scholarly journals X-Ray Study of Interfacial Interactions in Highly Milled Sn-Ge Powders

1991 ◽  
Vol 238 ◽  
Author(s):  
J.K.D.S. Jayanetti ◽  
S. M. Heald ◽  
Z. Tan
Keyword(s):  
Melting Point ◽  
Amorphous Phase ◽  
Room Temperature ◽  
Structural Changes ◽  
X Ray Diffraction ◽  
Interfacial Interactions ◽  
X Ray ◽  
Milled Powders

ABSTRACTWe have studied possible structural changes occur ing at the Sn/Ge interface of highly milled Sn/Ge composites. EXAFS and X-ray Diffraction measurements were made on mechanically milled powders having compositions ranging from 20 to SO vol.% Sn. X-ray diffraction measurements indicate the increasing amorphization of Sn as the Sn content is decreased. EXAFS results indicate that this amorphous phase is due to the formation of an a-Sn/Ge alloy. The EXAFS from this alloy did not change significantly at the Sn melting point. X-ray diffraction measurements made at room temperature show a systematic decrease in the intensity of Sn peaks and broadening of Ge peaks with the decreasing Sn content.

Influence of Aging Time on the Structural Changes of Cassava Thermoplastic Starch

2012 ◽  
Vol 1372 ◽  
Author(s):  
José H. Mina ◽  
Alex Valadez ◽  
Pedro J. Herrera-Franco ◽  
Tanit Toledano
Keyword(s):  
Yield Stress ◽  
Amorphous Phase ◽  
Structural Changes ◽  
Thermoplastic Starch ◽  
X Ray Diffraction ◽  
X Ray ◽  
Second Stage ◽  
Diffraction Patterns ◽  
Type V ◽  
Stress Drops

ABSTRACTIn this work the change in the structural properties of cassava (manihot sculenta Crantz) thermoplastic starch (TPS) under controlled environment (humidity and temperature) was studied. Fourier Transform Infrared spectroscopy (FTIR) and X-ray diffraction (XRD) results showed an evident increasing in the amorphous phase of the TPS regarding the native starch. There was a relative decrease of the band at 1047 cm-1 associated to crystalline structure of starch compared to the amorphous peak at 1022 cm-1. The X-ray diffraction patterns confirmed the increment of the amorphous phase in the TPS samples. Likewise the X-ray diffraction patterns shows evidence of residual type C crystallinity and the formation of a new crystalline phase type VH due to the orientation induced in plasticization process. In first stage of conditioning the tensile yield stress drops from 7.5 drops to 0.5 MPa and the break strain increases 1000%. At the same time it seems that the crystallinity of the samples increases as was evidenced by the gradually increasing of the FTIR band at 1047 cm-1. In a second stage, the yield stress increases, the break strain drops and the crystallinity continue growing steadily. These findings suggest that coexist two phenomena simultaneously in the samples. A phenomenon of re-crystallization (retrogradation) that tends to make the material more stiff and a process of plasticization that tends to softening it. It seems that the latter mechanism predominates in the first stage, at short times, and the former in the second stage, at older times.

scholarly journals Rb-=SUB=-1-x-=/SUB=-Cs-=SUB=-x-=/SUB=-NO-=SUB=-3-=/SUB=- (x=0.025, 0.05, 0.1) монокристаллы и их исследование методом высокотемпературной рентгенографии

2018 ◽  
Vol 52 (6) ◽  
pp. 565
Author(s):  
А.Ф. Хазиева ◽  
В.И. Насиров ◽  
Ю.Г. Асадов ◽  
Ю.И. Алыев ◽  
С.Г. Джабаров ◽  
...  
Keyword(s):  
Melting Point ◽  
Room Temperature ◽  
Diffraction Method ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Transformation Temperatures ◽  
X Ray ◽  
Cell Parameters

AbstractPolymorphic transformations in Rb_0.975Cs_0.025NO_3, Rb_0.950Cs_0.05NO_3, and Rb_0.90Cs_0.1NO_3 crystals grown by us have been studied by the X-ray diffraction method. Four different modifications are found for crystals in the range from room temperature to the melting point. The transformation temperatures and the unit-cell parameters are determined for the crystals of these modifications.

Room-temperature ferroelasticity and unusual sequence of phase transitions in the crystal of (N2H5)3[CdCl5]

2021 ◽  
Vol 77 (4) ◽  
Author(s):  
Monika K. Krawczyk ◽  
Zbigniew Czapla ◽  
Adam Ingram ◽  
Andrzej Kozdraś ◽  
Tadeusz Lis ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Room Temperature ◽  
Structural Changes ◽  
Structural Phase ◽  
Orthorhombic Phase ◽  
Orthorhombic Symmetry ◽  
Structural Phase Transitions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cl Atoms

On the basis of thermal analysis (DSC, DTA, DTG), single crystal X-ray diffraction experiments, dielectric studies and optical observation, it is found that the (N2H5)3[CdCl5] crystal exhibits several structural phase transitions. At room temperature, the studied crystal exhibits ferroelastic properties and undergoes phase transition from the monoclinic to the orthorhombic phase on heating above 327 K. Upon subsequent cooling, two structural phase transitions at about 323 and 319 K are observed, where the crystal adopts orthorhombic symmetry. The presented phase transitions are unique due to the fact the first heating run results in different structural changes compared to those observed during cooling and subsequent heating/cooling runs. In the studied crystal, N2H5 + ions and 1D chains built up from {CdCl5}3− units bridged by Cl atoms occur. The phase transitions observed can be associated with reorientation of cations and partial disorder of cations as well as Cl atoms.

Y-Type Hexaferrites: Structural, Dielectric and Magnetic Properties

2012 ◽  
Vol 189 ◽  
pp. 209-232 ◽  
Author(s):  
Rajshree B. Jotania ◽  
Hardev Singh Virk
Keyword(s):  
Magnetic Properties ◽  
Quantum Interference ◽  
Room Temperature ◽  
Structural Changes ◽  
Ferromagnetic State ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Lcr Meter ◽  
Co Precipitation

This paper attempts to provide a historical survey of structure of various types of hexaferrites. It provides information about synthesis, characterization, structural, magnetic and dielectric properties of Y-type hexagonal ferrites using various chemical routes. We have prepared a series of cobalt doped Sr2Cu2-xCoxFe12O22(x = 0.0 to 1.0) hexaferrites using a wet chemical co-precipitation technique. The prepared hexaferrite precursors were calcined at 950 °C for 4 hours in a furnace and slowly cooled to room temperature. The crystal structure of Y-type hexaferrites is rather complicated. The chemical and structural changes were examined in detail by X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Scanning electron microscopy (SEM), and Fourier transform infra-red (FTIR) spectroscopy. X-ray diffraction studies showed that sintering temperature as low as 950°C was sufficient to produce a single-phase Y-type hexaferrite material. The dielectric measurements were carried out over the frequency range of 100 Hz to 2 MHz at room temperature using an LCR meter to study the variation of dielectric constant and loss tangent with frequency. The magnetic properties of hexaferrite samples were investigated using a vibration sample magnetometer (VSM), and a superconducting quantum interference device (SQUID) magnetometer in the temperature range 30K to 200K. A change from ferromagnetic state to super paramagnetic state has been observed in Co doped Sr2Cu2-xCoxFe12O22(x= 0.6 to 1.0) hexaferrite. The novel applications of all types of hexaferrite materials have been described.

The thermal expansion and high temperature transformation of SnS and SnSe*

1979 ◽  
Vol 149 (1-2) ◽  
Author(s):  
Heribert Wiedemeier ◽  
Frank J. Csillag
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Melting Point ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Square Planar ◽  
Orthorhombic Modification ◽  
Temperature Transformation ◽  
Increasing Temperature

AbstractThe thermal expansion of SnS and SnSe has been studied above room temperature up to the melting point of 1163 ± 5K and 1135 ± 5K, respectively, by X-ray diffraction techniques using a 190 mm Unicam high temperature camera. The changes of the lattice parameters indicate that the atomic positions in the (010) plane approach a square planar arrangement with increasing temperature. The transformation of SnS and SnSe from orthorhombic to a pseudotetragonal orthorhombic modification with

Synthesis and Characterization of Ceramic Modified with Niobium for Biomedical Applications

2016 ◽  
Vol 869 ◽  
pp. 884-889
Author(s):  
Nadia Sueli Vieira Capanema ◽  
Alexandra A.P. Mansur ◽  
Herman Sander Mansur
Keyword(s):  
Biomedical Applications ◽  
Room Temperature ◽  
Structural Changes ◽  
Calcium Phosphates ◽  
Synthesis And Characterization ◽  
Body Parts ◽  
New Materials ◽  
X Ray Diffraction ◽  
X Ray

The need for obtaining new materials to replace human body parts that were destroyed or damaged led scientists from different areas of research for developing new biomaterials. Thus, the aim of this work was the synthesis and characterization of niobium-modified apatite bioceramics. Calcium phosphates (CaP) were synthesized with niobium partially replacing calcium sites using aqueous precipitation route at room temperature. The bioceramics, with and without Nb incorporation, were characterized by scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) as prepared and after heat treatments The results indicated that Nb was incorporated in the apatite structure promoting morphological and structural changes in the ceramic properties.

Amorphization of crystalline orthoboric acid on a vitreous B2O3 substrate

2002 ◽  
Vol 17 (12) ◽  
pp. 3098-3104 ◽  
Author(s):  
Eric McCalla ◽  
Ralf Brüning
Keyword(s):  
Amorphous Phase ◽  
Room Temperature ◽  
Metastable Equilibrium ◽  
Oxide Glass ◽  
X Ray Diffraction ◽  
Humid Air ◽  
Time Resolved ◽  
X Ray ◽  
Equilibrium Phases ◽  
State Amorphization

Time-resolved x-ray diffraction measurements were carried out during and after the exposure of anhydrous boron oxide glass films to humid air. B(OH)3 crystals grew on the glass substrate with planar sheets of B(OH)3 molecules aligned parallel to the surface. After the space above the sample was evacuated, the crystal peaks began to disappear. During the decay, new crystals of orthoboric acid grew with the orientation of the B(OH)3 sheets perpendicular to the substrate. Then crystals with all orientations decayed completely, and an amorphous scattering pattern remained. The water acquired by the sample during the exposure eventually reacted with the anhydrous B2O3 glass to produce amorphous BO(3+y)/2Hy. The decay of the crystals took from one to several days, depending on the length of the exposure to humid air. Measurements of the metastable equilibrium phases in the B2O3–H2O binary system showed that at room temperature the amorphous phase could reach the composition BO1.85H0.7. At higher water concentrations this saturated amorphous phase coexisted with crystalline B(OH)3. This result is consistent with the instability of the crystalline B(OH)3 film in contact with anhydrous glass, and we present a thermodynamic model for this process. In the present case, amorphization is driven by the outdiffusion of water from a crystalline phase rather than interdiffusion in conventional solid-state amorphization.

Tilting structures ininverseperovskites,M3TtO (M= Ca, Sr, Ba, Eu;Tt= Si, Ge, Sn, Pb)

2015 ◽  
Vol 71 (3) ◽  
pp. 300-312 ◽  
Author(s):  
Jürgen Nuss ◽  
Claus Mühle ◽  
Kyouhei Hayama ◽  
Vahideh Abdolazimi ◽  
Hidenori Takagi
Keyword(s):  
Phase Transitions ◽  
Room Temperature ◽  
Structural Changes ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Range ◽  
Tolerance Factors ◽  
Multiple Twinning ◽  
Perovskite Type ◽  
Perovskite Type Structure

Single-crystal X-ray diffraction experiments were performed for a series ofinverseperovskites,M3TtO (M= Ca, Sr, Ba, Eu;Tt= tetrel element: Si, Ge, Sn, Pb) in the temperature range 500–50 K. ForTt= Sn, Pb, they crystallize as an `ideal' perovskite-type structure (Pm\bar 3m,cP5); however, all of them show distinct anisotropies of the displacement ellipsoids of theMatoms at room temperature. This behavior vanishes on cooling forM= Ca, Sr, Eu, and the structures can be regarded as `ideal' cubic perovskites at 50 K. The anisotropies of the displacement ellipsoids are much more enhanced in the case of the Ba compounds. Finally, their structures undergo a phase transition at ∼ 150 K. They change from cubic to orthorhombic (Ibmm,oI20) upon cooling, with slightly tilted OBa6octahedra, and bonding angles O—Ba—O ≃ 174° (100 K). For the larger Ba2+cations, the structural changes are in agreement with smaller tolerance factors (t) as defined by Goldschmidt. Similar structural behavior is observed for Ca3TtO. SmallerTt4−anions (Si, Ge) introduce reduced tolerance factors. Both compounds Ca3SiO and Ca3GeO with cubic structures at 500 K, change into orthorhombic (Ibmm) at room temperature. Whereby, Ca3SiO is the only representative within theM3TtO family where three polymorphs can be found within the temperature range 500–50 K: Pm\bar 3m–Ibmm–Pbnm. They show tiny differences in the tilting of the OCa6octahedra, expressed by O—Ca—O bond angles of 180° (500 K), ∼ 174° (295 K) and 170° (100 K). For largerM(Sr, Eu, Ba), together with smallerTt(Si, Ge) atoms, pronounced tilting of the OM6octahedra, and bonding angles of O—M—O ≃ 160° (295 K) are observed. They crystallize in theanti-GdFeO3type of structure (Pbnm,oP20), and no phase transitions occur between 500 and 50 K. The observed phase transitions are all accompanied by multiple twinning, in terms of pseudo-merohedry or reticular pseudo-merohedry.

Sign in / Sign up

Export Citation Format

Share Document