阳离子型混凝土阻锈剂防腐蚀性能研究

利用电化学测试技术研究了乙醇胺(ETA)、四正丁基溴化胺(TBA)和氯化十六烷基吡啶(CPC)三种阳离子型阻锈剂在不同NaCl浓度的混凝土模拟孔溶液中对钢筋的防腐蚀性能的影响。研究结果表明:在低浓度的NaCl模拟体系中,阻锈剂对钢筋的腐蚀防护效果较好;结合动电位极化测试和交流阻抗谱测试结果得出,CPC阻锈剂属于混合型阻锈剂,通过在钢筋表面吸附成膜抑制腐蚀过程,CPC对钢筋的防腐蚀效果更佳。

Tb^(3+)在YAG中的发光及Tb^(3+)与Tm^(3 +)间的能量传递

采用溶胶 -凝胶方法合成了系列化合物 (Y1 -x- yTbxTmy) 3Al5O1 2 ,研究了Tb3+在该化合物中的发光及其浓度对发光性质的影响 ,以及Tb3+与Tm3+间的能量传递现象。

Effect of Strain and Chloride Concentration on Pitting Susceptibility for Type 304 Austenitic Stainless Steel

The effects of strain and chloride concentration on pitting susceptibility for type 304 stainless steel were studied in situ using the electrochemical technology under constant strain. The impact factor fc was brought forward to value the effect of strain on pitting. The pitting behaviors of type 304 stainless steel in various chloride concentrations under the strain levels 0%, 10%, and 30% were investigated. Potentiostatic polarization technology was used to study how the chloride concentration affected corrosion current density. The results indicated that fc increased substantially and pitting potential varied remarkably when chloride concentration was over 90 mg.L . Under the three levels of strain mentioned above, when chloride concentration was below 463 mg.L^-1,121 mg.L^-1, and 98 mg.L^-1 respectively, the pitting potential shifted towards positivity and, the passive film became more stable. When the strain was below 10%, the pitting susceptibility of type 304 stainless steel varied greatly as strain increased, whereas the susceptibility only changed a little when the strain was over 10%.

Porous ceramic coating formed on 316L by laser cladding combined plasma electrolytic oxidation for biomedical application

In order to improve the bioactivity of 316L stainless steel,a titanium layer was prepared on the surface of 316L by laser cladding(LC),followed by plasma electrolytic oxidation(PEO)to form a porous ceramic coating on titanium layer.The morphologies,microstructure and compositions of the coated samples were characterized by 3D surface profiler,SEM,EDS,XRD and XPS.The corrosion resistance and bioactivity of the coatings were evaluated by potentiodynamic polarization and immersion test in simulated body fluid(SBF),respectively.The results showed that the porous ceramic coating mainly consisted of anatase and rutile,and highly crystalline HA was also detected.The main elements of the PEO coating are Ca,P,Ti and O.The LC+PEO composite bio-coating has more excellent corrosion resistance than the 316L substrate in simulated body fluid.Furthermore,the composite coating could effectively improve the bioactivity of 316L stainless steel.

Surface treatment of 0Cr19Ni9 stainless steel SMAW joint by plasma melting

Micro plasma arc surface melting of 0Cr19Ni9 shielded metal arc welding joint with a micro plasma arc welder produced a thin surface melted layer with a refined microstructure. The surface treatment changed the anodic polarization behavior in 0.5 mol/L H 2SO 4 solution. The polarization tests showed that for the as welded joint both the heat affected zone and the weld metal decreased in resistance to corrosion compared with the as received parent material while for the micro plasma arc surface melted joint the corrosion resistance increased significantly. This increase in corrosion resistance is attributed to the rapid solidification of the melted layer. Rapid solidification of the melted layer refines its microstructure, decreases its microsegregation, and inhibits the precipitation of chromium carbides at the grain boundaries.

Study of the Protective Capacity of Cements Regarding Corrosion of Reinforcements under Joint Action of CO2 and Chloride Ions

To examine the protection against reinforcement corrosion due to the combined action of CO2 and chlorides, experimental results of the evaluation of a study with three types of cement are presented. The study was performed observing the behavior of reinforcements which were put in samples submitted to accelerated carbonatation tests and accelerated tests under the effect of chlorides. For the evaluation, intensity corrosion measurements were used using the Pr （polarization resistance） technique, employing these measures as a deterioration indicator. Three types of cement available in the national market were used. The obtained results enabled the classification of the used cements, comparing their profile behaviors in the conditions of the proposed tests.

Durability of calcium sulfoaluminate cement concrete

Calcium sulfoaluminate cement(CSAC),first developed in China in the 1970 s,has received significant attention because of its expansive(or shrinkage-compensating)and rapid-hardening characteristics,low energy-intensity,and low carbon emissions.The production and hydration of CSAC(containing ye’elimite,belite,calcium sulfate,and minors)have been extensively studied,but aspects of its durability are not well understood.Due to its composition and intrinsic characteristics,CSAC concrete is expected to have better performance than Portland cement(PC)concrete in several aspects,including shrinkage and cracking due to restrained shrinkage,freeze-thaw damage,alkali-silica reaction,and sulfate attack.However,there is a lack of consensus among researchers regarding transport properties,resistance to carbonation,and steel corrosion protectiveness of CSAC concrete,all of which are expected to be tied to the chemical composition of CSAC and attributes of the service environments.For example,CASC concrete has poorer resistance to carbonation and chloride penetration compared with its PC counterpart,yet some studies have suggested that it protects steel rebar well from corrosion when exposed to a marine tidal zone,because of a strong self-desiccation effect.This paper presents a succinct review of studies of the durability of CSAC concrete.We suggest that more such studies should be conducted to examine the long-term performance of the material in different service environments.Special emphasis should be given to carbonation and steel rebar corrosion,so as to reveal the underlying deterioration mechanisms and establish means to improve the performance of CSAC concrete against such degradation processes.