Investigation of porous asphalt microstructure using optical and electron microscopy

Direct observations of porous asphalt concrete samples in their natural state using optical and electron microscopy techniques led to useful information regarding the microstructure of two mixes and indicated a relationship between microstructure and in situ performance. This paper presents evidence that suboptimal microstructure can lead to premature failure thus making a first step in defining well or suboptimal performing pavements with a bottom-up approach (microstructure). Laboratory and field compaction produce different samples in terms of the microstructure. Laboratory compaction using the gyratory method has produced more microcracks in mineral aggregates after the binder had cooled. Well-performing mixes used polymer-modified binders, had a more homogeneous void structure with fewer elongated voids and better interlocking of the aggregates. Furthermore, well-performing mixes showed better distribution of the mastic and better coverage of the aggregates with bitumen. Low vacuum scanning electron microscopy showed that styrene butadiene styrene polymer modification in binder exists in the form of discontinuous globules and not continuous networks. A reduction in the polymer phase was observed as a result of aging and in-service use.     

镁合金轧制乳化液的配方设计

为开发镁合金板带轧制用冷却润滑剂,对以10#变压器油、7#主轴油和聚乙二醇600 (PEG600)为基础油,以Span80、Tween80、十二烷基磺酸钠(SDS)为复合乳化剂,以十二醇和油酸作为油性剂的水包油型乳化液进行性能检测.结果表明:乳化液的稳定性主要受到表面活性剂种类与加入量的影响,以非离子和阴离子型表面活性剂复配的乳化剂为佳,适宜的加入量在10％左右;复配乳化剂制备的乳化液的稳定性和离水展着性均优于单独使用某一种乳化剂,随着乳化剂加入量的增加,乳化液的离水展着性明显增加,表面张力明显下降;十二醇油性剂有利于提高乳液的稳定性,油酸油性剂有利于提高乳液的离水展着性.     

Effect of aging on the morphology of bitumen by atomic force microscopy

Effect of aging on the morphology of bitumen was investigated. Two bitumens were aged according to the thin film oven test (TFOT), pressure aging vessel (PAV) test and ultraviolet (UV) radiation, respectively. The morphology of the binders before and after aging was characterized by atomic force microscopy. The physical properties and chemical compositions of the binders were also measured. The results showed that aging affected the bitumen morphology significantly. Aging increased the overall surface stiffness of the bitumen and made the bitumen surface more solid-like. The extent of these changes was dependent on aging conditions. TFOT decreased the contrast between the dispersed domains and the matrix, which contributed to the single-phase trend of the binders. The effect of PAV aging on morphology of the binders was dependent on the base bitumen. In one case, it further accelerated the single-phase trend of bitumen in comparison with that after TFOT. In the other case, it caused the phase separation of bitumen. In both cases, PAV aging increased the surface roughness of the binders obviously. As a result of UV aging, the contrast between the matrix phase and dispersed phase was increased due to the difference in sensitivity to UV radiation of the bitumen molecules, which caused or further promoted the phase separation in the binders. Regardless of the aging procedure carried out, a strong correlation was observed between the changes in morphology and physical properties as well as chemical compositions of the binders before and after aging.     

The effect of emulsifier concentration on the lubricating properties of oil-in-water emulsions

Although the use of oil-in-water (O/W) emulsions as metalworking fluids is widespread, the mechanisms of emulsion lubrication are not yet well understood. Several theories have been proposed but there is not a clear agreement about the effect of different operating conditions and emulsion properties on the lubricating performance of O/W emulsions. In the present study, the film forming ability of O/W emulsions as a function of emulsifier concentration is studied. The emulsifier content exerts a strong influence on all the emulsion properties, such as stability, droplet size distribution, surface and interfacial tension, wetting ability, etc., as well as on the lubricating behaviour, so it has been used to ascertain the relationship between all the properties involved. Three different emulsifiers—anionic, nonionic and cationic—were used at different concentrations in the design of lubricant O/W emulsions. Experimental results show that the work of adhesion of oil droplets on the metal surface is a valuable parameter to predict the ability of emulsions to form thick films in elastohydrodynamic (EHD) contacts. The influence of pH value of O/W emulsions on their lubricating behaviour is also verified. The overall conclusion is that the interactions between metal and oil droplets rule the mechanism of lubrication and that this interaction is primarily controlled by emulsifier concentration.     

The microstructure of petroleum vacuum residue films for bituminous concrete: a microscopy approach

Selected carbon-rich refinery residues ('binders') mixed with mineral particles can form composite materials ('bituminous concrete') with bulk mechanical properties comparable to those of cement concrete. The microstructural mechanism underlying the remarkable composite properties has been related to the appearance of a rigid percolating network consisting of asphaltenes and mineral particles [Wilbrink M. et al. (2005) Rigidity percolation in dispersions with a structured visco-elastic matrix. Phys. Rev. E71, 031402]. In this paper, we explore the microstructure of thin binder films of varying thickness with a number of microscopic characterization techniques, and attempt to relate the observed microstructure to the distinctive mechanical behaviour. Two binders, only one of which has been proven to be suitable for bituminous concrete were investigated, and their microstructure compared. Both binders show the formation of asphaltene aggregates. The binder suitable for bituminous concrete is distinguished by the fact that the asphaltenes show a stronger tendency towards such aggregation, due to a higher concentration and less stabilization in the maltene phase. They also show a clear affinity to other species (such as waxes) and may act as nucleation sites for crystals and aggregates of those species.     

Evolution of the microstructure of unmodified and polymer modified asphalt binders with aging in an accelerated weathering tester

This paper presents findings on the evolution of the surface microstructure of two asphalt binders, one unmodified and one polymer modified, directly exposed to aging agents with increasing durations. The aging is performed using an accelerated weathering tester, where ultraviolet radiation, oxygen and an increased temperature are applied to the asphalt binder surface. Ultraviolet and dark cycles, which simulated the succession of day and night, alternated during the aging process, and also the temperature varied, which corresponded to typical summer day and night temperatures registered in the state of Qatar. Direct aging of an exposed binder surface is more effective in showing microstructural modifications than previously applied protocols, which involved the heat treatment of binders previously aged with standardized methods. With the new protocol, any molecular rearrangements in the binder surface after aging induced by the heat treatment is prevented. Optical photos show the rippling and degradation of the binder surface due to aging. Microstructure images obtained by means of atomic force microscopy show gradual alteration of the surface due to aging. The original relatively flat microstructure was substituted with a profoundly different microstructure, which significantly protrudes from the surface, and is characterized by various shapes, such as rods, round structures and finally ‘flower’ or ‘leaf’ structures.     

Impact of Oil-in-Water Emulsion Composition and Preparation Method on Emulsion Physical Properties and Friction Behaviors

Emulsions have been used as a model food system for many studies on food behavior, including tribological studies. Several studies have examined the effect of fat content and emulsifier on emulsion friction behavior; however, other emulsion parameters such as ionic strength, pH, and homogenization pressure have received little attention in the literature. Additionally, emulsion friction measurements are generally compared to sensory data rather than physical property data. Thus, the objective of this study was to investigate the effect of various emulsion parameters on emulsion physical properties and rheological and friction behavior. Emulsion salt content, pH, and homogenization pressure all affected friction behavior, with specific effects dependent on the emulsifying protein. All emulsions showed reduced friction coefficient with increased fat content. Emulsion rheological behavior was not strongly impacted by changes in the emulsion parameters. Changing emulsion pH had the strongest effect on emulsion physical properties. The results of this study suggest that tribology may be used to develop a “fingerprint” for emulsions prepared using different parameters, allowing improved differentiation of these emulsions compared to traditional rheometry.     

Effect of treatment temperature on the microstructure of asphalt binders: insights on the development of dispersed domains

This paper offers important insights on the development of the microstructure in asphalt binders as a function of the treatment temperature. Different treatment temperatures are useful to understand how dispersed domains form when different driving energies for the mobility of molecular species are provided. Small and flat dispersed domains, with average diameter between 0.02 and 0.70 μm, were detected on the surface of two binders at room temperature, and these domains were observed to grow with an increase in treatment temperature (up to over 2 μm). Bee‐like structures started to appear after treatment at or above 100°C. Moreover, the effect of the binder thickness on its microstructure at room temperature and at higher treatment temperatures was investigated and is discussed in this paper. At room temperature, the average size of the dispersed domains increased as the binder thickness decreased. A hypothesis that conciliates current theories on the origin and development of dispersed domains is proposed. Small dispersed domains (average diameter around 0.02 μm) are present in the bulk of the binder, whereas larger domains and bee‐like structures develop on the surface, following heat treatment or mechanical disturbance that reduces the film thickness. Molecular mobility and association are the key factors in the development of binder microstructure.     

Bituminous emulsions and their characterization by atomic force microscopy

We present a new method for observing oil-in-water emulsions with a continuous water phase and a dispersed bitumen phase. The fine polydispersed bitumen micelles were adsorbed to an atomically smooth mica substrate and imaged in solution by atomic force microscopy in a liquid cell. The height of the adsorbed bitumen sheet in wet and dry states can be measured and the homogeneity of film formation by coalescence can be determined. Localization of surfactant onto and between bitumen micelles is also visualized.     

柴油-含水乙醇乳化燃料液滴的微爆现象研究

文中对柴油-含水乙醇乳化燃料液滴的微爆现象进行了研究.利用修正的微爆数学模型,计算得到含水乙醇乳化燃料和水的微爆温度边界条件,同时进行了微爆温度观测试验,将试验结果与理论计算结果进行对比,验证了模型的正确性.对柴油-含水乙醇乳化燃料液滴蒸发过程和微爆现象进行了观察试验.结果表明:均匀成核通常会导致典型的微爆,而异相成核...     

Effect of aging on morphology of organo-montmorillonite modified bitumen by atomic force microscopy

The morphology of unmodified and organo-montmorillonite modified bitumens was investigated by atomic force microscopy. The influence of thin film oven test and ultraviolet aging on the morphology of the binders was also analysed. The atomic force microscopy results showed that bitumen displayed a 'bee-like' structure and the dimension of the 'bee-like' structures was decreased to some extent with the introduction of organo-montmorillonite. Organo-montmorillonite showed a better interaction with the dispersed domains in comparison with the matrix in bitumen, which led to an obvious increase in the contrast between the dispersed domains and the matrix in bitumen. Compared with the unmodified bitumen, the single-phase trend in the organo-montmorillonite modified bitumen could be effectively prevented during thin film oven test and ultraviolet aging, indicating its good aging resistance which was in accordance with changes in physical properties of the organo-montmorillonite modified bitumen before and after aging.     

水基流延法制备低温共烧陶瓷生带材料新工艺

为实现硼硅酸盐玻璃陶瓷基低温共烧陶瓷生带材料的低成本、安全无毒化生产,采用以水性乳胶作为粘结剂的水基流延工艺进行制备;采用数字旋转黏度计分别对分散剂、固相、粘结剂含量对浆料黏度的影响进行了研究,利用扫描电镜对烧结前后生带材料的微观形貌进行了分析.结果表明:利用硼硅酸盐玻璃+Al<,2>O<,3>粉体作为固相,苯丙乳液作为粘结剂,苯丙烯酸铵作为分散剂,甘油作为增塑剂,成功制备出了固含量高、稳定性好、干燥快的水基流延浆料;制备的生带材料表面光滑、强度高,容易在室温下叠层,经过850℃×30 min烧结,其致密度可以达到96.45%.     

The Influence of Lubricating Agents on the Formation of a Film of a Styrene/Butadiene Latex

The interactions between paper coating lubricants and a carboxylated styrene/butadiene latex emulsion and their effect on latex film morphology have been studied. Calcium stearate, non-ionic polyethylene emulsion and organic triglyceride lubricants showed different interaction characteristics with the latex emulsion according to viscosity, zeta potential and isothermal calorimetric measurements. Calcium stearate lowered the viscosity of the dilute latex emulsion at low concentration suggesting a strong interaction with the latex particles due to a change in the hydrodynamic dimensions of the latex particles. The exothermic enthalpy change supported the assumption of a dissociative interaction. In contrast, both non-ionic polyethylene and organic triglyceride emulsion showed less pronounced enthalpy changes, indicating lower affinity for the latex particles. The reduction in viscosity showed, however, that at low lubricant concentrations there is an interaction between the latex particles and particularly the organic triglyceride emulsion. This suggests a selective adsorption of stabilizing agents and species from the lubricant emulsion which alters the hydrodynamic radius of the latex particles. The effects of the colloidal interactions on the morphology of the latex films monitored by Atomic Force Microscopy (AFM) indicated that specific surface interaction occurring in aqueous media influenced the topography and the surface chemical heterogeneity of the latex films. Especially in the case of calcium stearate, it seems that the dissolved species arrange themselves around the latex particles inhibiting film formation. The organic triglyceride, on the other hand, showed a lower interaction potential in the aqueous phase and it had a different impact on the film formation.     

Physical and Chemical Impact of Sulphuric Acid on Cylinder Lubrication for Large 2-Stroke Marine Diesel Engines

The influence of sulphuric acid, H₂SO₄, on the physical and chemical behaviour of marine Diesel engine lubricant base oils was investigated. To understand the basic interaction of H₂SO₄ with the lubricant film, the saturated hydrocarbon squalane, C₃₀H₆₂, was chosen as a simple model oil in addition to a fully formulated lubricant and its corresponding API Group I base oil HVI160B. To understand droplet formation in the lubricant, the interfacial tension between aqueous H₂SO₄ (0?C98?%w/w) and C₃₀H₆₂ measured in a previous study (Sautermeister et al., Tribology International, 38th Leeds-Lyon Symposium on Tribology, 2011) and is compared with three different API Group I base oils. Interfacial tension decreases with increasing acid concentration, but is much lower for the base oil. Both oils were emulsified with a constant volume fraction of aqueous H₂SO₄. The droplet size was smaller and more distinct for the base oil under the same shearing conditions and the emulsions with base oil were are more stable. The concentration of the dispersed phase had no significant influence on the viscosity of the emulsions compared to the viscosity of the bulk oil alone. In addition to the physical measurements, chemical reaction between H₂SO₄ and the API Group I base oil HVI160B was observed yielding bituminous matter which appears to be a complex emulsion. The critical acid concentration for the formation of bitumen was found to be 40?%w/w. Between 50 and 80?%w/w, bitumen was formed spontaneously at 85?°C and above 85?%w/w, bitumen was formed spontaneously at room temperature. The observed concentrations for bitumen formation correlate well with the first and second dissociation steps of H₂SO₄. HSO₄ ^? ions are likely to be the driving force for bitumen formation. Finally, the viscosity characteristics of two different bitumen were measured. Both were found to exhibit shear thinning and the one formed with highly concentrated H₂SO₄ created a solid deposit on the measurement equipment above 120?°C.     

The effect of the additive concentration in emulsions to the tribological behavior of a cold rolling tube under sliding contact

The industrial steel tube in the cold rolling processes under liquid lubrication was simulated in a recovered cutting machine to study the tribological performances of an emulsion with four different concentrations of an emulsifier. The test machine was equipped with a device to measure the electrical contact resistance (ECR) between the rubbing surfaces of a steel tube and a roller. The ECR readings were useful to identify the existence of a surface absorption layer (a boundary layer film) between the contact surfaces and thus to realize the tribological effects. The tribological properties, including the friction coefficient, the electrical contact resistance, the wear loss of the tube and the worn surface area, were evaluated at these emulsifier concentrations. The displacement energy and the spraying coefficients for these emulsifier concentrations were applicable to interpret their relationships with the wear loss of the steel tube. The measures of the ECR are found to have a tendency more related to the values of the friction coefficient. Stribeck curves were also established for four emulsions; they are useful for assisting in the explanation for why a high friction coefficient in some cases does not necessarily produce a high wear loss. They were also provided to investigate the effects of the emulsifier concentrations on the friction coefficients at various lubrication stages. The emulsion with a dilute ratio of 50:1 proved to be the optimum choice of the four emulsifier concentrations because it leads to the lowest friction coefficient, the smallest wear loss and the worn surface as to the test time of 60 minutes.     

Direct observation of the asphaltene structure in paving-grade bitumen using confocal laser-scanning microscopy

The structure of the asphaltene phase in the bitumen is believed to have a significant effect on its rheological properties. It has traditionally been difficult to observe the asphaltene phase in unaltered samples of bitumen. The maltenes are thought to form a continuous phase in which the asphaltenes are ‘dispersed’. In this study, confocal laser‐scanning microscopy (CLSM) operating in fluorescence mode was used to examine the structure of paving‐grade Safaniya and San Joaquin bitumen. The asphaltene fraction fluoresces in the 515–545 nm wavelength range when irradiated with light with a wavelength of 488 nm. The major advantages of CLSM are that the bitumen sample requires little pretreatment or preparation that may affect the original dispersion of asphaltenes and the bitumen is observed at ambient temperature and pressure. This reduces the possibility of producing images that are not representative of the original material. CLSM was able to show the distribution of maltene and asphaltene components in bitumen. The asphaltene aggregates in the bitumen were observed to be 2–7 µm in size and formed a dispersed ‘sol’ structure in the continuous maltene matrix rather than a network ‘gel’ structure. Surprisingly, the structure and fluorescence of the asphaltene phase does not appear to alter radically upon oxidative ageing. The structure of the asphaltene phase of an AR4000 San Joaquin bitumen was found to be more homogeneous than that of Safaniya bitumen, illustrating the range of structures that can be observed in bitumens by this method.     

润滑剂和粘结剂的加入对铁粉流动性和松装密度的影响

本文研究了在铁粉加中加入聚乙二醇、硬脂酸锂、二硫化钼对后铁粉流动性和松装密度的影响作用，确定了粘结剂和润滑剂的合适加入量。实验结果表明：粘结剂和润滑剂加入量有一个最佳值，此时流动性最好，超过这一加入量，流动性下降。     

文物蛋白胶料的气相色谱-质谱分析方法探讨

为了探讨文物蛋白胶结材料的气相色谱-质谱（GC-MS）分析方法，以正亮氨酸为内标，N-(叔丁基二甲硅烷基)-N-甲基三氟乙酰胺(简称MTBSTFA)+1%特丁基二甲基氯代硅烷作为衍生化试剂，建立了蛋白胶料中常见的丙氨酸、甘氨酸等11种氨基酸的标准曲线，测定了每种氨基酸的精密度和检出限，并将该方法用于现代参考胶料和文物样品的分析测量。结果表明，GC-MS法对氨基酸的分离效果较好，除羟脯氨酸的稳定性略差外，其余10种氨基酸标准曲线的相关系数（R）均大于0.99，11种氨基酸的相对标准偏差（RSD）为2.7%~6.3%。甘氨酸的检出限最低，为0.066 μg/g；亮氨酸的检出限最高，为0.676 μg/g。在对猪皮胶、全蛋和牛奶3种现代参考胶料氨基酸分析的基础上，结合主成分分析（PCA）法揭示了3种胶料的特征性，并采用该方法鉴定了广西服饰金线文物样品中的蛋白胶料，表明该方法适用于文物蛋白胶料的定量分析。     

Effect of montmorillonite organic modification on microstructures and ultraviolet aging properties of bitumen

The effect of montmorillonite (MMT) organic modification on microstructures and ultraviolet (UV) aging properties of bitumen was investigated. The microstructures of MMT modified bitumen were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM), respectively. The binders were aged by UV radiation. The UV aging properties of MMT modified bitumen was studied by determining physical properties and AFM analysis. XRD and FTIR analyses show that the sodium montmorillonite (Na(+) -MMT) modified bitumen forms a phase-separated structure, whereas the organo-montmorillonite (OMMT) modified bitumen forms an intercalated structure. After Na(+) -MMT modification, the contrast between the matrix and the dispersed domains is inverted according to AFM analysis. However, this contrast inversion is prevented with the introduction of OMMT due to the good compatibility between the OMMT and the bitumen. As a result of UV aging, both viscosity aging index and softening point increment of OMMT modified bitumen are lower than that of the unmodified bitumen and Na(+) -MMT modified bitumen. Furthermore, the association interactions and single-phase trend in OMMT modified bitumen are further prevented in comparison with Na(+) -MMT modified bitumen during UV aging, indicating the good aging resistance of OMMT modified bitumen after organic modification of MMT.     

高分子材料3DP法三维打印坯的水浸法脱黏研究

以麦芽糊精粉末和聚乙烯醇粉末为黏结剂,采用3DP法三维打印制备得到高分子材料坯件,经过加热预熔合后,采用超声波清洗机进行水浸法脱黏,采用称重法和拉曼光谱分析检测黏结剂去除情况,研究了水温、超声振动和浸泡时间对脱黏效果的影响。结果表明,水温越高,脱黏效果越好;有超声振动时,可明显提高脱黏效率;浸泡时间越长,脱黏效果越好。得到本研究试样的两种较为理想的脱黏方案,即40℃水温超声振动下浸泡9 h和50℃水温超声振动下浸泡6 h。