Laser-engineered heavy hydrocarbons: Old materials with new opportunities

Abstract

Polycyclic heavy hydrocarbons (HHs) such as coal, tar, and pitch are a family of materials with extremely rich and complex chemistry, representing a massive opportunity for their use in a range of potential applications. The present work shows that optimal selection of initial HHs based on molecular constituents is essential in tuning the material for a particular and targeted electronic application. Combining the selection of feedstock chemistry (H:C and aromatic content) and controlling variable laser treatment parameters (laser power, speed, and focus) lead to full control over the H:C ratio, sp2 concentration, and degree of graphitic stacking order of the products. The broad intertunability of these factors results from a wide distribution of carbon material crystallinity from amorphous to highly graphitic and a broad distribution of electrical conductivity up to 103 S/m.

Upgrading carbonaceous materials: Coal, tar, pitch, and beyond

“…46 Zang et al showed a laser annealing process to carbonize tar thin films and printed a joule heater (Figures 2F-2H). 14,39 The H:C ratio and sp 2 aromatic content of films at various levels of annealing can be obtained from Urbach tail energies derived from the films' visible absorption spectra. 53 From this analysis, it was shown that the H:C ratio in tar thin films decreases from $1.20 to $0.95 upon ll laser annealing, compared with the same films processed by furnace annealing, which decrease in H:C ratio to $1.05.…”

“…59,60 By tuning the crystalline structures of their internal hydrocarbon network structures, broadly distributed conductivities of ablated HCM thin films were obtained. 14 The higher graphitization of ablated low-volatile bituminous (LvB) coal leads to an order of magnitude higher conductivity ($800 S/m) compared with ablated tar ($80 S/m), while the poorly graphitized ablated mesophase pitch (MP) still shows a large conductivity ($500 S/m) due to its interconnected structure (Figure 3C).…”

“…In addition, although the majority of the aforementioned strategies were intended for applications other than probing reaction pathways, they clearly demonstrated the complexity of HCM models that should be considered to fully leverage the potential insights from computational studies. Jian et al 14,76,77 showed two approaches based on characteristics of a specific HCM type to explore and compare reaction pathways. Molecular representations for tar were built by mixing commercially available compounds to specifically match densities, H:C ratios, and aromatic contents with experimental counterparts.…”

“…11,12 Another strategy to upgrade coals is to leverage their widely tunable chemistry in electronics or other functional structures. 6,13,14 Coal-derived sensors and energy harvesters could be produced at large scale and ultra-low cost, making them appealing for integration with large-volume applications such as construction and infrastructure.…”

Laser-Induced Tar-Mediated Sintering of Metals and Refractory Carbides in Air

“…Carbon materials such sparse vertical aligned carbon nanotube forest, carbon black and graphitic could function as near blackbody materials to increase the light absorptivity and emissivity. 24 The heavy polyaromatics in tar are transformed into a highly aromatic nano-scale framework during laser annealing, leading to the formation of nano-scale cavities acting as black-bodies with near-unity absorptivity, 12 similarly to nanoscale cavity absorption enhancements observed in carbon nanotubes. 24 Such structural property could enhance the laser absorptivity and emissivity within the tar-metal and lead to a higher internal temperatures.…”