Mechanical Loss Peak Research Articles

The transition mechanism of dynamic mechanical loss peaks and phase analysis in binary block copolymers of styrene/butadiene rubber

The transition mechanism of dynamic mechanical loss peaks and phase analysis in binary block copolymers of styrene/butadiene rubber

Optical properties of germania and titania at 1064 nm and at 1550 nm

One of the main noise sources in current gravitational-wave detectors is the thermal noise of the high-reflectivity coatings on the main interferometer optics. Coating thermal noise is dominated by the mechanical loss of the high-refractive index material within the coating stacks, Ta2O5 mixed with TiO2 . For upgrades to room-temperature detectors, a mixture of GeO2 and TiO2 is an interesting alternative candidate coating material. While the rather low refractive index of GeO2 increases with increasing TiO2 content, a higher TiO2 content results in a lower threshold temperature before heat treatment leads to crystallisation, and potentially to a degradation of optical properties. For future cryogenic detectors, on the other hand, a higher TiO2 content is beneficial as the TiO2 suppresses the low-temperature mechanical loss peak of GeO2. In this paper, we present the optical properties of coatings—produced by plasma-assisted ion-beam evaporation—with high TiO2 content at 1550 nm, a laser wavelength considered for cryogenic gravitational-wave detectors, as a function of heat-treatment temperature. For comparison, the absorption of pure GeO2 was also measured. Furthermore, results at the currently-used wavelength of 1064 nm are presented.

Cryogenic mechanical loss of amorphous germania and titania-doped germania thin films

The mechanical loss of amorphous thin films of germania (GeO2) and titania-doped germania (Ti:GeO2) deposited by ion-beam sputtering onto silicon double-paddle oscillators was studied from 10 K to 290 K. Undoped germania was found to show a wide cryogenic mechanical loss peak centered at K with , which decreases to as Ti-concentration increases to 44%. In addition to decreasing the height of this low-temperature peak, Ti-doping increases its width, and shifts its position toward lower temperatures. Annealing reduces the room temperature mechanical loss of Ti:GeO2 and increases its cryogenic mechanical loss, which is consistent with trends observed in most amorphous oxides.

Silicon Oxy-Nitride for the Low Refractive Index Layers in the Mirror Coatings of the Cryogenic Laser Interferometer Gravitational Waves Detector.

The low refractive index layers in the mirror coatings of the room-temperature laser interferometer gravitational waves detectors are silica deposited by the ion beam sputter method. However, the silica film suffers from the cryogenic mechanical loss peak, hindering its application for the next generation detector operated at cryogenics. New low refractive index materials need to be explored. We study amorphous silicon oxy-nitride (SiON) films deposited using the method of plasma-enhanced chemical vapor deposition. By changing the N_{2}O/SiH_{4} flow rate ratio, we can tune the refractive index of the SiON smoothly from nitridelike to silicalike of ∼1.48 at 1064nm, 1550nm, and 1950nm. Thermal anneal reduced the refractive index down to ∼1.46 and effectively reduced the absorption and cryogenic mechanical loss; the reductions correlated with the N─H bond concentration decrease. Extinction coefficients of the SiONs at the three wavelengths are reduced down to 5×10^{-6}∼3×10^{-7} by annealing. Cryogenic mechanical losses at 10K and 20K (for ET and KAGRA) of the annealed SiONs are significantly lower than the annealed ion beam sputter silica. They are comparable at 120K (for LIGO-Voyager). Absorption from the vibrational modes of the N─H terminal-hydride structures dominates over the absorption from other terminal hydrides, the Urbach tail, and the silicon dangling bond states in SiON at the three wavelengths.

Relaxation time shift of Cobalt related internal friction peak in WC-Co cemented carbide

Cemented carbides are widely used in the cutting tools industry for their mechanical properties. They are composite materials made of hard tungsten carbide grains jointed together by a ductile cobalt binder. Due to the extreme conditions of use of the tools, understanding the evolution of the microstructure of the two phases is essential. This evolution can be followed by Mechanical Spectroscopy, either as a function of the temperature, or of the frequency. A general overview of the spectrum reveals three mechanical loss peaks. The second peak presents a transition in its Arrhenius plot at 1140 K, when measured in isothermal frequency scans. The temperature of this transition corresponds with the Curie temperature of the cobalt in WC-Co. However, temperature scans do not reveal any shift in the Arrhenius plot. This result shows how the presence of a phase transition leads to the measurement of apparent activation energies when a relaxation peak is measured in out-of-equilibrium conditions.

Preparation of natural bio-based Eucommia ulmoides gum/styrene-butadiene rubber composites and the evaluation of their damping and sound absorption properties

To achieve effective sound absorption in wide frequency bands under high pressures, Eucommia ulmoides gum (EUG) as one of the natural biopolymers was incorporated into styrene-butadiene rubber (SBR) to prepare sound absorption materials. The morphology, crystalline structure, and macro-performance (damping, sound absorption, and mechanical properties) of the as-produced composites were systemically investigated. When the EUG content was less than 30 phr, the EUG was dispersed in the SBR matrix as nanocrystallites primarily existed in the β-crystal form, which is demonstrated by wide-angle X-ray diffraction (WAXD) and polarizing microscope (POM). The dynamic mechanical thermal analyzer (DMA) results expressed that EUG had two dynamic mechanical loss peaks, i.e. the glass transition peak (Peak 1, -60–40°C) and melting transition peak (Peak 2, 30–60°C). Thus, the addition of EUG improved the damping performance of the composites in high-temperature areas to some extent. Moreover, in comparison to the neat SBR, the average sound absorption coefficient of SBR/EUG (70/30) composite increased by 24.23% in the frequency range of 3–8 kHz under 2.5 MPa, which show the excellent sound absorption properties. And since the EUG nanocrystallites played the role of physical crosslingking points, the SBR/EUG (70/30) composite also had outstanding comprehensive mechanical properties. The SBR/EUG composites may be applied to underwater sound absorption materials.

Hysteretic Behavior of Twin Boundary Peak Due to Precipitation in Co-Ni-Cr alloy

Anelastic behavior and microstructural changes of a Co-Ni-Cr super-alloy were monitored over the temperature range 250-950oC, by using several complementary techniques. Two grades of this alloy were used, differing by the presence of small quantity of beryllium (<1.5% at.). Thermoelectric power reveals two distinct precipitation stages. The first precipitation (A), common to both the grades, and a second one (B), occurring solely in the beryllium-containing alloy. Cold-worked alloys exhibit a transient large mechanical loss peak, associated to the recrystallization of the deformed materials, and two relaxation peaks situated at around 600oC (P1) and 780oC (P2). Instead, only the peak P1 occurs on the fully recrystallized material. P1 and P2 can be associated to the diffusion process involved in the first precipitation stage (A) and to the twin boundary motion, respectively. The precipitation-dissolution process of precipitates B, localized on the twin boundary, provides a hysteretic behavior of the peak P2.

Silicon nitride films fabricated by a plasma-enhanced chemical vapor deposition method for coatings of the laser interferometer gravitational wave detector

Silicon is a potential substrate material for the large-areal-size mirrors of the next-generation laser interferometer gravitational wave detector operated in cryogenics. Silicon nitride thin films uniformly deposited by a chemical vapor deposition method on large-size silicon wafers is a common practice in the silicon integrated circuit industry. We used plasma-enhanced chemical vapor deposition to deposit silicon nitride films on silicon and studied the physical properties of the films that are pertinent to application of mirror coatings for laser interferometer gravitational wave detectors. We measured and analyzed the structure, optical properties, stress, Young's modulus, and mechanical loss of the films, at both room and cryogenic temperatures. Optical extinction coefficients of the films were in the ${10}^{\ensuremath{-}5}$ range at 1550-nm wavelength. Room-temperature mechanical loss of the films varied in the range from low ${10}^{\ensuremath{-}4}$ to low ${10}^{\ensuremath{-}5}$ within the frequency range of interest. The existence of a cryogenic mechanical loss peak depended on the composition of the films. We measured the bond concentrations of $\mathrm{N}─\mathrm{H}$, $\mathrm{Si}─\mathrm{H}$, $\mathrm{Si}─\mathrm{N}$, and $\mathrm{Si}─\mathrm{Si}$ bonds in the films and analyzed the correlations between bond concentrations and cryogenic mechanical losses. We proposed three possible two-level systems associated with the $\mathrm{N}─\mathrm{H}$, $\mathrm{Si}─\mathrm{H}$, and $\mathrm{Si}─\mathrm{N}$ bonds in the film. We inferred that the dominant source of the cryogenic mechanical loss for the silicon nitride films is the two-level system of exchanging position between a ${\mathrm{H}}^{+}$ and electron lone pair associated with the $\mathrm{N}─\mathrm{H}$ bond. Under our deposition conditions, superior properties in terms of high refractive index with a large adjustable range, low optical absorption, and low mechanical loss were achieved for films with lower nitrogen content and lower $\mathrm{N}─\mathrm{H}$ bond concentration. Possible pairing of the silicon nitride films with other materials in the quarter-wave stack is discussed.

Preparation and relaxation dynamics of ethylene–propylene–diene rubber/clay nanocomposites with crosslinking interfacial design

ABSTRACTEthylene–propylene–diene rubber (EPDM)/clay nanocomposites with crosslinking bonding at the interface were fabricated through the intercalation method involving double‐bond functional groups. For comparison, an organoclay modified with an intercalation agent without double bonds was also prepared. X‐ray diffraction indicated that the EPDM intercalated into the galleries of the nanoclay due to crosslinking with the organic intercalation reagent containing double bonds. According to the dielectric relaxation spectra, the segmental relaxation of EPDM was greatly confined, due to the strong filler/polymer interfacial interaction. And a new relaxation appeared at higher temperature and lower frequency than segmental relaxation when the content of clay with double bonds reached 10 phr; the new relaxation is attributed to interfacial relaxation. Whereas the new relaxation did not appear by adding ordinary organoclay, the dynamic mechanical analysis loss peak of EPDM, corresponding to the glass transition, moved to a higher temperature due to covulcanization. The presence of crosslinking in the EPDM/clay nanocomposites can play a significant role in improving their mechanical properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45553.

Synthesis of Methylacryloypropyl-POSS/Poly(fluorine-acrylate) Core-Shell Nanocomposites and Effect on Thermal Properties of Materials

Core-shell nanocomposites were prepared from acrylates, fluorine- containing methacrylate monomers and methylacryloypropyl polyhedral oligomeric silsesquioxanes (MAP-POSS) by emulsion polymerization. The properties of latex and nanocomposites were characterized by FTIR, NMR, TEM, laser particle diameter analyzer, DMA and TGA. The results showed that the particle diameter of composite latexes was about 33.5 nm, dynamic mechanical loss peak temperature Tp of the nanocomposites had the best high value at 99.6°C when 7 wt.% MAP-POSS was added, which is 7.8°C higher than the pure polyacrylates. MAP-POSS could increase the thermal stability of materials, the initial thermal decomposition temperature increases about 34°C.

Internal-friction spectra of poly(vinyl alcohol) with various molecular masses

Dissipative effects in poly(vinyl alcohol) films with different molecular masses and degrees of hydration have been investigated with the use of relaxation spectrometry. The mechanical-loss peaks in the internal-friction spectrum reflect two relaxation transitions (α and β peaks) and one first-order phase transition (δ peak). It has been found that a decrease in the degree of hydration and an increase in the crystallinity of poly(vinyl alcohol) substantially raises the α-transition temperature. The α peak shifts to higher temperatures as the molecular mass grows. The position of the β peak in the spectrum is independent of the molecular mass, but changes with the degree of hydration. A sharp drop of the oscillation frequency in the region of the α transition and a smooth decrease in frequency in the temperature range of the β transition have been recorded. It has been found that the shear-modulus defect determined from the frequency in the region of the α transition is independent of the molecular mass and degree of hydration of poly(vinyl alcohol).

Synthesis and Curing Kinetics of UV-Curable Waterborne Bisphenol-S Epoxy-Acrylate/Polyurethane-Acrylate/Methylacryloylpropyl-POSS Nanocomposites

In order to prepare waterborne UV-curable polyurethane-acrylate (PUA) /epoxyl-acrylate (ERA) nanocomposites, the PUA, bisphenol-S epoxy acrylate (BPSEA) and methylacryloylpropyl polyhedral oligomeric silsesquioxanes (MAP-POSS) were synthesized. UV-curable BPSEA/PUA/MAP-POSS nanocomposites were prepared. The curing process, kinetics, and properties of the nanocomposites were investigated by Fourier transform infrared spectrometer (FTIR), differential scanning calorimeter (DSC) and dynamic mechanical analyzer (DMA). The base-acid resistance ability, adhesive strength, and hardness of coating films were determined. The results showed that these nanocomposites could be cured by both UV-light irradiation and a thermal free radical polymerization. Under the UV-light irradiation, they could be cured basically completely in about 20 min. The thermal free radical curing reaction could be described by a two-parameter autocatalytic Šesták-Berggren (S-B) model. The dynamic mechanical loss peak temperature, Tp, of the cured nanocomposites increased with increasing MAP-POSS content up to 8 wt%, an enhancement of 5.8°C over the pure BPSEA/PUA system, and then decreased. Films of the nanocomposites also had better base-acid resistance ability and hardness than pure BPSEA/PUA.

Investigation on insulation material morphological structure of 110 and 220 kV XLPE retired cables for reusing

Most of the 110 and 220 kV cables are in service till the end of life, but part of them would be out of service by refurbishment. This research is focused on evaluating the cable insulation and determining whether the cable can be reused. All the cables used in this research satisfactorily passed the AC voltage and partial discharge tests. Then the fourier transform infrared spectroscopy, thermogravimetry analysis, differential scanning calorimetry, dynamic mechanical analysis, and tensile machine were used to analyze the insulation morphological structure and performance of 20 retired 110 and 220 kV crosslinked polyethylene cables obtained from the Beijing and Zhuhai districts. The results show that the structure parameters which can represent the physical change and the irreversible chemical change of cables have obvious time dependence characteristic. DSC result shows that crystallinity, melting range, and crystallization rate increase slightly with service years. DMA experiment illustrates that the temperature of mechanical loss peak, Tγ, shifts to a higher temperature while the mechanical loss increases slightly and temperature dependency of storage modulus increases with service years. The electrical treeing experiment utilized cable operated for 17 years, which is the longest operation year for the samples. Compared with new cable, the cable operated for 17 years has a slight decrease in tree initiation time and an obvious increase in tree propagation time. These experiment data show that the insulation material morphological structure is mainly stable, and the test results are also a contribution to the lifetime expectancy evaluation of the 110 and 220 kV XLPE cable.

Synthesis and Characterization of Emulsion Coating of Fluorinated Polymethacrylate Modified by POSS

The core-shell nanocomposite particles were prepared from acrylate monomers and octavinyl polyhedral oligomeric silsesquioxane (V-POSS) by emulsion polymerization. The structure and properties of emulsion and latex film were characterized by FT-IR, dynamic mechanical analysis (DMA) and TEM and laser particle diameter analyzer (LPDA). The results showed that the V-POSS/polyacrylated (V-POSS/PMA) composite latexes was prepared and the diameter is about 36.1 nm when added 5wt% V-POSS. DMA results showed that the mechanical loss (tanδ) peak temperature (Tp) of the film enhance with increasing V-POSS content and had the best high Tp at 88.4°C for added 7 wt% V-POSS, which increased 7.8 °C than had not V-POSS. Thermogravimetric analysis (TGA) showed that the addition of V-POSS can increase the thermal decomposition temperature and improved the thermal stability of polyacrylate.

New In–Pd mechanical loss peak in ternary gold alloys

A point defect relaxation peak has been observed in a ternary 18-carat gold alloy with the composition Au62.5Pd32.5In5. It shows a Curie–Weiss dependence on the temperature, as is commonly observed for a Zener peak. However, the peak is absent in the binary alloys AuPd and AuIn and therefore it is a new type of relaxation that is due to In–Pd pairs. The relaxation strength shows a linear dependence on the indium concentration. We have developed a model of elastic dipoles containing one palladium and one indium atom in a gold matrix. The model is based on the reorientation under stress of InPd dipoles in a gold matrix and takes into account the atom ordering. The model accounts for a linear dependence of the relaxation strength on the indium concentration in a dilute alloy and is also valid for more concentrated alloys.

Epoxy Resin Toughened by Polyester Hot Melt Adhesive

The micro structures of epoxy toughened by polyester hot melt adhesive PE30 was studied by SEM.The influence of addition polyester hot melt adhesive PE30 on heat stability of epoxy was studied by DSC,DMC,and TGA.The mechanical properties,including impact strength,bending strength,fracture strength were measured.The results showed that a suitable usage of PE30 is 15%.In the process of curing,the epoxy resin matrix containing polyester hot melt adhesive came out and induced a phase separation,from the single-phase to continuous phase and then to reverse phase.Comparing with the pure epoxy resin,the impact strength and fracture strength were increased by 250% and 127%,respectively.The bending strength and modulus were reduced by 27% and 44%,respectively.The glass transition temperature and starting thermo-gravimetric temperature were reduced by 1.5%,and mechanical loss peak temperature was reduced by 2.5%.It is show that the polyester hot melt adhesive PE30 can significantly toughen the epoxy resin while maintain its thermal performance.

Grain Boundary Relaxation in 18-Carat Yellow Gold

Au60Ag30Cu10(in at%) gold alloy exhibits a mechanical loss spectrum composed of a Zener peak due to Cu atoms in the solid solution and of a second relaxation peak at higher temperature or lower frequency. It is shown that this second peak is related to the presence of grain boundaries as it is absent in the spectrum of a single crystal. This mechanical loss peak, which is stable and reproducible in heating and cooling cycles, is thermally activated with an activation enthalpy of 2.35 eV and an apparent limit relaxation time of 9.6·10-17s. As it is hard to imagine that a whole grain should slip at once along a touching grain, the relaxation peak is interpreted by a dislocation model, which may account not only for the activation parameters but also for the stress amplitude dependency of the peak.

High Temperature Mechanical Spectroscopy Study of 3 mol% Yttria Stabilized Tetragonal Zirconia Reinforced with Carbon Nanotubes

Composites containing 3 mol% yttria stabilized tetragonal zirconia (3Y-TZP) reinforced with multiwalled carbon nanotubes (CNTs) with various amounts of CNTs (3Y-TZP / X wt% CNT, X= 0, 0.5, 1.5, 3 and 5) were processed by spark plasma sintering. Microscopic analysis proves that CNTs were well dispersed and embedded in grain boundaries of the sintered body. High temperature mechanical properties have been investigated using mechanical spectroscopy and low stress (6 MPa) creep. The isothermal spectrum (measured at 1600 K) consists of a mechanical loss peak at a frequency of about 0.1 Hz, which is superimposed on an exponential increase at low frequency. The absence of a well-marked peak in monolithic 3Y-TZP is justified considering that restoring force decreases at low frequencies or high temperatures due to the elasticity of neighboring grains. Therefore, strain is no more restricted and the mechanical loss increases exponentially, which is correlated to macroscopic creep. However, with CNT additions the mechanical loss decreases and a better resolved peak was observed. In parallel, the results have shown that the creep rate drastically decreases with CNT additions. These results can be interpreted by the pinning effect of CNTs which can hinder grain boundary sliding at high temperatures, resulting in a creep resistance improvement.

UV-Curable Coating of Unsaturated Polyester/Epoxy Resins Containing Polyhedral Oligomeric Silsesquioxanes

UV-curable coating of unsaturated polyester/epoxy resin (UP-ER) modified with methylacryloylpropyl polyhedral oligomeric silsesquioxanes (MAP-POSS) was prepared. The UV-cured process, kinetics, and some properties of coating were investigated. The results show that this coating has a better UV-curing property. The curing reaction can be described by a two-parameter autocatalytic Šesták-Berggren (S-B) model. The mechanical loss peak temperature T p of curing coating nanocomposites increased with increasing MAP-POSS content and has a highest value when MAP-POSS content is 12%, which is 121.8°C, and higher, about 18.3°C, than a pure UP-ER system. The coating film has lower volume shrinkage than pure UP-ER.

Preparation and Properties of Emulsion Coating of Polyacrylate Modified by &lt;i&gt;In-Situ&lt;/i&gt; Nano-Hybrid Silica

The polyacrylate emulsion coating modified by nano-silica was prepared by In-situ method. Tetraethoxysilane (TEOS) was added as the precursor of SiO2 in the late of the emulsion polymerization. The structure and properties of emulsion and latex film were characterized. The results showed that the nano-hybrid silica/polyacrylate emulsion coating with good performance can be prepared by In-situ method. FTIR analysis indicated that the -Si-O-Si- structure has embodied in the coating film. The particle diameter of emulsion is 378nm when nano-SiO2 content is 6% and the dispersing index is 0.164. The mechanical loss peak temperature (Tp) of coating film with 6% nano-SiO2 is 60.6°C which increase 6°C than pure emulsion film. The nano-hybrid emulsion coating has a good performance, such as good acid-alkali resistance and hardness.