STUDIES OF PROCESSES OF THE PRECURSOR FORMATION FOR PRODUCTION OF CuAlO NANOCERAMICS AT THE EFFECT OF DOUBLE LASER PULSES ON AD1 AND M2 ALLOYS IN THE AIR ATMOSPHERE

Проведено исследование процессов образования смешанных нанопорошков Al, оксидов меди и алюминия, прекурсоров для получения нанокерамик типа CuAlO и CuAlO при воздействии сдвоенных лазерных импульсов энергией 53 мДж и между импульсным интервалом 10 мкс на мишень, состоящую из пластинок алюминия марки АД1 и меди марки М2, склеенных между собой и помещенную в закрытую стеклянную прямоугольную кювету. Установлено, что последовательное воздействие серий сдвоенных лазерных на мишень из алюминия, а затем на мишень из меди приводит к многократному увеличению выхода субоксидов AlO, ионов и атомов алюминия и меди в лазерном факеле, направляемом на подложку, при напылении пленок, по сравнению с воздействием одиночными лазерными импульсами. Изучены процессы, происходящие на поверхности подложки при напылении пленок. Показана возможность получения прекурсоров для получения нанокерамик типа CuAlO и CuAlO. A study of formation of mixed Al nanopowders, copper and aluminum oxides, and precursors for production of CuAlO and CuAlO nanoceramics under the influence of double laser pulses with energy of 53 mJ and the interpulse interval of 10 microseconds on a target consisting of plates of aluminum grade AD1 and copper grade M2, 0,4 mm thick, glued together and placed in a closed rectangular glass cuvette. It is found that the successive exposure of a series of double laser beams to an aluminum target and then to a copper target leads to a multiple increase in the yield of AlO suboxides, aluminum and copper ions and atoms in the laser torch, compared with the exposure to single laser pulses. To better understand the hidden mechanisms of this dependence, we study the processes occurring both on the surface and in the near-surface laser plasma inside the resulting microchannel when the target is broken by a series of single and double laser pulses. The possibility of obtaining precursors for the production of nanoceramics such as CuAlO, CuAlO is shown.

Efficacy and safety of single-step transepithelial photorefractive keratectomy with the all-surface laser ablation SCHWIND platform without mitomycin-C for high myopia: A retrospective study of 69 eyes

Background Studies suggest that transepithelial photorefractive keratectomy (TransPRK) with the all-surface laser ablation (ASLA)-SCHWIND platform is effective and safe for both low-moderate myopia and high myopia. In most studies, mitomycin-C is administered immediately after surgery to prevent corneal opacification (haze), which is a significant complication of photorefractive keratectomy in general. However, there is evidence that adjuvant mitomycin-C induces endothelial cytotoxicity. Moreover, a recent study showed that omitting adjuvant mitomycin-C did not increase haze in low-moderate myopia. The present case-series study examined the efficacy, safety, and haze rates of eyes with high myopia that underwent ASLA-SCHWIND TransPRK without adjuvant mitomycin-C. Methods All consecutive eyes with high myopia (≤-6 D) that were treated in 2018–2020 with the SCHWIND Amaris 500E® TransPRK excimer laser without adjuvant mitomycin-C in a tertiary-care hospital (France) and were followed up for 6 months were identified. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and spherical equivalent (SE) were recorded before and after surgery. Postoperative haze was graded using the 4-grade Fantes scale. Efficacy rate (frequency of eyes with 6-month UCVA ≤0.1 logMAR), safety rate (frequency of eyes that lost <2 BSCVA lines), predictability (frequency of eyes with 6-month SE equal to target SE±0.5 D), efficacy index (mean UCVA at 6 months/preoperative BSCVA), and safety index (BSCVA at 6 months/preoperative BSCVA) were computed. Results Sixty-nine eyes (38 patients) were included. Mean preoperative and 6-month SE were -7.44 and -0.05 D, respectively. Mean 6-month UCVA and BSCVA were 0.00 and -0.02 logMAR, respectively. Efficacy rate and index were 95.7% and 1.08, respectively. Safety rate and index were 95.7% and 1.13, respectively. Predictability was 85.5%. Grade 3–4 haze never arose. At 6 months, the haze rate was zero. Conclusions ASLA-SCHWIND TransPRK without mitomycin-C appears to be safe as well as effective and accurate for high myopia.

Evaluation of Effectiveness of Heat Treatments in Boron Steel by Laser Thermography

The applicability of active thermography as a non-destructive method to distinguish heat treated from not-treated boron steel has been investigated. While the usual hardness semi-destructive tests influence the inspected surface, laser thermography is capable of verifying the effectiveness of heat treatment in boron steel in a non-destructive way without any surface modification. The procedure has been verified on two plates of boron steels with different structures (100% ferritic–pearlitic and 100% martensitic).

Impact of Laser Texturing on Ni-Based Single Crystal Superalloys

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.

Formation of Nanostructures on the Solid Surface

Forming nanostructures on the solids surface is one of the promising nanotechnological processes. It has been established that changes in the atomic structure of the solid surface due to the nanostructures formation result both in a significant change in various physical properties of the surface, and in an increase in its durability, strength, hardness, wear resistance. There are many different methods for forming nanostructures on solid surfaces: surface modification with nano-elements (nanoparticles, fullerenes and fullerites, graphene and nanotubes), formation of a nanocomposite layer on the surface, forming quantum dots and whiskers on the surface, implanting ions into the solid surface, laser surface treatment and other processes. The above processes are very complex and for their optimization require detailed research both by experimental and theoretical methods of mathematical modeling. The aim of this chapter was to provide a comparative review of different methods of forming nanostructures on the solids surface and mathematical modeling of these processes various aspects.