Mass Change Of Samples Research Articles

Catalytic alcoholysis of fiberglass reinforced epoxy resin composites

The article presents the results of a study of alcoholysis of fiberglass reinforced epoxy resin composites obtained by vacuum infusion. To intensify alcoholysis, chlorides, nitrates and sulfates of cobalt (II) and copper (II) were introduced into the reaction medium in an amount of 5% of the mass of ethyl alcohol for each system. The efficiency of the system was assessed based on data from the analysis of mass change of composite samples during alcoholysis, thermogravimetric analysis and scanning electron microscopy. It was found that the presence of metal chlorides contributes to 5 times increase of the alcoholysis velocity. The residual strength of the recovered fiber samples obtained is at least 95%.

Specific Erosion Resistance Behaviour of Cold Forged and Angular Extruded Aluminium.

Aluminium finds wide application in mechanical engineering due to its low density and corrosion resistance. In this research, aluminium was subjected to two different metal forming technologies-cold forging (upsetting) and equal channel angular pressing (ECAP)-to obtain improvement in its exploitation properties. Parallel to changing mechanical properties by using these two processes, there was a change in the microstructure of the material. The resulting microstructures were examined using an optical microscope. A different treated aluminium was subjected to erosion wear in various time intervals. Wear testing was conducted for two different impingement angles causing abrasive wear and impact wear. The erosion mechanisms were examined by scanning electron microscopy. These results showed that there is no statistically significant difference in erosion wear for different states at the same impingement angle. However, the difference is noticeable at different wear angles. The significance of the difference in wear of the samples treated with the forging and ECAP techniques was validated by statistical analysis with tests of different sensitivities. The results of the t-test showed that ECAPed samples present a statistically significant difference in the loss of mass due to variations in erosion angle during the 30, 45, and 60 min wearing. A substantial difference in the change in sample mass is also visible for the forged state worn for 60 min.

High-temperature corrosion testing of titanium beryllides in the presence of water vapor and oxygen

Beryllium-based intermetallics are promising materials for the blankets of future fusion reactors and have potential applications in other areas of the nuclear industry, such as fission reactor reflectors and space technology. Understanding the high-temperature corrosion behavior of these materials in a noble gas medium containing chemically active impurities is essential for evaluating their suitability and guiding their application.This study investigates the high-temperature corrosion of titanium beryllide Be12Ti in the form of plate and grinded samples, produced by JSC “Ulba Metallurgical Plant” (Ust-Kamenogorsk, Kazakhstan). The corrosion tests were conducted under non-isothermal vapor-gas mixture (Ar + D2O or Ar + H2O flowing atmospheres) purging conditions using thermogravimetric (TG) analysis, differential scanning calorimetry (DSC), and mass-spectrometry of the gas phase.As a result of the corrosion tests, new experimental data on thermal effects have been obtained, describing the corrosion processes of Be12Ti samples across a wide range of temperatures and various heating rates in the presence of water vapor in the purge gas. The dependencies of sample mass change under heating conditions have been determined, and the characterization results of the samples before and after high-temperature corrosion tests are presented.Corrosion of titanium beryllides, both for Be12Ti plate and grinded samples, follows similar mechanisms. At around 500 °C, the mass of the samples begins to increase, and hydrogen isotopes are released. The test results indicate that corrosion of titanium beryllides with varying surface inhomogeneities proceeds similarly within the temperature range of 500–900 °C, showing a linear dependence on temperature.The results revealed significant insights into the oxidation mechanisms and the formation of corrosion products, which are crucial for optimizing the material's performance in fusion reactor environments.

INVESTIGATION OF THE KINETICS OF THE COAL PYROLYSIS PROCESS

The study of the processes occurring in the temperature range of the main decomposition of the organic mass of coal (OMC) makes it possible to understand both the general patterns and the specifics of the decomposition of solid fuels. This temperature interval is used to calculate the kinetic parameters of the process, which carry important information both about the nature of the structural-chemical transformations and about the structure and direction of thermal destruction of OMC. In this article, to study the kinetics of pyrolysis of coal, the method of thermogravimetric analysis was used, in which heating of coal samples was carried out in ceramic crucibles in the temperature range of 25-900 °C at different heating rates (5-25 deg/min) in nitrogen and oxygen media. Coal from the Kenderlyk deposit was chosen as the object of study. Based on the constructed differential DTG curves (dependence of the sample mass change rate on time) at different heating rates, the kinetic parameters of pyrolysis of coal were calculated using the equations of non-isothermal formal kinetics. The effect of the rate and temperature of coal heating on the kinetic parameters of pyrolysis of coal has been studied. The main stages of OMC decomposition are revealed. It has been found that the heating rate of coal samples significantly affects the temperature and process rate corresponding to the main decomposition maxima on the differential DTG curves. The dependence between the kinetic parameters of pyrolysis of coal in the temperature range of the main decomposition of OMC on the rate and temperature of heating, as well as between the kinetic parameters at different stages of the main decomposition of coal, is analyzed.

The Influence of Selected Process Parameters on the Efficiency of the Process of Gas Nitriding of AISI 1085 Steel.

The main aim of the manuscript was to investigate the impact of modifying the parameters of the gas nitriding process of samples made from AISI 1085 steel on the course and results of the process carried out in a chemical reactor allowing for thermogravimetric measurements. The tested steel was subjected in a chemical reactor to the process of gas nitriding in the temperature range of 490-580 °C, using different sample heating rates (in the range of 1-25 °C/min) and various mixtures of nitriding gases (pure NH3, or NH3 with the addition of H2 or N2). To assess the impact of the tested process parameters on its efficiency, the thickness of the nitrided layers produced, the change in sample mass, the structure of the phases produced, the phase composition and the microhardness were examined. For the research methodology used, it was found that reducing the amount of NH3 and/or using H2 or N2 admixtures adversely affects the thickness of the nitride layers produced. At the same time, the use of a lower maximum process temperature with the same gas mixture resulted in a significant difference in the thickness of the layers. It was also found that the use of pure NH3 or a gas mixture (NH3 + H2) with higher NH3 contents resulted in higher surface microhardnesses of the samples and that for these samples, the hardness increased to a greater depth.

The Effect of Intumescent Coating Containing Expandable Graphite onto Spruce Wood

Wood, one of the materials predominantly employed in construction, possesses various advantageous properties alongside certain drawbacks, such as susceptibility to thermal degradation. To enhance wood fire resistance, one approach involves the application of flame retardants. This study compared the fire-retardant effectiveness of expandable graphite, bonded with water glass, as a coating for spruce wood against commercially available fire-retardant treatments. Spruce wood samples (Picea abies (L.) H. Karst) underwent treatment with three distinct retardants: expandable graphite in combination with water glass, Bochemit Antiflash, and Bochemit Pyro. The fire-technical characteristics of the samples were examined by a non-standard test method—a test with a radiant heat source. The experiment evaluated the fire-retardant properties by recording changes in sample mass, burning rate, and temperature difference. The best results among all flame retardants were achieved by expandable graphite in combination with water glass, in all evaluation criteria. Among all the flame retardants used, expandable graphite in combination with water glass achieved the best results in all evaluation criteria.

High-temperature interaction of water vapor with lithium ceramics Li2TiO3

Selection of materials for fusion reactors and, in particular, for blanket systems is one of the most important tasks that determine the development of fusion energy. Lithium ceramics Li2TiO3 is considered as prospective candidate for solid breeders of future fusion reactors' blankets. The paper presents the results of high-temperature tests of Li2TiO3 + 5 mol% TiO2 ceramics, performed under conditions of blowing with argon containing impurities of water vapor of different isotopic compositions (H2O, HDO, D2O) in the range of temperature from 100 °C to 1400 °C. The vapor–gas mixture for the experiment was prepared in a special mixing tank. The interaction of Li2TiO3 + 5 mol% TiO2 ceramics with chemically active gases and water vapors was investigated by thermogravimetry (TG), differential scanning calorimetry (DSC) and mass spectrometry (MS) methods. As a result of experiment, the dependences of the sample mass change during heating under single purge gas composition was obtained. Mass spectra that characterize the changes in the qualitative composition of the gas mixture in the reaction chamber with the investigated sample were recorded and subsequently analyzed. An isotope effect is observed during the experiment: the release of D2 gas begins significantly earlier than the release of HD gas. The observed effect appears only in the high-temperature region (above 1050 °C), which characterizes the investigated material as almost completely chemically neutral towards water vapor.

The mechanical strength of which in operation directly of the introduction into highly filled halogen-free plastics production

With the introduction into highly filled halogen-free plastics production, the mechanical strength of which in operation directly depends on the flame retardant content and application technology, it becomes important to control the cable sheath mechanical characteristics in a fireproof design. Polymeric materials and their compositions are viscoelastic materials for which the mechanical properties depend on the technological process of extrusion. The results of estimating the elongation at break of samples from the uniaxial stretching. It is shown that the inner and outer layers of the halogen-free plastic cable sheath have significantly different values of the plasticity normative parameter: differences evidence in the polymer structure in the inner and outer layers of the sheath due to the forced deformation process during extrusion, which is forced polymer structure orientation. It is shown that the inner and outer layers of the halogen-free plastic cable sheath have significantly different values of the relative change in specific mass of polymer samples. Analysis of the statistical covariance of the relative elongation at break and of the relative change in specific mass of polymer samples different in structure similar filled halogen-free polymers. With the introduction into highly filled halogen-free plastics application technology, it becomes important to control the cable sheath mechanical characteristics in fireproof design for the inner and outer layers

Impact of skin hydration on patterns of microthermal injury produced by fractional CO2 laser.

The impact of skin hydration on patterns of thermal injury produced by ablative fractional lasers (AFLs) is insufficiently examined under standardized conditions. Using skin with three different hydration levels, this study assessed the effect of hydration status on microchannel dimensions generated by a fractional CO2 laser. A hydration model (hyperhydrated-, dehydrated- and control) was established in ex vivo porcine skin, validated by changes in surface conductance and sample mass. After, samples underwent AFL exposure using a CO2 laser (10,600 nm) at two examined pulse energies (10 and 30 mJ/mb, fixed 10% density, six repetitions per group). Histological assessment of distinct microchannels (n = 60) determined three standardized endpoints in H&E sections: (1) depth of microthermal treatment zones (MTZs),(2) depth of microscopic ablation zones (MAZs), and (3) coagulation zone (CZ) thickness. As a supplemental in vivo assessment, the same laser settings were applied to hyperhydrated- (7-h occlusion) and normohydrated forearm skin (no pretreatment) of a human volunteer. Blinded measurement of MAZ depth (n = 30) was performed using noninvasive optical coherence tomography (OCT). Modest differences in microchannel dimensions were shown between hyperhydrated, dehydrated and control skin at both high and low pulse energy. Compared to controls, hyperhydration led to median reductions in MTZ and MAZ depth ranging from 5% to 8% (control vs. hyperhydrated at 30 mJ/mb; 848 vs. 797 µm (p < 0.003) (MAZ); 928 vs. 856 µm (p < 0.003) (MTZ)), while 14%-16% reductions were shown in dehydrated skin (control vs. dehydrated at 30 mJ/mb; MAZ: 848 vs. 727 µm (p < 0.003); MTZ: 928 vs. 782 µm (p < 0.003)). The impact of skin hydration on CZ thickness was in contrast limited. Corresponding with ex vivo findings, hyperhydration was similarly associated with lower ablative depth in vivo skin. Thus, median MAZ depth in hydrated skin was 10% and 14% lower than in control areas at 10 and 30 mJ/mb pulse energy, respectively (10 mJ: 210 vs. 180 µm (p < 0.001); 30 mJ: 335 vs. 300 µm (p < 0.001)). Skin hydration status can exert a minimal impact on patterns of microthermal injury produced by fractional CO2 lasers, although the clinical implication in the context of laser therapy requires further study.

Study on the Feasibility of the TG Method for Maximum Water Content Measurement of Waterlogged Archaeological Wood

ABSTRACT Thermogravimetry (TG) is used to measure the change of sample mass versus temperature or time under a program controlling temperature. It is a common thermal analysis tool with a precise built-in balance, and accurate data can be obtained through a small amount of sample at the level of milligrams. The feasibility of the TG method for determining maximum water content (MWC) measurement of waterlogged archaeological wood was studied. Simulated waterlogged wood and waterlogged archaeological wood were used to determine the test condition for the TG method. MWC data obtained through the oven-dry and TG methods with different mass gradients from 0–10 mg to >50 mg were analyzed statistically. Deviation, error bar, and coefficient of variation were evaluated. According to the results, when sample mass is no less than 30 mg, and holding time at 105°C is no less than 40 min, data deviation between these two methods is less than 5%. Effect of sampling depth and presence of inorganic deposits were also investigated. Specimens were taken from an archaeological wood with a sampling depth from 2 to 6 mm, then MWC was measured through the TG method. The results indicate MWC of the samples taken from a depth of 2–4 mm is higher than that taken from a depth of 0–2 mm and is lower than that taken from a depth of 4–6 mm, which is related to inorganic deposits. The presence of deposits was verified through SEM-EDX. MWC of three archaeological wood samples from China and five archaeological wood samples from Italy were measured to verify the effectiveness of the TG method when wood species and degradation degree are different.

The Impact of Heating Rate on the Kinetics of the Nitriding Process for 52100 Steel.

The aim of this study was to determine the impact of the heating rate of steel balls made of AISI 52100 alloy steel on the kinetics and efficiency of the gas nitriding process when carried out using a chemical reactor with precise thermo-gravimetric measurements, which allowed for changes in sample mass during heating and nitriding to be monitored with an accuracy of 50 µg. In the chemical reactor, the examined alloy steel was subjected to a heating process at the selected nitriding temperature of 590 °C. Two heating variants were used: the first variant relied on heating to the nitriding temperature with different rates-1 °C per minute, 2 °C per minute, 5 °C per minute and 10 °C per minute, respectively-whereas the second variant relied on the fast-25 °C per minute-heating of treated specimens to a temperature of 475 °C, at which, the nitrogenous potential of the atmosphere promotes faster nitrogen diffusion deep into the nitrided substrate, followed by reheating up to the nitriding temperature at different rates: 1 °C per minute, 2 °C per minute, 5 °C per minute, and 10 °C per minute, respectively. To evaluate the impact of heating rate kinetics and effectiveness during nitriding on the obtained surface layer quality, we investigated the phase composition, microhardness distribution, and thickness of the obtained diffusion layers. It was found that heating to a temperature of 475 °C in the nitriding process does not significantly affect the average mass gain of a sample. Above this temperature, within the range of nitriding temperatures, the extension of time increases the sample's mass gain. Simultaneously, it was found that the use of a constant heating rate allows for thicker nitrided layers and a greater sample hardness to be obtained. Dual-stage heating, in turn, is more effective in the context of sample mass gain per time unit.

Features of thermal analysis of ceramics

It is advisable to include in the results of the analysis the dimensions and shape of the samples, the temperature curve in the center of the analyzed sample, and also what the differential thermocouple measures, the temperature difference between the center and the surface of the sample between the centers of the samples, as well as the density and mass of the samples. It is shown that the temperature effect in the material is more accurately reflected by the sample mass change curve than by the DTG curve. Enthalpy change ― the thermal effect of the process should be determined, taking into account not the entire area under or above the peak of the DTA curve, but only its part between the DTA curve, the horizontal through the process start point and the vertical through the minimum or maximum of the DTA curve. The next part of the curve describes the entry of the sample into the regular mode after the end of the chemical or phase (recrystallization) process. Ill. 4. Ref. 13.

Whether mixed using polypropylene fiber and air-entraining agent can further improve the macro and micro durability of concrete in cold and sulfate regions

To explore the influence of mixed using polypropylene fiber (PF) and air entraining agent (AEA) on the durability of concrete in cold and sulfate regions, compressive strength, mass change, ultrasonic velocity and interface transition zone (ITZ) of samples with different admixtures were studied. In addition, the interaction between these two additives was explored. Results indicated that both PF and AEA can enhance the durability of concrete under freeze-thaw cycles and sulfate attack. Among which, AEA was more effective. However, mixed using these two additives cannot further improve the durability of concrete. On the macro level, samples with the best dosage of PF or AEA can resist 240 or more than 300 freeze-thaw cycles, respectively. Samples added both PF and AEA (AEPF) can also resist more than 300 cycles, but their strength and compactness were worse than that of the samples only added AEA (AE2). On the micro level, interpenetrating cracks formed at the ITZ of PF modified samples. Large numbers of ettringite generated, filled the cracks and presented a specific growth direction. Only some randomly distributed cracks formed at the ITZ of AE2 and AEPF. Ettringite also generated in these cacks but had no specific growth direction. However, more crystals were observed at the ITZ of AEPF compared with AE2. The interaction indicated that PF and AEA suppressed each other. PF reduced the proportion of surfactants responded for the formation and stability of air voids in AEA, and AEA reduced the connection effect between the fiber and mortar. These studies were meaningful for exploring and enhancing the durability of concrete in cold and sulfate regions.

Corrosion performance and possible mechanism of aluminium nitride-molybdenum gradient material in a simulated liquid metal battery environment

After being fabricated successfully by spark plasma sintering technology, corrosion performance of aluminum nitride-molybdenum gradient material was investigated using X-ray diffraction, scanning electron microscope, XPS techniques, etc. in a simulated liquid metal battery environment with LiF–LiBr–LiCl eutectic salt as electrolyte. The research results indicated that low temperature corrosion at 550 °C occurs mainly in pure aluminum nitride region with the corrosion products grown on the grain boundaries including alumina, nitrogen-lithium, aluminum-lithium intermediate phase or their complex compounds. Moreover, the formed corrosion product morphology is influenced significantly by aluminum nitride distribution. As the gradient compositions developed towards the pure molybdenum zone, the product morphologies tended to evolve in a sequence of sphere, flake and octahedron. At temperatures higher than 600 °C, alumina tends to be dissolved in molten salt vapor and molybdenum starts to be corroded simultaneously resulting in a substitute of the formed lithium aluminum molybdenum oxide phases for alumina in the final corrosion products. Mass change study on the samples suggested both the holding time and temperature have significant influences on the corrosion behavior of aluminum nitride-molybdenum gradient material. At temperatures higher than 700 °C, sudden change in sample mass accompanied by interface cracking would happen within the holding time of 100 h. Therefore, under long-term isothermal conditions, the serviced temperature of aluminum nitride-molybdenum functional gradient materials is suggested to be lower than 600 °C.

STUDY OF TRANSIENT RESISTANCE OF CONTACT MATERIALS AND CONTACTS OF ELECTRICAL DEVICES DURING INTERACTION WITH AGGRESSIVE ENVIRONMENT

It is proposed to replace serial contact parts based on silver with experimental contact units based on copper. Climatic tests of contact materials were carried out to determine the performance and production operation of experimental contacts. As a result of the change in contact resistance and mass of samples of copper-based contact materials with thermodynamically stable impurities and on the basis of petrographic analysis of their interaction products, transient resistance and corrosion resistance of electrical contact materials in chemically active environments were evaluated. Stable transient resistance and high corrosion resistance of the studied materials in NH3 and CO2+H2O environments are shown. To determine the operability of the starters, tests were carried out on the reliability of contact of the starters. These studies were carried out for serial contact parts of PML-1100O4 electromagnetic starters based on silver - СрН-90, СрМ-0.2+М1 and metal-ceramic contact parts based on copper with metal impurities and defined thermodynamically stable compounds. Contact units of the starters, made of experimental contact materials, have passed several years of production tests in real agricultural conditions. The reliability of the electrical contact is largely determined by the components that make up its composition, the structure and properties of the surface layers, which are formed as a result of erosion and transfer of the contact material in the electric arc.The main component for the contact materials of the most common electromagnetic starters is silver.Corrosion of the working surfaces of the contacts of the starters, which occurs under the influence of chemically active impurities in the environment, is also one of the main factors of wear and failure. Contacts of PML, PM, PMM, PME, PMA, PAE starters are made of silver-based material (СрН-90, СрМ-0.2+М1, СОК-15, КМК-А10м, etc.). Since the reliability of starters with developed test contacts involves the preservation over time of the parameters that characterize the ability of electromagnetic starters to perform their functions in all prescribed modes and in harsh operating conditions (environmental conditions of technological animal husbandry premises), the reliability indicators are controlled during all tests: when monitoring the functioning of the starter and when testing for the influence of external factors (control tests). In order to reduce the time and means of testing, one-stage control is used, in which one sample is tested (based on the results of the test, a decision is made about compliance with reliability requirements). As a rule, the technological equipment of livestock farms and complexes mainly includes electromagnetic starters of general industrial purpose of wear resistance class B, B. Such starters are unsuitable for long-term operation in specific conditions of agriculture, as they do not meet the requirements for protection against environmental influences, fail before reaching a certain resource of wear resistance, and this primarily concerns the contact system (up to 30% of all starter failures). Today's modern electrical engineering industry does not produce starters and relays for the needs of the agro-industrial sector. In order to improve the reliability of the contact system of the electromagnetic starter and relay in general, it is suggested to replace the serial contact parts with copper-based contact parts. The aim of the study -carrying outcomparative studies of the characteristics of electromagnetic starters with serial and experimental test contact parts and the identification of the influence of aggressive environment parameters on the nature of changes in the transient resistance of contact materials and contacts of starters.

Corrosion Compatibility of Stainless Steels and Nickel in Pyrolysis Biomass-Derived Oil at Elevated Storage Temperatures

Corrosion compatibility of stainless steels and nickel (Ni200) was assessed in fast pyrolysis bio-oil produced from pyrolysis of high ash and high moisture forest residue biomass. Sample mass change, ICP-MS and post-exposure electron microscopy characterization was used to investigate the extent of corrosion. Among the tested samples, type 430F and type 316 stainless steels (SS430F and SS316) and Ni200 (~98.5% Ni) showed minimal mass changes (less than 2 mg∙cm−2) after the bio-oil exposures at 50 and 80 °C for up to 168 h. SS304 was also considered to be compatible in the bio-oil due to its relatively low mass change (1.6 mg∙cm−2 or lower). SS410 samples showed greater mass loss values even after exposures at a relatively low temperature of 35 °C. Fe/Cr values from ICP-MS data implied that Cr enrichment in stainless steels would result in a protective oxide layer associated with corrosion resistance against the bio-oil. Post exposure characterization showed continuous and uniform Cr distribution in the surface oxide layer of SS430F, which showed a minimal mass change, but no oxide layer on a SS430 sample, which exhibited a significant mass loss.

A rapid and precise method for determining water content in nuts as a tool for determining their quality during storage

This study was designed to examine impact of storage conditions on hazelnut quality and to develop a quick method for testing hazelnut moisture. The change of sample mass and water content were assessed by convection drying method and by means of a moisture analyzer—IR radiation. The samples were tested as: nuts, nut kernels, crumbled nut kernels, husk of nuts. They were stored in closed and open packages at 45% and 80% humidity and at constant temperature (23 °C). It has been observed that at the humidity of 45%, the hermetic packaging reduced hazelnut mass loss by 18%, and the hazelnut husk caused reduction of mass loss of the kernel by 5.5%. It was found that the best storage effects were obtained at a relative air humidity of 80% (i.e. change in hazelnut weight 2.18%, kernels 0.78%, shell 1.4%). At this moisture content, in comparison with the moisture content equal to 45%, a lower loss of hazelnut weight by 4.65%, kernel weight by 10.79%, shell weight by more than two times was found when the samples were stored without packaging. Water desorption from hazelnut stored under these conditions was reduced to 0.4% for packaged kernels and to 3% for unpackaged product. Determining the water content by the IR radiation method, compared to the standard method, took much less time, it took about 1 h. 5 min (approx. 6 times faster) with a measurement accuracy of 0.26%. Therefore this paper proves that the described method positively influences time restrictions especially when the duration of water content analysis is a key determinant. According to the authors, it can be implemented in both laboratory and industrial tests, saving time and acting immediately when the technological process requires support.

Temperature effect on thermal changes and phase analysis of 3Y-TZP zirconia restorations

This study aimed to investigate the effect of final sintering on the thermal properties and phase composition of yttrium-stabilized zirconium dioxide. Totally 15 yttrium-stabilized zirconium oxide standard ovoid samples were studied (3Y-TZP, IPS e.max ZirCAD LT, Ivoclar Vivadent, Schaan, Liechtenstein). This material contains the following components: ZrO2 - 87.0 - 95.0%, Y2O3 - 4.0 - 6.0%, HfO2 - 1.0 - 5.0%, Al2O3 - 0.0 - 1, 0%. Initially, X-ray diffraction analysis was performed. After that, differential scanning calorimetry was carried out up to a temperature of 900°C. X-ray diffraction analysis was performed to assess the effect of the firing process on the phase analysis of zirconia samples (Selected samples were tested on an X-ray diffraction instrument (EMPYREAN, PANalytical, Lelyweg, The Netherlands) The thermal changes study in zirconia samples resulting from repetitive firing processes was performed then. Samples were placed in a differential scanning calorimeter (NETZSCH STA 409 PC Luxx, Bavaria, Germany) and heated at a rate of 10°C/min from 50°C to 900°C.) Then, differential scanning calorimetry data (the mass and structural changes of zirconia samples depending on temperature) was recorded. The percentage of the monoclinic phase increases on average from 3.6% to 7.5%, but this difference is not statistically significant (p=0.1). Two exothermic peaks were observed when the samples were heated from 50°C to 900°C. The final firing of 3Y-TZP zirconium crown up to 900°C slightly increases the content of the monoclinic phase and causes exothermal changes.

High Temperature Oxidation Performance of an Additively Manufactured Mo\u20139Si\u20138B Alloy

As reported in previous studies, the processing of Mo–Si–B alloys using additive manufacturing (AM) techniques, like directed energy deposition (DED) shows a high technical feasibility. The present work investigates the cyclic oxidation performance of an AM DED Mo–9Si–8B alloy. Depending on the temperature (800 °C, 1100 °C, 1300 °C), the oxidation mechanisms vary, which is due to different reactions at the surface of the alloys accompanied with mass changes of samples. These mass changes can be explained on the basis of microstructural investigations. However, compared to a powder metallurgically processed Mo–9Si–8B alloy, the AM-DED alloy shows competitive oxidation performance at potential application temperatures of 1100 °C and 1300 °C, while a catastrophic materials degradation occurs at 800 °C as also observed in other Mo-rich Mo–Si–B alloys.

Effects of Microwave Heating Paths on Pores and Cracks in Bituminous Coal.

To follow the effect of the microwave heating path on the structure of coal, eight 50 mm diameter, 30 mm long dry coal cores from the same coal seam with similar pore structure characteristics were microwave-treated using 4 pathways. The T2 spectrum, pore-volume, temperature, mass, and visual changes of coal samples were analyzed before and after microwave heating. The microwave heating path affected the macropores and microcracks and the crack development mode. When the same microwave energy was applied, microwave heating on the coal was mainly manifested by the opening of closed pores, before the pyrolysis temperature of the coal was reached. Increasing the energy density caused the water vapor to move from constant pressure expansion to constant volume expansion. This resulted in an exponential growth of the mesopore and macropore volumes. Meanwhile, the micropore volume increased due to the collapse of pore structures. As a result, high-power microwave heating could accelerate the vaporization rate of water. The rapid expansion of water vapor volume brought about a microwave heating effect similar to the “steam explosion”. The resulting local tensile stress enabled the cracks to develop, expand, and connect to others continuously. Thus, it formed a complex crack network leading to the outside of the coal sample.