析晶污垢生长影响因素概述

结垢问题存在于各个行业,尤其在油田表现更甚。但材料表面特性对油田采出水中析晶污垢的影响并没有得到太多关注。主要对影响析晶污垢生长的三种主要表面特性因素进行简要综述。     

The mechanical and thermal properties,CMAS corrosion resistance,and the wettability of novel thermal barrier material GdTaO4

Because the CMAS corrosion and phase transformation at elevated temperatures above 1250 °C have limited the applications of traditional YSZ, the design of novel thermal barrier materials is a hotspot. GdTaO₄ is considered as a type of potential novel thermal barrier material owing to its low thermal conductivity. In this study, the mechanical and thermal properties, CMAS corrosion resistance, and the wettability of the GdTaO₄ were studied and compared with that of YSZ. The results show that the coefficient of thermal expansion and hardness of GdTaO₄ are 14.1 × 10⁻⁶ K⁻¹ (1350 °C) and 534.2 Hv_0.3 respectively. The thickness of CMAS reaction layer of GdTaO₄ is ~30.8 μm after 24 h reaction at 1350 °C, which is thinner than that of YSZ. After corrosion reaction, the CMAS glass aggregated instead of completely disappearing or continuously extending over the surface of GdTaO₄. The main reaction product is Ca₂Ta₂O₇, and the anorthite phase may not be detected, which is similar to YTaO₄. By comparison, the dense substrate of YSZ became porous and CMAS glass has disappeared after 10 h. CMAS corrosion at 1350 °C. The on-line contact angle results show that the wettability of CMAS on GdTaO₄ is worse than that on YSZ at 1350 °C, while the opposite of the work of adhesion, which indicates that GdTaO₄ can remove liquid CMAS more easily than YSZ TBCs during the service. Furthermore, the corrosion depth and areas of GdTaO₄ are smaller than those of YSZ in the same situation. These findings suggest that GdTaO₄ possesses better high-temperature properties and CMAS corrosion resistance than YSZ as a kind of potential of thermal barrier material.     

Visible‐near infrared concealment of cotton/nylon fabrics using colored pigments and multiwalled carbon nanotube particles (MWCNTs)

To match the reflectance profile of desert colors including dark brown, light brown and olive green in the visible‐near IR (Vis‐NIR) bands, five selected colored pigments were utilized to print woven cotton/nylon fabrics. Multi‐walled carbon nanotube particles (MWCNT's) were also added to some of the printing pastes. The reflectance of printed fabrics was evaluated by using spectrophotometric technique. The effect of adding MWCNT's, on washing; light and crocking fastness alongside with colorimetric values of printed samples was evaluated. Furthermore, the water absorption time was measured in order to determine wettability of each printed sample. The results demonstrated that the presence of MWCNT's in concentration range of 0.04–0.12 g kg^?1 in printing formulations was found to cause considerable decline in Near Infrared (NIR) reflectance while a surprising increase in visible reflectance of samples was observed. Color characteristics of printed fabrics were noticeably changed even at concentrations as low as 0.12 g kg^?1 MWCNTs in printing formulations. Presence of MWCNTs in printing formulations was found to cause a significant increase in wetting time of samples. Also, the results indicated that air permeability of printed samples containing MWCNT's were higher than samples printed with no MWCNTs. Phenomena imposed by MWCNT's presence on pigment printed samples showed very good fastness levels in crocking, washing and light fastness tests. In dark brown sample, adding MWCNTs to the pigment printing pastes could tune the overall reflectance in order to match the standard reflectance profile accepted for use in concealment color of desert areas. © 2013 Wiley Periodicals, Inc. Col Res Appl, 40, 93–98, 2015     

石墨烯增强铜基复合材料的制备技术及发展

石墨烯由于其独特的二维结构和优异的物化性能,在改善复合材料的力学性能、电学性能和热学性能等方面具有很大的潜力,已成为金属基复合材料较理想的增强体。铜合金具有优异的导电导热性能和良好的延展性,但是其强度较低、不耐磨及高温下易变形的特点阻碍了其应用和发展。因此,结合石墨烯和铜的性能特点,将石墨烯作为增强体添加到铜中,制备性能优异的石墨烯增强铜基复合材料成为目前研究的热点之一。综述了目前石墨烯增强铜基复合材料的制备方法,并对各方法的特点进行了分析比较,提出未来可采用的制备工艺的方向以及在制备过程中面临的问题和挑战,并对其未来的研究方向进行了展望。     

TiO2-incorporated polyelectrolyte composite membrane with transformable hydrophilicity/hydrophobicity for nanofiltration separation

The wettability of the membrane surface has shown obvious influent on the separation performance of the membrane. In this work, a hydrophilic PDA-[PDDA/TiO₂]⁺ Cl⁻ membrane was prepared by a one-step codeposition of poly(diallyldimethylammonium chloride) (PDDA) polyelectrolyte solution containing positively charged TiO₂@PDDA nanoparticles with the assistance of dopamine (DA). Such positively charged membrane can be transformed into a hydrophobic membrane PDA-[PDDA/TiO₂]⁺ PFO⁻ via the counterion exchange between Cl⁻ and PFO⁻ (perfluorooctanoate). The transformation between hydrophilicity and hydrophobicity is reversible. For both hydrophilic and hydrophobic membranes, the nanofiltration performances were respectively investigated by the aqueous solution and ethanol solution of dyes including methyl blue (MB), Congo red (CR) and Evans blue (EB), and as well metal salt aqueous solution. The consecutive running stability and anti-fouling performance of both hydrophilic and hydrophobic membranes were explored. The results revealed that both membranes showed high nanofiltration performances for retention of dyes in (non)aqueous solution. For the hydrophilic membrane, the rejection of salts in a sequence is MgSO₄ > Na₂SO₄ > MgCl₂ > NaCl. Moreover, both of the hydrophilic and hydrophobic membranes showed high stability and antifouling property.     

Au-Ag-Si钎料合金的初步研究

针对目前熔点在450～500℃范围内的电子器件用钎料的空缺，通过分析Au-Ag-Si系三元相图，并根据其存在的共晶单变量线e1e2，制备了几种熔化温度在400～500℃的共晶钎料合金，并对其钎焊性和加工性能进行了初步的研究。DTA分析发现，合金的熔点在所选定的合金成分范围内随Ag含量的增加而升高。此钎料与Ni板浸润性较好；将钎料合金铸锭热轧后表明该合金作为可加工的实用钎料是合适的。同时，初步探讨了Cu元素对于Au-Ag-Si系合金的熔化特性和塑性变形能力的影响，结果表明Cu对于改善合金的加工性能和缩小固液相间距具有重要的意义。     

Evaluation about wettability,water absorption or swelling of excipients through various methods and the correlation between these parameters and tablet disintegration

Objective: To evaluate parameters about wettability, water absorption or swelling of excipients in forms of powders or dosage through various methods systematically and explore its correlation with tablet disintegration.

Material and methods: The water penetration and swelling of powders with different proportions of excipients including microcrystalline cellulose (MCC), mannitol, low-substituted hydroxypropyl cellulose (L-HPC), crospolyvinylpyrrolidone (PVPP), carboxymethyl starch sodium (CMS-Na), croscarmellose sodium (CCMC-Na) and magnesium stearate (MgSt) were determined by Washburn capillary rise. Both contact angle of water on the excipient compacts and surface swelling volume were measured by sessile drop technique. Moreover, the test about water absorption and swelling of compacts was fulfilled by a modified method. Eventually, the disintegration of tablets with or without loratadine was performed according to the method described in USP.

Results and discussion: These parameters were successfully identified by the methods above, which proved that excipient wettability or swelling properties varied with the structure of excipients. For example, MgSt could improve the water uptake, while impeded tablet swelling. Furthermore, in the present study it is verified that tablet disintegration was closely related to these parameters, especially wetting rate and initial water absorption rate. The higher wetting rate of water on tablet or initial water absorption rate, the faster swelling it be, resulting in the shorter tablet disintegration time.

Conclusion: The methods utilized in the present study were feasible and effective. The disintegration of tablets did relate to these parameters, especially wetting rate and initial water absorption rate.     

Joining of Cf/SiBCN composite with CuPd-V filler alloy

Two compositions of CuPd-V system filler alloy were designed for joining the Cf/SiBCN composite. Their dynamic wettability on the Cf/SiBCN composite was studied with the sessile drop method. The CuPd-8 V alloy exhibited a contact angle of 57° after holding at 1170℃ for 30 min, whereas for CuPd-13 V alloy,a lower contact angle of 28°can be achieved after heating at 1200 ℃ for 20 min. Sound C_f/SiBCN joints were successfully produced using the latter filler alloy under the brazing condition of(1170-1230)℃for 10 min. The results showed that the active element V strongly diffused to the surface of Cf/SiBCN composite, with the formation of V_2 C/VN reaction layer. The microstructure in the central part of the joint brazed at 1200 ℃ was characterized by the V_2 C/VN particles distributing scatteringly in CuPd matrix. The corresponding joints showed the maximum three-point bend strength of 82.4 MPa at room temperature.When the testing temperature was increased to 600 0 C, the joint strength was even elevated to 108.8 MPa.Furthermore, the joints exhibited the strength of 92.4 MPa and 39.8 MPa at 800 ℃ and 900 ℃, respectively.     

Wettability-patterned microchip for emerging biomedical materials and technologies

Microchip has long been studied and facilitated recent investigations in multiple biomedical and material fields. The advances in functional materials triggered several leaps in the development of microchip technology. Microarray chip, benefiting from micropatterning and nucleic acid nanotechnology, was firstly introduced around 1980 and rapidly facilitated genomics, proteomics, and biodetections. In the following generation, the microfluidic chips, raised from microelectromechanical systems (MEMS) and soft lithography, are revolutionizing several areas like biology, material fabrication, energy, and environmental science. More recently, the advances in materials fabrication keep expanding the frontiers of microchip platforms, like nanoscale fabrications and flexible device manufacturing. One of the most promising platforms is the wettability-patterned materials inspired by ubiquitous natural wetting creatures such as lotus leaf, spider silk, and Stenocara beetles. The unique property of handling liquids with no sophisticated equipment potentially facilitated the current microchip platform by combining the merits of microarray and microfluidics, and in turn, benefits material communities and beyond. In this featured article, we briefly introduce the state of art technologies to fabricate wettability-patterned chips and highlight some proof-of-concept demonstration of its emerging applications in material and biomedical science. We also give an outlook on its further developments including machine-learning micropattern manufacturing technology and reveal its potentiality to revolute several scientific areas.     

Wetting behaviour of Y2O3/AlN additive on SiC ceramics

The wetting of SiC plate by Y₂O₃/AlN additive was analysed using the sessile drop method. The wetting behaviour was observed by image capture system using a CCD camera during the heating, in argon atmosphere. The contact angle was measured as a function of temperature and time. After the wetting test the SiC plus additive samples were cut in order to observe the thickness plate cross section. The additive area and the interface between SiC and additive were analysed using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The wetting of SiC by Y₂O₃/AlN is influenced by the presence of a solid phase in some of the additive drops that depends mainly on the additive composition and consequently on the temperature. The measured contact angles were below 7°, reaching 0° for Y₂O₃/AlN additive tested at the eutectic composition, indicating a very good wettability of Y₂O₃/AlN on the SiC.