Growth and Structure of Tungsten Carbide-Transition Metal Superlattices

1987 ◽  
Vol 103 ◽  
Author(s):  
T. D. Moustakas ◽  
J. Y. Koo ◽  
A. Ozekcin
Keyword(s):  
Low Temperature ◽  
Tungsten Carbide ◽  
Ceramic Materials ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
Lattice Imaging ◽  
X Ray ◽  
First Time ◽  
Nanoscale Range ◽  
Low Temperature Process

ABSTRACTSuperlattices between ceramic materials, such as tungsten carbide, and transition metals have been synthesized for the first time. The growth and structure of these superlattices were investigated by low angle X-ray diffraction and TEM lattice imaging and microdiffraction. The data show that the low temperature process of forming these two dimensional composites leads to unique crystal structures and morphology in the nanoscale range.

scholarly journals c-Perpendicular Orientation of Poly(ʟ-lactide) Films

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1572
Author(s):  
Baku Nagendra ◽  
Paola Rizzo ◽  
Christophe Daniel ◽  
Lucia Baldino ◽  
Gaetano Guerra
Keyword(s):  
Low Temperature ◽  
Film Plane ◽  
Wide Angle ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
Amorphous Films ◽  
High Transparency ◽  
X Ray ◽  
Crystalline Forms ◽  
Induced Crystallization

Poly(ʟ-lactide) (PLLA) films, even of high thickness, exhibiting co-crystalline and crystalline α phases with their chain axes preferentially perpendicular to the film plane (c⊥ orientation) have been obtained. This c⊥ orientation, unprecedented for PLLA films, can be achieved by the crystallization of amorphous films as induced by low-temperature sorption of molecules being suitable as guests of PLLA co-crystalline forms, such as N,N-dimethylformamide, cyclopentanone or 1,3-dioxolane. This kind of orientation is shown and quantified by two-dimensional wide-angle X-ray diffraction (2D-WAXD) patterns, as taken with the X-ray beam parallel to the film plane (EDGE patterns), which present all the hk0 arcs centered on the meridian. PLLA α-form films, as obtained by low-temperature guest-induced crystallization, also exhibit high transparency, being not far from those of the starting amorphous films.

Low-Temperature (<300°C) Phosphate Ceramics from Reactive Aluminas

1989 ◽  
Vol 179 ◽  
Author(s):  
M. R. Silsbee ◽  
R. A. Steinke ◽  
D. M. Roy ◽  
D. K. Agrawal ◽  
R. Roy
Keyword(s):  
Mechanical Properties ◽  
Low Temperature ◽  
Low Temperatures ◽  
Ceramic Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Characterization Techniques ◽  
Exciting Potential

AbstractReactive aluminas, including rapidly calcined gibbsites, offer exciting potential for forming ceramic materials at low temperatures. New x-ray amorphous aluminas will react with water at room temperatures to form compacts with 10–50 MPa tensile strengths, via viscous slurries. The cementious behavior of these materials has been examined. The results of TGA, x-ray diffraction, SEM, mechanical properties, and other characterization techniques, as applied to these systems, will be discussed.

scholarly journals Низкотемпературный синтез стеклокерамики с кристаллитами YNbO-=SUB=-4-=/SUB=- : Eu-=SUP=-3+-=/SUP=-

2021 ◽  
Vol 129 (2) ◽  
pp. 207
Author(s):  
В.А. Кравец ◽  
Е.В. Иванова ◽  
К.Н. Орехова ◽  
Г.А. Гусев ◽  
В.В. Васькевич ◽  
...  
Keyword(s):  
Low Temperature ◽  
Electron Probe ◽  
Glass Ceramics ◽  
Luminescent Properties ◽  
X Ray Diffraction ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis ◽  
X Ray ◽  
Composition And Structure ◽  
First Time

The main purpose of this work was to carry out a low-temperature synthesis of glass ceramics containing YNbO4:Eu3+ crystallites and to study the structural and luminescent properties of the obtained samples. Within the framework of this work, the inclusions that crystallized under the conditions of low-temperature synthesis in the systems of SiO2-Na2O-K2O-Y2O3-Nb2O5-Eu2O3 (SiNaK) and B2O5-Na2O-Y2O3-Nb2O5-Eu2O3 (BNa) were investigated for the first time. It was shown that YNbO4: Eu3+ crystallized in both considered systems. In the SiNaK system the crystallization of SiO2 also occurred (quartz, crisstabolite, and tridymite) under the selected conditions. The BNa system proved to be the most promising for the synthesis of activated glass-ceramics with YNbO4, since the required crystallites crystallized only in ithis system. The luminescent properties of crystalline inclusions were investigated using the local cathodoluminescence technique. The composition and structure of glass ceramics were studied by electron-probe microanalysis and X-ray diffraction phase analysis.

Incommensurate density modulation in a Na-rich plagioclase feldspar:Z-contrast imaging and single-crystal X-ray diffraction study

2016 ◽  
Vol 72 (6) ◽  
pp. 904-915 ◽  
Author(s):  
Huifang Xu ◽  
Shiyun Jin ◽  
Bruce C. Noll
Keyword(s):  
Phase Transition ◽  
Low Temperature ◽  
Composition Range ◽  
Compositional Variation ◽  
X Ray Diffraction ◽  
Contrast Imaging ◽  
Slow Cooling ◽  
X Ray ◽  
Density Modulation ◽  
First Time

Plagioclase feldspars are the most abundant mineral in the Earth's crust. Intermediate plagioclase feldspars commonly display incommensurately modulated or aperiodic structures.Z-contrast images show both Ca–Na ordering and density modulation. The local structure of lamellae domains hasI1-like symmetry. The neighboring lamellae domains are in an inversion twinning relationship. With a state-of-the-art X-ray diffraction unit, second-order satellite reflections (f-reflections) are observed for the first time in andesine (An45), a Na-riche-plagioclase. Thef-reflections indicate a structure with a density modulation which is close to a Ca-riche-plagioclase. The similarity between thise-andesine structure and previously solvede-labradorite structure is confirmed. Refinement of the structure shows density modulation of ∼ 7 mol % in compositional variation of the anorthite (An) component. The results fromZ-contrast imaging and low-temperature single X-ray diffraction (XRD) provide a structure consistent with density modulation. The discovery off-reflections in Na-riche-plagioclase extends the composition range ofe1 structure with density modulation to as low as at least An45, which is the lower end of the composition range of Bøggild intergrowth. The new result supports the loop-shaped solvus for Bøggild intergrowth, below which is a homogenous stable area fore1 structure in the phase diagram. The phase transition betweene2 structure without density modulation ande1 structure with density modulation should happen at low temperature. There is a change in modulation period accompanying the phase transition, as well as higher occupancy of Al in theT1o site. The andesine with density modulation also indicates extremely slow cooling of its host rock.

scholarly journals A New Environmentally-Friendly System for Extracting Cellulose from Corn Straw: The Low Temperature Laccase System

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 437 ◽  
Author(s):  
Heming Song ◽  
Hongge Jia ◽  
Qingji Wang ◽  
Xinyi Zhao ◽  
Guoxing Yang ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Low Temperature ◽  
Agricultural Waste ◽  
Environmentally Friendly ◽  
Cellulose Content ◽  
X Ray Diffraction ◽  
Corn Straw ◽  
X Ray ◽  
First Time ◽  
New System

Corn straw is an agricultural waste. The system for extracting cellulose from corn straw at a high temperature has been widely reported by researchers. However, the system for extracting cellulose from corn straw at a low temperature has been rarely reported. In this paper, a new system for extracting cellulose from corn straw at a low temperature was reported for the first time. This new system is designated as the low temperature laccase system (LTLS). Cellulose was successfully extracted from corn straw by the LTLS, and the used solution could be recycled. Therefore, the low temperature laccase system is an environmentally-friendly system. The cellulose content in corn straw is 30–40%. The yield of cellulose extracted by LTLS was 33%. The obtained cellulose product was creamy white. The extracted cellulose samples were characterized by using infrared spectroscopy (IR), thermogravimetry (TG), and X-ray diffraction (XRD). The results were consistent with that of standard cellulose. We confirmed that the LTLS extracted cellulose from corn straw with high purity.

Vibrational Dynamics of Carbamazepine: Studies Based on Two-Dimensional Correlation Spectroscopy and X-ray Diffraction

2020 ◽  
Vol 74 (4) ◽  
pp. 473-484 ◽  
Author(s):  
Agnieszka Dołęga ◽  
Ewa Juszyńska-Gałązka ◽  
Aleksandra Deptuch ◽  
Teresa Jaworska-Gołąb ◽  
Piotr M. Zieliński
Keyword(s):  
Correlation Spectroscopy ◽  
Study Phase ◽  
Moving Window ◽  
Two Dimensional ◽  
Heating Cycle ◽  
X Ray Diffraction ◽  
Vibrational Dynamics ◽  
X Ray ◽  
Xrd Studies ◽  
First Time

Fourier transform infrared spectroscopy as well as X-ray diffraction (XRD) were employed to thoroughly study phase transitions taking place during heating–cooling–heating cycle of carbamazepine (CBZ), a well known and commonly used antiepileptic drug. Both techniques revealed cold crystallization taking place during second heating. Moreover, XRD studies for the first time proved the coexistence of CBZ (form I) and iminostilbene (product of the degradation of CBZ) after a heating–cooling cycle. Moving window two-dimensional correlation (MW 2D-COS) spectroscopy and two-dimensional correlation spectroscopy were shown to be effective tools to reveal phase sequences and to provide information about the order of sequential changes of bands’ intensities during each phase transition, respectively.

scholarly journals A mini-goniometer for X-ray diffraction studies down to 4 K on four-circle diffractometers equipped with two-dimensional detectors

2007 ◽  
Vol 40 (3) ◽  
pp. 526-531 ◽  
Author(s):  
Pierre Fertey ◽  
Roger Argoud ◽  
Pierre Bordet ◽  
Jacques Reymann ◽  
Cyril Palin ◽  
...  
Keyword(s):  
Low Temperature ◽  
Single Crystal ◽  
Mechanical Design ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
Original Design ◽  
Data Set ◽  
X Ray ◽  
Density Analysis ◽  
Data Collections

A `universal' low-temperature device for laboratory X-ray diffractometers equipped with two-dimensional detectors has been developed. Single-crystal data collections can be performed down to 4 K. Owing to its original design, the completeness of the data set is not affected by the limited number of accessible orientations of the sample. Classical structure analysis can therefore be performed as well as high-resolution (high-angle) studies for electron-density analysis. Derived from an idea of Argoud & Muller [J. Appl. Cryst.(1989),22, 584–591], the sample is mounted on a holder magnetically coupled to the diffractometer φ axis. The coupling is achieved by mounting a master magnet in place of the usual goniometer head. This magnet drives a slave magnet fixed on the crystal holder: a two-axis mini-goniometer. This low-temperature arrangement is adaptable to any kappa-geometry single-crystal diffractometer equipped with a two-dimensional detector, and can be placed into various types of cryostat. This paper reports the home-made mechanical design and the performance of this device.

Tubulin structure at intermediate resolution

1995 ◽  
Vol 53 ◽  
pp. 852-853
Author(s):  
K. H. Downing ◽  
S. G. Wolf ◽  
E. Nogales
Keyword(s):  
High Resolution ◽  
Structural Data ◽  
Therapeutic Drug ◽  
Zinc Ions ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Negative Stain ◽  
Functional Mechanisms ◽  
Tubulin Structure

Microtubules are involved in a host of critical cell activities, many of which involve transport of organelles through the cell. Different sets of microtubules appear to form during the cell cycle for different functions. Knowledge of the structure of tubulin will be necessary in order to understand the various functional mechanisms of microtubule assemble, disassembly, and interaction with other molecules, but tubulin has so far resisted crystallization for x-ray diffraction studies. Fortuitously, in the presence of zinc ions, tubulin also forms two-dimensional, crystalline sheets that are ideally suited for study by electron microscopy. We have refined procedures for forming the sheets and preparing them for EM, and have been able to obtain high-resolution structural data that sheds light on the formation and stabilization of microtubules, and even the interaction with a therapeutic drug.Tubulin sheets had been extensively studied in negative stain, demonstrating that the same protofilament structure was formed in the sheets and microtubules. For high resolution studies, we have found that the sheets embedded in either glucose or tannin diffract to around 3 Å.

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