Raman spectroscopy studies on the thermal stability of TiN, CrN, TiAlN coatings and nanolayered TiN/CrN, TiAlN/CrN multilayer coatings

2004 ◽  
Vol 19 (11) ◽  
pp. 3196-3205 ◽  
Author(s):  
Harish C. Barshilia ◽  
K.S. Rajam
Keyword(s):  
Thermal Stability ◽  
Raman Spectroscopy ◽  
Optical Phonon ◽  
Structural Changes ◽  
Single Layer ◽  
Multilayer Coatings ◽  
Phonon Modes ◽  
Optical Phonon Mode ◽  
Spectral Changes ◽  
Thermal Stability Of

About 1.5-μm-thick single-layer TiN, CrN, TiAlN coatings and nanolayered TiN/CrN, TiAlN/CrN multilayer coatings were deposited on silicon (111) substrates using a reactive direct current magnetron sputtering process. Structural characterization of the coatings was done using x-ray diffraction (XRD) and micro-Raman spectroscopy. All the coatings exhibited NaCl B1 structure in the XRD data. Raman spectroscopy data of as-deposited coatings exhibited two broad bands centered at 230–250 and 540–630 cm-1. These bands have been assigned to acoustical and optical phonon modes, respectively. Thermal stability of the coatings was studied by heating the coatings in air in a resistive furnace for 30 min in the temperature range 400–900 °C. Structural changes as a result of heating were characterized using Raman spectroscopy and XRD. Raman data showed that TiN, CrN, TiN/CrN, TiAlN, and TiAlN/CrN coatings started to oxidize at 500, 600, 750, 800, and 900 °C, respectively. To isolate the oxidation-induced spectral changes as a result of heating of the coatings in air, samples were also annealed in vacuum at 800 °C under similar conditions. The Raman data of vacuum-annealed coatings showed no phase transformation, and intensity of the optical phonon mode increased and shifted to lower frequencies. The origin of these spectral changes is discussed in terms of defect structure of the coatings. Our results indicate that the thermal stability of nanolayered multilayer coatings is superior to the single-layer coatings.

scholarly journals Role of Ionic Headgroups on the Thermal, Rheological, and Foaming Properties of Novel Betaine-Based Polyoxyethylene Zwitterionic Surfactants for Enhanced Oil Recovery

Processes ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 908 ◽  
Author(s):  
Muhammad Shahzad Kamal ◽  
Syed Muhammad Shakil Hussain ◽  
Lionel Talley Fogang
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Oil Recovery ◽  
Structural Changes ◽  
Foam Stability ◽  
Foaming Properties ◽  
Zwitterionic Surfactants ◽  
Reservoir Conditions ◽  
Thermal Stability Of

Long-term thermal stability of surfactants under harsh reservoir conditions is one of the main challenges for surfactant injection. Most of the commercially available surfactants thermally degrade or precipitate when exposed to high-temperature and high-salinity conditions. In this work, we designed and synthesized three novel betaine-based polyoxyethylene zwitterionic surfactants containing different head groups (carboxybetaine, sulfobetaine, and hydroxysulfobetaine) and bearing an unsaturated tail. The impact of the surfactant head group on the long-term thermal stability, foam stability, and surfactant–polymer interactions were examined. The thermal stability of the surfactants was assessed by monitoring the structural changes when exposed at high temperature (90 °C) for three months using 1H-NMR, 13C-NMR, and FTIR analysis. All surfactants were found thermally stable regardless of the headgroup and no structural changes were evidenced. The surfactant–polymer interactions were dominant in deionized water. However, in seawater, the surfactant addition had no effect on the rheological properties. Similarly, changing the headgroup of polyoxyethylene zwitterionic surfactants had no major effect on the foamability and foam stability. The findings of the present study reveal that the betaine-based polyoxyethylene zwitterionic surfactant can be a good choice for enhanced oil recovery application and the nature of the headgroup has no major impact on the thermal, rheological, and foaming properties of the surfactant in typical harsh reservoir conditions (high salinity, high temperature).

scholarly journals Effects of aluminum sulfate soaking pretreatment on dimensional stability and thermostability of heat-treated wood

2020 ◽  
Author(s):  
Lijie Qu ◽  
Zhenyu Wang ◽  
Jing Qian ◽  
Zhengbin He ◽  
Songlin Yi
Keyword(s):  
Heat Treatment ◽  
Thermal Stability ◽  
Thermal Degradation ◽  
Structural Changes ◽  
Aluminum Sulfate ◽  
Treated Wood ◽  
Treatment Temperature ◽  
Chinese Fir ◽  
Heat Treated ◽  
Thermal Stability Of

Abstract Acidic aluminum sulfate hydrolysis solutions can be used to catalyze the thermal degradation of wood in a mild temperature environment, and thus reduce the temperature required for heat treatment process. To improve the dimensional and thermal stability of Chinese fir during heat treatment at 120 °C, 140 °C and 160 °C, this study investigated the effects of soaking pretreatment with 5%, 10% and 15% aluminum sulfate on the chemical and structural changes of the heat-treated Chinese fir. The results indicated that the samples treated at 15% aluminum sulfate concentration and 160 °C heat treatment achieved the best dimensional and thermal stability. Chemical analyses by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) indicated that the catalysis of aluminum sulfate resulted in degradation of hemicelluloses during the heat treatment, and an increase in the soaking concentration and heat treatment temperature also affected the thermal degradation of celluloses. The scanning electron microscope (SEM) and mass changes test results proved that the hydrolyzed aluminum flocs mainly adhered to the inner wall of the wood tracheid as spherical precipitates, and when the soaking concentration reached 10% and 15%, a uniform soaking effect could be achieved. The thermogravimetric (TG) analysis revealed the soaking pretreatment effectively improved the thermal stability of the heat-treated wood by physically wrapping and promoting the formation of a carbon layer on the wood surface during heat treatment. Thus, aluminum sulfate soaking pretreatment exerted a great effect on the dimensional and thermal stability of wood, allowing heat treatment to be performed at a lower temperature.

Thermal Stability of Ultrafine Grains in Al-Fe-Mn-Si Foils Prepared by ARB and Subsequent Rolling

2008 ◽  
Vol 584-586 ◽  
pp. 905-910 ◽  
Author(s):  
Petr Homola ◽  
Margarita Slámová ◽  
P. Sláma ◽  
Miroslav Cieslar
Keyword(s):  
Thermal Stability ◽  
Structural Changes ◽  
High Strength ◽  
Electron Back Scatter Diffraction ◽  
Grain Structure ◽  
Fine Grain ◽  
Hardness Increase ◽  
Cold Rolled ◽  
The Stability ◽  
Thermal Stability Of

Accumulative Roll Bonding (ARB) is a severe plastic deformation process that allows producing ultrafine-grained materials (UFG). UFG sheets exhibit enhanced strength and very fine grain structure. Foils used as fins in heat exchangers have to be very thin but must exhibit high strength combined with relatively high formability. Thus, materials produced using ARB may fulfil the exacting requirements on foil properties for such applications. The thermal stability of Al-Fe- Mn-Si foils produced using ARB and subsequent cold rolling was studied and compared with conventionally cold rolled (CCR) counterparts. The stability was assessed by isothermal annealing in the temperature range from 200 to 450 °C. Electron back scatter diffraction in a scanning electron microscope and transmission electron microscopy examinations of foils microstructure in the deformed and annealed states allowed the monitoring of structural changes. The magnitude of mechanical properties changes due to annealing was evaluated by microhardness measurements. Significant hardness increase was observed after annealing at 200 °C only in the ARB samples and was assigned to an annealing-induced hardening. The CCR foil exhibits higher non-recrystallized fraction and smaller mean lamellae boundary spacing in the temperature interval of 200-250 °C than ARB foils. The annealing at 450 °C results in identical hardness values and fully recrystallized microstructure of all foils, regardless the method used for their manufacturing. However, the ARB samples show higher stability of the refined substructure than their cold rolled counterparts due to continuous recrystallization occurring in the ARB foils.

Characterization of Ni- and Ni(Pt)-Silicide Formation on Narrow Polycrystalline Si Lines by Raman Spectroscopy

1999 ◽  
Vol 591 ◽  
Author(s):  
P. S. Lee ◽  
D. Mangelinck ◽  
K. L. Pey ◽  
J. Ding ◽  
T. Osipowicz ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Raman Spectroscopy ◽  
Raman Mapping ◽  
Silicide Formation ◽  
Nucleation Sites ◽  
The Difference ◽  
The Stability ◽  
Non Destructive ◽  
Thermal Stability Of

ABSTRACTThe formation and thermal stability of Ni- and Ni(Pt) silicide on narrow polycrystalline Si (poly-Si) lines have been investigated using the non-destructive micro-Raman technique. The presence of Ni or Ni(Pt)Si on poly-Si lines with linewidths ranging from 0.5 gtm to 0.25 μm has been monitored by a distinct Raman peak at around 215 cm−1. Ni(Pt)Si was clearly identified to be present up to a RTA temperature of 900°C on narrow poly-Si lines as compared to pure NiSi which was found only up to 750°C. Raman scattering from the 100×100 μm2 poly-Si pads showed the formation of NiSi2 at 750°C for pure Ni-salicidation and 900°C for Ni(Pt)-salicidation respectively. The difference in the stability of NiSi on the poly-Si pads and lines is discussed in terms of agglomeration, inversion and/or nucleation of NiSi2that could be due to difference in nucleation sites and/or stress. In addition, a correlation between the line sheet resistance and the presence of Ni silicide was found using micro-Raman mapping along single poly-Si lines.

Nondestructive Characterizations of Au-Catalyzed GaAs Nanowires on GaAs(111)B Substrates via Identifications of 1st Order Optical Phonon Modes Using μ-Raman Spectroscopy

2020 ◽  
Vol 20 (7) ◽  
pp. 4358-4363
Author(s):  
Jeung Hun Park ◽  
Richard S. Kim ◽  
Se-Jeong Park ◽  
Gye-Choon Park ◽  
Choong-Heui Chung
Keyword(s):  
Raman Spectroscopy ◽  
Dose Rate ◽  
Raman Spectra ◽  
Optical Phonon ◽  
Longitudinal Optical ◽  
Transverse Optical ◽  
Longitudinal Optical Phonon ◽  
Phonon Modes ◽  
Gaas Nanowires ◽  
Beam Dose

We report the relation between the catalyst patterning conditions and the intensity of the 1st order Raman active modes in Au-catalyzed GaAs nanowire bundles. We fabricated e-beam lithographically Au-patterned GaAs(111)B substrates by varying the patterning conditions (e-beam dose rate, dot-size and interdot-spacings), and grew GaAs nanowires via vapor–liquid–solid process using a solid-source molecular beam epitaxy. To understand the effects of the substrate preparation conditions and resulting morphologies on the optical characteristics of 1st order transverse optical and longitudinal optical phonon modes of GaAs, we characterized the nanowire bundles using complementary μ-Raman spectroscopy and scanning electron microscopy as a function of the e-beam dose rate (145–595 μC/cm2), inter-dot spacing (100 and 150 nm) and pattern size (100 and 150 nm). Ensembles of single crystalline GaAs nanowires covered with different Au-thickness exhibit a downshift and asymmetric broadening of the 1st order transverse optical and longitudinal optical phonon peaks relative to GaAs bulk modes. We also showed that the sensitivity of a downshift and broadening of Raman spectra are directly related to morphological and surface coverage variations in as-grown nanowires. We observed clear increases of the transverse optical and longitudinal optical intensity as well as the relatively higher peak shift and broadening of Raman spectra from the 100 nm patterning in response to the dose rate change. Strong dependence of Raman spectra of the nanowire bundles on the e-beam dose rate changes are attributed to the variations in spatial density, size, shape and random growth orientation of the wires. We have shown that the identification of the changes in GaAs longitudinal optical and Arsenic anti-site peaks is good indicators to characterize the quality of as-grown GaAs nanowires. Our finding confirms the utilization of Raman spectroscopy as a powerful tool for characterizing chemical, structural, and morphological information of as-grown nanowires within the supporting substrate.

The thermal stability of maghemite-silica nanocomposites: An investigation using X-ray diffraction and Raman spectroscopy

2007 ◽  
Vol 434-435 ◽  
pp. 650-654 ◽  
Author(s):  
P.P.C. Sartoratto ◽  
K.L. Caiado ◽  
R.C. Pedroza ◽  
S.W. da Silva ◽  
P.C. Morais
Keyword(s):  
Thermal Stability ◽  
Raman Spectroscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Silica Nanocomposites ◽  
Thermal Stability Of

scholarly journals Structure, hardness and thermal stability of nanolayered TiN/CrN multilayer coatings

Vacuum ◽  
2003 ◽  
Vol 72 (3) ◽  
pp. 241-248 ◽  
Author(s):  
Harish C. Barshilia ◽  
Anjana Jain ◽  
K.S. Rajam
Keyword(s):  
Thermal Stability ◽  
Multilayer Coatings ◽  
Thermal Stability Of
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