Boron Nitride Nanosheets Strengthened PVA/Borax Hydrogels with Highly Efficient Self-Healing and Rapid pH-Driven Shape Memory Effect

Self-healing hydrogels often possess poor mechanical properties which largely limits their applications in many fields. In this work, boron nitride nanosheets are introduced into a network of the poly(vinyl alcohol)/borax (PVA/borax) hydrogels to enhance the mechanical properties of the hydrogel without compromising the self-healing abilities. The obtained hydrogels exhibit excellent mechanical properties with a tensile strength of 0.410 ± 0.007 MPa, an elongation at break of 1712%, a Young's Modulus of 0.860 ± 0.023 MPa, and a toughness of 3.860 ± 0.075 MJ m⁻³. In addition, the self-healing efficiency of the hydrogels is higher than 90% within 10 min at room temperature. Benefiting from the excellent self-healing properties, the shapeability of the hydrogel fragments is observed using different molds. In addition, the hydrogels display rapid pH-driven shape memory effects and can recover to their original shape within 260 s. Overall, this work provides a new approach to hydrogels with integrated excellent mechanical properties, self-healing abilities, and rapid pH-driven shape memory effects.     

Effect of ammonia concentrations on SCC of α-brass under mode III loading

Stress corrosion cracking (SCC) of α-brass in ammonia solution was studied under mode III loading. The results showed that SCC occurred on the principal stress planes where shear stresses are zero. No SCC occurred on the maximum shear stress plane. Ammonia concentration affected fracture behaviour. When the concentration was low, many cracks with spacing of 10–150 μm were found on 45 ° planes, i.e., the principal stress planes. When the concentration was high, the cracks on 45 ° planes were not clearly visible because of serious general corrosion.     

中空螺旋状不锈钢冷却水喷头的熔模精密铸造

采用熔模精密铸造工艺，生产中空螺旋状不锈钢冷却水喷头，其工艺要点是，采用热型重力浇注，在高温下进行自由浇注。同时采用先慢后快，流量由小到大的浇注方法。结果表明：铸件表面光洁，无砂眼、气孔等缺陷，铸件合格率高于90％；在实际使用中，雾化区域直径大于1．5m，雾化率大于90％，喷雾效果稳定良好；盐雾试验2000h没有锈蚀，具有优良的耐磨性和耐腐蚀性。     

Effect of laser fluences on the structure of carbon nitride films deposited by direct current plasma assisted pulsed laser ablation

Carbon nitride films were deposited by direct current plasma assisted pulsed laser ablation of a graphite target under a nitrogen atmosphere at room temperature. The surface morphology, composition and bonding structure of the deposited films were characterized by atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, Raman, and X-ray photoelectron spectroscopy (XPS). The effect of laser fluences in the range 0.5–3 J/cm² on the surface morphology, composition and bonding structure of the carbon nitride films were systematically studied. As laser fluence is increased, AFM results show a great decrease in the surface roughness of carbon nitride films. FTIR and XPS results indicate an increase in the N/C ratio and the content of N atoms bonded to sp³ C, as well as a decrease in the content of H atoms and the content of N atoms boned to sp² C in the deposited films, and Raman spectra indicate an increase in the content of disordered sp² C atoms and the sp² cluster size. The increase in the film density and the decrease in the particle fraction contribute to the decrease of surface roughness with increasing laser fluence.     

非稳态轧制时轧机振动稳定性的数值分析

利用轧制理论方程和机械振动理论的能量判据 ,给出了一个较精确的分析轧机传动系统扭转振动稳定性的数值计算方法     

复合助剂对低温常压烧结AIN性能的影响

研究了Y2O3,LiO2,CaO烧结助剂对AlN陶瓷常压烧结致密度和性能的影响。结果发现,同时添加Y2O3,LiO2,CaO作为助剂,在1600℃低温烧结就能获得具有高致密度、较小的晶粒尺寸(1μm~4μm)、较高的抗弯强度(331MPa)、断裂韧性(3.8MPa·m1/2)及导热率(118W·m-1·K-1)的AlN陶瓷。     

TC4合金管材挤压成型工艺研究

研究了不同的挤压温度、挤压比和挤压速度等挤压参数对TC4合金管材挤压成型工艺的影响,以及润滑方式对TC4合金挤压管材表面的影响。研究结果表明,采用热挤压方式生产φ47mm×3mmTC4合金管材,挤压比应选在3￣10之间,挤压速度选在50￣120m/s,润滑剂用玻璃粉,可得到显微组织为两相加工组织,变形充分均匀,力学性能匹配良好,表面质量合格的TC4合金管材。本研究得到的TC4合金管材挤压成型工艺研究可用于工业化生产。     

钛合金焊接热弹塑性应力应变过程全图

针对焊接冷却过程中是否有卸载发生这一问题展开讨论,采用数值模拟方法研究在移动热源情况下钛合金焊接应力应变发展过程,给出钛合金焊接热弹塑性应力应变过程全图的定量物理描述.结果表明,钛合金焊接冷却过程中有卸载发生;钛合金焊接热弹塑性应力应变过程全图由熔化区、压缩塑性区、拉伸塑性区、卸载区、受压弹性区五部分构成;在力学熔化区等温线内的拉伸塑性区的范围包括焊缝和近缝区,但在残余状态焊缝和近缝区均为卸载区.     

KINETICS OF CARBON OXIDATION IN CARBON-BEARING REFRACTORIES

ＫＩＮＥＴＩＣＳＯＦＣＡＲＢＯＮＯＸＩＤＡＴＩＯＮＩＮＣＡＲＢＯＮＢＥＡＲＩＮＧＲＥＦＲＡＣＴＯＲＩＥＳ①ＬｕｏＸｉｎｇｙｕａｎ，ＱｉａｏＺｈｉｙｕ，ＹａｎｇＴｉａｎｊｕｎＤｅｐａｒｔｍｅｎｔｏｆＰｈｙｓｉｃａｌＣｈｅｍｉｓｔｒｙ，Ｕｎｉｖｅｒｓｉ...     

空心微球表面化学镀Ni薄膜的工艺研究

比较空心微球表面化学镀Ni薄膜的工艺.分别以Sn-Pd胶体溶液和[Ag(NH3)2]+溶液作为活化剂,将空心微球表面进行活化,再采用化学镀的方法分别在其上淀积金属Ni薄膜.使用扫描电子显微镜(SEM)、能量色散光谱(EDS)和X-射线衍射光谱(XRD)对两种工艺所镀Ni薄膜的表面微观结构和组分进行表征.结果表明:用Sn-Pd胶体溶液活化后的空心微球表面淀积了均匀、致密的金属Ni薄膜,该薄膜是由大小约100 nm的颗粒组成;而以[Ag(NH3)2]+溶液活化后的空心微球表面淀积的金属Ni薄膜,是由大小约1 μm的颗粒组成.并分析了这两种镀层形成的机理.