Formation mechanism of elongated β–Si3N4 crystals in Fe–Si3N4 composite via flash combustion

Elongated β–Si₃N₄ crystals have a significant influence on the mechanical property of Fe–Si₃N₄ composite. In this paper, the formation mechanism of elongated β–Si₃N₄ crystals in Fe–Si₃N₄ composite was investigated. During the preparation process, β–Si₃N₄ crystals developed in a spiral and layer growth mechanism in the dense areas. They kept growing from the dense areas and formed radially distributed elongated crystals with hexagonal prismatic morphology as time went on. As for the formation mechanism, the (100) crystal plane of β–Si₃N₄ from Si-N-O melt is mainly the vicinal crystal planes growth with different angles from the (100) crystal plane. At the later stage, the crystallization and the diffusion forces in Si-N-O molten phase decreased. However, the short range diffusion remained active and resulted in the gradient distribution of N content near the boundary. With the temperature decreasing, the disappearance of the short range diffusion implied the end of the crystallization process of the elongated β–Si₃N₄ crystals.     

Preparation of in situ grown silicon carbide whiskers onto graphite for application in Al2O3-C refractories

C-SiC composite powders were prepared by salt-assisted synthesis from Si powders, graphite, and a molten salt medium (NaCl and NaF) with the molar ratio of Si/C =?1/2 at 1300?°C for 3?h. After the C-SiC composite powders part and complete replacement of the graphite, the mechanical properties, oxidation resistance and slag-corrosion resistance of the Al₂O₃-C materials were studied by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), as well as with dedicated equipment. The results indicated that SiC whiskers, with lengths of 10–50?nm, formed on the surface of the flake graphite, and the activation energy of oxidation of the C-SiC composite powder increased by 45.72?kJ?mol^?1 as compared to that of flake graphite. Furthermore, the decarburization area and slag erosion area of the Al₂O₃-C material decreased after 3?wt% of C-SiC composite powder was substituted for the flake graphite. Meanwhile, the cold modulus of rupture was maintained when 3?wt% of C-SiC composite powder was added. This improved both the oxidation and slag resistance of the Al₂O₃-C materials.     

Oxidation behavior and high-temperature flexural property of CVD-SiC-coated PIP-C/SiC composites

Polymer infiltration pyrolysis (PIP) was used to prepare carbon fiber-reinforced silicon carbide (C/SiC) composites, and chemical vapor deposition (CVD) was employed to fabricate SiC coating. The oxidation behavior at 1700?°C and the flexural property at 1200?°C were tested. SiC coating exerted remarkable oxidation effects on PIP-C/SiC composites. In the absence of coating, PIP-C/SiC composites lost 29.2% of its mass, with merely 6.74% of the original flexural strength retained. In contrast, CVD-SiC coated PIP-C/SiC composites had the mass loss of 10.2% and the flexural strength retention ratio of 23.4%. In high-temperature tests, SiC coating played an important role in the flexural strength of PIP-C/SiC composites. The flexural strength of uncoated composites became 330.7?MPa, and that of coated ones reduced from 655.3 to 531.2?MPa.     

Mechanism of significantly enhanced piezoelectric performance and stability in textured potassium-sodium niobate piezoelectric ceramics

In this study, the piezoelectric coefficient d₃₃ and planar electromechanical coupling coefficient k_p were enhanced 145% and 71%, respectively for the <001>-textured (K_0.5Na_0.5)_0.95Li_0.05Nb_0.93Sb_0.07O₃ piezoelectric ceramics compared with their randomly oriented counterpart. Significantly enhanced piezoelectric response in textured ceramics is originated from a combined effect of the intrinsic high piezoelectric activity of <001>-oriented grains in the tetragonal-orthorhombic phases, and easy polarization rotation of fine domains. Furthermore, a comparative analysis suggests that <001>-textured ceramics exhibit good thermal stability, benefiting from the weakened depolarization behavior via crystal orientation. The superior fatigue resistance in textured ceramics can be attributed to the reduced clamping effect as low defect density. These results show that high-performance textured ceramics reported in this work will be promising candidates in the field of lead-free piezoelectric materials.     

High bonding strength and boiling water resistance of soy protein‐based adhesives via organosilicon–acrylate microemulsion and epoxy synergistic interfacial enhancement

Boiling water resistance, an important indicator of wood adhesives, represents the capability of adhesives for exterior woodwork applications. However, soy‐based adhesives show poor behaviors in this respect, which limit their applications in outdoor environments. In this article, we report a synergistic modification method of integrating a cocrosslinking system of epoxied polyamideamine‐epichlorohydrin (PAE) and organosilicon–acrylate copolymer latexes (OACLs) to improve soybean meal (SM)‐based adhesive properties. Tailored PAE and OACL SM‐based adhesives demonstrated robust crosslinking structures via multi‐interfacial interactions, where PAE and OACL served as building blocks of an interpenetrating network, which was characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The dry‐shear strength, wet‐shear strength, and boiling water strength of the resulting SM‐based adhesives were 1.41 ± 0.13, 1.32 ± 0.17, and 1.20 ± 0.11 MPa, respectively, with 15 wt % OACL loading; these were 41, 45, and 90% increases, respectively, over the SM–PAE adhesive with which we compared them. Most importantly, the excellent boiling water resistance of the adhesives make them practical for exterior plywood. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46061.     

PCEC hydrogel used on sustained‐release hyaluronic acid delivery with lubrication effect

Injection of bionic synovial fluid (BSF) is a conventional method to improve the lubricity of artificial joints, but BSF cannot maintain long due to the dilution and degradation of BSF in human body. To prolong the effectiveness of hyaluronic acid (HA), which is the major component of BSF, this study applies a temperature‐sensitive poly(?‐caprolactone)–poly(ethylene glycol)–poly(?‐caprolactone) (PCEC) hydrogel loaded with HA to achieve long‐term lubrication. In addition, Fourier transform infrared, nuclear magnetic resonance analysis, X‐ray diffraction, scanning electron microscopy (SEM), and gel permeation chromatography spectra were used to analyze the structure of the synthetic hydrogel. Rheological test and test tube inverting method were used to characterize the thermosensitivity. The lubrication properties of the released solution were characterized by UV–vis, tribological tests, SEM, and 3D laser confocal scanning microscope. The experimental results reveal that the triblock PCEC hydrogel contains both hydrophilic block and hydrophobic block, and both PCEC and PCEC/HA hydrogels have phase‐changed effect when the temperature increases from room temperature to body temperature. Moreover, the friction coefficient of the released solution from PCEC/HA hydrogel is approximatively 38% lower than that of phosphate buffer saline. And the ability of shear resistance and creep recovery of PCEC/HA hydrogel are better than that of PCEC hydrogel. This study provides an effective approach to achieve long‐time lubrication effect for artificial joints. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46228.     

对甲氧基苯乙酮缩氨基硫脲Sn(Ⅱ)、Pb(Ⅱ)配合物的直接电化学合成

用电化学金属阳极氧化法在非水溶剂中合成了对甲氧基苯乙酮缩氨基硫脲 ( HL)与 Sn( )、Pb( )的配合物 ,通过元素分析、红外光谱、紫外光谱、摩尔电导等对配合物进行了表征。     

氯甲酸苄酯的合成及应用

对氯甲酸苄酯的合成进行了研究 ,介绍了其在多钛合成中的应用。     

高效规整填料塔技术在苯酐精制过程中的应用

介绍了国内苯酐精制新工艺和高效规整填料塔技术。实际应用结果表明新工艺比旧有技术和设备提高了产品质量和收率 ,处理能力也大幅提高 ,能耗明显下降。     

An Amphiphilic BODIPY‐Porphyrin Conjugate: Intense Two‐Photon Absorption and Rapid Cellular Uptake for Two‐Photon‐Induced Imaging and Photodynamic Therapy

The new amphiphilic BODPY‐porphyrin conjugate BZnPP and its precursor BZnPH were synthesised, and their linear and two‐photon photophysical properties, together with their cellular uptake and photo‐cytotoxicity, were studied. This amphiphilic conjugate consists of a hydrophobic BODIPY moiety and a hydrophilic tetra(ethylene glycol) chain bridging a cationic triphenylphosphonium group to an amphiphilic porphyrin ZnP through acetylide linkers at its meso positions. A large two‐photon absorption cross‐section (σ=1725 GM) and a high singlet oxygen quantum yield (0.52) were recorded. Intense linear‐ and two‐photon‐induced red emissions were also observed for both BZnPP and BZnPH. Further in vitro studies showed that BZnPP exhibited very efficient cellular uptake and strong photocytotoxic but weak dark cytotoxic properties towards human breast carcinoma MCF‐7 cells. In summary, the two‐photon‐induced emission and the potent photo‐cytotoxicity of BZnPP make it an efficacious dual‐purpose tumour‐imaging and photodynamic therapeutic agent in the tissue‐transparent spectral windows.