Temperature-Driven Hydrocarbon Generation-Expulsion and Structural Transformation of Organic-Rich Shale Assessed by in situ Heating SEM

Mud shale can serve as source or cap rock but also as a reservoir rock, and so the development of pores or cracks in shale has become of great interest in recent years. However, prior work using non-identical samples, varying fields of view and non-continuous heating processes has produced varying data. The unique hydrocarbon generation and expulsion characteristics of shale as a source rock and the relationship with the evolution of pores or cracks in the reservoir are thus not well understood. The present work attempted to monitor detailed structural changes during the continuous heating of shale and to establish possible relationships with hydrocarbon generation and expulsion by heating immature shale samples while performing in situ scanning electron microscopy (SEM) imaging and monitoring the chamber vacuum. Samples were heated at 20°C/min from ambient to 700°C with 30 min holds at 100°C intervals during which SEM images were acquired. The SEM chamber vacuum was found to change during sample heating as a consequence of hydrocarbon generation and expulsion. Two episodic hydrocarbon expulsion stages were observed, at 300 and 500°C. As the temperature was increased from ambient to 700°C, samples exhibited consecutive shrinkage, expansion and shrinkage, and the amount of structural change in the vertical bedding direction was greater than that in the bedding direction. At the same time, the opening, closing and subsequent reopening of microcracks was observed. Hydrocarbon generation and expulsion led to the expansion of existing fractures and the opening of new cracks to produce an effective fracture network allowing fluid migration. The combination of high-resolution SEM and a high-temperature heating stage allowed correlation between the evolution of pores or cracks and hydrocarbon generation and expulsion to be examined.

Continuous Heating Dissolution and Continuous Cooling Precipitation Diagrams of a Nickel-Titanium Shape Memory Alloy

Binary NiTi alloys are the most common shape memory alloys in medical applications, combining good mechanical properties and high biocompatibility. In NiTi alloys, the shape memory effect is caused by the transformation of an austenite phase to a martensite phase and the reverse process. Transformation temperatures are strongly influenced by the exact chemical composition of the NiTi phase and the presence of precipitates in the microstructure induced by thermo-mechanical treatment, especially solution annealing and ageing. Isothermal time–temperature precipitation diagrams can be found in the literature. Cooling is frequently not considered, as water quenching is typically assumed to be sufficient. To the best of our knowledge, continuous heating dissolution (CHD) and continuous cooling precipitation (CCP) diagrams do not exist. Differential scanning calorimetry (DSC) is a common method to analyse the austenite/martensite transformation in shape memory alloys, but it has not yet been used to analyse precipitation processes during continuous temperature changes. We have enabled DSC to analyse dissolution and precipitation processes in situ during heating as well as during cooling from the solution annealing temperature. Results are presented as CHD and CCP diagrams, including information from microstructure analysis and the associated changes in the austenite/martensite transformation temperatures.

Mathematical modeling of a new way of renal artery denervation

The aim of the work is to create a new design of electrodes for renal denervation. In standard RFA systems, monopolar heating is most often used, by introducing an RF electrode inside the vessel. This approach leads to the need to interrupt blood flow during the procedure. In addition, the monopolar mode of operation requires the contact of the inserted electrode with the vessel walls, which greatly complicates the design of the electrode system. Point contact of the electrode system with the vessel can damage the inner walls of the artery. It is proposed to use a multi-electrode structure for external stimulation by creating a hollow cylindrical thermal field for effective treatment. It has been established that external heating will create the required thermal field without direct contact with the walls of the artery. The external arrangement of the electrodes makes it possible to regulate the temperature on the external surface of the vessel. With such heating, it is not necessary to block the blood flow, and due to the symmetry of the arrangement, continuous heating can be obtained without moving the electrodes during the procedure. Mathematical modeling confirms the possibility of vascular denervation during external heating.

Phase Transformation Kinetics of High Nb-TiAl Alloy during Continuous Heating

In this work, the phase transformation behavior of Ti-45Al-8.5Nb-(W, B, Y) alloy during continuous heating was investigated using dilatometer and optical microscopy. Results indicated that the phase transformation process of high Nb-TiAl alloy during continuous heating included two stages: ordered α2 → disorder α and tetragonal γ → hexagonal α. According to the microstructure analysis, the initial α2/γ lamellar structure transformed into the massive γ phase and α phase (retained as α2) during the heating process. The activation energy of α2 → α and γ → α was 989.65 kJ/mol and 995.30 kJ/mol, respectively. Moreover, the lower the heating rate was, the faster the phase transformation reached the equilibrium state.

Thermogravimetric Experiment of Urea at Constant Temperatures

There are still many unsolved mysteries in the thermal decomposition process of urea. This paper studied the thermal decomposition process of urea at constant temperatures by the thermal gravimetric–mass spectrometry analysis method. The results show that there are three obvious stages of mass loss during the thermal decomposition process of urea, which is closely related to the temperature. When the temperature was below 160 °C, urea decomposition almost did not occur, and molten urea evaporated slowly. When the temperature was between 180 and 200 °C, the content of biuret, one of the by-products in the thermal decomposition of urea, reached a maximum. When the temperature was higher than 200 °C, the first stage of mass loss was completed quickly, and urea and biuret rapidly broke down. When the temperature was about 240 °C, there were rarely urea and biuret in residual substance; however, the content of cyanuric acid was still rising. When the temperature was higher than 280°C, there was a second stage of mass loss. In the second stage of mass loss, when the temperature was higher than 330 °C, mass decreased rapidly, which was mainly due to the decomposition of cyanuric acid. When the temperature was higher than 380 °C, the third stage of mass loss occurred. However, when the temperature was higher than 400 °C, and after continuous heating was applied for a sufficiently long time, the residual mass was reduced to almost zero eventually.

Effect of the Heating Rate on Austenite Formation

The extent of the heat-affected zone (HAZ) in welding is typically estimated from thermodynamic considerations of austenization; however, thermodynamics are a poor predictor of the HAZ location in microalloyed steels. This work addresses the problem through the study of austenite formation during continuous heating on a grade X80 pipeline steel with an initial ferritic and bainitic microstructure. The methodology involved dilatometry, electron microscopy, and thermodynamic calculations. A continuous heating transformation diagram was developed for heating rates varying from 1˚ to 500˚C/s. For the slower heating rates, austenite start-transformation temperature was higher than the one dictated by the equilibrium, while for the faster heating rates, start-transformation temperature gradually approached the theoretically calculated temperature at which the ferrite can transform (possibly through a massive transformation) without a long-range diffusion into austenite. Partial-transformation experiments suggested that austenite formation occurs in the following two stages: 1) the transformation of bainitic zones into austenite, and later, 2) the transformation of polygonal ferritic grains.

CYCLIC THERMORESISTIVITY OF CARBON NANOTUBE YARN/SILICONE RUBBER MATRIX MONOFILAMENT COMPOSITES

Thermoresistive characterization of CNTY monofilament composites was investigated by using the electrical response of a single carbon nanotube yarn (CNTY) embedded in a silicone polymer forming monofilament composites. Two room temperature vulcanizing (RTV) silicone rubbers with different polymerization mechanisms (OOMOO and Ecoflex) were used as the polymeric matrices. Continuous heating-cooling thermal cycling ranging from room temperature (RT~25 °C) to 80 °C was performed in order to determine the thermoresistive sensitivity, hysteresis and residual fractional change in electrical resistance after each cycle. The thermoresistive response was nearly linear, with negative temperature coefficient of resistance at the heating and cooling zones for CNTY/ OOMOO and CNTY/Ecoflex specimens. The average value of this coefficient at the heating and cooling sections was - 6.65×10-4 °C-1 for CNTY/OOMOO and -7.35×10-4 °C-1 for CNTY/Ecoflex. Both monofilament composites showed a negligible negative residual electrical resistance with an average value of ~ -0.08% for CNTY/OOMOO and ~ -0.20% for CNTY/Ecoflex after each cycle. The hysteresis yielded ~19.3% for CNTY/OOMOO and ~29.2% in CNTY/Ecoflex after each cycle. Therefore, the curing kinetics and viscosity play a paramount role in the electrical response of the CNTY immersed into these rubbery matrices.

Modelling the Efficacy of Febrile Heating in Infected Endotherms

Fever is a response to infection characterised by an increase in body temperature. The adaptive value of this body temperature increase for endotherms is unclear, given the relatively small absolute temperature increases associated with endotherm fever, its substantial metabolic costs, and the plausibility for pathogens to adapt to higher temperatures. We consider three thermal mechanisms for fever's antimicrobial effect: (1) direct growth inhibition by elevating temperature above the pathogens optimal growth temperature; (2) further differentiating the host body from the wider environment; and (3) through increasing thermal instability of the pathogen environment. We assess these by modelling their effects pathogen on temperature dependent growth, finding thermal effects can vary from highly to minimally effective depending on pathogen species. We also find, depending on the specification of a simple physical model, intermittent heating can inhibit pathogen growth more effectively than continuous heating with an energy constraint.

Influence of chemical composition and the processing conditions on structure, thermal stability and mechanical properties of rapidly cooled Al-TM-RE-based alloys

The results of t studies are directed to development of new competitive amorphous and nanocrystalline alloys as well as to improvement of technology of their manufacturing. The physical and technological aspects of interrelations between the conditions for production of rapidly quenched alloys, formation of different structural and phase states, and their properties are discussed. The influence of the chemical composition of alloys and the conditions of their quenching on the glass-forming ability, phase composition, and the structure of the rapidly cooled specimens is investigated; the regularities of the effect of alloying elements concentration on the structural features of the Al75–87(Ni,Co,B/Ga)8–20Gd1Y4 alloys obtained by superfast quenching from the liquid state are established. The thermal stability of the rapidly quenched ribbons with an amorphous structure is investigated and the temperature ranges of phase transformations at continuous heating and under isothermal conditions are found. The strength characteristics of the ribbons as a function of the content and nature of alloying elements as well as the melt cooling rate are determined. The methods of obtaining both Al-based bulk nanocrystalline composites with the shapes of rods and plates with thickness of 0.5–3.5 mm and metal matrix hardening coatings are worked out.