scholarly journals Role of Polymorphism in Materials Science

2014 ◽  
Vol 11 (1) ◽  
pp. 43-50 ◽  
Author(s):  
Pradip Mondal ◽  
Deepak Chopra
Keyword(s):  
Metal Oxides ◽  
Materials Science ◽  
Pharmaceutical Drugs ◽  
Nano Crystalline ◽  
Polymorphic Materials ◽  
Crystalline Metal

Polymorphism is a widespread and commonly occurring phenomenon in fields of chemistry, biology and materials science. In recent years, the development of technology has lead to the development of different instrumentation tools(such as SXRD, PXRD, IR, NMR, AFM) which are employed for the characterization of different polymorphic materials (namely polymers, nano crystalline metal oxides and pharmaceutical drugs) which are of great importance because of their applications in the field of materials science.

Elaboration and Mechanical Characterization of Al2O3-ZrO2-YAG Ultrafine Composites

2010 ◽  
Vol 62 ◽  
pp. 76-81 ◽  
Author(s):  
Paola Palmero ◽  
Valentina Naglieri ◽  
Giulia Spina ◽  
Laura Montanaro
Keyword(s):  
Mechanical Characterization ◽  
Alumina Powder ◽  
Nano Crystalline ◽  
Slip Cast ◽  
Second Phases ◽  
Crystalline Alumina ◽  
Inorganic Precursors ◽  
Full Densification

Al2O3-YAG-ZrO2 composites have been produced by surface modification of a commercial nano-crystalline alumina powder with inorganic precursors of the desired second phases. The doped powders were calcined at various temperatures and for different times: as a function of the thermal treatment, zirconia directly crystallized on the alumina surface, while YAG phase was yielded by solid state reaction among an amorphous yttrium-rich precursor and alumina powder. Several compositions, with increasing second phases volume fractions, were investigated, precisely, Alumina-5vol.%YAG-5vol.%ZrO2, Alumina-20vol.%YAG-20vol.%ZrO2 and Alumina- 33vol.%YAG-33vol.%ZrO. Slip cast bodies were produced by aqueous suspensions of calcined and well-dispersed powders; free-sintering performed at 1500°C for 3 h allowed to reach full densification. The role of the second phases amount on the microstructural features and on some mechanical data preliminary evaluated was established.

Synthesis, structure and characterization of five new organically templated metal sulfates with 2-aminopyridinium

2016 ◽  
Vol 72 (5) ◽  
pp. 432-441 ◽  
Author(s):  
Tamara J. Bednarchuk ◽  
Vasyl Kinzhybalo ◽  
Adam Pietraszko
Keyword(s):  
Materials Science ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
Hydrogen Bond Formation ◽  
Unit Cells ◽  
Science Community ◽  
Type 3

The chemistry of organically templated metal sulfates has attracted interest from the materials science community and the development of synthetic strategies for the preparation of organic–inorganic hybrid materials with novel structures and special properties is of current interest. Sulfur–oxygen–metal linkages provide the possibility of using sulfate tetrahedra as building units to form new solid-state materials. A series of novel organically templated metal sulfates of 2-aminopyridinium (2ap) with aluminium(III), cobalt(II), magnesium(II), nickel(II) and zinc(II) were obtained from the respective aqueous solutions and studied by single-crystal X-ray diffraction. The compounds crystallize in centrosymmetric triclinic unit cells in three structure types: type 1 for 2-aminopyridinium hexaaquaaluminium(III) bis(sulfate) tetrahydrate, (C5H7N2)[Al(H2O)6](SO4)2·4H2O, (I); type 2 for bis(2-aminopyridinium) tris[hexaaquacobalt(II)] tetrakis(sulfate) dihydrate, (C5H7N2)2[Co(H2O)6]3(SO4)4·2H2O, (II), and bis(2-aminopyridinium) tris[hexaaquamagnesium(II)] tetrakis(sulfate) dihydrate, (C5H7N2)2[Mg(H2O)6]3(SO4)4·2H2O, (III); and type 3 for bis(2-aminopyridinium) hexaaquanickel(II) bis(sulfate), (C5H7N2)2[Ni(H2O)6](SO4)2, (IV), and bis(2-aminopyridinium) hexaaquazinc(II) bis(sulfate), (C5H7N2)2[Zn(H2O)6](SO4)2, (V). The templating role of the 2ap cation in all of the reported crystalline substances is governed by the formation of characteristic charge-assisted hydrogen-bonded pairs with sulfate anions and the presence of π–π interactions between the cations. Additionally, both coordinated and uncoordinated water molecules are involved in hydrogen-bond formation. As a consequence, extensive three-dimensional hydrogen-bonding patterns are formed in the reported crystal structures.

scholarly journals The role of oxygen defects in metal oxides for CO2 reduction

2020 ◽  
Vol 2 (11) ◽  
pp. 4986-4995
Author(s):  
Zesheng Deng ◽  
Jiahui Ji ◽  
Mingyang Xing ◽  
Jinlong Zhang
Keyword(s):  
Metal Oxides ◽  
Co2 Reduction ◽  
Structure Activity Relationship ◽  
Activity Relationship ◽  
Oxygen Defects ◽  
Structure Activity

The formation and characterization of oxygen defects and their structure–activity relationship with CO2 reduction are reviewed in this article.

Porous Semiconductor Films For Photo-Electrical Applications

1996 ◽  
Vol 426 ◽  
Author(s):  
R. Könenkamp ◽  
P. Hoyer
Keyword(s):  
Quantum Dots ◽  
Semiconductor Devices ◽  
Experimental Results ◽  
Semiconductor Films ◽  
Trap States ◽  
Porous Films ◽  
Nano Crystalline ◽  
Pbs Quantum Dots

AbstractWe report on the preparation and characterization of semiconductor devices based on porous nano-crystalline TiO2 films. We present experimental results on photoconduction to elucidate the role of trap states in this material. We then analyse the behavior of a SnO2/TiO2/Pt Schottkydiode and finally present spectral photoresponse data obtained on a hetero-junction between TiO2 films and PbS quantum dots. We find that the porous films hold some promise for electronic applications, in which fast reponse times are not required.

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

Applications of ultramicrotomy for materials characterization

1993 ◽  
Vol 51 ◽  
pp. 232-233
Author(s):  
R.T. Blackham ◽  
J.J. Haugh ◽  
C.W. Hughes ◽  
M.G. Burke
Keyword(s):  
Materials Science ◽  
Microstructural Analysis ◽  
Analytical Electron Microscopy ◽  
Austenitic Stainless Steels ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Thermally Induced ◽  
Radiation Induced ◽  
Characterization Of Materials

Essential to the characterization of materials using analytical electron microscopy (AEM) techniques is the specimen itself. Without suitable samples, detailed microstructural analysis is not possible. Ultramicrotomy, or diamond knife sectioning, is a well-known mechanical specimen preparation technique which has been gaining attention in the materials science area. Malis and co-workers and Glanvill have demonstrated the usefulness and applicability of this technique to the study of a wide variety of materials including Al alloys, composites, and semiconductors. Ultramicrotomed specimens have uniform thickness with relatively large electron-transparent areas which are suitable for AEM anaysis.Interface Analysis in Type 316 Austenitic Stainless Steel: STEM-EDS microanalysis of grain boundaries in austenitic stainless steels provides important information concerning the development of Cr-depleted zones which accompany M23C6 precipitation, and documentation of radiation induced segregation (RIS). Conventional methods of TEM sample preparation are suitable for the evaluation of thermally induced segregation, but neutron irradiated samples present a variety of problems in both the preparation and in the AEM analysis, in addition to the handling hazard.

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