Method for detecting polyacrylonitrile fiber generalized orientation degree by two-dimensional X-ray diffraction
阅读说明：本技术 应用二维x射线衍射检测聚丙烯腈纤维广义取向度的方法 (Method for detecting polyacrylonitrile fiber generalized orientation degree by two-dimensional X-ray diffraction ) 是由 高忠民 唐海通 高宇 李向山 于 2018-09-07 设计创作，主要内容包括：本发明提供了一种应用二维X射线衍射检测聚丙烯腈纤维广义取向度的方法,属于材料结晶结构分析检测技术领域。国内外应用的PAN纤维X射线法测量取向度的方法均是针对结晶相(100)衍射线进行的,但有明显的不完整性和不准确性。因此本发明提出了一种以二维衍射图谱为基础,选择特征衍射角,进行积分求取衍射强度-方位角曲线,利用该曲线的半高峰宽计算得到结晶相取向度A<Sub>c</Sub>,取向非晶相取向度A<Sub>o</Sub>和非晶相取向度A<Sub>a</Sub>,完整的表征了PAN纤维中结晶相、取向非晶相及非晶相中的取向状态,相比现有技术结果更加准确。(The invention provides a method for detecting the generalized orientation degree of polyacrylonitrile fibers by applying two-dimensional X-ray diffraction, and belongs to the technical field of analysis and detection of material crystalline structures. The PAN fiber X-ray method for measuring the orientation degree applied at home and abroad is carried out aiming at the diffraction line of the crystalline phase (100), but has obvious incompleteness and inaccuracy. Therefore, the invention provides a method which is based on a two-dimensional diffraction pattern, selects a characteristic diffraction angle, integrates to obtain a diffraction intensity-azimuth angle curve, and calculates to obtain a crystal phase orientation degree A by utilizing the half-height peak width of the curve c Degree of orientation of oriented amorphous phase A o And degree of orientation A of amorphous phase a The orientation states of the crystalline phase, the oriented amorphous phase and the amorphous phase in the PAN fiber are completely characterized, and compared with the prior art, the result is more accurate.)
1. The method for detecting the generalized orientation degree of the polyacrylonitrile fiber by using two-dimensional X-ray diffraction is characterized in that the generalized orientation degree comprises three parameters, namely, a crystal phase orientation degree AcDegree of orientation of oriented amorphous phase AoAnd degree of orientation A of amorphous phasea；
The detection method comprises the following specific steps:
1) testing polyacrylonitrile fibers by using a two-dimensional X-ray diffractometer to obtain a two-dimensional diffraction pattern, and simultaneously obtaining an I (2 theta, kappa) curve, namely a diffraction intensity-diffraction angle-azimuth angle curve;
2) the (100) plane diffraction angle 2 theta is selected for the crystalline phasec16.9 deg. at diffraction angle 2 thetacSolving curve integral in the range of +/-delta 2 theta; the diffraction angle 2 theta is selected for the oriented amorphous phaseo25.2 deg. at diffraction angle 2 thetaoSolving curve integral in the range of +/-delta 2 theta; respectively obtaining I-kappa curves, namely diffraction intensity-azimuth angle curves; delta 2 theta is 1-5 degrees;
3) calculating the half-height peak width of two I-kappa curves respectively, and the half-height width of the crystalline phase curve is HcThe half height width of the oriented amorphous phase curve is HoThe width of the base line of the oriented amorphous phase curve is Ha＝180°；
4) The crystal phase orientation degree A was calculated according to the following formulacDegree of orientation of oriented amorphous phase AoAnd degree of orientation A of amorphous phasea；
Technical Field
The invention belongs to the technical field of analysis and detection of material crystal structures.
Background
Polyacrylonitrile fiber is a precursor for manufacturing high-quality carbon fiber, and the structural characteristics of the polyacrylonitrile fiber have important influence on the quality of the carbon fiber. PAN fiber belongs to macromolecular chain conformation, atoms in a molecular chain are connected by covalent strong bonds, and molecular chains have the functions of hydrogen bonds and van der Waals weak bonds. Therefore, the orientation state of molecular chains has an important influence on the axial strength and modulus of Polyacrylonitrile (PAN) fiber precursors, and therefore, the orientation behaviors of crystalline phases, oriented amorphous phases and amorphous phases along the fiber axis are key structural parameters of PAN fibers. The PAN fiber X-ray method used at home and abroad up to now measures the degree of orientation by aiming at the diffraction line of the crystalline phase (100), but has obvious incompleteness and inaccuracy.
Disclosure of Invention
The invention aims to create a brand-new PAN fiber generalized orientation degree characterization technology on the premise of comprehensively considering the contribution of multiple types of crystal types in PAN fibers to PAN fiber orientation parameters. Therefore, the invention provides a method for detecting the generalized orientation degree of polyacrylonitrile fibers by using two-dimensional X-ray diffraction, which adopts the following technical scheme:
1) testing polyacrylonitrile fibers by using a two-dimensional X-ray diffractometer to obtain a two-dimensional diffraction pattern, and simultaneously obtaining an I (2 theta, kappa) curve, namely a diffraction intensity-diffraction angle-azimuth angle curve;
2) the (100) plane diffraction angle 2 theta is selected for the crystalline phasec16.9 deg. at diffraction angle 2 thetacSolving curve integral in the range of +/-delta 2 theta; the diffraction angle 2 theta is selected for the oriented amorphous phaseo25.2 deg. at diffraction angle 2 thetaoSolving curve integral in the range of +/-delta 2 theta; respectively obtaining I-kappa curves, namely diffraction intensity-azimuth angle curves; delta 2 theta is 1-5 degrees;
3) calculating the half-height peak width of two I-kappa curves respectively, and the half-height width of the crystalline phase curve is HcThe half height width of the oriented amorphous phase curve is HoThe width of the base line of the oriented amorphous phase curve is Ha＝180°；
4) The crystal phase orientation degree A was calculated according to the following formulacDegree of orientation of oriented amorphous phase AoAnd degree of orientation A of amorphous phasea；
The invention has the beneficial effects that:
the invention comprehensively considers the orientation parameters of the PAN fiber by various types of crystals in the PAN fiber, and solves the problem that the PAN fiber is not accurately and comprehensively described by the structural parameters caused by detecting the orientation degree of the crystal phase only in the prior art.
Drawings
FIG. 1 example 1 two-dimensional diffraction pattern of polyacrylonitrile fibers;
FIG. 2I-kappa curves of the crystalline phase and the oriented amorphous phase of example 1.
Detailed Description
The technical solution of the present invention is further explained and illustrated below by way of specific examples.
1) Testing polyacrylonitrile fibers by using a two-dimensional X-ray diffractometer to obtain a two-dimensional diffraction pattern, and simultaneously obtaining an I (2 theta, kappa) curve, namely a diffraction intensity-diffraction angle-azimuth angle curve;
2) the (100) plane diffraction angle 2 theta is selected for the crystalline phasec16.9 deg. at diffraction angle 2 thetacSolving curve integral in the range of +/-delta 2 theta; the diffraction angle 2 theta is selected for the oriented amorphous phaseo25.2 deg. at diffraction angle 2 thetaoSolving curve integral in the range of +/-delta 2 theta; respectively obtaining I-kappa curves, namely diffraction intensity-azimuth angle curves; delta 2 theta is 1-5 degrees;
3) calculating the half-height peak width of two I-kappa curves respectively, and the half-height width of the crystalline phase curve is Hc50.74 DEG, and the half width of the oriented amorphous phase curve is Ho143.26 DEG, the baseline width of the oriented amorphous phase curve is Ha＝180°；
4) The crystal phase orientation degree A was calculated according to the following formulacDegree of orientation of oriented amorphous phase AoAnd degree of orientation A of amorphous phasea；
