This study aimed to evaluate particle emission characteristics and to evaluate several control methods used to reduce particle emissions during three-dimensional (3D) printing. Experiments for particle characterization were conducted to measure particle number concentrations, emission rates, morphology, and chemical compositions under manufacturer-recommended and consistent-temperature conditions with seven different thermoplastic materials in an exposure chamber. Eight different combinations of the different control methods were tested, including an enclosure, an extruder suction fan, an enclosure ventilation fan, and several types of filter media. We classified the thermoplastic materials as high emitter (>10 #/min), medium emitters (10 #/min -10 #/min), and low emitters (<10 #/min) based on nanoparticle emissions. The nanoparticle emission rate was at least 1 order of magnitude higher for all seven filaments at the higher consistent extruder temperature than at the lower manufacturer-recommended temperature. Among the eight control methods tested, the enclosure with a high-efficiency particulate air (HEPA) filter had the highest removal effectiveness (99.95%) of nanoparticles. Our recommendations for reducing particle emissions include applying a low temperature, using low-emitting materials, and instituting control measures like using an enclosure around the printer in conjunction with an appropriate filter (e.g., HEPA filter) during 3D printing.

Highly uniform ZrO 2 films were deposited by plasma enhanced atomic layer deposition ͑PEALD͒ using tetrakis͑ethylmethylami-no͒zirconium ͑TEMAZ͒ and O 2 as precursors. The deposition rates were 0.14 and 0.11 nm/cycle at temperatures of 110 and 250°C, respectively. ZrO 2 films deposited at 150°C contained ϳ3% nitrogen, incorporated from the Zr-precursor, which contains four amino-groups. In the absence of a plasma, a ZrO 2 film was not deposited with TEMAZ and O 2 at 150°C. The electrical characteristics including breakdown strength and permitivity were also evaluated. The permitivities for 110°C-and 200°C-ZrO 2 films were 16.1 and 26.9, respectively. Dielectric materials with high permitivity ͑͒ as a substitute for SiO 2 have been extensively examined, as SiO 2 layers thinner than 1.5 nm cannot be used as a gate dielectric in sub-0.1 micrometer metal oxide semiconductor technology due to its high tunneling current which exceeds 1 A/cm 2 at 1 V. 1 The possibility of using highdielectrics, such as ZrO 2 and HfO 2 , etc., has recently been widely investigated due to dielectric constants that are much higher than that of SiO 2 and lower leakage currents far below that of an equivalent SiO 2 layer. The high-material as a gate dielectric or a capacitor is also an emerging issue in the fabrication of high current and high mobility thin film transistors for display applications.Among the available thin film deposition techniques, thin highdielectric films can be uniformly deposited using chemical vapor deposition ͑CVD͒ and atomic layer deposition ͑ALD͒ techniques. The ALD technique is based on the alternating exposure of a surface to two or more gas phase precursors and self-limiting surface reactions between the sequentially adsorbing precursors. Thus, ALD is known to be superior to CVD because of its extraordinarily good conformality and precise thickness control. Conventional ALD typically involves the use of metal chloride precursors such as HfCl 4 and ZrCl 4 , etc. and several oxygen precursors including H 2 O, ozone, and alkoxides for depositing oxide films in combination with the metal chlorides. It also requires a relatively high deposition temperature. 2-5 However, low-temperature deposition is becoming important in applications to flexible and light plastic electronic devices. For low-temperature applications, plasma-enhanced ALD ͑PEALD͒ is a promising deposition technique. 6-8 The use of an O 2 plasma in ALD enhances the deposition rate and electrical properties as well as film density compared to those of conventional ALD.In this paper, the deposition and characteristics of high-ZrO 2 films are reported for low-temperature applications including thin film transistor on a plastic substrate. The deposition of ZrO 2 films was carried out for the first time by PEALD using tetrakis͑ethylm-ethylamino͒zirconium ͓Zr͕N(C 2 H 5 )(CH 3 )͖ 4 , TEMAZ͔ as a Zrprecursor and an O 2 plasma as the oxidant. The effect of deposition temperature was first investigated on the material characteristics of ZrO 2 at temperatures rangin...

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Graphene aerogel (GA) has shown great promise as reinforcement of polymeric composites with exceptional electrical and mechanical characteristics. Although there has been significant progress in controlling the structure of GAs, no studies have appeared on the enhanced properties of GAs by employing high-quality precursor graphene flakes (GFs). However, the assembly of high-quality GFs is particularly challenging due to their highly hydrophobic and agglomerative nature in aqueous media, and of the few methods available to synthesize high-quality GFs, most produce flakes with very small lateral sizes. Herein, we report the fabrication of highly crystalline GAs using large nonoxidized graphene flakes (NOGFs) prepared by a novel graphite intercalation compound-based method. Bidirectional freeze casting is utilized for aligning NOGFs in two orthogonal directions, vertically and laterally, where the NOGF walls individually function as effective conductive pathways. The as-prepared nonoxidized graphene aerogel (NOGA) exhibits a defect concentration as low as 1.4% of impurity oxygen with an excellent electrical conductivity of 202.9 S/m at a low density of 5.7 mg/cm3. The corresponding NOGA–epoxy composite shows a remarkable electrical conductivity of 122.6 S/m and a fracture toughness of 1.74 MPa·m1/2 at a low filler content of 0.45 vol %.

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