Low-temperature Softening Research Articles

Effect of glass frits on ceramifiable properties of polyethylene composites

AbstractCeramification of polymer composites is an excellent method for enhancing the flame retardancy of the materials. The low temperature softening glass frit added in the composites plays a key role in the ceramification process of the composites. Ceramizable polyethylene (PE)/wollastonite fiber (WF) composites are processed by mixing with three types of glass frit. The ceramic residues formed were characterized by the linear shrinkage, weight loss, flexural strength, apparent porosity, and self‐supporting property measurements. The density and strength of the ceramic increased with the increasing sintering temperature, but were affected by the wettability and fluidity of the glass frit. The addition of glass frit can increase the thermal decomposition temperature of PE. X‐ray diffraction (XRD) analysis found the form of a new phase of hydroxyapatite (Ca10(PO4)6(OH)2) in the ceramifiable PE/WF composites by adding phosphate glass frit, which improved the self‐supporting properties of the ceramic residues.

The effect of substrate wettability and modulus on gecko and gecko-inspired synthetic adhesion in variable temperature and humidity

Gecko adhesive performance increases as relative humidity increases. Two primary mechanisms can explain this result: capillary adhesion and increased contact area via material softening. Both hypotheses consider variable relative humidity, but neither fully explains the interactive effects of temperature and relative humidity on live gecko adhesion. In this study, we used live tokay geckos (Gekko gecko) and a gecko-inspired synthetic adhesive to investigate the roles of capillary adhesion and material softening on gecko adhesive performance. The results of our study suggest that both capillary adhesion and material softening contribute to overall gecko adhesion, but the relative contribution of each depends on the environmental context. Specifically, capillary adhesion dominates on hydrophilic substrates, and material softening dominates on hydrophobic substrates. At low temperature (12 °C), both capillary adhesion and material softening likely produce high adhesion across a range of relative humidity values. At high temperature (32 °C), material softening plays a dominant role in adhesive performance at an intermediate relative humidity (i.e., 70% RH).

Hardening of the soft phonon in bulkSrTiO3interfaced withLaAlO3andSrRuO3

The low-temperature softening of the TO1 phonon of SrTiO3 (STO), which determines its incipient ferroelectricity, is known to be partially hindered either in the bulk under strong electric fields, or in thin STO films. Here we show, by terahertz (THz) reflectivity measurements, that a similar effect is produced in bulk STO and at zero static field by ultrathin metallic films on its surface, like a 10-nm-thick film of SrRuO3 (SRO), or the two-dimensional electron system (2DES) present at the interface with LaAlO3. In SRO/STO, the observed hardening is well explained by the depolarizing action of the SRO free electrons which follow adiabatically the ion motion. In LAO/STO, a weaker TO1 hardening could be detected by patterning the 2DES in the form of microstripes and using a polarized THz field parallel (E-) or orthogonal (E-) to the stripes. At 10 K, when TO1 is excited together with the free electrons by E-, its absorbance is harder by about 7 cm-1 than that measured when TO1 is coupled to the plasmon-polariton confined within the stripes, being excited by E-.

Observation of Low-Temperature Softening of Transverse Elastic Modulus Due to Cobalt Impurities in Mercury Selenide

Influence on elastic moduli of donor electron d-states of cobalt impurities has been investigated in mercury selenide crystals. Experiments have been carried out at the frequency of 53 MHz in the temperature interval of 1.3–100 K. Softening of the \((C_{11} - C_{12})/2\) modulus below 10 K has been observed in the impurity crystals in contrast with the \((C_{11} + C_{12} + 2C_{44})/2\) and \(C_{44}\) moduli those have exhibited hardening at cooling typical for dielectric and semiconductor crystals. The softening of the elastic modulus has been interpreted as manifestation of hybridization of the impurity d-states in the conduction band of the crystal. Comparison of theoretical calculations with experimental data has been proved to be in good agreement and has made it possible to determine the parameters characterizing the hybridized electron states.

Surface acoustic wave diagnosis of vacancy orbital with electric quadrupoles in silicon

We demonstrate ultrasonic diagnosis of vacancies in boron-doped silicon wafers currently used in device manufacturing. The low-temperature softening of elastic constants measured by surface acoustic waves (SAW) as well as bulk ultrasonic waves is caused by a coupling of elastic strains to electric quadrupoles of the vacancy orbital in silicon wafers. Using interdigital transducers with a comb gap of 2.5 μm on a piezoelectric ZnO film deposited on the (001) surface of the wafer, we observed the softening of 1.9×10−4 in relative amount of the elastic constant Cs below 2 K down to 23 mK. Taking account of the strong quadrupole-strain interaction, we deduced a small vacancy concentration 3.1×1012 cm−3 in the surface layer of the wafer within a penetration depth 3.5 μm of the SAW.

Low Temperature Softening Modification of Ramie Fabrics

The rigid nature of ramie hairiness on fabrics cause severe itching feeling, which limited the application of ramie fabrics requiring for direct contact to skin. Current modification methods for ramie fabrics are ineffective, expensive or harmful to the main body of fabric. In our research, a low temperature softening method for ramie fabrics in NaOH, urea, glycerol, and Na2B4O7 treatment bath was developed and proven to be efficient in lowering the stiffness and scratchiness of ramie fabrics without significant adverse effect on the fabric strength. Since it is possible to reuse the chemical agents, this treatment was relatively cheap and environmentally friendly.

Strong Quadrupole-Strain Interaction of Vacancy Orbital in Boron-Doped Czochralski Silicon

We have carried out ultrasonic measurements of a boron-doped silicon ingot grown by the Czochralski method in order to determine the quadrupole-strain interaction constant of a vacancy orbital. The low-temperature softening of the elastic constant \(C_{44}\) shows a remarkable variation depending on positions of the ingot, which reflects the distribution of vacancy concentration \(N\) in the ingot. An infrared laser scattering tomograph was employed to measure the density and size of voids in the silicon wafers by determining the vacancy concentration \(N_{\text{cons}}\) consumed in void formation. Using a combination of laser scattering tomography and low-temperature softening, we have found a sum rule in which the initially created vacancy concentration \(N_{\text{total}}\) corresponds to the sum of the residual vacancy concentration \(N\) and the consumed vacancy concentration \(N_{\text{cons}}\) as \(N_{\text{total}} = N + N_{\text{cons}}\). Taking account of the sum rule, we deduce the interaction constant gΓ5 = (2.8±0.2)×105 K for the quadrupole-strain interaction HQS = -gΓ5Ozxεzx of the vacancy orbital. The huge deformation energy of \(1.6\times 10^{5}\) K per vacancy with the Γ8 ground state for unit strain \(\varepsilon_{zx} = 1\) verified the strong electron–lattice interaction of the vacancy orbital. Employing the one-to-one correspondence between the softening of ΔC44/C44 = 1.0×10-4 down to 30 mK and the vacancy concentration of \(N = 1.5 \times 10^{13}\) cm-3, we can determine the vacancy concentration by low-temperature ultrasonic measurements. The present work surely puts forward a novel semiconductor technology based on low-temperature ultrasonic measurements for evaluating vacancy concentration in silicon wafers.

Low-Temperature Softening Due to Vacancy Orbital with Γ8Quartet Ground State in Boron-Doped Floating Zone Silicon

We have carried out low-temperature ultrasonic measurements using shear-mode ultrasound to clarify the quantum state of a vacancy orbital in boron-doped silicon grown by the floating zone (FZ) method. The elastic constants \((C_{11}-C_{12})/2\) and \(C_{44}\) of the transverse mode exhibit considerable softening below 2 and 5 K down to the base temperature of 30 mK, respectively. The elastic constant \(C_{44}\) measured by the three ultrasonic modes \((k_{x},u_{y})\), \((k_{z},u_{x})\), and \((k_{x},u_{z})\) shows the different magnetic field dependences among the configurations under applied magnetic fields along the \(z\)-axis. The elastic softening and the magnetic field dependence of the elastic constants are accounted for by the quadrupole susceptibility based on the energy level scheme of the vacancy orbital with a \(\Gamma_{8}\) quartet ground state and \(\Gamma_{7}\) doublet excited state located at an energy of 1 K. The difference in \(C_{44}\) between the two ultrasonic modes \((k_{z},u_{x})\) a...

Temperature dependence of low-energy phonons in magnetic nonsuperconducting TbNi2B2C

We report temperature dependence of low-energy phonons in magnetic nonsuperconducting TbNi${}_{2}$B${}_{2}$C single crystals measured by inelastic neutron scattering. We observed low-temperature softening and broadening of two phonon branches, qualitatively similar to that previously reported for superconducting $R$Ni${}_{2}$B${}_{2}$C $(R=\text{rare}$ earth, $Y$) compounds. This result suggests that superconductivity in TbNi${}_{2}$B${}_{2}$C compounds is absent not because of weak electron-phonon coupling but as a result of pair breaking due to magnetism.

(Invited) Practical Method and Physics of Evaluation for Vacancy Concentration of Silicon Crystals by Measuring Low-Temperature Elastic Softening

The paper reports the recent progress of our research on the vacancies in boron-doped (B-doped) as-grown silicon crystals of commercial-base quality achieved by means of the low-temperature ultrasonic measurements. The paper also demonstrates how our research-base technique for the vacancy observation is established as the practical tool of evaluating the vacancy concentration of the commercial silicon crystals and wafers. An emphasis is made on the confirmation of the following findings obtained in our previous experiment for the elastic softening by the vacancies in boron-doped silicon crystals: (1) the steep softening that suddenly starts at 2-4 K in the cooling process, and (2) the complete disappearance of the softening by a weak magnetic field of 4 T applied along [111] direction. We further investigate in detail how the low-temperature softening at a fixed temperature responds to the applied magnetic field, to find the following characteristic anisotropy: The manner of disappearance of the softening strongly depends on the direction of the magnetic field. For the magnetic field imposed along [1-10] direction, nearly 60 % of the full softening still remains even at a strong magnetic field of 8 T, in contrast to the case of magnetic field applied along [111] direction.

Low-Temperature Elastic Softening due to Vacancies in Boron-Doped FZ Silicon Crystals

We confirm the following findings obtained in our previous experiment for the low-temperature elastic softening by the vacancies in boron-doped silicon crystals: (1) the steep softening that suddenly starts at 2-4 K in the cooling process, and (2) the complete disappearance of the softening by a weak magnetic field of 4 T applied along [111] direction. We further investigate in detail how the low-temperature softening at a fixed temperature responds to the applied magnetic field, to find the following characteristic anisotropy: The manner of disappearance of the softening strongly depends on the direction of the magnetic field. For the magnetic field imposed along [1-10] direction, nearly 60 % of the full softening still remains even at a strong magnetic field of 8 T, in contrast to the case of magnetic field applied along [111] direction.

Ultrasonic Dispersion in All Elastic Moduli and Softening at Low Temperatures in Filled Skutterudite LaFe4Sb12

To clarify the origin of ultrasonic dispersion due to the so-called rattling motion in LaFe 4 Sb 12 , we measured the temperature dependences of elastic moduli and ultrasonic attenuation. We found the ultrasonic dispersion to be between 35 and 80 K in all elastic moduli, suggesting no-mode-selectivity of ultrasound. Experimental results and theoretically calculated density of states indicate that the d -electronic states of transition metal ions play an important role in ultrasonic dispersion. The theory based on the coupling between an acoustic phonon and some optical phonons interacting with electrons is compatible with no-mode-selective ultrasonic dispersion, and it suggests a stronger electron–phonon coupling in all elastic modes in LaFe 4 Sb 12 . Low-temperature elastic softening was observed in all elastic moduli, and it continues down to 0.4 K. There is a possibility that low-temperature softening originates from quantum tunneling motion or a novel quantum effect of rattling motion.

Vacancies in Growth-Rate-Varied CZ Silicon Crystal Observed by Low-Temperature Ultrasonic Measurements

The low-temperature ultrasonic experiments are performed to measure the distribution of vacancy concentration in the ingot of the Czochralski (CZ) silicon crystal grown with the pulling rate gradually lowered. The elastic softening similar to that we recently found for the floating-zone-grown silicon crystals is observed for the so-called vacancy-rich region of the ingot which contains no voids or dislocation clusters. We further uncover that the interstitial-rich region in the ingot exhibits no such elastic softening, confirming our previous conclusion that the defects responsible for the low-temperature elastic softening are the vacancies. We also disclose that the elastic softening is absent for the ring-like oxidation stacking fault (R-OSF) region of the ingot. The measured distribution of the vacancy concentration indicates that the minority point defects are perfectly cancelled by the majority point defects during the CZ crystal growth.

Novel Ultrasonic Tool for Vacancy Observation in Crystalline Silicon

Low-temperature ultrasonic measurements were employed for observation of isolated vacancies in crystalline silicon. The elastic constants of FZ crystalline silicon revealed low-temperature softening below about 20 K down to base temperature 20 mK in present experiments. The softening of non-doped FZ silicon being free from applied filed indicates a non-magnetic charge state V0 of vacancy. The disappearance of softening in boron-doped FZ silicon under applied magnetic fields up 2T means magnetic charge state V+. This novel ultrasonic tool succeeded in observation of low-temperature softening in perfect crystal region of non-doped CZ silicon ingot indicating distribution of isolated vacancies.

Observation of vacancy in crystalline silicon using low-temperature ultrasonic measurements

We have successfully observed isolated vacancies in crystalline silicon using low-temperature ultrasonic measurements. The floating zone (FZ) silicon exhibits softening in longitudinal elastic constants consisting of transverse C 44 and ( C 11 – C 12 ) /2 in part with decreasing temperature below 20 K down to 20 mK. The applied magnetic fields of up to 16 T at the base temperature 20 mK show no effect on the low-temperature softening in non-doped FZ silicon, while the fields of up to 2 T suppress the low-temperature softening in boron-doped FZ silicon. This experiment suggests that isolated vacancies with non-magnetic charge state V 0 in the non-doped FZ silicon and with magnetic charge state V + in the boron-doped FZ silicon lead to the low-temperature softening. We have also observed the low-temperature softening in the Pv-region of non-doped Czochralski (CZ) silicon ingot, which indicates vacancy distribution. A coupling of electric quadrupoles of triplet state of vacancy orbital to the elastic strains of the sound waves is discussed for description of the low-temperature softening.

Comment on “Observation of Low-Temperature Elastic Softening due to Vacancy in Crystalline Silicon”

Comment on “Observation of Low-Temperature Elastic Softening due to Vacancy in Crystalline Silicon”

Improving the performance of the HYL-III unit at OAO Lebedinskii GOK

The cost of reduced pellets is associated with the quality and productivity of the shaft furnaces, which, in turn, depend on the properties of the initial roasted pellets—their structure and the type of binder. Methods for enhancing the quality of the roasted pellets used in shaft reduction furnaces were discussed in [1‐5]. The most interesting are associated with increase in the softening temperature of the binder, the hot strength, and the reducing properties [6‐8]. This is also associated with increase in temperature in the reduction zone, which provides the basis for the introduction of a technology such as oxygen injection in the shaft furnaces. The HYL-III unit at OAO Lebedinskii GOK has some scope for increase in the reducing-gas temperature, but its utilization is not always possible. Thus, increasing the temperature in the reducing zone above 855 ° C usually disrupts batch descent and discharge of the reduced pellets, on account of pellet deformation. The prevention of such disruptions, which are undesirable and in some cases dangerous, is mainly associated with the properties of the oxidized pellets: first, their degree of oxidation (their FeO content), which is determined by the heat treatment of the batch layer on the conveyer-type roasting machine and significantly influences the reduction process; and, second, the structure of the pellets and their binder, which must be difficult to melt and to reduce. The degree of pellet oxidization determines the minimum deformation of the reduced pellets under load, while the structure of the pellet binder determines how great a role it will play in low-temperature softening of the iron oxides. The effectiveness of this approach was confirmed in the startup of the HYL-III unit in 2001, using pellets with added bauxite. However, with the existing composition of the pelletization batch, whose use has allowed the unit to exceed its design parameters, it is impossible to increase the temperature in the reducing zone above 845‐847 ° C, on account of the high plasticity of the reduced pellets. Therefore, increasing the productivity of the HYL-III unit by further temperature rise in the reducing zone calls for two approaches: modification of the pelletization-batch composition, which permits the formation of stronger and more refractory binder; and optimization of the heat-treatment conditions, so as to form such binder and increase pellet oxidation. In the present work, we investigate these approaches. The role of the rock composition in forming the metallurgical properties of the pellets was outlined in detail in [1, 6‐8]. It is found that an effective means of optimizing the structure and metallurgical properties of the pellets for blast-furnace smelting and reduction is to modify the batch with additives that increase the melting point of the binder and facilitate the formation of more open porosity. The existing binder, corresponding to the Fe 2 O 3 ‐Al 2 O 3 ‐CaO‐SiO 2 system, is created by introducing bauxite as an additive in palletizing the concentrate [6‐8]. Using bauxite increases not only the pellet strength on reduction but also the oxidation rate on roasting and the rate of reduction. To increase the strength of the pellets on reduction, their structure and the binder properties are further modified by means of magnesium-bearing additives, to form the CaO‐MgO‐SiO 2 and MgO‐Al 2 O 3 ‐SiO 2 systems. In laboratory research, the batch for pellet production is modified not with chalk but with Mg-bearing serpentinite‐magnesite, of the following chemical composition: 3.76% Fe tot ; 0.99% FeO; 4.28% Fe 2 O 3 , 27.5% SiO 2 , 0.42% Al 2 O 3 , 5.69% CaO, 32.38% MgO, 0.012% TiO 2 , 0.172% MnO, 0.008% S, 3.21% C, 0.018% P 2 O 5 , 0.004% K 2 O, 0.016% Na 2 O, 22.28% calcination losses. In the laboratory apparatus, to obtain the masstransfer characteristics, characteristics such as the rate constant of pellet reduction at 900 ° C and the strength of pellets partially (up to ~30%) reduced at this temperature are determined. The influence of the batch composition on the shrinkage, sintering properties, and degree

Subsolidus phase equilibria in the PbO-poor part of the TiO2–PbO–SiO2 system and its application in low-temperature thick-film dielectrics

Subsolidus equilibria in the PbO-poor part of the TiO2–PbO–SiO2 diagram were studied with the aim of investigating possible applications for low-temperature thick-film dielectrics. The tie lines are between PbTiO2 and PbSiO3, and between PbTiO3 and SiO2. The results show that the TiO2, when added to low-temperature softening point glasses, reacts with the PbO from the glass, so forming PbTiO3. These results were applied to a low-temperature firing dielectric, consisting of a lead-rich PbO–SiO2–B2O3 glass filled with a TiO2 powder. The conversion of TiO2 to the PbTiO3 crystalline phase was observed above firing temperatures of approximately 600 °C. The kinetics of the reaction depend on the particle size of the TiO2.

Vacancies in defect-free zone of point-defect-controlled CZ silicon observed by low-temperature ultrasonic measurements

The low-temperature ultrasonic measurements are performed for the direct observation of the vacancies in Czochralski-grown (CZ-grown) silicon crystal. The elastic softening similar to that we recently found for the floating-zone-grown (FZ-grown) silicon crystals is observed also for the vacancy-rich region of the defect-free zone (DFZ) in the CZ silicon crystal. We further uncover that both of the interstitial-rich region in the DFZ and the region of the ring-like oxidation-induced stacking faults of the same crystal ingot exhibit no such elastic softening of detectable magnitude, confirming our previous conclusion that the defects responsible for the low-temperature softening are the vacancies. We observe how the vacancy concentration in the DFZ varies along the pulling direction.

Rattling and tunneling of off-center local oscillator in clathrate compounds

We have investigated an off-center local oscillator of a guest atom in cage of clathrate compounds R 3Pd 20Ge 6 ( R = La , Ce, Pr, Nd) and a filled skutterudite PrOs 4Sb 12 using ultrasonic measurements. The observation of ultrasonic dispersions in transverse C 44 mode of R 3Pd 20Ge 6 and in transverse ( C 11 - C 12 ) / 2 mode of PrOs 4Sb 12 revealed the rattling of the off-center oscillator characterized by a relaxation time with Arrhenius-type temperature dependence. A low-temperature softening of C 44 in La 3Pd 20Ge 6 below 3 K down to 20 mK and a softening of ( C 11 - C 12 ) / 2 in PrOs 4Sb 12 above the heavy Fermion superconducting transition indicate the charge fluctuation due to the degenerate off-center oscillators.