CN103529244A - Method based on atomic force microscope for researching microscopic characteristics of asphalt - Google Patents

Abstract

The invention provides a method based on an atomic force microscope for researching microscopic characteristics of asphalt. The method comprises the following steps: preparing an asphalt sample for atomic force microscope observation, imaging surface morphology, performing high-precision and quantitative analysis on roughness and analyzing adhesion; (1) preparing the asphalt sample so as to enable the asphalt sample to meet observation requirements of the atomic force microscope; (2) imaging the surface morphology: observing the size and density of a honeycomb structure in a selected area on the surface of the asphalt sample from a two-dimensional angle and with a high resolution by using the atomic force microscope; (3) performing high-precision and quantitative analysis on the roughness: acquiring a roughness parameter in the image area of the atomic force microscope by using proper data analysis software; (4) analyzing the adhesion: acquiring a force curve by using the atomic force microscope, and acquiring an adhesion value through the force curve; (5) quantitatively evaluating the adhesiveness and self-healing performance of the asphalt according to the roughness and adhesion. The method provides an effective way for recognizing and analyzing material properties from a microscopic view for researchers.

Description

A kind of research method of the pitch microscopic characteristics based on atomic force microscope

Technical field

The present invention relates to pitch micro-property and evaluate field, relate in particular to before and after a kind of research asphalt modification based on atomic force microscope or the research method of the variation of aging front and back physical form, evaluation pitch adhesion and self-healing ability.

Background technology

In recent decades, researcher has carried out extensive and deep research to the character of asphalt material macroscopic view, yet due to the restriction of Research scale, method means, it is phenomenological, unilateral mostly these achievements in research are.If want full appreciation pitch character and for a certain characteristic carry out physics, chemical modification just must be studied pitch from microcosmic level to design the material corresponding to actual needs, and from the angle of microcosmic, deduces out grand thin sight rule.Along with scientific and technological progress, increasing instrument makes this idea become possibility, atomic force microscope is exactly in road field, to be subject to nearly ten years one of means of testing of greatly paying attention to, it can help people to pass through the structure that material is familiar with in Analysis of Surface Topography, conclusion, summary more all sidedly---property relationship (structure-functionrelationship), and can provide the structural information that other method is difficult to acquisition.

The structure height that AFM can provide from nanometer to hundreds of micro-meter scale surface is differentiated picture, can be used for high precision and the high sensitivity quantitation analysis of surface microroughness, the component that can observe surface mass distributes, the material microstructure sights such as single large molecule, crystal grain and layer structure and the microphase-separated of superpolymer.

Summary of the invention

This method technical matters to be solved is to provide a kind ofly can study asphalt surface pattern to analyze modifier modification, the impact of factor on pitch microstructure composition structure such as aging from microcosmic angle, and evaluates the adhesion of pitch and the research means of self-healing ability by surface topography imaging, the high-precision fixed component analysis of surfaceness and adhesion test.Based on atomic force microscope, can effectively overcome the deficiency of macroscopic view test, can rational explanation be provided and provide theoretical foundation for material modification for macroscopic appearance from microcosmic angle.

The present invention proposes a kind of research method that can be used for studying asphalt modification front and back or the variation of aging front and back physical form, evaluation pitch adhesion and self-healing ability based on atomic force microscope, it comprises the following steps:

Utilize atomic force microscope pitch sample to be observed to size and the density degree of the honeybee shape structure in specimen surface selection area with high resolving power from two dimension angular;

Use atomic force microscope, under the pattern of rapping, pitch sample is carried out to scanning imagery and form image file, then utilize Nonoscopy Analysis software to process image, select a certain region, and obtain characterizing two kinds of roughness parameters of this image-region: arithmetic average roughness R _aand r.m.s. roughness R _q;

Use atomic force microscope by probe, to approach pitch specimen surface and carry out force curve test from pitch specimen surface rollback under contact mode.

Wherein, obtain pitch sample step as follows:

Step 1.1, asphalt heating is extremely liquid, wherein matrix pitch is heated to 120 ℃; Modified bitumen is heated to 160 ℃;

Step 1.2, get heating after pitch drip on 40mm * 15mm * 1mm microslide;

Step 1.3, this microslide is put into baking oven heats 10min so that pitch evenly scatters, diameter is about 1cm, and it is cooling as pitch sample to be taken out nature.

Wherein, each pitch specimen surface is got at random 10 some records and is obtained 10 force curves to calculate adhesive force mean value.

Compare with existing microexamination technology, atomic force microscope has the material microstructure analytic function of high spatial resolution, local microcell mechanics and determination of physical appearance and other ability such as micromachined such as nanoscale, the equipment that adds use is relatively simple, operation and sample are prepared the advantages such as easy, become the indispensable important means of testing of each science and technology field, for researcher provides effective approach from microcosmic angle understanding substance characteristics.

Accompanying drawing explanation

Fig. 1 is the pitch sample for atomic force microscope observation;

Fig. 2 (a1) is atomic force microscope observation figure before 50# pitch short ageing;

Fig. 2 (a2) is atomic force microscope observation figure after 50# pitch short ageing;

Fig. 2 (b1) is atomic force microscope observation figure before 70# pitch short ageing;

Fig. 2 (b2) is atomic force microscope observation figure after 70# pitch short ageing;

Fig. 3 is needle point and the interactional process of specimen surface.

Embodiment

(1) sample is prepared

1) asphalt heating is extremely liquid, wherein matrix pitch is heated to 120 ℃; Modified bitumen is heated to 160 ℃; 2) getting the rear pitch of heating drips on 40mm * 15mm * 1mm microslide; 3) this microslide is put into baking oven heats 10min so that pitch evenly scatters, diameter is about 1cm, and it is cooling as pitch sample to be taken out nature.

(2) surface topography imaging

Atomic force microscope utilizes the probe that is positioned at cantilever one end very responsive to External Force Acting, and the interaction force between detection needle point and sample is realized the imaging of specimen surface.

Imaging pattern is the pattern of rapping, and adopts silicon nitride cantilevers probe to carry out scanning imagery to sample, and semi-girder standard elastic number is 42N/m, probe height is 11um, and jib-length is 125um, and resonant frequency is 260kHz, sweep limit is 40um * 40um, and image pixel is 512 * 512.

Under microcosmic condition, there is honeybee shape structure in asphalt surface, should note size and the density degree of the honeybee shape structure in specimen surface selection area in observation process.The degree of uniformity of honeybee shape structure is relevant to the mutual harmony of pitch four components.

(3) the high-precision fixed component analysis of roughness

First pitch sample is carried out under the pattern of rapping to scanning imagery with atomic force microscope and form image file, then utilize NonoscopyAnalysis software to process image, select a certain region, and obtain characterizing two kinds of roughness parameters of this image-region: arithmetic average roughness R _aand r.m.s. roughness R _q.

The Two-dimensional Surfaces forming for M * N discrete point, R _aand R _qbe defined as respectively:

$R_a=\frac{1}{\mathrm{MN}}\underset{i=1}{\overset{M}{\mathrm{\Σ}}}\underset{j=1}{\overset{N}{\mathrm{\Σ}}}|z_{\mathrm{ij}}-\stackrel{-}{z}|$

$R_q={\left[\frac{1}{\mathrm{MN}}\underset{i=1}{\overset{M}{\mathrm{\Σ}}}\underset{j=1}{\overset{N}{\mathrm{\Σ}}}{(z_{\mathrm{ij}}-\stackrel{\‾}{z})}^2\right]}^{\frac{1}{2}}$

Z wherein _ijrepresent the height value on each discrete sampling point, average height for surperficial, is expressed as:

$\stackrel{\‾}{z}=\frac{1}{\mathrm{MN}}\underset{i=1}{\overset{M}{\mathrm{\Σ}}}\underset{j=1}{\overset{N}{\mathrm{\Σ}}}{z}_{\mathrm{ij}}$

If free face roughness is very greatly, show surface irregularity, blemish surface can be larger, has larger defect repair energy, and this asphalt surface adhesion or self-healing property are better.

(4) adhesive force analysis

Force curve describe needle point power or micro-cantilever be offset relative sample-needle tip spacing from funtcional relationship, can at large disclose needle point-sample interaction process, the abundant information of specimen surface and power relevant nature can be provided.

Atomic force microscope is adjusted to force curve pattern, when AFM probe along the path that approaches, contact and withdraw when a certain tiny area in testing sample surface carries out vertical axial relative motion, probe and sample room can apply acting force mutually because of variable in distance, produce force curve.In force curve, the power that jumps out of sample spot place corresponding to needle point is required adhesive force.Each sample surfaces is got at random 10 some records and is obtained 10 force curves to calculate adhesive force mean value.The effect that adhesive force has characterized between nanoscale contact is strong and weak, and adhesive force is larger, and surface adhesion or healing ability are better.

The above is only the preferred embodiment of the present invention; be noted that for those skilled in the art; under the premise without departing from the principles of the invention, can also make the some improvements and modifications that can expect, these improvements and modifications also should be considered as protection scope of the present invention.

Accompanying drawing explanation:

The pitch sample of observing for atomic force microscope as shown in Figure 1.

Surface topography imaging as shown in Figure 2, can observe asphalt surface by afm scan imaging and have honeybee shape structure, and this structure is a kind of wax crystal, take bituminous matter as core, outwards successively wraps up colloid, wax molecule and oil content.By afm image before and after contrast 50# and 70# ageing of asphalt, can find that 50# pitch honeybee shape structure attenuates diminishes; It is elongated greatly that 70# pitch honeybee shape structure becomes, and total quantity tails off.Draw thus to draw a conclusion: in ageing process, the character of four kinds of components, content all can change, when bituminous matter, gum level increase, on the one hand, it is many that crystallization point (nucleus) quantity of honeybee shape structure becomes, and on the other hand, bituminous matter, colloid can be adsorbed in the brilliant surface of wax as a kind of " natural pour-point depressant ", the surface energy and the structural strength that greatly reduce wax crystalline substance, play the effect of encirclement, dispersing wax crystalline substance.Angle from crystallography, first bituminous matter with long-chain is separated out along with lowering the temperature, play nucleation, colloid with strong polarity is adhered to its surface quickly, thereby having hindered the brilliant one-tenth of wax piece assembles, the bituminous matter, the colloid that in the bituminous matter of the brilliant adsorption of wax and colloid and crude oil, are not adsorbed form electrostatic double layer, though the molecular layer that their directed dipole molecule forms on the brilliant surface of wax is not to external diffusion, but can make to induce secondary molecular layer in its adjacent liquid phase, so the brilliant particle shape of wax becomes solvent covering.This covering, as stoping the approaching energy barrier of wax crystal grain, prevents that it from connecting, assembling (corresponding to 50# pitch).On the other hand, when bituminous matter quantity is increased to a certain degree, colloid cannot wrap well bituminous matter and will cause bituminous matter to assemble, and causes nucleus to tail off simultaneously, and pour-point depressing process also weakens thereupon, and crystal grain has the trend (corresponding to 70# pitch) that becomes large.Atomic force microscope imaging can provide microscopic explanation for pitch macroscopic property develops.

As shown in Figure 3, solid line and dotted line represent that respectively AFM probe approaches sample surfaces and lifts the variation of cantilever deflection direction and degree of deflection process from sample surfaces rollback to needle point-sample interaction process.When needle point does not contact with sample surfaces, cantilever does not have deflection (1), when needle point is downward and sample surfaces approaches very much, (2) start to deflect, needle point is further oppressed sample surfaces, and cantilever deflection becomes large (3), when cantilever deflection is lifted (4) during to setting value by rollback, last cantilever rollback is contactless to sample and needle point, and cantilever is got back to original zero deflection state (1).Apply this curve and can characterize sample surfaces adhesive force.

Claims (3)

1. the pitch microscopic characteristics research method based on atomic force microscope, it comprises the following steps:

Utilize atomic force microscope pitch sample to be observed to size and the density degree of the honeybee shape structure in specimen surface selection area with high resolving power from two dimension angular;

Use atomic force microscope, under the pattern of rapping, pitch sample is carried out to scanning imagery and form image file, then utilize Nonoscopy Analysis software to process image, select a certain region, and obtain characterizing two kinds of roughness parameters of this image-region: arithmetic average roughness R _aand r.m.s. roughness R _q;

Use atomic force microscope by probe, to approach pitch specimen surface and carry out force curve test from pitch specimen surface rollback under contact mode.

2. the pitch microscopic characteristics research method based on atomic force microscope as claimed in claim 1, wherein obtain pitch sample step as follows:

Step 1.1, asphalt heating is extremely liquid, wherein matrix pitch is heated to 120 ℃; Modified bitumen is heated to 160 ℃;

Step 1.2, get heating after pitch drip on 40mm * 15mm * 1mm microslide;

Step 1.3, this microslide is put into baking oven heats 10min so that pitch evenly scatters, diameter is about 1cm, and it is cooling as pitch sample to be taken out nature.

3. the pitch microscopic characteristics research method based on atomic force microscope as claimed in claim 1, each pitch specimen surface is got at random 10 somes records and is obtained 10 force curves to calculate adhesive force mean value.

Images