Metal Condensation Research Articles

Facile Synthesis of Novel Short-Chain Ligand-Capped Colloidal Metal Oxide Nanoparticles for Printed Flexible Devices.

Colloidal metal oxide nanoparticles are key materials for achieving cost-effective and large-scale production of flexible devices, as they enable the formation of functional oxide thin films at low temperatures (<400 °C) through printing techniques such as inkjet printing, gravure coating, and microcontact printing. The conventional solvothermal synthesis of colloidal metal oxide nanoparticles through the thermal decomposition of precursors results in particles with bulky, long-chain ligands on their surfaces, which hinder the formation of dense oxide films when depositing the colloidal metal oxide nanoparticles. Herein, we have developed a simple and versatile method for synthesizing colloidal metal oxide nanoparticles using base-induced hydrolysis and the condensation of metal acetates as precursors. Various binary and ternary colloidal metal oxide nanoparticles (CuO, Mn3O4, Co3O4, CeO2, In2O3, Co1.8Mn1.2O4) were synthesized using short-chain acetate ligands on their surfaces. The thin acetate ligand-containing colloidal Co1.8Mn1.2O4 nanoparticle film exhibited lower resistivity than the same with long-chain oleate ligands. The films coated onto a polyimide substrate formed a flexible negative temperature coefficient thermistor that exhibited the temperature dependence of resistance comparable to bulk materials with a bending durability of up to 5 mm radius. These findings highlight the effectiveness of utilizing colloidal metal oxide nanoparticles with short-chain ligands in flexible devices.

Characteristics and Outcomes of Lymphoid Malignancies in Veterans Exposed to Burn Pits

Introduction Military personnel were deployed to the Middle East for the Persian Gulf War (8/1990-7/1991), Operation Enduring Freedom (10/2001-12/2014), and Operation Iraqi Freedom (3/2003-11/2011), where they were exposed to environmental hazards including geological dust chemical smoke from burn pits, and heavy metal condensates 1. Burn pits are open-air fires that are used to dispose of food, human waste, plastic bottles, and electronic equipment during the conflicts in the Middle East and release high levels of dioxins, furans, particulate matter, polycyclic aromatic hydrocarbons, and volatile organic compounds, all well established as known human carcinogens 1. Outcomes in veterans diagnosed with lymphoid malignancies with and without burn pit exposure are unknown and warrant further study. Methods This is a retrospective case-case analysis of veterans diagnosed with mature lymphoid malignancies identified from the VA Cancer Registry 2. Descriptive statistics were used to compare cases with and without burn pit risk. Burn pit risk was defined as exposure to Iraq or Afghanistan from the VA Cancer Registry, combat in the Middle East from the VA disability database, or exposure to known chemical locations at Al Jubayl in Saudi Arabia or Khamisiyah in Iraq from USVETS. The Persian Gulf War began 8/2/90 and was considered the presumptive start date of burn pit risk, which was calculated from time at risk until exit from the military. Latency was defined as the time from exposure to the development of a lymphoid malignancy. Cases were excluded if veterans exited the military before 8/2/90 or entered after 12/31/14, latency of exposure to the diagnosis of lymphoid malignancy &amp;lt;6 months, or the burn pit risk was &amp;lt;1 month from 8/2/90 to exit from military. Overall survival (OS) was calculated by time from diagnosis to date of death or last contact, and disease specific survival (DSS) was calculated from time from diagnosis to date of death from a hematologic malignancy or last contact. OS and DSS by histologic subtype were compared by the Kaplan Meier method. Dates and causes of death were determined by the National Death Index, which provided data up to 12/31/20 (data cut off date) 3. Results Patient characteristics are summarized in Table 1. Veterans exposed to burn pits were diagnosed with a lymphoid malignancy at a younger age compared to the unexposed group (47 vs 52 years, p&amp;lt;0.0001). There were differences in racial distribution between the two groups (p=0.0463). More veterans who were exposed to burn pits enlisted in the army (56.8% vs 37.3%) and fewer in the navy (10.2% vs 21.0%) compared to the unexposed group (p&amp;lt;0.0001). Exposed patients had a higher frequency of Hodgkin lymphoma (17.5% vs 12.7%) and lower frequency of plasma cell neoplasms (17.8% vs 20.6%) and chronic lymphocytic leukemia (14.4% vs 16.2%) compared to those who were unexposed (p=0.0002). The difference in age between the exposed and unexposed group may contribute to the different frequencies of these subtypes. By histologic subtypes, the median OS and DSS were not significantly different between the two groups. More patients in the unexposed group died when compared to the exposed group (25.2% vs 18.9%, p&amp;lt;0.0001), but the causes of death did not differ. Conclusion Veterans exposed to burn pits may be diagnosed with a lymphoid malignancy at a younger age compared to unexposed veterans, but there is no difference in median OS or DSS by histologic subtype. More veterans who were unexposed to burn pits died but there were no differences in the causes of death between the two groups. This may be explained by the exposed group being younger and the “healthy soldier effect”. We are continuing to examine the effect of burn pits on the development and outcomes of lymphoid malignancies in more detail. Citations 1 Institute of Medicine. Long-Term Health Consequences of Exposure to Burn Pits in Iraq and Afghanistan. Washington, DC: The National Academies Press; 2011. 2 US Department of Veteran Affairs. VA Informatics and Computing Infrastructure (VINCI), VA ORD 22-D4V, U.S. Department of Veterans Affairs. 2008. Retrieved August 1, 2022, from https://vincicentral.vinci.med.va.gov. 3 Veterans Health Administration Center of Excellence for Suicide Prevention. Joint Department of Veterans Affairs and Department of Defense Mortality Data Repository. 2022. Data compiled from the National Death Index. Extract December 6, 2022.

(Invited) Record-High Charge Carrier Mobilities in 2D Covalent- and Metal- Organic Frameworks

Organic based 2D layered materials (2DLMs) including 2D covalent and metal organic frameworks (COFs and MOFs) are promising candidates for traditional applications in gas storage and separation as well as catalysis. This is due to the long-range crystalline order that can be achieved in them as well as their tunable porosity and chemistry. Synthetic chemistry efforts aiming an enhanced coupling between their building block constituents have recently led to the design of (semi-)conducting MOFs and COFs displaying high conductivities and record charge carrier mobilities. These achievements have opened the path for their application in opto-electronics. Yet, despite being a critical aspect for the development of 2DLM based electronics, understanding the true nature of charge transport in these novel materials by stabilising reliable structure-property-function relations is largely unexplored.Here I will present time-resolved high-frequency (terahertz) conductivity studies of state-of-the-art organic based 2DLMs materials revealing semiconducting behaviour and record charge carrier mobilities. First, I will present a detailed characterization for the electronic properties of Zn– and Cu–phthalocyanine-based pyrazine-linked 2D COFs [1,2]. These 2D COFs, synthesized by condensation of metal–phthalocyanine (M = Zn and Cu) and pyrene derivatives, are obtained as polycrystalline-layered semiconductors displaying p-type doping and a band gap of ∼1.2 eV. Hall effect measurements (dc limit) and terahertz (THz) spectroscopy (ac limit) in combination with density functional theory (DFT) calculations demonstrate that varying metal center from Cu to Zn in the phthalocyanine moiety has a negligible effect in the conductivity (∼5 × 10–7 S/cm), charge carrier density (∼1012 cm–3), charge carrier scattering rate (∼3 × 1013 s–1), and effective mass (∼2.3m0) of majority carriers (holes). However, both samples reveal slightly different mobilities that can be attributed to charge carrier localization at crystalline grain boundaries. Furthermore we analyse the effect of iodine doping on the Zn based 2D COFs. The resultant 2D c-COF ZnPc-pz-I2 maintains its structural integrity and displays enhanced conductivity by 3 orders of magnitude, as a result of improved charge carrier concentrations. Hall effect reveal a charge carrier mobility reaching ∼22 cm2/Vs for ZnPc-pz-I2, which represent a record value for 2D c-COFs. An improved mobility upon doping can be traced to an increase in scattering time for free charge carriers, indicating that scattering mechanisms limiting the mobility are mitigated by doping.In the second part of my talk, I present the results concerning a Fe3(THT)2 (THT=2,3,6,7,10,11-hexathioltriphenylene) 2D MOFs [3]. The π-d conjugated samples, synthesized through interfacial method at room temperature, are obtained as a large-area, free-standing films with tunable geometry (size and thickness). The Fe3(THT)2 films are porous (specific surface area of 526±5 m2/g) and semiconducting (with a ~250 meV direct bandgap), and remarkably display band-like charge transport. This finding is directly demonstrated from the Drude-type high-frequency (terahertz) photo-conductivity response obtained in the samples; revealing free-moving, delocalized charge carriers displaying ~220 cm2/Vs mobilities at room temperature; a record charge carrier mobility for MOFs. The temperature dependence of the mobility reveals that the main scattering mechanism limiting the mobility and hence band-like charge transport in this material is related to impurity scattering, so that material improvements may further increase the mobility.The demonstration of band-like charge transport and record-high mobilities in semiconducting 2D COFs and MOFs reveal the potential of (porous) electrically conductive 2DLMs to be employed as active materials in opto-electronics devices.

Surface Facet Dependent Cycling Stability of Layered Cathodes

AbstractHigh chemical and mechanical stability of cathode surface are the prerequisites enabling high‐performance rechargeable battery. Surface facet is among the surface properties that dictate surface stability and cycling performance, while its underlying mechanism remains elusive. Herein, it is reported that surface stability is closely related to the surface facet for a variety of layered cathodes. The investigation shows that surface structure of P2 layered cathode undergoes sequential transformation upon cycling, which results in severe surface degradation. This study finds that the surface facets perpendicular to the (002) planes experience severe cracking and corrosion, while other surface facets are much more stable. The surface stability difference mainly comes from a geometric effect on strain release, which determines the mechanical stability of surface. Chemically, transition metal condensation forms a passivation layer to effectively prevent the inward propagation of surface degradation. Therefore, the surface facets oblique to the layered‐planes are intrinsically more resistant to mechanical cracking and chemical corrosion, which is further verified as a common effect in several O3‐type layered cathodes. This work not only deepens the understanding of the mechanism how surface facet affects surface stability, but also validates surface facet regulation can be a promising strategy for optimizing battery materials.

High Performance Transparent Silver Grid Electrodes for Organic Photovoltaics Fabricated by Selective Metal Condensation.

We report silver grid electrodes on glass and flexible plastic substrates with performance that exceeds that of commercial indium-tin oxide (ITO) coated glass and show their suitability as a drop-in replacement for ITO glass in solution processed organic photovoltaics (OPVs). When supported on flexible plastic substrates these electrodes are stable towards repeated bending through a small radius of curvature over tens of thousands of cycles. The grid electrodes are fabricated by the unconventional approach of condensation coefficient modulation using a perfluorinated polymer shown to be far superior to the other compounds used for this purpose to date. The very narrow line-width and small grid pitch that can be achieved also opens the door to the possibility of using grid electrodes in OPVs without a conducting PEDOT:PSS layer to span the gaps between grid-lines. This article is protected by copyright. All rights reserved.

Theoretical algorithm for fast calculation of interatomic bonds as applied to metallic hydrogen and carbon condensates

A method for calculating the potential energy of interatomic interaction, an alternative to the use of significant computer resources, is proposed. The algorithm was tested on the example of 1S-1S bonds, in particular, in hydrogen, as well as 2S-2S and 2 P-2P bonds, in particular, in carbon. It is shown that bound states can be formed in all three cases, but the interacting atoms must overcome the potential barrier. The presence of a barrier makes it possible to explain a number of known features in the formation of the corresponding condensates.

Metal compositions of carbonaceous chondrites

FeNi metals represent an important fraction of chondritic components that remains relatively unexplored within most carbonaceous chondrite groups. The compositions of these metals can place constraints on the nature of their precursor materials as well as the physicochemical conditions of chondrule formation. In this study, we have analyzed the major, minor and trace element compositions of metal grains from relatively unaltered carbonaceous chondrites NWA 801 (CR), Leoville (CV3.1), Paris (CM2.9), Maribo (CM2.8) and Bells (CM-an). We observe a predominant and constant sub-solar Co/Ni ratio of CR, CM and CM-an metal grains. In Ni versus Co space, the metal grains fall below modelled curves for equilibrium condensation of metals from a solar gas. From Ni versus Cr plots, we infer that Paris (and possibly Leoville) metal grains could have maintained a primary condensation signature, although for most grains, condensation must have occurred under disequilibrium conditions. CR and isolated CM-an metals mostly fall outside of the predicted condensation fields. Based on metal-silicate partition coefficients of Ni and Co that vary with pressure, we interpret their Co/Ni signatures as having a planetary origin, with presumable extraction by impact jetting. Considering that almost all CM and CR metal grains have the same Co/Ni ratio, we cannot rule out a planetary origin for CM metal grains. We relate the highly siderophile element (HSE) patterns of carbonaceous chondrite metal to mixing and subsequent equilibration of refractory metal nuggets (RMN), FeNi alloys and silicate chondrule precursors. As with the Co/Ni ratios, the HSE patterns of CM, CM-an, CR and CV metal grains are nearly identical, suggesting that the abundance and nature of the metal precursor materials were similar for carbonaceous chondrites. The overall volatility patterns of CV, CM and CR chondrites, suggest that the latter form under more oxidizing conditions than CV chondrites. The volatility patterns of Paris metal grains overlap with CV and CR chondrule metals, implying variable P-T-fO2 conditions during CM chondrule formation. Finally, we comment on the origin of metal grains in various petrological settings. Chondrule rim and isolated metal grains are likely derived and expelled from the equilibrated core metal and were subsequently altered to include and re-equilibrate with materials from the disk. Trace element analyses of the anomalous CM chondrite Bells metal grains show potential relationships with CM chondrite and CH chondrite metal for the chondrule cores and isolated grains, respectively. Small metal grains from CM chondrite Maribo, which are located in the chondrite matrix, potentially have distinct volatility patterns from CR and Paris isolated grains, hinting at a distinct origin for small metal grains and large chondrule-derived metal. Future work on carbonaceous chondrite metal should include an investigation of small (micron scale) versus large isolated metal grains.

Non-aqueous synthesis of homogeneous molybdenum silicate microspheres and their application as heterogeneous catalysts in olefin epoxidation and selective aniline oxidation

In this work, a novel synthesis of homogeneous molybdenum silicate spheres under non-aqueous conditions is presented. A preparation method is based on the condensation of molybdenum metal–organic framework-based precursor solution prepared via a microwave-assisted approach from bis(acetylacetonato)dioxomolybdenum and biphenyl-4,4′-dicarboxylic acid with 3-aminopropyltriethoxysilane under non-aqueous conditions. The as-prepared product was calcined at 500 °C to obtain amorphous and porous molybdenum silicate microspheres with homogeneously distributed molybdenum species within silicate matrix. The microspheres exhibit an average size of about 480 nm. This material was further studied as a heterogeneous catalyst for the epoxidation of olefins via the model catalytic epoxidation of cyclohexene with cumylhydroperoxide. High catalytic activity at the moderate temperature (65 °C) with the conversion of 86% after 2 h and the high selectivity to cyclohexene oxide has been achieved. In addition, molybdenum silicate microspheres exhibit catalytic activity and high selectivity in the oxidation of aniline to nitrosobenzene.

Geochemical constraints on the formation of chondrules: Implication from Os and Fe isotopes and HSE abundances in metals from CR chondrites

CR chondrites are suitable for understanding the genetic linkage between metals and chondrules due to the unique characteristics of the coexisting metal phases with chondrules. Metal grains are found in three different locations of CR chondrites; chondrule interior (“interior grain”), chondrule surficial shells (“margin grain”), and the matrix (“isolated grain”). Here we report the abundances of highly siderophile elements (HSEs) and major elements in three types of metals (interior, margin, and isolated grains) from three CR chondrites (NWA 801, NWA 7184, and Dhofar 1432) by using femtosecond LA-ICP-MS (fs LA-ICP-MS) and EPMA. Additionally, we report the isotopic compositions of Os and Fe in the metals by using micro-milling sampling coupled with N-TIMS and MC-ICP-MS. The CR metals have variations in 187Os/188Os and δ57Fe values ranging from 0.1193 to 0.1314 and from −1.05 to +0.25, respectively. HSE abundances, except for Pd and Au, in the three types of metals increase as the abundance of Ir increases. A possible explanation for the variations of HSE abundances within and among grains, 187Os/188Os values within each grain, and δ57Fe values among grains, is the condensation of liquid metal from a gaseous reservoir followed by fractional crystallization. Most of the CR metals have negative δ57Fe values, suggesting that Fe in metal phases might have formed by condensation prior to Fe condensation in silicate phases. The chondrules and three types of metal grains in CR chondrites are believed to have formed contemporaneously in the same region. The existence of large isolated metals in matrix and compound chondrules might be the result of collision and merging of the metal and silicate droplets.

Structure and Mechanical Properties of Thick Metal Condensates Strengthened with Various Dispersed Particles. I. Strengthening Mechanism of Dispersion-Strengthened Metals

Structure and Mechanical Properties of Thick Metal Condensates Strengthened with Various Dispersed Particles. I. Strengthening Mechanism of Dispersion-Strengthened Metals

Structure and Mechanical Properties of Thick Metal Condensates Strengthened with Various Dispersed Particles. I. Structure and Yield Strength of Dispersion-Strengthened Thick Metal Condensates

Structure and Mechanical Properties of Thick Metal Condensates Strengthened with Various Dispersed Particles. I. Structure and Yield Strength of Dispersion-Strengthened Thick Metal Condensates

Thermohydraulics of Alkaline Liquid-Metal Coolant: A Retrospective-Perspective Look

Sixty years of experience in mastering alkaline liquid metals jointly with industry institutes, the Academy of Sciences, and engineering design agencies developing Nuclear Power Facilities (NPF) has culminated in the development of the scientific foundations for their use in nuclear power and the scientific substantiation of the hydraulic parameters and highly efficient technological processes ensuring successful operation of fundamentally new NPF. The primary directions of research were the hydrodynamics of and heat transfer in channels with complicated shapes and in nominal and deformed fuel-rod assemblies, including the blocking of flow sections, and the mechanisms of turbulent heat and mass transfer, interchannel mixing of the coolant, and the hydrodynamics of collector systems in reactors and heat-exchange equipment. Significant attention was devoted to heat exchange in intermediate heat-exchangers and steam generators of reactor facilities and the boiling and condensation of liquid metals. Questions concerning the generalization and experimental thermophysical databases, development of heat pipes, thermophysics of thermionic converters, high-temperature space NPF, and thermonuclear plants were examined. Future studies resulting from the need to improve the safety, cost-effectiveness, and reliability of developed nuclear power facilities are formulated.

Kinetic condensation of metals in the early solar system: Unveiling the cooling history of solar nebula by refractory metal nuggets

Refractory Metal Nuggets (RMNs; submicrometer highly siderophile element rich metal alloys) are observed in Ca, Al-rich inclusions (CAIs) and other components of primitive meteorites, and some RMNs could have condensed from the Solar Nebula. In order to study the condensation of RMNs in the Solar Nebula, NUCON – a kinetic condensation model – has been developed to simulate the nucleation and condensation of refractory siderophile metal phases. NUCON treats RMNs as solid solutions where multiple elements can accrete onto one RMN. To achieve this goal, the homogeneous nucleation theory is modified to compute the nucleation of solid solutions. Also, a numerical method is developed to compute the integration of condensation and evaporation rates of an RMN. Equilibrium among gaseous phases is also considered, including monatomic gases and oxides. The oxygen fugacity of the simulated Solar Nebula can also be modified by adjusting carbon abundance. NUCON shows that the nucleation of RMNs was inhibited even when the cooling rate of the Solar Nebula was below 0.1 K/year, and RMNs experienced kinetic condensation largely deviated from the equilibrium condensation.This study modeled the condensation of RMNs in the RMN-forming regions with different cooling rates, total pressures, and oxygen fugacities, and explored how these parameters affect the radii and Ni/Fe ratios of RMNs. To reproduce the RMNs reported in literature, most of which have radii from 100 to 1000 nm, the cooling rate during the accretion of refractory siderophile metals in RMN-forming regions should be in the order of 1 K/year. The timescale of refractory-metal condensation is in the order of 102 years. In addition, RMNs have been measured to have Ni/Fe ratios from almost zero to over unity, and NUCON shows that the cooling rate during FeNi accretion in RMN-forming regions should be in the order of 10 K/h so that the observed Ni/Fe ratios of RMNs can be reproduced. The timescale of FeNi condensation is in the order of 10 h. Thus, NUCON predicts a transition from slow cooling to rapid cooling that is likely to have occurred during RMN condensation.

Laser ablation in liquid

Laser ablation in a liquid (LAL) is an important and perspective way to create nanoparticles (NPs) necessary for modern technologies. LAL is not fully understood. Deep understanding is necessary to optimize processes and decrease high price of the LAL NPs. Today there are two groups of studies: in one of them scientists go from analyzing of bubble dynamics (thus they proceed from the late stages), while in another one, scientists investigate early stages of ablation. In the present paper we consider the process as whole: from ablation and up to formation of a bubble and its inflation. Thus we cover extremely wide range of spatiotemporal scales. We consider a role of absorbed energy and duration of pulse (femtosecond, multi-picosecond, nanosecond). Importance of supercritical states is emphasized. Diffusive atomic and hydrodynamic mixing due to Rayleigh–Taylor instability and their mutual interdependence are described. Liquid near contact with metal is heated by dissipation in strong shock and due to small but finite heat conduction in liquid; metal absorbing laser energy is hot and thus it serves as a heater for liquid. Spatial expansion and cooling of atomically mixed liquid and metal causes condensation of metal into NPs when pressure drops below critical pressure for metal. Development of bubble takes place during the next stages of decrease of pressure below critical parameters for liquid and below ambient pressure in liquid. Thin hot layer of liquid near contact expands in volume to many orders of magnitude filling the inflating bubble.

Performance of protective oxide films on Fe–Ni alloy anodes in molten KF–AlF3–Al2O3 salts at 700 °C

An oxide film containing NiFe2O4 was prepared by oxidizing Fe–Ni alloy in hot air, and the performance of the protective oxide film in molten KF–AlF3–Al2O3 salts at 700 °C was characterized by electrochemical methods, including electrochemical impedance spectroscopy, capacitance measurements, linear sweep voltammetry, and chronoamperometry to clarify the breakdown and growth process of the oxide film. For the pre-oxidized 57Fe–43Ni, 50Fe–50Ni, and 43Fe–57Ni alloys, the oxide films, with a thickness of 5 μm, are composed of Fe2O3 and NiFe2O4, according to X-ray diffraction and scanning electron microscopy analysis. The transfer resistance of ions in the oxide film increases with increasing nickel content, and reaches its maximum value of 91.39 Ω⋅cm2 for the pre-oxidized 43Fe–57Ni alloy based on electrochemical impedance spectroscopy measurements. Moreover, the carrier density in the oxide film determined from Mott–Schottky plots decreases as the nickel content increases. Under anodic polarization, the breakdown of oxide film follows the generation of metal cation vacancies and condensation of excess cation vacancies. Concurrently, a new oxide layer forms along the substrate owing to the annihilation of oxygen vacancies and diffusion of oxygen anion in the oxide film. After oxygen evolution, a new oxide film layer containing NiFe2O4 forms on the alloy substrate, leading to the passivation observed in the anodic polarization curves. The maximum polarization resistance in the passivation region is 4.86 Ω⋅cm−2 for the pre-oxidized 43Fe–57Ni alloy, indicating that the pre-oxidized 43Fe–57Ni alloy possesses better corrosion resistance to molten fluorides than the other two pre-oxidized Fe–Ni alloys. Chronoamperometry measurements show that the oxide film on the 43Fe–57Ni alloy is in a dynamically stable state during oxygen evolution.

Desulfurization using limestone during sludge incineration in a fluidized bed furnace: Increased risk of particulate matter and heavy metal emissions

Incineration of sludge can be an effective method to minimise waste whilst producing useful heat. However, incineration can cause secondary pollution issues due to the emission of SO2, therefore a set of experiments of sludge incineration in a bubble bed furnace were conducted with limestone addition to study desulfurization of sludge incineration flue gas. As expected, over 93% emission of SO2 was reduced with limestone addition, and that of CO and NOx were increased and decreased respectively when the fuel feeding rate raised. The distribution of fly ash was also increased by raising the fuel feeding rate due to increasing fragmentation of the ash. However, distributions of PM2.5 and heavy metals in submicron particles have dramatically increased with limestone desulfurization. The mechanism was revealed by SEM and EDS statistical analysis, indicating that the reaction between aluminosilicate and calcium made particles agglomerate and eutectic mixtures form, these larger ash particles were found to divide between collection as cyclone ash and fragmentation into finer particles that bypassed the cyclone. Those fine particles provided more surface area for heavy metal condensation. Furthermore, it was found that the reaction mechanism for semi-volatile metals involved them being released from the sludge and forming PM1 particles due to the vaporization-condensation mechanism, leading to higher emission of PM1 and distribution of heavy metals in PM1. Thus, it should be considered that there may actually be higher emission risks of PM and heavy metal emissions when aiming to desulfurize a flue gas using Ca-based minerals in certain circumstances.

ФУНДАМЕНТАЛЬНЫЕ ИССЛЕДОВАНИЯ В ОБЛАСТИ ТЕПЛОФИЗИКИ ЯЭУ: ДОСТИГНУТЫЕ РЕЗУЛЬТАТЫ И ПРОБЛЕМЫ ДАЛЬНЕЙШИХ ИССЛЕДОВАНИЙ

The results of experimental and theoretical calculations of fundamental research in the field of hydrodynamics, heat transfer, physical chemistry and nuclear power technology cooled by water and liquid metal coolants are analyzed, problems and tasks of further research are formulated. The effects and physical phenomena, laws and characteristics for a wide range of processes occurring in the first and second circuits of reactor facilities, including the flow part, the core, the heating equipment, the means of monitoring and cleaning coolants from impurities as applied to watercooled thermal neutron reactors, fast liquid metal reactors, fusion plants, etc. Particular attention in the field of hydrodynamics and heat transfer is given to studies of the heat transfer crisis in watercooled reactors, hydrodynamics of collector systems, stratification and mixing of jets, vibroacoustics, turbulent transfer in complex channels, heat transfer in the channels and assemblies of fast reactor fuel elements, contact thermal resistance, boiling in large volume and bundles of fuel rods, condensation of liquid metals. In the field of physical chemistry and the technology of liquid metal coolants, the types of impurities and the sources of their entry into the coolants for various nuclear power plants, the characteristics of the mass and heat transfer processes in the circuits and equipment of reactor facilities with liquid metal coolants (sodium, potassium, lithium, lead, bismuth lead), the efficiency of using various purification devices (cold and hot traps) and monitoring the state of impurities in coolants are analyzed.Problem questions and suggestions for further research are formulated. Information is given on the key thermophysical problems of basic research in relation to the development of innovative nuclear energy technologies: water-cooled reactors with supercritical water pressure, high-temperature fast reactors with sodium coolant for hydrogen production, thermonuclear installations, nuclear power plants with liquid-metal space coolants.

Investigation of Ash Deposition Dynamic Process in an Industrial Biomass CFB Boiler Burning High-Alkali and Low-Chlorine Fuel

The circulating fluidized bed (CFB) boiler is a mainstream technology of biomass combustion generation in China. The high flue gas flow rate and relatively low combustion temperature of CFB make the deposition process different from that of a grate furnace. The dynamic deposition process of biomass ash needs further research, especially in industrial CFB boilers. In this study, a temperature-controlled ash deposit probe was used to sample the deposits in a 12 MW CFB boiler. Through the analysis of multiple deposit samples with different deposition times, the changes in micromorphology and chemical composition of the deposits in each deposition stage can be observed more distinctively. The initial deposits mainly consist of particles smaller than 2 μm, caused by thermophoretic deposition. The second stage is the condensation of alkali metal. Different from the condensation of KCl reported by most previous literatures, KOH is found in deposits in place of KCl. Then, it reacts with SO2, O2 and H2O to form K2SO4. In the third stage, the higher outer layer temperature of deposits reduces the condensation rate of KOH significantly. Meanwhile, the rougher surface of deposits allowed more calcium salts in fly ash to deposit through inertial impact. Thus, the elemental composition of deposits surface shows an overall trend of K decreasing and Ca increasing.

Experimental observation of the heat transfer mechanisms that drive propagation in additively manufactured energetic materials

The rise of additive manufacturing has led to the development of new architectures and allowed researchers to 3D-print a variety of energetic composites with different formulations. However, reactive sintering within the composites can negatively impact overall performance of nanoenergetic or reactive materials via the loss of nanostructure. It has been previously proposed that the addition of a gas generator could reduce the impact of reactive sintering while enhancing reactivity. Iodine pentoxide (I2O5) is an extremely powerful oxidizer and a strong gas generator which has been proposed as an efficient source of molecular iodine for biocidal applications. However, fabricated Al/I2O5 nanocomposite propellants are unable to propagate. In this study, we demonstrate that the addition of small quantities of CuO enables consistent propagation. Employing high-speed pyrometry and microscopy, we estimate advective heat transfer in the system and demonstrate that the addition of CuO offers a pathway for enhanced energy-transfer by metal condensation that is not available when I2O5 is the sole oxidizer. Elimination of condensing metal vapor as a participant in energy transfer increased the reliance of the system on particle advection. Small additions of CuO yield a condensable product vapor which can effectively eliminate the reliance on heat transfer via advection, enabling consistent propagation in reactive solid materials. We conclude with a general comment that where reliable propagation is critical, such as a stable burn of a solid propellant or delivery of a biocide, small additions of an oxidizer with a condensable metal vapor could be the difference between guaranteed performance and critical failure.

Embedded-grid silver transparent electrodes fabricated by selective metal condensation

We report a new materials system for the fabrication of embedded silver grid electrodes with micron-sized linewidth &gt;10 times narrower than can be achieved using the conventional printing techniques of screen, inject and flexographic printing.