Mechanoluminescence and acoustical emission

It is reported on the measuring of the synchronic mechanoluminescent (ML) and acoustical emission (AE). The source of both ML and AE was the mechanical deformation of organic glass, of steel and copper plates. The results confirmed the connection between MA and AE stimulated by the same deformation source.     

Mechanoluminescence of halogenate crystals

Mechanoluminescence (ML) has been studied in twenty halogenate crystals. All piezoelectric crystals show ML similar to the emission from second positive group of molecular nitrogen, and all the crystals not exhibiting ML are non-piezoelectric. Some of the non-piezoelectric crystals also exhibit nitrogen emission ML which is comparable in intensity to that of piezoelectric crystals. The ML appears only during the different steps developing in the fracture region of the force versus compression curve of the crystals. No considerable change in the ML activity is found due to the number of crystallization or due to the addition of different impurities from 100 to 10.00 ppm. The ML activity per mole of the halogenate crystals varies around four orders of magnitude. It is concluded that in addition to the piezoelectrification of the newly created surfaces there exists some other process of electrification which may cause the ML exitation in halogenate crystals.     

Mechanoluminescence in Centrosymmetric Crystals

The paper reports that the mechanoluminescence (ML) is not an inherent property of only the non-centrosymmetric crystals. The ML may appear in number of centrosymmetric crystals due to variety of processes. The ML of 82 centrosymmetric crystals are reported and different models are proposed for the ML excitation. The models proposed are: space charge electrification model, triboelectrification model, phase transformation model, gas adsorption model, chemical reaction model, thermal population model, molecular deformation model, cleavage electrification model, defective piezoelectric phase model, dislocation defect stripping model, dislocation unpinning model, dislocation annihilation model, charged dislocation model and incandecent light emission model. It is shown that on the basis of the proposed model, intense mechanoluminescent materials with desired nature and characteristics may be prepared.     

Cleavage Mechanoluminescence in Crystals

When a crystal is cleaved, initially the mechanoluminescence (ML) intensity increases linearly with time, attains an optimum-value I_m at a particular value of timet_m, and then decays exponentially with time. Cleavage ML provides a new tool to determine the velocity, v of cracks in crystals, and it may be given by v = H/t_m, where H is the thickness of the crystal. Both, the peak ML intensity I_m and total ML intensity I_T increase linearly with the area of newly created surfaces A as well as with the surface charge density γ. The ML intensity decreases with temperature primarily due to the decrease in the surface charge density. Beyond a particular temperature, the surface charge density may decrease to such a value where the breakdown of gases and solids may not be possible and thereby the ML may not appear. Depending on the prevailing conditions either the ML emission resembling gas discharge or other types of the luminescence of solids, or that having these two characters may be obtained. There exists a good correlation between the theoretical and experimental results obtained for cleavage ML in crystals.     

Satatistical Model of Mechanoluminescence in Crtstals

The present paper reports on a statistical model of the mechanoluminescence (ML) excitation in crystals where attempts have been made to explain stress, temperature-, strain rate-, activator concentration dependence and several other aspects of ML. It is found that ML emission should take place only during the period at which stress will change with time. The total ML intensity should be directly proportional to the square of the stress and there should be phase difference between the ML pulse and the applied stress pulse. It is found that the ML intensity should decrease faster with temperature as compared to the corresponding photoluminescence intensity. within the limit of concentration quenching the ML intensity should increase directly with the defect centre concentration. The ML intensity should increase with the stress rate or strain rate of the solids. Furthermore, the concept of mechanoluminescent and non-mechanoluminescent materials is explored.     

Classification of hydrated oxygen compounds of boron

The known structural classifications of borates are based on the analysis of boron-oxygen radicals consisting of B-triangles and B-tetrahedra sharing O atoms to form more complicated structures. Such classifications ignore the possible presence and the role of hydrogen bonds, which may be the only bonds or additional bonds linking the [BO₃]-and [BO₄]-groups. A new detailed classification of hydrated boron compounds taking into account hydrogen bonds between the B-polyhedra is proposed.     

Classification of proton configurations of gas hydrate frameworks

All molecular configurations differing in the position of hydrogen atoms (protons) in hydrogen bonds and satisfying periodic boundary conditions have been calculated for the unit cells of CS-I, HS-III, and TS-IV gas hydrate frameworks. The configurations obtained are ranged according to the number of stronger trans-configurations of hydrogen-bound molecular pairs and according to the type of spatial symmetry. The configuration symmetry was analyzed taking into account the additional antisymmetry operation, which is related to the change in the direction of all hydrogen bonds. The strong dependence of the framework properties on the specific position of protons in H bonds is established.     

Crystalloluminescence and Mechanoluminescence Spectra of Ba(ClO3)2 · H2O and 2 K2SO4 · Na2SO4 Crystals

Crystalloluminescence and mechanoluminescence of Ba(ClO₃)₂ · H₂O and 2 K₂SO₄ · Na₂SO₄ crystals are investigated. The crystalloluminescence spectra are almost similar to the photoluminescence spectra; however, they differ completely from the mechanoluminescence spectra. The crystalloluminescence excitations may take place due to the various processes: (i) the recombination of ions, (ii) from amorphous to crystalline transition, (iii) from the phase change during the crystallization, and (iv) from the dielectric breakdown by the electric field produced due to the creation of microfracture during the crystal growth. It is concluded that the crystalloluminescence excitation in Ba(ClO₃)₂ · H₂O and 2K₂SO₄ · Na₂SO₄ crystals may be chemical in origin.     

蒙脱石的晶体化学式计算与分类

对四川和新疆5个矿山的膨润土进行了矿物组成和化学成分的测定,结合XRD、XRF分析确定了属性.采用11(O)为基础的计算方法对提纯后蒙脱石进行了晶体化学式计算;并根据层电荷的来源,对蒙脱石样品进行了属型划分.分析表明四川膨润土矿床样品属钙基膨润土,三台蒙脱石为切托-Otay型,盐亭蒙脱石为切托-Chambers型;新疆膨润土矿床样品属钠基膨润土,奇台蒙脱石为切托-Tatatilla型,吉木萨尔蒙脱石为怀俄明型.     

Modern Classification of Electrohydrodynamic Instabilities in the Nematic Phase

Physical models for various electrohydrodynamic instabilities are reviewed and an up-to-date classification is presented.     

Group-Theoretical Classification of Aristotypes of Cation and Anion Orders in Perovskites

Crystallography Reports - A group-theoretical classification of cation and anion orders of crystals with a perovskite structure is presented. Aristotypes are idealized structures (phases), from...     

水流分级对非晶微硅粉除杂效果研究

利用水流分级原理对冶金硅废弃物微硅粉进行除杂试验研究,确定微硅粉水流分级的最佳固液比为1∶2g/mL,最佳分级次数为4次;使微硅粉纯度提高了4.65;.同时分析了水流分级对微硅粉元素组成、回收率、粒径分布、粒型的影响.结果表明,水流分级使微硅粉中C元素的含量从4.5;降低为0.4;,去除率超过90;,其他杂质元素以硅酸盐或氧化物的形式存在而没被除去;最佳水流分级工艺下微硅粉的回收率为84.5;;水流分级后微硅粉平均粒径由0.334 μm变为0.557 μm,小颗粒被去除;颗粒尺寸更均一,并保持原有的光滑球状形貌.这种方法相比于焙烧除碳,能耗小、对形貌无破坏性,是一种绿色、环保废物再回收的方法.     

Classification of electrically conducting ‘electron-transfer’ compounds by crystal structure

Organic and metal-organic electron-transfer solids can be classified by crystal structure, those known to date being divided intohomosoric, in which identical molecules stack infinitely,heterosoric, in which different molecules stack alternately, andnonsoric, non-stacked types. Only homosoric solids have high electrical conductivity.     

一些溶液法生长的晶体非平衡枝状形貌及其对称性分类

本文基于一些简单的溶液法晶体生长实验及观察,对非平衡枝状晶体形貌进行了对称性探讨,并提出一种依据晶体的对称性对非平衡形貌进行分类的方案,即:形貌具各向异性且完全受晶体本身的对称性控制,称枝晶;形貌总体具各向同性但局部具各向异性,这种局部各向异性与晶体本身的对称不完全一样,但与晶体本身对称有关,称枝蔓晶;形貌具各向同性,不受晶体本身的对称控制,称密枝(或球粒晶).这一分类方案对进一步认清非平衡枝状形貌的本质特征、规范一些形貌术语有重要意义.     

Classification of Structural Motifs in Porphyrinic Coordination Polymers Assembled from Porphyrin Building Units, 5,10,15,20-Tetrapyridylporphyrin and Its Derivatives

Abstract  In this review, we classify 1D, 2D, and 3D structural motifs found in porphyrinic coordination polymers assembled from 5,10,15,20-tetrapyridylporphyrin (TPyP) and its derivatives. The classifications are based on dimensionality, metal-to-porphyrin linkage, porphyrin type, and metal-to-porphyrin ratio. 1D porphyrin polymers often share the same connectivity (or structural motifs) with analogous 2D and 3D polymers. We identify interrelationships among 1D, 2D, and 3D coordination polymers and examine the connectivity of such interrelated structures. We also discuss the broad similarities and differences of the synthetic methods of all structures presented here. Graphical Abstract  We classify 1D, 2D, and 3D structural motifs found in porphyrinic coordination polymers assembled from 5,10,15,20-tetrapyridylporphyrin (TPyP) and its derivatives. The classifications are based on dimensionality, metal-to-porphyrin linkage, porphyrin type, and metal-to-porphyrin ratio. We identify interrelationships among 1D, 2D, and 3D coordination polymers and examine the connectivity of such interrelated structures.      

Modelling of mechanism of agglomeration of KCl crystallization

The article presents an analysis into agglomeration during KCl vacuum crystallization. The theoretical and experimental investigations into the mechanism of agglomeration during mass crystallization result in an extension of the growth phenomena within the known model equations. The basis for this is essentially constituted by the collision model concepts of the theory of floculation in disperse systems. The parameters derived from the microprocess analysis (energy dissipation, content of solids, growth rate of individual grains) lead to model equations which are confirmed by laboratory and test trials.     

Relationship of Morphological Types of Dynamic Forms of Crystals

Crystallography Reports - The relationship of morphological spectra (sets of data on the morphological types of real polyhedral crystals and their probabilities under current physicochemical...     

Development of Pauling's concepts of geometric characteristics of atoms

The evolution of the geometric characteristics introduced by Pauling and their dependence on the specific features of the structure and chemical bonds have been considered. The values of the covalent and van der Waals radii are given as well as their relationships and mutual transitions.     

Velocities of Disappearance and Lifetime of Faces of Growing Crystals

The formulae for absolute R_disap and relative R velocities of disappearance and lifetime τ of faces of growing crystals have been derived for stationary growth. It was shown that the quantities are determined by the relative growth velocity R_A/R_critA of the vanishing face A with respect to the critical growth velocity R_critA and by the geometry of a crystal expressed by the trigonometric functions of interfacial angles β and γ formed between face A and the adjacent faces. R increases and τ decreases with the increase in R_A/R_critA to certain limiting values. The calculations have been verified and illustrated by the experimental results for triclinic potassium bichromate (KBC) crystals. Results enable ones to predict values of velocities of disappearance and lifetimes of undesirable, supplementary faces of any real crystal.