Boron-doped lamellar porous carbon supported copper catalyst for dimethyl oxalate hydrogenation

Doping heteroatoms on carbon materials could bring some special advantages for using as catalyst support.In this work, a boron doped lamellar porous carbon(B-LPC) was prepared facilely and utilized as carbonbased support to construct Cu/B-LPC catalyst for dimethyl oxalate(DMO) hydrogenation. Doping boron could make the B-LPC own more defects on surface and bigger pore size than B-free LPC, which were beneficial to disperse and anchor Cu nanoparticles. Moreover, the interaction between Cu species and B-LPC could be strengthened by the doped B, which not only stabilized the Cu nanoparticles, but also tuned the valence of Cu species to maintain more Cu^(+). Therefore, the B-doped Cu/B-LPC catalyst exhibited stronger hydrogenation ability and obtained higher alcohols selectivity than Cu/LPC, as well as high stability without decrease of DMO conversion and ethylene glycol selectivity even after 300 h of reaction at 240℃.

Synthesis of boron, nitrogen co-doped porous carbon from asphaltene for high-performance supercapacitors

Oxidized asphaltene （OA）, a thermosetting material with plenty of functional groups, is synthesized from asphaltene （A） using HNO3]HzSO4 as the oxidizing agent. Boron, nitrogen co-doped porous carbon （BNC-OA） is prepared by carbonization of the mixture of boric acid and OA at 1173 K in an argon atmosphere. X-ray photoelectron spectroscopy （XPS） characterization reveals that the BNC-OA has a nitrogen content of 3.26 at.% and a boron content of 1.31 at.%, while its oxidation-free counterpart （BNC-SA） has a nitrogen content of 1.61 at.% and a boron content of 3.02 at.%. The specific surface area and total pore volume of BNC-OA are 1103 m2·g^-1 and 0.921 cm3·g^-1, respectively. At a current density of 0.1 A·g^-1, the specific capacitance of BNC-OA is 335 F·g^-1 and the capacitance retention can still reach 83% at 1 A·g^-1. The analysis shows that the superior electrochemical performance of the BNC-OA is attributed to the pseudocapacitance behavior of surface heteroatom functional groups and an abundant pore-structure. Boron, nitrogen co-doped porous carbon is a promising electrode material for supercapacitors.

Effect of Water Stress and Foliar Boron Application on Seed Protein, Oil, Fatty Acids, and Nitrogen Metabolism in Soybean

Effects of water stress and foliar boron (FB) application on soybean (Glycine max (L) Merr.) seed composition and nitrogen metabolism have not been well investigated. Therefore, the objective of this study was to investigate the effects of water stress and FB on seed protein, oil, fatty acids, nitrate reductase activity (NRA), and nitrogenase activity (NA). A repeated greenhouse experiment was conducted where one set of soybean plants were subjected to water stress (WS), and the other set was watered (W). Foliar boron (B) was applied at rate of 0.45 kg·ha-1. Treatments were watered-plants with no FB (W), watered-plants with FB (WB), water-stress plants with no FB (WS), and water-stress plants with FB (WSB). The results showed that seed protein and oil percentage were significantly (P 15N/ 14N and 13C/12C natural abundance were altered between watered-and watered-stressed plants. These results suggest that water stress and FB can influence seed composition, and nitrogen metabolism, and 15N/14N and 13C/12C ratios, reflecting environmental and metabolic changes in carbon and nitrogen fixation pathways. Lack of B translocation from leaves to seed under water stress may suggest a possible mechanism of limited B translocation under water stress. These findings may be beneficial to breeders to select for B translocation efficiency under drought conditions. Altered 15N/14N and 13C/12C under water stress can be used as a tool to select for drought tolerance using N and C isotopes in the breeding programs.

Influence of Boron Additions on Mechanical Properties of Carbon Steel

This work aims at the development of carbon steel AISI 1536 through the microalloying addition of boron. Three grades of this steel with different content of boron up to 0.0055% were melted in 100 kg induction furnace. The pro- duced steels were hardened at 960°C for 30 min., followed by tempering at different temperatures and durations. All hardened steels have martensite phase as illustrated with microstructures and X-ray diffraction. Hardness of all tem- pered steel samples was measured to calculate the activation energies of carbon migration through martensite phase. The results indicated that the activation energies of carbon migration through martensite phase decreases with the in- crease of boron content due to its positive effect on the crystallinity of martensite phase. Also, the results showed that the addition of boron up to 0.0023% can improve the steel properties at the lowest temperature and tempered time.

Accurate theoretical evaluation of strain energy of all-carboatomic ring(cyclo[2n]carbon),boron nitride ring,and cyclic polyacetylene

Cyclocarbon fully consists of sp-hybridized carbon atoms,which shows quite unusual electronic and geometric structures compared to common molecules.In this work,we systematically studied strain energy(SE)of cyclocarbons of different sizes using regression analysis method based on electronic energies evaluated at the very accurate DLPNO-CCSD(T)/ccp VTZ theoretical level.In addition,ring strain of two systems closely related to cyclocarbon,boron nitride(BN)ring,and cyclic polyacetylene(c-PA),is also explored.Very ideal relationships between SE and number of repeat units(n)are built for cyclo[2n]carbon,B_(n)N_(n),and[2n]c-PA as SE=555.0·n^(-1),145.1·n^(-1),and 629.8·n^(-1)kcal·mol^(-1),respectively,and the underlying reasons of the difference and similarity in their SEs are discussed from electronic structure perspective.In addition,force constant of harmonic potential of C-C-C angles in cyclocarbon is derived based on SE values,the result is found to be 56.23 kcal·mol^(-1)·rad^(-2).The possibility of constructing homodesmotic reactions to calculate SEs of cyclocarbons is also explored in this work,although this method is far less rigorous than the regression analysis method,its result is qualitatively correct and has the advantage of much lower computational cost.In addition,comparisons show thatωB97XD/def2-TZVP is a good inexpensive alternative to the DLPNO-CCSD(T)/cc-p VTZ for evaluating energies used in deriving SE,while the popular and very cheap B3LYP/6-31G(d)level should be used with caution for systems with global electron conjugation such as c-PA.

Effect of Boron on Delayed Fracture Resistance of Medium-Carbon High Strength Spring Steel

The delayed fracture behavior of medium carbon high strength spring steel containing different amounts of boron （0. 000 5%, 0. 001 6 %） was studied using sustained load delayed fracture test. The results show that delayed fracture resistance of boron containing steels is higher than that of conventional steel 60Si2MnA at the same strength level and it increases with the increase of boron eontent from 0. 000 5% to 0. 001 6%. The delayed fracture mode is mainly intergranular in the boron containing steels tempered at 350℃, which indicates that the addition of boron does not change the fracture character. However, the increase of boron content enlarges the size of the crack initia tion area. Further study of phase analysis indicates that most boron is in solid solution, and only a very small quantity of boron is in the M3 （C, B） phase.

Pulsed Laser Deposition of Boron Carbon Nitride Coatings

oron carbon nitride coatings were synthesized using the pulsed laser deposition method. The hardness of the coatings was measured by a Vickers microhardness tester. It was found that the hardness of the coatings was between 15.45 and 34.05 GPa under a load of 0.5 N. The surface morphology was studied by optical microscopy and atomic force microscopy. There were spherical and irregular shaped particulates in the coatings. The density of the spherical particles was found being increased at high deposition temperatures. The rootmeansquared surface roughness of the coatings was about 4 nm.

Microstructure evolution and mechanical properties of high-boron steel with different ratios of boron and carbon

Boron and carbon contents are the main factors influencing the properties of high-boron steel.In this study,experimental samples with different boron-to-carbon ratios(%B/%C)were prepared.The microstructures of the different samples were observed,and their hardness,bending strength,and impact toughness were investigated.Results show that the main microstructures in the investigated high-boron steel samples are the eutectic Fe_(2)B structure with a fishbone shape and the ternary peritectic Fe_(3)(C,B)structure with a chrysanthemum shape.When the boron content is 2.5wt.%and the carbon content is 0.43wt.%(i.e.,%B/%C=5.82),the overall mechanical properties of the alloy are the best.The alloy's hardness,bending strength and impact toughness reach their maximums,which are 67.3 HRC,1,267.36 MPa and 6.19 J·cm^(-2),respectively.The optimized alloy is compared with conventional materials exhibiting excellent wear resistance(namely,high-manganese steel and high-chromium cast iron)through two-body and three-body abrasion tests.The wear resistance of this high-boron steelinvestigated in this work is found to be superior to those of the more common materials.

Synthesis of Boron-doped Diamond/Porous Ti Composite Materials——Effect of Carbon Concentration

Highly boron-doped diamond films were deposited on porous titanium substrates by hot filament chemical vapor deposition technique. The morphology variation of highly boron-doped diamond films grown on porous titanium substrates was investigated, and the effects of carbon concentration on nucleation density and diamond growth were also studied. The continuous change of surface morphology and structure of diamond film were characterized by scanning electron microscopy. The structures of diamond film and interlayer were analyzed by X-ray diffraction. The quality of boron-doped diamond film was confirmed by visible Raman spectroscopy. The experimental results reveal that surface morphology and quality of boron-doped diamond films are various due to the change of carbon concentration. The thickness of intermediate layer decreases with the carbon concentration increasing.

Replacement of Flake Graphite in Aluminacarbon Refractories by Hexagonal Boron Nitride

Three kinds of composite alumina refractories were prepared with tabular alumina （3-1 and 1-0 mm） as aggregates,tabular alumina powder,α-Al2 O3 micropowder,and Si powder as matrix,adding 3 mass％ hexagonal boron nitride （h-BN）,3 mass％ flake graphite and 10 mass％ flake graphite,respectively.Cold physical properties,hot modulus of rupture,oxidation resistance,thermal shock resistance and slag corrosion resistance of the specimens were compared.The results show that：（1） physical properties and hot modulus of rupture of Al2 O3-h-BN refractories are slightly different from those of low carbon Al2 O3-C refractories,but better than those of traditional Al2 O3-C refractories with 10 mass％ graphite ; （2） Al2 O3-h-BN refractories have better thermal shock resistance and oxidation resistance than the carbon containing refractories,while similar slag resistance with low carbon Al2 O3-C refractories ; （3） h-BN can replace flake graphite as a starting material for the preparation of composite alumina refractories,considering the overall properties of the material.

氧化硼对Al_(2)O_(3)-SiC-C质浇注料力学性能的影响

为了利用氧化硼“间接烧结”特性,进一步提升Al_(2)O_(3)-SiC-C质浇注料的力学性能,以氧化硼(≤0.075 mm)为助烧剂,制备了以FM60莫来石颗粒、致密刚玉、碳化硅、α-Al_(2)O_(3)微粉等为主要原料的浇注料,探究了氧化硼细粉加入量(加入质量分数分别为0、0.2%、0.4%和0.6%)对Al_(2)O_(3)-SiC-C质浇注料结构与性能的影响。结果表明,添加氧化硼细粉会显著提升浇注料的加水量,但其有利于晶须状莫来石的生成,从而加强骨料和基质间的结合强度,试样的力学性能得到明显提升。但当氧化硼细粉加入量提高至0.6%(w)时,试样中莫来石晶须长径比减小,试样的强度降低。综合以上结果,氧化硼最佳加入量为0.4%(w)。

造粒的氮掺杂碳纳米管基吸附剂对卤水中硼的吸附行为与机理

盐湖卤水中硼资源丰富,存在形式复杂多样,分离和回收硼的意义重大。基于N掺杂强静电与多羟基协同作用能够有效提高硼阴离子的分离机制,设计以水合肼为N源,多羟基的一维纳米材料碳纳米管(CNTs)为多羟基络合基,采用简单的一锅水热法合成了N掺杂的碳纳米管硼吸附材料(N-CNTs)。此外,以改性的聚丙烯腈为造粒剂,经造粒后,最大硼吸附容量为20.45 mg/g,特别在低浓度硼的分离中表现出优异的性能,这使N-CNTs成为硼的高效吸附材料。吸附机理为一维碳纳米管和改性聚丙烯腈的高比表面积上多羟基与N掺杂位置发生强静电协同增强络合吸附。硼吸附过程符合朗格缪尔吸附等温模型和准二阶动力学模型,在高浓盐多离子溶液中表现出优异的选择性硼吸附性能。该吸附剂在东台吉乃尔盐湖卤水中硼的吸附容量达18.92±1 mg/g,该技术在盐湖卤水及水处理行业具有较高的应用潜力。

熔盐辅助合成硼化铪工艺研究

这是一篇冶金工程领域的论文。以氧化铪和碳化硼为原料,采用氯化钠为熔盐介质,通过硼/碳热还原法合成了纯度较高的硼化铪粉体。研究了反应温度、保温时间等合成工艺参数以及原料配比对材料晶相组成和显微结构的影响。结果表明,以氯化钠为熔盐介质时,氧化铪在1300℃的合成温度下开始转化为硼化铪,其温度远低于传统的硼化铪合成所需温度。在硼过量20%,反应温度和保温时间分别为1400℃和2 h所制备的硼化铪粉体纯度较高,X射线衍射中可以明显观察到硼化铪结晶峰,且在扫描电镜中可以观察到紧密团聚形貌的硼化铪。

碳纳米管对混合粒径PcBN复合材料性能的影响

为提高高温高压制备的聚晶立方氮化硼(PcBN)复合材料的性能,以颗粒尺寸分别为0~0.5μm和0.5~1.0μm的混合粒径立方氮化硼(cBN)为原材料,Al-Ti-Al_(2)O_(3)为结合剂,加入不同质量分数的碳纳米管,在高温高压条件下烧结制备PcBN复合材料,研究碳纳米管质量分数对PcBN复合材料结构和性能的影响。结果表明:添加碳纳米管后,PcBN和碳纳米管间没有发生化学反应,碳纳米管以增强体的形式存在于复合材料内部;复合材料较致密,碳纳米管的添加使PcBN的相对密度先增大后减小。当碳纳米管添加质量分数为1.5%时,PcBN的相对密度有最大值97.9%,同时PcBN有最大的显微硬度和断裂韧性,分别为3892 HV和6.82 MPa·m^(1/2);当碳纳米管的添加质量分数为1.0%时,PcBN有最大的抗弯强度和磨耗比,分别为584 MPa和6873。碳纳米管拔出和桥连作用提高了PcBN复合材料的力学性能。

多孔硼/碳复合材料对水溶液中碘的吸附研究

放射性碘的泄漏将对环境和人类健康带来巨大威胁,发展简便高效、高选择性的新型碘吸附材料具有重要的理论和实践价值。本研究以廉价易得的淀粉为碳源、硼酸为硼源,通过一步退火处理,制备了多孔硼/碳复合材料(M-B/C)。结果表明,硼的引入不但提高了材料的机械强度,还增加了其微孔和介孔结构。将M-B/C用于水溶液中碘(I2)的吸附,其吸附容量为543 mg·g^(-1),比纯多孔碳(M-C)提高了5.8倍(94 mg·g^(-1)),同时具有良好的吸附选择性、稳定性和重复使用性能。将M-B/C装于吸附柱,成功实现了模拟海水中I2的高效连续去除,在1 mL·min^(-1)的流速下,去除率可达94.2%,表明本研究制备的M-B/C对水中I2的连续去除有良好的应用前景。

葡甲胺功能化rGO/MWCNTs-OH复合气凝胶的制备及对硼的吸附

气凝胶在吸附领域具有很好的应用前景。本文采用水热合成法和冷冻干燥法制备出葡甲胺功能化还原氧化石墨烯/羟基化碳纳米管气凝胶应用于盐湖卤水除硼,研究了吸附剂对水溶液中硼的吸附行为,吸附过程符合拟二级动力学和Freundlich等温吸附模型。当初始硼浓度为1000mg/L、pH为10、吸附时间为9h、温度298K时,最大吸附量为33.64mg/g。响应面法可以预测实验结果并优化反应条件,在最佳条件下硼吸附量为32.91mg/g。吸附机理分析表明,吸附过程主要是吸附剂上的—OH官能团与B的络合作用。吸附剂经过三次吸附-脱附实验,仍对B有较高吸附容量。吸附剂具有良好的抗共存盐干扰性,在真实卤水中吸附性能良好,吸附量为23.87mg/g。该气凝胶对于从盐湖卤水和废水中提硼具有潜在的价值。

环保型复配阻燃剂在木塑复合材料中的应用进展

木塑复合材料(WPC)兼具木材的生态性和塑料的可加工性,是一类生态环保材料。基于当前WPC易燃且燃烧后产生有害气体,从而造成了对人体健康的危害和对环境的污染等问题,围绕进一步提升WPC的阻燃效率和满足环保条件进行了讨论,着重介绍了WPC的燃烧特性,综述了碳系、金属系、矿质系、磷系、硼系环保型阻燃剂与其他元素阻燃剂进行复配协同提升WPC阻燃抑烟的研究进展,对比单一阻燃剂,环保型复配阻燃剂在阻燃和环保方面具有优越性。同时,还对环保型WPC阻燃剂的未来发展趋势提出了展望和建议。

硼酚醛环氧树脂共混体系制备基纳米碳纤维的研究

采用了共混静电纺丝法制备了硼酚醛环氧树脂基纳米碳纤维。在纺丝液的配制中选择硼酚醛树脂(BPF)和环氧树脂(EP)为原料,聚乙烯醇缩丁醛酯(PVB)为纺丝助剂,乙醇为溶剂。静电纺丝后采用阶梯式加热法进行固化处理,固化后在管式炉里进行碳化处理。多次实验对比分析后发现:BPF/EP共混纺丝液的最佳配比为BPF/EP=95%/5%,纺丝液浓度为40%,且在20 kV纺丝电压、1 ml/h推进速率、20 cm纺丝距离下纺丝效果最佳。在该最佳纺丝液配比以及纺丝工艺条件下制备出的BPF/EP纳米基碳纤维经表征检测:在1000℃下残炭率可达到64%左右,碳纤维结构方面比表面积为811.242 m^(2)/g,总孔容0.288 cm^(3)/g,其中微孔孔容为0.281 cm^(3)/g,平均孔径为0.590 nm。

亚东-谷露断裂带中北段地热流体碳硫硼同位素特征

亚东—谷露断裂带中北段地热系统深循环过程十分复杂,对该区域地热资源的评估具有较大影响。加深对地热水起源、演化和循环过程的研究,对地热资源的勘探和开发具有较大的意义。地热流体中碳硫硼稳定同位素特征分析是研究地热水来源、地热水循环深度和地热水作用过程的方法之一。对亚东—谷露断裂带中北段地热水进行了系统性采样,测量了碳硫硼同位素。进行了碳硫硼同位素分析,结果显示:稳定同位素特征源于地热流体对围岩和地层的淋滤作用和水-岩相互作用。该地热系统中碳的主要来源为碳酸盐的溶解,与区域上分布的碳酸盐地层有关。谷露和续迈地热田δ^(34)S具有较大的分散性,显示出硫来源的非单一性,δ^(34)S均在大气碳酸盐和蒸发碳酸盐范围内,δ^(34)S同位素的来源为大气降水和热储层中的硫酸盐矿物。谷露地热田具有较低的δ^(11)B值和较低的Cl/B比值,较高的硼含量,且硼含量和硼同位素值相对集中,表明硼主要源于地热流体对围岩的淋滤作用。大气降水和冰雪融水中硼含量极少,主要起到对地热水中硼含量的稀释作用,不改变地热水中的δ^(11)B值。本研究的结果验证了亚东—谷露断裂带中北段地热系统地下热水的起源主要为大气降水,在深循环过程中存在少量岩浆流体的混入。