Ablation Rate Research Articles

C/C-(Hf0.5Zr0.3Ti0.2)C–W–Cu composites: Long-term ablation resistance based on active-passive protection at 2600 °C

Compared with the traditional C/C composites modified by ultra-high-temperature ceramics (C/C-UHTCs), those modified by metal/medium-entropy ceramics have excellent mechanical properties, thermophysical properties, and long-term ablation resistance. These composites have great potential towards improving the high-temperature resistance and service life of thermal protection systems for spacecraft. In this study, a new type of (Hf0.5Zr0.3Ti0.2)C–W–Cu cermet-modified C/C composites (C/C-(Hf0.5Zr0.3Ti0.2)C–W–Cu) was prepared at 1500 °C. Compared with C/C-UHTCs, the bending strength and fracture toughness of C/C-(Hf0.5Zr0.3Ti0.2)C–W–Cu increased by 70 % and 110 % to 364.25 MPa and 14.64 MPa m1/2, respectively. Due to the high thermal conductivity of Cu and W, the thermal conductivity of this new composite was 106 % higher than that of C/C-(Hf0.5Zr0.3Ti0.2)C (44.26 versus 21.53 W/m·K). Under a high heat flow of 4.18 MW/m2, this material exhibited very low mass and linear ablation rates (−0.163 mg/s and −0.193 μm/s, respectively). Active and passive protection occur during ablation due to the evaporative cooling of Cu, CuO, and WO3 as well as a dense outer oxide layer that inhibits oxygen diffusion. The internal oxide layer forms a Hf-Zr-Ti-C-O framework mingled with Ti-rich Ti-Hf-Zr-C-O and an unoxidised W–Cu structure, effectively reducing the osmotic oxygen content. This work provides a new direction for developing thermal protection materials capable of long-term service in ultra-high-temperature environments.

Ultrasound-guided cryoablation of early breast cancer: safety, technical efficacy, patients' satisfaction, and outcome prediction with MRI/CEM: a pilot case-control study.

This pilot prospective study aimed to evaluate ultrasound-guided cryoablation of breast cancer (BC) by assessing: (i) technical efficacy as the presence of necrosis in surgical specimens and rate of complete tumor ablation; (ii) safety as incidence and severity of complications; and (iii) patients' satisfaction using a dedicated questionnaire. In addition, (iv) we tested the capability of magnetic resonance imaging (MRI) or contrast-enhanced mammography (CEM) to predict cryoablation efficacy. From 07/2022 to 01/2023, we enrolled 20 patients with early-stage BC scheduled for breast surgery. Ten of them, with a cryo-feasible cancer location, were sent to cryoablation (cryo-group) and ten to routine surgical practice (control group). Both groups underwent surgery and were asked to answer a satisfaction questionnaire. Of eleven patients screened for cryoablation, only one refused to be treated at another hospital (acceptance rate 10/11, 91%). Surgery was quadrantectomy in 19 cases and mastectomy in 1. In the cryo-group, the procedure was completed and steatonecrosis was observed in 10/10 cases, with complete tumor ablation in nine of them. The post-procedural status was evaluated with MRI in five patients, with CEM in four patients, and with ultrasound in one patient who refused MRI and CEM. MRI or CEM correctly predicted complete cryoablation in eight patients and incomplete cryoablation in one patient. Patients in both groups did not have serious complications and responded positively to satisfaction questionnaires. Ultrasound-guided cryoablation of early-stage BC is well accepted by patients, effective, and safe. MRI and CEM were able to predict the procedure's technical efficacy. https://clinicaltrials.gov/study/NCT05727813 updated February 14, 2023. Our pilot study showed that ultrasound-guided cryoablation is a promising nonsurgical alternative for treating early-stage BC. Ultrasound-guided cryoablation was effective and safe in early BC patients. The procedure was well-tolerated, with low morbidity and high patient satisfaction. MRI and CEM predicted cryoablation efficacy, in accordance with histopathologic findings. Cryoablation can be considered a potential alternative to surgery in selected patients.

Harmonizing lightweight and ablation resistance: Design and performance of multilayer composite insulation materials for solid rocket motors

AbstractThe realization of lightweight insulation materials is often accompanied by a decrease in ablation performance. Coordinating the contradiction between lightweight and ablation resistance is the key to the development of thermal protection technology. Addressing the need for high‐performance insulation materials within solid rocket motors (SRMs) combustion chambers, we designed three multilayer composite structural insulation materials and studied their properties. The results show that among these constructed multilayer composites, the bilayer structure exhibited the lowest density at a mere 0.72 g/cm3, marking a 27% reduction compared to the basic structure. Remarkably, the bilayer configuration demonstrated superior ablation resistance, showcasing a 25% decrease in the line ablation rate in contrast to the basic structure after oxygen‐acetylene test. This achievement embodies the successful harmonization of lightweight properties with ablation resistance. Furthermore, based on the performance and microstructure of the char layer, a further analysis revealed the enhancement mechanism of ablative performance by the multilayer composite structure. It was found that the synergistic effect of the compact/porous structure of the char layer grants the bilayer structure thermal insulation material optimal ablative performance. This work provides strong support for improving the performance of SRMs.Highlights Insulation materials with multilayer composite structures are designed. The materials exhibit both lightweight and superior ablation resistance. Compact/porous char layers enhance material ablation performance.

Deriving iceberg ablation rates using an on-iceberg autonomous phase-sensitive radar (ApRES)

Abstract The increase in iceberg discharge into the polar oceans highlights the importance of understanding how quickly icebergs are deteriorating and where the resulting freshwater injection is occurring. Recent advances in quantifying iceberg deterioration through combinations of modeling, remote sensing and direct in situ measurements have successfully calculated overall ablation rates, and surface and sidewall ablation; however, in situ measurements of basal melt rates have been difficult to obtain. Radar has successfully measured iceberg thickness, but repeat measurements, which would capture a change in iceberg thickness with time, have not yet been collected. Here we test the applicability of using an on-iceberg autonomous phase-sensitive radar (ApRES) to quantify basal ablation rates of a large (~800 m long) non-tabular Arctic iceberg during an intensive 2019 summer field campaign in Sermilik Fjord, southeast Greenland. We find that ApRES can be used to measure basal ablation even over a short deployment period (10 d), and also provide a lower bound on sidewall melt. This study fills a critical gap in iceberg research and pushes the limits of field instrumentation.

Microwave Ablation after VATS in Patients with Multiple Pulmonary Nodules.

The management of residual nodules after video-assisted thoracoscopic surgery (VATS) for multiple pulmonary nodules (MPNs) is challenging. Microwave ablation (MWA), which is highly repeatable and minimally invasive, has garnered widespread attention in the treatment of MPNs. Ninety-one patients with MPNs who underwent VATS for resection of high-risk nodules followed by MWA for residual nodules were examined. Clinical efficacy and complications were assessed. The primary end points were MWA success rate and complete ablation rate. Secondary end points were local progression-free survival (LPFS), overall survival (OS), and complications. MWA was successfully completed in all patients. Mean tumor diameter, ablation time, and ablation output power were 0.81 cm, 3.4 minutes, and 39 W, respectively. LPFS was 100% at 3, 6, 12, and 24 months, respectively. OS was 100% at 12 and 24 months, respectively. No intraoperative or postoperative deaths occurred. Complications with MWA were infrequent. Pneumothorax was most common, occurring in 31 patients (34.07%); among these, seven (7.69%) required closed thoracic drainage. Pleural effusion occurred in six patients (6.59%), hydropneumothorax in five (5.49%), and pneumonia in three (3.30%). The pain level after MWA was moderate-to-severe in 29 patients (31.87%). MWA is safe and feasible for treating residual nodules in patients with MPNs who have undergone VATS. The incidence of complications was low, and most complications were mild.

Effects of SiO2-coated CNTs on the directional formation of SiC whiskers and improvement in the ablative resistance of polymer-matrix composites

As the development of hypersonic aerospace technology progresses, greater challenges are presented for solid rocket motors (SRMs) thermal protection, and the ablation performance of insulation materials needs to be further improved. Carbon nanotubes (CNTs) as a new type of reinforcing nano-filler, readily react with the oxidative components in the working gas during SRMs operation, limiting their excellent performance. In this study, we propose to coat the commonly used reinforcing filler, SiO2, on the surface of CNTs to suppress their susceptibility to oxidation and investigate the effects of adding CNTs, SiO2, and CNTs@SiO2 to the matrix on material properties. The results show that the addition of CNTs@SiO2 significantly improves the ablation resistance of the insulation material, with the linear ablation rate of M-@SiO2-2 being 56 % lower than that of M-SiO2-2. Based on the analysis of the material's antioxidation performance and the strength of the resulting char layer after ablation, the reasons for the improvement of ablation performance are discussed. By conducting high-temperature tube furnace tests, the composition and structure of the char layer at different temperatures are studied, and it is found that CNTs in the CNTs@SiO2 formulation can directly provide the carbon source required for the carbon thermal reduction reaction, promoting the directional growth of SiC whiskers. Based on these findings, an ablation mechanism is proposed.

Surgical microwave ablation of 397 neuroendocrine liver metastases: a retrospective cohort analysis of 16 years of experience.

Neuroendocrine tumors (NET) constitute a heterogeneous group of malignancies whose incidence has been on the rise over the past two decades, currently documented at 5.25 per 100,000. Liver metastasis develops in over 60% of NET patients. Even after resection recurrence rates are high, underscoring the importance of parenchymal-sparing interventions. In this study, we conducted 105 surgical microwave ablations and examined outcomes related to survival and local recurrence. Retrospective review of patients who underwent a surgical microwave ablation (MWA) at a single-center, high-volume institution from September 2007 through December 2022 using a prospective database. Primary outcome was overall survival. A total of 105 operations were performed on 94 patients, with 397 tumors undergoing MWA. Median tumor size was 1.3cm (range 0.3-8.0), and the median number of tumors ablated was 2 (range 1-12). Laparoscopic approach was utilized 69.5% of the time. The most common concomitant procedure performed was hepatectomy (33.3%) and cholecystectomy (23.8%). Clavien-Dindo grade III or IV complications occurred in 9 patients (9.6%). Mortality within 30days occurred in 1 patient (1.1%). The rate of incomplete ablation was 0.3% per tumor. Local recurrence occurred in 2.8% of tumors. Median OS was 9.43years [95% CI 4.23-14.63years], with a 5- and 10-year survival probability of 70.2% and 48.2%, respectively. Surgical MWA offers an efficacious, parenchymal-sparing treatment of hepatic metastasis of NET, with low rates of incomplete ablation and local recurrence per tumor.

Ablation efficiency and laser safety of a novel superpulsed thulium fiber laser: a in vitro study.

To assess the ablation efficiency of the Superpulsed Thulium Fiber Laser (SP-TFL) and investigate the thermal effects of SP-TFL. A SP-TFLwas employed to evaluate ablation efficiency. Fresh ex-vivo pig kidneys and ureters were utilized to evaluate the renal pelvis and ureter temperature changes, different irrigation rates(0, 15, 38mL/min) and a long pulse width were used. The research indicated that as laser output power increased, ablation rates significantly increased. Ablation rates(mg/min) were higher and the energy per ablated mass(J/mg) was lower at lower frequencies(10-50Hz). Under the same frequency and single pulse energy, super short and short pulse widths demonstrated higher ablation rates at higher frequencies (exceeding 100Hz). The temperature of the renal pelvis and ureter decreased with increasing irrigation rates. In the renal pelvis, without irrigation, the temperature quickly reached the critical threshold of 43℃. The irrigation rate was 15ml/min and power was no more than 18W, the renal pelvis temperature did not reach 43℃. When the irrigation rate were 38ml/min, the temperature did not risen to 43℃. In the ureter, without irrigation, the temperature also quickly reached 43℃. The temperature reached 43℃ when the power exceeded to12W with an irrigation rate of 15ml/min. With an irrigation rate of 38ml/min, the temperature reached 43℃ at a laser power of 30W. The SP-TFL demonstrated promising ablation effectiveness especially for lower frequencies and super short and short pulse widths model. Proper irrigation rates, single pulse energy, frequency and pulse width are crucial during lithotripsy.

Convective Water Vapor Energy Ablation (Rezum®) Versus Prostatic Urethral Lift (Urolift®): A 2-Year Prospective Study.

Introduction: To compare the clinical outcomes and complication rates of convective water vapor energy ablation (Rezum®) and prostatic urethral lift (Urolift®). To identify predictive factors for treatment failures in both treatments. Materials & Methods: Prospective clinico-epidemiological data of patients who underwent Urolift® or Rezum® in a single institution for benign prostatic hyperplasia (BPH) was collected. The choice of intervention depended on the preference of the patients after patient-centric discussions. Results: From October 2019 to October 2022, 86 patients underwent Rezum®, and 62 patients underwent Urolift®. Rezum® involved a longer indwelling catheter duration (12.38 ± 5.548 vs 1.39 ± 3.010 days, p < 0.001) compared with Urolift®. Rezum® was associated with more complications compared with Urolift® (36 [41.9%] vs 10 [16.1%] cases, p < 0.001). Rezum® had more cases of hematuria (17 [19.8%] vs 4 [6.5%] cases [p = 0.022]) and urinary tract infections (27 [31.4%] vs 3 [4.8%] cases, p < 0.001) compared with Urolift®. There were no significant differences in Clavien-Dindo Grade 3-5 complications between the interventions. Urolift® was associated with higher reoperation rates (5 [8.1%] vs 0 [0%] cases, p = 0.010) compared Rezum®. Rezum® had higher anticholinergic usage rates compared with Urolift® post-operation (22 [25.6%] vs 8 [12.9%] cases, p = 0.024). Both interventions showed improvement in the International Prostate Symptom Score (IPSS), quality of life score, and peak velocity flow over the 2 years with no significant difference between the two. Based on receiver operating characteristic curve, preoperation IPSS ≥16 had 95.7% sensitivity and 38.4% specificity to predict the probability of treatment failures after the interventions. Conclusions: There was no difference in clinical outcomes of patients who underwent Rezum® and Urolift®. However, patients who had undergone Rezum® faced more minor complications and more required anti-cholinergic medications. Lastly, physicians should note that patients with IPSS ≥16 would unlikely benefit from either intervention.

In Vitro Comparison of Pulsed-Thulium:YAG, Holmium:YAG, and Thulium Fiber Laser.

Objective: To characterize the pulse characteristics and risk of fiber fracture (ROF) of the pulsed-Thulium:YAG (p-Tm:YAG) laser and to compare its ablation volumes (AVs) against Holmium:Yttrium-Aluminium-Garnet (Ho:YAG) laser and Thulium fiber laser (TFL). Materials and Methods: p-Tm:YAG (100 W-Thulio, Dornier-Medtech©, Germany) was characterized using single-use 272 μm core-diameter-fibers. p-Tm:YAG characterization included pulse shape, duration, and peak power (PP) studies. ROF was assessed after 5 minutes of continuous laser activation (CLA) at five decreasing fiber bend radii (1, 0.9, 0.75, 0.6, and 0.45 cm). p-Tm:YAG, Ho:YAG (120 W-Cyber-Ho, Quanta®, USA), and TFL (60 W-TFLDrive, Coloplast®, Denmark) AVs were compared using a 20-mm linear CLA at 2 mm/second velocity in contact with 20 mm3 hard stone phantoms (HSP) and soft stone phantoms (SSP) (15:3 and 15:5 water to powder ratio, respectively) fully submerged in saline at 0.5 J-20 Hz or 1 J-10 Hz. After CLA, phantoms underwent three-dimensional (3D) micro-scanning (CT) and subsequent 3D segmentation to estimate the AVs, using 3DSlicer©. Each experiment was performed in triplicate. Results: p-Tm:YAG presents a uniform pulse profile in all of the available preset modes. PP ranged from 564 to 2199 W depending on pulse mode. No laser fiber fracture occurred at any bend radius. p-Tm:YAG achieved similar mean AVs to TFL and Ho:YAG for HSP (8.96 ± 3.1 vs 9.78 ± 1.1 vs 8.8 ± 2.8 mm3, p = 0.67) but TFL was associated with higher AVs compared with p-Tm:YAG and Ho:YAG (12.86 ± 1.85 vs 10.12 ± 1.89 vs 7.56 ± 2.21 mm3, p = 0.002) against SSP. AVs for HSP increased with pulse energy for p-Tm:YAG and Ho:YAG and (11.56 ± 1.8 vs 6.36 ± 0.84 mm3 and 11.27 ± 1.98 vs 6.34 ± 0.55 mm3, p = 0.03 and p = 0.02), whereas AVs for SSP were similar across laser settings for all laser sources. AVs with TFL were similar across laser settings for both phantom types. Conclusion: p-Tm:YAG combines intermediate PP between Ho:YAG and TFL, a uniform pulse profile, no ROF with increasing deflection and effective ablation rates. Further clinical studies are needed to confirm these in vitro results.

Ablation resistance and high-temperature insulation capacity of TiB2-B4C modified Al-coated carbon fibre/boron phenolic resin ceramizable composites

The inherent susceptibility to oxidation limits the application of carbon fibre/phenolic resin composites (CF/Ph) in the thermal protection of hypersonic vehicle engines. Herein, TiB2-B4C modified Al-coated carbon fibre/boron phenolic resin ceramizable composites were fabricated. The optimal ceramizable composite (T30C10) exhibited excellent ablation resistance and high-temperature insulation capacity at a linear ablation rate and bottom-surface temperature of -0.00768 mm/s and 129.8 °C, respectively. Oxygen consumption and inhibition, carbon fixation, and self-healing effects contributed to the excellent ablation resistance, and the effects of the Al coatings and carbothermal reduction reactions led to excellent high-temperature insulation capacities.

Ultrasound Molecular Imaging Enhances High-Intensity Focused Ultrasound Ablation on Liver Cancer With B7-H3-Targeted Microbubbles.

High-intensity focused ultrasound (HIFU) is a promising minimally invasive treatment for liver cancer; however, its efficacy is often limited by the attenuation of ultrasonic energy. This study investigates the effectiveness of B7-H3-targeted microbubbles (T-MBs) in enhancing HIFU ablation of liver cancer and explores their potential for clinical translation. T-MBs and isotype control microbubbles (I-MBs) were synthesized through the conjugation of biotinylated anti-B7-H3 antibody and isotype control antibody to the microbubble surface, respectively. Contrast-enhanced ultrasound imaging was performed to compare the accumulation of T-MBs and I-MBs in liver cancer at various time points. The efficacy of T-MBs in enhancing HIFU treatment was evaluated by measuring the immediate tumor ablation rate and long-term tumor growth suppression. Additionally, the induced antitumor immune response was assessed through cytokine quantification in serum and tumor tissue, along with immunofluorescence staining conducted on days 1, 3, and 7 post-treatment. T-MBs demonstrated superior liver cancer-specific accumulation, characterized by higher concentrations and prolonged retention compared to I-MBs. The combination of T-MBs with HIFU resulted in significantly enhanced tumor ablation rates and superior tumor growth suppression. Post-treatment analysis revealed a gradual uptick in cytokine levels within the tumor microenvironment, along with progressive infiltration of antitumor immune cells. T-MBs effectively enhance the therapeutic efficacy of HIFU for liver cancer treatment while simultaneously promoting an antitumor immune response. These findings provide a strong experimental foundation for the clinical translation of ultrasound molecular imaging combined with HIFU as a novel approach for tumor therapy.

Assessing the impact of artificial geotextile covers on glacier mass balance and energy fluxes

As global warming accelerates, leading to the retreat of glaciers, the effectiveness of artificial coverings, in particular geotextiles, in reducing glacier ablation has emerged as a topic of increasing concern. Nevertheless, a critical gap in knowledge persists regarding the specific physical processes involved in the mitigation provided by these coverings. This study explores the underlying mechanisms that govern the interaction through field observations and COSIPY model simulations at Bailanghe Glacier No. 21 in the Qilian Mountains from 26 June to 17 September 2023. It compares covered and uncovered areas to evaluate differences in mass and energy balance fluxes. It was discovered that geotextiles could decrease ice melt by up to 1000 mm w.e. in comparison to the surface of glaciers without cover, primarily because of a 23% increase in albedo compared to ice, leading to a decrease in net short-wave radiation and available melt energy. The effect of covering the entire glacier with a geotextile, which has varying albedo properties, was also simulated. It was found that, with every 5% increase in the albedo of the geotextile, ablation was reduced by 10%‒25%, resulting in a decrease in ice volume loss of approximately 2.5 × 105 m3. While artificially covering glaciers can reduce ablation rates, it faces challenges such as high costs, environmental risks, and issues with replicability. Ultimately, this study aims to analyze the feasibility of glacier coverage from a mechanistic perspective for glacier management amidst ongoing climate change.

Lightweight and multiscale ZrO2-SiOC coated carbon/phenolic composites with enhanced oxidation and ablation resistance

The carbon/phenolic composites are extensively considered as an efficient ablative thermal protection material, but inferior oxidation-ablation resistance has limited their further application. In this work, a multiscale ZrO2-SiOC coated carbon/phenolic composite (NCF/ZSAx-PA) was fabricated through a dual-stage construction strategy. The as-prepared composites exhibited a low density (0.314–0.348 g/cm3), low thermal conductivity (0.0605–0.0725 W/(m·k)) and promoted compressive strength (2.95/5.08 MPa in the Z/XY direction). Benefiting from the formation of a protective ZrO2-SiO2 ceramic coating, the multiscale composites showed excellent anti-oxidation and ablation performance. The residual weight of NCF/ZSAx-PA was 19.41 % at 1000 °C while the unmodified carbon/phenolic composites were entirely burnt off under an air atmosphere. Besides, the NCF/ZSAx-PA exhibited low back temperature (53.6 °C), low linear ablation rate (0.0519 mm/s), and low mass loss rate (0.0100 g/s) under the 3.62 MW/m2 oxyacetylene assessment. All the superior properties enabled the NCF/ZSAx-PA a prospective application on the thermal protection system.

Synthesis of the ZrC whiskers and the ablation mechanism of the ZrC whisker-toughened ZrC coating

The ZrC coatings toughened by ZrC whiskers with different microstructures were prepared on C/C composites by chemical vapor deposition (CVD). The formation mechanisms of the different morphologies of ZrC whiskers were investigated. The mechanical properties and the ablation properties under oxyacetylene flame of ZrC coatings were evaluated. The results showed that the introduction of ZrC whiskers significantly improved the adhesion to the C/C substrate and elastic modulus of ZrC coatings. The coatings exhibited a denser oxide layer after ablation than before ZrC whiskers addition due to the forming of the ZrO2 skeleton structure, which provides a solid support to oxide layers. The linear ablation rate of the coating (-0.233 μm/s) decreased by 58.91% compared to the pure ZrC coating (-0.567 μm/s). Following detailed observation and characterization, a potential protective mechanism for ZrC whiskers was presented.

Effect of non-static pre-oxidation treatment on the cyclic ablation behavior of SiC-ZrC/SiC multilayer coated graphite

SiC-ZrC based ceramics have caught much attention as coatings for graphite materials. However, the coefficient of thermal expansion (CTE) mismatch between coatings and matrix severely limits their application in harsh environments. Herein, we proposed a non-static pre-oxidation treatment under an air pressure of 0.05 MPa to increase the surface roughness of graphite matrix to 18.054 μm and then prepared the SiC-ZrC/SiC multilayer coating on the pre-oxidized graphite. The results demonstrate that a firm interlocking structure was formed between SiC-ZrC/SiC multilayer coating and graphite matrix, which effectively improved the bonding strength and enhanced the cyclic ablation resistance of coatings. The bonding strength of SiC-ZrC/SiC multilayer coated on graphite pre-oxidized under negative pressure was 5.70±0.42 MPa, which was 54.89% higher than that on graphite pre-oxidized under atmospheric pressure (3.68±0.08 MPa). After the plasma ablation for 360 s (60 s × 6), the linear and mass ablation rates of SiC-ZrC/SiC multilayer coated graphite which was pre-oxidized under negative pressure were -0.083 μm/s and 0.101 mg/s, respectively.

Ablative property and mechanism of pitch-based carbon fiber modified C/C composites with high thermal conductivity

The novel C/C composites with thermal transport function were prepared using the mesophase-pitch carbon fibers (CFMP) as the thermal diffusion channels. The introduction of CFMP greatly improved the microstructure, thermal properties, and ablative resistance of the C/C composites. During the graphitization process, compared with PAN fibers (CFPAN), CFMP was more likely to be graphitized to form a highly ordered three-dimensional graphite structure. The highly organized microcrystalline structure of CFMP resulted in a tight interface with PyC that lessened the likelihood of flaws and cracks during graphitization. CFMP, which acted as a thermal conduction skeleton, significantly improved the thermal conductivity of C/C composites. After 3000 °C HTT, the thermal conductivity of C/C-3000-Z composites was increased to 51.70 and 225.02 W/(m K) in the XY and Z planes, respectively. During the ablation process, C/C-3000-Z specimen exhibited a lower temperature gradient and less thermal stress owing to the outstanding thermal properties and fewer defects. After 30 s ablation, the temperature difference of surface and backside was only 495.9 °C, and the mass and linear ablation rates were 0.3 μm/s and 0.9 mg/s, respectively.

Transient behavior of ablation and swelling for C/C composite and HfC-coated C/C composite in an arc-heated wind tunnel

This study investigated and modeled the transient behavior of surface recession, defined as the difference between ablative length and swelling length, for thermal protection materials within a high-enthalpy flow. Needle punch carbon-carbon (NPCC) and hafnium carbide coated carbon-carbon (HfC-coated NPCC) were exposed to high-enthalpy flow with a heat flux of 7.67 MW/m2 generated by an arc-heated facility. The NPCC and the HfC-coated NPCC represent an ablative surface and a non-ablative surface, respectively. Surface recession histories were estimated through an image analysis and visualizations monitored by a high-speed camera. Moreover, measured data including surface temperature histories, mass loss, and total length were presented. We proposed the models for the transient recession on the ablative surface and the non-ablative surface considering the ablation and the swelling. The ablative length was calculated using non-dimensional parameter B′, which computes ablation rates under equilibrium air conditions. While B’ modeling accurately predicted the ablation rates, it could not reflect the swelling phenomenon during an initial heating phase. The swelling was modeled with consideration of the thermal expansion. Specifically, the effect of increased porosity near the ablative surface was incorporated into the thermal expansion coefficient. The model developed in this study well agreed with the experimental data.

Impact of treatment trajectory on the thermal ablation rate and biological tissue volumetric lesion during irradiation by shock-wave focusing ultrasonic beam

Thermal ablation rates and the shapes of volumetric biological tissue lesion are compared in a numerical experiment, in which biological tissue is exposed to pulsed periodic shock-wave high intensity focused ultrasound. The comparison is performed across three different irradiation sequences of discrete foci placed uniformly within the target area.

Hydrogen Plasma Inhibits Ion Beam Restructuring of GaP.

Focused ion beam (FIB) techniques are employed widely for nanofabrication and processing of materials and devices. However, ion irradiation often gives rise to severe damage due to atomic displacements that cause defect formation, migration, and clustering within the ion-solid interaction volume. The resulting restructuring degrades the functionality of materials and limits the utility of FIB ablation and nanofabrication techniques. Here we show that such restructuring can be inhibited by performing FIB irradiation in a hydrogen plasma environment via chemical pathways that modify defect binding energies and transport kinetics, as well as material ablation rates. The method is minimally invasive and has the potential to greatly expand the utility of FIB nanofabrication techniques in processing functional materials and devices.