Contact-induced Damage in Ceramic Coatings on Compliant Substrates: Fracture Mechanics and Design

Simple explicit relations are presented for the onset of competing fracture modes in ceramic coatings on compliant substrates from Hertzian-like contacts. Special attention is given to a deleterious mode of radial cracking that initiates at the lower coating surface beneath the contact, in addition to traditional cone cracking and quasiplasticity in the near-contact area. The critical load relations are expressed in terms of well-documented material parameters (elastic modulus, toughness, hardness, and strength) and geometrical parameters (coating thickness and sphere radius). Data from selected glass, Al₂O₃ and ZrO₂ coating materials on polycarbonate substrates are used to demonstrate the validity of the relations. The formulation provides a basis for designing ceramic coatings with optimum damage resistance.     

活性炭固载磷钨酸催化合成丙酸丁酯

以活性炭固载磷钨酸为催化剂 ,甲苯为带水剂 ,实现了丙酸与正丁醇反应合成丙酸正丁酯。最佳合成条件为 :酸醇比为 1∶1.2 ,带水剂用量为 10ml,催化剂用量 1.5g ,反应时间为 2 .5h ,产率可达 99.2 %。重复试验表明 ,催化剂重复使用多次对实验结果无太大的影响     

HDPE／LDPE混合物熔融接枝GMA的研究

采用熔融接枝的方法,制备了(HDPE/LDPE)-g-GMA（甲基丙烯酸缩水甘油酯）接枝吻,研究了引发剂的用量、GMA的用量、苯乙烯（St)/GMA的配化、转速、反应时间等因素对接枝率的影响。确立了最佳的接枝配方和工艺条件：过氧化二异丙苯（CDP）用量0.1份、GMA用量3份、St用量3份、温度180℃、转速60r/min、反应时间为10min。接枝反应动力学曲线与接枝反应过程的机理特征相吻合。红外光谱的分析结果表明GMA确实接到了大分子链上;DTA分析结果表明,接枝物中GMA的引入导致大分子链的规整性降低,熔融温度略有下降。     

Al2O3／TiB2／SiCW陶瓷刀具加工镍基合金时的磨损机理研究

研究了Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣＷ陶瓷刀具加工Ｉｎｃｏｎｅｌ７１８镍基合金时的切削性能和磨损机理。结果表明；在低速切削条件下，Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣＷ和硬质合金刀具的抗后刀面磨损的能力相差不大；而在高速切削条件下，前者的抗后刀面磨能力远高于后者。     

Hydrophobic mesoporous acidic resin for hydroxyalkylation/alkylation of 2‐methylfuran and ketone to high‐density biofuel

Hydroxyalkylation/alkylation of biomass‐derived 2‐methylfuran with cyclic ketones (cyclopentanone and cyclohexanone) has great potential in synthesizing high‐density biofuel. But the conversion and selectivity are still unsatisfactory because the in‐situ formed water decreases the acidity of catalyst and induces side reaction. Herein, hydrophobic mesoporous resins with sulfonic acid group (PS) and fluoride sulfonic acid group (PCS) were synthesized by a simple solvothermal reaction and ion exchange treatment, which have good mesoporous structure with surface area of 300–700 m²/g. Notably, PS and PCS have better hydrophobicity and oleophilicity as compared to widely used sulfonic acid functional amberlyst‐15 and fluoride sulfonic acid functional nafion‐212. In the hydroxyalkylation/alkylation reaction, PS shows higher activity and selectivity than amberlyst‐15 while PCS surpasses nafion‐212. Furthermore, both PS and PCS have good recycling stability in consecutive 5 runs. After hydrodeoxygenation, two high‐density biofuels with density of 0.819 and 0.825 g/mL were obtained. © 2016 American Institute of Chemical Engineers AIChE J, 63: 680–688, 2017     

Modification of the reactive core-shell particles properties to prepare PBT/PC blends with higher toughness and stiffness

Glycidyl methacrylate (GMA) functionalized methyl methacrylate-butadiene-styrene core-shell particles (PB-g-MSG) were prepared to toughen poly (butylene terephthalate) (PBT) and polycarbonate (PC) blends. T-dodecyl mercaptan (TDDM) was used to modify the grafting character of the core-shell particles. The addition of TDDM decreased the grafting degree, particles size and crosslinking degree of PB-g-MSG particles. At the same time, the free methyl methacrylate-co-styrene-co-glyceryl methacrylate copolymer (f-MSG) increased. The f-MSG reacted with PBT and suppressed the transesterification between PBT and PC. On the other hand, f-MSG promoted the crystallization of PBT by heterogeneous nucleation. When the TDDM content was lower than 0.76%, PB-g-MSG particles dispersed in the matrix uniformly, otherwise, agglomeration took place. The change of TDDM content in the PB-g-MSG particles influenced the toughening ability and tensile properties. When the TDDM content was 0.76%, the PBT/PC/PB-g-MSG blend showed the optimum impact toughness and yield strength, which are 908 J/m and 49.4Mpa. Fracture mechanism results indicated that cavitation induced shear yielding occurred in the PBT/PC/PB-g-MSG blend when no TDDM addition for the core-shell particles. With the addition of TDDM, the interfacial strength decreased between the PB-g-MSG core-shell particles and the matrix. So voids appeared due to debonding, which also could promote the shear yielding process.     

Effects of composition on the properties of dual physically cross-linked hydrogel composed of polyvinyl alcohol and poly (acrylamide-co-acrylic acid)

In previous work, we have developed a dual physically cross-linked hydrogel composed of poly (acrylamide-co-acrylic acid) (PAM-co-PAA) and polyvinyl alcohol (PVA), named as PVA/CP DN gel, by facile copolymerization and freezing/thawing. The PVA/CP DN gel is featuring both excellent mechanical properties and self-healing ability. Additionally, we have preliminarily found that the comonomer ratio for PVA/CP DN gel have great influence on the self-healing efficiency. In this research article, we will further discuss the mechanical and self-healing properties of the PVA/CP DN gel by varying the comonomer ratio of PAM-co-PAA. The results proved that the structure of DN will be loosen when the number of PAA segments exceed that of PAM. More PAA segments in copolymer make the PVA/CP DN gel have better elongation at break but weak in tensile strength and young’s modulus because of less PVA crystalline domains formed in the gel. The energy dissipation value for the double-network hydrogel decrease with the addition of PAA segments, whereas self-healing efficiency of PVA/CP DN gel increased. Anyway, this work provides more information to further understand the effects of composition on the properties of dual physically cross-linked PVA/CP DN hydrogel.     

A/O—SBBR—氧化塘—人工湿地处理猪场沼液

针对猪场沼液氮磷浓度高、有机物含量大且可生化性差等特点,采用A/O—序批式生物膜反应器—氧化塘—人工湿地组合工艺对沼液进行深度处理。处理规模400 m~3/d,工程总投资117.5万,运行费用1.46元/(m~3·d)。运行结果表明,经过该组合工艺处理后COD_(Cr)、BOD_5、SS、NH_3-N、TP去除率分别为85.93%、79.84%、89.86%、94.78%、88.67%,出水指标均符合《畜禽养殖业污染物排放标准》(GB 18596—2001)要求。     

功能化环氧树脂研究概况

综述了环氧树脂功能化研究的主要途径,介绍了环氧树脂在粘结、防腐蚀、防辐射、阻燃、绝缘、导电、耐磨等方面功能化发展现状,总结了目前环氧树脂功能化发展存在的问题,展望了环氧树脂在功能化方向发展的趋势。     

固相微萃取技术在样品前处理中的应用研究

样品分析的第一步为样品前处理,样品前处理是整个样品分析过程中最为关键的环节。分析仪器随着科学技术的发展而发展,分析仪器灵敏度提高与分析对象基体的复杂化,对样品前处理提出了更高的要求。本文重点介绍了多种固相萃取技术及其在样品前处理技术中的应用,并对其应用现状和发展前景进行了综述。