不同CO2浓度和施氮水平对麦田CO2净通量的影响

为研究不同CO₂浓度和施氮量对麦田CO₂净通量的影响,利用开顶式气室(OTC)组成的CO₂浓度自动调控平台模拟CO₂浓度升高环境.以冬小麦为试验材料,设置CK (对照,环境大气CO₂浓度)、C₁(CO₂浓度比CK增加120 μmol·mol^-1)和C₂(CO₂浓度比CK增加200 μmol·mol^-1)3个CO₂浓度水平;施氮量设置常规施氮量(N₁,25 g·m^-2)和低氮(N₂,15 g·m^-2)2个水平.采用静态箱-高精度气体分析仪观测麦田CO₂净通量.结果表明:各处理的麦田CO₂净通量变化特征一致,均呈先增大后减小的趋势,在拔节期和抽穗期达到峰值.N₁处理下,在整个生育期,CK、C₁和C₂处理的CO₂累积量分别为-105.8±12.6、-123.1±11.5和-120.2±4.1 kg·hm^-2.N₂处理下,在整个生育期,CK、C₁和C₂处理的CO₂累积量分别为-82.3±9.2、-95.4±7.6和-96.7±2.8 kg·hm^-2;拔节期C₂处理的CO₂累积量比CK显著增加了31.8%(P=0.024).C₁处理下,拔节期N₁处理的CO₂累积量显著高于N₂处理55.0%(P=0.009);C₂处理下,N₁处理的整个生育期CO₂累积量显著高于N₂处理23.6%(P=0.010).各处理CO₂净通量跟土壤湿度的相关关系均达到显著;N₁处理下,C₁和C₂处理的CO₂净通量跟光合有效辐射的相关关系达到显著,N₂处理下,CK和C₁处理的CO₂净通量跟光合有效辐射的相关关系达到显著;N₁处理下,C₁处理的CO₂净通量跟空气温度的相关关系达到显著,其余处理未达到显著.本研究表明:在小麦的拔节期和抽穗期,相比于CO₂浓度升高,施氮量对麦田CO₂净通量的影响更为显著;CO₂浓度升高与施氮量对麦田CO₂净通量的影响没有显著的交互作用.     

KMnO4/NaOH溶液吸收SO2/NO的动力学研究

在典型湿法烟气脱硫系统运行条件下,研究了平面传质搅拌反应器中KMnO₄/NaOH溶液同时吸收SO₂和NO的动力学,确定了反应级数、反应速率常数以及活化能.实验结果表明,NO的吸收速率随着入口NO分压和KMnO₄浓度的增加而提高.在吸收剂溶液中加入NaOH可以提高NO的吸收速率,烟气中O₂的体积分数对于NO和SO₂的吸收速率几乎没有影响.当同时吸收烟气中的SO₂和NO时,SO₂会降低NO的吸收速率,而NO对SO₂的吸收速率几乎没有影响.在KMnO4/NaOH溶液中NO的吸收速率对NO相间浓度和KMnO4浓度均为一级反应,平均反应速率常数为5.79×103 m³/(mol•s),活化能为26.85 kJ/mol.     

大气CO2浓度缓增对冬小麦土壤呼吸的影响

为研究大气CO₂浓度缓增对冬小麦（Triticum aestivum）土壤呼吸的影响，基于开顶式气室组成的CO₂浓度自动调控平台，在2017—2019年开展了两季冬小麦CO₂浓度缓增试验.每季试验在背景大气CO₂浓度基础上（CK，对照），均设置了CO₂浓度缓增处理（C₈₀和C₁₂₀，即从2016年起逐年增加40 μmol·mol^-1，至2017—2018年和2018—2019年冬小麦生长季CO₂浓度分别为CK+80 μmol·mol^-1和CK+120 μmol·mol^-1）.采用静态暗箱-气相色谱法测定土壤呼吸速率.结果表明：CO₂浓度缓增没有显著改变土壤呼吸的季节变化规律，但是会显著影响冬小麦旺盛生长期的土壤呼吸速率.在2018—2019年冬小麦抽穗-扬花期，C₁₂₀处理使土壤呼吸速率显著增加50.2％（P=0.008），且使得生长季土壤碳排放显著增加25.9％（P=0.044），而在2017—2018年冬小麦生长季，与CK相比，C₈₀处理对土壤呼吸没有显著影响.土壤呼吸与土壤温度呈指数正相关，与CK相比，CO₂浓度缓增降低了土壤呼吸对温度的敏感性.研究表明，CO₂浓度缓增120 μmol·mol^-1增加了冬小麦生长季土壤碳排放.     

SO2-4对块体纳米晶铜阳极极化行为的影响

为了揭示SO₂^-4对块体纳米晶铜耐蚀性能的影响规律,利用电化学方法,结合X射线衍射、能谱分析、扫描电镜等表面分析技术,研究了惰性气体沉积原位温压法制备的块体纳米晶铜在不同质量分数（0.3%、1.3%、2.3%、3.3%和4.3%）Na₂SO₄溶液中的阳极极化行为.结果表明,随着SO₂^-4的增多,纳米晶铜的致钝电流密度增大,而致钝电位降低.在0.3%的Na₂SO₄溶液中加入1%的NaCl,纳米晶铜阳极极化行为发生明显变化,Cl^-在纳米晶铜表面形成难溶于水的CuCl保护钝化膜,纳米晶铜致钝电流密度降低,活化-钝化过渡区电流密度下降速率显著减小.     

二级出水残留有机物对PVDF超滤膜污染行为研究

为进一步识别二级处理水中残留有机物对聚偏氟乙烯（PVDF）超滤膜的优势污染物,采用DAX-8／XAD-4树脂将二级出水残留有机物分割成强疏水性、弱疏水性和亲水性组分,分别进行膜污染实验;使用原子力显微镜结合自制的PVDF膜材料探针和相应组分的污染物探针分别进行膜-污染物、污染物-污染物之间的黏附力测试,同时进行污染膜表面形貌分析．结果表明:使用微观作用力可有效预测膜污染行为;亲水性有机物与PVDF膜之间的作用力最大,弱疏水性有机物与PVDF膜之间的作用力最小;针对同一组分污染物,膜-污染物之间的作用力皆大于相应污染物-污染物之间的作用力,表明膜-污染物之间的作用力是控制PVDF超滤膜污染的关键因素,强疏水性组分之间的作用力是控制PVDF分离膜运行稳定期膜污染的关键因素;对二级处理水而言,减小亲水性组分与PVDF之间的作用力是控制PVDF超滤膜污染的重要手段．     

SO2浸出软锰矿体系连二硫酸锰的生成机制

副产物连二硫酸锰(MnS₂O₆)生成是限制废气二氧化硫还原浸出软锰矿副产硫酸锰工艺工业化应用的技术瓶颈和关键科学问题。迄今,MnS₂O₆的生成机制尚未明确,难以为探究其工艺控制措施提供有效理论依据。基于此,本文研究了SO₂浸出软锰矿体系MnS₂O₆的生成机制,阐明了MnS₂O₆生成速率控制步骤和动力学过程。首先基于反应体系理论分析,提出基于表面吸附和电化学模型的自由基生成机制可用于解释MnS₂O₆的生成机制,其生成速率微观上取决于自由基HSO₃形成速率,宏观上主要取决于体系H^₊和HSO- 3浓度,两者的反应级数均为1,推导的理论生成速率方程为 。随后通过动力学实验考察了体系SO₂浓度、pH和温度对MnS₂O₆生成的影响,研究结果表明,MnS₂O₆生成速率随体系酸度和温度的升高呈现先快速减小后趋势趋缓,随体系SO₂浓度的升高而升高,H^₊和SO₂浓度对MnS₂O₆生成速率的反应级数分别为-0.057和0.9954,反应的活化能为6894.05 J/mol。最后基于液相SO₂解离平衡关系,推导得到H^₊浓度和HSO- 3浓度对MnS₂O₆生成速率的反应级数分别为0.943和0.996,与理论速率方程的级数非常接近。研究结果验证了对MnS₂O₆生成机制的解释和动力学推导过程, 可为该工艺工业化应用时MnS₂O₆生成特性及抑制方法研究提供理论依据和有效途径。     

基于双金属MOFs 制备Co3O4/In2O3 复合物及其气敏性能的研究

以硝酸铟(In(NO₃)₃·xH₂O)、对苯二甲酸(H₂BDC)、六水合硝酸钴(Co(NO₃)· 6H₂O) 为原料, 首先采用一锅油浴法合成了含有Co²⁺ 的铟基金属有机框架材料(MOFs) Co²⁺/CPP-3(In) 材料, 然后在450 ℃ 下焙烧制备Co₃O₄/In₂O₃ 复合物气敏材料, 将Co₃O₄/In₂O₃ 复合物的粉体制作成传感器, 并对其气敏性能进行研究。利用扫描电子显微镜和X 射线衍射仪(XRD) 对双金属MOFs Co²⁺/CPP-3(In) 材料和Co₃O₄/In₂O₃ 复合物进行表征, 采用静态配气法测试其气敏性能。结果表明, Co₃O₄/In₂O₃(n_Co : n_In = 0.4 : 1) 样品的形貌保留了其MOFs 前驱体的棒状结构, 棱柱形框架更为突出, 表面呈凹陷状, 棒体中间粗两边细, 六角截面和棒体均布满了孔洞。结合EDX 和XRD 表征结果, Co²⁺/CPP-3(In) MOFs 前驱体完全转化成Co₃O₄/In₂O₃ 复合物; Co₃O₄/In₂O₃(n_Co : n_In = 0.4 : 1) 复合物在 70 ℃ 下对5×10^-6 H₂S 的气敏性能最优, 响应值达到153, 是同条件下纯备In₂O₃对H₂S 响应值的5 倍, 并且有较好的重复性、选择性和稳定性。     

纳米SiO2超高强高流态混凝土及改性机理

通过正交试验提出纳米超高强高流态混凝土的胶凝材料配合比设计参数,并研究了纳米SiO₂的掺入对传统掺硅灰、粉煤灰超高强水泥基胶凝材料强度及工作性能的影响。在保证水胶比不变的条件下,开展了混凝土配合比试验,并研究了纳米SiO₂对混凝土抗压强度的影响及其微观机理。结果表明：超高强高流态混凝土中胶凝材料最优比例为：纳米SiO₂：硅灰：粉煤灰：水泥=1：8：20：71;在胶凝材料用量为600~1 000 kg/m³范围内,随着其掺量的增加,混凝土流动度不断增加,抗压强度先增大后减小,当其掺量为800 kg/m³时,抗压强度最大。分析认为,纳米SiO₂、硅灰与粉煤灰形成的三元多尺度堆积体系能优化粉体材料在混凝土中的微集料密实填充效应,纳米SiO₂的二次水化反应也有效改善了硬化水泥石的微观结构,并优化其形态分布,进一步增大其强度。     

制备方法对CeO2及CoOx/CeO2催化燃烧甲苯的影响

挥发性有机物(VOCs)是形成雾霾和臭氧的主要前驱物,控制其污染排放十分必要。论文研究采用热分解法、化学沉淀法和水热法制备CeO₂,并通过浸渍-焙烧将15 wt%的CoO_x负载在不同方法制备的CeO₂上,以甲苯为目标污染物研究了不同制备方法对CeO₂及CoO_x/CeO₂催化性能影响,并通过XRD、BET、SEM、H₂-TPR和Raman对催化剂进行表征。结果表明：在甲苯浓度为1,000 ppm,空速为20,000 h^_-1测试条件下,化学沉淀法制备的CeO₂具有最好的催化活性,在375℃达到80%的甲苯去除率;将其与Co物种复合后,Co/CeO₂-P能在255℃达到90%的去除率。300 ℃下,经过78 h的长周期实验,Co/CeO₂-P依然保持100%甲苯去除率。BET和H₂-TPR结果表明：不同方法制备的CeO₂拥有不同有比表面积和表面氧化还原性能,这是影响其催化活性的主要因素。     

Fe2(SO4)3对活性污泥微生物活性的影响

为了解Fe₂(SO₄)₃作为絮凝剂对活性污泥中微生物活性的影响,向活性污泥系统中投加质量浓度为20、40、60、80,100 mg·L-1的Fe₂(SO₄)₃,反应4 h后测定活性污泥的脱氢酶活性、比耗氧速率(R_SOU)、胞外聚合物(EPS)及各组分含量,同时测定系统出水的COD等各项指标．结果表明:Fe₂(SO₄)₃质量浓度在20～60 mg·L-1时对活性污泥的脱氢酶活性、R_SOUEPS及各组分含量影响均不大,此时污水中COD、TP、UV₂₅₄等污染物随Fe₂(SO₄)₃质量浓度增加而有较大幅度去除．Fe₂(SO₄)₃质量浓度为80 mg·L-1时,污泥的脱氢酶活性、R_SOU、总EPS含量均明显下降．当Fe₂(SO₄)₃质量浓度增加到100 mg·L-1时,污泥的脱氢酶活性、R_SOU进一步受到抑制,而总EPS含量则大幅度提升．此时污水中COD、TP、UV₂₅₄等污染物去除率增加幅度变缓,SCOD及NH₃-N去除作用有所下降．     

Mechanism and behaviors of Cr3+-doped TiO2

TiO₂ powder and TiO₂ thin film on the surface of glazed ceramic tile were prepared by sol-gel method. The influences of different doping Cr³⁺ concentration on the photocatalytic activity of TiO₂ were discussed, UV-visible and X-ray diffraction analysis were used to test the performance of TiO₂ powder and film. The results indicate that photocatalytic activity of doping Cr³⁺-TiO₂ thin film is higher than that of powder, and the interaction between Cr³⁺-doped and substrate can greatly enhance the photocatalytic activity. The results of X-ray diffraction and photoabsorption show that the Cr³⁺-doped energy level in TiO₂ is 0.62 eV high from the top of valence band, which belongs to the type of deep energy level doping. On the basis of the semiconductor energy level theory and Cr³⁺ dopant energy level, the semiconductor energy level model of Cr³⁺ in TiO₂ powder and thin film were established, and the doping mechanisms of Cr³⁺-doped in TiO₂ powder and thin film were analyzed. Foundation item: Project (20466001) supported by the National Natural Science Foundation of China     

Luminescent properties of BaO-La2O3-B2O3 glasses with dopant

The luminescent properties of glasses synthesized in air atmosphere by conventional high temperature process were stud{ed. The emissions spectra of Eu^2 and Eu^3 were observed in BaO-La2O3-B2O3-Eu2O3 glasses.The results show that the broad emission peaks at 430 nm correspond to 5d→4f emission transition of Eu^2 , the sharp emission peaks at 592, 616, 650 and 250 nm correspond to 5^D0→1Fj(j=1--4) emission transition of Eu^3 ,respectively, which indicates that the BaO-La2O3a-B2O3-Eu2O3 glass can convert ultraviolet and green omponents of sunlight into blue and red light so as to increase the intensity of blue and red light, respectively. The luminescent in--tensity of Eu^2 increases with increasing the molar ratio of Tb^3 in BaO-La2O3-B2O3-Eu2O3a-Tb4O3 glasses, whereas the luminescent intensity of Eua^3 decreases. So the luminescent intensity of Eu(Ⅲ,Ⅱ) is influenced by Tb^3 .These phenomena can be explained by electron transfer mechanism; Eu^3 (4f6) Tb^3 (4f^8)→Eu^2 (4f′) Tb^4 (4f′). Taking advantage of the luminescent properties of BaO-La2O3-B2O3-Eu2O3 glasses, light-conversion glass for agriculture can be produced.     

有机物对聚酰胺复合纳滤膜硫酸钙结垢的影响

为揭示不同有机物形成的污染层对硫酸钙在纳滤膜面结垢行为的影响,选用牛血清蛋白(BSA)、腐殖酸(HA)、海藻酸(SA)作为典型有机污染物对聚酰胺复合纳滤膜进行污染,之后进行硫酸钙结垢实验.利用扫描电镜(SEM)观察不同污染条件下的硫酸钙形态,采用原子力显微镜(AFM)结合自制的硫酸钙探针测定不同污染条件下膜-硫酸钙及硫酸钙-硫酸钙之间的作用力.结果表明:与新膜结垢相比,有机物吸附在纳滤膜上改变了膜面性质,影响硫酸钙晶体成核机理.3种有机污染条件下硫酸钙结垢污染程度为SAHABSA.这是因为SA与Ca~(2+)的相互作用可缩短硫酸钙晶体成核时间,增大晶体尺寸,导致纳滤膜通量迅速下降;HA与Ca~(2+)络合增大了结垢层的厚度和密实度,导致纳滤膜通量衰减较大;而BSA与Ca~(2+)的结合能力较弱,加上其特殊的心形分子结构,导致该情况下硫酸钙结垢程度弱于其他两种有机物条件.     

Self-cleaning glass coated with Fe^3＋ -TiO2 thin film

The self-cleaning glass coated with Fe^3 -TiO2 photocatalytic thin film was prepared by sol-gel process from the system Ti(OC4H9),-NH(C2H4OH)2-C2H5OH-H2O containing FeCl3. The microstructure and properties of the film were studied using differential thermal analysis-thermogravimetry(DTA-TG), X-ray diffration (XRD) and scanning electron microscope(SEM). The transmittance of the self-cleaning glass was measured by using UV-Vis spectrometer. The effects of content of Fe^3 and the thickness of Fe^3 -TiO2 thin film on the photocatalytic ac-tivity were examined. The results show that the photocatalytic thin films are mainly composed of Fe3O4 and TiO2 particles within 10-100 nm. The appropriate amount of Fe^3 is effective for improving the photocatalytic activities of TiO2. The best photocatalytic activity is obtained when the molar ratio of Fe^3 to TiO2 is 0. 005 and the glass is coated with 9 layers.     

Study on the separation of Co2+ from Zn2+, Cd2+ by anion-exchange chromatography

The separation of Co²⁺ from Zn²⁺, Cd²⁺ by anion-exchange chromatography was discussed. The chromatographic column containing anion resin 201 × 7 which was saturated with a solution of ammonium chloride. The effects of the eluant acidity and eluant composition on the separation were investigated. The results indicate that this anion-exchange chromatography is suitable to the separation of Co²⁺ from Zn²⁺, Cd²⁺, and the condition of separation is simple and convenient. When the column is saturated with NH₄Cl solution (2.0 mol/L, pH=4.0), the separation can be completed effectively. Zn²⁺ and Cd²⁺ can also be separated when different eluants are used and the pure solution with high concentration of Zn²⁺, Cd²⁺ respectively can be obtained easily. Biography of the first author: WANG Xin-yan, born in Dec. 1975, majoring in extraction chemistry.     

Ferroelectric properties of Bi3.4Ho0.6Ti3O12 thin films prepared by sol-gel method

We have prepared the Ho-substituted bismuth titanate (Bi_3.4Ho_0.6Ti₃O₁₂, BHT) thin films on Pt/Ti/SiO₂/Si substrates using sol-gel method. The crystal structure and morphology of the films were characterized using X-ray diffraction and atomic force microscopy. The BHT film shows a single phase of Bi-layered Aurivillius structure and dense microstructure. The 2Pr and 2Ec of the 600-nm-thick BHT film were 38.4 μC/cm² and 376.1 kV/cm, respectively at applied electric field 500 kV/cm. The dielectric constant and dielectric loss are about 310 and 0.015 at a frequency of 1 MHz, respectively. The Pr value decreased to 93% of its pre-fatigue values after 4.46×10⁹ switching cycles at 1 MHz frenquency, and the BHT film shows good insulating behavior according to the test of leakage current. Supported by the Hubei Province Natural Science Foundation (Grant No. 2007ABA309)     

Mechanical characteristics of SiO<Subscript>2</Subscript> electrets

1μm SiO₂ layer was thermally grown on silicon wafer. Negative and positive charging of SiO₂ layer was performed by means of corona method at room temperature. By controlling grid voltage, we have obtained uniformly charged SiO₂ with surface potential from −500 to +200 V. With certain electric field, the electrostatic force between charged SiO₂ is investigated. Experimental results indicate that attraction not only exists between charged SiO₂ with different polarity, but also exists between charged SiO₂ with the same polarity, and no repulsion has been observed. The attractive force is related to both surface potential difference of charged SiO₂ and the uniformity of the electric field. Based on the experiment, the attractive force is supposed to be caused by polarization when two charged SiO₂ wafers are close.     

Preparation of LiFePO4 for lithium ion battery using Fe2P2O7 as precursor

In order to obtain a new precursor for LiFePO4, Fe2P2O7 with high purity was prepared through solid phase reaction at 650 ℃ using starting materials of FeC2O4 and NH4H2PO4 in an argon atmosphere. Using the as-prepared Fe2P2O7, Li2CO3 and glucose as raw materials, pure LiFePO4 and LiFePO4/C composite materials were respectively synthesized by solid state reaction at 700 ℃ in an argon atmosphere. X-ray diffractometry and scanning electron microscopy（SEM） were employed to characterize the as-prepared Fe2P2O7, LiFePO4 and LiFePO4/C. The as-prepared Fe2P2O7 crystallizes in the Cl space group and belongs to β-Fe2P2O7 for crystal phase. The particle size distribution of Fe2P2O7 observed by SEM is 0.4-3.0 μm. During the Li^＋ ion chemical intercalation, radical P2O7^4- is disrupted into two PO4^3- ions in the presence of O^2-, thus providing a feasible technique to dispose this poor dissolvable pyrophosphate. LiFePO4/C composite exhibits initial charge and discharge capacities of 154 and 132 mA·h/g, respectively.     

Study on the isothermal oxidation behavior in air of Ti3AlC2 sintered by hot pressing

The isothermal oxidation behavior at 900–1300°C for 20 h in air of bulk Ti₃AlC₂ with 2.8 wt% TiC sintered by means of hot pressing was investigated in the work. The isothermal oxidation behavior generally followed a parabolic rate law. The parabolic rate constants increased from 1.39×10⁻¹⁰ kg²·m⁻⁴·s⁻¹ at 900°C to 5.56×10⁻⁹ kg²·m⁻⁴·s⁻¹ at 1300°C. The calculated activation energy was 136.45 kJ/mol. It was demonstrated that Ti₃AlC₂ had excellent oxidation resistance due to the continuous, dense and adhesive protect scales consisted of a mass of α-Al₂O₃ and a little of TiO₂ and/or Al₂TiO₅. In principle, the oxide scale was grown by the inward diffusion of O²⁻ and the outward diffusion of Ti⁴⁺ and Al³⁺. The rapid outward diffusion of cations usually resulted in the formation of cracks, gaps, and holes.     

High temperature cyclic oxidation behavior of Y2O3-ZrO2 thermal barrier coatings irradiated by high-intensity pulsed ion beam

The high-temperature oxidation resistance behavior of 7% (mass fraction) Y₂O₃-ZrO₂ thermal barrier coatings (TBCs) irradiated by high-intensity pulsed ion beam (HIPIB) was investigated under the cyclic oxidation condition of 1 050 °C and 1 h. The columnar grains in the TBCs disappear after the HIPIB irradiation at ion current densities of 100–200 A/cm² and the irradiated surface becomes smooth and densified after remelting and ablation due to the HIPIB irradiation. The thermally grown oxide (TGO) layer thickness of the irradiated TBCs is smaller than that of the original TBCs. After 15 cycles, the mass gains of the original TBCs and those irradiated by ion current densities of 100 and 200 A/cm² due to the oxidation are found to be 0.8–0.9, 0.6–0.7, and 0.3–0.4 mg/cm², respectively. The inward diffusion of oxygen through the irradiated TBCs is significantly impeded by the densified top layer formed due to irradiation, which is the main reason for the improved overall oxidation resistance of the irradiated TBCs. Foundation item: Projects supported by The 2nd Stage of Brain Korea and Korea Research Foundation