CO2 Laser Radiation Research Articles

Mitigating Intraphase Catalytic‐Domain Transfer via CO2 Laser for Enhanced Nitrate‐to‐Ammonia Electroconversion and Zn‐Nitrate Battery Behavior

AbstractDeveloping sustainable energy solutions is critical for addressing the dual challenges of energy demand and environmental impact. In this study, a zinc‐nitrate (Zn−NO3−) battery system was designed for the simultaneous production of ammonia (NH3) via the electrocatalytic NO3− reduction reaction (NO3RR) and electricity generation. Continuous wave CO2 laser irradiation yielded precisely controlled CoFe2O4@nitrogen‐doped carbon (CoFe2O4@NC) hollow nanocubes from CoFe Prussian blue analogs (CoFe‐PBA) as the integral electrocatalyst for NO3RR in 1.0 M KOH, achieving a remarkable NH4+ production rate of 10.9 mg h−1 cm−2 at −0.47 V versus Reversible Hydrogen Electrode with exceptional stability. In situ and ex situ methods revealed that the CoFe2O4@NC surface transformed into high‐valent Fe/CoOOH active species, optimizing the adsorption energy of NO3RR (*NO2 and *NO species) intermediates. Furthermore, density functional theory calculations validated the possible NO3RR pathway on CoFe2O4@NC starting with NO3− conversion to *NO2 intermediates, followed by reduction to *NO. Subsequent protonation forms the *NH and *NH2 species, leading to NH3 formation via final protonation. The Zn−NO3− battery utilizing the CoFe2O4@NC cathode exhibits dual functionality by generating electricity with a stable open‐circuit voltage of 1.38 V versus Zn/Zn2+ and producing NH3. This study highlights the innovative use of CO2 laser irradiation to transform Prussian blue analogs into cost‐effective catalysts with hierarchical structures for NO3RR‐to‐NH3 conversion, positioning the Zn−NO3− battery as a promising technology for industrial applications.

Mitigating Intraphase Catalytic-Domain Transfer via CO2 Laser for Enhanced Nitrate-to-Ammonia Electroconversion and Zn-Nitrate Battery Behavior.

Developing sustainable energy solutions is critical for addressing the dual challenges of energy demand and environmental impact. In this study, a zinc-nitrate (Zn-NO3 -) battery system was designed for the simultaneous production of ammonia (NH3) via the electrocatalytic NO3 - reduction reaction (NO3RR) and electricity generation. Continuous wave CO2 laser irradiation yielded precisely controlled CoFe2O4@nitrogen-doped carbon (CoFe2O4@NC) hollow nanocubes from CoFe Prussian blue analogs (CoFe-PBA) as the integral electrocatalyst for NO3RR in 1.0 M KOH, achieving a remarkable NH4 + production rate of 10.9 mg h-1 cm-2 at -0.47 V versus Reversible Hydrogen Electrode with exceptional stability. In situ and ex situ methods revealed that the CoFe2O4@NC surface transformed into high-valent Fe/CoOOH active species, optimizing the adsorption energy of NO3RR (*NO2 and *NO species) intermediates. Furthermore, density functional theory calculations validated the possible NO3RR pathway on CoFe2O4@NC starting with NO3 - conversion to *NO2 intermediates, followed by reduction to *NO. Subsequent protonation forms the *NH and *NH2 species, leading to NH3 formation via final protonation. The Zn-NO3 - battery utilizing the CoFe2O4@NC cathode exhibits dual functionality by generating electricity with a stable open-circuit voltage of 1.38 V versus Zn/Zn2+ and producing NH3. This study highlights the innovative use of CO2 laser irradiation to transform Prussian blue analogs into cost-effective catalysts with hierarchical structures for NO3RR-to-NH3 conversion, positioning the Zn-NO3 - battery as a promising technology for industrial applications.

CO2-Laser Irradiation Affects Positively Surface Energy of Rough Titanium Surfaces.

The purpose of this study was to investigate the free surface energy before and after CO2 irradiation on rough titanium surfaces. Sandblasted, large grit, acidetched (SLA) implant surfaces were used for this study. Contact angle evaluations were performed for saline, albumin, and artificial blood using a contact angle goniometer in 25°C and 37°C (20 droplets in each group, 120 in total). The titanium disks were then irradiated with a CO2 laser (10,600 nm) using a non-contact, defocused, 2W continuous wave for 30 seconds. Contact angle measurements for saline, albumin and artificial blood were evaluated immediately after irradiation (new 120 in total contact angle measurements) and compared with the measurements before laser irradiation. Paired t-test using SPSS was performed for 5% statistical significance level. Lower numbers of contact angle measurements were found and changes after CO2-laser irradiation were statistically significant (p < 0.05) for all groups except for albumin at 25°C, as follows: 25℃: (saline) (Pre) 111.97° ±13.67°, (Post) 79.29° ±10.83° / p<0.0001; (albumin) (Pre) 89.04° ±12.02°, (Post) 83.29° ±20.71° / p&#61;0.297; (blood) (Pre) 97.79° ±14.44°, (Post) 86.29° ±10.82° / p&#61;0.019; 37℃: (saline) (Pre) 104.12° ±13.138°, (Post) 92.66° ±4.777° / p&#61;0.001; (albumin) (Pre) 89.04° ±12.02°, (Post) 83.29° ±20.71° / p&#61;0.297 (blood) (Pre) 80.42° ±19.00°, (Post) 58.62° ±24.34° / p&#61;0.012. The CO2 laser irradiation in general positively affected the wettability and hydrophilicity of rough titanium (SLA) surfaces.

Thin Film of Poly-peri-naphthalene (PPN) Fabricated by Direct Laser Writing and Its Use for Humidity Sensing.

Inspired by the versatility of the direct laser writing carbonization (DLWc) technique as well as the metal-ion-assisted coordination polymer of 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA), in the present study, we present a DLWc-enabled approach for cost-effectively fabricating a poly-peri-naphthalene (PPN) thin film with the advantages of patternability, environmental benignity, and scalability. Optical and scanning electron microscopy, as well as ultraviolet-visible-near-infrared, Fourier transform infrared, Raman, and X-ray photoelectron spectroscopies, were performed to confirm that the spray-coated thin film of the Mg-PTCDA coordination polymer can be in situ converted into a PPN thin film upon CO2 laser irradiation. The effects of the laser power and Mg2+ concentration on the structure and electrical properties of the laser-processed PPN thin films were investigated. Lastly, we demonstrated that the laser-processed PPN thin films can be used for humidity sensing with characteristics of a rapid response time and excellent hysteresis. It is expected that this new method for fabricating PPN thin films will lead to a wide range of applications of PPN in the fields of sensing, electronics, and energy storage.

Exceptional fabrication of dead-weight-free silicon and graphitic heterostructures anodes for the next advancement of Li-ion batteries

Silicon (Si)-graphite and graphite (without Si) anodes for Li-ion batteries are developed at ambient conditions through the direct irradiation of CO2 laser, resulting in avoiding the use of binders, conductive carbon additives, and organic and water-based solvents. Furfuryl alcohol (FA) is mixed with Si-graphite and graphite, prepared viscous slurry through the heating, cast on the copper foil, and dried. Irradiation of CO2 laser at the electrode of Si-graphite-FA generates in-situ hetero-structures of Si particles, SiC/Si-SiC nanowires made of spontaneously carbon-coated/oxidized nano-layer (∼ 3nm), and graphitic carbon containing few layers of graphene. All the laser-fabricated electrode material is electrochemically active (∼ 0% dead weight) in the Si-graphite and graphite anodes since the FA converts to the graphitic carbon containing few layers of graphene; thus, the fabrication method could benefit the next industrial development. The discharge capacity of the Si-graphite electrode with total material loading is recorded at 502.2 mAh/g (∼ 1.9 mAh cm−2) and capacity retention of ∼ 80 % over the 50 cycles vs. Li/Li+. Also, it shows good discharge capacity when fabricated with NMC622 in full-cell format. Therefore, this performance is highly stable without any binder and conductive carbon, especially for Si-based battery, which fails rapidly due to substantial volume changes (∼ 300 %). Moreover, the performance is highly stable for graphite anode with a discharge capacity retention of 91 % over the 160 cycles as considered 100 % (∼ 345 mAh/g) after the formation cycle.

Ag-La(OH)3@Dy2O3 hybrid composite modified laser-induced graphene surface for simultaneous electrochemical detection of bisphenol A and tartrazine

Laser-induced graphene (LIG), created through CO2 laser irradiation of polyimide film (PI) substrates, has emerged as a versatile and promising material in numerous fields. However, despite its potential, a comprehensive exploration of LIG’s surface structure and reactivity remains absent in the literature, which is crucial for advancing its applications in electrochemical and electroanalytical fields. In this study, we developed and examined the interfacial structure and electronic behavior of an Ag-La(OH)3@Dy2O3 hybrid composite-modified LIG system as a model. We employed scanning electrochemical microscopy (SECM) to investigate these properties, extending our analysis to the simultaneous detection of organic pollutants, such as bisphenol A (BPA) and tartrazine (TRZ), in real samples. Compared to previous LIG production techniques, the LIG-modified electrode demonstrated a high electron transfer rate at the interface. The tailored LIG substrate showed excellent electrochemical activity towards electrochemical oxidation and simultaneous electroanalytical applications for BPA and TRZ with low detection limits (BPA: 9.2 nM, TRZ: 0.96 nM) in neutral physiological conditions. As a proof of concept, an extension to the real-time application of simultaneous monitoring of BPA and TRZ in various food samples was successfully demonstrated.

An SEM study on the effect of 9.3-µm CO2 laser on dentinal tubules for hypersensitivity treatment.

In-vitro studies were performed on dentin of extracted human molars to investigate the effectiveness of 9.3μm CO2 laser irradiation to occlude dentinal tubules. The observed occlusion of dentinal tubules with the irradiation was compared with application of three reagents: 2% Sodium Fluoride gel, an aqueous solution of hydroxyapatite nanoparticles and an equal mix of the two. We show that 9.3μm CO2 laser irradiation occludes dentinal tubules, and the use of laser irradiation produces better occlusion of the opened tubules compared to the use of topical reagents. Nine extracted and cleaned human molars were cut to obtain dentin disks of thickness of 3-5mm. Each disc was divided into four quarters, and each quarter served as two samples corresponding to irradiated and non-irradiated group counterparts. Five disks were used to study the effect of various laser irradiation energies on the dentinal tubules to find a good pulse fluence for occlusion of the dentinal tubules, and four disks were used for studying the effects of reagents and irradiation at the pulse fluences found in the first part of the study. The samples were irradiated with a beam diameter of 1mm (1/e2) at 15Hz pulse repetition rate, scanned automatically using a set of scanning mirrors. Samples were imaged using Scanning Electron Microscope (SEM) which were processed to determine tubule diameter. Safety of the irradiation treatment was investigated on 6 samples by measuring pulpal temperature rise. The effect of three topical reagents corresponding to 2% Sodium Fluoride gel (F), Hydroxyapatite nanoparticles (HA) and an equal mix of F and HA (HAF) on dentinal tubule occlusion was evaluated and compared with the laser irradiation. In all examined cases, laser irradiation at a fluence of 0.81J/cm2 resulted in a temperature increase less than 3°C which is safe, and no surface cracking was observed. There is a threshold pulse fluence of 0.27J/cm2 above which, laser produced surface melting. At a pulse fluence of 0.81J/cm2 a layer of recast of melted dentin was formed. Under this layer, peritubular dentin melting and occluding of the dentinal tubules was observed. Application of either F or HA or HAF did not produce visible occlusion effect on open tubules after washing and microbrushing with excess distilled water. 9.3μm CO2 laser irradiation on extracted human molar dentin at pulse fluence of 0.81J./cm2 resulted in tubule area reduction by 97% without rising pulpal temperatures to unsafe levels.

Research on reversible bonding of microfluidic chips based on stretch release adhesive strips

AbstractThe reversible bonding of microfluidic chips has been developing rapidly with the requirement of reusable microfluidic devices or the need to obtain the samples inside the chip. Traditional bonding methods for polymer‐based microfluidics, e.g., thermal bonding, permanently attach the substrate and cover plate. Sometimes, once the chip flow channel is blocked, it is difficult to clean and affect the reusability of the chip. This study proposes a new reversible bonding method for poly (methyl methacrylate) (PMMA) microfluidic chips with the help of stretch release adhesive strips. The designed microchannels were fabricated on the surface of PMMA plates using CO2 laser irradiation. Then, stretch release adhesive strips were used as an intermediate layer between the substrate (with microchannels) and another flat PMMA/PS/PC plate to seal the microchannel. The assembled chip sets were bonded at room temperature with bonding strength comparable with other permanent bonding methods. Experimental results show that simply pulling the adhesive layer by applying a shear force can easily detach the intermediate adhesive layer from both the substrate and cover plate to separate the bonded chipset. The proposed reversible bonding method is simple, rapid and has low residue and high bonding strength. Bacterial culture experiments were also conducted to verify the biocompatibility of the proposed bonding method. The proposed reversible bonding technique can be used for polymer‐based microfluidic devices that require sample recovery or chip reuse.Highlights The stretch release adhesive strip can provide high bond strength. It allows easy peeling for reversible bonding. It bonds at room temperature with simple operation. It has good transparency for easy observation of experiments. It has good biocompatibility.

Low loss polycrystalline SiGe core fibers for nonlinear photonics

Polycrystalline silicon-germanium (SiGe) core fibers offer great potential as flexible platforms for microscale optoelectronic and nonlinear optical devices. Compared to silicon (Si) core fibers, the SiGe material provides the potential for higher nonlinear coefficients, extended mid-infrared wavelength coverage, and a means to tune the bandgap and index of refraction by varying the Ge composition. Here, SiGe core fibers (10 at% Ge) were fabricated using the molten core drawing method, followed by CO2 laser irradiation to improve the homogeneity of the core. The transmission properties of the fibers were further optimized using a fiber tapering method to tailor the core diameter and re-grow the crystal grains. The resulting tapered SiGe fiber exhibited an average linear loss of ∼3 dB cm−1 across the wavelength range 1.5 − 2.5 µm, allowing for nonlinear optical characterization of this new fiber type. Measurements of the nonlinear figure of merit demonstrate the potential for higher nonlinear performance compared to the pure Si core fibers, particularly for wavelengths &gt;2 µm, indicating that the SiGe fiber platform could open up new opportunities for mid-infrared nonlinear photonics.

Fabrication of fully bio-based malleable thermoset derived from cellulose, furfural and plant oil for advanced capacitive sensor

Fabrication of sustainable bio-based malleable thermosets (BMTs) with excellent mechanical properties and reprocessing ability for applications in electronic devices has attracted more and more attention but remains significant challenges. Herein, the BMTs with excellent mechanical robustness and reprocessing ability were fabricated via integrating with radical polymerization and Schiff-base chemistry, and employed as the flexible substrate to prepare the capacitive sensor. To prepare the BMTs, an elastic bio-copolymer derived from plant oil and 5-hydroxymethylfurfural was first synthesized, and then used to fabricate the dynamic crosslinked BMTs through Schiff-base chemistry with the amino-modified cellulose and polyether amine. The synergistic effect of rigid cellulose backbone and the construction of dynamic covalent crosslinking network not only achieved high tensile strength (8.61 MPa) and toughness (3.77 MJ/m3) but also endowed the BMTs with excellent reprocessing ability with high mechanical toughness recovery efficiency of 104.8 %. More importantly, the BMTs were used as substrates to fabricate the capacitive sensor through the CO2-laser irradiation technique. The resultant capacitive sensor displayed excellent and sensitive humidity sensing performance, which allowed it to be successfully applied in human health monitoring. This work paved a promising way for the preparation of mechanical robustness malleable bio-thermosets for electronic devices.

Graphene-loaded recycled PET: Exploring and enhancing electrical conductivity through processing and laser treatments near the electrical percolation threshold

The blend of polyethylene terephthalate (PET), among the most employed polymer, with graphene, among the most adopted conductive carbon materials, may represent a favorable and sustainable approach for the fabrication of value-added conductive composite materials. This work targeted on the fabrication of melt-compounded composites via injection molding process starting from homemade recycled PET (r-PET) and different loadings of graphene nanoplatelets (GnPs) with different lateral sizes (5 and 25 μm, respectively), used as conductive fillers. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) investigations of the different r-PET/GnP-based compounds provided information about composition, textural and structural properties of the melt-compounded specimens, which were correlated with their DC electrical properties. Graphene loadings higher than ca. 9.5–10 wt% were found enough to achieve the electrical percolation within the two material types. With higher graphene loadings, electrical conductivity increased, due to the formation of a progressively developed percolation network. Notably, the effects of the different GnP loadings, GnP lateral sizes and crystallinity degree of the polymer on the conductivity of the of the melt-compounded specimens were investigated. Furthermore, the effect on the electrical properties of CO2 laser irradiation at different scribing speeds on r-PET/GnP composites with graphene loading below the percolation threshold, was verified. By altering locally the morphology and structure, the irradiation process impacted the electrical properties. Notably, the resulting low sheet resistance suggests potential applications in low-power electronics. In brief, the approach and methodology adopted in the present work, along with the results, can contribute to the development of future upcycling into more valuable and sustainable conductive materials and devices based on recycled PET with a reduced environmental footprint.

On the role of target mass in extreme ultraviolet light generation from CO2-driven tin plasmas for nanolithography

Target conditioning is a crucial ingredient of high-power extreme ultraviolet (EUV) source operation in state-of-the-art nanolithography. It involves deforming tin microdroplets into tens of nanometer-thin sheets, sheets which are subsequently irradiated by intense CO2 laser radiation to form a hot, EUV-emitting plasma. Recent experiments have found that a substantial fraction of the initial droplet mass is lost in the deformation phase through fragmentation. The goal of the present study is to investigate, using radiation-hydrodynamic modeling, how variations in the sheet mass affect EUV source power and the laser-to-in-band conversion efficiency (CE). It is found that high-mass sheets can “feed” the plasma with sufficient mass to sustain the production of in-band-emitting charge states over the course of laser irradiation. Low-mass sheets, on the contrary, cannot supply enough mass to sustain this production over the pulse, thus leading to a reduction in in-band power and CE. The dependence of CE on laser energy and target thickness is quantified, and a rather weak reduction of CE with increasing laser energy for high-mass sheets is identified.

Experimental Study of the Drift Motion of SF6 Molecules under the Action of CO2-Laser Radiation

Experimental Study of the Drift Motion of SF6 Molecules under the Action of CO2-Laser Radiation

An experimental study on the effect of CO2 laser powers on melting characteristics of clear ice − part I: Horizontal irradiation

Icing phenomenon widely exists in traffic and industrial fields, and causes a lot of safety accidents. Laser deicing technology is a typical high-efficiency and non-contact deicing method. To accurately predict and control the laser-induced ice melting process, an experimental study on melting characteristics of clear ice under horizontal CO2 laser irradiation and natural convection is carried out, with the laser power varied at a range of 20 ∼ 60 W. As resulted, in the first 27 s of the melting process, the axial melting rate is around 1.2 mm/s at each power. After 27 s, the laser power effect on the melting rate is obviously different, and the maximum melting rate reaches 5.41 mm/s at 50 W. The higher the laser power, the more the ice melts, and the easier the path of melting ice deflects. At 20 W and 50 W, the maximum angles of melting height are 1.14° and 4.18°, respectively. The laser power effect on the maximum melting height is obvious. At 20 W and 50 W, the peaks of maximum melting height are 12.84 mm and 22.59 mm, respectively. The higher the laser power, the larger the volume melting rate of ice, but the greater the energy loss, and it directly influences the energy efficiency. The ice-melting energy efficiency decreases with the increase of laser power. For laser at 20 W and 60 W, the maximum energy efficiency are 81.5 % and 54.6 %, respectively. This study is meaningful for the optimization of laser deicing technology.

Effects of Two Remineralizing Agents in Combination with Er:YAG and CO2 Laser Irradiation on Microhardness of Demineralized Enamel: A Preliminary In Vitro Study.

Objectives: This study assessed the effects of two remineralizing agents namely MI Paste Plus containing casein phosphopeptide amorphous calcium phosphate fluoride (CPP-ACFP) and Remin Pro containing hydroxyapatite, fluoride and xylitol (HFX) with/without erbium-doped yttrium aluminium garnet (Er:YAG) and CO2 laser irradiation on demineralized enamel microhardness. Materials and Methods: In this in vitro study, 70 sound human premolars were mesiodistally sectioned, demineralized at a pH of 4.6 for 8 hours, and randomly divided into 7 remineralization groups (n=10): of (I) MI Paste Plus (CPP-ACFP), (II) Remin Pro (HFX), (III) MI Paste Plus+CO2 laser (0.7 W power, 50 Hz), (IV) Remin Pro+CO2 laser, (V) MI Paste Plus+Er:YAG laser (1 W power, 10 Hz), (VI) Remin Pro+Er:YAG laser, and (VII) negative control. The Vickers hardness number of specimens was then measured. The groups were compared by one-way ANOVA and Tukey's test (α=0.05). Results: The mean microhardness was 319.8±49.9, 325.3±44.6, 359.4±35.7, 296.4±33.7, 319.9±58.1, 358.9±28.4, and 240.0±41.6 kg/mm2 in groups 1 to 7, respectively. The difference in microhardness was significant among the groups (P<0.0001). Pairwise comparisons revealed significant differences in microhardness between all groups (P≤0.03) except between groups 1 and 2, 1 and 5, 2 and 5, and 3 and 6 (P>0.05). Conclusion: Both Remin Pro (containing HFX) and MI Paste Plus (containing CPP-ACFP) can cause enamel remineralization. MI Paste Plus+CO2 laser irradiation and Remin Pro+Er:YAG laser irradiation were significantly more effective than the application of each remineralizing agent alone.

Material migration and damage characteristics of fused silica optical surface treated by CO2 laser/short – pulse ultraviolet laser

Fused silica optics, as key components in high - power laser systems, are prone to be damaged under short - pulse ultraviolet (UV) laser irradiation. CO2 laser is usually used to repair the laser damage and extend the service life of optics. However, the anti - laser damage characteristics of repaired substrates sometimes can’t meet the expectation. To facilitate better application of CO2 laser repairing method, this work studied the CO2 laser irradiating mechanism of fused silica in detail and investigated the damage characteristics of repaired optical surface through experiments. Firstly, finite element level - set (FELS) method is adopted to simulate CO2 laser irradiating process. The simulation showed that CO2 laser irradiation would cause molten material migration, vapor material deposition and affect the formation of residual stress. Various tests of morphology, residual stress, and photo - thermal absorption were conducted to study the changes of laser damage characteristics of repaired craters. The experimental results presented that molten materials migration and vapor materials re deposition occurred in CO2 laser irradiation, which would promote the formation of residual stress, cause stronger laser absorption, or even induce laser damage. Through the experiment, accuracy of simulation was verified further. In this work, the CO2 laser repairing mechanism of fused silica and laser damage characteristics of repaired optics are clarified through FELS simulation and experiments. Relative results can provide a certain technical support for the performance improvement of repaired fused silica optics.

An experimental study on the effect of CO2 laser powers on melting characteristics of clear ice – Part II: Vertical irradiation

Icing phenomenon widely exists and plays negative effects in aviation and electricity fields. Laser deicing technology is a typical non-contact and high-efficiency deicing method. To accurately predict and control the laser-induced ice melting process, an experimental study on melting characteristics of clear ice under vertical CO2-laser irradiation and natural convection is carried out, with the laser power varied at a range of 20–60 W. As resulted, the axial melting rate tends to increase and then decrease with the increase of laser power. The maximum of average and instantaneous axial melting rate at 40 W are 5.85 mm/s and 13.95 mm/s, respectively. The higher the laser power, the larger the peaks of maximum melting length. At 20 W and 60 W, the peaks of maximum melting length are 10.51 mm and 12.19 mm, respectively. There is little correlation between the deflection of angle and laser power. At 30 W and 50 W, the maximum angles of melting length are 0.77° and 2.52°, respectively. When the melting depth is smaller than 81.5 mm, the maximum energy efficiency at 20 W is 64.8 %, while when it is greater than 81.5 mm, the maximum energy efficiency at 60 W is 63.6 %. Results of this study are meaningful for the optimization of laser deicing technology.

Effect of laser wavelength on the thermoelectric properties of Bi1.6Pb0.4Sr2Co2O8 textured ceramics processed by LFZ

Bi1.6Pb0.4Sr2Co2O8 samples have been textured by the Laser Floating Zone (LFZ) process using Nd:YAG, and CO2 laser radiation. Using different wavelengths resulted in significant structural and microstructural modifications. Powder XRD patterns showed that the thermoelectric phase is the major one in both cases. Microstructural studies revealed that all samples presented the same phases but with much lower content of secondary ones in those processed with the CO2 laser. Electrical resistivity showed different behavior for the two types of samples, being in general, lower for the CO2 grown rods. Seebeck coefficient is lower for the CO2 grown samples up to 300 °C, and higher in the high-temperature range, reaching 240 μV/K at 650 °C, which is one of the highest values obtained so far in these compounds. Moreover, thermal conductivity at 600 °C for these samples (0.93 W/K m) is among the lowest reported in the literature. As a consequence, ZT values at 600 °C reached 0.42 in CO2 textured materials, about two times higher than the obtained in Nd:YAG ones. This value is among the highest reported so far in the literature, and is comparable to the performance attained for the same composition containing nanoparticles addition. All these properties, combined with the fact that the processed materials can be directly integrated into thermoelectric modules, render them highly attractive for industrial production.

Laser irradiation of photothermal precursors - a novel approach to produce carbon materials for supercapacitors.

A wide array of carbon materials finds extensive utility across various industrial applications today. Nonetheless, the production processes for these materials continue to entail elevated temperatures, necessitate the use of inert atmospheres, and often involve the handling of aggressive and toxic chemicals. The prevalent method for large-scale carbon material production, namely the pyrolysis of waste biomass and polymers, typically unfolds within the temperature range of 500-700 °C under a nitrogen (N2 ) atmosphere. Unfortunately, this approach suffers from significant energy inefficiency due to substantial heat loss over extended processing durations. In this work, we propose an interesting alternative: the carbonization of photothermal nanocellulose/polypyrrole composite films through CO2 laser irradiation in the presence of air. This innovative technique offers a swift and energy-efficient means of preparing carbon materials. The unique interaction between nanocellulose and polypyrrole imparts the film with sufficient stability to retain its structural integrity post-carbonization. This breakthrough opens up new avenues for producing binder-free electrodes using a rapid and straightforward approach. Furthermore, the irradiated film demonstrates specific and areal capacitances of 159 F g-1 and 62 μF cm-2 , respectively, when immersed in a 2 M NaOH electrolyte. These values significantly surpass those achieved by current commercial activated carbons. Together, these attributes render CO2 -laser carbonization an environmentally sustainable and ecologically friendly method for carbon material production.

Evolution of point defects in mechanical cracks of fused silica after CO2 laser melting

The traditional polishing method inevitably results in subsurface cracks in the fused silica, which seriously degrades their ultraviolet laser damage resistance. CO2 laser irradiation can melt these cracks and improve their laser induced damage threshold (LIDT). Photoluminescence spectrum and SEM-FIB were employed to investigate the changes in the material microstructure at the crack location with CO2 laser melting. The density of the oxygen-deficient centers of type II (ODC II) defects decreases, while the density of the non-bridging oxygen hole center (NBOHC) defects increases after high-temperature melting. The reason for this change is related to the dihydroxylation reaction and the participation of environmental oxygen in the defect type conversion. The reduction of ODC II defects is most likely the reason for the improvement of LIDT.