纳米二氧化硅粒子在水性聚氨酯中分散性的研究

采用六甲基二硅胺烷(HMDS)对气相二氧化硅和硅溶胶中两种纳米二氧化硅（SiO2）粒子表面进行了化学接枝改性,然后将改性后的纳米SiO2粒子加入到水性聚氨酯(WPU)中,制备了一系列不同纳米SiO2粒子含量的共混改性WPU样品.通过FT-IR,SEM对纳米SiO2粒子共混改性WPU成膜物的织态结构进行了表征,并研究了SiO2/WPU共混乳液的成膜过程对成膜物织态结构的影响.结果表明,纳米SiO2粒子表面改性状态很大程度上决定了纳米SiO2粒子在共混成膜物中的分散状态和织态结构,具有一定表面两亲性的纳米Si     

H4SiW6Mo6O40／SiO2在H2O2催化氧化环己酮合成己二酸中的应用

采用溶胶一凝胶法制备了二氧化硅负载硅钨钼酸催化剂．以二氧化硅负载硅钨钼酸（H4SiW6M06040／SiO2）为催化剂,30％H202为氧源,催化氧化环己酮合成己二酸．探讨H4SiW6Mo6O40／SiO2对氧化反应的催化活性,较系统地研究了二氧化硅负载硅钨钼酸用量、反应温度、H。02用量、反应时间等因素对产物收率的影响．实验表明：H4SiW6Mo6O40／SiO2是合成己二酸的良好催化剂;在n（环日酮）：n（H2O2）：n（H4SiW6Mo6O40／SiO2）=100：198：0．124,反应温度为110℃,反应时间3．5h的最佳条件下,己二酸的收率可达86．7％．     

聚苯乙烯/二氧化硅（PS/SiO2）核壳型微球及SiO2空心球的可控制备及电镜观察

采用一种简单和低成本的方法制备单分散二氧化硅包覆聚苯乙烯（PS/SiO2）核壳型纳米复合微球.首先在氨水的醇溶液中,将聚乙烯吡咯烷酮（PVP）通过乳液聚合为聚苯乙烯核心,再在核心表面使正硅酸四乙酯（TEOS）水解缩聚,从而在PS微球表面包裹一层SiO2外壳.研究了氨水的用量对PS/SiO2纳米复合微球尺寸和形态的影响,利用透射电子显微镜（TEM）和扫描电子显微镜（SEM）对样品的超微结构与形貌进行表征,并探讨了其形成机理.     

原硅酸钙在铝酸钠溶液中的反应行为

以CaO和SiO2为原料合成2CaO·SiO2,通过测定SiO2浓度分析原硅酸钙反应活性的变化规律;基于质量守恒,计算渣中钠硅渣和钙硅渣分配比例.实验结果表明,在铝酸钠溶液体系中,反应时间的延长、氧化铝浓度的升高均有利于原硅酸钙的分解和溶出液中二氧化硅浓度的升高,溶出液中二氧化硅浓度最高增幅可分别达到9.97倍和11倍;同时,温度升高会显著促进原硅酸钙的分解与钙硅渣的生成,在136 ℃反应1 h后二氧化硅总反应率可达43.06%;在铝酸钠溶液中加入碳酸钠,可能因"协同效应"而促进原硅酸钙的分解;铝酸钠溶液苛性比变化对原硅酸钙的分解影响不明显.随着纯铝酸钠、碳酸钠和氢氧化钠溶液浓度的升高,原硅酸钙的Zeta电位绝对值增大,其原因可能是溶剂化层相应的Al(OH)4-,CO32-和OH-含量增多,有利于原硅酸钙的分解.     

氟硅酸钾容量法测定硅量

在当今社会飞速发展的进程当中,电子产业作为一种新型的产业,从20世纪中后期至今其发展尤为突出,而做为生产电子器材的基础物质—硅,其作用甚大。在自然界中硅主要以化合态（SiO2）形式存在,但SiO2直接转化生产出Si还比较困难,在国内目前大多采用先将石英矿（SiO2）在铁精粉（或氧化皮）在焦碳作为还原剂,然后在高温条件下为硅铁,而后从硅铁中提取硅的方法,因此工业中由石英矿生产硅铁其转化率的研究具有重要意义,准确地测定硅铁中硅含量更是其中不可缺少的一部分。     

真空碳热还原过程中二氧化硅的挥发行为

为了解在真空碳热还原过程中SiO2的还原特性以及还原过程中的主要影响因素,对二氧化硅的还原过程进行热力学分析,得出化学反应自由能和临界温度。在系统压力为2~200 Pa条件下,以分析纯SiO2和Fe2O3为原料,采用XRD,SEM,EDS和化学成分分析等手段,研究Fe/Si摩尔比、配碳量、反应时间、还原剂粒度和升温速率对硅的挥发率和还原反应速率的影响。实验结果表明:在100 Pa条件下,SiO2的临界反应温度为1 330~1 427 K。SiO2发生气化反应生成的SiO气体挥发至石墨冷凝系统歧化生成Si和SiO2,造成硅的损失,且有部分SiO气体和石墨反应生成SiC;增大Fe/Si摩尔比和配碳量以及减小还原剂粒度均降低了硅的挥发率,提高了SiO2还原反应速率;延长反应时间和提高升温速率增加了硅的挥发率。     

病虫害侵染对植物光合作用影响研究进展

随着人类商业运输和旅游活动扩大了病虫害的分布范围,气候变化增加了病虫害的爆发频率,造成了巨大的经济损失.光合作用是陆地生态系统吸收大气CO2的重要途径,也影响人类粮食生产.病虫害对植物光合作用的影响主要在两个方面:一方面通过采食植物的光和器官,减少了植物的光合能力.另一方面,病虫害侵染后植物的生理参数发生变化(如影响植物体中的叶绿素含量以及叶绿素a与b的比值、气孔导度和细胞内的CO2浓度),进而影响到植物的光合作用.因此,本文综述了近年来国内外关于病虫害对植物光合生理和光合作用的研究,并在此基础上对未来的研究方向进行了探讨和展望.     

介孔SBA-15/SiO2气凝胶硅-硅复合材料的制备和性能

以有序介孔二氧化硅颗粒SBA-15 为添加剂,利用酸碱两步法制备 SBA-15/SiO2气凝胶硅- 硅复合材料. 研究SBA-15添加量对气凝胶复合材料的形成过程和性能的影响,采用扫描电镜和氮气吸附-脱附对样品的结构进行表征,并测试其力学性能和热导率. 结果表明:少量有序介孔二氧化硅材料SBA-15的加入能大大缩短二氧化硅气凝胶形成时间,提高气凝胶复合材料的力学性能,并保持较低的热导率,而材料的比表面积仅略有下降.     

氮对土壤-植物系统中重金属的影响研究

氮肥可以影响土壤对重金属的吸附解吸,改变土壤重金属的形态,进而改变重金属在土壤中的活性,影响植物对其吸收、累积.结果表明,不同氮肥影响重金属吸附解吸的主要机制是土壤pH值的变化,水溶态重金属含量与pH值呈显著负相关.氮肥主要是通过影响土壤pH值的变化来影响土壤中重金属形态转化.不同氮肥形态及不同氮水平均对植物吸收积累重...     

天然水中氮素形态对菹草富集和降解DBP作用的影响

菹草是典型的沉水植物,在水体污染修复与生态重建中起重要作用．从海河干流和2个小型景观湖泊采集了4个氮素含量、氮素形态组成不同的水样,利用组培菹草研究了氮素形态对菹草富集和降解邻苯二甲酸二丁酯（DBP）作用的影响．结果表明：海河水中NO-3-N为氮的主要形态（59．4％～59．6％）,湖泊水中NH4~-N为主要形态（47．7％～6712％）;随着水中N03-N含量的增加,菹草对DBP的降解速率常数（0．8×10-2～11．7×10-2d-1）随之增大,植物富集系数（0．94～7．43L／kg）也相应增大．进一步研究了菹草对水中不同形态氮素的吸收作用及生理指标（叶绿素、可溶性蛋白和硝酸还原酶活性）变化发现,菹草主要吸收利用水中的N03-N,菹草的生理指标也主要受N03-N含量的影响;N03-N含量增加,菹草的生理活性增大．这说明N03-N含量较高的水中菹草的活性较高,菹草对DBP的富集和降解作用增强．     

A silicon transporter in rice

Silicon is beneficial to plant growth and helps plants to overcome abiotic and biotic stresses by preventing lodging (falling over) and increasing resistance to pests and diseases, as well as other stresses. Silicon is essential for high and sustainable production of rice, but the molecular mechanism responsible for the uptake of silicon is unknown. Here we describe the Low silicon rice 1 (Lsi1) gene, which controls silicon accumulation in rice, a typical silicon-accumulating plant. This gene belongs to the aquaporin family and is constitutively expressed in the roots. Lsi1 is localized on the plasma membrane of the distal side of both exodermis and endodermis cells, where casparian strips are located. Suppression of Lsi1 expression resulted in reduced silicon uptake. Furthermore, expression of Lsi1 in Xenopus oocytes showed transport activity for silicon only. The identification of a silicon transporter provides both an insight into the silicon uptake system in plants, and a new strategy for producing crops with high resistance to multiple stresses by genetic modification of the root's silicon uptake capacity.     

Progress of Si-based nanocrystalline luminescent materials

Si-based nanomaterials are some new photoelctronic and informational materials developed rapidly in recent years, and they have potential applications in the light emitting devices, e. g. Si light emitting diode, Si laser and integrated Si-based photoelectronics. Among them are nanoscale porous silicon (ps), Si nanocrystalline embedded SiO₂ (SiO_x, x < 2.0) matrices, Si nanoquantum dot and Si/SiO₂ superlattice, etc. At present, there are various indications that if these materials can achieve efficient and stable luminescence, which are photoluminescence (PL) and electroluminescence (EL), it is possible for them to lead to a new informational revolution in the early days of the 21st century. In this article, we will mainly review the progress of study on Si-based nanomaterials in the past ten years. The involved contents are the fabricated methods, structural characterizations and light emitting properties. Finally, we predicate the developed tendency of this field in the following ten years.     

改变镉生物有效性对植物吸收积累镉的影响

土壤镉的生物有效性受土壤成分和土壤环境条件的影响,有机质、pH、氧化还原电位等的变化都会影响土壤中镉由有机结合态和残渣态一不能被植物吸收积累的镉形态向可交换态、碳酸盐态、铁锰氧化态一容易被植物吸收利用的形态转化．一些土壤改良剂、有机物料、营养元素以及微生物都可以改变土壤镉的有效性,进一步影响植物积累镉的量,对植物生长及品质造成影响．由于有效态镉直接影响植物对镉的吸收积累,寻找有利途径以减少土壤有效态从而降低植物对镉的吸收显得非常关键．     

Effect of Fe metal on the growth of silicon oxide nanowires

Silicon oxide (SiO_x) nanowires are generally grown on Si substrate under the catalysis of Au in N₂ atmosphere at elevated temperatures. Because the price of Au metal is quite high, Fe metal is then used to replace a part of Au for catalyzing the growth of SiO_x nanowires. The results show that the Fe film can be used as the diffusion barrier of Au. SiO_x nanowires are grown on Au/Fe/Si substrate at 1030℃. Under the catalysis of Fe/Au, the efficiency for the growth of SiO_x nanowires is promoted.     

Occurrence mechanism of silicate and aluminosilicate minerals in Sarcheshmeh copper flotation concentrate

The Sarcheshmeh copper flotation circuit is producing 5×104 t copper concentrate per month with an averaging grade of 28% Cu in rougher, cleaner and recleaner stages. In recent years, with the increase in the open pit depth, the content of aluminosilicate minerals increased in plant feed and subsequently in flotation concentrate. It can motivate some problems, such as unwanted consumption of reagents, decreasing of the copper concentrate grade, increasing of Al₂O₃ and SiO₂ in the copper concentrate, and needing a higher temperature in the smelting process. The evaluation of the composite samples related to the most critical working period of the plant shows that quartz, illite, biotite, chlorite, orthoclase, albeit, muscovite, and kaolinite are the major Al₂O₃ and SiO₂ beating minerals that accompany chalcopyrite, chalcocite, and covellite minerals in the plant feed. The severe alteration to clay minerals was a general rule in all thin sections that were prepared from the plant feed. Sieve analysis of the flotation concentrate shows that Al₂O₃ and SiO₂ bearing minerals in the flotation concentrate can be decreased by promoting the size reduction from 53 to 38 μm. Interlocking of the Al₂O₃ and SiO₂ bearing minerals with chalcopyrite and chalcocite is the occurrence mechanism of silicate and aluminosilicate minerals in the flotation concentrate. The dispersed form of interlocking is predominant.     

TiO2/SiO2复合光催化剂制备工艺参数优化及其表征

先以无机钛盐、硅酸盐为原料制取聚合硅酸硫酸钛,再通过液相水解法制得TiO2/SiO2复合光催化剂,并用SEM、XRD、BET和甲基橙脱色率对复合光催化剂进行表征。结果表明,TiO2/SiO2复合光催化剂制备优化工艺参数为:Ti(SO4)2作钛源、Ti/Si摩尔比为12∶1、水解反应pH值为6、煅烧温度为650℃,以此条件制备的复合光催化剂对甲基橙脱色率可达98.6%以上;TiO2/SiO2复合光催化剂为一种分散均匀的纳米级球形颗粒,其成分为以锐钛矿为主的TiO2,SiO2的复合有效抑制了TiO2晶粒的生长,同时提高了TiO2的热稳定性。     

Distribution characteristics of soil organic matter and total nitrogen on the Yajiageng vertical belt,Gongga Mountain around the Dadu River banks

Distribution characteristics of soil organic matter（SOM） and total nitrogen（TN） were studied in different plant communities of the Yajiageng vertical belt in Gongga Mountain around the Dadu River banks. The results show： （1） the contents of SOM and TN of the plant communities gradually decreased with the following order： subalpine coniferous forest （3 027 m）, subalpine meadow （3 873 m）, coniferous broadleaved mixed forest（2 737 m）, subalpine shrub（3 565 m） and treeline（3 564 m）. （2） With soil profile depth increasing, the contents of SOM and TN gradually decreased. For different vegetation types, the contents of SOM and TN in sub-alpine coniferous forest were higher than that of other vegetational types. （3）The ratio of the content of carbon to the content of total nitrogen （Cc/CTN）WaS 13.5-27.6, which was relatively lower than the appropriate Cc/CTN of 25-30, and indicated that the soil in favor of the organic matter decomposed and nutrients released. Cc/CTN in the soil had no correlation with sea level altitude. However, its distribution in the soil x, aried with different vegetation types. （4） Nitrogen in SOM existed mainly in the form of organic nitrogen, and Cc/CTN in the soil was not obvious correlated with SOM and TN.     

Effect of elevated CO2 on CH4 emission

Global CH₄ emission may increase under CO₂ enrichment condition, which is projected for the future. CO₂ enrichment could affect CH₄ emission in two ways: (i) Photosynthesis of plants that also include plants in rice paddies and natural wetlands will be stimulated under CO₂ enrichment condition. CH₄ emission rate may be increased due to the accumulation of more plant biomass, root exudes and soil organic matters. (ii) Combined with other global warming forces, CO₂ enrichment may bring a change of atmospheric temperature and precipitation around the world. CH₄ emission will also be changed with the variation of the area and distribution of rice paddies and natural wetlands.     

Preparation and kinetic analysis of Li4SiO4 sorbents with different silicon sources for high temperature CO2 capture

Using diatomite and analytical pure SiO2 as silicon sources,Li4SiO4 sorbents for high temperature CO2 capture were prepared through solid-state reaction method.Phase composition was analyzed by X-ray diffraction,and the CO2 absorption capacity and absorptoin-desorption performance were studied by the simultaneous thermal thermogravimetric analyzer(TG-DSC).The results showed that silicon source had an important influence on CO2 absorption properties.The kinetic parameters for the chemisorption and diffusion processes were obtained by the isothermal study for different silicon sources.The results showed that the activation energies for these two processes were estimated to be 105.427 and 35.928 kJ/mol for the sample with analytical pure SiO2(AS).While for the sample with diatomite(DS),the activation energies for these two processes were estimated to be 78.500 and 20.439 kJ/mol,respectively.