High Temperature Excursions Research Articles

(Invited, Digital Presentation) 2-D Van Der Waal Materials for Advanced Interconnect Applications

Advanced interconnects require new materials to minimize high frequency signal loss and manage high temperature excursions due Joule heating. In this talk, we will review our on-going material selection modeling, and the thermo-mechanical reliability testing of interconnect prototypes that incorporate 2-D van der Waal thin films. Specifically, we will discuss our use of broadband microwave spectroscopy, that enables the accurate in-operando analysis of the electrical and magnetic properties without compromising the kinetic conditions of the experiment, to investigate high speed signal loss in 3-D integrated test circuits. The BDS method is sensitive to the actual electronic structure of the constituent materials and interfacial processes in the test structures. Using BDS, we have studied and characterized the 2-D van Der Wall, and other chalcogenide thin films in purposely built prototypical 3-D integrated circuit (3D-IC) during cycled high-temperature storage. We show that the microwave signal loss in these devices is attributable to the energy dissipation through the signal’s interactions with the copper barrier / cladding materials.

Evolution of Microstructure and Surface Characteristics of FeCrAl alloys when Subjected to Flow Boiling Testing

FeCrAl alloys are candidate materials for manufacturing accident-tolerant fuel (ATF) cladding intended for light water reactors to increase fuel reliability and safety during design-basis and beyond-design-basis accident scenarios. The evolution of the materials' surface characteristics, microstructure, and mechanical properties when exposed to the Critical Heat Flux (CHF) in flow boiling testing is crucial for safety analysis while providing insights into their thermal-hydraulic performance in nuclear reactors. After CHF, the surface chemistry of two FeCrAl alloys, APMT and C26M, was studied to understand their evolution at the early stage of high-temperature excursions in short time periods. The results indicated a thin layer composed of oxides and hydroxides of Al, Cr, and Fe with varying proportions at different depths in the layer, as indicated by X-ray photoelectron spectroscopy (XPS) and depth profiling. The cross-sections prepared by focused ion beam (FIB) revealed the growth of an oxide layer , in the range of 90-180 nm thick, on the alloys' surfaces. The evolution of the materials' surface chemistry also led to a noticeable post CHF excursion increase in their wettability , with a slight increase in roughness. The investigation of the materials' mechanical properties indicated a modest increase in hardness by 10-15% as well as an increase in their yield strength, as evidenced by the microindentation and ring compression tests conducted before and after CHF testing. Scanning electron Microscopy (SEM) and X-ray diffraction (XRD) were used to investigate microstructural features of the materials and their changes after CHF treatment.

Determination of nonlinearity parameter B/A of liquids by comparison with solutions of the three-dimensional Westervelt equation

Though nonlinear propagation depends upon the nonlinearity parameter B/A of the medium, it is often difficult to measure accurately. Thermodynamic methods often require high temperature and pressure excursions that can damage fragile molecules. Finite-amplitude methods often require unrealistic assumptions of ideal piston sources to account for diffraction effects. An alternative, described here, is to use the numerical solution of the three-dimensional Westervelt equation for weakly nonlinear fields (considering up to 10 s of harmonics of the fundamental frequency), and to match measured harmonic generation with that for simulated media. In particular, we follow Jafarzadeh et al. [Ultrasound Med. Biol. 47(3), 809–819 (2021)] to find that the nonlinearity parameter of a liquid can be recovered by determining the best match between measurements and simulations of media with different B/A values. Ideal piston sources with radial symmetry are not required, only a high-spatial-resolution hydrophone scan of the near-field source plane. Other techniques to determine the nonlinearity parameter by comparing propagation models with experiments, such as Richard et al. [New J. Phys. 22, 063021 (2020)], may improve on earlier measurement methods.

Turbulent dissipation, CH+ abundance, H2 line luminosities, and polarization in the cold neutral medium

ABSTRACT In the cold neutral medium, high out-of-equilibrium temperatures are created by intermittent dissipation processes, including shocks, viscous heating, and ambipolar diffusion. The high-temperature excursions are thought to explain the enhanced abundance of CH+ observed along diffuse molecular sightlines. Intermittent high temperatures should also have an impact on H2 line luminosities. We carry out simulations of magnetohydrodynamic (MHD) turbulence in molecular clouds including heating and cooling, and post-process them to study H2 line emission and hot-gas chemistry, particularly the formation of CH+. We explore multiple magnetic field strengths and equations of state. We use a new H2 cooling function for $n_{\text{H}}\le 10^5\, {\text{cm}}^{-3}$, $T\le 5000\, {\text{K}}$, and variable H2 fraction. We make two important simplifying assumptions: (i) the H2/H fraction is fixed everywhere and (ii) we exclude from our analysis regions where the ion–neutral drift velocity is calculated to be greater than 5 km s−1. Our models produce H2 emission lines in accord with many observations, although extra excitation mechanisms are required in some clouds. For realistic root-mean-square (rms) magnetic field strengths (≈10 μG) and velocity dispersions, we reproduce observed CH+ abundances. These findings contrast with those of Valdivia et al. (2017) Comparison of predicted dust polarization with observations by Planck suggests that the mean field is ≳5 µG, so that the turbulence is sub-Alfvénic. We recommend future work treating ions and neutrals as separate fluids to more accurately capture the effects of ambipolar diffusion on CH+ abundance.

Diffusion bonding effects on the adhesion of tungsten dust on tungsten surfaces

Abstract High temperature excursions have the potential to strongly enhance the room temperature adhesion of tokamak dust. Planar tungsten substrates containing adhered nearly monodisperse spherical tungsten dust have been exposed to linear plasmas and vacuum furnaces. Prolonged thermal treatments of varying peak temperature and constant duration were followed by room temperature adhesion measurements with the electrostatic detachment method. Adhesive forces have been observed to strongly depend on the thermal pre-history, greatly increasing above a threshold temperature. Adhesive forces have been measured up to an order of magnitude larger than those of untreated samples. This enhancement has been attributed to atomic diffusion that slowly eliminates the omnipresent nanometer-scale surface roughness, ultimately switching the dominant interaction from long-range weak van der Waals forces to short-range strong metallic bonding.

A vaccine cold chain temperature monitoring study in the United Mexican States

Vacine cold chain assessments conducted in various parts of the world indicate that maintaining equipment at the temperature range recommended by the World Health Organization (WHO) is not always observed. It has been also the case that staff rather prioritize protecting vaccine from heat damage, thus often exposing vaccines to freezing temperatures. As a result, inadvertent freezing of vaccines is a largely overlooked problem all over the world. In a recent systematic review, comparison of the occurrence of freezing temperatures during storage and transport were found to be a global problem occurring both in the resource-rich as well as the resource-limited settings. A vaccine cold chain temperature monitoring study was conducted using standard WHO study protocol with the objective to document potential problems and to identify appropriate control measures. Multiple temperature monitoring devices were used in the study to evaluate user friendliness of these devices and staff attitudes towards them. In general, majority of the time, temperatures were kept between recommended temperature range of 2–8 °C. Temperature variation got wider when products moved from 3PL Laboratory to service points. The wider variation is found at the service points. High temperature excursions were observed or short periods of time while exposures to freezing temperatures were more both higher in number and duration, however, shake test with these vaccines indicated no freeze damage. 91% of staff believed that they did not have the necessary tools to detect if a vaccine had been damaged by a temperature excursion outside the 2–8 °C range, and all staff believed that inclusion of such devices (e.g. vaccine vial monitor) in the system would improve cold chain operations as they have became aware of problematic areas through this study.

Lubricant Concepts for Electrified Vehicle Transmissions and Axles

It is anticipated that many future electrified vehicle transmissions and axles will incorporate the electric motor within the unit housing. In such an arrangement, the lubricant will be in direct contact with powered motor windings, which raises new concerns regarding its electrical conductivity and its propensity to corrode copper. The heat produced at the motor windings will challenge the lubricant’s heat transfer ability and its thermal stability. Expected high temperature excursions warrant the use of new plastics, which may give rise to new compatibility concerns. In this paper we share our learnings regarding the electrical properties of lubricants and discuss new methods to characterize copper corrosion. We review the factors that affect the heat transfer characteristics of lubricants and illustrate how improving heat transfer will favor the use of lower viscosity lubricants. We also share our early efforts to quantify lubricant compatibility with higher temperature plastics using tensile strength measurements. Finally, we discuss how these new concerns will shift the perception of what is required for lubricants used in different types of electrified transmission hardware.

Grasping at straws: a re-evaluation of sweepstakes colonisation of islands by mammals.

Natural rafting is an easy, non-evidence-based solution often used to explain the presence of a variety of species on isolated islands. The question arises as to whether this solution is based on solid scientific grounds. It is a plausible colonisation route only if intricate networks of variables are considered and many different conditions satisfied. This review provides a descriptive account of some of the most critical issues underlying the theory of natural rafting that should be addressed by its supporters. These include: (i) biological variables; (ii) characteristics of the vessels; and (iii) physical variables. Natural rafting may explain the dispersal of poikilotherms with low metabolic rates and low resource requirements that could withstand trans-oceanic crossings, but explaining the transport of homeothermic terrestrial mammals to oceanic islands is more problematic. Drifting at sea exposes organisms to high concentrations of salt, high temperature and humidity excursions, starvation, and above all to dehydration. A sufficiently large group of healthy reproductive individuals of the two sexes should either be transported together, or be able to reassemble after separate crossings, to prevent inbreeding, genetic drift and ultimately extinction. Any vessels of flotsam occupied must minimally provide the animals they transport with sufficient provisions to survive the journey, offer minimum friction and drag through water, and be transported by appropriately directed, sustained, high-speed currents. Thus, a 'sweepstakes colonisation' event would be the result of a lucky combination of all, or at least the majority, of these factors. Some cases throw doubt on the use of a natural rafting model to explain known animal colonisations, with one of the most striking examples being Madagascar. This island is far from the nearest mainland coasts and the sea currents in the Mozambique Channel are directed towards Africa rather than Madagascar, yet, the island was colonised by terrestrial mammals (e.g. extinct hippopotamuses, lemurs, carnivores, rodents and tenrecs) unable to swim and to survive long journeys at sea. In order to assess the feasibility of the natural rafting model in a case such as Madagascar, tests were performed using three variables for which enough information could be obtained from the literature: length of survival without food, survival without water, and sea current speed. The distributions of these variables appear to be log-normal and multiplicative, or follow a power-law, rather than being Gaussian. The tests suggest that a distributional analysis is a more suitable approach than the use of geometric probability to calculate the probabilities associated with the examined data. Such non-linear and self-organising systems may reach a critical point governed by different competing factors. Mammals with high survival requirements, such as lemurs and hippopotamuses, thus may have a virtually zero probability of reaching distant islands by natural rafting. Our results raise doubts as to the validity of a natural rafting model, and we urge a rethinking of the modes in which numerous islands were colonised by land mammals and a careful revision of past geological and phylogeographic work.

Selective catalytic reduction of NOx with NH3 over short-range ordered W[sbnd]O[sbnd]Fe structures with high thermal stability

The selective catalytic reduction (SCR) of NOx with NH3 was studied over poorly-crystalline WFe composite oxides (WaFeOx). The short-range order present within the WOFe structure was found to be responsible for the excellent SCR activity, in which the strong atomic-level interaction between Fe and W atoms promoted the formation of both Lewis and Brønsted acidity. The WOFe structure existed as amorphous overlayers, approximately 2 nm thick over the surface of crystalline particles after high-temperature aging as shown by high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). After treatment at 800 °C for 5 h, the WaFeOx catalysts still showed almost 100% NO conversion in the range 300–450 °C with 100% N2 selectivity, despite the loss in surface area. This resistance to the impacts of high temperature ageing guarantees high activity of SCR catalysts which often suffer during high-temperature excursions as in the case of diesel exhaust due to diesel particulate filter (DPF) regeneration.

Preventing lithium ion battery failure during high temperatures by externally applied compression

Lithium-ion cells can unintentionally be exposed to temperatures outside manufacturers recommended limits without triggering a full thermal runaway event. The question addressed in this paper is: Are these cells still safe to use? In this study, externally applied compression has been employed to prevent lithium ion battery failure during such events. Commercially available cells with Nickel Cobalt Manganese (NCM) cathodes were exposed to temperatures at 80°C, 90°C and 100°C for 10h, and electrochemically characterised before and after heating. The electrode stack structures were also examined using x-ray computed tomography (CT), and post-mortems were conducted to examine the electrode stack structure and surface changes. The results show that compression reduces capacity loss by −0.07%, 4.95% and 13.10% respectively, measured immediately after the thermal testing. The uncompressed cells at 80°C showed no swelling, whilst 90°C and 100°C showed significant swelling. The X-ray CT showed that the uncompressed cell at 100°C suffered de-lamination at multiple locations after test, and precipitations were found on the electrode surface. The post-mortem results indicates the compressed cell at 100°C was kept tightly packed, and the electrode surface was uniform. The conclusion is that externally applied compression reduces delamination due to gas generation during high temperature excursions.

The Microenvironment within and Pollen Transmission through Polyethylene Sorghum Pollination Bags

Bird damage is a problem in sorghum breeding and germplasm maintenance operations. Paper pollination bags are damaged by rain and provide minimal deterrent to birds. Earlier we reported upon bird resistance of spun polyethylene pollination bags. Herein, we report the potential for pollen transmission through, and the microenvironment within, hard form (HfT) and soft form (SfT) spun polyethylene pollination bags as compared to traditional Paper pollination bags. Within Paper pollination bags morning temperatures were 10°C - 15°C above ambient and high temperature excursions as high as 45°C were measured. Heating in Sft and HfT was 25% and 50% that of Paper, respectively. Temperature differences between bags were attributed to differences in albedo and air permeability of the bag materials. No difference in pollen transmission through Paper and HfT was found. Although SfT allowed 35% - 40% wind borne pollen through the pores as compared to controls, male sterile plants covered with SfT produced only 30 seeds/panicle, about 1% of a self-pollinating fertile plant. Our results suggested that SfT could adequately reduce or eliminate cross-pollination in self-pollinating plants while maintaining near ambient environmental conditions.

Reaction Kinetics of Aged NOx Storage Catalysts

NOx storage catalysts (NSCs) are utilized to reduce the emissions in lean-burning engines such as diesel and lean-burn Otto engines. One of the current limitations of this technology is catalyst aging due to high-temperature excursions. To guarantee high conversions and to adapt engine and catalyst management, simulations of the exhaust line require a proper description of the conversion behavior of aged NSCs. Because of their complex chemical constitution (three precious metals, two storage components), kinetic models of NSCs encompass a large number of model parameters, which are determined from extensive experimental investigations. In this contribution, we show that the kinetics of aged NSCs can be derived from the kinetics of the fresh catalyst plus a relatively small set of experiments needed to quantify catalyst degradation. Seven scaling factors are necessary, which can be regressed one by one from simple test experiments. The scaling factors account for precious-metal sintering, reduced barium an...

High-temperature fatigue life of flip chip lead-free solder joints at varying component stand-off height

The recent uses of microelectronics as sensors or control devices at high-temperature ambient increase the rate of visco-plastic degradation of solder joints of their components. The response of solder bumped joints to the induced thermal load culminates in plastic strain which over many cycles may accumulate damage in the joints, subsequently leading to their fatigue failures. Finite element modelling is employed to investigate the impact of static structural factors of flip chip (FC) assembly on its solder joint damage at high-temperature excursions. This paper discusses results of a modelling study focused on effects of component stand-off height (CSH) and intermetallic compound (IMC) on static structural integrity of lead-free solder joints in a flip chip FC48D6.3C457 package which is cycled between −38°C and 157°C temperatures. The result analysis is based on accumulation of damage indicators such as stress, strain and plastic work density in the solder joints. The accumulated damage was used to predict the thermo-fatigue life of different architectures of the FC assembly. It was found that the fatigue life of the joint assemblies decrease exponentially as the component stand-off height decreases in a cubic function. Based on our research results, it is proposed that the size of diameter of bond pad defined by solder mask on printed circuit board (PCB) should not exceed 110% of the size of diameter of bond pad at the chip side.

Molecules for Charge-Based Information Storage

The inexorable drive to miniaturize information storage and processing devices has fueled the dreams of scientists pursuing molecular electronics: researchers in the field envisage exquisitely tailored molecular materials fulfilling the functions now carried out by semiconductors. A bottom-up assembly of such all-molecular devices would complement, if not supplant, the present top-down lithographic procedures of modern semiconductor fabrication. Short of these grand aspirations, a more near-term objective is to construct hybrid architectures wherein molecules are incorporated in semiconductor-based devices. Such a combined approach exploits the advantages of molecules for selected device functions while retaining the well-developed lithographic approaches for fabrication of the overall chip. In this Account, we survey more than a decade of results from our research programs to employ porphyrin molecules as charge-storage elements in hybrid semiconductor-molecular dynamic random access memory. Porphyrins are attractive for a variety of reasons: they meet the stability criteria for use in real-world applications, they are readily prepared and tailored synthetically, they undergo read-write processes at low potential, and they store charge for extended periods (up to minutes) in the absence of applied potential. Porphyrins typically exhibit two cationic redox states. Molecular architectures with greater than two cationic redox states are achieved by combinations of porphyrins in a variety of structures (for example, dyads, wherein the porphyrins have distinct potentials, triple deckers, and dyads of triple deckers). The incorporation of porphyrins in hybrid architectures has also required diverse tethers (alkyl, alkenyl, alkynyl, aryl, and combinations thereof) and attachment groups (alcohol, thiol, selenol, phosphonate, and hydrocarbon) for linkage to a variety of surfaces (Au, Si, SiO(2), TiN, Ge, and so forth). The porphyrins as monolayers exhibit high charge density and are robust to high-temperature excursions (400 °C for 30 min) under inert atmosphere conditions. Even higher charge densities, which are invaluable for device applications, were achieved by in situ formation of porphyrin polymers or by stepwise growth of porphyrin-imide oligomers. The various molecular architectures have been investigated by diverse surface characterization methods, including ellipsometry, atomic force microscopy, FTIR spectroscopy, and X-ray photoelectron spectroscopy, as well as a variety of electrochemical methods. These studies have further revealed that the porphyrin layers are robust under conditions of deposition of a top metal contact. The results to date indicate the superior features of selected molecular architectures for molecular electronics applications. The near-term utilization of such materials depends on further work for appropriate integration in semiconductor-based devices, whereas ultimate adoption may depend on advances that remain far afield, such as the development of fully bottom-up assembly processes.

Transient temperature rise during regeneration of diesel particulate filters

A major technological challenge in the regeneration of diesel particulate filters (DPFs) is that sometimes the exothermic regeneration generates excessively hot local zones that melt the cordierite ceramic filter. The cause of this melting is still an open question. The temperature rise under stationary (constant feed conditions) regeneration is not sufficiently high to cause this melting. We investigated a conjecture that the high temperature excursions in a DPF may be the dynamic response to a shift from normal driving mode to idle. This shift affects three inputs: It increases the oxygen concentration and simultaneously decreases the feed temperature and filtration velocity. Infrared measurements of the spatio-temporal temperature during soot combustion on a single layer DPF confirmed that the response to such a simultaneous step change leads to a transient temperature that exceeds the highest attained for stationary operation under either the initial or final operation conditions. The transient temperature rise caused by a simultaneous step change of the three inputs was rather close to the sum of the responses the three individual changes. The amplitude of the temperature excursion depended in a complex way on several factors, such as the direction of the moving temperature front and whether the feed step-change was done before or after the formation of a moving front, and the period after the initiation of the temperature front.

Counter-intuitive temperature excursions during regeneration of a diesel particulate filter

A major technological challenge in the regeneration of diesel particulate filters (DPFs) is that sometimes local high temperature excursions melt the cordierite ceramic filter. The cause of this melting is still an open question as the highest temperature attained under stationary (constant feed) combustion of the accumulated particulate matter is too low to cause this melting (melting temperature ∼1250°C). We recently conjectured that the high temperature excursions are a counterintuitive response to a rapid deceleration, which decreases the exhaust gas temperature and flow rate and increases the oxygen concentration. Infrared measurements of the spatiotemporal temperature during soot combustion on a single-layer DPF showed that a simultaneous step change of the feed temperature, flow rate, and oxygen concentration can lead to a transient temperature that exceeds the highest attained for stationary operation under either the initial or the final operation conditions. The experiments revealed that the magnitude of the temperature rise depends in a complex way on several factors, such as the direction of movement of the propagating temperature front. The amplitude of the temperature rise is a monotonic decreasing function of the distance that the temperature front moved before the step change. The rapid response to the feed oxygen concentration increases initially the moving front temperature. The slow response of the ceramic DPF to a decrease in the feed temperature may eventually decrease the moving front temperature and even lead to premature extinction and partial regeneration. © 2010 American Institute of Chemical Engineers AIChE J, 2011

Optical investigation of the quenching of coated conductors

The superconducting fault current limiter (FCL) offers great opportunities to improve the security and the power quality for electric networks, two real demands today. This innovative device is based on the quench of a superconductor when its critical value is overstepped. The quench initiation and propagation are of prime importance for a safe operation. The hot spot problem with local high temperature excursions must be avoided. The visualization of the quench and its propagation can be observed at the beginning by filming the bubbles produced in the liquid nitrogen by local dissipations. We study YBaCuO coated conductors, which show great promises for superconducting FCL. A special cryostat has been used with windows in order to film the bubble generations. The nitrogen bath temperature may be adjusted by heating/pressurising the bath. We have indeed shown previously that the quench is much more "homogeneous" when the temperature goes closer to the critical one. This is confirmed by the optical measurements: the bubble generation is completely different when the temperature increases. Other parameters play an important part such as the tape itself (AMSC and IGC tapes show different behaviours) and the applied voltage or current (nature of the power source). In some conditions, the quench is initiated in bands across the tape and these bands are regularly distributed along the tape. The distance between the bands depends on the voltage inter alias. The experience and the different observations are presented. The tape nature and different parameters (temperature, voltage, ...) will be investigated. These works complete the magneto optical investigations carried out also in Grenoble

Annealing behavior of atomic layer deposited HfO2 films studied by synchrotron x-ray reflectivity and grazing incidence small angle scattering

New results are presented for the annealing behavior of ultrathin complementary-metal-oxide-semiconductor (CMOS) gate dielectric HfO2 films grown by atomic layer deposition (ALD). A series of ALD HfO2 dielectric films has been studied by a combination of x-ray reflectivity (XRR) and grazing-incidence small-angle x-ray scattering (GISAXS) measurements. By using these techniques together, we have shown that the surface, interfaces, and internal structure of thin ALD films can be characterized with unprecedented sensitivity. Changes in film thickness, film roughness, or diffuseness of the film/substrate interface as measured by XRR are correlated with the corresponding changes in the internal film nanostructure, as measured by GISAXS. Although the films are dense, an internal film structure is shown to exist, attributed primarily to ≈2 nm “missing island” porosity features close to the substrate; these are most likely associated with coalescence defects as a result of initial ALD growth, as they are not observed in the upper regions of the film. Some 8–9 nm heterogeneities are also present, which may indicate a widespread modulation in the film density pervading the entire film volume, and which likely also give rise to surface roughness. Comparison of the data between different scattering geometries and among a carefully designed sequence of samples has enabled important insights to be derived for the annealing behavior of the ALD HfO2 films. The main effects of single, brief, high temperature excursions to above 900 °C are to anneal out some of the fine voids and reduce the mean roughness and interfacial diffuseness of the film. These changes are indicative of densification. However, depending on the film thickness, the annealing behavior at temperatures between 650 and 800 °C is quite different for single excursion and cyclic anneals. Particularly for thin, just-coalesced films, XRR indicates marked increases in the film thickness and in the mean roughness/diffuseness dimension for cyclic anneals. GISAXS also shows an increase, rather than a reduction, in the void microstructure under these conditions. These changes in the film microstructure appear sufficient to overcome the expected film densification at elevated temperatures with implications for the gate dielectric performance of the films after extended high temperature exposure and cycling, as may occur during gate dielectric fabrication.

Thermostability of model protocell membranes

The earliest cells may have consisted of a self-replicating genetic polymer encapsulated within a self-replicating membrane vesicle. Here, we show that vesicles composed of simple single-chain amphiphiles such as fatty acids, fatty alcohols, and fatty-acid glycerol esters are extremely thermostable and retain internal RNA and DNA oligonucleotides at temperatures ranging from 0 degrees C to 100 degrees C. The strands of encapsulated double-stranded DNA can be separated by denaturation at high temperature while being retained within vesicles, implying that strand separation in primitive protocells could have been mediated by thermal fluctuations without the loss of genetic material from the protocell. At elevated temperatures, complex charged molecules such as nucleotides cross fatty-acid-based membranes very rapidly, suggesting that high temperature excursions may have facilitated nutrient uptake before the evolution of advanced membrane transporters. The thermostability of these membranes is consistent with the spontaneous replication of encapsulated nucleic acids by the alternation of template-copying chemistry at low temperature with strand-separation and nutrient uptake at high temperature.

Adiabatic Calorimetry of Telomerization Reactions in Ionic Liquids

The telomerization reaction between acrylonitrile (AN) and trichloroacetyl chloride (TCAC), which is one of the important intermediate steps in the manufacture of a commercial pesticide compound, often results in high temperature and pressure excursions if proper controls are not applied. Hence there is a need for upgrading the process safety of this reaction. Ionic liquid solvents, by virtue of their relatively low volatility and high thermal stability in some cases, have been investigated in this study as a means of improving intrinsic process saftey. Adiabatic calorimetry is a useful analytical technique to monitor the temperature and presssure excursions in reactions, and this technique is applied here for the first time to the telomerization reaction.