Journal articles: 'Chemical and thermal ablation'

1

Xiao, Jie, Lin Jiang, and Qiang Xu. "Insight into chemical reaction kinetics effects on thermal ablation of charring material." Thermal Science, no. 00 (2021): 85. http://dx.doi.org/10.2298/tsci201010085x.

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Thermal ablation plays an important role in the aerospace field. In this paper, to study the chemical kinetics effects on heat transfer and surface ablation of the charring ablative material during aerodynamic heating, a charring ablation model was established using the finite element method. AVCOAT5026-39H/CG material, one typical thermal protection material used in thermal protection system, was employed as the ablative material and heated by aerodynamic heating condition experienced by Apollo 4. The finite element model considers the decomposition of the resin within the charring material and the removal of the surface material, and uses Darcy?s law to simulate the fluid flow in the porous char. Results showed that the model can be used for the ablation analysis of charring materials. Then effects of chemical kinetics on ablation were discussed in terms of four aspects, including temperature, surface recession, density distribution, and mass flux of pyrolysis gas. The pre-exponential factor and activation energy have different effects on ablation, while the effect of the reaction order is little. This paper is helpful to understand the heating and ablation process of charring ablative materials and to provide technical references for the selection and design of thermal protection materials.

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Han, Qiuchen, Lei Chang, Zhaoqun Sun, Jiaqi Sun, Zengyan Wei, Pingping Wang, Ziyang Xiu, Huasong Gou, Pengchao Kang, and Gaohui Wu. "Ablation Mechanism of AlSiB-C/C Composites under an Oxy-Acetylene Torch." Metals 13, no. 1 (January 12, 2023): 160. http://dx.doi.org/10.3390/met13010160.

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In order to improve the ablation resistance of C/C composites, an AlSiB alloy (mass ratio of Al/Si/B = 2:4:1) was used as a dissipative agent to fill the pores of a C/C composites matrix by reactive melt infiltration to prepare AlSiB-C/C composites. The microstructure evolution and ablation behavior of the obtained AlSiB-C/C composites (mass ratio of Al/Si/B = 2:4:1) under oxy-acetylene flame were investigated by SEM after ablating for 25 s, 50 s, 100 s and 150 s. At the beginning of the ablation process, thermal chemical erosion played a leading part. By using the heat-absorption effect of sweating and the sealing protection effect of the oxide layer, AlSiB-C/C composites significantly reduced the ablation surface temperature, and the linear ablation rate was 4.04 μm/s. With the process of ablation, thermal mechanical erosion tended to dominate. The specimen surface could not form a continuous covering of oxide film to slow down the flame scour, resulting in non-uniform ablation and further expansion of the ablation pit. The self-transpiration cooling behavior and the self-sealing of the ablation products of the dissipative agent played an important role in reducing the extent of thermal chemical erosion and preventing matrix ablation.

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Zhang, Hao, Jinfeng Tian, Liwei Yan, Shengtai Zhou, Mei Liang, and Huawei Zou. "Improving the Ablation Properties of Liquid Silicone Rubber Composites by Incorporating Hexaphenoxycyclotriphosphonitrile." Nanomaterials 13, no. 3 (January 30, 2023): 563. http://dx.doi.org/10.3390/nano13030563.

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The ablative properties of epoxy-modified vinyl silicone rubber (EMVSR) composites containing hexaphenoxycyclotriphosphonitrile (HPCTP) have been systematically studied. The strength of the ablation char layer was greatly enhanced with the addition of HPCTP, which induced the formation of a more complete, denser, and thicker char during oxyacetylene ablation tests. Moreover, the HPCTP-containing EMVSR composites demonstrated lower thermal conductivity and pyrolysis rate when compared with those without HPTCP. At the same time, the thermal insulation properties of HPCTP-filled composites were improved under low heat flow ablation scenarios. The reduction of graphitic carbon content, the formation of phosphate-like crystals as well as the increase of SiC content contributed to strengthening the char layer, which was critical for improving the ablation properties. The optimum char layer strength and thermal insulation properties were achieved when the content of HPCTP was 15 phr, whereas an optimum ablation resistance was achieved at 25 phr HPCTP. This suggests that HPCTP-modified EMVSR composites can be used for thermal protection purposes, especially in the fields of aerospace and aeronautics.

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Gorskiy, V. V., M. G. Kovalsky, and V. G. Resh. "Method of Calculating Carbon Ablation in the Jet of Liquid Rocket Engine Combustion Products." Herald of the Bauman Moscow State Technical University. Series Mechanical Engineering, no. 5 (128) (October 2019): 4–21. http://dx.doi.org/10.18698/0236-3941-2019-5-4-21.

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Nowadays carbon materials are widely used as ablating thermal protection for high-temperature structural elements in aerospace technology. Prediction of changes in the shape of the external surfaces of these elements, due to the burning of thermal protection, is closely related to the use of computational-theoretical methods describing the flow of various physicochemical and mechanical processes associated with the occurrence of the phenomenon under consideration. At the same time, it is crucial to test such methods on the results of experimental studies conducted under conditions which are implemented during the process of testing thermal protection in jets of aerodynamic units. The main elements of ablation of carbon materials include their erosion, i.e., mechanical ablation of mass, observed in high-pressure gas flows. In the process of experimental development, it is necessary to carry out research on large-scale models, which has led to widespread use of underexpanded jets of combustion products of liquid rocket engine combustion products for modeling the erosion process of thermal protection. The theoretical model of ablation of thermal protection in such jets requires taking into account the complex chemical composition of the gas mixture flowing into the model; physical and chemical interaction of this gas with thermal protection, which causes gasification of the latter; use of mathematical models describing the process of material erosion due to mechanical impact of high-pressure gas flow. The paper describes the development of the carbon material ablation calculating and theoretical methodology which could be used to determine the material erosion characteristics on the basis of solving a complex problem of circumfluence, heating, heat penetration and ablation of thermal protection.

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Asghar, Muhammad, Nadeem Iqbal, Sadia Sagar Iqbal, Mohsin Farooq, and Tahir Jamil. "Ablation and thermo-mechanical tailoring of EPDM rubber using carbon fibers." Journal of Polymer Engineering 36, no. 7 (September 1, 2016): 713–22. http://dx.doi.org/10.1515/polyeng-2015-0337.

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Abstract Carbon fibers (CFs) are incorporated into ethylene propylene diene monomer (EPDM) rubber to fabricate charring elastomeric ablative composites for ultrahigh temperature applications. Ablation characteristics of the ablative composites were evaluated using ASTM E285-08. Variant content incorporation of short CFs in the basic composite formulation reduced the backface temperature acclivity and the ablation rate rose up to 48% and 78%, correspondingly. Thermal stability and endothermic capability were improved with increasing short fiber contents in the rubber matrix. Experimental thermal conductivity measurement results elucidate that thermal conductivity reduces 60% at 473 K with 6 wt% addition of the fibers. A remarkable improvement was scrutinized in the tensile strength and rubber hardness with increasing fiber to matrix ratio. Scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDS) analysis of the composite specimens revealed the uniform dispersion of CFs within the host matrix, formation of voids during ablation, char-reinforcement interaction and composition of the charred ablators and the impregnated fibers.

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Moskvicheva, L. I., D. V. Sidorov, M. V. Lozhkin, L. O. Petrov, and M. V. Zabelin. "Modern methods of ablation of malignant tumors of the liver." Research'n Practical Medicine Journal 5, no. 4 (December 22, 2018): 58–71. http://dx.doi.org/10.17709/2409-2231-2018-5-4-6.

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The purpose of this review is to demonstrate the possibility of performing various methods of thermal and non-thermal ablation in patients with primary and metastatic liver tumors on the basis of data available in the world medical literature.As conservative variants of local action in patients with non-resectable primary and secondary liver tumors and inoperable patients, various ablative techniques have been developed and used to achieve local control over the disease and increase the life expectancy of this group of patients. These include: radiofrequency ablation, microwave ablation, HIFU therapy, laser ablation, cryotherapy, chemical destruction of the tumor, irreversible electroporation, stereotactic radiation therapy.The effectiveness of these ablation methods depends on the size and localization of the tumor focus, and for thermal techniques — also on its location relative to large vessels. Ablative techniques have the maximum efficiency (in some cases, similar to surgical intervention) when exposed to early forms of primary cancer or secondary tumor formation of the liver in the presence of a solitary node with a maximum size up to 5 cm or 3 and less foci size up to 3 cm. The effectiveness of local destruction of tumor formations of the liver of larger diameter is increased by carrying out ablation by the second stage after performing chemoembolization of the hepatic artery or by combining various techniques of local action.The use of various modern methods of ablation of solid primary and secondary liver tumors in medical practice can expand the possibilities of antitumor treatment of this category of patients.

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Li, Weijie, Haiming Huang, and Xiaoliang Xu. "A coupled thermal/fluid/chemical/ablation method on surface ablation of charring composites." International Journal of Heat and Mass Transfer 109 (June 2017): 725–36. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2017.02.052.

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PENG, YAJING, YINGHUI WANG, BRUNO PALPANT, XING HE, XIANXU ZHENG, and YANQIANG YANG. "MODELING HEAT-INDUCED CHEMICAL REACTION IN NANOTHERMITES EXCITED BY PULSE LASER: A HOT SPOT MODEL." International Journal of Modern Physics B 24, no. 03 (January 30, 2010): 381–95. http://dx.doi.org/10.1142/s0217979210055135.

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A hot spot model, involving interaction of pulse laser with nanoparticles where heat diffusion and exothermic chemical reaction are considered and spread out of heat and chemical reaction, is developed to model the thermal reaction dynamic process of Al/NC (nitrocellulose) nanothermites excited by pulse laser for the purpose of verifying the experimental ablation criterion proposed recently and providing a microscopic insight into different physical pathways leading to ablation. In this model, the spatial position and conversion of matters taking place in chemical reactions are regarded as the functions of time, space, and temperature. An exact expression of power density absorbed by nanoparticles in matrix is incorporated to calculate the diameters of chemical reaction region. Calculation results justify experimental ablation criterion, and show that thermal decomposition mechanism predominates the nanosecond pulse-excited process before ablation but it is not suitable for the 100 ps regime which is qualitatively attributed to shock pressure. The effects of pulse duration and nanoparticle size on ablation threshold are examined.

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Willard, Johnson M. "Low-Density Resin-Based Ablative Heat Protection Materials." Science Insights 40, no. 6 (May 30, 2022): 541–44. http://dx.doi.org/10.15354/si.22.re063.

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The severe aerodynamic heating that occurs when a spacecraft reenters the atmosphere takes place. The material used for thermal protection is an essential part of the system used for thermal protection. A number of chemical and physical transformations take place in the ablation heat-resistant material that is based on resin. This material is an organic polymer. We herein briefly review the status quo of low-density resin-based ablative heat protection materials.

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Li Gan, Cheng Mou-Sen, and Li Xiao-Kang. "Thermal-chemical coupling model of laser induced ablation on polyoxymethylene." Acta Physica Sinica 63, no. 10 (2014): 107901. http://dx.doi.org/10.7498/aps.63.107901.

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Ren, Jingwen, Yan Qin, Zhengwei Peng, and Zhuangzhuang Li. "Influence of composite structure design on the ablation performance of ethylene propylene diene monomer composites." e-Polymers 21, no. 1 (January 1, 2021): 151–59. http://dx.doi.org/10.1515/epoly-2021-0015.

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Abstract By introducing functional fillers into the ethylene propylene diene monomer matrix, the anti-ablation, thermal insulation, and adhesive layer were prepared, respectively. We have studied the mechanical properties, ablation properties, thermal insulation properties, and bonding properties of different composite structures after design and analyzed the ceramic mechanism. The results showed that the content of ceramic fillers improved the thermal stability and ablation properties of anti-ablation layer composites. The formation of liquid structure can fill the hole defects and ablation pit. The foaming agent improved thermal insulation properties of the thermal insulation layer, and the strength of the bonding layer has been greatly improved. The design of the composite structure can not only reduce the density but also have an excellent thermal insulation effect. And as the thickness of the heat insulation layer increases, the heat blocking effect becomes more excellent.

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12

Pietrosanu, Catalina, Viorel Zainea, Irina Ionita, Cristian Dragos Stefanescu, Mura Hainarosie, and Razvan Hainarosie. "Chemical Ablation of the Tissue in ENT Surgery." Revista de Chimie 69, no. 1 (February 15, 2018): 286–89. http://dx.doi.org/10.37358/rc.18.1.6090.

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Various interventions require tissue ablation in ENT surgery. This can be achieved using a multitude of methods, but the tendency today is to use minimally invasive methods. The development of new technologies has allowed us to consider the use of coblation for tissue ablation, which is based on a chemical reaction, instead of a thermal or mechanical ablation. The technology proved to be extremely used in the field of ENT. Its indications range from functional surgery to benign or even malignant tumors and it can be used in the nose, pharynx and larynx, with probes of different length and angulation. This minimally invasive method of tissue ablation associates less scaring, a faster recovery and a lower postoperative discomfort. Although the time required for the intervention may be somewhat longer, the overall results are superior to the classical methods, considering it provides instant hemosthasis as well. We consider it to be a reliable method, fit for a wide range of indications.

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Li, Rui, Cheng Zhou, Lin Yu, Yang Chen, Huawei Zou, and Mei Liang. "Study on the thermal stability and ablation properties of metallic oxide-filled silicone rubber composites using uniform design method." Journal of Polymer Engineering 36, no. 8 (October 1, 2016): 805–11. http://dx.doi.org/10.1515/polyeng-2015-0317.

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Abstract The thermal stability and ablation properties of silicone rubber composites filled with Fe2O3, SnO2, CuO, MgO, and Al2O3 were researched using thermogravimetric analysis (TGA) and the oxyacetylene torch test. The effecting laws of metallic oxide on the thermal stability and ablation properties of silicone rubber composites were analyzed by uniform design method. TGA indicated that the thermal degradation process of silicone rubber composites took a two mass loss steps. The effecting order of metallic oxide on enhancing thermal stability property of silicone rubber composites in step 1 was MgO>SnO2> Fe2O3>Al2O3>CuO, whereas the order in step 2 was CuO> SnO2>MgO>Fe2O3>Al2O3. Furthermore, Fe2O3 and SnO2 had an evident synergistic effect on enhancing the thermal stability property and residual carbon of silicone rubber composites. The oxyacetylene torch test showed that the effecting order of metallic oxide on increasing ablation resistance property of silicone rubber composites in ablation process was CuO>MgO>Fe2O3>SnO2>Al2O3. Moreover, the line ablation rate of specimen 2 was 0.0499, which indicated that it had the best ablation resistance among all uniform samples. Furthermore, scanning electron microscopy also showed that the porous ceramic layer became much denser after the ablation process, and this will significantly improve the ablation resistance property.

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Ye, Chong, Dong Huang, Baoliu Li, Pingjun Yang, Jinshui Liu, Huang Wu, Jianxiao Yang, and Xuanke Li. "Ablation Behavior of the SiC-Coated Three-Dimensional Highly Thermal Conductive Mesophase-Pitch-Based Carbon-Fiber-Reinforced Carbon Matrix Composite under Plasma Flame." Materials 12, no. 17 (August 25, 2019): 2723. http://dx.doi.org/10.3390/ma12172723.

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This study is focused on a novel high-thermal-conductive C/C composite used in heat-redistribution thermal protection systems. The 3D mesophase pitch-based carbon fiber (CFMP) preform was prepared using CFMP in the X (Y) direction and polyacrylonitrile carbon fiber (CFPAN) in the Z direction. After the preform was densified by chemical vapor infiltration (CVI) and polymer infiltration and pyrolysis (PIP), the 3D high-thermal-conductive C/C (CMP/C) composite was obtained. The prepared CMP/C composite has higher thermal conduction in the X and Y directions. After an ablation test, the CFPAN becomes needle-shaped, while the CFMP shows a wedge shape. The fiber/matrix and matrix/matrix interfaces are preferentially oxidized and damaged during ablation. After being coated by SiC coating, the thermal conductivity plays a significant role in decreasing the hot-side temperature and protecting the SiC coating from erosion by flame. The SiC-coated CMP/C composite has better ablation resistance than the SiC-coated CPAN/C composite. The mass ablation rate of the sample is 0.19 mg·(cm−2·s−1), and the linear ablation rate is 0.52 μm·s−1.

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Teßarek, J. "Mechanochemical endovenous ablation (MOCA) for the treatment of varicose veins." Phlebologie 46, no. 03 (May 2017): 150–54. http://dx.doi.org/10.12687/phleb2369-3-2017.

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SummaryThe endovenous therapies for varicosal veins have partially replaced surgical procedures. Beside thermal ablation based on laser or high frequency other, catheter based techniques are at hand. The non thermal mechano-chemical ablation (MOCA), that can be performed under local anesthesia, has developed as a safe and effective alternative at reasonable costs since its certification in 2011. A combination of MOCA and surgical treatment or foam sclerotherapy can be per-formed in the same setting or sequentially.

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Eklöf, Bo, and Michel Perrin. "Review of randomized controlled trials comparing endovenous thermal and chemical ablation." Reviews in Vascular Medicine 2, no. 1 (March 2014): 1–12. http://dx.doi.org/10.1016/j.rvm.2013.10.001.

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Brody, Lynn. "Percutaneous Ablation (Thermal and Chemical) in the Liver and Bile Ducts." Journal of Vascular and Interventional Radiology 14, no. 2 (February 2003): P323. http://dx.doi.org/10.1016/s1051-0443(03)70242-5.

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Vondrak, T., J. M. C. Plane, S. Broadley, and D. Janches. "A chemical model of meteoric ablation." Atmospheric Chemistry and Physics Discussions 8, no. 4 (July 30, 2008): 14557–606. http://dx.doi.org/10.5194/acpd-8-14557-2008.

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Abstract. Most of the extraterrestrial dust entering the Earth's atmosphere ablates to produce metal vapours, which have significant effects on the aeronomy of the upper mesosphere and lower thermosphere. A new Chemical Ablation Model (CAMOD) is described which treats the physics and chemistry of ablation, by including the following processes: sputtering by inelastic collisions with air molecules before the meteoroid melts; evaporation of atoms and oxides from the molten particle; diffusion-controlled migration of the volatile constituents (Na and K) through the molten particle; and impact ionization of the ablated fragments by hyperthermal collisions with air molecules. Evaporation is based on thermodynamic equilibrium in the molten meteoroid (treated as a melt of metal oxides), and between the particle and surrounding vapour phase. The loss rate of each element is then determined assuming Langmuir evaporation. CAMOD successfully predicts the meteor head echo appearance heights, observed from incoherent scatter radars, over a wide range of meteoroid velocities. The model also confirms that differential ablation explains common-volume lidar observations of K, Ca and Ca+ in fresh meteor trails. CAMOD is then used to calculate the injection rates into the atmosphere of a variety of elements as a function of altitude, integrated over the meteoroid mass and velocity distributions. The most abundant elements (Fe, Mg and Si) have peak injection rates around 85 km, with Na and K about 8 km higher. The more refractory element Ca ablates around 82 km with a Na:Ca ratio of 4:1, which does therefore not explain the depletion of atomic Ca to Na, by more than 2 orders of magnitude, in the upper mesosphere. Diffusion of the most volatile elements (Na and K) does not appear to be rate-limiting except in the fastest meteoroids. Non-thermal sputtering causes ~35% mass loss from the fastest (~60–70 km s−1) and smallest (10−17–10−13g) meteoroids, but makes a minor contribution to the overall ablation rate.

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Vondrak, T., J. M. C. Plane, S. Broadley, and D. Janches. "A chemical model of meteoric ablation." Atmospheric Chemistry and Physics 8, no. 23 (December 5, 2008): 7015–31. http://dx.doi.org/10.5194/acp-8-7015-2008.

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Abstract. Most of the extraterrestrial dust entering the Earth's atmosphere ablates to produce metal vapours, which have significant effects on the aeronomy of the upper mesosphere and lower thermosphere. A new Chemical Ablation Model (CAMOD) is described which treats the physics and chemistry of ablation, by including the following processes: sputtering by inelastic collisions with air molecules before the meteoroid melts; evaporation of atoms and oxides from the molten particle; diffusion-controlled migration of the volatile constituents (Na and K) through the molten particle; and impact ionization of the ablated fragments by hyperthermal collisions with air molecules. Evaporation is based on thermodynamic equilibrium in the molten meteoroid (treated as a melt of metal oxides), and between the particle and surrounding vapour phase. The loss rate of each element is then determined assuming Langmuir evaporation. CAMOD successfully predicts the meteor head echo appearance heights, observed from incoherent scatter radars, over a wide range of meteoroid velocities. The model also confirms that differential ablation explains common-volume lidar observations of K, Ca and Ca+ in fresh meteor trails. CAMOD is then used to calculate the injection rates into the atmosphere of a variety of elements as a function of altitude, integrated over the meteoroid mass and velocity distributions. The most abundant elements (Fe, Mg and Si) have peak injection rates around 85 km, with Na and K about 8 km higher. The more refractory element Ca ablates around 82 km with a Na:Ca ratio of 4:1, which does therefore not explain the depletion of atomic Ca to Na, by more than 2 orders of magnitude, in the upper mesosphere. Diffusion of the most volatile elements (Na and K) does not appear to be rate-limiting except in the fastest meteoroids. Non-thermal sputtering causes ~35% mass loss from the fastest (~60–70 km s−1) and smallest (10−17–10−13 g) meteoroids, but makes a minor contribution to the overall ablation rate.

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Feng, Tao, Mingde Tong, Shuotian Yao, and Shifeng Wen. "A New Assistant Method for Characterizing Ablation Resistance of ZrC-SiC Dispersive Biphasic Coating on C/C Composites." Coatings 9, no. 11 (November 6, 2019): 735. http://dx.doi.org/10.3390/coatings9110735.

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To optimize the ablation resistance of ZrC coating, ZrC-SiC dispersive biphasic coating was prepared by chemical vapor co-deposition. The ablation resistances of the coatings were carried out by oxyacetylene flame tests. Compared with double-layered ZrC/SiC coating, the ablation resistance of ZrC-SiC coating was evaluated. On the basis of similar mass ablation rates of the two coatings, a new assistant method for characterizing the thermal protecting effect of coatings on carbon-carbon composites (C/C) composites was proposed. The thermal protecting ability of the coating was accurately reflected by the changes of hardness and elastic modulus of C/C substrate below the central region of ablated coatings before and after ablation. The ablation processes of two kinds of coatings were also discussed. The results showed that the hardness and elastic modulus of the C/C substrate protected by ZrC-SiC coating were higher than that of C/C coated with ZrC/SiC coating. The result convincingly illustrated the thermal protecting ability of ZrC-SiC coating was much better than that of ZrC/SiC coating, which attributed to the formation of Zr-Si-O glass.

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Chen, Xiong, Hai Feng Xue, and Hua Liang. "Thermal Response and Ablation Research of EPDM Thermal Protection Material in Ramjet." Advanced Materials Research 1092-1093 (March 2015): 534–38. http://dx.doi.org/10.4028/www.scientific.net/amr.1092-1093.534.

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Thermal protection materials are required to preserve the metal components of motor that suffer severe heat load. The research on thermal response of insulation of ramjet combustion chamber was carried out by the ground test and numerical simulation. During the working time of the ramjet, the back-face temperature of the thermal protection material was measured. The scanning electron microscope of samples was investigated. The calculation of thermo-chemical flow was solved by the CFD software FLUENT to provide the heat load boundary for simulation of heat transfer of EPDM insulation. The heat transfer model was solved by the FEA software ANSYS. Comparison of the temperature profile at the ablating surface between calculation and measurement shows the two results agree with each other. The simulation results can provide the temperature rising trend of insulation in a certain extent.

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Ashikbayeva, Zhannat, Arman Aitkulov, Timur Sh Atabaev, Wilfried Blanc, Vassilis J. Inglezakis, and Daniele Tosi. "Green-Synthesized Silver Nanoparticle–Assisted Radiofrequency Ablation for Improved Thermal Treatment Distribution." Nanomaterials 12, no. 3 (January 27, 2022): 426. http://dx.doi.org/10.3390/nano12030426.

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Thermal ablation therapy is known as an advantageous alternative to surgery allowing the treatment of multiple tumors located in hard-to-reach locations or treating patients with medical conditions that are not compatible with surgery. Appropriate heat propagation and precise control over the heat propagation is considered a weak point of thermal ablation therapy. In this work, silver nanoparticles (AgNPs) are used to improve the heat propagation properties during the thermal ablation procedure. Green-synthesized silver nanoparticles offer several attractive features, such as excellent thermal conductivity, biocompatibility, and antimicrobial activity. A distributed multiplexed fiber optic sensing system is used to monitor precisely the temperature change during nanoparticle-assisted radiofrequency ablation. An array of six MgO-based nanoparticles doped optical fibers spliced to single-mode fibers allowed us to obtain the two-dimensional thermal maps in a real time employing optical backscattering reflectometry at 2 mm resolution and 120 sensing points. The silver nanoparticles at 5, 10, and 20 mg/mL were employed to investigate their heating effects at several positions on the tissue regarding the active electrode. In addition, the pristine tissue and tissue treated with agarose solution were also tested for reference purposes. The results demonstrated that silver nanoparticles could increase the temperature during thermal therapies by propagating the heat. The highest temperature increase was obtained for 5 mg/mL silver nanoparticles introduced to the area close to the electrode with a 102% increase of the ablated area compared to the pristine tissue.

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Andreozzi, Assunta, Luca Brunese, Marcello Iasiello, Claudio Tucci, and Giuseppe Peter Vanoli. "A New Thermal Damage-Controlled Protocol for Thermal Ablation Modeled with Modified Porous Media-Based Bioheat Equation with Variable Porosity." Processes 10, no. 2 (January 26, 2022): 236. http://dx.doi.org/10.3390/pr10020236.

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Thermal ablation of tumors is a minimally invasive technique more and more employed in cancer treatments. The main shortcomings of this technique are, on the one hand, the risk of an incomplete ablation, and on the other hand, the destruction of the surrounding healthy tissue. In this work, thermal ablation of a spherical hepatocellular carcinoma tumor (HCC) surrounded by healthy tissue is modeled. A modified porous media-based bioheat model is employed, including porosity variability from tumor core to healthy tissue, following experimental in vivo measures. Moreover, three different protocols are investigated: a constant heating protocol, a pulsating protocol, and a new developed damage-controlled protocol. The proposed damage-controlled protocol changes the heating source from constant to pulsating according to the thermal damage probability on the tumor rim. The equations are numerically solved by means of the commercial software COMSOL Multiphysics, and the outcomes show that the new proposed protocol is able to achieve the complete ablation in less time than the completely pulsating protocol, and to reach tissue temperature on the tumor rim 10 °C smaller than the constant protocol. These results are relevant to develop and improve different patient-based and automated protocols which can be embedded in medical devices’ software or in mobile applications, supporting medical staff with innovative technical solutions.

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Mishra, Jai Krishna, C. S. P. Rao, P. S. C. Bose, N. Kishore Nath, and G. Rama Rao. "Experimental Studies of Resin Systems for Ablative Thermal Protection System." Defence Science Journal 71, no. 2 (March 10, 2021): 289–95. http://dx.doi.org/10.14429/dsj.71.16252.

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The present work was initiated to finalize resin for the development of thermal protection system (TPS) for the external surface of a polymeric composite rocket motor case made up of Carbon roving and Epoxy resin. The temperature on the outer surface of the composite case increases due to kinetic heating caused by aerodynamic drag and vehicle velocity. These rocket motor casings are functionally required only in the ascent phase of missile trajectory till motor action time and stage separation. Due to which the experienced heat flux is relatively less, and the temperature on the external composite case is in order of 250 °C - 300 °C depending on missile configuration & trajectory, unlike extreme thermal conditions on ablative nozzle liners exposed to rocket motor exhaust. The maximum allowable temperature in the present study for the Carbon-Epoxy case is 100 °C due to degradation in mechanical properties. The thermal protection system on the external surface will function as a heat-insulating layer based on the working mechanism of ablation. The resin of the thermal protection layer has a substantial impact on the manufacturing process and curing aspects, especially compatibility with the pre-cured carbon epoxy case layer. The generation of test results for thermal stability, cure characteristics and Tg for Epoxy resin has also been included in present studies as an additional objective that provides significant inputs for process development. The test results for Epoxy resin is also used as a basis for the finalization of resin for the thermal protection layer for processing aspects apart from its basic thermal stability characteristics. The ablative thermal protection working mechanism is based on the ablation phenomenon. In the case of ablation, resin plays a vital role due to pyrolysis and other thermal characteristics. In the present experimental studies, the Phenolic resin and Silicone resin are considered as candidate resin materials for ablative thermal protection system based on available literature and in house experience. The main objective of the present studies is to evaluate thermal stability, char yield after final decomposition through DSC and TGA techniques for both resins as these are fundamental characteristics needed for the present specific application. The test results for specific grades (formulation) of phenolic and Silicone resins are generated and compared. In the present work, the experimental studies to evaluate glass transition temperature (Tg), thermal stability, and cure characteristics for Epoxy resin is also carried through DSC. The test results of specific grade Epoxy resin provides a basis to assess thermal margins for resins selected for ablative thermal protection system and inputs for process development and design requirements. The scope of the present studies is aimed to finalize the resin system for external thermal protection of composite rocket motor case based on thermal characteristics test results and other compatibility aspects with the structural layer.

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Jiang, Tianxing, Yi Zeng, Xiang Xiong, Ziming Ye, Huilin Lun, Shiyan Chen, Jinrun Hu, Ge Yang, and Sen Gao. "Effect of heat treatment on the microstructure and ablation performance of C/C–SiC composites containing ZrSi2–Si." RSC Advances 11, no. 28 (2021): 16906–12. http://dx.doi.org/10.1039/d1ra01971f.

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Seifi, Azadeh, Ahmad Reza Bahramian, and Alireza Sharif. "Relationship of nanostructure and thermo-chemical response/thermal ablation of carbon aerogels." Experimental Heat Transfer 32, no. 4 (September 10, 2018): 303–21. http://dx.doi.org/10.1080/08916152.2018.1513431.

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Kabyshev, A. V., F. V. Konusov, and G. E. Remnev. "Thermal and chemical passivation of gallium-arsenide films deposited from ablation plasma." Journal of Surface Investigation. X-ray, Synchrotron and Neutron Techniques 8, no. 1 (January 2014): 158–63. http://dx.doi.org/10.1134/s1027451014010285.

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Liapi, Eleni, and Jean-Francois H. Geschwind. "Transcatheter and Ablative Therapeutic Approaches for Solid Malignancies." Journal of Clinical Oncology 25, no. 8 (March 10, 2007): 978–86. http://dx.doi.org/10.1200/jco.2006.09.8657.

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The purpose of this article is to present in a concise manner an overview of the most widely used locoregional transcatheter and ablative therapies for solid malignancies. An extensive MEDLINE search was performed for this review. Therapies used for liver cancer were emphasized because these therapies are used most commonly in the liver. Applications in pulmonary, renal, and bone tumors were also discussed. These approaches were divided into catheter-based therapies (such as transcatheter arterial chemoembolization, bland embolization, and the most recent transcatheter arterial approach with drug-eluting microspheres), ablative therapies (such as chemical [ethanol or acetic acid injection]), and thermal ablative therapies (such as radiofrequency ablation, laser induced thermotherapy, microwave ablation, cryoablation, and extracorporeal high-intensity focused ultrasound ablation). A brief description of each technique and analysis of available data was reported for all therapies. Locoregional transcatheter and ablative therapies continue to be used mostly for palliation, but have also been used with curative intent. A growing body of evidence suggests clear survival benefit, excellent results regarding local tumor control, and improved quality of life. Clinical trials are underway to validate these results. Image-guided transcatheter and ablative approaches currently play an important role in the management of patients with various types of cancer—a role that is likely to grow even more given the technological advances in imaging, image-guidance systems, catheters, ablative tools, and drug delivery systems. As a result, the outcomes of patients with cancer undoubtedly will improve.

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Fan, Jie, Chang Ling Zhou, Chong Hai Wang, Yan Yan Wang, and Rui Xiang Liu. "Preparation and Assessment of C/C-ZrB₂-SiC Ultra-High Temperature Ceramics." Key Engineering Materials 512-515 (June 2012): 719–22. http://dx.doi.org/10.4028/www.scientific.net/kem.512-515.719.

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With the background of thermal protection applications of anti-oxidation carbon fiber reinforced composites, carbon fiber reinforced ultra-high temperatureceramics with homogeneous disperse complex matrix of C-ZrB2-SiC (C/C-ZrB2-SiC) was prepared. Carbon fiber performs were deposited with pyrolytic carbon by chemical vapor infiltration method. Subsequently, the composite precursors were prepared by completely mutually dissolving of ZrB2 polymeric precursor and polycarbosilane dimethylbenzene solution. Then the nano-dispersed ZrB2-SiC composite ceramic was introduced into the C/C preforms by polymer impregnant and pyrolysis process. The C/C-ZrB2-SiC composite shows excellent ablation behavior with the ablating rate of 8*10-4mm/s. The microstructural and compositional characterizations of the C/C-ZrB2-SiC composites indicates that ZrB2 nanoparticle is distributed homogeneously in the continuous SiC phase, which is beneficial to enhance ultra-high temperature ablation resistance of the composites.

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Palaninathan, R. "Behavior of Carbon-Carbon Composite under Intense Heating." International Journal of Aerospace Engineering 2010 (2010): 1–7. http://dx.doi.org/10.1155/2010/257957.

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This paper is concerned with modeling of ablation behavior of carbon-carbon composites used in hot spot areas of reentry space and hypersonic vehicles. Of the three modes of ablation (thermal, chemical and mechanical), the chemical (oxidation) is considered to influence the performance of the material. Aerodynamic heat flux need to be computed separately and is the input for this. The thermal field is obtained by 3D finite element method. Nonlinear transient thermal analysis is carried out, as the material properties are dependent on temperatures. Oxidation rates are computed using the analytical relations available in literature. The oxidation is divided into two regimes: reaction rate and diffusion rate controlled. Mainly the surface temperature controls the regime. The oxidation protected materials are considered by using the parameter “activation energy.” The variations of ambient temperature, pressure and oxygen concentration with altitude are taken into consideration. As the recession takes place, newer surfaces are exposed to aerodynamic heating. Numerical examples are presented to show the effects of: heat flux, altitude and oxidation protection on the recession characteristics. Change of regime from reaction to diffusion rate control depends on parameters such as flow velocity and altitude. The latter has significant influence on ablation rate.

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Rusescu, Andreea, Catalina Pietrosanu, Irina Ionita, Cristian Dragos Stefanescu, Anca Mihaela Pantea Stoian, Adrian Camen, Viorel Zainea, and Razvan Hainarosie. "Chemical Ablation of the Submucosal Tissue in Volumetric Reduction of Inferior Turbinate." Revista de Chimie 69, no. 3 (April 15, 2018): 642–44. http://dx.doi.org/10.37358/rc.18.3.6166.

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Throughout the years, minimally invasive methods have gained ground when considering the surgical field. Most of all, these techniques are used in tissue ablation as they associate less operative and postoperative bleeding, high rate of recovery, as well as minimal scaring. One of these minimally invasive methods refers to the use of chemical ablation or coblation when regarding tissues ablation, thus using a chemical reaction based technique despite the regular use of mechanical or thermal interactions in order to achieve tissue ablation. Widely used in the area of ENT surgery, coblation could easily be defined as an extremely effective technique in dealing with the submucosal tissue in volumetric reduction of inferior turbinate. Different length and angulation probes ensure the applicability of this technique to better correlate with any anatomical variants and local features of the targeted structures to be ablated. Although the duration of surgery by using this method is slightly higher than with the use of other inferior tubinate volumetric reduction techniques such as radiofrequency or use of the shaver, the low degree of postoperative discomfort and the good local hemostasis provided by this technique are markers that support its elective use if it is available for the surgeon.

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Firouzmanesh, M. R., and A. Aref Azar. "STUDY OF THERMAL STABILITY AND ABLATION BEHAVIOR OF CARBON FABRIC/EPOXY-NOVOLAC ABLATIVE COMPOSITES." International Journal of Polymeric Materials 53, no. 6 (June 2004): 541–52. http://dx.doi.org/10.1080/00914030490450092.

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Abbas, Dina N. "A Novel Technique of Saddle Rhizotomy Using Thermal Radiofrequency for Intractable Perineal Pain in Pelvic Malignancy: A Pilot Study." January 2018 1, no. 21;1 (November 14, 2018): E651—E660. http://dx.doi.org/10.36076/ppj.2018.6.e651.

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Background: The prevalence of pain in advanced pelvic cancer may reach up to 95%. Control of such pain is often difficult owing to a variety of neuroanatomical and functional peculiarities. Different modalities have been utilized to treat this pain including saddle chemical rhizolysis with the potential for jeopardizing the neural control of the sphincters. Objective: The aim of this pilot study is to determine the feasibility of using selective thermal radiofrequency as an alternative to saddle chemical rhizolysis in patients with refractory perineal pain associated with pelvic malignancies. Study Design: Pilot study. Setting: Pain Relief Department of the National Cancer Institute, Cairo University. Methods: Forty patients, 18 years of age or older, who had pelvic malignancy and were complaining of moderate or severe perineal pain not controlled with maximum tolerable doses of morphine sulfate for at least 4 weeks were randomly allocated to receive selective saddle rhizotomy using thermal radiofrequency ablation of S3 on one side and bilateral ablation of S4 and S5 (RF group, n = 20) or conventional chemical rhizotomy using hyperbaric 6% phenol in glycerin (Phenol group, n = 20). Patients were assessed for the intensity of pain, daily consumption of analgesics, functional improvement, overall patient satisfaction, degree of disability and occurrence of procedure-related side effects at 1,4, and 12 weeks. Result: The results were comparable in both groups regarding the control of pain and functional improvement. The incidence of specific procedure-related adverse outcomes was also equivalent for both interventions, although per-patient incidence of major complications was significantly higher in the phenol group. Limitation: Small sample size to demonstrate statistical significance of the relatively small frequency of events, and the patients could not be blinded to the intervention they received owing to the technical uniqueness of either intervention. Conclusion: Selective thermal radiofrequency ablation of the S3 root on one side, S4 root on both sides, and S5 roots could serve as a feasible alternative to conventional saddle rhizotomy using hyperbaric phenol. Key Words: Perineal cancer pain, chemical rhizotomy, thermal radiofrequency

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Despres, Lucille, Sophie Costil, Jonathan Cormier, Patrick Villechaise, and Romain Cariou. "Impact of Laser Texturing on Ni-Based Single Crystal Superalloys." Metals 11, no. 11 (October 30, 2021): 1737. http://dx.doi.org/10.3390/met11111737.

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Surface laser texturing is used to ensure mechanical anchoring and strengthen adhesion between the interfaces of bond coatless thermal barrier coating system. To anticipate a possible loss of mechanical properties and to adapt to the perpetual evolutions of chemical compositions of the system, we analyzed the microstructural evolutions of different Ni-based single crystal superalloys, induced during infrared nanosecond laser ablation. Localized asperities composed of a melted, re-solidified matter, with a different microstructure from that of the bulk material, were generated. Regarding asperity morphologies, recrystallization within the latter could be avoided. Then, to compare different Ni-base single crystal superalloys, the thermal-affected volumes were characterized for two patterns textured under different energetic conditions. It seems that all the studied single crystal superalloys behaved quite similarly during nanosecond laser ablation. Finally, according to these results, ablation kinetics between the γ and γ′ phases of Ni-based superalloys could not be homogeneous.

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Mocan, Lucian, Cristian T. Matea, Dana Bartos, Ofelia Mosteanu, Teodora Pop, Teodora Mocan, and Cornel Iancu. "Advances in cancer research using gold nanoparticles mediated photothermal ablation." Medicine and Pharmacy Reports 89, no. 2 (April 21, 2016): 199–202. http://dx.doi.org/10.15386/cjmed-573.

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Recent research suggests that nanotechnologies may lead to the development of novel cancer treatment. Gold nanoparticles with their unique physical and chemical properties hold great hopes for the development of thermal-based therapies against human malignancies. This review will focus on various strategies that have been developed to use gold nanoparticles as photothermal agents against human cancers.

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Jun, Kang Woong, and Sungsin Cho. "Third-generation treatment of varicose veins: cyanoacrylate adhesive closure and mechanochemical ablation." Journal of the Korean Medical Association 65, no. 4 (April 10, 2022): 217–24. http://dx.doi.org/10.5124/jkma.2022.65.4.217.

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Background: The mainstream of incompetent saphenous veins treatment has dramatically changed from the first-generation conventional high ligation and stripping surgery to the second-generation endovenous thermal ablation as a minimally invasive technique using laser or radiofrequency. The third-generation treatment of nonthermal non-tumescent techniques is already available, including cyanoacrylate adhesive closure (CAC) and mechanochemical ablation (MOCA).Current Concepts: The non-thermal non-tumescent techniques are developed to overcome the complications of thermal ablation, including nerve injury and vein perforation. The technique also reduces the need for painful tumescent anesthesia and postoperative compression. MOCA employs a dual injury using a single-catheter-based delivery system consisting of a mechanical abrasion with a rotating wire and chemical ablation with a sclerosant. CAC is executed by injecting a glue that produces a polymer with the blood and obliterates the lumen. CAC does not need tumescent anesthesia and postoperative compression. Therefore, patient recovery is fast and satisfaction is excellent. However, the new devices are expensive and not included in the medical insurance in Korea, and long-term effects of the new treatments are unproven; therefore, the cost-effectiveness is unconfirmed.Discussion and Conclusion: MOCA and CAC are newly developed minimal invasive treatments for varicose veins. They are reported to be safe and effective techniques. However, further studies are needed to evaluate the long-term outcomes and cost-effectiveness.

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Jun, Kang Woong, and Sungsin Cho. "Third-generation treatment of varicose veins: cyanoacrylate adhesive closure and mechanochemical ablation." Journal of the Korean Medical Association 65, no. 4 (April 10, 2022): 217–24. http://dx.doi.org/10.5124/jkma.2022.65.4.217.

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Background: The mainstream of incompetent saphenous veins treatment has dramatically changed from the first-generation conventional high ligation and stripping surgery to the second-generation endovenous thermal ablation as a minimally invasive technique using laser or radiofrequency. The third-generation treatment of nonthermal non-tumescent techniques is already available, including cyanoacrylate adhesive closure (CAC) and mechanochemical ablation (MOCA).Current Concepts: The non-thermal non-tumescent techniques are developed to overcome the complications of thermal ablation, including nerve injury and vein perforation. The technique also reduces the need for painful tumescent anesthesia and postoperative compression. MOCA employs a dual injury using a single-catheter-based delivery system consisting of a mechanical abrasion with a rotating wire and chemical ablation with a sclerosant. CAC is executed by injecting a glue that produces a polymer with the blood and obliterates the lumen. CAC does not need tumescent anesthesia and postoperative compression. Therefore, patient recovery is fast and satisfaction is excellent. However, the new devices are expensive and not included in the medical insurance in Korea, and long-term effects of the new treatments are unproven; therefore, the cost-effectiveness is unconfirmed.Discussion and Conclusion: MOCA and CAC are newly developed minimal invasive treatments for varicose veins. They are reported to be safe and effective techniques. However, further studies are needed to evaluate the long-term outcomes and cost-effectiveness.

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Shi, Anhong, Xin Yang, Cunqian Fang, Yuanqi Weng, Xiao Luo, Ze Zhang, and Qizhong Huang. "Surface Optimization of ZrC–SiC Inner Layer to Enhance Ablation Property of SiC/ZrC–SiC Multi-Layer Coating for C/C Composites." Coatings 11, no. 4 (March 25, 2021): 378. http://dx.doi.org/10.3390/coatings11040378.

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A ZrC–SiC inner layer was fabricated on carbon/carbon composites by pack cementation at different temperatures, aiming to prepare a transition layer for subsequent deposition of SiC and ZrC–SiC layer by chemical vapor deposition and plasma spray. Results show that the structure and phase composition of the inner layer significantly affected the interface bonding strength and thermal shock resistance of the multilayer, which played a vital role in resisting ablation. The jagged and porous surface of the inner layer led to forming a root-like pinning interface, generating a sawtooth combination between the layers. Moreover, the inner layer with high SiC content decreased the coefficient of thermal expansion mismatch between the inner and outer layers. Therefore, the enhanced ablation resistance of the optimum coating was attributed to the improved interface bonding strength and thermal shock resistance caused by the ZrC–SiC inner layer with rough and porous surface structure.

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Wang, Lu, Zuobin Wang, Li Li, Jingran Zhang, Jinyun Liu, Jing Hu, Xiaomin Wu, et al. "Magnetic–plasmonic Ni@Au core–shell nanoparticle arrays and their SERS properties." RSC Advances 10, no. 5 (2020): 2661–69. http://dx.doi.org/10.1039/c9ra10354f.

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In this paper, large-area magnetic–plasmonic Ni@Au core–shell nanoparticle arrays (NPAs) with tunable compositions were successfully fabricated by a direct laser interference ablation (DLIA) incorporated with thermal dewetting method.

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Gorman, John, Winston Tan, and John Abraham. "Numerical Simulation of Microwave Ablation in the Human Liver." Processes 10, no. 2 (February 14, 2022): 361. http://dx.doi.org/10.3390/pr10020361.

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Microwave thermal ablation was developed as an alternative to other forms of thermal ablation procedures. The objective of this study is to numerically model a microwave ablation probe operating at the 2.45 GHz level using the finite element and finite volume methods to provide a comprehensive and repeatable study within a human male approximately 25 to 30 years old. The three-dimensional physical model included a human liver along with the surrounding tissues and bones. Three different input powers (10, 20, and 30 watts) were studied, along with the effect of the probe’s internal coolant flow rate. One of the primary results from the numerical simulations was the extent of affected tissue from the microwave probe. The resulting time and temperature results were used to predict tissue damage using an injury integral method. The numerical approach was validated with available experimental data and was found to be within 6% of the average experimentally measured temperatures.

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41

Rao, Golla Rama, Ivaturi Srikanth, and K. Laxma Reddy. "Effect of Organo Montmorillonite Nanoclay on Mechanical Properties Thermal Stability and Ablative Rate of Carbon fiber Polybenzoxazine Resin Composites." Defence Science Journal 71, no. 5 (September 2, 2021): 682–90. http://dx.doi.org/10.14429/dsj.71.16630.

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Organo-Montmorillonite (o-MMT) nanoclay added polybenzoxazine resin (type I composites) were prepared with varying amounts of clay (0, 1, 2, 4 and 6 wt %). Clay dispersion, changes in curing behaviour and thermal stability were assessed in type I composites. Findings from these studies of type I composites were used to understand thermal stability, mechanical, and mass ablation rate behaviour of nanoclay added carbon fiber reinforced polybenzoxazine composites (type II). Interlaminar shear strength and flexural strength of type II composites increase by 25% and 27%, respectively at 2 wt% addition of clay. An oxy-acetylene torch test with a constant heat flux of 125 w/cm2 was used to investigate mass ablation rate of type II composites. The ablation rate has increased as the weight percentage of clay has increased. This is contradicting to type I composites with up to 6 wt% clay and type II composites with up to 4 wt% clay, which have improved thermal stability. The microstructure of the ablated composites was examined using scanning electron microscopy. Increased ablation rates are due to the reaction of charred matrix with nanoclay, which exposes bare fibers to the ablation front, resulting in higher mechanical erosion losses.

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Chao, C. L., W. C. Chou, K. J. Ma, T. T. Chen, Y. M. Liu, S. W. Huang, and H. Y. Lin. "Machining of CVD diamond film by RIE, Laser Ablation and Thermo-chemical Polishing(Ultra-precision machining)." Proceedings of International Conference on Leading Edge Manufacturing in 21st century : LEM21 2005.3 (2005): 1063–68. http://dx.doi.org/10.1299/jsmelem.2005.3.1063.

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Nugroho, Johanes, Ardyan Wardhana, and Cornelia Ghea. "Mechanical Occlusion Chemically Assisted Ablation (MOCA) for Saphenous Vein Insufficiency: A Meta-Analysis of a Randomized Trial." International Journal of Vascular Medicine 2020 (January 29, 2020): 1–8. http://dx.doi.org/10.1155/2020/8758905.

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Purpose. A previous meta-analysis has conducted nonrandomized trials for mechanochemical ablation (MOCA). Since medium-term follow-up data from randomized clinical trials (RCTs) are becoming available, we chose to perform a meta-analysis of RCTs to assess the efficacy and safety of MOCA for saphenous vein insufficiency. Methods. A systematic search of all RCTs comparing the anatomical success of MOCA for saphenous vein insufficiency to thermal ablation was performed using the PubMed and Cochrane Library databases. We employed the Mantel-Haenszel random-effects meta-analysis of outcomes using RevMan 5.3. Results. Four studies (615 patients) were included in this meta-analysis. The MOCA group had 93.4% and 84.5%, whereas the thermal ablation group had 95.8% and 94.8% of anatomical success rate at 1 month (short-term) and a period of more than 6 months but less than 1-year follow-up (mid-term), respectively. According to intention-to-treat analysis, there were similar anatomical successes in MOCA and thermal ablation groups at the short-term follow-up (low-quality evidence; relative risk RR=0.98 (95% CI, 0.94–1.03); P=0.44; I2=53%). The estimated effect of MOCA on anatomical success showed a statistically significant reduction at the mid-term follow-up (moderate-quality evidence; RR=0.89 (95% CI, 0.84–0.95); P=0.0002; I2=0%). MOCA had fewer incidence of nerve injury, deep vein thrombosis, and skin burns compared to the thermal ablation procedure (low-quality evidence; RR=0.33 (95% CI, 0.09–1.28); P=0.11; I2=0%). Conclusion. MOCA offered fewer major complications but lesser anatomical success at the period of more than 6 months but less than 1-year follow-up than thermal ablation. Trial Registration. This trial is registered with UMIN Clinical Trial Registry (UMIN ID 000036727).

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Petrie, Simon. "Rethinking the Mesosphere's Magnesium Ion Chemistry." Environmental Chemistry 2, no. 1 (2005): 25. http://dx.doi.org/10.1071/en04070.

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Environmental Context. Meteoric ablation profoundly influences the spectroscopic, chemical, and thermal properties of Earth’s upper atmosphere, yet much of the chemical processing of meteor-derived material remains a mystery. As the most abundant main-group metal in meteoric material, magnesium likely plays an important or dominant role but its mesospheric chemistry has received comparatively little study to date. Abstract. High-level quantum chemical calculations address the structural and thermochemical properties of several novel magnesium-containing molecular ions which, we argue, are relevant to the Mg+ chemistry initiated by meteoric ablation in the mesosphere. A model for Mg+ chemistry is evaluated, with results indicating that most ionized magnesium at altitudes of 90 km and below is rapidly hydrated due to the association reactions of the pivotal HOMg+ ion. The implications of this new mechanism, apparently leading towards noctilucent cloud nucleation by Mg+, are briefly explored.

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Terlecki, Piotr, Marek Boryga, Paweł Kołodziej, Krzysztof Gołacki, Zbigniew Stropek, Dariusz Janczak, Maciej Antkiewicz, and Tomasz Zubilewicz. "Mechanical Characteristics of the Flebogrif System—The New System of Mechano-Chemical Endovenous Ablation." Materials 15, no. 7 (April 1, 2022): 2599. http://dx.doi.org/10.3390/ma15072599.

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Non-thermal endovenous ablations, due to the lowest probability of complications, are the new method of treating chronic venous insufficiency—one of the most common diseases globally. The Flebogrif system (Balton Sp. z o.o., Warsaw, Poland) is a new mechano-chemical ablation system causing the mechanical damage of endothelium that allows for better sclerosant penetration into its wall. The purpose of the article is to provide mechanical characteristics in the form of force–displacement dependence for a single cutting element, and a bundle of cutting elements of Flebogrif as a whole for different levels of protrusion of the bundle of cutting elements. A TA.HD plus (Stable Micro Systems, Godalming, UK) analyzer equipped with special handles, was used for characteristics testing. The head movement speed used was 5 mm·s−1. The Flebogrif system was tested for three cutting element protrusion levels: L = Lmax, L = 0.9·Lmax, and L = 0.8·Lmax. Before testing, geometric measurement of the spacing of the cutting elements for three proposed protrusions was performed. It was established that decreasing the working length of the cutting elements will increase their rigidity, and, as a result, increase the force exerted on the internal surface of the vein wall. The obtained characteristics will allow for specifying contact force variability ranges and the corresponding diameter ranges of operated veins.

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Ryu, Hyung, Hong-Seok Kim, Daeyoon Kim, Sang Lee, Wonjoon Choi, Sang Kwon, Jae-Hee Han, and Eou-Sik Cho. "Understanding of the Mechanism for Laser Ablation-Assisted Patterning of Graphene/ITO Double Layers: Role of Effective Thermal Energy Transfer." Micromachines 11, no. 9 (August 29, 2020): 821. http://dx.doi.org/10.3390/mi11090821.

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Demand for the fabrication of high-performance, transparent electronic devices with improved electronic and mechanical properties is significantly increasing for various applications. In this context, it is essential to develop highly transparent and conductive electrodes for the realization of such devices. To this end, in this work, a chemical vapor deposition (CVD)-grown graphene was transferred to both glass and polyethylene terephthalate (PET) substrates that had been pre-coated with an indium tin oxide (ITO) layer and then subsequently patterned by using a laser-ablation method for a low-cost, simple, and high-throughput process. A comparison of the results of the laser ablation of such a graphene/ITO double layer with those of the ITO single-layered films reveals that a larger amount of effective thermal energy of the laser used is transferred in the lateral direction along the graphene upper layer in the graphene/ITO double-layered structure, attributable to the high thermal conductivity of graphene. The transferred thermal energy is expected to melt and evaporate the lower ITO layer at a relatively lower threshold energy of laser ablation. The transient analysis of the temperature profiles indicates that the graphene layers can act as both an effective thermal diffuser and converter for the planar heat transfer. Raman spectroscopy was used to investigate the graphite peak on the ITO layer where the graphene upper layer was selectively removed because of the incomplete heating and removal process for the ITO layer by the laterally transferred effective thermal energy of the laser beam. Our approach could have broad implications for designing highly transparent and conductive electrodes as well as a new way of nanoscale patterning for other optoelectronic-device applications using laser-ablation methods.

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Zhang, Dai Xian, Rui Zhang, Zhen He, Jian Jun Wu, and Fan Zhang. "Numerical Investigation on Laser Ablation Characteristics of PTFE in Advanced Propulsion Systems." Applied Mechanics and Materials 229-231 (November 2012): 727–31. http://dx.doi.org/10.4028/www.scientific.net/amm.229-231.727.

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The Polytetrafluoroethylene (PTFE or Teflon) based propellants may be used in Pulsed Plasma Thruster, laser ablation thruster and other advanced propulsion systems. Because of the complex behaviors and phenomena of PTFE in ablation process, the study on thrusters’ operation process becomes complicated. Thermal and mechanical events are investigated, including phase transition, thermo-chemical and optical property variations, and multi-pulses laser ablation of PTFE. Considering more details including internal absorption of radiation, reflectivity of material, surface emission, a one-dimensional ablation model is developed and implemented numerically using a non-uniform grid, and implicit finite-volume method to gain greater insight into the process of laser ablation. The model is validated against analytical solutions and is in accordance with previous experimental results. The parameters of optical transmittance, reflectance and absorption coefficients are measured in experiments and are used in the numerical simulation. The laser ablation characteristics of PTFE are investigated, including the effects of wavelength and multipulses. It’s indicated that the laser ablation processes are influenced intensively by changing the laser wavelength and the effects of multiple pulses are also significant. The above numerical simulation provides insight into physical mechanisms of laser ablation, and suggests potential ways of improving thruster’s efficiency

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48

Tulej, Marek, Niels F. W. Ligterink, Coenraad de Koning, Valentine Grimaudo, Rustam Lukmanov, Peter Keresztes Schmidt, Andreas Riedo, and Peter Wurz. "Current Progress in Femtosecond Laser Ablation/Ionisation Time-of-Flight Mass Spectrometry." Applied Sciences 11, no. 6 (March 12, 2021): 2562. http://dx.doi.org/10.3390/app11062562.

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The last decade witnessed considerable progress in the development of laser ablation/ionisation time-of-flight mass spectrometry (LI-TOFMS). The improvement of both the laser ablation ion sources employing femtosecond lasers and the method of ion coupling with the mass analyser led to highly sensitive element and isotope measurements, minimisation of matrix effects, and reduction of various fractionation effects. This improvement of instrumental performance can be attributed to the progress in laser technology and accompanying commercialisation of fs-laser systems, as well as the availability of fast electronics and data acquisition systems. Application of femtosecond laser radiation to ablate the sample causes negligible thermal effects, which in turn allows for improved resolution of chemical surface imaging and depth profiling. Following in the footsteps of its predecessor ns-LIMS, fs-LIMS, which employs fs-laser ablation ion sources, has been developed in the last two decades as an important method of chemical analysis and will continue to improve its performance in subsequent decades. This review discusses the background of fs-laser ablation, overviews the most relevant instrumentation and emphasises their performance figures, and summarizes the studies on several applications, including geochemical, semiconductor, and bio-relevant materials. Improving the chemical analysis is expected by the implementation of laser pulse sequences or pulse shaping methods and shorter laser wavelengths providing current progress in mass resolution achieved in fs-LIMS. In parallel, advancing the methods of data analysis has the potential of making this technique very attractive for 3D chemical analysis with micrometre lateral and sub-micrometre vertical resolution.

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Ding, Minghui, Yanqing Liu, Xinru Lu, and Weizhong Tang. "Effect of Laser Ablation on Microwave Attenuation Properties of Diamond Films." Materials 12, no. 22 (November 9, 2019): 3700. http://dx.doi.org/10.3390/ma12223700.

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Thermal conductivity is required for developing high-power microwave technology. Diamond has the highest thermal conductivity in nature. In this study, a diamond film was synthesized by microwave plasma chemical deposition, and then long and short conductive graphite fibers were introduced to the diamond films by laser ablation. The permittivity of the samples in the K-band was measured using the transmission/reflection method. The permittivity of diamond films with short graphite fibers increased. The increase in real part of permittivity can be attributed to electron polarization, and the increase in the imaginary part can be ascribed to both polarization and electrical conductivity. The diamond films with long graphite fibers exhibited a highly pronounced anisotropy for microwave. The calculation of microwave absorption shows that reflection loss values exceeding −10 dB can be obtained in the frequency range of 21.3–23.5 GHz when the graphite fiber length is 0.7 mm and the sample thickness is 2.5 mm. Therefore, diamond films can be developed into a microwave attenuation material with extremely high thermal conductivity.

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Razak, S. A., N. N. Nordin, M. A. Sulaiman, M. Yusoff, and M. N. Masri. "A Brief Review on Recent Development of Carbon Nanotubes by Chemical Vapor Deposition." Journal of Tropical Resources and Sustainable Science (JTRSS) 4, no. 2 (August 13, 2021): 68–71. http://dx.doi.org/10.47253/jtrss.v4i2.607.

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Abstract:

Development of carbon nanotubes was done by several methods like arc discharge, laser ablation, silane solution, flame synthesis method but the standard or famous technique using chemical vapor deposition (CVD). CVD is one of the approaches to develop CNT, due to easy control of the reaction course and high purity of the obtained materials. Various type of CVD present like thermal CVD, plasma enhanced CVD, or microwave plasma CVD. These kinds of types give the different advantage and drawbacks to the production of CNT and its preparations.

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Journal articles on the topic 'Chemical and thermal ablation'

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