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.

Surface modification with SiO_2 coating on biomedical TiNi shape memory alloy by sol-gel method

The effect of heat treatment on the transformation temperature of Ti?52.2%Ni (mole fraction) alloy was studied using differential scanning calorimetry (DSC). The transformation temperatures of the alloy can be adjusted effectively by heat treatment. Dense and stable SiO2 coatings were deposited on the surface of the pre-oxidized TiNi alloy by sol?gel method. The bonding strength of films and matrix was (65.9±1.5) N. The electrochemical corrosion test shows that the TiNi alloy with SiO2 coating has excellent corrosion resistance in the Hank’s simulated body fluid. The release behaviors of Ni ion of the alloy with and without SiO2 coating implanted in the acoustic vesicle of guinea pig were studied by EDS testing, which was inhibited effectively by the dense and stable SiO2 coating on the alloy.

Fabrication and Microstructure of SiO_2-GeO_2 Sol-gel Glass Coatings

SiO 2-GeO 2 sols and gel glass coatings with different contents of germanium dioxide were fabricated.Stable and transparent sols could only be obtained when the content of GeO 2 was under 35%.It is shown by SEM that only one continuous phase is observed in the coating of 65SiO 2·35GeO 2 and plenty of Ge,O and Si were all found in it.However,the separated phase is found in the coating of 60SiO 2·40GeO 2 and a large number of Ge and O.It is proved by the Raman scattering investigation that the separated phase in the coating of 60SiO 2·40GeO 2 is germanium dioxide.The congeries of hydrolystates of Cl 3GeCH 2CH 2COOH play the main role in the formation of the separated phase when the proportion of GeO 2 is much higher.Si-O-Ge,Si-O-Si,and Ge-O-Ge bonds form in the coating of 65SiO 2·35GeO 2 and this coating is homogenous.

Influence of heat treatment on microstructures and micro-hardness of n-SiO2/Ni composite coating

The n-SiO2/Ni composite electro-brush plating coating was prepared on the 1045 steel substrate. SEM and TEM were utilized to analyze the surface and cross-section morphologies or the microstructures of the composite coating before and after heat treatment, as well as a micro-hardness tester was used to measure the micro-hardness before and after heat treatment. The results show that the entrance of nano SiO2 particles into composite coating makes the micro-hardness higher. After heat treatment, due to the obstruction to growth of Ni crystals from nano particles, the composite coating still possesses a higher micro-hardness than that of common Ni-base coating.

Application of Nano Coating （SiO2） on Textile Products

Liquid SiO2 solutions produced by silicon-based nano- powder are covered on the fabric surface by using spray method. Fabric surfaces were coated at the room temperature in air with the different spray nozzles. Surface analysis of the coated fabric was performed by using Contact Angle and SEM pictures. According to the Contact Angles measurements, the coated fabric surfaces showed hydrophobic character between 126 and 146 degrees, and the SiO2 particles sticked to the fabric fibers as seen from SEM picture.

Luminescent Properties of BaMgAl_(10)O_(17)∶Eu^(2+) Phosphors Coated with Y_2SiO_5

BaMgAl10O17： Eu^2＋ phosphors was prepared by the solid-reaction method. Y2SiO5 was coated uniformly on the surface of phosphor by the surface-coated method, and the luminescent and deterioration properties were discussed. The XRD and SEM results show that Y2SiO5 film is produced on the surface of BAM phosphor. The emission spectrum analysis shows that the peak of the phosphor does not change after coating. The two phosphors were applied to lamps and the deterioration was tested at different ignited time. The keep ratio of luminous flux of the phosphor coated with Y2SiO5 is higher than that of the uncoated phosphor.

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.

塔河油田H_(2)S-CO_(2)-O_(2)共存体系下伴生气管道选材和内涂层评价

研究伴生气管道常用3种管材在H_(2)S-CO_(2)-O_(2)3种气体共存体系下的腐蚀行为,可为塔河油田伴生气管道的腐蚀防控提供指导依据。基于塔河油田典型腐蚀工况,以20钢、L245NS钢和3Cr钢为研究对象,利用高温高压釜试验对3种钢材典型H_(2)S-CO_(2)-O_(2)共存工况下的腐蚀速率和腐蚀产物进行研究,得到20钢腐蚀速率最大,L245NS钢腐蚀速率次之,3Cr钢腐蚀速率最小,3种管材的腐蚀产物主要是Fe、FeS、FeCO_(3)和Fe_(2)O_(3)。对塔河油田4种典型内防腐涂层进行腐蚀前后增重法和附着力测试研究涂层的耐蚀行为,涂层2的抗腐蚀性能和附着力效果最好。考虑性价比,最后选用“L245NS+涂层2”作为塔河油田伴生气管线的防腐措施。

SiO_2/S涂层抑制结焦性能的中试对比研究

为了抑制乙烯裂解炉管结焦,对SiO2/S涂层的抑制结焦性能进行了中试试验,并与未涂层炉管和加入结焦抑制剂炉管的结焦结果进行了对比。利用SEM和EDS表征了炉管出口部位结焦层的形貌及成分。结果表明,与未涂层炉管相比,SiO2/S涂层的结焦抑制率为39%,而结焦抑制剂的结焦抑制率为41%,2种工艺条件的抑制结焦效果相当。未涂层、涂层和加入结焦抑制剂的炉管出口结焦层均发生了片状剥落,剥落焦层主要由碳元素组成,且无丝状催化焦存在。涂层和加入结焦抑制剂的炉管剥落焦层厚度约为30μm,而未涂层炉管剥落焦层厚度约为50μm。焦层剥落后的未涂层炉管和加入结焦抑制剂炉管表面为粒状焦,而涂层炉管表面为松散的粉末状焦。

纳米TiO_2表面包覆致密SiO_2膜的试验研究

用液相沉积法对纳米二氧化钛进行了表面改性。用XRD、FT IR分析手段对其进行了表面结构表征 ,采用X衍射荧光光谱仪 (XRF)测定SiO2 包覆量随陈化时间的变化。通过煅烧失重法比较改性前后样品的失重 ,并用动态法测量样品与水的湿润角。结果表明在TiO2 表面存在致密非晶态的硅氧化合物膜 ,纳米TiO2 与水的湿润角增大 ,并且充分分散后在水中的稳定性却得到了很大提高。

SiO_2包覆超细CaCO_3的结构和机理分析

合成了表面包覆 Si O2 的超细 Ca CO3 。通过 XPS,XRD对包覆表面层结构的分析 ,证实了 Si O2 以无定形包覆于 Ca CO3 表面 ,并在其表面形成了 Si- O- Ca键。对 Si O2 包覆超细 Ca CO3 的机理分析结果可知 :Na2 Si O3 的加入量是影响包覆效率的重要因素 ,由于硅酸易自聚 ,控制 Si O2 与 Ca CO3 的重量比约为4 %～ 5 %时为包覆的最佳点 ;Ca CO3 晶粒度大小影响分散性能 ,进而影响包覆效率 ,分散性能好的包覆效率较高。

SiO2复合Pt-Cd0.53Zn0.47S固溶体的光催化性能

采用共沉淀法制备了Cd0.53Zn0.47S固溶体光催化剂,以光还原沉积法负载Pt,水解正硅酸乙酯负载SiO2,得到了负载Pt的SiO2复合光催化剂SiO2/Pt-Cd0.53Zn0.47S,并研究了水解pH值对其催化活性的影响.通过X射线衍射(XRD)、比表面(BET)、荧光光谱(PL)、紫外-可见漫反射光谱(UV-Vis DRS)和扫描电镜(SEM)等测试技术对催化剂进行了表征.结果表明,SiO2复合光催化剂有效地抑制了Pt-Cd0.53Zn0.47S光催化过程中发生的光腐蚀和粒子团聚,促使光生电子和空穴分离,从而使可见光制氢催化剂活性和稳定性大大提高.

纳米SiO_2复合涂料的稳定性研究

介绍了纳米SiO2 的特性 ,分析了影响纳米SiO2 复合涂料稳定性的因素 ,对纳米SiO2 进行改性 ,将涂料粒径。

SiO_2/S涂层和硫磷抑制剂的抑制结焦性能研究

采用常压化学气相沉积法(APCVD)在退役25Cr35Ni乙烯裂解炉管内表面制备了SiO_2/S涂层,分别研究了表面涂层与裂解原料中添加结焦抑制剂的抗结焦性能;并对表面涂层与结焦抑制剂的联合结焦抑制性能进行研究。利用扫描电子显微镜(SEM)、能量色散谱仪(EDS)和Raman光谱对SiO_2/S涂层形貌、成分和结构进行分析,对焦层形貌进行表征。结果表明:SiO_2/S涂层粒子结合紧密,粒径为6～10μm,涂层厚度约为7μm;涂层由Si—O—Si三节环结构和非晶态的Si—O—S结构构成;炉管内表面经过涂层处理后,结焦抑制率为65.07%;裂解反应原料中加入结焦抑制剂的质量分数为200μg/g时,结焦抑制率为69.20%;表面涂层与结焦抑制剂联合使用时,结焦抑制剂最佳质量分数约为50μg/g,联合结焦抑制率为98.50%。

纳米SiO_2在紫外光固化涂料中的应用

考察了纳米ＳｉＯ２对紫外光固化涂膜性能的影响。结果表明，ＳｉＯ２的加入，可提高涂膜的固化速度、涂膜硬度、附着力和低温下的热稳定性。

Ni-SiC和Ni-SiO_2复合镀层性能的研究

对Ni SiC、Ni SiO2 复合镀层在 5 %NaCl+0 .5 %H2 O2 溶液中的腐蚀性能 ,80 0℃高温下的抗氧化性能以及导热性能进行了研究。并利用扫描电镜 (SEM)对镀层微观组织形貌进行了观察和分析。实验结果表明 :与Ni SiC复合镀层比较 ,Ni SiO2 复合镀层在 5 %NaCl+0 .5 % /H2 O2 溶液中以及在 80 0℃高温环境中 ,均表现出较好的耐蚀和抗氧化能力 ;而Ni SiC复合镀层的导热性则明显强于Ni SiO2 ,两者的导热系数随时间延长均略有减少。文中对产生这些性能差异的原因进行了初步的探讨与分析。

Ni/SiO_2复合电镀层高温氧化性能的研究

本试验在普通镀镍液中添加了 10～ 4 0 g/L的二氧化硅微粒 ,成功地制备了 Ni/Si O2 复合镀层 ,随后在 80 0℃下进行了高温氧化试验。研究结果表明 :不同粒径的微粒均可复合进入镀层 ,微粒的进入对镀层的高温抗氧化性有明显影响 ;初始氧化阶段 ,微粒的存在有利于提高镀层的抗高温氧化性能 ;在高温氧化过程中 ,还明显存在基底铜向镍镀层的扩散 ,这可能有利于增强镀层与基底之间的结合力。X射线衍射分析表明 :高温氧化后在镀层表面主要生成 Ni O产物。

SiO_2溶胶-凝胶转变过程的动力学研究及应用

以硅酸乙酯为前驱体,通过水解法制备SiO2溶胶,系统研究了SiO2胶体的溶胶-凝胶转变过程。讨论了不同参数(如pH值、温度、硅酸乙酯的浓度等)对溶胶体系胶凝时间的影响,并对该过程的活化能进行了计算。结果表明:在酸性条件下,溶胶分子的生长模式为线性;随pH值增加,体系胶凝时间先增加后减少,拐点在pH等于2处;活化能与体系的pH有关。同时对上述结果从化学键、电荷密度、反应机理等方面进行了合理的解释。

纳米SiO_2在钢结构防火涂料中的应用

本文将纳米SiO2 应用在水性超薄型钢结构防火涂料中 ,经耐火实验发现适量的添加可以明显提高涂料燃烧后炭质层的强度 ,延长其耐火极限 ;同时纳米SiO2 的紫外屏蔽光谱和涂料的人工老化实验表明纳米SiO2 具有特殊的光学性能 ,可以屏蔽大部分紫外光 ,将其使用在钢结构防火涂料中可以有效延缓涂料的老化进程 ,保持防火性能的稳定。

SiO_2添加剂对8%Y_2O_3稳定的ZrO_2涂层热震前后表面形貌的影响

在 8 %Y2 O3 稳定的ZrO2 陶瓷涂层中添加SiO2 ,使陶瓷涂层的抗热震性能得到提高 ,这主要是SiO2 的加入使涂层抗热震前后的表面形貌发生了很大的变化。由于ZrO2与SiO2 热膨胀系数不同 ,使涂层利于产生细微的网状裂纹 ,增加了微裂纹密度和孔隙 ,从而降低了涂层的弹性模量 ,释放了涂层中的应力 ,使涂层的抗热震失效能力得到提高。其中 ,SiO2 加入量为 3% (质量分数 )效果最佳 ,过量的加入 ,会使孔洞加大 ,促进裂纹的扩展、断裂 ,不利于提高涂层的抗热震性能。