Energy Input Conditions Research Articles

Solar-Driven membrane reactors with wide temperature range for chemical looping dry reforming of Methane: Concept validation and one-dimensional analysis

Solar thermochemical fuel conversion technology offers a significant potential to mitigate the challenges of intermittency and variability inherent in solar energy utilization. Traditional two-step methane chemical looping processes for fuel production are often hampered by complex apparatus requirements, operational intermittency, and persistent temperature variations, contributing to energy loss. In contrast, the chemical looping dry reforming of methane (CL-DRM) membrane reactor technology, as developed in this study, facilitates continuous fuel synthesis under isothermal conditions. Through the construction and analysis of a one-dimensional + one-dimensional model for a single channel of this innovative reactor, the impact of structural and operational parameters on the reactor performance is elucidated. This model enables a swift prediction of the membrane reactor’s operational efficacy. The results indicate that the reactor sustains a high energy conversion efficiency across a broad temperature spectrum, thereby enhancing its adaptability to the dynamic conditions of solar energy input. Notably, temperature and feed ratio (RCH4/CO2) are pivotal determinants of the conversion rate and the concentration of products. At a temperature of 1000 °C, with an optimal RCH4/CO2 ratio of 1, the efficiency is projected to attain 78 %, considering heat dissipation and thermal recovery mechanisms. These results underscore the promise of the solar-driven CL-DRM membrane reactor as a viable and efficient method for solar fuel production. This study provides a new perspective on the design of continuous solar fuel conversion reactors.

Catalytic Light-Driven Strategy for Transforming Oximes to Carbonyls.

Oxime and carbonyl functional groups serve as powerful chemical hubs for constructing complex synthetic targets and valuable molecular scaffolds. In furthering this value, we report a photopromoted catalytic deoximation protocol for converting oximes and their derivatives to carbonyl functional groups. This strategic approach benefits from the use of renewable light energy input and ambient air conditions, in addition to demonstrating good substrate scope, functional group tolerance, and product yields. In offering, insights into these reactivity mechanistic studies are communicated, and the value of this protocol is further shown through one-pot operations.

Low-temperature upcycling of polypropylene waste into H2 fuel via a novel hydrothermal tandem process.

Plastic waste is a promising and abundant resource for H2production. However, upcycling plastic waste into H2fuel via conventional thermochemical routes requires relatively considerable energy input and severe reaction conditions, particularly for polyolefin waste. Here, we report a tandem strategy for the selective upcycling of polypropylene (PP) waste into H2fuel in a mild and clean manner. PP waste was first oxidizedinto small-molecule organic acids usingpure O2as oxidantat 190 °C, followed by the catalytic reforming of oxidation aqueous products over ZnO-modified Ru/NiAl2O4catalysts to produce H2at 300 °C. A high H2yield of 44.5 mol/kgPPand a H2mole fraction of 60.5% were obtained from this tandem process. The entire process operated with almost no solid residue remaining and equipment contamination, ensuring relative stability and clean of the reaction system. This strategy provides a new route for low-temperature transforming PP and improving the sustainability of plastic waste disposal processes.

Effect of energy input on flotation of particles with different sizes: Perspective of hydrodynamics characteristics

By employing a torque sensor to measure energy input in a flotation machine, this paper investigates the flotation behavior of modified quartz particles with different sizes but similar surface hydrophobicity under various energy input conditions. Numerical simulations of the mechanical flotation machine were conducted to obtain the fluid dynamic characteristics including the flow velocity, turbulence kinetic energy, and turbulent eddy scale. With the flotation results and numerical simulations combined, the potential collision, attachment, and detachment behaviors of fine particles (―45 µm), intermediate particles (45―74 µm), and coarse particles (74―125 µm) were analyzed. The results demonstrate that under different conditions of energy input, the recovery of intermediate-sized particles was optimal for the above size fractions. As the particle size increases, the energy input required to achieve optimal recovery decreases. The flotation rate constants increase nearly linearly with energy input. Compared to the medium-sized particles in the range of 45―74 µm, finer and larger particles exhibit lower floatability. When the energy input exceeds a certain range, no stagnation zone is observed. The rupture of bubble-particle aggregates becomes more pronounced, which may be a reason why flotation recovery begins to decrease. Increasing energy input enhances turbulence energy dissipation and reduces the Kolmogorov turbulence length scale, in this study, the ―45 µm, 45―74 µm, and 74―125 µm particle sizes reached the optimal flotation performance at dp / η values of 1.35, 1.83, 2.54, respectively. The particle diameter-to-integral length scale ratio (dp/L) is also discussed as an important parameter for turbulent dispersion.

Effect of in-situ post-heating on the microstructure and tensile performance of TiAl alloys produced via selective electron beam melting

Selective electron beam melting (SEBM) is an additive manufacturing technique commonly used to fabricate TiAl alloys. Changing the process parameters to adjust the alloy structure for enhanced mechanical performance is an effective means in this field. Herein, we investigated the effects of the in-situ post-heating process on the microstructure and tensile performance characteristics of SEBM Ti–48Al–2Cr–2Nb alloys. Two processes were designed: without and with post-heating after melting under identical melting process and total energy input conditions. The tensile strength of the samples with the post-heating process reached 707 ± 12 MPa and strain reached 1.8 ± 0.1%. Compared with the other process, the strain increases by 50%, and the strength decreases by 4.8%. This phenomenon was mainly caused by the more precipitation of γ-phase during the phase transformation of TiAl via an in-situ post-heating process. Even with the same energy input, different heating strategies still significantly affect the tensile performance of TiAl alloy, showing that post-heating is an effective way to improve mechanical properties of additive manufactured material.

Material Transport Characteristics in Planetary Roller Melt Granulation.

Melt granulation for improving material handling by modifying particle size distribution offers significant advantages compared to the standard methods of dry and wet granulation in dust reduction, obviating a subsequent drying step. Furthermore, current research in pharmaceutical technology aims for continuous methods, as these have an enhanced potential to reduce product quality fluctuations. Concerning both aspects, the use of a planetary roller granulator is consequential. The process control with these machines benefits from the enhanced ratio of heated surface to processed volume, compared to the usually-applied twin-screw systems. This is related to the unique concept of planetary spindles flowing around a central spindle in a roller cylinder. Herein, the movement pattern defines the transport characteristics, which determine the energy input and overall processing conditions. The aim of this study is to investigate the residence time distribution in planetary roller melt granulation (PRMG) as an indicator for the material transport. By altering feed rate and rotation speed, the fill level in the granulator is adjusted, which directly affects the average transport velocity and mixing volume. The two-compartment model was utilized to reflect these coherences, as the model parameters symbolize the sub-processes of axial material transport and mixing.

Robust and Temperature‐Sensitive Hydrogels for High‐Efficiency Water Harvesting Under Low Solar Energy Radiation

Solar‐driven evaporation using hydrogels and photothermal materials is a promising freshwater harvesting technology. Clean water is generally collected through evaporation and subsequent condensation, which requires high energy input due to the inherent high vaporization enthalpy of water. Therefore, it is a great challenge to harvest fresh water efficiently under natural irradiation. Herein, a temperature‐sensitive polyacrylamide‐poly(N‐isopropylacrylamide) (A‐PNIPAm) gel is designed to pursue a high water collection rate under low energy input conditions, where the facile and reversible hydrophilic/hydrophobic transition in gels enables the quick acquisition of liquid water. A multifunctional hydrogel (ADS‐PNIPAm) is prepared using polydopamine and sodium alginate with excellent adsorption/filtration properties, which can remove pollutants and generate fresh water rapidly. Consequently, the water collection rate of the ADS‐PNIPAm hydrogel reaches up to 5.89 and 9.8 kg m−2 h−1 under 0.6 and 1 sun irradiation, respectively, which are superior to the previously reported values. Furthermore, ADS‐PNIPAm displays an excellent effect on purifying sewage, such as oils, algae, and dyes pollutants. ADS‐PNIPAm is a promising material for a rapid freshwater generation with solar irradiation only, which provides a new avenue to alleviate water source scarcity.

Approximation Algorithm for X-ray Imaging Optimization of High-Absorption Ratio Materials

In the application of X-ray industrial flaw detection, the exposure parameters directly affect the image quality. The voltage of the tube is the most important factor, which is difficult to be accurately calculated. Especially in the detection of a workpiece composed of both high absorption coefficient and low absorption coefficient materials, the improper symmetric balance of the tube voltage would lead to an overexposure or underexposure phenomenon. In this paper, based on the X-ray absorption model, combined with the performance of the X-ray imaging detector, and taking the optimal symmetry and contrast as the model constraint condition, the key factors of high absorption ratio material imaging are decomposed. Through expansion and iteration, the calculation process is simplified, the optimal imaging convergence surface is found, and then the optimal energy input conditions of high absorptivity materials are obtained and symmetrically balanced. As a result, this paper solves the problem of fast selection and symmetric factor chosen of the optimal tube voltage when imaging materials with high absorption ratios. It reduces the subsequent complications of the X-ray image enhancement process and obtains a better image quality. Through experimental simulation and measurement verification, the error between the theoretical calculation results and the measured data was better than 5%.

Performance and mechanisms for tetrabromobisphenol A efficient degradation in a novel homogeneous advanced treatment based on S2O42− activated by Fe3+

Tetrabromobisphenol A (TBBPA), a representative brominated flame retardant (BFR), generally could be debrominated and degraded effectively in photolysis systems with the high energy consumption. In this study, the novel sulfate radical (SO4•-) generation resource of dithionite (S2O42−), activated by the common transition metal of Fe3+, has been applied for establishing an innovative homogeneous advance treatment system for BFR treatment in water. When coupling Fe3+ with S2O42−, TBBPA degradation efficiency could be remarkably improved from 38.7% to 93.8% with the debromination and mineralization efficiency of 83.9% and 18.5% in 60 min, respectively. The primary reactive species also have been identified as SO3•-, SO4•- and •OH responsible for TBBPA treatment and the contributions of SO4•- and •OH have been calculated as 43.8% and 28.4% for TBBPA degradation, respectively. In Fe3+/S2O42− system, TBBPA was effectively degraded in a wide initial pH range (3.0–9.0), whose activation energy was calculated as 32.01 kJ mol−1. Due to the only operation of reagents dosing, the energy consumption and cost could be decreasing significantly without any light energy input and reaction conditions (e.g., pH and dissolved oxygen) adjustment compared with the general photolysis process. Moreover, some possible degradation approaches of TBBPA also have been proposed via GC–MS including debromination, hydroxylation, methylation, and mineralization in Fe3+/S2O42− system. And these probable degradation pathways also have been confirmed with the decreased Gibbs free energy (ΔG) based on density functional theory (DFT). This study has revealed that it was promising of Fe3+/S2O42− system for BFRs degradation and detoxification efficiently through the simple operation and mild condtions.

RF05 | PSUN341 Role of sirtuins in breast cancer cells response to Fulvestrant

Abstract Endocrine therapies reduce glucose and glutamine uptake and total cellular ATP production in breast cancer (BC) cells, resulting in changes in cellular nutrient balance that could lead to cell cycle arrest and to cell death. Understanding the ability of cells to bypass these metabolic effects is fundamental to understand acquisition of endocrine resistance and cross-resistance to other drugs by BC cells. Sirtuins (SIRTs) are NAD+-dependent deacylases involved in a variety of cellular processes, including metabolism and stress responses. SIRT1 deacetylates histones and transcription factors, and regulates glucose metabolism through TORC2, PGC1α, FOXO1. SIRT3 modulates mitochondria adaptation to conditions of low energy input by promoting the production of energy from sources different from glucose. SIRT3 mediates metabolic reprogramming by also destabilizing HIF-1α, regulating glycoytic gene expression. SIRT 3 regulation of the mitochondrial unfolded protein response and mitophagy machinery has been described. SIRT3expression is higher in early (≤3 years) vs. late (≥5 years) recurrences (measure of resistance vs. dormancy) in 4 clinical datasets. Using Differential Dependency Network analysis to compare the wiring of the SIRTs and key metabolism-related genes in matched antiestrogen- sensitive vs. resistant BC cells, guided by gene related to the nicotinate and nicotinamide metabolism, and associated with clinical outcome in ER+ patients treated with an endocrine therapy, we identified several novel signaling hubs including: CDKN2A (p16) Hub, linking SIRT3 to cell proliferation; TP53 Hub, linking SIRT5 to clinical resistance to aromatase inhibitors, cell survival and proliferation; ATM Hub that comprises ATM/SIRT2/SIRT4/HIF1A and may functionally link endocrine resistance to chemoresistance, consistent with the relatively poor responses of ER+ BC to cytotoxic drugs. Ability of SIRTs to sense and respond to changes in energy could provide a mechanism for an acquired drug-resistant phenotype enabled by epigenetically maintained changes in genes that control metabolism.Using endocrine sensitive (LCC1) and resistant (LCC9) BC cells, we confirmed the higher expression of SIRT1 and 3 in LCC9, compared to LCC1 cells. Upregulation of SIRT3 and SIRT5 expression within 24 hrs of Fulvestrant (ICI; 1 µM) treatment (p=0.0176) was observed in LCC1, but not in LCC9 cells. Conversely, treatment with 17β-estradiol (10 nM) did not significantly affect SIRT3 or SIRT5 expression within 72h in either LCC1 or LCC9 cells. Silencing of SIRT3 induced cell death, reducing growth of LCC9 after 72h of ICI treatment, compared to the untreated control, but no G1/G2 phase arrest in cell cycle was observed during same treatment. In ER+ BC patients, lower expression of SIRT3 is associated with poor relapse free survival (RFS) (HR=0.57; CI=0.43-0.76); p= 7.7x 10-5) whereas higher expression of SIRT5 is associated with poor RFS (HR=2.5; CI=0.99-6.59; p=4.4×10-2). These data indicate an involvement of SIRTs in response to Fulvestrant by BC cells and will be more investigated. Presentation: Saturday, June 11, 2022 1:12 p.m. - 1:17 p.m., Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m.

Theoretical study of stability of nodal completely conservative difference schemes with viscous filling for gas dynamics equations in Euler variables

For the equations of gas dynamics in Eulerian variables, a family of twolayer time-fully conservative difference schemes (FCDS) with space-profiled time weights is investigated. Nodal schemes and a class of divergent adaptive viscosities for FCDS with spacetime profiled weights connected with variable masses of moving nodal particles of the medium are developed. Considerable attention is paid to the methods of constructing regularized flows of mass, momentum and internal energy that preserve the properties of fully conservative difference schemes of this class, to the analysis of their stability and to the possibility of their use on uneven grids. The effective preservation of the internal energy balance in this class of divergent difference schemes is ensured by the absence of constantly operating sources of difference origin that produce “computational” entropy (including entropy production on the singular features of the solution). Developed schemes may be used in modelling of hightemperature flows in temperature-disequilibrium media, for example, if it is necessary to take into account the electron-ion relaxation of temperature in a short-living plasma under conditions of intense energy input.

2000W Blue laser directed energy deposition of AlSi7Mg: process parameters, molten pool characteristics, and appearance defects

ABSTRACT Aluminium alloys are difficult to be manufactured by directed energy deposition (DED) with the widely used infrared laser because of the low absorptivity. A blue laser with a 450 nm wavelength has a significantly higher laser absorptivity in processing aluminium. Here, we developed a 2000 W blue laser directed energy deposition (BL-DED) system for additive manufacturing. In this system, a coaxial camera, a paraxial high-speed camera, and a paraxial infrared camera were simultaneously adopted to analyze the formation and evolution of molten pool characteristics. The relationships among the molten pool characteristics, depositing states, and appearance defects were built. We successfully printed the curved thin wall with good appearance quality by the manual in-situ control of appearance defects. This work demonstrated the advantages of the blue laser in DED of aluminium alloy, which could melt the powders under lower energy input conditions and result in a more stable deposition process.

Solar Wind Energy Input: The Primary Control Factor of Magnetotail Reconnection Site

AbstractIn this paper, we examine the solar wind energy input (expressed by −Vx × Bs, where Vx is the x component of the solar wind velocity and Bs is the southward component of the interplanetary magnetic field IMF Bz) for an onset of magnetic reconnection in the near‐Earth magnetotail. There are 41 events in which in situ observations of magnetic reconnection were made by Geotail. Magnetic reconnection in the postmidnight (premidnight) sector of the plasma sheet occurred under strong (weak) solar wind energy input conditions. Furthermore, we study temporal variations in the solar wind energy input with two different approaches using ground magnetic field observations and proton injections at geosynchronous altitude. These two analyses confirmed the preference of the postmidnight sector for the onset of magnetic reconnection under the strong solar wind energy input conditions. It is also found that the medium and weak solar wind energy input may move the onset location to earlier magnetic local times. The onset location of magnetic reconnection in the near‐Earth magnetotail is controlled by the solar wind energy input through the global magnetospheric dynamics during the loading period.

A robust PVA/C/sponge composite hydrogel with improved photothermal interfacial evaporation rate inspired by the chimney effect

Solar-driven interfacial evaporation has attracted significant research attention owing to its high conversion efficiency of solar energy and transformative industrial potential. The evaporation rate depends on the intrinsic properties of the photothermal conversion materials and external environmental factors. The development of a photothermal evaporation device with a high evaporation rate is urgently required for the application of photothermal interfacial evaporation. Here, we introduce a chimney in a hydrogel composite material to create a novel photothermal evaporation device. First, we fabricated a hydrogel composite material by in situ polymerization in the sponge. The porous structure of the sponge endows the resulting composite hydrogel with a high water-absorption rate. Thus, it improves the water supply rate of traditional hydrogel materials. Meanwhile, we applied a 26 cm high chimney to the photothermal evaporation device and demonstrated that the evaporation rate highly increased from 1.56 to 5.90 kg m−2 h−1 for pure water evaporation, 1.43 to 4.47 kg m−2 h−1 for seawater evaporation under 1 sun illumination. The evaporation system requires no additional energy input or other external conditions. In addition, the improved device structure is simple and can be applied to previously reported photothermal evaporation systems to achieve a higher evaporation rate.

Palladium (Pd0) Loading-Controlled Catalytic Activity and Selectivity for Chlorophenol Hydrodechlorination and Hydrosaturation.

Reductive catalysis by zero-valent palladium nanoparticles (Pd0NPs) has emerged as an efficient strategy for promoting the detoxification of chlorophenols (CPs) via hydrogenation. Most studies achieved hydrodechlorination of CP to phenol for detoxification, but it requires considerably high energy input and harsh conditions to further hydrosaturate phenol to cyclohexanone (CHN) as the most desired product for resource recovery. This study documented 4-CP hydrodechlorination and hydrosaturation catalyzed by Pd0NPs deposited on H2-transfer membranes in the H2-based membrane catalyst-film reactor, which yielded up to 99% CHN selectivity under ambient conditions. It was further discovered that the Pd0 morphology and size, both determined by Pd0 loading, were the key factors controlling the catalytic activity and selectivity: while sub-nano Pd particles catalyzed only 4-CP hydrodechlorination, Pd0NPs were able to catalyze the subsequent hydrosaturation that requires more Pd0 reactive sites than hydrodechlorination. In addition, better dispersion of Pd0, caused by lower Pd0 loading, yielded higher activity for hydrodechlorination but lower activity for hydrosaturation. During the 15 day continuous tests, the substantial product from 4-CP hydrogenation was constantly phenol (>98%) for 0.2 g-Pd/m2 and CHN (>92%) for 1.0 g-Pd/m2. This study opens the door for selectively manipulating desired products from Pd0-catalyzed CP hydrogenation under ambient conditions.

Balancing surface acidity, oxygen vacancies and Cu+ of CuOx/CeO2 catalysts by Nb doping for enhancing CO oxidation and moisture resistance and lowering byproducts in plasma catalysis

The development of a non-noble metal catalyst is a challenging task in plasma catalysis to achieve high CO conversion and low amount of by-products (O3 and NOx) under low energy input and high humidity conditions. In this study, we have prepared several Nb-doped CuOx/CeNbOx catalysts with various Ce/Nb molar ratios. Among them, CuOx/Ce0.9Nb0.1Ox catalyst exhibited the highest CO conversion (>90%) and the lowest by-product emissions (O3 < 5 ppm; NOx < 20 ppm) at low energy density (~600 J/L) in plasma catalytic CO oxidation. Furthermore, it remained good stability under moisture-rich conditions (5.2% H2O). We employed XPS, UV-Raman, O2-TPD, NH3-TPD and in situ DRIFTS to elucidate the origin of enhancement effects. It was found that the appropriate amount of niobium doping well balanced the relationship among Cu+, oxygen vacancies and surface acidity, and inhibited the competitive adsorption of H2O. The findings can provide an avenue to solve the problems of incomplete oxidation and by-product emissions in the application of plasma technology.

Parasitic lasing and thermoelastic deformations in Fe2+:ZnSe crystals under high-power pulsed optical pumping

The results of numerical simulation of thermoelastic stresses arising in F e 2 + : Z n S e crystals, in which the profile of doping with iron ions is a curved surface, are presented. For the conditions of the same specific energy input in the doped region, for different doping profiles, the arising thermoelastic stresses and strains of the crystal were determined, and the thresholds for the appearance of parasitic generation were calculated. It was found that the doping profile in the form of a spherical surface is inferior to the checker doping profile from the point of view of the thermoelastic stresses arising during optical pumping and the possibility of scaling the laser energy.

Influence of Laser Energy Input and Shielding Gas Flow on Evaporation Fume during Laser Powder Bed Fusion of Zn Metal.

Laser powder bed fusion (LPBF) of Zn-based metals exhibits prominent advantages to produce customized biodegradable implants. However, massive evaporation occurs during laser melting of Zn so that it becomes a critical issue to modulate laser energy input and gas shielding conditions to eliminate the negative effect of evaporation fume during the LPBF process. In this research, two numerical models were established to simulate the interaction between the scanning laser and Zn metal as well as the interaction between the shielding gas flow and the evaporation fume, respectively. The first model predicted the evaporation rate under different laser energy input by taking the effect of evaporation on the conservation of energy, momentum, and mass into consideration. With the evaporation rate as the input, the second model predicted the elimination effect of evaporation fume under different conditions of shielding gas flow by taking the effect of the gas circulation system including geometrical design and flow rate. In the case involving an adequate laser energy input and an optimized shielding gas flow, the evaporation fume was efficiently removed from the processing chamber during the LPBF process. Furthermore, the influence of evaporation on surface quality densification was discussed by comparing LPBF of pure Zn and a Titanium alloy. The established numerical analysis not only helps to find the adequate laser energy input and the optimized shielding gas flow for the LPBF of Zn based metal, but is also beneficial to understand the influence of evaporation on the LPBF process.

Influence of drug-carrier compatibility and preparation method on the properties of paclitaxel-loaded lipid liquid crystalline nanoparticles.

The main objective of this paper is to elucidate the influence of drug-carrier compatibility and preparation method on the properties of Paclitaxel (PTX)-loaded lipid liquid crystalline nanoparticles (LLCNs). Here, glyceryl monooleate (GMO), glycerol monolinoleate (GML), glyceryl monolinolenate (GMLO) were selected as the lipids, and Soluplus, Poloxamer 407 (P407), Tween 80 were selected as the stabilizer to prepare LLCNs. First of all, PTX-carrier compatibility was screened by molecular dynamic simulation using Flory-Huggins interaction parameter as the criteria. Thereafter, PTX-loaded LLCNs were prepared under different energy input conditions and were characterized. Influence of lipid type, stabilizer type, drug-lipid ratio and preparation method on properties of the LLCNs was explored. It was found that both lipid and stabilizer type had significant influence on drug encapsulation efficiency. Compared to the LLCNs prepared under high energy condition, PTX-loaded LLCN prepared under low energy input had higher drug encapsulation efficiency, smaller particle size (211.6 nm versus 346.8 nm) and a sustained release behavior. In conclusion, molecular dynamic simulation is an effective tool to select the most appropriate composition of LLCNs for a specific drug substance, and LLCNs prepared using low energy input methods was particularly applicable for industrial manufacture.

Processing window for laser metal deposition of Al 7075 powder with minimized defects

There is a relative lack of data on the processing parameters suitable for laser metal deposition (LMD) of Al alloys, particularly high strength alloys. The objective of this study is to outline a systematic investigation to define the processing window for LMD of Al alloy 7075. Single linear tracks were fabricated by varying the powder mass flow rate, laser power, and scan speed according to a 3 3 factorial experimental design, in order to determine conditions that produce deposits with suitable cross section geometries. Single layer multi-track deposits were fabricated using parameters selected from the linear track experiments, and with varying track overlap values. Low energy input and powder deposition conditions were found to produce single track and multi-track deposits with porosity less than 0.3 and 1 %, respectively. Cuboid samples were produced using parameters selected from the single layer multi-track processing window. However, porosity of at least 4 % was observed in the cross section for all cuboid samples. Liquation cracking was not observed in the samples, despite clear signs of grain boundary liquation. Microcracks with a width of ∼1 μm were observed in the deposited material, and the results indicate that these are solidification cracks due to insufficient eutectic liquid to backfill and ‘heal’ incipient cracks. It is concluded that low energy density and powder mass deposition conditions can produce crack-free single layer deposits of 7075 with low porosity, but the elimination of interlayer porosity and microcracks in multi-layer deposits requires further study.