Laser-induced Graphitization Research Articles

One-step ultrafast laser-induced graphitization on PS-SiC surfaces for superior friction performance

Pressureless sintered silicon carbide (PS-SiC) ceramics are widely used as friction materials in the aerospace industry, and enhancing the self-lubricating properties of PS-SiC ceramics under dry friction is highly significant. In this study, an infrared femtosecond laser was used to treat the surface of PS-SiC ceramics, and the effects of various processing parameters on surface microstructure, chemical composition, and graphitization degree were investigated. More importantly, SiC decomposes into amorphous carbon and stays on the surface of PS-SiC ceramics under the photothermal effect, and the amorphous carbon realizes the transition to the ordered graphite structure by controlling the laser energy. The highly graphitized, carbon-containing micro/nanostructures on the surface of laser-treated PS-SiC ceramics promote the formation of stable carbon-based tribofilms during sliding, which significantly enhances the tribological properties of PS-SiC ceramics under dry friction. This study proposes a method for inducing graphitization on the surface of PS-SiC ceramics using an infrared femtosecond laser, providing a manufacturing approach and theoretical support for the development of high-performance PS-SiC ceramic friction materials.

Direct writing of calcium phosphate/graphite nanocomposite film using laser-induced graphitization of polyimides

We report the direct writing of calcium phosphate/graphite nanocomposite using laser-induced graphitization of suspension-covered polyimide (PI) films. Calcium phosphate/graphite nanocomposites are desirable for the osteoconductive, osteoconductive, and resorptive properties of calcium phosphate and the electrical conductivity of graphitic carbon. Two forms of calcium phosphate, namely, EggCaP and CaOP, were synthesized by chemomechanical alloying of diammonium hydrogen phosphate (DHP) with eggshells – a waste material – and reagent-grade calcium oxide (CaO) powders, respectively. Fourier transform infrared (FTIR) spectroscopy of the synthesized powders revealed the phase change of starting materials to calcium phosphates (CaP), and powders were suspended in methanol to form printing suspension. Laser irradiation of synthesized CaP powder suspension-covered polyimide (PI) surfaces resulted in the formation of electrically conductive films due to laser-induced graphitization of PI. Laser-induced graphited films based on EggCaP suspension (ELIG) and CaOP (CLIG) had a sheet resistance of 25 Ω/∎ and 30 Ω/∎, respectively, and had lower resistance than the LIG films formed from bare PI (60 Ω/∎). Raman spectroscopy revealed that repeated laser irradiation of ELIG and CLIG film led to decreased defects and higher graphitization. ELIG had an ID/IG ratio of 0.65 after the first irradiation, but repeated irradiation reduced the ratio to 0.38. Similarly, CLIG had a higher ID/IG ratio of 0.55 during the first irradiation, and repeated irradiation reduced it to 0.42. Furthermore, CO, CO stretch modes, and various PO4 groups were also found in the Raman spectrum, indicating the formation of CaP/graphite nanocomposites in the graphitized films. SEM results showed that both graphitized films had closed foam-like microstructure with CaP particles deposited on the pore walls. Films formed after single irradiation had discrete CaP particle deposits on the surface, but repeated laser irradiation led to the integration of CaP particles into the pore walls. The ELIG films showed higher incorporation of the CaP particles and the highest electrical conductivity. The laser-induced graphitic transformation leads to incorporating the CaP particles into a conductive substrate, resulting in a CaP/graphite nanocomposite. The high electrical conductivity, closed-foam-like microstructure, porosity, biocompatibility, and hierarchical surface roughness of the ELIG and CLIG films make them attractive for biosensors, bioelectronics, and implant applications.

Iron-Catalyzed Laser-Induced Graphitization - Multiscale Analysis of the Structural Evolution and Underlying Mechanism.

The transition to sustainable materials and eco-efficient processes in commercial electronics is a driving force in developing green electronics. Iron-catalyzed laser-induced graphitization (IC-LIG) has been demonstrated as a promising approach for rendering biomaterials electrically conductive. To optimize the IC-LIG process and fully exploit its potential for future green electronics, it is crucial to gain deeper insights into its catalyzation mechanism and structural evolution. However, this is challenging due to the rapid nature of the laser-induced graphitization process. Therefore, multiscale preparation techniques, including ultramicrotomy of the cross-sectional transition zone from precursor to fully graphitized IC-LIG electrode, are employed to virtually freeze the IC-LIG process in time. Complementary characterization is performed to generate a 3D model that integrates nanoscale findings within a mesoscopic framework. This enabled tracing the growth and migration behavior of catalytic iron nanoparticles and their role during the catalytic laser-graphitization process. A three-layered arrangement of the IC-LIG electrode is identified including a highly graphitized top layer with an interplanar spacing of 0.343nm. The middle layer contained γ-iron nanoparticles encapsulated in graphitic shells. A comparison with catalyst-free laser graphitization approaches highlights the unique opportunities that IC-LIG offers and discuss potential applications in energy storage devices, catalysts, sensors, and beyond.

Experimental Parametric Investigation of Nanosecond Laser-Induced Surface Graphitization of Nano-Crystalline Diamond.

While nano-crystalline diamond (NCD) is a promising engineering composite material for its unique mechanical properties, achieving the ultrahigh surface quality of NCD-based components through conventional grinding and polishing is challenging due to its exceptional hardness and brittleness. In the present work, we experimentally investigate the nanosecond laser ablation-induced graphitization characteristics of NCD, which provides a critical pretreatment method of NCD for realizing its superlative surface finish. Specifically, systematic experimental investigations of the nanosecond pulsed laser ablation of NCD are carried out, in which the characteristics of graphitization are qualitatively characterized by the Raman spectroscopy detection of the ablated area of the microhole and microgroove. Subsequently, the influence of laser processing parameters on the degree and morphological characteristics of graphitization is evaluated based on experimental data and related interpretation, from which optimized parameters for maximizing the graphitization of NCD are then identified. The findings reported in the current work provide guidance for promoting the machinability of NCD via laser irradiation-induced surface modification.

Fabrication of Laser-Induced Graphene on Carbon Electrodes for Efficient Hydrogen Evolution Reaction

Hierarchical porous carbon materials have received significant attention for application in catalytic water splitting because of their high efficiency, cost-effectiveness, and biocompatibility. In this study, laser-induced graphene (LIG) was fabricated on a carbon film- (CF-) type substrate for an efficient hydrogen evolution reaction (HER). The LIG-CF electrode was fabricated via laser-induced graphitization on a commercial polyimide (PI) film, followed by the pyrolysis of the LIG on the PI film (LIG-PI). During pyrolysis, the microscopic and material properties of the LIG remained intact, as verified through various characterizations. The as-prepared all-carbon electrode was then utilized as an electrode for the HER study in a 1.0 M KOH electrolyte and compared with LIG-PI and Pt electrodes. In the HER experiments, the optimized LIG-CF electrode exhibited excellent catalytic performance with zero-onset potential, and the potentials required to achieve high current densities of 10 and 20 mA/cm2 were 134 and 139 mV (vs. reversible hydrogen electrode (RHE)), respectively. The excellent performance of the LIG-CF electrode originates from the hierarchical porous structure of the LIG material, which serves as an electrochemically active site, and carbon substrate that facilitates the fast transport of ions at the electrode/electrolyte interface. Additionally, the carbon substrate shortens the transportation length of electrons which played a significant role for the enhanced performance of the LIG-CF electrode.

Direct writing of graphitic carbon/polydimethylsiloxane bimorph thermal microactuator via two-photon polymerization and laser-induced graphitization

Direct writing of graphitic carbon/polydimethylsiloxane bimorph thermal microactuator via two-photon polymerization and laser-induced graphitization

Laser-Induced Graphitization of Polydopamine on Titania Nanotubes.

Since the discovery of laser-induced graphite/graphene, there has been a notable surge of scientific interest in advancing diverse methodologies for their synthesis and applications. This study focuses on the utilization of a pulsed Nd:YAG laser to achieve graphitization of polydopamine (PDA) deposited on the surface of titania nanotubes. The partial graphitization is corroborated through Raman and XPS spectroscopies and supported by water contact angle, nanomechanical, and electrochemical measurements. Reactive molecular dynamics simulations confirm the possibility of graphitization in the nanosecond time scale with the evolution of NH3, H2O, and CO2 gases. A thorough exploration of the lasing parameter space (wavelength, pulse energy, and number of pulses) was conducted with the aim of improving either electrochemical activity or photocurrent generation. Whereas the 532 nm laser pulses interacted mostly with the PDA coating, the 365 nm pulses were absorbed by both PDA and the substrate nanotubes, leading to a higher graphitization degree. The majority of the photocurrent and quantum efficiency enhancement is observed in the visible light between 400 and 550 nm. The proposed composite is applied as a photoelectrochemical (PEC) sensor of serotonin in nanomolar concentrations. Because of the suppressed recombination and facilitated charge transfer caused by the laser graphitization, the proposed composite exhibits significantly enhanced PEC performance. In the sensing application, it showed superior sensitivity and a limit of detection competitive with nonprecious metal materials.

Instantaneous formation of covalently bonded diamond–graphite–graphene with synergistic properties

Diamond and graphene are the most widely used carbon allotropes and offer great potential for developing mechanical, electronic, energy-storage, and sensor applications. Their combination, especially interfacial covalent bonding, can impart excellent properties. However, achieving interfacial covalent bonding with superior performance using flexible and low-power strategies remains challenging. This study developed a novel instantaneous transformation method from diamond to graphene to prepare a new covalent structure of diamond–nano-graphite–graphene (CDGG). That is, a nanosecond-pulse laser induces sp3-to-sp2 instantaneous transformations from diamond to graphite in air, and the subsequent mechanical cleavage overcomes the weak van der Waals forces to achieve the final transformation of graphite to graphene. First, the key factors influencing laser-induced graphitization and mechanical cleavage were investigated, and a covalent carbon structure with multidirectional graphene was obtained. Furthermore, the mechanisms encompassing the lattice transformation, interface relationships, transformation time, and interface bonding were elucidated. The obtained new structure synergized the excellent properties of diamond, nano-graphite, and graphene, exhibiting superior lubrication, mechanochemical wear resistance, durability, and load-capacity. Compared to polished diamond, the obtained structure exhibited a significant decrease in the stable coefficient of friction by 49–59 % and a reduction of more than one order of magnitude in the relative wear rate under high friction against ferrous metals with a normal load of 1–9 N. Even under a heavy load of 100 N, it still exhibited superior lubrication and mechanochemical wear resistance. Finally, the preparation and patterning of covalent carbon structures were achieved on various diamond surfaces with high efficiency, environmental friendliness, and low power. This study is expected to broaden the scope of developing and applying diamond, diamond films, and graphene devices.

Laser-Induced Graphitization of Thermosetting Polymer Substrate and its Application—A Review

Laser-Induced Graphitization of Thermosetting Polymer Substrate and its Application—A Review

Direct Laser Writing of Chitosan-Borax Composites: Toward Sustainable Electrochemical Sensors.

In this study, the laser-induced graphitization process of sustainable chitosan-based formulations was investigated. In particular, optimal lasing conditions were investigated alongside the effect of borax concentration in the chitosan matrix. In all cases, it was found that the obtained formulations were graphitizable with a CO2 laser. This process gave rise to the formation of high surface area, porous, and electrically conductive laser-induced graphene (LIG) structures. It was found that borax, as a cross-linker of chitosan, enabled the graphitization process when its content was ≥30 wt % in the chitosan matrix, allowing the formation of an LIG phase with a significant content of graphite-like structures. The graphitization process was investigated by thermogravimetric analysis (TGA), Raman, X-ray photoemission (XPS), and Fourier transform infrared (FTIR) spectroscopies. LIG electrodes obtained from CS/40B formulations displayed a sheet resistance as low as 110 Ω/sq. Electrochemical characterization was performed after a 10 min electrode activation by cycling in 1 M KCl. A heterogeneous electron transfer rate, k0, of 4 × 10-3 cm s-1 was determined, indicating rapid electron transfer rates at the electrode surface. These results show promise for the introduction of a new class of sustainable composites for LIG electrochemical sensing platforms.

Simulation study on the effect of different wavelengths of laser on graphitization of diamond surface

A temperature field simulation study of CVD diamonds under nanosecond laser processing was carried out to investigate the characteristics of diamond graphitization and material removal mechanisms during nanosecond laser processing. Experimental results show that diamond undergoes significant burn and graphitization during laser processing. The graphite layer thickness and width of the diamond surface were measured to determine the regularity of nanosecond laser-induced diamond graphitization. Analysis of the simulation results for the diamond temperature profile shows that the nanosecond laser irradiation energy is mainly distributed over the diamond surface, and the thermal effect zone of nanosecond laser irradiation on the diamond is small, resulting in a graphite layer thickness of about 3.25 μm.

Fabrication of High-Temperature Polymer- Derived Ceramic Thin-Film Heat Flux Sensor by 3-D Printing and Laser Pyrolysis

Heat flux density is an important parameter for evaluating the high-temperature performance of turbine blades. Accurate heat flux density data play a significant role in the design and manufacture of turbine blades and their heat-dissipation performance. Current studies have shown that thin-film heat flux sensors (TFHFSs) are suitable for signal monitoring of complex turbine blade surfaces. However, TFHFSs have a multi-layer structure, which is difficult to achieve using traditional physical vapor deposition (PVD). In this paper, we propose an approach to fabricating high-temperature polymer-derived ceramic (PDC) TFHFSs using 3D printing and laser pyrolysis. Through direct ink writing (DIW), sensitive, antioxidant, and thermal resistance layers were written directly on an alumina substrate. The sensitive layer was rendered electrically conductive owing to laser-induced graphitization. Thus, the structure of multi-layer TFHFS can be quickly achieved using the proposed method. The results showed that the sensor can operate at 800 °C. Its sensitivity was 1.349 mV/(kW/m²). Thus, it is feasible to prepare thin-film heat flux sensors by 3D printing and laser pyrolysis, which provides a new in situ integrated manufacturing method for fabricating heat flux sensors suitable for working in harsh environments such as aviation.

Wooden Tongue Depressor Multiplex Saliva Biosensor Fabricated via Diode Laser Engraving

Since wood is a renewable, biodegradable naturally occurring material, the development of conductive patterns on wood substrates is a new and innovative chapter in sustainable electronics and sensors. Herein, we describe the first wooden (bio)sensing device fabricated via diode laser-induced graphitization. For this purpose, a wooden tongue depressor (WTD) is laser-treated and converted to an electrochemical multiplex biosensing device for oral fluid analysis. A low-cost laser engraver, equipped with a low-power (0.5 W) diode laser, programmably irradiates the surface of the WTD, forming two mini electrochemical cells (e-cells). The two e-cells consist of four graphite electrodes: two working electrodes, a common counter, and a common reference electrode. The two e-cells are spatially separated via programmable pen-plotting, using a commercial hydrophobic marker pen. Proof-of-principle for biosensing is demonstrated for the simultaneous determination of glucose and nitrite in artificial saliva. This wooden electrochemical biodevice is an easy-to-fabricate disposable point-of-care chip with a wide scope of applicability to other bioassays, while it paves the way for the low-cost and straightforward production of wooden electrochemical platforms.

Bio-Graphene Sensors for Monitoring Moisture Levels in Wood and Ambient Environment.

Wood is an inherently hygroscopic material which tends to absorb moisture from its surrounding. Moisture in wood isa determining factor for the quality of wood being employed in construction, since it causes weakening, deformation, rotting, and ultimately leading to failure of the structures resulting in costs to the economy, the environment, and to the safety of residents. Therefore, monitoring moisture in wood during the construction phase and after construction is vital for the future of smart and sustainable buildings. Employing bio-based materials for the construction of electronics is one way to mitigate the environmental impact of such electronics. Herein, a bio-graphene sensor for monitoring the moisture inside and around wooden surfaces is fabricated using laser-induced graphitization of a lignin-based ink precursor. The bio-graphene sensors are used to measure humidity in the range of 10% up to 90% at 25°C. Using laser induced graphitization, conductor resistivity of 18.6 Ω sq-1 is obtained for spruce wood and 57.1 Ω sq-1 for pine wood. The sensitivity of sensors fabricated on spruce and pine wood is 2.6 and 0.74 MΩ per % RH. Surface morphology and degree of graphitization are investigated using scanning electron microscopy, Raman spectroscopy, and thermogravimetric analysis methods.

A Machine Learning-Combined Flexible Sensor for Tactile Detection and Voice Recognition.

Intelligent sensors have attracted substantial attention for various applications, including wearable electronics, artificial intelligence, healthcare monitoring, and human-machine interactions. However, there still remains a critical challenge in developing a multifunctional sensing system for complex signal detection and analysis in practical applications. Here, we develop a machine learning-combined flexible sensor for real-time tactile sensing and voice recognition through laser-induced graphitization. The intelligent sensor with a triboelectric layer can convert local pressure to an electrical signal through a contact electrification effect without external bias, which has a characteristic response behavior when exposed to various mechanical stimuli. With the special patterning design, a smart human-machine interaction controlling system composed of a digital arrayed touch panel is constructed to control electronic devices. Based on machine learning, the real-time monitoring and recognition of the changes of voice are achieved with high accuracy. The machine learning-empowered flexible sensor provides a promising platform for the development of flexible tactile sensing, real-time health detection, human-machine interaction, and intelligent wearable devices.

Rapid Printing of High-Temperature Polymer-Derived Ceramic Composite Thin-Film Thermistor with Laser Pyrolysis.

Polymer-derived ceramic (PDC)-based high-temperature thin-film sensors (HTTFSs) exhibit promising applications in the condition monitoring of critical components in aerospace. However, fabricating PDC-based HTTFS integrated with high-efficiency, high-temperature anti-oxidation, and customized patterns remains challenging. In this work, we introduce a rapid and flexible selecting laser pyrolysis combined with a direct ink writing process to print double-layer high-temperature antioxidant PDC composite thin-film thermistors under ambient conditions. The sensitive layer (SL) was directly written on an insulating substrate with excellent conductivity by laser-induced graphitization. Then, the antioxidant layer (AOL) was written on the surface of the SL to realize the integrated manufacturing of double-functional layers. Through characterization analysis, it was shown that B2O3 and SiO2 glass phases generated by the PDC composite AOL could effectively prevent oxygen intrusion. Therefore, the fabricated PDC composite thermistors exhibited a negative temperature coefficient in the temperature range from 100 to 1100 °C and high repeatability below 800 °C. Meanwhile, it has excellent high-temperature stability at 800 °C with a resistance change of only 2.4% in 2 h. Furthermore, the high-temperature electrical behavior of the thermistor was analyzed. The temperature dependence of the conductivity for this thermistor has shown an agreement with the Mott's variable range hopping mechanism. Additionally, the thermistor was fabricated on the surface of an aero-engine blade to verify its feasibility below 800 °C, showing the great potential of this work for state sensing on the surface of high-temperature components, especially for customized requirements.

Laser-Induced Graphitization of Lignin/PLLA Composite Sheets for Biodegradable Triboelectric Nanogenerators

With the rapid development of the Internet of Things (IoT), numerous electronic devices are expected to be installed in the natural environment. Triboelectric nanogenerators (TENGs) can be reliable devices providing on-site, clean, and sustainable power generation in nature. The fabrication of metal-free, biodegradable TENGs will reduce the environmental burden and disposal cost after usage. In this study, we demonstrate the direct fabrication of conductive graphitic carbon on a biodegradable polymer composite by laser-induced graphitization and apply the structures for metal-free biodegradable TENGs. Laser-induced graphitization of poly(lactic acid) (PLA) composite sheets was achieved for the first time by mixing alkaline lignin powder as a filler. The fabricated TENGs could generate electricity, and the power density reached ∼1.98 mW/m2 at a load resistance of 200 MΩ when the fabricated TENG was driven at a contact frequency of ∼1 Hz and a contact pressure of 1 N. Power generation by contact with water and plants was also demonstrated, showing its applicability for power generation in natural environments. The proposed method in this study offers the facile fabrication of biodegradable devices and the development of sustainable power generation devices.

Laser-induced graphitized electrodes enabled by a 3D printer/diode laser setup for voltammetric detection of hormones

Contraceptive pills have helped to shape modern society and their use has become more popular over the years. β-estradiol, one of the molecules present in this type of medication, is considered an endocrine disrupting compound (EDC), being nowadays commonly found in water resources. Due to their adverse effects on human health and the environment, even at trace levels, low-cost and rapid-detection approaches capable of reliably detecting EDCs such as β-estradiol are highly keen. As an alternative to the classic and well-established analytical methods for hormone detection, here we propose a simple and low-cost strategy that relies on the use of laser-induced graphitization (LIG) to manufacture electrodes for voltammetric detection of hormone in river and tap water. The LIG electrodes were produced by attaching a diode laser to a commercially available Fused Deposition Modelling (FDM) 3D printer, in which the laser promoted the controlled ablation of the polyimide film adhered to the PLA substrates. Specifically, the manufacturing steps included the 3D printing of the substrate followed by laser scribing a double-sided tape made of polyimide glued onto the surface of the substrate. The 3D printer was able to control the laser movement at specifics positions to manufacture the carbon-based three-electrode system (TES) layout. The usability of the electrochemical sensor was evaluated towards β-estradiol detection, which presented a linear response from 0.25 to 10 µmol L−1 and a limit of detection (LOD) = 80 nM. Spiked samples using tap water and river water reached 91 and 110% of recovery respectively. Our results suggest the proposed approach as an innovative and versatile way to produce low-cost, easily customizable, and reliable electrochemical sensors based on laser ablation on polyimide films.

Raman Study of the Diamond to Graphite Transition Induced by the Single Femtosecond Laser Pulse on the (111) Face.

The use of the ultrafast pulse is the current trend in laser processing many materials, including diamonds. Recently, the orientation of the irradiated crystal face was shown to play a crucial role in the diamond to graphite transition process. Here, we develop this approach and explore the nanostructure of the sp2 phase, and the structural perfection of the graphite produced. The single pulse of the third harmonic of a Ti:sapphire laser (100 fs, 266 nm) was used to study the process of producing highly oriented graphite (HOG) layers on the (111) surface of a diamond monocrystal. The laser fluence dependence on ablated crater depth was analyzed, and three different regimes of laser-induced diamond graphitization are discussed, namely: nonablative graphitization, customary ablative graphitization, and bulk graphitization. The structure of the graphitized material was investigated by confocal Raman spectroscopy. A clear correlation was found between laser ablation regimes and sp2 phase structure. The main types of structural defects that disrupt the HOG formation both at low and high laser fluencies were determined by Raman spectroscopy. The patterns revealed give optimal laser fluence for the production of perfect graphite spots on the diamond surface.

Impact of Laser‐Induced Graphitization on Diamond Schottky Barrier Diodes

Schottky Barrier Diodes Laser dicing is applied for diamond Schottky barrier diodes (SBDs) to develop the back-end process for future diamond electronics. The structural and electrical impact of laser-induced graphitization which takes place during the laser-dicing process is investigated by Shinya Ohmagari and colleagues in article number 2100846. Herein, an appropriate measure to minimize the influence of laser dicing on SBD properties is proposed.