Effect of ball milling time on the microstructure and compressive properties of the Fe–Mn–Al porous steel

In the present work,Fe–Mn–Al–C powder mixtures were manufactured by elemental powders with different ball milling time,and the porous high-Mn and high-Al steel was fabricated by powder sintering.The results indicated that the powder size significantly decreased,and the morphology of the Fe powder tended to be increasingly flat as the milling time increased.However,the prolonged milling duration had limited impact on the phase transition of the powder mixture.The main phases of all the samples sintered at 640℃ were α-Fe,α-Mn and Al,and a small amount of Fe2Al5 and Al8Mn5.When the sintering temperature increased to 1200℃,the phase composition was mainly comprised of γ-Fe and α-Fe.The weight loss fraction of the sintered sample decreased with milling time,i.e.,8.3wt% after 20 h milling compared to15.3wt% for 10 h.The Mn depletion region(MDR) for the 10,15,and 20 h milled samples was about 780,600,and 370 μm,respectively.The total porosity of samples sintered at 640℃ decreased from ~46.6vol% for the 10 h milled powder to ~44.2vol% for 20 h milled powder.After sintering at 1200℃,the total porosity of sintered samples prepared by 10 and 20 h milled powder was ~58.3vol% and ~51.3vol%,respectively.The compressive strength and ductility of the 1200℃ sintered porous steel increased as the milling time increased.

考虑相含量的TC17钛合金线性摩擦焊中的残余应力

为了获得准确的TC17钛合金线性摩擦焊中的残余应力,建立TC17钛合金弹性常数与相分数之间的数值关系。结合焊接区域的相分数,获得呈梯度分布的弹性常数,并将其引入轮廓法进行计算。结果表明,TC17钛合金的弹性常数与α相分数呈正相关,在宽度约4 mm的焊接区域呈现明显的梯度分布特征;若忽略相分数的梯度分布,计算残余应力时相对误差可达36.06%;修正后的残余应力呈双峰分布,在热影响区边缘处达到峰值,约为442 MPa。这说明考虑相分数的梯度分布是必要的。

Influence of cross correlation step length on the surface stress of thin laser cladding Fe314 alloy coatings

To measure the surface stress of thin laser cladding coatings with Rayleigh waves based on the cross correlation function, this pa-per introduced the influence of cross correlation step length on the stress measurement. Flat-shaped specimens made of laser cladding Fe314 alloy coatings were performed by static tensile tests, and Rayleigh wave signals were collected during the test process with an ultrasonic pulser and receiver instrument combined with two Rayleigh wave transducers. The difference in time of flight between two signals was de-termined based on the cross correlation function. The microstructure was observed by scanning electronic microscopy. The influence of the stress on the propagation velocity of Rayleigh waves and the relationship between the difference in time of flight and tensile stress under dif-ferent cross correlation step lengths were analyzed. The inhomogeneous deformation of the coatings affects the relationship between the dif-ference in time of flight and tensile stress; the stress measurement of the coatings is nearly constant with the increase of cross correlation step length when it attains one cycle.

An efficient green route for hexamethylene-1,6-diisocyanate synthesis by thermal decomposition of hexamethylene-1,6-dicarbamate over Co3O4/ZSM-5 catalyst： An indirect utilization of CO2

The utilization of CO_2 as raw material for chemical synthesis has the potential for substantial economic and green benefits. Thermal decomposition of hexamethylene-1,6-dicarbamate(HDC) is a promising approach for indirect utilization of CO_2 to produce hexamethylene-1,6-diisocyanate(HDI). In this work, a green route was developed for the synthesis of HDI by thermal decomposition of HDC over Co_3O_4/ZSM-5 catalyst, using chlorobenzene as low boiling point solvent. Different metal oxide supported catalysts were prepared by incipient wetness impregnation(IWI), PEG-additive(PEG) and deposition precipitation with ammonia evaporation(DP) methods. Their catalytic performances for the thermal decomposition of HDC were tested. The catalyst screening results showed that Co_3O_4/ZSM-5_(25) catalysts prepared by different methods showed different performances in the order of Co_3O_4/ZSM-5_(25)(PEG)N Co_3O_4/ZSM-5_(25)(IWI)N Co_3O_4/ZSM-5_(25)(DP). The physicochemical properties of Co_3O_4/ZSM-5_(25) catalyst were characterized by XRD, FTIR, N2 adsorption-desorption measurements, NH3-TPD and XPS.The superior catalytic performance of Co_3O_4/ZSM-5_(25)(PEG)catalyst was attributed to its relative surface content of Co^(3+), surface lattice oxygen content and total acidity. Under the optimized reaction conditions: 6.5% HDC concentration in chlorobenzene, 1 wt% Co_3O_4/ZSM-5_(25)(PEG)catalyst, 250 °C temperature, 2.5 h time, 800 ml·min-1 nitrogen flow rate and 1.0 MPa pressure, the HDC conversion and HDI yield could reach 100% and 92.8%respectively. The Co_3O_4/ZSM-5_(25)(PEG)catalyst could be facilely separated from the reaction mixture, and reused without degradation in catalytic performance. Furthermore, a possible reaction mechanism was proposed based on the physicochemical properties of the Co_3O_4/ZSM-5_(25) catalysts.

The adsorption properties of NaY zeolite for separation of ethylene glycol and 1,2-butanediol: Experiment and molecular modelling

The separation of ethylene glycol(EG)and 1,2-butanediol(1,2-BDO)azeotrope in the synthesis process of EG via coal and biomass is becoming of increasing commercial and environmental importance.Selective adsorption is deemed as the most promising methods because of energy saving and environment favorable.In this paper,NaY zeolite was used to separate 1,2-BDO from EG,and its adsorption properties was then investigated.The isotherms of EG and 1,2-BDO in vapor and liquid phases from 298 to 328 K indicated that they fitted Langmuir model quite well,and the NaY zeolite absorbent favored EG more than 1,2-BDO.The Grand Canonical Monte Carlo(GCMC)and molecular dynamics(MD)simulation techniques were conducted to investigate the competition adsorption and diffusion characteristics in different adsorption regions.It was observed that EG and 1,2-BDO molecules all have the most probable locations of the center of the 12-membered ring near the Na cations.The diffusivities of EG are lower than those of 1,2-BDO at the same adsorption concentration.At last,the breakthrough curves of the binary mixture regressed from the empirical Dose–Response model in fixed-bed column showed that the adsorption selectivity of EG could reach to as high as 2.43,verified that the NaY zeolite could effectively separate EG from 1,2-BDO.This work is also helpful for further separation of other dihydric alcohol mixtures from coal and biomass fermentation.

Non-phosgene synthesis of hexamethylene-1,6-diisocyanate from thermal decomposition of hexamethylene-1,6-dicarbamate over Zn–Co bimetallic supported ZSM-5 catalyst

A non-phosgene route for the synthesis of hexamethylene-1,6-diisocyanate(HDI) was developed via catalytic decomposition of hexamethylene-1,6-dicarbamate(HDC) over Zn–Co bi-metallic supported ZSM-5 catalyst.The catalyst was characterized by FTIR and XRD analyses. Three solvents dioctyl sebacate(DOS), dibutyl sebacate(DBS) and 1-butyl-3-methylimidazolium tetrafluoroborate(BMIMBF_4) were investigated and compared; DOS gave better performance. The catalytic performances for thermal decomposition of HDC to HDI using DOS as solvent were then investigated, and the results showed that, under the optimized reaction conditions, i.e.,10 wt%concentration of HDC in DOS, 250 °C temperature, 60 min reaction time, 83.8% yield of HDI had been achieved over Zn–Co/ZSM-5. Decomposition of the intermediate hexamethylene-1-carbamate-6-isocyanate(HMI) over Zn–Co/ZSM-5 in DOS solvent was further studied and the results indicated that yield of HDI from HMI reached to 69.6%(98.6% HDI selectively) at 270 °C, which further increased the yield of the total HDI(HDI_(tol)) to as high as 95.0%. Recycling of catalyst showed that HDI and HMI yield slightly decreased, and by-product yield increased after the catalyst was reused for 4 times. At last possible reaction mechanism was proposed.

Straw mulch-based no-tillage improves tillering capability of dryland wheat by reducing asymmetric competition between main stem and tillers

The moisture-conserving effect of straw mulch-based no-tillage(SMNT)is expected to increase fertile spikes and grain yield in environments with rainfall less than 200 mm.However,the mechanisms under-lying the positive effect of SMNT on wheat tillering are not fully elucidated.A split-plot experiment was designed to investigate the combined effects of SMNT and cultivars on tillering of dryland wheat grown under both dry and favorable climates.Application of SMNT to a cultivar with 1-2 tillers exploited both tillering and kernel-number plasticity,increasing the mean grain yield by 20.5%.This increase was attrib-uted primarily to an increased first-tiller emergence rate resulting from increased N uptake,leaf N con-tent,and N remobilization from tillers to their grain.The second and third tillers,as transient sinks,contributed to the tiller survival rate,which depends on tiller leaf number.The increased total N uptake by SMNT also increased the dry mass yield of tillers and the C:N ratio,reducing the asymmetric compe-tition between main stem and tillers.Owing to these beneficial effects,reduced mitogen-activated pro-tein kinase(MAPK)and abscisic acid signals were observed under SMNT,whereas indole-3-acetic acid(IAA)signals and genes involved in DNA replication and mismatch repair were increased.These signals activated three critical transcription factors(the calmodulin-binding transcription activator,GRAS domain,and cysteine-2/histidine-2 family)and further increased rapid drought response and tiller main-tenance after stem extension.Phenylpropanoid biosynthesis,sphingolipid biosynthesis,and galactose metabolism were most relevant to increased tillering under SMNT because of their critical role in drought response and lignin biosynthesis.Our results suggest that straw mulch-based no-tillage activates rapid drought response and improved wheat tillering by coordinating root N uptake,N remobilization,and asymmetric competition between main stem and tillers.

Isobaric vapor–liquid equilibrium for binary system of aniline+methyl-N-phenyl carbamate

In this study,the quasi-static ebulliometric method was used to measure both of the vapor pressures of methyl N-phenyl carbamate(MPC),and the isobaric vapor–liquid equilibrium(VLE) data of the aniline and MPC binary system.The measured vapor pressure data of MPC,at different temperature ranging from 369.60 to 389.54 K,fitted well with the Antoine equation.The VLE data for the aniline and MPC system at(2.00,4.00,6.00,7.00 and 8.00) k Pa were correlated by both of nonrandom two-liquid(NRTL) and Wilson models.The parameters of the two models were obtained by regressing the experimental data,with the absolute temperature deviations of 0.54 K and 0.53 K,respectively.The relative volatility of the binary system calculated was all far more than 1,which gives the conclusion that the high purity MPC can be separated from aniline and MPC binary system by rectification or distillation technology.

Metallogenesis and ore-forming time of the Changtuxili Mn-Ag-Pb-Zn deposit in Inner Mongolia:Evidence from C-O-S isotopes and U-Pb geochronology

This paper reports new geochronological(U-Pb) and isotope(C,O,and S) data to investigate the timing of mineralization and mode of ore genesis for the recently discovered Changtuxili Mn-Ag-Pb-Zn deposit,located on the western slopes of the southern Great Hinggan Range in NE China.The mineralization is hosted by intermediate-acidic lavas and pyroclastic rocks of the Baiyingaolao Formation.Three stages of mineralization are identified:quartz-pyrite(Stage I),galena-sphalerite-tetrahedrite-rhodochrosite(Stage II),and quartz-pyrite(Stage Ⅲ).δ13C and δ18O values for carbonate from the ore vary from-8.51‰ to-4.96‰ and 3.97‰ to 15.90‰,respectively,which are indicative of a low-temperature alteration environment.δ34SV-CDT values of sulfides range from-1.77‰ to 4.16‰ and show a trend of equilibrium fractionation(δ34SPy>δ34SSp>δ34SGn).These features indicate that pyrite,sphalerite,and galena precipitated during the period of mineralization.The alteration mineral assemblage and isotope data indicate that the weakly acidic to weakly alkaline ore-forming fluid was derived largely from meteoric water and the ore-forming elements C and S originated from magma.During the mineralization,a geochemical barrier was formed by changes in the pH of the ore-forming fluid,leading to the precipitation of rhodochrosite.On the basis of the mineralization characteristics,new isotope data,and comparison with adjacent deposits,we propose that the Changtuxili Mn-Ag-Pb-Zn deposit is an intermediate-to lowsulfidation epithermal deposit whose formation was controlled by fractures and variability in the pH of the oreforming fluid.The surrounding volcanic rocks yield zircon U-Pb ages of 160-146 Ma(Late Jurassic),indicating that the mineralization is younger than 146 Ma.

Green and selective hydrogenation of aromatic diamines over the nanosheet Ru/g-C_(3)N_(4)-H_(2) catalyst prepared by ultrasonic assisted impregnation-deposition method

In this study,nanosheet g-C_(3)N_(4)-H_(2) was prepared by thermal exfoliation of bulk g-C_(3)N_(4) under hydrogen.A series of Ru/g-C_(3)N_(4)-H_(2) catalysts with Ru species supported on the nanosheet g-C_(3)N_(4)-H_(2) were synthesized via ultrasonic assisted impregnation-deposition method.Ultrafine Ru nanoparticles(<2 nm)were highly dispersed on nanosheet g-C_(3)N_(4)-H_(2).Strong interaction due to Ru-Nx coordination facilitated the uniform distribution of Ru species.Meanwhile,the involvement of surface basicity derived from abundant nitrogen sites was favourable for enhancing the selective hydrogenation performance of bi-benzene ring,i.e.,almost complete 4,40-diaminodiphenylmethane(MDA)conversion and>99%4,40-diaminodicyclohexylmethane selectivity,corresponding to a reaction activity of 35.7 mol_(MDA) mol_(Ru)^(-1) h^(-1).Moreover,the reaction activity of catalyst in the fifth run was 36.5 mol_(MDA) mol_(Ru)^(-1) h^(-1),which was comparable with that of the fresh one.The computational results showed that g-C_(3)N_(4) as support was favorable for adsorption and dissociation of H_(2) molecules.Moreover,the substrate scope can be successfully expanded to a variety of other aromatic diamines.Therefore,this work provides an efficient and green catalyst system for selective hydrogenation of aromatic diamines.

Dynamics of NDVI and its influencing factors in the Chinese Loess Plateau during 2002-2018

Understanding the spatio-temporal changes of vegetation and its climatic control factors can provide an important theoretical basis for the protection and restoration of eco-environments.In this study,we analyzed the normalized difference vegetation index(NDVI)in the Chinese Loess Plateau(CLP)from 2002 to 2018 via trend analysis,stability analysis,and Mann-Kendall mutation test to investigate the change of vegetation.In addition,we also used the skewness analysis and correlation analysis to explore the contribution of climate change and human activities on regional vegetation changes.The results indicated that the overall increasing trend of NDVI from 2002 to 2018 was significant The areas showing increased NDVI were mainly distributed in the south-eastern CLP and the irrigation districts of the Yellow River to the north and west of the CLP,while the areas showing decreased NDVl were concentrated in the desert of the westem Ordos Plateau,Longzhong Loess Plateau,and the built-up and adjacent areas.Precipitation was the dominant factor contributing to vegetation growth in the CLP,while vegetation was less dependent onprecipitation in the irigation districts.The increasement of NDVI has led to a prolonged responsetime of vegetation to water stress and a lag effect of less than two months in the CLP.The effect of temperature on NDVI was not significant;significant negative correlations between NDVI and temperature were found only in the desert,the Guanzhong Plain,the southem Liupan Mountains,and the southeastem Taihang Mountains,owing to high temperatures,urban heat islands,and large cloud cover in mountainous areas.Affected by the"Grain for Green Program"(GGP),NDVIin the CLP increased from 2002 to 2018;however,the increasing trends of NDNI for differentvegetation cover types were significantly different owing to the difference in background status.The increasing contribution rate of NDVI in the CLP mainly came from crops and steppes.Urban not only led to the destruction of vegetation but also had radiation effect causing negative impact of NDVI around the cities.This resulted in the aggravation of the negative bias of NDVI with time in the CLP.The results provide a long-term perspective for regional vegetation protection and utilization in the CLP.

Effect of neoadjuvant chemotherapy in combined with laparoscopy on the molecular markers and immune function in patients with locally advanced cervical cancer

Objective: To explore the efficacy of paclitaxel plus cisplatin (TP) neoadjuvant chemotherapy in combined with laparoscopy in the treatment of locally advanced cervical cancer and their effect on the molecular markers and immune function. Methods: A total of 92 patients with locally advanced cervical cancer were included in the study and divided into the control group (n=46) and the treatment group (n=46) according to the admission number. The patients in the control group were given 5- fluorouracil plus cisplatin (PF);neoadjuvant chemotherapy in combined with laparoscopic radical hysterectomy. The patients in the treatment group were given TP neoadjuvant chemotherapy in combined with laparoscopic radical hysterectomy. The clinical efficacy in the two groups was compared. The levels of molecular markers and the change of immune function in the two groups were detected and compared. The adverse reactions in the two groups were observed and compared. Results: After chemotherapy;in the treatment group;CR was 39.13%;PR was 41.30%;NC was 13.04%;PD was 6.52%;and the total effective rate was 80.43%;while those in the control group were 21.74%;26.09%;30.43%;21.74%;and 47.83%;respectively. The total effective rate in the treatment group was significantly higher than that in the control group. The comparison of the occurrence rate of adverse reactions between the two groups was not statistically significant. CEA;SCC-Ag;CYFRA21-1;and CA125 levels 2 weeks after operation in the two groups were significantly reduced when compared with before treatment;and those in the treatment group were significantly lower than those in the control group. MMP-2;TIMP-2;VEGF-C;and VEGF-D levels 2 weeks after operation in the two groups were significantly reduced when compared with before treatment;and those in the treatment group were significantly lower than those in the control group. CD3+;CD4+;and CD8+ 2 weeks after operation in the two groups were significantly reduced when compared with before treatment;while CD4+/CD8+was significantly elevated;but the comparison between the two groups was not statistically significant. Conclusions: Given TP neoadjuvant chemotherapy in combined with laparoscopy in patients with locally advanced cervical cancer can obviously enhance the patient's clinical efficacy;reduce the molecular markers in the body;effectively improve the patient's immune functionwith less adverse reactions and accurate efficacy;therefore;they are safe and reliable.

Generalized or general mixed-effect modelling of tree morality of Larix gmelinii subsp.principis-rupprechtii in Northern China

Tree mortality models play an important role in predicting tree growth and yield,but existing mortality models for Larix gmelinii subsp.principis-rupprechtii,an important species used for regeneration and afforestation in northern China,have overlooked potential regional influences on tree mortality.This study used data acquired from 102 temporary sample plots(TSPs)in natural stands of Prince Rupprecht larch in the state-owned Guandi Mountain Forest(n=67)and state-owned Boqiang Forest(n=35)in northern China.To model stand-level tree mortality,we compared seven model forms of county data.Three continuous(dominant height,plot mean diameter,and basal area per hectare)and one dummy variable with two levels(region)were used as fixed effects variables.Tree morality variations caused by forest blocks were accounted for using forest blocks as a random effect in selected models.Results showed that tree mortality significantly positively correlated with stand basal area and dominant height,but negatively correlated with stand mean diameter.Incorporating both the dummy variables and random effects into the tree mortality models significantly increased the fitting improvements,and Hurdle Poisson mixed-effects model showed the most attractive fit statistics(largest R^(2)and smallest RMSE)when employing leave-one-out cross-validation.These mixed-effects dummy variable models will be useful for accurately predicting Larix tree mortality in different regions.

Tailoring microstructure evolution and mechanical properties of a high-performance alloy steel through controlled thermal cycles of a direct laser depositing process

Direct laser deposition(DLD),as a popular metal additive manufacturing process,shows advantages of technical flexibility and high efficiency to gain a high-performance alloy steel component.However,during the processing of DLD,the deposited steel layer is affected by the subsequent layer depositing.The DLD block shows different microstructure and mechanical properties at the bottom,middle and top of the deposited parts.To date,there are few research works about the effects of inter-layer interval time and laser power on the microstructure evolution and mechanical properties of the deposited layers.In this study,the idle time and laser power layer by layer during DLD of 12CrNi2 steel were controlled to cause the deposited layers to maintain a high cooling rate,while the bottom deposited layer was subjected to a weak tempering effect.Results show that a high proportion of martensite is produced,which improves the strength of the deposited layer.Under the laser scanning strategy of laser power 2,500 W,scanning velocity 5 mm·s^(-1),powder feeding rate 11 g·min^(-1),overlap rate 50%,and a laser power difference of 50 W and a 2 min interval,the tensile strength of the deposited layer of 12CrNi2 steel is in the range of 873-1,022 MPa,and the elongation is in the range of 16.2%-18.9%.This study provides a method to reduce the tempering effect of the subsequent deposition layers on the bottom layers,which can increase the proportion of martensite in the low-alloy high-strength steel,so as to improve the yield strength of the alloy steel.

Anthropogenic ^(129)I in seawaters along the north-central part of the English Channel:Levels and tracer applications

The English Channel(the Channel)represents a major sink and transport pathway of anthropogenic radioactive ^(129)I.Despite this important role,data concerning the distribution of ^(129)I in seawater of the Channel are scarce,and most of existing data are restricted to the eastern part of the Channel.The advection and dispersion of ^(129)I from the French coast toward the central and further the English coast,especially in the Channel west of Cap de La Hague,are not fully investigated.We present results of iodine isotopes( ^(127)I and ^(129)I)analyses of surface water samples collected along the central English Channel in October,2010.The data show high ^(129)I concentrations between Dover Strait and La Hague,followed by a dramatic drop towards the Celtic Sea and reveal the dispersal of ^(129)I towards central and northern part of the Channel.Our observation also implies that the entire British coast is contaminated by ^(129)I. ^(129)I levels in the westernmost English Channel,close to the English coast,may reflect combined influences from La Hague and Sellafield.Evolution of ^(129)I between 2005 and 2010 suggests a strong link to temporal marine discharges from La Hague plant.The discharges from the nuclear reprocessing facility have continued since 2010 and thus an ecological evaluation of ^(129)I radioactive hazards in the environment of the Channel may be needed.

Efficacy of neoadjuvant chemotherapy in the treatment of locally advanced cervical cancer and safety evaluation

Objective: To explore the efficacy of different neoadjuvant chemotherapy (NACT ) i n t h e treatment of locally advanced cervical cancer (LACC) and safety evaluation. Methods: A total of 68 patients with LACC who were admitted in our hospital from April;2015 to August;2016 were included in the study and divided into the observation group (n=34) and the control group (n=34) according to different chemotherapy regimens. The patients in the observation group were given docetaxel and oxaliplatin (DTX+OXA);while the patients in the control group were given TAX and DDP. 21 d-treatment was regarded as one course;for 2 courses. After treatment;the patients in the two groups were given laparoscopic extensive hysterectomy;pelvic lymph node dissection;and abdominal aortic lymph node sampling. The short-term efficacy and adverse reactions in the two groups were observed. Pathological evaluation of postoperative specimens in the two groups was performed. The peripheral blood T lymphocyte subsets and NK cell in the two groups were detected and compared. Results: ORR and DCR in the observation group were 47.09% and 91.18%;respectively;while those in the control group were 44.12% and 85.29%;respectively;and the comparison between the two groups was not statistically significant. When compared with before treatment;CD4+;CD8+;and NK cell after treatment in the two groups were significantly reduced;while CD4+/CD8+ was significantly increased;but the comparison between the two groups was not statistically significant. It was proved by the postoperative pathology that the comparison of PCR;PR1;and PR2 between the two groups was not statistically significant. Meanwhile;the comparison of cervical infiltration depth;surgical incision;parametrial infiltration;and pelvic lymph node metastasis between the two groups was not statistically significant. The proportion of alopecia;gastrointestinal reaction;and renal toxicity in the observation was significantly lower than that in the control group;but the proportion of peripheral neurotoxicity was significantly higher than that in the control group. Conclusions: Before laparoscopy;the short-term efficacy of DTX+OXA and TAX+DDP in the treatment of LACC is equal;but DTX+OXA has a lower toxic reaction;and higher safety;therefore;it deserves to be recommended in the clinic.

铝合金仿生非光滑MAO-HDTM复合膜的构建及减黏脱附研究

铝合金是农业机械潜在的主要轻量化材料之一,但是硬度低,耐磨、耐蚀性差,土壤黏附现象严重等问题限制了其在现代农业机具中的应用.该文以6061铝合金为研究对象,首先采用微弧氧化(MAO)技术对其进行表面处理,构建硬度、耐磨和耐蚀性能较好的非光滑膜层,然后借鉴仿生理论,使用十六烷基三甲氧基硅烷(HDTM)水浴法对其疏水改性,获得了MAO-HDTM复合膜.对复合膜微观形貌、显微硬度、疏水性及土壤黏附进行了测试与分析.形貌检测结果显示:MAO-HDTM复合膜与MAO膜表面形貌相似,均存在类似荷叶表面的仿生凹凸结构.元素分析结果和傅里叶变换红外光谱(FT-IR)图谱显示:HDTM改性剂负载至MAO膜表面及孔隙之中,完成了疏水改性处理.硬度测试结果显示:铝合金基体硬度值为59.94 HV50,而MAO膜和MAO-HDTM复合膜硬度值分别为893.4 HV50和914.4 HV50,硬度得到较大提升.静态接触角测量结果显示:MAO膜为68°,而MAO-HDTM复合膜为147.3°,接近超疏水状态.土壤黏附测试结果显示:在20%,25%和30%含水率的土壤中MAO-HDTM复合膜黏附力值分别低于MAO膜测试值的5%,8%和4%.采用微弧氧化技术与HDTM疏水改性技术相结合构建的仿生非光滑MAO-HDTM复合膜,不但具有高硬度的力学特性,还具有减黏脱附的功能特性,可以为铝合金运用于农业机械轻量化设计提供一种新思路.

8-HQ插层铝合金MAO-LDHs复合膜的自修复行为研究

为进一步提高铝合金微弧氧化(MAO)膜的抗腐蚀能力,通过三步处理获得了MAO-LDHs/8-HQ复合膜,即制备基础MAO膜、负载铝镁水滑石(LDHs)和插层8羟基喹啉(8-HQ)。对三种膜的形貌与物相进行分析,并将三种膜破损后浸入3.5%(质量分数)NaCl水溶液中48 h,利用电化学工作站、SEM、EDS等设备与手段着重探讨了复合膜的抗腐蚀自修复行为。形貌表征与物相分析结果显示,基础MAO膜呈典型疏松多孔状;经水热合成后,铝镁LDHs呈片状结构负载在基础膜表面,将微孔完全封闭;插层处理后,HQ-进入LDHs层间,其SEM形貌无明显改变。电化学测试结果显示,MAO-LDHs/8-HQ复合膜、MAO-LDHs复合膜和MAO膜的自腐蚀电流密度分别为5.877×10^(-7)、2.262×10^(-6)和7.832×10^(-6)A/cm^(2),前者明显小于后两者;自腐蚀电位分别为-0.633、-0.611、-0.613 V,三者基本一致,这说明8-HQ的存在可以显著抑制MAO膜的腐蚀行为。经48 h盐浴腐蚀后,MAO-LDHs/8-HQ复合膜划痕处出现了富含HQ-特征元素(N)的花瓣状沉积物,该沉淀物附着在基体上。上述结果推测,破损后的复合膜在腐蚀环境下释放出HQ-并与基体中的Al 3+发生螯合反应形成沉积物,进而实现膜层的自修复。

基于有源耦合单元的级联光伏系统直流电压传感器故障穿越策略

级联H桥具有模块化、多端口和直挂中压电网等优势,是大规模光伏并网的理想电力电子变换器之一。然而,过多元器件会增加系统故障率。直流环节电压传感器故障作为常见故障之一,会引起控制环路误跟踪、端口功率不匹配等问题,进一步导致直流链路电压不均衡甚至引起系统失稳。因此,该文提出一种基于有源耦合单元的直流电压传感器故障穿越运行策略。通过开关模态推导、分析直流电压自均衡模态及其等效电路,根据不同故障情况优化模态组合并形成直流电压传感器故障穿越调制策略。最后,搭建实验硬件平台,验证理论分析的正确性与所提策略的可行性。