Crystallization of Amorphous Metastable Ceramic PVD-Coatings

1993 ◽  
Vol 321 ◽  
Author(s):  
O. Knotek ◽  
F. Löffler ◽  
L. Wolkers
Keyword(s):  
Amorphous Materials ◽  
Amorphous State ◽  
Amorphous Structure ◽  
Pvd Coatings ◽  
Additional Element ◽  
X Ray ◽  
High Temperature Wear ◽  
Wear Protection ◽  
New Applications ◽  
Thermal Stability Of

ABSTRACTCeramic PVD coatings have got very often an X-ray Amorphous structure. This is regarded for all classes of ceramics like covalent and ionic Materials. These Amorphous materials start to crystallize at temperatures about 800 °C, a quite low temperature for the practical use of such Materials. This prevents the propagation of this materials in applications like high temperature wear protection, oxidation resistivity etc.This paper describes several possible techniques to increase the thermal stability of the Amorphous state of ceramic PVD-coatings like A1203 and SiC up to 1200 °C. The best way is the incoporation of an additional element like nitrogen into the thin filmsl. The change of the mechanical properties of alumina leads to new applications like diffusion barriers.

New method for the production of bulk amorphous materials of Nd–Fe–B alloys

2005 ◽  
Vol 20 (3) ◽  
pp. 563-566 ◽  
Author(s):  
Tetsuji Saito ◽  
Hiroyuku Takeishi ◽  
Noboru Nakayama
Keyword(s):  
Electron Microscopy ◽  
Amorphous Materials ◽  
Room Temperature ◽  
Amorphous Structure ◽  
X Ray Diffraction ◽  
Bulk Materials ◽  
X Ray ◽  
Transmission Electron ◽  
Melt Spun ◽  
Melt Spun Ribbons

We report a new compression shearing method for the production of bulk amorphous materials. In this study, amorphous Nd–Fe–B melt-spun ribbons were successfully consolidated into bulk form at room temperature by the compression shearing method. X-ray diffraction and transmission electron microscopy studies revealed that the amorphous structure was well maintained in the bulk materials. The resultant bulk materials exhibited the same magnetic properties as the original amorphous Nd–Fe–B materials.

Phase Decomposition in Cu-Ti Metallic Glass

1983 ◽  
Vol 28 ◽  
Author(s):  
R. D. Shull ◽  
S. P. Singhal ◽  
B. Mozer ◽  
A. Maeland
Keyword(s):  
Neutron Diffraction ◽  
Metallic Glass ◽  
Melt Spinning ◽  
Large Angle ◽  
Amorphous State ◽  
Glass Ribbon ◽  
Amorphous Structure ◽  
Phase Decomposition ◽  
X Ray ◽  
Diffraction Patterns

ABSTRACTA metallic glass ribbon of Cu55Ti45 prepared by melt spinning was examined by x-ray, neutron, and electron diffraction, by small angle neutron diffraction (SANS), transmission electron microscopy (TEM), and by differential thermal analysis (DTA). In the liquid quenched condition large angle diffraction data (both x-ray and neutron) show the broad banded structure typical of the amorphous state. The SANS data, however, exhibit highly anisotropic patterns arising from the phase decomposition during solidification. Ribbons annealed below the glass transition temperature (Tg ) produced neutron diffraction patterns of materials with the same amorphous structure combined with a new short range order; and the SANS patterns retained the asymmetry of the as-quenched material. Ribbons annealed above the crystallization temperature (Tc) show both isotropic and anisotropic contributions to the SANS patterns. Formation of the equilibrium TiCu phase occurs directly from the metallic glass at Tc. The equilibrium Ti3Cu4 phase, however, forms from the TiCu phase at slightly higher temperatures.

Extended X-ray absorption fine-structure analysis of vacuum-deposited amorphous germanium

1989 ◽  
Vol 67 (4) ◽  
pp. 358-364 ◽  
Author(s):  
G. W. Johnson ◽  
D. E. Brodie ◽  
E. D. Crozier
Keyword(s):  
Fine Structure ◽  
Amorphous Materials ◽  
Amorphous Material ◽  
Amorphous Structure ◽  
Low Energy ◽  
X Ray Diffraction ◽  
Two Phase ◽  
Edge Structure ◽  
X Ray ◽  
Low Energy Electrons

In this study, thin films of germanium have been vacuum deposited in four regimes. Care was taken to prepare reproducible films, which required that the partial pressure of water be below 10−8 Torr during deposition (1 Torr = 133.3 Pa). First, films deposited onto substrates held during deposition at a temperature Ts that is below 473 K are amorphous. Once annealed above 423 K, their electrical conductivity and optical band gap are independent of deposition temperature and rate, and of whether or not low-energy electron irradiation of the substrate is used during deposition. This suggests that a well-defined and reproducible structure is being prepared. Second, a "precrystallization regime" is obtained when Ts is between 473 and 513 K. Extended X-ray adsorption fine-structure and X-ray diffraction confirm that this regime is a two-phase mixture of amorphous material and crystallites. Third, films deposited with Ts near 513 K, while using low-energy electrons to bombard the substrate, are amorphous, but these films have different electrical and optical properties from the films m the first regime. From this, we infer that a second well-defined amorphous structure exists. Fourth, films deposited with Ts above 513 K are polycrystalline. Extended X-ray adsorption fine-structure and X-ray adsorption near-edge structure could not distinguish between the two amorphous materials in the first and third regimes.

Thermal stability of carbon nitride thin films

2001 ◽  
Vol 16 (11) ◽  
pp. 3188-3201 ◽  
Author(s):  
Niklas Hellgren ◽  
Nian Lin ◽  
Esteban Broitman ◽  
Virginie Serin ◽  
Stefano E. Grillo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Photoelectron Spectroscopy ◽  
Carbon Nitride ◽  
Amorphous Structure ◽  
X Ray ◽  
Bonding Structure ◽  
Higher Temperature ◽  
Electron Energy Loss ◽  
Thermal Stability Of

The thermal stability of carbon nitride films, deposited by reactive direct current magnetron sputtering in N2 discharge, was studied for postdeposition annealing temperatures TA up to 1000 °C. Films were grown at temperatures of 100 °C (amorphous structure) and 350 and 550 °C (fullerenelike structure) and were analyzed with respect to thickness, composition, microstructure, bonding structure, and mechanical properties as a function of TA and annealing time. All properties investigated were found to be stable for annealing up to 300 °C for long times (>48 h). For higher TA, nitrogen is lost from the films and graphitization takes place. At TA = 500 °C the graphitization process takes up to 48 h while at TA = 900 °C it takes less than 2 min. A comparison on the evolution of x-ray photoelectron spectroscopy, electron energy loss spectroscopy and Raman spectra during annealing shows that for TA > 800 °C, preferentially pyridinelike N and –C≡N is lost from the films, mainly in the form of molecular N2 and C2N2, while N substituted in graphite is preserved the longest in the structure. Films deposited at the higher temperature exhibit better thermal stability, but annealing at temperatures a few hundred degrees Celsius above the deposition temperature for long times is always detrimental for the mechanical properties of the films.

scholarly journals Facile Synthesis of Amorphous C3N4ZnxOy (x, y = 0.32–1.10) with High Photocatalytic Efficiency for Antibiotic Degradation

Catalysts ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 514
Author(s):  
Ran Zhang ◽  
Jing Xian Dong ◽  
Guo Liang Gao ◽  
Xue Lu Wang ◽  
Ye-Feng Yao
Keyword(s):  
Noble Metal ◽  
Amorphous Materials ◽  
High Efficiency ◽  
Amorphous State ◽  
Amorphous Structure ◽  
Photocatalytic Efficiency ◽  
Metal Free ◽  
Synthetic Strategy ◽  
Photocatalytic Reactions ◽  
Antibiotic Degradation

The development of novel, noble metal-free semiconductor catalysts with high efficiency is of great importance for the degradation of organic compounds. Among them, amorphous materials have been extensively studied for their unique and commercially useful properties. Here, a completely amorphous, noble metal-free photocatalyst C3N4ZnxOy (x, y = 0.32–1.10) was successfully synthesized from urea and ZnO by a simple high-temperature polymerization method. As the Zn content increased, the short-range ordered structures of the amorphous samples were still retained, as revealed by XPS, FTIR, and ssNMR. Meanwhile, the -CN3 structures were observed to be gradually destroyed, which may make the amorphous state more favorable for photocatalytic reactions. Compared with g-C3N4, the amorphous samples showed significantly reduced intensities in the photoluminescence spectra, indicating that the recombination rate of the photo-generated charge carriers was greatly reduced. It was confirmed that the optimized sample (C3N4Zn0.61O0.61) achieved a photocatalytic efficiency of 86.1% in the degradation of tetracycline hydrochloride under visible light irradiation within 1 h. This is about 2 times higher than that of both g-C3N4 and ZnO. This study emphasizes the importance of the amorphous structure in photocatalytic reactions, and this synthetic strategy may provide an effective model for designing other novel catalysts.

Influence of the Process for Obtaining Massive Amorphous Materials on the Defects of the Structure in the Alloy Fe61+xCo10-xY8W1B20 , where x = 0 or 1

2018 ◽  
Vol 69 (9) ◽  
pp. 2546-255 ◽  
Author(s):  
Marcin Nabialek ◽  
Bartlomiej Jez ◽  
Kinga Jez
Keyword(s):  
Amorphous Materials ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
Amorphous Structure ◽  
Stiffness Parameter ◽  
Copper Mold ◽  
X Ray Diffraction ◽  
X Ray ◽  
Magnetic Hysteresis Loops ◽  
Vibration Magnetometer

As part of the work, a rapid cooled alloy was produced with the chemical composition Fe61+xCo10-xY8W1B20, where: x = 0 or 1 using two methods, suction in and injecting the molten alloy into the copper mold. The material was obtained in the form of 10 mm x 5 mm x 0.5 mm plates. Studies on the structure of the obtained alloys were carried out using X-ray diffraction. Obtained X-ray diffraction images are typical for amorphous materials. Using the vibration magnetometer, static magnetic hysteresis loops and primary magnetization curves were measured. The produced samples are characterized by a saturation value above 1T and a coercive field value below 200 A/m. Based on the theory of H. Kronm�ller, numerical analysis of the curves of the original magnetization was carried out. It has been found that the process of magnetizing the produced materials has defects of the amorphous structure in the form of pseudo-location dipoles and free volumes. In addition, the spin wave stiffness parameter was determined.

THE EFFECT OF Ph ON THE PROPERTIES OF Ni-Mo NANOCRYSTALLINE ELECTRODEPOSITS

2008 ◽  
Vol 22 (18n19) ◽  
pp. 3060-3068 ◽  
Author(s):  
R. MOUSAVI ◽  
K. RAEISSI ◽  
A. SAATCHI
Keyword(s):  
Grain Size ◽  
Amorphous State ◽  
Amorphous Structure ◽  
Line Broadening ◽  
Softening Effect ◽  
X Ray ◽  
Grain Sizes ◽  
Ph Values ◽  
Base Solution ◽  
Mo Content

Nanocrystalline pure metals with grain size below 10nm are very difficult to prepare. Alloying enables the production of such a fine grains, even down to an amorphous state. In this work, Ni - Mo nanocrystalline coatings were electrodeposited from a citrate-ammonia base solution using a direct current (DC) technique. The grain sizes were estimated from X-ray line broadening. Mo content of the coatings was determined by energy dispersive X-ray analysis (EDS). The results showed that the grain size decreased when the Mo content of alloy was increased through reducing the bath pH. The microhardness measurements showed an increase in hardness with decreasing the pH, a maximum hardness of 820 Vickers was obtained for the coating deposited at pH9 with a 17 wt% Mo . Although, at pH values lower than 9, alloys with higher than 17wt% Mo were obtained, a softening effect was observed despite the decrease in grain size which is the result of transition from a nanocrystalline to amorphous structure.

Structure of pure metallic and semiconductor glasses

1990 ◽  
Vol 48 (4) ◽  
pp. 142-143
Author(s):  
Louis M. Holzman ◽  
Yeon-Wook Kim ◽  
Thomas F. Kelly
Keyword(s):  
Distribution Function ◽  
Radial Distribution Function ◽  
Amorphous Alloys ◽  
Amorphous Materials ◽  
Room Temperature ◽  
Amorphous State ◽  
Amorphous Structure ◽  
Pure Element ◽  
Diffraction Patterns ◽  
Semiconductor Glasses

There has been a great deal of interest in amorphous materials as the advance of technology has enabled a greater variety of alloys and elements to be quenched into the amorphous state and as new uses for amorphous materials have been developed. Because the analysis of the structure of amorphous alloys is quite complicated, it is highly desirable to have specimens available of pure elements in the amorphous state in order to more easily study amorphous structure and for comparison with theory. However, very few pure elements have been quenched into the amorphous state and most of those that have been are only stable at temperatures close to absolute zero. This has limited the methods available for the study of their structure. We have produced room-temperature-stable amorphous samples of pure elements (V,Nb,Ta,Mo,W,Fe,Co,Ni,Si,Ge) from the melt using electrohydrodynamic (EHD) atomization. Diffraction patterns of these samples were obtained using a Vacuum Generators HB501 STEM and these patterns were analyzed to obtain the radial distribution function for the pure element specimens.

scholarly journals Synthesis of Bulk Amorphous Alloy from Fe-Base Powders by Explosive Consolidation

Metals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 727 ◽  
Author(s):  
Jianbin Li ◽  
Ming Lu ◽  
Yongbao Ai ◽  
Cong Tao ◽  
Yun Xiong
Keyword(s):  
Glass Transition ◽  
Amorphous Alloy ◽  
Supercooled Liquid ◽  
Amorphous Structure ◽  
Bulk Amorphous Alloy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Explosive Consolidation ◽  
Crystallization Onset ◽  
Thermal Stability Of

A Fe61Cr2Nb3Si12B22 amorphous alloy rod sample of 8.8 mm diameter has been successfully prepared through explosive consolidation. The structure and thermal stability of the as-synthesized sample have been analyzed through X-ray diffraction (XRD) and differential scanning calorimeter (DSC) analysis. The results demonstrate that the sample still retains an amorphous structure, and the glass transition temperature (Tg), the crystallization onset temperature (Tx), the supercooled liquid zone (ΔTx) (Tx − Tg) and the reduced glass transition temperatures (Trg) (Tg/Tm) are 784 K, 812 K, 28 K, and 0.556, respectively. Its microstructure has been investigated by optical microscopy (OM) and scanning electron microscopy (SEM). The average microhardness of the alumina compact is about 1069 HV.

On the Formation of Amorphous and Metastable PVD-Coatings

1990 ◽  
Vol 187 ◽  
Author(s):  
O. Knotek ◽  
A. Barimani ◽  
F. Löffler
Keyword(s):  
Electron Microscope ◽  
Electron Spectroscopy ◽  
Auger Electron ◽  
Protective Coatings ◽  
Wear Test ◽  
Corrosion And Wear ◽  
Pvd Coatings ◽  
X Ray ◽  
Structure Morphology ◽  
Thermal Stability Of

AbstractBy using differing target materials and admitting reactive atmospheres, thin protective coatings having an amorphous and/or metastable character such as sialon, (Ti, Al)N and (Ti, Zr)N are deposited. Phase formation, crystalline structure, morphology and mechanical properties of these films are investigated by X-ray analysis, transmisison electron microscope (TEM), scanning electron microscope, Auger electron spectroscopy (AES) and metallographic measurements. The thermal stability of the coating systems are examined and corrosion and wear test carried out.

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