Kinetic Evolution of Laser Ablating Alloy Materials

Through the theoretical simulation and analysis of the whole process of laser ablating target and producing plasma with high spatio-temporal resolution, it is helpful for people to gain a more complete understanding of the ablation process of target and the evolution process of plasma parameters, which has an important guiding role for the improvement and optimization of laser ablation technology. Alloys are commonly used in daily life, but there are few researches on laser-induced alloy targets at present. Therefore, based on the thermal model of laser ablation and the two-dimensional axisymmetric multi-species hydrodynamic model, the process of laser ablating Al-Mg alloy under atmospheric pressure argon is theoretically simulated, and the ablation process of alloy target and the spatio-temporal evolution results of plasma parameters under different laser irradiances are compared. At high laser irradiance, the melt and evaporation depth, laser energy absorption and plasma characterization parameters are much greater than those at low laser irradiance, and the species energy distribution at different laser irradiance also presents different trends. In addition, the velocity of different species is calculated according to the position-time diagram of the maximum emission intensity, and they expand at a constant speed during the studied time. These results can provide some theoretical guidance for the early application of laser-induced breakdown spectroscopy in metallurgy.

Evolution of the properties of nanomaterials obtained by pulsed laser ablation

The synthesis and application of metal and ceramic nanoparticle are significant subject in science and engineering. The metal nanoparticles such as gold, silver, and copper nanoparticles have more application in material science, nanomedicine, electronic, photonic, and art. One of the green methods for preparation of metal nanoparticles is laser ablation technique that offers a unique tool for nanofabrication of nanoparticles. In this work, gold colloids were prepared by pulsed laser ablation of high purity gold plate immersed in deionized water and 10μM NaCl solution. After ablation process, we study the change in the size distribution of nanoparticles after the ablation process for a month.

Severe Accidents in Sodium-Cooled Fast Reactors: CFD Sensitivity Studies on the Thermal Ablation of Core-Catcher

The present work aims at testing the CFD capabilities to simulate erosion of materials which interact with a corium mass. The main foreseen applications are the design of external/internal core catchers or in-vessel retentions devices used to mitigate severe accidents for Sodium-cooled Fast Reactors (SFR). 2D axisymmetric simulations of a corium jet impinging a sacrificial solid material show evidence of a pool-effect, previously observed in experiments, which contributes to limit the ablation process. Complementary sensitivities assess the influence of jet diameter, temperature and velocity.

Stagnation of the Pensilungpa glacier, western Himalaya, India: causes and implications

This study investigates stagnation conditions of the Pensilungpa glacier, western Himalaya. Multiple glacier parameters (length, area, debris extent and thickness, snowline altitude (SLA), velocity, downwasting and ice cliffs) were studied using field measurements (2016–18), high-resolution imagery from GoogleEarth (2013–17) and spaceborne Landsat, ASTER and SRTM data (1993–2017) to comprehend the glacier's current state. Results show a moderate decrease in length (6.62 ± 2.11 m a−1) and area (0.11 ± 0.03% a−1), a marked increase in SLA (~6 m a−1) and debris cover (2.86 ± 0.29% a−1) and a slowdown of ~50% during 1993–2016. Notable thinning of −0.88 ± 0.04 m a−1 was observed between 2000 and 2017 showing a similar trend as field measurements during 2016–17 (−0.88 m) and 2017–18 (−1.54 m). Further, results reveal a stagnation of the lower ablation zone (LAZ). Less mass supply and heterogeneous debris growth (6.67 ± 0.41% a−1) over the previous decade resulted in slowdown, margin insulation and slope-inversion, leading to stagnation. Stagnation of LAZ caused bulging in the dynamic upper ablation zone and favored the development of supraglacial ponds and ice cliffs. Ice cliffs have grown significantly (48% in number; 41% in area during 2013–17) and their back-wasting now dominates the ablation process.

LASER ABLATION OF PAINT COATINGS IN INDUSTRY

A comparison is made between the laser and sandblasting methods for removing paint from industrial facilities. The advantages of laser ablation are discussed. The possibilities of laser paint removal systems - stationary and moving - are shown. The main factors influencing the laser ablation process and the indicators that determine the quality of the obtained surface are systematized. Researchers' publications on this technological process are analyzed.

Synthesis of Gadolinium Nanoparticles as a CT-Scan Contrast Agent with Pulse Laser Ablation Method

The use of iodine contrast agents on CT Scan clinically shows a short-term blood circulation, non-specific biodistribution and causes side effects on kidneys. Nanoparticles have a longer half-time vascular than molecular contrast agents so it can be observed for a longer time after injection. Gadolinium (Z = 64) has a higher atomic number and X-ray absorbance coefficient than iodine (Z = 53) and does not have the negative effect on kidneys. The Gd nanoparticles development as a CT Scan contrast agent has potential to give more effectiveness than iodine contrast agents. In this study, Gd nanoparticles were synthesized using pulsed laser ablation method with wavelength 1064 nm, energy 45 mJ, and pulse width 7 ns. The ablation process was carried out for 180 minutes with repetition rate of 10 Hz and 15 Hz. The formation of Gd Nanoparticles was analyzed using UV-Vis spectrophotometer and FTIR (Fourier-Transform Infrared Spectroscopy). Testing the ability of Gd nanoparticles as a contrast agent was done in the diagnosis of head and abdomen using a CT Scan GE CT Optima 580 RT type 229156-3. UV-Vis spectrophotometer analysis showed that Gd nanoparticles had high absorbance at the wavelength less than 250 nm which indicated the formation of Gd2(OH)3 compounds. The repetition rate difference in ablation process resulted in the same concentration of Gd nanoparticles with different contrasts. Repetition rate of 10 Hz produced Gd nanoparticles with HU greater than repetition rate of 15 Hz and closer to HU of iodine. The results indicate that Gd nanoparticles can be used as a CT Scan contrast agent.

Investigation of Microwave Ablation Process in Sweet Potatoes as Substitute Liver

The microwave ablation technique to destroy cancer tissues in liver is practiced clinically and is the subject of ongoing research, e.g., ablation monitoring. For studies, liver tissue from cattle or pigs is often used as a substitute material. In this work, sweet potato is presented as an alternative material for microwave ablation experiments in liver due to similar material properties. Sweet potatoes as a substitute for liver have the advantages of better handling, easy procurement and stable material properties over time for microwave ablation experiments. The dielectric constant and electrical conductivity of sweet potato are characterized for temperature variation with the help of high-temperature dielectric probe. Furthermore, a test setup is presented for microwave ablation experiments in which a bowtie slot antenna matched to sweet potato is placed on its surface to directly receive the microwave power from a self-developed microwave applicator inserted into a sweet potato 4 cm below the surface antenna. A high-power source was used to excite the microwave powers up to 80 W and a spectrum analyzer was used to measure the signal received by the surface antenna. The experiments were performed in an anechoic chamber for safety reasons. Power at 50 W and 80 W was stimulated for a maximum of 600 s at the 2.45 GHz ISM band in different sweet potato experiments. A correlation is found between the power received by the surface antenna and rise of temperature inside sweet potato; relative received power drops from 1 at 76 ∘C to 0.6 at 88 ∘C (max. temperature) represents a 40% relative change in a 50 W microwave ablation experiment. The received power envelope at the surface antenna is between 10 mW and 32 mW during 50 W microwave ablation. Other important results for 10 min, 80 W microwave ablation include: a maximum ablation zone short axis diameter of 4.5 cm and a maximum ablation temperature reached at 99 ∘C, 3 mm away from the applicator’s slot. The results are compared with the state of the art in microwave ablation in animal liver. The dielectric constant and electrical conductivity evolution of sweet potato with rising temperature is comparable to animal liver in 50–60 ∘C range. The reflection loss of self-developed applicator in sweet potato is below 15 dB which is equal to reflection loss in liver experiments for 600 s. The temperature rise for the first 90 s in sweet potato is 76 ∘C as compared to 73 ∘C in liver with 50 W microwave ablation. Similarly, with 80–75 W microwave ablation, for the first 60 s, the temperature is 98 ∘C in sweet potato as compared to 100 ∘C in liver. The ablation zone short-axis diameter after 600 s is 3.3 cm for 50 W microwave ablation in sweet potato as compared to 3.5 cm for 30 W microwave ablation in liver. The reasons for difference in microwave ablation results in sweet potato and animal liver are discussed. This is the first study to directly receive a signal from microwave applicator during a microwave ablation process with the help of a surface antenna. The work can be extended to multiple array antennas for microwave ablation monitoring.