| 1. |
- Mu, Wei, 1985, et al.
(författare)
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Tape-Assisted Transfer of Carbon Nanotube Bundles for Through-Silicon-Via Applications
- 2015
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Ingår i: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 1543-186X .- 0361-5235. ; 44:8, s. 2898-2907
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Tidskriftsartikel (refereegranskat)abstract
- Robust methods for transferring vertically aligned carbon nanotube (CNT) bundles into through-silicon vias (TSVs) are needed since CNT growth is not compatible with complementary metal–oxide–semiconductor (CMOS) technology due to the temperature needed for growing high-quality CNTs (∼700°C). Previous methods are either too complicated or not robust enough, thereby offering too low yields. Here, a facile transfer method using tape at room temperature is proposed and experimentally demonstrated. Three different kinds of tape, viz. thermal release tape, Teflon tape, and Scotch tape, were applied as the medium for CNT transfer. The CNT bundle was adhered to the tape through a flip-chip bonder, and the influence of the bonding process on the transfer results was investigated. Two-inch wafer-scale transfer of CNT bundles was realized with yields up to 97% demonstrated. After transfer, the use of several different polymers was explored for filling the gap between the transferred CNT bundle and the sidewalls of the TSV openings to improve the filling performance. The current–voltage characteristic of the CNT TSVs indicated good electrical performance, and by measuring the via resistance as a function of via thickness, contact resistances could be eliminated and an intrinsic CNT resistivity of 1.80 mΩ cm found.
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| 2. |
- Di, Wei, 1986
(författare)
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A tandem Catalyst for hydrogenation of CO2 to light olefins — The role of the zeolite component
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The catalytic conversion of waste CO2 into light olefins offers a sustainable pathway for green chemicals production in the future. Over a tandem catalyst with the bifunctional active sites for methanol synthesis (CTM) and methanol to olefins (MTO), CO2 can be efficiently converted via intermediate methanol into a mixture of light olefins (ethylene, propene, butene). In the study of CO2 hydrogenation, the moderately acidic SAPO-34 molecular sieve is often used as the MTO catalyst component. SAPO-34 performs well for the formation of C-C bonds without fast coking, and minimal further hydrogenation of olefins. These qualities give the catalyst a long lifetime and high selectivity for light olefins. Unfortunately, under high-pressure hydrothermal conditions, it easily suffers structural damage. In this context, the SSZ-13 zeolite, an alternative MTO catalyst with higher hydrothermal stability, but also stronger acidity, was systematically investigated and modulated with the aim to achieve high selectivity for light olefins and high stability during CO2 hydrogenation. Firstly, in order to identify the effect of zeolite acidity on product distribution and coke deposition, two types of SSZ-13 zeolites with similar bulk composition, but different protonic acid site distributions, were synthesized. They were combined with a stable CTM catalyst (bulk indium oxide, In2O3) as a tandem catalyst and were evaluated in CO2 hydrogenation. The SSZ-13 with isolated acid sites had a lower Brønsted acid site (BAS) density and exhibited a higher selectivity for light olefins compared with the one with paired protonic acid sites. By exchanging Na+ cations to tailor the BAS density of SSZ-13 zeolite, the comparative experiments further indicated that the BAS density, rather than BAS distribution, had a high correlation with the selectivity for light olefins, which proved that the BAS density had the primary impact on the product distribution. The high BAS density promoted hydrogenation which reduced the selectivity for light olefins, while low BAS density tended to accumulate excessive coke leading to catalyst deactivation, but with improved selectivity for olefins. Thereafter, over the tandem catalysts with the optimized BAS density, a transient experiment with varying reaction conditions was carried out to investigate the coke evolution during CO2 hydrogenation. The results indicated that the coking behavior of SSZ-13 zeolite was significantly affected by reaction conditions. By manipulating the reaction temperature and pressure, the active coke species, or so-called hydrocarbon pool species (HCPS), can be deposited inside the zeolite in a targeted manner, thereby modifying the catalyst to achieve a higher MTO activity and lower olefin hydrogenation activity. Continuous transient experiments further revealed a dynamic equilibrium between the formation and degradation of coke inside SSZ-13 zeolite. This balance is established under the appropriate BAS density and optimized reaction temperature and pressure. Using the conditions of 20 bar and 375 ℃, with a H2 to CO2 mole ratio of 3, the results obtained for the pre-coked tandem catalysts of In2O3 and SSZ-13 (BAS density = 0.23 mmol*g-1) exhibited very stable activity, with selectivity for light olefins around 70% ± 2% (among hydrocarbon products), and low average coke deposition rate of 0.016 wt.%*h-1 over 100 h time-on-stream. This result also experimentally confirmed the success of pre-coking modification and verified the balance mechanism of coke accumulation.
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| 3. |
- Di, Wei, 1986, et al.
(författare)
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CO2 hydrogenation to light olefins using In2O3 and SSZ-13 catalyst-Understanding the role of zeolite acidity in olefin production
- 2023
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Ingår i: Journal of CO2 Utilization. - 2212-9820. ; 72
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Tidskriftsartikel (refereegranskat)abstract
- With the aim to explore the effect of acidic properties of zeolites in tandem catalysts on their performance for CO2 hydrogenation, two types of SSZ-13 zeolites with similar bulk composition, but different arrangements of framework Al, were prepared. Their morphology, pore structure, distribution of framework Al, surface acid strength and density, were explored. The results showed that SSZ-13 zeolites with isolated aluminum distribution could be successfully synthesized, however, they contained structural defects. During calcination, the framework underwent dealumination, resulting in weaker Brønsted acidity and lower crystallinity. The morphologies were, however, well preserved. Compared with the SSZ-13 zeolites, synthesized conventionally, these low acidity SSZ13 zeolites with isolated aluminum were good zeolite components in bifunctional catalysts for CO2 hydrogenation to light olefins. By combining with In2O3, they exhibited better catalytic performance for light olefin production during CO2 hydrogenation at low temperatures. Na+ cation exchange was used to adjust the Brønsted acid site (BAS) density with only minor changes to the cavity structure. Comparative experiments established that the BAS density of the zeolite, rather than the framework Al distribution (BAS distribution), overwhelmingly affected catalyst stability and product selectivity. A higher acid density reduced the selectivity for light olefins, while lower acid density tended to form inert coke species leading to rapid deactivation. The ideal amount of BAS density in the bifunctional catalyst was approximately 0.25 mmol/g, which exhibited 70% selectivity for light olefins among hydrocarbons, and 74% selectivity for CO without deactivation, after 12 h reaction at 325 celcius and 10 bar.
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| 4. |
- Di, Wei, 1986, et al.
(författare)
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Modulating the Formation of Coke to Improve the Production of Light Olefins from CO2 Hydrogenation over In2O3 and SSZ-13 Catalysts
- 2023
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Ingår i: Energy & Fuels. - 1520-5029 .- 0887-0624. ; 37:22, s. 17382-17398
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Tidskriftsartikel (refereegranskat)abstract
- Moderately acidic aluminophosphates (SAPOs) are often integrated with methanol synthesis catalysts for the hydrogenation of CO2 to olefins, but they suffer from hydrothermal decomposition. Here, an alternative SSZ-13 zeolite with high hydrothermal stability is synthesized and coupled with an In2O3 catalyst in a hybrid system. Its performance regarding selectivity for olefins and coke formation was investigated for CO2 hydrogenation under varying temperatures and pressures. Various reactions occur, producing mainly CO and different hydrocarbons. The results indicate that the hydrogenation of hydrocarbons are dominant at high temperatures (around 400 °C) over SSZ-13 zeolite with a high acid density and that the coke deposition rate is slow. Polymethylbenzenes are the main coke species, but the selectivity for light olefins is low among hydrocarbons at high temperatures. However, at low temperatures (around 325 °C), and especially under high pressure (40 bar), methanol disproportionation becomes significant. This results in an increased selectivity for light olefins; however, it also leads to a rapid coke deposition, which gives inactive adamantanes as the main coke species that block the pores and cause rapid deactivation. However, after coking at 325 °C and regeneration at 400 °C under the reaction atmosphere, the accumulated adamantanes can be decomposed into smaller coke species, which reopens the channel structure and generates modulated active sites within the zeolite, resulting in a higher yield of olefins without deactivation. The performances of acidic SSZ-13 zeolites, with varying ratios of Si/Al in transient experiments, further verified that a dynamic balance exists between the formation and degradation of coke within the SSZ-13 zeolite during a long-term CO2 hydrogenation reaction. This balance can be achieved by optimizing the reaction conditions to match the acid density of the catalyst. Using the conditions of 20 bar and 375 °C, with a H2 to CO2 mole ratio of 3, the results obtained for the precoked hybrid catalysts of In2O3 and SSZ-13 (Si/Al = 25) exhibited very stable activity, with the selectivity for light olefins (based on hydrocarbons formed) of max. 70% after 100 h time-on-stream. This work provides new insights into the design of stable hybrid catalysts, especially the influence of a precoking process for SSZ-13 zeolite in the production of light olefins.
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| 5. |
- Ho, Hoang Phuoc, 1983, et al.
(författare)
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Effect of the Preparation Methods on the Physicochemical Properties of Indium-Based Catalysts and Their Catalytic Performance for CO 2 Hydrogenation to Methanol
- 2024
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Ingår i: Energy & Fuels. - 1520-5029 .- 0887-0624. ; 38:6, s. 5407-5420
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Tidskriftsartikel (refereegranskat)abstract
- Indium oxides (In2O3) and indium oxides supported zirconia (ZrO2) have been known possible alternatives for conventional copper-based catalysts in the CO2-hydrogenation to methanol. This study aims to investigate the effect of preparation techniques on the physicochemical properties of indium-based materials and their catalytic performance for the hydrogenation of CO2 to methanol. Two series of both single oxide In2O3 and binary In2O3-ZrO2 have been synthesized by combustion, urea hydrolysis, and precipitation with different precipitating agents (sodium carbonate and ammonia/ethanol solution). Physicochemical properties of materials are characterized by elemental analysis, XRD, N2 physisorption, SEM/EDX, micro-Raman, XPS, H2-TPR, and CO2-TPD. Cubic In2O3 was the common phase generated by all four synthesis methods, except for urea hydrolysis, where rhombohedral In2O3 was additionally present. The combustion method produced the materials with the lowest specific surface areas while the precipitation using ammonia/ethanol aided in creating more oxygen defects. The synthesis methods strongly influenced the degree of interaction between the oxides and resulted in improvements in properties that boosted the catalytic performance of the binary oxides compared to their single-oxide counterparts.
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| 6. |
- Ho, Hoang Phuoc, 1983, et al.
(författare)
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Role of the supports during phosphorus poisoning of diesel oxidation catalysts
- 2023
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Ingår i: Chemical Engineering Journal. - 1385-8947. ; 468
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Tidskriftsartikel (refereegranskat)abstract
- Phosphorus (P) poisoning is one of the main factors accounting for the deactivation of diesel oxidation catalysts (DOC) apart from sulfur poisoning and sintering of the Pt active sites. This study compares the impact of P with loading up to 2.4 wt% on the catalytic performance of monometallic and bimetallic Pt-Pd catalysts using alumina and high silica BEA zeolites as the supports. P poisoning caused deactivation for CO, C3H6, C3H8 and NO oxidation; however, the degree of the impact of P in terms of temperatures at which 50% of the component is converted (T50) depends not only on the types of the active phase (Pt and Pt-Pd) but also on the types of supports (alumina and BEA zeolite). The influence of P impregnation on the textural properties of the materials is more significant for zeolite than alumina-based catalysts, which is in line with the activity measurements. A weak interaction between P and high silica zeolite resulted in the formation of a prominent fraction of P2O5 in the P-Pt/BEA, whereas a strong binding between P and alumina accounted for a dominant fraction of phosphate in the P-Pt/Al2O3 as revealed by XPS and NMR measurements. Phosphorus compounds partially covered the available surface of the active sites and this lowered the catalytic activity. For alumina-based catalysts, P mainly reacted with the support and only deactivated a part of the active noble metals. Whereas, for zeolite-based catalysts, P existed mainly in the form of phosphorus oxides that significantly blocked the catalyst surface and thereby deactivated more of the available active sites than that on alumina-based materials, which is consistent with the CO chemisorption data.
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| 7. |
- Jiang, Di, 1983, et al.
(författare)
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Carbon nanotube/solder hybrid structure for interconnect applications
- 2014
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Ingår i: Proceedings of the 5th Electronics System-Integration Technology Conference, ESTC 2014. - 9781479940264 ; , s. Art. no. 6962751-
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Konferensbidrag (refereegranskat)abstract
- A carbon nanotube (CNT)/Solder hybrid bump structure is proposed in this work in order to overcome the drawbacks of high CNT resistivity while retaining the advantages of CNTs in terms of interconnect reliability. Lithographically defined hollow CNT moulds are grown by thermal chemical vapor deposition (TCVD). The space inside the CNT moulds is filled up with Sn-Au-Cu (SAC) solder spheres of around 10 μm in diameter. This CNT/Solder hybrid material is then reflowed and transferred onto target indium coated substrate. The reflow melts the small solder spheres into large single solder balls thus forming a hybrid interconnect bump together with the surrounding densified CNT walls, which the CNT and the solder serve as resistors in parallel. The electrical resistance of such a CNT/Solder structure is measured to be around 6 folds lower than pure CNT bumps.
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| 8. |
- Jiang, Di, 1983, et al.
(författare)
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Embedded Fin-Like Metal/CNT Hybrid Structures for Flexible and Transparent Conductors
- 2016
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Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 12:11, s. 1521-1526
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, an embedded fin-like metal-coated carbon nanotube (Fin-M/CNT) structure is demonstrated for flexible and transparent conductor wire applications. Embedded in a polydimethylsiloxane polymeric substrate, Fin-M/CNT wires with a minimum width of 5 μm and a minimum pitch of 10 μm have been achieved. Direct current resistances of single Fin-M/CNT wires, where the supporting CNT structures have been covered by Ti/Al/Au metal coatings of different thicknesses, have been measured. The high aspect ratio of the fin-like structures not only improves the adhesion between the wires and the polymeric substrate, but also yields a low resistance at a small surface footprint. In addition, transparent Fin-M/CNT grid lines with hexagonal patterns, with a sheet resistance of as low as 45 Ω sq−1, have been achieved at an optical transmittance of 88%. The robustness of the Fin-M/CNT structures has been demonstrated in bending tests up to 500 cycles and no significant changes in wire resistances are observed.
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| 9. |
- Luo, Yifei, et al.
(författare)
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Technology Roadmap for Flexible Sensors
- 2023
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Ingår i: ACS Nano. - : American Chemical Society. - 1936-0851 .- 1936-086X. ; 17:6, s. 5211-5295
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Forskningsöversikt (refereegranskat)abstract
- Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and emphasizing nontechnical issues such as business, regulatory, and ethical considerations. Additionally, we look at future intelligent flexible sensors. In proposing a comprehensive roadmap, we hope to steer research efforts towards common goals and to guide coordinated development strategies from disparate communities. Through such collaborative efforts, scientific breakthroughs can be made sooner and capitalized for the betterment of humanity.
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| 10. |
- Shao, Jieling, 1993, et al.
(författare)
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Pt-based catalysts for NOx reduction from H2 combustion engines
- 2024
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Ingår i: Catalysis Science and Technology. - 2044-4753 .- 2044-4761. ; 14:11, s. 3219-3234
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Tidskriftsartikel (refereegranskat)abstract
- Platinum supported on SSZ-13 zeolite has been found to be a potential catalyst for the selective catalytic reduction of NO by H-2. This work has studied the effects of the H-2/NO molar feed ratios (0/4.4/8.8/13.2) and the impact of water on the performance of the H-2-SCR of NO on the Pt/SSZ-13 catalyst. A higher H-2/NO ratio promoted the start of the reaction at lower temperatures and favoured the production of N-2. The effect of Pt loadings was also studied with three loadings of 0.5/1.0/2.0 wt%. It was found that the 0.5 wt% Pt sample displayed the highest N-2 selectivity of 75%. In addition, an inhibiting effect of water for H-2-SCR at low temperatures was proved. Pt/SSZ-13 has shown good hydrothermal durability after 6 h in total ageing pretreatment at 800 degrees C and interestingly the nitrogen formation even increased. The support effect of SSZ-13, BETA and Al2O3 on H-2-SCR was evaluated in terms of catalytic performance and their catalytic durabilities by hydrothermal ageing experiments, showing that zeolites are significantly better for H-2 SCR. In situ DRIFT measurements helped to explore the mechanism of H-2-SCR on the Pt catalyst. A careful design of the measurements was used to distinguish the overlapping peaks of the water on the DRIFT spectrum. NH4+ ions are formed and it was shown that they play a role as intermediates during the reaction to assist the NO reduction.
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