盐酸溶液中六次甲基四胺对黄铜的缓蚀作用及吸附热力学研究

采用失重法研究了不同温度下不同浓度的六次甲基四胺在10%盐酸介质中对黄铜的缓蚀作用.结果表明,六次甲基四胺在10%盐酸介质中对黄铜的腐蚀有良好的抑制作用,六次甲基四胺吸附于黄铜表面,其吸附规律服从Langmuir等温式,由此获得了相关热力学参数.     

六次甲基四胺对AZ31镁合金的缓蚀作用研究

为了表征六次甲基四胺(HMTA)对AZ31镁合金在MgSO4溶液中的缓蚀性能,用线性电位扫描、电化学阻抗谱等方法研究了合金在溶液中的电化学行为.结果表明,少量HMTA的加入能使AZ31镁合金的开路电位正移,极化电阻增大,从而发挥缓蚀效果.HMTA的添加量在0.1～0.15mmol/L范围时具有较好的缓蚀性能,并使活化电位负移,确保合金具有较好的电化学活性.     

Effect of electrolyte additives on anti-corrosion ability of micro-arc oxide coatings formed on magnesium alloy AZ91D

Oxide coatings on AZ91D alloy were prepared using micro-arc oxidation techniques at a low applied voltage, in electrolyte solutions with hexamethylenetetramine and sodium borate additives. The different electrolyte solutions changed the applied voltage from 400 to 200 V and reduced the micro-pore size of the oxide coating on the AZ91D alloy.The corrosion current of the oxide coating changed from 3.6 × 10^− 5 to 4.2 × 10^− 7 A/cm² when the additives were added to the plating solution. When sodium borate was added to the plating solution, the Na content of the oxide coating was increased, improving its anti-corrosion ability. Moreover, the surface roughness (Ra) was reduced from 10.12 to 1.22 by the addition of 0.1 M hexamethylenetetramine to the electrolyte. The cracks in the oxide coating were also smoothed by the addition of 0.1 M hexamethylenetetramine, reducing the thermal stress.In this work, the addition of the aforementioned additives to the alkaline silicate phosphate electrolyte reduced the applied voltage and modified the oxide coating, resulting in better anti-corrosion ability.     

Synergism and antagonism in mild steel corrosion inhibition by sodium dodecylbenzenesulphonate and hexamethylenetetramine

The inhibition effects of sodium dodecylbenzenesulphonate (SDBS) and hexamethylenetetramine (HA) on the corrosion of mild steel in sulphuric acid solution have been studied using weight loss, electrochemical impedance and Tafel polarisation measurements. For HA, a monotonous increase in inhibition efficiency is observed as a function of concentration. For SDBS, however, an optimum in the inhibition efficiency is observed for a concentration close to 250 ppm, which is ascribed to the formation of hemi-micellar aggregates that provoke inhibitor desorption from the metal/solution interface at higher concentrations. Upon mixing HA and SDBS, concentration regions showing synergistic and antagonistic inhibition behaviour are identified, and it is concluded that electrostatic interactions between adsorbate ions are likely responsible for both phenomena. Langmuir and Frumkin isotherms were tested for relevance in describing the adsorption behaviour of both HA and SDBS.     

Preparation of HMX by Perfluorooctanesulfonic Acid Catalyzed Nitrolysis of Hexamethylenetetramine in Fluorous Media

Perfluorooctanesulfonic acid (CF₃(CF₂)₇SO₃H, PFOS) efficiently catalyzes the nitrolysis of hexamethylenetetramine in fluorous media, affording a good yield of the explosive HMX. The reaction can be carried out without acetic anhydride or acetic acid. The fluorous phase containing the catalyst could be easily separated and can be reused several times without significant loss of catalytic activity.     

Reduction of KMnO4 to Mn3O4 via hydrothermal process

A simple, inexpensive, low temperature and environmentally benign hydrothermal reduction route has been developed for the synthesis of octahedral Mn₃O₄ nanoparticles by using KMnO₄ and hexamethylenetetramine (HMT). It has been found that, Mn₃O₄ formation during hydrothermal process involves two steps. In the first step, an intermediate MnOOH is formed under the influence of self generated pressure in the autoclave. In the second step, formic acid produced via hydrolysis followed by oxidation of HMT, reduces MnOOH to Mn₃O₄. The powder X-ray diffraction (XRD) data confirms the formation of tetragonal γ-Mn₃O_4. Scanning electron micrograph images exhibit a good octahedral morphology of the product. The formation γ-Mn₃O₄ is further confirmed by Raman and FTIR spectroscopy.     

水解聚丙烯腈钠盐高温堵水剂的改进

以六次甲基四胺取代水解聚丙烯腈钠盐为主剂的高温堵水剂原配方中的甲醛，以草酸取代盐酸调节ｐＨ值，经改进的堵水剂使用安全、无毒，成胶时间的控制比较准确，适用温度下限由１００℃扩展到了８０℃。     

Synthesis of RDX by nitrolysis of hexamethylenetetramine in fluorous media

Perfluorooctanesulfonic acid (CF₃(CF₂)₇SO₃H, PfOS) catalyses the highly efficient nitrolysis of hexamethylenetetramine in fluorous media, affording high yield of explosive RDX. The reaction can be carried out at room temperature in the absence of acetic anhydride and produces smaller amounts of waste acid and nitrate than in traditional process. The fluorous phase containing catalyst could be easily and efficiently recovered for reuse by simple phase separation.     

Structural,dielectric, magnetic,and ferroelectric properties of bismuth ferrite (BiFeO3) synthesized by a solvothermal process using hexamethylenetetramine (HMTA) as precipitating agent

Multiferroic BiFeO₃ (BFO) has been synthesized by the solvothermal technique for 4 h at 180 °C using Hexamethylenetetramine (HMTA) as a precipitating agent. Optimizations on HMTA concentration were performed to attain BFO in a narrow possible time using the solvothermal method. The effect of HMTA concentration on structural properties was investigated by XRD, FE-SEM, FT-IR, and Raman techniques. Moreover, the magnetic, ferroelectric, dielectric, and optical properties were studied by VSM, Ferroelectric analyser, Dielectric spectrometer, and UV–Vis–NIR spectrometer, respectively. The XRD data has unveiled the significant role of HMTA, as a precipitating agent, in obtaining the pure phase BFO at a particular concentration. A high concentration of HMTA (6 M) is found to be more favourable for producing pure phase BFO within the short reaction time of 4 h without any impurity phase formations. The FE-SEM images have shown the formation of granular structures that are inhomogeneously distributed throughout the powdered BFO with porosities. In addition, the magnetic measurements confirmed that the BFO synthesized with varying HMTA concentration exhibits a reasonable week ferromagnetic behaviour. However, the pure BFO powder synthesized at 6 M HMTA shows high magnetization value (0.72 emu/g) compared to the other samples synthesized at low concentrations of HMTA. Further, the dielectric measurements of all the synthesized BFO samples have shown a decrease in dielectric loss with an increase in frequency. Whereas the dielectric behaviour exhibited by the pure BFO synthesized at 6 M HMTA has shown a high dielectric constant value with moderate dielectric loss. A ferroelectric analyser studies the ferroelectric behaviour of BFO powder. The study revealed that pure phase BFO synthesized with 6 M HMTA exhibits a high value of remanent polarization with unsaturated P-E loops due to the high leakage current in the sample. The UV–Vis data shows that the BFO samples exhibited an excellent optical absorption in the visible range with narrow optical band gaps. Therefore, all the characterizations related to magnetic, structural, dielectric, ferroelectric, and optical properties of synthesized pure BFO have proven the significance of precipitating agent HMTA in the solvothermal synthesis method. Based on our findings, the synthesized pure phase BFO can be an excellent semiconducting photocatalyst for multiferroic based photocatalysis applications.