Effect of thermal cycle on Ni-Cr based nanostructured thermal spray coating in boiler tubes

Ni-Cr based nanostructured feedstock powder was prepared by mechanical milling technique involving repeated welding, fracturing, and re-welding of powder particles in a planetary ball mill. The milled nanocrystalline powders were used to coat carbon steel tubes using high velocity oxygen fuel（HVOF） thermal spraying process. The characterization of the feedstock powder and HVOF coated substrates was performed using optical microscope, X-ray diffractometer（XRD）, scanning electron microscope（SEM）, high resolution transmission electron microscope（HR-TEM）, energy dispersive spectrometer（EDS） and microhardness tests. The coated and uncoated samples were subjected to different thermal cycles and characterized for their phase changes, metallurgical changes and microhardness variations. Ni-Cr nanostructured coated samples exhibited higher mechanical and metallurgical properties compared to their conventionally coated counter parts. The results showed that the nanostructured coating possessed a more uniform and denser microstructure than the conventional coating.

High-Temperature Corrosion of Protective Coatings for Boiler Tubes in Thermal Power Plants

High-temperature corrosion is a serious problem for the water-wall tubes of boilers used in thermal power plants. Oxidation, sulfidation and molten salt corrosion are main corrosion ways.Thereinto, the most severe corrosion occurs in molten salt corrosion environment. Materials rich in oxides formers, such as chromium and aluminum, are needed to resist corrosion in high-temperature and corrosive environment, but processability of such bulk alloys is very limited. High velocity electric arc spraying (HVAS) technology is adopted to produce coatings with high corrosion resistance. By comparison, NiCr (Ni-45Cr-4Ti) is recommended as a promising alloy coating for the water-wall tubes, which can even resist molten salt corrosion attack. In the study of corrosion mechanism, the modern material analysis methods, such as scanning electron microscopy (SEM), X-ray diffractometry (XRD) and energy dispersive spectrometry (EDS), are used. It is found that the corrosion resistances of NiCr and FeCrAI coatings are much better than that of 20g steel, that the NiCr coatings have the best anti-corrosion properties, and that the NiCr coatings have slightly lower pores than FeCrAI coatings.It is testified that corrosion resistance of coatings is mainly determined by chromium content, and the microstructure of a coating is as important as the chemical composition of the material. In addition, the fracture mechanisms of coatings in the cycle of heating and cooling are put forward. The difference of the thermal physical properties between coatings and base metals results in the thermal stress inside the coatings. Consequently, the coatings spall from the base metal.

The Hot Corrosion Performance of NiCr-Cr_3C_2 Cermet Coating to Boiler Tube

Three kinds of NiCr-Cr 3C 2 cermet coatings were designed and deposited by the subsonic velocity flame spraying, and their performances of hot corrosion performance were evaluated in comparison with 102G, 20G boiler tube steel, FeCrAl, NiCrTi, Ni50Cr and NiCrAlMoFe-Cr 3C 2 coatings, which are widely used at present for protection of boiler tubes. Meanwhile,the influence of sealer on the hot corrosion resistance of various coatings and the mechanisms of coating corrosion were explored.

Extended Anode Effect for Tube Inner Coating of Non-Conductive Ceramics by Pulsed Coaxial Magnetron Plasma

For uniform tube inner coating of non-conductive thin films, the double-ended coaxial magnetron pulsed plasma (DCMPP) method was investigated. In this study, coating of TiN and TiO2 was performed. It was clearly shown that the extended anode effect was strongly influenced by the electric resistance of the coated thin films on the inner surface of an insulator tube. Additionally, high frequency (100 kHz) was better for relatively high plasma density. On the other hand, in the case of titanium oxide deposition, negative ion productions drastically decrease the deposition rate and the shifting velocity of plasma main position for coated TiO2 films.

Preparation and Anti-coking Property of SiO_2/S Coating on HP40 Tube

SiO2/S coating was prepared on the inner surface of an HP40 tube using dimethyldisulfide and tetraethylorthosilicate by atmospheric pressure chemical vapor deposition(APCVD) to alleviate catalytic coking on the inner surface of radiant tube for ethylene production in petrochemical plants.The comparative coking experiments with the coated and uncoated HP40 tubes were carried out under the same cracking conditions.SiO2/S coating was compact and had excellent anti-coking property.The coke on the coated HP40 tube was about 22% of that on the uncoated HP40 tube,and only small granular coke was deposited on the coated HP40 tube.However,the filamentous coke formed on the uncoated HP40 tube.The thermal stability of SiO2/S coating was satisfactory at cracking temperature,and the anti-coking property of SiO2/S coating was still over 60% after 3 coking and decoking cycles.

Measurement of Young's Modulus and Poisson's Ratio of Thermal Barrier Coatings

In gas turbines, thermal barrier coatings （TBCs） applied by air plasma spraying are widely used to lower the temperature of hot components. To analyze the characteristics of TBCs such as residual stress, bond strength, fracture toughness, and crack propagation ratio, the Young＇s modulus and Poisson＇s ratio are important parameters. For TBC is a brittle and thin film, it is desirable to evaluate those properties while the coatings are bonded to a substrate. An atmospheric plasma spray MCrAIY bond coat and Yttria stabilized zirconia （YSZ） top coat are deposited onto a nickel-base superalloy GH150 substrate. The Young＇s modulus and Poisson＇s ratio are measured by cantilever beam bending with NDI. The method will be developed to test the Young＇ s modulus and Poisson ratio of other multilayer systems.

Nasogastric tube syndrome:A Meta-summary of case reports

BACKGROUND Since its description in 1790 by Hunter,the nasogastric tube(NGT)is commonly used in any healthcare setting for alleviating gastrointestinal symptoms or enteral feeding.However,the risks associated with its placement are often underes-timated.Upper airway obstruction with a NGT is an uncommon but potentially life-threatening complication.NGT syndrome is characterized by the presence of an NGT,throat pain and vocal cord(VC)paralysis,usually bilateral.It is poten-tially life–threatening,and early diagnosis is the key to the prevention of fatal upper airway obstruction.However,fewer cases may have been reported than might have occurred,primarily due to the clinicians'unawareness.The lack of specific signs and symptoms and the inability to prove temporal relation with NGT insertion has made diagnosing the syndrome quite challenging.AIM To review and collate the data from the published case reports and case series to understand the possible risk factors,early warning signs and symptoms for timely detection to prevent the manifestation of the complete syndrome with life-threatening airway obstruction.METHODS We conducted a systematic search for this meta-summary from the database of PubMed,EMBASE,Reference Citation Analysis(https://www.referencecitation-analysis.com/)and Google scholar,from all the past studies till August 2023.The search terms included major MESH terms"Nasogastric tube","Intubation,Gastrointestinal","Vocal Cord Paralysis",and“Syndrome”.All the case reports and case series were evaluated,and the data were extracted for patient demographics,clinical symptomatology,diagnostic and therapeutic interventions,clinical course and outcomes.A datasheet for evaluation was further prepared.RESULTS Twenty-seven cases,from five case series and 13 case reports,of NGT syndrome were retrieved from our search.There was male predominance(17,62.96%),and age at presentation ranged from 28 to 86 years.Ten patients had diabetes mellitus(37.04%),and nine were hypertensive(33.33%).Only three(11.11%)patients were reported to be immunocompromised.The median time for developing symptoms after NGT insertion was 14.5 d(interquartile range 6.25-33.75 d).The most commonly reported reason for NGT insertion was acute stroke(10,37.01%)and the most commonly reported symptoms were stridor or wheezing 17(62.96%).In 77.78%of cases,bilateral VC were affected.The only treatment instituted in most patients(77.78%)was removing the NG tube.Most patients(62.96%)required tracheostomy for airway protection.But 8 of the 23 survivors recovered within five weeks and could be decannulated.Three patients were reported to have died.CONCLUSION NGT syndrome is an uncommon clinical complication of a very common clinical procedure.However,an under-reporting is possible because of misdiagnosis or lack of awareness among clinicians.Patients in early stages and with mild symptoms may be missed.Further,high variability in the presentation timing after NGT insertion makes diagnosis challenging.Early diagnosis and prompt removal of NGT may suffice in most patients,but a significant proportion of patients presenting with respiratory compromise may require tracheostomy for airway protection.

Prediction and optimization of process variables to maximize the Young’s modulus of plasma sprayed alumina coatings on AZ31B magnesium alloy

Like other manufacturing techniques,plasma spraying has also a non-linear behavior because of the contribution of many coating variables.This characteristic results in finding optimal factor combination difficult.Subsequently,the issue can be solved through effective and strategic statistical procedures integrated with systematic experimental data.Plasma spray parameters such as power,stand-off distance and powder feed rate have significant influence on coating characteristics like Young’s modulus.This paper presents the use of statistical techniques in specifically response surface methodology(RSM),analysis of variance,and regression analysis to develop empirical relationship to predict Young’s modulus of plasma-sprayed alumina coatings.The developed empirical relationships can be effectively used to predict Young’s modulus of plasma-sprayed alumina coatings at 95%confidence level.Response graphs and contour plots were constructed to identify the optimum plasma spray parameters to attain maximum Young’s modulus in alumina coatings.A linear regression relationship was established between porosity and Young’s modulus of the alumina coatings.

Effect of Rare Earth on the Corrosion-Resisting Performance of Zinc-Based Alloy Coatings

The corrosion behavior of coatings of pure zinc and Zn-Al,Zn-Al-RE alloys in NaCl solu- tions was studied by salt-spray experiments,even corrosion experiments and electrochemical measurements of bi-directional polarization curves and a.c.impedance in weak polarization region consistent regularities were obtained by these different methods,viz.,the corrosion resistance of Zn could be enhanced by alloying it with Al,and particularly with Al-RE.The causes of enhancement of corrosion resistance by RE were also discussed.

Kinetic Study of SiO_2/S Coating Deposition by APCVD

To alleviate catalytic coking on the inner surface of radiant tube for ethylene production in petrochemical plants,SiO2/S coatings were deposited on HP40 alloy specimens using dimethyldisulfide （DMDS） and tetraethoxysilane （TEOS） by atmospheric pressure chemical vapor deposition （APCVD）. A two-dimension mathematical model was made to predict the growth rate of SiO2/S coating and to study the effects of deposition parameters on the deposition rate. The results show that the predicted deposition rate is in good agreement with the experimental one. The deposition rate mainly depends on the concentrations of precursors in the total gas flow, concentrations of intermediates on the deposition surface, total gas flow rate and deposition temperature. The weight of SiO2/S coating linearly increases with the deposition time. When the gas flow rate is below 0.3 m/s, the rate-limiting step of SiO2/S coating deposition is the diffusions of intermediates.However, the surface reactions of intermediates will be the rate-limiting step after the gas flow rate is above 0.3 m/s. When the deposition temperature is below 780℃, the rate-limiting step of SiO2/S coating deposition mainly depends on the surface reactions of intermediates. When the deposition temperature is above 780℃,the rate-limiting step depends on the diffusions of intermediates. The deposition rate increases with increasing the concentrations of the intermediates. However, when the partial pressures of the intermediates reach 8 Pa,the deposition rate keeps constant.

ZnS coating of cathode facilitates lean‐electrolyte Li‐S batteries

Tremendous effort has been devoted to lithium‐sulfur batteries,where flooded electrolytes have been employed ubiquitously.The use of lean electrolytes albeit indispensable for practical applications often causes low capacity and fast capacity fading of the sulfur cathode;thus,the electrolyte/sulfur active mass ratios below 5μL/mg have been rarely reported.Herein,we demonstrate that ZnS coating transforms sulfur cathode materials electrolyte‐philic,which tremendously promotes the performance in lean electrolytes.The ZnS‐coated Li2S@graphene cathode delivers an initial discharge capacity of 944mAh/g at an E/S ratio of 2μL/mg at the active mass loading of 5.0 mg Li2S/cm^2,corresponding to an impressive specific energy of 500Wh/kg based on the mass of cathode,electrolyte,and the assumed minimal mass of lithium metal anode.Density functional theory calculations reveal strong binding between ZnS crystals and electrolyte solvent molecules,explaining the better wetting properties.We also demonstrate the reversible cycling of a hybrid cathode of ZnS‐coated Li2S@graphene mixed with VS2 as an additive at an E/AM(active mass)ratio of 1.1μL/mg,equivalent to the specific energy of 432 Wh/kg on the basis of the mass of electrodes and electrolyte.

Studies on electroless Ni-P-Cr_2O_3 and Ni-P-SiO_2 composite coatings

本文对化学镀镍及化学镀镍磷基质中SiO2与Cr2O3的共沉积进行了研究。微粒在不断生长的膜层中共沉积引起了新的化学复合镀层的出现,这些复合镀层许多都具有优异的耐磨及耐蚀性能。通过选取镀层合金/复合微粒/金属基体的组分可改进镀层,获得所需的性能,以满足特别的需求。在对这些复合镀层的应用需求正在迫近与增长的同时,其市场正在迅速扩张。本文开发出了一种合适的复合化学镀镍液,并通过维氏硬度法对化学复合镀镍层进行了表征。采用动电位极化及交流阻抗法测定了镀层的Taber耐磨性能及耐蚀性能。采用SEM及XRD对复合镀层的表面形貌进行了分析。

Study on Tongue Coating Microbiota in Patients with Atrophic Gastritis

Aims: To explore the tongue coating microbiota composition in patients with atrophic gastritis by using the 16S rRNA gene sequencing technology. Methods: The study included 29 atrophic gastritis patients and 29 age and gender-matched non-atrophic gastritis controls. By sequencing the V3-V4 region of the 16S rRNA, we investigated the microbial community structure and diversity on the tongue coating. Results: There was no significant difference in the microbial diversity on the tongue coating between the two groups. However, compared with the control, the atrophic gastritis group had a smaller number of operational taxonomic units (OTUs). At the class level, patients with atrophic gastritis had lower relative abundances of Betaproteobacteria and Spirochaetia than the control group. At the gene level, the abundance of Neisseria and Aggregatibacter in atrophic gastritis group had significantly decreased compared with control ones. Furthermore, functional prediction revealed that 24 metabolic pathways significantly differed between the two groups. Conclusions: Our findings provide novel evidence that tongue coating microbiota may be a biomarker for characterizing patient with atrophic gastritis, but its mechanism needs to be further elaborated.

Iron casting skin management in no-bake mould – Effects of magnesium residual level and mould coating

The relative performance of coatings for furan resin sand moulds [P-toluol sulphonic acid(PTSA) as hardener] [FRS-PTSA moulds], was compared by analyzing the surface layer for degenerated graphite in Mg treated iron with 0.020 wt.% to 0.054 wt.% Mgres. It was found that the iron nodularising potential(Mg, Ce, La content) and whether the mould coatings contained S, or were capable of desulphurizing were important factors. These moulds have S in the PTSA binder, which aggravates graphite degeneration in the surface layer, depending strongly on the Mgres with lower Mgres increasing the layer thickness. The application of a mould coating strongly influenced graphite deterioration in the surface layer of castings. It either promoted graphite degeneration to less compact morphologies when using S-bearing coatings, or conversely, limited the surface layer thickness using desulphurization type coatings. Independently of the S-source at the metal – mould interface, the presence of sulphur had an adverse effect on graphite quality at the surface of Mg-treated irons, but its negative effect could also reach the graphite phase within the casting section. If the coatings employed desulphurization materials, such as Mg O, or a mixture(Ca O + Mg O + Talc) or Mgbearing Fe Si, they protected the graphite shape, improving graphite nodularity, at the metal – mould interface, and so decreased the average layer thickness in FRS-PTSA moulds. Fe Si Mg was highly efficient in minimizing the casting skin by improving graphite nodularity. It is presumed that the Mg O or(Mg O + Ca O + Talc) based coatings acted to remove any S released by the mould media. The Mg-Fe Si coatings also reacted with S from the mould but additionally supplemented the Mg nodularising potential prior to solidification. This dual activity is achievable with coatings containing active magnesium derived from fine Mg-Fe Si materials.

Application of Epoxy Coatings to Increase the Efficiency of Wax Oils Production

When producing hydrocarbons,an important task relates to the optimization of the stock of the producing well.The main complications for wells in non-working mode are represented by the formation of asphalt-resinparaffin deposits.This issue is one of the most common problems in the production and transportation of oil.A promising method to deal with these deposits is the application of smooth coatings made of epoxy polymers on the inner surface of the production well tubing.In this work,a number of laboratory studies were carried out on the“Cold Finger”installation to assess the effectiveness of this approach.These laboratory studies have shown that the efficiency related to smooth coatings is 27%while the resulting thermal conductivity ranges from 0.259 to 0.279 W/(m°C).These results demonstrate that this technology can reduce the amount of organic deposits and increase the temperature of oil.

Preparation and Performance of Corona-proof Conductive Composite Coatings

Because of its merits,acrylic resin was chosen to improve the mechanical,conductive and hydrophobic properties.Carbon fiber powders (CF),carbon nanotubes (MWCNT),and nano-TiO_(2) were incorporated into the acrylic resin to prepare the corona-proof conductive composite coatings.The incorporation of CF and MWCNT may improve the conductivity and mechanical strength of the coatings.However,the addition of nano-TiO_(2) may increase the hydrophobicity of the coatings.Thus,the effects of different additives on the mechanical properties,conductivity,hydrophobicity and heat resistance of the conductive film were studied.The experimental results show that the incorporation of carbon fiber powders and multi walled carbon nanotubes can significantly improve both the conductivity and mechanical properties of the conductive coatings,and the addition of nano titanium dioxide can improve the hydrophobicity of the conductive film.

Characterization of functionally graded ZrO_2 thermal barrier coatings sprayed by supersonic plasma spray with dual powder feed ports

The functionally graded thermal barrier coatings （FG-TBCs） with 80%ZrO2-13%CeO2-7%Y2O3 （C-YSZ）/NiCoCrAlY were prepared using a recently developed supersonic plasma spraying（S-PS） with dual powder feed ports system. The thermal shock experiment of FG-TBCs specimens was carried out by means of the automatic thermal cycle device, in which the samples were heated to 1200℃ by oxygen-acetylene flame jet then water-quenched to ambient temperature. The temperature—time curves of specimens and photographs can be watched on-line and recorded by a computer during the test. The results show that the totally 1mm-thick FG-TBCs have excellent thermal shock resistance due to the fact that the coatings have no any peeling-off after 200 thermal cycles. The microstructures and morphologies of FG-TBCs were characterized and analyzed by SEM.

Numerical simulation of multistage induction heating of coated steel tubes in Baosteel

The electromagnetic and temperature fields in the multistage intermediate-frequency induction heating of coated steel tubes were calculated using a numerical simulation.The influence of the voltage and frequency on the parameters of power circuit and heating temperature of the steel pipe was also analyzed.The results indicate that:(1) the electromagnetic field of induction heating is concentrated between the induction coil and steel tube and dissipated more at both ends of the coil;(2) during the induction heating,the temperature difference between the outer and inner walls of the steel pipe is approximately 3040 K,and the two temperatures rapidly tend to be the same after exiting the induction heater;(3)during the natural cooling,the temperature drop of the steel tube in the low-temperature section is approximately 10 K,and that in the high-temperature section is approximately 20 K;(4)the appropriate induction heating frequency and matching capacitance should be selected,so that the temperature of the steel pipe,especially at the outer wall,meets the coating process requirements,and as to achieve a synchronous improvement of the power efficiency and heating efficiency.This study is beneficial to building a more low-consumption and high-efficiency coating line of large-diameter steel pipes in Baosteel.

Study on the relationship between the structure of bacterial flora onthe tongue and types of tongue coating in patients with type 2diabetes mellitus

Objective:To analyze the characteristics of bacterial flora on the tongue and types of tongue coating between healthy individuals and patients with type 2 diabetes mellitus(T2DM)via detecting 16S rDNA of oral tongue coating microbial group.Methods:A total of 42 patients with T2DM were recruited,including 6 with thin white coating,9 with mirror-like coating,27 with yellow thick coating(YTC),and 28 healthy individuals.The V4 region of 16S rDNA from the tongue coating microbiota was sequenced using the Linux ubuntu sequencing platform,and the structure of bacterial flora in the tongue was analyzed.Treeplot construction,principal coordinates analysis,redundancy analysis,and linear discriminant analysis were conducted using R software to analyze the differences of bacterial flora in the tongue coating in each group.Results:A total of 8131 different operational taxonomic units(OTUs)were obtained via sequencing,of which 719 OTU samples showed significant differences(P<0.05).Comparing OTUs with the 16S rDNA database of known species and annotation of parallel species revealed 16 species with differences at the phylum level,31 at the class level,54 at the order level,88 at the family level,and 161 at the genus level.The dominant bacteria found in patients with T2DM included Lactobacillus,Streptophyta,Chloroplast,Cyanobacteria-Chloroplast,and Bifidobacteriaceae,etc.Dominant bacteria in the control group belonged to Pasteurellales,Pasteurellaceae,Leptotrichiaceae,Lachnoanaerobaculum,and Ignavibacteria among other bacterial families.All samples were clustered into three groups,each group characterized by dominant bacteria.The order of dominant bacteria in group 1 were Prevotella>Neisseria>Veillonella>Streptococcus>Fusobacterium>Leptotrichia and so on.The order of dominant bacteria of group 2 were Neisseria>Prevotella>Fusobacterium>Streptococcus>porphyromonas and so on.The dominant bacteria of group 3 were Prevotella>Fusobacterium>Streptococcus>Neisseria>Leptotrichia>Rothia>Veillonella>porphyromonas>f_Pasteurellaceae>Capnocytophaga>Actinomyces>Alloprevotella and so on.Single factor risk estimation:with group 1 used as the reference(OR=1),the risk of carrying group 2 and group 3 microflora with T2DM increased(OR values were 4.77 and 7.78,respectively).The proportion of group 1 microflora in the control group(25.9%)was higher than that in the T2DM group(5.4%)(χ2=3.873,P=0.049).Compared with group 1 and group 2,group 3 had a significantly dominant microflora structure in YTC group(χ2=7.120,P=0.008).RDA analysis indicated that Neisseria,Fusobacterium,and Prevotella were associated with HbA1c values>10 mmol/L,whereas Rothia,Streptococcus,and Veillonella were more correlated with HbA1c≤10 mmol/L.Conclusion:The incidence of T2DM is related to the imbalance of oral microflora in the human body.The tongue coating flora structure may influence the formation of different tongue coating types in this metabolic condition.Additionally,flora structures of Prevotella,Neisseria,and Fusobacterium were associated with elevated HbA1c.

Coat's病的光凝与冷凝治疗(附35例报告)

目的:评价氩激光光凝配合巩膜外冷凝方法在临床上治疗Coat's病的效果及意义。方法:22例23眼用氩激光(德国欧波同Mediek CLu40 E氩离子激光机,能量0.2w,光斑100～500μ,脉冲时间0.1～0.2秒,Ⅱ级反应)或配合巩膜外冷凝(-60～-80℃,冷凝时间5秒,随后重复一次,见视网膜有灰白色水肿反应为宜)治疗。结果:有18只眼获得了不同程度的疗效(治疗有效率占治疗眼数的78.2％)。眼底病变好转或稳定,视力有提高,随访时间1—3年。结论:氩激光或配合巩膜外冷凝方法治疗Coat's病的效果是肯定的。一经诊断为Coat's病,只要患眼有一定的视功能,就应该及时给予光凝或光凝加巩膜外冷凝治疗,这对于防止病情进一步恶化,保存患眼一定的视功能具有重要意义。眼科学报1996;12:199～201。