配位负载法制备CoS2/AOCF复合材料及其电催化析氢性能

以硫酸钴、硫代硫酸钠、硫和偕胺肟化聚丙烯腈纤维(AOCF)为原料,采用配位负载法制备了CoS2/AOCF复合材料,采用SEM、XRD、TEM、XPS和BET对CoS2/AOCF进行物相分析和形貌表征,并对CoS2/AOCF复合材料的电催化析氢性能进行了测试.结果表明,AOCF链上—OH、—NH2与Co(Ⅱ)的配位作用极大地提高了活性组分CoS2的比表面积,改变了活性组分的晶体结构,增大了有效活性位点的数量.CoS2/AOCF在10 mA/cm2的电流密度下过电势为92 mV,Tafel斜率仅为43 mV/dec,具有良好的析氢稳定性,展现了优异的电化学性能.     

纳米氧化银/偕胺肟复合纤维的制备及抑菌性能研究

以聚丙烯腈纤维(PAN)为原料,化学改性制得含有偕胺肟基团的螯合纤维(AOCF),使其与纳米氧化银反应,制得纳米氧化银/偕胺肟复合纤维(nano-Ag2O/AOCF)。运用扫描电镜(SEM)及X-衍射能谱仪(EDX)对样品进行了相应的表征,并研究纤维对大肠杆菌和枯草芽孢杆菌的抑菌性能。结果表明,在改性纤维表面生成了分散均匀的纳米氧化银,纳米氧化银/偕胺肟复合纤维对大肠杆菌和枯草芽孢杆菌具有良好的抑菌性能。     

纳米硫化镉/偕胺肟复合纤维的制备及抗菌性能研究

以聚丙烯腈纤维(PAN)为原料,改性制得含有偕胺肟基团的螯合纤维(AOCF),使其与纳米硫化镉反应,制得纳米硫化镉/偕胺肟复合纤维(nano-CdS/AOCF)。运用扫描电镜(SEM)及X-衍射能谱仪(EDX)对样品进行了表征,并研究了纤维对大肠杆菌和枯草芽孢杆菌的抗菌性能。结果表明,在纤维表面生成了分散均匀的纳米硫化镉,纳米硫化镉/偕胺肟复合纤维具有良好的抗菌性能。     

纳米硫化银/偕胺肟复合纤维的制备及表征

将聚丙烯腈纤维化学改性制得含有偕胺肟基团的螯合纤维(AOCF),AOCF经硝酸银溶液处理后形成AOCF-Ag(Ⅰ)配合物纤维,再分别与Na2S、Na2S2O3、硫脲等硫源反应,制得纳米硫化银/偕胺肟复合纤维(nano-Ag2S/AOCF).探讨了硫源对制备nano-Ag2S/AOCF的影响;运用红外光谱仪及扫描电镜对纤...     

纳米硫化汞/偕胺肟复合纤维的制备及抑菌性能研究

以聚丙烯腈纤维(PAN)为原料,改性制得含有偕胺肟基团的螯合纤维(AOCF),使其与纳米硫化汞反应,制得纳米硫化汞/偕胺肟复合纤维(nano-HgS/AOCF).运用扫描电镜(SEM)及X-衍射能谱仪(EDX)对样品进行了表征,并研究了纤维对大肠杆菌和枯草芽孢杆菌的抑菌性能.结果表明,偕胺肟纤维表面生成了分散均匀的纳米硫化汞,0.15g的nano-HgS/AOCF对大肠杆菌的抑菌能力与5.0万单位的青霉素相当,而对枯草芽孢杆菌的抑菌能力与2.0万单位的青霉素相当.     

纳米二硫化钴/偕胺肟改性聚丙烯腈纤维的制备及抑菌性能研究

以聚丙烯腈纤维(PAN)为原料,化学改性制得含有偕胺肟基团的螯合纤维(AOCF),使其与纳米二硫化钴反应,制得纳米二硫化钴/偕胺肟改性聚丙烯腈纤维(nano-CoS_2/AOCF)。运用红外光谱仪(IR)、扫描电镜(SEM)及X衍射能谱仪(EDX)对样品进行了表征,并研究了纤维对大肠杆菌和金黄色葡萄球菌的抑菌性能。结果表明,在纤维表面生成了分散均匀的纳米二硫化钴,0.08 g的nano-CoS_2/AOCF对大肠杆菌的抑菌能力与6 000 U的青霉素相当,而对金黄色葡萄球菌的抑菌能力与4 000 U的青霉素相当。     

纳米钼酸铋/偕胺肟纤维光催化剂的制备及性能研究

以Bi(NO3)3和Na2Mo O4为原料,偕胺肟纤维作为配体,采用液相法合成钼酸铋/偕胺肟纤维(Bi2Mo O6/AOCF),通过X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、能谱(EDS)对样品进行了表征分析。结果显示,颗粒状的Bi2Mo O6均匀分布在纤维表面,并以配位键的形式与纤维结合。以罗丹明B(Rh B)为模拟污染物来考察Bi2Mo O6/AOCF的光催化活性,实验表明,Bi2Mo O6/AOCF有着很好的光催化活性,并且在酸性条件下的催化活性更好。催化剂对活性黄、亚甲基蓝和甲基橙也表现出较好的光催化活性,且重复使用5次后对Rh B的降解率仍可以达到91.4%。光催化反应过程符合一级反应动力学。     

纳米硫化镍/偕胺肟复合纤维的制备及性能研究

以含偕胺肟基团的螯合纤维(AOCF)为原料,使其与纳米硫化镍反应,制得纳米硫化镍/偕胺肟复合纤维(nano-NiS_2/AOCF)。运用扫描电镜(SEM)及X-衍射能谱仪(EDX)对样品进行了相应的表征,并研究纤维对大肠杆菌和枯草芽孢杆菌的抗菌性能。结果表明,在纤维表面生成了分散均匀的纳米硫化镍,0.18g的nano-NiS_2/AOCF对大肠杆菌的抗菌能力与0.8万单位的青霉素相当,而0.10g的nano-NiS_2/AOCF对枯草芽孢杆菌的抗菌能力与0.5万单位的青霉素相当。     

偕胺肟基聚丙烯腈螯合纤维中金属离子含量与其力学性能关系的研究

以聚丙烯腈(PAN)为原料纤维,与羟胺溶液反应,制得偕胺肟纤维(AOCF)。以偕胺肟纤维与金属离子Cu(Ⅱ)、Co(Ⅱ)、Hg(Ⅱ)、Zn(Ⅱ)、Cd(Ⅱ)反应生成一系列的金属螯合纤维(M-AOCF),测定了各M-AOCF的单纤强力。结果显示:制得的金属螯合纤维,随着金属离子含量的增加,纤维断裂强度逐渐降低;且当含量较低时,纤维断裂强度大于原AOCF;当含量超过一定值时,断裂强度小于原AOCF。     

纳米硫化铅/偕胺肟复合纤维的制备与表征

利用聚丙烯腈(PAN)纤维为原料,经羟胺改性后得到具有螯合性能的偕胺肟纤维(AOCF),然后将AOCF浸渍于硫化铅(PbS)纳米溶胶中,利用物理吸附以及微粒表面与AOCF中的羟基和胺基的键合作用,合成了纳米PbS/AOCF复合纤维。分别对产物进行TEM、XRD、IR及AFM表征,结果表明:纤维上纳米PbS的粒径大小平均为30nm,呈规则的纳米球形,且分散性较好,均匀分布在纤维的表面。     

Study of the hydration of CaO powder by gas–solid reaction

Hydration of CaO powders by reaction with water vapor has been studied in isothermal and isobaric conditions. Experimental tests were performed within the temperature range of 70 °C–420 °C and with a water vapor pressure from 5 to 160 hPa by means of a thermogravimetric device. Two powders, exhibiting slight differences in their physical properties, were studied. However, for one of the powders and under some temperature and pressure conditions, the reaction is not complete. The difference of behavior between both CaO powders was interpreted by considering the effect of the morphological properties on the mechanism of growth of Ca(OH)₂.     

The influence of water removal techniques on the composition and microstructure of hardened cement pastes

The removal of water from hardened cement paste for analysis or to arrest ongoing hydration has been reported to affect the composition of hydrated phases and microstructure. The effect that arresting the hydration of hardened cement paste by replacing the pore water with acetone before drying, and by removing the water by freeze, vacuum and oven drying has on the hardened cement paste has been investigated. Two pastes were studied, a cemented iron hydroxide floc where a high proportion of ordinary Portland cement (OPC) had been replaced by pulverised fuel ash, and a pure hydrated OPC. The results showed that none of the water removal techniques caused any major deterioration in the composition and microstructure of the hardened cement pastes studied, but the pores appeared better preserved after arresting hydration using acetone quenching. Freeze drying appeared to cause more cracking of the microstructure than the other water removal techniques.     

Quantification of Phospholipids Classes in Human Milk

Phospholipids are integral constituents of the milk fat globule membranes and they play a central role in infants’ immune and inflammatory responses. A methodology employing liquid chromatography coupled with evaporative light scattering detector has been optimized and validated to quantify the major phospholipids classes in human milk. Phospholipids were extracted using chloroform and methanol and separated on C18 column. Repeatability, intermediate reproducibility, and recovery values were calculated and a large sample set of human milk analyzed. In human milk, phospholipid classes were quantified at concentrations of 0.6 mg/100 g for phosphatidylinositol; 4.2 mg/100 g for phosphatidylethanolamine, 0.4 mg/100 g for phosphatidylserine, 2.8 mg/100 g for phosphatidylcholine, and 4.6 mg/100 g for sphingomyelin. Their relative standard deviation of repeatability and intermediate reproducibility values ranging between 0.8 and 13.4 % and between 2.4 and 25.7 %, respectively. The recovery values ranged between 67 and 112 %. Finally, the validated method was used to quantify phospholipid classes in human milk collected from 50 volunteers 4 weeks postpartum providing absolute content of these lipids in a relatively large cohort. The average content of total phospholipids was 23.8 mg/100 g that corresponds to an estimated mean intake of 140 mg phospholipids/day in a 4-week old infant when exclusively breast-fed.     

Effect of plasma treatment of polymeric tape carriers on wetting behaviour of aqueous ceramic tape casting slurry

Due to environmental and health aspects, aqueous ceramic slurries are preferred to traditional organic solvent systems in tape casting. An important obstacle associated with the high surface energy of water is poor wetting of aqueous ceramic slurries on polymeric tape carriers. Therefore, we measured the contact angles of an aqueous epoxy-based ceramic slurry on polyethylene terephtalate (PET), polypropylene (PP), polymethyl methacrylate (PMMA), and aluminium-coated polyethylene terephtalate (PET-Al) films and investigated approaches to improving their wetting. We evaluated the effect of plasma treatment of the tape carrier surface on the wetting behaviour and compared it with the effect of adding non-ionic amphiphilic surfactants to the ceramic slurry. The treatment of the tape carrier surface by low-temperature plasma substantially improved the wetting behaviour of aqueous ceramic slurry. The lowest contact angle of 31° was obtained on the PET film. Although the addition of non-ionic surfactants improved both the wetting behaviour of the slurry and the detachment of the polymeric carrier from the ceramic tape even better than the plasma treatment of the carrier surface did, the plasma-treated carriers still present a useful alternative to the surfactants. In the case of the plasma-treated PET carrier the surfactants could be fully eliminated and potential drawbacks related to the use of surfactants could be prevented.     

The hydration of reactive cement-in-polymer dispersions studied by nuclear magnetic resonance

The behaviour of two novel cement-in-polymer (c/p) dispersions, namely cement-in-poly(vinyl acetate) and cement-in-poly(vinyl alcohol) upon exposure to water at room temperature was investigated by a combination of various NMR methods. The swelling, cracking, and the water ingress were monitored non-destructively using ¹H single point imaging. The hydration of the cement matrix was investigated using ²⁹Si NMR whilst ¹³C CPMAS NMR spectra allowed the quantification of the kinetics of the hydrolysis reaction of poly(vinyl acetate) into poly(vinyl alcohol). The polymer controls the rate of water ingress and swelling which in turn determines the behaviour of the c/p dispersions upon exposure to water. For the cement-in-poly(vinyl alcohol), the rates of water ingress and swelling are much faster than the hydration of the clinker whilst for the cement-in-poly(vinyl acetate) the slow rates of the two processes allow the formation of a cementious matrix which assures the stability of the sample.     

Effect of carbonation on the hydro-mechanical properties of Portland cements

We evaluate experimentally the effect of carbonation on the hydro-mechanical properties of Portland cement. Samples were carbonated at 90 °C and 28 MPa under wet supercritical CO₂. Two types of carbonation features were achieved, either the samples were homogeneously carbonated or they displayed sharp carbonation fronts. Using a tri-axial apparatus, the static elastic moduli and the mechanical strength were measured at in-situ pressure conditions (28 MPa) and showed a degradation of the mechanical properties of the samples where a carbonation front prevailed. Water and gas permeabilities were measured and showed that the samples with a carbonation front exhibit a stress sensitive permeability. P and S elastic wave velocities were measured to evaluate dynamic (ultrasonic range, 1 MHz) elastic moduli. The use of an effective medium theory approach enabled us to characterize the density and distribution of cracks within the samples. This approach outlines that the samples which developed a carbonation front were damaged.     

Assessment of the long-term stability of cementitious barriers of radioactive waste repositories by using digital-image-based microstructure generation and reactive transport modelling

Cement-based grout plays a significant role in the design and performance of nuclear waste repositories: used correctly, it can enhance their safety. However, the high water-to-binder ratios, which are required to meet the desired workability and injection ability at early age, lead to high porosity that may affect the durability of this material and undermine its long-term geochemical performance.In this paper, a new methodology is presented in order to help the process of mix design which best meets the compromise between these two conflicting requirements. It involves the combined use of the computer programs CEMHYD3D for the generation of digital-image-based microstructures and CrunchFlow, for the reactive transport calculations affecting the materials so simulated. This approach is exemplified with two grout types, namely, the so-called Standard mix 5/5, used in the upper parts of the structure, and the “low-pH” P308B, to be injected at higher depths.The results of the digital reconstruction of the mineralogical composition of the hardened paste are entirely logical, as the microstructures display high degrees of hydration, large porosities and low or nil contents of aluminium compounds.Diffusion of solutes in the pore solution was considered to be the dominant transport process. A single scenario was studied for both mix designs and their performances were compared. The reactive transport model adequately reproduces the process of decalcification of the C-S-H and the precipitation of calcite, which is corroborated by empirical observations. It was found that the evolution of the deterioration process is sensitive to the chemical composition of groundwater, its effects being more severe when grout is set under continuous exposure to poorly mineralized groundwater. Results obtained appear to indicate that a correct conceptualization of the problem was accomplished and support the assumption that, in absence of more reliable empirical data, it might constitute a useful tool to estimate the durability of cement-based structures.     

Experimental determination of the effective anionic charge density of polycarboxylate superplasticizers in cement pore solution

The specific anionic charge density of polycarboxylate superplasticizers can be determined experimentally by titration with a cationic polyelectrolyte. In this study, the anionic charge densities of several polycarboxylates based on methacrylate ester chemistry were measured in aqueous solution at pH 7 and 12.6, resp., and in cement pore solution. The anionic charge of the polycarboxylates increases with increasing pH value as a result of deprotonation of the carboxylate groups in the polymer backbone. Addition of Ca²⁺ ions generally causes a decrease of the anionic charge density. The reduction in anionic charge varies and depends on the architecture of the polycarboxylate. The effect results from the binding of calcium ions by the carboxylate groups, both through complexation and counter-ion condensation. Consequently, the effective anionic charge density of polycarboxylates in cement pore solution can differ significantly from the charge density which is calculated based on the chemical composition. Generally the -COO⁻ functionality may coordinate Ca²⁺ as a monodentate or bidentate ligand. The type of coordination depends on the steric accessibility of the carboxyl group. In PC molecules possessing high side chain density, the -COO⁻ group is shielded by the side chains and coordinates as bidentate ligand, producing a neutral Ca²⁺-PC complex. Accordingly, this type of PC shows almost no anionic charge anymore in cement pore solution. In PCs possessing high amount of -COO⁻, Ca²⁺ is coordinated monodentate, resulting in an anionic complex. Consequently, this type of PC shows significant anionic character in pore solution. Its adsorption behaviour is determined by a gain in enthalpy which derives from the electrostatic attraction between the PC and the surface of cement. This way, by utilizing the relatively simple method of charge titration, it is possible to assess the electrostatic attraction which, besides entropy gains, is the driving force behind the adsorption of polycarboxylates on the cement surface and thus determines their effectiveness as dispersing agent. The findings are generally applicable to other anionic admixtures used in cement.     

Influence of bleed water reabsorption on cement paste autogenous deformation

The effects of bleed water reabsorption and subsequent early age expansion on observed autogenous deformation are investigated in this research. Bleeding was induced by varying superplasticizer and shrinkage-reducing admixture dosages and by increasing the water-to-cement ratio. This research revealed that significant early age expansion occurs with increasing chemical admixture dosages and higher water-to-cement ratios, as expected, due to increasing bleeding of those samples. When samples were rotated, negligible early age expansion was observed. Thus, bleed water reabsorption is shown to be the primary mechanism causing initial expansion in sealed autogenous deformation samples. Thermal dilation and ettringite growth appear to have a minimal influence on the observed expansion. Rotating the samples during setting eliminates the potential for bleed water reabsorption and is recommended for all autogenous deformation testing.