甲烷氯化物生产中的腐蚀原因分析及对策

介绍了HCl-H2O-CMS体系对20#钢的腐蚀现象和腐蚀特征,探讨了该体系对20#钢的腐蚀机理,并根据现场的统计数据给出了HCl-H2O-CMS体系对20#钢的腐蚀速率图,拟合了腐蚀速率方程,最后针对上述体系腐蚀的现象和特征提出了防止腐蚀的方案。

辐射制冷高反射Ag薄膜的腐蚀条件及防护

高反射Ag薄膜在空气中易老化,通过改变环境中的湿度、温度、反应气体浓度三个条件对Ag薄膜的腐蚀行为进行研究。结果显示:Ag薄膜试样在60℃,90%RH大气环境中12 d后的黄边占比为7.2%,湿度对Ag薄膜腐蚀的影响最显著,温度次之。反应气体浓度降低到水中溶解度时对Ag薄膜的腐蚀抑制效果明显。SiNx/Ag-Cu/SiNx膜系结构可以减少水汽吸附,延缓反应气体在薄膜中的扩散并阻隔水汽,实现对Ag薄膜的防护。在60℃,90%RH大气环境中12 d后,SiNx/Ag-Cu/SiNx反射膜未观察到腐蚀。

08Cr2AlMo钢制管壳式换热器制造技术探讨

上海材料研究所、上海炼油厂和江苏兴澄集团联合研制开发的 0 8Cr2 Al Mo钢无缝钢管 ,具有较高的抗 H2 S-H2 O,H2 S-HCl-H2 O系应力腐蚀的能力 ,并具有抗高温硫腐蚀和耐稀有机酸腐蚀的能力。近年来 ,江苏张家港市中圣江南化工机械有限公司 ,采用 0 8Cr2 Al Mo无缝钢管与 1 6Mn (锻件 )管板 +堆焊层搭配 ,制作了几十台管壳式换热器用于石化企业 ,收到了较好的效果 ,并积累了不少此类换热器的制造经验。

TDC Model for PSG Sacrificial Layer Etching with Hydrofluoric Acid

HF etching of sacrificial layers with different The existing model cannot fit the experimental data well perimental data increases with etching time. A modified structures, namely channel, bubble, and joint-channel, is studied. The error of etching rate between the existing model and the exmodel considering the diffusion coefficient as a function of HF concentration and temperature is proposed. The etching rate coefficient as a function of temperature and the effect of reaction production are also considered in the modified model. For the joint-channel structure, a new mathematical model for the etching profile is also adopted. Experimental data obtained with channel, bubble, and joint-channel structures are compared with the modified model and the previous model. The results show that the modified model matches the experiments well.

PRE-CORROSION FATIGUE NOTCH FACTOR

The notched and smooth specimens of aluminum alloy LC4CS soaked in EXCO solution for different time are tested under the constant amplitude cyclic loading to obtain S-N curves and fatigue notch factors with different pre-corrosion time. By analyzing the corrosion process of LC4CS specimens in EXCO solution, the influ- ence mechanism of corrosion on fatigue notch factor is expounded. Then, a two-parameter model used to describe the change of corrosion fatigue notch factor with time is established and verified by experiment. The results show that the pre-corrosion fatigue notch factor of LC4CS material decreases at first and then increases with the increasing pre-corrosion time. The inflection point appears at the beginning of denudation stage.

Frequency response of a new kind of silicon nanoelectromechanical systems resonators

Diffraction effects will bring about more difficulties in actuating resonators,which are electrostatically actuated ones with sub-micrometer or nanometer dimensions,and in detecting the frequency of the resonator by optical detection.To avoid the effects of diffraction,a new type of nanoelectromechanical systems（NEMS） resonators is fabricated and actuated to oscillate.As a comparison,a doubly clamped silicon beam is also fabricated and studied.The smallest width and thickness of the resonators are 180 and 200 nm,respectively.The mechanical oscillation responses of these two kinds of resonators are studied experimentally.Results show that the resonant frequencies are from 6.8 to 20 MHz,much lower than the theoretical values.Based on the simulation,it is found that over-etching is one of the important factors which results in lower frequencies than the theoretical values.It is also found that the difference between resonance frequencies of two types of resonators decreases with the increase in beam length.The quality factor is improved greatly by lowering the pressure in the sample chamber at room temperature.

An Air-Breathing Micro Direct Methanol Fuel Cell with 3D KOH-Etched Cathode Structure

A micro direct methanol fuel cell （μDMFC） using MEMS technology is reported. The prototype features a unique 3D air-breathing cathode structure fabricated using KOH etching and double-side lithography. The optimization of the MEMS fabrication process is analyzed. The experimental results show the prototype generates a maximum power density of 2.52mW/cm^2 at room temperature. This performance is better than the published resuits of other silicon-based passive μDMFCs. Moreover,it is comparable with that of our previous active μDMFCs which require an external pump, certificating the feasibility of this new configuration.

APPLICATION OF SWAT MODEL IN THE UPSTREAM WATERSHED OF THE LUOHE RIVER

In the Huanghe (Yellow) River basin,soil erosion is a serious problem,while runoff and sediment yield simulation has not been extensively studied on the basis of GIS (Geographic Information System) and distributed hydrological model. GIS-based SWAT (Soil and Water Assessment Tool) model was used to simulate runoff and sediment in the Huanghe River basin. The objective of this paper is to examine the applicability of SWAT model in a large river basin with high sediment runoff modulus,which could reach 770t/(km2·a). A two-stage "Brute Force" optimization procedure was used to calibrate the parameters with the observed monthly flow and sediment data from 1992 to 1997,and with input parameters set during the calibration process without any change the model was validated with 1998-1999’s observed data. Coefficient of examination (R2) and Nash-Suttcliffe simulation efficiency (Ens) were used to evaluate model prediction. The evaluation coefficients for simulated flow and sediment,and observed flow and sediment were all above 0.7,which shows that SWAT model could be a useful tool for water resources and soil conservation planning in the Huanghe River basin.

Comparative study on corrosion behaviors of Mg-Al-Zn alloys

A comparative study on corrosion behaviors of various Mg-Al-Zn alloys(AZ21,AZ41,AZ61 and AZ91 series,cast under same cooling conditions and controlled alloying composition)was carried out.Scanning electron microscopy(SEM)and X-ray diffraction(XRD)were used for microstructural examinations.The corrosion behaviors were evaluated by immersion tests and potentiodynamic polarization measurements in 3.5%NaCl solution.The results showed that the influence of Al addition on corrosion resistance was more pronounced up to 4%(i.e.AZ41)above which its influence was at less extent.The deterioration of the corrosion resistance of the alloys,at higher Al contents,was attributed to the amount and morphology ofβ-Mg17Al12 intermetallics and the interruption of continuity of the oxide film on the surface of the alloys owing to coarsenedβintermetallics.

A comparative study on corrosion of Mg-Al-Si alloys

Corrosion behavior of various Mg-Al-Si alloys(AS11,AS21,AS41,AS61and AS91series),cast under the same coolingconditions and controlled alloying composition,was investigated systematically.Optical microscopy and scanning electronmicroscopy were used for microstructural examinations.The corrosion behavior was evaluated by immersion tests andpotentiodynamic polarization measurements in3.5%NaCl solution.The results from both immersion tests and the potentiodynamicpolarization measurements showed that marginal improvement in corrosion resistance was observed with2.0%Al(mass fraction)containing alloy(AS21)whereas Al addition above2.0%(AS41,AS61and AS91)deteriorated the corrosion resistance which wasattributed toβphase,acting as cathode,and the interruption of continuity of the oxide film on the surface of the alloys owing tocoarsenedβand Mg2Si phases.

Corrosion risk assessment of chloride-contaminated concrete structures using embeddable multi-cell sensor system

Monitoring the service condition of concrete structures requires the quantitative assessment of properties and corrosion rate of structural steels surrounded by concrete.A multi-cell sensor system that included a reference electrode,a chloride content sensor,a macrocell current unit and an electrical resistance measurement unit was developed.This system provided the following important electrochemical data in the cover-zone concrete on site:open circuit potential,macrocell current from anodes to cathode,chloride profile,concrete resistance and corrosion rate of built-in anodes.The experimental results show that the macrocell current increases when the chloride content in concrete is higher.Thus,monitoring the chloride content is a good method for monitoring the corrosion state.The chloride ion content and cover depth are the key factors that affect the electrical resistance of concrete.Without considering the temperature and time,a simplified model of the instantaneous corrosion rate of steel rebar in a concrete structure based on the measured chloride contents and concrete resistance was proposed.The test results further prove the reliability of this simplified predicting model.

Influence of aging on microstructure,mechanical properties and stress corrosion cracking of 7136 aluminum alloy

The microstructure,mechanical properties and stress corrosion cracking(SCC)of 7136 aluminum alloy under T 6,T 79 and T 74 aging treatments were studied and the effects of microstructure on the mechanical properties and SCC were discussed.The results show that the ultimate tensile strength and yield strength of the aging 7136 alloys follow this sequence from high to low:T 6>T 79>pre-aging>T 74.For 7136 Al alloy after T 6 aging,the average diameter of the precipitates was(5.7±1.7)nm,and the diameter of 60.7%(number fraction)precipitates was 2−6 nm,leading to a good precipitation strengthening.The K_(IC)of T 74-aging alloy is 38.2 MPa·m^(1/2),which is 26.1%more than that of T 6-aging alloy and 17.5%more than that of T 79-aging alloy.The improved fracture toughness in T 74-aging alloy is mainly due to the reduction of the strength difference between intragranular and grain boundary.The SCC resistance of the aging 7136 alloys follows this sequence from high to low:T 79>T 74>T 6.After T 79 aging,the discontinuous grain boundary precipitates and narrow precipitate free zones were obtained in 7136 alloy,which was beneficial to SCC resistance.

Corrosion life of artificial reef under natural seawater conditions

Corrosion of steel bars with chloride salt erosion is one of the main reasons for the deterioration of the performance of reinforced concrete structures.The key to the service life of concrete members is the transport rate of chloride ions and the time for rusting of steel bars.In this paper,the artificial reef concrete member is taken as the research object,and the diffusion coefficient of seawater chloride ion in C30,C35 and steel slag composite artificial reef concrete is analyzed.The critical chloride ion concentration of steel corrosion in concrete is used as the boundary condition for life prediction.The chloride ion diffusion model predicts the corrosion life of C30,C35 and steel slag composite artificial reefs in seawater.The results show that the diffusion law of chloride ions in concrete artificial reefs basically meets Fick's second law.The corrosion life of C30,C35 and steel slag composite concrete reefs was calculated by the model to be 51.6,54.8 and 56.8 years,respectively.

High-Thermal Conductive Coating Used on Metal Heat Exchanger

Based on modified silicon polyester resin in addition to several functional fillers such as corrosion-resistant fillers, heat-resistant fillers and thermal conductive fillers, a high thermal conductive coating can be made. On the basis of boronnitride(BN) and aluminum nitride(AIN) used as thermal conductive fillers and by means of the testing system of hot disk and heat transfer experiment, researches on the varieties of thermal conductive fillers and the effects of the contents of high-thermal conductive coating have been done, which shows that the thermal conductivity of coating increases with the increase of the quality fraction and the coefficient of thermal conductivity of the thermal conductive fillers of coating. With guaranteeing better heat resistance, stronger corrosion resistance and adhesive force, the coefficient of coating can reach a level as high as 3 W·m-1·K-1.

A Field Investigation on the Effects of Background Erosion on the Free Span Development of a Submarine Pipeline

The safety of submarine pipelines is largely influenced by free spans and corrosions. Previous studies on free spans caused by seabed scours are mainly based on the stable environment, where the background seabed scour is in equilibrium and the soil is homogeneous. To study the effects of background erosion on the free span development of subsea pipelines, a submarine pipe- line located at the abandoned Yellow River subaqueous delta lobe was investigated with an integrated surveying system which in- eluded a Multibeam bathymetric system, a dual-frequency side-scan sonar, a high resolution sub-bottom profiler, and a Magnetic Flux Leakage （MFL） sensor. We found that seabed homogeneity has a great influence on the free span development of the pipeline. More specifically, for homogeneous background scours, the morphology of scour hole below the pipeline is quite similar to that without the background scour, whereas for inhomogeneous background scour, the nature of spanning is mainly dependent on the evolution of seabed morphology near the pipeline. Magnetic Flux Leakage （MFL） detection results also reveal the possible connec- tion between long free spans and accelerated corrosion of the pipeline.

Heuristic tabu search scheduling algorithm for wet-etching systems in semiconductor wafer fabrications

To improve overall equipment efficiency(OEE) of a semiconductor wafer wet-etching system,a heuristic tabu search scheduling algorithm is proposed for the wet-etching process in the paper,with material handling robot capacity and wafer processing time constraints of the process modules considered.Firstly,scheduling problem domains of the wet-etching system(WES) are assumed and defined,and a non-linear programming model is built to maximize the throughput with no defective wafers.On the basis of the model,a scheduling algorithm based on tabu search is presented in this paper.An improved Nawaz,Enscore,and Ham(NEH) heuristic algorithm is used as the initial feasible solution of the proposed heuristic algorithm.Finally,performances of the proposed algorithm are analyzed and evaluated by simulation experiments.The results indicate that the proposed algorithm is valid and practical to generate satisfied scheduling solutions.

Corrosion Rate and Scale of Cast Iron in Water Distribution Systems

A specialised electrochemical measurement cell was plugged into a pilot water distribution system to simulate the pipe inner-wall corrosion. The linear polarisation resistance(LPR) technique and electrochemical impedance spectroscopy(EIS) were measured in real time to study the variation of the corrosion rate(CR) and scale of cast iron. Three corrosion stages were observed according to the LPR analysis: an initial stage with significantly fluctuating CR, a developmental stage with slowly decreasing CR, and a stable stage with a low CR of approximately 0.157 5 mm·a^(-1). The EIS revealed that the scales with a compact outer layer and a porous inner layer finally formed in the stable stage, and the polarisation resistance was approximately 2 175 ?·cm^2. A physicochemical analysis of the scales showed that ferric oxides, oxyhydroxides and calcite made the outer layer compact and effectively limited the diffusion of oxygen through the scales, which resulted in a low CR.

Influences on Generation of White Etching Crack Networks in Rolling Bearings

In rare cases rolling bearings fail by WEC （white etching crack） damage before reaching their calculated rating life, if so called additional loads are applied on the bearing in addition to the normal Hertzian stress （PHz）. A number of additional loads have been identified by means of tests with rolling bearings. These can be small direct currents as a result of electrostatic charge or large alternating currents from inverter-fed drives that unintentionally flow through the bearing. WEC damages can also be initiated by a pure mechanical additional load which is dependent on factors including the bearing kinematics but also on the dynamics of the drive train. The current state of knowledge on this subject is presented and taken as the basis for developing a hypothesis on the WEC damage mechanism. If load situations critical for WEC cannot be avoided, the risk of WEC can be considerably reduced by the selection of suitable materials and coatings as well as, in some cases, of suitable lubricants.

Deterioration of Water Ballast Tank Coating Systems by Active Substances in Ballast Water Management Systems

Sodium hypochlorite and ozone are the principal active substances and usually employed in ballast water management systems. In the present study, the authors focus on the effect of these active substances to the maaix polymer of coating. In order to obtain such information, the authors investigated the penetration of active substances to the polymer from cross section of specimens introduced by SAICAS （surface and interracial cutting analysis system）, followed by FT-IR-ATR （Fourier transform infrared and attenuated total reflectance） spectroscopy analysis from Z direction of cross section. The corrosion test of coating panels by these active substances （control as artificial seawater） has been conducted for 120 days. The results show that the depth profile of each active substance is around few dozens of micrometers from coating surface. The criteria of corrosion test cannot be determined by these results due to lacking in actual corrosion data immersed for 15 years under active substances. However, the authors evaluated the effect on ballast tank coating systems by active substances using analytical methods of SAICAS and FT-IR-ATR spectroscopy.

Silicon Deep Etching Techniques for MEMS Devices

Silicon deep etching technique is the key fabrication step in the development of MEMS. The mask selectivity and the lateral etching control are the two primary factors that decide the result of deep etching process. These two factors are studied in this paper. The experimental results show that the higher selectivity can be gotten when F - gas is used as etching gas and Al is introduced as mask layer. The lateral etching problems can be solved by adjusting the etching condition, such as increasing the RF power, changing the gas composition and flow volume of etching machine.