Environmental microscopy in stone conservation

The natural weathering of stone is accelerated by the combined effects of acid rain, salt crystallization, and the freeze-thaw cycles of water. Since weathering will take place until the system reaches chemical equilibrium, we can mitigate the loss to historic stone monuments and structures by treatments of the stone that retard hydrolysis and impart mechanical strength. While macroscopic studies of stone weathering have been performed addressing the causes, the reactions, and the kinetics involved, the mechanisms of weathering, and the chemical remediation of stone need to be better understood at a microscopic level. Our approach uses environmental scanning electron microscopy where samples can be imaged in their wet, natural state, thus facilitating the in situ study of the weathering processes. The environment in the microscope is set up to simulate the conditions of degradation by introducing corrosive liquids and gases and varying the temperature, pressure, and water content in the environmental chamber of the microscope. In this study, we observed specimens of limestone, treated calcite, and sandstone. We have characterized the morphology, structure, and chemical constituents of the samples for comparison at a later stage when protective coatings will be applied. In situ leaching tests were performed on limestone samples to study the mechanisms of degradation. Granular disintegration due to leaching of the binding material between the grains was seen. We have also observed, in situ, the changes in the structure of sodium sulfate, used in salt crystallization tests, during hydration and dehydration cycles; it changed from that of dense grains to hydrated mesoporous granules with the generation of new surface area.     

福建沿海地区花岗岩残积土工程特性探讨

花岗岩在各种风化力作用下会形成厚度不等的残积土,垂直与水平方向上形成较大差异,决定其物理力学性质、结构性、不均匀性,及具崩解软化的特征,使其强度发生较大的变化。明确其具有明显的垂直差异性,影响到其强度上的差异性。     

高强度铁道车辆用钢的焊接研究

研究了宝钢高强度铁道车辆用钢的焊接性。针对焊接材料熔敷金属、焊接接头塑韧性不能满足新型铁道车辆焊接中梁制造要求的现状，开发了新的配套气体保护焊耐候焊丝。结果表明，新开发焊丝的熔敷金属及其焊接接头，不但强度高，抗焊接冷裂能力强，塑性好，-40℃的低温冲击性能Axv≥60J，而且具有高耐候性。该钢种与焊丝已用于铁道车辆新车型的试制。     

窄带SPA—H耐候钢转炉冶炼的开发

采用“转炉-窄带”工艺路线开发生产SPA—H耐候钢带替代同品种“电炉-窄带”。研究转炉冶炼SPA—H耐候钢带的内控成分，探讨为改善力学性能、中间裂纹而采取的工艺措施。     

焊接结构用耐候钢板Corten B的研制与开发

介绍了南钢通过150吨转炉及3500炉卷轧机生产焊接结构用耐候钢CortenB的研制与开发过程，并对生产结果进行分析，提出改进措施。     

江西大吉山花岗岩风化壳稀土矿床稀土元素地球化学

本文系统采集分析了江西大吉山花岗岩体及其风化壳样品，通过研究其不同类型花岗岩风化壳的矿物组成、稀土元素组成和稀土元素的分配，得出了风化壳中稀土元素的分布特征和规律，讨论了风化作用过程中稀土元素的迁移机制。     

稀土改善09CuPTiRE耐候钢耐蚀性的作用机理

应用扫描电镜(SEM)、离子探针(IMA)、X射线光电子能谱(XPS)和交流阻抗法研究含不同稀土耐候钢稀土提高耐大气腐蚀作用机理。结果表明,合适的稀土含量可显著提高钢的耐腐蚀性,稀土能促进Si、Cu和P在内锈层中以Si~(4+)、Cu~+和P~(5+)形态富集,并观察到锈层中的稀土。钢中加入稀土形成了致密连续厚而粘附性好的含硅铜稀土的复合铁锈层,从而提高了抗大气腐蚀性能。     

钢的大气腐蚀防护的研究进展

回顾了近年来耐候钢研究的进展概况,重点总结了耐候钢的实验研究方法、锈层的形成机理、锈层的显微组织及生长过程中的影响因素,分析了钢的腐蚀防护情况.指出了以往研究的不足以及今后的研究方向.     

From the Cover: In situ carbonation of peridotite for CO2 storage

The rate of natural carbonation of tectonically exposed mantle peridotite during weathering and low-temperature alteration can be enhanced to develop a significant sink for atmospheric CO₂. Natural carbonation of peridotite in the Samail ophiolite, an uplifted slice of oceanic crust and upper mantle in the Sultanate of Oman, is surprisingly rapid. Carbonate veins in mantle peridotite in Oman have an average ¹⁴C age of ≈26,000 years, and are not 30–95 million years old as previously believed. These data and reconnaissance mapping show that ≈10⁴ to 10⁵ tons per year of atmospheric CO₂ are converted to solid carbonate minerals via peridotite weathering in Oman. Peridotite carbonation can be accelerated via drilling, hydraulic fracture, input of purified CO₂ at elevated pressure, and, in particular, increased temperature at depth. After an initial heating step, CO₂ pumped at 25 or 30 °C can be heated by exothermic carbonation reactions that sustain high temperature and rapid reaction rates at depth with little expenditure of energy. In situ carbonation of peridotite could consume >1 billion tons of CO₂ per year in Oman alone, affording a low-cost, safe, and permanent method to capture and store atmospheric CO₂.     

Natural and artificial weathering characteristics of stabilized acrylic–urethane paints

Depth-profiling by Fourier transform infrared (FTIR) spectroscopy, dynamic mechanical analysis (DMA), microhardness and scanning electron microscopy (SEM) observations have been used to monitor degradation chemistries in two-package acrylic–urethane coatings when exposed to different exposure conditions. Three artificial and three natural weathering protocols (QUV, ASTM D5894, ISO20340, Pipady (south of France), Bandol (south of France) and Kure Beach (USA)) were selected for this study. The same chemical events were found to occur under all conditions, particularly under natural and artificial exposures. Both loss of the amide II band at 1520 cm⁻¹ and carbonyl growth occurred but at relatively low rate owing to the presence of hindered-amine light stabilizers in the film. A less typical loss of urea biuret linkages also occurs during all exposures and results in a change in the balance between urethane and urea links across the depth of the film during weathering. The chemical degradation of the polymer matrix involves the formation of species that are readily ablated from the surface and results in loss of gloss, increase in hardness and a rougher topology. The dramatic loss of gloss observed after Pipady and Bandol exposures show that loss of gloss should not be systematically correlated to the advance in chemical degradation.