纳米CeO2对SY-1硅橡胶臭氧老化性能影响的初步研究

目的初步研究纳米CeO2(纳米二氧化铈)对SY-1硅橡胶臭氧老化性能的影响及纳米CeO2的最适加入量,并探讨其机制。方法将纳米CeO2分别按ω(CeO2)=0.00%、0.50%、1.00%、1.50%、2.00%、2.50%加入SY-1硅橡胶中,在相同条件下,按国家标准要求,对6组硅橡胶进行臭氧老化实验,并评价其老化性能。结果按照纳米CeO2与SY-1硅橡胶胶料质量分数为1.50%的比率,在SY-1硅橡胶中加入纳米CeO2,臭氧老化后,SY-1硅橡胶的断后伸长率、永久变形率及撕裂强度的百分变化率与对照组存在显著差异,邵氏硬度与抗张强度的百分变化率与对照组无显著差异。结论纳米CeO2能够显著提高SY-1硅橡胶在断后伸长率、永久变形率及撕裂强度3个方面的耐臭氧老化性能。     

赝复硅橡胶经rHBD3浸泡消毒后机械性能变化的研究

目的研究赝复硅橡胶材料在重组人β防御素-3（rHBD3）溶液中浸泡消毒2个月后,拉伸强度、扯断伸长率、邵氏硬度、撕裂强度和重量的变化。方法将制作好的赝复硅橡胶试件分别浸泡在pH5和pH7.5的rHBD3溶液中2个月后,在万能材料试验机上,按ASTM D412标准测量扯断强度、扯断伸长率;按ASTM D624标准测量撕裂强度;利用邵氏A硬度计,按ASTM2240标准测量邵氏A硬度。硅胶试件浸泡5d、15d、30d和60d后,在电子天平上称重。结果 A-2186硅橡胶浸泡在pH5 rHBD溶液中机械性能的改变大于在pH7.5碱性环境中的改变。在酸性环境中浸泡前后,A-2186的拉伸强度变化为5.8~6.3Mpa;扯断伸长率430%~412%;邵氏硬度36.3~41.1。撕裂强度浸泡前后没有明显的变化;吸水率的变化为0.01%~0.36%。结论赝复硅橡胶浸泡在酸性rHBD3溶液中机械性能改变比浸泡在碱性溶液中大,但并不影响临床的使用。     

牙科修复用CuO掺杂纳米二氧化钛的制备与表征

目的 通过氧化铜掺杂,制备改性氧化铜纳米二氧化钛光催化剂,检测氧化铜掺杂对CuO/TiO₂复合光催化剂吸收光谱的影响,为研制口腔临床修复功能性材料提供依据。方法 采用共沉淀法制备CuO/TiO₂（CuO掺杂纳米二氧化钛）,通过X射线衍射仪（XRD）、扫描电镜（SEM）和紫外-可见光吸收光谱（UV-vis谱）对其形态、结构、组成和性质进行表征。结果 成功制备了CuO/TiO₂复合光催化剂,不同CuO掺杂比的TiO₂的形貌基本不变,CuO掺杂使CuO/TiO₂吸收光谱发生红移,增加了可见光的吸收边界,提高可见光响应。结论 掺杂CuO后的光催化剂有效地提高其可见光响应能力,减少了空穴和电子复合,提高了可见光响应的性能。本研究对解决口腔临床修复对抗菌抑菌自洁特性材料的需求具有参考意义。     

The effect of doping Mg on the structure and electrochemical properties of Li3V2(PO4)3 cathode materials for lithium-ion batteries

The Mg-doped Li₃V_2−xMg_x(PO₄)₃ (x = 0.00, 0.01, 0.02, 0.05, 0.10, 0.20, 0.30, 0.33, 0.50, 1.00 and 1.33) compounds have been prepared by a sol–gel method in reducing atmosphere (70%Ar + 30%H₂) using citric acid as a chelating agent and a carbon source coated on the samples. The Mg-doped effects on the structural and electrochemical performance of Li₃V₂(PO₄)₃ are investigated by X-ray diffraction, galvanostatic, charge/discharge and four-point probe measurement method. The Li₃V_2−xMg_x(PO₄)₃ solid solution phase can exist stable in the composition range between x = 0.00 and 0.27. The simple improve mechanism of the electrochemical performance for Mg-doped Li₃V_2−xMg_x(PO₄)₃ system is discussed too. In the Mg-doped Li₃V_2−xMg_x(PO₄)₃ system, at a lower charge/discharge rate (0.1C), the cycle performance has no much improvement with the increasing Mg doping content. However, at higher rates, there has an excited improvement in both cycle performance and rate capability due to the increase of electrical conductivity (more than one order of magnitude). At 5C charge/discharge rate, for the Li₃V_1.95Mg_0.05(PO₄)₃ sample, the discharge capacities for the 1st and 100th cycle were 138.9 and 123.3 mAh g⁻¹. The discharge capacity retention reached to 89% (more than 51% for undoped Li₃V₂(PO₄)₃ system). More important is that, except for the first 15 cycles, the discharge capacities kept almost a constant. Based on the excellent electrochemical performance, Li₃V_1.95Mg_0.05(PO₄)₃ will be a promising cathode material for rechargeable lithium-ion batteries.     

交联剂加入量对SY—1型硅橡胶物理性能的影响

目的确定固化SY-1型硅橡胶时交联剂的最适加入量.方法测试了交联剂5种不同加入量0.5%、1%、1.5%、2%、2.5%(与胶料的质量之比)时SY-1型硅橡胶的物理性能.结果交联剂加入量为胶料的1%时固化后的硅橡胶其物理性能综合来看为最好扯断伸长率为(440±54)%,扯断强度为(4.3±0.28)MPa,撕裂强度为(18.2±3.1)kN/m,邵氏A硬度为(24±3.6)U;结论在交联剂加入量与胶料的质量分数为ω=1%时,SY-1型硅橡胶可获得更好的物理性能.     

Electrocatalytic oxidation and reduction of H2O2 on vertically aligned Co3O4 nanowalls electrode: Toward H2O2 detection

Single crystal and vertically aligned cobalt oxide (Co₃O₄) nanowalls were synthesized by directly heating Co foil on a hot-plate under ambient conditions. The vertically aligned Co₃O₄ nanowalls grown on the plate show excellent mechanical property and were facilely attached to the surface of a glassy carbon (GC) electrode using conductive silver paint. The prepared Co₃O₄ nanowalls electrode was then applied to study the electrocatalytic oxidation and reduction of hydrogen peroxide (H₂O₂) in 0.01 M pH 7.4 phosphate buffer medium. Upon the addition of H₂O₂, the Co₃O₄ nanowalls electrode exhibits significant oxidation and reduction of H₂O₂ starting around +0.25 V (vs. Ag/AgCl), while no obvious redox activity is observed at a bare GC electrode over most of the potential range. The superior electrocatalytic response to H₂O₂ is mainly attributed to the large surface area, minimized diffusion resistance, high surface energy, and enhanced electron transfer of the as-synthesized Co₃O₄ nanowalls. The same Co₃O₄ nanowalls electrode was also applied for the amperometric detection of H₂O₂ and showed a fast response and high sensitivity at applied potentials of +0.8 V and −0.2 V (vs. Ag/AgCl), respectively. The results also demonstrate that Co₃O₄ nanowalls have great potential in sensor and biosensor applications.     

Pt nanoparticles-assisted electroless deposition of Prussian blue on the electrode: Detection of H2O2 with tunable sensitivity

In this communication, electroless deposition of Prussian blue (PB) on the electrode promoted by Pt nanoparticles (Pt_nano) is proposed for detecting H₂O₂ with adjustable sensitivity. Pt_nano/carbon nanotubes hybrid was initially used to modify the working electrode, followed by immersing it into the Fe³⁺[Fe^III(CN)₆] aqueous solution for electroless deposition of PB through a simple chemical reaction, which was catalyzed by Pt_nano. The amount of PB deposit was controllable through varying the deposition time or the Pt_nano amount on carbon nanotubes. Detection of H₂O₂ was successfully realized, sensitivity being dependent upon the amount of PB in the system. This work first demonstrates the feasibility of controlling the sensitivity of PB-based amperometric sensors through nanoparticles-assisted chemical deposition of PB, offering new insight into the development of electrochemical sensors using PB as the transducer.     

EQCM study of electrochemical modification of Bi2S3 films in the Zn-containing electrolyte

The electrochemical behavior of Bi₂S₃ as-deposited on Au using the successive ionic layer adsorption and reaction method has been investigated in the Zn²⁺-free background and Zn²⁺-containing electrolytes at different pH by electrochemical quartz crystal microbalance coupled with cyclic voltammetry and X-ray photoelectron spectroscopy. It has been shown that when the Bi₂S₃ film is reduced in the Zn²⁺-containing electrolyte Zn²⁺ ions are involved in electrochemical bismuth sulfide reduction and are partially reduced together with the bismuth sulfide film. The bismuth sulfide film initiates the adsorbed Zn²⁺ ions reduction prior to the traditional overpotential deposition of it. Reduction of Zn²⁺ ions prior to the overpotential deposition of Zn depends on solution pH: at pH 5 it occurs at more negative potential values and the observed mass changes due to Zn electrodeposition are greater than at solution pH 3. After bismuth sulfide film reduction in the Zn²⁺-containing electrolyte, Zn was detected as ZnO and metallic Zn at pH 5, while at pH 3 only ZnO was detected.     

不同浓度的过氧化氢对银汞合金表面性能的影响

目的研究不同浓度过氧化氢对银汞合金表面性能的影响。方法采用表面轮廓仪和扫描电镜对0 wt%、3.6 wt%、10 wt%和30 wt%四种浓度过氧化氢浸泡112 h后的牙科银汞合金的表面粗糙度、表面形貌进行比较,并运用光电子能谱仪分析0%和30%两种浓度过氧化氢浸泡后银汞合金的表面腐蚀产物。结果过氧化氢浸泡112 h后,不同银汞合金表面粗糙度的Ra和Rz的大小顺序均为0 wt%<3.6 wt%<10 wt%<30 wt%;且表面均有不同程度的腐蚀,主要表现为分布不均匀、孔径大小不一的点蚀,其中以30wt%过氧化氢浸泡组的腐蚀最明显;此外,0 wt%和30 wt%过氧化氢浸泡后,银汞合金表面分别检测到Cu、Sn、Hg、Ag、O元素,表面氧化物主要为SnO₂,与0 wt%过氧化氢相比,30 wt%过氧化氢浸泡后,银汞合金表面Ag、Hg、O元素含量明显下降,而Sn、Cu元素含量则升高。结论随着过氧化氢浓度的升高,银汞合金表面粗糙度增加,表面形貌有不同程度腐蚀,表面腐蚀产物成分有所改变,氧化程度减弱。     

牙科修复用BiOIO3/g-C3N4复合纳米光催化剂的制备与表征

目的 研究不同剂量NaOH条件对制备BiOIO3/g-C3N4复合纳米光催化剂的结构形貌及其可吸收光谱的影响,为研制适用于口腔修复纳米光催化功能性材料提供依据.方法 水热法制备BiOIO3/g-C3N4,通过XRD(X射线衍射仪)、SEM(扫描电镜图)和UV-vis(紫外-可见光吸收光谱)对其形貌、结构、分子组成和理化...     

Spectroelectrochemical investigation of MnO2 electro-generation and electro-reduction in acidic media

Spectroscopic investigations of Mn²⁺ electro-oxidation and MnO₂ electro-reduction in acidic media (0.5–2 M H₂SO₄) have been performed using optically transparent electrodes (OTE). Reticulated vitreous carbon (RVC) has been used as the electrode material. Our results show that in the first step of Mn²⁺ ions electro-oxidation the unstable in aqueous media Mn³⁺ ions are formed. In the next step Mn³⁺ ions can hydrolyse to MnOOH and/or disproportionate to Mn²⁺ and Mn⁴⁺ ions. Contrary to the electro-oxidation of Mn²⁺ to MnO₂, the electro-reduction of MnO₂ proceeds in two steps. The first step is strictly connected with electro-generation of MnOOH and the next with regeneration of Mn²⁺ ions.     

Synthesis and electrochemical characterizations of nano size Ce doped LiMn2O4 cathode materials for rechargeable lithium batteries

LiCe_xMn_2−xO₄ (x = 0.00–0.10) cathode materials for rechargeable lithium-ion batteries were synthesized by simple sol–gel technique using aqueous solutions of metal nitrates and succinic acid as the chelating agent. The gel precursors of metal succinates were dried in vacuum oven for 10 h at 120 °C. After drying, the gel precursors were ground and heated at 900 °C. The structural characterization was carried out by X-ray powder diffraction and X-ray photoelectron spectroscopy to identify the valence state of Mn and Ce in the synthesized materials. The sample exhibited a well defined spinel structure and the lattice parameter linearly increased with increasing the cerium contents in LiCe_xMn_2−xO₄. Surface morphology and particle size of the synthesized materials were determined by scanning electron microscopy and transmittance electron microscopy respectively. Electrochemical properties were characterized for assembled Li/LiCe_xMn_2−xO₄ coin type cells using galvanostatic charge/discharge studies at 0.5C rate and cyclic voltammetry in the potential range between 2.75 and 4.5 V at a scan rate of 0.1 mV s⁻¹. Among them cerium doped spinel LiCe_0.05Mn_1.90O₄ has improved structural stability, high reversible capacity and excellent electrochemical performance of rechargeable lithium batteries.     

Effect of CO2 laser on pulpal temperature and surface morphology: an in vitro study

Objectives: The objective of this study was to evaluate the potential effects on underlying dental hard tissues of a high pulse rate carbon dioxide (CO₂) laser that was designed for soft tissue surgery.Methods: Eighteen extracted human teeth were sectioned longitudinally, cleaned, and varnished, leaving nine exposed windows on each: six on the coronal surface (enamel) and three on the root surface (cementum, dentin). The CO₂ irradiation conditions used were: wave length 10.6 μm; 1.2–2.6 J/cm² fluence per pulse; repetition rate 120–1000 Hz; 100–200 ms pulse duration; and cumulative fluences ranging from 14 to 2200 J/cm². Each window was irradiated with a 0.3 mm beam diameter at one of nine power settings for 0.1, 0.5, or 1.0 s. The pulp chamber temperature was measured with a microthermocouple. The irradiated teeth were evaluated by Polarized Light Microscopy (PLM) and Scanning Electron Microscopy (SEM).Results: The pulp chamber temperature rise ranged from 0.5 to 19° C depending on the location of the window and distance to pulp chamber. SEM revealed crystal fusion in both enamel and dentin at all cumulative fluences. At cumulative fluences of 40 J/cm², 200 pulses/second and higher, measurable tissue loss was observed with PLM both in dentin and enamel.Conclusions: These results indicate there are threshold conditions above which pulsed CO₂ laser light used for soft tissue surgery may cause detrimental changes to underlying oral hard tissue and to the pulp.     

Microwave assisted chemical bath deposition of CdS on TiO2 film for quantum dot-sensitized solar cells

A simple, rapid and effective method of microwave assisted chemical bath deposition (MACBD) has been used to deposit CdS quantum dots on the surface of TiO₂ film as photoanode of quantum dot-sensitized solar cells. The photovoltaic performance of the as-prepared cell is investigated. The results show that the cell based on MACBD deposited TiO₂/CdS electrode achieves an improved short circuit current density of 6.69 mA cm⁻² and power conversion efficiency of 1.03% at one sun (AM 1.5G, 100 mW cm⁻²) as compared with the one employing conventional sequential chemical bath deposition method.     

Electrodeposition of submicron/nanoscale Cu2O/Cu junctions in an ultrathin CuSO4 solution layer

The electrodeposition experiments were carried out in an ultrathin CuSO₄ solution layer under lower growth driving forces and the structure of electrodeposits were characterized by FESEM, chemical etching, EDS and DC conducting measurement. It was found that the Cu₂O crystallites distributed over the entire sample surface and formed submicron/nanoscale Cu₂O/Cu junctions. Meanwhile, the abnormal growth of Cu₂O crystallites in the electrodeposit front area was found for the first time. In the study, we present the obvious evidences for clarifying the relationship between the morphology and the compositional distribution of electrodeposits at grain size level. This result may be helpful for us to prepare the electrodeposits with controlled surface morphology at micro–nanoscale.     

Preparation and characterization of TiO2-NTs/SnO2-Sb electrodes by electrodeposition

The novel Sb-doped SnO₂ electrodes (TiO₂-NTs/SnO₂-Sb) have been prepared by anodization, electrodeposition and annealing. TiO₂ nanotubes (TiO₂-NTs) after Sb and Sn electrodeposited were characterized using field-emission scanning electron microscopy (FE-SEM). In contrast with the traditional Sb-doped SnO₂ coating prepared by thermal decomposition, the Sb-doped SnO₂ coating prepared by electrodeposition processes show more compact. X-ray diffraction (XRD) analysis indicates that the Sb-doped SnO₂ coating prepared by electrodeposition processes are firmly combined with the TiO₂-NTs formed on the Ti substrate. Accelerated service life tests reveal that the electrodeposition processes enhance the electrochemical stability of the Sb-doped SnO₂ electrode. The cyclic voltammetry analysis shows that TiO₂-NTs/SnO₂-Sb electrodes have higher overpotential for oxygen evolution and higher electrochemical porosity. Besides, the enhanced stabilization mechanism of the TiO₂-NTs/SnO₂-Sb electrode prepared by electrodeposition processes has been studied.     

Titanium dioxide nanoparticles addition to a conventional glass-ionomer restorative: influence on physical and antibacterial properties

Objectives

The aim of this study was to evaluate the addition of titanium dioxide (TiO₂) nanoparticles to a conventional glass-ionomer (GI) on physical and antibacterial properties.

Methods

TiO₂ nanoparticles were incorporated into the powder component of Kavitan^® Plus (SpofaDental, Czech Republic) at 3%, 5% and 7% (w/w). Unblended powder was used as control. Fracture toughness, compressive strength, flexural strength and microtensile bond strength were evaluated using a universal testing machine. Surface microhardness was measured using Vickers microhardness tester. Setting time was determined as specified in the ISO standard. The antibacterial activity was evaluated using direct contact test against Streptococcus mutans. Fluoride release and SEM analysis were carried out. Data were analysed using ANOVA and Tukey's test.

Results

GI-containing 3% and 5% (w/w) TiO₂ nanoparticles improved the fracture toughness, flexural strength and compressive strength compared to the unmodified GI. However, a decrease in the mechanical properties was found for GI-containing 7% (w/w) TiO₂ nanoparticles. GI-containing 5% and 7% (w/w) TiO₂ nanoparticles compromised the surface microhardness. Setting time of GI-containing TiO₂ nanoparticles decreased but the values remained within ISO limits. The addition of TiO₂ nanoparticles to the conventional GI did not compromise its bond strength with dentine or fluoride release of the GI. GI-containing TiO₂ nanoparticles possessed a potent antibacterial effect.

Conclusions

GI-containing 3% (w/w) TiO₂ nanoparticles is a promising restorative material with improved mechanical and antibacterial properties. This novel experimental GI may be potentially used for higher stress-bearing site restorations such as Class I and II.