Compact Density Research Articles

Effect of different pre-existing dislocation densities on the microstructure evolution of W-0.5ZrC alloy during in-situ He+ irradiation

The evolution of dislocation loops and helium bubbles in W-0.5ZrC alloy with different pre-existing dislocation densities was investigated by in-situ transmission electron microscopy during 30 keV He+ irradiation at 800 °C. The nucleation, migration, aggregation, and growth of dislocation loops and helium bubbles occurred with the whole irradiation process. The variation trends of average size and volume number density of dislocation loops and helium bubbles with the increase of irradiation dose in the regions with different pre-existing dislocation densities were obtained. It was found that the growth of dislocation loops was inhibited in the region with a low pre-existing dislocation density (about 5.2 × 1013 /m2), and the nucleation of dislocation loops was inhibited in the region with the dispersed medium density (about 1.6 × 1014 /m2, dislocations were crossed but dispersed), while both the nucleation and growth of dislocation loops were inhibited in the region with the compact medium density (about 1.5 × 1014 /m2, dislocations were crossed and compact). During the irradiation process, the pre-existing dislocations would interact with the irradiation-induced dislocation loops and helium bubbles, but their influence weakened with the increase of irradiation dose, and finally resulted in the disappearance or deformation of pre-existing dislocations. The irradiation hardening caused by dislocation loops and helium bubbles was increased with the increase of irradiation dose, and the corresponding mechanism was analyzed.

Processing and Properties of Tungsten-Steel Composites and FGMs Prepared by Spark Plasma Sintering

Tungsten is the prime candidate material for the plasma-facing components of fusion reactors. For the joining of tungsten armor to the cooling system or support structure, composites or graded interlayers can be used to reduce the stress concentration at the interface. These interlayers can be produced by several technologies. Among these, spark plasma sintering appears advantageous because of its ability to fabricate fully dense parts at lower temperatures and in a shorter time than traditional powder metallurgy techniques, thanks to the concurrent application of temperature, pressure, and electrical current. In this work, spark plasma sintering of tungsten-steel composites and functionally graded layers (FGMs) was investigated. As a first step, pure tungsten and steel powders of different sizes were sintered at a range of temperatures to find a suitable temperature window for fully dense compacts. Characterization of the sintered compacts included structure (by SEM); porosity (by the Archimedean method and image analysis); thermal diffusivity (by the flash method) and mechanical properties (microhardness and flexural strength). Compacts with practically full density and fine grains were obtained; while the temperature needed to achieve full sintering decreased with decreasing powder size (down to about 1500 °C for the 0.4 μm powder). For fully sintered compacts, the hardness and thermal diffusivity increased with decreasing powder size. Composites with selected tungsten/steel ratios were produced at several conditions and characterized. At temperatures of 1100 °C or above, intermetallic formation was observed in the composites; nevertheless, without a detrimental effect on the mechanical strength. Finally, the formation of graded layers and tungsten-steel joints in various configurations was demonstrated.

Effects of the confinement potential parameters and optical intensity on the linear and nonlinear optical properties of spherical quantum dots

We study the linear and nonlinear optical properties of a spherical GaAs quantum dot with screened modified Kratzer potential (SMKP) by solving the time-independent Schrödinger wave equation using the diagonalization method. The obtained electronic properties of the system alongside the compact density formalism are used to evaluate the linear, third-order nonlinear and total optical absorption coefficients and change in the relative refractive index of the system. We show that the confinement potential parameters and optical intensity significantly affects the behaviour of absorption coefficients and refractive index changes. It is important to note that the findings of this study will find application in optoelectronics and related areas.

MAX phase Ti2AlN synthesis by reactive sintering in vacuum

The synthesis of MAX phase Ti2AlN from several mixtures of Ti, Al, TiN, and AlN powders by vacuum sintering of greensamples in the form of dense compacts, bulk powder in silica tubes, and plain layer in a closed rectangular molybdenum boat was studied upon variation in charge composition and sintering temperature Ts. The sintering of 2 : 1 Ti–AlN mixture was carried out at 1100, 1200, 1300, 1400, and 1500 °С with exposure time of 60 min. The largest MAX phase content (94 wt.%) was reached at Ts = 1400 °С. The sintering of 1 : 1 TiAl : TiN composition at the same temperature gave 93 wt.% Ti2AlN. The best result (singlephase Ti2AlN in a 100-% yield) was achieved upon the sintering of 1 : 1 : 1 Ti–Al–TiN composition at Ts = 1400 °С. The scalability of our process was checked by the fabrication of a large (0.5 kg) and uniform cake of single-phase Ti2AlN. In experiments we used green samples with shielded lateral surface (bulk powder in silica tubes, plain layer in a closed molybdenum boat) and without shield (dense compacts). It has been shown that shielding of Ti–Al–TiN samples restricts the escape of Al vapor from a sintered mixture, thus providing more favorable conditions for the synthesis of single-phase Ti2AlN. Our process can be readily recommended for practical implementation.

The Electrophoretic Deposition of Nanopowders Based on Yttrium Oxide for Bulk Ceramics Fabrication

In the present work, a study was carried out to investigate the key factors that determine the uniformity, mass, thickness, and density of compacts obtained from nanopowders of solid solutions of yttrium and lanthanum oxides ((LaxY1−x)2O3) with the help of the electrophoretic deposition (EPD). Nanopowders were obtained by laser ablation of a mixture of powders of yttrium oxide and lanthanum oxide in air. The implemented mechanisms of the EPD and factors of stability of alcohol suspensions are analyzed. It has been shown that acetylacetone with a concentration of 1 mg/m2 can be used as a dispersant for stabilization of isopropanol suspensions of the nanoparticles during the EPD. It was shown that the maximum density of dry compacts with a thickness of 2.4 mm reaches 37% of theoretical when EPD is performed in vertical direction from a suspension of nanopowders with addition of acetylacetone.

Pore structure effects on the water retention behaviour of a compacted silty sand soil subjected to drying-wetting cycles

Most of the previous studies on the effects of pore structure on soil water retention behaviour are limited to a single drying and wetting cycle. This study evaluated the effects of pore structure on water retention behaviour for specimens prepared at different pore structures of similar density, subjected to drying-wetting cycles. Specimens were compacted at two density states equivalent to loosely compacted fill slopes (80% relative compaction, e = 0.78), and densely compacted slopes or subgrade compaction specifications (95% relative compaction, e = 0.50) at different water contents on the wet side (20%) and dry side (10%) of the optimum water content. The results show that loosely compacted specimens prepared on the wet side have a lower water retention ability due to the larger formed macropores. They also show a significantly higher degree of hysteresis which decreases with drying and wetting cycles. For loosely compacted specimens, there is a higher increase in water retention ability with cycles for specimens prepared on the dry side, due to more drying and wetting-induced pore evolution and volumetric changes. Increasing compaction density results in a higher water retention ability but reduces the number of cycles needed to achieve water retention equilibrium with drying-wetting cycles, subsequently behaving as scanning curves. This is attributed to the less pore evolution and smaller volumetric strain at lower void ratios. Pore structure effects on water retention behaviour subjected to drying-wetting cycles should be considered in civil engineering designs for earth structures, such as loosely compacted fill materials.

Recombination lines and maser effects

AbstractMaser effects occur in recombination lines when the plasma departs from local thermodynamic equilibrium (LTE). Its consequence is not as dramatic as that found in molecular masers, and therefore it is more difficult to recognize. Besides, it occurs in compact high density regions, and its lines fall at millimeter and submillimeter wavelengths, only recently available with good angular resolution. This review will focus on the theoretical aspects of maser recombination lines and on the recent detection of these masers in different astronomical objects.

Revealing Li-ion diffusion kinetic limitations in micron-sized Li-rich layered oxides

• Li + diffusion kinetic limitations have great influence on electrochemical performance • Diffusion coefficient and diffusion distance have synergistic effect • Micron-sized Li-rich materials tend to have uneven lithium concentration • Reasonable structural design is very important Micron-sized cathode materials can usually alleviate the surface/interface side reaction to enhance cycling stability and endure high pressure to achieve a higher compacted density. However, the poor Li + transport kinetic properties in micron-sized Li-rich layered oxides impede their practical applications. Here, we find a faster Li + diffusion coefficient with the order of magnitudes of about 10 −12 cm 2 s −1 in micron-sized grains (compared with nano-sized grains about 10 −14 cm 2 s −1 ). By contrast, much lower initial capacity can be achieved in micron-sized grains. Simulated by finite element analysis, the increased diffusion distance would yet result in an extremely uneven Li + concentration distribution during the charge-discharge process between surface and bulk. The undesired Li + gradient distribution results in an accumulation of strain stress inside the grains during cycling, which also consequently contributes to an unsatisfied capacity retention of 78.4% as well as a rapid voltage decay of 738 mV under 0.2C after 200 cycles in micron-sized grains. This work provides a research direction to construct a novel structure with Li + homogeneous distribution in micron-sized Li-rich layered oxides. The Li + diffusion kinetic limitations directly results in the poor electrochemical performance of large-sized Li-rich layered oxides.

Technical Analysis of Soil Cement as A Construction Material Applied in Rural Houses

The project reveals the properties of soil cement as a construction material in rural houses. The context of this research was in Pilcomayo district, Huancayo, Peru, due to the high abundance of poor constructions without any security or comfort for the inhabitants of the area. In the experiment, the technical analysis of the soil cement was carried out with doses of 5%, 9%, 13%, 17% and 21% of cement, applying tests of Granulometry, Compaction, Compression and Durability established by the Portland Cement Association. It was found that the soil of the district has an efficient granulometry for the use of soil cement, and also that it has a resistance of 129.42 kg-f/cm² with 21% cement at 28 days of curing. The lab test results also showed that the cement soil loses just 4.22% in weight with 17% of cement in the durability test, as well as with this same percentage, the soil cement presents a higher maximum compaction density of 2,255 g/cm³. These results propose alternative applications for soil cement according to their resistance, granulometry and durability. According to the Peruvian Technical Standard, the minimum f'c for floor concrete base is 100 kg/cm², a dosage of 19% cement was proposed for this element, and for brick masonry the minimum f'c is 50kg/cm², so it was proposed 12% cement to meet this requirement, in addition, the soil cement was proposed as a slope protection with 17% cement since it achieved good results in the durability test.

A bi-functional strategy involving surface coating and subsurface gradient co-doping for enhanced cycle stability of LiCoO2 at 4.6 V

Layered LiCoO2 (LCO) acts as a dominant cathode material for lithium-ion batteries (LIBs) in 3C products because of its high compacted density and volumetric energy density. Although improving the high cut-off voltage is an effective strategy to increase its capacity, such behavior would trigger rapid capacity decay due to the surface or/and structure degradation. Herein, we propose a bi-functional surface strategy involving constructing a robust spinel-like phase coating layer with great integrity and compatibility to LiCoO2 and modulating crystal lattice by anion and cation gradient co-doping at the subsurface. As a result, the modified LiCoO2 (AFM-LCO) shows a capacity retention of 80.9% after 500 cycles between 3.0 and 4.6 V. The Al, F, Mg enriched spinel-like phase coating layer serves as a robust physical barrier to effectively inhibit the undesired side reactions between the electrolyte and the cathode. Meanwhile, the Al, F, Mg gradient co-doping significantly enhances the surficial structure stability, suppresses Co dissolution and oxygen release, providing a stable path for Li-ions mobility all through the long-term cycles. Thus, the surface bi-functional strategy is an effective method to synergistically improve the electrochemical performances of LCO at a high cut-off voltage of 4.6 V.

A Paradigm of Calendaring‐Driven Electrode Microstructure for Balanced Battery Energy Density and Power Density

AbstractThe microstructure of an electrode plays a critical role in the electrochemical performance of lithium‐ion batteries, including the energy and power density. Using a micrometer‐scale Wadsley–Roth phase TiNb2O7 active material with Li intercalation chemistry as a model system, the relationship between electrochemical performance and microstructure of calendared electrodes with same mass loading but different electrode parameters is studied by both experimental investigation and theoretical modeling, providing a paradigm of calendaring‐driven electrode microstructure for balanced battery energy density and power density. Along with the reduction in porosity, ion and electron diffusion distance decreases, which is beneficial for charge transfer and rate capability. Nevertheless, the narrowed ion diffusion pathway increases the resistance for ion diffusion. The rate capability, volumetric capacity, and materials utilization are thus predominantly restricted by the microstructures of the electrode, providing fundamental insights into electrode microstructure design for different applications. As an example, an optimized TiNb2O7 electrode with compaction density of ≈2.5 g cm‐3 and mass loading of ≈8.5 mg cm‐2 provides the highest specific charge capacity of 271.3 mAh g‐1 at 0.2 C in half cell configuration and 70.4% capacity retention at 6 C in full configuration, enabling balanced energy density and power density of batteries.

Nutrient content and physical characteristics linkage of palm kernel meal and coconut meal after wet separation using molecular weight approac

The use of palm kernel meal and coconut meal is restriction in broiler feed due to the high crude fiber content, caused by the mixture of shells. This study aims to analyze the nutrient content, i.e., crude protein and crude fiber of palm kernel meal and coconut meal before and after using wet separation and molecular weight approach. The wet separation process for palm kernel meal and coconut meal was carried out for 6 hours to obtain a precipitate. The palm kernel meal and coconut meal that have been separated is divided into 3 fractions, i.e., upper, middle and lower. Each fraction was analyzed for crude fiber and crude protein content for chemical characteristics, and bulk density (g l-1), compacted bulk density (g l-1), specific gravity (kg l-1), angle of purpose (o). Crude protein and crude fiber content of palm kernel meal before being separated by wet separation were 11.72% and 13.11%, for coconut meal were 12.65% and 8.67%. The fraction of palm kernel meal has the highest crude protein content of 22.21% with the lowest crude fiber content 9.68%. Coconut meal in the middle fraction had the highest crude protein content 18.92% and the lowest crude fiber content of 11.95% in the upper fraction. The physical characteristics of the upper fraction of palm kernel meal and coconut meal had the lowest values (P0.05) of specific gravity (kg l-1), bulk density (g l-1) and compacted bulk density (g l-1). It can be concluded that the wet separation process with the molecular weight approach is able to increase the nutrient content especially of each fraction and can minimize the mixture of shells in palm kernel meal and coconut meal

Effects of co-carbonization of medium and low temperature refined pitch and high temperature refined pitch on the structure and properties of needle coke

Needle coke has attracted much attention as a high-quality raw material for high-power graphite electrodes and other advanced functional materials. In this study, needle coke was prepared by co-carbonization of medium and the low temperature coal tar refined pitch (RCTP) and the high temperature coal tar refined pitch (RHCTP). The effect of co-carbonization of blended refined pitches with different proportions on the structure and properties of needle coke was studied. Elemental analysis, 1H NMR spectroscopy, Fourier transform infrared spectroscopy, and gas chromatography-mass spectrometry revealed the effect of changes in the key components of the blended refined pitch on the structure of needle coke. In addition, the structure and properties of needle coke were analyzed by polarized light microscopy, scanning electron microscopy, X-ray diffraction, Raman spectroscopy and powder resistivity. The results showed that adding RHCTP to RCTP can increase the content of aromatic hydrocarbons and reduce the content of heterocyclic compounds in the blended refined pitch, which was beneficial to the evolution and growth of carbonaceous structures. The fiber content of needle coke (N-R-C-15) prepared by adding 15 wt% RHCTP to RCTP was 50 wt%, the optical texture index (OTI) of the coke was 63.04, Lc= 8.387 nm, La= 18.17 nm, d002 = 0.3427 nm, the content of well-aligned carbon microcrystals was 91.17 wt%, and the content of perfect graphite crystals reached 24.37 wt%. As the ratio of RHCTP in RCTP increased, the needle coke exhibited more fibrous structures, the degree of defects in graphite crystals decreasing, and the degree of graphitization increasing. In addition, with the increasing proportion of RHCTP in RCTP, the average resistivity of needle coke decreased from 167.55 μΩ·m to 144.5 μΩ·m, and the average powder compaction density increased from 1.065 g/cm3 to 1.206 g/cm3.

Structural transformation of porous and disordered carbon during ball-milling

Mechanical ball-milling is a commonly used method to shattering crystals or introducing defects in carbon materials. But herein, we observe that the highly porous and disordered carbon lattice of activated carbon is converted to graphitic structure during ball-milling, along with the introduction of oxygen in the bulk phase. The well-developed pores are gradually eliminated, leading to obviously decreased surface area from 1364 to 156 m2 g-1 and improved compaction density from 0.573 to 1.423 g cm-3. Due to the continuous particle cleavage, re-assembly, and cold-welding, the as-formed carbon blocks show 2 times larger in size and 4 times higher bulk oxygen content. This simultaneous crystallinity enhancement and oxygen functionalization is barely observed in other methods. The mechanism is that highly reactive carbon radicals generated by mechanical cleavage of carbon skeleton enable atom rearrangement to form large graphitic domains or being terminated by oxygenated groups. Interestingly, the capacitive energy storage performance of the ball-milled activated carbon is changed from electric-double-layer to pseudo-capacitance in aqueous electrolyte, showing significantly improved volumetric capacitances and high-rate performance. Our work provides a theoretical guidance for mechanochemistry of porous and disordered carbon materials.

Agrophysical indicators of black soil typical in agrocenose of winter wheat (Triticum vulgare) in the right bank Forest Steppe of Ukraine

The article presents the results of scientific research on the influence of four systems of basic tillage such as shelf tillage (ploughing at 20–22 cm), shelfless (chisel-deep-ripper at 20–22 cm), shelf-less tillage shallow (disk harrow at 10–12 cm) and shelflesstillage surface (disk harrow at 6–8 cm), and five preceding crops — peas, soybeans, corn for silage, winter rape, sunflower on compaction density and general porosity of black soil typical for growing winter wheat in the right-bank forest-steppe of Ukraine. According to the results of the research carried out in the stationary field experiment of the LLC «Agrofirma Kolos» educational-scientific-innovative center of agricultural technologies», the soil density and its total porosity determined at the time of sowing winter wheat had optimal parameters for all studied systems of the main tillage and placement of winter wheat after various preceding crops. With an increase in the depth of the studied soil layer, an increase in the index of soil density and a decrease in its total porosity were noted, which is natural. Depending on the system of the main tillage, the soil density in the 0–10 cm soil layer during the sowing period varied from 1.11 to 1.14 g/cm3, with lower values in the version with shelf and non-shelf tillage for 20–22 cm. Analyzing the entire studied layer (0–30 cm) of the soil at the time of crop sowing, it should be noted that both shelf (plow) and shelf-less tillage (chiseldeep-ripper) had close indicators of soil density in the studied layers, the values of which increased from the top to the bottom. With systematic shallow tillage by 12–14 cm and surface tillage by 6–8 cm, the soil layer of 10–20 cm was most compacted, with tendencies towards loosening in the 20–30 cm layer. Among the preceding crops, the higher soil density in the variant with placement of winter wheat after corn on silage is 1.14 g/cm3. The porosity indicator of the upper 0–10 cm soil layer at the time of sowing varied from 57.1% for shelf-less shallow tillage to 58% in the option with shelf tillage at 20–22 cm. The studied predecessors provided parameters of total porosity at the level of 57.5–58.0% for lower indicators in the version with sunflower. The analysis of the investigated indicators during the recovery of vegetation and before harvesting showed an increase in the soil density and a decrease in the number of pores in the soil for all investigated systems of the main tillage and preceding crops. It should be noted that the shelf cultivation of the soil (plowing at 20–22 cm) provided the most optimal parameters of the soil density and porosity of the soil in its individual horizons and in the arable layer as a whole. Other systems of basic tillage, despite the optimal values of agrophysical indicators on average in the arable layer, worsened the physical condition of the soil compared to plowing. The optimal combination of options in the experiment can be considered the use as preceding crops of winter wheat, legumes and winter rape in a complex with chisel tillage of the soil at 20–22 cm. This made it possible to ensure optimal indicators of soil density and general porosity not only in the upper 0–10 cm its thickness, but also in deeper layers.

A hydraulic actuator for joint robots with higher torque to weight ratio

AbstractJoint actuators with a compact size and high power density are necessary for robots with rotating joints, making the hydraulic actuator (HyA) an ideal actuator candidate. This paper presents a joint HyA with the following characteristics: compact installation size of 70 mm × 92.5 mm × 145 mm, low weight of 1.93 kg, high output torque of 742.2 Nm/531.09 Nm in two directions under 210 bar, high torque to weight ratio of 265.5 Nm/kg, low internal leakage of about 9 mL/min, zero external leakage, low starting pressure of 0.26 MPa/0.39 MPa in two directions, and a large rotation angle of 135 degrees. Compared with HyAs that have been applied in robot joints, the HyA proposed in this paper can greatly reduce the joint weight, reduce the joint size, and ensure the control performance of the joint movement.In addition, a dynamic model of the HyA is established. Based on this, some dynamic design suggestions are given. Furthermore, a simple position and torque control algorithm for the HyA is proposed. Finally, some experiments are carried out to verify the performance of the HyA.

Pomegranate-Like KVPO4 F@C Microspheres as High-Volumetric-Energy-Density Cathode for Potassium-Ion Batteries.

KVPO4 F is one of the most competitive cathode candidates for potassium-ion batteries (KIBs) because of its high output voltage and energy density. Although the gravimetric energy density of KIBs is intensively discussed in literature, little attention is paid to the volumetric energy density. In view of this, pomegranate-like carbon-coated KVPO4 F microspheres with a high volumetric energy density are designed in this work. The nano-sized primary particles with carbon sheets in KVPO4 F microspheres enable promis rate capability by enhancing the K+ diffusion kinetics, while the micro-sized spheres guarantee the improvement of cycling stability. Owing to the dense hierarchical microspheres, the volumetric energy density of cells is greatly improved compared to bulk materials. This cathode delivers a reversible capacity of 101.5mA h g-1 at 0.3 C with an average output voltage of 4.0V and a capacity retention of 85.1% after 200 cycles. The KVPO4 F@C microspheres have a compact density of 2.45g cm-3 and further offer a high volumetric energy density up to 891.3Wh L-1 . The overcharge behavior of KVPO4 F in the first three cycles is also revealed. The presented KVPO4 F@C microspheres cathode provides a new sight for developing KIBs with large volumetric energy density.

Effects of external fields on the nonlinear optical rectification and second harmonic generation of GaAs/GaAlAs zigzag quantum well

For the first time, the impact of externally applied static electric and magnetic field on the nonlinear optical rectification (NOR) and second harmonic generation (SHG) coefficients of GaAs/GaAlAs zigzag quantum well is theoretically investigated in this study. Additionally, we examined the effect of physical parameters such as width and depth of the structure on these coefficients. We have numerically solved the time-independent Schrödinger equation by using the diagonalization method under the effective mass approximation for obtaining subband energy levels and wave functions of the structure, and then we have used the compact density matrix method to obtain the analytical expressions of NOR and SHG coefficients. The obtained numerical results showed that when the magnitude of the externally applied electric and magnetic fields is increased, the peak position of NOR and SHG shifts to blue, and by increasing the width and potential depth of the quantum well, it shifts to red.

Study on the Relationship between Fermentation-Accumulated Temperature and Nutrient Loss of Whole-Plant Corn Silage

The nutrition loss of silage is partly due to the heat production of silage. In this study, the amount of nutrition loss of silage was estimated by measuring the heat production of silage, and the concept of the accumulated temperature of fermentation was put forward. The laboratory measured the fermentation-accumulated temperature of whole-plant corn silage with different compaction densities. The samples were analyzed to establish a multiple linear regression model with nutrition loss. The results demonstrated a significant non-linear relationship between the whole-plant corn silage compaction density and fermentation-accumulated temperature. The multiple linear regression model between the accumulated-fermentation temperature and nutrition loss was significant under different densities. The amount of silage nutrition loss can be predicted by the fermentation-accumulated temperature.

The effectiveness of published continuum constitutive laws to predict stress‐assisted densification of powder compacts

AbstractCommonly used constitutive laws for crystalline and viscous materials have been compared to predict the densification behavior under hot‐pressing and sinter‐forging. Experimental results, from literature for one loading condition, have been used to extract the constitutive laws for amorphous and crystalline materials and, these in‐turn, have been used to predict behavior under a different set of loading conditions. Ideally, the constitutive parameters obtained from one set of loading conditions and thermal history should apply to a different set of conditions. However, there is a lack of systematic experimental studies in which this can be checked. In this paper, we use constitutive parameters obtained from one set of conditions to predict the densification response under a different set of loading conditions. For both sintering of amorphous and crystalline materials, we use two different constitutive parameters and compare the predictions of these for the case where experimental results are not available. In addition, the effect of temperature on densification behavior for stress‐assisted sintering has been investigated. It is shown that the two commonly used constitutive models for viscous sintering (Scherer and Skorohod–Olevsky) predict similar behavior for amorphous materials. However, for crystalline materials, the predictions of the Riedel–Svoboda and the Kuhn–Sofronis–McMeeking (KSM) models are different. Finally, it is shown that the dependence of the normalized densification on temperature, under constant heating rate conditions, with parameters obtained from isothermal experiments, is a good test for the models.