Although numerous porous adsorbents have been investigated for NH3 capture applications, these materials often exhibit insufficient NH3 uptake, low NH3 affinity at the ppm level, and poor chemical ...stability against wet NH3 conditions. The NH3 capture properties of M2(dobpdc) complexes (M=Mg2+, Mn2+, Co2+, Ni2+, and Zn2+; dobpdc4−=4,4‐dioxidobiphenyl‐3,3‐dicarboxylate) that contain open metal sites is presented. The NH3 uptake of Mg2(dobpdc) at 298 K was 23.9 mmol g−1 at 1 bar and 8.25 mmol g−1 at 570 ppm, which are record high capacities at both pressures among existing porous adsorbents. The structural stability of Mg2(dobpdc) upon exposure to wet NH3 was superior to that of the other M2(dobpdc) and the frameworks tested. Overall, these results demonstrate that Mg2(dobpdc) is a recyclable compound that exhibits significant NH3 affinity and capacity, making it a promising candidate for real‐world NH3‐capture applications.
A metal–organic framework adsorbent with open metal sites is presented. It has record high capacities over a wide range of NH3 concentrations as well as an exceptional stability upon exposure to wet NH3.
Despite the unique characteristics of urban forests, the motivating factors of urban forest visitors have not been clearly differentiated from other types of the forest resource. This study aims to ...identify the motivating factors of urban forest visitors, using latent Dirichlet allocation (LDA) topic modeling based on social big data. A total of 57,449 cases of social text data from social blogs containing the keyword “urban forest” were collected from Naver and Daum, the major search engines in South Korea. Then, 17,229 cases were excluded using morpheme analysis and stop word elimination; 40,110 cases were analyzed to identify the motivating factors of urban forest visitors through LDA topic modeling. Seven motivating factors—“Cafe-related Walk”, “Healing Trip”, “Daily Leisure”, “Family Trip”, “Wonderful View”, “Clean Space”, and “Exhibition and Photography”—were extracted; each contained five keywords. This study elucidates the role of forests as a place for healing, leisure, and daily exercise. The results suggest that efforts should be made toward developing various programs regarding the basic functionality of urban forests as a natural resource and a unique place to support a diversity of leisure and cultural activities.
Abstract
In this study, an isotropic etching process of SiO
2
selective to Si
3
N
4
using NF
3
/H
2
/methanol chemistry was investigated. HF was formed using a NF
3
/H
2
remote plasma, and in order ...to remove the F radicals, which induces spontaneous etching of Si-base material, methanol was injected outside the plasma discharge region. Through this process, etch products were formed on the surface of SiO
2
, and then the (NH
4
)
2
SiF
6
was removed by following heating process. When the H and F radicals were abundant, the highest SiO
2
etch per cycle (EPC) was obtained. And, the increase of H
2
and methanol percentage in the gas chemistry increased the etch selectivity by decreasing the F radicals. The etch products such as (NH
4
)
2
SiF
6
were formed on the surfaces of SiO
2
and Si
3
N
4
during the reaction step and no noticeable spontaneous etching by formation of SiF
4
was observed. By optimized conditions, the etch selectivity of SiO
2
over Si
3
N
4
and poly Si higher than 50 and 20, respectively, was obtained while having SiO
2
EPC of ~ 13 nm/cycle. It is believed that the cyclic process using NF
3
/H
2
remote plasma and methanol followed by heating can be applied to the selective isotropic SiO
2
etching of next generation 3D device fabrication.
Atomic layer etching (ALE) has advantages such as precise thickness control, high etch selectivity, and no‐increase in surface roughness which can be applied to sub 10 nm semiconductor device ...fabrication. In this study, anisotropic ALE of tungsten (W), which is used as an interconnect layer and gate material of semiconductor devices, was investigated by sequentially exposing to F radicals by NF3 plasma to form a WFy layer and following exposure to an oxygen ion beam to remove the WFy layer by forming volatile WOxFy at room temperature. A wide ALE window of F radical adsorption time of ( ≥ 10 s/cycle) and Ox+ ion desorption time of (10 ≤ t ≤ 50 s/cycle at + 44–51 eV of Ox+ ion energy) could be identified, and at the ALE conditions, a precise etch rate of ~2.6 Å/cycle was obtained while increasing the W etch depth linearly with increasing the number of etch cycles. At the optimized W ALE conditions, the W surface roughness after the W ALE was similar to the as‐received W and the etch selectivity over SiO2 was close to infinite. However, after the W ALE, ~ 10% F diffused into W was observed on the etched W surface, and which could be removed by a following process.
Anisotropic atomic layer etching (ALE) of tungsten (W) was investigated by sequentially exposing to F radicals by NF3 plasma to form a WFy layer and following exposure to an oxygen ion beam to remove the WFy layer by forming volatile WOxFy. At the optimized W ALE conditions, a precise etch rate of ~2.6 Å/cycle was obtained while increasing the W etch depth linearly with increasing the number of etch cycles.
•Method of using EAF (electric arc furnace) oxidizing slag aggregates to efficiently reduce environmental loads.•Bond strength of RC beams using EAF oxidizing slag aggregates.•Excellent bond ...performance of concrete with EAF oxidizing slag aggregates.•Performance evaluation of RC members with EAF oxidizing slag aggregates, reflecting mechanical properties.
The present study was conducted to evaluate the bonding performance of reinforced concrete beams with electric arc furnace oxidizing slag aggregates. The specimens were tested by varying the aggregates, and the top and bottom longitudinal reinforcement position, depending on concrete placement. The specimens containing electric arc furnace oxidizing slag aggregates showed bond performance that was on average of about 8% to 20% higher than that of the specimens using natural aggregates. The bond strength was higher at the corner longitudinal reinforcement than at the inner longitudinal reinforcement and higher at the bottom reinforcement than at the top reinforcement, regardless of the aggregate type. The experimental results were consistent with results from previous studies with concrete containing natural aggregates. Comparison with previous studies confirmed the excellent bond performance of the concrete with electric arc furnace oxidizing slag aggregates, and demonstrated the use of concrete containing electric arc furnace oxidizing slag aggregates for structural members.
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•Anisotropic atomic layer etching of ruthenium by oxidation and removal process.•For oxidation, we compared direct plasma, remote plasma, and gas molecules.•Ar-based inductively ...coupled plasma and ion beam were compared to remove the oxidation layer.•For ideal atomic layer etching, the ion beam type etching method is more advantageous.
Ruthenium (Ru) is a next-generation metal interconnect material, and the demand for precise etching is on the rise. This study explores anisotropic atomic layer etching (ALE) of Ru, utilizing various oxygen adsorption methods (O radical, oxygen plasma, or O2 molecule) and two types of plasma sources: inductively coupled plasma (ICP) and ion beam source. Through ICP ALE, an etch per cycle (EPC) of ∼ 1.5 Å/cycle was achieved using oxygen plasma for adsorption. For ion beam ALE, EPC values of ∼ 0.8 Å/cycle were obtained using oxygen radical, and ∼ 0.4 Å/cycle through physisorption using oxygen molecule without plasma generation. The higher EPC with the ICP ALE was attributed to spontaneous etching during oxygen adsorption during the oxygen plasma generation. Conversely, the lower EPC with ion beam ALE during oxygen adsorption using O2 molecule without plasma generation resulted from nonuniform oxidation of Ru during the adsorption step. Among the three ALE methods, optimal Ru ALE with 100 % ALE synergy was achieved with ion beam ALE, likely due to the absence of ion bombardment during oxygen adsorption and the precise Ar+ ion energy for removing RuOx formed on the surface.
A Mg(II)‐based coordination polymer was synthesized by a solvothermal reaction between Mg2+ and 2,5‐dimercaptoterephthalic acid (H4dmtp) in N,N‐diethylformamide (DEF). The thiol (─SH) groups in the ...H4dmtp ligand were oxidized to form the sulfinato (─SO2−) groups, which were structurally stabilized through coordination to the Mg2+ centers. The temperature‐dependent proton conductivities exhibited relatively low activation energy (0.19 eV) for proton transfer, suggesting that the hydrogen‐bonded networks formed by the water molecules and the sulfinato oxygen atoms produced efficient proton‐hopping pathways.
Mg(II)‐based coordination polymer was prepared via a solvothermal reaction between Mg2+ and H4dmtp. The ─SH group in H4dmtp was oxidized to the unusual ─SO2− group in dstp4−, which was structurally stabilized through coordination to the Mg2+ centers.
Selective isotropic cyclic dry etching of silicon oxide (SiO2) was investigated using a three‐step cyclic process composed of hydrogen fluoride (HF) adsorption by NF3/H2 remote plasma and reaction ...with NH3 gas flow to form ammonium fluorosilicate ((NH4)2SiF6), and desorption by heating. The variation of the ratio of NF3:H2 (2:1 to 1:3) and adsorption time (10–180 s) showed the highest etch selectivity of SiO2 over Si3N4 at 1:2 ratio of NF3:H2 and with the adsorption time of 20 s. The etch selectivity higher than 40 was observed with 20 s of adsorption time with a 1:2 ratio of NF3:H2 remote plasma and the total etch depth was linearly increased with the increase of cycles with the SiO2 EPC of ~7.5 nm/cycle.
Selective isotropic cyclic dry etching of SiO2 was investigated using a three‐step cyclic process composed of HF adsorption by NF3/H2 remote plasma and reaction with NH3 gas flow to form (NH4)2SiF6, and desorption by heating. The etch selectivity higher than 40 was observed and the total etch depth was linearly increased with the increase of cycles with the SiO2 EPC of ~7.5 nm/cycle.
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•A novel method for coating of epn-Mg2(dobpdc)@SBS composites was developed.•The composites showed a significant CO2 working capacity with full recyclability.•Facile, generally ...applicable coating route with the composite ink was demonstrated.•The coated materials exhibited excellent recycable working capacity.•Long-term durability under realistic indoor CO2 conditions was obtained.
Reducing the concentration of indoor carbon dioxide (CO2) to an acceptable safe level of 1,000 ppm is an important issue because a high level of CO2 in closed spaces causes lethargy and fatigue. Although diamine-functionalized metal–organic framework (MOF) adsorbents with high CO2 capacities under indoor air conditions are available, the moisture-induced degradation of MOFs and their shaping remains a challenge for practical applications. Herein, we report the fabrication of epn-functionalized Mg2(dobpdc) composites, which proceeded by mixing with a polystyrene-block-polybutadiene-block-polystyrene (SBS) hydrophobic polymer (epn = 1-ethylpropane-1,3-diamine; dobpdc4− = 4,4′-dioxido-3,3′-biphenyldicarboxylate). The composites were successfully shaped in the form of membranes with different amounts of MOF (epn-MOFX@SBS; X = 60–80 wt%). Specifically, epn-MOF80@SBS exhibited a significant CO2 adsorption of 2.8 mmol g−1 at 1,000 ppm with recyclable working capacity. The composites were further coated on the surfaces of different supports, such as a Ti mesh, an air filter, and granular activated carbon via a facile and simple spraying method. The experimental conditions were 1,000 ppm CO2 and 60% relative humidity in a 50-L chamber; the coated materials displayed invariant CO2 removal performances over 10 cycles and even after 7 days of exposure. The recyclable and long-term CO2 adsorption capacities demonstrate that the MOF-polymer composites and their coating on various supports provide a useful and effective route for indoor CO2 capture under realistic conditions.
Etch characteristics of ovonic threshold switch (OTS) materials composed of Ge-As-Te for a phase-change random access memory (PCRAM) has been investigated using reactive ion etching
via
...hydrogen-based gases such as H
2
, CH
4
, NH
3
, CH
4
+ H
2
, and CH
4
+ NH
3
. Among the investigated hydrogen-based gases, NH
3
showed the highest etching rate of about 0.52 nm s
−1
, but the formation of nitride compounds and the increased roughness were observed on the OTS surface by nitrogen. The use of other hydrogen-based gases such as CH
4
and CH
4
+ H
2
showed the deposition and low OTS etch rate, respectively, due to the presence of carbon in CH
4
. Even though H
2
showed the better etch characteristics due to the no surface residues or compounds on the OTS surface related to carbon or nitrogen in the etch gases, the best OTS etch characteristics such as the second highest etch rate of 0.45 nm s
−1
, the lowest surface roughness of 0.21 nm, and no surface residues or compounds were observed with CH
4
+ NH
3
due to the removal of carbon and nitrogen on the surface by the formation of volatile CN compounds while maintaining a high hydrogen atomic concentration in the plasma.
Etch characteristics of ovonic threshold switch (OTS) materials composed of Ge-As-Te for a phase-change random access memory (PCRAM) has been investigated using reactive ion etching by hydrogen-based gases such as H
2
, CH
4
, NH
3
, CH
4
+ H
2
, and CH
4
+ NH
3
.
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