Fused deposition modeling possesses great advantages in fabricating high performance composites with controllable structural designs. As such, it has attracted attention from medical, automatic, and aerospace fields. In this paper, the influence of short carbon fibers (SCFs) and the orthogonal building orientation on the flexural properties of printed polyether ether ketone (PEEK) composites are systematically studied. The results show that the addition of SCFs raises the uniform nucleation process of PEEK during 3D printing, decreases the layer-to-layer bonding strength, and greatly changes the fracture mode. The flexural strength of vertically printed PEEK and its CF-reinforced composites show strengths that are as high as molded composites. X-ray micro-computed tomography reveals the microstructure of the printed composites and the transformation of pores during bending tests, which provides evidence for the good mechanical properties of the vertically printed composites. The effect of multi-scale factors on the mechanical properties of the composites, such as crystallization in different positions, layer-by-layer bonding, and porosity, provide a successful interpretation of their fracture modes. This work provides a promising and cost-effective method to fabricate 3D printed composites with tailored, orientation-dependent properties.

Heteroatom-doped graphene exhibits high energy storage performance when used as an active electrode, and which can been applied to various advanced applications, but challenging in synthesis, e.g., hazardous chemical reagents usage, difficult processing steps, and energy consumption. We demonstrated a ready, rapid and normal method for generating phosphorus-doped graphene (LIPG) using a CO₂ laser on polyimide (PI) substrate mixed with ammonium polyphosphate (APP) in ambient air. LIPG was approved and successfully synthesized via TEM, SEM, XRD and Raman observations. Moreover, we discussed the flame-retardant performance of APP for synthesizing LIPG on PI substrates, increasing the degree of graphitization. Furthermore, LIPG prepared using supercapacitors as an electrode showed good electrochemical performance. Remarkably, the highest specific capacitance of porous LIPG is about 206 F g⁻¹ at the current density of 0.025 A g⁻¹, the value is about 2 times higher than those undoped laser induced graphene (LIG). Such great performance of the LIPG electrode material is attributed to the formation of a hierarchical porous structure, phosphorus atom doping, and manufacturing deficiency. Hence, LIPG showed considerable potential in the electrochemical application field. The proposed preparation of LIPG is best suited for synthesis and applicable to the doping of other heteroatoms doped into graphene.

Developing superior properties of epoxy resin composites with high fire resistance, light smoke, and low toxicity has been the focus of the research in the flame-retardant field. In particular, it is essential to decrease the emissions of toxic gases and smoke particles generated during the thermal decomposition of epoxy resin (EP) to satisfy the industrial requirements for environmental protection and safety. Consequently, the PZS@ZIF-67 composite was designed and synthesized by employing the hydroxyl group-containing polyphosphazene (poly(cyclotriphosphazene-co-4,4′-dihydroxydiphenylsulfone), PZS) as both the interfacial compatibility and an in situ template and the ZIF-67 nanocrystal as a nanoscale coating and flame-retardant cooperative. ZIF-67 nanocrystal with multidimensional nanostructures was uniformly wrapped on the surface of PZS microspheres. Subsequently, the acquired PZS@ZIF-67 composite was incorporated into the epoxy resin to prepare composite samples for the study of their fire safety, toxicity suppression, and mechanical performance. Herein, the EP/5% PZS@ZIF-67 passed the V-0 rating in a UL-94 test with a 31.9% limit oxygen index value. More precisely, it is endowed with a decline of 51.08%, 28.26%, and 37.87% of the peak heat release rate, the total heat release, and the total smoke production, respectively. In addition, the unique structure of PZS@ZIF-67 microsphere presented a slight impact on the mechanical properties of EP composites at low loading. The PZS@ZIF-67 possible flame-retardant mechanism was speculated based on the analysis of the condensed phase and the gas phase of EP composites.

The development of highly efficient and low-cost electrocatalysts for the oxygen evolution reaction (OER) has great significance in various renewable energy systems. Herein, we report the rational design and synthesis of cobalt nanoparticles encapsulated in nitrogen-doped carbon nanotube-grafted carbon nanosheets (LDH-R@Co(v-Zn)-NCNTs), via the in situ growth of ZnCo bimetallic zeolitic imidazolate frameworks (ZnCo-ZIFs) on the surface of layered double hydroxides (LDHs) and their subsequent reductive calcination. The incorporation of volatile zinc spatially isolates the cobalt atoms, thus suppressing the aggregation of cobalt nanoparticles, while the use of LDHs prevents the aggregation of ZnCo-ZIFs. The optimal composite exhibits good catalytic activity toward the OER in alkaline media, with a small overpotential of 344 mV at 10 mA cm⁻² and a low Tafel slope of 75 mV dec⁻¹, values that are superior to those of commercial IrO₂. The superior catalytic activity is attributed to the highly sufficient exposure of active sites and the enhanced electron conductibility of the composite. This work demonstrates an effective strategy by which to regulate a nanostructure and develop highly efficient OER catalysts.