纳米SiO2对混凝土性能影响的研究进展

混凝土是土木工程中使用最为广泛的材料之一，当今普通混凝土已无法完全满足超限建筑业的需求，因此高性能纳米SiO₂改性混凝土应运而生。为更好地了解纳米SiO₂改性混凝土的各项性能，对其和易性、凝结时间、抗压强度和抗氯离子渗透性的研究进行了回顾和总结。相关研究表明：在混凝土中添加适量纳米SiO₂，可有效提高混凝土的抗压强度，且对早期抗压强度的影响大于后期的影响，但纳米SiO₂含量过高会使混凝土的抗压强度下降；适量的纳米SiO₂，还可以有效填充混凝土中的孔隙，改善其微观结构，提高混凝土的抗氯离子渗透性；然而，混凝土中掺入纳米SiO₂，会缩短其初凝时间和终凝时间，同时也会大幅影响混凝土的和易性，使之不利于长距离输送，增加施工难度。     

粉煤灰的微观结构及其对工程性质的影响

<正>针对山东十里泉电厂库区粗、细粉煤灰做了偏光镜下分析,其主要矿物成分有碳粒、玻珠及少量莫来石、石英、磁铁等。粗灰含玻珠量较细灰低些,而碳粒含量前者较后者为高;经化学成分分析,其主要化学成分为SiO₂（55.71％）、AI。03（24.22％）、Fe₂O₃（9.28％）。通过电镜扫描分析发现,粉煤灰主要有四种微观结构类型,即玻珠结构、串珠结构、碳粒结     

几内亚博凯红土型铝土矿赋存特征及开采技术条件

博凯铝土矿床位于几内亚铝土矿矿集区——博韦盆地的西南部,属典型的红土型铝土矿矿床。为了使矿区勘查和开发工作更为经济、高效,本文详细研究了区内铝土矿床的赋矿岩系和矿体地质特征、矿床成因及开采技术条件。研究认为,该区赋矿岩系自上而下可划分为铁铝富集带、风化淋滤带和成矿母岩带,且成矿母岩为玄武岩和辉长岩。矿体空间形态多呈层状、似层状和透镜体状,平面形态呈不规则状、港湾状、锯齿状、短轴状、弧形状、带状等,其产状随地形起伏而变化。矿体中Al₂O₃含量变化均匀,与SiO₂含量呈弱负相关、与铝硅比（A/S）呈弱正相关,但Al₂O₃含量与Fe₂O₃含量呈明显的相互消长关系。矿区水文地质、工程地质和环境地质条件简单,适宜露天开采。     

黔南碳酸盐岩区水稻-根系土中硒、重金属的迁移与积累特征

为了查明黔南碳酸盐岩区水稻-根系中土硒、重金属的迁移与积累特征、水稻-土壤系统硒与重金属元素的相互关系,研究影响水稻对硒和重金属元素吸收的影响因素。本文通过对黔南独山—荔波一带稻作区水稻及对应根系土样品各项指标的采集分析,测试了水稻的Se、As、Cd、Cr、Pb、Hg含量与根系土的Se、As、Cd、Cr、Pb、Hg、SiO₂、Al₂O₃、Fe₂O₃、pH、SOM含量。结果表明根系土中Se、Cd、Cr、Pb、As呈伴生关系,稻米对Se和重金属的富集能力为：Cd＞Se＞Cr＞As。其中根系土中Al₂O₃、Fe₂O₃、SOM与硒、重金属为正相关关系,稻米K_Se与根系土中Se、Cr、Hg、Pb、As、Al₂O₃、Fe₂O₃、SOM呈极显著负相关关系,稻米中Se、Cd富集系数K_Cr、K_Cd与根系土中Se、Al₂O₃、TFe₂O₃、SOM为极显著负相关关系。研究区有生产富硒大米的条件,可通过适当的农艺措施改善土壤的理化条件,在降低重金属Cd、Cr的危害的同时提高水稻对Se的吸收富集,达到对重金属元素超标富硒耕地的科学开发利用。     

浙江省燕山期花岗岩化学元素丰度及特征

本研究从浙江省87个燕山期花岗岩体中系统采集了189件样品,采用等离子体光谱法等11种分析方法,获得了Ag、As、Au、B、Ba、Be、Bi、Br、Cd、Cl、Co、Cr、Cs、Cu、F、Ga、Ge、Hf、Hg、I、In、Li、Mn、Mo、N、Nb、Ni、P、Pb、Rb、S、Sb、Sc、Se、Sn、Sr、Ta、Te、Th、Ti、Tl、U、V、W、Zn、Zr、La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb、Lu、Y、SiO₂、Al₂O₃、TFe₂O₃、MgO、CaO、K₂O、Na₂O共68项主量、微量、稀土元素值以及TC、pH的实测数据,计算了扬子板块东缘与华南造山带燕山期花岗岩的化学元素丰度。岩石地球化学特征显示,这些花岗岩为高硅、富碱、弱过铝质的高钾钙碱性花岗岩,具有较强的Eu负异常,富集Rb、Th、U、K,亏损Sr、Ba、P、Ti、Nb、Ta等元素的特征,其普遍富铝和低MgO含量的岩石化学特征,指示它们的岩浆源区以壳源为主。     

河南西簧钒矿V2矿体地质特征及找矿标志

西簧矾矿区位于东秦岭造山带内,成矿区带属于秦岭造山带金银多金属成矿区,矿体呈层状产出于下寒武统水沟口组底部的炭质页岩段内,硅质岩为矿体底板,含炭灰岩为矿体顶板。矿体严格受下寒武统水沟口组控制,为典型的沉积型钒矿,矿石的化学成分主要有SiO₂、Al₂O₃、Na₂O、CaO、K₂O、MgO等,有用组分为V₂O₅,钒矿石属酸性矿石类型。寒武系下统水沟口组中下段地层为矿体的含矿地层,突出地表的硅质岩及山脊突然降低的部位为找矿的重要标志,此外,人为开采及地球化学特征也为矿床的找矿标志。该矿床在深部尚有待开发的潜力。     

热处理5Mg（OH）2·MgSO4·7H2O晶须对硫氧镁水泥抗压强度的影响

为了提高硫氧镁（MOS）水泥早期抗压强度，向MOS体系中掺入热处理后的5Mg（OH）₂·MgSO₄·7H₂O（517）晶须，分析了热处理前后的517晶须对MOS水泥凝结时间、抗压强度、物相组成、微观形貌和孔结构的影响. 结果表明：5Mg（OH）₂·MgSO₄·4H₂O和5Mg（OH）₂·MgSO₄在MOS浆体中均可吸附水分子形成517晶须，并在体系中发挥胶结-晶种协同作用，促进517晶须生长，这缩短了MOS水泥初、终凝时间，优化了MOS水泥孔结构，提高了MOS水泥早期和后期抗压强度； MOS体系中517晶须的掺量不宜超过4%，且经100、150 ℃热处理的517晶须较未经热处理的517晶须对MOS水泥性能优化效果更强.     

滇东南建水离子吸附型稀土矿边界品位与工业品位的确定方法

如何实现“规范”规定的边界品位与工业品位与矿山开发利用品位互相协调是评价离子吸附型稀土矿床资源量的重点和难点。本文对建水离子吸附型稀土矿床黏土层、全风化层、半风化层、弱风化层中全相稀土氧化物（TRE₂O₃）和离子相稀土氧化物（SRE₂O₃）变化规律进行研究。研究表明,建水稀土矿的SRE₂O₃受风化层位控制,黏土层较高→全风化层最高→半风化层较低→弱风化层最低,TRE₂O₃含量越高,则SRE₂O₃含量越高,越有利于形成离子吸附型稀土矿床（弱风化层除外）。建水稀土矿床的上矿层与下矿层SRE₂O₃含量、稀土配分及每吨稀土价格等具有显著差异,研究认为应采用“双指标”圈定矿体和估算资源量,即全风化层工业边界品位≥0.070%,最低工业品位≥0.100%;半风化层边界品位≥0.100%,最低工业品位≥0.150%。该方法在同类型稀土矿的资源量评价工作具有推广应用价值。     

TA/SiO2疏水涂层及其对混凝土抗侵蚀性能的影响

基于贻贝仿生原理，成功制备了单宁酸（TA）/SiO₂疏水涂层，通过设置22组工艺组合，综合水接触角、电通量和表面微观结构，得到了涂层的最优制备工艺.针对最优制备工艺涂层，通过自然扩散试验研究了其对混凝土抗离子渗透性能的影响，并采用磨耗和酸碱腐蚀试验研究了涂层稳定性.结果表明，TA/SiO₂疏水涂层表面具有丰富的微纳米结构，水接触角达148.1°，至少能够减少75.31%的离子渗透进入混凝土，且稳定性优良.     

东昆仑阿克苏河地区上三叠统鄂拉山组火山岩地球化学及构造环境研究

东昆仑阿克苏河地区发育上三叠统鄂拉山组（T₃e）火山岩,出露岩石以英安质岩屑晶屑凝灰岩、流纹质岩屑晶屑凝灰岩及英安岩为主,岩石SiO₂含量为65.65%~73.28%,Al₂O₃含量为11.31%~15.58%,K₂O+Na₂O含量为5.14%~6.05%,属高钾钙碱性系列。岩石LREE/HREE为8.64~11.75,属轻稀土富集型,微量元素Rb、Nb强富集,P、Sr明显亏损。在鄂拉山组英安岩中获得锆石U-Pb同位素年龄值为（227.7±3.1）Ma,形成时代为晚三叠世。综合分析认为鄂拉山组火山岩可能形成于南北向挤压为主的陆-陆后碰撞过程中地壳物质部分熔融的产物,属于后碰撞火山盆地的产物。     

Greywater treatment by UVC/H2O2

Greywater treatment by UVC/H₂O₂ was investigated with regard to the removal of chemical oxygen demand (COD). A COD reduction from 225 to 30 mg l⁻¹ (overall removal of 87%) was achieved after settling overnight and subsequent irradiation for 3 h with 10 mM H₂O₂. Most of the contaminants were removed by oxidation since only 13% COD was removed by settlement.The removal of COD in the greywater followed a second-order kinetic equation, r = 0.0637[COD][H₂O₂], up to 10 mM H₂O₂. A slightly enhanced COD removal was observed at the initial pH of 10 compared with pH 3 and 7. This was attributed to the dissociation of H₂O₂ to O₂H⁻. The treatment was not affected by total concentration of carbonate (c_T) of at least 3 mM, above which operation between pH 3 and 5 was essential. The initial biodegradability of the settled greywater (as BOD₅:COD) was 0.22. After 2 h UVC/H₂O₂ treatment, a higher proportion of the residual contaminants was biodegradable (BOD₅:COD = 0.41) which indicated its potential as a pre-treatment for a biological process.     

Ti/SnO2,Ti/SnO2-Sb2O3阳极电催化氧化酸性品红的试验研究

采用热氧化法制备了Ti/SnO2和Ti/SnO2-Sb2 O3电极,以酸性品红为研究对象,对两种电极材料进行了性能比较,考察槽电压、电流密度、电解质浓度对电催化氧化处理系统的影响.结果表明:热氧化法制备出的Ti/SnO2-Sb2 O3电极,其电催化性能明显优于Ti/SnO2电极;以Ti/SnO2-Sb2 O3为阳极,在酸性品红初始浓度为100 mg/L、电极间距为2.5 cm、电流密度为75mA/cm2、电解质浓度取12 g Na2SO4/L时,60 min后酸性品红的去除率达到了95.41％.     

含Al2O3的碲铌铅玻璃的性能研究

研究了含Al2O3的碲铌铅玻璃的性能并将之与不含Al2O3的玻璃的性能作了比较,结果表明,在碲铌铅玻璃中掺入Al2O3后,玻璃的密度和红外透过性能有所降低,玻璃转变温度升高,但此举并不改变其它组分对其性能变化趋势的影响。     

Production of H2O2 in hydrocarbon-O2-CF3Br systems

Hydrogen peroxide is produced when CF₃Br is added to flowing hydrocarbon-oxygen mixtures at approximately 350 °C. The H₂O₂ concentration is dependent on the amount of CF₃Br added to the hydrocarbon-oxygen mixture and maximizes at approximately 40 mole% CF₃Br.     

TiO2、Cu2O和氧化石墨烯复合氧化垃圾渗滤液效能

针对垃圾渗滤液中成分复杂的污染物,在自然光照条件下,使用TiO₂/氧化石墨烯、Cu₂O/氧化石墨烯和TiO₂/Cu₂O三种复合催化剂分别对垃圾渗滤液原液进行催化氧化。结果表明,3种复合催化剂中,TiO₂/氧化石墨烯复合催化剂对有机物的去除效果最好,当催化剂与渗滤液COD的质量比为0.7时为该催化剂的最佳投加量,最佳反应时间为2 h。在最佳试验条件下,对垃圾渗滤液原液进行催化氧化后,对COD的去除率达到92.57%,此时渗滤液出水COD为964.79mg/L,出水NH4⁺-N为2015.84 mg/L,BOD₅/COD值达到0.83。     

Degradation of 40 selected pharmaceuticals by UV/H2O2

The occurrence of pharmaceuticals in source waters is increasing. Although UV advanced oxidation is known to be an effective barrier against micropollutants, degradation rates are only available for limited amounts of pharmaceuticals. Therefore, the degradation of a large group of pharmaceuticals has been studied in this research for the UV/H₂O₂ process under different conditions, including pharmaceuticals of which the degradation by UV/H₂O₂ was never reported before (e.g., metformin, paroxetine, pindolol, sotalol, venlafaxine, etc.). Monochromatic low pressure (LP) and polychromatic medium pressure (MP) lamps were used for three different water matrices. In order to have well defined hydraulic conditions, all experiments were conducted in a collimated beam apparatus. Degradation rates for the pharmaceuticals were determined. For those compounds used in this research that are also reported in literature, measured degradation results are in good agreement with literature data. Pharmaceutical degradation for only photolysis with LP lamps is small, which is increased by using a MP lamp. Most of the pharmaceuticals are well removed when applying both UV (either LP or MP) and H₂O₂. However, differences in degradation rates between pharmaceuticals can be large. For example, ketoprofen, prednisolone, pindolol are very well removed by UV/H₂O₂, whereas metformin, cyclophosphamide, ifosfamide are very little removed by UV/H₂O₂.     

Summer fluxes of atmospheric greenhouse gases N2O, CH4 and CO2 from mangrove soil in South China

The atmospheric fluxes of N₂O, CH₄ and CO₂ from the soil in four mangrove swamps in Shenzhen and Hong Kong, South China were investigated in the summer of 2008. The fluxes ranged from 0.14 to 23.83 μmol m⁻² h⁻¹, 11.9 to 5168.6 μmol m⁻² h⁻¹ and 0.69 to 20.56 mmol m⁻² h⁻¹ for N₂O, CH₄ and CO₂, respectively. Futian mangrove swamp in Shenzhen had the highest greenhouse gas fluxes, followed by Mai Po mangrove in Hong Kong. Sha Kong Tsuen and Yung Shue O mangroves in Hong Kong had similar, low fluxes. The differences in both N₂O and CH₄ fluxes among different tidal positions, the landward, seaward and bare mudflat, in each swamp were insignificant. The N₂O and CO₂ fluxes were positively correlated with the soil organic carbon, total nitrogen, total phosphate, total iron and NH₄⁺-N contents, as well as the soil porosity. However, only soil NH₄⁺-N concentration had significant effects on CH₄ fluxes.     

Glyphosate degradation in water employing the H2O2/UVC process

Glyphosate is the organophosphate herbicide most widely used in the world. Any form of spill or discharge, even if unintentional, can be transferred to the water due to its high solubility. The combination of hydrogen peroxide and UV radiation could be a suitable option to decrease glyphosate concentration to acceptable limits. In this work, the effects of initial pH, hydrogen peroxide initial concentration, and incident radiation in glyphosate degradation were studied. The experimental device was a cylinder irradiated with two tubular, germicidal lamps. Conversion of glyphosate increases significantly from pH = 3-7. From this value on, the increase becomes much less noticeable. The reaction rate depends on the initial herbicide concentration and has an optimum plateau of a hydrogen peroxide to glyphosate molar concentration ratio between 7 and 19. The expected non linear dependence on the irradiation rate was observed. The identification of critical reaction intermediaries, and the quantification of the main end products were possible and it led to propose a plausible degradation path. The achieved quantification of the mineralization extent is a positive indicator for the possible application of a rather simple technology for an in situ solution for some of the problems derived from the intensive use of glyphosate.     

Electronic and mechanical responses of two-dimensional HfS2, HfSe2, ZrS2, and ZrSe2 from first-principles

During the last decade, numerous high-quality two-dimensional (2D) materials with semiconducting electronic character have been synthesized. Recent experimental study (Sci. Adv. 2017;3: e1700481) nevertheless confirmed that 2D ZrSe₂ and HfSe₂ are among the best candidates to replace the silicon in nanoelectronics owing to their moderate band-gap. We accordingly conducted first-principles calculations to explore the mechanical and electronic responses of not only ZrSe₂ and HfSe₂, but also ZrS₂ and HfS₂ in their single-layer and free-standing form. We particularly studied the possibility of engineering of the electronic properties of these attractive 2D materials using the biaxial or uniaxial tensile loadings. The comprehensive insight provided concerning the intrinsic properties of HfS₂, HfSe₂, ZrS₂, and ZrSe₂ can be useful for their future applications in nanodevices.     

Abrasion resistance of concrete containing SiO2 and Al2O3 nanoparticles in different curing media

In the present study, abrasion resistance and compressive strength of concrete specimens containing SiO₂ and Al₂O₃ nanoparticles which are cured in different curing media have been investigated. Portland cement was partially replaced by up to 2.0 wt.% SiO₂ and Al₂O₃ nanoparticles and mechanical properties of the produced specimens were measured. Increasing the nanoparticles content have found to increase the abrasion resistance of the specimens which were cured in water and saturated limewater, while this condition was not observed for compressive strength in both curing media. The enhancement of abrasion resistance was more for the specimens containing SiO₂ nanoparticles in both curing media. Since, abrasion resistance and compressive strength of the specimens follow a similar regime by increasing the nanoparticles content when they are cured in saturated limewater, some experimental relationships has been presented to correlate these two properties of concrete for this curing medium. On the whole, it has been concluded that the abrasion resistance of concrete does not only depend on the corresponding compressive strength.