不同阻燃剂对PVC热解释放HCI的影响

利用热重分析仪并借助电导率测定法探讨了5种常见阻燃剂（Al（OH）3、Mg（OH）2、DBDPO、C3H4N6和硼酸锌）对PVC热解时HCl释放过程的影响。结果表明：加入Mg（OH）2和Al（OH）3的PVC体系在第一阶段的最大热解速率提高近1倍，DBDPO使PVC体系在第一阶段的热解速率和第二阶段的热解质量增加，C3...     

Mg(OH)_2对聚氯乙烯热解燃烧特性及产生氯化氢的影响

采用锥形量热仪、烟密度仪和电导率测定法研究了Mg(OH)_2对聚氯乙烯(PVC)燃烧特性的影响,并探讨了体系中HCl的释放规律以及能体现出协同效应并最大限度降低HCl生成量的复配法。结果表明:将Mg(OH)_2加入到PVC中后,PVC的起始分解温度略有提高,体系残炭量较纯PVC明显增加,促进了PVC的热解,有利于PVC形成炭骨架;Mg(OH)_2加入后在300～500 s内使烟对光吸收率和热解质量损失都达到最大,在500 s后开始呈现下降趋势,将其与Sb_2O_3混合能产生极大的阻燃协同效应,烟对光吸收率最大值、烟对光吸收率平均值及热解残留物质量分别为Sb_2O_3的6.38%,10.34%和1.32倍;Mg(OH)_2能使体系的HCl释放总量减少。     

Al(OH)_3阻燃剂含量对麦秸纤维/废旧聚丙烯再生复合材料性能的影响

制备了阻燃麦秸纤维增强废旧聚丙烯再生复合材料,研究了阻燃剂Al(OH)_3含量对复合材料阻燃及力学性能的影响。结果表明:Al(OH)_3的加入极大地提高了复合材料的阻燃性能,并减少了融滴现象,当Al(OH)_3质量分数为40%时,垂直燃烧级别达到FV-0级,极限氧指数达到28.9;Al(OH)_3的添加使复合材料的热分解温度明显提高;随着Al(OH)_3含量的增加,复合材料的拉伸强度、弯曲强度、冲击强度呈现先升高后降低的趋势,当Al(OH)_3质量分数为30%时,复合材料的阻燃性能和力学性能达到最佳组合。     

AZ31镁合金在Al(NO_3)_3溶液中的电化学行为和放电性能

通过对腐蚀析氢行为、开路电位、动电位极化曲线、交流阻抗谱和恒流放电性能等的测试与分析,研究了AZ31镁合金在不同浓度Al(NO_3)_3溶液中的电化学行为和放电性能。结果表明:随着Al(NO_3)_3溶液浓度的增大,AZ31镁合金的开路电位和自腐蚀电位负移,交流阻抗值减小,放电活性增强;与镁盐电解液相比,AZ31镁合金在0.6mol·L~(-1) Al(NO_3)_3溶液中的恒流放电电压较高、放电曲线平稳、放电效率高、放电容量大;放电过程中AZ31镁合金电极表面生成2Mg(OH)_2·Al(OH)_3,促进Mg(OH)_2从电极表面脱落,有利于电解液与电极表面充分接触,使AZ31镁合金电极具有较高的放电活性与放电稳定性。     

ATC自润滑陶瓷刀具摩擦磨损性能实验研究

用力学性能较好的Al(OH)3把力学性能较差的CaF2进行包覆,用于制备以CaF2为核、以Al(OH)3为壳的CaF2@Al(OH)3复合微粒,以包覆性固体润滑剂的形式添加到陶瓷基体材料中。利用热压烧结工艺制备A12O3/TiC/CaF2@Al(OH)3自润滑陶瓷刀具,然后对其制备流程与工艺、微观构造、力学及切削性能进行了研究分析。     

铝合金与镁合金直流双脉冲MIG焊接头组织与性能研究

以ER4043焊丝为填充金属,对5 mm厚的7020铝合金和AZ31B镁合金的直流双脉冲MIG焊接头进行组织成分和力学性能分析。结果表明,在合适的焊接参数下,焊缝近镁侧熔合区存在柱状晶和200μm左右的铝镁金属间化合物层,其主要成分为β(Al3Mg2)和γ(Al12Mg17)。拉伸试样断裂发生在近镁侧熔合区,呈现脆性断裂的特征,焊缝显微硬度值波动较大,在近镁侧熔合线处达到最大值,铝镁金属间化合物层的存在严重降低了接头力学性能,平均拉伸强度只有16.4 MPa。     

Al2O3纤维填充PTFE复合材料摩擦磨损性能分析

利用M-200型摩擦磨损试验机考察了填料含量及载荷对粉状Al2O3纤维填充PTFE复合材料摩擦磨损性能的影响，采用扫描电子显微镜观察分析磨损表面形貌及磨损机理。结果表明：Al2O3纤维填料可提高PTFE的硬度，从而可提高PTFE的耐磨性，但复合材料中Al2O3含量较高时会导致磨粒磨损，且AL2O3含量越高相应的磨粒磨损越严重。在本试验条件下，当Al2O3的质量分数为20%左右时，PTFE复合材料的耐磨性最佳；PTFE复合材料同钢对磨时的摩擦系数比纯PTFE大，且随Al2O3含量的增加而增大。     

Al5TiB对Mg-8Zn-4Al-0.3Mn合金显微组织的影响

研究了Al5TiB对Mg-8Zn-4Al-0．3Mn铸造镁合金显微组织的影响。结果表明，Mg-8Zn-4Al-0．3Mn铸造镁合金的显微组织主要由Mg相、φ(Al2Mg5Zn2)相、τ(Mg32(Al，Zn)49)相组成。加入0．5％的Al5TiB可显著细化合金的铸态组织，晶粒大小由120～130μm减少到30～40μm。随着Al5TiB加入量的增加，合金的共晶α(Mg)相数量和合金的显微硬度均呈增加趋势。     

NTC401对超细氧化铝粉体表面改性的研究

研究了偶联剂NTC401对Al2O3超细粉表面改性，活化指数的测定评定了改性效果，选择并确定了偶联剂最佳用量(1．8％)及最佳改性时间(40min)，浅析了偶联剂对粉体表面改性的作用机理。红外光谱分析得出偶联剂在粉体粒子表面产生化学吸附，从而使填料表面有机化，改变了填料的表面性质。     

锌对Mg-3%Al合金铸态显微组织和力学性能的影响

通过光学显微镜、万能力学试验机、X射线衍射仪和电子探针等分析了锌质量分数(1%~8%)对Mg-3%Al合金显微组织和力学性能的影响。结果表明:在Mg-3%Al合金中加入锌后对铸态显微组织和性能均有较大影响;锌质量分数为6%时,其主要组成相为-αMg基体相、-βMg17Al12相和-τMg32(Al,Zn)49三元相;合金的显微组织得到明显细化,各相分布也得到改善;此时其综合力学性能最好,抗拉强度、伸长率和断面收缩率分别达到了215 MPa,11.3%和11.2%。     

Response of mice connective tissue to intracanal dressings containing chlorhexidine

Substances containing chlorhexidine (CHX) have been studied as intracanal medicaments. The aim of the present study was to characterize the response of mouse subcutaneous connective tissue to CHX‐containing medications by conventional optical microscopy. The tissue response was evaluated by implanting polyethylene tubes containing one of the substances evaluated: Calen paste + 0.5% CHX, Calen + 2% CHX, 2% CHX gel, and Calen paste (control). After experimental periods of 7, 21, and 63 days, the implants (n = 10) were removed along with the subcutaneous connective tissue. Tissue samples were subjected to histological processing, and sections were stained with hematoxylin and eosin. Qualitative and quantitative analyses of the number of inflammatory cells, blood vessels, and vascularized areas were performed. Results were analyzed by ANOVA and Tukey tests with the significance level set at 5%. We concluded that Calen + 0.5% CHX led to reparative tissue response in contrast with Calen + 2% CHX and 2% CHX gel, which induced persistent inflammatory response, pointing to the aggressive nature of this mixture. When Calen + 2% CHX and 2% CHX gel were compared, the latter induced more intense inflammatory response. Microsc. Res. Tech., 2012. © 2012 Wiley Periodicals, Inc.     

Influence of different calcium hydroxide removal protocols on the bond strength of epoxy resin-based sealer in long oval root canals

This study evaluated the effect of different protocols for Ca(OH)₂ removal on the bond strength (BS) of epoxy resin-based sealer in long oval root canals. Forty-eight mandibular incisors with long oval root canals were selected by CBCT. Biomechanical preparation was performed, the samples were filled with Ca(OH)₂ paste and distributed in four groups (n = 12): G-without Ca(OH)₂ paste (C); G2-syringe/needle (SN); G3-SN + XP-Endo® Finisher (XPF); G4-SN + passive ultrasonic irrigation (PUI). After 7 days, Ca(OH)₂ was removed and teeth were filled using AHPlus and guttapercha. In four samples from each group, the sealer was manipulated with 0.1% rhodamine to assess sealer penetration by fluorescent laser confocal microscopy (FLCM). Samples were sectioned in slices for BS, scanning electron microscopy, and FLCM analysis. The BS data were analyzed by ANOVA and Tukey tests (α = 0.05). The lowest BS values were found for the SN group (12.89 ± 4.36) compared to C (35.55 ± 10.05), while PUI group presented intermediate values (28.57 ± 9.35) and the XPF group (31.34 ± 9.8) showed values that were sometimes similar to C group and sometimes similar to PUI group (p > .05). The analysis of the adhesive interface showed evident gaps, with the presence of residues between the dentin and the filling material for the SN group, and for C, XPF and PUI groups juxtaposed adhesive interface. FLCM images showed sealer penetration in the dentinal tubules along the entire perimeter for C, XPF, and PUI groups. Ca(OH)₂ removal with XPF and PUI from long oval root canals resulted in higher bond strength values compared to SN, besides better sealer penetration on dentinal tubules and juxtaposed adhesive interface.     

碱处理剑麻纤维/聚丙烯复合材料的性能研究

选用氢氧化钠溶液对剑麻纤维(SF)进行表面改性,采用注塑成型的方法制备SF/聚丙烯(PP)复合材料,借助扫描电镜(SEM)观察碱处理效果及剑麻纤维在聚丙烯基体中的分散性,通过力学性能和摩擦磨损性能测试研究不同含量SF对复合材料性能的影响。结果表明:氢氧化钠质量分数为10%时可获得最佳的纤维处理效果,但仅用碱处理未在纤维与基体之间形成有效的化学结合。随着SF含量的增加,复合材料的拉伸强度和弹性模量增加,摩擦因数和磨损率下降,SF质量分数为20%时拉伸强度和弹性模量达到最大值,SF质量分数为10%时摩擦因数和磨损率达到最小值。     

Study on the tribological behaviors of polyelectrolyte multilayers containing copper hydroxide nanoparticles

In this paper, we reported the tribological behaviors of polyelectrolyte multilayers (PEMs) containing copper hydroxide nanoparticles, polymer films were prepared by the sequential adsorption Poly(diallyldimethylammonium chloride) (PDDA) and poly(sodium 4-styrenesulfonate) (PSS) alternately on substrate. The nucleation of copper hydroxide nanoparticles was achieved using a cyclical absorption-hydrolysis process in which copper ions were absorbed into the polymer matrix (which bind to the sulfonate groups) and then hydrolysis in an alkali solution. The structure and the morphology of before and after the in-situ synthesis copper hydroxide nanoparticles in the PEMs matrix have been explored. The coefficient of friction as a function of sliding velocity and normal load also has been studied. The composites exhibited increased wear resistance compared with the pristine polymer films. This may partly be attributed to the enhanced load-carrying capacity of the inorganic nanoparticles in the PEMs. Dr. Pingyu Zhang, Professor of Laboratory for Special Functional Materials, Henan University. He received his Ph. D. in physical chemistry from Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences. He worked on tribological study in State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences 1983 to 2003. After that he was engaged as a special visiting professor of Henan University. His main research interest is in study on tribology of ultrathin films of ordered assembling systems, tribology of coatings and Micro-nanotribology. And he has authored and co-authored over 40 journal articles in Langmuir, Thin Solid Films, and Wear etc.     

The effect of radiopacifiers agents on pH,calcium release,radiopacity, and antimicrobial properties of different calcium hydroxide dressings

The aim of this study was to evaluate the antimicrobial activity, pH level, calcium ion release, and radiopacity of calcium hydroxide pastes associated with three radiopacifying agents (iodoform, zinc oxide, and barium sulfate). For the pH and calcium release tests, 45 acrylic teeth were utilized and immersed in ultrapure water. After 24 h, 72 h, and 7 days the solution was analyzed by using a pH meter and an atomic absorption spectrophotometer. Polyethylene tubes filled with the pastes were used to perform the radiopacity test. For the antimicrobial test, 25 dentin specimens were infected intraorally in order to induce the biofilm colonization and treated with the pastes for 7 days. The Live/Dead technique and a confocal microscope were used to obtain the ratio of live cells. Parametric and nonparametric statistical tests were performed to show differences among the groups (P < 0.05). The pH analysis at 7 days showed significant differences (P < 0.05) among the groups. No differences among the pastes were found in the calcium release test on the 7th day (P > 0.05). The calcium hydroxide/iodoform samples had the highest radiopacity and antimicrobial activity against the biofilm‐infected dentin in comparison to the other pastes (P < 0.05). Calcium hydroxide mixed with 17% iodoform and 35% propylene glycol into a paste had the highest pH, calcium ion release, radiopacity, and the greatest antimicrobial action versus similar samples mixed with BaSO4 or ZnO. Microsc. Res. Tech. 78:620–625, 2015. © 2015 Wiley Periodicals, Inc.     

砂磨机结构优化改进

论述了我国微粉氢氧化铝行业现状及在种子制备中使用砂磨机技术发展的必然趋势.介绍了砂磨机的工作原理、特点.重点介绍了一种应用在微粉氢氧化铝种子制备中的ssb-50砂磨机存在的问题,并针对存在问题对砂磨机结构进行优化.     

裂解同时烷基化气相色谱/质谱研究环氧酯树脂结构

采用裂解同时烷基化气相色谱-质谱联用技术对不同类型的环氧酯树脂进行分析研究(SPM-GC-MS)。以衍生化试剂四甲基氢氧化胺与样品同时入射,经高效毛细管气相色谱分离,质谱检测,可鉴定不同类型环氧酯树脂结构。较直接裂解-气相色谱-质谱联用技术,快速、准确、谱图直观、灵敏度高。     

Persistence of resinous cement residues in dentin treated with different chemical removal protocols

The aim of this study was to evaluate the persistence of resin cement residues after dentin surface cleaning with different alcohol-based solutions or an essential oil (eucalyptol). Forty bovine teeth were sectioned in order to expose pulp chamber dentin to be washed with 1.0 mL of 2.5% sodium hypochlorite (NaOCl), followed by 0.1 mL of 17% EDTA application for 3 min, and final irrigation with 2.5% NaOCl. The specimens were air dried and resin-based cement was rubbed onto the dentine surface with a microbrush applicator. After 15 min, the surface was scrubbed with a cotton pellet and moistened with different dentin cleaning solutions, compounding the following groups: G1--95% ethanol, G2--70% ethanol, G3--70% isopropyl alcohol, or G4--eucalyptol. The dentin was scrubbed until the cement residues could not be visually detected. Sections were then processed for SEM and evaluated at × 500 magnification. Scores were attributed to each image according to the area covered by residual sealer, and data were subjected to Kruskal-Wallis at 5% significance. Eucalyptol promoted the most adequate dentin cleaning, although no statistical difference was detected amongst the groups (P > 0.05), except between the eucalyptol and 70% ethanol groups (P < 0.05). All the evaluated dentin cleaning solutions were unable to completely remove the cement residues from the dentin surface.     

以氢氧化铝为原料制备亚微米级α-Al_2O_3粉体

以氢氧化铝为原料,将其洗涤预处理后在1 200,1 230,1 250,1 350,1 430℃下煅烧,然后再球磨不同时间制得Al2O3粉体,研究了原料预处理、煅烧温度及球磨时间对煅烧后Al2O3产物中α相的转化率、比表面积及粒径的影响。结果表明:原料预处理可以明显降低原料中Na2O的含量,从而提高煅烧后Al2O3产物中α相的转化率,并降低产物中Na2O的含量;最佳的煅烧温度为1 250℃,该温度下制备的α-Al2O3具有较高的转化率和较好的活性,经球磨8h后,其粒径可以达到亚微米级。