Energetic Co-Crystal of a Primary Metal-Free Explosive with BTF. Ideal Pair for Co-Crystallization

Co-crystallization is an elegant technique to tune the physical properties of crystalline solids. In the field of energetic materials, co-crystallization is currently playing an important role in the engineering of crystals with improved performance. Here, based on an analysis of the structural features of the green primary explosive, tetramethylammonium salt of 7-oxo-5-(trinitromethyl)-4,5,6,7-tetrahydrotetrazolo[1,5-a][1,3,5]triazin-5-ide (1), a co-former such as the powerful secondary explosive, benzotrifuroxan (BTF, 2), has been proposed to improve it. Compared to the original 1, its co-crystal with BTF has a higher detonation pressure and velocity, as well as an initiating ability, while the impact sensitivity and thermal stability remained at about the same level. Both co-formers, 1 and 2, and co-crystal 3 were characterized by single-crystal X-ray diffraction and their crystal packing was analyzed in detail by the set of approaches, including periodic calculations. In the co-crystal 3, all intermolecular interactions were significantly redistributed. However, no new types of intermolecular interactions were formed during co-crystallization. Moreover, the interaction energies of structural units in crystals before and after co-crystallization were approximately the same. A similar trend was observed for the volumes occupied by structural units and their densifications. The similar nature of the organization of the crystals of the co-formers and the co-crystal gives grounds to assert that the selected co-formers are an ideal pair for co-crystallization, and the invariability of the organization of the crystals was probably responsible for the preservation of some of their properties.

A Scalable Prototype by In Situ Polymerization of Biodegradables, Cross-Linked Molecular Mode of Vapor Transport, and Metal Ion Rejection for Solar-Driven Seawater Desalination

Water scarcity in mass populated areas has become a major global threat to the survival and sustainability of community life on earth, which needs the prompt attention of technological leadership. Solar evaporation has emerged as a renewable energy resource and a novel technique for clean water production and wastewater treatment. Indeed, mounting a scalable solar evaporator including high evaporation efficiency and thermal management remains a significant challenge. Herein, we demonstrate a self-floatable, ecofriendly polypyrrole/wood sponge-based (PPy@WS) steam generator. The low-cost and easy to fabricate evaporator system consists of a single-step in situ polymerization of a 2-D (two-dimensional) hydrophilic wood sponge abundantly available for commercialization. The as-prepared PPy@WS solar evaporator exhibits excellent wettability and is super hydrophilic (contact angle ∼ 0), salt-resistant, and has an excellent light absorption of ∼94% due to omnidirectional diffusion reflection in PPy Nanoparticles (NPs). The capacity of the PPy@WS evaporator to absorb broadband solar radiation and convert it into thermal energy has enabled it to achieve excellent surface temperature (38.6 °C). The accumulated heat can generate vapors at the rate of 1.62 kg·m−2·h−1 along with 93% photothermal conversion efficiency under one sun (1 kW·m−2). Moreover, the presented prototype possesses the capability to be installed directly without the use of any complex protocol to purify seawater or sewage with an efficient rejection ratio of primary metal ions present in seawater (approximately 100%). This simple fabrication process with renewable polymer resources and photothermal materials can serve as a practical model towards high-performance solar evaporation technology for water-stressed communities in remote areas.

Rare Earth Electrolysis: key issues for measurement of greenhouse gases from oxide-fluoride systems

Over the past decade, the reduction of greenhouse gases (GHG) has been recognized as one of the key factors for sustainable primary metal production, in which the rare earth (RE) industry can be affected both in terms of price and use by GHG reduction policies and non-tariff technical barriers. From environmental and economic standpoint, the perfluorocarbons (PFC) emissions generated in RE electrolysis during events known as anode effects (AE) are strong infrared-absorbing GHG and play an important role for RE metals process improvements. However, there is no standard methodology to account these GHG emissions from RE metal production industry and the assessment of the contribution of PFC emissions from different technologies to the global warming is urgently needed. This paper focuses on the analysis of PFC measurements from RE metal production in terms of GHG inventory and sustainable production. The state of art of RE fused oxide-fluoride electrolysis, particularly of neodymium electrolysis, provides the technical fundamentals for the evaluation of PFC emissions factors reported in scientific articles. Based on International Panel on Climate Change (IPCC) standard methods and US Environmental Protection Agency (EPA) and International Aluminium Institute (IAI) protocol applied to analogous industrial process, the analysis of key issues for estimate CF4 and C2F6 emission factors from electrolytic RE production indicates the additional refinements are necessary to optimize the accuracy of total PFC emission amount from each currently RE technology. Additionally, the selection of emission estimation technique (EET) or mix EET should be considered on case-by-case basis as to their purposes and suitability for a particular process and facility. Finally, this paper highlights the technological implications related to the PFC emissions measurements and trends towards to set goals and develop strategies for GHG mitigation.

Towards Understanding the Cathode Process Mechanism and Kinetics in Molten LiF–AlF3 during the Treatment of Spent Pt/Al2O3 Catalysts

Electrochemical decomposition of spent catalyst dissolved in molten salts is a promising approach for the extraction of precious metals from them. This article reports the results of the study of aluminum electrowinning from the xLiF–(1-x)AlF3 melt (x = 0.64; 0.85) containing 0–5 wt.% of spent petroleum Pt/γ-Al2O3 catalyst on a tungsten electrode at 740–800 °C through cyclic voltammetry and chronoamperometry. The results evidence that the aluminum reduction in the LiF–AlF3 melts is a diffusion-controlled two-step process. Both one-electron and two-electron steps occur simultaneously at close (or same) potentials, which affect the cyclic voltammograms. The diffusion coefficients of electroactive species for the one-electron process were (2.20–6.50)∙10−6 cm2·s–1, and for the two-electron process, they were (0.15–2.20)−6 cm2·s−1. The numbers of electrons found from the chronoamperometry data were in the range from 1.06 to 1.90, indicating the variations of the partial current densities of the one- and two-electron processes. The 64LiF–36AlF3 melt with about 2.5 wt.% of the spent catalysts seems a better electrolyte for the catalyst treatment in terms of cathodic process and alumina solubility, and the range of temperatures from 780 to 800 °C is applicable. The mechanism of aluminum reduction from the studied melts seems complicated and deserves further study to find the optimal process parameters for aluminum reduction during the spent catalyst treatment and the primary metal production as well.

Rare Earth Electrolysis: key issues for measurement of greenhouse gases from oxide-fluoride systems

Over the past decade, the reduction of greenhouse gases (GHG) has been recognized as one of the key factors for sustainable primary metal production, in which the rare earth (RE) industry can be affected both in terms of price and use by GHG reduction policies and nontariff technical barriers. From environmental and economic standpoint, the perfluorocarbons (PFC) emissions generated in RE electrolysis during events known as anode effects (AE) are strong infrared-absorbing GHG and play an important role for RE metals process improvements. However, there is no standard methodology to account these GHG emissions from RE metal production industry and the assessment of the contribution of PFC emissions from different technologies to the global warming is urgently needed. This paper focuses on the analysis of PFC measurements from RE metal production in terms of GHG inventory and sustainable production. The state of art of RE fused oxide-fluoride electrolysis, particularly of neodymium electrolysis, provides the technical fundamentals for the evaluation of PFC emissions factors reported in scientific articles. Based on International Panel on Climate Change (IPCC) standard methods and US Environmental Protection Agency (EPA) and International Aluminium Institute (IAI) protocol applied to analogous industrial process, the analysis of key issues for estimate CF4 and C2F6 emission factors from electrolytic RE production indicates the additional refinements are necessary to optimize the accuracy of total PFC emission amount from each currently RE technology. Additionally, the selection of emission estimation technique (EET) or mix EET should be considered on case-by-case basis as to their purposes and suitability for a particular process and facility. Finally, this paper highlights the technological implications related to the PFC emissions measurements and trends towards to set goals and develop strategies for GHG mitigation.

Facilitated Synthesis of Mg2Ni Based Composites with Attractive Hydrogen Sorption Properties

Composites based on Mg2Ni with 5% activated carbon from apricot stones (ACAP) have been prepared by ball milling and subsequent annealing in hydrogen atmosphere. The purpose of the primary metal (Mg, Ni, and V) milling was to reduce the particle size and achieve a good contact between them, without forming intermetallic compounds. During hydriding/dehydriding at 300 °C the amount of the Mg2Ni phase progressively increased, and after 10 cycles about 50% Mg2(Ni,V) was achieved. The hydrogenation produced mainly Mg2NiH4, but small amounts of MgH2 and VHx were also detected in the powder mixture. Relatively high hydrogen storage capacity and fast hydriding/dehydriding kinetics of the Mg2.1Ni0.7V0.3—5 wt.% ACAP composite were determined both from hydrogen gas phase and electrochemically.

Separation of Aluminum from More Noble Elements in an Electrolysis Cell with Side-by-Side Geometry

Currently, recycled metal is diluted with primary metal to keep the concentration of alloying elements within specification. This will be more difficult in the future, when a larger proportion of the metal is made from scrap. Particularly, there is a need for a process that can remove elements more noble than aluminum from the scrap metal. While electrolytic refining in a three-layer cell (the Hoopes process) is a possibility; the present paper presents a simpler and more flexible electrolysis cell where the anode metal (alloy) and the cathode metal (purified metal) are placed side-by-side. The principle was demonstrated in a laboratory cell. The current efficiency was above 80 pct and the specific energy consumption was about 7 kWh/kg Al. The refining effect was very good, e.g., the copper content in the 7xxx alloy used was reduced from 2.1 wt pct to less than 20 ppm. An industrial version of the cell used in the present work is suggested. The principles and design are generic and can be used for other purposes than recycling aluminum.

Investigation on Analysis Method of Environmental Fatigue Correction Factor of Primary Coolant Metal Materials in LWR Water Environment

The environmental fatigue correction factor (Fen) is mainly used to analyze the influence of the coolant environment on the fatigue life of primary metal materials. Because the calculation of the transformed strain rate is related to the stress history of the component structure, how to determine the strain rate is the most critical step in calculating the Fen. The approaches of the detailed method were given by the Electric Power Research Institute (EPRI) guidelines and RCC-M-2017 Edition Section VI- RPP No. 3 separately, so a gap analysis was performed between the two methods. Furthermore, another average method was also proposed to determine the average strain rate and strain range. Based on the analysis benchmark provided in the EPRI guideline, a simple case study was performed to account for the effect on the fatigue life in applications with different strain rate approaches and different Fen expressions. Finally, two industry case studies were also completed, including on materials of low alloy steel, austenitic stainless steel, and nickel-base alloy. We suggest adopting a more accurate detailed method, and its methodology is recommended to provide more reasonable solutions.

Noncanonical Heme Ligands Steer Carbene Transfer Reactivity in an Artificial Metalloprotein

<a>Changing the primary metal coordination sphere is a powerful strategy for modulating metalloprotein properties. Taking advantage of this approach, we have replaced the proximal histidine ligand in myoglobin with the histidine analogues N_d-methylhistidine (NMH), 5‑thiazoylalanine (5ThzA), 4-thiazoylalanine (4ThzA) and 3-(3-thienyl)alanine (3ThiA) by amber stop codon suppression using engineered pyrrolysyl-tRNA synthetases, including two newly evolved enzymes. In addition to tuning the heme redox potential over a >200 mV range, these noncanonical ligands modulate the protein’s promiscuous carbene transfer activity with ethyl diazoacetate. Myoglobin variants with increased reduction potentials (NMH and 5ThzA) proved superior for cyclopropanation and N-H insertion, especially under aerobic conditions, and could even promote these reactions in the absence of reducing agent. In contrast, the variants with the lowest <i>E</i>^o values (4ThzA and 3ThiA) exhibit comparatively high S-H insertion activity even though the respective histidine surrogates do not coordinate the heme iron. Given the important functional roles played by histidine in many enzymes, these genetically encoded histidine analogues represent valuable tools for probing mechanism and enabling new chemistries in metalloprotein</a>s.

Noncanonical Heme Ligands Steer Carbene Transfer Reactivity in an Artificial Metalloprotein

<a>Changing the primary metal coordination sphere is a powerful strategy for modulating metalloprotein properties. Taking advantage of this approach, we have replaced the proximal histidine ligand in myoglobin with the histidine analogues N_d-methylhistidine (NMH), 5‑thiazoylalanine (5ThzA), 4-thiazoylalanine (4ThzA) and 3-(3-thienyl)alanine (3ThiA) by amber stop codon suppression using engineered pyrrolysyl-tRNA synthetases, including two newly evolved enzymes. In addition to tuning the heme redox potential over a >200 mV range, these noncanonical ligands modulate the protein’s promiscuous carbene transfer activity with ethyl diazoacetate. Myoglobin variants with increased reduction potentials (NMH and 5ThzA) proved superior for cyclopropanation and N-H insertion, especially under aerobic conditions, and could even promote these reactions in the absence of reducing agent. In contrast, the variants with the lowest <i>E</i>^o values (4ThzA and 3ThiA) exhibit comparatively high S-H insertion activity even though the respective histidine surrogates do not coordinate the heme iron. Given the important functional roles played by histidine in many enzymes, these genetically encoded histidine analogues represent valuable tools for probing mechanism and enabling new chemistries in metalloprotein</a>s.