scholarly journals Thermal stress, cooling-rate and fictive temperature of silicate melts

2021 ◽  
Vol 176 (10) ◽  
Author(s):  
Sharon L. Webb
Keyword(s):  
Heat Capacity ◽  
Cooling Rate ◽  
Heating Rate ◽  
Calibration Curve ◽  
Silicate Melts ◽  
Internal Stresses ◽  
Heating Rates ◽  
Fictive Temperature ◽  
Slow Cooling ◽  
Cooling Rates

AbstractThe unknown cooling-rate history of natural silicate melts can be investigated using differential scanning heat capacity measurements together with the limiting fictive temperature analysis calculation. There are a range of processes occurring during cooling and re-heating of natural samples which influence the calculation of the limiting fictive temperature and, therefore, the calculated cooling-rate of the sample. These processes occur at the extremes of slow cooling and fast quenching. The annealing of a sample at a temperature below the glass transition temperature upon cooling results in the subsequent determination of cooling-rates which are up to orders of magnitude too low. In contrast, the internal stresses associated with the faster cooling of obsidian in air result in an added exothermic signal in the heat capacity trace which results in an overestimation of cooling-rate. To calculate cooling-rate of glass using the fictive temperature method, it is necessary to create a calibration curve determined using known cooling- and heating-rates. The calculated unknown cooling-rate of the sample is affected by the magnitude of mismatch between the original cooling-rate and the laboratory heating-rate when using the matched cooling-/heating-rate method to derive a fictive temperature/cooling-rate calibration curve. Cooling-rates slower than the laboratory heating-rate will be overestimated, while cooling-rates faster than the laboratory heating-rate are underestimated. Each of these sources of error in the calculation of cooling-rate of glass materials—annealing, stress release and matched cooling/heating-rate calibration—can affect the calculated cooling-rate by factor of 10 or more.

Cooling and Heating Characteristics of Ti-Ni Based Shape Memory Alloy Wire Actuators

2007 ◽  
Vol 124-126 ◽  
pp. 1649-1652 ◽  
Author(s):  
Jung Min Nam ◽  
Jae Hwa Lee ◽  
Yun Jung Lee ◽  
Tae Hyun Nam
Keyword(s):  
Cooling Rate ◽  
Heating Rate ◽  
Vacuum Induction Melting ◽  
Induction Melting ◽  
Heating Rates ◽  
Cooling Rates ◽  
Alloy Wire ◽  
Heating And Cooling ◽  
High Heating ◽  
Better Than

Ti-51Ni(at%) and Ti-40Ni-10Cu(at%) alloy wires with diameters of 0.3mm, 0.5mm and 0.7mm were prepared by drawing the alloy ingots fabricated by vacuum induction melting. Heating rates of the wires were investigated by measuring changes in temperatures of them while applying currents in the range of 1 A and 6 A to them and cooling rates were investigated by measuring changes in temperatures of them after cutting currents. Heating rate increased with increasing the amount of current, while cooling rate was kept constant. Both heating rate and cooling rate increased with decreasing diameter of wire. This suggested that high amount of current and small wire diameter were required for high heating and cooling rate. Comparing Ti-50Ni alloy wires with Ti-40Ni-10Cu alloy wires, heating rates of the latter was faster than that of the former, although cooling rates were almost same. This suggested that Ti-40Ni-10Cu alloy wires is better than Ti-50Ni alloy wires for the applications requiring high actuating rates.

116 IMPROVED SURVIVAL BY CRYOPRESERVING RHESUS MACAQUE (MACACA MULATTA) SPERMATOZOA WITH DIRECTIONAL FREEZING TECHNIQUE

2010 ◽  
Vol 22 (1) ◽  
pp. 217 ◽  
Author(s):  
W. Si ◽  
Y. Lu ◽  
X. He ◽  
S. Ji ◽  
Y. Niu ◽  
...  
Keyword(s):  
Rhesus Monkey ◽  
Cooling Rate ◽  
Sperm Motility ◽  
Genetically Engineered ◽  
Human Diseases ◽  
Slow Cooling ◽  
Cooling Rates ◽  
Important Species ◽  
Directional Freezing ◽  
Acrosomal Integrity

A significant increase in nonhuman primate models of human diseases will be expected in the near future since the successes in production of genetically engineered rhesus monkey models of human diseases. Sperm banking can provide an effective way to preserve valuable genetic resources. Our objective was to (1) develop a protocol using directional freezing technique (DFT) for rhesus monkey spermatozoa cryopreservation, which allows precise control of the velocity and the morphology of the ice-front propagation by transferring the tubes loaded with 2 mL sperm samples at a controllable velocity through two separate chambers with controllable temperature settings, and (2) achieve survival rate that was higher than that achieved with conventional freezing technique (CFT), by which sperm samples were cryopreserved in 0.25 mL straws with liquid nitrogen vapor in a styrofoam box. Sperm motility, acrosomal integrity, and in vitro fertilization (IVF) assay were used to assess the function of frozen-thawed spermatozoa. Data were analyzed by ANOVA and Fisher protected LSD test. Experiment 1 was aimed at optimizing the cooling rate using DFT. Tubes were frozen using the multi-thermal gradient freezing device (MTG 516, Harmony CryoCareTM, IMT Ltd.) at fast (16°C/min), medium (12°C/min), and slow (7°C/min) cooling rates, which corresponded to the transferring velocities (2.5, 1.5, and 0.5 mm s-1, respectively). The results showed that spermatozoa frozen at fast and medium cooling rates showed significantly higher frozen-thawed motility than those frozen at slow cooling rate (61% and 59% v. 50%, P < 0.05). However, no difference was observed on sperm acrosomal integrity among the experimental groups (84, 80, and 78%, respectively, P > 0.05). The purposes of Experiment 2 were determined to examine if using DFT at the optimized cooling rate (12°C/min) can improve the cryo-survival of rhesus monkey spermatozoa compared with CFT. Our results showed that spermatozoa cryopreserved by using DFT achieved significantly higher frozen-thawed sperm motility that those cryopreserved by using CFT (64 v. 54%, P < 0.05). However, no difference was observed on acrosomal integrity between spermatozoa cryopreserved by DFT and CFT (84 and 83%, respectively; P > 0.05). The function of spermatozoa cryopreserved by using DFT was further evaluated by IVF. Females were treated with rhFSH twice-daily for 8 days after the onset of menses and following a treatment of hCG injection on Day 9. Cumulus-oocyte complexes were collected by laparoscopic follicular aspiration 32 h later. Of the inseminated oocytes, 79% were fertilized and 90 and 53% of the resulting zygotes developed into 2-cell and blastocysts, respectively. The fertilization rate was lower and the blastocyst rate was slightly higher than our previous report when fresh spermatozoa were used for IVF (94 and 52%, respectively). Our results indicate that spermatozoa of rhesus monkeys can be effectively cryopreserved using DFT in large volume. This finding provided a new and effective way for genetics preservation purposes in this important species.

Influence of Cooling Rates on Phase Transitions of Bent-Core Liquid Crystal 1,3-Phenylene-bis[4-(hexylcarboyloxyl)benzylideneamine]

2010 ◽  
Vol 428-429 ◽  
pp. 247-250 ◽  
Author(s):  
Yuan Ming Huang ◽  
Qing Lan Ma ◽  
Bao Gai Zhai
Keyword(s):  
Differential Scanning Calorimetry ◽  
Phase Transitions ◽  
Liquid Crystal ◽  
Optical Microscopy ◽  
Cooling Rate ◽  
Scanning Calorimetry ◽  
Slow Cooling ◽  
Cooling Rates ◽  
Polarized Optical Microscopy ◽  
Fast Cooling

The influence of cooling rate on the phase transitions of a three-benzene-ring containing bent-core liquid crystal 1,3-phenylene-bis[4-(hexylcarboyloxyl)benzylideneamine] has been investigated by means of differential scanning calorimetry and polarized optical microscopy. Our results show that the cooling rates in the second cooling run pose significant effects on the phase transitions of the bent-core liquid crystal despite the cooling rates in the first cooling run pose little effects on the phase transitions. In the second cooling run, the banana phases survived only when the cooling rates were in the range of 14~15oC/min whereas both slow cooling rates which were less than 13oC/min and fast cooling rates which were higher than 16oC/min made the banana phases disappeared.

Achieving the Dual Phase Structure in Low Alloyed Steel with Slow Cooling Rate

2008 ◽  
Vol 575-578 ◽  
pp. 1117-1122
Author(s):  
Tarja Jäppinen ◽  
Seppo Kivivuori
Keyword(s):  
Cooling Rate ◽  
Phase Structure ◽  
Steel Wire ◽  
Optical Microscope ◽  
Carbon Steels ◽  
Alloying Elements ◽  
Dual Phase ◽  
Low Carbon ◽  
Slow Cooling ◽  
Cooling Rates

In steel wire processing it is difficult to reach a homogenous structure throughout the cross-section of the wire particularly in greater diameters. One alternative for producing a homogenous structure is to find a cooling path with a wide transformation temperature range. Fully austenite steel wire rolled at high temperatures can be decomposed into ferritic-martensitic dual phase structure using relatively slow cooling rates. Test materials were low alloyed low carbon steels with variations in alloying elements. Gleeble-1500 thermomechanical simulator was utilised to study the effect of cooling rate on decomposition of austenite after deformation. The microstructures were studied with an optical microscope. In certain low alloyed steels slow cooling rates eliminate the bainite transformation and instead martensite is formed. The final microstructure depends mainly on the carbon content but also on the amount of other alloying elements and their effects on the austenite phase.

Effect of Molecular Weight on Glass Transition by Differential Scanning Calorimetry

1974 ◽  
Vol 52 (18) ◽  
pp. 3170-3175 ◽  
Author(s):  
Louis-Philippe Blanchard ◽  
Jean Hesse ◽  
Shadi Lal Malhotra
Keyword(s):  
Molecular Weight ◽  
Differential Scanning Calorimetry ◽  
Heat Capacity ◽  
Glass Transition ◽  
Heating Rate ◽  
Low Molecular Weight ◽  
Glass Transitions ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Polystyrene Sample

The influence of molecular weight (900 to 1.8 × 106) on the glass transition temperature of low polydispersity polystyrene (anionically prepared) has been studied by differential scanning calorimetry at heating rates of 5 to 80 °C min−1. Over the range of molecular_weight studied, and at an extrapolated heating rate of 1 °C min−1,[Formula: see text] A thermally prepared polystyrene sample ([Formula: see text]and Pd = 3.2) showed a Tge value of 93 °C, some 10° below the value predicted by the above equation. Low molecular weight species in the highly polydisperse sample are believed to be responsible for the discrepancy. The changes in heat capacity brought about by the glass transitions are accompanied in all cases on heating by an endothermic peak and this regardless of the heating rate (even extrapolated to 1 °C min−1) or the molecular weight of the sample, suggesting that the glass transition phenomenon encountered with polystyrene is a process involving a positive heat effect.

Validation of a Simple Two-Point Method To Assess Restaurant Compliance with Food Code Cooling Rates

2020 ◽  
Vol 84 (1) ◽  
pp. 6-13
Author(s):  
MATTHEW J. IGO ◽  
NICOLE HEDEEN ◽  
DONALD W. SCHAFFNER
Keyword(s):  
Cooling Rate ◽  
Screening Tool ◽  
Point Method ◽  
Cooling Curves ◽  
Simple Linear Regression ◽  
Point Model ◽  
Slow Cooling ◽  
Cooling Rates ◽  
Novel Method ◽  
Almost All

ABSTRACT Outbreaks from improperly cooled foods continue to occur despite clearly described Food Code cooling guidelines. It is difficult for regulators to enforce these guidelines because they are typically in an establishment for less than the 6 h needed to document proper cooling. Prior research proposed using a novel method to estimate cooling rates based on two time-temperature points, but this method has not yet been validated. Time-temperature profiles of 29 different foods were collected in 25 different restaurants during cooling. Cooling curves were divided into two categories: typical (21 foods) and atypical (eight foods) prior to further analysis. Analysis of the typical cooling curves used simple linear regression to calculate cooling rates. The atypical cooling profiles were studied using Monte Carlo simulations of the cooling rate. Almost all linearized typical cooling curves had high (&gt;0.90) R2 values. Six foods with typical cooling profiles that did not pass Food Code cooling times were correctly identified by the two-point model as having slow cooling rates. Three foods that did not pass Food Code cooling times were identified by the two-point model as having marginal cooling rates. Ten of 12 foods identified by the two-point model as having acceptable cooling rates met Food Code cooling times. Most (six of eight) foods that were considered to have atypical cooling curves failed to meet the Food Code cooling times. The two-point model was also able to determine whether these foods would fail based on Food Code guidelines depending upon the simulation criteria used. Our data show that food depth has a strong influence on cooling rate. Containers with a food depth ≥7.6 cm (3 in.) were more likely to have cooling rates slower than the U.S. Food and Drug Administration Model Food Code cooling rate. This analysis shows that the two-point method can be a useful screening tool to identify potential cooling rate problems during a routine restaurant inspection visit. HIGHLIGHTS

scholarly journals Melting and crystallization DSC profiles of different types of meat

2017 ◽  
Vol 23 (4) ◽  
pp. 473-481 ◽  
Author(s):  
Danica Savanovic ◽  
Radoslav Grujic ◽  
Sladjana Rakita ◽  
Aleksandra Torbica ◽  
Ranko Bozickovic
Keyword(s):  
Cooling Rate ◽  
Heating Rate ◽  
Melting Process ◽  
Longissimus Dorsi ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Beef Meat ◽  
Freezable Water ◽  
Different Types ◽  
Thermo Physical Properties

The aim of this study was to test the influence of scanning rate and meat type on the thermo-physical properties of meat and content of the freezable water in frozen meat, using differential scanning calorimetry (DSC). In this study, three types of meat were investigated: beef (M. Longissimus dorsi), pork (M. Longissimus dorsi), and chicken meat (Pectoralis major). The cooling rate affected the onset (Tcon), peak (Tc) and end (Tcend) temperatures of crystallization process of beef meat (p < 0.05). Decreasing cooling rate from 20 to 2?C/min resulted in significant (p < 0.05) change of the crystallization enthalpy (?Hc) of beef meat, from -220.17 to -168.20 J/g, respectively. Reduction of the heating rate caused significant (p < 0.05) decrease in enthalpy of melting (?Hm) for beef meat, from 228.87 to 161.13 J/g. The heating rate affected the peak (Tm) and end temperatures (Tmend) of melting process of beef meat (p < 0.05). The type of meat did not have effect on ?Hc and ?Hm as well as temperature of crystallization (Tcon, Tc and Tcend) and temperature of melting (Tm and Tmend) in meat. Significant (p < 0.05) change in freezable water content were recorded between heating rate 20 ?C/min and other heating rates, for all three meat types.

The survival of Escherichia coli from freeze–thaw damage: permeability barrier damage and viability

1975 ◽  
Vol 21 (11) ◽  
pp. 1724-1732 ◽  
Author(s):  
Peter H. Calcott ◽  
Robert A. MacLeod
Keyword(s):  
Escherichia Coli ◽  
Cooling Rate ◽  
Permeability Barrier ◽  
Freezing And Thawing ◽  
Slow Cooling ◽  
Cooling Rates ◽  
Rate Range ◽  
Permeability Damage ◽  
Extent Of Damage ◽  
Glucose 6 Phosphate Dehydrogenase

The effect of cooling rate and subsequent warming rate on survival of lactose-limited Escherichia coli was investigated. As previously reported, in the slow cooling rate range, a peak of survival was noted at 8 °C/min with survival decreasing as the cooling rate was increased or decreased from this value. Minimal survival was noted at 100 °C/min; increasing the cooling rate above 100 °C/min increased survival. At cooling rates greater than 200 °C/min, the survival became dependent on subsequent warming rates.Permeability damage, as measured by release of UV-absorbing material, potassium and β-galactosidase, and increased accessibility of glucose-6-phosphate dehydrogenase to its substrates, was dependent on the cooling rate when cells were frozen in either water or saline. For cooling rates less than about 8 °C/min, there was minimal permeability damage to cells frozen in water. However, at rates greater than this value, damage and viability were related; the lower the viability the more the damage to the permeability barrier. The relationship was strengthened by the observations that protectants which increased survival reduced damage as well and that at ultrarapid cooling rates where survivals were dependent on warming rates, the extent of damage was likewise dependent on the warming rate.Saline frozen cells were damaged by freezing and thawing more than comparable water-frozen cells over the whole cooling rate range. At cooling rates less than 8 °C/min, frozen in water, permeability damage of cells frozen in saline increased as the cooling rate decreased. As the cooling rate was increased from 8 °C/min, the damage increased as viability decreased.The relevance of these findings to the two-factor hypothesis of cell death is discussed.

Influence of Quenched Defects on Thermal Expansion and Glass Transition in Diopside (CaMgSi2O6)

1985 ◽  
Vol 61 ◽  
Author(s):  
S. V. Raman
Keyword(s):  
Thermal Expansion ◽  
Glass Transition ◽  
Relaxation Rate ◽  
Heating Rate ◽  
Transition Region ◽  
Expansion Coefficient ◽  
Supercooled Liquid ◽  
Liquid Region ◽  
Heating Rates ◽  
Fictive Temperature

ABSTRACTThis study was conducted to investigate the possible occurrence of non-equilibrium defects and their influence on glass transition in a relatively depolymerized silicate structure. The glass of interest has an average bridging/non-bridging oxygen ratio of 1:2. It was prepared by fast quenching and was examined in the alumina pushrod dilatometer at heating rates of 5 and 15 ° C/min. The thermal expansion decreases with increase in the rate of heating although, the expansion coefficient is independent of heating rate at temperatures below the transition region. In the supercooled liquid region the expansion coefficient is higher at the higher heating rate. In the transition region it is both heating rate and temperature dependent. Three distinct temperatures are revealed in the transition region from temperature dependence of expansion rate. Their dependence on heating rate is described by a low activation energy of about 3Kcal/mol for transition. The single parameter fictive temperature is not in agreement with kinetics of relaxation due to a wide temperature interval of 600 to 750° C for the transition region. The transition kinetics is perhaps enhanced by the presence of defects whose annealing is impedded with increase in heating rate. Thus under the influence of higher defect concentration a spiked change in relaxation rate occurs and points to the presence of a critical temperature in the transition region. In the neighborhood of this temperature the relaxation rate of supercooled liquid is significantly lower than its solid analog. For short relaxation times in the supercooled liquid thermal expansion coefficient is relatively higher at the higher heating rate.

scholarly journals Determination of Eutectoid Transformation Temperatures in Ductile Cast Iron

2015 ◽  
Vol 15 (4) ◽  
pp. 51-54 ◽  
Author(s):  
A.W. Orłowicz ◽  
A. Trytek ◽  
M. Mróz ◽  
M. Tupaj
Keyword(s):  
Cast Iron ◽  
Cooling Rate ◽  
Ductile Cast Iron ◽  
Eutectoid Transformation ◽  
Heating Rates ◽  
Cooling Rates ◽  
Metallographic Examination ◽  
Transformation Temperatures ◽  
Rate Of Cooling

Abstract The paper proposes a methodology useful in verification of results of dilatometric tests aimed at determination of temperatures defining the start and the end of eutectoid transformation in the course of ductile cast iron cooling, based on quenching techniques and metallographic examination. For an industrial melt of ductile cast iron, the effect of the rate of cooling after austenitization at temperature 900°C carried out for 30 minutes on temperatures TAr1start and TAr1end was determined. The heating rates applied in the study were the same as the cooling rates and equaled 30, 60, 90, 150, and 300°C/h. It has been found that with increasing cooling rate, values of temperatures TAr1start and TAr1end decrease by several dozen degrees.

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