CaCO_3结垢过程控制机理分析

为了掌握结垢过程的控制机理,通过分析CaCO3在换热面上的结垢过程,得到了控制结垢过程的阻力关系式。计算结果表明流速越大,过饱和度越小,结垢过程越易为表面反应所控制;流速越小,过饱和度越大,结垢过程越易为对流传质所控制,且往往发生在液壁温差较大,壁温较高的情况下。垢层生长过程中,在恒壁温条件下,对流传质与表面反应共同控制的结垢过程可能转变为只由表面反应控制结垢过程;在恒热流条件下,控制机理没有变化。

微波法合成红色荧光粉CaCO_3:Eu^(3+)

采用微波法合成了红色荧光粉CaCO_3:Eu^(3+)。通过SEM,XRD和PL-PLE光谱等对样品的性能进行了表征和分析。同时,研究了微波功率对样品发光性能的影响。结果表明:样品在不同功率下会生成球霰石型的花片状、方解石型的立方体和文石型的针状等不同晶型的碳酸钙,颗粒的分散性好。波谱分析说明,掺杂Eu^(3+)作为发光中心进入到CaCO_3晶格中,其激发光谱主要由200～300 nm的Eu^(3+)—O^(2-)电荷迁移跃迁形成,属于宽带激发,在319,395,465,535 nm等处有窄的激发峰出现。在发射光谱中,由于磁偶极跃迁~5D_0→~7F_1受到不同晶体场的作用而分裂为593和589 nm两个峰,最强的发射峰为614 nm,对应于Eu^(3+)的电偶极跃迁~5D_0→~7F_2,属于纯正的红色发光。此外,随着微波功率的提高,基质的晶型逐渐由花片状的球霰石向针状的文石型过渡,样品的红色发射强度也逐渐增强。

中国北方四剖面CaCO_3含量变化及其反映的古降水量

中国北方自西向东的4个剖面,各地层CaCO3的含量呈现逐渐减少的规律。科尔沁剖面和延长剖面、西宁盘子山剖面CaCO3含量曲线表现出的特征为:在每一个古土壤单元的下部一定深度内CaCO3曲线都表现为一个明显的峰;新疆塔勒德剖面的各古土壤的CaCO3含量表现为表层比中、下部要高。利用CaCO3淀积深度恢复出来的部分区域的古降水量显示,末次间冰期期间盘子山剖面的古降水量大为352mm,延长剖面和科尔沁剖面的古降水量大约为500～550mm;末次冰期的间冰阶阶段科尔沁剖面的古降水量大致为320～360mm;延长剖面古降水量大约为443mm;全新世以来盘子山剖面的古降水量大约为306mm,延长剖面和科尔沁剖面的古降水量大约为320～380mm。这些数据可为半定量恢复地质历史时期古环境状况提供依据。

纳米CaCO_3对PE–HD/CF复合材料力学性能的影响

针对高密度聚乙烯(PE–HD)/碳纤维(CF)二元复合材料随CF含量的增加,拉伸强度和弯曲强度增大、冲击强度却逐渐下降的情况,在二元体系中添加纳米CaCO3制得PE–HD/CF/CaCO3三元复合材料,对比分析了两种复合材料的力学性能,并采用扫描电子显微镜对三元复合材料的冲击断面进行观察。结果表明,纳米CaCO3的加入使得三元复合材料的拉伸强度略有降低,但弯曲强度和冲击强度在一定范围内增大;当纳米CaCO3含量为10份时,复合材料的综合力学性能最佳。

CaCO_3改性对UV固化木器涂料性能的影响

在木器漆应用领域,UV涂料与传统涂料相比以明显优势,逐渐成为当下主流,同时也引领着未来的发展。但UV也有其缺陷,笔者着重于利用CaCO_3对木地板UV涂料进行改性,并对其力学性能和光学性能进行测试研究,旨在寻找一种具有较高性能的木质地板改性UV涂料。

改性方法对PP/纳米CaCO_3复合材料性能的影响

分别采用熔融共混法和原位聚合法制备了聚丙烯 (PP) /纳米CaCO3 复合材料 ,比较了用两种方法制备的PP/纳米CaCO3 复合材料的力学性能及纳米CaCO3 的分散状况。结果表明 :当纳米CaCO3 质量分数分别为 5 %和 0 73 %时 ,两种方法制备的复合材料的冲击强度达到最大值 ,分别为纯PP的 2 2倍和 2倍 ;两种方法中CaCO3 均可达到纳米级分散 ;原位聚合法制备的复合材料的韧性断裂比熔融共混法更为明显 ,且综合性能与共混法相近 ,并有工艺上的优越性。

有机膦酸防垢剂对CaCO_3溶液动电性质的影响

为了探讨有机膦酸防垢剂的防垢机理,将等量的CaCl2溶液和Na2CO3溶液混合,适时测定了加入不同有机膦酸防垢剂时CaCO3生成过程中的Zeta电位,并与加入EDTA的实验进行了比较.结果表明,CaCO3表面带有负电,反应刚开始时Zeta电位变化较快,30 min后趋于稳定;生成过程中加入有机膦酸防垢剂会使碳酸钙表面Zeta电位绝对值变小.最后,从配位化学及胶体化学的角度对实验结果进行了分析,认为加防垢剂后Zeta电位的变化对防垢作用有利.

PP/CaCO_3复合过滤板失效分析

介绍PP/CaCO3 复合过滤板在使用过程中存在的质量问题 ,如表面黄斑、熔接痕、小凸台成型不好、表层剥离、板内有气孔及易脆断等 ,着重从成型工艺和刚性填料对过滤板相结构、性能的影响上来分析这些问题 。

CaCO_3在CaCO_3-CuO和CaCO_3-Bi_2O_3体系中的分解动力学

用恒温热重法研究了CaCO_3在CaCO_3-CuO和CaCO_3-Bi_2O_3体系中的分解动力学,求出CaCO_3的分解方程式。实验结果表明:在上述两体系中,CaCO_3的表观分解活化能均为120 kJ·mol^(-I),并初步分析了CaCO_3的分解机理。

Effects of Soil Texture and CaCO_3 on Turnover of Organic Material in Chao Soils

Decomposition experiments of 14C-labelled sickle alfalfa in chao soils of different texture and these soils after removal of CaCO3 were carried out under field and laboratory conditions respectively. The amount of residual 14C in, or 14CO2 evolved from, the soils at intervals after the beginning of decomposition were measured and the distribution of native and labelled C between particle size fractions isolated from these soils was edtermined. Results showed that contents of both labelled (14C) and non-labelled (12C) carbon decreased with increasing particle size. The enrichment factor for 14C was higher than that for 12C in the clay fraction, the reverse being true for the silt enrichment factors. The effect of soil texture on the decomposition of plant material could not be observed in chao soils when the clay content was lower than 270g kg-1, while it became obvious once CaCO3 was removed from these soils. The decomposition rate of plant material in the soil from which the native CaCO3 was removed was correlated significantly to both the clay content of the soil and the application rate of CaCO3. A preliminary correction equation describing the effect of clay and CaCO3 on the decomposition of organic material in chao soil was derived from the results obtained.

Scale-up of biomass conversion using 1-ethyl-3-methylimidazolium acetate as the solvent

This scale-up study demonstrated the feasibility of an ionic liquid(IL)pretreatment process at 40 kg scale,using the IL 1-ethyl-3-methylimidazolium acetate([C2C1Im][OAc])as the solvent.The pretreatment was followed by enzymatic hydrolysis through which the process efficiency for biomass conversion to monomeric sugars was determined.The results show that 43 wt%of switchgrass was dissolved in IL after 2 h of pretreatment at 160℃ with 15 wt%solid loading.A 120 h enzymatic hydrolysis of the pretreated switchgrass results in 96%glucan and 98%xylan conversion.[C2C1Im][OAc]pretreatment has been successfully scaled up to 40 kg with improved sugar titers and yields relative to bench scale(6 kg).The mass flow of the overall process was established and the major scale-up challenges of the process were identified.

Large-Scale Synthesis of Porous Bi2O3 with Oxygen Vacancies for Efficient Photodegradation of Methylene Blue

Photocatalytic degradation of organic pollutants has become a hot research topic because of its low energy consumption and environmental-friendly characteristics.Bismuth oxide(Bi2O3)nanocrystals with a bandgap ranging from 2.0 eV to 2.8 eV have attracted increasing attention due to high activity of photodegradation of organic pollutants by utilizing visible light.Though several methods have been developed to prepare Bi2O3-based semiconductor materials over recent years,it is still difficult to prepare highly active Bi2O3 catalysts in large scale with a simple method.Therefore,developing simple and feasible methods for the preparation of Bi2O3 nanocrystals in large scale is important for the potential applications in industrial wastewater treatment.In this work,we successfully prepared porous Bi2O3 in large scale via etching commercial Bi Sn powders,followed by thermal treatment with air.The acquired porous Bi2O3 exhibited excellent activity and stability in photocatalytic degradation of methylene blue.Further investigation of the mechanism witnessed that the suitable band structure of porous Bi2O3 allowed the generation of reactive oxygen species,such as O2^-·and·OH,which effectively degraded MB.

Influence of Cr_2O_3-Al_2O_3 Composite Oxide Scale on Oxidation Resistance of ZG40Cr24

Test alloys ZG40Cr24 with alloying of 3 wt% aluminium were cast by intermediate frequency induction furnace. The oxidation resistance of test alloys at 1 000 ℃ for 500 hours was examined according to oxidation weight gain method. The scale morphology and composition were studied using scanning electron microscope （SEM） and X-ray diffraction （XRD） respectively. By energy dispersive spectroscopy （EDS） studies, a kind of composite oxide scale compounded highly by Cr2O3, Al2O3 and spinel MCr2O4 in molecule scale came into being at high temperature. With flat and compact structure, fine and even grains, such composite scale granted complete oxidation resistance to alloy ZG40Cr24. The oxidation resistance mechanism was studied deeply in electrochemistry corrosion. The P＋N semiconductor composite scale composed plenty of inner PN junctions, of which the unilateral conductive and the out-of-order arrangement endowed itself insulating in all directions. The positive and negative charges in scale could not move, and the mobile number and transferring rate of them both dropped enormously, as a result, the oxidation rate of the matrix metal was cut down greatly. So the composite scale presented excellent oxidation resistance.

P123/Mg^(2+)水溶液中CaCO_3结晶及形貌的调控研究

在三嵌段共聚物P123与Mg2+的混合水溶液中,通过控制反应条件对CaCO3的微粒形貌进行调控。探讨了Mg2+浓度、反应时间、反应温度及P123浓度对CaCO3粒子形貌和晶型的影响。采用扫描电子显微镜(SEM)、X射线粉末衍射仪(XRD)对合成样品进行了表征。结果表明,Mg2+与Ca2+的质量比对CaCO3粒子形貌和晶型具有重要的影响。

Nano CaCO_3 : An Unique Condensation Agent for the Preparation of Monosubstituted Calix[4]arene by Ring-opening Reaction

Nano CaCO3 was used as a condensation agent in the ring-opening reaction of p-tert-butylcalix[4]arene with epichlorohydrin to afford 5,11,17,23-tetra-tert-butyl-26,27,28-trihyd- roxy-25-(1-chloro-2-hydroxy-3-propyl)calix[4]arene regioselectively in 52% yield. The yield was less than 2% by using normal CaCO3 instead of nano one under the same conditions.

THE EFFECT OF MATRIX TOUGHNESS ON THE BRITTLE-DUCTILE TRANSITION OF HDPE/CaCO_3 BLENDS

The effects of HDPE matrix toughness on the brittle-ductile transition of HDPE/CaCO_3blends are investigated. Not all HDPE can be toughened by CaCO_3 particles. The ability of thematrix to yield plays a fundamental role in determing whether HDPE can be toughened or not.There exists a critical matrix toughness (I_(sc)≈45J/m) below which HDPE can not be toughenedobservably by CaCO_3 particle at given average size, and above which the critical matrix ligamentthickness (τ_?) is proportional to matrix impact strength.

Effect of Hot-Rolled Oxide Scale on Dry/ Wet Cyclic Corrosion Behavior of Q370qNH Steel in Simulated Industrial Atmosphere Environment

The corrosion behavior of Q370qNH steel in the presence and absence of hot-rolled oxide scale in simulated industrial atmospheric environment was studied by dry/wet cycle accelerated corrosion experiments.The experimental results show that the corrosion type of bare steel is uneven overall corrosion and large size pitting corrosion in small areas;that of oxide scale sample is local dissolution corrosion and small size pitting corrosion in large areas,and corrosion rate is much smaller than that of bare steel.The corrosion products of both steels are composed ofα-FeOOH,γ-FeOOH,Fe_(2)O_(3),and Fe_(3)O_(4),but the formation mechanism is different.The bare steel generatesα-FeOOH andγ-FeOOH through“acid regeneration cycle mechanism”;the oxide scale sample generates hydroxides mainly through the gradual dissolution of the oxide film,and then through“the acid regeneration cycle mechanism”.With the extension of corrosion time,the electrochemical stability of the sample with oxide scale increases,but the change of tafel curve of bare steel sample is not obvious.In simulated industrial atmosphere,the existence of hot-rolled oxide scale can facilitate the formation of dense rust layer on the surface of Q370qNH steel,which is more protective than bare steel.

Study on the influence of La_2O_3 on Stress in α－Al_2O_3 Scale by a Novel Two－side Oxidation Bending Method

The influence of La2O3 on stress in the scales of NiAl-type coatings were studied by a novel two-side oxidation bending method during isothermal and anisothermal oxidation. The results indicate that. differences of thermal expansion coefficients of the coatings applied on the two sides of the bending sample can be analyzed by detecting the deflection behaviour of the sample, the growth stress in La2O3 added x-Al2O3 coating is reduced by some 350 kgf/ mm2 for 50 h isothermal oxidation at 900℃ . and the mechanism is that the grain size of scale is reduced due to addition of La2O3 and its plasticity is increased, the magnitude of thermal expansion coefficients of coatings influences the thermal stress developing during cooling. Stress in the scale on simple NiAl is relieved mainly in way of cracking and spalling of the scale at temperature 400￣ 600℃ ,but that on La2O3-added coating is relieved slightly due to good integrity and adherence of the scale.

3D Model Construction and Ecological Environment Investigation on a Regional Scale Using UAV Remote Sensing

The acquisition of digital regional-scale information and ecological environmental data has high requirements for structural texture,spatial res-olution,and multiple parameter categories,which is challenging to achieve using satellite remote sensing.Considering the convenient,facilitative,and flexible characteristics of UAV(unmanned air vehicle)remote sensing tech-nology,this study selects a campus as a typical research area and uses the Pegasus D2000 equipped with a D-MSPC2000 multi-spectral camera and a CAM3000 aerial camera to acquire oblique images and multi-spectral data.Using professional software,including Context Capture,ENVI,and ArcGIS,a 3D(three-dimensional)campus model,a digital orthophoto map,and multi-spectral remote sensing map drawing are realized,and the geometric accuracy of typical feature selection is evaluated.Based on a quantitative remote sensing model,the campus ecological environment assessment is performed from the perspectives of vegetation and water body.The results presented in this study could be of great significance to the scientific management and sustainable development of regional natural resources.

3-D Modelling of the Confederation Bridge Using Data of Full Scale Tests

Long-span bridges are special structures that require advanced analysis techniques to examine their performance. This paper presents a procedure developed to model the Confederation Bridge using 3-D beam elements. The model was validated using the data collected before the opening of the bridge to the public. The bridge was instrumented to conduct fullscale static and dynamic tests. The static tests were to measure the deflection of the bridge pier while the dynamic tests to measure the free vibrations of the pier due to a sudden release of the static load. Confederation Bridge is one of the longest reinforced concrete bridges in the world. It connects the province of Prince Edward Island and the province of New Brunswick in Canada. Due to its strategic location and vital role as a transportation link between these two provinces, it was designed using higher safety factors than those for typical highway bridges. After validating the present numerical model, a procedure was developed to evaluate the performance of similar bridges subjected to traffic and seismic loads. It is of interest to note that the foundation stiffness and the modulus of elasticity of the concrete have significant effects on the structural responses of the Confederation Bridge.