Sensitivity Of Heating Rate Research Articles

Reducing the annealing heating rate sensitivity of Fe83.5Si3B10P2Cu1.5 soft magnetic nanocrystalline alloy by adjusting the melt spinning cooling rate

Reducing the annealing heating rate sensitivity of Fe83.5Si3B10P2Cu1.5 soft magnetic nanocrystalline alloy by adjusting the melt spinning cooling rate

Heating Rate Sensitive Polyethylene Terephthalate.

Smart materials react to external triggers by changing size, color, mechanical properties, or permeability. The next generation of smart materials will be able to not only recognize and react to external triggers but also to their dynamics. The only existing example of such a material is heating rate-sensitive polymorphous cross-linked syndiotactic polypropylene. This study presents a new principle of a heating rate-sensitive material on the example of cross-linked and fully amorphous quenchable semi-crystalline polyethylene terephthalate (x-PET). The x-PET is stretched to high elongation above its melting temperature and constrained quenched to a fully amorphous state. Then the polymer is heated to 120-170°C with different heating rates. Due to its heating-rate sensitivity, x-PET shrinks to different stabilized lengths dependent on the heating rate. The new length can be used to read out the heating rate and to specifically answer to this by mechanically switching a process. Detailed analytics of this process reveal that amorphous stretched x-PET is starting the retraction above Tg and simultaneously stopping it by crystallization. The different rates of these processes result in the heating rate sensitivity of x-PET.

High Bs Fe-B-P-C-Cu nanocrystalline alloy with longtime annealing stability and low heating rate sensitivity

To solve the sensitivity of soft magnetic properties of Fe-B-P-C-Cu alloy system without transition metal addition on heat treatment process parameters, the effect of P content on the heat treatment process parameters and soft magnetic properties of Fe83B12-xPxC4Cu1 (x = 3, 5 and 7) alloys have been investigated. It is found that increasing P can effectively reduce the sensitivity of microstructure and soft magnetic properties on the annealing holding time (th). The th of Fe83B7P5C4Cu1 and Fe83B5P7C4Cu1 alloys can be extended to 60 min compared to the th of 6 min for Fe83B9P3C4Cu1 alloy to obtain a low coercivity (Hc) below 8.5 A/m. However, too high P content will reduce the stability of residual amorphous phase and shorten the optimal th. The results indicate that increase of P can also reduce the sensitivity of microstructure and soft magnetic properties on the heating rate (β). The β of Fe83B7P5C4Cu1 and Fe83B5P7C4Cu1 alloys can be as low as 40 K/min and 20 K/min to obtain high saturation magnetic flux density (Bs) of 1.80 T and 1.73 T, and low Hc of 8.4 A/m and 8.1 A/m, respectively.

Burst-like shape recovery and caloric effects in Ni–Fe–Ga–Co single crystalline shape memory alloys

Shape recovery in conventional shape memory alloys is typically a relatively slow process showing low heating rate sensitivity. In contrast to that, some shape memory alloys such as Ni–Fe–Ga–Co, Cu–Al–Ni, Cu–Al–Fe–Mn can exhibit the effect of burst-like shape recovery when the original shape is restored almost instantaneously in a very narrow temperature range. Here we report on an abnormal stress-strain behavior of Ni49Fe18Ga27Co6 single crystals upon uniaxial compression along the [110] axis and caloric effects during burst-like recovery of shape memory strain in the samples. Differential scanning calorimetry (DSC) study revealed that DSC peak shifts to lower temperatures with increasing heating rate.

The effect of Ag addition on the non-isothermal crystallization kinetics and fragility of Zr56Co28Al16 bulk metallic glass

The non-isothermal crystallization kinetics and fragility of Zr56Co28Al16 and Zr56Co24Ag4Al16bulk metallic glasses (BMGs) were studied by differential scanning calorimetry (DSC). The X-ray diffraction (XRD), transmission electron microscopy (TEM) and microhardness test were used to investigate the glassy alloys structure. DSC traces exhibited two crystallization processes for both alloys. The activation energies of characteristic temperatures were obtained by Kissinger and Ozawa methods. Also, the heating rate sensitivity of characteristic temperatures was determined. The Ag-bearing Zr-based BMG presented higher activation energies and lower heating rate sensitivity in regard to characteristic temperatures, indicating a higher stabilization of the supercooled liquid, which can be correlated with the existence of strong icosahedral short range order (ISRO) clusters in the structure. In addition, the local Avrami exponents at various heating rates were calculated by the Johnson–Mehl–Avrami equation. The n value variations for each crystallization process pursued almost similar trends for both alloys with n>2.5, revealing that the transformation kinetics is dominated by a diffusion-controlled three-dimensional growth, as well as an increase in the nucleation rate. Moreover, both BMGs were classified into “strong glasses”, depending on the fragility index calculated values.

Effect of Chemical Reaction Rates on Aeroheating Predictions of Reentry Flows

The present work deals with the sensitivity of aero-heating predictions to variations in chemical reaction rates in high enthalpy flows over re-entry capsules. With in this scope, numerical simulations are performed by varying the reaction rate constants over their uncertainty range. FIRE II re-entry capsule at 35 km altitude is chosen as the test case. At these conditions, recombination of oxygen atoms is the dominant chemical reaction in the thermal boundary layer next to the wall. The flow solutions computed by altering the reaction rates in this region are carefully analyzed to understand the physical effects that influence the surface heat transfer rate. It is found that the chemical state of the gas i.e. equilibrium, non-equilibrium or frozen, and the extent of recombination reactions in the boundary layer are the critical factors that determine the sensitivity of the heating rate to variations in the reaction rate constants. The analysis is carried out at different points on the vehicle surface, and the heating rate sensitivity is found to be the highest at the shoulder. This is due to the non-equilibrium chemical state of the gas prevailing in the shoulder expansion region. By comparison, the equilibrium state of the gas on the forebody and the frozen chemistry on the afterbody result in lower sensitivity of the heating rate to variations in the chemical reaction rates.

Effects of Heating Rate and Ion-Exchangeable Cations on the Pyrolysis Yields from a Victorian Brown Coal

A Victorian low-rank coal (Loy Yang) was acid-washed and ion-exchanged with Na and Ca to prepare the H-form, Na-form, and Ca-form coal samples. Two more H-form samples were also prepared by rewashing the Na-form and Ca-form samples with acid. These coal samples were pyrolyzed in a wire-mesh reactor where the secondary reactions of the evolved volatiles were minimized. The ion-exchanged coal samples were found to give very different tar yields from those of the raw coal samples. While the tar yields from the pyrolysis of the raw and H-form coal samples were observed to be very sensitive to changes in heating rate, the tar yields from the Ca-form and Na-form samples showed little heating rate sensitivity. Unlike higher rank coals studied previously, the tar yields from the pyrolysis of the raw coal and the H-form coal samples at 600 °C were found to increase much more than the corresponding increases in the total volatile yields as the heating rate was increased from 1 to 2000 K s-1. Reexchanging Na in the ...

Radiative sensitivities of tropical anvils to small ice crystals

Stratiform anvils in the upper tropical troposphere were simulated to determine the sensitivities of their radiative properties to the presence of small ice crystals. Cloud evolution was modeled in a one‐dimensional (vertical) framework incorporating an updraft, deposition, sublimation, sedimentation, nucleation, and radiation. The sensitivities of cloud radiative forcing, albedo, emissivity, and heating rate were derived from a test that included and then excluded the presence of numerous small crystals. These crystals sizes (3 < L < 20 μm) have been measured in recent observations but are smaller than the detection limit of most past observations. The shortwave forcing and albedo were very sensitive to the presence of the small crystals, even though these crystals accounted for less than 2% of total cloud mass. For optically thick anvils the longwave forcing and emissivity were, in general, much less sensitive to the small ice crystals than their shortwave counterparts. Radiative treatments assuming a hexagonal crystal habit yielded the same sensitivities as the spherical habit. The results agreed with previous studies in that the increased backscatter from hexagonal crystals enhanced the planetary albedo by ∼10–15%. The heating rate sensitivity to the small crystals depended on vertical location within the cloud and showed cancelation between the longwave and the shortwave heating perturbations. The small crystals changed heating rates by up to 50% at cloud top and base.

The Influence of RTA Heating Rate on the TiSi2 and Si - TiSi2 Interface Roughness

ABSTRACTIn TiSi2 metallized devices, the second distribution of leakage current (I>lμA) is caused by the Si/TiSi2 interface roughness. In this work, 40gm thick Ti films are sputtered onto Si waters. RTA was done in N2 atmosphere. Heating rates of 0, 0.5, 1, 5, and 100°C S−-1 are examined. Samples are characterized by AFM, RBS, XRD and laser light scattering methods. The parameters related to roughness are heating rate sensitivity and oxygen contamination which decreases the roughness on the interface.

Heating Rates in Flexible Packages Containing Entrapped Air During Overpressure Processing

ABSTRACTExperiments were performed in two steam/air retorts and one water immersion retort to test the influence of included air on heating rate index (fh) values at the center of thin plastic bricks packaged in retort pouches and processed under various temperature and overpressure conditions. In general, high air overpressures (>80 kPa) allowed up to 30 mL air to be included with no detrimental effect on heating rates; however, even small amounts of entrapped air (<5 mL) degraded heat transfer when processed at low air overpressures (<40 kPa). Processing medium and retort type were important factors in the sensitivity of heating rate to increases of air volumes beyond a threshold value.