Purpose: We developed a better method of accounting for the effects of heterogeneity in convolution algorithms. We integrated this method into our GPU‐accelerated, multi‐energetic ...convolution/superposition (C/S) implementation. In doing so, we have created a new dose algorithm: heterogeneity compensated superposition (HCS). Methods: Convolution in the spherical density‐scaled distance space, a.k.a. C/S, has proven to be a good estimator of the dose deposited in a homogeneous volume. However, near heterogeneities electron disequilibrium occurs, leading to faster fall‐off and re‐buildup than predicted by C/S. We propose to filter the actual patient density in a position and direction sensitive manner, allowing the dose deposited near interfaces to be increased or decreased relative to traditional C/S. We implemented the effective density function as a multivariate first‐order recursive filter. We compared HCS against traditional C/S using the ICCR 2000 Monte‐Carlo accuracy benchmark, 23 similar accuracy benchmarks and 5 patient cases. For the patient cases, we created custom routines capable of using the discrete material mappings used by Monte‐Carlo. C/S normally considers each voxel to be a mixture of materials based on a piecewise‐linear density look‐up table. Results: Multi‐energetic HCS increased the dosimetric accuracy for the vast majority of voxels; in many cases near Monte‐Carlo results were achieved. HCS improved the mean Van Dyk error by 0.79 (% of Dmax or mm) on average for the patient volumes; reducing the mean error from 1.93%|mm to 1.14%|mm. We found a mean error difference of up to 0.30 %|mm between linear and discrete material mappings. Very low densities (i.e. <0.1 g / cm3) remained problematic, but may be solvable with a better filter function. Conclusions: We have developed a novel dose calculation algorithm based on the principals of C/S that better accounts for the electron disequilibrium caused by patient heterogeneity. This work was funded in part by the National Science Foundation under Grant No. EEC9731748, in part by Johns Hopkins University internal funds and in part by Elekta.
Ultrasonic-assisted pulse electrodeposition of nanocrystalline nickel (NC-Ni) coatings from Watts bath on copper substrate was investigated. Direct (DC), pulsed (PC), and pulse reversed (PRC) current ...electrodeposition techniques were employed to electrodeposit NC-Ni coatings in the absence and presence of ultrasound wave with a nominal power ranging from 95 W to 200 W and their surface morphology, hardness, and crystalline microstructure were compared. We observed that as the ultrasound power increases, the cathodic efficiency and the microhardness increase, whereas the crystallite size and surface roughness decrease for NC-Ni electrodeposited by the three techniques in the same way. However, the effect of pulse waveform is dominant. The finest crystallite size (24 nm) and highest hardness (585 HV) were achieved for NC Ni coatings PC electrodeposited using an ultrasound with 200 W nominal power. It is believed that the coating produced by PC and PRC techniques develops a preferential orientation in (111) and (100) planes, respectively. The application of ultrasound wave and increasing its nominal power changes the preferential orientation of all obtained coatings to (111) planes. The corrosion behavior of NC Ni coatings, as investigated by potentiodynamic polarization and electrochemical impedance spectroscopy in NaOH solution, demonstrates the effect of nanocrystalline on the passivation and corrosion resistance of NC-Ni coatings.
•Ultrasonic-assisted pulse electrodeposition of nanocrystalline nickel (NC-Ni) coatings from Watts bath was exploited.•Effect of ultrasound wave with different nominal power ranging from 95 W to 200 W was studied.•Effect of direct, pulse and pulse-reverse current on nucleation and growth of nickel films was studied.•Increasing ultrasound power boosts cathodic efficiency and microhardness while decreasing crystallite size and surface roughness.•NC Ni coatings in NaOH solution show that corrosion behavior is influenced by crystallite size and morphology
The present work investigates the applicability of laser assisted electrodeposition (LAE) to the plating of binary metallic alloys from aqueous solutions and in absence of any external polarization. ...PdPt was chosen as prototypical system and the deposition was carried out from phosphate-based electrolytes. The effect of electrolyte formulation and laser parameters on the composition, thickness and physical properties of the alloys was studied. In order to provide more insight on the LAE deposition process of alloys, the electrochemical properties of the electrolytes employed were correlated with the properties of the materials obtained. In analogy with standard alloy plating processes, a clear link between the currents observed for the reduction of the two single metals and the composition/thickness of the coated PdPt layers could be established. Compositionally tunable and continuous PdPt coatings were obtained and their chemical, morphological and mechanical properties were determined. Finally, the possibility to selectively deposit the PdPt alloy was demonstrated by patterning a complex figure.
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•Binary alloys are deposited for the first time by laser assisted electrodeposition.•Platinum-palladium is selected as a representative alloy example.•Electrochemical tests are done to support laser assisted electrodeposition outcomes.•Compositionally tunable and compact platinum-palladium layers are obtained.•Platinum-palladium can be easily patterned at the sub-millimeter scale.
We offer an explanation for how dendrite growth can be inhibited when Li metal pouch cells are subjected to external loads, even for cells using soft, thin separators. We develop a contact mechanics ...model for tracking Li surface and sub-surface stresses where electrodes have realistically (micron-scale) rough surfaces. Existing models examine a single, micron-scale Li metal protrusion under a fixed local current density that presses more or less conformally against a separator or stiff electrolyte. At the larger, sub-mm scales studied here, contact between the Li metal and the separator is heterogeneous and far from conformal for surfaces with realistic roughness: the load is carried at just the tallest asperities, where stresses reach tens of MPa, while most of the Li surface feels no force at all. Yet, dendrite growth is suppressed over the entire Li surface. To explain this dendrite suppression, our electrochemical/mechanics model suggests that Li avoids plating at the tips of growing Li dendrites if there is sufficient local stress; that local contact stresses there may be high enough to close separator pores so that incremental Li+ ions plate elsewhere; and that creep ensures that Li protrusions are gradually flattened. These mechanisms cannot be captured by single-dendrite-scale analyses.
The renaissance of aqueous Zn ion batteries has drawn intense attention to Zn metal anode issues, including dendrites growth, dead Zn, low efficiency, and other parasitic reactions. However, against ...the widely used 2D Zn foil, in fact, the Zn powder anode is a more practical choice for Zn-based batteries in industrial applications, but the related solutions are rarely investigated. Herein, we focus on the Zn powder anode and disclose its unknown failure mechanism different from Zn foils. By utilization of 2D flexible conductive Ti3C2Tx MXene flakes with hexagonal close-packed lattice as electrons and ions redistributor, a stable and highly reversible Zn powder anode without dendrite growth and low polarization is constructed. Low lattice mismatch (∼10%) enables a coherent heterogeneous interface between the (0002) plane of deposited Zn and (0002) plane of the Ti3C2Tx MXene. Thus, the Zn2+ ions are induced to undergo rapid uniform nucleation and sustained reversible stripping/plating with low energy barriers via the internally bridged shuttle channels. Paired with cyano group iron hexacyanoferrate (FeHCF) cathode, the FeHCF//MXene@Zn full battery delivers superior cycle durability and rate capability, whose service life with a CE of near 100% touches 850% of bare Zn powder counterparts. The proposed Ti3C2Tx MXene redistributor strategy concerning high-speed electrons/ions channel, low-barrier heterogeneous interface, is expected to be widely applied to other alkali metal anodes.
Ionometallurgy is a new development aiming at the sustainable low‐temperature conversion of naturally occurring metal ores and minerals to their metals or valuable chemicals in ionic liquids (ILs) or ...deep eutectic solvents. The IL betainium bis((trifluoromethyl)sulfonyl)imide, HbetNTf2, is especially suited for this process due to its redox‐stability and specific‐functionalization. The potentiostatic electrodeposition of zinc and lead starting directly from ZnO and PbO, which dissolve in HbetNTf2 in high concentrations is reported. The initial reduction potentials of zinc(II) and lead(II) are about −1.5 and −1.0 V, respectively. The ionic conductivity of the solution of ZnO in HbetNTf2 is measured and the effect of various temperatures and potentials on the morphology of the deposited material is explored. The IL proves to be stable under the chosen conditions. From IL‐solutions, where ZnO, PbO, and MgO have been dissolved, metallic Zn and Pb are deposited under potentiostatic control either consecutively by step‐electrodeposition or together in a co‐electrodeposition. Using the method, Zn is also deposited on 3D copper foam and assembles into high‐voltage zinc‐graphite battery. It exhibits a working‐voltage up to 2.7 V, an output midpoint discharge‐voltage of up to 2.16 V, up to 98.6% capacity‐retention after 150 cycles, and good rate performance.
Ionometallurgy step‐electrodeposition can allow separate deposition of metals with sufficiently distinct electrochemical potential from mixtures of ZnO, PbO, and MgO dissolved in betainium bis((trifluoromethyl)sulfonyl)imide (HbetNTf2) to a large extend. Zinc can also be deposited on 3D copper foam (Zn/3DCu) to directly assemble a high‐voltage zinc‐graphite cell, which has an operating‐voltage of up to 2.7 V and exhibit excellent long‐cycle and rate performance.
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•The most efficient route was designed for 3D mesoporous α-Co(OH)2 on Ni foam (NF).•Extraordinary catalytic activity of Co(OH)2/NF for peroxymonosulfate was observed.•The cobalt ...leaching was alleviated by the macroscopic Co(OH)2/NF.•The readily recyclable monolith catalyst benefits the practical application.
Cobalt-based catalysts with high stability and facile recovery for heterogeneous peroxymonosulfate (PMS) activation are still rather sparse and therefore highly desirable. Herein, 3D mesoporous α-Co(OH)2 nanosheets was created on robust nickel foam (NF) via facile electrodeposition approach at 6 mA/cm2 for only 400 s. Almost complete removal of phenol can be achieved within 7 min with a degradation rate of 0.39 min−1, 2 times higher than that with ever-prevalent Co3O4 derived from direct calcination of α-Co(OH)2/NF. This can be attributed to the hydrotalcite-like hexagonal structure of α-Co(OH)2 with large interlayer spacing for enhancing the catalytic performance. The low activation energy of Co(OH)2/NF (53.8 kJ/mol) indicates its lower reaction energy barrier for PMS activation. Moreover, the influences of electrodeposition parameters (i.e. current density, deposition time), PMS dosage, initial pH and coexisting anions (HCO3−, SO42−, Cl−) on the phenol degradation were systematically evaluated. The recycling tests revealed the prominent stability of Co(OH)2/NF. The quenching tests verified that SO4− radicals acted as the predominant reactive species for phenol decomposition. The possible reaction mechanisms were proposed based on the intermediates identification. The findings of this work suggest the great potentials of the 3D macroscopic Co(OH)2/NF in water purification, and open up new avenues for scalable preparing recyclable heterogeneous catalysts.
The propensity of Zn‐metal anodes to form non‐uniform or dendritic electrodeposits is bound up with the nature of the electrode surface. However, the effect of surface structure on the inherent ...nucleation and deposition of Zn is not yet well understood. Here, the surface structure of a Zn‐metal anode is reconstructed with Sn‐crystal textures via a facile chemical displacement reaction. Compared to the bare Zn, the high‐affinity Zn binding sites of Sn afford lower deposition energy barrier, which promotes deposition kinetics. What is more, a Sn‐textured surface with moderate Zn affinity but high average surface energy ensures a better wettability from the deposits, leading to the lateral growth of Zn crystals. The resultant Sn‐textured Zn‐metal anode exhibits an extremely low voltage hysteresis of 20 mV and achieves a prolonged cycling stability over 500 h cycles without dendrite formation. This work provides new insights into the crystal‐texture‐dependent Zn electrodeposition process and offers direction for direct surface texturing to better stabilize Zn‐metal anodes with improved reversibility.
The surface of a Zn‐metal anode is reconstructed with Sn‐crystal textures via a facile chemical displacement reaction. Such a Sn‐textured surface not only endows a reduced Zn deposition energy barrier but also regulates the lateral growth of Zn crystals, which promotes dendrite‐free electrodeposits and leads to the achievement of an extremely low voltage hysteresis of 20 mV and prolonged cycling performance over 500 h.
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