SiO2增强口腔复合树脂性能的研究

以双酚A-甲基丙烯酸缩水甘油酯（Bis—GMA）和二甲基丙烯酸三甘醇酯（TEGDMA）作为树脂基质,SiO2作为增强填料制备口腔复合树脂。研究SiO2的添加量对口腔复合树脂的收缩率、弯曲强度的影响。实验结果表明,口腔复合树脂的弯曲强度随着SiO2充填比例的增加呈现先增加后降低的趋势;口腔复合树脂的聚合体积收缩率随着SiO2含量的增加呈现降低的趋势,当SiO2含量为70wt％时,聚合体积收缩率最低,达到2．4％。     

Properties of a new dental photocurable resin based on the expanding monomer and three-component photoinitiator system

The purpose of this study was to use. a three-component photoinitiation system comprising 1wt% CQ （camphorquinone）, 2wt% DMAEMA （2-（dimethylamino） ethyl meth acrylate） and 2wt% ph^2I^＋PF6^- （diphenyliodonium hexafluorophosphate） to initiate the copolymerization of the matrix resins which combine bisphenol-S-bis （3-methacrylate-2-hydroxy propyl） ether （BisS-GMA） with the expanding monomer unsaturated spiro orthoesters 2-methylene-l,4,6-tdspiro[4,4] nonane （MTOSN）, for minimizing the volumetric shrinkage that generally occurs during polymerization. It was hypothesized that MTOSN would expand volumetrically during polymerization under the three-component photoinitiator system and further reductions in volumetric shrinkage would be obtained. The performance study which consists of degree of conversion and condition of the ring-opening reactions of MTOSN, volumetric shrinkage and mechanical properties including tensile bond strength, compressive strength and Vicker＇s hardness were carried out respectively by Fourier transfer infrared, the dilatometer and the universal testing machine. The results supported that the dental composites based on the expanding monomer and three-component photoinitiator system engendered a greater decrease of volumetric shrinkage and better mechanieal properties.     

Carbon nanotube coating on titanium substrate modified with TiO<Subscript>2</Subscript> nanotubes

A combination of carbon nanotubes (CNTs) and titanium (Ti) modified with TiO2 nanotubes (TiO2 NTs) was fulfilled with the aim of improving bioactivity of Ti implant.First,well-ordered TiO2 NTs were prepared by the electrochemical anodization of Ti in an ethylene glycol electrolyte containing 1 wt% NH4F and 10 wt% H2O at 20 V for 50 min,followed by annealing.Then,the carboxylated CNTs were coated onto the TiO2 NTs using electrophoretic deposition (EPD) technique.The growth of hydroxyapatite (HA) on the samples was investigated by soaking them in simulated body fluid (SBF).The result showed the CNTs-coated Ti with the modification of TiO2 NTs (CNTs-TiO2 NTs) was more efficient to induce HA formation than the CNTs-coated smooth Ti (CNTs-Ti).The vitro cell response was evaluated using osteoblast cells (MC3T3-E1).The good cell proliferation and strong cell adhesion could be obtained on the CNTs-TiO2 NTs.These results indicated that CNT coating on the Ti modified with TiO2 NTs could be potentially useful for the periodontal ligament combination on dental implants.     

干氧SiO2的氢氟酸缓冲腐蚀研究

根据对掺三氯乙烯(TCE)干氧氧化的SiO2在不同配比氢氟酸缓冲腐蚀液(BHF)中的腐蚀特性的研究结果表明, 在HF wt%保持不变的条件下,腐蚀速率先随着NH4F wt%的增大而上升;NH4F大于15wt%～20wt%以后,腐蚀速率反而随之降低.值得注意的是,干氧SiO2同湿氧SiO2相比,在1wt% HF条件下,前者的腐蚀速率要比后者高,直到HF酸浓度大于3wt%时,前者的腐蚀速率才低于后者,这一现象可用NH 4 阻挡模型结合TCE在SiO2中引入浅电子陷阱的方式得到解释.     

Degradation Behavior of Ti-6Al-4V Alloys for Dental Applications in Acidic Artificial Saliva Containing Fluoride Ion

The aim of this work was to study the degradation behavior of Ti-6Al-4V alloys for dental applications in acidic artificial saliva with fluoride ion using electrochemical techniques, optical microscopy, scanning electron microscopy(SEM), and energy dispersive spectrometry(EDS). The experimental results showed that fluoride ion had significant influence on the degradation of Ti-6Al-4V alloys, and there was an obvious critical concentration of fluoride ion(about 0.1wt%). With increasing fluoride ion concentration, the corrosion potential(Ecorr) of alloys moved toward negative and the impedance of alloys decreased, meanwhile, noticeable transformation from minimum corrosion to severe pitting corrosion was observed on alloys surface following the dissolution of TiO_2 passive films, leading to the decrease of the corrosion resistance of alloys. The electrochemical dissolution of TiO_2 passive films involved a nucleophilic attack of fluoride atom to the titanium atom of TiO_2. In addition, Ca~(2+)and Na~+ in acidic saliva may involve the surface reactions and make the reactions more complex.     

Preparation and Properties of Heat Resistant Polylactic Acid(PLA)/Nano-SiO_2 Composite Filament

In order to improve the thermal properties of polylactic acid(PLA) filament,nano-SiO_2 was applied to mix with PLA,then they were spun as composite filament by melt-spinning.The dispersion of nano SiO_2 and the fracture surfaces of filaments were studied by scanning electron microscopy(SEM).The properties of composite filament,such as orientation degree,mechanical properties,and surface friction properties,were analyzed.The thermal performances of composite filament were analyzed by differential scanning calorimetry(DSC) and thermo gravimetric analysis(TGA).The results showed that the nano-SiO_2 modified by 5% KH-550 could disperse evenly and loosely in nano-scale,and 1 wt% and 3 wt% nano-SiO_2 dispersed throughout PLA evenly.As the quantity of nano-SiO_2 increased,the properties of composite filament,such as orientation degree,friction coefficient,thermal decomposition temperature,and glass transition temperature,increased more or less.The breaking tenacity increased when 1 wt% SiO_2 was added in PLA,but declined when 3 wt% SiO_2 was added.     

Combustion Synthesis of TiB_2 Ceramics Powder from B_2O_3-TiO_2-Mg System in Air Atmosphere

1Introduction Titaniumdiborideisanincreasingimportantceramic materialbecauseofitschemicalstability,highwearresis tance,andsuperiorelectricalandthermalconductivities,whichmakeTiB2ceramicsidealforapplicationsincutting tools,armormaterials,wearresistantcoati…     

Synthesis of Cordierite from Rectorite-Talc-Alumina without Additives

Rectorite, Talc and ahumina were used to obtain high-quality cordierite with stoichiometric eompo.position (5t .3 wt% SiO2,34.9 wt% Al2O3,13.8 wt% A12O3 ). The water absorption, apparent porosity, bulk deasiy, thermal expansion coefficient, crystalline phases and mierostrueture were tested by means of X-ray diffraetometer (XRD), scanning eleetronic microstopy(SEM), Archimedes immersion technique,etc. This work systematically studied the syntthesizing prvcess of the cordierite. The result shows that the cordierite can be synthesized at a lower temperature and within a wider temperature range by using the retrofire as clay raw materials.     

Microwave sintering of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-ZrO<Subscript>2</Subscript>-WC-Co cermets

Composite powders of nanocrystalline WC-10Co (15wt%),Y2O3 (8mol%) stabilized nanocrystalline ZrO2 (30wt%),industrial cobalt powder (4.5wt%) and submicron Al2O3 (55wt%) composite powders were fabricated by high-energy ball-milling process.The nanocomposite powders were consolidated by microwave sintering process at temperature ranged 1300℃-1550℃ for 15min,respectively.The optimum consolidation conditions,such as temperature,were researched during microwave sintering process.Vickers Hardness of the consolidated cermets was measured by using a Vickers indentation test,and density of specimens was also determined by Archimedes’ principle.Microwave sintering process could not only increase the density of Al2O3-ZrO2-WC-Co cermets and reduce the porosity,but also inhibit abnormal grain growth.     

Magnetic and flotation studies of banded hematite quartzite （BHQ） ore for the production of pellet grade concentrate

To identify and establish beneficiation techniques for banded hematite quartzite (BHQ) iron ore, a comprehensive research on BHQ ore treatment was carried out. The BHQ ore was assayed as 38.9wt% Fe, 42.5wt% SiO2, and 1.0wt% Al2O3. In this ore, hematite and quartz are present as the major mineral phases where goethite, martite, and magnetite are present in small amounts. The liberation of hematite particles can be enhanced to about 82% by reducing the particle size to below 63 μm. The rejection of silica par...     

Activation pretreatment of limonitic laterite ores by alkali-roasting using NaOH

Activation pretreatment of Cr-containing limonitic laterite ores by NaOH roasting to remove Cr,Al,and Si,as well as its effect on Ni and Co extraction in the subsequent pressure acid leaching process w...     

Influence of Nd and Y additions on the corrosion behaviour of extruded Mg-Zn-Zr alloys

To improve the corrosion resistance of wrought magnesium alloys through rare earth (RE) additions, the corrosion behaviour of Mg-5Zn-0.3Zr-xNd (x=0, 1, and 2; wt%) and Mg-5Zn-0.3Zr-2Nd-yY (y=0.5 and 1; wt%) alloys in a 5wt% NaCl solution was investigated using immersion test and electrochemical measurements. The results of immersion test show that Mg-5Zn-0.3Zr-2Nd alloy exhibits the best corrosion resistance among the tested alloys. Electrochemical measurements show that secondary phases in RE-containing Mg...     

Tribological Properties of Polyvinyl Mcohol Hydrogel Reinforced with Nanometer Hydroxy Apatite

As a potential artificial cartilage material,the friction and wear properties of nano-hydroxy apatite(HA)particles filled poly(vinyl alcohol)hydrogel(PVA-H)composites sliding against stainless steel disk under water lubrication condition were studied by using a four ball tester.The worn surfaces were investigated by using a scanning electron microscope(SEM)to determine the wear mechanisms.Experimental results show that filling HA to PVA-H will slightly increase the friction coefficient of composites with the increasing of HA content under water lubrication condition.Meanwhile,HA particles can greatly reduce the wear mass loss of the PVA-H composites and enhance the load carrying capacity,the wear loss of the 1 wt% HA reinforced PVA-H composites can be decreased by 30 percent under 2.0 MPa to 50 percent under 0.5 MPa contact pressure.We also found that 2 wt% HA content of composites increase the wear mass loss under the same condition.SEM examination shows that the worn surface of low HA containing(1 wt%)composites are much smoother than that of pure PVA-H or high HA containing(2 wt%)composites under 1.5 MPa contact pressure.It is also found that there are big hole and big reunited HA particles in the surface of 2 wt% HA containing composites,which leads to deterioration of the surface of samples under higher loads in water lubrication.These results may be useful in the tribological design of artificial articular cartilage material.     

Tribological Properties of Polyvinyl Alcohol Hydrogel Reinforced with Nanometer Hydroxy Apatite

As a potential artificial cartilage material, the friction and wear properties of nano-hydroxy apatite （HA） particles filled poly （vinyl alcohol） hydrogel （PVA-H） composites sliding against stainless steel disk under water lubrication condition were studied by using a four ball tester. The worn surfaces were investigated by using a scanning electron microscope （SEM） to determine the wear mechanisms. Experimental results show that filling HA to PVA-H will slightly increase the friction coefficient of composites with the increasing of HA content under water lubrication condition. Meanwhile, HA particles can greatly reduce the wear mass loss of the PVA-H composites and enhance the load carrying capacity, the wear loss of the 1 wt% HA reinforced PVA-H composites can be decreased by 30 percent under 2.0 MPa to 50 percent under 0.5 MPa contact pressure. We also found that 2 wt% HA content of composites increase the wear mass loss under the same condition. SEM examination shows that the worn surface of low HA containing （1 wt%） composites are much smoother than that of pure PVA-H or high HA containing （2 wt%） composites under 1.5 MPa contact pressure. It is also found that there are big hole and big reunited HA particles in the surface of 2 wt% HA containing composites, which leads to deterioration of the surface of samples under higher loads in water lubrication. These results may be useful in the tribological design of artificial articular cartilage material.     

Thermodynamic analysis and preparation of β-SiC/ZrO_2 composites

A predominance area diagram for the Zr-Si-C-O system at 1773 K was plotted according to correlative thermodynamic data.β-SiC/ZrO2 composites were prepared based on the phase diagram by carbothermal reduction of zircon(ZrSiO4) in argon atmosphere.Zircon and carbon black were mixed according to the C/ZrSiO4 mass ratio of 0.2,and with 0,1wt% and 2wt% extra addition of La2O3.Phase evolution of the mixture was investigated at 1723-1803 K by X-ray powder diffraction,and the microstructure of the product prepared ...     

HA-ZrO2生物复合材料的制备

首先以H3PO4和Ca(OH)2为主要原料利用湿化学方法合成了结晶良好的羟基磷灰石粉体(HA),在该粉体中分别引入15%、20%和25wt%的m-ZrO2粉体,经成型后分别在900℃、1 000℃、1 100℃和1 200℃温度下煅烧1h,详细研究ZrO2含量和烧结温度对该复合材料物相及体积密度的影响规律.结果表明:随着烧成温度的升高,该复合材料的体积密度呈上升趋势,当温度为1 000℃时达到最大值,当温度进一步升高时,体积密度下降.而复合材料中的HA相随温度的升高而不断降低,当温度超过1 000℃时该趋势更加明显.随ZrO2的引入材料体积密度有一定提高,但当ZrO2含量超过20%时,其体积密度有所降低,当ZrO2含量为20%时,杂质含量最低.     

NOx reduction in the sintering process

A new process, NOx reduction with recycling flue gas and modifying coke breeze, was proposed. The effects of modified coke breeze and recycled flue gas on NOx reduction were investigated by sinter pot tests. The results show that the NOx reduction rate is over 10wt% in the sintering of modified coke breeze, the effects of the additives on NOx reduction are: CeO2CaOK2CO3.The NOx reduction rate increases with the amount of recycled flue gas, and is 22.35wt% in the sintering with recycling 30vo1% of the flue gas. When 30vo1% of the flue gas is recycled into the sintering of CeO2, CaO, and K2CO3 modified coke breeze, the NOx reduc-tion rates are 36.10wt%, 32.56wt%, and 32.17wt%, respectively.     

Preparation and characterization of transparent conductive zinc doped tin oxide thin films prepared by radio-frequency magnetron sputtering

High transparent and conductive thin films of zinc doped tin oxide (ZTO) were deposited on quartz substrates by the radio-frequency (RF) magnetron sputtering using a 12 wt% ZnO doped with 88 wt% SnO2 ceramic target.The effect of substrate temperature on the structural,electrical and optical performances of ZTO films has been studied.X-ray diffraction (XRD) results show that ZTO films possess tetragonal rutile structure with the preferred orientation of (101).The surface morphology and roughness of the films was investigated by the atomic force microscope (AFM).The electrical characteristic (including carrier concentration,Hall mobility and resistivity) and optical transmittance were studied by the Hall tester and UV- VIS,respectively.The highest carrier concentration of -1.144×1020 cm-3 and the Hall mobility of 7.018 cm2(V ·sec)-1 for the film with an average transmittance of about 80.0% in the visible region and the lowest resistivity of 1.116×10-2 Ω·cm were obtained when the ZTO films deposited at 250 oC.     

Zn ~(2 ) Release Performance in Simulated Uterine Solution and Surface Characteristics of ZnO/LDPE Nanocomposites

1Introduction Intrauterinedevices(IUDs)areeffectivedevicesfor contraceptionandarewidelyusedintheworld[1,2].Espe ciallyinChina,thenumberofwomenadoptingIUDshas beenthehighestofallthoseadoptingcontraceptive measures[3].Asaneffectivecontraceptive,copper bear …     

Microstructure and Hydrogen Absorption/Desorption Behavior of Mg_(23-x)La_xNi_(10) Alloy

Induction melting was used as a routine method to synthesize Mg_(23)Ni_(10), Mg_(22)LaNi_(10) and Mg_(21)La_2Ni_(10) alloys, and followed by a detailed microstructural characterization which included X-ray diffraction(XRD), scanning electron microscopy(SEM) with energy dispersive spectrometer(EDS), high resolution transmission electron microscope(HRTEM) and hydrogen absorption/desorption measurements. XRD analysis results showed that Mg_2Ni and Mg phases were detected in the XRD pattern of the Mg_(23)Ni_(10) alloy, however, the La addition results in conversion from Mg to LaMg_3 and La_2Mg_(17) phases and appearance of crystal defects included dislocations, twin grain boundary and vacancy in the Mg_(22)LaNi_(10) and Mg_(21)La_2Ni_(10) alloy textures. The total maximum hydrogen absorption capacity was 4.45 wt% for the Mg_(23)Ni_(10) alloy, however, the Mg_(22)LaNi_(10) and Mg_(21)La_2Ni_(10) alloys with vacancy, dislocations and twin grain boundary, absorbed 3.66 wt% and 3.60 wt%, respectively, indicating that the La addition led to decreasing of the maximum hydrogen absorption capacity. Besides, hydrogen absorption/desorption of 90% of saturated state expended for about 456 and 990 s for pristine Mg_(23)Ni_(10) alloy, by contrast, the time decreased owing to improvement of hydrogen absorption and desorption kinetics in the alloy with La element, with which the uptake time for hydrogen content to 90% of saturated state was 150 and 78 s, and 90% hydrogen can be released in 930 and 804 s for Mg_(22)LaNi_(10) and Mg_(21)La_2Ni_(10) alloys in the experimental condition.