Properties of concrete pavements prepared with ferrochromium slag as concrete aggregate

This paper presents the results of investigation related to both the properties of the ferrochromium slag and the standard physical and mechanical properties of Portland cement concrete pavements (PCCP) made with this slag as aggregate, according to the relevant Croatian standards. Slag is formed as a liquid at 1700 °C in the manufacture of the high-carbon ferrochromium metal and, by slow cooling in the air, the slag crystallizes to give a stable CaO–MgO–Al₂O₃–silicate product with mechanical properties similar to basalt. With a proper selection of slag as an artificial aggregate, concrete pavements with compressive strengths, wear resistance and specific weight higher than in those from natural (limestone) aggregate in commercial Portland cement, type CEM II/B-S 42.5 (EN 197), can be made. The 28-day compressive strength of the concretes made with original unfractioned slag and with standard limestone as aggregates (w/c=0.64 and 350 kg/m³) reached the values of 57.00 MPa and 36.70 MPa, respectively. Volume stability, high volume mass, good abrasion resistance to wear and crushability make this reinforced slag concrete suitable for wearing courses of concrete pavements for traffic load classes 1 and 2 where carbonate stone material (limestone) mainly does not meet the Standard Technical Requirements for cement concrete slab pavements according to the relevant Croatian standard.     

Synthesis, characterization and thermal properties of soluble aromatic poly(amide imide)s

Novel diamines such as N,N′-bis(aminoaryl)terephthalamido-2-carboxylic acids (BATCA), which contain primary amine, amide and carboxylic acid groups and are soluble in dilute aqueous NaOH solution, were synthesized by reacting aromatic diamines with trimellitic anhydride chloride in dimethylformamide. Poly(amide imide)s containing 3:1 ratio of amide:imide groups in the polymer chain were prepared by low temperature solution polymerization of BATCAs with isophthaloyl chloride or terephthaloyl chloride in dimethylformamide at 5-10 °C to form poly(amide amic acid)s, and followed by treating with a mixture of triethylamine and acetic anhydride. The PAIs were soluble in polar aprotic solvents like dimethylformamide, dimethylacetamide, dimethylsulphoxide and N-methylpyrrolidone, and have inherent viscosities in the range of 0.30-0.66 dL/g. The PAIs were characterized by IR, ¹H NMR and ¹³C NMR techniques. Thermogravimetric analysis (TGA) has shown that the initial decomposition temperatures of the polymers are in the range of 250-440 °C, depending upon the structures of diamine and diacid chloride. The glass transition temperatures of the PAIs are in the range of 128-320 °C. The IDT and T_g values of the polymers containing terephthaloyl unit are higher by about 20-40 °C than those of the polymers with isophthaloyl unit. BATCA could be utilized for the preparation of thin film composite membranes having PAA/PAI barrier layer on PES by in situ interfacial polymerization with IPC/TPC/TMC.     

Synthesis and characterization of porous media produced by a sol-gel method

Mesoporous silica materials were synthesized by sol-gel method using tetraethoxysilane (TEOS) as precursors and surfactants i.e., cetyltrimethyl ammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and polyoxyethylene cetyl ether (Brij 56) as templates. Surfactant templates were completely removed by calcination to form mesoporous structure. The effects of type and amount of surfactants on the characteristics of samples were studied. The textural characteristics such as surface area, pore volume, pore size, and pore size distribution were determined by nitrogen sorption isotherms. Fourier transform infrared (FTIR) spectroscopy was employed to qualitatively identify the chemical functionality and to confirm the removal of surfactant template. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to directly observe surface morphology and mesoporous structure, respectively. The adsorption capacity of the synthesized adsorbent for toluene vapor was examined. We found that the pore volume and pore size of mesoporous materials affected the adsorption capacity. The sample prepared with high content of CTAB under basic condition (pH ∼7) yielded large pore volumes and pore sizes and subsequently possessed the high adsorption capacity for toluene vapor.     

Intercalation of methylene blue in n-alkanethiolated self-assembled monolayers: Versatile electrochemical platforms for characterizing surfactant adsorption on hydrophobic surfaces

A versatile electrochemical platform for characterizing the adsorption of neutral and positively charged surfactants on hydrophobic surfaces was established using methylene blue (MB) as the probe. As a rigid, planar and electroactive species, MB can intercalate inside the regular self-assembled monolayers (SAMs) of n-hexanethiol and exhibit well-defined electrochemical responses. The adsorption of surfactants on the hydrophobic SAMs through the intercalation interaction between the hydrophobic tails of surfactants and the SAMs might change the density of the SAMs and influence the electrochemical behaviors of MB, providing a simple but effective approach for characterizing surfactant adsorption on hydrophobic surfaces. As an example, the adsorptive behaviors of cetyltrimethylammonium bromide (CTAB), a positively charged surfactant, and Triton X-100, a neutral surfactant, on hydrophobic surfaces were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The results showed that these surfactants generally experienced three different adsorptive behaviors: the monomer adsorption at low concentrations, the loose monolayer adsorption at intermediate concentrations and the dense monolayer adsorption at high concentrations. In the case of CTAB, a new additional submonolayer adsorptive behavior between the monomer and the loose monolayer adsorption was observed for the first time, due to its rather long hydrophobic tail.     

爪形大分子CBC—NO的合成、表征及降滤性能研究

以1,3-丁二醇、柠檬酸为原料、甲苯为溶剂,在120℃油浴中反应,合成了柠檬酸-1,3-丁二醇-柠檬酸（CBC）爪状物小分子;然后,以甲基苯磺酸为催化剂,使CBC依次与环烷酸、十八醇分别在140℃和180℃油浴下接枝,合成了新型的爪形大分子柠檬酸-1,3-丁二醇-柠檬酸-环烷酸-十八醇（CBC—NO）。采用^1H—NMR及IR对合成的两种化合物进行了结构表征。结果表明,合成的CBC和CBC—NO与所设计的分子结构相吻合。用元素分析确定了CBC的化学组成为C16H22O14。合成的CBC—NO溶于有机溶剂,不溶于水。将CBC—NO按600μg／g的加剂量添加到不同的轻柴油中,柴油的冷滤点最大可降低8℃。     

Impedance spectroscopy study of hardened Portland cement paste

In this paper, the differential impedance analysis (DIA) has been applied to the study of the dielectric properties of hardened Portland cement paste. Two time constants are found in the impedance spectra obtained in the frequency region form 100 kHz to 15 MHz. One time constant has been attributed to the solid matrix and the other one to the liquid phase filling the pores. The effect of the cement paste-electrodes interface has been quantified using two different experimental set-ups. Measurements using direct contact between electrodes and cement paste have been compared with measurements using an air gap technique in which the specimen “floats” between the electrodes. The two referred time constants have been found in both types of measurements. The influence of drying on the dielectric parameters is also studied.     

Structural characterization of 1,2-polybutadiene by 13C-n.m.r. spectroscopy: 2. Sequence distribution of 1,2-unit in hydrogenated polybutadienes

The configurational sequences of 1,2-unit in a series of hydrogenated syndiotactic 1,2-polybutadienes were determined in relation to the sequence distribution of 1,2- and 1,4-units on the basis of the ¹³C-n.m.r. signal assignment of the methyl carbons. The observed triad distributions of 1,2- and 1,4-units and configurational distributions of the 1,2-unit are in good agreement with the calculated distributions from transition probabilities. The number average sequence lengths of the 1,2-unit and the 1,2-unit in the racemic addition are 5.7 to 8.0 and 4.1 to 5.4, respectively. From the extrapolation of the plot of the number average sequence length against the crystallinity of the starting 1,2-polybutadienes, the minimum sequence length for crystallization is estimated to be 3.7 for the 1,2-unit in the racemic addition.     

Characterization of the Oum El Khacheb phosphorites(South Tunisia)and enrichment of big rejections by grinding

In the last decade, the phosphate reserves have started to decrease. In this study, both phosphate of Oum El Khacheb's(O.E.K) region(South of Tunisia) and its big rejections were characterized mineralogically and chemically by several analysis methods such as the binocular magnifying glass, X-rays diffraction technique, Technicon auto-analyzer, atomic absorption spectroscopy, and carbon sulfur analyzer. Then,this work focuses on the coarse rejections of O.E.K's phosphorites which can be valorized by the wet grinding method. Therefore, we have used the methodology of experimental research to determine the optimal grinding conditions. Results found by Doelhert matrix are: a duration at about 4 min, a pulp on solid concentration of 45.00%, a number of cycles equals to 60 rpm and 3.87 as the jar's loading.The enhancement of the weight yields of phosphate recuperation increased significantly by 46.39% from big rejections with 24.60% of P_2O_5 concentration.     

二次过热器炉管的腐蚀损伤分析与表征

采用金相检验、扫描电镜、三维视频系统及能谱分析等方法，对350MW火力发电机组经13万h运行后二次过热器炉管内表面严重腐蚀损伤进行了检测与表征。结果表明，该炉管内表面的损伤主要是由水中的氯离子及溶解氧作用下引起的点腐蚀所致，为此提出了相应的预防措施。     

电化学改性不锈钢钝化膜的XPS/SERS研究

应用Ｘ射线光电子能谱（ＸＰＳ）和表面增强拉曼光谱（ＳＥＲＳ）考察１８－８不锈钢表面电化学改性钝化膜各层次的化学组成。ＸＰＳ的结果表明电化学改性处理可使钝化膜老化。膜层中含大量的ＣｒＯ３,但未检测到ＣｒＯ４＾２－,在膜的各个层次均发生铬的富集,而在最外层铬的含量并非最大。表明在改性处理过程中,铬优先溶解,铁在膜的以存在Ｆｅ（Ⅱ）和ＦｅⅡ两种氧化态,同时有利于非晶态结构的形成。原位ＳＥＲＳ测试的结果指