锥形碳氮结构的发光性能

利用偏压增强化学气相沉积系统,以CH4、H2和NH3为反应气体,分别在沉积有钛膜和碳膜的Si衬底上制备锥形碳结构,并用扫描电子显微镜、X射线能谱仪和显微Raman光谱仪对其进行表征,结果表明所制备的样品为锥形碳氮结构。用显微Raman光谱仪对锥形碳氮结构在室温下的发光性能进行了研究,发光谱显示出中心在621,643,726 nm的发光带。根据碳氮薄膜的发光机理对锥形碳氮结构的发光性能进行了分析。

碳氮结构空心管材料及其对钍离子的吸附性能研究

目的合成碳氮结构空心管材料,用于稀土矿山开采中放射性钍离子的吸附去除,方法通过三聚氰胺和三聚氰酸超分子自组装,经水热碳化及高温热解,制备碳氮结构空心管材料。采用SEM、XRD等对材料进行表征。在不同热解温度和pH值下进行钍离子吸附实验,比较不同钍离子的初始浓度和吸附时间下吸附容量的差异。结果600℃时,材料形貌为均匀的中空管状结构;pH=3.5,热解温度为800℃时,材料最大吸附容量达到133.87 mg/g,吸附过程符合Langmuir等温吸附模型且遵从准二级动力学规律。结论碳氮结构空心管材料对钍离子具有良好的吸附效果,有望用于稀土开采过程中产生的放射性废钍离子的去除。

改性淀粉基碳氮硫硅环钢结构防火涂料的研究

本试验对淀粉进行改性,制备了改性淀粉基碳氮硫硅环保钢结构防火涂料,探究了改性淀粉加入量对涂料性能的影响,并对其进行阻燃机理分析。结果表明,改性淀粉的加入能显著增强涂层黏结性能,对其余基本性能无影响,符合GB 14907—2018的规定;改性淀粉能显著提高涂层发泡性能和耐火性能,改性淀粉加入量为2%~6%时,涂层发泡厚度大于3.0 cm,涂层背面温度小于183.6℃;改性淀粉在受热时形成熔融状态钠醚盐,具有较好传质传热作用,有利于气源物质同步气化,与碳源炭化协调一致,改性淀粉在289.1℃左右时开始分解,相变结束后残碳量约为36.5%,在涂层中主要起碳源和小部分气源作用,且能改善涂层的成膜性能,降低成本,具有较好应用前景。

碳氮纳米结构材料的Raman和XPS分析

利用等离子体增强热丝化学气相沉积在不同条件下制备了不同结构的碳氮纳米结构材料。用扫描电子显微镜(SEM)、显微Raman光谱仪和X射线光电子谱(XPS)仪对它们的形貌和结构进行了分析。SEM照片表明在不同的生长条件下可制备出碳氮纳米尖锥、碳氮柱。Raman谱中位于1350和1607cm-1的D和G峰,表明制备的碳氮纳米结构材料主要由sp2碳组成。根据D和G峰的强度比,估计的sp2碳颗粒为4nm。XPS谱在398.4eV处显示出与氮有关的峰,表明制备的碳氮纳米结构材料中含有氮。对N1sXPS谱的峰进行拟合后,发现位于398.4eV的峰由位于398.3和约400.0eV的两个峰组成,分别与sp3和sp2 C—N键有关,表明材料中的部分碳原子被氮原子所替代。

施氮量对沙地羊草叶片非结构碳氮的影响

在人工建植的沙地羊草草地设不同水平N肥(0、100、200、300、400kg/hm^2)处理,分别用N0、N1、N2、N3、N4表示,研究不同N肥水平对沙地羊草叶片非结构碳氮的影响。结果表明:施氮可增加羊草叶片可溶性糖含量;随氮肥施入水平的增加,沙地羊草上部叶片的淀粉含量呈降低的变化趋势,第2茬沙地羊草下部叶片的淀粉含量呈先增加后降低的趋势;施N可显著增加沙地羊草叶片的可溶性蛋白含量(P<0.05),亦可增加第1茬羊草叶片的游离氨基酸含量;沙地羊草叶片C/N均随施氮的增加呈先降低后增加的变化趋势,上部叶片在N1水平下的C/N最小,试验得出N1(100kg/hm^2)水平为该地区最佳施氮量。

氮掺杂碳包覆的氧化镍和钼酸镍复合材料用于尿素氧化电催化

通过分步水热以及退火的方法合成了氮掺杂碳包覆的氧化镍和钼酸镍复合材料(CN@NiO-NiMoO_(4)),并将其负载于泡沫镍(NF)上,直接用作催化尿素氧化反应UOR的电极材料。实验表明:氮掺杂碳包覆结构以及C-N@NiO与NiMoO_(4)的协同作用可以增强催化剂的导电性、电荷转移能力、抗中毒能力并增大电活性表面积,显著提高了C-N@NiO-NiMoO_(4)的电催化活性和长期稳定性。研究还发现,C-N@NiO-NiMoO_(4)/NF在1.8 V的电流密度是NiMoO_(4)/NF的1.7倍,C-N@NiO/NF的3.6倍,在10 mA·cm^(-2)的电流密度下催化UOR 57 h,催化性能无显著变化。综上,C-N@NiO-NiMoO_(4)具有良好的实际应用前景。

末次刈割时间对3种紫花苜蓿越冬前后根颈非结构碳氮含量的影响

【目的】研究科尔沁沙地3种2年生紫花苜蓿品种越冬前后根颈非结构碳氮含量对末次刈割时间的响应。【方法】选择3种2年生紫花苜蓿(WL168HQ、WL298HQ、佳盛),在不同时间(2020年8月11日(C1)、8月26日(C2)、9月13日(C3)、9月27日(C4)、10月13日(C5))进行末次刈割,于2020年10月15日(T1)、11月10日(T2)、2021年3月10日(T3)、4月10日(T4)、5月10日(T5)挖根采样,测定3种紫花苜蓿越冬前(T1、T2)和越冬后(T3、T4、T5)根颈中的非结构碳氮含量。【结果】越冬前随时间推移,3种紫花苜蓿不同末次刈割处理根颈淀粉含量均呈现降低趋势,可溶性糖含量均呈现升高趋势;越冬前11月份和越冬后3月份,WL298HQ品种C2刈割处理根颈淀粉和可溶性糖含量显著高于其他末次刈割处理(P<0.05);越冬前11月份和越冬后4月份,佳盛品种C2刈割处理、WL168HQ品种C3处理根颈淀粉和可溶性糖含量显著高于其他末次刈割处理(P<0.05)。从秋冬到翌年返青,根颈游离氨基酸含量呈先上升后下降的趋势;在晚秋时节(T1),3种紫花苜蓿均以C5刈割处理游离氨基酸含量最高;次年3月份(T3)和5月份(T5),3种紫花苜蓿各末次刈割处理根颈游离氨基酸含量变化无规律性。晚秋时节(T1),WL168HQ和佳盛的C4刈割处理可溶性蛋白含量显著低于其他末次刈割处理(P<0.05);晚秋时节(T1)和返青萌动期(T4),WL298HQ的C4和C3刈割处理可溶性蛋白含量分别显著低于其他3个末次刈割处理(P<0.05)。在4月份返青萌动期,WL298HQ所有刈割处理根颈淀粉和可溶性糖含量均低于WL168HQ和佳盛;在越冬前的10和11月份,WL168HQ所有刈割处理根颈可溶性蛋白含量均高于WL298HQ和佳盛。【结论】越冬前的10月和11月,抗寒性强的苜蓿品种根颈可溶性蛋白含量高于抗寒性弱的品种;越冬后的4月份,抗寒性强的苜蓿品种根颈淀粉和可溶性糖含量高于抗寒性弱的品种。抗寒性越强的苜蓿品种,较晚进行末次刈割对其抗寒能力的影响越小。

二氧化锰/多孔氮掺杂碳复合材料的制备及线性超级电容器的性能

线性超级电容器在便携式和可穿戴电子产品中有着巨大的应用前景.本研究以尿素为氮源,葡萄糖为碳源,通过牺牲自模板法,制备了二维超薄多孔结构的氮掺杂碳纳米片(2D-PNC).然后在其表面均匀负载了针状结构的二氧化锰(MnO_(2)),从而得到一种高性能的MnO_(2)@2D-PNC纳米复合材料.在此基础上,将MnO_(2)@2D-PNC涂覆到碳纤维线和铝箔上,分别作为柔性内电极和外电极,利用离子液体凝胶作为固态电解质,制备出具有高能量密度的共轴线性超级电容器,其能量密度可达40.5(W·h)/kg,并且具有良好的循环稳定性能.本研究成果不仅在电极材料结构设计的研究上具有指导意义,而且将为可穿戴储能器件的发展提供新思路和可靠的实验依据.

电沉积制备氮化钴纳米片超级电容器

采用一种简单的电化学沉积和退火方法,实现了在碳布基底上碳氮结构修饰氮化钴(CC@Co_(2)N@CN)材料的制备,并将其用于高性能超级电容器.氮化钴表面修饰的碳氮结构不仅可以提高整个电极的电容,而且可以缓解氮化钴的氧化,从而提高整体的导电性能.同时,CC@Co_(2)N@CN表现出极长的寿命,在10000次循环后容量仍能保持其初始值的77%.在电流密度为1 mA·cm^(-2)时,该电极的面积电容最高可达429.4 mF·cm^(-2).因为具有较大的面积电容和良好的循环稳定性能,此类基于碳布基底的氮化钴碳氮结构超级电容器在储能领域具有广阔的应用前景.

Study on the Changes of Non-structural Carbohydrates and Nitrogen Contents of Quercus aquifolioides Scrub along Different Elevation Gradient

[Objective] The aim was to compare the content changes between the non-structural carbohydrates（NSC）and the total nitrogen in various growing seasons,and to explore the response relationship between altitude and the contents.[Method] Taking Quercus aquifolioides scrub which widely distributed in Zheduoshan in the west of Sichuan as the experimental objects,the changes between NSC and the toal nitrogen in various growing seasons at different altitude were studied.[Result] The results showed that the content of NSC in Quercus aquifolioides underground increased with the lift of elevation in the dormancy,but decreased in the early germination,growing period and growth stage.The content of NSC in the ground tissue changed non-linearly with increasing elevation.In addition,the total nitrogen of Quercus aquifolioides organizations was decreasing with increasing elevation in the dormant period,which did not change significantly in the other periods.This result implied that the content of NSC in Quercus aquifolioides underground was more sensitive to temperature.[Conclusion] The experiment laid basis for the exploration of the physical and ecological mechanism of underground plants adaptability to highland environment,their response to global climate changes and adjustment to high altitude ecological system.

Computation of Diffusion Activation Energies of C, N in γFe

A structure relaxation model based on the empirical electron theory of solids and molecules is developed to compute the diffusion active energies of C, N in γFe. First, adding a restriction, the lattice maintains rigidity when solute atom migrates to the saddle point. In this step, the hybridization classes of every atom do not change. Then, the restriction is loosed and the atoms are relaxed under the coulomb repulsive forces. It is supposed that the energy needed in the first step would be compensated partly by the second step. In this way, the diffusion active energies of C, N in γFe are computed. Compared with the experiment data, the relative errors are less than 5%, which are good results in the computation of activation energy of diffusion.

Fabrication of porous g-C_3N_4 and supported porous g-C_3N_4 by a simple precursor pretreatment strategy and their efficient visible-light photocatalytic activity

Porous g-C_3N_4 and supported porous g-C_3N_4 were fabricated for the first time by a simple strategy using pretreated melamine as a raw material and pretreated quartz rod as a substrate.The formation of a richly porous microstructure can be attributed to the co-existence of different pore-fabricating units in the preparation system for porous g-C_3N_4.The richly porous microstructure endowed the as-prepared porous g-C_3N_4 with an excellent photocatalytic activity.The as-prepared supported porous g-C_3N_4 exhibited considerable stability because of the existence of chemical interaction between porous g-C_3N_4 and the quartz rod substrate.The photocatalytic activity of the supported porous g-C_3N_4 was competitive with that of porous g-C_3N_4 in powder form because neither the surface migration of photogenerated electrons nor the diffusion of the target organic pollutant were affected by the construction of the quartz rod reactor.The photocatalytic activity of the as-prepared porous g-C_3N_4 and supported porous g-C_3N_4 was preliminarily evaluated by the treatment of single-component organic wastewater under visible-light irradiation.Subsequently,the as-prepared porous g-C_3N_4 was further applied in conventional hydrogen evolution and a new system for simultaneous hydrogen evolution with organic-pollutant degradation.The hydrogen yield and degradation efficiency both increased with increasing photocatalytic activity of the as-prepared materials in the system for simultaneous hydrogen evolution with organic-pollutant degradation.

High-performance Pt catalysts supported on hierarchical nitrogen-doped carbon nanocages for methanol electrooxidation

Hierarchical nitrogen-doped carbon nanocages （hNCNC） with large specific surface areas were used as a catalyst support to immobilize Pt nanoparticles by a microwave-assisted polyol method. The Pt/hNCNC catalyst with 20 wt% loading has a homogeneous dispersion of Pt nanoparticles with the average size of 3.3 nm, which is smaller than 4.3 and 4.9 nm for the control catalysts with the same loading supported on hierarchical carbon nanocages （hCNC） and commercial Vulcan XC-72, respec- tively. Accordingly, Pt/hNCNC has a larger electrochemical surface area than Pt/hCNC and Pt/XC-72. The Pt/hNCNC catalyst exhibited excellent electrocatalytic activity and stability for methanol oxidation, which was better than the control catalysts. This was attributed to the en- hanced interaction between Pt and hNCNC due to nitrogen participation in the anchoring function. By making use of the unique advantages of the hNCNC support, a heavy Pt loading up to 60 wt% was prepared without serious agglomeration, which gave a high peak-current density per unit mass of catalyst of 95.6 mA/mg for achieving a high power density. These results showed the potential of the Pt/hNCNC catalyst for methanol oxidation and of the new hNCNC support for wide applications.

Red-blood-cell-like nitrogen-doped porous carbon as an efficient metal-free catalyst for oxygen reduction reaction

A red-blood-cell-like nitrogen-doped porous carbon catalyst with a high nitrogen content(9.81%)and specific surface area(631.46 m^2/g)was prepared by using melamine cyanuric acid and glucose as sacrificial template and carbon source,respectively.This catalyst has a comparable onset potential and a higher diffusion-limiting current density than the commercial 20 wt%Pt/C catalyst in alkaline electrolyte.The oxygen reduction reaction mechanism catalyzed by this catalyst is mainly through a 4e pathway process.The excellent catalytic activity could origin from the synergistic effect of the in-situ doped nitrogen(up to 9.81%)and three-dimensional(3D)porous network structure with high specific surface area,which is conducive to the exposure of more active sites.It is interesting to note that the catalytic activity of oxygen reduction strongly depends on the proportion of graphic N rather than the total N content.

2D metal‐free heterostructure of covalent triazine framework/g‐C_(3)N_(4) for enhanced photocatalytic CO_(2) reduction with high selectivity

Solar‐driven CO_(2)conversion to precious fossil fuels has been proved to become a potential way to decrease CO_(2)with producing renewable fuels,which mainly relies on photocatalysts with efficient charge separation.In this work,a metal free heterostructure of covalent triazine framework(CTF)and graphite carbon nitride(g‐C_(3)N_(4),abbreviated as CN)is applied in the CO_(2)photoreduction for the first time.Detailed characterization methods such as photoluminescence(PL)and time‐resolved PL(TR‐PL)decay are utilized to reveal the photo‐induced carries separating process on g‐C_(3)N_(4)/CTF(CN/CTF)heterostructure.The introduced CTF demonstrated a great boosting photocatalytic activity for CN,bringing about the transform rates of CO_(2)to CO reaching 151.1μmol/(g·h)with a 30 h stabilization time,while negligible CH_(4)was detected.The optimal CN/CTF heterostructure could more efficiently separate charges with a lower probability of recombination under visible light irradiation,which made the photoreduction efficiency of CO_(2)to CO be 25.5 and 2.5 times higher than that of CTF and CN,respectively.This investigation is expected to offer a new thought for fabricating high‐efficiency photocatalyst without metal in solar‐energy‐driven CO_(2)reduction.

Few‐layer carbon nitride photocatalysts for solar fuels and chemicals:Current status and prospects

Converting sunlight directly to fuels and chemicals is a great latent capacity for storing renewable energy.Due to the advantages of large surface area,short diffusion paths for electrons,and more exposed active sites,few‐layer carbon nitride(FLCN)materials present great potential for production of solar fuels and chemicals and set off a new wave of research in the last few years.Herein,the recent progress in synthesis and regulation of FLCN‐based photocatalysts,and their applications in the conversion of sunlight into fuels and chemicals,is summarized.More importantly,the regulation strategies from chemical modification to microstructure control toward the production of solar fuels and chemicals has been deeply analyzed,aiming to inspire critical thinking about the effective approaches for photocatalyst modification rather than developing new materials.At the end,the key scientific challenges and some future trend of FLCN‐based materials as advanced photocatalysts are also discussed.

Wear Behavior of Ductile Cast Irons with Nanoparticles Additives

The work in this study is focused on the investigation of the structure and properties of ductile cast iron with nanoparticle additives： TiN （titanium nitride）, TiN ＋ TiCN （titanium carbonitride） and cBN （cubic boron nitride）. The nanoparticles are coated with nickel prior to addition to the iron melt to improve their wetting and uniform distribution in the volume of the casting. The metallographic observation and wear test are performed to study the influence of the nanoparticle additives on the microstructure and and cast iron tribological properties.

Atomic modulation of Fe‐Co pentlandite coupled with nitrogen‐doped carbon sphere for boosting oxygen catalysis

Reversible oxygen reaction plays a crucial role in rechargeable battery systems,but it is limited by the slow reaction kinetics.Herein,the ionic modulation of cobalt pentlandite coupled with nitrogen‐doped bowl‐like hollow carbon sphere is well designed on octahedral and tetrahedral sites.The robust FexCo9−xS8‐NHCS‐V with iron replacing at the octahedron possesses prolonged metal sulfur bond and exhibits excellent bifunctional electrocatalytic performance towards oxygen reduction reaction(ORR,E_(1/2)=0.80 V vs.RHE)and excellent oxygen evolution reaction(OER,E_(j=10)=1.53 V vs.RHE)in 0.1 mol/L KOH.Accordingly,a rechargeable Zn‐air battery of Fe_(x)Co_(9−x)S_(8)‐NHCS‐V cathode endows high energy efficiency(102 mW cm^(−2)),and a microbial fuel cell achieves a high‐power density(791±42 mW m^(−2)),outperforming the benchmark Pt/C catalyst.

Independent and Combined Effect of Some Soil Tillage Systems on Nitrogen and Carbon Concentration in Soil Structural Units of Haplic Chernozems

This paper aimed at studying the effect of different types of soil tillage systems on the change of total carbon （C） and nitrogen （N） in the soil structural units of different size after dry structural analysis of soil. The research was carried out in a 6-field rotation system （grain maize-wheat-sunflower-wheat-bean-wheat） at the end of the 2nd rotation. Six out of 24 soil tillage systems were selected; they were applied independently and in combination in the crop rotation. After that, they were compared to the system with constant deep plowing. So a total of seven soil tillage systems were investigated. The selected systems for main soil tillage were the following： plowing （control variant）, disking, cutting, nil tillage （direct sowing）, plowing-disking, plowing-nil tillage, disking-nil tillage. Three depths of 0-10, 10-20 and 20-30 cm were studied, as well as soil structural units were of the following sizes： 〉 10 mm, 10-5, 5-3, 3-1, 1-0.25 mm and 〈 0.25 mm. As a result of systematic implementation of different soil tillage systems, higher N and C concentrations were established by the layers according to constant plowing. Constant disking and its alternation with nil tillage increased the total N concentration with 15.6% and 11.1%, respectively, in comparison with the constant plowing. The same was valid for C concentration in soil, but the highest increase was established in the variants with constant cutting and nil tillage. The exceeding was with 14.0% and 13.2%, in comparison to constant plowing. The redistribution of N and C depending on the structural soil units was most expressed in the 0-10 cm and 10-20 cm layers. The highest amounts of C and N were found in the soil units with size less than 5 mm, mainly in the 〈 0.25 mm fraction. At depth of 20-30 cm, the role of the size of soil structural units for C and N redistribution decreased strongly. The values of C/N ratio were moderate only under the use of constant disking. This index was low under all other soil tillage systems. The correlation of total N with C in soil was high, positive and significant depending on the size of structural soil units and the tillage systems, as average for the investigated factors in this experiment. The minimal tillage and the tillage without turning of soil, used independently and in combination, had the highest contribution to preserving the organic matter in the haplic Chernozems of Dobrudzha region.

Two-dimensional polymeric carbon nitride: structural engineering for optimizing photocatalysis

As a two-dimensional(2D) material, polymeric carbon nitride(g-C_3N_4) nanosheet holds great potentials in environmental purification and solar energy conversion. In this review, we summarized latest progress in the optimization of photocatalytic performance in 2D g-C_3N_4. Some of the latest structural engineering methods were summed up, where the relevant influences on the behaviors of photoinduced species were emphasized. Furthermore, the construction strategies for band structure modulation and charge separation promotion were then discussed in detail. A brief discussion on the opportunity and challenge of 2D g-C_3N_4-based photocatalysis are presented as the conclusion of this review.