Gold Foam Research Articles

Tamping the movement of the laser absorption cutoff position using gold foam hohlraum

In indirect-driven laser fusion experiments, the movement of the laser absorption layer will distort the radiation uniformity on the capsule. The gold foam has advantages in symmetry control and lowering wall plasma blowoff when used in an inertial confinement fusion (ICF) hohlraum. This work investigates the motion of the laser absorption cutoff position using low-density foam gold walls. It is found that the motion of the laser absorption cutoff position can be significantly mitigated through optimal initial low density, tailored to a specific laser shape. For a short square laser pulse, the laser absorption cutoff position remains almost stationary at an initial density of approximately 0.6 g cm−3. For a long-shaped laser pulse, the minimal motion of the laser absorption cutoff position is observed at an initial density of about 0.1 g cm−3. This approach allows for the adjustment of the symmetry of the hohlraum radiation source. The insights gained from this study serve as a crucial reference for optimizing the hohlraum wall density.

Preparation of Macroscopic Low-Density Gold Foams with Good Machinability

Uniform, macroscopic monoliths (ranging from a few millimeters to a centimeter) of low-density gold foams with ~95% porosity and ~10-μm-diameter pores were prepared by the casting of gold-coated polystyrene core-shell particles followed by the thermal removal of the polymer core. The Au foams were composed of unique hollow gold spheres and showed superior mechanical integrity and resilience compared to the foams we previously reported. Highly efficient seeding and electroless gold-plating methods in this study caused a significant morphological transition in the gold coatings from coarse particles to fine particles, and finally, to a continuous layer. A modified, scalable casting approach to form large uniform monoliths (up to ~1-cm diameter) and a gentle baking condition to minimize undesirable densification of the final foams enabled us to develop a simple, efficient synthetic route to nanostructured macroscopic low-density gold foams. To demonstrate the improved mechanical stability and machinability, a representative monolithic Au foam (~0.9 g/cm3) was carefully cut into the hollow cylinder of gold foams by a series of machining and processing steps. Finally, we tried to understand the unique mechanical behaviors and properties of this gold foam by nanoindentation measurement.

Enhanced Photothermal Steam Generation and Gold Using the Efficiency of Ultralight Gold Foam with Hierarchical Porosity

Controlling the optical properties of metal plasma nanomaterials through structure manipulation has attracted great attention for solar steam generation. However, realizing broadband solar absorption for high-efficiency vapor generation is still challenging. In this work, a free-standing ultralight gold film/foam with a hierarchical porous microstructure and high porosity is obtained through controllably etching a designed cold-rolled (NiCoFeCr)99Au1 high-entropy precursor alloy with a unique grain texture. During chemical dealloying, the high-entropy precursor went through anisotropic contraction, resulting in a larger surface area compared with that from the Cu99Au1 precursor although the volume shrinkage is similar (over 85%), which is beneficial for the photothermal conversion. The low Au content also results in a special hierarchical lamellar microstructure with both micropores and nanopores within each lamella, which significantly broadens the optical absorption range and makes the optical absorption of the porous film reach 71.1-94.6% between 250 and 2500 nm. In addition, the free-standing nanoporous gold film has excellent hydrophilicity, with the contact angle reaching zero within 2.2 s. Thus, the 28 h dealloyed nanoporous gold film (NPG-28) exhibits a rapid evaporation rate of seawater under 1 kW m-2 light intensity, reaching 1.53 kg m-2 h-1, and the photothermal conversion efficiency reaches 96.28%. This work demonstrates the enhanced noble metal gold using efficiency and solar thermal conversion efficiency by controlled anisotropic shrinkage and forming a hierarchical porous foam.

Three-dimensional flexible and stretchable gold foam scaffold for real-time electrochemical sensing in cells and in vivo

Compared with typical two-dimensional electrodes, the three-dimensional (3D) cell culture platform can simulate the real cell survival environment for cell growth to accurately reproduce cell functions. Moreover, considering that living cells are exposed to various of mechanical force in the microenvironment, the construction of 3D electrodes with excellent flexible, stretchable, and biocompatibility is of great significance to real-time monitor mechanically evoked biomolecule release from cells. Herein, we demonstrated a straightforward and effective three-step approach to fabricate three-dimensional flexible and stretchable gold foam scaffold (3D Au foam scaffold) for construction of 3D cell culture integrated electrochemical sensing platform. The excellent biological and electrical properties of Au nanostructures and porous networks of the 3D scaffold endow the platform with desirable biocompatibility and sensitive electrochemical sensing performance. As a proof of concept, the 3D Au foam scaffold functionalized with cobalt based nanocubes (Co NCs/Au foam scaffold) was validated to provide 3D culture for human umbilical vein endothelial cells (HUVECs), and synchronously real-time monitor superoxide anion (O2•-) released by HUVECs under mechanical stretching. Furthermore, 3-mercaptopropionic acid (3-MPA) modified 3D Au foam (3-MPA/Au foam scaffold) was successfully used for real-time monitoring of catecholamines in rat brain. The results demonstrate the great potential of this 3D Au foam scaffold for real-time electrochemical monitoring biomolecules in vitro and in vivo, providing convenience for future research on mechanotransduction relevant processes.

An atomistic–continuum multiscale analysis for heterogeneous nanomaterials and its application in nanoporous gold foams

In this paper, an atomistic–continuum homogenization multiscale method is developed to study the nonlinear behavior of heterogeneous nanomaterials. The atomistic representative volume element (RVE) with vacancy and/or void defects are analyzed by employing the fully atomistic method, in which the nucleation, migration, and elimination of dislocation, as well as the dislocation-vacancy interaction, are captured. The coarse-scale material domain is modeled within the framework of the nonlinear finite element method, and the impression of nanoscale material defects is investigated by upscaling the stress tensor and tangent modulus from the atomistic RVE based on the Hill-Mandel principle. The principle of inter-scale kinematic compatibility is implemented using the periodic boundary condition. The mechanical behavior of atomistic RVE under various deformation modes is elucidated through stress – strain and dislocation density – strain curves. Due to the random nature of defects on the atomistic scale, a statistical procedure is exerted to numerically investigate the effect of influential parameters on the RVE mechanical behavior. Finally, the impression of vacancy and/or nanoscale void defects on the multiscale simulation of coarse-scale materials is illustrated in several numerical examples. The obtained results of the multiscale analysis is also verified with experimental data. Moreover, the compaction behavior of nanoporous gold foam is studied through the proposed multiscale method that highlights a good agreement with the fully atomistic analysis.

Three-Dimensional Flexible and Stretchable Gold Foam Scaffold for Real-Time Electrochemical Sensing in Cells and in Vivo

Three-Dimensional Flexible and Stretchable Gold Foam Scaffold for Real-Time Electrochemical Sensing in Cells and in Vivo

Curcumin graphite pencil electrode modified with molybdenum disulfide nanosheets decorated gold foams for simultaneous quantification of nitrite and hydrazine in water samples

A non-enzymatic sensor based on a curcumin modified pencil graphite electrode, loaded with molybdenum disulfide nanosheets decorated gold foam, was constructed. Herein, the electrochemical deposition strategy was adopted throughout the sensing platform design stepwise. The electroactivity of the pencil electrode platform enables sensitive simultaneous quantification of hydrazine and nitrite where the respective working potentials typically are at + 0.2 V for hydrazine and + 0.75 V for nitrite (both vs. Ag/AgCl, saturated KCl). It is shown that the resulting sensor demonstrates excellent analytical performances in terms of limits of detection (18.3, 21.7 nM), sensitivities (0.051, 0.061 μA μM−1), and reproducibility standard deviations (RSD) of 3.1 and 2.7% for hydrazine and nitrite, respectively. Furthermore, long term stability studies showed that the electrodes exhibited an effectively unchanged response after some 30 days. The sensor was used to analyze spiked samples of river water and industrial wastewater.

A dual-enzyme, micro-band array biosensor based on the electrodeposition of carbon nanotubes embedded in chitosan and nanostructured Au-foams on microfabricated gold band electrodes.

We report the development of a dual-enzyme electrochemical biosensor based on microfabricated gold band array electrodes which were first modified by gold foam (Au-foam) in order to dramatically increase the active surface area. The resulting nanostructured Au-foam deposits then served as a highly porous 3D matrix for the electrodeposition of a nanocomposite film consisting of multi walled carbon nanotubes embedded in a chitosan matrix (CS:MWCNT) designed to provide a conducting, biocompatible and chemically versatile surface suitable for the attachment of a wide range of chemically or biologically active agents. Finally, a dual enzyme mixture of glucose oxidase (GOx) and horseradish peroxidase (HRP) was immobilised onto the CS:MWCNT nanocomposite film surface. It is shown that the resulting sensing platform developed demonstrates excellent analytical performance in terms of glucose detection with a sensitivity of 261.8 μA mM-1 cm-2 and a reproducibility standard deviation (RSD) of 3.30% as determined over 7 measurements. Furthermore, long term stability studies showed that the electrodes exhibited an effectively unchanged response to glucose detection after some 45 days. The example of glucose detection presented here illustrates the fact that the particular combination of nanostructured materials employed represents a very flexible platform for the attachment of enzymes or indeed any other bioactive agent and as such may form the basis of the fabrication of a wide range of biosensors. Finally, since the platform used is based on lithographically-deposited gold electrodes on silicon, we note that it is also very suitable for further miniaturisation, mass production and packaging- all of which would serve to reduce production costs.

Demonstration of gold foam plasma as bright x-ray source and slow ion emitters

In this paper, enhancement in x-ray emission and reduction of kinetic energy of ions from low density foam plasma is demonstrated by performing experiment and hydrodynamic simulation. The plasma is produced by irradiation of solid gold and gold foam targets (densities 0.2 g/cc, 0.13 g/cc and 0.1 g/cc) at intensities in the range of 4 × 1013–1 × 1014 W cm−2. Time resolved x-ray emission is measured by an x-ray streak camera with 10 ps resolution. The x-ray flux measured by the streak camera from low density gold foam shows a 13% enhancement in comparison to solid gold in the spectral range >0.8 keV and above. Decrease in velocity of ions is observed in low density gold foam. In solid gold, thermal ions peak velocity is 31 × 104 m s−1 and spread in narrow energy width, however, in case of 0.1 g/cc, peak velocity reduces to 6 × 104 m s−1 towards target normal and emitted in broad energy range. Shadowgraphy results also provide evidence of narrower expansion of plasma from solid gold. However, total ion flux from low density gold foam is comparable to ion flux of solid gold indicating the process of volumetric absorption.

Laser-driven shock compression of gold foam in the terapascal pressure range

Shock compression experiments are carried out on gold foam with an initial density of 3.2 g/cm3 through indirectly laser-driven shock waves at the SG-III prototype laser facility. The impedance-matching technique is applied to determine the equation-of-state (EOS) data of the shocked gold foam. A passive shock breakout diagnostic system is employed to obtain the shock velocities in both the standard material and gold foam. The gold foams are compressed to a maximum density of 20 g/cm3 under a shock pressure of about 2 TPa. The effects of the unsteadiness of shock waves on the EOS measurement are quantitatively analyzed and corrected. The correction of unsteady waves, as well as the good planarity of the shock waves and the low preheating of the gold foam, contributes high-confidence EOS data for the gold foam. The corrected experimental data are compared with the Hugoniot states from the SESAME library. The comparison suggests that the database is suitable for describing the states of gold foam with an initial density of 3.2 g/cm3 under a pressure of about 2 TPa.

Efficient soft x-ray sources from laser-irradiated gold foam targets with well-controlled impurities

As an important x-ray source, enhancement of x-ray emissions from laser-produced plasmas is significant for various applications. Due to less expanding kinetic loss, gold foam with low initial density can have an enhanced x-ray conversion efficiency compared with solid-density gold. However, low-Z impurities within gold foam targets will diminish the enhancement remarkably, and should be tightly controlled. This paper presents an experimental study of a high brightness laser plasma soft x-ray source, based on a g gold foam target with negligible impurities irradiated by nanosecond laser pulses with power density around 3 × 10 W at the Shenguang II laser facility. A conversion efficiency, from multi-eV to multi-keV, of % is achieved in the x-ray emissions—about 21% relative enhancement compared with a solid-density gold target, and the highest conversion efficiency for Au foam planar targets yet. Good agreement has been achieved between the semi-analytical model prediction and the experimental results.

X-ray nanotomography characterizations of gold foams

Observation of the three-dimensional interior microstructure of low-density gold foams is very important for the optimization of their physical and chemical properties. We report on the three-dimensional internal microstructural imaging of gold foams by using X-ray computed tomography with a resolution of 50nm. The gold foams are synthesized by the chemical dealloying method. By using focused ion beam milling technology, a foam micro-cylinder with a diameter of approximately 55μm is prepared. The tomographical data sets of the micro-cylinder foam are collected in the angle range of ±90° at a photon energy of 8keV. The data sets are then used to reconstruct the three-dimensional microstructure of the gold foams. The three-dimensional reconstruction information obtained from computed tomography provides an intuitive understanding of the gold foam structure.

Experimental study on improving hohlraum wall reemission ratio by low density gold foam

It is important to improve the hohlraum radiation temperature for the research of high energy density physics, especially for study of inertial confinement fusion. Increasing the wall reemission ratio is an effective way to improve the temperature. It is found in theory that low density foam could reduce hohlraum wall energy loss, and then increase hohlraum temperature. In previous studies, experiments have shown that laser-to-X-ray conversion is enhanced by Au foam. However, improving reemission ratio is more important to increase hohlraum radiation temperature, because most of energy is lost in the wall.In this paper, we report our experiments carried out on SGⅢ prototype to compare the X-ray flux reemitted by Au foam and that by Au. For the experimental design, Au solid and Au foam are irradiated symmetrically along the axis by hohlraum radiation source Tr(t), which is assessed by broadband X-ray spectrometer flat-response X-ray diodes. The measured peak temperature is about 190 eV. Reemission flux from sample is measured by transmission grating spectrometer (TGS). The space-resolved image for pure Au sample shows that the hohlraum radiation is asymmetrical along the axis in the experimental conditions, temperature of top is higher than that at the bottom, which is consistent with simulation results obtained by using IRAD3D code. In order to compare the reemission flux from Au solid sample and that from Au foam sample in same conditions, we need to correct the symmetry of hohlraum radiation. By multiplying the ratio of top flux to bottom flux in pure Au target by the bottom flux in Au-Au foam target, where Au foam is on, we make sure that they are ablated by the same radiation source. The calculated results show that X-ray flux is increased by 20% by Au foam of 0.4 g/cc density when the hohlraum temperature is 190 eV. The typical observed time-integrated X-ray reemission spectra for Au solid and Au foam by TGS are also shown. We see that N-band and O-band reemission are clearly enhanced by Au foam, and the O-band reemission is almost the same as M-band reemission. The increased flux concentrates below 1 keV of the soft X-ray emission.The self-similar solution results and MULTI 1D simulation results show that the wall loss energy fraction is saved by Au foam, whose relation to reemission flux can be described by a simple expression. The theoretical solution shows that the emission flux increases about 10%, and the MULTI simulation indicates that the emission flux increases about 6.8%. They are in qualitative agreement with the experiments results. These results show an alluring prospect for Au foam to be used as hohlraum wall.

Reducing wall plasma expansion with gold foam irradiated by laser

The experimental study on the expanding plasma movement of low-density gold foam (∼1% solid density) irradiated by a high power laser is reported in this paper. Experiments were conducted using the SG-III prototype laser. Compared to solid gold with 19.3 g/cc density, the velocities of X-ray emission fronts moving off the wall are much smaller for gold foam with 0.3 g/cc density. Theoretical analysis and MULTI 1D simulation results also show less plasma blow-off, and that the density contour movement velocities of gold foam are smaller than those of solid gold, agreeing with experimental results. These results indicate that foam walls have advantages in symmetry control and lowering plasma fill when used in ignition hohlraum.

X射线CT技术体积重构法表征异形泡沫金密度

X射线CT技术体积重构法表征异形泡沫金密度

Density characterization of gold foam sample with abnormal surface using X-ray CT technology

Density characterization of gold foam sample with abnormal surface using X-ray CT technology

The impact of low-Z impurities on x-ray conversion efficiency from laser-produced plasmas of low-density gold foam targets

It is an important approach to improve the x-ray conversion efficiency of laser-ablated high-Z plasmas by using low initial density materials for various applications. However, unavoidable low-Z impurities in the manufacture process of low-density high-Z foam targets will depress this effect. A general easy-to-use analytical model based on simulations was developed to evaluate the quantitative impact of impurities within the gold foam target on laser to x-ray conversion efficiency. In addition, the x-ray conversion efficiencies of 1 g∕cm3 gold foams with two different initial contents of impurities were experimentally investigated. Good agreements have been achieved between the model results and experiments.

Pultrusion 복합 샌드위치 패널의 신뢰성 평가

Article history: Research on decreasing the weight of composite sandwich panels is in progress. This paper reports the experimental results for the mechanical behavior of a composite sandwich panel. The skins of sandwich panels were made of glass fiber sheets and plywood matrix composites. Their interior layers consisted of glass fiber pultrusion pipes and gold foam. Experimental tests were performed to obtain the mechanical properties and complex mechanical behavior. Before fatigue tests, tensile tests and 3-point bending tests were carried out to obtain the optimal design and determine their strength and failure mechanisms in the flat-wise position. After the static test, a fatigue test were conducted at a load frequency of 5 Hz, stress ratio (R) of 0.1, and endurance limit for the S-N curve. It showed that the failure modes were related to both the core design and skin failure.

Simulation of laser to X-ray conversion features influenced by low density gold foam

In the laser indirect-driven inertial confinement fusion, laser light is converted into X-rays by laser-plasma interactions in the hohlraum, then at the surface of the capsule the re-emission of hohlraum inner wall would drive a symmetrical radiation source to motivate implosion. It is of great importance to improve the features of laser to X-ray conversion in the hohlraum. The influence of low density gold foam on conversion features was investigated numerically with the help of one-dimensional hydrodynamics code. The numerical simulation results show that conversion efficiency increases with the decrease in gold density under the given laser condition. In particular, it can indeed have more than 19% extra conversion efficiency relatively when solid gold is replaced by gold foam of 0.1 g/cm3 density. In addition, the percentage of M-band decreases. There is an appropriate density of gold foam, at which the movement of plasma are restrained. According to the simulation results of energy balance, we get a higher radiation energy proportion when low density gold foam is selected as the target, and this is due to the decrease of kinetic energy losses compared with solid gold. Anyway, it is an effective approach to optimize the hohlraum by using low density gold foam to improve the features of laser to X-ray conversion, and these simulations would provide a scientific basis for further attempting correlative experiments.

Electrochemical Fabrication of Low Density Metal Foam with Mono-Dispersed-Sized Micro- and Submicro-Meter Pore

This paper deals with the fabrication of low-density metal using micro-template and electrochemical plating techniques. Tin and gold foam films were demonstrated. For both cases, porous foam plating required 0.5 V negatively higher bias potential than that for conventional metal plating. The electric current density values for them are smaller than those for bulk metal plating. In spite of these differences, the coulomb efficiency was almost the same as those for bulk metal plating. The density was almost close to the rest of closed packing density; 23 % of bulk metal for gold and 20 % of bulk metal for tin. These low-density foams will be applied for extreme ultraviolet (EUV) generation or other application through laser produced plasma.