scholarly journals A general method to determine twinning elements

2010 ◽  
Vol 43 (6) ◽  
pp. 1426-1430 ◽  
Author(s):  
Yudong Zhang ◽  
Zongbin Li ◽  
Claude Esling ◽  
Jacques Muller ◽  
Xiang Zhao ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Physical Phenomenon ◽  
Significant Advance ◽  
Type I ◽  
Simple Method ◽  
Promising Tool ◽  
Twinning Plane ◽  
Complex Crystal Structure ◽  
Twinning Direction

The fundamental theory of crystal twinning has been long established, leading to a significant advance in understanding the nature of this physical phenomenon. However, there remains a substantial gap between the elaborate theory and the practical determination of twinning elements. This paper proposes a direct and simple method – valid for any crystal structure and based on the minimum shear criterion – to calculate various twinning elements from the experimentally determined twinning plane for Type I twins or the twinning direction for Type II twins. Without additional efforts, it is generally applicable to identify and predict possible twinning modes occurring in a variety of crystalline solids. Therefore, the present method is a promising tool to characterize twinning elements, especially for those materials with complex crystal structure.

Calculation Methods to Determine Crystallographic Elements Based on Electron Diffraction Orientation Measurements by SEM/EBSD or TEM

2012 ◽  
Vol 706-709 ◽  
pp. 2674-2679
Author(s):  
Yu Dong Zhang ◽  
Zong Bin Li ◽  
Claude Esling ◽  
Xiang Zhao ◽  
Liang Zuo
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Sample Surface ◽  
Type I ◽  
Type Ii ◽  
Calculation Methods ◽  
Orientation Relationships ◽  
Prepared Sample ◽  
Twinning Plane ◽  
Twinning Direction

In the present work, we summarized two calculation methods to determine some specific crystallographic elements based on electron diffraction orientation measurements by SEM/EBSD or TEM. The first one is to determine the twin type and twinning elements of crystal twins based on the minimum shear criterion, using the experimentally determined twinning plane for Type I twin and compound twin or twinning direction for Type II twin as initial input. The method is valid for any crystal structure. The second one is one to determine the plane indices of the faceted interfaces where the orientation relationships (ORs) between the adjacent crystals are reproducible. The method requires one prepared sample surface instead of two perpendicular surfaces. These methods are expected to facilitate the related microstructural characterizations.

Crystal structure of modulated martensite and crystallographic correlations between martensite variants of Ni50Mn38Sn12alloy

2016 ◽  
Vol 49 (4) ◽  
pp. 1276-1283 ◽  
Author(s):  
Chunqing Lin ◽  
Haile Yan ◽  
Yudong Zhang ◽  
Claude Esling ◽  
Xiang Zhao ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Electron Backscatter Diffraction ◽  
Type I ◽  
Type Ii ◽  
Plate Interface ◽  
Modulated Structure ◽  
Austenite Grain ◽  
Twinning Plane ◽  
Backscatter Diffraction ◽  
Comprehensive Study

A comprehensive study on the crystal structure, the microstructure and the crystallographic features of the martensite in an Ni50Mn38Sn12alloy has been conducted in the present work. The results show that the martensite possesses a 4O modulated structure. The martensite is organized into broad plates in the original austenite grain. The plates contain irregularly shaped colonies with two characteristic microstructural patterns: a classical lamellar pattern and a herringbone pattern. Crystallographic analyses by scanning electron microscopy/electron backscatter diffraction demonstrate that in each colony there are four orientation variants (A, B, C and D) and they form three types of twins (type I, type II and compound twin). The interfaces between corresponding variants are coincident with their twinning planeK1. The interface planes of the compound twin pairs A&D and B&C can have one or two different orientations, which leads to the two microstructural patterns. The corresponding variants in neighboring colonies within one broad plate (intra-plate colonies) possess close orientations, but the type I and the type II twin relationships are interchanged. The variants in neighboring colonies situated in adjacent plates (inter-plate colonies) are type I or type II twin related but with some angular deviations. The plate interface is defined by the {221} plane of the variant pair with largest thickness. The results of the present work provide comprehensive microstructural and crystallographic information on modulated martensite in NiMnSn alloys that is useful for the understanding of their specific functionalities and helpful for further investigation on property optimization of these materials.

Crystal Structure and Microstructure of Martensite in Ni-Mn-In Alloys and the Behavior of Variant Rearrangement under Uniaxial Loading

2016 ◽  
Vol 879 ◽  
pp. 518-523
Author(s):  
Hai Le Yan ◽  
Yu Dong Zhang ◽  
Zon Bin Li ◽  
Claude Esling ◽  
Xiang Zhao ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Type I ◽  
Modulated Structure ◽  
Self Organized ◽  
Fundamental Information ◽  
Twinning Plane ◽  
Plate Shape ◽  
Schmid Factor ◽  
Underlying Mechanisms ◽  
Structure And Microstructure

In the present work, the crystal structure and microstructure of martensite in Ni-Mn-In alloys and the variant rearrangement behavior under the external mechanical loading were investigated. Results show that the martensite has an incommensurate 6M modulated structure (I2/m (α0γ)00) with the modulation wave vector q = 0.3437c*. Microstructure of martensite is in plate shape and self-organized with four orientation variants that are alternately distributed and related in either type-I, or type-II or compound twin relation. The variant interfaces are in coincidence with their corresponding twinning plane and then should be considered coherent. Under the uniaxial compression, the loading located in the common positive Schmid factor zone of the three types of detwinning systems might be favorable to obtain the single variant state. This study is expected to offer a fundamental information of crystal structure, microstructures and variant rearrangement behaviors in Ni-Mn-In alloys, so as to understand the underlying mechanisms of their multifunctional magneto-responsive properties.

scholarly journals SPECIFIC PRECIPITATION AND MOUSE PROTECTION IN TYPE I ANTIPNEUMOCOCCUS SERA

1930 ◽  
Vol 52 (4) ◽  
pp. 477-483 ◽  
Author(s):  
Michael Heidelberger ◽  
Richard H. P. Sia ◽  
Forrest E. Kendall
Keyword(s):  
Approximate Determination ◽  
Type I ◽  
Simple Method ◽  
Specific Polysaccharide ◽  
Close Parallel ◽  
Precipitable Protein

1. A rapid and simple method is given for the approximate determination of the specifically precipitable protein in Type I antipneumococcus sera. 2. It is shown that a close parallel exists between the specifically precipitable protein and the number of mouse protection units in a wide variety of Type I antipneumococcus sera. 3. Owing to the consistent results obtained and the rapidity, simplicity, and economy of the method, its use is proposed instead of the mouse protection test as a basis for the titration of standard sera and the comparison of others with a standard. 4. A method is given for conveniently preparing highly purified specific polysaccharide of Type I pneumococcus.

scholarly journals Determination of a complex crystal structure in the absence of single crystals: analysis of powder X-ray diffraction data, guided by solid-state NMR and periodic DFT calculations, reveals a new 2′-deoxyguanosine structural motif

2017 ◽  
Vol 8 (5) ◽  
pp. 3971-3979 ◽  
Author(s):  
Colan E. Hughes ◽  
G. N. Manjunatha Reddy ◽  
Stefano Masiero ◽  
Steven P. Brown ◽  
P. Andrew Williams ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Solid State Nmr ◽  
Structural Motif ◽  
X Ray Diffraction ◽  
X Ray ◽  
Complex Crystal Structure ◽  
Complex Crystal ◽  
Periodic Dft Calculations ◽  
Periodic Dft

A multi-technique strategy reveals a new hydrogen-bonding motif for a 2′-deoxyguanosine derivative.

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