change behaviors of microscopic phases of HVMAs were contrastively investigated using atomic force microscopy (AFM) testing, and the relationship between the microscopic phases and the cohesion and adhesion properties was illustrated. Results showed that NA type, high-viscosity additive dosage and type, and aggregate type notably influenced the cohesion and adhesion of HVMAs, and the high-viscosity additive dosage influenced their cohesion the most. Aging weakened the cohesion and adhesion of asphalts, and the HVMAs possessed the superior cohesion and adhesion at each aging period. Under aging, the NA type, aggregate type, and aging level remarkably affected the cohesion and adhesion of HVMAs, among which the NA type affected their cohesion most prominently. Besides, the aggregate type was the most influential variable on the adhesion of HVMAs whether the HVMAs were aged or not. AFM testing demonstrated that aging reduced the component of microscopic phase structures of HVMAs and the amount of their bee structures, and diminished the surface roughness Ra of asphalt binders; in contrast, aging did not alter the component of microstructural morphology of SBSMAs and NAs. The cohesion and adhesion indexes of HVMAs under aging obeyed the high Pearson correlation and the moderate linear correlation with the Ra index.

Assessment of testing methods for higher temperature performance of emulsified asphalt

High-temperature features are crucial for evaluating the performance of emulsified asphalt. As effective binders, evaporation residues directly determine the high-temperature performance of emulsified asphalt. This study aims to systematically investigate the laboratory preparation process for different emulsified asphalt evaporation residues (EAERs) and proposes appropriate testing and evaluation methods. First, emulsified asphalt was prepared using five different material samples (cations M, A, L, T, and latex). Secondly, three evaporation methods were used to obtain EAERs: the direct heating method, low-temperature evaporation method, and improved evaporation method. Then, the high-temperature rheological parameters were determined using the Brookfield viscosity test, temperature-sweep test, and multiple stress creep recovery tests. Finally, microscopic test methods were adopted for the mechanism analysis, including the fourier transform infrared spectroscopy (FTIR) and the atomic force microscopy (AFM). The results show that different evaporation methods can significantly affect the high temperature performance evaluation results of EAERs. These differences are more obvious between high temperature evaporation and low temperature evaporation conditions. Moreover, the rutting resistance factor and phase angle of styrene-butadiene rubber (SBR) modified emulsified asphalt residues prepared by direct heating method present completely different change laws. From the FTIR and the AFM tests, it is found that these different change laws are due to the chemical reaction during the preparation of SBR modified emulsified asphalt residue by direct heating, which may be the aging of material or the degradation of polymer. In conclusion, the low-temperature evaporation method is recommended to prepare EAERs for a more realistic evaluation of the high-temperature performance of emulsified asphalt. The improved evaporation method should be prioritized as it further standardizes the parameters for subsequent laboratory testing.

Performance of Rejuvenated Asphalt and Mixtures with Waste Engine Oil Bottom and Liquid Styrene-Butadiene Rubber

To address the inadequate performance of rejuvenated asphalt when waste engine oil bottom (WEOB) is used as an asphalt rejuvenator, liquid styrene-butadiene rubber (liquid SBR) was used to enhance the performance of WEOB-rejuvenated asphalt. By testing the basic physical properties of asphalt and using the high- and low-temperature rheology, differential scanning calorimetry, Fourier infrared spectroscopy, and atomic force microscopy (AFM) tests, the index and microstructure changes of asphalt before and after aging and regeneration, from macrolevels and microlevels, were studied, along with the high- and low-temperature performance and water stability of the rejuvenated asphalt mixture. The WEOB decreased the glass transition temperature and low-temperature performance grade of aged asphalt and resulted in a significant effect on the recovery of penetration and softening point of aged asphalt; however, the recovery of low-temperature ductility was inadequate. Compared with WEOB, a rejuvenator comprising WEOB and liquid SBR (WEOB-S) further decreased the glass transition and continuous grading temperatures of aged asphalt, improved its low-temperature performance, and significantly influenced its ductility recovery. The AFM test showed that WEOB-S effectively dispersed the agglomerated bee-like wax crystals or macromolecular asphaltene structures in the aged asphalt, decreased the number and crests of the bee-like structures, and improved the microscopic uniformity, thus obtaining better macroscopic physical properties. Both WEOB and WEOB-S improved the low-temperature performance and water stability of rejuvenated asphalt mixtures; however, WEOB-S was more effective.

Optimization of the Evaluation Indexes for Asphalt UV Aging Behaviors based on Multi-scale Characterization Methods: from the Evolution of Their Physical-Chemical Properties and Microscope Morphology

Aiming to propose some suitable evaluation indexes to quantitatively characterize the UV aging resistance of asphalt binders, firstly, effects of UV aging on asphalt’s properties were comprehensively explored from the multiple scales, including their physical rheological properties, chemical compositions and microscope morphology. The above properties of asphalt binders before and after UV aging were respectively measured with the conventional physical properties tests, dynamic shear rheometer (DSR) test, thin-layer chromatography test (TLC) test, gel permeation chromatography (GPC) test and atomic force microscopy (AFM) test. Subsequently, based on some principles for establishing evaluation indexes, such as discrimination, regularity and consistency, the optimal evaluation indexes were proposed to quantitatively characterize the UV aging resistance of asphalt binders. Finally, relationships between the physical properties, chemical compositions and micro morphology of asphalt binders were discussed with the Pearson correlation coefficient method. Test results show that UV aging has a significant effect on physical rheological properties of asphalt, and ranking of aging resistances among asphalt binders evaluated by different macro indices are nearly consistent. Among these macro indexes, the G-R parameter aging index are proved to be the evaluation index with the highest discrimination degree, followed by complex shear modulus G* aging index (60 °C, 10 rad/s, 1 %) and zero shearing viscosity ZSV aging index (60 °C). Chemical composition test results demonstrate that with the growth of UV aging degree, resins components in asphalt increase gradually, while aromatics components decrease, which results in the proportion of larger molecular size (LMS) in asphalt gradually increases. And AFM test results show that UV aging will cause the number of the “bee structure” and roughness values of asphalt gradually decrease, thus promoting the transformation of the asphalt micro structure to smooth. Pearson correlation analysis indicates the compared with the roughness Ra, the Gel index Ic and LMS possesses higher correlation with G-R and G*, whose R values both exceed 0.8. Thus, it may be appropriate to adopt some chemical composition evaluation indexes (such as Ic, LMS) to characterize the UV aging degree of asphalt binders from the microscope perspective.

Electrospinning strategy for the preparation of nano‐porous fibers as modifier for inducing the network structure and enhancing mechanical properties of SBS‐modified asphalt

AbstractElectrospinning is used to control the interface structure of macro‐polyacrylonitrile (PAN) fibers, and nano‐porous fibers (E‐PAN) which possess enhanced adhesion and interface effects. Herein, E‐PAN was prepared via electrospinning and was in turn incorporated into styrene‐butadiene‐styrene (SBS) asphalt to prepare PAN modified asphalt. The effect of E‐PAN addition on the performance of modified asphalt was explored. Fourier transform infrared (FT‐IR) spectroscopy, X‐ray diffraction, scanning electron microscopy, atomic force microscopy (AFM), and AFM tests confirmed that E‐PAN exhibited a highly rough nano‐porous skeleton without any prominent structural damage during the preparation process. The three major indexes, dynamic shearing rheometer, MSCR, rotational viscosity, and thermogravimetric analysis tests results showed that E‐PAN modified asphalt exhibited excellent viscoelasticity, anti‐rutting and anti‐fatigue properties and thermal stability (THRI of 192.7°C). FT‐IR test of the four components of modified asphalt confirmed that E‐PAN chemically crosslinked with the saturates and aromatics in the base asphalt and SBS, which resulted in a uniform and well‐developed network structure. In addition, Brauner‐Emmett‐Teller and fluorescence microscopy results confirmed that E‐PAN got fully swollen in a behavior similar to that of SBS in the base asphalt, and hence helped SBS to form an excellent network structure in asphalt. E‐PAN played the important role of stress buffer, mutual entanglement, and good thermal insulation inside the asphalt.